| white level | <microscopy> Also reference white level. The IEEE scale, or voltage level, of the video picture signal that corresponds to a specified maximum limit for white peaks. (05 Aug 1998) |
|---|---|
| white matter | <anatomy> Brain tissue composed of myelin-coated nerve cell fibres. White matter carries information between the nerve cells in the brain and spinal cord. The inner portion of the cerebrum is composed of white matter. See: grey matter. (13 Nov 1997) |
| white-matter disease | <radiology> Demyelinating (myelinoclastic), destruction of existing myelin, acquired diseases with inflammatory characteristics, includes: MS, PML, encephalomyelitis, also may be due to anoxia, infarct, tumour, radiation dysmyelinating, abnormal myelin formation or maintenance, two groups: primary white-matter diseases: leukodystrophies, involve gray matter: Niemann-Pick, Gaucher, Tay-Sachs (12 Dec 1998) |
| white mercuric precipitate | Used in ointment for the treatment of skin diseases. Synonym: ammoniated mercuric chloride, white mercuric precipitate. (05 Mar 2000) |
| white muscle | <anatomy> A rapid or fast-twitch muscle in which pale large "white" fibres predominate; mitochondria and myoglobin are relatively sparse compared with red muscle; involved in phasic contraction. (05 Mar 2000) |
| white muscle disease | A myodegeneration most frequent in calves and lambs whose dams have been fed during gestation or longer on feeds, especially legumes, grown in certain areas where selenium is either deficient or unavailable in the soil. It has been recorded in many countries. It has been produced experimentally in several species of animals on low-selenium intake. A similar myopathy occurs naturally in goats, deer, foals, and dogs but proof of the aetiology is lacking. (merck veterinary manual, 5th ed) (12 Dec 1998) |
| white mustard | The ripe seeds of Brassica (Sinapis) alba; less pungent than black mustard, but with the same constituents and uses. (05 Mar 2000) |
| white-out syndrome | <syndrome> A psychosis which occurs in Arctic explorers or others similarly exposed to the stimulus deprivation of a snow-clad environment. See: sensory deprivation. (05 Mar 2000) |
| White, Paul Dudley | <person> U.S. Cardiologist, 1886-1973. See: Lee-White method, Wolff-Parkinson-White syndrome. (05 Mar 2000) |
| white piedra | <microbiology> A fungal infection (tinea albigena) caused by the yeast Trichosporon beigelii that forms light-coloured nodules on the beard and mustache. (13 Nov 1997) |
| white pine | The dried inner bark of Pinus strobus, used as an ingredient in cough syrups. (05 Mar 2000) |
| white pitch | A resinous exudation from the spruce fir or Norway spruce, Picea excelsa; has been used as a counterirritant in the form of a plaster. Synonym: white pitch. (05 Mar 2000) |
| white pulp | That part of the spleen that consists of nodules and other lymphatic concentrations. (05 Mar 2000) |
| white pupillary reflex | Reflection from a white mass within the eye giving the appearance of a white pupil. Synonym: leukokoria, white pupillary reflex. Origin: Leuko-white, + G. Kore, pupil (05 Mar 2000) |
| white rami communicantes | Short nerves arising from the initial portion of the ventral primary rami of the thoracic and upper lumbar spinal nerves through which all presynaptic sympathetic nerve fibres must pass to reach the sympathetic trunks; also conveyed by the white rami communicans are visceral afferent (sensory) fibres which were conveyed to the sympathetic trunks in splanchnic nerves. Most fibres conveyed by the white rami communicantes are myelinated. Synonym: rami communicantes nervorum spinalium, communicating branches of spinal nerves. (05 Mar 2000) |