Crouzon's syndrome is characterized by cranial synostosis, hypertelorism, exophthalmos and external strabismus, parrot-beaked nose, short upper lip, hypoplastic maxilla, and a relative mandibular prognathism. This condition is usually familial.

2002. crown
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The part of a tree or shrub above the level of the lowest branch.

2003. crown gall plasmids
Definition:

A plasmid, or type of circular DNA, found in the bacteria Agrobacterium tumefaciens which infects dicot plants. Part of the plasmid inserts itself into the plant genome and causes tumors to form in the roots or in the stems nearest the roots. The plasmid has been used by geneticists, minus the tumor-causing parts, as a vector towards the genetic engineering of plants.

2004. crown gall tumor
Definition:

A disease which afflicts dicot plants, caused by the bacteria Agrobacterium tumefaciens. The disease causes large tumors to form in the roots or in the stems nearest the roots, deforming the plant along its base (where it meets the ground).

2005. CRP (cyclic adenosine monophosphate receptor protein)
Definition:

A protein present in the catabolic repression system.

2006. cruciform structure
Definition:

A structure, shaped like a cross, which can form during homologous recombination when inverted base-pair repeats pair with each other on the same strand of DNA instead of with homologous sections on a different strand of DNA.

2007. crude drug
Definition:

Any raw or unrefined medicinal compound in its natural form, especially one taken from a plant.

2008. crude fiber
Definition:

The indigestible parts of plant-based food.

2009. crude protein
Definition:

Incomplete proteins which lack essential amino acids.

2010. crustacean
Definition:

A member of the class Crustacea in the phylum Arthropoda (arthropods). The majority of these animals are marine; the rest are aquatic. Examples: crab, lobster, shrimp, barnacle, water flea, crayfish.

2011. crustaceous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Brittle; of marine algae, encrusted with calcium carbonate.

2012. crustecdysone
Definition:

A hormone, or biochemical substance produced by one part of the body to trigger an event elsewhere in the body, which causes molting (shedding of the exoskeleton) in crustaceans (such as crabs, lobster, shrimp, etc.), so that the crustacean can undergo a growth spurt before a new exoskeleton hardens.

2013. cryalgesia
Definition:

Pain caused by exposure to cold.

2014. cryo-
Definition:

A prefix indicating that the word has to do with freezing or coldness.

2015. cryoablation
Definition:

The removal of a body part, such as a wart, by freezing.

2016. cryobiology
Definition:

The study of the effects of low temperatures on living organisms.

2017. cryocautery (cold cautery)
Definition:

The surgical destruction of tissue via the application of extreme cold, as with liquid nitrogen.

2018. cryofixation
Definition:

A process of preparing cells to be examined under an electron microscope by freezing them.

2019. cryogenics
Definition:

The science of freezing at very low temperatures.

2020. cryoglobulin
Definition:

An abnormal blood protein which will fall out of solution and become solid under low temperatures (21 degrees Celsius or lower) and redissolve at normal body temperature (37 C°). This protein is often found in patients with the cancer multiple myeloma.

2021. cryonics
Definition:

Any of several medical techniques that use cold for therapeutic purposes, such as using ice to deaden pain.

2022. cryophilous
Definition:

Thriving at very low temperatures.

2023. cryoprecipitate
Definition:

A solid that settles out of a biological fluid when it is cooled to low (but not freezing) temperatures.

2024. cryopreservation
Definition:

The technique of freezing tissues or cells or other biological materials at very low temperatures in which the materials remain genetically stable and metabollically inert. Cryopreservation may involve freezers (-80 degrees Centigrade), or preservation with dry ice (-79 degrees) or liquid nitrogen (-196 degrees).

2025. cryoprobe
Definition:

A surgical instrument used to apply extreme cold to tissues.

2026. cryoprotective (cryoprotectant)
Definition:

Describes a substance which is able to protect the body or organic matter from being harmed by freezing.

2027. cryoprotein
Definition:

Any protein that precipitates when blood is cooled.

2028. cryotherapy
Definition:

The therapeutic use of cold or refrigeration in medicine.

2029. cryptic plasmid
Definition:

A plasmid which has no apparent effect on the phenotype of its host cell and has no genes other than the ones needed for itself to replicate and spread to other cells.

2030. cryptogam
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A plant whose sexual reproductive parts are not conspicuous; a plant that produces spores, not seeds, in its sexual reproductive cycle, e.g. ferns, mosses, algae. Compare phanerogam.

2031. cryptorchidism
Author: Fertilitext
Definition:

Failure of one or both testicles to descend into the scrotum.

2032. cryptorchidism (undescended testes)
Author: Guo Li
Definition:

Cryptorchidism is the condition in which one or both testes fail to descend into the scrotum during the fetal or infant period. If both testes are involved, sperm are not formed and the patient is fertile. There is also a higher incidence of testicular cancer for an undescended testicle.

2033. crystalline protein (crystallin)
Definition:

The major protein found in the lens of the vertebrate eye; it can be dissolved in water easily.

2034. CT scan
Author: Guo Li
Definition:

This is an x-ray study of the body in which radiographic images of cross-sections of the body is obtained. CT scan of the brain may reveal tumor, infarction, hydrocephalus, cortical atrophy, cerebral aneurysm, hematoma, A-V malformation. Study of the chest may reveal tumor, lymph nodes, cysts, abscess, effusion, and aortic aneurysm. Study of the abdomen may reveal tumor, hematoma, cysts. In some studies the image can be improved by contrast dye. The major complication is allergy to the dye in some patients.

2035. CT Scan (computer tomography scan)
Definition:

A diagnostic imaging technique which uses x-rays and a computer to view organs and other features inside the body.

2036. Ct value (C0t value)
Definition:

Concentration of DNA molecules (in moles) multiplied by time. The value is used to plot the renaturing (complementary single strands of DNA spontaneously forming into a double-stranded molecule) of DNA after it has been denatured (DNA molecule which has been broken into two individual single strands).

2037. cubic feet per second (cfs or ft 3/sec)
Author:
Definition:

A unit of measurement expressing rates of water flow or discharge. One cubic foot per second is equal to the discharge of a stream of rectangular cross section, one foot wide and one foot deep, flowing at an average velocity of one foot per second. (Equals approximately 450 gallons per minute.)

2038. cucullate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Hooded; hood-shaped.

2039. cul-de-sac
Definition:

1. A French term meaning "dead end" or "blind alley."
2. In women, a pouch located at the bottom of the abdominal cavity between the uterus and rectum.

2040. culdoscopy
Author: Fertilitext
Definition:

Examination of the internal female pelvic organs through an incision in the vagina.

2041. cultigen (cultivar)
Definition:

A cultivated plant or or animal that has no known wild ancestor.

2042. culture
Definition:

Any organism or living cell growing in a laboratory medium (such as bacteria growing on a plate of agar).

2043. culture medium
Author: ForBio Ltd.
Definition:

A nutrient material, either solid or liquid, used to support the growth of cells or entire organisms (such as plants, plant cells, bacteria, fungi) in vitro.

2044. culvert
Author:
Definition:

1. Buried pipe structure that allows streamflow or road drainage to pass under a road.
2. A large-diameter pipe used to transport water under a roadway or through a levee, or a buried cement channel used to transport water a long distance through an urban area.

2045. culverting
Author:
Definition:

The placement or construction of a pipe or box-shaped conduit in a creek bed for the purpose of conducting water.

2046. cuneate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Wedge-shaped.

2047. cupule
Definition:

A cuplike structure in plants (such as the little cup holding an acorn) which is made of hardened, joined bracts.

2048. cupuliform
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Nearly hemispherical, cup-shaped.

2049. curie (Ci)
Definition:

A unit of radioactive decay; equal to 3.70 x 10¹⁰ disintegrations per second.

2050. curing
Definition:

1. Removing all traces of a disease from the body so that the body is perfectly healthy again.
2. A process of improving the flavor, color, tenderness, and shelf life of a meat, such as by using smoke, spices, and chemicals.
3. Making a finished product out of a raw material by using heat or chemicals, such as tanned leather or vulcanized rubber.
4. Causing the loss of a plasmid from a bacterial culture or the loss of a dormant virus which has inserted itself into the bacterial genome (a lysogenized virus).

2051. current
Author:
Definition:

1. The continuously downstream flow of water in a river, resulting from the tendency of water to move downhill toward sea level.
2. Flow of water, both as a phenomenon and as a vector (usually qualified by adjectives like downward, littoral, tidal, etc. to show relation to a pattern of movement)
3. The amount of electricity moving through a conductive material such as a wire.

2052. curvinerved
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

With curved parallel veins.

2053. Cushing's syndrome
Author: Guo Li
Definition:

Cushing's syndrome results from high cortisol levels due to any cause and is characterized by:
• central obesity with apparent excess fat especially on the face, hence coining the description of "moon face"
• delicate, friable, smooth and thin skin
• easy bruising
• muscle wasting
• hyperglycemia, hypertension, hypokalemia
• psychosis

2054. cusp
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A rigid, sharp point, especially on a leaf.

2055. cuspidate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Tapering into a sharp, rigid point.

2056. cut-off wall
Author:
Definition:

A subsurface wall on an instream structure installed to prevent the structure from being undercut.

2057. cuticle
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A continuous layer of waxy substances covering over the outer surfaces of the epidermis of plants; it contains cutin and protects against water loss / water gain and other damage.

2058. cutin
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A wax which, together with cellulose, forms the outer layer of the skin of many plants.

2059. cutting
Author:
Definition:

Portion of a stem, root, or leaf cut from the parent plant for the production of a new independent plant by inducing it to form shoots and roots under favorable environmental conditions (e.g., stem cuttings, leaf cuttings, leaf-bud cuttings, and root cuttings).

2060. cuvette
Definition:

A transparent or translucent box-shaped container with precisely-measured dimensions for holding liquid samples to be put into a spectrophotometer.

2061. Cy VADIC
Definition:

"vincristine," "Adriamycin," and "imidazole" "carboxamide: A combination of drugs used in cancer chemotherapy treatment.

2062. cyanobacteria
Definition:

A division of photosynthetic bacteria formerly known as blue-green algae.

2063. cyanogen bromide (CNBr)
Definition:

An inorganic, toxic substance with the chemical formula CNBr which is white and crystalline with a sharp odor, is an irritant, and can be dissolved in water, alcohol, and ether. It melts at 52 degrees Celsius and boils at 61.4 degrees Celsius. It is used to extract gold, in pesticides, and in the chemical synthesis of organic substances. It is also used in genetic engineering to cleave polypeptide chains, especially synthetic proteins, wherever the amino acid methionine occurs. It is also used to attach protein ligands to various supporting substances in preparation for affinity chromatography.

2064. cyanosis
Definition:

A bluish or purplish coloring of the skin, nails and mucuous membranes caused by a lack of oxygen in the blood. This occurs when more than 50 g/L of hemoglobin in the blood becomes deoxygenated.

2065. cyathium
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

An inflorescence of unisexual flowers surrounded by inwardly-rolled bracts.

2066. cybrid
Author: ForBio Ltd.
Definition:

A hybrid cell or line formed by the fusion of cell parts from different individuals.

2067. cyclic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of floral organs, several borne at the same level on the axis; whorled. Compare spiral.

2068. cyclic AMP (cAMP)
Image: View the chemical structure
Definition:

A cellular messenger molecule that is triggered by hormones or other signaling molecules. It is formed by adenylate cyclase.

2069. cyclic AMP-dependent protein kinases
Definition:

Enzymes which attach phosphate groups to the serine or tyrosine amino acids on proteins as a means of regulating the proteins' activity in metabolic reactions.

2070. cyclic guanosine monophosphate (c-GMP)
Definition:

A cyclic version of the nucleotide guanosine monophosphate. It plays a role in communicating vision from the eyes to the brain.

2071. cyclic photophosphorylation
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The formation of ATP when light energy is used to move electrons cyclically through an electron transport chain during photosynthesis; only photosystem I participates.

2072. cyclin
Definition:

A protein found in certain eukaryotic cells which helps regulate the cell cycle by causing cells to begin mitosis (a form of nuclear division). The protein is made during all parts of the cell cycle but is destroyed during mitosis.

2073. cyclodextrin
Image: View the chemical structure
Definition:

A cyclic oligomer of alpha-D-glucopyranose. The most common cyclodextrins are alpha, beta and gamma cyclodextrin having 6,7 and 8 glucopyranose units respectively. They occur naturally in starch digests of the bacteria Bacillus Macerans. With a hydrophobic interior cavity, they can complex small hydrophobic molecules while remaining soluble in water. Potential applications include water-soluble pharmaceuticals and herbicides and pesticides.

2074. cyclodialysis (Heine's operation)
Definition:

A treatment for glaucoma (a disease causing increased pressure in the eyeball) in which a passage is made between the suprachordial space and the anterior chamber of the eyeball to relieve pressure.

2075. cycloheximide
Image: View the chemical structure
Definition:

An antibiotic derived from the bacterium Streptomyces griseus which inhibits protein synthesis in eukaryotic (nucleated) cells by blocking the traslation of messenger RNA on ribosomes.

2076. cyclophosphamide
Image: View the chemical structure
Definition:

A cytotoxin in the nitrogen mustard family which is used both as a chemotherapy agent (Hodgkin's disease, lymphosarcoma, lymphocytic leukemia, ovarian cancer, etc.) and as an immune system suppressor to prevent transplant rejections.

2077. cyclopiazonic acid
Definition:

A fungal toxin produced by members of the Aspergillus and Penicillium species.

2078. cycloserine
Image: View the chemical structure
Definition:

A broad-spectrum antibiotic synthesized by the bacterium Streptomyces orchidaceus which is used most often to treat urinary tract infections and tuberculosis. This antibiotic is a structural analog of the amino acid D-alanine and it inhibits bacteria's ability to make peptidoglycan, an important component of the bacterial cell wall.

2079. Cyclospora cayetanensis
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Cyclospora cayetanensis is an acid-fast, coccidian-like, parasitic protozoan with the size of 8-10 micrometer in diameter. Cyclospora cayetanesis was recently recognized as a new (intestinal) protozoan pathogen of human (1993, species name was proposed in 1994) and was identified as the cause of the prolonged diarrhea of travelers as well as immunocompetent and immunocompromised patients.

2080. cyclosporin A
Image: View the chemical structure
Definition:

A ring-shaped peptide produced by some fungi. It inactivates helper T cells, and is therefore used to suppress the immune system to prevent graft rejections.

2081. cyme
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

An inflorescence in which each flower, in turn, is formed at the tip of a growing axis and further flowers are formed on branches arising below it.

2082. cymose
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Bearing a cyme or group of cymes.

2083. cymule
Definition:

A small cyme, usually with few flowers.

2084. cypsela
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A dry, indehiscent, one-seeded fruit formed from an inferior ovary. Compare achene.

2085. cyst
Definition:

1. A closed sac or pouch which generally contains semisolids, fluids, or gases, that may be a normal or abnormal part of the body.
2. A dormant form assumed by some bacteria, reproductive bodies, or embryos. The word can refer to either the structure or the stage of resting.

2086. cyst
Author: Guo Li
Definition:

A cyst is an abnormal sac or cavity that is filled with fluid, parasites, or other non-pus materials.

2087. cyst-
Definition:

A prefix indicating that the word has to do with cysts or bladders.

2088. cysteine
Image: View the chemical structure
Author: Courtesy of MacMolecule
Definition:

One of the twenty naturally occurring amino acids. Has the following chemical characteristics:


pKa1   pKa2    pKa3      pI      Water Solubility (30deg C)
1.71   8.33   10.78     5.02

2089. cysteine carboxypeptidase
Definition:

An enzyme which removes the last peptide bond on a protein (the one at the carboxyl end). Its active site contains the sulfur part of the amino acid cysteine.

2090. cysteine proteinase
Definition:

An enzyme that destroys proteins by hydrolysis, turning them back into individual amino acids.

2091. cystic fibrosis
Definition:

A recessive genetic disease in which the exocrine glands of afflicted individuals produce abnormally thick mucus which block the intestines and lung passageways and produce scarring and lesions in the lungs and pancreas. People with the disease have a very hard time breathing and often die from suffocation. CF patients used to die in childhood, but with the advent of modern treatments, patients now live an average of 21-25 years.

2092. cystic fibrosis
Author: Guo Li
Definition:

About half of cystic fibrosis patients first appear for medical care as failure-to-thrive infants with recurrent respiratory problems such as infections, and small airway obstructions. 15% appear for medical care because of intestinal obstruction due to the presence of thick meconium in the large bowel. More than 95% of males affected with cystic fibrosis are infertile.

The problem is in the excretion of an abnormal mucus that obstructs exocrine glands (glands that excrete outside of the body as versus endocrine glands that excrete into the circulation). The protein that is defective is the cystic fibrosis transmembrane conductance regulator (CFTR) which is involved in chloride channel activity. The disease is autosomal recessive inherited condition affecting 1 in 2000 Caucasian births; the disease is caused by an abnormal gene on chromosome 7.

Cystic fibrosis is diagnosed by symptoms coupled with a sweat sodium and chloride test.

Sweat sodium and chloride values:

sodium:

normal: < 70 mEq/L
abnormal: > 90 mEq/L
borderline: 70 to 90 mEq/L

chloride:
normal: < 50 mEq/L
abnormal: > 60 mEq/L
borderline: 50 to 60 mEq/L

2093. cystic fibrosis transmembrane conductance regulator protein (CFTCR protein)
Definition:

A protein which is embedded in the cell membrane and acts as a channel for certain ions to be transported into or out of the cell. The disease cystic fibrosis is caused by a defect in the gene for this protein.

2094. cystine
Image: View the chemical structure
Definition:

An amino acid which can be formed when proteins are destroyed by digestion or acid hydrolysis; it contains sulfur. It is sometimes found as crystals in the kidneys or in urine.

2095. cystitis
Definition:

Cystitis is an infection of the bladder (the organ that temporarily stores urine).

2096. cystoblast
Definition:

A germ cell found in the ovaries of insects which instead of turning into a reproductive cell, becomes the insect equivalent of a platelet (a blood cell which helps bring about blood clots), called a cystocyte.

2097. cystocarcinoma (cystoepithelioma)
Definition:

A type of carcinoma, or epithelial cancer, where the main symptom is the formation of cysts (fluid-filled sacs).

2098. cystocopy
Author: Guo Li
Definition:

This is the direct examination of the urethra, bladder, and the ureter by means of a metal tube throgh the urethral opening. This procedure can be done under local anesthesia if only examination is involved. Otherwise, general anesthesia will be needed. This procedure is used for the collection of urine specimen, measurement of bladder capacity, and placement of ureteric stents. It is also used for the biopsy and resection of bladder and prostate tumors, benign hypertrophic prostate, and manipulation and removal of bladder and ureteric stones.

2099. cystocyte
Definition:

The insect equivalent of a platelet (a blood cell which helps bring about blood clots). At a site of injury, these cells will break down into threads around which plasma can gel, stopping the flow of hemolymph (the arthropod equivalent of blood) from the site.

2100. cystofibroma
Definition:

A type of fibroma, or type of benign tumor, which is covered with cysts (fluid-filled sacs). A type of cystoma.

2101. cystolith
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

1. A stalked structure growing from a cell wall into the cell cavity, encrusted with calcium carbonate.
2. A mass of calcium carbonate concretion, occasionally silica, formed on ingrowths of modified epidermal cell walls in some plants, esp. of the Acanthaceae family.

2102. cystoma
Definition:

A tumor which contains cysts (fluid-filled sacs).

2103. cystometry
Author: Guo Li
Definition:

Cystometry is a method of investigating the urodynamics of the urinary bladder by measurement of urine flow and bladder pressure.

normal values:


residual urine: 5 - 10 ml
max. detrusor pressure: 15 cm H₂O
sensation of bladder distension: 225 ml
max. capacity of bladder: 425 ml

2104. cytidine (cytosine riboside)
Image: View the chemical structure
Definition:

A cytosine ribonucleoside (where the nitrogenous base cytosine is linked to the sugar ribose) which plays an important role in the metabolism of all living things.

2105. cytidine monophosphate (CMP, cytidylic acid)
Definition:

A cytosine ribonucleotide (where the nitrogenous base cytosine is linked to the sugar ribose and a phosphate group) that helps make glycoproteins (a protein linked to a sugar or polysaccharide).

2106. cytidine triphosphate (CTP)
Definition:

A molecule which consists of the nitrogenous base cytosine linked to the sugar ribose and which has a chain of three phosphate groups attached to the ribose in a linear fashion. CTP is required for the synthesis of DNA since it is a direct precursor molecule.

2107. cyto-
Definition:

A prefix indicating that the word has to do with cells.

2108. cytobiosis
Definition:

A type of symbiosis in which one partner lives inside the cell or cells of the other.

2109. cytochalasin
Definition:

A substance produced by fungus or mold which inhibits most cellular activities but not the activities within the nucleus which prepare for cell division.

2110. cytochemistry
Definition:

The scientific study of the chemical makeup, structure, and metabolism of cells.

2111. cytochrome c
Definition:

A type of cytochrome, a protein which carries electrons, that is central to the process of respiration in mitochondria (an organelle found in eukaryotes which produces energy).

2112. cytochrome oxidase
Definition:

A protein which carries electrons that is embedded in the inner of the two membranes of the mitochondrion. It oxidizes cytochrome c (takes the electrons that it is carrying), another protein which carries electrons.

2113. cytochrome P450
Definition:

An electron-carrying enzyme that inserts one of the oxygen atoms of the molecule O2 into its substrates. It is found in animals, plants, and bacteria. It plays an important role in mammalian livers and the making of steroid hormones in the adrenal cortex.

2114. cytochromes
Definition:

Heme proteins that carry electons during oxidation-reduction reactions such as photosynthesis and respiration.

2115. cytocrine gland
Definition:

A cell which secretes things that move directly from cell to cell.

2116. cytodifferentiation
Definition:

Differentiation between cells caused by changes in the cells' appearance or morphology rather than through changes to their chromosomes.

2117. cytofluorometry
Definition:

A technique for separating and analyzing cells or chromosomes which relies on the detection of specific fluorescent markers.

2118. cytogenetics
Author: Susan A.Hagedorn
Definition:

Study that relates the appearance and behavior of chromosomes to genetic phenomena.

2119. cytohet
Definition:

An eukaryotic cell which has one or more genes that occur outside the nucleus ( cytoplasmic genes) that are heterozygous.

2120. cytokine
Definition:

In immunology, any of many soluble molecules that cells produce to control reactions between other cells.

2121. cytokinesis
Definition:

The division of the cell's cytoplasm to produce two daughter cells, which occurs soon after mitosis (division of the cell's nucleus). This process also has been classified as being a late part of telophase of mitosis (or telophase II for meiosis).

2122. cytokinin
Definition:

A plant growth hormone that stimulates cell division, metabolism, and the synthesis of protein and RNA.

2123. cytology brush
Definition:

A small brush which is used to collect cells during the course of a biopsy.

2124. cytolysis
Definition:

The process of destroying a cell by rupturing its cell membrane.

2125. cytolysosome
Definition:

A large lysosome, an organelle which contains digestive enzymes, that is destroying its own cell.

2126. cytoma
Definition:

General term for a cell tumor, such as a sarcoma.

2127. cytomegalic inclusion disease
Definition:

An illness in newborns caused by viral infection; symptoms include fever, cellular enlargement, microscopically-visible clumps of viral particles or proteins in the cytoplasm and nuclei of affected cells, enlargement of the spleen and liver. Long-term effects of the disease may include mental retardation.

2128. Cytomegalovirus (Betaherpesvirinae)
Definition:

A subfamily of viruses in the family Herpesviridae. The viruses of this group are characterized by a long replication cycle (equivalent to the life cycles of true living things) and a narrow range of hosts (per virus). The viruses infect the kidneys and salivary glands of a number of vertebrate species, including humans.

2129. cyton
Definition:

The main part of a neuron cell (which consists of the main body plus a number of long extensions from it called axons, axon terminals, and dendrites).

2130. cytopathic
Definition:

Causing disease symptoms in cells.

2131. cytopenia
Definition:

A deficiency or inadequacy of cells or cellular constituents in the blood.

2132. cytophilic
Definition:

Refers to substances which are attracted to binding cells, like cytophilic antibodies.

2133. cytoplasm
Definition:

The contents of a cell; includes the organelles but not the nucleus.

2134. cytoplasmic gene
Definition:

A gene which occurs outside the nucleus of an eukaryote or outside the regular chromosomes of a bacteria.

2135. cytoplasmic inheritance (extrachromosomal inheritance)
Definition:

The inheritance of traits coded by genes found outside the normal genome, such as from DNA found in mitochondria or chloroplasts.

2136. cytoplasmic membrane (cell membrane, plasma membrane)
Definition:

The membrane that surrounds a cell's cytoplasm, separating it from the environment. It consists of a double layer of phospholipids and has proteins embedded in it.

2137. cytoplasmic polyhedrosis virus group
Definition:

A group of viruses in the family Reoviridae which infects arthropods (like spiders, insects, crustaceans, horseshoe crabs, etc.).

2138. cytoplasmic streaming
Definition:

The directional flow of cytoplasm in some of the larger cells. This is thought to help the cell get rid of waste products.

2139. cytoplast
Definition:

A cell without a nucleus which is produced by treatment with the substance cytochalasin.

2140. cytosine (C)
Image: View the chemical structure
Definition:

A nitrogenous base, one member of the base pair G- C (guanine and cytosine).

2141. cytoskeleton
Definition:

A network of molecular filaments (actin, microtubules, etc.) that provide a structure for the cytoplasm.

2142. cytosol
Definition:

The fluid portion of a cell's cytoplasm.

2143. cytosome
Definition:

All of the parts of a cell except the nucleus.

2144. cytostatic
Definition:

1. Refers to the inhibition of cell growth or cell division, possibly by a drug or other chemical substance.
2. An area or process in the body where there is less movement and blood cell accumulation than normal.

2145. cytotaxis
Definition:

The movement of a cell toward or away from some sort of stimulus. (The stimulus would then be called the "cytotaxin").

2146. cytotoxic
Definition:

Refers to a toxic, or poisonous, effect on cells.

2147. cytotoxic T cell
Definition:

A type of T lymphocyte which can recognize and destroy foreign cells (like bacteria) and cells that have been infected with a virus.

2148. cytotoxin
Definition:

Any substance that poisons living cells.

2149. cytotropism
Definition:

The movement of cells or groups of cells toward or away from each other.

2150. Czapek's medium
Definition:

An agar medium used to grow fungi and soil bacteria which feed on decaying organic material (called saprobes). The medium contents include sugars, water, and salt.

2151. D loop
Definition:

A structure that can sometimes be seen on DNA which forms when a small area of the double-stranded molecule comes apart and becomes two single strands. The result is a structure shaped like the letter D. Single-stranded binding proteins are usually present to hold the strands apart for the purpose of DNA replication.

2152. D4DR gene
Definition:

A gene which regulates a protein that plays a role in transmitting messages carried by dopamine between neurons (brain cells). A particular form of the gene may have an affect on an individual's personality since it seems to occur in individuals with novelty-seeking behavior.

2153. dacryoadenitis
Author: Guo Li
Definition:

Dacryoadenitis is the inflammation of the lacrimal gland. This condition is often associated with nonbacterial infection of other parts of the body and is self-limiting.

2154. dacryocystostomy
Author: Guo Li
Definition:

Dacryocystostomy is surgery to create an opening (a drainage) into the tear sac.

2155. dalapon
Image: View the chemical structure
Definition:

A herbicide that is used mainly to kill grasses; it was a major part of Agent Orange, a defoliant used in the Vietnam War.

2156. dalton
Definition:

A unit of mass that equals the weight of a hydrogen atom, or 1.657 x 10^-24 grams. Named for John Dalton, an early nineteenth century British chemist who proposed the atomic theory of matter.

2157. dam gene
Definition:

A gene that codes for the synthesis of a DNA adenine methylase.

2158. Danazol (Danocrine)
Author: Fertilitext
Definition:

A synthetic androgen frequently prescribed for endometriosis.

2159. dansyl chloride (dansyl acid, DANS)
Definition:

A yellow-orange crystalline substance which cannot be dissolved in water but can be dissolved in acetone (a type of ketone), and has the chemical formula C₁₂H₁₂ClNO₂S. It will melt at temperatures between 66.5 and 68 degrees Celsius. &Quot;Dansyl" is an acronym for 5 dimethylamino-1 naphthalenesulfonyl. Dansyl chloride is fluorescent when it is attached to a protein or polypeptide, and is used to identify the amino acid which is on the amino terminal end of a polypeptide chain.

2160. dark field microscopy (dark field microscope, dark field imaging, dark-field illumination, dark-ground illumination)
Definition:

The use of a microscope which is lit by a beam of light or electrons that has been refracted, diffracted, or condensed and diffused, so that only certain parts of the object being studied are lit while the rest of the field of view is dark, to study tiny particles or lines.

2161. Darwin, Charles
Definition:

An English naturalist who lived from 1809 to 1882; he studied and documented the flora and fauna of parts of coastal South America, including the Galapagos Islands, but is most famous for developing the theories of evolution and natural selection.

2162. datum
Author:
Definition:

A base elevation used as a reference from which to reckon heights and depths. It is called a tidal datum when defined by a certain plane of the tide.

2163. day neutral plants
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Plants that flower regardless of day length.

2164. DDT (dichloro-diphenyl-trichloroethane)
Image: View the chemical structure
Definition:

This chlorinated organic insecticide was discovered by Swiss chemist Paul Muller in 1939. DDT has been especially useful in controlling mosquitos that carry malaria, but some strains of the insects have become resistant to it. DDT has comparatively low acute toxicity in humans (it is thought to cause cancer), but it persists for a long time in the environment and is disastrously toxic to birds, especially top-level predators such as hawks and eagles (see biomagnification). The chemical interferes with birds' ability to metabolize calcium, and thus affected birds lay eggs with fatally thin shells. DDT has been banned in most countries, but it is still widely used on crops in Latin America.

2165. de novo pathway
Definition:

A pathway for synthesizing a biomolecule from simple precursor molecules; compare salvage pathway.

2166. De Sanctis-Cacchione syndrome
Author: Guo Li
Definition:

De Sanctis-Cacchione syndrome includes xeroderma pigmentosum, mental deficiency, dwarfism, and gonadal hypoplasia; this disease has autosomal recessive inheritance.

2167. deaminase (aminohydrolase, deamidase)
Definition:

An enzyme which removes amino groups from compounds, producing ammonia in the process.

2168. deamination
Definition:

The process through which enzymes strip amino groups off biomolecules.

2169. death (brain death)
Author: Guo Li
Definition:

The definitions of death and life may be a philosophical, ethical, cultural, and legal issue.

Traditionally, a physical examination of the patient confirming the absence of clinical signs (pulses, respiration, movements, pupillary size and reactions to light) is sufficient prior to a declaration of death.

Three major considerations lead to a more elaborate set of criteria for the clinical definition of death:

1. Complete absence of clinical signs on a patient can be maintained with modern anesthetic techniques.
2. Some patients found with no pulse or respiration due to exposure to hypothermia can be later resuscitated.
3. A patient without integrated brain function may be mechanically ventilated, have a strong pulse and good circulation, as is often found in patients of trauma, or patients with intracerebral hemorrhage, despite the fact that there is no expectation of the patient ever regaining brain function.
The concept of brain death is now accepted by many jurisdictions as the legal definition of death.

2170. death phase
Author: Susan A.Hagedorn
Definition:

The final growth phase in a culture, during which nutrients have been depleted and cell number decreases.

2171. debridement
Author: Guo Li
Definition:

Debridement is the surgical excision of dead or dying tissue from a wound. The aim of debridement is to remove material which has poor or no circulation and which is therefore more likely to become infected.

2172. debris
Author:
Definition:

Driftwood and detritus (leaves, trash, etc.) carried or deposited by a stream.

2173. debris dams
Author:
Definition:

Detention dams constructed to trap sediment.

2174. debris loading
Author:
Definition:

The quantity of debris located within a specific reach of stream channel, due to natural processes or human activities.

2175. debris torrent
Author:
Definition:

Deluge of water charged with soil, rock and organic debris down a steep stream channel.

2176. debulking
Author: Guo Li
Definition:

Debulking is the surgery to remove a large portion of tumor; this is usually done in preparation of further treatment such as chemotherapy, or radiotherapy, or both.

2177. debulking of tumor
Definition:

The surgical removal of as much of a tumor as is possible, although the surgeon is unable to remove the whole thing.

2178. decatenation
Definition:

The opposite of catenation.
1. The unlinking of chemical elements within a ring or chain from each other.
2. The unlinking of identical units in a large molecule from each other.

2179. decerebrate posture
Author: Guo Li
Definition:

Decerebrate posture is the manifestation of clenched jaw, retracted neck, and the arms and legs extended and internally rotated (pronated). This condition is usually due to lesions in the mid-brain, upper pons or metabolic causes such as hypoglycemia and hypoxia.

2180. decibel
Author: Guo Li
Definition:

A decibel is a relative measurement of the intensity of a sound wave. A quiet whisper at 1 meter is about 10 decibels, noise from a motor car at 5 meters is about 70 decibels and noise from a large jet plane at 40 meters is about 110 decibels.

2181. decidua
Author: Guo Li
Definition:

The decidua is the changed endometrium (the lining of the uterus) after the blastocyst (fertilized ovum after 4 - 9 days of development) is implanted onto the endometrium. At this stage, there are 3 regions of decidua:
decidua basalis: between the blastocyst and the uterine muscular wall,
decidua capsularis: covers the blastocyst;
decidua parietalis: the rest of the lining of the uterus.

2182. deciduous
Definition:

Refers to a plant (usually a tree or shrub) that sheds its leaves at the end of the growing season

2183. decisional capacity
Author: Guo Li
Definition:

Decisional capacity is a medicolegal term referring to a person's ability to decide for the type of care he wish to receive. This ability implies that the person is able to understand information that is relevant to making a decision and also able to appreciate the reasonably foreseeable consequences of accepting or refusing the proposed type of care. It should be noted that the same person may have capacity to understand one type of procedure or treatment and not be able to understand others. Only an individual with capacity can give informed consent.

2184. decompound
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

More than once compound.

2185. decompression sickness (caisson disease, dysbaric illness, DCS, the bends)
Author: Guo Li
Definition:

Decompression sickness is a condition precipitated by rapid changes in the ambient atmospheric pressure, mostly in rapid ascent from underwater but can also be from rapidly reaching high altitudes in jets. Onset is in 30 minutes to 6 hours after decompression. It occurs because at high atmospheric pressures (such as when one is several hundred feet under water) the blood can contain more dissolved nitrogen than at lower pressures; when the diver ascends rapidly, the blood can no longer contain this dissolved nitrogen and tiny gas bubbles begin to form in the blood.

Symptoms include: body pain (mainly in the joints), headache, confusion, itchy skin rash, visual disturbances, weakness or paralysis, dizziness or vertigo. The condition can be fatal. Compliance with the schedules set out in dive tables may lessen the chance of decompression sickness.

2186. decongestant
Author: Guo Li
Definition:

A decongestant is a drug (such as pseudoephedrine) which relieves nasal congestion.

2187. decorticate posture
Author: Guo Li
Definition:

Decorticate posture is the manifestation of one or both arms flexed, legs extended and tonic neck flexion to one side may be present. This condition is usually due to lesions in the cerebral white matter, internal capsules, and/or the thalamus.

2188. decubitus (decubitus ulcer)
Author: Guo Li
Definition:

A decubitus ulcer is a bedsore which is caused by pressure over bony areas. The most common sites for decubitus to occur are the hips, elbows and heels.

2189. decumbent
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Spreading horizontally but then growing upwards.

2190. decurrent
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Extending downwards beyond the point of insertion.

2191. decussate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In pairs, with successive pairs borne at right angles to each other.

2192. deep fascia
Author: Guo Li
Definition:

This is a membranous layer of connective tissue that covers muscles and other deep body structures.

2193. deep vein thrombosis (DVT)
Author: Guo Li
Definition:

Deep vein thrombosis is the formation of a solid mass of platelets in the deep veins of the leg. This process often occurs in patients confined in bed, with sluggish flow of blood in the veins, and traumatized veins. The risk of developing a deep vein thrombosis rises with increasing age.

2194. deepwater habitat
Author:
Definition:

Any open water area in which the mean water depth exceeds 6.6 feet at mean low water in nontidal and freshwater tidal areas, or is below extreme low water at spring tides in salt and brackish tidal areas, or the maximum depth of emerging vegetation, whichever is greater.

2195. defective virus (incomplete virus)
Definition:

A virus which is unable to reproduce by itself because it is missing some important genes and is unable to make the necessary proteins. Such a virus can only spread if another virus, which has working copies of the genes and can supply the missing proteins, also infects the same host cell.

2196. defibrillation
Author: Guo Li
Definition:

Defibrillation is a procedure using an electric current to correct abnormal rhythms of the heart.

2197. defined medium (synthetic medium)
Definition:

A growth medium used to culture microorganisms, in which all of the ingredients are known and thus the medium can be duplicated.

2198. degeneracy
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

In relation to the genetic code, the fact that more than one codon can code for the same amino acid.

2199. degenerate code
Definition:

The fact that in most cases in the genetic code used by all life on Earth, one particular amino acid is specified by more than one three-base combination of the four nitrogenous bases (called a codon). There are enough different codons to specify 64 different amino acids, but there are in actuality only 20 amino acids (and three stop codons) used in the making of proteins.

2200. degeneration
Author: Guo Li
Definition:

Degeneration is the impairment or worsening of the function of an organ.

2201. degradation
Definition:

The destruction of a molecule into its components. The breaking down of large molecules into smaller ones.

2202. degradation
Author:
Definition:

1. Erosional removal of materials from one place to another. Degradation lowers the elevation of streambeds and flood plains. (Opposite of aggradation.)
2. Downgrading of a streambed by scour.

2203. degraded wetland
Author:
Definition:

A wetland which has been altered by man through impairment of some physical property and in which the alteration has resulted in a reduction of biological complexity in terms of species diversity of wetland-associated species which previously existed in the wetland areas.

2204. degrading stream
Author:
Definition:

A stream (or reach of stream) that is removing more material than it is depositing. The elevation of the streambed is dropping and, usually, the banks are eroding. (Usually found in the upper reaches of a stream or immediately below a culvert, dam, or weir.)

2205. dehiscence (adj. dehiscent)
Author: Guo Li
Definition:

Dehiscence is the separation of previously surgically-closed wounds.

2206. dehiscent
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Breaking open at maturity to release the contents.

2207. dehydration
Author: Guo Li
Definition:

"Dehydration" is often used in clinical practice to indicate the combined loss of both water and sodium. Many physiologists would have preferred the term to be used to indicate pure water loss. However, patients never lose only water. Likewise, the term "re-hydration" is never used by clinician to mean giving patients pure water. Miscommunication between clinicians does not occur because detailed laboratory data such as serum electrolytes, creatinine, blood urea nitrogen and glucose levels as well as the type of fluids used to "re-hydrate" are always included in their conversation.

2208. dehydration-condensation reaction
Definition:

The joining of two molecules to each other with the release of a water molecule in the process. This is the opposite of hydrolysis.

2209. dehydrogenase
Definition:

Any of many enzymes that strip pairs of hydrogen atoms from other molecules.

2210. dehydrogenation
Definition:

The removal of one or more hydrogen ions or protons from a molecule. This can be done by a dehydrogenase enzyme.

2211. deja vu
Author: Guo Li
Definition:

Deja vu is a subjective sensation; that an experience which is really happening for the first time is perceived to have occurred on a previous occasion. The term is French for "already seen".

2212. delayed hypersensitivity
Definition:

Hypersensitivity (increased reaction by the body to a foreign substance such as an antigen or allergen) that does not appear until 24 to 48 hours after the body is exposed to the foreign substance.

2213. deletion
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A removal of a portion of a gene.

2214. deletion mutation
Definition:

A mutation cause by the removal of one or more nucleotides from a gene or chromosome.

2215. delirium
Author: Guo Li
Definition:

Delirium is a clinical syndrome characterized by disordered cognition (thinking, perception, and memory). Delirium is often associated with persecutory delusions and perceptual disturbances (visual and/or auditory illusions and hallucinations). The DSM of the American Psychiatric Association has a summary of diagnostic criteria for delirium.

2216. delivery system
Definition:

A manmade system with the purpose of delivering a drug or another chemical directly into a cellular target, such as a via a manmade vesicle called a liposome.

2217. delta
Author:
Definition:

1. Silt deposits, generally triangular in shape, collected at or in a river's mouth.
2. System of channels through an alluvial plain at the mouth of a stream.

2218. delta virus (hepatitis delta virus)
Definition:

The hepatitis delta virus is a defective virus which uses single-stranded RNA as its genetic material. It is only able to replicate when a helper virus from the family Hepadnaviridae is present in the same host cell. When combined with the virus that causes the disease of hepatitis B, it results in the disease of hepatitis delta.

2219. deme
Definition:

A locally interbreeding group within a geographic population.

2220. dementia
Author: Guo Li
Definition:

Dementia is clinical syndrome characterized by the organic loss of intellectual functioning, such as impairment of orientation, memory, comprehension, calculation, learning capacity and judgment. The DSM of the American Psychiatric Association has a summary of diagnostic criteria for dementia. The prevalence of dementia increases with age, starting with 1 percent at age 60, and double the rate every 5 years. Alzheimer's disease is associated with dementia.

2221. Demerol (Meperdine)
Definition:

A prescription narcotic drug that is used to kill pain. Demerol, like other narcotics, is an addictive drug.

2222. demyelinating neuropathy
Author: Guo Li
Definition:

This type of neuropathy (which is characterized by degeneration of the myelin sheath surrounding nerves) occurs after infections, such as in Guillain-Barré syndrome.

2223. demyelinization
Definition:

The destruction of the protective myelin sheath that surrounds nerve fibers, resulting in the loss of function of those nerves. Demyelinization happens in some degenerative nerve diseases like multiple sclerosis and polio.

2224. denaturation
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Irreversible destruction of a macromolecule, as for example the destruction of a protein by heat.

2225. denature
Author: Susan A.Hagedorn
Definition:

To induce structural alterations that disrupt the biological activity of a molecule. Often refers to breaking hydrogen bonds between base pairs in double-stranded nucleic acid molecules to produce in single-stranded polynucleotides or altering the secondary and tertiary structure of a protein, destroying its activity.

2226. denatured protein
Definition:

A protein that, because of heat or detergent application, has lost its native conformation.

2227. dendric
Author:
Definition:

1. Channel pattern of streams with tributaries that branch to form a tree-like pattern.
2. Anything that is treelike or has a treelike pattern.

2228. dendrite
Definition:

A long extension of the cytoplasm of a neuron with thin, treelike branches. It receives nerve signals and transmits them to the main body of the cell (called the cyton).

2229. dendrites
Author: The Alzheimer's Association
Definition:

Branched extensions of the nerve cell body which receives signals from other nerve cells. Each nerve cell usually has many dendrites.

2230. dendroid
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Tree-like in form but not in size. Compare arborescent.

2231. Denhardt's solution
Definition:

A solution commonly used during probe hybridizations that involve filters (such as Southern, Northern, or Western blots). The solution contains ficoll, bovine serum albumin, polyvinylpyrrolidone (PVP), and a high concentration of nonspecific DNA so the probe won't hybridize nonspecifically.

2232. Denil fishway
Author:
Definition:

Fishway that dissipates the water's energy so fish can swim over low barriers without undue stress. A Denil fishway has lateral baffles projecting at an angle from each side of a straight chute and a clear passage up the middle.

2233. denitrification
Definition:

1. The removal of an oxygen atom from a nitrogen compound (like NO₃ to NO₂, NO₂ to NO, or NO to N₂). This is something soil bacteria do successively until they release nitrogen gas, and is the opposite of nitrogen fixation.
2. The removal of nitrogen or nitrogen compounds from a substance.

2234. denitrification
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Conversion of nitrate into nitrogen gases under anaerobic conditions, resulting in loss of nitrogen from ecosystems.

2235. density gradient
Definition:

A solution in which the concentration of the solute is lowest at the top and gradually becomes more dense as it gets deeper, and is highest at the bottom. It can be stepwise (each level of density is discrete from other levels of density, and forms a separate layer) or continuous (the density changes gradually).

2236. density gradient centrifugation
Author: Susan A.Hagedorn
Definition:

High-speed centrifugation in which molecules "float" at a point where their density equals that in a gradient of cesium chloride or sucrose.

2237. dental plaque
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Bacterial cells encased in a matrix of extracellular polymers and salivary products, found on the teeth.

2238. denticle
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A small tooth or toothlike projecting point.

2239. dentistry
Definition:

This is a medical profession that deals with the treatment and prevention of diseases of the teeth and gums.

2240. dentur tales doses No. IV (d.t.d. No. IV)
Definition:

This Latin term, which is frequently used in medicine and pharmacy, means "let four such doses be given".

2241. denture stomatitis
Author: Guo Li
Definition:

This condition is characterized by inflammatory lesions of the mouth caused by dentures which are usually ill-fitted, dirty and superimposed with Candida (yeast) infections. The prevalence rate of denture stomatitis is about 60% of denture-wearing elderly patients.

2242. deoxynucleoside
Definition:

A molecule composed of a nitrogenous base attached to the five-carbon sugar deoxyribose.

2243. deoxyribonucleotide
Definition:

A molecule composed of a nitrogenous base attached to the five-carbon sugar deoxyribose, which also has a phosphate group attached to it.

2244. dependence
Author: Guo Li
Definition:

This usually refers to "drug dependence", which is the compulsion (physical or mental) to continue taking a drug as the result of habitual administration of the drug.

2245. Dependovirus
Definition:

A genus of viruses in the family Parvoviridae which are all defective viruses (unable to replicate by themselves) and depend on the co-infection of their host cell by other, nondefective viruses to help them replicate.

2246. depletion
Definition:

In general, the often harmful decrease in the supply of something:
1. In ecology, it refers to the consumption of a resource (such as timber or oil) faster than it can be replaced through natural processes;
2. In agriculture, it refers to impaired soil productivity due to a loss of nutrients.

2247. depletion method
Definition:

A lab technique to isolate mRNA molecules from a specific gene by hybridizing all of the mRNA molecules from a cell to a specific segment of DNA. The one mRNA molecule type which actually sticks is the one looked for.

2248. depolarization
Definition:

1. A change in the electrical charge between the inside and the outside of a membrane. For example, neurons which are receiving signals become momentarily more positively charged than the outside of their membranes.
2. The turning of polarized light into random light by reflecting it in all directions, so that it no longer vibrates in a single plane.

2249. depolymerization
Definition:

The dismantling of a polymer (a chain of monomer units) into individual monomers.

2250. deposit
Author:
Definition:

An earth mass of particles settled or stranded from moving water or wind.

2251. deposition
Author:
Definition:

The settlement or accumulation of material out of the water column and onto the stream bed. Occurs when the energy of flowing water is unable to support the load of suspended sediment.

2252. depositional areas
Author:
Definition:

Local zones with in a stream where the energy of flowing water is reduced and suspended material settles out, accumulating on the streambed. (Compare scoured areas.)

2253. depressed
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Flattened as if pressed down from the top or end.

2254. depression
Author: Guo Li
Definition:

Depression is the mental state of excessive sadness characterized by persistently low mood or extensive loss of pleasure and interest. To be considered a clinical condition, depression symptoms must have a duration of at least 2 weeks and include: decreases or sometimes increases in weight, agitated or sluggish activity, disturbance in sleep, appetite, and concentration.

2255. depression storage
Author:
Definition:

Water retained in puddles, ditches and other depressions in the surface of the ground.

2256. depth
Author:
Definition:

1. Vertical distance from the water surface to the streambed.
2. Vertical distance from crest or crown to invert of a conduit.

2257. depurination
Definition:

The removal of a purine ( adenine or guanine) from a molecule of DNA, leaving the sugar and phosphate backbone (the rest of the nucleotide) still attached to the DNA.

2258. dermabrasion
Author: Guo Li
Definition:

This is a surgical procedure for the removal of scars on the face (often acne scars). It usually involves the application of a sclerosing agent on the face (e.g. mixture of pheno, trichloroacetic acid (TCA), and croton oil). After a few minutes, a pneumatic powered drill fitted with a tungsten carbide grit-coated cylinder is used as a mechanical sander to lightly remove the superficial layer of the skin which has been softened by the sclerosing agent.

2259. dermal irritation
Definition:

This is a localized skin reaction resulting from either single or multiple exposure to a physical or chemical agent at the same site. It is characterized by redness and swelling and may be accompanied by local death of skin cells.

2260. dermatitis (eczema)
Author: Guo Li
Definition:

Dermatitis is a skin disorder involving the epidermis and dermis layers of the skin; can produce a rash, blisters, or sore, cracked skin.

2261. dermatology
Definition:

The medical discipline dealing with the diagnosis and treatment of skin diseases and problems.

2262. dermatomyositis
Author: Guo Li
Definition:

The skin rash associated with polymyositis.

2263. dermis (corium, true skin)
Definition:

The layer of skin just beneath the epidermis; it is composed of dense vascular connective tissue.

2264. dermoid cyst
Author: Guo Li
Definition:

A dermoid cyst is the growth of a piece of skin underneath the surface as the result of abnormal development. The dermoid cyst can be an ovarian neoplasm (benign teratoma) that may contain mature tissues (skin, hair, bone, teeth etc) or embryonal tissues (e.g. trophoblast).

2265. derris (rotenone, tubatoxin)
Definition:

1. Derris: a tropical shrub in the legume family.
2. An insecticide containing rotenone (tubatoxin), a chemical extracted from the derris shrub.

2266. desalting
Definition:

To remove salt.

2267. desaturase
Definition:

Any of several enzymes that put double bonds into the hydrocarbon areas of fatty acids.

2268. descending aorta
Definition:

The part of the aorta after the aortic arch which branches into the thoracic and abdominal aortas.

2269. desensitization
Author: PharmInfoNet
Definition:

A method to reduce or stop a response such as an allergic reaction to something. For instance, if a person with diabetes has a bad reaction to taking a full dose of beef insulin, the doctor gives the person a very small amount of the insulin at first. Over a period of time, larger doses are given until the person is taking the full dose. This is one way to help the body get used to the full dose and to avoid having the allergic reaction.

2270. design flood capacity
Author:
Definition:

The flow volume, state, or frequency of the event for which protection is provided or activities need to be regulated.

2271. design level of flood protection
Author:
Definition:

The computed flow, state, or frequency of the event that the waterway has been designed to safely carry.

2272. designated floodway
Author:
Definition:

The channel of the stream and that portion of the adjoining floodplain required to reasonably provide for passage of a design flood.

2273. desipramine (Norpramin, Pertofrane)
Definition:

This tricyclic prescription drug is used to treat depression. It has a wide variety of side effects, and may interact dangerously with many other medications.

2274. desmin
Definition:

A muscle protein which joins with other desmins to become long chains of fibrous polymers. The protein is found in both types of muscle (smooth and skeletal) and is especially abundant in heart muscle.

2275. desmoplaquin
Definition:

A protein component of the desmosome, which is an area along the outside of an epithelial cell that is in very close contact with another epithelial cell.

2276. desmosome
Definition:

An area along the outside of an epithelial cell that is in very close contact with another epithelial cell. The areas of contact help different cells of the same tissue function together, and adds strength to the tissue.

2277. desmotubule
Definition:

A tube that connects two plant cells to each other and facilitates cell-to-cell communication. The tube lies within a channel created by fusing the cell membranes of the two cells to each other, through pores in their cell walls.

2278. desolvation
Definition:

The release of the water electrostatically bound to a particle in a water-based solution.

2279. desulfurization
Definition:

The process of removing sulfur from a molecule. The process of removing sulfur and sulfur compounds from minerals, ores, petroleum, etc.

2280. detention basin
Author:
Definition:

A pond designed as a sediment trap. Usually designed to slow the flow of sediment carrying water so that the sediment will drop out. (For heavy sediment loads these ponds are often built with two or three in series. Sediment must be periodically bailed out to allow the ponds to continue to function.)

2281. detention dam
Author:
Definition:

Detention dams are constructed to retard flood run-off and minimize the effect of sudden floods. The water is temporarily stored and released through an outlet structure at a rate which will not exceed the carrying capacity of the channel downstream.

2282. detergent
Definition:

A substance which has a nonpolar, hydrophobic part (avoids water) and a polar, hydrophilic part (attracted to water). It can dissolve fats and oils (collectively, lipids) with the hydrophilic end, and as a result can increase the cleaning abilities of its solvents (whatever it's dissolved in).

2283. detergent
Definition:

A detergent is a cleaning or wetting agent, classed as anionic if it has a negative charge and cationic if it has a positive charge.

2284. determination
Definition:

The irreversible commitment of an embryonic cell to form a particular structure. The cell, once determined, will not form a different structure even if it were transplanted to a place where its structure is inappropriate.

2285. detoxify
Definition:

To reduce the toxicity of a substance by either
1. making it less harmful or
2. treating patients suffering from poisoning in such a way as to reduce the probability and/or severity of harmful effects.

2286. detritivore
Author:
Definition:

Animal that consumes decomposing organic particles, deriving nutrition primarily from microbes on the particles.

2287. detritus
Author:
Definition:

Undissolved organic or inorganic matter resulting from the decomposition of parent material.

2288. Deuteromycetes (imperfect fungi)
Image: Penicillium
Definition:

A class of fungi known as imperfect fungi. The members of this class, which includes Penicillium and Aspergillus and other fungi important in medicine and food science, all lack a sexual stage but are otherwise unrelated to each other.

2289. developmental biology
Definition:

The study of how a multicellular organism develops from its early immature forms (zygote, larva, embryo, etc.) into an adult.

2290. dewatering
Author:
Definition:

Lowering of the water table in stream channel deposits caused by a channel shift or a flow reduction.

2291. dextran
Definition:

A polysaccharide (chain of simple sugars) composed of glucose (a type of simple sugar) monomers (units of a polymer, such as a polysaccharide), used as a means of storing food by bacteria and yeasts. When dextrans are formed out of sucrose (another type of sugar) by bacteria in the mouth, it makes dental plaque.

2292. dextranase
Definition:

An enzyme that breaks down dextran, which is a polysaccharide (chain of simple sugars) composed of glucose (a type of simple sugar) monomers (units of a polymer, such as a polysaccharide).

2293. dextroamphetamine (Dexedrine)
Definition:

This prescription stimulant drug is used to treat narcolepsy, epilepsy, Parkinson's syndrome, and hyperactivity in children. As with all other amphetamines, this drug can be easily abused and may cause a wide range of nervous and cardiovascular side effects.

2294. dextrorotatory isomer
Definition:

A stereoisomer that does a clockwise rotation of plane-polarized light.

2295. diabetes insipidus (water diabetes)
Author: PharmInfoNet
Definition:

A disease of the pituitary gland or kidney, not diabetes mellitus. Diabetes insipidus is often called "water diabetes" to set it apart from "sugar diabetes." The cause and treatment are not the same as for diabetes mellitus. "Water diabetes" has diabetes in its name because most people who have it show most of the same signs as someone with diabetes mellitus-they have to urinate often, get very thirsty and hungry, and feel weak. However, they do not have glucose (sugar) in their urine.

2296. diabetes mellitus (sugar diabetes)
Author: PharmInfoNet
Definition:

A disease that occurs when the body is not able to use sugar as it should. The body changes carbohydrates into glucose. A hormone called insulin is needed for the glucose to be taken up and used by tissues. Diabetes occurs when the body cannot make use of the glucose in the blood for energy because either the pancreas is not able to make enough insulin or the insulin that is available is not effective. The beta cells in areas of the pancreas called the islets of Langerhans usually make insulin.

The signs of diabetes include having to urinate often, losing weight, getting very thirsty, and being hungry all the time. Other signs are blurred vision, itching, and slow healing of sores. People with untreated or undiagnosed diabetes are thirsty and have to urinate often because glucose builds to a high level in the bloodstream and the kidneys are working hard to flush out the extra amount. People with untreated diabetes often get hungry and tired because the body is not able to use food the way it should.

The causes of diabetes are not known. Scientists think that insulin- dependent diabetes may be more than one disease and may have many causes. They are looking at genetic factors and at other factors, including viruses.

2297. diabetic retinopathy
Author: PharmInfoNet
Definition:

A disease of the small blood vessels of the retina of the eye. When retinopathy first starts, the tiny blood vessels in the retina become swollen, and they leak a little fluid into the center of the retina. The person's sight may be blurred. This condition is called background retinopathy. About 80 percent of people with background retinopathy never have serious vision problems, and the disease never goes beyond this first stage.

However, if retinopathy progresses, the harm to sight can be more serious. Many new, tiny blood vessels grow out and across the eye. This is called neovascularization. The vessels may break and bleed into the clear gel that fills the center of the eye, blocking vision. Scar tissue may also form near the retina, pulling it away from the back of the eye. This stage is called proliferative retinopathy, and it can lead to impaired vision and even blindness.

2298. diadelphous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having the stamens united into two groups, or all but one united in a group and one free.

2299. diagnosis
Definition:

To identify the cause of a disease or condition based on observations of symptoms and other signs.

2300. diallel
Author: ForBio Ltd.
Definition:

A mating design comprising a balanced series of all pairwise combinations of crosses (e.g. AxB, AxC, and BxC).

2301. dialysis
Definition:

The process of taking specific small molecules (such as uric acid) out of a solution (such as blood) by letting them diffuse across a semi-permeable membrane into water.

2302. diameter at breast height (dbh)
Author:
Definition:

The width of a plant stem (e.g., tree trunk) as measured at 4.5 feet above the ground surface.

2303. diaper rash
Author: Guo Li
Definition:

Diaper rash is a form of contact dermatitis due to prolonged contact of the skin with urine and feces. Diaper rash is often colonized with the yeast Candida albicans.

2304. diaphanous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Extremely thin and transparent.

2305. diatomaceous earth (tripolite, fossil flour, rock meal, kieselguhr)
Definition:

A type of silica-rich dirt which is soft, fine-grained, porous, light-colored, and composed of the skeletons of diatoms (one-celled marine organisms with skeletons based on silicon). It is used as a filter.

2306. diazepam (T-Quil, Valium)
Definition:

This prescription drug is used as a sedative, muscle relaxant and antianxiety medication. It is also used to treat some muscle spasms. It may cause birth defects and may make epilepsy and depression worse. Side effects include drowsiness, vertigo and impaired coordination, but many other side effects are possible.

2307. dibasic
Definition:

An acid which has two hydrogen atoms that it can donate to bases to form salts.

2308. dibble
Author:
Definition:

A hand tool used to make holes in the ground for planting seeds, bulbs, or small seedlings.

2309. DIC screening test (disseminated intravascular coagulation test)
Author: Guo Li
Definition:

This is a batch of tests to confirm the clinical diagnosis of disseminated intravascular coagulation (DIC). There is no agreement on what these tests are. In general, the following tests are done, although in many cases one or more of these abnormalities may not be present.

Results in a DIC screen
TEST	NORMAL RANGE	in DIC
prothrombin time	11.5 - 13 sec	elevated
fibrinogen	1.75 - 4.3 g/L	decreased
platelet count	150 - 400 109 /L	decreased
fibrin-fibrinogen degradation products	< 10 ug/mL	present
red cell fragments	not present	present

2310. dicentric chromosome
Definition:

A chromosome with two centromeres instead of the normal one. Such an oddity can form if chromosomes break and then the fragments re-fuse with one another in a different combination than before they broke.

2311. dichasium
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A cymose inflorescence with opposite branching below the flower which terminates each axis. Compare monochasium.

2312. dichlamydeous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of a flower, having two whorls of perianth parts.

2313. dichotomous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Forking into two equal branches resulting from division of the growing point.

2314. diclinous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having the stamens and the carpels in separate flowers.

2315. dicotyledon (dicot)
Definition:

A subclass of of Angiosperms. They tend to have:

• broad leaves
• two cotyledons
• netlike veins in the leaves
• flower parts are usually in fours or fives
• a ring of primary vascular bundles in the stem
• taproot system
Compare: monocot

2316. dictyosome
Definition:

A stack of two or more cisternae.

2317. dideoxy sequencing (Sanger sequencing)
Definition:

A lab technique to find out the sequence of nucleotide bases in a DNA molecule, invented by Fred Sanger. The technique involves putting the DNA molecule and the components needed to replicate it into each of four test tubes, along with one of the four types of dideoxynucleotides (ddA, ddT, ddC, ddG), which are molecules that cause the premature termination of replication at the base that they substitute for. The result is that each of the test tubes contains fragments of the DNA molecule that all end at the same base, but at different points on the molecule where the base occurs. The contents of the test tubes are then separated by size with gel electrophoresis (one gel well per test tube; four total wells); the smallest fragments will travel the farthest and the largest will travel the least far from the well. The sequence can then be determined from the picture of the finished gel by noting the sequence of the marks on the gel and from which well they came from.

2318. dideoxynucleotide (didN)
Author: Susan A.Hagedorn
Definition:

A deoxynucleotide that lacks a 3' hydroxyl group, and is thus unable to form a 3'-5' phosphodiester bond necessary for chain elongation. Dideoxynucleotides are used in DNA sequencing and the treatment of viral diseases.

2319. didymous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Carried in pairs; of anthers, having two lobes, with scarcely any tissue connecting them.

2320. didynamous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of stamens: four in number, two being distinctly longer than the other two.

2321. dieldrin
Image: View the chemical structure
Definition:

A toxic chlorinated organic compound that is used as an insecticide. It causes cancer and is restricted to non-agricultural applications.

2322. Diethylstilbestrol (DES)
Author: Fertilitext
Definition:

A synthetic estrogen (originally prescribed to prevent miscarriage) that caused malformations of the reproductive organs in some who were exposed to the drug during fetal development.

2323. differential centrifugation
Definition:

A technique for separating organelles or other differently-sized cell components in a centrifuge; particles of the same size and weight will settle out into common layers.

2324. differential medium
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A medium which is used to differentiate different types of microorganisms based on their different colors or colony shapes. Examples of differential media are: Macconkey's agar and SS agar.

2325. differentiation
Definition:

The process by which cells become structurally and functionally specialized during embryonic development.

2326. differentiation antigen
Definition:

A biomolecule which can be found by immunoassay (testing for the presence of the biomolecule) only in a particularly type of cell in the body. Thus, the biomolecule can serve as a marker for that cell type.

2327. diffusion coefficient (diffusion constant)
Definition:

A constant which is a measure of how well a dissolved substance can spread, or diffuse, through a concentration gradient (a fluid which has a higher concentration on one end and a lower concentration on the other end of the container). This depends on the particle size of the substance, the temperature, and the polarity of the substance. The constant has the symbol of k(subscript D), and is used to calculate diffusion rates of the substance.

2328. digger log
Author:
Definition:

Log anchored to the stream banks and/or channel bottom in such a way that a scour pool is formed.

2329. digitalis
Definition:

A heart-stimulating drug extracted from the purple foxglove Digitalis purpurea.

2330. digoxigenin
Definition:

A plant steroid hormone which, when combined with a probe biomolecule, can be used to attract antibodies in certain probe systems.

2331. dihydrouridine
Definition:

An unusual pyrimidine which is the result of adding two hydrogen atoms to a uridine (another nitrogenous base). It is found only in tRNA molecules.

2332. dihydroxyacetone phosphate
Image: View the Chemical Structure
Definition:

This is an intermediate molecule involved in the fourth step of glycolysis. Dihydroxyacetone phosphate is created from fructose 1,6-bisphosphate. In step 5, it is converted into its positional isomer, glyceraldehyde 3-phosphate, with the aid of triose phosphate isomerase.

2333. dikaryon
Definition:

A hypha with two nuclei.

2334. dike
Author:
Definition:

An embankment (usually of earth) constructed to keep water in or out of a given area.

2335. dike
Author:
Definition:

1. An embankment outside a channel to restrict overflow.
2. A levee.

2336. dilatation and curettage (D&C)
Author: Fertilitext
Definition:

An operaton that involves stretching the cervical opening to scrape out the uterus.

2337. dimethoxytrityl (DMT)
Definition:

A molecule which blocks unwanted reactions during the automatic making of oligonucleotides (a short polymer, or chain, of nucleotides).

2338. dimethyl sulfoxide (DMSO)
Definition:

A substance with the formula (CH₃)₂SO that is used as a cryoprotectant to protect cultured animal cells from the damaging effects of cryopreservation (storage by freezing). It is also used in transfection to increase the chances that the target eukaryotic cells will actually pick up, incorporate and express the DNA.

2339. dimorphic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of two different forms.

2340. dimorphism
Definition:

Having two different distinct forms of individuals within the same species or two different distinct forms of parts within the same organism. For plants, it could refer to different leaf types, flowers, etc. For animals, it could refer to different coloring, sizes, features, etc. Sexual dimorphism is a common case, where the two sexes have different shapes, sizes, etc. from each other.

2341. dioecious
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having the male and female reproductive structures on separate plants. Compare monoecious.

2342. dioxin
Definition:

Any in a family of over 200 chlorinated organic chemicals (all heterocyclic hydrocarbons). The term is most commonly applied to a particular chemical, 2,3,7,8-tetrachlorodibenzo-paradioxin (2,3,7,8-TCDD, simply called TCDD), which is an impurity in the defoliant Agent Orange and in the pesticide 2,4,5-T (see auxin). Dioxins are also produced when chlorinated materials such as plastics are burned. Dioxins are known to cause skin diseases (chloracne), birth defects, miscarriages, and cancer.

2343. diphenhydramine (Benadryl)
Definition:

This antihistamine medication is used to treat allergies (hay fever, rashes, etc.) and postoperative nausea and vomiting. It can cause sleepiness and generally acts as a sedative.

2344. diplecolobous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of cotyledons in a seed: twice folded transversely.

2345. diploblastic
Definition:

Describes an animal which, as an embryo, had two distinct embryonic tissue layers - the ectoderm and endoderm. This is in contrast to animals which are triploblastic (has three distinct tissue layers) and those which do not have any distinct tissue layers as an embryo (nor organs and distinct tissues as an adult). Jellyfish and comb jellies are diploblastic animals.

2346. diplococcus
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A pair of cocci.

2347. diploid
Definition:

A full set of genetic material, consisting of paired chromsomes one chromosome from each parental set. Most animal cells except the gametes have a diploid set of chromosomes. The diploid human genome has 46 chromosomes. Compare haploid.

2348. diplopia
Author: Guo Li
Definition:

Diplopia is double vision; a symptom due to paralysis of one or more muscles that control the movement of the eyeball.

2349. diplotene
Definition:

A substage of the prophase I stage of meiosis, a type of nuclear division, during which chiasmata (points where the arms of homologous chromosomes cross over each other, just before recombination occurs) can be seen.

2350. dipole
Definition:

A molecule that has both negative and positive charges.

2351. diprotic acid
Definition:

An acid that can donate two protons.

2352. direct terminal repeats
Definition:

A particular sequence of nucleotides which appears on both ends of a DNA or RNA molecule.

2353. directional cloning
Author: Susan A.Hagedorn
Definition:

DNA insert and vector molecules are digested with two different restriction enzymes to create noncomplementary sticky ends at either end of each restriction fragment. This allows the insert to be ligated to the vector in a specific orientation and prevents the vector from recircularizing.

2354. disaccharidase deficiency
Definition:

A digestive disorder caused by the body being unable to produce enough disaccharidase, an enzyme responsible for breaking down carbohydrates in the small intestine. This may cause symptoms such as intestinal gas and diarrhea.

2355. disaccharide
Definition:

A sugar such as sucrose, which is made up of two monosaccharides: one glucose molecule and one fructose molecule.

2356. disc
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A plate or rim of tissue, derived from the receptacle of a flower, occurring between whorls of floral parts.

2357. disc electrophoresis
Definition:

Short for "discontinuous electrophoresis," it is a type of polyacrylamide gel electrophoresis. This electrophoresis method uses gels of two different concentrations of polyacrylamide (a synthetic polymer), the one of lower concentration stacked on top of the one with higher concentration, in order to better resolve bands of whatever is being separated (DNA, RNA, or protein) that would otherwise be very close together.

2358. disc flowers
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

The radially symmetrical flowers in the family Compositae, as distinguished from the ligulate ray flowers.

2359. discharge
Author:
Definition:

1. Volume of water flowing past a reference point per unit time (usually expressed as m3/s or cfs).
2. Outflow of a water course. Rate of flow expressed in volume per unit of time (e.g., c.f.s. or acre feet per year).
3. The flow of a stream in unit time, usually expressed in second-feet (cubic feet per second).

2360. discharge of dredged material
Author:
Definition:

Any addition of dredged material into the waters of the U.S. The term includes, without limitation, the addition of dredged material to a specified discharge site located in waters of the U.S. and the runoff or overflow from a contained land or water disposal area. Discharges of pollutants into waters of the U.S., resulting from the onshore subsequent processing of dredged material that is extracted from any commercial use (other than fill), are not included within this term and are subject to Section 402 of the CWA even though the extraction and deposit of such material may require a permit from the Corps of Engineers. The term does not include plowing, cultivating, seeding, and harvesting for the production of food, fiber, and forest products. The term does not include de minimis, incidental soil movement occurring during normal dredging operations.

2361. discharge of fill material
Definition:

The addition of fill material into waters of the U.S. The term generally includes, without limitation, the following activities: placement of fill that is necessary for the construction of any structure in a water of the U.S.; the building of any structure or impoundment requiring rock, sand, dirt, or other material for its construction; site-development fills for recreational, industrial, commercial, residential, and other uses; causeways or road fills; dams and dikes; artificial islands; property protection and/or reclamation devices such as riprap, groins, seawalls, breakwaters, and revetments; beach nourishment; levees; fill for structures such as sewage treatment facilities, intake and outfall pipes associated with power plants and subaqueous utility lines; and artificial reefs. The term does not include plowing, cultivating, seeding, and harvesting for the production of food, fiber, and forest products.

2362. discoid
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Having the form of a disk; discoid flower; a compound flower not radiated but with tubular florets.

2363. disinfectant
Definition:

A chemical which kills bacteria and viruses and other microorganisms on a nonliving surface. A "complete disinfectant" will also kill spores of microorganisms; an "incomplete disinfectant" will not.

2364. dislocation
Author: Guo Li
Definition:

Dislocation is the complete displacement of a joint.

2365. dispensa (disp.)
Definition:

This Latin term, which is frequently used in medicine, means "dispense".

2366. disproportionation
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The splitting of a chemical compound into two new compounds, one more oxidized and one more reduced than the original compound.

2367. dissecting aneurysm
Author: Guo Li
Definition:

A form of false aneurysm extended by blood.

2368. dissepiment
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A partition (septum) within an ovary or fruit, derived by fusion of adjacent carpels.

2369. dissipate
Author:
Definition:

Expend or scatter harmlessly, as of energy of moving water.

2370. dissociation constant
Definition:

A constant which quantifies the dissociation between two atoms, molecules, or larger particles. This constant is used in the equation K=[A][B]/[AB], where K is the dissociation constant, A and B are the two substances which are dissociating from each other, and [] means "concentration of (in moles)."

2371. dissolved organic matter (DOM, dissolved organic carbon, DOC)
Author:
Definition:

Organic material having a least dimension smaller than 0.45 micron (passes through a 0.45 micron filter).

2372. dissolved oxygen
Author:
Definition:

The concentration of oxygen dissolved in water, expressed in mg/l or as percent saturation, where saturation is the maximum amount of oxygen that can theoretically be dissolved in water at a given altitude and temperature.

2373. distal
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Remote from the point of origin or attachment. Compare proximal.

2374. distichous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Arranged in two rows on opposite sides of a stem and thus in the same plane.

2375. distillation
Definition:

A lab technique used to purify a substance, to remove a solvent (a liquid that a substance is dissolved in) from the substance, or to separate two or more components in a liquid mixture.

Ideally, this is done by taking advantage of the fact that the different chemicals have different boiling points. The temperature is raised so the chemical with the lowest boiling point boils first, its vapor is shunted out of the flask and towards a different container, and then it is cooled so that it condenses back into a (more purified) liquid. The temperature can then be raised to boil the next chemical, etc., until only the chemical with the highest boiling point remains in the original container.

2376. disulfide bond
Definition:

A covalent bond between two sulfur atoms. This bond is used to stabilize the tertiary, 3D configuration of a polypeptide chain or protein by the linking of the sulfurs between cysteines (a type of amino acid) at different points of the chain.

2377. disulfide bridge
Definition:

A covalent link made by a cystine residue that joins two polypeptide chains.

2378. disulfiram (Antabuse)
Definition:

This prescription drug is used to treat alcoholism; it causes an extremely unpleasant reaction if the person taking the drug drinks even a tiny amount of alcohol. It works by blocking the oxidation of alcohol at the acetaldehyde stage.

2379. diurnal
Definition:

1. Active or occuring during daylight hours.
2. Describes a flower that is open only during the day.

2380. divalent (bivalent)
Definition:

An atom or radical group which has a valence of two, or which can combine with two (rather than one) different other atoms or molecules.

2381. divaricate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Widely spreading.

2382. divergent
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Separated from one another, having tips further apart than the bases.

2383. diversion
Author:
Definition:

1. The direction of water in a stream away from its natural course (i.e., as in a diversion that removes water from a stream for human use).
2. Draft of water from one channel to another.
3. Interception of runoff by works which discharge it through unnatural channels.

2384. diversity
Author:
Definition:

The number and variety of species present in an area and their spatial distribution.

2385. diversity index
Author:
Definition:

The relationship of the number of taxa (richness) to the number of individuals per taxon (abundance) for a given community.

2386. diverticulate
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Having short offshoots approximately at right angles to the main stem.

2387. diverticulitis
Definition:

An inflammation of the diverticula, which can cause extreme pain and sometimes fever.

2388. diverticulitis
Author: Guo Li
Definition:

Diverticulitis is inflammation and complications involving diverticula, the small pouches formed at weak points in the muscular coat of the intestinal tract.

2389. diverticulosis
Author: Guo Li
Definition:

Diverticulosis is the condition of the existence of diverticula, small pouches formed at weak points in the muscular coat of the digestive tract.

2390. diverticulum (pl. diverticula)
Definition:

A small sac-like structure that sometimes forms in the walls of the intestines; diverticula can trap particles of food (especially small seeds and undigested grains) and become very inflammed and painful (this condition is called diverticulitis).

2391. diverticulum (pl. diverticula)
Author: Guo Li
Definition:

A diverticulum is a pouch or a sac formed at weak points in the muscular coat of the digestive tract (especially the small intestine). Inflammation of the diverticula is called diverticulitis.

2392. division
Definition:

1. The act of dividing.
2. The second highest taxonomic classification for the kingdoms Plantae (plants) and Fungi, between kingdom level and class level.

2393. Division Chrysophyta (diatoms, golden-brown algae, yellow-green algae)
Definition:

This biological division contains the diatoms, golden-brown algae, and yellow-green algae. Scientists estimate that there are about 12,000 species in this division. These organisms are all single-celled and are mainly found in marine environments. They conduct photosynthesis and contain chlorophylls a and c; diatoms and golden-brown algae also contain the acessory pigment fucoxanthin. They store their food as large droplets of oil or in the form of the carbohydrate leucosin. These organisms usually reproduce by cell division.

There are about 10,000 living species of diatoms, 1500 species of golden-brown algae, and 600 species of yellow-green algae.

2394. Division Cyanophyta (cyanophytes, cyanobacteria, blue-green algae)
Definition:

Division Cyanophyta (which is in Kingd om Monera) contains the cyanobacteria, which are one-celled or colonial prokaryotes that contain chlorophyll (but not chloroplasts, which contain the chlorophyll in true plants). Cyanobacteria are autotrophs (create their own energy via photosynthesis) and reproduce by fission (splitting in two). There are over 7,500 species of cyanobacteria and they are found in many environments: damp soil and rocks, fresh water, and salt water.

2395. Division Euglenophyta (euglenoids, Euglena)
Definition:

This biological division contains the algal species Euglena and over 1,000 species of related algae; they are all unicellular (single-celled) and are mainly found in freshwater environments. They are all photosynthetic (though some are secondary heterotrophs) and they all contain chlorophylls a and b. A unique feature of this division is that they store the energy they produce from photosynthesis as paramylum, an unusual carbohydrate. Members of this division have a contractile vacuole and a single flagellum.

2396. Division Pyrrophyta (fire algae)
Definition:

This division is composed of marine organisms known as "fire" algae, so named because most of them are red in color. Fire algae are an important component of ocean plankton. The major class within this division is Class Dinophyceae, the dinoflagellates. There are over 1100 species in this division. Members of Pyrrophyta are single-celled, photosynthetic organisms that move via two flagella. They store their food as starch, and their cell walls are made of cellulose. They usually reproduce asexually.

2397. Division Schizophyta (bacteria)
Definition:

This taxonomic division (which is in Kingdom Monera) contains the bacteria (over 2,500 species). These are one-celled prokaryotes that usually reproduce asexually via binary fission (splitting in two).

2398. dizygotic twins (fraternal twins)
Definition:

Twins which are the result of two separate zygotes, or two separate eggs fertilized by two separate sperm. They can be any combination of sexes (two males, two females, one of each). Compare monozygotic twins.

2399. dizziness
Author: Guo Li
Definition:

Dizziness is a symptom in which one commonly complains of lightheadness, sensation of turning, spinning, or rocking.

2400. DNA (deoxyribonucleic acid)
Definition:

The molecule that encodes genetic information. DNA is a double-stranded molecule held together by weak bonds between base pairs of nucleotides. The four nucleotides in DNA contain the bases: adenine (A), guanine (G), cytosine (C), and thymine (T). In nature, base pairs form only between A and T and between G and C; thus the base sequence of each single strand can be deduced from that of its partner.

2401. DNA annealing
Definition:

The sticking together (renaturing) of complementary single strands of DNA to make a double-stranded DNA after the strands have first been pulled apart (denatured). This involves forming hydrogen bonds between the base pairs.

2402. DNA diagnosis
Author: Susan A.Hagedorn
Definition:

The use of DNA polymorphisms to detect the presence of a disease gene.

2403. DNA duplex
Definition:

The double-stranded DNA molecule, which has a double helix (usually "right-handed") structure.

2404. DNA excision
Definition:

The removal of a damaged segment of a DNA molecule by a group of DNA repair enzymes in order to repair the molecule.

2405. DNA filter assay
Definition:

A lab technique used to identify the complementary base sequences of DNA. It involves immobilizing the DNA on a filter and putting it in a solution that contains radioactively-labeled probe DNA or RNA molecules.

2406. DNA fingerprint
Author: Susan A.Hagedorn
Definition:

The unique pattern of DNA fragments identified by Southern hybridization (using a probe that binds to a polymorphic region of DNA) or by polymerase chain reaction (using primers flanking the polymorphic region).

2407. DNA fingerprinting
Definition:

A lab technique that compares the patterns of bands on analogous DNA fragments from two or more separate individuals; this is done to find out how closely related they are to each another.

2408. DNA footprinting
Definition:

A lab technique that uses gel electrophoresis to find out which parts of a DNA molecule have sites for proteins to attach to them. The technique compares DNA which has been in the presence of DNA binding proteins with DNA that is "pure."

2409. DNA gene
Definition:

Any of a number of genes found in the bacteria Escherichia coli which makes proteins that are essential for DNA replication.

2410. DNA glycosylase
Definition:

A DNA repair enzyme which recognizes and removes nitrogenous bases in the DNA molecule that have lost an amino group, leaving a hole that then undergoes further repair.

2411. DNA gyrase
Definition:

An enzyme found in the bacteria Escherichia coli that introduces negative supercoiling into DNA molecules. DNA molecules are normally positively supercoiled or relaxed.

2412. DNA helicase
Definition:

Normally, DNA is in a supercoiled state which makes its genes and other sites difficult to access. This enzyme removes the supercoiling from DNA, or unwinds it, so that replication can occur.

2413. DNA homology
Definition:

How closely related two or more separate strands of DNA are to each other, based on their base sequences.

2414. DNA hybridization
Definition:

A lab technique used to find out how closely related two or more separate strands of DNA from different species are to each other. The technique involves radioactive labeling.

2415. DNA ligation
Definition:

The joining of two DNA strands by their ends with a phosphodiester bond.

2416. DNA melting (duplex melting)
Definition:

Denaturation of a DNA molecule with heat. The double-stranded molecule breaks up into two single-stranded molecules as a result of heat.

2417. DNA methylation
Definition:

The attachment of a methyl group (a -CH₃ group) to a cytosine (one of four nitrogenous bases found in DNA) in an eukaryotic DNA. This is done routinely, as a way to protect self DNA from the enzymes and chemicals produced to destroy foreign DNA, and as a way to regulate transcription of genes in the DNA.

2418. DNA modification
Definition:

A variety of chemical changes made to a DNA molecule just after it has been replicated. An example is DNA methylation.

2419. DNA photolyase (photoreactivating enzyme)
Definition:

A DNA repair enzyme which recognizes and removes dimers that have formed between pyrimidine nitrogenous bases on the same strand as each other, as a result of too much ultraviolet radiation. The enzyme can only do this if visible light is present.

2420. DNA Polymerase I
Definition:

DNA Polymerase I is an enzyme that aids in DNA replication. It has the following 3 functions:

1) polymerizes in the 5« to 3« direction on single-stranded template;
2) degrades single or double-stranded DNA from a free 3«-OH end; and
3) degrades double-stranded DNA from a free 5« end.

2421. DNA polymerase II
Definition:

An enzyme that aids in DNA replication. It has a number of different functions, including the repair of ultraviolet radiation damaged DNA.

2422. DNA polymerase III
Definition:

An enzyme that aids in DNA replication. It has a number of different functions, such as:
1. proofreading newly replicated DNA;
2. removing nucleotides from the 3' end of the strand one by one; and
3. binding nucleotides from the 5' end of the strand.

2423. DNA polymerization
Definition:

The making of a DNA molecule from nucleotide monomers by linking them together in a long chain (a polymer).

2424. DNA puff
Definition:

An area on a chromosome where transcription of DNA into mRNA, or replication of DNA is occurring, resulting in an enlarged, puffy appearance of the area. Similar to chromosome puff, except generalized to any type of chromosome in any type of organism.

2425. DNA repair
Definition:

Any of a number of processes to repair damaged DNA. In general, the damaged portions of the molecule are removed by enzymes (this could range from a single nitrogenous base to a large number of them, and the enzymes doing the removing depend on the specific type of damage), leaving holes where bases should be. Then other enzymes remove an entire segment of DNA, in the middle of which was the hole or holes. A DNA polymerase I then comes and fills the gap with new nitrogenous bases, based on what bases are on the opposite (presumably unharmed) strand of DNA (if both strands are harmed, a process is invoked which inserts bases at random into the strand). Finally a ligase enzyme seals the phosphate backbone back together.

2426. DNA sequence
Definition:

The relative order of base pairs, whether in a fragment of DNA, a gene, a chromosome, or an entire genome. See base sequence analysis.

2427. DNA sequencing
Definition:

Any lab technique used to find out the sequence of nucleotide bases in a DNA molecule or fragment. Examples are dideoxy sequencing and Maxam-Gilbert sequencing.

2428. DNA shearing
Definition:

The tearing apart of unusually long DNA molecules by mechanical rather than chemical means, sometimes by accident when the molecule is being prepared in the lab for testing.

2429. DNA supercoiling
Definition:

The condition of DNA coiling up on itself because its helix has been bent, overwound or underwound.

2430. DNA synthesizer
Definition:

A machine which automatically makes short, artificial polynucleotides or oligonucleotides with any desired sequence of nucleotide bases.

2431. DNA tumor virus
Definition:

A virus which uses DNA to code its genome and causes tumors in animals.

2432. DNA twisting
Definition:

The coiling of a double-stranded DNA molecule in the opposite direction than the direction that the helix turns.

2433. DNA unwinding protein
Definition:

A protein that will attach to single-stranded DNA after it has been unwound for replication or recombination, and help it stay unwound.

2434. DNA writhing
Definition:

Coiling of a double-stranded DNA molecule in such a way that it crosses its own (longitudinal) axis.

2435. DNA-driven reaction
Definition:

A lab technique to mark highly-repeated DNA sequences with a radioactive RNA tracer, by having a much larger amount of complementary DNA molecules than radioactive RNA tracer molecules.

2436. DNA-protein interaction
Definition:

Any complex that forms between a protein molecule and DNA. Examples are nucleosomes (structures formed for the purpose of DNA storage) and any gene regulatory protein (a protein which regulates transcription by binding to a regulatory region on the DNA).

2437. DNA-RNA hybridization
Definition:

A type of hybridization. In this case, a strand of DNA is joined with a complementary strand of RNA to form a double-stranded molecule (or one which is partly double-stranded, if one of the original single strands is shorter than the other).

2438. dnaA gene
Definition:

A defective gene of the bacteria Escherichia coli which produces a defective protein that influences DNA replication.

2439. dnaB gene
Definition:

A gene found in the bacteria Escherichia coli which makes a protein that is involved in the formation of primer polynucleotide chains, which are precursors of DNA replication.

2440. dnaE gene (polC gene)
Definition:

A gene found in the bacteria Escherichia coli which makes some of the components of the DNA Polymerase III protein, an enzyme which plays an important role in DNA replication.

2441. dnaF gene (nrdA gene)
Definition:

A gene which codes for an enzyme (ribonucleotide reductase) which breaks down ribonucleotides.

2442. dnaG gene
Definition:

A gene found in the bacteria Escherichia coli which makes the enzyme primase, an enzyme which helps make primers, which are precursors to DNA replication.

2443. dnaH gene (dnaZ gene)
Definition:

A gene found in the bacteria Escherichia coli which makes some of the components of the DNA Polymerase III protein, an enzyme which plays an important role in DNA replication.

2444. dnaI gene
Definition:

A gene that makes a protein which plays a role in DNA replication.

2445. dnaJ gene
Definition:

A gene found in the bacteria Escherichia coli which helps the bacteria survive at high temperatures. It also plays an important role in the replication of the DNA of bacteriophage lambda. It is closely linked with the dnaK gene.

2446. dnaK gene
Definition:

A gene found in the bacterium Escherichia coli which helps the bacterium survive at high temperatures. It also is important in the replication of the DNA of bacteriophage lambda. It is closely linked with the dnaJ gene.

2447. dnaL gene
Definition:

A type of DNA gene which has not been described.

2448. dnaQ gene
Definition:

A gene found in the bacteria Escherichia coli which makes some of the components of the DNA Polymerase III protein, an enzyme with an important role in DNA replication.

2449. DNase (deoxyribonuclease, DNAase)
Definition:

An enzyme which breaks the DNA molecule into smaller pieces (or oligonucleotides).

2450. DNase footprinting
Definition:

A lab technique used to find out which segments of a DNA molecule are protected by DNA-binding proteins from attack by endonuclease enzymes, which break down DNA into smaller fragments by cleaving its phosphodiester bonds. The technique does this with gel electrophoresis to find out which parts of the DNA have sites for proteins to attach to them, by comparing DNA which has been in the presence of DNA-binding proteins with DNA that is "pure."

2451. DNase I
Definition:

A type of endonuclease, or enzyme that breaks down DNA molecules at their phosphodiester bonds. It is found in large quantities in the pancreas.

2452. DNase I hypersensitivity site (DNase I hypersensitive site)
Definition:

A site on a DNA molecule that is especially prone to being cut apart by the endonuclease enzyme DNase I, which breaks down DNA into smaller fragments by cleaving phosphodiester bonds. These sites tend to be near active genes, which are regularly transcribed.

2453. DNase I sensitivity
Definition:

The likelihood that a particular DNA segment will be attacked by the endonuclease enzyme DNase I, which breaks down DNA into smaller fragments by cleaving its phosphodiester bonds. DNA segments which contain active genes that are regularly transcribed are more prone to being cut apart by DNase I than inactivated genes, because the inactivated genes are generally within condensed regions of the chromosome, while the active genes are in more open configurations for easy access for transcription.

2454. dnaT gene
Definition:

A gene that helps dismantle the replication complex (the combination of proteins and enzymes which work together to replicate the DNA) when the end of the DNA molecule has been reached and replication is finished.

2455. docetaxel (Taxotere)
Image: View the chemical structure
Definition:

This taxoid is found in the English yew, Taxus baccata. It inhibits microtubule disassembly and is being investigated as a chemotherapy agent.

2456. docking protein (DP)
Definition:

A protein attached to the membrane of the rough endoplasmic reticulum which helps ferry other proteins that are destined to be secreted out of the cell into the rough endoplasmic reticulum. It does this by binding with an SRP ("signal-recognition particle": a protein-RNA complex) that has previously attached itself to the lead end of the protein while the protein is still being synthesized.

2457. dodine
Definition:

A pesticide used to prevent fungal infections of fruit trees.

2458. domain
Definition:

1. A discrete portion of a protein with its own function. The combination of domains in a single protein determines its overall function.
2. The highest level of biological classification, superseding kingdoms. The three domains of biological organisms are the Bacteria, the Archaea, and the Eukarya.

2459. domatia
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Small structures on the lower surface of a leaf in some woody dicotyledons, usually consisting of depressions, partly enclosed by leaf tissue or hairs, located in the axils of the primary veins. sing. domatium.

2460. dominance
Author:
Definition:

Refers to the spatial extent of a species; commonly the most abundant species in each vegetation stratum that, when ranked in descending order of abundance and cumulatively totaled, immediately exceeds 50 percent of the total dominance measure (e.g., areal cover or basal area) for the stratum, plus any additional species comprising 20 percent or more of the total dominance measure for the stratum.

2461. dominance measure
Author:
Definition:

The means or method by which dominance is established, including areal coverage and basal area; the total dominance measure is the sum total of the dominance measure values for all species comprising a given stratum.

2462. dominance threshold number
Author:
Definition:

The number at which 50 percent of the total dominance measure for a given stratum is represented by one or more plant species when ranked in descending order of abundance (i.e., from most to least abundant); when this number is immediately exceeded, the dominant species for the stratum are realized.

2463. dominant
Author: Susan A.Hagedorn
Definition:

A gene is said to be dominant if it expresses its phenotype even in the presence of a recessive gene.

2464. dominant discharge
Author:
Definition:

The cycle of rising and falling flows in the vicinity of backfill flows, sustained over a long enough period that it alters a natural channel by dislodging, transporting, and distributing bed materials.

2465. dominant oncogene
Author: Susan A.Hagedorn
Definition:

A gene that stimulates cell proliferation and can drastically increase the risk of cancer development when present in a single copy.

2466. dominant species
Author:
Definition:

For each stratum, dominant species are those that, when ranked in descending rank order and cumulatively totaled, immediately exceed 50 percent of the total dominance measure, plus any additional species comprising 20 percent or more of the total dominance measure for the stratum.

2467. dopa (3,4-dihydroxyphenylalanine)
Definition:

An amino acid derived from the amino acid tyrosine. It is formed as the first intermediate in the production of dopamine, a neurotransmitter.

2468. dopamine (3,4-dihydroxyphenylethylamine)
Definition:

A hormonelike substance with the chemical formula C₈H₁₁NO₂. It is found in the nervous system as an important neurotransmitter, or substance which transmits nerve signals from neuron to neuron. It is also an intermediate in the productions of the hormones epinephrine (adrenaline) and norepinephrine.

2469. dopaminergic system
Author: The Alzheimer's Association
Definition:

The system of nerve cells that uses dopamine as its neurotransmitter.

2470. dormancy
Author: Susan A.Hagedorn
Definition:

A period in which a plant does not grow, awaiting necessary environmental conditions such as temperature, moisture, nutrient availability, etc.

2471. dorsal
Definition:

1. In animals, refers to their "back."
2. In plants, refers to a lateral organ which faces away from the main stem.
Compare ventral.

2472. dorsiventral
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having structurally different upper and lower surfaces.

2473. dosage effect
Definition:

The alteration of a phenotype by an increased dosage, or amount, of the product of the gene.

2474. dose-effect curve
Definition:

This is a graph drawn to show the relationship between the dose of a drug or other chemical and the magnitude of the graded effect that it produces.

2475. dose-response curve
Definition:

This is a graph to show the relation between the dose of a drug or other chemical and the degree of response it produces, as measured by the percentage of the exposed population showing a defined, often quantal, effect.

2476. double crossover
Definition:

Two events of recombination occuring on the same chromosome.

2477. double digestion
Definition:

Treating DNA with two different restriction enzymes, or enzymes which will cleave DNA at specific nucleotide sequences.

2478. double helix
Definition:

The spiral shape that two linear strands of DNA assume when they join.

2479. double minutes
Definition:

Small pieces of a chromosome containing many copies of the same gene.

2480. double reciprocal plot
Definition:

A graph made to analyze how fast an enzyme can convert its substrate into its product, depending on how much substrate is present (its concentration) and to determine its maximum speed (after which the enzyme does not get any faster no matter how high the concentration of substrate gets), called Vmax. It is a plot of 1/v versus 1/[S], where v=rate of product formation and [S]=the concentration of the substrate.

2481. double thymidine block
Definition:

A lab technique used to synchronize the cell cycles of all the cells in a culture. This is done by adding excessive amounts of thymidine (a deoxynucleoside) to the culture so that DNA replication is blocked. Eventually, all of the cells will reach the same point in the cell cycle and stop.

2482. double-blind, placebo-controlled study
Author: The Alzheimer's Association
Definition:

A research procedure in which neither researchers nor patients knows who is receiving the experimental substance or treatment and who is receiving a placebo.

2483. double-stranded complimentary DNA (dscDNA)
Author: Susan A.Hagedorn
Definition:

A duplex DNA molecule copied from a copy DNA template.

2484. doubling time
Definition:

The amount of time it takes for a population to double in size. Also used synonymously with generation time, or the average amount of time between the appearances of two successive generations (parent and offspring).

2485. down promoter mutation
Definition:

A mutation (a change in base pair sequence) in a promoter region; this results in lower gene expression (less transcription of the gene occurs).

2486. Down syndrome (Down's syndrome, trisomy 21).
Definition:

An uncommon (1 in 1000 births) congenital disorder in which a person is born with three copies of chromosome 21. It is more common among children born to mothers over the age of 35. People with this disorder have physical and mental retardation to varying degrees and typically have facial defects, vision, respiratory and cardiac problems. This disorder was formerly known as mongolism.

2487. Down's syndrome (Down syndrome, Trisomy 21)
Author: Guo Li
Definition:

Physical characteristics of a person with Down's syndrome include small and short head, flat nasal bridge, reddish cheeks, dry lips, large, protruding tongue, small ears, epicanthal folds, and short neck. Mental retardation and hypotonia are also major symptoms, the degree of which varies with individuals. There is also a high incidence of congenital heart diseases and duodenal atresia. With good support, persons with this syndrome can develop their full potential. An Alzheimer-like dementia often occurs in the fourth and fifth decades and leads to a shortened life expectancy.

The chromosomal abnormality is diagnostic. In 95% of cases, trisomy 21 is present (one extra chromosome 21), and in the rest which has the usual 46 chromosomes present, there is an abnormal translocation involving chromosome 21.

2488. downstream
Definition:

Any area away from a gene, but on the same strand of DNA, that is located past the gene if one moves along the strand in a 5'-3' direction (the normal direction of transcription and leading strand replication).

2489. doxepin (Adapin, Sinequan)
Definition:

This drug is used as a prescription sedative and as an antidepressant. It is classed as a tricyclic antidepressant.

Its side effects include low or high blood pressure, drowsiness, agitation, numbness, dry mouth, blurred vision, weight loss/gain, and a host of other symptoms. In high doses, it can cause heart arrhythmias, circulatory problems and seizures (the latter only in people who already have convulsive disorders). Overdoses can cause coma, heart attack and death.

2490. DPC4
Definition:

This gene, which is located on chromosome 18, is thought to be a tumor-suppressor gene; defective mutations of this gene have been strongly implicated in pancreatic cancer, a highly lethal disease which kills more than 25,000 people a year (based on 1995 statistics).

2491. drain
Author:
Definition:

Conduit intercepting and discharging surplus surface or groundwater.

2492. drainage area
Author:
Definition:

Total land area draining to any point in a stream, as measured on a map, aerial photo or other horizontal, two-dimensional projection. (See also catchment area; watershed; basin.)

2493. drainage basin
Author:
Definition:

A large surface area whose waters are drained off into a principal river system.

2494. drainage density
Author:
Definition:

Total length of natural drainage channels in a given area, expressed as kilometers of stream channel per square kilometer of drainage area.

2495. drawdown
Author:
Definition:

Depression of a water surface by acceleration of flow toward a drop or free outfall.

2496. dredge
Author:
Definition:

To remove material from the bed of a body of water in order to increase its water carrying capacity or to allow for the passage of boats.

2497. dredge spoils
Author:
Definition:

The mud removed from a body of water during dredging.

2498. Dressler's syndrome
Author: Guo Li
Definition:

Dressler's syndrome is pericarditis (inflammation of the sac encasing the heart and the root of great blood vessels -- pericardium) as a result of trauma to the heart or pericardium. Myocardial infarction and open heart surgery are two major causes of Dressler' syndrome.

2499. drift (invertebrate drift)
Author:
Definition:

Collectively, stream invertebrates (almost wholly the aquatic larval stages of insects) that voluntarily or accidentally leave the substrate to move or float with the current, as well as terrestrial invertebrates that drop into the stream. Also, any detrital material transported in the water current.

2500. drift feeders
Author:
Definition:

Fish and other predators that forage on invertebrates drifting on the water surface or in the water column.

2501. drift line
Author:
Definition:

An accumulation of water-carried debris along a contour or at the base of vegetation that provides direct evidence of prior inundation and often indicates the directional flow of flood waters.

2502. drop
Author:
Definition:

Controlled fall in a stream to dissipate energy.

2503. drop inlet (DI)
Author:
Definition:

A vertical inlet to a buried culvert or storm drain attached at the upstream end of a horizontal culvert. The drop inlet can be constructed as filter to prevent debris from entering the culvert and causing it to fail.

2504. Drosophila (fly)
Definition:

A genus of small flies which are extensively used as test animals to study genetics, cell biology, and developmental biology. The most well-known species used is Drosophila melanogaster, the common fruit fly.

2505. Drosophila heat shock proteins (hsp)
Definition:

Proteins which are immediately produced when the Drosophila fruit fly is exposed for a short time to extreme heat or other stress, such as toxic substances or alcohol.

2506. drug metabolism
Definition:

This is the study of how drugs are processed and broken down by the body. Specifically, it may involve the study of enzymes that break down drugs, the study of how different drugs interact within the body, and how diet and other ingested compounds affect the way the body processes drugs.

2507. drupe
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A succulent fruit, such as a cherry, formed from one carpel, having the seed(s) enclosed in an inner stony layer of the fruit wall. adj. drupaceous (which is often used to mean drupe-like but not strictly a drupe). Compare berry, pyrene.

2508. Dubin-Johnson's syndrome
Author: Guo Li
Definition:

Dubin-Johnson's syndrome is characterized by the failure of excretion of conjugated bilirubin by the hepatocytes (liver cells). As a result patients have abnormally large livers, abdominal pain, and jaundice. This is an autosomal recessive inherited disease.

2509. duff
Author:
Definition:

The matted, partly decomposed, organic surface layer of forested soils.

2510. dumping syndrome
Author: Guo Li
Definition:

Dumping syndrome is characterized by hypovolemic symptoms (palpitations, flushing, sweating, weakness, dyspnea, dizziness) after eating. It is usually the result of rapid passage of large amount of food from the stomach into the small intestine, often after surgery of the stomach (which may cause the stomach to lose its ability to regulate its rate of emptying). The incompletely digested food absorbs fluid from plasma and causes hypovolemia.

2511. dumposome
Definition:

A protein, possibly even a new organelle, found in the one-celled ciliated protozoan "tetrahymena," an organism which contains two nuclei (unlike most other organisms which only contain one) - the macronucleus and the micronucleus. During sexual reproduction, in which two tetrahymena fuse and produce four offspring, this protein destroys the two parental macronuclei (whose genetic material were not used during the sexual reproduction) and removes the genes related to sexual reproduction from all offspring macronuclei.

2512. duodenum
Definition:

The first part of the small intestine (the part food enters immediately after it leaves the stomach).

2513. duration flow
Author:
Definition:

A curve which expresses the relation of all the units of some item (e.g., head, flow, etc.) arranged in order or magnitude along the ordinate, and time, frequency expressed in percentage, along the abscissa. A graphical representation of the number of times given quantities are equaled or exceeded during certain periods of record.

2514. dyad
Definition:

A pair. Two units. Half of a tetrad (four units). What happens to bivalent (tetrad) chromosomes after the first nuclear division of meiosis.

2515. dyad symmetry of DNA
Definition:

Two areas of a DNA molecule whose base pair sequences are repeats of each other, inverted relative to each other, or are palindromes.

2516. dysarthria
Definition:

A condition where movement of the joints is impaired by loss of muscle control. Generally this condition comes about when parts of the nervous system have been damaged.

2517. dysarthria
Definition:

Dysarthria is a speech disorder characterized by the mispronunciation of words.

2518. dysfunctional uterine bleeding
Author: Guo Li
Definition:

This is abnormal uterine bleeding (bleeding not due to menstruation) that is not due to a pathologic cause (infection, cancer, injury, etc.), but instead due to hormonal inbalance.

2519. dysgerminoma (ovarian seminoma)
Definition:

A cancerous neoplasm, or abnormal growth, of the ovary which is thought to arise from primordial germ line cells while the individual is still an embryo and the ovary has not yet been sexually differentiated from the generic gonad.

2520. dyslexia
Definition:

Dyslexia is a learning disorder; specifically, it means an inability to read properly. People are diagnosed as dyslexic when their reading problems can't be explained by lack of intellectual ability, or by inadequate instruction, or by sensory problems such as poor eyesight. Because reading is a complex mental process, dyslexia has many potential causes.

2521. dysmotility
Definition:

1. Any abnormal movement of a mobile cell (such as a spermatozooan) or microorganism. For instance, if a sperm cell were to go round and round in a circle instead of heading in a straight path toward an egg cell, it would be considered dysmotile.
2. An abnormality of the muscular contractions of the gut, which interfere with the movement of food through the digestive tract.

2522. dyspareunia
Author: Guo Li
Definition:

Dyspareunia is a woman's sensation of pain or discomfort during sexual intercourse.

2523. dysphagia
Definition:

A medical term meaning difficulty in swallowing food or liquids.

2524. dysplasia
Definition:

Any abnormal tissue, which is not cancerous, but which could become cancerous.

2525. dyspnea
Author: Guo Li
Definition:

Dyspnea is an awareness by the individual of abnormal breathing (rate, pattern, etc.)

2526. dystonia
Author: Guo Li
Definition:

Dystonia the condition of sustained contractions or spasms of muscles of the shoulders, neck, and trunk. It frequently causes twisting and repetitive movements or abnormal postures. Often this is due to disease involving the basal ganglia of the brain which could be related to perinatal anoxia, birth trauma, and kernicterus.

2527. E. coli (Escherichia coli)
Definition:

A common bacterium that has been studied intensively by geneticists because it has a small genome and is usually harmless and easy to grow.

2528. E1A
Definition:

An early gene (a gene of a virus which is expressed early in the viral life cycle) found in adenoviruses associated with cancer which is responsible for their cancer-causing aspects.

2529. ear
Author: Guo Li
Definition:

The ear consists of three parts: external, middle, and internal ear and serves two functions: hearing and equilibrium.

2530. early development
Definition:

An early stage in the life cycle of a bacteriophage (a virus which infects bacteria) that occurs after infection but before replication of the bacteriophage genome.

2531. early genes
Definition:

The genes of a virus which are expressed first, soon after the virus infects its host. Generally, they replicate the viral genome and signal expression of the late genes of the virus at a later point in the viral life cycle.

2532. Eaton-Lambert syndrome (Lambert-Eaton syndrome, myasthenic syndrome)
Author: Guo Li
Definition:

Eaton-Lambert syndrome is characterized by weakness of the proximal muscles of the limbs, often associated with small cell carcinoma (of the lung) and some autoimmune diseases. This condition is caused by the body creating antibodies against its own motor nerve axon terminals.

2533. ebb
Author:
Definition:

Falling stage or outward flow, especially of tides.

2534. Ebola virus
Definition:

An RNA-containing virus in the family Filoviridae that causes an acute, fatal type of hemorrhagic fever characterized by massive bleeding. This virus is native to the Zaire and Sudan areas of Africa.

2535. ecchymosis
Author: Guo Li
Definition:

Ecchymosis is the discoloration due to hemorrhage under the skin. It can be a sign of bleeding tendency secondary to poor nutrition or liver dysfunction.

2536. ecdysone
Image: View the chemical structure
Definition:

Any of several insect hormones that triggers the expression of critical genes during larval development; these hormones are being researched as safer alternatives to pesticides.

2537. ECF (extracellular fluid)
Author: Guo Li
Definition:

ECF is the abbreviation often used to indicate extracellular fluid. It is the volume of body fluid exclusive of that in the cells (intracellular fluid, ICF). Therefore ECF includes fluid in the blood vessels, and in the interstitial space (the space between cells). About 20 percent of body weight is ECF: 5 percent is plasma, and 15 percent is interstitial fluid.

2538. echinate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Bearing stiff, stout, prickly hairs.

2539. echocardiogram
Author: Guo Li
Definition:

An echocardiogram is a method of studying the heart ventricular size, function, wall thickness, motion, and valves by using Doppler ultrasound.

2540. eclampsia
Author: Guo Li
Definition:

Eclampsia is a complication of pregnancy characterized by four conditions: elevated blood pressure, proteinuria (protein in the urine), edema (fluid buildup in the tissues) and seizure.

2541. ECn
Definition:

This is the commonly used abbreviation for the exposure concentration of a poisonous substance causing a defined effect on n% of a test population; for instance, the EC₅₀ would affect 50% of the population.

2542. eco-
Definition:

A prefix which indicates that the word has to do with the environment or with ecology.

2543. eco-organ
Definition:

An ecological feature which mirrors environmental conditions. A type of vegetation based on such a feature.

2544. ecological protection
Author:
Definition:

Protection consists of measures undertaken to protect and preserve elements of an ecosystem's structure and functions against future degradation.

2545. ecological restoration
Author: Society for Ecological Resoration
Definition:

1. The process of renewing and maintaining ecosystem health.
2. Ecological restoration is the process of intentionally altering a site to establish a defined, indigenous, historic ecosystem. The goal of this process is to emulate the structure, function, diversity, and dynamics of the specified ecosystem.

2546. ecology
Definition:

The scientific study of the relationship of organisms to each other and to their environment.

2547. economic botany
Definition:

The study of plants and plant products that can be used for profit, such as in the field of agriculture or medicine.

2548. economic entomology
Definition:

The study of insects which are able to cause economic losses by destroying plants or animals that are commercially valuable.

2549. ecophene
Definition:

The variety of phenotypes (visible physical characteristics or behaviors), from a single genotype (a specific combinations of alleles in a gene), that can be observed in a population within a particular habitat.

2550. ecophenotype (adj. ecophenotypic)
Definition:

A phenotype (visible physical characteristics or behaviors) that is a result of environmental or ecological conditions rather than genetic expression (nurture instead of nature).

2551. EcoRI methylase
Definition:

An enzyme that will methylate (attach a methyl group (-CH₃ group) to the nitrogenous base adenine on DNA molecules) the cutting site (the sequence GAATTC) of the EcoRI restriction enzyme (an enzyme which will cleave DNA at specific nucleotide sequences).

2552. EcoRI restriction enzyme
Definition:

A commonly-used restriction enzyme (enzyme which will cleave the phosphodiester bonds of DNA at specific nucleotide sequences) that came from the bacteria Escherichia coli and recognizes the sequence GAATTC. The enzyme will make a staggered cut of the double-stranded DNA molecule by cutting between the G and A on both strands.

2553. ecospecies
Definition:

A species consisting of different subspecies, or breeds, of an organism which despite being adapted to slightly different environments and/or having distinctly different appearances and behaviors, can still successfully interbreed.

2554. ecosphere
Definition:

1. In astronomy: the region of space around a star that is considered able to support life.
2. In ecology: the Earth, all of the organisms living on it, and all of the environmental factors which act on the organisms.

2555. ecosystem (ecological system, holocoen)
Author:
Definition:

1. An ecosystem is the dynamic and interrelating complex of plant and animal communities and their associated non-living environment.
2. The physical and climactic features and all the living and dead organisms in an area that are interrelated in the transfer of energy and material.
3. An interacting complex of a community and its environment functioning as an ecological unit in nature. Differs from "system" in being a more rigorous definition that encompasses and requires assumptions of energetics, ecological interactions, species adaptations and so forth.

2556. ecosystem altering
Author:
Definition:

Any activity that modifies the biota including species composition, distribution, and abundance and any activity that modifies the physical environment, including soils and the water cycle.

2557. ecosystem dynamics
Author:
Definition:

Those intrinsic ecological functions through which an ecosystem becomes self-regulating, self-sustaining, and capable of recovery from external forces (e.g., damaging storm events). These intrinsic processes may cause continual change in biotic composition and structure at specific localities. Collectively, these changes represent internal flux, rather than substantive and permanent alteration of the ecosystem regionally.

2558. ecosystem function
Definition:

1. The collective intraspecific and interspecific interactions of the biota, such as primary and secondary production and mutualistic relationships.
2. The interactions between organisms and the physical environment, such as nutrient cycling, soil development, water budgeting, and flammability.

2559. ecosystem structure
Author:
Definition:

The physical and spatial aspects of an ecosystem that are contributed by the biotic composition. Biotic composition is generally determined by the collective physiognomy of the dominant plants, including life forms, vertical stratification, and size.

2560. ecotone
Definition:

A transition area between two distinct habitats, where the ranges of the organisms in each bordering habitat overlap, and where there are organisms unique to the transition area.

2561. ecotoxicology
Definition:

Ecotoxicology is the scientific study of harmful effects caused by manmade chemicals to the natural environment, especially effects on populations, communities, and ecosystems; an essential part of ecotoxicology is the study of the movement of potentially toxic substances through food webs and through the water cycle, etc.

2562. ecotropic
Definition:

A retrovirus (virus which uses RNA instead of DNA to encode its genome) that can reproduce only in the host of the species in which it originated.

2563. ecotype (adj. ecotypic)
Definition:

A subspecies, or breed, that has adapted to its local environment and as a result is distinctive from other members of the species, but can still successfully interbreed with other members of the species.

2564. ecto-
Definition:

A prefix which indicates that the word has to do with "external" or "outer."

2565. ectocommensal organism
Definition:

An organism that benefits from living on the outer surface of another organism without harming the other organism. A type of commensalism.

2566. ectoderm (ectoblast, epiblast)
Definition:

The outermost layer of tissue in a developing animal embryo which will eventually become the skin and/or other outer surface of the organism, the outermost parts of the nervous system, and various other outer and external organs, structures, and systems (depends on the organism). Occurs in all animals except for sponges and placozoans.

2567. ectoenzyme
Definition:

An enzyme that is secreted to the outside of the cell and acts extracellularly (between cells, outside of all cells). Compare endoenzyme.

2568. ectogenesis
Definition:

Developing an embryo or embryonic tissue in vitro, or within an artificial environment.

2569. ectomere
Definition:

A blastomere (one of the cells formed during the first few divisions of the zygote) which takes part in forming the ectoderm (the outermost tissue layer of an embryo).

2570. ectoparasite
Definition:

A parasite that lives on the outside of its host rather than within the host's body. Fleas and lice are examples.

2571. ectophyte (epiphyte)
Definition:

A plant that lives and grows on the outer surface of another organism, such as moss on trees.

2572. ectopia
Definition:

An organ or other structure which is positioned abnormally within the body.

2573. ectopic
Definition:

A biological event or process (such as a pregnancy) that occurs in an abnormal location or position within the body.

2574. ectopic pairing
Definition:

Pairing of heterochromatin randomly, without regard to whether they are homologous.

2575. ectopic pregnancy
Definition:

Implantation of an embryo and its subsequent development outside the uterus, most commonly in a fallopian tube.

2576. ectopic pregnancy
Author: Guo Li
Definition:

Ectopic pregnancy is a pregnancy implanted at a site which does not permit development of the embryo. 98 percent of ectopic pregnancies are implanted in one of the fallopian tubes. The incidence of ectopic pregnancy is increased in the following conditions:
1. pelvic inflammatory disease;
2. the use of an intrauterine device as birth control;
3. the use of progestin-only oral contraceptives.
Aside from the fallopian tubes, ectopic pregnancies can occur in an ovary, the abdominal cavity, and in the broad ligament. Ectopic pregnancy is a medical emergency as a ruptured ectopic pregnancy can often result in severe hemorrhage leading to death. Other complications are: chronic salpingitis, sterility, intestinal obstruction and fistulae formation.

2577. ectoplasm
Definition:

Cytoplasm embedded with microfilaments (to give it rigidity) and lacking organelles that is found just under the cytoplasmic membrane in ciliates (one-celled organisms with cilia).

2578. ectosymbiont
Definition:

An organism which is participating in ectosymbiosis (a form of symbiosis in which the organisms involved are physically separated).

2579. ectosymbiosis
Definition:

Symbiosis between two organisms which are physically separated from each other. Compare endosymbiosis.

2580. ectothermic
Definition:

Able to maintain a constant body temperature with an external heat source.

2581. ectotrophic
Definition:

Describes an organism that gets its nutrients from the outside surface of its host.

2582. ectrogeny
Definition:

An organ or bodily structure which is flawed or missing from the body as a congenital condition.

2583. eczema (adj.: eczematous)
Definition:

A noncontagious skin condition where red and itchy blisters appear, then crusty and thickened skin. The condition can be acute (occurs suddenly and once) or chronic (is present for a long time) and has numerous causes.

2584. edaphic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Pertaining to the soil.

2585. edaphic community
Definition:

A community of plants which results from or is influenced by factors about the soil, for example amount of drainage, level of salinity (salt concentration), or amount of sediment movement. Marsh environments often have edaphic communities of plants specially adapted to marsh conditions.

2586. edaphon
Definition:

An organism (nematode worm, fungus, bacterium, etc.) that lives in the soil.

2587. EDC (estimated date of confinement)
Author: Guo Li
Definition:

EDC is the abbreviation often used to indicate the "estimated date of confinement" in pregnancy. This is the date when child birth is most likely to take place. Many tables and charts are available to obtain the EDC.

Nagele's rule is a mathematical formula to obtain the EDC assuming a normal 28-day cycle of menstruation:

• to obtain the month of EDC, subtract 3 from the month of the last normal menstrual period
• to obtain the day of EDC, add 7 to the first day of the last normal menstrual period

2588. eddy (eddy current)
Author:
Definition:

1. Rotational flow around a vertical axis.
2. Circular current of water, sometimes quite strong, diverging from the main current. (It usually forms where the flow passes some obstruction or at the inside of river bends, and often forms backwater pools or pocket water in riffles.)
3. A circular water movement that develops between the main flow and the bank. (An eddy usually forms downstream of a structure or an abrupt change in the shape of the bank. Eddies are often the cause of bank erosion.)

2589. edema
Definition:

Abnormal buildup of watery fluid in the tissues.

2590. Edman degradation
Definition:

A lab technique used to find out the order of amino acids in a polypeptide (chain of amino acids). It involves using the Edman reagent, phenyl isothiocyanate (PITC), to react one by one with each amino acid, in order. The technique is used in machines which automatically sequence (determine the order of subunits) polypeptides.

2591. EDn
Definition:

This is the commonly used abbreviation for the dose of a toxicant causing a defined effect on n% of a test population; for instance, the ED₅₀ would affect 50% of the population.

2592. Edward's Syndrome ( Edwards' syndrome, trisomy 18, trisomy E)
Definition:

A congenital disorder caused by a baby having an extra copy of chromosome 18 (three instead of the normal two). Characteristics of the disorder include a large number of different malformed organs and malformed physical features of the face and skeletal structure. In most cases, the child dies before it is born; 90% of babies born live die within a year of birth. Symptoms may be less severe when the trisomy occurs after fertilization during mitosis in the zygote (10% of cases), than when the trisomy occurs during the meiosis which produced the egg or sperm (90% of cases).

For more information, visit http://www.icondata.com/health/pedbase/files/TRISOMY2.HTM.

2593. effacement
Author: Guo Li
Definition:

Effacement is the thinning out of the cervix during the first stage of labor from 0 percent to 100 percent when it is less than 0.25 centimeters thick.

2594. effectively drained
Author:
Definition:

A condition where ground or surface water has been removed by artificial means to the point that an area no longer meets the wetland hydrology criterion.

2595. effector
Definition:

A molecule, chemical, or structure that regulates a pathway by increasing or decreasing the pathway's reaction rate.

2596. efferent
Definition:

Moving or carrying outward or away from a central part. Refers to vessels, nerves, etc. For example, blood vessels carrying blood away from the heart or nerves carrying signals from the brain. Compare afferent.

2597. efficacious (efficacy)
Definition:

Having the ability or power to produce a desired effect.

2598. effluent
Definition:

Liquid waste from sewage treatment or industrial processes, especially such liquid waste that is released into a river or other waterway.

2599. egg
Definition:

A structure which the females of certain animal species lay as a means of reproduction; it contains a fertilized zygote and nutrition in the form of yolk for the developing offspring, sometimes contains other substances (eg., the "white" of a hen's egg), sometimes surrounded by a protective outer shell.

2600. egg coat
Definition:

A layer of glycoproteins and other stuff which surrounds an egg (ovum), just outside of the egg's cell membrane. The coat protects the egg, and for organisms which practice external fertilization (fertilization outside of the parents' bodies) it can help prevent the sperm of other species from entering the egg. For the eggs of mammals, the egg coat is called the zona pellucida and for sea urchins (a popular study organism for developmental biologists) it is called the vitelline layer.

2601. egg donation
Definition:

Donation of an ovum by one woman to another who attempts to become pregnant by in vitro fertilization.

2602. Ehlers-Danlos syndrome
Author: Guo Li
Definition:

Ehlers-Danlos syndrome is characterized by a collagen abnormality resulting in hyperelasticity and fragile tissues. It is inherited as an autosomal dominant condition.

2603. eicosanoid
Definition:

A type of hormone which forms when the body breaks down arachidonic acid. Examples include the leukotrienes, lipoxins, prostaglandins, and thrombaxanes.

2604. Eisenmenger's syndrome
Author: Guo Li
Definition:

Eisenmenger's syndrome is characterized by pulmonary hypertension and a right-to-left or bi-directional shunt. The shunt can be atrial or ventricular. Most patients can not survive beyond age 40 and demise occurs when the fraction of right-to-left shunt increases.

2605. ejaculation
Author: Guo Li
Definition:

Ejaculation is a two-part spinal reflex that involves:
1. movement of semen into the urethra in response to signals from the internal pudendal nerves (afferent), and hypgastric nerves (efferent), and
2. propulsion of the semen out of the urethra by contraction of the bulbocavernosus muscle in response to signals from the sacral roots and the internal pudendal nerves.

2606. elaiosome
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

An appendage of a seed, usually rich in oil, not essential for the viability of the seed but attractive to animals (especially ants) as a food for larvae etc. and hence an aid to dispersal by such animals.

2607. elater
Definition:

An elongated, spirally thickened, water-attracting cell in the capsule of a liverwort, derived from sporogenous tissue and assisting in spore dispersal.

2608. electroblotting
Definition:

The use of an electric field to transfer proteins or nucleic acids from the electrophoresis gel to the blotting membrane as a part of Southern blotting, Northern blotting, or Western blotting.

2609. electrocardiogram (EKG, ECG)
Author: Guo Li
Definition:

This is a recording of the electrical signals from the heart. From an EKG, it is possible to identify arrythmias, myocardial ischemia or infarction, the type and timing of damage, ventricular hypertrophy and some abnormalities of serum electrolytes.

2610. electrocautery
Definition:

Cauterization via the use of an electrical current.

2611. electrocautery
Author: Guo Li
Definition:

Electrocautery is the destruction of tissue by means of electric current. In surgery, high frequency electric current is used to cauterize small blood vessel to stop bleeding.

2612. electrochemical potential
Definition:

The energy needed to maintain separate concentrations and charges on each side of a membrane.

2613. electroconductivity (EC)
Author:
Definition:

A measure of the total dissolved ions in a substance, which indicates the material's ability to conduct electricity. Soil EC's are determined from distilled water extracts of saturated soil pastes.

2614. electrode
Definition:

A terminal of an electric source through which electricity passes when the circuit is completed.

2615. electrodialysis
Definition:

The use of an electric field to speed up the dialysis process. The electric field is applied across the dialysis membrane.

2616. electrodiffusion
Definition:

The use of an electric field to induce substances with positive or negative charges to move in a particular direction.

2617. electroejaculation
Author: Fertilitext
Definition:

Controlled electrical stimulation, usually applied to the prostate gland with a probe, to induce ejaculation in a man who has nerve damage that prevents him from ejaculating normally.

This technique is also used in veterinary medicine, especially by zoo vets who are trying to increase the populations of endangered mammal species by artificially inseminating females of the species in question.

2618. electroencephalogram
Definition:

A graph of very tiny changes in the electrical potential associated with neural activity in the cerebral cortex. The graphed electrical activity is picked up by scalp electrodes.

2619. electroencephalogram (EEG)
Author: Guo Li
Definition:

This is the recording of electrical signals of the brain. It identifies epileptic activities (paroxysmal abnormalities containing spikes or sharp waves), and is used during surgery to localize the epileptogenic source for excision.

2620. electroendosmosis
Definition:

1. The effect of an electric field on the diffusion of water through or into a membrane or gel.
2. The movement of the liquid medium of a colloid solution towards an electrode.

2621. electrogenic
Definition:

Refers to a substance that contributes to an electrical potential across a membrane.

2622. electrolysis
Definition:

1. The process where an electric current is passed through an electrolytic solution or other appropriate medium, causing a chemical reaction. Similar to what happens within a battery.
2. In medicine, the process where an electric current is used to destroy tumors. 
3. In cosmetology, the removal of unwanted body hair by electrocuting the hair roots with an electrified needle.

2623. electrolyte
Author: Guo Li
Definition:

"Electrolyte" refers to ionized salts in the body fluids. The major electrolytes are made from sodium, potassium, magnesium, calcium, chloride, bicarbonate, phosphate and protein.

2624. electromagnetic wave (electromagnetic radiation)
Definition:

A wave of electric and magnetic fields that can move through space. Particles which make up the waves are called photons.

2625. electromyogram
Definition:

A graphical representation of the electrical activity in a muscle.

2626. electromyograph
Definition:

A device that senses and graphs on paper the electrical activity in a muscle.

2627. electron
Definition:

A stable atomic particle that has a negative charge; the flow of electrons through a substance constitutes electricity.

2628. electron acceptor
Definition:

A molecule or compound that gets electrons during an oxidation-reduction reaction.

2629. electron carrier
Definition:

A protein which can either accept or donate electrons in oxidation-reduction reactions.

2630. electron donor
Definition:

A molecule or compound that gives up electrons in an oxidation-reduction reaction.

2631. electron microscope
Definition:

A microscope (device used to magnify small objects) which beams electrons at and through the object of interest instead of light beams. Instead of a glass lens to bend the light, a powerful magnet is used to bend the electron beam. The microscope can only be operated in a vacuum. This type of microscope provides the greatest resolution of extremely small details available and has been used to see individual atoms in an object or substance.

2632. electron microscopy
Definition:

The use of an electron microscope (a microscope that uses electron beams instead of light beams) to magnify extremely fine details of an object or substance. Since the microscope can only be operated in a vacuum, biological specimens of interest must first be protected by coating it with a thin metal layer, which also outlines the structural features of the specimen.

2633. electron transport
Definition:

The transport of electrons through a number of electron carriers in a set sequence.

2634. electron transport chain
Definition:

A group of electron carriers in mitochondria (energy-making organelles found in eukaryotes) which transports electrons to and from each other in a set sequence, for the purpose of generating the energy needed to convert ADP and inorganic phosphate into ATP (used to store energy in units by all living things).

2635. electron-transport phosphorylation (oxidative phosphorylation)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Synthesis of ATP involving a membrane associated electron transport chain and the creation of a proton-motive force.

2636. electronegativity
Definition:

1. The likelihood that an atom or molecule will attract electrons; the strength of the attraction.
2. The tendency of an atom or molecule to become negatively charged.

2637. electronic potential
Definition:

The measure (in volts) of electron pressure. A measure of the difference in electron concentrations between two compartments, such as either side of a cell membrane.

2638. electrophile
Definition:

A molecule or group that doesn't have enough electrons and will tend to take them from a molecule or group with an excess of elecrons (nucleophile).

2639. electrophoresis (ionophoresis)
Definition:

A method of separating large molecules (such as DNA fragments or proteins) from a mixture of similar molecules. An electric current is passed through a medium containing the mixture, and each kind of molecule travels through the medium at a different rate, depending on its electrical charge and size. Separation is based on these differences. Agarose and acrylamide gels are the media commonly used for electrophoresis of proteins and nucleic acids. Specific electrophoretic methods include Northern blot, Southern blot, and Western blot.

2640. electroporation
Definition:

The exposure of cells to rapid pulses of high-voltage current which renders the plasma membrane of the cells permeable and thus allowing transfection.

2641. elimination half-life
Author: PharmInfoNet
Definition:

The time it takes for the body to eliminate or breakdown half of a dose of a pharmacologic agent.

2642. ELISA (enzyme-linked immunosorbent assay)
Definition:

A highly sensitive technique for detecting and measuring antigens or antibodies in a solution; the solution is run over a surface to which immobilized antibodies specific to the substance have been attatched, and if the substance is present, it will bind to the antibody layer, and its presence is verified and visualized with an application of antibodies that have been tagged in some way.

2643. elliptic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Oval in outline, widest at the center.

2644. elongation factors
Definition:

Certain proteins that ribosomes need to make polypeptide chains longer.

2645. eluant
Definition:

The term for the fluid (such as a buffer solution) that is used in column chromatography to separate the components of a mixed sample. The fluid is run through the column and brings out the separated substances (separately). Also see elution.

2646. eluate
Definition:

The waste liquid produced during chromatography.

2647. elution profile
Definition:

A graph made to show how much material is being carried out of the column by the eluant in column chromatography over time. The graph will show a number of different peaks; each peak represents a different separated material from the original mixed substance.

2648. elution volume
Definition:

The amount of eluant which has passed through the column in column chromatography before a particular peak in an elution profile appears, or before a specific substance of interest comes out with the eluant, separated out of the original mixed substance.

2649. emaciated
Definition:

Extremely thin or physically wasted.

2650. emarginate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having a broad, shallow notch at the top.

2651. embankment
Definition:

A structure made of packed soil built above the natural ground.

2652. Embden-Meyerhof-Parnas pathway (Embden-Meyerhof pathway; EMP pathway)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A pathway that degrades glucose to pyruvate; the six-carbon stage converts glucose to fructose-1,6-bisphosphate, and the three-carbon stage produces ATP while changing glyceraldehyde-3-phosphate to pyruvate. Compare with Entner-Doudoroff pathway.

2653. embeddedness
Author:
Definition:

Degree to which large particles (boulders, rubble, gravel) are surrounded or covered by fine sediment, usually measured in classes according to percent coverage.

2654. embolectomy
Author: Guo Li
Definition:

An embolectomy is the surgery to remove the obstruction in a blood vessel, aiming at improving circulation.

2655. embolism
Definition:

Obstruction in a blood vessel; can be caused by a blood clot or mass of bacteria or other material.

2656. embolism
Author: Guo Li
Definition:

An embolism is the disorder of lodging a substance in a blood vessel so that blood flow is totally or partially obstructed. The substance could be air, a blood clot, tumor fragments, fat, amniotic fluid, bacteria, or parasites.

2657. embryo
Definition:

1. A stage of development in a multicelled organism between the time that the zygote is fertilized and the point at which the organism developing from that zygote becomes free-living.
2. Specifically, in vertebrate animals, the developmental stage from after the long axis appears until all major anatomical structures form.
3. In human development, this is from about two weeks after fertilization until the seventh or eighth week of pregnancy.
4. In higher plants, this is the rudimentary plant encased in a viable seed before germination; a plant embryo usually consists of an epicotyl, hypocotyl, radicle and one or two cotyledons.
5. In primitive plants, the young sporophyte that develops from the union of male and female sex cells.

2658. embryo transfer
Author: Fertilitext
Definition:

The placement of a laboratory-fertilized egg into the uterus.

2659. embryogenesis
Author: ForBio Ltd.
Definition:

1. A process of differentiation which results in the formation of embryo-like structures from undifferentiated cells.
2. Process which leads to the formation of embryos.

2660. embryologist
Author: Fertilitext
Definition:

A specialist in embryo development.

2661. embryology
Definition:

The study of the embryo and its development from a one-celled zygote (fertilized ovum) to the establishment of form and shape (at which point, if it is an animal, it becomes a fetus). A subfield of developmental biology.

2662. embryotoxin (embryotoxic)
Definition:

This describes any chemical which is harmful to an embryo.

2663. emergence (fish emergence)
Author:
Definition:

Departure of fry from the incubation gravel into the water column.

2664. emergency medicine
Definition:

This medical field encompasses:
1. clinical issues and techniques concerning the treatment of patients who are critically injured and need fast (and often extensive) treatment;
2. the management and administration of a hospital emergency room.

2665. emergent
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Any of various plants (as a cattail) rooted in shallow water and having most of the vegetative growth above the water.

2666. emersed
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Standing out of or rising above a surface as an aquatic plant with flower stalk emersed.

2667. emersed plants
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Plants growing with their roots and a portion of the shoot below the water and the remainder of the shoot above the surface of the water.

2668. emission standard
Definition:

This regulatory value is a quantitative limit on the emission or discharge of a potentially toxic substance from a source. The simplest form for regulatory purposes is a uniform emission standard (UES) where the same limit is placed on all emissions of a particular contaminant.

2669. emphysema
Author: Guo Li
Definition:

Emphysema is the abnormal condition of air in the tissues. In pulmonary emphysema, the lung tissues are destroyed so that alveolar sacs are replaced with useless air space. Chronic tobacco smoking is a major cause of emphysema.

2670. empyema
Author: Guo Li
Definition:

Empyema is the collection of pus in a body cavity.

2671. emulsifier (emulsifying agent)
Definition:

A substance which can be used to produce an emulsion out of two liquids that normally cannot be mixed together (such as oil and water). Emulsifiers are common in foods to maintain consistency within puddings, powders, etc.

2672. emulsion
Definition:

A mixture of two normally unmixable liquids (e.g., oil and water) in which one is colloidally suspended in the other (one exists as tiny particles within the other).

2673. enantiomers
Definition:

A pair of chiral isomers that are direct, nonsuperimposable mirror images of each other.

2674. enation
Definition:

An epidermal outgrowth.

2675. encapsulation
Definition:

The coating or engulfing of particles within a continuous matrix.

2676. encephalitis
Definition:

Inflammation of the brain; it's most often caused by a virus transmitted by a mosquito that has recently fed on an infected person, but bacteria, bleeding, or poison can cause the illness.

2677. encephaloma
Definition:

Any swelling or tumor of the brain.

2678. encephalopathy
Definition:

Any disease of the brain.

2679. end plate (end-plate)
Definition:

The flat end of a part of the body, usually against another part. Most often refers to the end of a nerve fiber against a skeletal muscle fiber, to which it transmits nerve signals.

2680. end point (end-point, endpoint)
Definition:

1. In analytical chemistry, it is the point during a titration reaction where there are equal amounts of titrant and whatever is being titrated. A color change in the sample usually indicates this point.
2. In immunology, it is the most dilute an antibody or antiserum solution can be while still detectably reacting with the antigen.

2681. end product
Definition:

The final product of after a series of reactions with enzymes in a biochemical metabolic pathway has taken place.

2682. end-filling
Definition:

The use of DNA polymerase to create a blunt end (both strands are the same length and end together) on double-stranded DNA that has a staggered end (one strand is longer than the other so there is a single-stranded section at the end of the molecule).

2683. endangered species
Definition:

Any species which is in danger of extinction throughout all or a significant portion of its range.

2684. endemic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having a natural distribution confined to a particular geographical region.

2685. endemic
Definition:

Native to a particular region.

2686. endo-
Definition:

A prefix indicating that the word has to do with internal, inside, inner, or within.

2687. endocarditis
Author: Guo Li
Definition:

Endocarditis is an inflammatory disorder of the heart valves or the mural endocardium (the innermost layer of the three layered walls of the heart). It can be caused by bacterial infection, or by other means. Libman-Sacks endocarditis is nonbacterial and is caused by systemic lupus erythematosus. In bacterial versions of this disorder, valvular lesions from previous infections or congenital heart disease are the predisposing factors.

2688. endocarp
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The innermost layer of the wall of a fruit; in a drupe, the stony layer surrounding the seed.

2689. endocrine gland
Definition:

A gland, such as the pituitary or thyroid, that secretes its products directly into the bloodstream. Compare exocrine gland.

2690. endocrinologist
Author: PharmInfoNet
Definition:

A doctor who treats people who have problems with their endocrine glands. diabetes is an endocrine disorder.

2691. endocrinology
Definition:

The scientific study of the function and pathology of the endocrine glands (e.g. the thyroid gland, pituitary gland, etc.)

2692. endocytic vesicle
Definition:

The vesicle (membrane-bound bubble within the cell) which is formed during the process of endocytosis and which contains substances being imported from outside of the cell.

2693. endocytosis
Definition:

Process by which extracellular materials are taken up by a cell. Compare exocytosis. A blanket term for phagocytosis and pinocytosis.

2694. endodeoxyribonuclease
Definition:

A hydrolase enzyme that hydrolyzes the interior bonds of deoxyribonucleotides and strings them together into oligonucleotides or polynucleotides.

2695. endoderm (entoderm, endoblast, entoblast, hypoblast)
Definition:

The innermost layer of tissue in a developing animal embryo which will eventually become the digestive tract, respiratory tract, and various other things depending on the organism. Occurs in all animals except for sponges and placozoans.

2696. endoenzyme
Definition:

1. An enzyme which is not secreted or exported out of the cell, but is kept and used by the cell which made it. Compare ectoenzyme.
2. An enzyme that makes bonds within polymers (chains of similar units).

2697. endogamy
Definition:

The opposite of exogamy:
1. Sexual reproduction between organisms which are closely related to each other.
2. Production of a zygote (an egg that has been fertilized by a sperm) by a simultaneous hermaphrodite (an organism which produces both sperm and eggs) using only its own gametes (eggs and sperm) without gamete contributions from other individuals.
3. Marriage between members of the same restricted group, class, or caste.

2698. endogenote
Definition:

The original complete genome of a bacterium, before addition of new genetic material (an exogenote) from a donor by the process of genetic recombination or by genetic engineering.

2699. endogenous
Definition:

1. In general, means anything developing or growing from within.
2. In immunology, it means a disease or illness that is caused by a problem within the organism.

2700. endogenous pyrogen
Definition:

A protein which produces a fever when the body has been invaded by foreign antigens.

2701. endogenous retrovirus
Definition:

A retrovirus that has become dormant and exists as DNA copies in every cell in the body of its host and is passed down from generation to generation.

2702. endogenous virus
Definition:

1. A virus with the ability to integrate into the genome of its host and become dormant, so that it exists as DNA copies in every cell in the body of the host and is passed down from generation to generation.
2. A virus that causes a persistent infection.

2703. endometrial biopsy
Author: Fertilitext
Definition:

The removal of a fragment of the lining of the uterus for study under a microscope.

2704. endometriosis
Definition:

Growth of the tissue lining the uterus (the endometrium) outside the uterus, usually in the lower abdomen. This mislocated tissue bleeds during the woman's period, causing pain and inflammation.

2705. endometritis
Definition:

Inflammation of the endometrium (the tissue lining the uterus), often due to infection by bacteria, which can occur after childbirth or abortion and which can result in lesions, tubercles, or the sloughing off of tissue.

2706. endometrium (adj.: endometrial)
Definition:

The tissue lining the uterus; it is sloughed off during the woman's menstrual period, and afterward grows back and slowly gets thicker and thicker until the next period.

2707. endomitosis
Definition:

Replication of the DNA in a cell's nucleus without subsequent mitosis (nuclear division).

2708. endomixis
Definition:

1. Self-fertilization; the union of an egg and a sperm which are both from the same individual.
2. In certain ciliated protozoans, a process of nuclear division and reorganization.

2709. endomysium
Definition:

A sheath of connective tissue that surrounds muscle fibers.

2710. endonuclease
Definition:

An enzyme that cleaves its nucleic acid substrate at internal sites (the phosphodiester bonds) in the nucleotide sequence.

2711. endonuclease S1
Definition:

A nuclease enzyme from the fungus Aspergillus oryzae which cuts the phosphodiester bonds between nucleotides in single-stranded DNA or RNA, producing individual nucleotide molecules.

2712. endopeptidase
Definition:

A hydrolase enzyme that cleaves peptide bonds between amino acids in a polypeptide (chain of amino acids) by hydrolyzing them.

2713. endoplasm
Definition:

The portion of the cell's cytoplasm which is closest to the cell's nucleus.

2714. endoplasmic reticulum
Definition:

A system of double-membraned, tubular organelles that aid in protein synthesis in eukaryotic cells.

2715. endopolyploidy
Definition:

Many multiple copies of the chromosomes of a cell which has been repeatedly duplicating and dividing them without undergoing cell division afterwards.

2716. endoribonuclease
Definition:

A hydrolase enzyme which makes oligonucleotides and polynucleotides by hydrolyzing the interior bonds of ribonucleotides.

2717. endorphin
Image: View the chemical structure
Definition:

Any of several morphine-like peptides naturally produced in the brain which bind to certain neuron receptors and have the effect of diminishing pain.

2718. endoscope
Definition:

A medical instrument used to view inside the body.

2719. endoskeleton (neural skeleton)
Definition:

A skeleton, or support structure, which is on the inside of the organism's body. All vertebrates possess one that is made of either bone or cartilage. (Note: teeth are not counted as part of the endoskeleton.) Compare exoskeleton.

2720. endosmosis
Definition:

The movement of liquid from outside the cell to its interior by osmosis through the cell membrane. The opposite of exosmosis.

2721. endosome (receptosome)
Definition:

A large membrane-bound structure that is the result after several coated vesicles fuse together following endocytosis. The structure contains the combined contents of all of the former vesicles.

2722. endosperm (albumen)
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Nutritive tissue in a seed; in angiosperms it's triploid and is formed in the embryo sac after fertilization. In gymnosperms, it's haploid and is derived from the sterile portion of the female gametophyte. Compare perisperm.

2723. endospore
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A differentiated cell formed within the cells of certain Gram-positive bacteria and extremely resistant to heat as well as to other harmful agents.

2724. endosulfan
Definition:

A toxic chemical used as an insecticide; it has the chemical formula of C₉H₆Cl₆O₃S. At room temperature, endosulfan is composed of brown crystals. It cannot be dissolved in water, but can be dissolved in most organic solvents. In pure form, it melts at 106°C.

2725. endosymbiont
Definition:

An organism which lives within the body of another organism (its host) as part of an endosymbiotic relationship.

2726. endosymbiosis
Definition:

A symbiotic relationship between two organisms in which one of the two organisms (the endosymbiont) lives inside the body of the other one (the host). Compare ectosymbiosis.

2727. endosymbiosis theory
Definition:

The scientific theory that the organelles of eukaryotic cells arose when free-living procaryotic cells began living within other, larger free-living procaryotic cells and formed mutualistic symbiotic relationships with them.

2728. endosymbiotic infection (endosymbiosis)
Definition:

A situation where a cell that has been infected by a virus is prevented from dividing but is not immediately killed.

2729. endothelial cell
Definition:

A thin, flattened cell; a layer of them lines the inside surfaces of body cavities, blood vessels, and lymph vessels, making up the endothelium.

2730. endothelin
Definition:

A polypeptide (chain of amino acids) that induces the smooth muscles of the blood vessel walls to contract. It is made by the endothelial cells which line the inner surface of the blood vessels.

2731. endothelioma
Definition:

A tumor (usually benign) which is formed from tissues of the endothelium.

2732. endotheliotoxin
Definition:

A poison that causes hemorrhages (internal bleeding) by attacking the endothelium (inner lining) of small blood vessels.

2733. endothelium (endothelial)
Definition:

A layer of cells (called endothelial cells) that lines the inside surfaces of body cavities, blood vessels, and lymph vessels.

2734. endotherm
Definition:

1. An organism which is capable of generating its own body heat and maintaining a constant body temperature; a warm-blooded organism.
2. A graph which shows the difference in temperature between a test compound and a reference compound that is thermally inert, when the compounds are both heated at the same rate.

2735. endotoxin
Definition:

Any of a group of poisonous lipopolysaccharides found in the outer membranes of Gram-negative bacteria. These toxins cause illnesses such as diarrhea and hemorragic shock.

2736. endotracheal tube
Definition:

In surgery, a tube which is passed through the mouth or nose into the trachea to provide a free passage for air into the lungs.

2737. energy coupling
Definition:

The tranfer of energy produced in one reaction to another.

2738. energy dissipater
Author:
Definition:

A device which fits on the downstream end of a culvert pipe or sluiceway which reduces the hydraulic energy of high velocity water flows. Arranging for the discharge to strike a large rock, log, etc., can also dissipate the energy of the flow. This is sometimes used in the absence of a downspout on the downstream end of a culvert or sluiceway to prevent severe erosion of a stream bank where the outlet is high above natural stream grade.

2739. enhancement
Author:
Definition:

Altering an object, substance or site for the improvement of a specific value.

2740. enhancement flow
Author:
Definition:

An improvement of flow that provides improvement over natural conditions for the aquatic, terrestrial, and other recreation resources.

2741. enhancers
Definition:

1. DNA sequences that positively influence the expression of a gene and which may be some distance from that gene.
2. A protein which binds to such a sequence of DNA.

2742. enriched medium
Definition:

A growth medium which contains extra unusual nutrients or contains higher concentrations of regular nutrients than a standard medium. It is used to grow auxotrophs (organisms which lack the ability to make something essential for growth).

2743. ensiform
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Having sharp edges and tapering to a slender point; having a shape suggesting a sword.

2744. enteric bacteria
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A large group of Gram negative rod-shaped bacteria characterized by a facultatively aerobic metabolism. Many of them are commonly found in the intestines of animals.

2745. enteric coating (enteric-coated)
Definition:

A coating put on a capsule or pill so that it doesn't dissolve until it reaches the small intestine.

2746. enteritis
Definition:

Inflammation of the intestine, particularly of the small intestine.

2747. Enterobacteriaceae
Definition:

A family of bacteria which are gram-negative, shaped like rods, and are facultative anaerobes. They live in soil, water, plants, and animals (especially the intestines), and can cause diseases in vertebrate animals.

2748. enthalpy (H)
Definition:

The heat in a system.

2749. enthalpy change (H)
Definition:

In a reaction, this is more or less equal to the the difference between the energy put into breaking bonds and the enery gained from new bond formation.

2750. entire
Definition:

1. Complete; not missing parts.
2. Having a smooth margin, not dissected or toothed.

2751. entisols
Author:
Definition:

Soils of slight and recent development; common along rivers and flood plains.

2752. Entner-Doudoroff pathway (ED pathway)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A pathway that converts glucose to pyruvate and glyceraldehyde-3 phosphate by producing 6-phosphogluconate and then dehydrating it.

2753. entomophilous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Pollinated by insects.

2754. entropy
Definition:

The amount of disorder in a system.

2755. enuresis
Author: Guo Li
Definition:

Enuresis is the involuntary urinary incontinence (involuntary urination) in a child 5 years or older when there exists no physical abnormality to account for this condition.

2756. env genes
Definition:

One of three retrovirus genes which codes for the env glycoproteins.

2757. env glycoproteins
Definition:

An important protein component of the mature retrovirus protein outer coat (the capsid). It is coded for by the env genes.

2758. environment
Author:
Definition:

1. The complex of climatic, edaphic and biotic factors that act upon an organism or an ecological community and ultimately determine its form and survival.
2. Califonia state law defines environment as "the physical conditions which exist within the area which will be affected by a proposed project, including land, air, water, mineral, flora, fauna, noise, and objects of historic or aesthetic significance."

2759. environmental output
Author:
Definition:

Environmental outputs are the desired or anticipated measurable products or results of restoration measures and plans.

2760. Environmental Protection Agency (EPA)
Author: Susan A.Hagedorn
Definition:

The U.S. regulatory agency for biotechnology of microbes. The major laws under which the agency has regulatory powers are the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA); and the Toxic Substances Control Act (TSCA).

2761. environmental quality objective (EQO)
Definition:

This is a regulatory value defining the quality to be aimed for in a particular aspect of the environment. Unlike an environmental quality standard, an EQO is not usually expressed in quantitative terms and cannot be enforced legally.

2762. environmental quality standard (EQS, ambient standard, air quality standard)
Definition:

This regulatory value defines the maximum concentration of a potentially toxic substance which can be allowed in an environmental compartment, usually air (air quality standard - AQS) or water, over a defined period.

2763. environmental tobacco smoke
Author: Stephen J. Jay, MD
Definition:

A complex mixture of chemical constituents and particulates released into the atmosphere from the burning tip of a cigarette, pipe or cigar or from smoke exhaled by the smoker.

2764. environmental variance
Definition:

Within a population, the measure of how much of the variation of a particular phenotype is due to environmental factors (as opposed to variations in genotype - see genetic variance). An example might be the height of a human as determined by such factors as nutrition or infectious diseases during childhood.

2765. enzyme derepression
Definition:

Removing or turning off the inhibitor or inhibitors (molecules which repress or prevent other molecules from acting) enzyme so that enzyme activity can resume.

2766. enzyme immobilization
Definition:

The attachment of an enzyme to a solid matrix so that it cannot escape but can still act on its substrate.

2767. enzyme inactivation
Definition:

The disappearance of an enzyme’s activity during in vitro conditions, such as during a lab preparation of the enzyme, where the enzyme is exposed to conditions not normally found within its environment inside a living cell (like different pH, excess or too little salt, temperature changes, etc.)

2768. enzyme kinetics
Author: ForBio Ltd.
Definition:

Quantitative characteristics of enzymatic reactions.

2769. enzyme replacement therapy
Definition:

A type of medical treatment for patients who lack an important enzyme; the missing enzyme is injected into the patient.

2770. enzyme stabilization
Definition:

Reducing the chances that an enzyme will inactivate in vitro (see enzyme inactivation) by changing the environmental conditions (such as pH, temperature, concentration of salt, etc.) or by attaching organic groups to it or changing some of its amino acid subunits.

2771. enzymes
Definition:

Proteins that act as catalysts, speeding the rate at which biochemical reactions proceed but not altering the direction or nature of the reactions.

2772. enzymic process (enzymatic process)
Definition:

Any chemical reaction or series of reactions catalysed by an enzyme.

2773. eosin
Definition:

1. A red, fluorescent, bromine-containing, water-insoluble dye used mainly in toner and cosmetics.
   
2. A red or brown potassium or sodium salt of the above dye; it is used as a biological stain and in pharmaceuticals.

2774. eosinophil
Definition:

A type of granular leukocyte that is an amoeba-like scavenger that disposes of cellular debris. This cell takes its name from the fact that it can be stained with eosin. People with parasitic infections typically have increased numbers of these cells in their bloodstream.

2775. ephemeral
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Short-lived.

2776. ephemeral stream
Author:
Definition:

A stream that flows briefly and only in direct response to local precipitation, and whose channel is always above the water table.

2777. epibenthic
Author:
Definition:

Living on the surface of bottom sediments in a water body.

2778. epicalyx
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A whorl of bracts, just below a flower, looking like a second calyx.

2779. epicarp
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The outer layer of the wall of a fruit, i.e. the 'skin'.

2780. epicormic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of buds, shoots or flowers, borne on the old wood of trees (applied especially to shoots arising from dormant buds after injury or fire).

2781. epicortical
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

On top of the bark, i.e. outside the bark.

2782. epicotyl
Definition:

The part of the stem of an embryonic plant which is above the cotyledons but below the first true leaves (which are attached to the apex of the epicotyl). The epicotyl develops into the shoot of the plant upon germination of the seed. (The rest of the embryonic stem, which is below the cotyledons, is called the hypocotyl).

2783. epidemic
Definition:

A virulent, widespread disease in a human or animal population.

2784. epidemiology
Definition:

The scientific study of diseases; includes analyzing the occurence and distribution of diseases and the factors that govern their spread.

2785. epidermal growth factor (EGF)
Definition:

A polypeptide growth factor that stimulates the growth of epithelial cells. It was discovered by Stanley Cohen, and a part of the gene which codes for the receptor on the cells that heed its signals is extremely similar to the erb-b oncogene (proto-cancer gene).

2786. epidermis
Definition:

1. The outer epitheial layer of the skin, consisting of a basal layer, a prickle-cell (spinous) layer, a a glandular layer, a clear layer, and a horny layer.
2. The outermost layer of parenchyma in plants which protects against water loss, abrasions, etc.

2787. epididymis
Author: Fertilitext
Definition:

The tightly-coiled, thin-walled tube that conducts sperm from the testicles to the vas deferens.

2788. epididymitis
Author: Fertilitext
Definition:

Inflammation of the epididymis.

2789. epididymitis
Definition:

Epididymitis is inflammation/infection of the epididymis.

2790. epifauna
Author:
Definition:

Animals living on the surface of the substrate.

2791. epigeal
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of germination, having the cotyledon(s) emerging from the seed coat and becoming photosynthetic. Compare hypogeal.

2792. epigenetic
Definition:

Describes something which influences the behavior of a cell without directly affecting its DNA or other genetic machinery, such as an environmental effect.

2793. epigenetic changes
Definition:

Any changes in an organism brought about by alterations in the action of genes are called epigenetic changes. Epigenetic transformation refers to those processes which cause normal cells to become tumor cells without the occurrence of any mutations.

2794. epigynous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of floral parts (especially stamens), attached above the level of insertion of the ovary, and arising from tissue that is fused to the ovary wall. Compare hypogynous, perigynous.

2795. epilepsy
Author: Guo Li
Definition:

Epilepsy is a clinical condition characterized by recurrent attacks of seizures of sudden onset. The seizures may range in severity from a brief loss of consciousness (which may resemble simple daydreaming or dozing to the observer) to grand mal seizures that may involve several minutes of powerful convulsions.

2796. epilithic
Author:
Definition:

Living on rocks or other stony matter.

2797. epimer
Definition:

A stereoisomer of a compound that has at least two asymmetric centers that differs from its alternate form at a single asymmetric center.

2798. epimerase
Definition:

An enzyme that catalyzes the reversible conversion of an epimer into its counterpart form.

2799. epinephrine (adrenaline)
Definition:

A chemical produced and secreted by the adrenal glands. It can act as a stimulant, increasing blood pressure, heart rate, and other functions. It is a neurotransmitter, or substance which transmits nerve signals from neuron to neuron, and is also a hormone that helps break glycogen (a polysaccharide) down into glucose (a simple sugar). It has the chemical formula C₉H₁₃NO₃.

2800. epipetalous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Borne on the petals.

2801. epiphyllous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Growing on leaves, e.g. applied to vegetatively propagated plantlets in some members of the family Crassulaceae.

2802. epiphyte
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A plant growing on, but not parasitic on, another plant (often loosely applied to plants, such as orchids, that grow on vertical rock faces). Compare parasite, saprophyte.

2803. epiphytotic
Definition:

A virulent, widespread disease in a plant population. Often called an epidemic.

2804. episome
Definition:

DNA in a bacterium that is not part of the bacterium’s chromosomes, so that it replicates separately and can have a different number of copies. Plasmids are an example.

2805. epistasis (epistatic)
Definition:

The condition where one gene suppresses the expression of another gene (and therefore whatever phenotype it is responsible for), when the two genes are not alternate alleles of the same phenotype. The gene which does the suppressing is called the epistatic gene.

2806. epistatic gene
Definition:

A gene which suppresses another gene when the two are not alternate alleles.

2807. epistaxis
Definition:

This is the medical term for a nose bleed.

2808. epithelium (epithelial)
Definition:

The covering of an organism or an organ. The layer(s) of cells between the organism or its tissues or organs and the environment. Examples include the skin cells, the inner linings of the lungs and the digestive tract, etc.

2809. epitope
Definition:

The particular site within a macromolecule to which a specific antibody binds.

2810. Epstein-Barr virus (mononucleosis)
Definition:

A virus in the family Herpesviridae which infects humans. It causes infectious mononucleosis, which is characterized by debility, fever, sore throat, enlarged lymph nodes, and an increase in white blood cell count. This virus is transmitted mainly via saliva and is associated with carcinomas of the nasal passages and throat and with Burkitt's lymphoma.

2811. equatorial plate
Definition:

1. The plate or plane along which the chromosomes align during metaphase (an intermediate stage of mitosis or meiosis).
2. An unconnected cytoplasmic membrane which forms in the middle of a cell during early cytokinesis, when the cell is about to divide into two daughter cells.

2812. equilateral
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of stamens, with anthers regularly spaced around the style.

2813. equilibrium centrifugation
Definition:

A type of density gradient centrifugation used to separate proteins or nucleic acids from a mixture.

2814. equilibrium potential
Definition:

The membrane potential at which a particular type of ion or other particle does not diffuse through the membrane in either direction.

2815. equitant
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of leaves, folded in half along the midline so that the adaxial surface disappears, and overlapping the edges of a similarly folded leaf on the opposite side of the stem.

2816. Erb's palsy
Author: Guo Li
Definition:

Erb's palsy is an injury to the upper brachial plexus (mainly the fifth and sixth cervical roots) related to birth trauma of newborns. Its occurrence is about 0.1 percent in spontaneous delivery, 1.2 percent in breech delivery, and 1.3 percent in forceps delivery. The result is partial paralysis of the muscles of the shoulder and flexors of the elbow such that the arm hangs at the side and internally rotated at the shoulder.

2817. erb-a
Definition:

One of two oncogenes (proto-cancer gene) found in the avian erythroblastosis retrovirus (a retrovirus which affects red blood cell formation in birds). It is incredibly similar to a gene which codes for the receptor protein that recognizes hormones from the thyroid gland for the cell.

2818. erb-b
Definition:

One of two oncogenes (proto-cancer gene) found in the avian erythroblastosis retrovirus (a retrovirus which affects red blood cell formation in birds). It is incredibly similar to a gene which codes for the receptor protein that recognizes signals from the epidermal growth factor (EFG) for the cell.

2819. ERCP (endoscopic retrograde cholangiopancreatography)
Author: Guo Li
Definition:

In this procedure, a fiberoptic endoscope is passed through the oral pharynx, esophagus, stomach, into the duodenum. A catheter is passed through the endoscope and canulates the Ampulla of Vater, the bile duct and the pancreatic duct. This procedure can identify gallstones and tumors.

2820. erectile impotence
Author: Guo Li
Definition:

Erectile impotence is the failure of penile erection under any conditions. This includes failure of penile tumescence (swelling with accumulation of blood in the penile tissues) occurring during sleep often in association with rapid eye movement (REM) episodes. The decrease of penile tumescence with REM sleep has been reported to be associated with aging.

2821. ergon
Definition:

A unit used to measure/represent the stability of a gene over the lifetime of a given organism. It is a function of the ratio of the adenine-thymine to the guanine-cytosine content of the gene, and is evidenced by the continual physical expression of the trait coded by the gene.

2822. ergot
Definition:

A disease of cereal plants (rye, wheat, etc.) caused by the fungus Claviceps purpurea; this fungus produces toxic alkaloids that, if ingested, cause symptoms such as hallucinations, severe gastrointestinal upset, a burning sensation in the limbs and extremities (a.k.a. Saint Anthony's Fire) and a form of gangrene.

2823. Erlenmeyer flask
Definition:

A piece of chemistry laboratory equipment, a container often made of glass, which has a narrow cylindrical mouth and a cone-shaped main body that ends in a wide, flat bottom. It may also have a smaller straight tube-shaped opening from the side of the cylindrical part, where tubes can be attached.

2824. erosion
Author:
Definition:

1. The wearing away of the earth's surface by natural forces, such as water, wind and ice.
2. The loosening and transportation of rock and soil debris by wind, rain, or running water.
3. Wearing away of land by physical and chemical action in moving water or air.

2825. error-prone repair (SOS repair)
Definition:

A type of DNA repair which occurs when both nucleotides in a base pair are missing, such that it is not possible to maintain accuracy. In general, the repair proteins replace the missing nucleotides randomly. The idea is that "bad" DNA is better than no DNA at all.

2826. erysipelas
Author: Guo Li
Definition:

Erysipelas is a streptococcal infection of the dermis layer of the face.

2827. erythema
Definition:

General term for redness of the skin due to capillary congestion; can be caused by anything from blushing to contact with a skin irritant to radiation damage.

2828. erythema multiforme
Author: Guo Li
Definition:

Erythema multiforme is an acute inflammatory condition of the skin presenting in various types: urticarial, erythematous macular, papular, vesicular, and bullous. Although the exact cause is unknown, many precipitating factors are identified: infection, vaccination, x-ray therapy, certain medications, and pregnancy.

2829. erythroblast
Definition:

A stem cell in bone marrow that gives rise to red blood cells.

2830. erythroblastosis fetalis
Definition:

A type of anemia which can occur in newborns that have Rh⁺ blood and which are born to mothers with Rh^- blood (see Rh factor). Symptoms include lots of erythroblast cells which are circulating in the blood instead of being within bone marrow, liver and spleen enlargement, and edema (tissue swelling due to excessive fluid).

2831. erythroblastosis fetalis
Author: Guo Li
Definition:

Erythroblastosis fetalis is the condition in which a pregnant women produces an antibody (IgG) to the red blood cells of the fetus she is carrying, which causes the destruction of her fetus' red blood cells. This condition is worse in successive at-risk pregnancies. The antigens could be Rh (most commonly RhD), Kell, Duffy, Lutheran, and Kidd. The mother whose pregnancy is at risk is negative for these antigens.

2832. erythrocyte (red blood cell, RBC)
Image: red blood cell
Definition:

A red blood cell; erythrocytes carry oxygen in the blood via hemoglobin. RBCs are disk-shaped and indented on both sides and are about 7 micrometers in diameter. A red blood cell lives about 120 days.

2833. erythrocyte ghost
Definition:

A red blood cell that has had its contents removed and replaced with drugs and other bioactive chemicals to be delivered to target cells. A type of delivery system.

2834. erythrocyte sedimentation rate (ESR)
Author: Guo Li
Definition:

ESR is elevated in inflammation due to many clinical conditions such as tumor, infections, rheumatoid arthritis. As such, it is a non-specific test. However, it is useful for monitoring the progression of the disease. With more specific tests available, ESR is used less often now.

2835. erythromycin
Image: View the chemical structure
Definition:

An antibiotic that disrupts bacterial protein synthesis by binding to their ribosomes and inhibiting translocation.

2836. erythropoesis
Definition:

The process of turning erythroblasts (bone marrow stem cells) into erythrocytes (red blood cells) within the bone marrow.

2837. erythropoetin
Definition:

A glycoprotein (a molecule combining sugar and protein) that induces erythropoesis (the making of red blood cells in the bone marrow). It is made by the kidneys.

2838. erythropoiesis
Author: Guo Li
Definition:

Erythropoiesis is the process of red blood cell production (which occurs in red bone marrow).

2839. erythropoietin
Author: Guo Li
Definition:

Erythropoietin is a hormone secreted by certain cells in the kidney in response to low oxygen levels. It stimulates red blood cell production (which occurs in bone marrow).

2840. escapement
Author:
Definition:

That portion of an anadromous fish population that escapes the commercial and recreational fisheries and reaches the freshwater spawning grounds.

2841. eschar
Definition:

In medical terminology, this is a dry scab that forms on skin that has been burned or exposed to corrosive agents.

2842. esophagitis
Author: PharmInfoNet
Definition:

Inflammation of the esophagus.

2843. esophagitis
Definition:

Inflammation of the esophagus.

2844. esophagus (adj. esophageal)
Definition:

The tube-like upper portion of the digestive tract which carries food and fluid from the mouth to the stomach.

2845. esotropia
Definition:

This is a misalignment of the eye in which the eye is turned inward.

2846. essential amino acid
Definition:

Any amino acid that can't be synthesized by an organism and must be taken in as a nutrient; in humans, about half of the 20 amino acids we use for growth and metabolism are essential.

2847. essential fatty acid
Definition:

Any polyunsaturated fatty acid involved in human physiologic processes that is synthesized by plants but not by the human body and is therefore a dietary requirement.

2848. essential gene
Definition:

Any gene that, if it doesn't work correctly, kills the organism.

2849. EST
Definition:

Expressed Sequence Tag. See sequence tagged site.

2850. established cell line
Definition:

A stable culture of cells that can be maintained indefinitely. A lineage of cells that has become immortalized.

2851. ester
Definition: