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At least 19 recordsLinked to original sources

PubMed1975

Isometric training of young rats--effects upon hind limb muscles. Histochemical, morphometric, and electron microscopic studies.

The soleus, rectus femoris, and gastrocnemius muscles of young rats trained isometrically for 4 weeks were studied by light and electron microscopy.--The percentage of fast-twitch oxidative muscle fibers decreased at the cost of the fast-twitch glycolytic fibers in the rectus femoris muscle. The percentages of the slow-twitch oxidative fibers did not change significantly in any of the muscles studied. The changes in the areas of the muscle fibers were specific for the muscle and the fiber type and indicate geometrical rearrangements of the fibers in the trained muscles. The Z and M lines were broader in the soleus (containing about 85% slow-twitch oxidative fibers) than in the rectus femoris muscle (containing about 90% fast-twitch glycolytic fibers), while the sarcomere length and the pseudo-H zone were similar. The length of the myosin filaments appeared to be slightly shorter in the fast rectus femoris than in the slow soleus muscle.--The hypothesis on the temporal progress of muscle adaptation to training (Müller, 1974) was substantiated. Correlations between biochemical (Exner et al., 1973a) and histochemical parameters measuring the oxidative capacity were preserved during adaptation to training. The comparison of the histochemical results with the physiological data on similar animals (Exner et al., 1973a) suggests a complex relationship between the contraction time and the percentage of fast-twitch muscle fibers.

Adaptation, Physiological↗

PubMed1979

Loss of thick filaments from fast-twitch glucolytic muscle fibers of the pigeon pectoralis after chronic administration of dantrolene sodium.

Adult pigeons received dantrolene sodium, a skeletal muscle relaxant which blocks the release of calcium during excitation-contraction coupling, for 12 to 16 weeks. The pectoralis muscles of these birds were analyzed for changes occurring in the various fiber types of the muscle. Both histochemistry (ATPase and SDH activity) and electron microscopy (mitochondrial and lipid volume percentages) differentiated two fiber types. The two fiber-types consisted of fast-twitch glycolytic fibers (FG) and fast-twitch oxidative-glycolytic (FOG) fibers. After dantrolene treatment some FG fibers showed little or no ATPase activity. Dantrolene treatment also produced a disappearance of thick filaments in some FG fibers. We infer that the fibers without thick filaments are the ones lacking ATPase activity. The FOG fibers were nearly normal. Since drug-fed birds lose weight, a few birds were starved to determine whether the filament loss was related solely to the bird's loss in weight. No fibers in starved birds showed reduced ATPase activity or loss of thick filaments. In fibers that showed thick filament disappearance, the I-bands remained organized and intact, suggesting that the I-band maintains its integrity without interaction with the thick filaments. Changes in activity patterns may cause loss of thick filaments by inhibiting either their synthesis or assembly.

Adenosine Triphosphatases↗

PubMed2025

Lysine-rich rice enhanced muscle growth and development in young rats.

Rice is the staple food for half of the world's population but is low in lysine content. We previously developed transgenic lysine-rich rice with enhanced free lysine content in rice seeds and demonstrated that it could improve skeletal growth and development in rats. However, the effects of lysine-rich rice on muscle remain to be studied. We hypothesized that lysine-rich rice was able to improve muscle growth in weaning rats via its anabolic effects on muscle metabolism. Male weaning Sprague-Dawley rats received lysine-rich rice (HFL) diet, wild-type rice (WT) diet, or wild-type rice with various doses of lysine supplementation (WT + Lys) diet (+ 0%, + 10%, + 20%, and + 40% lysine) for 70 days. Muscle strength and quality were analyzed by biomechanical test and muscle fiber typing of the extensor digitorum longus (EDL) muscles. Molecular mechanisms of lysine on muscle growth were also explored by rat serum biochemistry and cell culture systems. Results indicated that the HFL diet improved rats' muscle growth, strength, and physiological cross-sectional area (CSA) over the WT diet group. The CSAs of fast-twitch muscle fibers (Type IIb and IIx) were also increased. In addition, the HFL increased serum insulin-like growth factor 1 (IGF-1) and decreased serum myostatin (MSTN) concentrations. The cell culture model showed that lysine deficiency reduced IGF-1 expression and inhibited myoblast differentiation associated with muscle growth. Our findings showed that lysine-rich rice improved muscle growth and development in weaning rats. Higher dietary lysine possibly inhibited MSTN and activated of IGF-1 signaling pathway for muscle growth and development.

Animals↗

PubMed2025

The frequency of the ACTN3 polymorphism in Brazil: a systematic review and meta-analysis.

BACKGROUND: The ACTN3 gene encodes the protein alpha-actinin-3, which is crucial for fast-twitch muscle fibers, contributing to rapid and forceful contractions. The distribution of these genotypes and their impact on sports performance in Brazilian populations are not well-documented. This study aimed to determine the allelic and genotypic frequency of the ACTN3 R/X polymorphism in Brazil and its association with sports performance. METHODS: A systematic review was conducted, including studies sourced from PubMed, Scielo, LILACS, LIPECS, Coleciona SUS, CUMED, BINACIS, IBECS, and MEDLINE databases, resulting in 42 studies included. The quality of these studies was assessed using the Strengthening the Reporting of Genetic Association (STREGA) guidelines. RESULTS: Among all the 8,746 participants, 35.2% had the RR genotype, 46.2% had the RX genotype, and 18.6% had the XX genotype. Regarding allelic frequency, 58.3% were R allele carriers, while 41.7% were X allele carriers. Meta-analysis showed that there was no consistent association between the ACTN3 genotypes and sports performance, although some data suggested potential benefits in athletic performance. CONCLUSION: This study revealed that the RX genotype of the ACTN3 R577X polymorphism is the most prevalent in Brazil, followed by the RR and XX genotypes. While the R allele was more frequent, the meta-analysis did not confirm a consistent association between ACTN3 genotypes and sports performance, suggesting that other genetic and environmental factors contribute to athletic success.

Actinin↗

PubMed1977

Time course adaptations in cardiac and skeletal muscle to different running programs.

The effects of chronic "steady-state" and high-speed interval running were investigated on time-course changes in certain biochemical properties of cardiac and skeletal muscle fiber types of rats. Nine weeks of the interval program resulted in significant increased (15%) in both cardiac enlargement and ATPase activity of myofibrils; whereas increases in these parameters were only transient and not significant at the termination of the program involving steady-state running. Neither program induced appreciable alterations in citrate synthase and phosphofructokinase activity in cardiac muscle. In fast-twitch white fibers, "steady-state" training induced only a transient 45% increase in citrate synthase activity in contrast to a progressive twofold change with interval training. Both programs resulted in similar increases (45-50%) in citrate synthase activity in fast-twitch and slow-twitch red fibers. However, the patterns of increase for both fiber types differed between the two programs. These findings suggest that training programs incorporating elements of both "steady-state" incline and high-speed interval running can potentially induce respiratory enzyme adaptations in the greatest spectrum of rodent skeletal muscle fibers in addition to inducing adaptations to enhance contractile potential in cardiac muscle.

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↗

PubMed1977

Oscillatory changes in muscle lipoprotein lipase activity of fed and starved rats.

Lipoprotein lipase activity was measured at short time intervals in cardiac and skeletal muscles of normal and streptozotocin-treated diabetic rats fed ad libitum or deprived of food. In normal animals fed ad libitum, lipoprotein lipase activities of heart, diaphragm, soleus, and fast-twitch red fibers of the quadriceps muscle showed rhythmic oscillations that appeared to coincide with the nocturnal feeding habits of the animals. During the day (7 A.M. to 7 P.M.), when food consumption by the rats was greatly reduced, lipoprotein lipase activity in all muscles increased, followed by a decline to basal levels during the night. Similar oscillatory changes in lipoprotein lipase activity were observed in the muscles of diabetic rats fed ad libitum. In normal rats deprived of food, however, the oscillatory changes in muscle lipoprotein lipase activity were not abolished and persisted for at least 48 h. In diabetic rats starved during a 48-h period, the oscillatory changes in muscle lipoprotein lipase activity were markedly altered. In all animals, muscle lipoprotein lipase activities were not correlated to plasma glucagon levels.

Animals↗

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↗

PubMed1979

Localization of sarcoplasmic reticulum proteins in rat skeletal muscle by immunofluorescence.

Ca++-Mg++-dependent ATPase and calsequestrin, the major intrinsic and extrinsic proteins, respectively, of the sarcoplasmic reticulum, were localized in cryostat sections of adult rat skeletal muscle by immunofluorescent staining and phase-contrast microscopy. Relatively high concentrations of both the ATPase and calsequestrin were found in fast-twitch myofibers while a very low concentration of the ATPase and a moderate concentration of calsequestrin were found in slow-twitch myofibers. These findings are consistent with previous biochemical studies of the isolated sarcoplasmic reticulum of slow-twitch and fast-twitch mammalian muscles. The distribution of the ATPase in muscle fibers is distinctly different from that of calsequestrin. While calsequestrin is present only near the interface between the I- and A-band regions of the sarcomere, the ATPase is found throughout the I-band region as well as in the center of the A-band region. In comparing these results with in situ ultrastructural studies of the distribution of sarcoplasmic reticulum in fast-twitch muscle, it appears that the ATPase is rather uniformly distributed throughout the sarcoplasmic reticulum while calsequestrin is almost exclusively confined to those regions of the membrane system which correspond to terminal cisternae. Fluorescent staining with these antisera was not observed in vascular smooth muscle cells present in the cryostat sections of the mammalian skeletal muscle used in this study.

Animals↗

PubMed1976

Histological and histochemical comparisons of muscle spindles in three hind limb muscles of the guinea pig.

Guinea pig soleus, medial gastrocnemius and vastus lateralis muscles were compared for spindle density and distribution, number of intrafusal fibers per spindle and histochemical appearance of the axial bundle. A total of 326 spindles was used in the comparisons. Spindle density was over four times greater in the soleus than in either the medial gastrocnemius or vastus lateralis. In the soleus the spindles were distributed at random, but in the other two muscles no spindles were found in those fascicles in which fast-twitch glycolytic extrafusal fibers predominated. The average number of intrafusal fibers per spindle varied by less than 5% between the three kinds of muscles. About 80% of all spindles located had four intrafusal fibers, two of the nuclear bag type and two of the nuclear chain type. The histochemical appearance of the axial bundle was the same in each kind of muscle. Based on intensities of the myofibrillar adenosine triphosphatase reaction product at polar regions nuclear bag fibers were separable into two histochemical groups; nuclear chain fibers were of only one histochemical type.

Adenosine Triphosphatases↗

PubMed1977

Effect of functional overload on enzyme levels in different types of skeletal muscle.

The effects of bilateral functional overload on enzyme changes in fast-twitch plantaris muscles were studied on different groups of rats: 1) normal-control; 2) normal-exercise; 3) overload-control; and 4) overload-exercise. Overload was accomplished by surgical elimination of synergists. Exercising groups walked up a 65% grade, 3 m/min, 2 h/day. Peak muscle enlargement of the overload groups was reached after 5 wk. Citrate synthase, phosphofructokinase, and myofibril ATPase activities were consistantly depressed by approximately 30%, 40%, and 18%, respectively, in overload as compared to normal groups. Daily exercise prevented the decrease in only citrate synthase activity. Unilateral overload of medial gastrocnemius muscle indicated that both fast-twitch oxidative-glycogenolytic and fast-twitch glycogenolytic fiber types undergo enzyme changes in response to the functional stress. However, changes in the former were in closer agreement with the net changes seen in the plantaris than the latter. Soleus muscle responded to overload primarily with marked reductions in respiratory capacity. These findings suggest that certain enzyme systems are altered with functional overload in different fiber types. However, the alterations in certain enzyme systems may, in part, be independent of the process of hypertrophy.

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↗

PubMed1976

Human muscle fiber types in power lifters, distance runners and untrained subjects.

Muscle biopsies were taken from the vastus lateralis of 12 males: 5 control subjects, 4 power lifters and 3 distance runners. Three fiber "types" were distinguished by comparing serial sections for alkaline myofibrillar adenosine triphosphatase (ATPase) and succinic dehydrogenase (SDH) activities: 1. high ATPase and low SDH; fast-twitch-glycolytic (FG). 2. High ATPase and high SDH; fast-twitch-oxidative-glycolytic (FOG). 3. Low ATPase and high SDH; slow-twitch-oxidative (SO). In some cases the distinction between the FOG and FG classess was not clear and a group termed "transitional" was employed. A variation in percentage of fiber types and fiber area was found among individuals. The percentage of SO fibers varied from 19.6-60.1% within all 3 groups, with a mean of 40.5%. In the control group approximately 75% of the fibers were oxidative (FOG + SO). The major characteristics of the lifters were a decrease in the percentage of FOG fibers and a hypertrophy of FOG and FG fibers. The distance runners had a high percentage of oxidative fibers with few FG fibers. It is suggested that the fast-twitch fibers are mainly involved in the adaptation of muscle to exercise since the percentage of SO fibers varies greatly among individuals within and between the 3 groups studied.

Adenosine Triphosphatases↗

PubMed1978

Free autografting of entire limb muscles in the cat: histochemistry and biochemistry.

Fifty extensor digitorium longus muscles of 25 cats were autografted, 33 with and 17 without prior denervation. After 50 days, no significant differences were observed between predenervated and nonpredenervated autografts. Autografted muscles weighed 48% of the weight of control muscles. Few original muscle fibers survived and within 2 wk autografts contained regenerating muscle fibers. The mean cross-sectional area of muscle fibers in the autografts reached 125% of the value for control nontransplanted muscles. The mean percentage of fibers classified high oxidative in autografted muscles was 67% of values for control muscles. SDH activity of autografted muscle homogenates reached 55% of control values. Up to 60 days after surgery autografts had only fast-twitch fibers. At 170 days autografts remained 95% fast twitch in composition. Revascularization began within 4 days, but the capillary to fiber ratio of long term autografts reached only 60% of control values. Although fiber hypertrophy suggests that cats use autografted muscles, lower than control succinate dehydrogenase activity may result from altered recruitment.

Action Potentials↗

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↗

PubMed1976

Enzymatic changes in hypertrophied fast-twitch skeletal muscle.

Fast-twitch plantaris muscles of female rats were subjected to unilateral compensatory overload, induced by partial excision of synergistic muscles. One group of rats remained sedentary whereas another was subjected to a supplemental program of treadmill exercise consisting of walking 3 m/min, 65% grade, 2 h/day, 5 days/week. Groups of rats were sacrificed after 1, 2, 4, and 8 weeks and their muscles were weighed and analyzed for protein, citrate synthase, phosphofructokinase (PFK) and myofibril ATPase. Absolute and relative (muscle weight/body weight) muscle weights were much greater in both overloaded groups as compared to contralateral controls. However, treadmill exercise also increased the absolute and relative muscle mass of control plantaris muscles in the exercising group as compared tonormal sedentary contralateral controls. Citrate synthase activity was decreased in overloaded, sedentary muscles as compared to contralateral controls, but after 8 weeks of exercise, it returned to normal levels. PFK was decreased in both sedentary and exercised overloaded muscles throughout the 8 week period. Myofibril ATPase showed a tendency to be reduced in sedentary, overloaded muscles, and was significantly reduced in overloaded, exercising muscles. These results collectively suggest that certain fibers of overloaded fast-patterns take on similar in certain aspects to that normally seen in differentiated slow-twitch muscle fibers.

Adenosine Triphosphatases↗

PubMed1977

In vitro studies of skeletal muscle membranes. Effects of denervation on the macromolecular components of cation transport in red and white skeletal muscle.

The effects of denervation on the macromolecular components of active monovalent cation transport in skeletal muscle have been studied using purified sarcolemma membranes. A comparison of membrane activities of fast-twitch, slow-twitch, and mixed-fiber muscles was made to determine what role, if any, the motor nerve has in regulating this important aspect of muscle metabolism. A dramatic increase in the basal sarcolemmal Mg++ ATPase activity (three- to fourfold) was found for both major muscle types. An increase in the ouabain-inhibitable (Na+ + K+)-stimulated enzyme was also found, but the effect was substantially less (1.5- to twofold). [3H]-ouabain binding, as an index of glycoside receptor sites, also increased (two- to threefold) midway in the course of denervation. On the other hand, the phosphorylated intermediate activity, a functional component of the transport system, clearly decreased over the same time course and remained below control values for the remainder of the course. This resulted in a two- to threefold increase in the turnover number, suggesting that active transport of cations should increase dramatically with denervation. The membrane protein patterns on SDS gels were less obvious than the changes observed in the functional components. The major effects appeared after only one week and seemed to be restricted to high molecular weight membrane proteins, especially in the 100,000 to 250,000 daltons range. This effect was more prominent in slow-twitch membranes with an apparent semiquantitative decrease in stain at 240,000 daltons. In gels of membranes from fast-twitch muscles a decreased stain in the range of 100,000 to 110,000 daltons occurred, and this became more obvious with longer periods of denervation. The results suggest that considerable influence on the macromolecular components of active cation transport in skeletal muscle is exerted by the motor nerve. No appreciable difference was found in this effect when the two major types of skeletal muscle, fast-twitch and slow-twitch, were compared, suggesting that motor nerve regulation of this membrane property is qualitatively the same.

Adenosine Triphosphatases↗

PubMedDate not supplied

Morphology and physiology of skeletal muscle in aging rodents.

Aging in the rodent is accompanied by a progressive loss of skeletal muscle fibers. The muscle twitch also becomes slower, probably as a result of fiber-type conversion from "fast-twitch" to "slow-twitch." The loss of muscle fibers precedes signs of obvious weakness and appears to involve the loss of entire functioning motor units. In the mouse, this loss of motor units correlated with a loss of axons from the innervating nerve trunks.

Adenosine Triphosphatases↗