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.     

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.     

Radioimmunoassay of an invertebrate peptide hormone — the crustacean neurosecretory hyperglycemic hormone

Summary Antibodies against hyperglycemic hormone (CHH) ofCarcinus were raised in rabbits by injection of extract from sinus glands which contain high concentrations of CHH. The antiserum neutralizes the biological activity of CHH and binds¹²⁵J-CHH. A RIA for CHH was established and was used to measure the hormone content of sinus glands.Dedicated to Prof. M. Gersch, Jena, on the occasion of his 70th birthday.This study was supported by the Deutsche Forschungsgemeinschaft (Ke 206/2).We thank S. Grabig. E. schmid and B. Reichwein for expert technical assistance, and Dr D. Breitig and G. Kegel for critical discussions.     

Radioimmunoassay of an invertebrate peptide hormone - the crustacean neurosecretory hyperglycemic hormone.

Antibodies against hyperglycemic hormone (CHH) of Carcinus were raised in rabbits by injection of extract from sinus glands which contain high concentrations of CHH. The antiserum neutralizes the biological activity of CHH and binds 125-J-CHH. A RIA for CHH was established and was used to measure the hormone content of sinus glands.     

Presynaptic inhibition in crustacean muscle: Axo-axonal synapse

Zusammenfassung Es ist anzunehmen, dass die präsynaptische Hemmung der Crustaceen-Muskeln durch Reaktion eines hemmenden Überträgerstoffs mit Rezeptoren der Endigungen der motorischen Nervenfasern zustande kommt. Synaptische Kontakte des hemmenden Axons mit den Endigungen der motorischen Nervenfasern sind mit dem Elektronenmikroskop beobachtet worden. Wahrscheinlich vermitteln diese Strukturen den präsynaptischen Effekt.     

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.     

Induction of electrical excitability in crustacean muscle by 4-cyclopentene-1,3-dione

Summary 4-Cyclopentene-1,3-dione induces electrical activity in inexcitable crustacean muscle. This effect is blocked by previous treatment with p-chloromercuribenzoic acid. These results suggest that crustacean muscle becomes excitable when certain-CH₂-SH side chains are converted to thioethers having carbonyl groups.Acknowledgments. This work was supported by USPHS Nos NS-07464, NS-14938 and GM-05784. Contribution No. 80 of the Laboratory of Neurobiology.     

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     

AMP-activated protein kinase in skeletal muscle: From structure and localization to its role as a master regulator of cellular metabolism

The AMP-activated protein kinase (AMPK) is a metabolite sensing serine/threonine kinase that has been termed the master regulator of cellular energy metabolism due to its numerous roles in the regulation of glucose, lipid, and protein metabolism. In this review, we first summarize the current literature on a number of important aspects of AMPK in skeletal muscle. These include the following: (1) the structural components of the three AMPK subunits (i.e. AMPKα, β, and γ), and their differential localization in response to stimulation in muscle; (2) the biochemical regulation of AMPK by AMP, protein phosphatases, and its three known upstream kinases, LKB1, Ca²⁺/calmodulin-dependent protein kinase kinase (CaMKK), and transforming growth factor-β-activated kinase 1 (TAK1); (3) the pharmacological agents that are currently available for the activation and inhibition of AMPK; (4) the physiological stimuli that activate AMPK in muscle; and (5) the metabolic processes that AMPK regulates in skeletal muscle. Received 04 May 2008; received after revision 14 June 2008; accepted 14 July 2008     

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.