Does tenotomy of skeletal muscle alter Z-line width in older animals?

Summary Results of unilateral achilles tenotomy on older (350–410 g) male rats, showed that the general width of Z-lines in the tenotomized muscles was not significantly altered by this procedure. Streaming of the Z-lines and rod formations was still present, as in younger rats.This investigation was supported in part by NIH grants 1-RO1-NS-14033 and 1-T32-07224.     

The effect of tilting ultrathin sections on the image of the Z-disc of skeletal muscle

Résumé A l'aide du microscope électronique muni d'un goniomètre, la structure tri-dimensionelle du disque Z de la fibre musculaire striée a été analysée. Les résultats obtenus sont comparés avec un modèle construit en perspex et avec les images conventionnelles du disque Z.

---

---

Acknowledgment. We wish to thank Pye Unicam (Philips) an Jeol (U. K.) Ltd. for kindly allowing us to use their electron microscopes. Technical assistance from Messrs.H. Fisher, J. Manston andR. Birchenough is gratefully acknowledged.     

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.     

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.     

‘Compensatory’ muscle hypertrophy in the rat induced by tenotomy of synergistic muscles

Zusammenfassung Nachweis, dass die schnelle Hypertrophie des M. soleus nach Tenotomie des synergistischen M. gastrocnemius durch passive Spannung des antagonistischen Muskels verursacht wird. Denervierung dieser Antagonisten verzögert eine Hypertrophie des M. soleus, während die Deafferenzierung des ganzen Gliedes ohne Effekt bleibt; auch zusätzliche Arbeitsleistung führt auf dem Höhepunkt der Hypertrophie zu keinerlei Gewichtszunahme.     

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     

A regular actin filament lattice in a vertebrate smooth muscle

Zusammenfassung In den glatten Muskelfasern aus dem Dickdarm der Maus wurde eine charakteristische Verteilung der Aktinfilamente gefunden. Die Filamente sind zu BÜndeln zusammengelagert, die parallel zur Faserlängsachse ausgerichtet sind. Innerhalb der BÜndel liegen die Filamente in dichter hexagonaler Packung. Die Dimensionen des gefundenen Filamentmusters stimmen sehr gut mit den durch Röntgenbeugungsanalysen ermittelten Überein.     

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.     

Glutaminase activity in rat skeletal muscle mitochondria

Isolated rat skeletal muscle mitochondria took up about 40-ng-atoms O 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.     

Development of acetylcholine sensitivity in cultured skeletal muscle

Résumé Nous avons étudié in vitro la réaction des fibres musculaires, à l'action de l'acétylcholine, de la tubocurarine et du décaméthonium. L'acétylcholine a provoqué une contraction un peu après la fusion des myoblastes, avant que les fibres ne deviennent striées. La sensibilité des fibres à l'acétylcholine a augmenté avec le développement morphologique. Elle s'est manifestée le long des fibres et les drogues de blocage neuromusculaire ont agi comme prévu.     

Control of respiration in skeletal muscle at rest

The suggestion is made that, under resting conditions in situ, muscle cell respiration is dependent on the way O2 and substrates are distributed to the cells by the microcirculation. (Delivery is measured as arterial-blood concentration multiplied by flow to the organ.) Microscale heterogeneity of this distribution, which is more marked but less stable than the more easily demonstrated larger-scale heterogeneity (0.1 to 0.5-g sampling grain), might indeed ration O2 and substrates in a large population of the cells of a resting organ at any given moment, and microscale heterogeneity of distribution may thus take part in the normal control of cell respiration.     

Cholinesterase activity in skeletal muscle after botulinum toxin

Zusammenfassung Bei Zufuhr von Botulinum-A-Toxin in den Muskel Tibialis anterior der Ratte war die Cholinesteraseaktivität nach zwei Wochen herabgesetzt, jedoch weniger ausgesprochen als nach zweiwöchiger Denervierung des Muskels.