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Adult Skeletal Muscle (adult + skeletal_muscle)
Selected AbstractsExpression and alternative splicing of N-RAP during mouse skeletal muscle development,CYTOSKELETON, Issue 12 2008Shajia Lu Abstract N-RAP alternative splicing and protein localization were studied in developing skeletal muscle tissue from pre- and postnatal mice and in fusing primary myotubes in culture. Messages encoding N-RAP-s and N-RAP-c, the predominant isoforms of N-RAP detected in adult skeletal muscle and heart, respectively, were present in a 5:1 ratio in skeletal muscle isolated from E16.5 embryos. N-RAP-s mRNA levels increased three-fold over the first 3 weeks of postnatal development, while N-RAP-c mRNA levels remained low. N-RAP alternative splicing during myotube differentiation in culture was similar to the pattern observed in embryonic and neonatal muscle, with N-RAP-s expression increasing and N-RAP-c mRNA levels remaining low. In both developing skeletal muscle and cultured myotubes, N-RAP protein was primarily associated with developing myofibrillar structures containing ,-actinin, but was not present in mature myofibrils. The results establish that N-RAP-s is the predominant spliced form of N-RAP present throughout skeletal muscle development. Cell Motil. Cytoskeleton 2008. Published 2008 Wiley-Liss, Inc. [source] Muscle stem cells and model systems for their investigationDEVELOPMENTAL DYNAMICS, Issue 12 2007Nicolas Figeac Abstract Stem cells are characterized by their clonal ability both to generate differentiated progeny and to undergo self-renewal. Studies of adult mammalian organs have revealed stem cells in practically every tissue. In the adult skeletal muscle, satellite cells are the primary muscle stem cells, responsible for postnatal muscle growth, hypertrophy, and regeneration. In the past decade, several molecular markers have been found that identify satellite cells in quiescent and activated states. However, despite their prime importance, surprisingly little is known about the biology of satellite cells, as their analysis was for a long time hampered by a lack of genetically amenable experimental models where their properties can be dissected. Here, we review how the embryonic origin of satellite cells was discovered using chick and mouse model systems and discuss how cells from other sources can contribute to muscle regeneration. We present evidence for evolutionarily conserved properties of muscle stem cells and their identification in lower vertebrates and in the fruit fly. In Drosophila, muscle stem cells called adult muscle precursors (AMP) can be identified in embryos and in larvae by persistent expression of a myogenic basic helix,loop,helix factor Twist. AMP cells play a crucial role in the Drosophila life cycle, allowing de novo formation and regeneration of adult musculature during metamorphosis. Based on the premise that AMPs represent satellite-like cells of the fruit fly, important insight into the biology of vertebrate muscle stem cells can be gained from genetic analysis in Drosophila. Developmental Dynamics 236:3332,3342, 2007. © 2007 Wiley-Liss, Inc. [source] Neurovascular Alignment in Adult Mouse Skeletal MusclesMICROCIRCULATION, Issue 2 2005SHAWN E. BEARDEN ABSTRACT Objective: Muscle blood flow increases with motor unit recruitment. The physical relationships between somatic motor nerves, which control muscle fiber contraction, and arterioles, which control microvascular perfusion, are unexplored. The authors tested the hypothesis that motor axons align with arterioles in adult skeletal muscle. Methods: Transgenic mice (C57BL/6 background, n = 5; 10 months of age) expressing yellow fluorescent protein in all motor nerves underwent vascular casting (Microfil). Excised epitrochlearis, gracilis, gluteus maximus, and spinotrapezius muscles were imaged at 380× and 760× and a computer-integrated tracing system (Neurolucida) was used to acquire 3-dimensional digital renderings of entire arteriolar and neural networks within each muscle. Results: Arteriolar networks were typically ,3-fold longer than neural networks. Nerves coursed with arterioles until terminating at motor endplates. Across muscles, proximity analyses revealed that , 75% of total nerve length (9.8,48.8 mm) lay within 200 ,m of the nearest arteriole (diameters of 15,60 , m). Conclusions: Somatic motor nerves and arterioles align closely within adult mammalian skeletal muscle. Understanding the signals governing neurovascular alignment may hold important clues for the advancement of tissue engineering and regeneration. [source] The expression patterns of Pax7 in satellite cells during overload-induced rat adult skeletal muscle hypertrophyACTA PHYSIOLOGICA, Issue 4 2009M. Ishido Abstract Aim:, Activated satellite cells (SCs) have the ability to reacquire a quiescent, undifferentiated state. Pax7 plays a crucial role in allowing activated SCs to undergo self-renewal. Because the increase in the SC population is induced during overload-induced skeletal muscle hypertrophy, it is possible that Pax7-regulated SC self-renewal is involved in the modulation of the SC population during the functional overload of skeletal muscles. However, the characteristics of the expression patterns of Pax7 in SCs during the functional overload of adult skeletal muscles are poorly understood. Methods:, Using immunohistochemical approaches, we examined the temporal and spatial expression patterns of Pax7 expressed in SCs during the functional overloading of rat skeletal muscles. Results:, The time course of Pax7 expression in SCs was similar to that of the expression of the differentiation regulatory factor myogenin during the early stage of functional overload. However, the percentage of SCs that expressed Pax7 was markedly higher than that of the SCs that expressed myogenin. Coexpression of Pax7 and myogenin was not detected in SCs. In addition, the expression of cyclin-dependent kinase inhibitor p21, which regulates cell cycle arrest and differentiation, was not detected in Pax7-positive SCs. Conclusion:, These results suggest that Pax7-regulated self-renewal of SCs may be induced during the early stage of functional overload and may contribute to modulating the SC population in hypertrophied muscles. Furthermore, it was suggested that the numbers of SCs which underwent self-renewal may be higher than that of SCs which were provided as the additional myonuclei for hypertrophying myofibres. [source] Development-dependent disappearance of caspase-3 in skeletal muscle is post-transcriptionally regulatedJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2002Louis-Bruno Ruest Abstract Caspase-3, a major player in apoptosis, engages apoptosis-activated cells into an irreversible pathway leading to cell death. In this article, we report that caspase-3 protein is absent from rat and mouse adult skeletal muscles, despite the abundant presence of its mRNA. During skeletal muscle development, caspase-3 protein is present in neonatal animals, but its expression gradually decreases, and disappears completely by 1 month of age, when there is still abundant caspase-3 mRNA. This discordance between caspase-3 message and protein expression is unique to skeletal muscle, as in all other analyzed tissues the protein presence correlates with the presence of the mRNA. The only circumstance in which caspase-3 protein appears in adults is in regenerating muscles; once regeneration is complete, however, it again becomes undetectable in repaired muscles. We conclude that caspase-3 protein in skeletal muscle is uniquely regulated at the post-transcriptional level, unseen in other tissues such as brain, heart, lung, kidney, thymus, spleen, liver, or testis. The post-transcriptional regulation of caspase-3 might serve as a fail-safe mechanism to avoid accidental cell death. J. Cell. Biochem. 86: 21,28, 2002. © 2002 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] | ||||||||||