vitamin B (redirected from vitamin B Bc)

vitamin B

n.

1. Vitamin B complex.

2. A member of the vitamin B complex, especially thiamine.

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vitamin B, vitamin B complex

a group of water-soluble substances described separately. Includes biotin, choline, folic acid, niacin, pantothenic acid, pyridoxine, riboflavin, thiamin and vitamin B₁₂ (below). Most domestic animals do not require dietary supplementation if they are fed natural feeds. Artificially prepared feeds are usually supplemented because losses may occur during storage and preparation.

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vitamin B B₁

thiamin.

vitamin B B₂

riboflavin.

vitamin B B₃

the niacin group of B-vitamins, nicotinic acid and nicotinamide.

vitamin B B₆

a group of methylpyridine derivatives that includes pyridoxine, pyridoxamine, pyridoxal.

vitamin B B₇

an uncharacterized promoter of digestion in pigeons, possibly a mixture of compounds; called also vitamin I.

vitamin B B₁₂

a generic term describing all corrinoids with biological activity of cyanocobalamin. Required by all cells for nuclear maturation and cell division but required particularly for erythropoiesis. The vitamin is produced by ruminants who require only cobalt in sufficient quantities in their diet. A nutritional deficiency of the vitamin causes a maturation failure anemia, anorexia and failure to thrive. An inherited defect in absorption of vitamin B₁₂ has been described in Miniature schnauzers. Called also cyanocobalamin. See also hydroxocobalamin.

vitamin B B₁₂ absorption test

measurement of radiolabeled cyanocobalamin excreted in the urine after oral administration (with parenteral administration to saturate the vitamin B₁₂ binding sites). Used as a measure of intestinal absorption and, in humans, the presence of intrinsic factor. Called also Schilling test.

vitamin B B_c

folic acid.

vitamin B B_T

see carnitine.

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neuritis, optic

Inflammation of the optic nerve, which can occur anywhere along its course from the ganglion cells in the retina to the synapse of these cell fibres in the lateral geniculate body. If the inflammation is restricted to the optic nerve head the condition is called papillitis (or intraocular optic neuritis) and if it is located in the orbital portion of the nerve it is called retrobulbar optic neuritis (or orbital optic neuritis).In papillitis the optic nerve head is hyperaemic with blurred margins and slightly oedematous. Haemorrhages and exudates may also appear. In retrobulbar optic neuritis, there are usually no visible signs in the fundus of the eye until the disease has advanced and optic atrophy may appear. However, both types are accompanied by a loss of visual acuity along with a central scotoma and impairment of colour vision. The loss of vision may occur abruptly over a few hours and recovery may be equally rapid but in some patients the loss may be slow. In retrobulbar optic neuritis, there is also pain on movement of the eyes and sometimes tenderness on palpation. The disease is usually unilateral although the second eye may become involved later. It is usually transient and full or partial recovery takes place within weeks. The primary cause of optic neuritis is multiple sclerosis but it may also be associated with severe inflammation of the retina or choroid, vitamin B deficiency, diabetes mellitus, thyroid disease, lactation, toxicity or syphilis. See Devic's disease; papilloedema; Marcus Gunn pupil; Kollner's rule; photostress test.