Biochemical Properties Of Skeletal Muscle Research Articles

Properties of skeletal muscle in the teleost Sternopygus macrurus are unaffected by short-term electrical inactivity.

Skeletal muscle is distinguished from other tissues on the basis of its shape, biochemistry, and physiological function. Based on mammalian studies, fiber size, fiber types, and gene expression profiles are regulated, in part, by the electrical activity exerted by the nervous system. To address whether similar adaptations to changes in electrical activity in skeletal muscle occur in teleosts, we studied these phenotypic properties of ventral muscle in the electric fish Sternopygus macrurus following 2 and 5 days of electrical inactivation by spinal transection. Our data show that morphological and biochemical properties of skeletal muscle remained largely unchanged after these treatments. Specifically, the distribution of type I and type II muscle fibers and the cross-sectional areas of these fiber types observed in control fish remained unaltered after each spinal transection survival period. This response to electrical inactivation was generally reflected at the transcript level in real-time PCR and RNA-seq data by showing little effect on the transcript levels of genes associated with muscle fiber type differentiation and plasticity, the sarcomere complex, and pathways implicated in the regulation of muscle fiber size. Data from this first study characterizing the acute influence of neural activity on muscle mass and sarcomere gene expression in a teleost are discussed in the context of comparative studies in mammalian model systems and vertebrate species from different lineages.

Impact of denervation-induced muscle atrophy on housekeeping gene expression in mice.

Immobilization induced by experimental denervation leads to rapid and progressive alterations in structural and biochemical properties of skeletal muscle. Real-time reverse transcription-polymerase chain reaction (RT-PCR) is a popular method of elucidating the molecular mechanisms involved in muscle atrophy. Identification of suitable reference genes that are not affected by experimental conditions is a critical step in accurate normalization of real-time RT-PCR. We investigated the impact of denervation-induced muscle atrophy for 2 weeks on the expression of common housekeeping genes. Denervation differentially affected the expression levels of these genes. RefFinder software identified TATA box binding protein (Tbp) as the most stable gene and showed that the stability of glyceraldehyde-3-phosphate dehydrogenase (Gapdh) and hypoxanthine guanine phosphoribosyl transferase (Hprt) genes was low, even though they are widely used for normalization. The appropriate reference gene for normalization of genes of interest in denervated muscle is Tbp.

Does adiponectin mimic exercise?

Does adiponectin mimic exercise?

Changes in muscle T 2 relaxation properties following spinal cord injury and locomotor training

Magnetic resonance (MR) is frequently used to study structural and biochemical properties of skeletal muscle. Changes in proton transverse relaxation (T2) properties have been used to study muscle cellular damage, as well as muscle activation during exercise protocols. In this study, we implemented MR imaging to characterize the T2 relaxation properties of rat hindlimb muscles following spinal cord injury (SCI) and locomotor training. After moderate midthoracic contusion SCI, Sprague-Dawley rats were assigned to either treadmill training, cycle training or an untrained group. T2 weighted images were obtained and mean muscle T2 times were calculated in the tibialis anterior, soleus, and gastrocnemius (GAS) muscles at pre-injury as well as at 1, 2, 4, 8, and 12 weeks post-injury. Following SCI, hindlimb muscles in untrained animals showed a significant increase in muscle T2, with the most dramatic shift (+5.46 ms) observed in soleus muscle at 1 week post-SCI. Subsequently, all muscle groups showed a spontaneous recovery in muscle T2 with normalized T2 values in the GAS and tibilias anterior muscles at 4 weeks and the soleus at 12 weeks post-SCI. Both training paradigms, treadmill and cycling training, accelerated the recovery of soleus muscle T2. As a result, soleus muscle T2 recovered back to pre-injury values within 3 weeks of training in both training groups. Finally, in vitro histological assessments of rat skeletal muscles demonstrated that there was no apparent muscle injury in any of the muscles studied at 1 week post-SCI.

Adaptations biochimiques et structurales du muscle à l'entraînement en force

Aims. – This paper was aimed to present the current knowledge concerning the structural and biochemical properties of skeletal muscle after strength training. The main mechanisms which account for adaptive responses will be specified. Current knowledge. – Skeletal muscle commonly increase their mass after heavy-resistance training. The increased muscle mass mainly results from myofiber hypertrophy rather than hyperplasia of muscle cells. The myosin heavy-chain (MHC) composition of skeletal muscles is affected by strength training; an increased percentage of MHC-IIa isoform, in parallel with a decrease in MHC-IIx (or MHC-IIb) isoform are commonly reported. Moreover, a decrease in oxidative capacity occurred in skeletal muscle, while the transcription rate of some genes encoding glycolytic enzymes, and responsive to oxygen-sensitive transcription factors, is enhanced with strength training. An increased capillary network occurred in skeletal muscle during strength training; the general increase in capillaries is aimed to maintain a correct oxygen supply in the hypertrophied fibres. The mechanisms of the training-induced angiogenesis remain poorly understood, but the role played by the oxygen stimulus needs to be examined in further studies. Future prospects. – In contrast to endurance training, the mechanisms by which skeletal muscle responds to strength remain largely unknown. Further studies are needed to examine the molecular mechanisms of MHC isoform transitions and angiogenesis.

Botulinum neurotoxin type A causes shifts in myosin heavy chain composition in muscle

Botulinum neurotoxin type A has gained widespread use for treatment of a host of neuromuscular conditions. However, the potential effect of this toxin has on the histological and biochemical properties of skeletal muscle remains largely unexplored. The purpose of this study was to characterize the myosin heavy chain (MHC) distribution of adult rat skeletal muscle treated with botulinum neurotoxin type. Varying doses of the toxin were injected into the triceps surae muscle group of one hind limb. Force production was assessed periodically to access the functional deficit incurred. After 10 weeks, animals were sacrificed, muscles removed, and MHC composition determined. Body weight, muscle weight and force of the injected leg were significantly reduced in all groups, while loss of muscle weight and force in the contralateral leg was variable. In the injected plantaris and gastrocnemius muscles, type I MHC increased ∼100%, while type IIa/x decreased ∼50%. In the contralateral gastrocnemius, types I and IIa/x MHC increased ∼100%, while type IIb decreased ∼45%. These data suggest that botulinum neurotoxin causes shifts in MHC composition in injected and contralateral muscles that are contrary to those seen with denervation and similar to those seen with aging.

Dystrophin and utrophin influence fiber type composition and post-synaptic membrane structure

The X-linked muscle wasting disease Duchenne muscular dystrophy is caused by the lack of dystrophin in muscle. Protein structure predictions, patient mutations, in vitro binding studies and transgenic and knockout mice suggest that dystrophin plays a mechanical role in skeletal muscle, linking the subsarcolemmal cytoskeleton with the extracellular matrix through its direct interaction with the dystrophin-associated protein complex (DAPC). Although a signaling role for dystrophin has been postulated, definitive data have been lacking. To identify potential non-mechanical roles of dystrophin, we tested the ability of various truncated dystrophin transgenes to prevent any of the skeletal muscle abnormalities associated with the double knockout mouse deficient for both dystrophin and the dystrophin-related protein utrophin. We show that restoration of the DAPC with Dp71 does not prevent the structural abnormalities of the post-synaptic membrane or the abnormal oxidative properties of utrophin/dystrophin-deficient muscle. In marked contrast, a dystrophin protein lacking the cysteine-rich domain, which is unable to prevent dystrophy in the mdx mouse, is able to ameliorate these abnormalities in utrophin/dystrophin-deficient mice. These experiments provide the first direct evidence that in addition to a mechanical role and relocalization of the DAPC, dystrophin and utrophin are able to alter both structural and biochemical properties of skeletal muscle. In addition, these mice provide unique insights into skeletal muscle fiber type composition.

Physiological implications of altitude training for endurance performance at sea level: a review.

Acclimatisation to environmental hypoxia initiates a series of metabolic and musculocardio-respiratory adaptations that influence oxygen transport and utilisation, or better still, being born and raised at altitude, is necessary to...

THE INTERACTION OF OVARIECTOMY AND SWIM TRAINING ON SKELETAL MUSCLE METABOLISM AND MYOSIN ISOENZYME EXPRESSION 542

Available data suggests that estrogen levels can influence metabolic and contractile properties of striated muscle in young rats (Horm Metab Res) 20 609. Cir Res 61:12) Because older rats are more likely to experience changes in estrogen levels, this study investigated 1) how an ovariectomy impacted cardiac biochemistry in older rats, and 2) if swim training would ameliorate any ovariectomized induced biochemical changes Ovariectomized and sham operated. 9-10 month old retired breeders were assigned to one of four groups (N=6) sedentary sham treated, sedentary ovariectomized, exercised sham treated, and exercised, ovariectomized. Trained animals progressively increased daily swimming times until they were exercising 75 min/day, 5 times per week. After 9 weeks animals were sacrificed, the soleus and the red and white vastus lateralis were removed and spectrophotometrically analyzed for peak activities of hexokinase, citrate synthase, and 3-hydroxyacylCo A-dehydrogenase. Native myosin isoenzymes were separated by PAGE and quantified. These manipulations either alone or together did not alter the measured biochemical properties of these skeletal muscles. However, swim training did tend to improve the metabolic potential of all three muscles studied. Results suggest that an estrogen deficiency in older animals 1) does not affect the studied biochemical properties of skeletal muscle and 2) may not prevent beneficial metabolic adaptations to swim training.

Effects of clenbuterol on contractile and biochemical properties of skeletal muscle.

We investigated the effects of clenbuterol on the muscle mass, contractile properties, myosin phenotype, and bioenergetic enzyme activity in the gastrocnemius (GS)-plantaris (PL)-soleus (SO) muscle complex. Rats were sham-injected or treated with clenbuterol (2 mg.kg-1, subcutaneously) for 14 d. Clenbuterol increased (P < 0.05) body weight and muscle complex weight. Also, clenbuterol treatment resulted in an increase in total muscle force production and maximal shortening velocity (P < 0.05). No difference (P > 0.05) in relative force production (force.g-1 muscle) existed between experimental groups. However, muscle fatigue increased with clenbuterol treatment. Myosin heavy chain (MHC) composition was not altered in the GS or PL muscles, but shifted toward the fast Type II MHC in the SO. Myosin light chain (MLC) composition was not altered in any of the muscles. Clenbuterol caused a decrease in oxidative and glycolytic enzyme activity in the GS and PL, but not the SO. These data suggest that the clenbuterol-induced increase in muscle mass and maximal force generation is due to hypertrophy of both fast and slow fibers. Furthermore, these findings support the notion that beta-agonists may be beneficial in combating conditions that result in muscle wasting and dysfunction.

Effects of 5 ppm Hydrogen Sulfide Inhalation on Biochemical Properties of Skeletal Muscle in Exercising Men and Women

This study compared the acute effects of 5 ppm hydrogen sulfide (H2S) inhalation (50% of its occupational exposure limit) on the biochemical properties of skeletal muscle in exercising men and women. Twenty-five healthy volunteers, 13 men and 12 women, completed two 30-minute submaximal tests at 50% of their predetermined maximal aerobic power (VO2max) while breathing 0 ppm (control) or 5 ppm H2S from a specially designed flow system in a single-blind manner. Immediately after exercise, biopsies were obtained from the vastus lateralis muscle under local anaesthesia. They were subsequently analyzed for concentrations of the following markers of anaerobic and aerobic metabolism: lactate (La), lactate dehydrogenase (LDH), citrate synthase (CS), and cytochrome oxidase (CytOx). Repeated measures analysis of variance indicated that in men, the CS concentration decreased significantly (p=0.006) as a result of H2S exposure. There was also a tendency for their La and LDH concentrations to increase and CytOx concentration to decrease in the presence of H2S, but these changes were not significant (p>0.05). In women no significant changes were observed in any of these biochemical properties. These results suggest that (1) exposure to H2S at 50% of its OEL might inhibit aerobic metabolism during exercise in healthy men, thereby increasing their dependency on anaerobic metabolism; and (2) there could be a significant gender difference in the acute response to sub-OEL exposures of H2S.

Effects of 5 ppm Hydrogen Sulfide Inhalation on Biochemical Properties of Skeletal Muscle in Exercising Men and Women

This study compared the acute effects of 5 ppm hydrogen sulfide (H2S) inhalation (50 % of its occupational exposure limit) on the biochemical properties of skeletal muscle in exercising men and women. Twenty-five healthy volunteers, 13 men and 12 women, completed two 30-minute submaximal tests at 50% of their predetermined maximal aerobic power (VO2max) while breathing 0 ppm (control) or 5 ppm H2S from a specially designed flow system in a single-blind manner. Immediately after exercise, biopsies were obtained from the vastus lateralis muscle under local anaesthesia. They were subsequently analyzed for concentrations of the following markers of anaerobic and aerobic metabolism: lactate (La), lactate dehydrogenase (LDH), citrate synthase (CS), and cytochrome oxidase (CytOx). Repeated measures analysis of variance indicated that in men, the CS concentration decreased significantly (p = 0.006) as a result of H2S exposure. There was also a tendency for their La and LDH concentrations to increase and CytOx concentration to decrease in the presence of H2S, but these changes were not significant (p > 0.05). In women no significant changes were observed in any of these biochemical properties. These results suggest that (1) exposure to H2S at 50% of its OEL might inhibit aerobic metabolism during exercise in healthy men, thereby increasing their dependency on anaerobic metabolism; and (2) there could be a significant gender difference in the acute response to sub-OEL exposures of H2S.

SIZE- AND DIET-RELATED VARIATIONS IN ENZYMIC ACTIVITY AND TISSUE COMPOSITION IN THE SABLEFISH,ANOPLOPOMA FIMBRIA

The influences of body size, ration size, season, and latitude on several biochemical properties of skeletal muscle and liver were examined in the sablefish, Anoplopoma fimbria, to understand how these factors interact to establish the biochemical and physiological condition of the organism. Activities in muscle of the glycolytic enzymes lactate dehydrogenase (LDH) and pyruvate kinase (PK) increased significantly with increasing body size. This size-dependent variation in enzymic activity must be corrected for when the effects of other enzyme activity influencing variables, e.g., ration size, are studied. Ration size had a strong influence on muscle enzyme activities and on the water and lipid content of muscle. Starvation led to large decreases in glycolytic enzyme activity and lipid content. The LDH content of muscle was directly proportional to the amount of food ingested (expressed as percent body weight ingested per day). Latitudinal differences among sablefish collected between Alaska (Bering Sea) and southern California and seasonal differences among individuals collected off southern California also may be due to varying ration quantity and quality. During starvation, lipid reserves in muscle appear to be mobilized as a major energy source in preference to protein.

Neural control of muscle

Cholinergic innervation regulates the physiological and biochemical properties of skeletal muscle. The mechanisms that appear to be involved in this regulation include soluble, neurally-derived polypeptides, transmitter-evoked muscle activity and the neurotransmitter, acetylcholine, itself. Despite extensive research, the interacting neural mechanisms that control such macromolecules as acetylcholinesterase, the acetylcholine receptor and glucose 6-phosphate dehydrogenase remain unclear. It may be that more simplified in vitro model systems coupled with recent dramatic advances in the molecular biology of neurally-regulated proteins will begin to allow researchers to unravel the mechanisms controlling the expression and maintenance of these macromolecules.