Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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Heart and skeletal muscle from rats of different ages were incubated in vitro in an oxygen-free medium supplied with substrates in order to investigate the effect of anoxia on muscle fine structure, particulary on the mitochondria. In skeletal muscle fibers anoxia has been found to induce changes similar to those previously described in ischemic muscles in vivo namely giant mitochondria, apparently derived by mitochondrial fusion, and intermembrane inclusions with a paracrystalline structure. The plate-like inclusions are mostly located in the intracristal spaces and are closely associated to cristal membranes even in markedly swollen mitochondria. Identical inclusions have been observed in cardiac muscle cells following anoxic injury, whereas they are never found in non-muscle cells such as endothelia, fibroblasts and nerve fibers. Cardiac and skeletal muscle fibers from newborn rats maintained in an oxygen-free medium show mitochondrial swelling but no intermembrane inclusions. The different response of mitochondria from developing vs adult striated muscle to anoxia may be due to changes during postnatal development in the quality or quantity of the protein component(s) involved in paracrystal formation.
Virchows Arch B Cell Pathol Incl Mol Pathol 1979 Oct
PMID:Intermembrane inclusions induced by anoxia in heart and skeletal muscle mitochondria. 4 13

The primary structure of the major component of human skeletal muscle troponin C has been established. The troponin C was purified by ammonium sulphate and isoelectric fractionation, followed by two chromatographic steps on DEAE Sephadex. The sequence was determined from the different overlapping enzymic peptides and by dansyl-Edman degradation. The only difference between rabbit skeletal muscle troponin C and the major component of human skeletal troponin C was found at position 112: Ala (rabbit), Pro (human). The partial amino acid sequence of the first 86 residues of the minor component of human skeletal troponin C was found to resemble the troponin C from bovine cardiac muscle. The only difference between them, has tentatively been located at position 62: Glu (human), Asp (bovine). These similarities suggest that troponin C is, from the point of view of molecular, one of the most conservative proteins so far studied.
J Mol Evol 1976 Oct 27
PMID:Human skeletal muscle proteins. The primary structure of troponin C. 97 49

In order to analyze the transcriptional regulation of the muscle-specific subunit of the human phosphoglycerate mutase (PGAM-M) gene, chimeric genes composed of the upstream region of the PGAM-M gene and the bacterial chloramphenicol acetyltransferase (CAT) gene were constructed and transfected into C2C12 skeletal myocytes, primary cultured cardiac muscle cells, and C3H10T1/2 fibroblasts. The expression of chimeric reporter genes was restricted in skeletal and cardiac muscle cells. In C2C12 myotubes and primary cultured cardiac muscle cells, the segment between nucleotides -165 and +41 relative to the transcription initiation site was sufficient to confer maximal CAT activity. This region contains two E boxes and one MEF-2 motif. Deletion and substitution mutation analysis showed that a single MEF-2 motif but not the E boxes had a substantial effect on skeletal and cardiac muscle-specific enhancer activity and that the cardiac muscle-specific negative regulatory region was located between nucleotides -505 and -165. When the PGAM-M gene constructs were cotransfected with MyoD into C3H10T1/2, the profile of CAT activity was similar to that observed in C2C12 myotubes. Gel mobility shift analysis revealed that when the nuclear extracts from skeletal and cardiac muscle cells were used, the PGAM-M MEF-2 site generated the specific band that was inhibited by unlabeled PGAM-M MEF-2 and muscle creatine kinase MEF-2 oligomers but not by a mutant PGAM-M MEF-2 oligomer. These observations define the PGAM-M enhancer as the only cardiac- and skeletal-muscle-specific enhancer characterized thus far that is mainly activated through MEF-2.
Mol Cell Biol 1992 Oct
PMID:A single MEF-2 site is a major positive regulatory element required for transcription of the muscle-specific subunit of the human phosphoglycerate mutase gene in skeletal and cardiac muscle cells. 132 54

To assess the distribution of gap junctions in relation to the cardiac myocyte surface in paraffin sections of dog and rat ventricle, the sarcolemma was labeled with wheat germ agglutinin (WGA1) and gap junctions were labeled with antibodies to cardiac muscle gap junction protein connexin43. WGA labeled all of the myocyte sarcolemma, including that in intercalated discs and transverse tubules. Sarcolemmal WGA labeling was often interrupted at the sites of gap junctions, which were found both at the extreme ends of myocytes and along the length of adjacent myocytes. Small gap junctions predominated at plicate transverse portions of the intercalated disc; larger and sometimes ribbon-like gap junctions predominated at longitudinal portions. The longitudinal portions of the intercalated disc often extended over multiple sarcomere lengths, with ribbon-like gap junctions and linear arrays of smaller gap junctions arranged in parallel overlying successive sarcomeres. Morphometric study showed that ribbon-like gap junctions were relatively infrequent in both dog and rat left ventricular epimyocardium, and that animals with larger myocytes tended to have smaller gap junctions. In dog left ventricular epimyocardium, neither myocytes nor their larger gap junctions were randomly oriented with respect to perimysial separations; myocytes were usually somewhat flattened with their maximal diameters parallel to the separations, whereas large gap junctions were least often oriented parallel or perpendicular to the separations. Overall, the data indicate that myocyte geometry influences gap junction size and distribution; the double-label technique is ideally suited for the further exploration of that influence.
J Mol Cell Cardiol 1992 Dec
PMID:Distribution of gap junctions in dog and rat ventricle studied with a double-label technique. 133 12

Anabolic steroids are synthetic molecules developed in the hope of obtaining a complete separation of the androgenic and myotrophic (anabolic) actions of testosterone. Such a goal has never been fully achieved. However, some synthetic steroids present a partial dissociation between these two activities. Since a single hormonal receptor apparently mediates the androgenic as well as the anabolic actions of testosterone, differences in patterns of androgen metabolization in the muscles and the sex accessory organs have been proposed as a possible cause of this phenomenon. Undoubtedly, androgens are able to exert a trophic effect on skeletal and cardiac muscle fibres in subjects with low circulating levels of testosterone such as prepubertal or hypogonadal males and females; however, the widespread use of anabolic steroids in male athletes to increase their physical performances poses the question of whether these compounds are active in the presence of normal circulating levels of testosterone. Most experimental animal studies indicate that anabolic steroids are ineffective in this situation. Since the results of the experiments performed in humans are largely contradictory, it is still not clear whether anabolic steroids are able to improve athletic performances. These and other relevant issues are reviewed.
J Steroid Biochem Mol Biol 1992 Oct
PMID:Anabolic steroids: a review of their effects on the muscles, of their possible mechanisms of action and of their use in athletics. 139 Feb 96

The ultrastructural quantitative composition of normal myocardial cells has been studied in 10 different species: man, dog, pig, cat, rabbit, ferret, guinea-pig, rat, mouse, and bat. Volume densities of mitochondria, myofibrils, and cytoplasm were determined using morphometry. It was found that the content of mitochondria differs in various species ranging between 22.0-37.0%. It is a very specific and constant value for any particular species, the smallest having the highest content. A close correlation exists between the mitochondrial volume density, heart rate and the rate of basal oxygen consumption in any group of animals. The myofibrillar volume density shows no species variability. It was about 60.0% in all species. It is concluded that the mitochondrial volume density is a good indicator of the oxidative capacity of cardiac muscle and that the species specific normal ultrastructural myocyte composition should be a useful baseline in pathophysiological studies of the heart in various animals.
J Mol Cell Cardiol 1992 Jul
PMID:Ultrastructural quantitation of mitochondria and myofilaments in cardiac muscle from 10 different animal species including man. 140 7

The thyroid status markedly influences the contractile function of muscle, and changes in the activity of the Ca2+ ATPase of the sarcoplasmic reticulum (SR) contribute to these alterations. Two separate genes encode the major isoforms of SR Ca2+ ATPase. In fast skeletal muscle, sarcoplasmic endoplasmic reticulum Ca2+ ATPase type 1 (SERCa1) presents the major isoform, whereas in slow skeletal muscle SERCa type 2 (SERCa2) predominates. Cardiac muscle contains only SERCa2. To examine the mechanisms responsible for changes in contractile function, we quantitated SERCa1 and SERCa2 mRNA levels in fast extensor digitorum longus muscle (EDL), slow soleus muscle, and cardiac muscle in rats of different thyroid status. Hypothyroidism led in soleus to a marked decrease in SERCa1 mRNA and SERCa2 mRNA levels, in cardiac muscle SERCa2 mRNA decreased markedly, as previously shown by us, and in EDL SERCa1 mRNA decreased. These findings are compatible with a hypothyroidism induced decrease in SR Ca2+ ATPase activity and a delay in muscle relaxation. In contrast, SERCa2 mRNA of EDL, representing only a small percent of total SERCa mRNA in this muscle, increased to 175% of control values. Muscle specific and SERCa gene specific changes also occur after acute triiodothyronine (T3) administration to hypothyroid rats. T3 does not induce a significant change in SERCa1 or SERCa2 mRNA levels in soleus, but in the heart SERCa2 mRNA increases about 3-fold. In EDL, T3 increases SERCa1 mRNA from a hypothyroid level of 59 +/- 6% to 138 +/- 4% of control values but SERCa2 mRNA is decreased to 75 +/- 5% of control levels.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1992 Sep
PMID:Thyroid hormone response of slow and fast sarcoplasmic reticulum Ca2+ ATPase mRNA in striated muscle. 144 89

Recent studies have identified a conserved 28-bp element (HF-1) within the rat cardiac MLC-2 gene which confers cardiac muscle-specific and inducible expression during myocardial cell hypertrophy. Utilizing a combination of independent experimental approaches, this study characterizes two cardiac nuclear factors which bind to HF-1, a ubiquitous factor (HF-1a), and an A + T-rich binding factor (HF-1b) which is preferentially expressed in differentiated cardiac and skeletal muscle cells. The HF-1a binding site is located in a core region of the 28-bp conserved element, immediately upstream from the A + T-rich HF-1b site, which is homologous to the MEF-2 site found in a number of muscle genes. By a number of separate criteria (gel mobility shift, competition, and mutagenesis studies), HF-1b and MEF-2 appear to be indistinguishable and thus are either identical or closely related muscle factors. Transient assays of luciferase reporter genes containing point mutations throughout the 28-bp HF-1 regulatory element document the importance of both the HF-1a and HF-1b sites in transient assays in ventricular muscle cells. In the native 250-bp MLC-2 promoter fragment, mutations in the single E box had little effect on cardiac muscle specificity, while point mutations in either the HF-1a or HF-1b binding site significantly reduced promoter activity, underscoring the importance of both the HF-1a and HF-1b sites in the transcriptional activation of this cardiac muscle gene. Thus, this study provides evidence that a novel, ubiquitous factor (HF-1a) and a muscle factor (HF-1b/MEF-2) can form a novel, E-box-independent pathway for muscle-specific expression in ventricular cardiac muscle cells.
Mol Cell Biol 1992 Apr
PMID:A ubiquitous factor (HF-1a) and a distinct muscle factor (HF-1b/MEF-2) form an E-box-independent pathway for cardiac muscle gene expression. 153 29

The transcription of the chicken cardiac myosin light chain-2 (MLC-2) promoter containing a 1.3 Kb 5'-flanking DNA segment is repressed upon co-transfection with an expression vector (pMMV) containing the proto-oncogene fos in embryonic chicken cardiac muscle cells in culture. Similar concentrations of co-transfectants containing other genes e.g. luciferase were ineffective. To identify the DNA element(s) in MLC-2 gene that responds to fos-mediated inhibition, 5'-sequential deletion mutants of MLC-2 promoter were tested in a transient transfection assay. A mutant, in which the 5' distal sequence was deleted upto -1200 bp upstream of the mRNA start site was sensitive to fos inhibition, but the mutant containing -1130 bp was not, suggesting that a fos responsive element (FRE) is located between -1130 to -1200 bp upstream of the transcription initiation site. The same FRE sequence was also responsive to fos-inhibition in chicken skeletal muscle cells as well. Since over-expression of fos is implicated in repression of myogenic process, the selective inhibition of MLC-2 promoter activity by fos and identification of FRE sequence potentially important in understanding the relationship between myogenesis and the oncoprotein-mediated signal pathway(s).
Cell Mol Biol 1992 Feb
PMID:fos-mediated repression of cardiac myosin light chain-2 gene transcription. 155 44

A mathematical model is developed to investigate the kinetics of electrical, mechanical and molecular processes in mammalian cardiac muscle. Isometric contractions at different muscle length and frequency of stimulation in response to a rhythmically applied clamp pulse or artificial action potential are simulated. Numerical results show that concentration of Ca2+ ions, bound to Ca(2+)-specific sites on protein troponin C, could be a regulatory factor in actin-myosin interactions and subsequent production of force in Huxley's mathematical approach for the sliding mechanism. The behavior of the model is compared to that of living cardiac muscle.
J Mol Cell Cardiol 1992 Jan
PMID:Theoretical model and computer simulation of excitation-contraction coupling of mammalian cardiac muscle. 156 35


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