The gene that codes for the variable region on an immunoglobulin chain.

2. V weir
Author:
Definition:

A dam shaped like a "V" pointing upstream, with the ends of the "V" buried into the stream banks at a 45-degree angle.

3. V-notch
Author:
Definition:

1. A narrow, steep-sided ravine or valley with V-shaped cross-section whose bottom usually contains a watercourse.
2. A type of weir containing a V-shaped notch used for gauging discharge in small streams.

4. vaccination
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Artificial introduction of a killed or attenuated pathogen to promot protective immunity. See vaccine.

5. vaccine
Author: Susan A.Hagedorn
Definition:

A preparation of dead or weakened pathogens, or of derived antigenic determinants, that is used to induce formation of antibodies or immunity against the pathogen.

6. Vaccinia (cowpox virus)
Author: Susan A.Hagedorn
Definition:

Vaccinia is the cowpox virus used to vaccinate against smallpox and, experimentally, as a carrier of genes for antigenic determinants cloned from other disease organisms.

7. vaccuum fermentation
Definition:

A system for producing ethanol (grain alcohol) and other volatile fermentation products; in this process, fermentation occurs continuously under reduced pressure, which lets the volatile product leave the cycle as an exhaust gas, which is then collected in a separate chamber.

8. vacuole
Definition:

A large, fluid-filled compartment in the cytoplasm of a plant cell or a smaller vesicle (a compartment that can involve cellular secretion, storage or nutrient uptake) in the cytoplasm of any eukaryotic cell.

9. vacuum extractor
Author: Guo Li
Definition:

A vacuum extractor is an instrument to assist the delivery of babies. A hand-held pump produces low vacuum which is applied to a suction cup attached to the exposed fetal head. Traction is applied to the fetal head to assist each contraction. The current trend for instrument assisted delivery is toward less and less use of forceps. Many more practioners feel that Caesarean sections should be performed in place of high and mid forceps and vacuum extractor should be used instead of low forceps. The slightly elevated scalp from the use of the vacuum is called caput succedaneum; it will resolve in 48 hours.

10. vacuum pan
Definition:

A device for growing crystals from solutions by gradually lowering the pressure within the sealed container holding the liquid.

11. vagal
Author: PharmInfoNet
Definition:

Pertaining to the vagus nerve, which supplies sensory connections to the ear, tongue, and pharynx.

12. vagile
Definition:

Showing an ability or tendency to change or adapt to new situations; in ecological terms, this refers to an organism that changes its location or distribution over time.

13. vagina
Author: Fertilitext
Definition:

The female organ of sexual intercourse; the birth canal.

14. vagina
Author: Guo Li
Definition:

The vagina is part of the internal female genitalia. Anterior to the vagina is the urinary bladder and posterior to the vagina is the rectum. The vaginal mucosa is lined with stratified epithelium.

15. vaginitis
Author: Fertilitext
Definition:

Inflammation of the vagina.

16. vagotomy
Author: Guo Li
Definition:

Vagotomy is surgery to interrupt the branches of vagus nerve near the stomach. This is a procedure for the treatment of stomach and duodenal ulcers. Often, pyloroplasty (surgery on the valve leading from the stomach to the intestines) is performed at the same time to improve the emptying of the stomach.

17. vagus nerve
Definition:

The major nerve that provides connections to the ear, pharynx and tongue.

18. vagus nerve (cranial nerve X)
Author: Guo Li
Definition:

The vagus nerve is located near the stomach and consists of:

1. motor fibers to the muscles of the soft palate and pharynx;
2. parasympathetic fibers to the thoracic and abdominal viscera.
3. somatic sensory fibers
4. visceral sensory fibers to the pharynx, larynx, trachea, esophagus, and the thoracic and abdominal viscera.

19. valence
Definition:

1. Biochemistry: The number of binding sites on a molecule.
    
2. Chemistry: A number which reflects an element's ability to combine with other elements
    
3. Immunology:The number of antigen binding sites an antibody has, or the number of antigenic determinants an antigen has

20. valgus
Author: Guo Li
Definition:

Valgus is a medical term meaning bending or twisting outward.

21. valine
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     pI      Water Solubility (30deg C)
2.32   9.62    5.97              7

22. valproic acid (Depakene, Depakote, Valproate, Valrelease)
Definition:

This drug is used to treat seizures. It may cause liver damage and has side effects such as drowsiness, nausea, and hair loss.

23. Valsalva's maneuver
Author: Guo Li
Definition:

Valsalva's maneuver is forced expiration against a closed glottis. It triggers a series of physiologic responses the result of which is bradycardia and drop in arterial blood pressure. In the elderly micturition or defecation can cause syncope because of the circulatory changes as seen in the Valsalva's maneuver.

24. valvate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Describes sepals or petals in a bud which meet edge to edge, but don't overlap. Compare imbricate.

25. valve
Definition:

1. A device that controls the flow of a fluid through a pipe.
2. One shell of a double shelled mollusc such as a clam or oyster.
3. In botany terminology, a portion of an organ that has fragmented; of a capsule, the teeth like portions into which the dehiscing part of the pericarp splits at maturity.

26. valve
Author: Guo Li
Definition:

A valve is a membranous fold in a hollow organ to allow fluid to flow in one direction only.

27. VAMP
Definition:

An acronym for a chemotherapy treatment made up of the drugs vincristine, amethopterin, 6-mercaptopurine, and prednisone.

28. vancomycin
Image: View the chemical structure
Definition:

An antibiotic that is mainly used to treat severe staph infections that have resisted other drugs. It inhibits peptidoglycan synthesis in Gram-positive bacteria and is synthesized by Streptomyces orientalis, a soil bacterium.

29. vancomycin resistant enterococcus
Author: Jim Sloan
Definition:

A form of intestinal bacteria (formerly classed under streptococcus faecalis) which is not sensitive to the "big gun" antibiotic, vancomycin. This organism is usually only fatal in those who are, for reasons of age or infirmity, immunosuppressed. The pathology of the illness is exacerbated when hemosepsis (blood-stream infection) develops.

30. vapor pressure (equilibrium vapor pressure, volatility)
Definition:

The amount of pressure which is exerted by the vapor phase of a liquid that has undergone some evaporation. When the rate of evaporation of the liquid into the vapor phase and the rate of condensation of the vapor back into the liquid phase are equal, the amount of pressure is called the "equilibrium vapor pressure." A liquid which has no measurable vapor pressure (and barely evaporates) is "nonvolatile." Vapor pressure (and volatility) increases with increasing temperature.

31. variable region (V region)
Definition:

The N-terminal half of light chains and the Fd fragments of heavy chains in immunoglobulin molecules.

32. variable surface glycoprotein (variant surface glycoprotein, VSG)
Author: Susan A.Hagedorn
Definition:

One of a battery of antigenic determinants expressed by a microorganism to elude immune detection.

33. variation
Author: Susan A.Hagedorn
Definition:

Differences in the frequency of genes and traits among individual organisms within a population.

34. varicocele
Author: Fertilitext
Definition:

Varicose veins in the scrotum.

35. varicose vein
Author: Guo Li
Definition:

A varicose vein is a peripheral vein that is dilated (abnormally expanded), tortuous (twisted), and thick-walled. Varicose veins are often found in the lower extremities. Both increased venous pressure, as from heart failure or vena cava compression due to pregnancy, resulting in the incompetence of the valves of the veins, as well as weakened vessel wall of the veins may be contributory to the formation of varicose veins.

36. variety
Definition:

A taxonomic rank below subspecies in botany; varieties are usually the result of selective breeding and diverge from the parent species or subspecies in relatively minor ways.

37. variola virus (smallpox virus)
Definition:

A virus in the genus Orthopoxvirus (family Poxviridae) which causes smallpox, an acute, highly infectious disease that has been all but eradicated by worldwide vaccination programs. Smallpox, which killed millions of people in epidemics through the ages, causes vomiting, chills, fever, and skin eruptions that often cause permanent scars (pocks).

38. varney jar
Definition:

A jar used for anaerobic experiments or processes; the jar is made oxygen-free through phosphorous combustion.

39. varus
Definition:

Varus means bending or twisting inward.

40. vas deferens
Author: Fertilitext
Definition:

The tubes that conduct sperm and testicular fluid to the ejaculatory ducts.

41. vascular
Definition:

1. Refering to veins or arteries.
2. Specialized for conducting fluid; vascular plants.

42. vascular bundle
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A group of specialized cells consisting of xylem and phloem, sometimes separated by a strip of cambium and arranged in different patterns.

43. vascular cambium
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Lateral meristem that forms the secondary tissue and is located between the xylem and phloem.

44. vascular plant
Author:
Definition:

A plant which possesses a well-developed system of conducting tissue to transport water, mineral salts and sugars.

45. vascular surgery
Definition:

A branch of medicine dealing with the use of surgery to diagnose/treat diseases of the blood vessels.

46. vascular-streak dieback
Definition:

A fungal disease of the cacao tree caused by Oncobasidium theobromae.

47. vasculitis
Author: PharmInfoNet
Definition:

The inflammation of a blood vessel.

48. vasculitis
Author: Guo Li
Definition:

Vasculitis is a group of disorders with various causes but which are all characterized by inflammation of the blood vessels.

49. vasectomy
Author: Fertilitext
Definition:

The surgical sterilization of a man by blocking both vas deferens.

50. vasectomy
Author: Guo Li
Definition:

A vasectomy is surgery for the sterilization of male. In this operation, the ductus deferens (also called vas deferens) from either testes is ligated with suture and severed. Sperm can no longer pass to the urethra. Secretions from the seminal vesicle can still be ejaculated.

51. vasoconstriction
Definition:

The constriction, or narrowing, of blood vessels, so that less blood is able to flow through at a time. This can be caused by a chemical substance or by a signal from the nervous system.

52. vasoconstrictor
Definition:

Something which causes vasoconstriction, or the narrowing of blood vessels so that less blood is able to flow through at a time. This can either be a chemical substance or a nerve.

53. vasodilation
Definition:

The expansion of a blood vessel.

54. vasodilator
Author: Guo Li
Definition:

A vasodilator is a substance that relaxes the blood vessels (increases the cross-sectional diameter), often resulting in lowering the blood pressure.

55. vasogram
Author: Fertilitext
Definition:

An X-ray study of the vas deferens.

56. vasopressin (antidiuretic hormone, ADH)
Image: View the chemical structure
Definition:

A peptide hormone that increases blood pressure and the rate at which the kidneys absorb water, and is therefore used as an antidiuretic. It is secreted by the hypothalamus and stored in/released by the posterior pituitary gland.

57. vasopressor
Author: Guo Li
Definition:

A vasopressor is a substance that stimulates the contraction of the blood vessels, often resulting in a higher blood pressure.

58. vasotocin
Definition:

A non-human hormone that increases the permeability of skin and bladder tissue in amphibians.

59. vector
Definition:

1. An organism that spreads an infectious disease; often, this infectious host is not affected by the illness.
2. A DNA molecule that replicates on its own in a host cell and can be used as a vehicle in the laboratory for replicating other types of DNA.

60. vegetation
Author:
Definition:

1. The plant growth forms that generally occupy a given area (e.g., forest, hydrophytes or chaparral).
2. The sum total of macrophytes that occupy a given area.

61. vegetation unit
Author:
Definition:

A patch, grouping or zone of plants evident in overall plant cover, which appears distinct from other such units because of the vegetation's structure and floristic composition; a given unit is typically topographically distinct and typically has a rather uniform soil, except possibly for relatively dry microsites (e.g., tree bases, old tree stumps, mosquito ditch spoil piles and small earth hummocks) in an otherwise wet area or relatively wet microsites (e.g. small depressions) in an otherwise dry area.

62. vegetative fish cover
Author:
Definition:

Vegetation materials, such as algal mats and organic debris, capable of providing protection for fish and other aquatic organisms.

63. vegetative fish cover
Author:
Definition:

Vegetation materials (e.g., algal mats, organic debris) capable of providing protection for fish and other aquatic organisms.

64. vegetative propagation
Author:
Definition:

Propagation without pollination by way of separating vegetative parts (i.e., branches, stolons, buds) from the mother plant and planting them so they take root and grow.

65. vehicle
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Nonliving source of pathogens which infect large numbers of individuals; common vehicles are food and water.

66. vein
Definition:

1. A blood vessel that carries blood to the heart from other parts of the body.
2. In plants, a strand of vascular tissue.

67. velamen
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A water-retaining outer layer of the aerial roots of some epiphytes, especially orchids.

68. velocity
Author:
Definition:

The time rate of motion; the distance traveled divided by the time required to travel that distance.

69. velocity
Author:
Definition:

The time rate of motion; the distance traveled divided by the time required to travel that distance.

70. velum
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A membranous covering; a veil.

71. vena cava
Definition:

One of two major veins which returns oxygen-poor blood from the body to the heart. The superior vena cava enters the right atrium from the top and the inferior vena cava enters the right atrium through the bottom.

72. venation
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The arrangement of veins in a leaf.

73. venipuncture
Author: Guo Li
Definition:

Venipuncture is the insertion of a needle through the wall of a vein. It is a process to obtain blood from a vein or for the provision of intravenous infusion of fluid.

74. venlafaxine (Effexor)
Definition:

This prescription drug is used to treat depression. It is phenethylamine bicyclic derivative, chemically unrelated to tricyclic, tetracyclic and other antidepressant medications. It is believed to work by preventing the reuptake of serotonin, norepinephrine and (to a lesser extent) dopamine.

75. venom
Author: Guo Li
Definition:

Venom is a poisonous substance secreted by an animal (for instance, a snake, spider, scorpion, jellyfish, etc.)

76. venous
Author: Guo Li
Definition:

Pertaining to the veins.

77. ventilation
Author: Guo Li
Definition:

Ventilation is the process of exchange of air in the lungs.

78. ventral
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

1. The "belly" side of an organism.
2. Of a lateral organ in plants, facing towards the subtending main stem; of a thallus, facing towards the substratum.

Compare dorsal.

79. ventricle
Definition:

1. A chamber in the lower part of the heart which pumps blood entering from an atrium (another part of the heart) to some other part of the body. In mammals, there are two ventricles -- one on the left and one on the right.
2. A normally-occuring cavity in any organ.

80. verapamil (Calan, Isoptin)
Definition:

This drug is a calcium ion influx inhibitor (calcium channel blocker) which is used to treat hypertension (high blood pressure), angina (chest pain) and irregularities in the heartbeat.

81. vernal
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Belonging to the spring; appearing or occurring in spring; of the spring season.

82. vernal pools
Author:
Definition:

Perched wetlands which are seasonally to semi-permanently flooded depressions typically occurring on sites with poor drainage.

83. vernation
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The arrangement of unexpanded leaves in a bud. Compare aestivation.

84. verrucologen
Definition:

A tumor-promoting fungal toxin produced by certain species of Penicillium.

85. verrucose
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Covered with wart-like outgrowths.

86. verruculose
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Covered with closely spaced, minute wart-like outgrowths.

87. versatile
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of anthers: swinging freely about the point of attachment to the filament, which is approximately central.

88. vertebra (pl. vertebrae, adj. vertebral)
Author: Guo Li
Definition:

A vertebra is any of the 33 bones which forms the spinal column (vertebral column). Each vertebra has a body and posterior to the body is the vertebral arch which protects the spinal cord. The 33 vertebrae are:

• 7 cervical (neck) vertebrae
• 12 thoracic (upper back) vertebrae
• 5 lumbar (lower back) vertebrae
• sacrum (5 fused vertebrae)
• coccyx (4 fused vertebrae)

89. vertebrate
Definition:

Generally, any animal that has a spine (vertebrae). Specifically, any animal which is taxonomically classified within phylum Chordata and subphylum Vertebrata.

90. vertex
Author: Guo Li
Definition:

The vertex is the top of the head.

91. verticillate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Arranged in one or more whorls.

92. Verticillium
Definition:

Verticillium is a genus of fungi (class Hyphomycetes) that cause many different wilt diseases in plants and infections in humans.

93. vertigo
Definition:

Vertigo is the sensation in which a person feels that he/she is spinning or rotating (or that their surroundings are rotating around them), but the person (and their surroundings) are in fact stationary. Vertigo is often a symptom of inner ear problems that alter a person's sense of equilibrium.

94. vertisols
Author:
Definition:

Shrinking and swelling dark clay soils; most common in Texas.

95. very poorly drained soil
Author:
Definition:

A condition is which water is removed from the soil so slowly that free water remains at or on the surface during most of the growing season.

96. vesicant
Definition:

Refers to a chemical or agent that causes blisters.

97. vesicle
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A bladder-like sac or cavity filled with gas or liquid.

98. vesicle
Definition:

1. A bubble within the cell which is surrounded by cell membrane material and is formed by pinching off part of the cell membrane. Vesicles contain particles which the cell is importing ( endocytosis), or waste products and secretions which the cell is exporting (exocytosis).
2. A small (less than one centimeter in diameter), fluid-filled skin lesion, usually raised; a blister.

99. vesicular stomatitis virus
Definition:

Any virus in the genus Vesiculovirus (family Rhabdoviridae) that causes vesicular stomatitis, an acute disease of pigs and cattle that causes fever and blisters on the mouth and feet. Some forms of this virus can cause a mild, flulike illness in humans.

100. vessel
Author: Guo Li
Definition:

A vessel is a duct or channel that contains fluid; they could be arteries, veins, or lymphatic vessels.

101. vestibular nerve (cranial nerve VIII)
Author: Guo Li
Definition:

The vestibular nerve is a nerve in the head involved in the function of equilibrium (the ability to keep one's balance).

102. vestibular system
Author: PharmInfoNet
Definition:

The organ of the inner ear containing several three semicircular ducts at right angles to one another; helps keep the body balanced.

103. vestigial
Definition:

Refers to an organ or part (e.g., the human appendix) which is greatly reduced from the original ancestral form and is no longer functional.

104. vestiture
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

That which covers a surface, as hairs, scales, etc.

105. veterinarian
Definition:

A professional who is medically trained to diagnose and treat diseases in animals (usually domesticated mammals such as cats, dogs, horses, etc.)

106. veterinary medicine
Definition:

A branch of medicine that deals with the diagnosis and treatment of diseases in animals, usually domesticated animals such as cats, dogs, horses etc., though veterinarians are also employed by zoos.

107. vexar tube
Author:
Definition:

A biodegradable plastic mesh tube used to protect young plants from browsing by deer or other animals.

108. viable
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Alive; able to reproduce.

109. viable count
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Measurement of the concentration of live cells in a microbial population.

110. Vibrio
Definition:

Vibrio is a genus of motile, Gram-negative rod-shaped bacteria (family Vibrionaceae); some species in this genus cause cholera in humans and other diseases in animals.

111. vidarabine (vir-A, adenosine arabinofuranoside)
Definition:

An antiviral agent secreted by the bacterium Streptomyces antibioticus which is used mainly to treat severe herpesvirus infections in people with compromised immune systems.

112. view corridor
Author:
Definition:

1. The line of sight (identified as to height, width, and distance) of an observer looking toward an object of significance to the community (e.g., ridgeline, river, historic building, etc.)
2. The route that directs the viewer's attention.

113. viewshed
Author:
Definition:

The area within view from a defined observation point.

114. vigabatrin (Sabril)
Definition:

This prescription drug is used to treat epilepsy.

115. vigor
Definition:

1. Health; hardiness.
2. A measure of the increase in plant growth or foliage volume through time after planting.

116. villous
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Pubescent; shaggy; covered with fine long hairs, but the hairs not matted.

117. villus (pl. villi)
Author: Guo Li
Definition:

A villus is a small, hair-like vascularized process on the free surface of a membrane. Example:

 

villi of the small intestine : 20 to 40 villi per mm² of mucosa. Each villi is a fingerlike projection, 0.5 to 1 mm long, covered by a single layer of columnar epithelium and containing a network of capillaries and a lymphatic vessel called a lacteal.

118. vimentin
Definition:

A structural protein found in filaments in many eukaryotic cells, particularly muscle cells.

119. vinblastine (Exal, Velban, Velbe)
Image: View the chemical structure
Definition:

A chemotherapeutic alkaloid extract of the common periwinkle Catharantus roesus which is used to treat lymphomas such as Hodgkin's disease.

120. vinca alkaloids
Definition:

Any of several chemotherapeutic alkaloids (such as vinblastine or vincristine) which are found in the common periwinkle Catharantus roseus.

121. vincristine (Oncovin, Kyocristine, Vincosid, Vincrex)
Image: View the chemical structure
Definition:

A chemotherapeutic alkaloid extract of the common periwinkle Catharantus roseus which is used to treat acute lymphocytic leukemia.

122. vindesine (Eldisine, Fildesin)
Image: View the chemical structure
Definition:

A drug, derived from vinblastine, which is used to inhibit the maturation and proliferation of tumor cells (benign or malignant).

123. vinum (vin.)
Definition:

This Latin term, which is frequently used in medicine and pharmacy, means "wine".

124. viomycin
Definition:

A rather toxic antibiotic produced by the bacterium Streptomyces puniceus that, because it can cause nervous system and kidney damage, is only used as a last-ditch treatment for antibiotic-resistant tuberculosis.

125. viral oncogene
Author: Susan A.Hagedorn
Definition:

A viral gene that contributes to cancer development in vertebrate hosts.

126. viral vector
Definition:

Viral DNA that has been modified to serve as a vector for recombinant DNA.

127. viremia
Definition:

The existence of viruses or viral particles in the bloodstream.

128. virino
Definition:

A proposed infectious particle composed of protein and a short sequence of nucleic acids that doesn't code for any proteins.

129. virion
Definition:

A complete virus particle.

130. virogene
Definition:

A viral gene that has become a part of the host's chromosome.

131. viroid
Author: Susan A.Hagedorn
Definition:

A plant pathogen that consists of a naked RNA molecule of approximately 250-350 nucleotides, whose extensive base pairing results in a nearly correct double helix.

132. virologist
Definition:

A virologist is a scientist who studies viruses.

133. virology
Definition:

The scientific study of viruses and viral infections.

134. viroplasm (factory area)
Definition:

An inclusion body in a cell where viral replication/assembly occurs.

135. virucide
Definition:

A chemical that destroys or inactivates a virus.

136. virulence
Author: Susan A.Hagedorn
Definition:

The degree or ability of a pathogenic organism to cause disease.

137. virus
Definition:

1. A noncellular biological entity that can reproduce only within a host cell. Viruses consist of nucleic acid covered by protein; some animal viruses are also surrounded by membrane. Inside the infected cell, the virus uses the synthetic capability of the host to produce progeny virus.
2. A computer program designed to covertly infiltrate and usually damage a computer system, either by repeatedly copying itself so that it takes up needed memory or by erasing, modifying or damaging other files.

138. virusoid
Definition:

A type of small (300-400 nucleotides) single-stranded RNA found in the virions of some plant viruses.

139. viscera (adj. visceral)
Definition:

The internal organs of the abdomen and thorax; specifically, the hollow organs such as intestines, bladder, etc.

140. viscid
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of a surface, sticky; coated with a thick, syrupy secretion.

141. viscosity (adj.: viscose)
Definition:

Viscosity refers to the quality of a liquid being thick and slow-to-flow. For instance, cold honey has a much higher viscosity than water.

142. viscous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of a liquid, not pouring freely; having the consistency of syrup or honey.

143. viscus
Definition:

Any hollow organ, such as the bladder, the stomach, etc.

144. visible light
Definition:

Electromagnetic radiation with wavelengths between 400 nanometers and 750 nanometers. Electromagnetic radiation within this range can be detected by the human eye. Colors depend on the wavelength lengths; a short wavelength (the 400 nm side) looks blue and a long wavelength (the 750 nm side) looks red.

145. visna virus
Definition:

A virus in the subfamily Lentivirinae which causes encephalitis and chronic pneumonitis in sheep.

146. vital capacity (VC)
Author: Guo Li
Definition:

The total lung capacity minus the residual volume.

147. vital signs
Author: Guo Li
Definition:

Vital signs are signs of life. The clinical vital signs usually refer to temperature, pulse and respiration. The term "vital signs absent (VSA)" simply means that after gross inspection the patient does not seem to have signs of life. However it should be stressed that an individual with VSA is not necessarily dead as some drown victims who were initially VSA but later resuscitated without much lasting neurological damage. A review of the criteria for brain death is helpful.

148. vitamin
Definition:

An organic molecule needed in trace amounts for normal growth and metabolic processes; vitamins usually serve as components of coenzymes.

149. vitamin A (retinol, retinoic acid, antixerophthalmic vitamin)
Image: View the chemical structure
Definition:

Any chemical relative of retinol; this vitamin is the precursor of visual pigments and is vital for the differentiation of epithelial tissues. It is thought to have anticancer properties and is used to treat skin problems such as acne, wrinkling and icthyosis. This vitamin is found in liver oils and is synthesized from carotenoids.

150. vitamin B1 (thiamine)
Image: View the chemical structure
Definition:

A water-soluble vitamin the body needs to make enzymes to break down carbohydrates. It is found in foods such as beans, green vegetables, egg yolk, liver, corn, and brown rice.

151. vitamin B12 (cobalamine)
Definition:

This ring-shaped, cobalt-containing vitamin is a crucial part of the entry of amino acids and fatty acids into the Krebs cycle. It is the only biomolecule known to have a carbon-metal bond.

152. vitamin B2 (riboflavin, lactoflavin)
Image: View the chemical structure
Definition:

A water-soluble vitamin that serves as a hydrogen carrier in coenzymes involved in oxidation-reduction metabolic processes.

153. vitamin B3 (pantothenic acid)
Image: View the chemical structure
Definition:

A vitamin found in all human cells which is a constituent of coenzyme A; it is a vital nutrient for some animal species, but humans don't seem to show any ill effects from a dietary deficiency of this vitamin.

154. vitamin B6 (pyridoxine, pyridoxal phosphate)
Image: View the chemical structure
Definition:

Any of the various derivatives of pyroxidine; this water-soluble vitamin is a critical coenzyme in the metabolism of amino acids. It is found in most foods, such as meats, liver, vegetables, whole-grain cereals and egg yolks.

155. vitamin B7 (niacin, nicotinic acid)
Image: View the chemical structure
Definition:

This vitamin is necessary for the synthesis of various enzymes and acts to reduce blood cholesterol. A deficiency in this vitamin causes pellagra, which is characterized by dermatitis, diarrhea, and inflammation of the mucous membranes.

156. vitamin C (ascorbic acid)
Image: View the chemical structure
Definition:

An important vitamin that the body needs to form collagen, a protein that makes up connective tissues. Collagen formed without ascorbic acid is structurally unsound, thus producing the skin lesions associated with the nutritional disease scurvy.

157. vitamin D
Image: View the chemical structure
Definition:

This steroid vitamin is needed for calcium metabolism, and is found in egg yolk, fatty fish and enriched milk, but, since it is synthesized in the skin when an individual is exposed to sunlight, it isn't normally needed in the diet. It is used to treat rickets, a nutritional disease that causes poor bone growth in children.

158. vitamin E (tocopherol)
Image: View the chemical structure
Definition:

Any of eight antioxidant, fat-soluble compounds found in vegetable oils. This vitamin is necessary for muscle and red blood cell development and normal reproduction. Deficiency in this vitamin causes excessively dry skin in some individuals.

159. vitamin K
Image: View the chemical structure
Definition:

A fat-soluble vitamin needed to synthesize blood-clotting factors such as prothrombin; it is synthesized by certain harmless bacteria that normally live in the human intestine.

160. vitellin
Definition:

A phosphoprotein in egg yolk.

161. vitiligo
Author: Guo Li
Definition:

Vitiligo is the condition of having abnormally white or discolored areas on the skin.

162. vitreous humor
Author: Guo Li
Definition:

The vitreous humor is the gelatinous substance that fills the cavity behind the lens of the eye

163. vivax malaria (benign tertian malaria)
Definition:

A type of malaria caused by the protozoan Plasmodium vivax; it is the most common form of the disease, is rarely fatal but is the most difficult to cure, and is characterized by fevers that typically occur every other day.

164. viviparous
Definition:

1. Describes an animal that gives birth to live offspring (as opposed to laying eggs).

2. Describes seeds or fruit which sprout before they fall from the parent plant.

165. viviparous
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

1. Producing young alive rather than in eggs, as in most mammals.
2. Multiplying by vegetative means such as buds or bulbils in the position of flowers.

166. vivisection
Definition:

To dissect a live animal; this is done to observe functioning body systems (such as to observe the effects of certain stimulants or depressants on a beating heart). The animal is rendered unconscious before the vivisection is done.

167. VLSI
Definition:

Very large-scale integration allowing over 100,000 transistors on a chip.

168. Vmax
Definition:

The maximum speed at which an enzymatic reaction can go when the binding site is totally saturated with substrate.

169. volume loading rate
Definition:

The rate of raw materials put into a fermenter or aerobic digester, expressed in terms of material weight per unit volume per unit time.

170. Volvox
Definition:

Volvox is a genus of green, flagellated aquatic algae that exist in spherical colonies.

171. volvulus
Author: Guo Li
Definition:

This is the twisting of bowels, causing obstruction. Delayed treatment of a volvulus may lead to perforation of the bowel.

172. vomiting (regurgitation)
Author: Guo Li
Definition:

Vomiting is a reflex integrated in the medulla oblongata. It starts with a sensation of nausea, then closing of the glottis, strong contraction of the abdominal muscles which forces the stomach contents to be ejected as the gastro-esophageal sphincter relaxes.

173. von Gierke's disease (glycogen storage disease, glycogenosis)
Definition:

A congenital disease caused by a metabolic error in which the body deposits an abnormally high amount of glycogen in the kidneys and liver; the disease produces symptoms such as hypoglycemia (low blood sugar) and hyperlipemia (an excess of lipid molecules in the blood, which can lead to problems such as clogged arteries and heart attacks).

174. von Hippel-Lindau disease (retinocerebral angiomatosis)
Definition:

A congenital disease characterized by the development of blood vessel tumors in the retina of the eye and in the brain; lesions and cysts can also develop in the spinal cord, pancreas, kidneys, and other organs.

175. von Recklinghauser's disease (neurofibromatosis, neuromatosis, multiple neurofibromas)
Definition:

This hereditary disease ranges widely in severity, and is characterized by pigmented skin lesions ("cafe-au-lait" spots) which can develop into dense, benign tumors under the skin along peripheral nerves. Disfiguring tumors (neurofibromas) also tend to develop in or on the skull.

176. von Willebrand's disease (pseudohemophilia)
Definition:

This congenital disease, which is caused a deficiency of a blood factor that promotes platelet adhesion, is characterized by prolonged bleeding and poor blood coagulation.

177. vulva
Author: Guo Li
Definition:

The vulva is composed of the female external genital organs, including: the mons pubis, the labia majora, the labia minora, the vestibule of the vagina, the clitoris, the bulb of the vestibule, and the greater vestibular glands.