Biomedical subjects
Publications and source records attributed to E M Scott.
The phosphatase activity of bisphosphoglyceromutase (DPGM) was used to determine the phenotypes of the enzyme. DPGM was polymorphic in four Alaskan ethnic groups.
1 The reduction in the sympathetic efferent discharge observed after propranolol may be due to either a central or a peripheral effect. The beta-adrenoceptor blocking drug, atenolol, is not thought to enter the brain and therefore any reduction in the level of sympathetic efferent discharge observed after atenolol is likely to be mediated peripherally rather than centrally. 2 Cats were anaesthetized with alpha-chloralose and artificially ventilated and a number of variables known to affect the sympathetic nerves were monitored throughout the experiment and maintained within normal limits. Recordings were made from few fibre preparations from the lumber trunk and the renal nerves. Blood pressure was either raised or lowered by the injection of phenylephrine (1-4 microgram/kg) or glyceryl trinitrate (2-20 microgram/kg) and the sympathetic efferent discharge was recorded over a range of blood pressures when the blood pressure was steady. 3 Thirty min after giving atenolol (3 mg/kg) the blood pressure, heart rate and sympathetic efferent discharge were significantly reduced. Atenolol also attenuated the reflex responses of the sympathetic nerves to changes in the blood pressure. 4 It is suggested tht atenolol has its actions on sympathetic nerves at a site outside the CNS and some possible mechanisms are discussed.
Recordings were made of the discharge of single fibres from renal sympathetic efferent nerves in the anaesthetized dog. Stimulation of left atrial receptors by distension of small balloons at the junctions of the pulmonary veins and the left atrium resulted in a reduction in the discharge of one group of these single fibres and no change in the discharge of a second group of fibres. Bilateral occlusion of the common carotid arteries resulted in an increase in the discharge of all single fibres tested. All fibres tested which responded to stimulation of atrial receptors also responded to carotid occlusion. These results provide evidence for convergence of the central pathways from atrial receptors and baroreceptors on individual sympathetic efferent neurones.
A two-stage procedure using MTT tetrazolium for the demonstration of aminotransferases (GPT and GOT) either singly or together was developed. Identification of phenotypes was unequivocal in over 99% of the individuals studied.
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Rhodanese of human erythrocytes was monomorphic in most populations tested, but was polymorphic in Ahtna and Upper Tanana Indians. This enzyme is under the control of a single autosomal locus.
Glutathione transferase (GST) of human erythrocytes, while homogeneous upon electrophoresis, varied more than sixfold in amount in individuals. The levels of this enzyme were found to be inherited, but no practical way was devised to use this enzyme as a genetic marker.
The common type of pyrimidine nucleoside monophosphate kinase (ATP:CMP phosphotransferase, EC 2.7.4.14), purified 50 000-fold from human erythrotes, reacted with a wide variety of nucleotides, but only ATP, dATP, UMP and CMP were good substrates. The optimum Mg2+ concentration, 2-3 mM, was generally independent of substrate concentration, of the nature of the substrate, and of the direction of the reaction. Kinetic studies indicated that a ternary complex was formed, that the substrates were bound at two unlike sites, and that the order of addition of substrates was random. Equilibrium constants were ATP + UMP 0.98, ATP + CMP 1.59, dATP + UMP 1.13, and ATP + AMP 1.20.
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1. Gene frequencies of esterase D, glyoxalase I and uridine monophosphate kinase in Alaskan populations were determined. 2. Improved methods for demonstrating phenotypes of glyoxalase I and uridine monophosphate kinase are presented. 3. Rare variants of adenylate kinase (AK1) and diaphorase (DIA) were found. One of the AK1 variants is new. 4. Gene frequencies were notably diverse within major ethnic groups. This variability was consistent with a population structure composed of small groups that were relatively isolated from one another.
Esterase D (EsD), purified from human erythrocytes and tested with a variety of substrates, hydrolyzed only triacetin, tributyrin, and certain soluble aryl esters of aliphatic acids. Esters of 4-methylumbelliferone were easily the best substrates. When the three genetically different isozymes were compared, the less common forms, EsD 2 and EsD 2-1, were less stable than EsD 1. With some substrates, the Michaelis constant of the EsD 2 form differed from that of the EsD 1 form. The EsD 2-1 hybrid form was usually, but not invariably, intermediate in properties. The physiologic significance of the genetic variability of this enzyme is unknown.
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