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.
2. 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.
3. da
Definition:
This Latin term, which is frequently used in medicine, means "give".
4. dacryagogue
Author: Guo Li
Definition:
A dacryagogue is an agent that induces tears.
5. 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.
6. dacryocystectomy
Author: Guo Li
Definition:
Dacryocystectomy is surgery for the excision of the walls of the tear sac.
7. dacryocystitis
Author: Guo Li
Definition:
Dacryocystitis is the inflammation of the tear sac which is often associated with bacterial infection and obstruction of the nasolacrimal duct.
8. dacryocystostomy
Author: Guo Li
Definition:
Dacryocystostomy is surgery to create an opening (a drainage) into the tear sac.
9. dactyl
Author: Guo Li
Definition:
Refers to a digit, a finger, or a toe.
10. dactylitis
Author: Guo Li
Definition:
Dactylitis is inflammation of fingers and toes, e.g. as caused by tissue ischemia due to sickle cell anemia.
11. 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.
12. 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.
13. dam
Author:
Definition:
A barrier constructed of earth or man-made materials to hold back the flow of a river. Dams are generally for storage or diversion. Storage dams store water; diversion dams divert water.
14. dam gene
Definition:
15. Danazol (Danocrine)
Author: Fertilitext
Definition:
A synthetic androgen frequently prescribed for endometriosis.
16. 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.
17. 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.
18. 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.
19. 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.
20. day neutral plants
Author: Mirrored from
Dave Sutton's Aquatic Plant
Glossary
Definition:
Plants that flower regardless of day length.
21. 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.
22. de novo pathway
Definition:
A pathway for synthesizing a biomolecule from simple precursor molecules; compare salvage pathway.
23. 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.
24. deadheads
Author:
Definition:
Logs that are not embedded, lodged, or rooted in the stream channel, but are submerged and close to the surface.
25. deadman
Author:
Definition:
A log or block of concrete buried in a streambank that is used as an anchor for a revetment or other structure.
26. deaminase (aminohydrolase, deamidase)
Definition:
An enzyme which removes amino groups from compounds, producing ammonia in the process.
27. deamination
Definition:
The process through which enzymes strip amino groups off biomolecules.
28. 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:
The concept of brain death is now accepted by many jurisdictions as the legal definition of death.
29. death phase
Author: Susan
A.Hagedorn
Definition:
The final growth phase in a culture, during which nutrients have been depleted and cell number decreases.
30. 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.
31. debris
Author:
Definition:
Driftwood and detritus (leaves, trash, etc.) carried or deposited by a stream.
32. debris dams
Author:
Definition:
Detention dams constructed to trap sediment.
33. debris jam (log jam, logjam)
Author:
Definition:
An accumulation of logs and other organic debris which blocks the flow of a stream of water.
34. debris loading
Author:
Definition:
The quantity of debris located within a specific reach of stream channel, due to natural processes or human activities.
35. debris torrent
Author:
Definition:
Deluge of water charged with soil, rock and organic debris down a steep stream channel.
36. 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.
37. 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.
38. decatenation
Definition:
The opposite of catenation.
39. 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.
40. 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.
41. 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.
42. deciduous
Definition:
Refers to a plant (usually a tree or shrub) that sheds its leaves at the end of the growing season
43. decimeter (dm)
Author: Mirrored from
Dave Sutton's Aquatic Plant
Glossary
Definition:
3.973 inches, 10 cm, or 0.1 m.
44. 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.
45. declinate
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
Bent downwards or forwards.
46. decompound
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
More than once compound.
47. 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.
48. decongestant
Author: Guo Li
Definition:
A decongestant is a drug (such as pseudoephedrine) which relieves nasal congestion.
49. 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.
50. 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.
51. decumbent
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
Spreading horizontally but then growing upwards.
52. decurrent
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
Extending downwards beyond the point of insertion.
53. decussate
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
In pairs, with successive pairs borne at right angles to each other.
54. deep fascia
Author: Guo Li
Definition:
This is a membranous layer of connective tissue that covers muscles and other deep body structures.
55. 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.
56. 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.
57. 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.
58. defibrillation
Author: Guo Li
Definition:
Defibrillation is a procedure using an electric current to correct abnormal rhythms of the heart.
59. 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.
60. deflexed
Definition:
Bent downward or outward.
61. 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.
62. 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.
63. degeneration
Author: Guo Li
Definition:
Degeneration is the impairment or worsening of the function of an organ.
64. degradation
Definition:
The destruction of a molecule into its components. The breaking down of large molecules into smaller ones.
65. degradation
Author:
Definition:
66. 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.
67. 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.)
68. dehiscence (adj. dehiscent)
Author: Guo Li
Definition:
Dehiscence is the separation of previously surgically-closed wounds.
69. dehiscent
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
Breaking open at maturity to release the contents.
70. 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.
71. 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.
72. dehydrogenase
Definition:
Any of many enzymes that strip pairs of hydrogen atoms from other molecules.
73. dehydrogenation
Definition:
The removal of one or more hydrogen ions or protons from a molecule. This can be done by a dehydrogenase enzyme.
74. 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".
75. 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.
76. deleterious
Definition:
Harmful.
77. deletion
Author: Mirrored from
Tsute Chen's
Glossary of Microbiology
Definition:
A removal of a portion of a gene.
78. deletion mutation
Definition:
A mutation cause by the removal of one or more nucleotides from a gene or chromosome.
79. 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.
80. 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.
81. delta
Author:
Definition:
82. 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.
83. deltoid
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
Triangular with the sides of about equal length.
84. deme
Definition:
A locally interbreeding group within a geographic population.
85. dementia
Author: The Alzheimer's Association
Definition:
Loss of intellectual functions, (such as thinking, remembering, and reasoning) of sufficient severity to interfere within an individual's daily functioning.
86. 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.
87. Demerol (Meperdine)
Definition:
A prescription narcotic drug that is used to kill pain. Demerol, like other narcotics, is an addictive drug.
88. 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.
89. 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.
90. 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.
91. 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.
92. denatured protein
Definition:
A protein that, because of heat or detergent application, has lost its native conformation.
93. dendric
Author:
Definition:
94. 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).
95. 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.
96. dendroid
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
Tree-like in form but not in size. Compare arborescent.
97. 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.
98. 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.
99. denitrification
Definition:
100. 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.
101. 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).
102. 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.
103. 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.
104. dentate
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
Toothed.
105. denticle
Author: Mirrored from
Dave Sutton's Aquatic Plant
Glossary
Definition:
A small tooth or toothlike projecting point.
106. denticulate
Author: Mirrored from
Jim Croft's Flora of
Australia
Definition:
Finely toothed.
107. dentistry
Definition:
This is a medical profession that deals with the treatment and prevention of diseases of the teeth and gums.
108. 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".
109. 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.
110. deoxynucleoside
Definition:
A molecule composed of a nitrogenous base attached to the five-carbon sugar deoxyribose.
111. 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.
112. 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.
113. 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.
114. depletion
Definition:
In general, the often harmful decrease in the supply of something:
