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S Torr

Publications and source records attributed to S Torr.

7 recordsLinked to original sources
PubMed1990

Inhibition of acute platelet thrombosis formation in stenosed canine coronary arteries by specific serotonin 5HT2 receptor antagonist ritanserin.

STUDY OBJECTIVE: The aim of the study was to test the hypothesis that platelet serotonin 5HT2 receptors are important in the genesis of thrombosis in stenosed coronary arteries. DESIGN: The specific serotonin 5HT2 receptor antagonist, ritanserin was used as a pharmacological tool to examine the effect of removal of the participation of the 5HT2 receptors on thrombus growth, in a paired statistical design. EXPERIMENTAL MATERIAL: The study involved 10 open chest anaesthetised dogs, with constrictors of critical diameter applied to the left circumflex coronary artery. MEASUREMENTS AND MAIN RESULTS: Blood flow was monitored in the left circumflex coronary arteries, distal to the critical stenosis. Flow reductions occurred that have previously been shown to be caused by the accumulation of platelet thrombi. By embolising the thrombi, the process could be monitored cyclically (cyclic flow reductions). The specific serotonin 5HT2 receptor antagonist, ritanserin, abolished cyclic flow reductions at a dose of 0.5 mg.kg-1. There was no effect on blood pressure or heart rate on administration of ritanserin at any dose. The serotonin blockade by ritanserin also prevented the reestablishment of cyclic flow reductions by adrenaline infusion (0.4 micrograms.kg-1.min-1), but required ritanserin doses up to 1.5 mg.kg-1. Ex vivo aggregation of platelets was reduced in blood taken from the dogs after ritanserin administration. CONCLUSIONS: These results constitute further evidence of the possible importance of serotonin as a mediator of platelet thrombosis in stenosed coronary arteries.

Animals↗
PubMed1971

Red cell sodium in hyperthyroidism.

A simple method of measuring red cell sodium has shown that about 90% of thyrotoxic patients have values above the upper limit of the normal range. Patients taking 0.3 mg of L-thyroxine daily were found to have a significantly higher mean value for red cell sodium than that of the normal controls. It is suggested that patients taking this amount of thyroxine may be hypermetabolic. The determination of red cell sodium may prove useful as a measure of the peripheral action of thyroid hormone.

Adult↗
PubMedDate not supplied

Effects on infarct size of reperfusion and pretreatment with beta-blockade and calcium antagonists.

The "mass of tissue at risk" and the myocardial infarct developed was studied in dogs subjected to either 24-h occlusion of the left anterior descending coronary artery or 2-h occlusion followed by 22-h reperfusion. The "mass of tissue at risk" was defined under anaesthesia at the time of occlusion using the microsphere technique. Twenty-four hours later the hearts were removed, sliced transversely and stained with 2,3,5-triphenyltetrazolium chloride to define the infarcted tissue. All myocardial tissue was mapped and cut into small pieces for weighing and radioactive counting. Radioactivity was present in all tissue, including the infarct. In the centre of the infarct, counts remained low and then increased very rapidly with distance just beyond the edge. Tissue at risk from infarction was taken as that with less than 15% of the peak left ventricular (non-ischaemic) counts. A linear relationship was found between the mass of the left ventricular infarct and the left ventricular "mass of tissue at risk". The effect of 22 hours reperfusion was examined by this method and expressed by a regression equation. There was a significant decrease in slope for the regression line of the reperfusion data, (p less than 0.05, analysis of covariance), indicating less infarcted tissue for each gram of underperfused tissue. None of the drug pretreatments explored had any effect on infarct size in the 24-h occlusion model. With reperfusion, propranolol and flunarizine diminished infarct size compared with reperfusion only (p less than 0.05 for reduced slope, the new slope being not significantly different from zero). The effect of diltiazem was not so marked. Thus infarct size can be reduced with pretreatment, as long as the myocardium is reperfused.

Adrenergic beta-Antagonists↗