Stimulation by aldosterone of the sodium efflux in barnacle muscle fibres

Zusammenfassung Es wurde gezeigt, dass die Natrium-Ausscheidung in der Muskelfaser von Entenmuskeln auf aldosteron reagiert.     

Enhanced excitability in locust muscle fibres induced by calcium free saline

Summary The membrane of locust muscle fibres normally exhibits a graded electrical response to outward current pulses of increasing strength. On removal of Ca⁺⁺ ions from the external medium, these fibres are shown to exhibit depolarizing membrane responses of variable time course and duration. These responses are abolished in Na⁺-free solutions, and by the addition of Mn⁺⁺ ions.D.A.M. was the recipient of a Royal Society and Science Research Council European Exchange Fellowship. We thank the Centre for Overseas Pest Research, Kensington for supplying the locusts.     

γ-Aminobutyric acid and crab muscle fibres

Zusammenfassung Eine Reihe von Krabbenmuskeln zeigt zwei Arten von Muskelfasern: «phasische» und «tonische» mit sehr unterschiedlichen Membraneigenschaften. Die phasischen Muskelfasern zeigen verhältnismässig kleine Permeabilitätsänderungen der Membranen nach Zugabe von GABA oder nach Stimulierung des peripheren hemmenden Axons. Die tonischen Muskelfasern zeigen sehr deutliche Permeabilitätsänderungen nach Zugabe von GABA oder Stimulierung des hemmenden Axons. Die Grundlagen dieses unterschiedlichen Verhaltens werden analysiert.     

Activation of the electrogenic Na-pump of cardiac muscle fibres by ACh in K-free solutions

Summary The ionic mechanism of the membrane outward current (ACh-current) of bullfrog atrium muscle, induced by acetylcholine in K-free solution, was analyzed by a voltage-clamp experiment. The results suggested that the ACh-current was induced not only by an increase in K-conductance but also by an activation of the electrogenic Na-pump.Acknowledgment. This work was supported by a grant (257037) from the Ministry of Education of Japan.     

The diffusion coefficient of sodium in barnacle muscle fibres

Zusammenfassung In Muskelfasern der Entenmuschel (Balanus nubilus undBalanus aquila) beträgt der Natrium Diffusions-Koeffizient 2,2×10^–6 cm²/sec.

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Acknowledgment. This work was supported in part by grants from the Office of Naval Research and the National Science Foundation.     

Electro-mechanical noise in atrial muscle fibres of the carp

Summary Steady membrane voltage fluctuations have been observed in atrial muscle fibres of the carp. These voltage fluctuations produce minute mechanical oscillations, as revealed by an interference contrast microscope. The steady voltage fluctuations may be related to abnormal automaticity in the heart.Supported by the U.S. Israel Binational Science Foundation, Jerusalem, and is part of a thesis to be submitted by Ms Akselrod to the Tel-Aviv University. We thank Ms M. Bendikowski for her efficient technical assistance.     

Activation of the electrogenic Na-pump of cardiac muscle fibres by ACh in K-free solutions.

The ionic mechanism of the membrane outward current (ACh-current) of bullfrog atrium muscle, induced by acetylcholine in K-free solution, was analyzed by a voltage-clamp experiment. The results suggested that the ACh-current was induced not only by an increase in K-conductance but also by an activation of the electrogenic Na-pump.     

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.     

Histochemical differentiation of skeletal muscle fibres in the bovine foetus

Zusammenfassung Die Entwicklung der histochemischen Unterschiede in den Muskelfasern von Rinderfeten wurden mittels der Succinodehydrogenaseaktivität untersucht. Nach 155–175 Trächtigkeitstagen wurden helle und dunkle Fasern beobachtet, doch sind die Unterschiede erst nach 200 Trächtigkeitstagen deutlich. Die intermediären Fasern treten erstmals nach 215 Trächtigkeitstagen auf. Die Muskeln M. gastrocnemius, rectus femoris und longissimus dorsi zeigen eine gleichmässige Entwicklungsfolge.

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Supported by the FAO Veterinary Faculty for FAO Fellows and Scholars, Copenhagen (Denmark).

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On deputation from the Department of Anatomy, Kerala Veterinary College, Trichur (Kerala, India).     

Histochemical characterization of the red fibres in pigeon pectoralis muscle

Summary Red fibres of the pigeon pectoralis muscle showed high ATPase reaction at pH 9.4. Veronal-acetate pretreatment completely inhibited the ATPase reaction in these red fibres but not in type I fibres of the gastrocnemius. The former are type II red muscle fibres and hence are unlike type I red, the so-called slow-twitch muscle fibres.     

Coordinated activation of muscle fibres by different conduction velocities in branches of a crustacean motor axon

Summary Higher conduction velocities in branches of the fast excitor axon to distal muscle fibres ensure that these fibres are activated almost simultaneously with proximal fibres in the claw closer muscle of lobsters, producing a contraction of maximal force.Supported by Muscular Dystrophy Association and National Research Council of Canada.Supported by National Institute of Health and Muscular Dystrophy Association of America.     

Electron microscope and optical diffraction studies on glycerol-extracted insect flight muscle fibres relaxed by pyrophosphate

Zusammenfassung Elektronenmikroskopische Aufnahmen von einfacher Filament-Lagen Mg-Pyrophosphaterschlaffter Fasern der dorsolongitudinalen Flugmuskulatur vonLethocerus spec. gleichen weitgehend dem Bild ATP-erschlaffter Muskeln. Optische Transformationen scheinen dagegen die Charakteristika von ATP-erschlafften Fasern und solchen, die sich im Rigor mortis befinden, zu kombinieren. Die Überführung der Fasern aus einer Mg-Pyrophosphat- in eine Rigor-Lösung stellte das Rigor-Muster wieder her.

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Supported by a short term fellowship of the EMBO to one of us (G.B.).

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Acknowledgment. We are greatly indebted to Dr.Louise N. Johnson, P. Eagle andL. J. Stumpp, Oxford, Dept. of Zoology, for their help with the optical diffraction measurements, to Mrs.Hiltrud Gülker for her expert technical assistance and to Prof.Pringle and Dr.R. T. Tregear for their hospitality and many helpful discussions and criticism.     

Tension and structure in crustacean fast and slow muscle fibres

Résumé Les fibres de l'abdomen du homard pourvues de longues striations ont développé une plus grande tension par unité de surface, en coupe transversale, que les fibres munies de striations courtes.     

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.