| d'Herelle phenomenon | The lysis of bacteria by bacteriophage. Synonym: bacteriophagia, d'Herelle phenomenon, Twort phenomenon. (05 Mar 2000) |
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| dip phenomenon | Complete disappearance of ventricular excitability followed by progressive recovery within a few microseconds at the end of excitation; the muscle as a whole repolarises somewhat inhomogeneously, so that this period is one of special sensitivity to exogenous or endogenous stimuli and reentry. (05 Mar 2000) |
| Donath-Landsteiner phenomenon | The haemolysis which results in a sample of blood of a subject of paroxysmal haemoglobinuria when the sample is cooled to around 5캜 and then warmed again. (05 Mar 2000) |
| Doppler phenomenon | <radiobiology> Variation in the frequency of a wave (as measured by an observer) due to relative motion between the observer and the source of the wave. (The observed frequency increases if the source is moving towards the observer and vice versa.) The equation can be found in most optics texts and many introductory physics texts. (09 Oct 1997) |
| Duckworth's phenomenon | Respiratory arrest before cardiac arrest as a result of intracranial disease. (05 Mar 2000) |
| immune adherence phenomenon | A phenomenon manifested by the adherence of antigen-antibody-complement complex to "indicator cells" (microorganisms, platelets, leukocytes, or erythrocytes), the reaction being sensitive and specific for the antigen and antibody in the complex. Synonym: erythrocyte adherence phenomenon, immune adherence phenomenon, red cell adherence phenomenon. (05 Mar 2000) |
| quellung phenomenon | Increase in opacity and visibility of the capsule of capsulated organisms exposed to specific agglutinating anticapsular antibodies. Synonym: Neufeld reaction, quellung phenomenon, quellung reaction, quellung test. Scrotal swelling, the swelling formed after the embryonic genital swellings have fused together, become spherical, and migrated caudally to the base of the penis; just before birth the testis comes to lie within it. Spielmeyer's acute swelling, a form of degeneration of nerve cells in which the cell body and its processes swell and stain palely and diffusely. (05 Mar 2000) |
| on-off phenomenon | A state in the treatment of Parkinson's disease by l-dopa, in which there is a rapid fluctuation of akinetic (off) and choreoathetotic (on) movements. (05 Mar 2000) |
| orbicularis phenomenon | A constriction of both pupils when an effort is made to close eyelids forcibly held apart. A variant of the pupil response to near vision. Synonym: Galassi's pupillary phenomenon, Gifford's reflex, lid-closure reaction, orbicularis phenomenon, orbicularis pupillary reflex, Piltz sign, Westphal's pupillary reflex, Westphal-Piltz phenomenon. (05 Mar 2000) |
| Theobald Smith's phenomenon | A phenomenon observed in guinea pigs that had survived use for diphtheria antitoxin standardization, the animals having been rendered highly susceptible to subsequent inoculation of horse serum. (05 Mar 2000) |
| tibial 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) |
| Ehret's phenomenon | A sudden throb felt by the finger on the brachial artery, as the pressure in the cuff falls during a blood pressure estimation; said to indicate fairly accurately the diastolic pressure. (05 Mar 2000) |
| Ehrlich's phenomenon | The difference between the amount of diphtheria toxin that will exactly neutralise one unit of antitoxin and that which, added to one unit of antitoxin, will leave one lethal dose free is greater than one lethal dose of toxin; i.e., it is necessary to add more than one lethal dose of toxin to a neutral mixture of toxin and antitoxin to make the mixture lethal (the basis of the L+ dose). (05 Mar 2000) |
| toe phenomenon | <clinical sign> Extension of the great toe and abduction of the other toes instead of the normal flexion reflex to plantar stimulation, considered indicative of pyramidal tract involvement ("positive" Babinski). Synonym: Babinski reflex, Babinski's phenomenon, great-toe reflex, paradoxical extensor reflex, toe phenomenon. (05 Mar 2000) |
| tongue phenomenon | <clinical sign> In latent tetany, tapping the tongue causes its depression with a concave dorsum. Synonym: tongue phenomenon. (05 Mar 2000) |