| PAR | participating provider; passive avoidance reaction; perennial allergic rhinitis; photosynthetically ... |
|---|---|
| PAS | para aminosalicylate; Parent Attitude Scale; patient administration system; patient appointments and... |
| PCR | patient contact record; phosphocreatinine; plasma clearance rate; polymerase chain reaction; post-co... |
| PFAS | performic acid-Schiff [reaction] |
| PK | penetrating keratoplasty; pericardial knock; pharmacokinetics; pig kidney; Prausnitz-Kustner [reacti... |
| Feulgen reaction | <procedure> A specific staining procedure for DNA: mild acid hydrolysis makes the aldehyde group of deoxyribose available to react with Schiff's reagent to give a purple colour. (18 Nov 1997) |
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| fight or flight reaction | The theory advanced by Walter Cannon, that in the autonomic nervous system and the effectors connected with it, the organism in situations of danger requiring either fight or flight is provided with a check-and-drive mechanism that puts it in readiness to meet emergencies with undivided energy output. Also known as the emergency theory. (05 Mar 2000) |
| first-order reaction | A reaction the rate of which is proportional to the concentration of the single substance undergoing change; radioactive decay is a first-order process, defined by the equation -(dN/dt)=kN, where N is the number of atoms subject to decay (reaction), t is time, and k is the first-order decay (reaction) constant, i.e., the fraction of all atoms decaying per unit of time. See: decay constant, order. (05 Mar 2000) |
| fixation reaction | <immunology> Binding of complement as a result of its interaction with immune complexes (the classical pathway) or particular surfaces (alternative pathway). (18 Nov 1997) |
| flocculation reaction | A form of precipitin reaction in which precipitation occurs over a narrow range of antigen-antibody ratio, due chiefly to peculiarities of the antibody (precipitin). (05 Mar 2000) |
| focal reaction | A reaction which occurs at the point of entrance of an infecting organism or of an injection, as in the Arthus phenomenon. Synonym: local reaction. (05 Mar 2000) |
| Folin's reaction | The reaction of amino acids in alkaline solution with 1,2-naphthoquinone-4-sulfonate (Folin's reagent) to yield a red colour; useful for quantitative assay. Synonym: Folin's reagent. (05 Mar 2000) |
| foreign-body reaction | Chronic inflammation and granuloma formation around irritating foreign bodies. (12 Dec 1998) |
| Forssman antigen-antibody reaction | The combination of Forssman antibody with heterogenetic antigen of the Forssman type, as in the agglutination of sheep erythrocytes (which contain Forssman antigen) by serum from a person with infectious mononucleosis which contains Forssman antibody. Synonym: Forssman reaction. (05 Mar 2000) |
| Forssman reaction | The combination of Forssman antibody with heterogenetic antigen of the Forssman type, as in the agglutination of sheep erythrocytes (which contain Forssman antigen) by serum from a person with infectious mononucleosis which contains Forssman antibody. Synonym: Forssman reaction. (05 Mar 2000) |
| late reaction | A local or generalised response that begins 24 to 48 hours after exposure to an antigen. See: cell-mediated reaction. Synonym: contact hypersensitivity, delayed hypersensitivity, late reaction, tuberculin-type hypersensitivity. (05 Mar 2000) |
| fragment reaction | A reaction used to assay the activity of peptidyl transferase. (05 Mar 2000) |
| Frei-Hoffmann reaction | <investigation> A clinical test where dead disease-causing microbes are injected into the skin to see if this causes a skin reaction. It indicates whether the patient is infected with the the injected microbe and is not used commonly. (07 Apr 1998) |
| fright reaction | After section and degeneration of the facial nerve of an animal, the denervated facial muscles contract if the animal is frightened or becomes angry; due to the release of acetylcholine into the circulation. (05 Mar 2000) |
| lengthening reaction | In the decerebrate animal, the rather sudden relaxation with lengthening of the extensor muscles when a limb is passively flexed; associated with clasp-knife spasticity. (05 Mar 2000) |