Tendon shortening in striated muscle.

Tendon shortening in the digastric muscle of the rabbit resulted in a short term increase in gross muscle length and sarcomere length. Subsequently, muscle and sarcomere lengths decreased to less than control values. Long-term measurements suggested that a return to control sarcomere length may have been achieved by a reduction in sarcomere number.     

Fine structure of a neurosecretory axon in a crustacean skeletal muscle

Résumé Un axone neuro-sécréteur à extrémités localisées dans le muscle squelettique du craneCarcinus est décrit. Ces extrémités contiennent 6 sortes de vésicules ayant les diamètres de 1300 a 3700 . Il est suggéré que es petites vésicules correspondent à la phase de rétablisement de la membrane, pendant la décharge des granules euro-sécréteurs. On suppose aussi que cet axone peutêtre l'intermédiaire d'une influence trophique du nerf sur le muscle.

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I am most grateful to Mr.K. Oates and Mr.G. R. Abram for excellent technical assistance.

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Supported by a Research Studentship from the Science Research Council.     

Histochemical fibre types in striated muscle from the guinea-pig oesophagus

Summary Histochemical techniques have been used to classify the striated muscle fibres found in the guinea-pig oesophagus. The functional significance of these results is discussed.     

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.     

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.     

Frequency-domain study of the mechanical response of living striated muscle

Summary Small-amplitude sinusoidal displacements, in the frequency rang 4–100 Hz, were applied to intact whole frog sartorius muscle whilst in a state of tetanus. At low frequencies the muscle, was observed to do oscillatory work, while at higher frequencies it tended towards elastic behaviour. Frequency-response plots obtained were compared with those from other muscle preparations. Results were interpreted in terms of mechano-chemical transduction properties of muscle.The authors wish to thank the Australian Research Grants Commission for provision of the laser, and L. I. Patterson for construction of the mechanical apparatus.     

Changes in the A-band width during contraction in horseshoe crab striated muscle

Summary Cinematographic recordings of Ca-activated contraction in glycerinated bundles of myofibrils of the horseshoe crab striated muscle indicated that the A-band width did not change during rapid sarcomere shortening from 11 to 4 m, while it increased by about 10% in nearly isometric conditions.We wish to thank T. Taniguchi, M. Kusama and M. Goto for their excellent technical assistance in taking cinematographic recordings.     

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     

Calcitonin gene related peptide stimulates adenylate cyclase activity in rat striated muscle

Summary Rat calcitonin gene related peptide (CGRP) and salmon calcitonin (CT) stimulated adenylate cyclase activity in a dose-dependent manner in the rat diaphragm and in the kidney. The ED₅₀ value of rat CGRP was lower and that of salmon CT was higher in the diaphragm than in the kidney. These results suggest that CGRP stimulates adenylate cyclase activity in the striated muscle by reacting with sites distinct from the site in the kidney.     

Calcitonin gene related peptide stimulates adenylate cyclase activity in rat striated muscle

Rat calcitonin gene related peptide (CGRP) and salmon calcitonin (CT) stimulated adenylate cyclase activity in a dose-dependent manner in the rat diaphragm and in the kidney. The ED50 value of rat CGRP was lower and that of salmon CT was higher in the diaphragm than in the kidney. These results suggest that CGRP stimulates adenylate cyclase activity in the striated muscle by reacting with sites distinct from the site in the kidney.     

Special forms of amitotic nuclear division in striated muscle and other insect tissues

Résumé On décrit quelques aspects morphologiques de l'appareil nucléaire des fibres musculaires striées des insectes. Le nom Polykaryonéma est proposé pour désigner les noyaux filamenteux géants qui par fragmentations successives produisent des chaÎnes de noyaux indépendants, placées dans le centre des fibres musculaires adultes. Ce phénomène offre un bon exemple de division nucléaire amitotique.     

Glutaminase activity in rat skeletal muscle mitochondria

Summary Isolated rat skeletal muscle mitochondria took up about 40-ng-atoms O per min per mg protein, with glutamine as the only respiratory substrate. The mitochondria incubated in the presence of glutamine and KCN formed both ammonia and glutamate in equivalent amounts. The experiments reported here provide suggestive evidence that rat skeletal muscle mitochondria contain glutaminase (L-glutamine amidohydrolase EC 3.5.1.2.) activity.This work was supported by the Polish Academy of Sciences within the project II. 1, 2, 6.