| P ring | <microbiology> One of the bushes at the base of the flagellum of gram-negative bacteria, anchoring it in the peptidoglycan layer of the cells wall. Lies below the L ring. (18 Nov 1997) |
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| P site | <molecular biology> The peptidyl tRNA binding site on the ribosome, the one to which the growing chain is attached, the incoming aminoacyl tRNA attaches to the A site. (18 Nov 1997) |
| P wave | The first complex of the electrocardiogram, representing depolarisation of the atria; if the P wave is retrograde or ectopic in axis or form, it is labelled P'. (05 Mar 2000) |
| P with a subscript for the ion | <abbreviation> Permeability constant. (05 Mar 2000) |
| p,p'-dichlorodiphenyl methyl carbinol | A synthetic compound found effective as a miticide. Acronym: DMC (05 Mar 2000) |
| P-A conduction time | See: atrioventricular conduction. (05 Mar 2000) |
| P-A interval | The time from onset of the P wave to the initial rapid deflection of the A wave in the His bundle electrogram (normally 25-45 msec); it represents the intra-atrial conduction time. (05 Mar 2000) |
| p-aminoazobenzene | <chemical> Used in the form of its salts as a dye and as an intermediate in manufacture of acid yellow, diazo dyes, and indulines. Pharmacological action: dyes. Chemical name: Benzenamine, 4-(phenylazo)- (12 Dec 1998) |
| p-aminobenzoic acid | A factor in the vitamin B complex, a part of all folic acids and required for its formation; neutralises the bacteriostatic effects of the sulfonamides since it furnishes an essential growth factor for bacteria, the utilization with which the sulfonamides interfere; used as an ultraviolet screen in lotions and creams. Synonym: paraaminobenzoic acid, vitamin Bx. Acronym: PABA (05 Mar 2000) |
| p-aminohippurate clearance | A good measure of renal plasma flow, which it slightly underestimates; when a low plasma concentration of p-aminohippurate (PAH) is maintained by intravenous infusion, the kidney extracts and excretes almost all of the PAH from the plasma before it reaches the renal vein. (05 Mar 2000) |
| p-aminohippuric acid | <chemical> N-(4-aminobenzoyl)glycine. A diagnostic aid used as the sodium salt in renal function tests. Chemical name: Glycine, N-(4-aminobenzoyl)- (12 Dec 1998) |
| p-aminohippuric acid synthase | <enzyme> An enzyme in the liver that catalyses the synthesis of p-aminohippuric acid from p-aminobenzoic acid (or the CoA-derivative) and glycine. It may be identical with glycine acyltransferase. Acronym: PAH (05 Mar 2000) |
| p-aminopropiophenone | <drug> An antidote for cyanide poisoning. Chemical name: 1-(4-Aminophenyl)-1-propanone Acronym: PAPP (21 Jun 2000) |
| p-aminosalicylic acid | <chemical> 4-amino-2-hydroxybenzoic acid. An antitubercular agent often administered in association with isoniazid. The sodium salt of the drug is better tolerated than the free acid. Pharmacological action: antitubercular agents. Chemical name: Benzoic acid, 4-amino-2-hydroxy- (12 Dec 1998) |
| p-azobenzenearsonate | <chemical> 4,4'-azodibenzenearsonic acid. A hapten capable of eliciting both antibody formation and delayed hypersensitivity when bound to aromatic amino acids, polypeptides or proteins. It is used as an immunologic research tool. Chemical name: Arsonic acid, (azodi-4,1-phenylene)bis- (12 Dec 1998) |