| OHS | obesity hypoventilation syndrome; occipital Horn syndrome; occupational health service; ocular histo... |
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| OMVC | open mitral valve commissurotomy |
| OPA | open procurement agency |
| OR | a logical binary relation that is true if any argument is true, and false otherwise; [o]estrogen rec... |
| ORF | open reading frame |
| glycogen debranching enzyme system | 1,4-alpha-d-glucan-1,4-alpha-d-glucan 4-alpha-d-glucosyltransferase/dextrin 6 alpha-d-glucanohydrolase. An enzyme system having both 4-alpha-glucanotransferase (ec 2.4.1.25) and amylo-1,6-glucosidase (ec 3.2.1.33) activities. As a transferase it transfers a segment of a 1,4-alpha-d-glucan to a new 4-position in an acceptor, which may be glucose or another 1,4-alpha-d-glucan. As a glucosidase it catalyses the endohydrolysis of 1,6-alpha-d-glucoside linkages at points of branching in chains of 1,4-linked alpha-d-glucose residues. Amylo-1,6-glucosidase activity is deficient in glycogen storage disease type III. (12 Dec 1998) |
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| respiratory system | The organs that are involved in breathing. These include the nose, throat, larynx, trachea, bronchi, and lungs. (12 Dec 1998) |
| respiratory system abnormalities | Congenital structural abnormalities of the respiratory system. (12 Dec 1998) |
| respiratory system agents | Drugs used for their effects on the respiratory system. (12 Dec 1998) |
| reticular activating system | <physiology> A physiological term denoting that part of the brainstem reticular formation that plays a central role in the organism's bodily and behavorial alertness. It extends as a diffusely organised neural apparatus through the central region of the brainstem into the subthalamus and the intralaminar nuclei of the thalamus; by its ascending connections it affects the function of the cerebral cortex in the sense of behavioural responsiveness; its descending (reticulospinal) connections transmit its activating influence upon bodily posture and reflex mechanisms (e.g., muscle tonus), in part by way of the gamma motor neurons. See: reticular formation. Synonym: non-specific system. (05 Mar 2000) |
| reticuloendothelial system | The phagocytic system of the body, including the fixed macrophages of tissues, liver and spleen. Rather old fashioned term that is coming back into use, mononuclear phagocyte system is probably better when only phagocytes are meant. (18 Nov 1997) |
| cerebrospinal system | The combined central nervous system and peripheral nervous system. (05 Mar 2000) |
| charge transfer system | A complex between two organic molecules in which an electron from one (the donor) is transferred to the other (the acceptor), becoming generally distributed throughout the latter; subsequent transfer of a hydrogen atom completes the reduction of the acceptor; such complex's are generally highly coloured and may be so observed, a network of hydrogen bridges at the catalytic centre of certain proteases. Synonym: charge transfer system. (05 Mar 2000) |
| rh-hr blood-group system | Erythrocyte isoantigens of the rh (rhesus) blood group system, the most complex of all human blood groups, because the genes differ by determining a different number of the over thirty antigens thus far described and do so with remarkably different quality. The major antigen rh or d is the most common cause of erythroblastosis foetalis. (12 Dec 1998) |
| periodic system | The arrangement of the chemical elements in a definite order as indicated by their respective atomic numbers in such a way that groups of elements with similar chemical properties (similar valence shell electron number) are grouped together. See: Mendeleeff's law. (05 Mar 2000) |
| peripheral nervous system | One of the two major divisions of the nervous system. Nerves in the PNS connect the central nervous system (CNS) with sensory organs, other organs, muscles, bloodvessels and glands. (22 May 1997) |
| peripheral nervous system agents | Drugs that act principally at one or more sites within the peripheral neuroeffector systems, the autonomic system, and motor nerve-skeletal system. (12 Dec 1998) |
| peripheral nervous system diseases | Diseases of the peripheral nervous system, including disorders of the peripheral autonomic system, the cranial nerves, and the spinal nerves and roots, but not including neuromuscular and spinal cord diseases. (12 Dec 1998) |
| metameric nervous system | That part of the nervous system which innervates body structures developed in ontogeny from the segmentally arranged somites or, in the head region, branchial arches. The term implies reference to the neural mechanisms intrinsic to the spinal cord and brainstem (represented by the sensory nuclei, motoneuronal cell groups, and their associated interneurons in the reticular formation); by strict definition it should exclude the autonomic nervous system. (05 Mar 2000) |
| meter-kilogram-second system | An absolute system based on the meter, kilogram, and second; the basis of the International System of Units. (05 Mar 2000) |