Devices to measure left ventricular pressure, diameter and heart rate in animals with closed chests were placed on the hearts of dogs. After recovery from this operation the dogs were trained to exercise on a treadmill and the cardiovascular responses to this exercise were recorded. Stimulating electrodes were then stereotaxically placed in the diencephalon. In some dogs the electrodes were chronically implanted, and the stimulation was carried out after recovery from this second operation. In other animals stimulation was carried out immediately while they were under chloralose anesthesia. Stimulation of the H1 and H2 fields of Forel and the periventricular gray of the third ventricle resulted in cardiovascular responses similar to those which result from exercise.
The effect of total thyroidectomy on the production and maintenance of experimental hypertension has been studied in 8 dogs.In 4 animals hypertension was induced by the application of Goldblatt clamps to the renal arteries. After the stabilization of this, total thyroidectomies were done. This procedure was followed by no significant change in the level of the systolic blood pressure.In the remaining 4 dogs total thyroidectomies were done. No change in blood pressure resulted. Constriction of the renal arteries in these animals was followed by a well sustained rise in blood pressure.Blood cholesterol determinations were used as an index of the severity of the myxedema in both groups.Our conclusion, therefore, is that total thyroidectomy in dogs does not effect either the production or maintenance of this type of hypertension.
9774Streptococci.T h e Bi-Phasic Nature of Certain Alpha-Prime ( P) Hemolytic
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