| PPN | partial parenteral nutrition; pedunculopontine nucleus |
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| PPT | parietal pleural tissue; partial prothrombin time; peak-to-peak threshold; Pfeiffer-Palm-Teller [syn... |
| PRD | partial reaction of degeneration; physician relations department; postradiation dysplasia |
| PRF | partial reinforcement; patient report form; perforin; plasma recognition factor; pontine reticular f... |
| PtcCO2 | transcutaneous partial pressure of carbon dioxide |
| triaxial reference system | The figure resulting from rearranging the lines of derivation of the three standard limb leads of the electrocardiogram (as represented in Einthoven's triangle) so that, instead of forming the sides of an equilateral triangle, they bisect one another. Synonym: Dieuaide diagram. (05 Mar 2000) |
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| trigeminal system | <neurology> Neurons associated with the fifth or trigeminal nerve, the largest cranial nerve. The trigeminal system provides sensory innervation to the face and mucous membrane of the oral cavity, along with motor innervation to the muscles of mastication. It is called trigeminal because it has three major peripheral branches, the opthalmic, the maxillary and the mandibular nerves. (18 Nov 1997) |
| T system | The transverse tubules that are continuous with the sarcolemma in skeletal and cardiac muscle fibres. (05 Mar 2000) |
| esthesiodic system | A system of neurons and fibre tracts in the spinal cord and brain subserving sensation. (05 Mar 2000) |
| Jamin Lebedeff system | <apparatus> Interference microscopy in which object and reference beams are split and later recombined by birefringent calcite plates, but pass through the same optical components (in contrast to the Mach Zehnder system). (18 Nov 1997) |
| turnkey system | A system which is built, engineered, and installed to the point of readiness for operation by the owner. (05 Dec 1998) |
| expert system | Expert systems are computer programs designed to simulate the problem-solving behaviour of human experts within very narrow domains or scientific disciplines (entomology, plant pathology, etc.). This discipline is a sub-set of Artificial Intelligence. See: artificial intelligence. Synonym: knowledge-based systems (13 Jan 1998) |
| expression system | <molecular biology> Combination of an expression vector, its cloned DNA, and the host for the vector that provide a context to allow foreign gene function in a host cell, that is, produce proteins at a high level. (13 Nov 1997) |
| exterofective system | Name applied by Cannon to the somatic nervous system as opposed to the interofective or autonomic system. (05 Mar 2000) |
| extrapyramidal motor system | Literally: all of the brain structures affecting bodily (somatic) movement, excluding the motor neurons, the motor cortex, and the pyramidal (corticobulbar and corticospinal) tract. Despite its very wide literal connotation, the term is commonly used to denote in particular the striate body (basal ganglia), its associated structures (substantia nigra; subthalamic nucleus), and its descending connections with the midbrain. (05 Mar 2000) |
| extrapyramidal motor system disease | A general term for a number of disorders caused by abnormalities of the basal ganglia or certain brain stem or thalamic nuclei; characterised by motor deficits, loss of postural reflexes, bradykinesia, tremor, rigidity, and various involuntary movements. Synonym: extrapyramidal motor system disease. (05 Mar 2000) |
| kallikrein-kinin system | A system produced in the distal nephron of the kidney. Its components are kallikrein, kinins, kininase I and II, and enkephalinase. It is involved in mediation and modulation of the renin-angiotensin-aldosterone system, prostaglandins, vasopressins, and in the regulation of sodium-water balance, renal haemodynamics, and particularly blood pressure. The system participates in the control of renal functions and the physiopathology of renal diseases. (12 Dec 1998) |
| kallikrein system | A blood serum system, the activity of which is initiated by factor XII (Hageman factor) leading to the production of prekallikrein activator and then to kallikrein which, after activation by plasmin, splits bradykinin from kininogen. (05 Mar 2000) |
| kidd blood-group system | A group of antigens consisting principally of jk(a) and jk(b), determined by allelic genes. Amorphs are encountered. Antibodies of these substances are usually weak and quite labile, stimulated by erythrocytes. (12 Dec 1998) |
| Zaffaroni system | A chromatographic system for the separation of steroids. (05 Mar 2000) |