[Energy metabolism and contractile function of the heart in diabetic cardiomyopathy: effect of ischemia and reperfusion]. / Issledovanie énergeticheskogo metabolizma i sokratitle'noi funktsii serdtsa s diabeticheskoi kardiomiopatiei: deistvie ishemii i reperfuzii.

Physiological parameters, rates of mitochondrial respiration, high energy phosphate levels and creatine phosphokinase (CPK) activity were investigated in the hearts from control and alloxan-induced diabetic rabbits before and after 40-min total ischemia and reperfusion. Diabetic hearts demonstrated significant decreases in the rates of contraction (+dP/dt) and relaxation (-dP/dt), heart rates and cardiac work compared to control hearts. Determination of mitochondrial respiration rates in saponin-skinned fibers showed a low mitochondrial respiratory function in diabetic hearts. It was found that the ATP and ADP levels and the total and mitochondrial isoenzyme activities of CPK in diabetic hearts were lowered in comparison with control. A post-ischemic recovery of cardiac performance for diabetic hearts was better than in controls. After reperfusion diabetic hearts had increased ATP levels. The data obtained demonstrate some abnormalities of both cardiac performance and energy metabolism in the hearts of diabetic animals and a decreased sensitivity of the latter to ischemic injury.

[Two forms of glutamine synthetase from pumpkin leaves]. / Dve formy glutaminsintetazy v list'iakh tykvy.

Two molecular forms of glutamine synthetase localized in the cytoplasm and in chloroplasts, respectively, were detected in pumpkin leaves. Ammonium infiltrated into intact pumpkin leaves activated the synthesis of both enzyme forms. Glutamine synthetase from chloroplasts and the cytoplasmic enzyme were purified to homogeneity by ammonium sulfate fractionation, ion-exchange chromatography on DEAE-cellulose DE-32, selective adsorption on potassium phosphate gel and preparative electrophoresis in polyacrylamide gel. The molecular weights of both forms of glutamine synthetase as determined by gel-filtration through Sephacryl S-200 are equal to 370,000 and 480,000, respectively. During SDS polyacrylamide gel electrophoresis the enzymes from both sources produced polypeptide chains with respective molecular weights of 50,000 and 58,000. The amino acid composition of the enzymes differed considerably. The content of alpha-helix moities in the chloroplast and cytoplasmic enzyme made up to 17% and 34%, respectively. In the presence of Mg+ the pH optima for the enzymes were equal to 7.75 and 7.25, respectively, and the Km values for L-glutamate were 46 and 13 mM, respectively. It may be concluded that the enzyme forms under study are isoenzymes.