Fluxes of magnesium and calcium during induced activity of frog sartorius muscle

Resumen La representación del influjo de Ca y de Mg en músculo esquelético en reposo de rana as cualtitativamente differente; sin embargo la magnitud de dicho influjo as inicialmente similar. Estímulo mediante pulsos eléctricos o cafeina aumenta significamente el influjo de Ca pero no el de Mg durante un período de 10 min.     

The role of calcium and zinc in the electrical and mechanical responses of frog sartorius muscle

Zusammenfassung Membranpotential, Aktionspotential und Spannung der Einzelzuckung einer Einzelfaser des M. sartorius vonRana temporaria nehmen in der calciumfreien Badeflüssigkeit progressiv ab. Extrazelluläres Zink hingegen ist für die Kontraktion nicht notwendig, beeinflusst aber in physiologischen Konzentrationen die Dauer der Aktivität.     

The decremental propagation of the action potential and loss of mechanical response in frog sartorius muscle in the absence of calcium

Zusammenfassung Die Herabsetzung der Kontraktionsleistung einer Sartoriusmuskelfaser des Frosches, bevor sie wegen Calciummangel elektrisch unerregbar wird, kann weitgehend mit einer ungenügenden Aktivierung des kontraktilen Systems durch das Abklingen des Aktionspotentials erklärt werden.

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On leave of absence from Human Biomechanics Laboratory, Medical Research Council, Hampstead, London (England).     

The force-velocity relation of frog sartorius muscle at constant velocities of lengthening

Zusammenfassung Für Muskelverlängerungen zeigt die Kraft-Geschwindigkeit-Beziehung des Frosch-Sartoriusmuskels bei konstanten Geschwindigkeiten der Verlängerung eine Doppeldeutigkeit, wobei der Aktivierungsgrad des Muskels einen wesentlichen Einflussfaktor darstellt.     

The effect of intracellular potassium ions on active sodium efflux in frog sartorius muscle

Zusammenfassung Radioaktive Untersuchungen zeigen. dass intrazelluläre K⁺-Ionen den aktiven Na⁺-Austausch hemmen.     

Relationship between light diffraction intensity and tension development in frog skeletal muscle

Summary Laser diffraction intensity decrease in active muscles precedes tension development at sarcomere lenghts below 2.76 m, but not at greater lenghts. This suggests that the time lag is caused by random sarcomere shortenings inside each myofibril.     

Calcium transients in a molluscan smooth muscle

Summary The changes in myoplasmic calcium concentration during contraction were recorded in the anterior byssal retractor muscle ofMytilus edulis using murexide as calcium indicator, and were found to be qualitatively similar to those in striated muscles except for their slow time course.     

The effect of charatoxin, 4-methylthio-1,2-dithiolane,on the frog sartorius neuromuscular junction

Summary The insecticide 4-methylthio-1,2-dithiolane, named charatoxin, blocks the frog muscular twitches elicited through the neuromuscular junction. The activity level and the course of inhibition is comparable to that of 4-dimethyl-amino-1,2-dithiolane, nereistoxin.The authors are grateful to Dr N. Jacobsen, Cheminova A/S for synthesizing the toxins and the 2 analogues.     

Contraction of frog stomach muscle and frog heart in electrolyte-free solutions

Zusammenfassung Der Verlust der Reizbarkeit bei Froschherz- und Magenmuskulatur auf verschiedenen Temperaturstufen verläuft parallel mit einem Adenosintriphosphat-Verlust, was andeutet, dass das Nichtfunktionieren in natriumfreier Lösung von einem Adenosintriphosphat-Verlust abhängig ist.     

The effect of charatoxin, 4-methylthio-1,2-dithiolane, on the frog sartorius neuromuscular junction

The insecticide 4-methylthio-1,2-dithiolane, named charatoxin, blocks the frog muscular twitches elicited through the neuromuscular junction. The activity level and the course of inhibition is comparable to that of 4-dimethyl-amino-1,2-dithiolane, nereistoxin.     

The origin of the action potential in frog stomach muscle and heart

Zusammenfassung Das Aktionspotential von Herz- und Magenmuskulatur des Frosches scheint nicht vom Einund Ausstoss der Ionen, sondern vom elektronischen Aufbau der Zellmembran abhängig zu sein.     

The origin of the instantaneous elasticity in single frog muscle fibres

Summary High-speed cinematographic recordings of single tetanized muscle fibres during a quick decrease in length revealed that the shortening was mostly localized at the fibre segment nearest the released end of the fibre, indicating that the instantaneous elasticity may not originate from the elasticity of the cross-bridges.We wish to thank Dr H. Hashizume of the Engineering Research Institute, Tokyo University for providing facilities to use the ultra high-speed cinecamera, and Mr T. Tsuno, Mr Y. Nakamura and Miss S. Gomi for their technical assistance.     

Cytosolic calcium in platelet activation

Experiments with permeabilised platelets, and with intact platelets loaded with fluorescent Ca2+-indicators, over the past several years have greatly extended our knowledge and understanding of cytosolic Ca2+ as a platelet activator and its interactions with other cytosolic regulators. This article outlines insights, gained from the use of the fluorescent dyes, into maintenance and restoration of basal [Ca2+]i, mechanisms of receptor-mediated Ca2+-mobilisation and quantitation of [Ca2+]i/response relations in intact human platelets.     

Cytosolic calcium in platelet activation

Experiments with permeabilised platelets, and with intact platelets loaded with fluorescent Ca²⁺-indicators, over the past several years have greatly extended our knowledge and understanding of cytosolic Ca²⁺ as a platelet activator and its interactions with other cytosolic regulators. This article outlines insights, gained from the use of the fluorescent dyes, into maintenance and restoration of basal [Ca²⁺]_i, mechanisms of receptor-mediated Ca²⁺-mobilisation and quantitation of [Ca²⁺]_i/response relations in intact human platelets.