SEARCH · Search PubMed

Results for “Muscle development”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources

PubMed1987

Developing muscle spindles in the mouse masseter muscle studied by electron microscopy.

The morphogenesis of the muscle spindles of the masseter muscle was investigated by electron microscopy. The mice used in this study were those from the 16-day-old fetuses to the four-day-old young, and the three-month-old adult ICR mice. At the time of observation the formation of the masseter muscle spindle had already started in the 16-day-old fetus. In the 17-day-old fetus, the sensory nerve terminated not only in the myotube but also in the myoblast in which no myofilaments were yet formed. From the observations on the 16-day-old and 17-day-old fetuses, it is suggested that the myotubes of the intrafusal muscle fibers are formed by the fusion of the myocytes already containing the myofilaments. The gamma motor end-plate appeared two days later than the sensory nerve terminal formation in the muscle spindle. The initial inner capsule of the spindle was observed in the four-day-old young. The cell without the myofilaments appeared amidst the cluster of the intrafusal muscle fibers in the three-day-old young. It is considered that this cell may be the origin of the inner capsule cell. The periaxial space formation and the myelination of the masseteric nerve fiber occurred in the four-day-old young. The formation of the postsynaptic folds was observed in the extrafusal muscle fiber at the same stage. Thus, the muscle spindles, nerve fibers and the extrafusal muscle fibers showed a remarkable development at the same time in this early postnatal stage.

Animals↗

PubMed1988

Quantitative relationships between motoneuron and muscle development in Xenopus laevis: implications for motoneuron cell death and motor unit formation.

A common approach to the study of neural regression has been to correlate the timing of cell loss with other events such as target development. Most of these studies have areas of uncertainty. First, the analysis is normally carried out on groups of neurons that innervate a variety of targets. Second, there are some doubts about the reliability of light microscopic quantitation of muscle development. In this study, the period of cell death in the semimembranosus motor pool of Xenopus laevis has been estimated and correlated with an electron microscopic study of the development of the semimembranosus. The period of cell death of semimembranosus motoneurons was estimated on the basis of their position in the spinal cord and from the number of myelinated axons in the semimembranosus motor nerve. The semimembranosus motor pool contained approximately 70 motoneurons and was located 17-37% along the rostrocaudal axis of the lumbar cord. Cell loss from this motor pool occurred between stages 53-54 and 56, whereas cell death in the entire lumbar cord extended beyond stage 58. Primary myogenesis occurred between stages 53 and 54 in the semimembranosus. There was then a hiatus in myotube production until secondary myogenesis began around stage 56. It is concluded that secondary myotubes are not involved in regulating motoneuron cell death and that the number of primary myotube clusters is similar in magnitude to the number of motoneurons that will ultimately survive the period of cell death. The implications of these observations for theories of cell death and motor unit formation are discussed.

Aging↗

PubMed1992

Localization of mRNAs coding for CMD1, myogenin and the alpha-subunit of the acetylcholine receptor during skeletal muscle development in the chicken.

Myogenin and CMD1, the chicken homologue of MyoD, transactivate the promoter of the alpha-subunit of the acetylcholine receptor (AChR) in chicken fibroblasts. The expression of these three genes was followed by in situ hybridization. In two-day-old embryos the CMD1 gene is expressed shortly before the AChR alpha-subunit and the myogenin genes. At day 19 extrajunctional AChR mRNA clusters have disappeared and myogenin mRNAs are no longer detected in PLD muscle. Moreover, both myogenin and CMD1 mRNA levels increase after muscle denervation in chicks. These data are compatible with a role for myogenic factors in the induction and maintenance of extra-junctional expression of the AChR genes during early muscle development. Using digoxygenin labelled RNA probes, we also show that the mRNAs for the AChR alpha-subunit display a punctated, probably perinuclear distribution, whereas mRNAs for myogenic genes accumulate in the sarcoplasm around subsets of nuclei in the muscle fiber.

Animals↗

PubMed2000

Embryonic muscle development in rainbow trout (Oncorhynchus mykiss): a scanning electron microscopy and immunohistological study.

Embryonic muscle development was studied in rainbow trout (Oncorhynchus mykiss) at low and high temperature using scanning electron microscopy (SEM) and immunohistology. Somite development was described starting at stage 16 (Vernier JM. 1969. Ann Embryol Morphogen 4:495-520) for both temperatures, with special interest in their shape and size. Muscle differentiation, associated with somite growth, is characterized by a larger increase in height compared to width and by acquisition of a chevron shape. Thin structures such as striation, sarcomeres, and myofibrils within muscle cells and myotubes were observed starting at the eyed stage (stage 24). Immunohistological analyses showed appearance of embryonic fast myosin at stage 20 in the deep part of the somite. The area where myosin was expressed extended in the somite throughout embryonic development and the presence of myosin was observed in the entire somite at hatching (stage 30). Slow myosin was expressed in a monolayer of superficial cells at the eyed stage and during the entire embryonic development. Then it was expressed in a few layers of cells located in the red muscle area. These results suggest that muscle differentiation, characterized by myosin expression, is engaged at stage 20. Myogenesis starts in the deep part of the somite, near the notochord and progresses laterally to cover the complete somite at hatching when the somite is composed of muscle fibres exhibiting a high degree of maturity. No significant difference was observed in terms of muscular development between low- and high-temperature conditions. J. Exp. Zool. 286:379-389, 2000.

Animals↗

PubMed1989

Myosin light chain 3 synthesis during chick pectoralis muscle development in ovo.

The level of myosin light chain 3 (LC3) in vertebrate skeletal muscle is developmentally regulated in a tissue-specific manner. We have used the RNA-cDNA hybridization assay to quantitate LC3 mRNA levels at various stages of chick pectoralis muscle development in ovo. The LC3 mRNA was found significantly in breast muscle only on Day 16 in ovo and later, the level of mRNA ranging from about 30 to 32% of that present in adult tissue. These values are in good agreement with the corresponding levels of LC3 in embryonic muscle. These results do not support the earlier reports that the protein and mRNA for LC3 accumulate in a noncoordinate manner in embryonic pectoralis muscle and they suggest that LC3 synthesis in ovo is regulated primarily at the transcriptional level.

Animals↗

PubMed2000

Muscle development: molecules of myoblast fusion.

The fusion of myoblasts to make multinucleate muscle fibres is central to muscle development. Recent work on Drosophila has identified two members of the immunoglobulin superfamily that have key roles in controlling the specificity of myoblast fusion.

Animals↗

PubMed1977

The distribution of alpha-bungarotoxin binding sites of mammalian skeletal muscle developing in vivo.

1. The distribution of alpha-bungarotoxin binding sites on embryonic and neonatal rat skeletal muscle fibres was determined by autoradiography. Most of the bungarotoxin binding could be inhibited by curare. This observation, together with the spatial distribution of toxin-binding sites, indicates that the distribution of bound toxin reflects that of acetylcholine (ACh) receptors on these developing muscle cells.2. At 15 days of embryogenesis, muscle fibres showed an essentially uniform distribution of receptors. By 16 days, many fibres showed an accumulation of receptors in their mid-region. This accumulation was at the same location as histochemically demonstrated cholinesterase activity.3. At 16 days ACh receptors were distributed over the entire length of the fibres, with a gradient of increasing density as the accumulation was appoached. The density of toxin binding sites in the accumulation was greater than the general level on 15 day cells, suggesting that the high junctional density does not develop solely by the loss of extrajunctional receptors.4. The accumulations of ACh receptors became more pronounced and circumscribed with embryonic development, and after birth the extent of the localizations appeared to follow the size of the neuromuscular junction. The extrajunctional receptor density decreased with development, and by 1 week after birth was undetectable by the methods used.5. The results suggest that the high junctional receptor density found on adult, innervated skeletal muscle fibres develops after the formation of the neuromuscular junction.

Age Factors↗

PubMed1984

Muscle development in thyroidectomised chickens (Gallus domesticus).

The metabolic and contractile activity of muscle was determined in immature cockerels made hypothyroid by surgical thyroidectomy at 6 weeks of age. Four weeks after thyroidectomy the activity of Mg2+-activated myofibrillar ATPase and total phosphorylase was reduced in the fast-phasic, posterior latissimus dorsi (PLD) and scapulotriceps (ST) muscles. The activities of these enzymes were unaffected in the slow-tonic, anterior latissimus dorsi (ALD) muscle. Thyroidectomy had no effect on length of the muscles studied but reduced the weight of the ALD and ST muscles. These results suggest that hypothyroidism results in a "slowing down" of fast-phasic muscles, although it does not affect the activity of slow-tonic muscles.

Adenosine Triphosphatases↗

PubMed1990

Segregation of the myogenic cell lineage in mouse muscle development.

With increasing interest in the idea of therapeutic implantation of normal muscle precursor cells into muscle lacking the protein product of the dystrophin gene, it has become important to obtain enriched populations of myogenic cells from biopsied muscle sources. Myogenic cells for implantation are highly favoured as they are the only cells that will fuse readily with host muscle fibres into which they are implanted, thus carrying the introduced gene into the target fibre with the maximum of efficiency. Second, myogenic cells appear less immunogenic than those of a non-myogenic nature; and third, the use of mononuclear myogenic cells may permit the introduction of multiple copies of a deficient gene into the patient's own cells. From a mixed population of cells obtained by the enzymic disaggregation of neonatal murine muscle we have selected, utilising a modification of the panning technique, for a cell population rich in myogenic cells. Segregation was accomplished using Mab H28, an antibody to the mouse neuronal cell adhesion molecule (N-CAM), derived from mouse/rat hybridoma cells. Following incubation with Mab H28, disaggregated muscle was applied to the surface of a bacteriological grade dish previously coated with anti-rat immunoglobulin. Cells segregated into two populations; those bearing N-CAM, and hence labelled with Mab H28, were adherent to the dish, whereas those not expressing N-CAM remained in suspension. Use of this technique, which involves minimal cell loss, resulted in the segregation of prefusion myogenic cells together with fibroblasts in the 'non-adherent' fraction, whereas cells in the adherent fraction consisted of a highly enriched population of actively dividing myogenic cells.

Animals↗

PubMed1986

Growth and muscle development characteristics of purebred Angus and Brahman bulls.

Thirty-eight purebred bulls (10 to 17 mo of age) were used to determine the effects of breed (Angus or Brahman) and slaughter weight (60, 80, 90 or 100% of the average mature dam's weight for the respective breed) on growth and muscle development characteristics. Angus bulls grazed summer forage after weaning whereas Brahman bulls were fed to simulate gains achieved on forage by Angus. Bulls were then placed in a confinement feedlot for finishing to their appropriate slaughter weight (293, 369, 411, and 469 kg for Angus and 307, 427, 464 and 520 kg for Brahman). No major differences due to breed were found for predicted carcass composition. The LD muscle from Brahman bulls contained more total DNA (2.27 v. 1.19 g), more total protein (768.22 v. 593.59 g) and generally less total lipid (70.56 v. 101.26 g) when expressed on a total muscle (wet tissue) basis. The percentages and areas for all three muscle fiber types were not affected by breed. As carcass weight increased, muscle weights, total protein, lipid, protein:DNA and muscle fiber size for the three fiber types increased. Total DNA content increased only up to the 90% weight group and then leveled off. The percentage of alpha R fibers decreased while the percentage of alpha W fibers increased with increasing carcass weight. These data suggest that slaughtering animals based on a percentage of their dam's mature weight seems to be a practical method for making comparisons of animals on an equivalent compositional basis. Moreover, it appears that histochemical and biochemical evaluations of skeletal muscle can successfully identify what point in the growth cycle an animal is in.

Aging↗

PubMed1989

Geographutoxin-sensitive and insensitive sodium currents in mouse skeletal muscle developing in situ.

1. The whole-cell voltage-clamp technique was used to examine developmental changes of Na+ current properties in single fibres of mouse flexor digitorum brevis muscles developing in situ from birth to 20 days post-natal. 2. Geographutoxin II (GTX II), a novel polypeptide toxin from the marine snail Conus geographus, distinguished two different types of voltage-sensitive Na+ currents: GTX II-sensitive and GTX II-insensitive currents, which corresponded respectively to currents with high or low TTX sensitivity. 3. Voltage-dependent activation and inactivation of the GTX II-insensitive currents occurred at membrane potentials 10-20 mV more negative than those for the GTX II-sensitive currents. 4. The GTX II-insensitive current in fibres from mice older than 8 days inactivated more slowly than the GTX II-sensitive current. However, in fibres from younger mice, the two currents decayed with similar speed. 5. The mean specific Na+ conductance (gNa) for the total (GTX II-sensitive plus GTX II-insensitive) Na+ channels was 0.22 mS/muF at a Na+ concentration of 5 mM at birth. The total gNa increased 6-fold to 1.32 mS/muF during the first 20 days after birth. 6. The mean specific gNa for the GTX II-insensitive channels was 0.15 mS/muF at birth, remained at approximately the same level for the first 8 days, and then decreased progressively to become undetectable by day 16. 7. In muscle fibres denervated 12 days after birth, the GTX II-insensitive gNa increased over the next 8 days, whereas the total gNa increased less than normal. 8. By contrast, in fibres denervated on day 4, the total gNa increased more than normal in the following 8 days, and the GTX II-insensitive specific gNa increased above the level seen at birth. 9. Half-maximal activation and inactivation potentials of the total and the GTX II-insensitive currents shifted in the negative direction by 9-17 mV in the first 8 days after birth. 10. We conclude that the regulatory effects of innervation on the total gNa are either suppressive or enhancing depending on the stage of development. On the other hand, denervation elicits an increase in GTX II-insensitive Na+ currents at all ages studied.

Aging↗

PubMed1992

Actin and myosin genes are transcriptionally regulated during mouse skeletal muscle development.

During primary and secondary myotube formation in utero and subsequent maturation of muscle fibers after birth there are complex changes in the pattern of contractile protein gene expression at the RNA and protein levels. In order to determine the degree of transcriptional regulation of actin and myosin genes we have carried out "nuclear run-on" experiments using nuclei prepared from the limb muscle of mice at 14.5, 15.5, 17.5, and 18.5 days in utero and at 10-12 and 12.5 days after birth. We show that transitions in the expression of these genes in vivo are regulated transcriptionally. Transcription of the sarcomeric alpha-actins changes from cardiac to predominantly skeletal actin over this time period; transcription of the beta-actin gene is repressed. The myosin heavy chain and myosin light chain genes also undergo transcriptional transitions during muscle development. Notably, transcription from the MLC3F promoter is activated after that of the MLC1F promoter, which is part of the same gene. These results are discussed in the context of published RNA data.

Actins↗

PubMed1994

The expression pattern of contractile and intermediate filament proteins in developing skeletal muscle and rhabdomyosarcoma of childhood: diagnostic and prognostic utility.

In order to investigate whether rhabdomyosarcoma (RMS) can be related to equivalent stages of skeletal muscle development, muscle tissue of 21 human foetuses and 112 primary RMSs were characterized immunohistochemically using antibodies directed against vimentin, desmin, muscle-specific actin (HHF35), sarcomeric actin (sr-actin), smooth muscle actin (sm-actin), and troponin-T. During fetal skeletal muscle development, all myotubes/fibres of the first and second generations expressed desmin, HHF35, and sr-actin. Vimentin was almost exclusively present in immature primary and secondary myotubes/fibres. Troponin-T was expressed in immature myotubes/fibres of the first and second generations as well as mature fibres of the second generation. Sm-actin was never expressed. Vimentin was expressed in 96 per cent of primary and 98 per cent of relapsed RMS; HHF35 in 96 and 98 per cent, respectively; desmin in 95 and 100 per cent; troponin-T in 82 and 75 per cent; sr-actin in 71 and 86 per cent; and sm-actin in 13 and 17 per cent. The proportion of RMS cells reacting with vimentin, HHF35, and desmin was consistently higher than those expressing sr-actin and troponin-T. Neither the shape nor size of neoplastic RMS cells nor the histopathological types were related to the expression pattern of the investigated markers. RMS with aberrant expression of two or more markers predicted a worse prognosis than RMS in which at most one marker was aberrantly expressed (25 per cent and 54 per cent 10-year survival, P = 0.01). These results demonstrate that HHF35, desmin, sr-actin, and troponin-T have the potential to confirm the commitment of the tumours to the myogenic pathway which supports the diagnosis of RMS. However, it was impossible to relate RMS to equivalent stages of skeletal muscle development. Aberrant marker expression by RMS cells correlated significantly with patients' survival.

Actins↗

PubMed1996

Three zebrafish MEF2 genes delineate somitic and cardiac muscle development in wild-type and mutant embryos.

The zebrafish is an important experimental system for vertebrate embryology, and is well suited to the molecular analysis of muscle development. Transcription factors, such as the MEF2s, regulate skeletal and cardiac muscle-specific genes during development. We report the identification of three zebrafish MEF2 genes which, like their mammalian counterparts, encode factors that function as DNA-binding transcriptional activators of muscle specific promoters. The pattern of MEF2 expression in zebrafish defines discrete cell populations in the developing somites and heart and has mechanistic implications for developmental regulation of the MEF2 genes, when compared with other species. Alteration of MEF2 expression in two mutants affecting somitogenesis provides insight into the control of muscle formation in the embryo.

Amino Acid Sequence↗

PubMed1988

Shedding of cytoplasmic actins by developing muscle cells.

Young myotubes develop spots or macules of actin and alpha actinin under and adjacent to slender actin strands. Macules are found only before sarcomere formation. They contain cytoplasmic actin, small amounts of alpha actin, and alpha actinin but are devoid of tubulin, myosin and vimentin. In the electron microscope, they are seen to contain small filaments but no other organelles. Macules are found on the culture dish and in the culture medium, as well as on the lower and lateral surfaces of the cells. Both emetine and cycloheximide, at doses that inhibit protein synthesis, accelerate formation and shedding of macules. This presents the first observation of a cellular system in which the changeover from a generalized cytoskeleton to a tissue-specific cytoskeleton involves shedding of the cytoplasmic isoforms of cytoskeletal proteins.

Actins↗

PubMed1985

Muscle development in the grasshopper embryo. III. Sequential origin of the flexor tibiae muscle pioneers.

The flexor (FlTi) and extensor (ETi) tibiae are antagonist muscles located in the femur of the metathoracic leg of the grasshopper. Both are complex, consisting of an array of bundles of muscle fibers connecting the ectoderm of the wall of the femur with their respective apodemes. In the previous paper (E. E. Ball and C. S. Goodman, 1985, Dev. Biol. 111, 399-416) we described the embryonic development of the ETi muscle, focusing in particular on its syncytial origin from a giant supramuscle pioneer which later divides into an array of individual muscle pioneers. Here we describe the embryonic development of the FlTi muscle. In contrast to the development of the ETi muscle, the array of individual muscle pioneers for the FlTi does not have a syncytial origin but rather arises by sequential recruitment from the mass of smaller, undifferentiated mesoderm cells. The FlTi MPs first appear as two cells symmetrically placed on the corners of the FlTi apodeme at around 37%. A third MP is then added between these two; this third MP later dies. Subsequent growth occurs by symmetrical addition of MPs distally along the sides of the developing apodeme and by enlargement of the individual MPs. Initially each MP contains only a single nucleus; by about 50% there are at least two to three nuclei per MP and each is surrounded by a cluster of smaller, undifferentiated mesoderm cells. Each MP develops into a bundle of muscle fibers by a cycle of fusion and division. The individual mesoderm cells surrounding each MP fuse with it starting at about 60%. At the same time, the large MP begins to divide into smaller muscle fibers.

Animals↗

PubMed1997

Ectopic expression of MEF2 in the epidermis induces epidermal expression of muscle genes and abnormal muscle development in Drosophila.

Myocyte-specific enhancer-binding factor 2 (MEF2) is a myogenic regulatory factor in vertebrates and Drosophila. Whereas the role of MEF2 in regulating vertebrate myogenesis and muscle genes has been extensively studied, little is known of the role of MEF2 in regulating Drosophila myogenesis. We have shown in a recent analysis of the regulation of the Drosophila Tropomyosin I (TmI) gene in transgenic flies that MEF2 is a positive regulator of TmI expression in the somatic body-wall muscles of embryos, larvae, and adults. To understand further the role of MEF2 in myogenesis and test the role of MEF2 in regulating TmI expression, we have used the yeast GAL4/UAS system to generate embryos in which MEF2 is ectopically expressed in tissues where it is not normally expressed or embryos in which MEF2 is overexpressed in the mesoderm and muscles. We observe that ectopic expression of MEF2 in the epidermis and the ventral midline cells in embryos activates the expression of TmI and other muscle genes in these tissues and that this activation is stage-dependent suggesting a requirement for additional factors. Furthermore, ectopic expression of MEF2 in the epidermis results in a decrease in the expression of signaling molecules in the epidermis and a failure of the embryo to properly form body-wall muscles. These results indicate that MEF2 can function out of context in the epidermis to induce the expression of muscle genes and interfere with a requirement for the epidermis in muscle development. We also find that the level of MEF2 in the mesoderm and/or muscles in embryos is critical to body-wall muscle formation; however, no effect is observed on the development of the visceral muscle or dorsal vessel.

Animals↗

PubMed1995

Posthatching growth and pectoralis muscle development in broiler strain chickens, bantam chickens and the reciprocal crosses between them.

Body weight, pectoralis muscle weight, pectoralis protein and DNA concentration, and plasma GH and IGF-I concentrations of broiler chicks (BrBr), bantam chicks (BaBa) and reciprocal crosses between them (BaBr and BrBa) were measured between 0 and 42 days after hatching. At hatch, body weight and pectoralis weight of the two types of chicks from broiler eggs (BrBr and BaBr) were equal to each other but greater than the two types of chicks from bantam eggs (BaBa and BrBa), which were not different from each other. BrBr chicks grew more rapidly than crossbreds and BaBa chicks grew more slowly. Weights of the reciprocal crosses (BaBr and BrBa) were markedly different at day of age, but converged by day 14. The increase in pectoralis muscle mass of BrBr chicks exceeded that of the reciprocal crosses which in turn exceeded that of BaBa chicks. The increase in pectoralis DNA content and protein content followed the same pattern. The DNA unit size, as expressed by the protein:DNA ratio, was markedly lower in pure bantam chicks from 14 to 42 days of ages, whereas the unit size did not differ between the intermediate sized reciprocal crosses and the large bodied broiler chicks. Differences in muscle mass were primarily achieved by differences in the number of DNA units although a difference in unit size was also a factor. There were no clear relationships between growth and plasma growth hormone or insulin-like growth factor I concentrations. Thus while satellite cell proliferation is primarily responsible for genotypic differences in muscle mass, the plasma growth hormone-IGF-I axis does not appear to be regulating their proliferation.

Age Factors↗