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EDL Muscles (edl + muscle)
Selected AbstractsThe energetic cost of activation in mouse fast-twitch muscle is the same whether measured using reduced filament overlap or N -benzyl- p -toluenesulphonamideACTA PHYSIOLOGICA, Issue 4 2008C. J. Barclay Abstract Aim:, Force generation and transmembrane ion pumping account for the majority of energy expended by contracting skeletal muscles. Energy turnover for ion pumping, activation energy turnover (EA), can be determined by measuring the energy turnover when force generation has been inhibited. Most measurements show that activation accounts for 25,40% of isometric energy turnover. It was recently reported that when force generation in mouse fast-twitch muscle was inhibited using N -benzyl- p -toluenesulphonamide (BTS), activation accounted for as much as 80% of total energy turnover during submaximal contractions. The purpose of this study was to compare EA measured by inhibiting force generation by: (1) the conventional method of reducing contractile filament overlap; and (2) pharmacological inhibition using BTS. Methods:, Experiments were performed in vitro using bundles of fibres from mouse fast-twitch extensor digitorum longus (EDL) muscle. Energy turnover was quantified by measuring the heat produced during 1-s maximal and submaximal tetanic contractions at 20 and 30 °C. Results:,EA measured using reduced filament overlap was 0.36 ± 0.04 (n = 8) at 20 °C and 0.31 ± 0.05 (n = 6) at 30 °C. The corresponding values measured using BTS in maximal contractions were 0.46 ± 0.06 and 0.38 ± 0.06 (n = 6 in both cases). There were no significant differences among these values. EA was also no different when measured using BTS in submaximal contractions. Conclusion:, Activation energy turnover is the same whether measured using BTS or reduced filament overlap and accounts for slightly more than one-third of isometric energy turnover in mouse EDL muscle. [source] Reversible changes in Ca2+ -activation properties of rat skeletal muscle exposed to elevated physiological temperaturesTHE JOURNAL OF PHYSIOLOGY, Issue 3 2002Chris van der Poel Exposure of relaxed rat extensor digitorum longus (EDL; predominantly fast-twitch) muscle to temperatures in the upper physiological range for mammalian skeletal muscle (43-46 °C) led to reversible alterations of the contractile activation properties. These properties were studied using the mechanically skinned fibre preparation activated in Ca2+ -buffered solutions. The maximum Ca2+ -activated force (maximum force per cross-sectional area) and the steepness of force-pCa (-log10[Ca2+]) curves as measured by the Hill coefficient (nH) reversibly decreased by factors of 8 and 2.5, respectively, when the EDL muscle was treated at 43 °C for 30 min and 5 and 2.8, respectively, with treatment at 46 °C for 5 min. Treatment at 47 °C for 5 min produced an even more marked depression in maximum specific force, which fully recovered after treatment, and in the Hill coefficient, which did not recover after treatment. After all temperature treatments there was no change in the level of [Ca2+] at which 50 % maximum force was generated. The temperature-induced depression in force production and steepness of the force-pCa curves were shown to be associated with superoxide (O2,) production in muscle (apparent rate of O2, production at room temperature, 0.055 ± 0.008 nmol min,1 (g wet weight),1; and following treatment to 46 °C for 5 min, 1.8 ± 0.2 nmol min,1 (g wet weight),1) because 20 mm Tiron, a membrane-permeant O2, scavenger, was able to markedly suppress the net rate of O2, production and prevent any temperature-induced depression of contractile parameters. The temperature-induced depression in force production of the contractile apparatus could be reversed either by allowing the intact muscle to recover for 3-4 h at room temperature or by treatment of the skinned fibre preparation with dithiothreitol (a potent reducing agent) in the relaxing solution. These results demonstrate that mammalian skeletal muscle has the ability to uncouple force production reversibly from the activator Ca2+ as the temperature increases in the upper physiological range through an increase in O2, production. [source] Inhibition of calcineurin increases monocarboxylate transporters 1 and 4 protein and glycolytic enzyme activities in rat soleus muscleCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2005Masataka Suwa SUMMARY 1.,The present study was designed to examine the role of calcineurin in muscle metabolic components by the administration of the specific calcineurin inhibitor cyclosporine A (CsA) to rats. 2.,Male Wistar rats were divided into either a CsA-treated group (CT) or a vehicle-treated group (VT). Cyclosporine A was administered subcutaneously to rats at a rate of 25 mg/kg bodyweight per day for 10 successive days. Thereafter, changes in muscle enzyme activities and glucose transporter (GLUT)-4 and monocarboxylate transporter (MCT)-1 and MCT-4 proteins in the slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles were examined. 3.,There was a significant increase in MCT-1 and MCT-4 proteins in the soleus muscle in the CT group, but not in the EDL muscle. The activities of hexokinase, pyruvate kinase and lactate dehydrogenase in the soleus muscle also increased significantly in the CT group, but a similar increase in enzyme activity was not seen in EDL muscle. The activities of citrate synthase or malate dehydrogenase and the GLUT-4 protein content were not altered by CsA treatment in either the soleus or EDL muscles. 4.,These results seem to imply that calcineurin negatively regulates the components of glucose/lactate metabolism, except for GLUT-4, especially in slow-twitch muscle. [source] Is the efficiency of mammalian (mouse) skeletal muscle temperature dependent?THE JOURNAL OF PHYSIOLOGY, Issue 19 2010C. J. Barclay Myosin crossbridges in muscle convert chemical energy into mechanical energy. Reported values for crossbridge efficiency in human muscles are high compared to values measured in vitro using muscles of other mammalian species. Most in vitro muscle experiments have been performed at temperatures lower than mammalian physiological temperature, raising the possibility that human efficiency values are higher than those of isolated preparations because efficiency is temperature dependent. The aim of this study was to determine the effect of temperature on the efficiency of isolated mammalian (mouse) muscle. Measurements were made of the power output and heat production of bundles of muscle fibres from the fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus muscles during isovelocity shortening. Mechanical efficiency was defined as the ratio of power output to rate of enthalpy output, where rate of enthalpy output was the sum of the power output and rate of heat output. Experiments were performed at 20, 25 and 30°C. Maximum efficiency of EDL muscles was independent of temperature; the highest value was 0.31 ± 0.01 (n= 5) at 30°C. Maximum efficiency of soleus preparations was slightly but significantly higher at 25 and 30°C than at 20°C; the maximum mean value was 0.48 ± 0.02 (n= 7) at 25°C. It was concluded that maximum mechanical efficiency of isolated mouse muscle was little affected by temperature between 20 and 30°C and that it is unlikely that differences in temperature account for the relatively high efficiency of human muscle in vivo compared to isolated mammalian muscles. [source] Muscle magnetic resonance imaging shows distinct diagnostic patterns in Welander and tibial muscular dystrophyACTA NEUROLOGICA SCANDINAVICA, Issue 2 2004I. Mahjneh Objectives , This is a report on a retrospective muscle magnetic resonance imaging (MRI) study on 11 patients affected by Welander distal myopathy (WDM) and 22 patients with tibial muscular dystrophy (TMD) carried out in order to define the pattern and characteristics of muscle involvement. Results , WDM patients showed involvement of gastrocnemius, soleus, tibial anterior (TA) and extensor digitorum longus (EDL), as well as hamstrings and hip adductor muscles. TMD patients showed involvement of the TA and EDL muscles, and in some patients also hamstring and posterior compartment muscles of the legs. Some patients showed asymmetry of muscle involvement. Conclusion , We conclude that muscle MRI examination proved to be very useful in the determination of the exact pattern of muscle involvement in WDM and TMD. Clinical testing using the Medical Research Council scale is not sensitive enough to establish the pattern of muscle involvement in focal muscle diseases. [source] Inhibition of calcineurin increases monocarboxylate transporters 1 and 4 protein and glycolytic enzyme activities in rat soleus muscleCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2005Masataka Suwa SUMMARY 1.,The present study was designed to examine the role of calcineurin in muscle metabolic components by the administration of the specific calcineurin inhibitor cyclosporine A (CsA) to rats. 2.,Male Wistar rats were divided into either a CsA-treated group (CT) or a vehicle-treated group (VT). Cyclosporine A was administered subcutaneously to rats at a rate of 25 mg/kg bodyweight per day for 10 successive days. Thereafter, changes in muscle enzyme activities and glucose transporter (GLUT)-4 and monocarboxylate transporter (MCT)-1 and MCT-4 proteins in the slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles were examined. 3.,There was a significant increase in MCT-1 and MCT-4 proteins in the soleus muscle in the CT group, but not in the EDL muscle. The activities of hexokinase, pyruvate kinase and lactate dehydrogenase in the soleus muscle also increased significantly in the CT group, but a similar increase in enzyme activity was not seen in EDL muscle. The activities of citrate synthase or malate dehydrogenase and the GLUT-4 protein content were not altered by CsA treatment in either the soleus or EDL muscles. 4.,These results seem to imply that calcineurin negatively regulates the components of glucose/lactate metabolism, except for GLUT-4, especially in slow-twitch muscle. [source] Endurance training adaptations modulate the redox,force relationship of rat isolated slow-twitch skeletal musclesCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2003David R Plant Summary 1.,Studies have shown that, in isolated skeletal muscles, maximum isometric force production (Po) is dependent on muscle redox state. Endurance training increases the anti-oxidant capacity of skeletal muscles, a factor that could impact on the force-producing capacity following exogenous exposure to an oxidant. We tested the hypothesis that 12 weeks treadmill training would increase anti-oxidant capacity in rat skeletal muscles and alter their response to exogenous oxidant exposure. 2.,At the conclusion of the 12 week endurance-training programme, soleus (slow-twitch) muscles from trained rats had greater citrate synthase (CS) and catalase (CAT) activity compared with soleus muscles from untrained rats (P < 0.05). In contrast, CAT activity of extensor digitorum longus (EDL; fast-twitch) muscles from trained rats was not different to EDL muscles of untrained rats. The CS activity was lower in EDL muscles from trained compared with untrained rats (P < 0.05). 3.,Equilibration with exogenous hydrogen peroxide (H2O2, 5 mmol/L) increased the Po of soleus muscles from untrained rats for the duration of treatment (30 min), whereas the Po of EDL muscles was affected biphasically, with a small increase initially (after 5 min), followed by a more marked decrease in Po (after 30 min). The H2O2 -induced increase in Po of soleus muscles from trained rats was less than that in untrained rats (P < 0.05), but no differences were observed in the Po of EDL muscles following training. 4.,The results indicate that 12 weeks endurance running training conferred adaptations in soleus but not EDL muscles. These adaptations were associated with an attenuation of the oxidant-induced increase in Po of soleus muscles from trained compared with untrained rats. We conclude that endurance training-adapted soleus muscles have a slightly altered redox,force relationship. [source] | |||||||||||||