| Weigert-Gram stain | <technique> A stain for bacteria in tissues in which sections are stained in alum-haematoxylin, then in eosin, aniline methyl violet, and Lugol's solution. (05 Mar 2000) |
|---|---|
| half-a-gram stain | <technique> A lab technique used to detect the presence of members from the bacterial family Legionellaceae in samples of sputum. (09 Oct 1997) |
| Stirling's modification of Gram's stain | <technique> A stable aniline-crystal violet stain. (05 Mar 2000) |
| bone scan: falsely negative metastases | <radiology> Anaplastic tumours, reticulum cell sarcoma, renal cell carcinoma, thyroid carcinoma, histiocytosis, neuroblastoma, multiple myeloma (positive scan usually due to recent or impending fracture) (12 Dec 1998) |
| ventilators, negative-pressure | Body ventilators that assist ventilation by applying intermittent subatmospheric pressure around the thorax, abdomen, or airway and periodically expand the chest wall and inflate the lungs. They are relatively simple to operate and do not require tracheostomy. These devices include the tank ventilators ("iron lung"), portalung, pneumowrap, and chest cuirass ("tortoise shell"). (12 Dec 1998) |
| contingent negative variation | An increasing negative shift of the cortical electrical potentials associated with an anticipated response to an expected stimulus. It is an electrical event indicative of a state of readiness or expectancy. (12 Dec 1998) |
| positive-negative pressure breathing | Inflation of the lungs with positive pressure and deflation with negative pressure by an automatic ventilator. (05 Mar 2000) |
| negative | Not affirming the presence of the organism or condition in question (a negative diagnosis). (18 Nov 1997) |
| negative accommodation | The decrease of accommodation that occurs when shifting from near vision to distance vision. (05 Mar 2000) |
| negative afterimage | An afterimage in which the lightness relationship is reversed; if chromatic, it appears in complementary colour. (05 Mar 2000) |
| negative anergy | A reduction of the normal or usual immunologic responses because of unrelated intervening disease. Synonym: non-specific anergy. (05 Mar 2000) |
| negative base excess | A measure of metabolic acidosis, usually predicted from the Siggaard-Andersen nomogram; the amount of strong alkali that would have to be added per unit volume of whole blood to titrate it to pH 7.4 while at 37캜 and at a carbon dioxide pressure of 40 mm Hg. (05 Mar 2000) |
| negative binomial distribution | <epidemiology> A distribution which is parameterised by a mean m and an aggregation parameter k which is large when aggregation is small; in fact as k becomes large, the negative binomial distribution approximates the Poisson distribution. (05 Dec 1998) |
| negative control | Regulation of an enzyme activity by an inhibitor of that enzyme or regulation of a protein by repression of transcription. (05 Mar 2000) |
| negative convergence | The slight divergence of the visual axes when convergence is at rest, as when observing the far point or during sleep. (05 Mar 2000) |