Circulation Research

TØNNESEN, KNUD H.

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The isolated gastrocnemius muscle of the cat was used to study the relation between the desaturation of The metered blood flow agreed with that calculated from the initial slope of the desaturation curve from tissue equilibrated by prolonged intra-arterial infusion and also by atraumatic gas labelling of a local area of the muscle (approximately 0.15% of the muscle weight). In this sense the concept of uniform distribution of blood flow in skeletal muscle has received substantial support. The identity of the results obtained by local gas labelling and by intra-arterial equilibration of the whole muscle with gas implies that there is, at least initially, diffusion equilibrium between tissue and blood in both. However, the clearance curves could in no instance be fitted by a single exponential function. This indicates that the diffusion equilibrium is not maintained after the initial phase. It is suggested that this is not due to the presence of anatomical arteriovenous shunts or other types of uneven perfusion, but to counter current exchange of inert gas through the walls of vessels, i.e. shunting by diffusion explains the shape of the desaturation curves.

REID, DAVID W. J.

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Right and left ventricular outputs were measured by a dye dilution technique in fetal lambs before and during graded reduction of umbilical blood flow by constriction of the abdominal portion of the umbilical vein. PO

Berne, Robert M.

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Bilateral adrenalectomy resulted in a decrease (4.97 to 2.79 mg/g) in cardiac glycogen concentration in pentobarbital-anesthetized rats. Similar differences were observed at 10 to 14 days and at 27 days after adrenalectomy. Sham-adrenalectomized rats had normal cardiac glycogen concentration (4.98 mg/g). Total phosphorylase and phosphorylase α activities and glucose-6-phosphate concentrations in hearts obtained from adrenalectomized rats were not significantly different from controls. Total glycogen transferase activity was decreased in adrenalectomized rats and for any given glycogen concentration, the percent of the glycogen transferase in the independent form (percent transferase I) was significantly lower in the adrenalectomized rats than in the intact controls. The glucocorticoid dexamethasone (40 μg/day) prevented the decreases in cardiac glycogen concentration and percent transferase I in adrenalectomized rats. In the intact rat dexamethasone (40 μg/day) increased cardiac glycogen concentration and total transferase activity to above control levels as did larger doses in both adrenalectomized and control rats. The mineralocorticoid deoxycorticosterone acetate (DOCA), had relatively little effect on cardiac glycogen concentration. Conclusion: glucocorticoids exert a regulatory role in cardiac glycogen metabolism.

DILTS, P. V.

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The effects of hyperbaric oxygen (at 3 atmospheres absolute) on uteroplacental and fetal circulations were studied in pregnant ewes near term. The ewe was given spinal anesthesia, the fetus was marsupialized to the abdominal walls to protect the umbilical circulation, and the fetal head was covered with a saline-filled glove to prevent breathing. During hyperbaric oxygenation, maternal arterial blood PO

AXELROD, JULIUS

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Norepinephrine turnover was estimated in the rat heart from the rate of release of tracer Cardiac atrophy and decreased blood pressure occurred concomitantly with increased norepinephrine turnover in the hypophysectomized rat and were restored to normal with thyroid treatment. Ganglionic blockade of the hypophysectomized rat also restored the turnover toward normal. The metabolites of This evidence suggests that thyroid deficiency and, to a lesser extent, adrenal deficiency are associated with an increase in cardiac norepinephrine turnover mediated by an increase in sympathetic nervous activity. The role of the increased turnover in relation to the hormonal deficiencies is discussed.

DU PERRON, JEANNY C.

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Hemodynamic variability in patients with atrial fibrillation may originate from a direct influence of the variations in RR intervals on myocardial contractility. With the aid of a computer the serial autocorrelation function and the histogram of the RR intervals of patients with atrial fibrillation receiving no medication were produced. The RR intervals were randomly distributed and the histograms rather skew. Next, random rhythms with histograms matching those of the patients were produced with a radioactive source and a Geiger-Müller counter. These rhythms were used to stimulate isolated perfused rat hearts to study the relationship between the RR interval and a number of contractile parameters. The ECG and the isotonic contractions were digitized and processed by the computer. Serial crosscorrelation coefficients were computed between the RR interval on the one hand, and contraction height, contraction area, and maximum of the first derivative of the contraction on the other hand. The zero order crosscorrelation coefficient between the RR interval and contraction height was 0.6, between the RR interval and contraction area 0.8, and between the RR interval and maximum of first derivative 0.5. Although small, the first and second to approximately the tenth order coefficients were definitely negative. It is concluded that during a random rhythm the contractile parameters of an isolated heart are strongly related to the preceding RR interval. It is conceivable that this relation contributes to the variability of hemodynamic parameters during atrial fibrillation in man.

CLARK, JAMES G.

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A cylindrical ultrasonic transducer on a catheter tip lodged in the cleft between the free wall of the right ventricle and the interventricular septum provides an easily measured echo from the posteroinferior left ventricular epicardial surface. The sonic path represents a diameter of the left ventricle at approximately its largest cross-sectional area. Experiments in six dogs demonstrated that measurements by ultrasound agree within ±6% with simultaneous radiographic measurements of left ventricular diameter. Procedures designed to alter left ventricular volume were employed in 14 dogs to clarify the physiologic meaningfulness of the left ventricular diameter measured by ultrasound. Both end-diastolic and end-systolic diameter increased with anoxia, with sudden injections of saline into the left ventricle, after propranolol, and after inflation of a balloon in the thoracic aorta. These diameters decreased with isoproterenol, with increased heart rate, and after inflation of a balloon in the inferior vena cava. The present technique provides accurate and physiologically meaningful estimates of left ventricular diameter. Ventricular diameter measurements obtained during cardiac catheterization should permit assessment of ventricular distensibility and of ventricular function.

GOODKIND, M. JAY

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Maximum left ventricular systolic pressure response to aortic constriction served as a measure of myocardial contractility in anesthetized euthyroid and hyperthyroid guinea pigs. This response in hyperthyroid guinea pigs (155.4 ± 1.40 mm Hg) was significantly greater than in euthyroid animals (147.3 ± 1.33 mm Hg) (

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JACOBSON, ADA L.

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The effect of ouabain (10