| HCl | hydrogen chloride |
|---|---|
| HDP | hexose diphosphate; high-density polyethylene; hydrogen diphosphonate; hydroxydimethylpyrimidine |
| HF | Hageman factor; haplotype frequency; hard filled [capsule]; hay fever; head of fetus; head forward; ... |
| HVSD | hydrogen-detected ventricular septal defect |
| HX | histiocytosis X; hydrogen exchange; hypophysectomized |
| active centre | The part of a macromolecule at which a substrate or ligand, upon binding, produces biological activity; for an enzyme, this is the catalytic centre, the site on an enzyme that catalyses the reaction. (05 Mar 2000) |
|---|---|
| active congestion | Congestion due to an increased flow of arterial blood to a part. (05 Mar 2000) |
| active electrode | A small electrode whose exciting effect is used to stimulate or record potentials from a localised area. Synonym: exciting electrode, localizing electrode, therapeutic electrode. (05 Mar 2000) |
| active formaldehyde | A hydroxymethyl derivative of tetrahydrofolate or thiamin pyrophosphate, N5,N10-methylenetetrahydrofo late. (05 Mar 2000) |
| active formyl | The formyl group taking part in transformylation reactions with a folic acid derivative in the role of carrier. (05 Mar 2000) |
| active immunity | <immunology> An organisms resistance to disease or infection, developed because the organisms immune system has produced antibodies after an infection or innoculation. (06 May 1997) |
| active immunization | The production of active immunity. (05 Mar 2000) |
| active inflammation | Any inflammation that has a fairly rapid onset, quickly becomes severe, usually manifested for only a few days, but may persist for several days or even a few weeks. Synonym: active inflammation. (05 Mar 2000) |
| active labour | Contractions resulting in progressive effacement and dilation of the cervix. (05 Mar 2000) |
| active length-tension curve | The relationship between active isometric tension and preload (rest length) for a contracting muscle. (05 Mar 2000) |
| active metal | <chemistry> Any very reactive metal, such as magnesium or sodium, most are located in the first two columns of the periodic table. (15 Jan 1998) |
| active methionine | S-(5'-deoxy-5'-adenosyl)-l-methionine;condensation product of adenosine and l-methionine involving replacement of the -OPO3H2 of adenylic acid by -S+ (CH3)CH2CH2CH(NH3+)CO 2 of methionine; a sulfonium compound bearing a methyl group that is transferred in transmethylation reactions. See: methionine adenosyltransferase. Synonym: active methionine. Acronym: SAM (05 Mar 2000) |
| active methyl | A methyl group attached to a quaternary ammonium ion or a tertiary sulfonium ion that can take part in transmethylation reactions; e.g., methyl groups in choline and in S-adenosyl-l-methionine, which are thus methyl donors. (05 Mar 2000) |
| active movement | Movement effected by the organism itself, unaided by external influences. (05 Mar 2000) |
| active mutant | A mutant with overt phenotypic expression. (05 Mar 2000) |