| lactose repressor | Protein (tetramer of 37 kD subunits) that normally binds with very high affinity to the operator region of the lactose operon and inhibits transcription of the downstream genes by blocking access of the polymerase to the promoter region. When the lactose repressor binds allolactose, its binding to the operator is reduced and the gene set is derepressed. (18 Nov 1997) |
|---|---|
| aberrant complex | An anomalous electrocardiographic complex, more specifically an abnormal ventricular complex caused by abnormal intraventricular conduction of a supraventricular impulse. (05 Mar 2000) |
| activated complex | <chemistry> State of highest energy during a reaction. When reactants form the activated complex, bond breaking and bond formation is occurring. Synonym: transition state. (09 Jan 1998) |
| AIDS dementia complex | <immunology> A frequent cerebral condition in people with AIDS that results in the loss of cognitive capacity, affecting the ability to function in a social or occupational setting. Its cause has not been determined exactly, but may result from HIV infection of cells in the brain or an inflammatory reaction to such infection. (09 Oct 1997) |
| aids-related complex | A prodromal phase of infection with the human immunodeficiency virus (HIV). Laboratory criteria separating aids-related complex (arc) from aids include elevated or hyperactive B-cell humoral immune responses, compared to depressed or normal antibody reactivity in aids; follicular or mixed hyperplasia in arc lymph nodes, leading to lymphocyte degeneration and depletion more typical of aids; evolving succession of histopathological lesions such as localization of kaposi's sarcoma, signaling the transition to the full-blown aids. (12 Dec 1998) |
| alpha-keto acid dehydrogenase complex | See: alpha-keto acid dehydrogenase. Anaerobic dehydrogenase, an enzyme (usually a pyridinoenzyme) catalyzing the transfer of hydrogen from some metabolite to some acceptor molecule (e.g., NAD+, cytochrome) other than oxygen; e.g., lactate dehydrogenase's, isocitrate dehydrogenase's, and others in EC class 1, excluding those listed under aerobic dehydrogenase. (05 Mar 2000) |
| alpha-ketoglutarate dehydrogenase complex | alpha-ketoglutarate dehydrogenase |
| amygdaloid complex | Almond-shaped group of basal nuclei anterior to the inferior horn of the lateral ventricle of the brain, within the temporal lobe. The amygdala is part of the limbic system. (12 Dec 1998) |
| anomalous complex | A complex in the electrocardiogram differing significantly from the physiologic type in the same lead. (05 Mar 2000) |
| antennal complex | <cell biology> Light harvesting complexes (LHC) of protein and pigment in or on photosynthetic membranes of bacteria are organised into arrays, called antennae. They transfer photon energy to reaction centres. (18 Nov 1997) |
| antennapedia complex | A set of mutations that cause developmental defects in the limbs and appendages of the fruit fly Drosophila melanogaster, such as the development of legs (-pedia) in the places where antennae are supposed to be. (09 Oct 1997) |
| antigen-antibody complex | The complex formed by the binding of antigen and antibody molecules. The deposition of large antigen-antibody complexes leading to tissue damage causes immune complex diseases. If the antigen is polyvalent the complex may be insoluble. Immune complexes activate complement through the classical pathway. See: glomerulonephritis, Arthus reaction, type III hypersensitivity. (12 Dec 1998) |
| antigenic complex | A composite of different antigenic structures, such as a cell or a bacterium, or, by extension, a molecule containing two or more determinant groups of different antigenic specificities. (05 Mar 2000) |
| apical complex | A set of anterior structures that characterise one or several developmental stages of members of the protozoan phylum Apicomplexa; includes the following structures, visible by electron microscopy: polar ring, conoid, rhoptries, micronemes, and subpellicular tubules. (05 Mar 2000) |
| atrial complex | P wave in the electrocardiogram. Synonym: auricular complex. (05 Mar 2000) |