| OAS | old age security; oral allergy syndrome; osmotically active substance |
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| OAW | oral airways |
| OC | obstetrical conjugate; occlusocervical; office call; on call; only child; optic chiasma; oral contra... |
| OCA | oculocutaneous albinism; olivopontocerebellar atrophy; oral contraceptive agent |
| OCC | object-centered coordinate [method]; oral cholecystography |
| binary complex | A noncovalent complex of two molecules; often referring to the enzyme-substrate complex in an enzyme-catalyzed reaction. Compare: central complex, Michaelis complex. Synonym: enzyme-substrate complex. (05 Mar 2000) |
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| bithorax complex | <genetics, molecular biology> A group of homeotic mutations of Drosophila that map to the bithorax region on chromosome III. The mutations all cause the third thoracic segment to develop like the second thoracic segment to varying extents. The genes of the bithorax complex are thought to determine the differentiation of the posterior thoracic segments and the abdominal segments. (18 Nov 1997) |
| brain wave complex | A specific combination of fast and slow electroencephalographic activity that recurs frequently enough to be identified as a discrete phenomenon. (05 Mar 2000) |
| brother complex | Extreme envy or jealousy of a brother, leading to hatred. Synonym: brother complex. Origin: Cain, biblical personage (05 Mar 2000) |
| Cain complex | Extreme envy or jealousy of a brother, leading to hatred. Synonym: brother complex. Origin: Cain, biblical personage (05 Mar 2000) |
| MAC complex | complement |
| major histocompatabilty complex | <immunology> A cluster of genes on chromosome 6 concerned with antigen production and critical to transplantation. The MHC includes the human leukocyte antigen (HLA) genes. (12 Dec 1998) |
| major histocompatibility complex | The set of gene loci specifying major histocompatibility antigens, for example HLA in man, H 2 in mice, RLA in rabbits, RT 1 in rats, DLA in dogs, SLA in pigs, etc. Acronym: MHC (18 Nov 1997) |
| VATER complex | A constellation of vertebral defects, anal atresia, tracheoesophageal fistula with oesophageal atresia, and renal and radial anomalies; associated with Fanconi's anaemia. (05 Mar 2000) |
| rancke complex | <radiology> Combination of: calcified peripheral nodule (Ghon lesion), calcified hilar nodes, occurs in 50% of patients with primary TB (12 Dec 1998) |
| ventricular complex | The continuous QRST waves of each beat in the electrocardiogram. (05 Mar 2000) |
| receptor-CD3 complex, antigen, T-cell | Molecule composed of the non-covalent association of the T-cell antigen receptor (receptors, antigen, T-cell) with the CD3 complex (antigens, CD3). This association is required for the surface expression and function of both components. The molecule consists of up to seven chains: either the alpha/beta or gamma/delta chains of the T-cell receptor, and four or five chains in the CD3 complex. (12 Dec 1998) |
| Ghon's complex | Calcification seen in pulmonary parenchyma (usually mid-lung area) and hilar nodes resulting from earlier, usually childhood, infection with tuberculosis. Synonym: Ghon's complex, Ghon's focus, Ghon's primary lesion. (05 Mar 2000) |
| castration complex | A child's fear of injury to the genitals by the parent of the same sex as punishment for unconcious guilt over oedipal feelings, fantasied loss of the penis by a female or fear of its actual loss by a male, unconscious fear of injury from those in authority. Synonym: castration anxiety. (05 Mar 2000) |
| caudal pharyngeal complex | The ultimobranchial body associated with the embryonic fourth and transitory fifth pharyngeal pouches. (05 Mar 2000) |