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PubMed2005

The development of muscle fiber type identity in zebrafish cranial muscles.

Cranial skeletal muscles underlie breathing, eating, and eye movements. In most animals, at least two types of muscle fibers underlie these critical functions: fast and slow muscle fibers. We describe here the anatomical distribution of slow and fast twitch muscle in the zebrafish (Danio rerio) head in the adult and at an early larval stage just after feeding has commenced. We found that all but one of the cranial muscles examined contain both slow and fast muscle fibers, but the relative proportion of slow muscle in each varies considerably. As in the trunk, slow muscle fibers are found only in an anatomically restricted zone of each muscle, usually on the periphery. The relative proportion of slow and fast muscle in each cranial muscle changes markedly with development, with a pronounced decrease in the proportion of slow muscle with ontogeny. We discuss our results in relation to the functional roles of each muscle in larval and adult life and compare findings among a variety of vertebrates.

Animals↗
PubMed1989

Cytochemistry for lectins, actin, nucleotide tetrazolium reductases and several phosphatases in the porcine semitendinosus muscle: vascular development in young pigs.

An ontogeny study of the porcine semitendinosus muscle was conducted to meet two objectives: 1) to evaluate enzyme histochemistry, lectin cytochemistry and actin staining for usefulness as quantitative markers of muscle capillaries and 2) to describe the ontogeny of capillary density changes in developing porcine muscle. Muscle samples were obtained from three to eight crossbred pigs at each of the following ages: newborn, 1 to 2 d and 1, 2, 3, 4.5 and 24 wk. Cryostat sections were stained or reacted for alkaline and neutral phosphatase, dehydrogenase, actin, a panel of nine plant lectins (fluorescein isothiocyanate conjugated) and routine cytochemical tests for muscle fiber typing. Capillaries were quantitatively marked by reactions for dehydrogenase activity in the young pigs but not in the oldest animals. The lectins, soybean agglutinin, Bauhinia purpuria agglutinin, Ulex europeus agglutinin-I and Griffonia simplicifolia agglutinin-I (GS-I) quantitatively stained capillaries at all ages. Histological observations of thin sections of epon-embedded tissues served to validate the lectin and cytochemical capillary staining. Micrographs of sections stained with the lectin GS-I were used to count capillaries and muscle fibers so the capillary:fiber ratio (C/F) could be calculated. Deep (red) and superficial (white) aspects of muscle sections had different C/F at birth, 2, 4 and 24 wk. The deep aspects (DA) had higher C/F than superficial (SA) aspects (at all four ages), and there were age-dependent increases (P less than .001) in C/F of DA and SA. This study demonstrates the usefulness of lectin staining for determining C/F in porcine muscle.

Actins↗
PubMed1997

Maternal constraint influences muscle fibre development in fetal lambs.

The objective was to examine myogenesis in two situations expected to be characterized by maternal constraint: (i) in fetuses due to be born in spring (n=10) or autumn (n=10); and (ii) in single (n=16) and twin (n=20) fetal lambs. Maternal constraint operating through limitation of placental size, as measured by placentome weight per fetus, was evident in each study. Although a lower placental weight did not influence body and muscle weights of fetuses due to be born in the spring or autumn, twins had lower body and muscle weights than singles. Fibre number and average fibre cross-sectional (CS) area were differentially affected by season and fetal number. The differences in muscle fibre morphology between spring- and autumn-born fetuses suggest that muscle fibre development was influenced by maternal constraint in the absence of an effect on fetal weight. The differences in muscle fibre number and CS area in particular muscles from twin and single fetuses suggest that more severe maternal constraint, reflected in a lower placental size per fetus, not only influences fetal weight but can also affect muscle development.

Animals↗
PubMedDate not supplied

Maturation of ovine uterine smooth muscle during development and the effects of parity.

OBJECTIVES: To characterize changes in myometrial contractile proteins and myosin heavy chain (MHC) isoforms during ovine fetal and neonatal development and after pregnancy. We hypothesized that ovine myometrium demonstrates progressive cellular differentiation and maturation which begins in utero and extends into the postnatal period, and that pregnancy causes further cellular alterations. METHODS: Myometrium was obtained from female fetal (72- to 140-days of gestation, n = 19; term = approximately 145 days), postnatal (1 day to 3 months, n = 25), and parous noncycling nonpregnant (n = 9) sheep to measure total and soluble proteins, actin, MHC, and MHC isoforms. Contractile proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and expression of 200-kD MHC isoforms were determined with Western immunoblots. RESULTS: The contents of total and soluble proteins and actin and total myosin gradually increase (P <.003) during ovine development. Although the contribution of smooth-muscle 204-kD MHC increased (P <.001) from 23 +/- 8% of total MHC at <100 days of gestation to 75 +/- 2% 3 to 4 months postnatally, the 200-kD species fell proportionately. Before birth, MHC-B, a fetal isoform, is the predominant 200-kD protein; postnatally, it is replaced by SM2, demonstrating a switch from a synthetic to a mature contractile smooth-muscle phenotype. Pregnancy is associated with further increases in actin contents and redistribution of the contents of the 204-kD and SM2 MHC isoforms. CONCLUSIONS: Although the fetal and postnatal uterus has no known functional demand, ovine myometrial differentiation and maturation begin in the midtrimester and continue throughout the postnatal period. Thus, changes in smooth-muscle phenotype occur prenatally, as evidenced by a switch from MHC-B to SM2, which may signal completion of organ development and preparation for adult function. Pregnancy results in further modifications in myometrial proteins.

Actins↗
PubMed1993

Non-quantal release of acetylcholine affects polyneuronal innervation on developing rat muscle fibres.

The membrane potential at endplates of the rat hemidiaphragm for 9-day-old rats increases by 1.8 mV after addition of D-tubocurarine. The endplate depolarization before the addition of D-tubocurarine is considered to be due to non-quantal release (NQR) of acetylcholine (ACh). In the presence of an anticholinesterase this depolarization increased. It was further enhanced by 0.1-1.0 mM Mg2+ and reduced by 4 mM Mg2+ concentration. Thus the regulation of NQR at neuromuscular junctions of developing rat muscles is similar to that seen in adult mammalian species. The effect of NQR of Ach on neuromuscular contacts of muscle fibres from 8-9-day-old rat diaphragm and soleus muscles was studied. Pre-incubating the muscles in solutions where NQR was increased by lowering Mg2+ caused a significant (P < 0.01) reduction of neuromuscular contacts. This reduction did not occur when muscles were incubated in high Mg2+, when NQR is reduced. Increasing quantal release by high Ca2+ also caused a reduction of neuromuscular contacts. Histological examination of soleus muscle fibres treated with an anticholinesterase showed that muscles incubated in solutions with low (0.1 mM) concentrations of Mg2+ had significantly fewer neuromuscular contacts (38%) than those incubated in high concentrations of Mg2+ (61%). It is concluded that the NQR as assessed here contributes to the elimination of polyneuronal innervation during postnatal development of rat muscles.

Acetylcholine↗
PubMed1994

Initial fall in skeletal muscle force development during ischemia is related to oxygen availability.

We examined the hypothesis that the initial decline (first 1-2 min) in force development that occurs in working muscle when blood flow is halted is caused by O2 availability and not another factor related to blood flow. This was tested by reducing O2 delivery (muscle blood flow X arterial O2 content) to working muscle by either stopping blood flow [ischemia (I)] or maintaining blood flow with low arterial O2 content [hypoxemia (H)]. If initial decline in force development were similar between these two methods of reducing O2 delivery, it would suggest O2 availability as the common pathway. Isolated dog gastrocnemius muscle was stimulated at approximately 60-70% of maximal O2 uptake (1 isometric tetanic contraction every 2 s) until steady-state conditions of muscle blood flow and developed force were attained (approximately 3 min). Two conditions were then sequentially imposed on the working muscle: I, induced by shutting off pump controlling arterial perfusion of the muscle and clamping venous outflow, and H, induced by perfusing the muscle with deoxygenated blood (collected before testing while animal breathed N2) at steady-state blood flow level. Rates of the fall in force production in 17 matched conditions of H and I (approximately 40 s for each condition) were compared in 6 muscles tested. The blood perfusing the muscle during H had arterial PO2 = 8 +/- 1 (SE) Torr, arterial PCO2 = 37 +/- 1 Torr, and arterial pH = 7.39 +/- 0.03. The rate of decline in developed force was not significantly different (P = 0.46) between the 17 matched conditions of H (0.66 +/- 0.10 g force.g mass-1.s-1) and I (0.79 +/- 0.15 g force.g mass-1.s-1). These findings suggest that the initial fall in developed force in working skeletal muscle that occurs with ischemia is related to O2 availability.

Animals↗
PubMed1990

Determinative mechanisms in secondary muscle lineages of ascidian embryos: development of muscle-specific features in isolated muscle progenitor cells.

Muscle cells of the ascidian larva originate from three different lines of progenitor cells, the B-line, A-line and b-line. Experiments with 8-cell embryos have indicated that isolated blastomeres of the B-line (primary) muscle lineage show autonomous development of a muscle-specific enzyme, whereas blastomeres of the A-line and b-line (secondary) muscle lineage rarely develop the enzyme in isolation. In order to study the mechanisms by which different lines of progenitors are determined to give rise to muscle, blastomeres were isolated from embryos of Halocynthia roretzi at the later cleavage stages when conspicuous restriction of the developmental fate of blastomeres had already occurred. Partial embryos derived from B-line muscle-lineage cells of the 64-cell embryo (B7.4, B7.5 and B7.8) showed autonomous expression of specific features of muscle cells (acetylcholinesterase, filamentous actin and muscle-specific antigen). In contrast, b-line muscle-lineage cells, even those isolated from the 110-cell embryo (b8.17 and b8.19), did not express any muscle-specific features, even though their developmental fate was mainly restricted to generation of muscle. Isolated A-line cells from the 64-cell embryos (A7.8) did not show any features of muscle differentiation, whereas some isolated A-line cells from the 110-cell embryos (A8.16) developed all three above-mentioned features of muscle cells. This transition was shown to occur during the eighth cell cycle. These results suggest that the mechanism involved in the process of determination of the secondary-lineage muscle cells differs from that of the primary-lineage muscle cells. Interaction with cells of other lineages may be required for the determination of secondary precursors to muscle cells. The presumptive b-line and A-line muscle cells that failed to express muscle-specific features in isolation did not develop into epidermal cells. Thus, although interactions between cells may be required for muscle determination in secondary lineages, the process may represent a permissive type of induction and may differ from the processes of induction of mesoderm in amphibian embryos.

Acetylcholinesterase↗
PubMed1988

Mammalian neuromuscular development accelerated with early but slowed with late gestational administration of ACTH peptide.

The neuropeptide ACTH 4-10, a nonsteroidogenic fragment of adrenocorticotropic hormone, has two distinct and opposite effects on developing nerve and muscle. Muscle is positively influenced by ACTH during the first part of gestation (G days 3-12) before innervation occurs. Subsequent effects on innervation are largely depressive and exerted only during G13-21. Treatment during G3-12 increases twitch amplitude, rise time and speed of contraction of directly and indirectly stimulated extensor digitorum longus (EDL) muscle of two wk old rats. Treatment during G13-21 slows contractions of indirectly stimulated EDL, whereas treatment throughout gestation (G3-G21) shows little effect. Thus, ACTH first accelerates muscle development then modulates this development through neuronal depression.

Adrenocorticotropic Hormone↗
PubMed1991

Arterial wall and smooth muscle cell development in young Wistar rats and the effects of surgical denervation.

Development of the muscular saphenous artery and the effect of surgical denervation on normal development was investigated in young rats at 3 and 6 weeks of age. During this interval, the weight and blood pressures (systolic, diastolic, and mean) of the animals increased significantly. The tunica media of the artery and the lumen increased significantly with age, but the proportion of smooth muscle cell to paracellular matrix did not alter. Computer-assisted three-dimensional reconstructions were used to investigate the smooth muscle cells. They increased significantly in length, volume, and angle of orientation within the vessel wall with age but maintained an approximate surface area-to-volume ratio. The cells in any one vessel tended to be oriented in either a clockwise or counterclockwise direction. The size of the nucleus also increased significantly in length and volume with age, but an approximate surface area-to-volume ratio and a constant nucleocytoplasmic ratio were maintained. The nuclei tended to be eccentrically located, with less than half of all nuclei wholly within the middle third of the cell. Surgical denervation at 10 days of age resulted in abnormalities of growth in vessel dimensions, thinner tunica media at 3 weeks (denervated 11 days previously), and smaller lumen at 6 weeks (denervated 32 days previously). Elevated amounts of paracellular matrix occurred in both age groups, but denervation did not alter smooth muscle cell size. In the 3-week-old animals, denervation resulted in smooth muscle cells with hypertrophied nuclei. This may account for the increase in growth of the tunica media between 3 and 6 weeks of age in the denervated artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1994

New insights into the pathogenesis of congenital myopathies.

Congenital myopathies are developmental disorders of muscle that are best understood in the context of ontogenesis. Segmental amyoplasia results from a defective somite, usually because of lack of induction by the notochord and neural tube; the connective tissue matrix of the muscle is derived from lateral mesoderm and is present, but the myocytes are derived from somitic mesoderm and are replaced by adipose cells. Generalized amyoplasia is due to defective myogenic regulatory genes. X-linked recessive myotubular myopathy is associated with overexpression of vimentin and desmin, fetal intermediate filaments that attach to nuclear, mitochondrial, and inner sarcolemmal membranes and Z-bands of sarcomeres to preserve the morphologic organization of the myotube. Neonatal myotonic dystrophy is a true maturational delay in muscle development. Congenital muscle fiber-type disproportion is a syndrome of multiple etiologies but in some cases is associated with cerebellar hypoplasia and may be the result of abnormal suprasegmental stimulation of the developing motor unit at 20 to 28 weeks' gestation, mediated through bulbospinal pathways but not the corticospinal tract. Maturational delay of muscle in late developmental stages is less specific than in stages before midgestation. The Proteus syndrome is a muscular dysgenesis; abnormal paracrine growth factors and perhaps altered genes that regulate muscle differentiation and growth, such as myoD and myogenin, are the suspected cause. Focal proliferative myositis may be another example of a "paracrine myopathy."

Cell Differentiation↗
PubMed1992

Beneficial effects of training on developing dystrophic muscle.

The objective of this study was to determine whether increased contractile activity is beneficial or detrimental to developing dystrophic muscle. Hamsters (20-days-old) were gradually introduced to running at a speed of 14 m/min at 10% grade for 2 (T2) or 4 (T4) h/d for 4 weeks, 5 d/wk. Histological and fiber type properties were determined in the soleus (SOL), plantaris (PL), and extensor digitorum longus and contractile properties in SOL and PL from 5 animals/group, including 5 controls. Experimental animals had normal body and muscle mass. Training for 2 h/d had little effect on SOL contractile properties, whereas 4 h/d resulted in significant increases in force, percentage of type I fibers, and type I hypertrophy. Force also increased in PL. Muscle necrosis was reduced in SOL (T2 and T4) and unchanged in PL. In conclusion, endurance training generally had a beneficial or, at least, no detrimental effect on developing dystrophic muscles.

Animals↗
PubMed2006

Identification and analysis of putative regulatory sequences for the MYF5/MYF6 locus in different vertebrate species.

The myogenic factors (MYF) 5 and 6 are integral to the initiation and development of skeletal muscle and to the maintenance of its phenotype. Thus, they are candidate genes for growth- and meat quality-related traits. We performed a comparative sequence analysis of the MYF5/MYF6 locus in swine, cattle, dog, chicken and zebrafish on the basis of structural and functional information from human and mouse. Beside the characterization of upstream regulatory elements recently identified in mice, we demonstrate the existence of further highly conserved elements (E1 to E4) which may play a role in the regulation of MYF5 and MYF6 expression. Comparative sequence analysis of putative regulatory sequences in swine revealed a total of 21 single nucleotide polymorphisms (SNP) including 1 and 6 SNPs new for the promoters of MYF5 and MYF6, respectively. The conserved organization of the locus in vertebrates indicates a common basic mechanism of muscle development. However, the existence of numerous regulatory elements at large distances to MYF5 and MYF6 points to a very complex pattern of the gene regulation with significant differences between species.

Animals↗
PubMed2005

Nervous and muscle system development in Phascolion strombus (Sipuncula).

Recent interpretations of developmental gene expression patterns propose that the last common metazoan ancestor was segmented, although most animal phyla show no obvious signs of segmentation. Developmental studies of non-model system trochozoan taxa may shed light on this hypothesis by assessing possible cryptic segmentation patterns. In this paper, we present the first immunocytochemical data on the ontogeny of the nervous system and the musculature in the sipunculan Phascolion strombus. Myogenesis of the first anlagen of the body wall ring muscles occurs synchronously and not subsequently from anterior to posterior as in segmented spiralian taxa (i.e. annelids). The number of ring muscles remains constant during the initial stages of body axis elongation. In the anterior-posteriorly elongated larva, newly formed ring muscles originate along the entire body axis between existing myocytes, indicating that repeated muscle bands do not form from a posterior growth zone. During neurogenesis, the Phascolion larva expresses a non-metameric, paired, ventral nerve cord that fuses in the mid-body region in the late-stage elongated larva. Contrary to other trochozoans, Phascolion lacks any larval serotonergic structures. However, two to three FMRFamide-positive cells are found in the apical organ. In addition, late larvae show commissure-like neurones interconnecting the two ventral nerve cords, while early juveniles exhibit a third, medially placed FMRFamidergic ventral nerve. Although we did not find any indications for cryptic segmentation, certain neuro-developmental traits in Phascolion resemble the conditions found in polychaetes (including echiurans) and myzostomids and support a close relationship of Sipuncula and Annelida.

Animals↗
PubMed1993

Distribution of GAP-43 in relation to CGRP and synaptic vesicle markers in rat skeletal muscles during development.

GAP 43 in nerve terminal structures of rat skeletal muscles, was investigated during postnatal development using immunofluorescence and confocal laser scanning microscopy. Comparison with synaptophysin, synapsin, SV2, CGRP, SP and NF was done in double immunoincubation studies. GAP 43-like immunoreactivity (LI) was demonstrated in preterminal axons and motor endplates in all age groups (from E18 to adult), although the intensity of immunofluorescence was considerably higher in the younger rats. The outgrowing nerve sprouts in E18 muscles were strongly GAP 43-positive. The intensity decreased with increasing age, but even in adult animals GAP 43-LI was present in some p38- or SV2-positive endplates. GAP 43-LI was also present in muscle spindles and preterminal nerve branches, and likewise decreased with age. Perivascular nerve terminals (around arteries mainly) were, however, strong in GAP 43-LI during both development and adulthood. GAP 43-LI was strong, and present in both small and large granules. SP-LI was observed in a few thin, presumably sensory, axons around vessels, which also contained a few GAP 43-positive large granules. Most of the strongly GAP 43-positive terminals around vessels were probably autonomic postganglionic terminals. The results suggest that GAP 43, in addition to development and regeneration, may play a significant role also in normal adult rats, especially in perivascular nerve terminals, possibly connected with a high potential for plasticity in this kind of nerve terminals.

Aging↗
PubMed1991

Switching of bovine cytochrome c oxidase subunit VIa isoforms in skeletal muscle during development.

A cDNA encoding the liver isoform of bovine cytochrome c oxidase subunit VIa (VIaL) was cloned from bovine liver RNA by reverse transcription and the polymerase chain reaction. The nucleotide and deduced amino acid sequences show high conservation with the corresponding rat and human liver subunits. The sequence similarity between beef heart and beef liver VIa is 60%. Northern analyses of the steady-state levels of the VIa-heart (VIaH) and VIa-liver (VIaL) transcripts showed that adult liver and brain contained only VIaL transcripts, the VIaH transcript predominated in heart with a small amount of VIaL also present, while in adult skeletal muscle VIaH was present exclusively. The VIaL transcript was found in heart with a small amount of VIaL also present, while in adult skeletal muscle VIaH was present exclusively. The VIaL transcript was found in fetal heart and skeletal muscle from 104-215-day-old fetuses, in as much as 25% of the amount of VIaH transcript. The down-regulation of VIaL transcript in skeletal muscle at or close to birth may be correlated with a change in amount of cytochrome c oxidase relative to the bc1 complex (complex III) observed spectrally when fetal and adult muscle samples were compared.

Amino Acid Sequence↗
PubMed1983

Neural control of embryonic acetylcholine receptor and skeletal muscle.

The manner by which motor neurons exert control over the distribution and number of acetylcholine receptors, and muscle development was investigated in the superior oblique muscle of white Peking duck embryos. Clusters of receptors in the normally developing muscle first appeared on day 10 of incubation as determined with I125 alpha-bungarotoxin autoradiography. The initial appearance of receptor clusters coincided with the arrival of motor nerve fibers in the muscle. Clusters of receptors also appeared in normal fashion in muscles made aneural by destruction of motor neurons on day 7. But after day 14 these clusters had disappeared and no new clusters were seen thereafter in the aneural muscle. Receptor clusters persisted throughout development in muscle in which neuromuscular transmission was blocked with either curare or botulinum toxin and in muscles denervated on day 10.5, i.e., shortly after the initial nerve-muscle contact but prior to the onset of muscle activity. A progressive increase in the total number of receptors and in the total amount of protein occurred during the course of normal development. However, the specific activity of the receptor protein declined sharply following innervation on day 10. The total number of receptors and the specific activity of the receptor was affected depending on whether the motor neurons were destroyed before or after innervation and following chronic blockade of neuromuscular transmission. The half-life of the receptor protein was similar in normal, aneural, and paralyzed muscles (26, 25, 26 h, respectively). Measurements of total protein indicated that essentially no muscle growth occurred in the complete absence of innervation. Paralyzed muscles continued to develop but at a slower pace.

Animals↗
PubMed1975

Changes in creatine kinase and its isoenzymes in human fetal muscle during development.

The total creatine kinase activity and its isoenzyme patterns were investigated in the skeletal muscle of 87 fetuses, of which 80 were presumed normal, 5 were anencephalic and 2 were "at risk" for Duchenne muscular dystrophy (DMD). No differences, either in total enzyme activity or in the isoenzyme distributions, were found between the anencephalic fetuses or those at risk for DMD, when compared to normal fetuses of similar gestation. Creatine kinase activity was found to rise steadily throughout embryonic life. During fetal development, the isoenzyme pattern in skeletal muscle was observed to change from the initial prevalence of the brain (BB) type, to the predominance of the muscle (MM) form. The most pronounced change occurred between the 6th and the 16th week of gestation, a period characterized by the rapid fusion of myoblasts to form myotubes and the concomitant production of myofibrils. It is proposed that there is a close association between the creatine kinase isoenzymes spectrum and the stage of muscle development.

Anencephaly↗