The Ca2+-transport ATPases in smooth muscle

Summary A calmodulin stimulated Ca²⁺-transport ATPase which has many of the characteristics of the erythrocyte type Ca²⁺-transport ATPase has been purified from smooth muscle. In particular, the effect of calmodulin on these transport enzymes is mimiced by partial proteolysis and antibodies against erythrocyte Ca²⁺-transport ATPase also bind to the smooth muscle (Ca²⁺+Mg²⁺)ATPase. A correlation between the distribution of the calmodulin stimulated (Ca²⁺+Mg²⁺)ATPase and (Na⁺+K⁺)ATPase activities in smooth muscle membranes separated by density gradient centrifugation suggests a plasmalemmal distribution of this (Ca²⁺+Mg²⁺)ATPase. A phosphoprotein intermediate in smooth muscle which strongly resembles the corresponding phosphoprotein in sarcoplasmic reticulum of skeletal muscle may indicate the presence in smooth muscle of a similar type of Ca²⁺-transport ATPase.     

Potentials in mammalian skeletal muscle from collagenase-treated tissue

Summary Transmembrane potentials were recorded from skeletal muscle fibres dissected with the aid of collagenase perfusion. Collagenase treatment had little or no effect on the action or resting potentials.     

Potentials in mammalian skeletal muscle from collagenase-treated tissue.

Transmembrane potentials were recorded from skeletal muscle fibres dissected with the aid of collagenase perfusion. Collagenase treatment had little or no effect on the action or resting potentials.     

Studies on muscle fibre splitting in skeletal muscle

Summary Autoradiographic, stereological and histological studies have been carried out to determine the origin of muscle fibre splitting which supposedly occurs during muscle hypertrophy. The results obtained clearly indicate that the supposedly split fibres are a transient response probably derived from satellite cells and are not derived from pre-existing fibres by true splitting. Similarly, increases in muscle fibre size are not achieved by recruitment of satellite structures as indicated by lack of myonuclear recruitment.Acknowledgment. This work was carried out with the aid of a grant from the Medical Research Council of Great Britain. The authors are grateful for the excellent technical assistance of Miss H. Caulton, M.J. Wild and M. Fenner.     

Clofibrate-induced myotonia in the rat

Summary Clofibrate induced electromyographic and contractile responses in rats consistent with myotonia.This work was supported in part by the Muscular Dystrophy Associations of America. The authors are grateful to Ayerst Laboratories for the generous supply of clofibrate used in this study.     

The genetics of a soluble acidic protein in skeletal muscle

Zusammenfassung Ein Hauptbestandteil von wässerigem Skelettmuskelextrakt ist ein dimeres, saures Protein mit einem Molekulargewicht von 120 000. In der WachtelCoturnix coturnix japonica und in der KröteBufo americanus wird dieses Protein von einem einzelnen autosomalen Locus kontrolliert.

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Supported by grants No. CA 10619 and No. CA 05138 from the National Institutes of Health, U.S. Public Health Service.

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This work was performed during Dr. Wohnus' sabbatical leave from Bennington College, Bennington, Vermont.     

On the heterogeneity of skeletal muscle fibers: The intermediate fibers

Résumé Les mesures d'intensité de la réaction à la succino-déshydrogénase et de la surface des fibres des muscles quadriceps et soléaire chez le rat nous ont permis d'individualiser un groupe de fibres intermédiaires qui se situe entre les fibres rouges (type I) et blanches (type II). Les fibres intermédiaires ont une activité enzymatique et une population mitochondriale distinctes, une taille moyenne et une teneur élevée en glycogène.     

The response of human skeletal muscle tissue to hypoxia

Hypoxia refers to environmental or clinical settings that potentially threaten tissue oxygen homeostasis. One unique aspect of skeletal muscle is that, in addition to hypoxia, oxygen balance in this tissue may be further compromised when exercise is superimposed on hypoxia. This review focuses on the cellular and molecular responses of human skeletal muscle to acute and chronic hypoxia, with emphasis on physical exercise and training. Based on published work, it is suggested that hypoxia does not appear to promote angiogenesis or to greatly alter oxidative enzymes in skeletal muscle at rest. Although the HIF-1 pathway in skeletal muscle is still poorly documented, emerging evidence suggests that muscle HIF-1 signaling is only activated to a minor degree by hypoxia. On the other hand, combining hypoxia with exercise appears to improve some aspects of muscle O₂ transport and/or metabolism.     

The acetylcholine content and choline-acetyltransferase activity in human skeletal muscle

Riassunto Sono descritte le tecniche per la determinazione della ACH e attività CHA nel muscolo umano normale. I risultati indicano che il rapporto fra capacità sintetizzante e neurormone è più alto in muscoli con maggior impegno funzionale.     

Action of hydroxychloroquine on the skeletal muscle in vitro

Zusammenfassung Hydroxychloroquine vermindert die Acetylcholinwirkung am M. rectus abdominis des Frosches.     

The experimental induction of ultrastructural damage in cardiac muscle

Experimentally-induced rises in intracellular calcium ([Ca2+]i) promote rapid myofilament degradation in amphibian and mammalian cardiac muscle strips. The relevance of these studies to the subcellular injury produced by ischaemia, the possible involvement of lysosomal enzymes and similarities with skeletal muscle are discussed.     

Pleiotropic effects of sphingolipids in skeletal muscle

Studies of the last two decades have demonstrated that sphingolipids are important signalling molecules exerting key roles in the control of fundamental biological processes including proliferation, differentiation, motility and survival. Here we review the role of bioactive sphingolipids such as ceramide, sphingosine, sphingosine 1-phosphate, ganglioside GM3, in the regulation of skeletal muscle biology. The emerging picture is in favour of a complex role of these molecules, which appear implicated in the activation of muscle resident stem cells, their proliferation and differentiation, finalized at skeletal muscle regeneration. Moreover, they are involved in the regulation of contractile properties, tissue responsiveness to insulin and muscle fiber trophism. Hopefully, this article will provide a framework for future investigation into the field, aimed at establishing whether altered sphingolipid metabolism is implicated in the onset of skeletal muscle diseases and identifying new pharmacological targets for the therapy of multiple illnesses, including muscular dystrophies and diabetes. Received 30 April 2008; received after revision 19 June 2008; accepted 14 July 2008