Membrane constants and sodium conductance of a single muscle fibre

Riassunto Nella singola fibra muscolare di cavia a 38°C sono state determinate, applicando la «square pulse analysis», la resistenza, la costante di tempo, la costante di spazio e la capacità della membrana a riposo. È stato inoltre possibile calcolare la massima conduttanza per il sodio,gn a, che è risultata di 35,3 mmho/cm².     

Action potentials of the guinea pig heart in sodium deficient solutions

Zusammenfassung Es werden Aktionspotentiale vom Meerschweinchenvorhof in Badelösungen verschiedener Na-Konzentrationen mittels intrazellulärer Elektroden registriert. Während das Aktionspotential desVentrikels relativ unempfindlich gegen Veränderungen der Na-Konzentration bleibt^{4, 6}, lässt sich die «Na-Hypothese» für denVorhof anwenden.

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Aided by a grant from the Italian Consiglio Nazionale delle Ricerehe.     

Early functional differentiation of heart muscle cells

Zusammenfassung Von embryonalen Hühnerherzen wurdenin vivo Membranpotentiale verschiedenen Regimes registriert. Bereits auf sehr frühen Entwicklungsstadien (37 h) wird eine Differenzierung in Schrittmachergasern und spätere Vertrikelfasern gefunden.

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Aided by a grant from the Italian Consiglio Nazionale delle Ricerche.     

Effects of octylguanidine on the electrical activity of Xenopus heart.

The effects of laboratory synthesized octylguanidine are described. There is an early decease of the maximum rate of rise of the action potential with negligible reduction of the overshoot although the membrane resting potential is unchanged. Subsequently, there is a remarkable reduction of both membrane potential and overshoot, while the plateau is shortened. The former effects resemble those seen with tetrodotoxin, the latter ones, with metabolic poisons.     

Effect of platelet activating factor on guinea-pig papillary muscle

Summary Platelet activating factor (PAF) induces a biphasic effect on guinea-pig papillary muscle: 1. a transient positive inotropic effect preceded by an increase in action potential duration (APD); 2. a marked negative effect on inotropism and on APD. Since Ca⁺⁺ slow action potentials were initially enhanced by PAF and then markedly depressed, it is suggested that PAF specifically interferes with the Ca⁺⁺ slow channel.     

Effect of platelet activating factor on guinea-pig papillary muscle

Platelet activating factor (PAF) induces a biphasic effect on guinea-pig papillary muscle: 1. a transient positive inotropic effect preceded by an increase in action potential duration (APD); 2. a marked negative effect on inotropism and on APD. Since Ca++ slow action potentials were initially enhanced by PAF and then markedly depressed, it is suggested that PAF specifically interferes with the Ca++ slow channel.