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At least 19 recordsLinked to original sources
PubMed2001

Development of muscle pathology in canine X-linked muscular dystrophy. II. Quantitative characterization of histopathological progression during postnatal skeletal muscle development.

We have characterized the time course of muscle pathology development during the postnatal maturation of quadriceps and tibialis anterior muscle in dystrophic golden retriever dogs. We determined the percentages of degenerating, regenerating, calcium-positive, hypercontracted, albumin-positive, and C3 complement fraction-positive muscle fibers and the extent of connective tissue proliferation in animals from neonate to adult. Necrotic fibers increased from days 2 to 30, decreased at 60 days (to 0.8%) and increased in older animals to a stable level of around 2%. Hypercontracted fibers peaked at 15 days (19.1%) and declined to 3.7% in adults. Regenerating fibers were numerous at 15 and 30 days (10%), declined at 60 days to 4.7% and declined further in adults. Calcium- and albumin-positive fibers peaked at 30 days (6.5% and 13.8%, respectively) and then declined to around 3% and 5%, respectively, in older dogs. In dystrophic dogs, the extent of fibrosis was significantly greater on 15 days than in controls, but did not then increase with age. In carriers, calcium- and albumin-positive fibers always expressed dystrophin abnormally. Muscle damage occurs before completion of muscle maturation in dystrophic dogs. While necrosis and hypercontraction remain stable in adults, fiber regeneration declines to very low levels. In contrast to Duchenne muscular dystrophy, muscle fibrosis in the muscle studied does not increase with age.

Aging↗
PubMed1985

Antigenic specificity of acetylcholine receptor in developing muscle. Studies with monoclonal antibodies.

Monoclonal antibodies (mcAbs) elicited against the nicotinic acetylcholine receptor (AChR) from Torpedo, were used to follow antigenic changes in AChR during muscle development. Newborn rat muscle and denervated mouse muscle were used as sources of extrajunctional AChR; adult innervated rat and mouse muscle were used as sources of junctional AChR. Most of the mcAbs tested reacted preferably, but not exclusively with extrajunctional AChR (EJR), as compared to junctional AChR (JR). None was found to react with only one of the two forms of AChR. We conclude that the anti-AChR monoclonal antibodies used in this study detect antigenic determinants which are shared by EJR and JR, but which probably undergo structural changes during muscle development.

Animals↗
PubMed2005

Endoplasmic reticulum stress signaling transmitted by ATF6 mediates apoptosis during muscle development.

Although apoptosis occurs during myogenesis, its mechanism of initiation remains unknown. In a culture model, we demonstrate activation of caspase-12, the initiator of the endoplasmic reticulum (ER) stress-specific caspase cascade, during apoptosis associated with myoblast differentiation. Induction of ER stress-responsive proteins (BiP and CHOP) was also observed in both apoptotic and differentiating cells. ATF6, but not other ER stress sensors, was specifically activated during apoptosis in myoblasts, suggesting that partial but selective activation of ER stress signaling was sufficient for induction of apoptosis. Activation of caspase-12 was also detected in developing muscle of mouse embryos and gradually disappeared later. CHOP was also transiently induced. These results suggest that specific ER stress signaling transmitted by ATF6 leads to naturally occurring apoptosis during muscle development.

Activating Transcription Factor 6↗
PubMed2000

Thyroid hormones differentially modulate enolase isozymes during rat skeletal and cardiac muscle development.

During muscle development, an isozymic transition of the glycolytic enzyme enolase occurs from the embryonic and ubiquitous alphaalpha-isoform to the muscle-specific betabeta-isoform. Here, we demonstrate a stimulatory role of thyroid hormones on these two enolase genes during rat development in hindlimb muscles and an inhibitory effect on the muscle-specific enolase gene in cardiac muscle. In hindlimb muscles the ubiquitous alpha-transcript level is diminished by hypothyroidism, starting at birth. On the contrary, the more abundant muscle-specific beta-transcript is insensitive to hypothyroidism before establishment of the functional diversification of fibers and is greatly decreased thereafter. Our data support the hypothesis of a role of thyroid hormones in coordinating the expressions of contractile proteins and metabolic enzymes during muscle development. The subcellular localization of isoenolases, established here, is not modified by hypothyroidism. Our results underline the specificity of action of thyroid hormones, which modulate differentially two isozymes in the same muscle and regulate, in opposite directions, the expression of the same gene in two different muscles.

Animals↗
PubMed1985

The effect of 4-aminopyridine-induced increased neuromuscular activity on the metabolism of developing muscles in chick embryos.

Chick embryos were treated with 4-aminopyridine (4 X 100 micrograms) during a critical stage of muscle development, and the effect of enhanced neuromuscular activity upon energy metabolism was studied in two fast-twitch muscles and a slow-tonic muscle. In the slow-tonic muscles of treated embryos, the specific activities of creatine kinase (CK) and lactate dehydrogenase (LDH) were reduced by 11 and 21%, respectively, compared with control values, whereas the ratios of the CK-MB isoforms and the LDH-H subunits increased to 125 and 135% of the control values, respectively. No significant changes could be shown in the enzymatic pattern of fast muscles. These results indicate that a moderate increase in neuromuscular activity of the chick embryo primarily influences the metabolism of developing slow muscles, promoting the development of an enzyme profile characteristic of slow oxidative fibres.

4-Aminopyridine↗
PubMed2006

Defining the transcriptional redundancy of early bodywall muscle development in C. elegans: evidence for a unified theory of animal muscle development.

Myogenic regulatory factors (MRFs) are required for mammalian skeletal myogenesis. In contrast, bodywall muscle is readily detectable in Caenorhabditis elegans embryos lacking activity of the lone MRF ortholog HLH-1, indicating that additional myogenic factors must function in the nematode. We find that two additional C. elegans proteins, UNC-120/SRF and HND-1/HAND, can convert naïve blastomeres to muscle when overproduced ectopically in the embryo. In addition, we have used genetic null mutants to demonstrate that both of these factors act in concert with HLH-1 to regulate myogenesis. Loss of all three factors results in embryos that lack detectable bodywall muscle differentiation, identifying this trio as a set that is both necessary and sufficient for bodywall myogenesis in C. elegans. In mammals, SRF and HAND play prominent roles in regulating smooth and cardiac muscle development. That C. elegans bodywall muscle development is dependent on transcription factors that are associated with all three types of mammalian muscle supports a theory that all animal muscle types are derived from a common ancestral contractile cell type.

Animals↗
PubMed1990

Myosin heavy and light chain expression during human skeletal muscle development and precocious muscle maturation induced by thyroid hormone.

It has now been well established that during mammalian muscle development there is a sequential transition of the myosin isoforms, with the developmental isoforms being replaced just before or just after birth by the adult isozymes. In a previous study of human fetal muscle, we demonstrated the differentiation of two fiber populations as early as 15 weeks: one population of large diameter fibers containing predominantly slow myosin heavy and light chains, and another population which stained homogeneously for fetal myosin heavy chain and corresponded to histochemical type IIC fibers. We have carried out an immunocytochemical and biochemical study of human fetal quadriceps between 7 and 40 weeks. A chronology of the changes which occur in the expression of the myosin heavy and light chains is correlated with the results obtained by enzyme histochemistry. Evidence is also presented that in man excessive amounts of thyroid hormone act directly on the muscle, and result in a precocious accumulation of the adult myosin heavy chains and a precocious maturation of the muscle.

Adenosine Triphosphatases↗
PubMed1999

The role of the extracellular matrix in skeletal muscle development.

Skeletal muscle fibers are surrounded by an extracellular matrix. The extracellular matrix is composed of glycoproteins, collagen, and proteoglycans. Proteoglycans have been suggested to play an important functional role in tissue differentiation; however, an understanding of how the extracellular matrix affects skeletal muscle development and function is largely unknown. Proteoglycans can regulate collagen fibrillogenesis, inhibit cell growth, and modulate the response to growth factors. Our studies have focused on the proteoglycan decorin, which interacts with transforming growth factor-beta and regulates collagen fibrillogenesis and cellular growth properties in the avian genetic muscle weakness Low Score Normal. Low Score Normal pectoral muscle development is characterized by a late embryonic increase in the expression of decorin followed by a subsequent increase in collagen crosslinking and modified collagen fibril organization. This paper reviews the interaction of extracellular matrix molecules, cell-extracellular matrix interactions, and modulation of growth factor activity. How proteoglycans may interface with each of these key events during skeletal muscle myogenesis is discussed.

Animals↗
PubMed2006

The p38 MAPK signaling pathway: a major regulator of skeletal muscle development.

Skeletal muscle development is regulated by extracellular growth factors that transmit largely unknown signals into the cell affecting the muscle-transcription program. One intracellular signaling pathway activated during the differentiation of myogenic cell lines is p38 mitogen-activated protein kinase (MAPK). As a result of modifying the activity of p38 in myoblasts, the pathway proved essential for the expression of muscle-specific genes. P38 affects the activities of transcription factors from the MyoD and MEF2 families and participates in the remodeling of chromatin at specific muscle-regulatory regions. P38 cooperates with the myogenic transcription factors in the activation of a subset of late-transcribed genes, hence contributing to the temporal expression of genes during differentiation. Recent developmental studies with mouse and Xenopus embryos, substantiated and further extended the essential role of p38 in myogenesis. Evidence exists supporting the crucial role for p38 signaling in activating MEF2 transcription factors during somite development in mice. In Xenopus, p38 signaling was shown to be needed for the early expression of Myf5 and for the expression of several muscle structural genes. The emerging data indicate that p38 participates in several stages of the myogenic program.

Aging↗
PubMed1961

Sarcomere size in developing muscles of a tarsonemid mite.

The embryo of a tarsonemid mite was found to be suitable for in vivo observations of muscle development by polarization microscopy. The four dorsal muscles of the metapodosoma each contain three sarcomeres, the anterior two of which can be seen clearly. These sarcomeres can be identified and followed during much of their development. Sarcomeres are about 2.5 micra long when first detected and increase in length until they are about 10 micra long. The change in length is associated with a slow, approximately constant rate of increase in the length of the A region, and an initially slow then much more rapid increase in the length of the I band. Preceding the period when the I band elongates rapidly there is an increase in the diameter of the muscle fibers and an increase in the retardation of the A band. A, I, Z, and H bands are visible during most of these changes. The change in A band length has been interpreted in terms of the growth of the A filaments which have been observed by electron microscopy in muscles of other animals. It is suggested that the exceptionally long sarcomeres in this mite result from the early fixing of the number of sarcomeres in a given muscle fiber.

Animals↗
PubMed2002

Limb muscle development.

Skeletal muscle precursors for the limbs originate from the epithelial layer of the somites, the dermomyotomes. We summarize the steps of limb muscle development from the specification of precursor cells in the dermomyotome, the directed migration of these cells to and within the limb buds to muscle growth and differentiation. All steps are controlled by local signaling between embryonic structures. In dermomyotome development, signals from the neural tube, the ectoderm and the intermediate and lateral mesoderm result in a medio-lateral patterning. Only the lateral portions of the dermomyotomes give rise to muscle precursor cells destined to enter the limb buds. As a prerequisite for migration, precursor cells have to de-epithelialize as a result of interactions between SF/HGF and its receptor c-met. Precursor cells adopt a mesenchymal morphology without losing their myogenic specification. This is achieved by the expression of the transcription factors Pax3, Pax7 and myf5. During migration, premature differentiation has to be kept at bay to enable motility and proliferation. After having reached their target sites, the dorsal and ventral myogenic zones, myogenesis is initiated by the activation of the muscle determination factors MyoD, myogenin and MRF4. Finally, we briefly summarize the process of muscle hypertrophy and regeneration during which aspects of developmental processes are reinitiated.

Animals↗
PubMed2001

Distinct mechanisms regulate slow-muscle development.

Vertebrate muscle development begins with the patterning of the paraxial mesoderm by inductive signals from midline tissues [1, 2]. Subsequent myotome growth occurs by the addition of new muscle fibers. We show that in zebrafish new slow-muscle fibers are first added at the end of the segmentation period in growth zones near the dorsal and ventral extremes of the myotome, and this muscle growth continues into larval life. In marine teleosts, this mechanism of growth has been termed stratified hyperplasia [3]. We have tested whether these added fibers require an embryonic architecture of muscle fibers to support their development and whether their fate is regulated by the same mechanisms that regulate embryonic muscle fates. Although Hedgehog signaling is required for the specification of adaxial-derived slow-muscle fibers in the embryo [4, 5], we show that in the absence of Hh signaling, stratified hyperplastic growth of slow muscle occurs at the correct time and place, despite the complete absence of embryonic slow-muscle fibers to serve as a scaffold for addition of these new slow-muscle fibers. We conclude that slow-muscle-stratified hyperplasia begins after the segmentation period during embryonic development and continues during the larval period. Furthermore, the mechanisms specifying the identity of these new slow-muscle fibers are different from those specifying the identity of adaxial-derived embryonic slow-muscle fibers. We propose that the independence of early, embryonic patterning mechanisms from later patterning mechanisms may be necessary for growth.

Animals↗
PubMed1991

E and F alpha series prostaglandins in developing muscles.

Prostaglandins are known to affect myoblast proliferation and fusion in vitro and are putative regulators of in vivo myogenesis. The levels of E and F alpha series prostaglandins in the thigh muscles of chicken embryos were measured by radioimmunoassays and correlated with indicators of muscle development. Just prior to the onset of secondary myogenesis, the amounts of PGE1, PGE2 and PGF1 alpha plus PGF2 alpha per mg of protein were high. In temporal association with myotube formation, the amount of PGE1 and PGE2 per mg of protein decreased. PGF alpha levels also fell, but at a slower rate than observed with the E series prostaglandins. The decreases in the amounts of prostaglandins per mg protein appeared to be due to a decline in the total amount of prostaglandin within each muscle. These observations are consistent with prostaglandins being one of the factors that controls in vivo muscle formation.

Alprostadil↗
PubMed2002

The Drosophila zinc finger transcription factor CF2 is a myogenic marker downstream of MEF2 during muscle development.

The Drosophila C(2)-H(2)-type zinc-finger transcription factor CF2 has been shown to regulate follicular cell fate determination during oogenesis. Here we show that CF2 is also expressed in the developing muscles of the embryo where it first appears at stage 12 at the time of skeletal myoblast fusion. Later it is expressed in all muscle lineages including skeletal, visceral and cardiac. Epistatic analysis showed that CF2 expression is dependent on the myogenic factor MEF2.

Animals↗
PubMed1989

Tissue-specific transcriptional control of alpha- and beta-tropomyosins in chicken muscle development.

During muscle maturation, isoform switching of contractile proteins to attain the adult phenotype involves both stage-specific and muscle-specific regulatory mechanisms. Chicken pectoralis major (PM) provides an interesting model to study the latter since a specific pattern of tropomyosin (TM) with repression of the beta TM isoform is displayed by the adult PM. The developmental pattern of alpha and beta fast skeletal muscle tropomyosins' (alpha f and beta TM) RNAs was investigated with 3' untranslated region specific probes. In PM, the beta TM messenger ceased to accumulate after hatching through a transcriptional control, as shown by run-on assays, so that, at Day 8 ex ovo, no beta TM mRNA was detected. In this same muscle, in parallel with the disappearance of the beta TM mRNA, there was a boost in the accumulation of the alpha f TM mRNA. In the leg muscles, following hatching, there was only a moderate increase in the level of the alpha f TM mRNA, together with a slight decrease in the accumulation of the beta TM mRNA. Taken together, these results show that chicken muscle maturation involves tissue-specific transcriptional control of tropomyosin genes and could suggest a possible coordinate regulation of the two genes.

Animals↗
PubMed1999

Dynamic expression of proteoglycans during chicken skeletal muscle development and maturation.

Skeletal muscle development is a complex process in which cell migration and adhesion play important roles. Because these cellular activities involve cell surface and extracellular matrix molecules, proteoglycan analysis was performed for developing chick skeletal muscle. Proteoglycans are macromolecular conjugates of protein and carbohydrate found in the extracellular matrix and at the cell surface. In developing muscle, both in vivo and in vitro, there is a development-related progression from synthesis of primarily large proteoglycans at earlier stages to mainly small proteoglycans at later stages. This progression was demonstrated by radiolabeling developing muscle and extracting and characterizing the proteoglycans. The large proteoglycans synthesized earlier in myogenesis have been identified as the large chondroitin sulfate proteoglycan, versican. Among the small proteoglycans synthesized at later stages is the small dermatan sulfate proteoglycan, decorin. Immunolocalization of these proteoglycans shows that versican is initially present in pericellular locations around developing myotubes, whereas decorin is observed in the epimysium early in development, and then its distribution gradually spreads to also include the perimysium and endomysium. Studies of regenerating muscle show that there is a recapitulation of the embryonic pattern of proteoglycan synthesis, which, coupled with the results from embryonic muscle development, suggests a role for versican in some early aspect of myogenesis.

Animals↗