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Muscle Fibers (muscle + fiber)
Kinds of Muscle Fibers Terms modified by Muscle Fibers Selected AbstractsMolecular regulation of postsynaptic differentiation at the neuromuscular junctionIUBMB LIFE, Issue 11 2005Raghavan Madhavan Abstract The neuromuscular junction (NMJ) is a synapse that develops between a motor neuron and a muscle fiber. A defining feature of NMJ development in vertebrates is the re-distribution of muscle acetylcholine (ACh) receptors (AChRs) following innervation, which generates high-density AChR clusters at the postsynaptic membrane and disperses aneural AChR clusters formed in muscle before innervation. This process in vivo requires MuSK, a muscle-specific receptor tyrosine kinase that triggers AChR re-distribution when activated; rapsyn, a muscle protein that binds and clusters AChRs; agrin, a nerve-secreted heparan-sulfate proteoglycan that activates MuSK; and ACh, a neurotransmitter that stimulates muscle and also disperses aneural AChR clusters. Moreover, in cultured muscle cells, several additional muscle- and nerve-derived molecules induce, mediate or participate in AChR clustering and dispersal. In this review we discuss how regulation of AChR re-distribution by multiple factors ensures aggregation of AChRs exclusively at NMJs. IUBMB Life, 57: 719-730, 2005 [source] Histopathological effects in tissues of snail Lymnaea stagnalis (Gastropoda, Pulmonata) exposed to sublethal concentration of Thiodan® and recovery after exposureJOURNAL OF APPLIED TOXICOLOGY, Issue 6 2005Erhan Ünlü Abstract Histopathological alterations induced by Thiodan® in three tissues, namely, digestive gland, foot and mantle, of the freshwater snail Lymnaea stagnalis were investigated. Specimens of Lymnaea stagnalis were exposed to 0.36% and 0.72% Thiodan® 35 EC, a commercial grade of endosulfan, for 96 h followed by a recovery period of 30 days. Thiodan® caused significant dose dependent histopathological changes in all the tissues of the snail. Irreversible necrotic changes occurred in the digestive gland of the snail following Thiodan® exposure. Degenerative changes in the muscle fiber of the foot, protein and pigment cells of the foot and the connective tissue element of the mantle were recovered after 30 days of recovery of the snail in pesticide-free freshwater. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effect of Temperature (,5 to 130 °C) and Fiber Direction on the Dielectric Properties of Beef Semitendinosus at Radio Frequency and Microwave FrequenciesJOURNAL OF FOOD SCIENCE, Issue 6 2008N. Basaran-Akgul ABSTRACT:, The dielectric properties must be defined to design efficient radio frequency (RF) and microwave (MW) processes by the food manufacturers. The objective of this study was to understand how frequency, temperature, and muscle fiber orientation influence the dielectric properties. The eye of round (Semitendinosus) muscle was selected because it contains large, relatively uniform muscle cells with similar muscle fiber orientation and relatively uniform chemical composition throughout the tissue. Dielectric properties were measured using an open-ended coaxial probe technique at 27, 915, and 1800 MHz and temperatures between ,5 and 130 °C. Power penetration depth was calculated. Since many commercially prepared, thermally processed, ready-to-eat entrees are made with frozen meat, dielectric property measurements were started from ,5 °C. The dielectric constant and dielectric loss factors were often higher for muscle with the muscle fiber measured in a parallel orientation to the probe compared to samples of the same treatment (for example, fresh or frozen) in a perpendicular tissue orientation at the same frequency and temperature. Dielectric constant and loss values for frozen beef tended to be higher than fresh beef at the same temperature and frequency. Tissue orientation appeared to have a greater effect on dielectric loss values at lower frequencies. Penetration depth tended to be greater when the direction of propagation was perpendicular to the muscle fiber. [source] Comparative analysis of masseter fiber architecture in tree-gouging (Callithrix jacchus) and nongouging (Saguinus oedipus) callitrichidsJOURNAL OF MORPHOLOGY, Issue 3 2004Andrea B. Taylor Abstract Common marmosets (Callithrix jacchus) and cotton-top tamarins (Saguinus oedipus) (Callitrichidae, Primates) share a broadly similar diet of fruits, insects, and tree exudates. Common marmosets, however, differ from tamarins by actively gouging trees with their anterior teeth to elicit tree exudate flow. During tree gouging, marmosets produce relatively large jaw gapes, but do not necessarily produce relatively large bite forces at the anterior teeth. We compared the fiber architecture of the masseter muscle in tree-gouging Callithrix jacchus (n = 10) to nongouging Saguinus oedipus (n = 8) to determine whether the marmoset masseter facilitates producing these large gapes during tree gouging. We predict that the marmoset masseter has relatively longer fibers and, hence, greater potential muscle excursion (i.e., a greater range of motion through increased muscle stretch). Conversely, because of the expected trade-off between excursion and force production in muscle architecture, we predict that the cotton-top tamarin masseter has more pinnate fibers and increased physiological cross-sectional area (PCSA) as compared to common marmosets. Likewise, the S. oedipus masseter is predicted to have a greater proportion of tendon relative to muscle fiber as compared to the common marmoset masseter. Common marmosets have absolutely and relatively longer masseter fibers than cotton-top tamarins. Given that fiber length is directly proportional to muscle excursion and by extension contraction velocity, this result suggests that marmosets have masseters designed for relatively greater stretching and, hence, larger gapes. Conversely, the cotton-top tamarin masseter has a greater angle of pinnation (but not significantly so), larger PCSA, and higher proportion of tendon. The significantly larger PCSA in the tamarin masseter suggests that their masseter has relatively greater force production capabilities as compared to marmosets. Collectively, these results suggest that the fiber architecture of the common marmoset masseter is part of a suite of features of the masticatory apparatus that facilitates the production of relatively large gapes during tree gouging. J. Morphol. 261:276,285, 2004. © 2004 Wiley-Liss, Inc. [source] Localization of the membrane-anchored MMP-regulator RECK at the neuromuscular junctionsJOURNAL OF NEUROCHEMISTRY, Issue 2 2008Satoshi Kawashima Abstract Nerve apposition on nicotinic acetylcholine receptor clusters and invagination of the post-synaptic membrane (i.e. secondary fold formation) occur by embryonic day 18.5 at the neuromuscular junctions (NMJs) in mouse skeletal muscles. Finding the molecules expressed at the NMJ at this stage of development may help elucidating how the strong linkage between a nerve terminal and a muscle fiber is established. Immunohistochemical analyses indicated that the membrane-anchored matrix metalloproteinase regulator RECK was enriched at the NMJ in adult skeletal muscles. Confocal and electron microscopy revealed the localization of RECK immunoreactivity in secondary folds and subsynaptic intracellular compartments in muscles. Time course studies indicated that RECK immunoreactivity becomes associated with the NMJ in the diaphragm at around embryonic day 18.5 and thereafter. These findings, together with known properties of RECK, support the hypothesis that RECK participates in NMJ formation and/or maintenance, possibly by protecting extracellular components, such as synaptic basal laminae, from proteolytic degradation. [source] Morphometric analysis of canine skeletal muscles following experimental callus distraction according to the ilizarov methodJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2000Bernd Fink Muscle fiber diameter and fiber-type distribution were analyzed during callus distraction. The right tibia in 24 beagles was lengthened 2.5 cm by callus distraction after osteotomy and application of a ring fixator. Distraction was started at the fifth postoperative day, at a rate of two times for 0.5 mm per day. Twelve dogs that underwent limb-lengthening and three dogs in the control group that did not undergo limb-lengthening were killed at the end of the 25-day distraction phase (group A). The remaining dogs (12 that underwent limb-lengthening and three that did not) were killed after an additional consolidation period of 25 days (group B). The tibialis anterior, extensor digitorum longus, peroneus longus, and gastrocnemius muscles were removed from the right limb (which had undergone distraction) and the left control side of each animal. Crosscut cryostat sections were stained by adenosine triphosphatase at pH 4.3 and 9.4 to determine the size and distribution of types I and II fibers. Morphometric analysis of the muscle fibers was performed by a computer-assisted two-point technique. On the lengthened side, the muscles revealed marked atrophy affecting predominantly type-II fiber in the dogs in group A and affecting both fiber types in dogs in group B. Fiber density increased in both groups. In addition, fiber-type grouping indicative of reinnervation was obvious in group B. Fiber-type distribution in the dogs in group B showed a shift toward type I in the tibialis anterior (p = 0.043) and extensor digitorum longus (p = 0.034) muscles and a shift toward type II in the gastrocnemius (p = 0.038). The data show that tension-stress during tibial lengthening leads to atrophy of type-II fiber, reflecting disuse of muscle fiber in the distraction period as well as neurogenic atrophy followed by the reinnervation processes. Furthermore, the data are consistent with the occurrence of histoneogenesis during limb-lengthening resulting in an increase in fiber density. [source] Perisynaptic 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] Differential expression of sarcoplasmic proteins in four heterogeneous ovine skeletal musclesPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 2 2007Muriel Hamelin Abstract Fiber-type distribution is known to vary widely within and between muscles according to differences in muscle functions. 2-DE and MALDI-MS were used to investigate the molecular basis of muscle fiber type-related variability. We compared four lamb skeletal muscles with heterogeneous fiber-type composition that are relatively rich in fast-twitch fiber types, i.e., the semimembranosus, vastus medialis, longissimus dorsi, and tensor fasciae latae (TL). Our results clearly showed that none of the glycolytic metabolism enzymes detected, including TL which was most strongly glycolytic, made intermuscular differentiation possible. Muscle differentiation was based on the differential expression of proteins involved in oxidative metabolism, including not only citric acid cycle enzymes but also other classes of proteins with functions related to oxidative metabolism, oxidative stress, and probably to higher protein turnover. Detected proteins were involved in transport (carbonate dehydratase, myoglobin, fatty acid-binding protein), repair of misfolding damage (heat shock protein (HSP) 60,kDa, HSP-27,kDa, alpha-crystallin beta subunit, DJ1, stress-induced phosphoprotein), detoxification or degradation of impaired proteins (GST-Pi, aldehyde dehydrogenase, peroxiredoxin, ubiquitin), and protein synthesis (tRNA-synthetase). The fractionating method led to the detection of proteins involved in different functions related to oxidative metabolism that have not previously been shown concomitancy. [source] Mechano-biology of skeletal muscle hypertrophy and regeneration: Possible mechanism of stretch-induced activation of resident myogenic stem cellsANIMAL SCIENCE JOURNAL, Issue 1 2010Ryuichi TATSUMI ABSTRACT In undamaged postnatal muscle fibers with normal contraction and relaxation activities, quiescent satellite cells of resident myogenic stem cells are interposed between the overlying external lamina and the sarcolemma of a subjacent mature muscle fiber. When muscle is injured, exercised, overused or mechanically stretched, these cells are activated to enter the cell proliferation cycle, divide, differentiate, and fuse with the adjacent muscle fiber, and are responsible for regeneration and work-induced hypertrophy of muscle fibers. Therefore, a mechanism must exist to translate mechanical changes in muscle tissue into chemical signals that can activate satellite cells. Recent studies of satellite cells or single muscle fibers in culture and in vivo demonstrated the essential role of hepatocyte growth factor (HGF) and nitric oxide (NO) radical in the activation pathway. These experiments have also reported that mechanically stretching satellite cells or living skeletal muscles triggers the activation by rapid release of HGF from its extracellular tethering and the subsequent presentation to the receptor c-met. HGF release has been shown to rely on calcium-calmodulin formation and NO radical production in satellite cells and/or muscle fibers in response to the mechanical perturbation, and depend on the subsequent up-regulation of matrix metalloproteinase (MMP) activity. These results indicate that the activation mechanism is a cascade of events including calcium ion influx, calcium-calmodulin formation, NO synthase activation, NO radical production, MMP activation, HGF release and binding to c-met. Better understanding of ,mechano-biology' on the satellite cell activation is essential for designing procedures that could enhance muscle growth and repair activities in meat-animal agriculture and also in neuromuscular disease and aging in humans. [source] Relationships between tropomyosin and myosin heavy chain isoforms in bovine skeletal muscleANIMAL SCIENCE JOURNAL, Issue 2 2009Mika OE ABSTRACT The composition of tropomyosin (TPM) and myosin heavy chain (MyHC) isoforms was analyzed in 10 physiologically different bovine muscles (masseter, diaphragm, tongue, semispinalis, pectoralis profundus, biceps femoris, psoas major, semimembranosus, longissimus thoracis and semitendinosus) to clarify the relationships between TPM and MyHC isoforms in different muscle fiber types. The content of TPM1 and TPM3 was different in muscles according to their function in muscle contraction, although the content of TPM2 was constantly about 50% of the total TPM in all muscles. The content of TPM1 was higher in semimembranosus, longissimus thoracis and semitendinosus, while that of TPM3 was higher in masseter and diaphragm. The high positive correlation between MyHC-slow content and TPM3 content (r = 0.92) suggested a coexpression of TPM3 and MyHC-slow isoforms in a muscle fiber. MyHC-slow and TPM3 were expressed at the same level in masseter and diaphragm, whereas there was more TPM3 than MyHC-slow in tongue and semispinalis, so it appears that the excess TPM3 in tongue and semispinalis is expressed with other MyHC isoforms. MyHC-2a was the only fast type isoform expressed in tongue and semispinalis. Therefore, the excess TPM3 was composed of myofibrils with MyHC-2a. The results suggested that a fiber expressing MyHC-2a would be regulated delicately by changing the TPM isoform types. [source] Formation of zinc protoporphyrin IX in Parma-like ham without nitrate or nitriteANIMAL SCIENCE JOURNAL, Issue 2 2009Jun-ichi WAKAMATSU ABSTRACT Zinc protoporphyrin IX (ZPP) is a characteristic red pigment in meat products that are manufactured without the addition of a curing agent such as nitrate or nitrite. To examine the effects of impurities such as mineral components in sea salt on the formation of ZPP, we manufactured Parmatype dry-cured hams that were salted with refined salt or sea salt and examined the involvement of oxidation-reduction potential (ORP) in the formation of ZPP. The content of ZPP was increased drastically after 40 weeks. Microscopic observation showed strong fluorescence caused by ZPP muscle fiber after 40 weeks. Conversely, heme content varied considerably during processing. ORP increased during processing. However, there was no obvious difference between ham salted with refined salt and that salted with sea salt. Therefore, it was concluded that impurities in sea salt were not involved in the formation of ZPP. [source] Real-time Polymerase Chain Reaction to Follow the Response of Muscle to TrainingARTIFICIAL ORGANS, Issue 8 2008Lauren M. Moore Abstract:, The adaptive response of muscle to changes in activity or loading can take many weeks. Changes in the levels of RNA within a muscle fiber can give an early indication of the nature of the response of that fiber to changes in activity or loading. We have designed a new primer set for quantitative polymerase chain reaction (PCR) that will allow us to follow these early transcriptional changes in rat muscle, and have shown that analysis can be performed by standard techniques on as little as 5 mg of muscle, an amount that can be obtained by needle biopsy. [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] Decreased Tear Expression with an Abnormal Schirmer's Test Following Botulinum Toxin Type A for the Treatment of Lateral Canthal RhytidesDERMATOLOGIC SURGERY, Issue 2 2002Seth L. Matarasso MD background. Inactivation of muscles of facial expression by chemodenervation with botulinum toxin remains an off-label indication. Nevertheless, it continues to be a safe and effective technique to improve dynamic rhytides and is the treatment of choice for the hypertrophic lateral fibers of the orbicularis oculi muscle that can cause the superimposed crow's feet. objective. Although infrequent and self-limiting, the complication of unexpected muscle weakness from toxin diffusion or erroneous placement is documented. methods. However, injection into the pretarsal portion of the orbicularis oculi muscle resulting in unilateral ocular irritation and diminished tear expression as evidenced by a dry eye and an abnormal Schirmer's test has rarely been reported. Direct injection into the pretarsal fibers of the muscle as opposed to diffusion of the toxin into the muscle fibers or the lacrimal gland was consistent with the onset of action of the toxin and the prolonged duration of the ocular symptoms. results. Treatment consisted of ocular lubrication until the effects of the toxin dissipated and muscle tone returned. Subsequent treatment did not result in a result in a recurrence of adverse sequelae. conclusions. Facial muscles are small, not isolated, and often have fibers that interdigitate. An important factor in the administration of botulinum toxin is the identification of the muscles responsible for the corresponding rhytide. Precise knowledge of muscular anatomy and function will aid in minimizing this and other potential complications. [source] Rapid accumulation of nucleostemin in nucleolus during newt regenerationDEVELOPMENTAL DYNAMICS, Issue 4 2007Nobuyasu Maki Abstract In newt regeneration, differentiated cells can revert to stem cell,like cells in which the proliferative ability and multipotentiality are restored after dedifferentiation. However, the molecular events that occur during the dedifferentiation still remain obscure. Nucleostemin has been identified in mammals as a nucleolar protein specific to stem cells and cancer cells. In this study, a newt nucleostemin homologue was cloned and its regulation was analyzed. During lens regeneration, the expression of nucleostemin was activated and nucleostemin rapidly accumulated in the nucleoli of dedifferentiating pigmented epithelial cells 2 days before cell cycle reentry. During limb regeneration, nucleostemin also accumulated in the nucleoli of degenerating multinucleate muscle fibers before blastema formation. These findings suggest that nucleostemin plays a role in the dedifferentiation of newt cells and can provide crucial clues for addressing the molecular events at early steps of cellular dedifferentiation in newts. Developmental Dynamics 236:941,950, 2007. © 2006 Wiley-Liss, Inc. [source] Ultrastructural analysis of the smooth-to-striated transition zone in the developing mouse esophagus: Emphasis on apoptosis of smooth and origin and differentiation of striated muscle cellsDEVELOPMENTAL DYNAMICS, Issue 3 2005Jürgen Wörl Abstract The exact mechanism of smooth-to-striated muscle conversion in the mouse esophagus is controversial. Smooth-to-striated muscle cell transdifferentiation vs. distinct differentiation pathways for both muscle types were proposed. Main arguments for transdifferentiation were the failure to detect apoptotic smooth and the unknown origin of striated muscle cells during esophageal myogenesis. To reinvestigate this issue, we analyzed esophagi of 4-day-old mice by electron microscopy and a fine-grained sampling strategy considering that, in perinatal esophagus, the replacement of smooth by striated muscle progresses craniocaudally, while striated myogenesis advances caudocranially. We found numerous (1) apoptotic smooth muscle cells located mainly in a transition zone, where smooth intermingled with developing striated muscle cells, and (2) mesenchymal cells in the smooth muscle portion below the transition zone, which appeared to give rise to striated muscle fibers. Taken together, these results provide further evidence for distinct differentiation pathways of both muscle types during esophagus development. Developmental Dynamics 233:964,982, 2005. © 2005 Wiley-Liss, Inc. [source] The zebrafish ennui behavioral mutation disrupts acetylcholine receptor localization and motor axon stabilityDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2008Louis Saint-Amant Abstract The zebrafish ennui mutation was identified from a mutagenesis screen for defects in early behavior. Homozygous ennui embryos swam more slowly than wild-type siblings but normal swimming recovered during larval stages and homozygous mutants survived until adulthood. Electrophysiological recordings from motoneurons and muscles suggested that the motor output of the CNS following mechanosensory stimulation was normal in ennui, but the synaptic currents at the neuromuscular junction were significantly reduced. Analysis of acetylcholine receptors (AChRs) in ennui muscles showed a marked reduction in the size of synaptic clusters and their aberrant localization at the myotome segment borders of fast twitch muscle. Prepatterned, nerve-independent AChR clusters appeared normal in mutant embryos and dispersed upon outgrowth of motor axons onto the muscles. Genetic mosaic analysis showed that ennui is required cell autonomously in muscle fibers for normal synaptic localization of AChRs. Furthermore, exogenous agrin failed to induce AChR aggregation, suggesting that ennui is crucial for agrin function. Finally, motor axons branched more extensively in ennui fast twitch muscles especially in the region of the myotome borders. These results suggest that ennui is important for nerve-dependent AChR clustering and the stability of axon growth. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2008 [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] HGF induction of postsynaptic specializations at the neuromuscular junctionDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2006Raghavan Madhavan Abstract A critical event in the formation of vertebrate neuromuscular junctions (NMJs) is the postsynaptic clustering of acetylcholine receptors (AChRs) in muscle. AChR clustering is triggered by the activation of MuSK, a muscle-specific tyrosine kinase that is part of the functional receptor for agrin, a nerve-derived heparan sulfate proteoglycan (HSPG). At the NMJ, heparan sulfate (HS)-binding growth factors and their receptors are also localized but their involvement in postsynaptic signaling is poorly understood. In this study we found that hepatocyte growth factor (HGF), an HS-binding growth factor, surrounded muscle fibers and was localized at NMJs in rat muscle sections. In cultured Xenopus muscle cells, HGF was enriched at spontaneously occurring AChR clusters (hot spots), where HSPGs were also concentrated, and, following stimulation of muscle cells by agrin or cocultured neurons, HGF associated with newly formed AChR clusters. HGF presented locally to cultured muscle cells by latex beads induced new AChR clusters and dispersed AChR hot spots, and HGF beads also clustered phosphotyrosine, activated c-Met, and proteins of dystrophin complex; clustering of AChRs and associated proteins by HGF beads required actin polymerization. Lastly, although bath-applied HGF alone did not induce new AChR clusters, addition of HGF potentiated agrin-dependent AChR clustering in muscle. Our findings suggest that HGF promotes AChR clustering and synaptogenic signaling in muscle during NMJ development. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005 [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] Blockade of the central generator of locomotor rhythm by noncompetitive NMDA receptor antagonists in Drosophila larvaeDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2001Daniel Cattaert Abstract The noncompetitive antagonists of the vertebrate N -methyl- D -aspartate (NMDA) receptor dizocilpine (MK 801) and phencyclidine (PCP), delivered in food, were found to induce a marked and reversible inhibition of locomotor activity in Drosophilamelanogaster larvae. To determine the site of action of these antagonists, we used an in vitro preparation of the Drosophila third-instar larva, preserving the central nervous system and segmental nerves with their connections to muscle fibers of the body wall. Intracellular recordings were made from ventral muscle fibers 6 and 7 in the abdominal segments. In most larvae, long-lasting (>1 h) spontaneous rhythmic motor activities were recorded in the absence of pharmacological activation. After sectioning of the connections between the brain and abdominal ganglia, the rhythm disappeared, but it could be partially restored by perfusing the muscarinic agonist oxotremorine, indicating that the activity was generated in the ventral nerve cord. MK 801 and PCP rapidly and efficiently inhibited the locomotor rhythm in a dose-dependent manner, the rhythm being totally blocked in 2 min with doses over 0.1 mg/mL. In contrast, more hydrophilic competitive NMDA antagonists had no effect on the motor rhythm in this preparation. MK 801 did not affect neuromuscular glutamatergic transmission at similar doses, as demonstrated by monitoring the responses elicited by electrical stimulation of the motor nerve or pressure applied glutamate. The presence of oxotremorine did not prevent the blocking effect of MK 801. These results show that MK 801 and PCP specifically inhibit centrally generated rhythmic activity in Drosophila, and suggest a possible role for NMDA-like receptors in locomotor rhythm control in the insect CNS. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 58,73, 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] Female reproductive biology of Platygaster diplosisae (Hymenoptera: Platygastridae) and Aprostocetus procerae (Hymenoptera: Eulophidae), two parasitoids associated with the African Rice Gall Midge, Orseolia oryzivora (Diptera: Cecidomyiidae)ENTOMOLOGICAL SCIENCE, Issue 2 2008Souleymane NACRO Abstract We investigated the female reproductive system of Platygaster diplosisae (Hymenoptera: Platygastridae) and Aprostocetus procerae (= Tetrastichus pachydiplosisae) (Hymenoptera: Eulophidae), two parasitoids associated with the African rice gall midge, Orseolia oryzivora (Diptera: Cecidomyiidae). Both optical and electron microscopy were used. The female reproductive system of P. diplosisae includes two large ovaries of the meristic polytrophic-type, each composed of several tens of ovarioles. The system includes also a venomous gland that extends to a common oviduct. This gland had a filiform secretory portion, in which the epithelium was thin and surrounded a common evacuation canal. The secretory cells secrete into a large reservoir. Parasitism due to P. diplosisae is gregarious. The female reproductive system of A. procerae includes two ovaries of the meristic polytrophic-type, and each ovary has a few ovarioles. Each ovariole includes one or two oocytes, which can be seen in the vitellarium. Two accessory glands, which extend to the oviduct, are also visible. The secretory epithelium of the accessory gland is made up of a dense network of secretory cells surrounded by muscle fibers. Females of A. procerae pierce the tissues of the gall and probably deposit one egg on or close to the pupa of the midge. Aprostocetus procerae is a solitary parasitoid of the midge. The two parasitoids exploit the same host at different developmental stages. These findings improve our knowledge of the reproductive biology of these two parasitoids associated with the African rice gall midge, an important pest in Africa. [source] Ultrastructural localization of salivary mucins MUC5B and MUC7 in human labial glandsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2010Monica Piras Piras M, Hand AR, Tore G, Ledda GP, Piludu M. Ultrastructural localization of salivary mucins MUC5B and MUC7 in human labial glands. Eur J Oral Sci 2010; 118: 14,18. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci As a result of their presence throughout the mouth in the submucosa or between muscle fibers, minor salivary glands secrete directly and continuously into the oral cavity, providing mucosal surfaces with highly glycosylated proteins that are active in bacterial aggregation and in oral tissue lubrication. In this study, we investigated the ultrastructural localization of the MUC5B and MUC7 mucins in human labial glands by means of a postembedding immunogold technique. Thin sections of normal human labial glands, obtained during surgery, were incubated with polyclonal antibodies to human salivary mucins MUC5B and MUC7, and then with gold-labeled secondary antibodies. Specific MUC5B reactivity was found in the secretory granules of mucous cells of all glands examined, and was associated with the luminal membrane of duct cells. MUC7 labeling was observed in the granules of both mucous and seromucous secretory cells of the glandular parenchyma. Quantitative analyses demonstrated that seromucous granules have higher immunogold labeling densities for MUC7 than mucous granules. Our immunohistochemical data extend the results of previous light microscopic studies of MUC5B and MUC7 localizations, pointing out the significant contribution of human labial glands in the secretion process of these two mucins. [source] Parvalbumin deficiency in fast-twitch muscles leads to increased ,slow-twitch type' mitochondria, but does not affect the expression of fiber specific proteinsFEBS JOURNAL, Issue 1 2006Peter Racay Parvalbumin (PV), a small cytosolic protein belonging to the family of EF-hand calcium-binding proteins, is highly expressed in mammalian fast-twitch muscle fibers. By acting as a ,slow-onset' Ca2+ buffer, PV does not affect the rapid contraction phase, but significantly contributes to increase the rate of relaxation, as demonstrated in PV,/, mice. Unexpectedly, PV,/, fast-twitch muscles were considerably more resistant to fatigue than the wild-type fast-twitch muscles. This effect was attributed mainly to the increased fractional volume of mitochondria in PV,/, fast-twitch muscle, extensor digitorum longus, similar to levels observed in the slow-twitch muscle, soleus. Quantitative analysis of selected mitochondrial proteins, mitochondrial DNA-encoded cytochrome oxidase c subunit I and nuclear DNA-encoded cytochrome oxidase c subunit Vb and F1-ATPase subunit , revealed the PV,/,tibialis anterior mitochondria composition to be almost identical to that in wild-type soleus, but not in wild-type fast-twitch muscles. Northern and western blot analyses of the same proteins in different muscle types and in liver are indicative of a complex regulation, probably also at the post-transcriptional level. Besides the function in energy metabolism, mitochondria in both fast- and slow-twitch muscles act as temporary Ca2+ stores and are thus involved in the shaping of Ca2+ transients in these cells. Previously observed altered spatio-temporal aspects of Ca2+ transients in PV,/, muscles are sufficient to up-regulate mitochondria biogenesis through the probable involvement of both calcineurin- and Ca2+/calmodulin-dependent kinase II-dependent pathways. We propose that ,slow-twitch type' mitochondria in PV,/, fast muscles are aimed to functionally replace the slow-onset buffer PV based on similar kinetic properties of Ca2+ removal. [source] Tissue Repair: Wet-Spun Biodegradable Fibers on Conducting Platforms: Novel Architectures for Muscle Regeneration (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Mater. Bio-synthetic platforms, consisting of a conducting polymer substrate overlaid with aligned biodegradable fibers promote the linear growth (ex vivo) of partially differentiated muscle fibers, consistent with the structural requirements of skeletal muscle in vivo, as described by J. M. Razal et al. on page 3381. The conducting surface facilitates development of electrical stimulation paradigms for optimizing muscle growth and development ex vivo that may potentially be applied to repair diseased or damaged muscle. [source] Adult extracardiac rhabdomyoma: Light and immunohistochemical studies of two cases in the parapharyngeal spaceHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 3 2006Kristine Bjørndal Sørensen MD Abstract Background. We present two cases of adult rhabdomyoma in the parapharyngeal space. They are rare benign tumors with a characteristic histologic appearance. Methods. The tumors were studied by light and immunohistochemical analysis using stains characteristic of striated muscle fibers. Results. Cross-striation was demonstrated by phosphotungstic acid hematoxylin (PTAH), muscle specific actin, desmin, and myoglobin while dystrophin was expressed in the cell membranes. Clonal origin was confirmed by expression of myosin heavy chain-fast only. Expression of myosin-neonatal and myogenin proved slight proliferation with incipient differentiation in an otherwise mature tumor. Conclusion. The head and neck area harbors 90% of adult rhabdomyomas and should be considered in a differential diagnosis in this region. Immunohistochemistry confirms that the tumors are almost totally mature neoplasms of clonal origin. © 2006 Wiley Periodicals, Inc. Head Neck28: XXX,XXX, 2006 [source] Aedes aegypti transducing densovirus pathogenesis and expression in Aedes aegypti and Anopheles gambiae larvaeINSECT MOLECULAR BIOLOGY, Issue 5 2001T. W. Ward Abstract Aedes aegypti densovirus (AeDNV) is a small DNA virus that has been developed into an expression and transducing vector for mosquitoes [Afanasiev et al. (1994) Exp Parasitol 79: 322,339; Afanasiev et al. (1999) Virology 257: 62,72; Carlson et al. (2000) Insect Transgenesis: Methods and Applications (Handler, A.M. & James, A.A., eds), pp. 139,159. CRC Press, Boca Raton]. Virions carrying a recombinant genome expressing the GFP gene were used to characterize the pathogenesis of the virus in 255 individual Aedes aegypti larvae. The anal papillae of the larvae were the primary site of infection confirming previous observations (Afanasiev et al., 1999; Allen-Muira et al. (1999) Virology 257: 54,61). GFP expression was observed in most cases to spread from the anal papillae to cells of the fat body, and subsequently to many other tissues including muscle fibers and nerves. Infected anal papillae were also observed to shrink, or melanize and subsequently fall off in a virus dependent manner. Three to four day-old larvae were less susceptible to viral infection and, if infected, were more likely to survive into adulthood, with 14% of them still expressing GFP as adults. Higher salt concentrations of 0.10,0.15 m inhibited viral infection. Anopheles gambiae larvae also showed infection of the anal papillae (17%) but subsequent viral dissemination did not occur. The persistence of the reporter gene expression into adulthood of Aedes aegypti indicates that transduction of mosquito larvae with recombinant AeDNV may be a means of introducing a gene of interest into a mosquito population for transient expression. [source] Ultrastructure of the tentacle nerve plexus and putative neural pathways in sea anemonesINVERTEBRATE BIOLOGY, Issue 3 2002Jane A. Westfall Abstract. Neurons of sea anemone tentacles receive stimuli via sensory cells and process and transmit information via a plexus of nerve fibers. The nerve plexus is best revealed by scanning electron microscopy of epidermal peels of the tentacles. The nerve plexus lies above the epidermal muscular layer where it appears as numerous parallel longitudinal and short interconnected nerve fibers in Calliactis parasitica. Bipolar and multipolar neurons are present and neurites form interneuronal and neuromuscular synaptic contacts. Transmission electron microscopy of cross sections of tentacles of small animals, both C. parasitica and Aiptasia pallida, reveals bundles of 50,100 nerve fibers lying above groups of longitudinal muscle fibers separated by intrusions of mesoglea. Smaller groups of 10,50 slender nerve fibers are oriented at right angles to the circular muscle formed by the bases of the digestive cells. The unmyelinated nerve fibers lack any glial wrapping, although some bundles of epidermal fibers are partially enveloped by cytoplasmic extensions of the muscle cells; small gastrodermal nerve bundles lie between digestive epithelial cells above their basal myonemes. A hypothetical model for sensory input and motor output in the epidermal and gastrodermal nerve plexuses of sea anemones is proposed. [source] | ||||||||||||||||||||||||||||||||||