The effects of the ‘calcium-antagonist’, prenylamine,on the action potential of crayfish muscle (Oronectes virilis)

Zusammenfassung Der organische Ca⁺⁺-Antagonist Prenylamin blockiert die leicht reversiblen Ca⁺⁺-Aktions-potentiale in der Muskelfaser des FlusskrebsesOronectes virilis. Etwas niedrigere Konzentrationen erhöhen die Schwelle und verlängern die Dauer, während schwache Konzentrationen von Prenylamin nur wirksam waren, wenn dieses verwendet wurde, bevor der Muskel dem Aktionspotentialerreger Procain oder Sr⁺⁺ ausgesetzt war.     

Spontaneous junctional currents in Drosophila muscle fibres: effects of temperature, membrane potential and ethanol.

Fast, slow and fast multiquantal spontaneous junctional currents were recorded from glutamate sensitive muscle fibres of Drosophila larvae. Decrease of temperature and hyperpolarization prolonged the time course of fast currents. Ethanol (0.4 M) markedly shortened their duration, whereas several other drugs known to modify the time course of currents at cholinergic synapses were ineffective at this neuromuscular junction.     

The length-tension diagram of single muscle fibres of the crayfish

Zusammenfassung An isolierten Muskelfasern vonAstacus fluviatilis wurde mittels Kaliumkontraktur die Spannung-Sarkomerlängenrelation untersucht. Maximale Faserspannung wird bei einer Sarkomerlänge von 10,5 entwickelt. Werden Fasern zu einer Sarkomerlänge von 16,5 gedehnt, so ist die Spannung nicht mehr messbar. Diese Sarkomerlänge ist etwas grösser als diejenige (14.45), die aus der Länge der dicken Filamente (3.95) und der optimalen Länge hervorgeht.     

The control of contraction activation by the membrane potential

Summary Force measurements under voltage-clamp control were performed in short toe muscles of the frog. The results show a) that the activation of force development and its repriming process can at least qualitatively be correlated to charge movement kinetics; b) that caffeine improves EC coupling by potentiating the potential dependent activation process.This work was supported by DFG (SFB 114 Bionach) and DAAD.     

The origin of the series elastic component in single crayfish muscle fibres

Summary High-speed cinematographic studies on the length changes of single tetanized crayfish muscle fibres during a step decrease in length revealed a fairly uniform distribution of a highly compliant series elastic component along the fibre length, suggesting that it mainly originates from some structures in each sarcomere other than 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 cine-camera, and Mr T. Tsuno, Mr Y. Nakamura and Miss S. Gomi for their technical assistance.     

Effects of nitric oxide on the contraction of skeletal muscle

A review of the literature suggests that the effects of nitric oxide (NO) on skeletal muscles fibers can be classified in two groups. In the first, the effects of NO are direct, due to nitrosation or metal nitrosylation of target proteins: depression of isometric force, shortening velocity of loaded or unloaded contractions, glycolysis and mitochondrial respiration. The effect on calcium release channels varies, being inhibitory at low and stimulatory at high NO concentrations. The general consequence of the direct effects of NO is to ‘brake’ the contraction and its associated metabolism. In the second group, the effects of NO are mediated by cGMP: increase of the shortening velocity of loaded or unloaded contractions, maximal mechanical power, initial rate of force development, frequency of tetanic fusion, glucose uptake, glycolysis and mitochondrial respiration; decreases of half relaxation time of tetanus and twitch, twitch time-to-peak, force maintained during unfused tetanus and of stimulus-associated calcium release. There is negligible effect on maximal force of isometric twitch and tetanus. The general consequence of cGMP-mediated effects of NO is to improve mechanical and metabolic muscle power, similar to a transformation of slow-twitch to fast-twitch muscle, an effect that we may summarize as a ‘slow-to-fast’ shift.     

The origin of the series elastic component in single crayfish muscle fibres.

High-speed cinematographic studies on the length changes of single tetanized crayfish muscle fibres during a step decrease in length revealed a farily uniform distribution of a highly compliant series elastic component along the fibre length, suggesting that it mainly originates from some structures in each sarcomere other than the cross-bridges.     

The effect of urethane on histamine-induced contraction of guinea-pig tracheal smooth muscle

Summary Urethane possesses a direct depressant action on histamine-induced contractions of guinea-pig tracheal smooth muscle both in vivo and in vitro.     

Dependence of the contractility of coronary muscle on substances favouring contraction and relaxation

Zusammenfassung Es werden die Besonderheiten der am isolierten Koronargefäss von Rind und Pferd nach elektrischer Reizung, Verabreichung von Adrenalin oder Kalium registrierten Mechanogramme beschrieben. Es wird darauf hingewiesen, dass die Kontraktilität der Muskelzellen des Rinderkoronargefässes von zwei Stoffen abhängig ist, wovon der eine die Kontraktion und der andere die Erschlaffung fördert.

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I thank the Schweizerischer Nationalfonds für wissenschaftliche Forschung for help.     

The influence of the extracellular potassium concentration on the glycoside effects upon contractile force and action potential duration of the guinea-pig papillary muscle

Zusammenfassung Eine Verringerung der extrazellulären Kaliumkonzentration im Bereich zwischen 9,6 und 2,4 mM führt zu einer Zunahme der positiv inotropen Glykosidwirkung am Meerschweinchenpapillarmuskel; die Wirkung des Adrenalins wird nicht beeinflusst. Die Vergrösserung der inotropen Wirkung geht parallel einer starken Zunahme der Verkürzung der Aktionspotentialdauer, besonders in Höhe des Plateaus (30% Repolarisation).