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At least 19 recordsLinked to original sources
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↗
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↗
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↗
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↗
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↗
PubMed1990

Striated muscle tropomyosin-enriched microfilaments of developing muscles of chicken embryos.

The striated muscle tropomyosin-enriched microfilaments were isolated from developing muscles in ovo by the previously described method with a monoclonal antibody against striated muscle isoforms of tropomyosin (Lin & Lin, 1986). Two-dimensional gel analysis of the isolated microfilaments from developing heart, thigh and breast muscles revealed the coexistence of non-muscle isoforms of tropomyosin and actin throughout all stages of embryogenesis. A small but significant amount of skeletal muscle isoforms (alpha, beta) of tropomyosins and their phosphorylated forms was detected in the microfilaments isolated from hearts of 6-15-day-old embryos. These skeletal isoforms of tropomyosins disappeared after this stage of embryogenesis. In addition, we also detected both embryonic and adult isoforms of troponin T in early developing hearts. In developing thigh and breast muscles, the presence of non-muscle tropomyosin isoforms 2, 3a and 3b in the isolated microfilaments was apparent. The contents of tropomyosin isoform 2 were decreased with development and this non-muscle isoform completely disappeared at the 15th day of embryogenesis. On the other hand, the non-muscle tropomyosin isoforms 3a and 3b were present throughout all stages of development. Double-label immunofluorescence microscopy with monoclonal CH1 (anti-striated muscle isoforms of tropomyosin) and CG beta 6 (anti-non-muscle isoforms of tropomyosin) on the isolated, glycerinated skeletal and cardiac muscle cells of 10-day-old or 13-day-old embryos confirmed the colocalization of muscle and non-muscle isoforms of tropomyosins within the same cells. These results suggest that different isoforms of actin and tropomyosin can assemble into a class of microfilaments (i.e. striated muscle tropomyosin-enriched microfilaments) in ovo, which may transform into the thin filaments of mature muscle cells.

Actin Cytoskeleton↗
PubMed1992

Cell culture as a tool for the study of poultry skeletal muscle development.

Postnatal development of skeletal muscle is the responsibility of the myogenic satellite cells. Satellite cells, isolated from the pectoralis major muscle of young growing tom turkeys, have been cultured in vitro to provide a system for studying cellular and hormonal aspects of poultry skeletal muscle development. Satellite cell clones derived from primary cultures have been developed so that in vitro observations would not be confounded by the presence of nonmyogenic cells. Likewise, a serum-free medium that promotes proliferation of the turkey satellite cell has been developed to provide a hormonally controlled environment for in vitro developmental studies. These two techniques have enabled us to examine the following: 1) factors that influence satellite cell proliferation and differentiation, 2) the interaction of hormones with cellular receptors, 3) secretion of biologically important proteins from cells and 4) the expression of genes important to muscle development.

Animals↗
PubMed1985

Muscle development in the grasshopper embryo. I. Muscles, nerves, and apodemes in the metathoracic leg.

Much is known about the development of nerve pathways in the metathoracic limb bud of the grasshopper embryo. In this series of three papers, we report on the development of muscles in the same embryonic appendage. In a fourth paper (E. E. Ball, R. K. Ho, and C. S. Goodman, 1985, J. Neurosci, in press) we examine the development of specific neuromuscular connections for one of these muscles (coxal muscle 133a). In this first paper, we present an overview of the development of muscles, nerves, and apodemes (tendons). We previously reported on a class of large mesodermal cells, called muscle pioneers (MPs), that arises early in development and appears to act as a scaffold for developing muscles and guidance cue for motoneuron growth cones (R. K. Ho, E. E. Ball, and C. S. Goodman, 1983, Nature (London) 301, 66-69). We have used the I-5 monoclonal antibody (which specifically labels the MPs as well as the nerve pathways), HRP immunocytochemistry, and Normarski optics to visualize muscle, nerve, and apodeme development in the embryonic metathoracic limb bud from 27.5% (before the appearance of the MPs) to 55% (after the muscles have attained their basic adult pattern). Cell fusions, cell migration, and cell death all appear to play important roles in the development of MPs. The patterns of muscle development vary greatly, ranging from (i) single MPs for simple muscles (which in the adult have only one bundle of muscle fibers, e.g., coxal muscle 133a), to (ii) arrays of MPs for complex muscles [which in the adult have many bundles of muscle fibers each with separate sites of insertion, e.g., the extensor tibiae (ETi) and flexor tibiae (FlTi) muscles in the femur].

Animals↗
PubMed1991

Muscle-specific gene expression in rhabdomyosarcomas and stages of human fetal skeletal muscle development.

Rhabdomyosarcomas (RMS) bear a morphological resemblance to developing striated muscle. It has been reported that two histologically distinct subtypes of RMS, embryonal and alveolar, behave differently in many clinical aspects, such as age distribution, primary site, and prognosis. We have investigated the expression of various genes, which are preferentially expressed in normal muscle tissue or cell culture (actins, myosins, and creatine kinases, and myogenic regulatory genes MyoD, myogenin, MRF4, and Myf5), in embryonal and alveolar subtypes and compared the results to the stages of developing human fetal limb muscle. The data showed that each of the RMS tumors tested, regardless of histological features, expressed MyoD1 and MRF4 transcripts. Expression of the myogenin gene was detectable in all alveolar RMS (n = 8), whereas only 5 of 8 embryonal RMS expressed myogenin transcripts. Trace levels of Myf5 transcripts were visible in all alveolar RMS and 7 of 8 embryonal RMS. The alpha-skeletal, alpha-cardiac, and beta- and gamma-cytoplasmic actin transcripts were detectable in all alveolar RMS. While the beta- and gamma-cytoplasmic actin transcripts were evident in all embryonal RMS, only 3 of 8 and 6 of 8 embryonal RMS expressed detectable levels of alpha-skeletal and alpha-cardiac actin transcripts, respectively. The embryonic form of myosin heavy chain was detectable in 1 of 8 of each type of tumor. Myosin light chain-1/3 transcripts were detectable in 4 of 8 alveolar RMS and 5 of 8 embryonal RMS. Brain creatine kinase transcripts were detectable in all alveolar RMS and 4 of 8 embryonal RMS, whereas none of the RMS samples contained detectable levels of the muscle form of creatine kinase. A comparison of the expression profiles with those of normal developing human fetal limb muscle (from 7.5 to 24 weeks' gestation) suggested that RMS resembled a relatively restricted segment of fetal muscle development. Furthermore, the data also showed a great deal of overlap in the differentiation state achieved by the embryonal and alveolar subtypes of RMS, suggesting that the clinicopathological difference between these two may not be due to malignant transformation of the cells from different positions in the normal pathway of myogenesis.

Actins↗
PubMed1990

Differential distribution of myosin isoforms among the myofibrils of individual developing muscle fibers.

Myosin was localized in situ in the posthatch chicken pectoralis using isoform-specific mAbs. The distribution among myofibrils was demonstrated by immunofluorescence and by immunogold EM. Fluorescein- or rhodamine-labeled antibody (12C5) specific for the head region (S1) of myosin was used as a marker to identify "embryonic" myosin. In longitudinal semithin frozen sections, a minority population of myofibrils stained intensely with 12C5. All other myofibrils in the same cell stained only weakly. Similarly, in Lowicryl-embedded ultrathin sections prepared for EM, a minority population reacted preferentially with gold-labeled 12C5. An antibody (5B4) specific for the rod portion of "neonatal" myosin reacted strongly with nearly all myofibrils, and this was evident by light and electron microscopy. A few of the fibrils that reacted strongly with 12C5 reacted weakly with 5B4. These observations demonstrate that an epitope reacting with 12C5 is more abundant in some myofibrils than in others within the same cell. Three categories of myofibrils can be identified by their relative proportions of embryonic and neonatal forms of myosin: in nearly all fibrils, a neonatal isoform predominates; in a minority population, embryonic and neonatal isoforms are both abundant; and in a few fibrils, an embryonic isoform predominates. It is concluded that there are distinct populations of myofibrils in which specific isoforms are segregated within an individual cell.

Aging↗
PubMed1990

Ornithine and S-adenosylmethionine decarboxylase activities and polyamine contents in developing muscle tissues and primary cultures of normal and polymyopathic hamsters.

Polyamine (putrescine, spermidine, and spermine) contents and ornithine (ODC) and S-adenosylmethionine (SAMDC) decarboxylase activities have been assessed in an age-dependent manner, in normal and polymyopathic (dystrophic) hamster skeletal muscle, heart, and tongue extract and in primary tongue myoblast and skin fibroblast cultures. At 2 weeks of age, polyamine contents were significantly elevated in all of the dystrophic hamster tissues studied when compared with their age-matched controls. The degree of this elevation decreased with the age of the animals, generally, to a level where no significant difference in polyamine contents could be noted between normal and dystrophic hamster tissues. ODC and SAMDC activities in whole tissue extracts were consistently highest in 2-week-old muscle extracts and also declined with age. However, no significant changes in ODC or SAMDC activities were evident in any of the dystrophic muscle tissues studied when compared with their age-matched controls. Polyamine contents in dystrophic hamster myoblast and fibroblast primary cultures were also during proliferation (1 and 2 days after the initial seeding) compared with cultures prepared from normal hamsters. ODC and SAMDC activities in primary myoblast and fibroblast cultures clearly reflected the rate of cell proliferation, with highest activities found in subconfluent cell cultures. However, in general, no significant dystrophic-related abnormality in ODC or SAMDC activity was evident in proliferating myoblast or fibroblast cultures. These results suggest that the elevated polyamine contents of dystrophic hamster tissues and primary cultures may be due to a deficiency in polyamine catabolism or transport.

Adenosylmethionine Decarboxylase↗