PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Muscle Fibers, Skeletal”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 19 recordsLinked to original sources
PubMed1975

Regeneration of single skeletal muscle fibers in vitro.

A culture system utilizing single skeletal muscle fibers from adult rats was developed to study the origin and behavior of mononucleated myoblasts during muscle regeneration. The single fibers are removed manually from the leg and thigh muscles at 300-400 gm rats and maintained in vitro embedded in a fibrin clot overlain with culture medium. Regenerative events were monitored by continuous observations of the cultured fibers. During the first few hours in vitro the fibers undergo degenerative changes including the formation of myofibrillar contraction clots and pyknosis of myonuclei. The endomysial tube (basement lamina) remains intact along the entire length of the fiber and forms transparent chambers bridging the contraction clots. Single fibers are free of endomysial cells and display no cellular outgrowth in cultures, except at the cut ends. In contrast, a rich outgrowth of endomysial connective tissue cells is found with bundles consisting of two or more fibers. Isolated mononucleated cells, presumed to be muscle satellite cells, are present within the endomysial tube of single fibers at the onset of the culture period. There is no evidence that myonuclei contribute to the formation of mononucleated cells. The satellite cells enlarge and begin to proliferate during the second day in vitro to form clones of presumptive myoblasts within the endomysial tube. The early clones have a cell doubling time of about 22 hours and exhibit mitotic synchrony. After 5-7 days in vitro the satellite cell progeny begin to fuse to form multinucleated myotubes within the endomysial tube of the original fiber. The myotubes display spontaneous contractile activity and may extend throughout the length of the endomysial tube.

Animals↗
PubMed1978

Helicoids in the T system and striations of frog skeletal muscle fibers seen by high voltage electron microscopy.

Reconstruction from thick serial transverse slices of frog skeletal muscle fibers stained with peroxidase and examined by high-voltage electron microscopy has revealed that the T system networks at successive sarcomeres are connected together in a helicoidal fashion. From zero to eight helicoids have been found in each of a group of 21 fibers reconstructed in cross section. Helicoids can have either right- or left-handed screw senses, and both senses can be found in one fiber cross section. Because the T system maintains a relatively precise alignment with the myofibrillar striations, it follows that the striations must also have a helicoidal arrangement. This has been found before, but has not been widely accepted in recent times. The presence of helicoids in the bands and membrane networks is not thought per se to alter very much our thinking about excitation and contraction mechanisms in skeletal muscle fibers.

Animals↗
PubMed1977

Denervated skeletal muscle fibers develop discrete patches of high acetylcholine receptor density.

Denervated skeletal muscle fibers of mice develop discrete patches of high acetylcholine receptor density. The patches vary in size from less than 1 micrometer up to 30 micrometers, depending on the muscle and the period of denervation. Within the patches the acetylcholine receptor density is some 20 times greater than elsewhere along the muscle fiber and probably approaches that in the subsynaptic membrane.

Acetylcholine↗
PubMed1978

Ultrastructural study of the mitochondria in the skeletal muscle fibers in the diabetic Chinese hamster.

An ultrastructural study of skeletal muscle fiber biopsies from the tongue and soleus muscle of diabetic Chinese hamsters revealed the presence of lipid droplets within the muscle fibers. These droplets often were found in the cyptoplasm near mitochondira, sometimes inside or surrounded by one or more mitochondria. Glycogen granules were found in great quantities in the cytoplasm of the tongue and soleus muscle. Granules which appeared to be glycogen were also found within the mitochondria of the tongue muscle.

Animals↗
PubMed1978

An analysis of the electrical properties of a skeletal muscle fiber containing a helicoidal T system.

The linear electrical properties of skeletal muscle fibers have been analyzed using lumped circuit analogues of helicoidal T system. The geometry of a helicoid is assumed to produce two electrical effects, modeled separately. One model is motivated by the pitch or tilt of the T system, which forces the current flowing in the lumen of the tubules to have a longitudinal projection. The second model is motivated by the longitudinal continuity of a helicoid, which forms a structure similar to a cable within the fiber. The pitch or tilting of the T system plane modified the longitudinal resistance of the fiber, making it slightly frequency dependent; however, the magnitude of the change was less than 0.1%. The longitudinal connections between T system networks had a more complicated effect; the magnitude of the correction was again less than 0.1%. The conclusion from this analysis is that a helicoidal T system, whose pitch is constrained by the sarcomere spacing, will not affect electrical signals recorded intracellularly in intact fibers.

Electric Conductivity↗
PubMed1979

Distribution of myosin isoenzymes among skeletal muscle fiber types.

Using an immunocytochemical approach, we have demonstrated a preferential distribution of myosin isoenzymes with respect to the pattern of fiber types in skeletal muscles of the rat. In an earlier study, we had shown that fluorescein-labeled antibody against "white" myosin from the chicken pectoralis stained all the white, intermediate and about half the red fibers of the rat diaphragm, a fast-twitch muscle (Gauthier and Lowey, 1977). We have now extended this study to include antibodies prepared against the "head" (S1) and "rod" portions of myosin, as well as the alkali- and 5,5'dithiobis (2-nitrobenzoic acid) (DTNB)-light chains. Antibodies capable of distinguishing between alkali 1 and alkali 2 type myosin were also used to localize these isoenzymes in the same fast muscle. We observed, by both direct and indirect immunofluorescence, that the same fibers which had reacted previously with antibodies against white myosin reacted with antibodies to the proteolytic subfragments and to the low molecular-weight subunits of myosin. These results confirm our earlier conclusion that the myosins of the reactive fibers in rat skeletal muscle are sufficiently similar to share antigenic determinants. The homology, furthermore, is not confined to a limited region of the myosin molecule, but includes the head and rod portions and all classes of light chains. Despite the similarities, some differences exist in the protein compositions of these fibers: antibodies to S1 did not stain the reactive (fast) red fiber as strongly as they did the white and intermediate fibers. Non-uniform staining was also observed with antibodies specific for A2 myosin; the fast red fiber again showed weaker fluorescence than did the other reactive fibers. These results could indicate a variable distribution of myosin isoenzymes according to their alkali-light chain composition among fiber types. Alternatively, there may exist yet another myosin isoenzyme which is localized in the fast red fiber. Those red fibers which did not react with any of the antibodies to pectoralis myosin, did react strongly with an antibody against myosin isolated from the anterior latissimus dorsi (ALD), a slow red muscle of the chicken. The myosin in these fibers (slow red fibers) is, therefore, distinct from the other myosin isoenzymes. In the rat soleus, a slow-twitch muscle, the majority of the fibers reacted only with antibody against ALD myosin. A minority, however, reacted with antiboddies to pectoralis as well as ALD myosin, which indicates that both fast and slow myosin can coexist within the same fiber of a normal adult muscle. These immunocytochemical studies have emphasized that a wide range of isoenzymes may contribute to the characteristic physiological properties of individual fiber types in a mixed muscle.

Adenosine Triphosphatases↗
PubMed1977

Polymorphism of myosin among skeletal muscle fiber types.

An immunocytochemical approach was used to localize myosin with respect to individual fibers in rat skeletal muscle. Transverse cryostat sections of rat diaphragm, a fast-twitch muscle, were exposed to fluorescein-labeled immunoglobulin against purified chicken pectoralis myosin. Fluorescence microscopy revealed a differential response among fiber types, identified on the basis of mitochondrial content. All white and intermediate fiber but only about half of the red fiber reacted with his antimyosin. In addition, an alkali-stable ATPase had the same pattern of distribution among fibers, which is consistent with the existence of two categories of red fibers. The positive response of certain red fibers indicates either that their myosin has antigenic determinants in common with "white" myosin, or that the immunogen contained a "red" myosin. Myosin, extracted from a small region of the pectorlis which consists entirely of white fibers, was used to prepare an immunoadsorbent column to isolate antibodies specific for white myosin. This purified anti-white myosin reacted with the same fibers of the rat diaphragm that had reacted with the white, intermediate, and some red fibers are sufficiently homologous to share antigenic determinants. In a slow-twitch muscle, the soleus, only a minority of the fiber reacted with antipectoralis myosin. The majority failed to respond; hence, they are not equivalent to intermediate fibers of the diaphragm; despite their intermediate mitochondrial content. Immunocytochemical analysis of two different musles of the rat has demonstrated that more than one isoenzyme of myosin can exist in a single muscle, and that individual fiber types can be recognized by immunological differences in their myosin. We conclude that, in the rat diaphragm, there are at least two immunochemically distinct types of myosin and four types of muscle fibers: white, intermediate, and two red. We suggest that these fibers correspond to the four types of motor units described by Burke et al. (Burke, R. E., D. N. Levine, P. Tsairis, and F. E. Zajac, III 1973. J. Physiol. (Lond) 234:723-748.)in the cat gastrocnemius.;

Adenosine Triphosphatases↗
PubMed1979

The effects of pH on Ca2+-activated force in frog skeletal muscle fibers.

Ca2+-activated isometric force was recorded is skinned (sarcolemma mechanically removed) segments of frog skeletal muscle fibers immersed in bathing solution of different pH (5.0--10.5) and Ca2+ concentrations. Force in maximally activated fibers was near zero at pH 5.5, increased as pH increased to 7.5, remained relatively constant until pH 9.0 and then rapidly declined to zero by pH 10.5. The Ca2+ concentration at which 50% of maximum force was developed decreased 25-fold as pH increased from 5.5--7.5. The data also indicate that, while the fibers remains viable with acidosis, they deteriorate rapidly with alkalosis. These observations may be relevant clinically, since they parallel known effects of acidosis on cardiac contractility. The possible sites of action of H+ on the Ca2+-activated force generating mechanisms are discussed.

Animals↗
PubMed1979

Histochemical methods for dissociated muscle fibers.

Skeletal or cardiac muscle fibers can be separated by brief (3--5 second) dissociation of formalin-fixed pieces with a Willems Polytron (Brinkmann Instrument Co.). Such separated fibers are useful for demonstration of abnormal accumulations of lipids, carbohydrates, proteins and minerals in metabolic diseases. Staining techniques for demonstration of various stored materials include: 1) toluidine blue at pH 2.8 for acid mucopolysaccharide in skeletal muscle fibers in Pompe's glycogenesis 2, 2) one-step trichrome stain for nemaline myopathy and for abnormal mitochondria in X-linked infantile cardiomyopathy, 3) periodic acid-methenamine silver stain for glycolipid-containing lysosomes in I-cell disease (mucolipidosis 2), 4) Sudan black B stain for lipid in skeletal muscle fibers in Reye's syndrome, infantile lactic acidosis, Leigh's infantile subacute necrotizing encephalopathy and Jansky-Bielschowsky late infantile ceroid lipofuscinosis, 5) iron stain for iron in cardiac and skeletal muscle fibers in thalassemia with advanced hemosiderosis, and 6) autofluorescence for "ceroid" in skeletal muscle fibers in Jansky-Bielschowsky disease.

Carbohydrates↗
PubMed1977

Light diffraction studies of sarcomere dynamics in single skeletal muscle fibers.

A position-sensitive optical diffractometer has been used to examine the diffraction spectra produced by single skeletal muscle fibers during twitch and tetanic contraction. First-order diffraction lines were computer-analyzed for mean sarcomere length, line intensity, and percent dispersion in sarcomere length. Line intensity was observed to decrease rapidly by about 60 percent during a twitch, with an exponential recovery to resting intensity persisting well beyond cessation of sarcomere shortening; recovery was particularly prolonged at zero myofilament overlap. A number of single fibers at initial lengths from 2.5 to 3.5 MICRON EXHIBITED a splitting of the first-order line into two or more components during relaxation, with components merging back into a single peak by 200 ms after stimulation. This splitting reflects the asynchronous nature of myofibrillar relaxation within a single fiber. During tetanus, the dispersion decreased by more than 10 percent from onset to plateau, implying a gradual stabilization of sarcomeres.

Animals↗
PubMed1979

Catalase in skeletal muscle fibers.

Catalase has been localized immunocytochemically with anti-bovine catalase in long thin filament structures in aerobic type I fibers in the skeletal muscles of normal and genetically dystrophic hamsters. The filaments range in length from 1 to 60 micron, are orientated regularly along the long axis of the fibers, and also seem to surround and project from muscle nuclei. The enzyme thus appears to be more prominent in the sarcoplasmic reticulum than in peroxisomes, and in this situation is suitably placed for destroying toxic hydrogen peroxide which may be continously generated in aerobic fibers.

Animals↗
PubMed1977

Compensatory hypertrophy of skeletal muscle fibers in streptozotocin-diabetic rats.

Previous studies have demonstrated an apparent differential response of the fiber types in mixed skeletal muscles of rats to streptozotocin diabetes. The purpose of the present study was to examine the ability of the different fiber types to hypertrophy in muscles from diabetic rats, which should further clarify the apparent differential trophic influence of insulin on the fibers. One group of rats was injected with streptozotocin to induce diabetes. The gastrocnemius muscle was then removed from one hindlimb of rats of both the diabetic and a second, normal group, resulting in compensatory growth of ipsilateral plantaris muscle. Rats were sacrificed 60 days following the surgery. Experimental muscles in normal and diabetic rats enlarged 79% and 61% over control muscles, respectively. In normal hypertrophied muscles there was an 8% increase in relative cross-sectional area composed of slow-twitch fibers, whereas in diabetic rats the slow-twitch component increased 17%. The results indicate that slow-twitch fibers in diabetic rats were capable of responding to the chronic power overloaded condition, but that the fast-twitch fibers had a reduced capacity to undergo compensatory growth. These findings support our previous observations suggesting that insulin may exert a differential trophic effect upon the muscle fiber types.

Animals↗
PubMed1978

Fluorescent localization of membrane sites in glycerinated chicken skeletal muscle fibers and the relationship of these sites to the protein composition of the Z disc.

Didansyl derivatives of amino acids and N-phenyl-1-naphthylamine were used to localize membrane hydrophobic sites in glycerol-extracted chicken skeletal muscle fibers. Epifluorescence microscopy revealed that such sites coincide with the distribution of mitochondria, the transverse tubular (T) system and the sarcoplasmic reticulum (SR). They are specifically associated with myofibril Z lines and occasionally extend from one Z plane to the next longitudinally along the muscle fiber. The hydrophobic probes interact noncovalently with the Z lines, and their induced fluorescence can be eliminated by exposure of the myofibrils to ionic detergents, nonionic detergents, or phospholipase C, before or after addition of the hydrophobic label. Extraction of glycerinated fibers with 0.6 M KI removes the majority of sarcomeric actin and myosin and leaves a scaffold of longitudinally interconnected Z planes. Membrane fluorescence remains tightly associated with these Z planes and with the remnant mitochondria. Shearing of such scaffolds results in the cleavage of the longitudinal connections and the production of large sheets of interconnected, close-packed Z discs in a honeycomb-like array. Comparison of the localization of two Z disc proteins, desmin and alpha-actinin, with that of the membrane material reveals that alpha-actinin is localized in the interior of each myofibril Z disc whereas both desmin and the membrane material surround each disc. Thus, glycerination and KI extraction of muscle fibers leaves remnants of T system and SR membranes tightly associated with the Z disc honeycomb lattice. Because the Z discs are connected at their peripheries through the T system appear to the plasma membrane, desmin and this membrane structure appear to be connected throughout the whole Z plane up to and including the plasma membrane. The congruent localization of desmin and the T system strongly suggests that this molecule mediates the adhesion of this membrane system around each Z disc.

Actinin↗
PubMed1977

Skeletal muscle fiber splitting induced by weight-lifting exercise in cats.

Adult skeletal muscle hypertrophy induced by exercise has been thought to be exclusively related to an increase in cross-section area of individual muscle fibers and not to an increase in the number of muscle fibers. Recent experiments using surgical intervention to cause muscle overload have induced an increase in fiber numbers; however, the muscle also exhibited pathological alterations. The purpose of this study was to determine if an exercise regimen also induced hyperplasia. Cats were trained to lift weights with their right forelimb to receive a food reward. After 19-46 weeks of training, the flexor carpi radialis muscle (FCR) was removed and prepared for histochemical examination. The total number of muscle fibers of the right exercised FCR increased significantly (19.3%) when compared with that of the unexercised left FCR (p less than 0.05). This increase was found to be due to muscle fiber splitting.

Adenosine Triphosphatases↗
PubMed1975

Histochemical properties of skeletal muscle fibers in streptozotocin-diabetic rats.

The response of rat gastrocnemius muscle fibers to chronic streptozotocindiabetes was studied. Transverse sections of this muscle from normal and diabetic rats were histochemically assayed for reduced diphosphopyridine nucleotide-diaphorase, myofibrillar adenosine triphosphatase, mitochondrial alpha-glycerophosphate dehydrogenase, beta-hydroxybutyrate dehydrogenase, and alkaline phosphatase activities. Cross-sectional areas of the fiber types were measured, and fiber capillarization and populations estimated. Chemically-induced diabetes appeared to have little effect on the metabolic or morphological properties of slow-twitch fibers. However, a general dedifferentiation occurred in the 2 fast-twitch fiber populations. There was a loss of oxidative potential in the fast-twitch-oxidative-glycolytic fibers, and a significant decrease in size in the fast-twitch-glycolytic fibers. No change in the proportions of slow- and fast-twitch fibers in the muscles of diabetic rats occurred. It is concluded that hypoinsulinism has differential effects on the 3 fiber types in heterogeneous rat skeletal muscle, and that slow-twitch fibers are least affected by the diabetic condition.

Adenosine Triphosphatases↗
PubMed1976

Ultrastructural alterations in skeletal muscle fibers of streptozotocin-diabetic rats.

The ultrastructure of fast-twitch-oxidative-glycolytic (FOG), fast-twitch-glycolytic (FG) and slow-twitch-oxidative (SO) fibers in plantaris and soleus muscles of normal and streptozotocin-diabetic rats was studied. In the diabetic animals, the mitochondria of FOG and SO fibers showed a loss of cristae and an increase in electron-dense granules. There was also an increased number of lipid droplets in close proximity to the mitochondria and the nuclei, and a separation of individual muscle nuclei to form satellite cells. Higher incidences of surface projections and sarcoplasmic splittings at the nuclear region were noticed in SO fibers. The FG fibers showed some disorientation of the T-tubular system. It is concluded that streptozotocin-diabetes has differential effects on the fine structure of the three fiber types of rat skeletal muscle.

Animals↗
PubMed1977

Simultaneous determination of skeletal muscle fiber, types I, IIA, and IIB by histochemistry.

We describe a simplified technique for the histochemical determination of three fiber types from a single section of skeletal muscle. Preincubation in a solution of formaldehyde, glycine, and calcium followed by routine myofibrillar adenosine triphosphatase (ATPase) incubation clearly differentiates type I, type IIA, and IIB fibers in human, rat, rabbit, and porcine muscle. In addition, glycine-formaldehyde-calcium preincubation offers better preservation of cytoarchitecture and standardization of incubation time.

Adenosine Triphosphatases↗