| vitamin A1 alcohol | Vitamin A1alcohol; 2,6,6-trimethyl-1-(9'-hydroxy-3',7'-dimethylnona-1',3',5',7'-tetraenyl)cyclohex-1-ene;a half-carotene bearing the b (or beta-ionone) form of the cyclic end group and a CH2OH at the C-15 position (numbering as in carotenoids) or 9'-position (numbering as a nonyl side chain on a cyclohexene ring); an intermediate in the vision cycle, it also plays a role in growth and differentiation. See: dehydroretinol. Synonym: vitamin A1 alcohol, vitamin A1. Retinol dehydrogenase, an oxidoreductase catalyzing interconversion of retinal and NADH to retinol and NAD+. (05 Mar 2000) |
|---|---|
| vitamin A2 | 3-Dehydroretinol;retinol with an additional double bond in the 3-4 position of the cyclohexane ring. Synonym: vitamin A2. (05 Mar 2000) |
| vitamin A2 aldehyde | 3-Dehydroretinaldehyde;dehydroretinol with -CHO instead of -CH2OH at the terminal carbon of the side chain. Synonym: retinene-2, vitamin A2 aldehyde. (05 Mar 2000) |
| vitamin A aldehyde | <chemical> A carotenoid constituent of visual pigments. It is the oxidised form of retinol which functions as the active component of the visual cycle. It is bound to the protein opsin forming the complex rhodopsin. When stimulated by visible light, the retinal component of the rhodopsin complex undergoes isomerization at the 11-position of the double bond to the cis-form; this is reversed in "dark" reactions to return to the native trans-configuration. Chemical name: Retinal (03 Jul 1999) |
| vitamin a deficiency | A nutritional condition produced by a deficiency of vitamin a in the diet, characterised by night blindness and other ocular manifestations such as dryness of the conjunctiva and later of the cornea (xerophthalmia). Vitamin a deficiency is a very common problem worldwide, particularly in developing countries as a consequence of famine or shortages of vitamin a-rich foods. In the united states it is found among the urban poor, the elderly, alcoholics, and patients with malabsorption. (12 Dec 1998) |
| vitamin A unit | The specific biologic activity of 0.3 ug of vitamin A (alcohol form). See: Sherman-Munsell unit. (05 Mar 2000) |
| vitamin B | A group of water-soluble substances originally considered as one vitamin. (05 Mar 2000) |
| vitamin B1 | <biochemistry> A member of the water-soluble B vitamin group, necessary for energy production and carbohydrate metabolism. Deficiency is known as beriberi. (27 Sep 1997) |
| vitamin B12 | <biochemistry> Member of the water soluble B vitamin group, important in the proper function of the nervous system and important in proper carbohydrate, protein and fat metabolism. (27 Sep 1997) |
| vitamin b 12 | <chemical> A cobalt-containing coordination compound produced by intestinal micro-organisms and found also in soil and water. Higher plants do not concentrate vitamin b 12 from the soil and so are a poor source of the substance as compared with animal tissues. Pharmacological action: haematinics. Chemical name: Vitamin B12 (12 Dec 1998) |
| vitamin B12 absorption test | <investigation> This test measures the amount of vitamin B12 in the urine after ingesting a dose of B12. This test evaluates vitamin B12 absorption. The cells in the stomach produce a substance known as intrinsic factor. This substance combines with B12 to allow absorption in the distal ileum. The patient is given a small dose of radioactive B12 which can then be detected in the patients urine. Pernicious anaemia is the clinical result of B12 deficiency. Conditions that can result in an abnormal Schilling test include: deficiency of intrinsic factor, malabsorption or the development of an antibody to intrinsic factor. The Schilling test can be performed with or without administration of intrinsic factor to determine what the underlying cause for pernicious anaemia. Laxative use, renal insufficiency and hypothyroidism can all interfere with the results of this test. (27 Sep 1997) |
| vitamin B12 deficiency | A form of anaemia (low red blood cell counts) that results when the bone marrow fails to produce adequate numbers of red blood cells due to a deficiency in vitamin B12. Intrinsic factor, necessary for normal B12 absorption, may be the underlying cause for B12 deficiency if is not produced in the gastric glands (in the stomach). (27 Sep 1997) |
| vitamin b 12 deficiency | A nutritional condition produced by a deficiency of vitamin b 12 in the diet, characterised by megaloblastic anaemia. Since vitamin b 12 is not present in plants, humans have obtained their supply from animal products, from multivitamin supplements in the form of pills, and as additives to food preparations. A wide variety of neuropsychiatric abnormalities is also seen in vitamin b 12 deficiency and appears to be due to an undefined defect involving myelin synthesis. (12 Dec 1998) |
| vitamin B12 neuropathy | A subacute or chronic disorder of the spinal cord, such as that occurring in certain patients with vitamin B12 deficiency, characterised by a slight to moderate degree of gliosis in association with spongiform degeneration of the posterior and lateral columns. Synonym: combined sclerosis, combined system disease, funicular myelitis, Putnam-Dana syndrome, vitamin B12 neuropathy. (05 Mar 2000) |
| vitamin B12 with intrinsic factor concentrate | A combination of vitamin B12 with suitable preparations of the mucosa of the stomach or intestine of domestic animals used for food by humans. (05 Mar 2000) |