Relationship between the potentiation of potassium-induced contracture of cardiac muscle by four cardenolides and their inhibitory effects on the sodium potassium activated adenosine triphosphatase of brain

Zusammenfassung Bei Digitoxigenin und 3 weiteren Derivaten wurde die Stärke der potenzierenden Wirkung auf die Kalium-Kontraktur des Froschherzmuskels und der hemmende Effekt auf den Transport der ATPase des Schweinehirns verglichen und eine eindeutige Korrelation zwischen diesen beiden Wirkungen festgestellt.     

Relationship between the effectiveness of cardiac glycosides in cats and their interference with red cell potassium transport

Zusammenfassung Bei neun untersuchten Herzglykosiden konnte eine direkte Beziehung zwischen der Kardiotoxizität und dem Grad der Beeinflussung des aktiven Kaliumtransportes festgestellt werden.

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The able assistance of Mrs.G. Tóthová is gratefully acknowledged. Statistical analysis of the data was performed by Ing.R. tukovský. Digitoxin, ouabain, andk-strophanthine were kindly supplied by E. Merck A.G., digoxin by C. F. Boehringer & Söhne GmbH and Lanatoside-A,- B, -C by Richter Gedeon.     

Relationship between steady-state activation and availability of cardiac sodium channel: evidence of uncoupling

The coupling between steady-state activation and availability from inactivation was characterized for the cardiac Na⁺ channel. To evaluate this coupling, we plotted the relationship between the conductance and availability curve midpoint potentials measured in 92 rat ventricular cardiomyocytes and applied a correlation analysis. We found a high correlation between the midpoints (correlation coefficient = 0.86, slope = 0.95) within the availability midpoint potential range positive to -100 mV. In contrast, the midpoints were not correlated in the myocytes (37 of 92 cells) having mid point potential negative to -100 mV, indicating an uncoupling between activation and availability. Received 1 October 1997; received after revision 28 October 1997; accepted 13 November 1997     

The influence of oestradiol-17β on the rat uterine Na+, K+-Mg++ activated adenosine triphosphatase activity

Zusammenfassung 17--Östradiol wirkt am Rattenuterus hemmend auf die ATPase, von der bekannt ist, dass sie auf die sogenannte Natriumpumpe in der Zelle wirkt.     

Effect of glycerol treatment on sodium and potassium in isolated muscle fibres of the frog

Summary The sodium concentration in single frog muscle fibres vacuolated by glycerol treatment was significantly higher than in devacuolated fibres. Intracellular potassium concentration did not show any significant change. It is concluded that the transverse tubular system forms vacuoles with a high NaCl concentration upon glycerol removal.     

Low temperature-induced contracture of depolarized smooth muscle and the effects of calcium and multivalent cations

Summary Lowering of temperature caused tension development in the smooth muscle of the guinea-pig vas deferens, which was dependent on extracellular Ca. Mn²⁺ and La³⁺ reversed the effect and induced phasic contraction on rewarming.Part of the results were presented at the 14th Int. Congress of Physiological Science, Budapest 1980.     

Relationship between the molecular weights of pesticides and their bioconcentration factors by fish

Summary A significant positve correlation was found between the molecular weights (187–412) of 19 pesticides and their bioconcentration factors (4–37,800) in 2 fresh-water fishes; topmouth gudgeon and fathead minnows.     

Voltage-clamp analysis of the sodium and potassium currents in skeletal muscle fibres treated with 4-aminopyridine

Summary External application of low concentrations of 4-aminopyridine blocks potassium currents without affecting sodium currents in pieces of single frog skeletal muscle fibres. The blockade of potassium currents was voltage-dependent, being partially relieved on depolarization.This study was supported by a grant from the Oficina técnica de Desarrollo Cientifico of the University of Chile (Project 4437-R, 1977).     

Comparison of a natural heparinoid with sodium and calcium heparin for their effect on the inhibitor of activated factor X

Summary The reaction between activated factor X (Xa) and its natural inhibitor (XaI) was accelerated in vitro by both sodium heparin and an heparinoid, which was about 3 times less potent than heparin. The s. c. administration in humans of 5,000 units of sodium and calcium heparin was followed by the detection of a plasma activity potentiating XaI. In the majority of subjects, the heparinoid was not effective. These observations indicate that the use of heparinoids should not be considered as an alternative to heparin in the prevention of thromboembolism.     

Opposite effects of beta-adrenoceptor stimulation and 8-bromo-cyclic AMP on potassium efflux in mammalian heart muscle

beta-adrenoceptor stimulation by isoprenaline increases the potassium efflux in beating guinea-pig atria. This effect is not mimicked by 8-bromo-cyclic AMP, a cyclic AMP analogue which exerts a positive inotropic effect in this preparation.     

Spectral properties of methemoglobins prepared by the action of sodium nitrite and potassium ferricyanide

Summary Methemoglobin was prepared by the addition of sodium nitrite or potassium ferricyanide to oxy or deoxyhemoglobin. The spectral properties of these methemoglobins were studied before and after extensive dialysis. It is shown that the methemoglobin formed by sodium nitrite has substantial spectral differences in visible and Soret band compared to that formed by potassium ferricyanide. These differences are proportional to the excess of sodium nitrite only. This suggests that both methemoglobins are similar compounds.Supported by NIH grant No. 5R01AM 20181-03 and VA grant No. 5455-003.Acknowledgments. The technical assistance of Ms Carol A. Perry and the secretarial assistance of Ms Wanda Stewart are highly appreciated.     

Comparison of a natural heparinoid with sodium and calcium heparin for their effect on the inhibitor of activated factor X.

The reaction between activated factor X (Xa) and its natural inhibitor (XaI) was accelerated in vitro by both sodium heparin and an heparinoid, which was about 3 times less potent than heparin. The s. c. administration in humans of 5,000 units of sodium and calcium heparin was followed by the detection of a plasma activity potentiating XaI. In the majority of subjects, the heparinoid was not effective. These observations indicate that the use of heparinoids should not be considered as an alternative to heparin in the prevention of thromboembolism.     

The effects of acute and chronic morphine on regional distribution of cardiac output in brain

Both acute and chronic administration of morphine resulted in an increase in the percent cardiac output received by brain. However, various brain regions were affected differently by the drug treatments. The greatest increases in percent cardiac output received after chronic administration of morphine occurred in pons and cerebellum, while the greatest increases after acute administration occurred in cortex and midbrain. The changes found are in contrast with earlier studies which suggest that morphine has no effect on cerebral blood flow.     

The effects of acute and chronic morphine on regional distribution of cardiac output in brain

Summary Both acute and chronic administration of morphine resulted in an increase in the percent cardiac output received by brain. However, various brain regions were affected differently by the drug treatments. The greatest increases in percent cardiac output received after chronic administration of morphine occurred in pons and cerebellum, while the greatest increases after acute administration occurred in cortex and midbrain. The changes found are in contrast with earlier studies which suggest that morphine has no effect on cerebral blood flow.