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PubMedDate not supplied

[Patterns of adaptive mobilization of proteins from skeletal muscles during development of compensatory hypertrophy of internal organs].

These studies were dealing with muscle protein depletion in rats under the heart hypertrophy induced by aorta coarctation or under liver regeneration after partial hepatectomy. The last experimental model was also used in order to establish how far such protein mobilization from muscles is realized during their simultaneous adaptation to local overload or disuse induced by a surgical method. 3 and 7 days after induction of hypertrophy of organs investigated, the quantities of sarcoplasmic, myofibrillar and stroma proteins were measured in last-twitch (m. extensor digitorum longus, m. biceps brachii) and slow-twitch (m. soleus) muscles. The contributions of protein biosynthesis and/or protein degradation change into muscle protein loss were evaluated by specially elaborated radiotracer method. The data obtained demonstrate that the pattern of muscle protein mobilization depends on nature of organ and rate of its hypertrophy. The process occurs differently in muscle of different type and in various muscle structures. It appears to be potentiated in overloaded muscles and to a lesser extent in unused ones. The loss of muscle proteins is certainly associated with inhibition of their biosynthesis. Increased degradation (or release) of preformed (non-labelled) protein molecules may also contribute to this loss whereas degradation of newly-formed (labelled) molecules does not change appreciably, possibly because their distribution in muscle structures is non-uniform.

Animals↗
PubMed2000

Effects of birth weight and postnatal nutrition on neonatal sheep: II. Skeletal muscle growth and development.

This study investigated effects of birth weight and postnatal nutrition on growth and development of skeletal muscles in neonatal lambs. Low (L; mean +/- SD 2.289 +/- .341 kg, n = 28) and high (H; 4.840 +/- .446 kg, n = 20) birth weight male Suffolk x (Finnsheep x Dorset) lambs were individually reared on a liquid diet to grow rapidly (ad libitum fed, ADG 337 g, n = 20) or slowly (ADG 150 g, n = 20) from birth to live weights (LW) up to approximately 20 kg. At birth, weight of semitendinosus (ST) muscle in L lambs was 43% that in H lambs; aggregate weights of ST and seven other dissected muscles were similarly reduced. In ST muscle of L lambs, mass of DNA, RNA, and protein were also significantly reduced to levels 67, 60, and 34%, respectively, of those in H lambs. However, myofiber numbers of ST, tibialis caudalis, or soleus muscles did not differ between the L and H birth weight lambs and did not change during postnatal growth. During postnatal rearing, daily accretion rate of dissected muscle was lower in L than in H lambs. Accretion of muscle per kilogram of gain in empty body weight (EBW) was reduced in the slowly grown L lambs compared with their H counterparts, although the difference was less pronounced between the rapidly grown L and H lambs. Throughout the postnatal growth period, ST muscle of L lambs contained less DNA with a higher protein:DNA ratio at any given muscle weight than that of H lambs. Slowly grown lambs had heavier muscles at any given EBW than rapidly grown lambs. Content of DNA and protein:DNA ratio in ST muscle were unaffected by postnatal nutrition, but RNA content and RNA:DNA were greater and protein:RNA was lower at any given muscle weight in rapidly grown lambs. Results suggest that myofiber number in fetal sheep muscles is established before the presumed, negative effects of inadequate fetal nutrient supply on skeletal muscle growth and development become apparent. However, proliferation of myonuclei may be influenced by fetal nutrition in late pregnancy. Reduced myonuclei number in severely growth-retarded newborn lambs may limit the capacity for postnatal growth of skeletal muscles.

Animal Nutritional Physiological Phenomena↗
PubMed2001

AlphaB-crystallin in lens development and muscle integrity: a gene knockout approach.

PURPOSE: To study the role of alphaB-crystallin (alphaB) in the developing lens and its importance in lens structure and function. METHODS: Gene targeting in embryonic stem cells was used to generate mouse lines in which the alphaB gene and its protein product were absent. Gene structure and expression were characterized by genomic Southern blot, immunoblot, and Northern blot analyses, and two-dimensional gel electrophoresis. The gene knockout mice were screened for cataract with slit lamp biomicroscopy, and dissected lenses were examined with dark-field microscopy. Lenses and other tissues were analyzed by standard histology and immunohistochemistry. Chaperone activity was determined by heating lens homogenate supernatants and measuring absorbance changes. RESULTS: In an unexpected result, lenses in the alphaB gene knockout mice developed normally and were remarkably similar to wild-type mouse lenses. All the other crystallins were present. The thermal stability of a lens homogenate supernatant was mildly compromised, and when oxidatively stressed in vivo with hyperbaric oxygen, the knockout lenses reacted similarly to wild type. In targeting the alphaB gene, the adjacent HSPB2 gene, which is not expressed in the lens, was also disrupted. Loss of alphaB and/or HSPB2 function leads to degeneration of some skeletal muscles. CONCLUSIONS: AlphaB is not essential for normal development of a transparent lens in the mouse, and therefore is more dispensable to the lens than the closely related alphaA-crystallin. It may play a small role in maintaining transparency throughout life. alphaB and/or the closely related HSPB2 is required to maintain muscle cell integrity in some skeletal muscles.

Aging↗
PubMed1992

Comparison of the effects of cassava (Manihot esculenta Crantz) organic cyanide and inorganic cyanide on muscle and bone development in a Nigerian breed of dog.

Effects of cassava (Manihot esculenta Crantz)-borne organic cyanide and inorganic cyanide in the form of sodium cyanide on bone and muscle development were investigated in eighteen dogs of Nigerian breed. After 16 weeks of stabilization in the laboratory from the time of purchase when the dogs were fed on the same diet, they were randomly assigned to three experimental groups of six dogs each. The control group was fed on rice while the other two groups were fed on either cassava (gari) or rice plus cyanide. The three diets were made isoenergetic and isonitrogenous by varying the quantity of meat incorporated into them. The results obtained after 14 weeks of feeding the respective diets indicated that there was retardation of muscle development in the gari-fed dogs. This may have resulted from gluconeogenesis from muscle protein associated with suppression of production of insulin by the pancreas in this group. The results indicated also that the effects of inorganic dietary cyanides on muscle development were different. Both forms of dietary cyanides, however, had no adverse effect on bone development.

Animals↗
PubMed1995

Enhanced expression of mouse c-ski accompanies terminal skeletal muscle differentiation in vivo and in vitro.

Overexpression of either v-ski, or the proto-oncogene, c-ski, in quail embryo fibroblasts induces the expression of myoD and myogenin, converting the cells to myoblasts capable of differentiating into skeletal myotubes. In transgenic mice, overexpression of ski also influences muscle development, but in this case it effects fully formed muscle, causing hypertrophy of fast skeletal muscle fibers. In attempts to determine whether endogenous mouse c-ski plays a role in either early muscle cell determination or late muscle cell differentiation, we analyzed mRNA expression during muscle development in mouse embryos and during in vitro terminal differentiation of skeletal myoblasts. To generate probes for these studies we cloned coding and 3' non-coding regions of mouse c-ski. In situ hybridization revealed low c-ski expression in somites, and only detected elevated levels of mRNA in skeletal muscle beginning at about 12.5 days of gestation. Northern analysis revealed a two-fold increase in c-ski mRNA during terminal differentiation of skeletal muscle cell lines in vitro. Our results suggest that c-ski plays a role in terminal differentiation of skeletal muscle cells not in the determination of cells to the myogenic lineage.

Amino Acid Sequence↗
PubMed2002

Na,K-ATPase alpha- and beta-isoform expression in developing skeletal muscles: alpha(2) correlates with t-tubule formation.

This study examined the developmental expression of Na,K-ATPase alpha- and beta-subunit isoforms in different skeletal muscles of the mouse, and the relationship of Na,K-ATPase alpha(2) isoform expression to the developing transverse tubules (t-tubules). We measured Na,K-ATPase and dihydropyridine receptor (DHPR) mRNA and protein in the diaphragm and hindlimb muscles from embryonic day 18.5 (E18.5) to 6 weeks postnatal, using DHPR expression to mark the timing of t-tubule formation. The Na,K-ATPase subunits showed developmental age-dependent and muscle-specific expression that was controlled by both transcriptional and post-transcriptional mechanisms. The alpha(1) isoform is expressed at more constant levels in both diaphragm and hindlimb muscles, while the alpha(2) and beta(2) isoforms increase postnatally and show greater muscle variation. beta(1) is the sole expressed beta-subunit in the diaphragm throughout development, and in the hindlimb muscles at birth. The Na,K-ATPase alpha(2) subunit is expressed during development when the t-tubules form. These results suggest that the alpha(2) isoform may serve, in part, a physiological role in the muscle t-tubules.

Aging↗
PubMed2001

Temperature and myogenic factor transcript levels during early development determines muscle growth potential in rainbow trout (Oncorhynchus mykiss) and sea bass (Dicentrarchus labrax).

The influence of changes in environmental temperature on the mRNA levels of myogenic regulatory factors (MRFs), i.e. MyoD and myogenin, as well as myosin heavy chain (MyHC) were studied during early larval development in rainbow trout and sea bass. Phosphoimager analysis of northern blots indicated that there is an optimum temperature for the RNA transcript levels of MRF and MyHC RNA in trout and in sea bass larvae. In the trout strain studied, the highest concentration for MRF and MyHC transcripts was found at 8 degrees C rather than 4 degrees C or 20 degrees C. In European sea bass, the highest concentrations of MRF and MyHC mRNA were observed at 15-20 degrees C rather than 13 degrees C. Raising sea bass larvae at 15 degrees C was associated with higher MyHC gene expression as well as a trend towards an increase in total muscle fibre number and higher growth rates after transfer at ambient temperature. Results suggest that mRNA levels of MRF and MyHC can be used to optimise early development. An experiment in which the temperature was changed illustrates the consequence of precise temporal expression of MRF genes in specifying muscle fibre number at critical stages during early development.

Animals↗
PubMed1992

Morphometric analysis of coated vesicles in developing rat muscle spindles.

The incidence of coated vesicles under sarcolemmal surfaces of equatorial, juxta-equatorial and polar regions in developing and adult spindles of the rat soleus muscle was examined by quantitative morphometry of transverse ultrathin sections. Coated vesicles were more numerous: 1) under primary sensory endings than under other types of neuromuscular contacts; 2) under the appositional sarcolemma between neighbouring intrafusal fibres than under free surfaces of the sarcolemma; and 3) in developing than in mature spindles. Factors such as location and age of the animal often interacted to produce an additive effect on the incidence of coated vesicles. Although there was a high incidence of coated vesicles at the postsynaptic surface under sensory terminals of bag2 fibres in 18 and 19 day gestational embryonic rats, it peaked in 4 day postnatal animals. The high incidence of coated vesicles at sensory endings supports the view that coated vesicles mediate neurotrophic interactions between afferents and intrafusal fibres during the critical late gestation and early postnatal time period, as sensory axons first contact their target fibres and exert a maximal directing influence on the differentiation of intrafusal fibre types. In addition, the preferential localization of coated vesicles under appositional rather than free surfaces of developing intrafusal fibres in 0-4 day rats suggests that they play a role in the transport of active substances among intrafusal fibres exhibiting different stages of maturity.

Aging↗
PubMed1993

Development of muscle power in preterm infants: individual trajectories after term age.

In a longitudinal study individual trajectories were traced for the developing relationship between active and passive muscle power in preterm (n = 37) and fullterm (n = 20) infants from term to 24 weeks (corrected) age. Such trajectories should enable the identification of those infants at highest risk for later neurological dysfunctions. This contention is supported by the findings of this study: those preterm infants who showed marked discrepancies between the two sorts of muscle power or rigidity in both beyond 12 weeks corrected age were most likely to manifest neurological problems at 52 weeks of age.

Female↗
PubMedDate not supplied

A history of the development of muscle perforator flaps and their specific use in burn reconstruction.

Only rarely does coverage in the burn patient require the use of a vascularized flap. However, when mandatory, a knowledge of all alternatives is essential because common donor sites may have been badly burned and unavailable. The recent development of the muscle perforator flap may prove to be another valuable option. These flaps are nourished by the familiar musculocutaneous perforators but differ in that their complete intramuscular dissection is required during flap elevation so that no muscle need be included with the flap. A review of six cases using muscle perforator free flaps specifically for burn reconstruction or rehabilitation demonstrates how the same large cutaneous territory of a musculocutaneous flap can still be captured while the muscle and therefore its function is preserved.

Adult↗
PubMed2004

Troponin I is required for myofibrillogenesis and sarcomere formation in Drosophila flight muscle.

Myofibrillar proteins assemble to form the highly ordered repetitive contractile structural unit known as a sarcomere. Studies of myogenesis in vertebrate cell culture and embryonic developmental systems have identified some of the processes involved during sarcomere formation. However, isoform changes during vertebrate muscle development and a lack of mutants have made it difficult to determine how these proteins assemble to form sarcomeres. The indirect flight muscles (IFMs) of Drosophila provide a unique genetic system with which to study myofibrillogenesis in vivo. We show in this paper that neither sarcomeric myosin nor actin are required for myoblast fusion or the subsequent morphogenesis of muscle fibres, i.e. fibre morphogenesis does not depend on myofibrillogenesis. However, fibre formation and myofibrillogenesis are very sensitive to the interactions between the sarcomeric proteins. A troponin I (TnI) mutation, hdp(3), leads to an absence of TnI in the IFMs and tergal depressor of trochanter (TDT) muscles due to a transcript-splicing defect. Sarcomeres do not form and the muscles degenerate. TnI is part of the thin filament troponin complex which regulates muscle contraction. The effects of the hdp(3) mutation are probably caused by unregulated acto-myosin interactions between the thin and thick filaments as they assemble. We have tested this proposal by using a transgenic myosin construct to remove the force-producing myosin heads. The defects in sarcomeric organisation and fibre degeneration in hdp(3) IFMs are suppressed, although not completely, indicating the need for inhibition of muscle contraction during muscle development. We show that mRNA and translated protein products of all the major thin filament proteins are reduced in hdp(3) muscles and discuss how this and previous studies of thin filament protein mutants indicate a common co-ordinated control mechanism that may be the primary cause of the muscle defects.

Actins↗
PubMed1982

The development of muscle spindles in human fetuses.

Investigations were performed on the gastrocnemius muscle in 27 human fetuses aged 9-32 weeks, 2 fetuses of 74 and 220 C.-R. length were examined electron microscopically. The first muscle spindles were observed at 11 and 12 weeks and were covered by a capsule composed of single layer of cells. The intrafusal fibers, being in myotube stage, contained well developed regular actin as well as myosin filaments. Among the myotube cells interdigitating myoblasts are observed. Well developed sensory nerve endings covered by a basal lamina were found in the sockets on the surface of the intrafusal fibers. During the further stages of development an increase in diameter and number of intrafusal fibers have been noted. The capsule was composed of several layers. However, the inner and outer layers of the capsule consisted of cells resembling those of the perineurium. Within the muscle spindles satellite cells were observed. The results of these investigations have shown that the muscle spindles are established early in the fetal period. Furthermore, it was found that the development of muscle proprioceptors was not finished before birth.

Fetus↗
PubMed1998

Protein synthesis in fast and slow muscles of developing cockerels loaded with 2G for 3 weeks.

BACKGROUND: In our previous study, the increment of RNA and protein content ratios against body weight in the whole skeletal muscle were determined in young developing cockerels under 2G hypergravity for 3 weeks. In the present study, protein synthesis rate, RNA activity and protein content were investigated in different types of muscles [slow muscle (soleus) and fast muscle (extensor digitorum longus; EDL)] in similar experimental conditions. HYPOTHESIS: It is believed that slow and fast muscle will show different responses to hypergravity. METHOD: Young cockerels were raised standing vertically in a centrifuge and lived in a hypergravity (2G) environment for 3 weeks. At the end of the 3 weeks, the soleus and EDL muscles in their legs were immediately removed and the protein and RNA extracted. The fractional rate of protein synthesis in the muscles were determined by incorporation of L-[4-3H]-phenylalanine. RESULTS: The feed intake of centrifuged cockerels was reduced on the first day but recovered on the second day. Thus, the growth curve was parallel although 2G-loaded cockerels were smaller in size. In a slow muscle (soleus) the protein synthesis rate, protein content and muscle mass were significantly increased after 2G loading. While fast muscle (EDL) protein synthesis rate (Ks) and RNA activity decreased, muscle mass and protein content had no significant change in the 2G loading group. CONCLUSION: Soleus, which supports the body against gravity, apparently responded to hypergravity, while EDL may be repressed in protein turnover under the same condition. These findings imply that slow and fast muscles show different responses to hypergravity according to their function.

Aerospace Medicine↗
PubMed1988

The levator ani of the female rat: a suitable model for studying the effects of testosterone on the development of mammalian muscles.

The present results give evidence by using cytochemical markers of motor end-plates (ChE, AchR) and ultrastructural techniques that the Levator ani (LA) muscle is also present in adult females: it is composed of differentiated and innervated fibres. A significant difference, both on the number of fibres per muscle (n) and on their average cross-sectional area (acsa), was observed between sexes:-male: n = 5300 +/- 687, acsa: 522 +/- 68.6 microns 2;-female: n = 565 +/- 246.9, acsa: 68 +/- 8.6 microns 2. These results suggest that testosterone could control, at least partially, the number and the diameter of muscle fibres during development.

Aging↗
PubMed1992

Expression of transforming growth factor-beta (TGF-beta 1) and insulin-like growth factor II (IGF-II) messenger RNA in the developing subcutaneous tissue (SQ) of the fetal pig.

Studies (in situ hybridization) were performed on the developing subcutaneous tissue (SQ) of the pig fetus to determine sites of synthesis of TGF-beta 1 and IGF-II. Tissues from 50, 70, 90, 110-day-old pig fetuses and 7-day-old postnatal pigs were Bouin's fixed, paraffin embedded and hybridized with biotin labelled cDNA probes. The expression of TGF-beta 1 messenger RNA was detectable primarily in the dermis, hair follicle fat lobule, outer and inner SQ areas at all ages. Cells adjacent to adipocyte clusters and some small adipocytes were positive for TGF-beta 1. There was no positive hybridization of TGF-beta 1 probes in the developing muscle below the SQ. The expression of IGF-II was evident in the developing muscle below the SQ at 50 d and 70 d, and could be detected in the outer and inner SQ at 70 d. Much lower levels of IGF-II expression were observed in 90 and 110 d fetuses, but an increase in IGF-II expression was evident in the muscle of 7d postnatal pigs. Our results suggest that paracrine and autocrine regulatory systems may be operative for developing adipocytes (TGF-beta 1) and muscle (IGF-II), with specific areas and times of TGF-beta 1 and IGF-II expression being evident in developing pig SQ tissue.

Animals↗
PubMed2005

Acetylcholine and calcium signalling regulates muscle fibre formation in the zebrafish embryo.

Nerve activity is known to be an important regulator of muscle phenotype in the adult, but its contribution to muscle development during embryogenesis remains unresolved. We used the zebrafish embryo and in vivo imaging approaches to address the role of activity-generated signals, acetylcholine and intracellular calcium, in vertebrate slow muscle development. We show that acetylcholine drives initial muscle contraction and embryonic movement via release of intracellular calcium from ryanodine receptors. Inhibition of this activity-dependent pathway at the level of the acetylcholine receptor or ryanodine receptor did not disrupt slow fibre number, elongation or migration but affected myofibril organisation. In mutants lacking functional acetylcholine receptors myofibre length increased and sarcomere length decreased significantly. We propose that calcium is acting via the cytoskeleton to regulate myofibril organisation. Within a myofibre, sarcomere length and number are the key parameters regulating force generation; hence our findings imply a critical role for nerve-mediated calcium signals in the formation of physiologically functional muscle units during development.

Acetylcholine↗
PubMed1999

Apoptosis of skeletal muscles during development and disease.

Cells from multicellular organisms self-destroy when no longer needed or when damaged. They do this by activating genetically controlled machineries that lead to apoptosis. Skeletal muscles in adult animals are fully differentiated syncytial cells. Apoptosis has been described in developing and, recently, in adult skeletal muscle. The cellular and molecular aspects of myoblast and myofibre apoptosis and their role in disease are analysed in this review. Alterations in the pathways that regulate myoblasts proliferation/differentiation lead to induction of apoptosis during myogenesis both in vivo and in vitro. In adult muscle myofibres apoptosis seems to start from segmental areas of myofibres often producing loss of a single myonucleus. The bcl2/bax system is active in muscle when apoptosis occurs. On the other hand conflicting results are reported on the role played by FasL/Fas system. These findings are confirmed by in vitro results on myotubes and on their susceptibility to apoptosis. Though apoptosis has been shown to occur in the skeletal muscle, the role played in diseases and the pattern followed in myogenic cells are far from being clear.

Adult↗