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Y Hasin

Publications and source records attributed to Y Hasin.

148 records · Page 9Linked to original sources
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Mechanical and metabolic performance of the rat heart: effects of combined stress of heat acclimation and swimming training.

Although the individual effects of heat acclimation and swimming exercise on cardiovascular reserve and efficiency have been studied, the relative and cumulative effects of these interventions have not. Myocardial developed force, coronary flow (CF), and oxygen consumption during baseline conditions and during pacing-induced tachycardia were therefore studied in isolated perfused hearts from four groups of rats: normothermic sedentary (C), heat acclimated sedentary (AC), normothermic swimmers (CS), and heat acclimated swimmers (ACS). Normothermic temperature was 24 degrees C. Heat acclimation was attained by continuous exposure to 34 degrees C for one and two months. Swimmers had two daily 75 minute sessions for five days a week with water temperatures of 33-35 degrees C and 36-38 degrees C for CS and ACS rats, respectively. After one month AC animals showed a remarkable decrease in O2 consumption. In contrast, ACS increased both O2 consumption and the maximal isometric force generated. After two months, O2 consumption of AC rats continued to be low. The heart failed to restitute the force developed at high pacing frequency. In these rats CF was remarkably low and remained unchanged with increased pacing. In contrast ACS maintained the ability to develop force at all pacing rates at a level similar to that of the normothermic C and ACS rat hearts, but at high oxygen cost. The data suggest that the AC heart is more efficient but cannot meet demands at high pacing rates. In contrast, swimming in the heat improved performance of ACS temporarily, without decreasing the metabolic rate.

Acclimatization↗
PubMedDate not supplied

The effect of quinidine and myocardial ischemia on the isolated rat heart with fat-free diet.

Fat-free diet changes the lipid content and the electrophysiological properties of the rat myocardium. Five percent fat supplementation to the diet does not alter the basic electrophysiological properties but still has a biochemical effect on the lipid content of the myocardium. The purpose of this work was to determine whether these biochemical alterations affect the response of the myocardium to quinidine and ischemia, both of which interact with the lipid component of the membrane. We used strength-duration, strength-interval and threshold of ventricular fibrillation to measure the electrophysiological properties of the isolated rat heart at baseline and after 30 minutes of quinidine perfusion or coronary artery ligation. The fatty acid composition of the myocardium was analyzed. We found that a fat-free diet caused essential fatty-acid deficiency, while 5% fat supplementation had a partial protective effect. Quinidine decreased excitability and increased refractoriness in both groups but had more effect on the fat-free diet hearts group. There was no difference in the ventricular fibrillation threshold. Ischemia increased myocardial excitability in the fat-free diet hearts group and had no effect on refractoriness or ventricular fibrillation threshold. These results support the theory that the lipid composition of the myocardial membrane affects its response to lipophilic drugs and ischemia.

Animals↗
PubMedDate not supplied

Right and left ventricular flow during mechanical alternans.

Pulmonary and aortic blood flow simultaneous with right and left ventricular isometric tension were measured in anesthetized dogs during mechanical alternans induced by rapid atrial driving. It was found that any steady state of mechanical alternation can be altered to another steady state by a single premature or delayed beat. The relationship between the force of the alternating beats was not necessarily equal in the two ventricles. Pulmonary and aortic flow changed markedly with changing steady states of mechanical alternation, at the same heart rate, within wide range of flow levels. Moreover, inequality between the mechanical alternation of the two ventricles was at times associated with disparity of aortic and pulmonic flow. The possible mechanism and clinical significance have been mentioned.

Animals↗