The Experts below are selected from a list of 4155 Experts worldwide ranked by ideXlab platform
Kristian Gundersen - One of the best experts on this subject based on the ideXlab platform.
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myogenin induces a shift of enzyme activity from glycolytic to oxidative metabolism in Muscles of transgenic mice
Journal of Cell Biology, 1999Co-Authors: Simon M Hughes, Maggie M Y Chi, Oliver H Lowry, Kristian GundersenAbstract:Physical training regulates Muscle metabolic and contractile properties by altering gene expression. Electrical activity evoked in Muscle Fiber Membrane during physical activity is crucial for such regulation, but the subsequent intracellular pathway is virtually unmapped. Here we investigate the ability of myogenin, a Muscle-specific transcription factor strongly regulated by electrical activity, to alter Muscle phenotype. Myogenin was overexpressed in transgenic mice using regulatory elements that confer strong expression confined to differentiated post-mitotic fast Muscle Fibers. In fast Muscles from such mice, the activity levels of oxidative mitochondrial enzymes were elevated two- to threefold, whereas levels of glycolytic enzymes were reduced to levels 0.3–0.6 times those found in wild-type mice. Histochemical analysis shows widespread increases in mitochondrial components and glycogen accumulation. The changes in enzyme content were accompanied by a reduction in Fiber size, such that many Fibers acquired a size typical of oxidative Fibers. No change in Fiber type-specific myosin heavy chain isoform expression was observed. Changes in metabolic properties without changes in myosins are observed after moderate endurance training in mammals, including humans. Our data suggest that myogenin regulated by electrical activity may mediate effects of physical training on metabolic capacity in Muscle.
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myogenin induces a shift of enzyme activity from glycolytic to oxidative metabolism in Muscles of transgenic mice
Journal of Cell Biology, 1999Co-Authors: Simon M Hughes, Oliver H Lowry, Kristian GundersenAbstract:Physical training regulates Muscle metabolic and contractile properties by altering gene expression. Electrical activity evoked in Muscle Fiber Membrane during physical activity is crucial for such regulation, but the subsequent intracellular pathway is virtually unmapped. Here we investigate the ability of myogenin, a Muscle-specific transcription factor strongly regulated by electrical activity, to alter Muscle phenotype. Myogenin was overexpressed in transgenic mice using regulatory elements that confer strong expression confined to differentiated post-mitotic fast Muscle Fibers. In fast Muscles from such mice, the activity levels of oxidative mitochondrial enzymes were elevated two- to threefold, whereas levels of glycolytic enzymes were reduced to levels 0.3–0.6 times those found in wild-type mice. Histochemical analysis shows widespread increases in mitochondrial components and glycogen accumulation. The changes in enzyme content were accompanied by a reduction in Fiber size, such that many Fibers acquired a size typical of oxidative Fibers. No change in Fiber type-specific myosin heavy chain isoform expression was observed. Changes in metabolic properties without changes in myosins are observed after moderate endurance training in mammals, including humans. Our data suggest that myogenin regulated by electrical activity may mediate effects of physical training on metabolic capacity in Muscle.
Simon M Hughes - One of the best experts on this subject based on the ideXlab platform.
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myogenin induces a shift of enzyme activity from glycolytic to oxidative metabolism in Muscles of transgenic mice
Journal of Cell Biology, 1999Co-Authors: Simon M Hughes, Maggie M Y Chi, Oliver H Lowry, Kristian GundersenAbstract:Physical training regulates Muscle metabolic and contractile properties by altering gene expression. Electrical activity evoked in Muscle Fiber Membrane during physical activity is crucial for such regulation, but the subsequent intracellular pathway is virtually unmapped. Here we investigate the ability of myogenin, a Muscle-specific transcription factor strongly regulated by electrical activity, to alter Muscle phenotype. Myogenin was overexpressed in transgenic mice using regulatory elements that confer strong expression confined to differentiated post-mitotic fast Muscle Fibers. In fast Muscles from such mice, the activity levels of oxidative mitochondrial enzymes were elevated two- to threefold, whereas levels of glycolytic enzymes were reduced to levels 0.3–0.6 times those found in wild-type mice. Histochemical analysis shows widespread increases in mitochondrial components and glycogen accumulation. The changes in enzyme content were accompanied by a reduction in Fiber size, such that many Fibers acquired a size typical of oxidative Fibers. No change in Fiber type-specific myosin heavy chain isoform expression was observed. Changes in metabolic properties without changes in myosins are observed after moderate endurance training in mammals, including humans. Our data suggest that myogenin regulated by electrical activity may mediate effects of physical training on metabolic capacity in Muscle.
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myogenin induces a shift of enzyme activity from glycolytic to oxidative metabolism in Muscles of transgenic mice
Journal of Cell Biology, 1999Co-Authors: Simon M Hughes, Oliver H Lowry, Kristian GundersenAbstract:Physical training regulates Muscle metabolic and contractile properties by altering gene expression. Electrical activity evoked in Muscle Fiber Membrane during physical activity is crucial for such regulation, but the subsequent intracellular pathway is virtually unmapped. Here we investigate the ability of myogenin, a Muscle-specific transcription factor strongly regulated by electrical activity, to alter Muscle phenotype. Myogenin was overexpressed in transgenic mice using regulatory elements that confer strong expression confined to differentiated post-mitotic fast Muscle Fibers. In fast Muscles from such mice, the activity levels of oxidative mitochondrial enzymes were elevated two- to threefold, whereas levels of glycolytic enzymes were reduced to levels 0.3–0.6 times those found in wild-type mice. Histochemical analysis shows widespread increases in mitochondrial components and glycogen accumulation. The changes in enzyme content were accompanied by a reduction in Fiber size, such that many Fibers acquired a size typical of oxidative Fibers. No change in Fiber type-specific myosin heavy chain isoform expression was observed. Changes in metabolic properties without changes in myosins are observed after moderate endurance training in mammals, including humans. Our data suggest that myogenin regulated by electrical activity may mediate effects of physical training on metabolic capacity in Muscle.
Dario Farina - One of the best experts on this subject based on the ideXlab platform.
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strength training increases conduction velocity of high threshold motor units
Medicine and Science in Sports and Exercise, 2020Co-Authors: Andrea Casolo, Dario Farina, Deborah Falla, Ilenia Bazzucchi, Francesco Felici, Alessandro Del VecchioAbstract:PURPOSE Motor unit conduction velocity (MUCV) represents the propagation velocity of action potentials along the Muscle Fibers innervated by individual motor neurons and indirectly reflects the electrophysiological properties of the sarcolemma. In this study, we investigated the effect of a 4-wk strength training intervention on the peripheral properties (MUCV and motor unit action potential amplitude, RMSMU) of populations of longitudinally tracked motor units (MU). METHODS The adjustments exhibited by 12 individuals who participated in the training (INT) were compared with 12 controls (CON). Strength training involved ballistic (4 × 10) and sustained (3 × 10) isometric ankle dorsiflexions. Measurement sessions involved the recordings of maximal voluntary isometric force and submaximal isometric ramp contractions, whereas high-density surface EMG was recorded from the tibialis anterior. High-density surface EMG signals were decomposed into individual MU discharge timings, and MU was tracked across the intervention. RESULTS Maximal voluntary isometric force (+14.1%, P = 0.003) and average MUCV (+3.0%, P = 0.028) increased in the INT group, whereas normalized MU recruitment threshold (RT) decreased (-14.9%, P = 0.001). The slope (rate of change) of the regression between MUCV and MU RT increased only in the INT group (+32.6%, P = 0.028), indicating a progressive greater increase in MUCV for higher-threshold MU. The intercept (initial value) of MUCV did not change after the intervention (P = 0.568). The association between RMSMU and MU RT was not altered by the training. CONCLUSION The increase in the rate of change in MUCV as a function of MU RT, but not the initial value of MUCV, suggests that short-term strength training elicits specific adaptations in the electrophysiological properties of the Muscle Fiber Membrane in high-threshold MU.
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time frequency analysis and estimation of Muscle Fiber conduction velocity from surface emg signals during explosive dynamic contractions
Journal of Neuroscience Methods, 2005Co-Authors: E Merlo, Dario Farina, Roberto Merletti, Marco Pozzo, G Antonutto, Pietro Enrico Di PramperoAbstract:Time-frequency analysis of the surface electromyographic (EMG) signal is used to assess Muscle Fiber Membrane properties during dynamic contractions. The aim of this study was to compare the direct estimation of average Muscle Fiber conduction velocity (CV) with instantaneous mean frequency (iMNF) of surface EMG signals in isometric and explosive dynamic contractions. The Muscles investigated were the vastus lateralis and medialis of both thighs in 12 male subjects. The isometric contractions were at linearly increasing force (0-100% of the maximal voluntary contraction in 10s). The explosive contractions were performed on a multipurpose ergometer-dynamometer (MED). The subject, sitting on the MED, performed six explosive contractions, separated by 2 min rest, by pushing against two force platforms and thrusting himself backwards with the maximum possible speed, while completely extending his legs. The estimated CV significantly increased with force in both the isometric (mean+/-S.D., from 3.24+/-0.34 to 5.12+/-0.31 m/s for vastus lateralis and from 3.17+/-0.26 to 5.11+/-0.34 m/s for vastus medialis, with force in the range 10-100% of the maximal voluntary contraction level) and explosive contractions (from 4.36+/-0.49 to 5.00+/-0.47 m/s for vastus lateralis, and from 4.32+/-0.46 to 4.94+/-0.44 m/s for vastus medialis, with force in the range 17.5-100% of maximal thrusting force). Moreover, estimated CV was not significantly different at the maximal force in the two exercises. On the contrary, iMNF, computed from the Choi-Williams time-frequency transform, was significantly lower in the explosive (57.7+/-8.2 and 66.5+/-10.3 Hz for vastus laterialis and medialis, respectively) than in the isometric exercises (73.7+/-9.2 and 75.0+/-8.5 Hz for vastus laterialis and medialis, respectively) and did not change with force in any of the conditions. It was concluded that EMG spectral features provide different information with respect to average Muscle Fiber CV in dynamic contractions. Thus, in general, they cannot be used to infer CV changes during the exertion of a dynamic task. A joint analysis of CV and EMG spectral features is necessary in this type of contractions.
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the linear electrode array a useful tool with many applications
Journal of Electromyography and Kinesiology, 2003Co-Authors: Roberto Merletti, Dario Farina, Marco GazzoniAbstract:In this review we describe the basic principles of operation of linear electrode arrays for the detection of surface EMG signals, together with their most relevant current applications. A linear array of electrodes is a system which detects surface EMG signals in a number of points located along a line. A spatial filter is usually placed in each point for signal detection, so that the recording of EMG signals with linear arrays corresponds to the sampling in one spatial direction of a spatially filtered version of the potential distribution over the skin. Linear arrays provide indications on motor unit (MU) anatomical properties, such as the locations of the innervation zones and tendons, and the Fiber length. Such systems allow the investigation of the properties of the volume conductor and its effect on surface detected signals. Moreover, linear arrays allow to estimate Muscle Fiber conduction velocity with a very low standard deviation of estimation (of the order of 0.1-0.2 m/s), thus providing reliable indications on Muscle Fiber Membrane properties and their changes in time (for example with fatigue or during treatment). Conduction velocity can be estimated from a signal epoch (global estimate) or at the single MU level. In the latter case, MU action potentials are identified from the interference EMG signals and conduction velocity is estimated for each detected potential. In this way it is possible, in certain conditions, to investigate single MU control and conduction properties with a completely non-invasive approach. Linear arrays provide valuable information on the neuromuscular system properties and appear to be promising tools for applied studies and clinical research.
T Voit - One of the best experts on this subject based on the ideXlab platform.
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direct visualization of the dystrophin network on skeletal Muscle Fiber Membrane
Journal of Cell Biology, 1992Co-Authors: Volker Straub, R E Bittner, J J Leger, T VoitAbstract:Dystrophin, the protein product of the Duchenne muscular dystrophy (DMD) gene locus, is expressed on the Muscle Fiber surface. One key to further understanding of the cellular function of dystrophin would be extended knowledge about its subcellular organization. We have shown that dystrophin molecules are not uniformly distributed over the humen, rat, and mouse skeletal Muscle Fiber surface using three independent methods. Incubation of single-teased Muscle Fibers with antibodies to dystrophin revealed a network of denser transversal rings (costameres) and finer longitudinal interconnections. Double staining of longitudinal semithin cryosections for dystrophin and alpha-actinin showed spatial juxtaposition of the costameres to the Z bands. Where peripheral myonuclei precluded direct contact of dystrophin to the Z bands the organization of dystrophin was altered into lacunae harboring the myonucleus. These lacunae were surrounded by a dystrophin ring and covered by a more uniform dystrophin veil. Mechanical skinning of single-teased Fibers revealed tighter mechanical connection of dystrophin to the plasma Membrane than to the underlying internal domain of the Muscle Fiber. The entire dystrophin network remained preserved in its structure on isolated Muscle sarcolemma and identical in appearance to the pattern observed on teased Fibers. Therefore, connection of defined areas of plasma Membrane or its constituents such as ion channels to single sarcomeres might be a potential function exerted by dystrophin alone or in conjunction with other subMembrane cytoskeletal proteins.
Oliver H Lowry - One of the best experts on this subject based on the ideXlab platform.
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myogenin induces a shift of enzyme activity from glycolytic to oxidative metabolism in Muscles of transgenic mice
Journal of Cell Biology, 1999Co-Authors: Simon M Hughes, Maggie M Y Chi, Oliver H Lowry, Kristian GundersenAbstract:Physical training regulates Muscle metabolic and contractile properties by altering gene expression. Electrical activity evoked in Muscle Fiber Membrane during physical activity is crucial for such regulation, but the subsequent intracellular pathway is virtually unmapped. Here we investigate the ability of myogenin, a Muscle-specific transcription factor strongly regulated by electrical activity, to alter Muscle phenotype. Myogenin was overexpressed in transgenic mice using regulatory elements that confer strong expression confined to differentiated post-mitotic fast Muscle Fibers. In fast Muscles from such mice, the activity levels of oxidative mitochondrial enzymes were elevated two- to threefold, whereas levels of glycolytic enzymes were reduced to levels 0.3–0.6 times those found in wild-type mice. Histochemical analysis shows widespread increases in mitochondrial components and glycogen accumulation. The changes in enzyme content were accompanied by a reduction in Fiber size, such that many Fibers acquired a size typical of oxidative Fibers. No change in Fiber type-specific myosin heavy chain isoform expression was observed. Changes in metabolic properties without changes in myosins are observed after moderate endurance training in mammals, including humans. Our data suggest that myogenin regulated by electrical activity may mediate effects of physical training on metabolic capacity in Muscle.
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myogenin induces a shift of enzyme activity from glycolytic to oxidative metabolism in Muscles of transgenic mice
Journal of Cell Biology, 1999Co-Authors: Simon M Hughes, Oliver H Lowry, Kristian GundersenAbstract:Physical training regulates Muscle metabolic and contractile properties by altering gene expression. Electrical activity evoked in Muscle Fiber Membrane during physical activity is crucial for such regulation, but the subsequent intracellular pathway is virtually unmapped. Here we investigate the ability of myogenin, a Muscle-specific transcription factor strongly regulated by electrical activity, to alter Muscle phenotype. Myogenin was overexpressed in transgenic mice using regulatory elements that confer strong expression confined to differentiated post-mitotic fast Muscle Fibers. In fast Muscles from such mice, the activity levels of oxidative mitochondrial enzymes were elevated two- to threefold, whereas levels of glycolytic enzymes were reduced to levels 0.3–0.6 times those found in wild-type mice. Histochemical analysis shows widespread increases in mitochondrial components and glycogen accumulation. The changes in enzyme content were accompanied by a reduction in Fiber size, such that many Fibers acquired a size typical of oxidative Fibers. No change in Fiber type-specific myosin heavy chain isoform expression was observed. Changes in metabolic properties without changes in myosins are observed after moderate endurance training in mammals, including humans. Our data suggest that myogenin regulated by electrical activity may mediate effects of physical training on metabolic capacity in Muscle.
