| Purkinje's phenomenon | <ophthalmology> In the light-adapted eye, the region of maximal brightness is in the yellow; in the dark-adapted eye, the region of maximal brightness is in the green. Synonym: Purkinje effect, Purkinje shift. (05 Mar 2000) |
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| hunting phenomenon | An unusual reaction of digital blood vessels exposed to cold; vasoconstriction is alternated with vasodilation in irregular repeated sequences, in an apparent hunting of equilibrium of skin temperature. Synonym: hunting phenomenon. (05 Mar 2000) |
| Hunt's paradoxical phenomenon | In dystonia musculorum deformans, if an attempt is made at plantar flexion of the foot when the foot is in dorsal spasm the only response is an increase of the extensor, or dorsal, spasm; if, however, the patient is told to extend the foot which is already in a state of strong dorsal flexion, there will be a sudden movement of plantar flexion; the same phenomenon, mutatis mutandis, is observed when there is a condition of strong plantar flexion. (05 Mar 2000) |
| Sherrington phenomenon | After the muscles of the leg have been deprived of their motor innervation by sectioning the ventral roots containing fibres for the sciatic nerve, and allowing time for the degeneration of the fibres to occur, stimulation of the sciatic nerve causes slow contraction of the muscles. (05 Mar 2000) |
| shot-silk phenomenon | The appearance of numerous wavelike, glistening reflexes, like the shimmer of silk, observed sometimes in the retina of a young person. Synonym: shot-silk phenomenon, shot-silk reflex. (05 Mar 2000) |
| shwartzman phenomenon | A two-stage reaction in which a first encounter with endotoxin produces intravascular fibrin thrombi whose clearance results in reticuloendothelial blockade which prevents the clearance of thrombi caused by a second encounter with endotoxin, resulting in tissue necrosis and/or haemorrhage. In pregnancy gram-negative septicaemia during delivery or abortion may serve as the first or provocative encounter. The phenomenon is non-immunologic and is known to occur only in rabbits and man. (12 Dec 1998) |
| Somogyi phenomenon | A rebound phenomenon of reactive hyperglycaemia following a period of relative hypoglycaemia, which may be subclinical and difficult to detect; the hyperglycaemia induces use of more insulin, thus aggravating the problem. Synonym: posthypoglycaemic hyperglycaemia. (05 Mar 2000) |
| Soret's phenomenon | In a solution kept in a long, upright tube at room temperature, the upper part, being the warmer, is also the more concentrated. (05 Mar 2000) |
| sparing phenomenon | The manner in which a nonessential nutritive component, by its presence in the diet, lowers the dietary requirement for an essential component; thus, nonessential l-cysteine spares essential l-methionine and nonessential l-tyrosine spares essential l-phenylalanine. Synonym: sparing phenomenon. (05 Mar 2000) |
| Splendore-Hoeppli phenomenon | Radiating or annular eosinophilic deposits of host-derived materials, and possibly of parasite antigens, which form around fungi, helminths, or bacterial colonies in tissue. (05 Mar 2000) |
| staircase phenomenon | A phenomenon in cardiac muscle first observed by H.P. Bowditch; if a number of stimuli of the same intensity are sent into the muscle after a quiescent period, the first few contractions of the series show a successive increase in amplitude (strength). Synonym: staircase phenomenon. Origin: Ger. Treppe, staircase (05 Mar 2000) |
| Staub-Traugott phenomenon | The increased rate of removal of loads of glucose given shortly after administration of an initial glucose load. (05 Mar 2000) |
| Negro's phenomenon | A sudden brief halt in usually smooth respiration or other motor activity. Synonym: Negro's phenomenon. (05 Mar 2000) |
| Strassman's phenomenon | In the third stage of labour, failure of placental detachment indicated by transmission of pressure from the fundus uteri to the umbilical vein which becomes engorged; obsolete term. (05 Mar 2000) |
| Strumpell's phenomenon | Dorsal flexion of the great toe, sometimes of the entire foot, in a paralysed limb when the extremity is drawn up against the body, flexing both knee and hip. Synonym: tibial phenomenon. (05 Mar 2000) |