| active | Characterised by action, not passive, not expectant. (18 Nov 1997) |
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| active acetate | <enzyme> Condensation product of coenzyme A and acetic acid, symbolised as CoAS~COCH3; intermediate in transfer of two-carbon fragment, notably in its entrance into the tricarboxylic acid cycle and in fatty acid synthesis. This coenzyme plays a huge role in intermediary metabolism, in which cells synthesise, break down or use nutrient molecules for energy production, growth, etc. Acetyl-coenzyme A synthase is found in bacteria and plants and catalyses the reaction in which acetate enters metabolic pathways and forms acetyl-coenzyme A. Synonym: acetyl-coenzyme A, active acetate. (05 Mar 2000) |
| active aldehyde | Any aldehyde derivative of thiamin pyrophosphate. (05 Mar 2000) |
| active anaphylaxis | Reaction following inoculation of antigen in a subject previously sensitised to the specific antigen, in contrast to passive anaphylaxis. (05 Mar 2000) |
| active biomass | <cell biology> The amount of a given culture that is actively growing. (06 May 1997) |
| active carbon dioxide | Activated carbon dioxide, a complex of N-carboxybiotin (biotin + CO2) and an enzyme; the form in which carbon dioxide is added to other molecules in carboxylations; e.g., to methylcrotonyl-CoA to form beta-methylglutaconyl in the catabolism of leucine, and to acetyl-CoA to form malonyl-CoA. See: acetyl-CoA carboxylase. (05 Mar 2000) |
| active caries | Microbial-induced lesions of teeth that are increasing in size. (05 Mar 2000) |
| 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) |
| artificial active immunity | See: acquired immunity. (05 Mar 2000) |
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| biological transport, active | The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy. (12 Dec 1998) |
| chronic active hepatitis | <pathology> This is a form of continuing liver inflammation that results in liver cell death. Causes include viral infection (hepatitis D, hepatitis B, hepatitis C), autoimmune disease, drug ingestion or metabolic causes. Chronic active hepatitis will lead to hepatic failure and death in a small percentage of these patients. (27 Sep 1997) |
| chronic active inflammation | The coexistence of chronic inflammation and superimposed acute inflammation. (05 Mar 2000) |
| chronic active liver disease | Any of several types of hepatitis persisting for more than six months, often progressing to cirrhosis. Synonym: chronic active liver disease. (05 Mar 2000) |
| specific active immunity | See: acquired immunity. (05 Mar 2000) |
| surface-active | Indicating the property of certain agents of altering the physicochemical nature of surfaces and interfaces, bringing about lowering of interfacial tension; they usually possess both lipophilic and hydrophilic groups. See: surfactant. (05 Mar 2000) |
| surface-active agent | Agents that modify interfacial tension of water; usually substances that have one lipophilic and one hydrophilic group in the molecule; includes soaps, detergents, emulsifiers, dispersing and wetting agents, and several groups of antiseptics. (12 Dec 1998) |
| surface active compound | <biochemistry> Usually, in biological systems, means a detergent like molecule that is amphipathic and that will bind to the plasma membrane or to a surface with which cells come in contact, altering its properties from hydrophobic to hydrophilic or vice versa. (18 Nov 1997) |
| immunity, active | Resistance to a disease agent resulting from the production of specific antibodies by the host, either after exposure to the disease or after vaccination. (12 Dec 1998) |
| immunotherapy, active | Active immunization where vaccine is administered for therapeutic or preventive purposes. This can include administration of immunopotentiating agents such as bcg vaccine and corynebacterium parvum as well as biological response modifiers such as interferons, interleukins, and colony-stimulating factors in order to directly stimulate the immune system. (12 Dec 1998) |
| optically active | <chemistry> A material which can rotate plane-polarized light. (09 Jan 1998) |
| tensio active | Having an effect on surface tension. (18 Nov 1997) |