6,146 research outputs found
The XXV European Muscle Congress: La Grand-Motte, Montpellier, France 14-17 September 1996.
No full text
The contribution of the rate of ATP induced acto-myosin dissociation and of the rate of ADP release from acto-myosin in determining unloaded shortening velocity depends on temperature
No full textFunctional heterogeneity of mammalian single muscle fibres: do myosin isoforms tell the whole story?
No full textLa pubblicazione è una review sui meccanismi della plasticità del muscolo scheletric
Reactive oxygen and nitrogen species in skeletal muscle: acute and long-term effects
No full textIt is a common belief that oxidative stress imposes a considerable threat to our health and that antioxidants promote health. Along these lines, foodstuffs are considered healthy if they contain antioxidants and advertisements for expensive supplements to increase our defence against oxidants are commonplace. Unfortunately, the term oxidative stress is poorly defined and it is uncertain whether relatively minor changes in the dietary intake of antioxidants are important in relation to the internal systems that control the redox balance. Although it is clear that excessive amounts of reactive oxygen and nitrogen species (ROS/RNS) can induce pathological processes, numerous recent studies have also shown important effects of ROS/RNS in integral physiological signalling events. The complex effects of ROS/RNS in skeletal muscles were addresses in The Journal of Physiology Symposium ‘Reactive oxygen & nitrogen species in skeletal muscle – acute and long-term effects’, which was held in September 2010 in association with the XXXIX European Muscle Conference in Abano Terme, Italy. The goal of this well-attended symposium was to review, and thereby increase our understanding of, how ROS/RNS affect skeletal muscle acutely and in the long term
Maximum speed of shortening and ATPase activity in atrial and ventricular myocardia of hyperthyroid rats
No full textThe kinetic properties of the myofibrillar system of atrial and ventricular myocardia of hyperthyroid rats were analyzed by determining ATPase activity and maximum shortening velocity. Hyperthyroidism was induced by daily subcutaneous injections of triiodothyronine (0.2 mg/kg body wt) for 2 wk. The treatment induced a marked atrial and ventricular hypertrophy and, in ventricular myocardium, an isomyosin shift toward a homogeneous V1 composition. Skinned trabeculae and purified myofibrils were prepared from atrial and ventricular myocardia. Enzymatic assays on the myofibrils showed that both Ca-stimulated ATPase activity and Ca-Mg-dependent ATPase activity had equal values in atrial and ventricular myocardia. In skinned trabeculae during maximal Ca activations, force-velocity curves were determined by load-clamp maneuvers, and unloaded shortening velocity (Vo) was obtained with the slack-test method. Both maximum shortening velocities extrapolated from the force-velocity curves (Vmax) and Vo were significantly higher (+68 and +52%, respectively) in atrial than in ventricular preparations. Developed tension was significantly greater in ventricular preparations. Maximum power output was not significantly different. Previous findings (V. Cappelli, R. Bottinelli, C. Poggesi, R. Moggio, and C. Reggiani. Circ. Res. 65: 446-457, 1989) had led to the conclusion that variations in ATPase activity and shortening velocity of ventricular myocardium can be accounted for by changes in isomyosin composition. In this light, the present results suggest that 1) ATPase activity is equal in atrial and ventricular myocardia as the two tissues contain the same myosin heavy chain isoform, 2) the difference in maximum speed of shortening between atrium and ventricle might be due to the presence of tissue-specific isoforms of myosin light chains
Force-velocity properties and myosin light chain isoform composition of an identified type of skinned fibres from rat skeletal muscle.
No full textForce-velocity relations, myosin heavy chain (MHC) and myosin light chain (MLC) isoform composition of single skinned fibres from rat plantaris muscle were determined. In fibres containing the same (2X) isoform of myosin heavy chain, several parameters derived from the force-velocity relation and isometric force (Po) were tested for relation with the fibre content in alkali myosin light chain (MLC) isoforms. Whereas maximum shortening velocity was found to be proportional to the relative content in the 3f isoform of alkali MLC, velocity of shortening at 5\% relative load, maximum power output, and Po were not. These results strengthen the idea that, in mammalian skeletal fibres, alkali MLC isoforms modulate shortening velocity at zero load, but suggest that they do not control the contractile behaviour at loads higher than zero
Essential myosin light chain isoforms and energy transduction in skeletal muscle fibers.
No full text- …
