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Skeletal Muscle Fibers (skeletal + muscle_fiber)
Selected AbstractsPerisynaptic Schwann cells of the vertebrate motor endplate bear modified ciliaMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2004Tilman Voigt Abstract Perisynaptic Schwann cells (PSCs), descendants of the myelinating Schwann cells, cover the axon terminal of the vertebrate motor endplate of the skeletal muscle fiber. PSCs are assumed to support the function of the axon terminal. This function suggests a net material transport in the direction of the axon terminal. Morphologically it is to be expected that these cells have a cytoskeleton aligned to the axon terminal. Investigations clarifying this statement have not yet been undertaken. From previous investigations we know, however, that the PSCs have a microtubule-organizing center, which is a part of this cytoskeleton. The centrioles of the organizing center may also participate in the formation of a modified cilium structure whose function is unknown. In the present investigation, characteristic ultrastructural features of the modified cilium structure and its relationship to the Golgi apparatus and the axon terminal are presented. A function for the modified cilium structure is discussed. Microsc. Res. Tech. 63:149,154, 2004. © 2004 Wiley-Liss, Inc. [source] Cell death and apoptosis-related proteins in muscle biopsies of sporadic amyotrophic lateral sclerosis and polyneuropathyMUSCLE AND NERVE, Issue 8 2001Benedikt G.H. Schoser MD Abstract To investigate disease-related differences of cell death and apoptosis in human denervation atrophy, we studied DNA fragmentation by the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) method in 38 biopsies of clinically nonaffected and affected muscles from patients with sporadic amyotrophic lateral sclerosis (sALS), in 13 muscle biopsies from patients with chronic peripheral neuropathies, and in 8 biopsies from control subjects. In addition, expression of apoptosis-related proteins, bax, bcl-2, and Fas, was studied in 20 biopsies of sALS and 10 chronic peripheral neuropathies. We identified DNA cleavage in 10% of myofibers of patients and in up to 1.5% of control samples. In clinically affected muscles of ALS, a larger amount of TUNEL-positive myofibers (mean 10.5 ± 5.9%) was detected, similar to chronic peripheral neuropathies (mean 10.0 ± 7.4%). Atrophic myofibers were immunopositive for bax, bcl-2, and, to a weaker extent, for Fas. However, bax-, bcl-2-, or Fas-positive atrophic myofibers did not reveal consecutive DNA cleavage. Differences between sALS subgroups and chronic peripheral neuropathies were not found. In human denervation atrophy the bcl-2/bax and the FasL/Fas systems are apparently active independently of DNA fragmentation and apoptosis. DNA fragmentation thus displays an additional reaction that is not disease-specific at chronic stages of human denervation processes, probably recapitulating events like skeletal muscle fiber remodeling in embryonic skeletal tissue development. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1083,1089, 2001 [source] Transient production of ,-smooth muscle actin by skeletal myoblasts during differentiation in culture and following intramuscular implantationCYTOSKELETON, Issue 4 2002Matthew L. Springer Abstract ,-smooth muscle actin (SMA) is typically not present in post-embryonic skeletal muscle myoblasts or skeletal muscle fibers. However, both primary myoblasts isolated from neonatal mouse muscle tissue, and C2C12, an established myoblast cell line, produced SMA in culture within hours of exposure to differentiation medium. The SMA appeared during the cells' initial elongation, persisted through differentiation and fusion into myotubes, remained abundant in early myotubes, and was occasionally observed in a striated pattern. SMA continued to be present during the initial appearance of sarcomeric actin, but disappeared shortly thereafter leaving only sarcomeric actin in contractile myotubes derived from primary myoblasts. Within one day after implantation of primary myoblasts into mouse skeletal muscle, SMA was observed in the myoblasts; but by 9 days post-implantation, no SMA was detectable in myoblasts or muscle fibers. Thus, both neonatal primary myoblasts and an established myoblast cell line appear to similarly reprise an embryonic developmental program during differentiation in culture as well as differentiation within adult mouse muscles. Cell Motil. Cytoskeleton 51:177,186, 2002. © 2002 Wiley-Liss, Inc. [source] Development of ionic currents of zebrafish slow and fast skeletal muscle fibersDEVELOPMENTAL NEUROBIOLOGY, Issue 3 2006Christopher A. Coutts Abstract Voltage-gated Na+ and K+ channels play key roles in the excitability of skeletal muscle fibers. In this study we investigated the steady-state and kinetic properties of voltage-gated Na+ and K+ currents of slow and fast skeletal muscle fibers in zebrafish ranging in age from 1 day postfertilization (dpf) to 4,6 dpf. The inner white (fast) fibers possess an A-type inactivating K+ current that increases in peak current density and accelerates its rise and decay times during development. As the muscle matured, the V50s of activation and inactivation of the A-type current became more depolarized, and then hyperpolarized again in older animals. The activation kinetics of the delayed outward K+ current in red (slow) fibers accelerated within the first week of development. The tail currents of the outward K+ currents were too small to allow an accurate determination of the V50s of activation. Red fibers did not show any evidence of inward Na+ currents; however, white fibers expressed Na+ currents that increased their peak current density, accelerated their inactivation kinetics, and hyperpolarized their V50 of inactivation during development. The action potentials of white fibers exhibited significant changes in the threshold voltage and the half width. These findings indicate that there are significant differences in the ionic current profiles between the red and white fibers and that a number of changes occur in the steady-state and kinetic properties of Na+ and K+ currents of developing zebrafish skeletal muscle fibers, with the most dramatic changes occurring around the end of the first day following egg fertilization. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Sodium channel distribution on uninnervated and innervated embryonic skeletal myotubesDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2001Blake D. Anson Abstract Acetylcholine receptor (AChR) and sodium (Na+) channel distributions within the membrane of mature vertebrate skeletal muscle fibers maximize the probability of successful neuromuscular transmission and subsequent action potential propagation. AChRs have been studied intensively as a model for understanding the development and regulation of ion channel distribution within the postsynaptic membrane. Na+ channel distributions have received less attention, although there is evidence that the temporal accumulation of Na+ channels at developing neuromuscular junctions (NMJs) may differ between species. Even less is known about the development of extrajunctional Na+ channel distributions. To further our understanding of Na+ channel distributions within junctional and extrajunctional membranes, we used a novel voltage-clamp method and fluorescent probes to map Na+ channels on embryonic chick muscle fibers as they developed in vitro and in vivo. Na+ current densities on uninnervated myotubes were approximately one-tenth the density found within extrajunctional regions of mature fibers, and showed several-fold variations that could not be explained by a random scattering of single channels. Regions of high current density were not correlated with cellular landmarks such as AChR clusters or myonuclei. Under coculture conditions, AChRs rapidly concentrated at developing synapses, while Na+ channels did not show a significant increase over the 7 day coculture period. In vivo investigations supported a significant temporal separation between Na+ channel and AChR aggregation at the developing NMJ. These data suggest that extrajunctional Na+ channels cluster together in a neuronally independent manner and concentrate at the developing avian NMJ much later than AChRs. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 42,57, 2001 [source] Ultrastructural changes in skeletal muscle of the tail of the lizard Hemidactylus mabouia immediately following autotomyACTA ZOOLOGICA, Issue 4 2010Tomaz Henrique Araújo Abstract Araújo, T.H., Faria, F.P., Katchburian, E. and Freymüller, E. (2009). Ultrastructural changes in skeletal muscle of the tail of the lizard Hemidactylus mabouia immediately following autotomy. ,Acta Zoologica (Stockholm) 91: 440,446. Although autotomy and subsequent regeneration of lizard tails has been extensively studied, there is little information available on ultrastructural changes that occur to the muscle fibers at the site of severance. Thus, in the present study, we examine the ultrastructure of the musculature of the remaining tail stump of the lizard Hemidactylus mabouia immediately after autotomy. Our results show that exposed portions of the skeletal muscle fibers of the stump that are unprotected by connective tissue bulge to produce large mushroom-like protrusions. These exposed portions show abnormal structure but suffer no leakage of cytoplasmic contents. Many small and large vesicular structures appeared between myofibrils in the interface at this disarranged region (distal) and the other portion of the fibers that remain unchanged (proximal). These vesicles coalesce, creating a gap that leads to the release of the mushroom-like protrusion. So, our results showed that after the macroscopic act of autotomy the muscular fibers release part of the sarcoplasm as if a second and microscopic set of autotomic events takes place immediately following the macroscopic act of autotomy. Presumably these changes pave the way for the formation of a blastema and the beginning of regeneration. [source] The role of neurotrophins in muscle under physiological and pathological conditionsMUSCLE AND NERVE, Issue 4 2006Guillaume Chevrel MD Abstract This review summarizes the various effects of neurotrophins in skeletal muscle and how these proteins act as potential regulators of development, maintenance, function, and regeneration of skeletal muscle fibers. Increasing evidence suggests that this family of neurotrophic factors not only modulates survival and function of innervating motoneurons and proprioceptive neurons but also development and differentiation of myoblasts and muscle fibers. Neurotrophins and neurotrophin receptors play a role in the coordination of muscle innervation and functional differentiation of neuromuscular junctions. However, neurotrophin receptors are also expressed in differentiating muscle cells, in particular at early developmental stages in myoblasts before they fuse. In adults with pathological conditions such as human degenerative and inflammatory muscle disorders, variations of neurotrophin expression are found, but the role of neurotrophins under such conditions is still not clear. The goal of this review is to provide a basis for a better understanding and future studies on the role of these factors under such pathological conditions and for treatment of human muscle diseases. Muscle Nerve, 2005 [source] Is muscle spindle proprioceptive function spared in muscular dystrophies?MUSCLE AND NERVE, Issue 6 2004A muscle tendon vibration study Abstract Muscular dystrophies (MDs) are characterized by the degeneration of skeletal muscle fibers. The aim of the present study was to determine whether the intrafusal fibers of muscle spindles are also affected in MD. The functional integrity of muscle spindles was tested by analyzing their involvement in the perception of body segment movements and in the control of posture. Twenty MD patients (4 with dystrophinopathy, 5 with myotonic dystrophies, 5 with fascioscapulohumeral MD, and 6 with limb-girdle dystrophies) and 10 healthy subjects participated in the study. The MD patients perceived passive movements and experienced illusory movements similar to those perceived by healthy subjects in terms of their direction and velocity. Vibratory stimulation applied to the neck and ankle muscle tendons induced postural responses in MD patients with spatial and temporal characteristics similar to those produced by healthy subjects. These results suggest that the proprioceptive function of muscle spindles is spared in muscular dystrophies. Muscle Nerve 29: 861,866, 2004 [source] How selective is the reinnervation of skeletal muscle fibers?MUSCLE AND NERVE, Issue 6 2002V. Reggie Edgerton PhD No abstract is available for this article. [source] Recovery from fatigue in fast and slow single intact skeletal muscle fibers from aging mouseMUSCLE AND NERVE, Issue 9 2001Estela González MS Abstract In the present work, we studied the recovery from fatigue (RF) of single intact fast- and slow-twitch muscle fibers from young (age 5,7 months) and old (age 22,24 months) mice. To examine whether differences in RF underlie decreases in muscle strength and endurance with aging, we performed in vitro experiments in manually dissected extensor digitorum longus (EDL) and soleus muscle fibers. We measured the recovery of the maximum force every 5 min for a total period of 30 min after inducing fiber fatigue. Fibers were classified, according to the fatigue index, into the following three groups: 0.75,0.99, 0.5,0.74, and <0.5. Although the tetanic tension of EDL and soleus fibers from young and old mice recovered significantly, no statistically significant difference in tension or recovery time was observed between age groups. These data support the concept that the reported decline in muscle force and endurance with aging is not related to changes in RF of individual muscles fibers. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1219,1224 [source] | |||||||||||||