Science.gov

Sample records for skeletal muscle amino

  1. Amino acids in healthy aging skeletal muscle.

    PubMed

    Riddle, Emily S; Stipanuk, Martha H; Thalacker-Mercer, Anna E

    2016-01-01

    Life expectancy in the U.S. and globally continues to increase. Despite increased life expectancy quality of life is not enhanced, and older adults often experience chronic age-related disease and functional disability, including frailty. Additionally, changes in body composition such as the involuntary loss of skeletal muscle mass (i.e. sarcopenia) and subsequent increases in adipose tissue can augment disease and disability in this population. Furthermore, increased oxidative stress and decreased antioxidant concentrations may also lead to metabolic dysfunction in older adults. Specific amino acids, including leucine, cysteine and its derivative taurine, and arginine can play various roles in healthy aging, especially in regards to skeletal muscle health. Leucine and arginine play important roles in muscle protein synthesis and cell growth while cysteine and arginine play important roles in quenching oxidative stress. Evidence suggests that supplemental doses of each of these amino acids may improve the aging phenotype. However, additional research is required to establish the doses required to achieve positive outcomes in humans. PMID:26709665

  2. Induction of amino acid transporters expression by endurance exercise in rat skeletal muscle

    SciTech Connect

    Murakami, Taro Yoshinaga, Mariko

    2013-10-04

    Highlights: •Regulation of amino acid transporter expression in working muscle remains unclear. •Expression of amino acid transporters for leucine were induced by a bout of exercise. •Requirement of leucine in muscle cells might regulate expression of its transporters. •This information is beneficial for understanding the muscle remodeling by exercise. -- Abstract: We here investigated whether an acute bout of endurance exercise would induce the expression of amino acid transporters that regulate leucine transport across plasma and lysosomal membranes in rat skeletal muscle. Rats ran on a motor-driven treadmill at a speed of 28 m/min for 90 min. Immediately after the exercise, we observed that expression of mRNAs encoding L-type amino acid transporter 1 (LAT1) and CD98 was induced in the gastrocnemius, soleus, and extensor digitorum longus (EDL) muscles. Sodium-coupled neutral amino acid transporter 2 (SNAT2) mRNA was also induced by the exercise in those three muscles. Expression of proton-assisted amino acid transporter 1 (PAT1) mRNA was slightly but not significantly induced by a single bout of exercise in soleus and EDL muscles. Exercise-induced mRNA expression of these amino acid transporters appeared to be attenuated by repeated bouts of the exercise. These results suggested that the expression of amino acid transporters for leucine may be induced in response to an increase in the requirement for this amino acid in the cells of working skeletal muscles.

  3. Exercise and amino acid anabolic cell signaling and the regulation of skeletal muscle mass.

    PubMed

    Pasiakos, Stefan M

    2012-07-01

    A series of complex intracellular networks influence the regulation of skeletal muscle protein turnover. In recent years, studies have examined how cellular regulators of muscle protein turnover modulate metabolic mechanisms contributing to the loss, gain, or conservation of skeletal muscle mass. Exercise and amino acids both stimulate anabolic signaling potentially through several intracellular pathways including the mammalian target of rapamycin complex 1 and the mitogen activated protein kinase cell signaling cascades. As novel molecular regulators of muscle integrity continue to be explored, a contemporary analysis of the literature is required to understand the metabolic mechanisms by which contractile forces and amino acids affect cellular process that contribute to long-term adaptations and preservation of muscle mass. This article reviews the literature related to how exercise and amino acid availability affect cellular regulators of skeletal muscle mass, especially highlighting recent investigations that have identified mechanisms by which contractile forces and amino acids modulate muscle health. Furthermore, this review will explore integrated exercise and nutrition strategies that promote the maintenance of muscle health by optimizing exercise, and amino acid-induced cell signaling in aging adults susceptible to muscle loss. PMID:22852061

  4. Skeletal muscle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There are approximately 650-850 muscles in the human body these include skeletal (striated), smooth and cardiac muscle. The approximation is based on what some anatomists consider separate muscle or muscle systems. Muscles are classified based on their anatomy (striated vs. smooth) and if they are v...

  5. Regulation of protein degradation pathways by amino acids and insulin in skeletal muscle of neonatal pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rapid gain in lean mass in neonates requires greater rates of protein synthesis than degradation. We previously delineated the molecular mechanisms by which insulin and amino acids, especially leucine, modulate skeletal muscle protein synthesis and how this changes with development. In the curre...

  6. Taurine: the appeal of a safe amino acid for skeletal muscle disorders.

    PubMed

    De Luca, Annamaria; Pierno, Sabata; Camerino, Diana Conte

    2015-01-01

    Taurine is a natural amino acid present as free form in many mammalian tissues and in particular in skeletal muscle. Taurine exerts many physiological functions, including membrane stabilization, osmoregulation and cytoprotective effects, antioxidant and anti-inflammatory actions as well as modulation of intracellular calcium concentration and ion channel function. In addition taurine may control muscle metabolism and gene expression, through yet unclear mechanisms. This review summarizes the effects of taurine on specific muscle targets and pathways as well as its therapeutic potential to restore skeletal muscle function and performance in various pathological conditions. Evidences support the link between alteration of intracellular taurine level in skeletal muscle and different pathophysiological conditions, such as disuse-induced muscle atrophy, muscular dystrophy and/or senescence, reinforcing the interest towards its exogenous supplementation. In addition, taurine treatment can be beneficial to reduce sarcolemmal hyper-excitability in myotonia-related syndromes. Although further studies are necessary to fill the gaps between animals and humans, the benefit of the amino acid appears to be due to its multiple actions on cellular functions while toxicity seems relatively low. Human clinical trials using taurine in various pathologies such as diabetes, cardiovascular and neurological disorders have been performed and may represent a guide-line for designing specific studies in patients of neuromuscular diseases. PMID:26208967

  7. Effect of exercise and obesity on skeletal muscle amino acid uptake

    SciTech Connect

    Friedman, J.E.

    1988-01-01

    To determine if amino acid uptake by muscle of the obese Zucker rat is impaired, epitrochlearis (EPI) and soleus strip (SOL) muscles from 32 pairs of female lean (Fa/-) and obese (fa/fa) Zucker rats were incubated using ({sup 14}C){alpha}-aminoisobutyric acid (AIB). Because contractile activity also influences amino acid uptake, the effect of acute endurance exercise on amino acid uptake by skeletal muscle from lean and obese rats was also studied. Muscle wet and dry weights were similar in lean and obese rats. However, both muscle protein content and concentration from obese rats were significantly reduced. In preliminary studies, pinning EPI at resting length during incubation significantly increased AIB uptake and reduced muscle water accumulation. AIB uptake was similar in stripped and intact SOL. Lean and obese rats were studied at rest or following a 1 hr treadmill run at 8% grade Muscles were pinned, and preincubated for 30 min at 37{degree}C in Krebs Ringer bicarbonate buffer (KRB) containing 5mM glucose under 95:5 O{sub 2}/CO{sub 2}, followed by 30, 60, 120, or 180 min of incubation in KRB with 0.5 mM AIB, ({sup 14}C)-AIB to measure amino acid, and ({sup 3}H)-inulin to determine extracellular water.

  8. Peptide Antibody Specific for the Amino Terminus of Skeletal Muscle ? -actin

    NASA Astrophysics Data System (ADS)

    Bulinski, Jeannette Chloe; Kumar, Santosh; Titani, Koiti; Hauschka, Stephen D.

    1983-03-01

    The NH2-terminal peptide of skeletal muscle ? -actin (S? N peptide), which contains a primary sequence unique to this actin isozyme, was used to prepare an isozyme-specific peptide antibody. S? N peptide was purified from chicken breast muscle actin by preparative reverse-phase HPLC and was coupled to hemocyanin. This complex was used to immunize rabbits in order to elicit actin antibodies specific for the skeletal muscle ? -actin isozyme. The antibody obtained, called S? N antibody, was reactive with S? N peptide and with skeletal muscle ? -actin as well as with cardiac muscle ? -actin. S? N antibody did not react with either of the actin isozymes present in smooth muscle (smooth muscle ? and ? ) or in brain (nonmuscle ? and ? ). S? N antibody was used to detect muscle-specific actin in differentiating mouse and human myoblasts by using immunoblots of myoblast extracts and immunofluorescent staining of fixed cells.

  9. Stimulation of skeletal muscle protein synthesis in neonatal pigs by long-term infusion of leucine is amino acid dependent

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Infusing leucine for 1 hr increases skeletal muscle protein synthesis in neonatal pigs, but this is not sustained for 2 h unless the leucine-induced fall in amino acids is prevented. We aimed to determine whether continuous leucine infusion can stimulate protein synthesis for a prolonged period whe...

  10. Influence of ageing and essential amino acids on quantitative patterns of troponin T alternative splicing in human skeletal muscle

    PubMed Central

    Berg, Arthur; Drummond, Micah J.; Rasmussen, Blake B.; Kimball, Scot R.

    2015-01-01

    Ageing is associated with a loss of skeletal muscle performance, a condition referred to as sarcopenia. In part, the age-related reduction in performance is due to a selective loss in muscle fiber mass, but mass-independent effects have also been demonstrated. An important mass-independent determinant of muscle performance is the pattern of expression of isoforms of proteins that participate in muscle contraction, e.g. the troponins. In the present study we tested the hypothesis that ageing impairs alternative splicing of the pre-mRNA encoding fast troponin T (Tnnt3) in human vastus lateralis muscle. Furthermore, we hypothesized that resistance exercise alone or in combination with consumption of essential amino acids will attenuate age-associated effects on Tnnt3 alternative splicing. Our results indicate that ageing negatively affects the pattern of Tnnt3 pre-mRNA alternative splicing in a manner that correlates quantitatively with age-associated reductions in muscle performance. Interestingly, whereas vastus lateralis Tnnt3 alternative splicing was unaffected by a bout of resistance exercise 24 hour prior to muscle biopsy, ingestion of a mixture of essential amino acids after resistance exercise resulted in a significant shift in the pattern of Tnnt3 spliceform expression in both age groups to one predicted to promote greater muscle performance. We conclude that essential amino acid supplementation after resistance exercise may provide a means to reduce impairments in skeletal muscle quality during ageing in humans. PMID:26201856

  11. Myosin heavy chain 2A and ?-Actin expression in human and murine skeletal muscles at feeding; particularly amino acids

    PubMed Central

    2012-01-01

    Background Protein dynamics during non-steady state conditions as feeding are complex. Such studies usually demand combinations of methods to give conclusive information, particularly on myofibrillar proteins with slow turnover. Therefore, time course transcript analyses were evaluated as possible means to monitor changes in myofibrillar biosynthesis in skeletal muscles in conditions with clinical nutrition; i.e. long term exposure of nutrients. Methods Muscle tissue from overnight intravenously fed surgical patients were used as a model combined with muscle tissue from starved and refed mice as well as cultured L6 muscle cells. Transcripts of acta 1 (?-actin), mhc2A (myosin) and slc38 a2/Snat 2 (amino acid transporter) were quantified (qPCR) as markers of muscle protein dynamics. Results Myosin heavy chain 2A transcripts decreased significantly in skeletal muscle tissue from overnight parenterally fed patients but did not change significantly in orally refed mice. Alpha-actin transcripts did not change significantly in muscle cells from fed patients, mice or cultured L6 cells during provision of AA. The AA transporter Snat 2 decreased in L6 cells refed by all AA and by various combinations of AA but did not change during feeding in muscle tissue from patients or mice. Conclusion Our results confirm that muscle cells are sensitive to alterations in extracellular concentrations of AA for induction of protein synthesis and anabolism. However, transcripts of myofibrillar proteins and amino acid transporters showed complex alterations in response to feeding with provision of amino acids. Therefore, muscle tissue transcript levels of actin and myosin do not reflect protein accretion in skeletal muscles at feeding. PMID:23190566

  12. Regeneration of skeletal muscle.

    PubMed

    Turner, Neill J; Badylak, Stephen F

    2012-03-01

    Skeletal muscle has a robust capacity for regeneration following injury. However, few if any effective therapeutic options for volumetric muscle loss are available. Autologous muscle grafts or muscle transposition represent possible salvage procedures for the restoration of mass and function but these approaches have limited success and are plagued by associated donor site morbidity. Cell-based therapies are in their infancy and, to date, have largely focused on hereditary disorders such as Duchenne muscular dystrophy. An unequivocal need exists for regenerative medicine strategies that can enhance or induce de novo formation of functional skeletal muscle as a treatment for congenital absence or traumatic loss of tissue. In this review, the three stages of skeletal muscle regeneration and the potential pitfalls in the development of regenerative medicine strategies for the restoration of functional skeletal muscle in situ are discussed. PMID:21667167

  13. Amino acid sequence of myoglobin from emu (Dromaius novaehollandiae) skeletal muscle.

    PubMed

    Suman, S P; Joseph, P; Li, S; Beach, C M; Fontaine, M; Steinke, L

    2010-11-01

    The objective of the present study was to characterize the primary structure of emu myoglobin (Mb). Emu Mb was isolated from Iliofibularis muscle employing gel-filtration chromatography. Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry was employed to determine the exact molecular mass of emu Mb in comparison with horse Mb, and Edman degradation was utilized to characterize the amino acid sequence. The molecular mass of emu Mb was 17,380 Da and was close to those reported for ratite and poultry myoglobins. Similar to myoglobins from meat-producing livestock and birds, emu Mb has 153 amino acids. Emu Mb contains 9 histidines. Proximal and distal histidines, responsible for coordinating oxygen-binding property of Mb, are conserved in emu. Emu Mb shared more than 90% homology with ratite and chicken myoglobins, whereas it demonstrated only less than 70% sequence similarity with ruminant myoglobins. PMID:20621424

  14. Muscle free amino acid profiles are related to differences in skeletal muscle growth between single and twin ovine fetuses near term.

    PubMed

    Sales, Francisco; Pacheco, David; Blair, Hugh; Kenyon, Paul; McCoard, Sue

    2013-01-01

    Twin sheep fetuses have reduced skeletal muscle weight near birth relative to singles as a result of restricted muscle hypertrophy. Intracellular free amino acids (FAA) are reported to regulate metabolic pathways which control muscle protein accretion, whereby reduced intracellular content of specific FAA may reduce their activation and therefore, muscle hypertrophy. The aim of this study was to determine whether differences in muscle weight between singleton and twin fetuses, under different maternal conditions is associated with reduced concentration of specific FAA. The FAA content in the semitendinosus muscle (ST) in singleton and twin fetuses (rank) at 140 days of gestation from heavy (H) or light (L) ewes fed ad libitum (A) or maintenance (M) level of nutrition was measured. Muscle weight was reduced in twin fetuses compared to singletons in all groups. Reduced concentrations of leucine, threonine and valine, but higher concentrations of methionine, ornithine, lysine and serine were found in twin fetuses compared to singletons. Maternal size and nutrition interaction with rank resulted in reduced glutamine in twins from HM-ewes (H-ewes under M nutrition) compared to their singleton counterparts. Maternal weight interaction with pregnancy rank reduced the concentration of arginine in twins, with a larger effect on H-ewes compared with L-ewes. Maternal size interaction with pregnancy rank resulted in twins from M-ewes to have lower alanine, while twins from A-ewes had lower aspartic acid concentration compared to singletons. The ST muscle weight was positively correlated only with arginine concentration after taking into account rank, size and nutrition. The present results indicate that reduced concentrations of specific intracellular FAA, such as arginine, leucine, valine, glutamine, which are known to play a role in muscle growth, could be acting as limiting factors for muscle hypertrophy in twin fetuses during late gestation. Ewe size and nutrition can influence the concentration of specific FAA in muscle and should be considered in any intervention plan to improve twin fetal muscle growth. PMID:24133643

  15. Activation by insulin and amino acids of signaling components leading to translation initiation in skeletal muscle of neonatal pigs is developmentally regulated

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Insulin and amino acids act independently to stimulate protein synthesis in skeletal muscle of neonatal pigs, and the responses decrease with development. The purpose of this study was to compare the separate effects of fed levels of INS and AA on the activation of signaling components leading to tr...

  16. Skeletal Muscular system Know muscle

    E-print Network

    Houde, Peter

    Skeletal Muscular system Objectives Know muscle Group or compartment Location Function Origin through space includes skeletal striated muscle every cell innervated (neuropathy or denervation atrophy) (levels of severity: neuropraxia, axonotmesis, neurotmesis) Origin ­ stationary point of muscle attachment

  17. Hydrolyzed protein supplementation improves protein content and peroxidation of skeletal muscle by adjusting the plasma amino acid spectrums in rats after exhaustive swimming exercise: a pilot study

    PubMed Central

    2014-01-01

    Background This study was designed to evaluate the effects of hydrolyzed protein supplementation upon skeletal muscle total protein and peroxidation in rats following exhaustive swimming exercise. Methods Twenty-four rats were randomized to 4 experimental groups (n?=?6 per group): control group fed standard diet without exercise (SD), exercise (EX), exercise plus standard diet for 72 hours (EX?+?SD), and exercise plus standard diet supplemented with hydrolyzed protein (2 g/kg/d) for 72 hours (EX?+?HP). Immediately following exercise, the EX group was euthanized for collecting plasma and skeletal muscle samples. The EX?+?SD and EX?+?HP groups were fed their respective diets for 72 hour still plasma and skeletal muscle collection. Skeletal muscle samples were used to measure levels of total protein (TP), malondialdehyde (MDA), and protein carbonyl (PC). Plasma samples were used to analyze the amino acids spectrum. Results Compared with the EX?+?SD, EX?+?HP presented the significantly increased TP (P?=?0.02) and decreased MDA and PC levels (P?=?0.035). MDA was negatively correlated with the methionine levels. Moreover, EX?+?HP maintained higher levels of plasmaleucine, isoleucine, and methionine than EX?+?SD, which may be associated with the increased skeletal muscle TP levels observed (P?skeletal muscle TP and ameliorate peroxidation damage in rats subjected to exhaustive exercise stress, which may be, at least in part, related with the maintenance of plasma leucine, isoleucine, and methionine levels. PMID:24565110

  18. LEUCINE STIMULATION OF SKELETAL MUSCLE PROTEIN SYNTHESIS DURING PROLONGED LEUCINE INFUSION IS DEPENDENT ON AMINO ACID AVAILABILITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Leucine stimulates protein synthesis in cultured cells, mature rats and neonatal pigs. We have reported that leucine infusion increases protein synthesis in skeletal muscle of neonatal pigs during a 60-min infusion. When leucine infusion was prolonged for 120 min, however, protein synthesis was no...

  19. Expression of genes coding for selected amino acid transporters in small intestine, liver, and skeletal muscle of pigs fed excess branched-chain amino acids.

    PubMed

    Cervantes, M; Arce, N; García, H; Cota, M; Htoo, J K; Morales, A

    2015-01-01

    Excess Leu reduces the availability of Ile and Val in pigs likely by reducing absorption of the latter amino acids (AA). Twenty-four crossbred pigs were used to evaluate the effect of excess Leu alone or with surplus Ile and Val on the expression of cationic (b(0),(+)AT and CAT1) and neutral (B(0)AT1) AA transporters in the small intestine, liver, and skeletal muscle. Dietary treatments included: 1) basal diet; 2) basal plus 0.43% L-Leu (excess Leu); 3) basal plus 0.43% Leu, 0.20% L-Ile, and 0.25% L-Val (excess Leu, Ile, and Val). The basal diet contained 0.90% standardized ileal digestible Lys, as well as crystalline L-Lys, L-Thr, DL-Met, L-Trp, L-Leu, L-Ile, L-His, and L-Val. Diets 2 and 3 contained 52% more Leu and diet 3 contained 42% more Ile and Val compared with the basal diet. Excess Leu or excess Leu, Ile, and Val reduced b(0),(+)AT expression in the jejunum (P < 0.05) but had no effect in the ileum and liver. Excess Leu increased CAT1 expression in the ileum but reduced expression in the liver (P < 0.05). Excess Leu, Ile, and Val increased (P < 0.05) B(0)AT1 expression in the jejunum and tended to increase (P = 0.10) expression in the ileum. In general, b(0),(+)AT expression was higher but CAT1 expression was lower in the jejunum than in the ileum; B0AT1 was similarly expressed in the jejunum and ileum. Excess Leu or any branched-chain AA affects AA transporter expression, which may affect the absorption and availability of AA for animal growth. PMID:26345911

  20. Sepsis-induced changes in amino acid transporters and leucine signaling via mTOR in skeletal muscle

    PubMed Central

    Laufenberg, Lacee J.; Pruznak, Anne M.; Navaratnarajah, Maithili; Lang, Charles H.

    2015-01-01

    The etiology for the sepsis-induced leucine (Leu) resistance has not been fully elucidated and the present study investigated various aspects of amino acid activation of the mammalian target of rapamycin (mTOR). Sepsis in adult male rats decreased basal protein synthesis in gastrocnemius, associated with a reduction in mTOR activation as indicated by decreased 4EBP1 and S6K1 phosphorylation. The ability of oral Leu to increase protein synthesis and mTOR kinase after 1 h was largely prevented in sepsis. Sepsis increased CAT1, LAT2 and SNAT2 mRNA content 2- to 4-fold, but only the protein content for CAT1 (20% decrease) was significantly different. Conversely, sepsis decreased the proton-assisted amino acid transporter (PAT)-2 mRNA by 60%, but without a coordinate change in PAT2 protein. There was no sepsis or Leu effect on the protein content for RagA-D, LAMTOR-1 and -2, raptor, Rheb or mTOR in muscle. The binding of mTOR, PRAS40 and RagC to raptor did not differ for control and septic muscle in the basal condition; however, the Leu-induced decrease in PRAS40•raptor and increase in RagC•raptor seen in control muscle was absent in sepsis. The intracellular Leu concentration was increased in septic muscle, compared to basal control conditions, and oral Leu further increased the intracellular Leu concentration similarly in both control and septic rats. Hence, while alterations in select amino acid transporters are not associated with development of sepsis-induced Leu-resistance, the Leu-stimulated binding of raptor with RagC and the recruitment of mTOR/raptor to the endosome-lysosomal compartment may partially explain the inability of Leu to fully active mTOR and muscle protein synthesis. PMID:25218136

  1. Effects of resistance exercise combined with essential amino acid supplementation and energy deficit on markers of skeletal muscle atrophy and regeneration during bed rest and active recovery

    PubMed Central

    Brooks, Naomi E.; Cadena, Samuel M.; Vannier, Edouard; Cloutier, Gregory; Carambula, Silvia; Myburgh, Kathryn H.; Roubenoff, Ronenn; Castaneda-Sceppa, Carmen

    2010-01-01

    INTRODUCTION Space flight and bed rest (BR) lead to muscle atrophy. This study assessed the effect of essential amino acid supplementation (EAA) and resistance training with decreased energy intake on molecular changes in skeletal muscle after 28d BR and 14d recovery. METHODS Thirty-one men (31–55yr) subjected to an 8±6% energy deficit were randomized to receive EAA without resistance training (AA, n=7), EAA 3 h after (RT, n=12), or 5 min before (AART, n=12) resistance training. RESULTS During BR, myostatin transcript levels increased 2-fold in the AA group. During recovery, IGF1 mRNA increased in all groups while Pax7, MyoD, myogenin and MRF4 transcripts increased in AA only (all p<0.05). MAFbx transcripts decreased 2-fold with AA and RT. Satellite cells did not change during BR or recovery. DISCUSSION This suggests that EAA alone is the least protective countermeasure to muscle loss, and several molecular mechanisms are proposed by which exercise attenuates muscle atrophy during bed rest with energy deficit. PMID:20928906

  2. Skeletal muscle hypertrophy after aerobic exercise training.

    PubMed

    Konopka, Adam R; Harber, Matthew P

    2014-04-01

    Current dogma suggests that aerobic exercise training has minimal effects on skeletal muscle size. We and others have demonstrated that aerobic exercise acutely and chronically alters protein metabolism and induces skeletal muscle hypertrophy. These findings promote an antithesis to the status quo by providing novel perspective on skeletal muscle mass regulation and insight into exercise countermeasures for populations prone to muscle loss. PMID:24508740

  3. Adult skeletal muscle stem cells.

    PubMed

    Sambasivan, Ramkumar; Tajbakhsh, Shahragim

    2015-01-01

    Skeletal muscles in vertebrates have a phenomenal regenerative capacity. A muscle that has been crushed can regenerate fully both structurally and functionally within a month. Remarkably, efficient regeneration continues to occur following repeated injuries. Thousands of muscle precursor cells are needed to accomplish regeneration following acute injury. The differentiated muscle cells, the multinucleated contractile myofibers, are terminally withdrawn from mitosis. The source of the regenerative precursors is the skeletal muscle stem cells-the mononucleated cells closely associated with myofibers, which are known as satellite cells. Satellite cells are mitotically quiescent or slow-cycling, committed to myogenesis, but undifferentiated. Disruption of the niche after muscle damage results in their exit from quiescence and progression towards commitment. They eventually arrest proliferation, differentiate, and fuse to damaged myofibers or make de novo myofibers. Satellite cells are one of the well-studied adult tissue-specific stem cells and have served as an excellent model for investigating adult stem cells. They have also emerged as an important standard in the field of ageing and stem cells. Several recent reviews have highlighted the importance of these cells as a model to understand stem cell biology. This chapter begins with the discovery of satellite cells as skeletal muscle stem cells and their developmental origin. We discuss transcription factors and signalling cues governing stem cell function of satellite cells and heterogeneity in the satellite cell pool. Apart from satellite cells, a number of other stem cells have been shown to make muscle and are being considered as candidate stem cells for amelioration of muscle degenerative diseases. We discuss these "offbeat" muscle stem cells and their status as adult skeletal muscle stem cells vis-a-vis satellite cells. The ageing context is highlighted in the concluding section. PMID:25344672

  4. Muscle Biophysics 1 THE BIOMECHANICS OF SKELETAL MUSCLES1

    E-print Network

    Prestwich, Ken

    Muscle Biophysics 1 THE BIOMECHANICS OF SKELETAL MUSCLES1 You are probably comfortable with the notion that muscles convert chemical potential energy responsible for this conversion. However, it may surprise you that muscles also

  5. Signaling Pathways Related to Protein Synthesis and Amino Acid Concentration in Pig Skeletal Muscles Depend on the Dietary Protein Level, Genotype and Developmental Stages

    PubMed Central

    Liu, Yingying; Li, Fengna; Kong, Xiangfeng; Tan, Bie; Li, Yinghui; Duan, Yehui; Blachier, François; Hu, Chien-An A.; Yin, Yulong

    2015-01-01

    Muscle growth is regulated by the homeostatic balance of the biosynthesis and degradation of muscle proteins. To elucidate the molecular interactions among diet, pig genotype, and physiological stage, we examined the effect of dietary protein concentration, pig genotype, and physiological stages on amino acid (AA) pools, protein deposition, and related signaling pathways in different types of skeletal muscles. The study used 48 Landrace pigs and 48 pure-bred Bama mini-pigs assigned to each of 2 dietary treatments: lower/GB (Chinese conventional diet)- or higher/NRC (National Research Council)-protein diet. Diets were fed from 5 weeks of age to respective market weights of each genotype. Samples of biceps femoris muscle (BFM, type I) and longissimus dorsi muscle (LDM, type II) were collected at nursery, growing, and finishing phases according to the physiological stage of each genotype, to determine the AA concentrations, mRNA levels for growth-related genes in muscles, and protein abundances of mechanistic target of rapamycin (mTOR) signaling pathway. Our data showed that the concentrations of most AAs in LDM and BFM of pigs increased (P<0.05) gradually with increasing age. Bama mini-pigs had generally higher (P<0.05) muscle concentrations of flavor-related AA, including Met, Phe, Tyr, Pro, and Ser, compared with Landrace pigs. The mRNA levels for myogenic determining factor, myogenin, myocyte-specific enhancer binding factor 2 A, and myostatin of Bama mini-pigs were higher (P<0.05) than those of Landrace pigs, while total and phosphorylated protein levels for protein kinase B, mTOR, and p70 ribosomal protein S6 kinases (p70S6K), and ratios of p-mTOR/mTOR, p-AKT/AKT, and p-p70S6K/p70S6K were lower (P<0.05). There was a significant pig genotype-dependent effect of dietary protein on the levels for mTOR and p70S6K. When compared with the higher protein-NRC diet, the lower protein-GB diet increased (P<0.05) the levels for mTOR and p70S6K in Bama mini-pigs, but repressed (P<0.05) the level for p70S6K in Landrace pigs. The higher protein-NRC diet increased ratio of p-mTOR/mTOR in Landrace pigs. These findings indicated that the dynamic consequences of AA profile and protein deposition in muscle tissues are the concerted effort of distinctive genotype, nutrient status, age, and muscle type. Our results provide valuable information for animal feeding strategy. PMID:26394157

  6. Occurrence of a novel acetylated amino acid, N(alpha)-acetylhistidine, in skeletal muscle of freshwater fish and other ectothermic vertebrates.

    PubMed

    Yamada, Shoji; Kawashima, Kazuto; Baba, Kyoko; Oku, Takahiro; Ando, Seiichi

    2009-03-01

    The occurrence of N(alpha)-acetylhistidine (NAH) in skeletal muscle of 91 species of freshwater fish and 9 species of other ectothermic vertebrates was investigated, with consideration of phylogenetic relationships. Of the 91 freshwater fish species examined, 13 species (7 cichlids, 5 anabantids, and 1 catfish) contained considerable amounts (>1 micromol/g) of NAH in their skeletal muscles. The highest level (10.37 micromol/g) of NAH was found in the tissue of Betta splendens (Siamese fighting fish). Moreover, the NAH contents in the tissues of Trichogaster trichopterus (three spot gourami), Kryptopterus bicirrhis (glass catfish), Oreochromis niloticus (Nile tilapia), Mikrogeophagus ramirezi (ram cichlid) and Parachromis managuensis (Guapote tigre) were 3.17-6.16 micromol/g. The skeletal muscle of amphibians (5 species) and reptiles (4 species) had a low level (<0.25 micromol/g) of NAH. The present findings clearly demonstrate NAH as the fifth imidazole-related compound, in addition to histidine, carnosine, anserine and ophidine (balenine), recognized as a major non-protein nitrogenous constituent in the skeletal muscle of vertebrate animals. PMID:19100335

  7. Skeletal muscle satellite cells

    NASA Technical Reports Server (NTRS)

    Schultz, E.; McCormick, K. M.

    1994-01-01

    Evidence now suggests that satellite cells constitute a class of myogenic cells that differ distinctly from other embryonic myoblasts. Satellite cells arise from somites and first appear as a distinct myoblast type well before birth. Satellite cells from different muscles cannot be functionally distinguished from one another and are able to provide nuclei to all fibers without regard to phenotype. Thus, it is difficult to ascribe any significant function to establishing or stabilizing fiber type, even during regeneration. Within a muscle, satellite cells exhibit marked heterogeneity with respect to their proliferative behavior. The satellite cell population on a fiber can be partitioned into those that function as stem cells and those which are readily available for fusion. Recent studies have shown that the cells are not simply spindle shaped, but are very diverse in their morphology and have multiple branches emanating from the poles of the cells. This finding is consistent with other studies indicating that the cells have the capacity for extensive migration within, and perhaps between, muscles. Complexity of cell shape usually reflects increased cytoplasmic volume and organelles including a well developed Golgi, and is usually associated with growing postnatal muscle or muscles undergoing some form of induced adaptive change or repair. The appearance of activated satellite cells suggests some function of the cells in the adaptive process through elaboration and secretion of a product. Significant advances have been made in determining the potential secretion products that satellite cells make. The manner in which satellite cell proliferative and fusion behavior is controlled has also been studied. There seems to be little doubt that cellcell coupling is not how satellite cells and myofibers communicate. Rather satellite cell regulation is through a number of potential growth factors that arise from a number of sources. Critical to the understanding of this form of control is to determine which of the many growth factors that can alter satellite cell behavior in vitro are at work in vivo. Little work has been done to determine what controls are at work after a regeneration response has been initiated. It seems likely that, after injury, growth factors are liberated through proteolytic activity and initiate an activation process whereby cells enter into a proliferative phase. After myofibers are formed, it also seems likely that satellite cell behavior is regulated through diffusible factors arising from the fibers rather than continuous control by circulating factors.(ABSTRACT TRUNCATED AT 400 WORDS).

  8. [Regeneration capacity of skeletal muscle].

    PubMed

    Wernig, A

    2003-07-01

    The organotypic stem cell of skeletal muscle has previously been known as satellite cell. They allow muscle fiber growth during ontogenesis, enable fiber hypertrophy and are responsible for the very efficient repair of muscle fibers. This efficient apparatus is to some degree counterbalanced by an enormous use of the satellite cell pool: fiber atrophy probably is accompanied by loss of myonuclei such that every reversal of atrophy is bound to use new myonuclei i.e. satellite cells. How often in life does this occur? Hard to say. Moreover, the potent repair capacity is challenged by an unexpected vulnerability of skeletal muscle fibers: Passive stretching of contracted muscles may cause multiple "microdamage," disruption of contractile elements or tiny areas of true necrosis (focal necrosis). How often does this happen? Well, for many of us at least once per year when we go up and down mountains during vacation time, followed by sour muscles. Others may decide to change his/her (locomotor) behaviour by severe onset of jogging; it may happen that they suffer kidney failure on Monday due to muscle microdamage and the transfer of myoproteins into the serum over weekend. Also 20 minutes of stepping up and down something like a chair will do: There is a remarkable increase in kreatin kinase and other muscle derived proteins which lasts for days and is bound to reflect some muscle damage. How about sportsmen and worker who repeatedly use their muscles in such a way? We don't have answers yet to most of these questions, but considerable amount of information has been collected over the last years both in animal and--less--in human. What is common in all cases of growth and repair is the proliferation of the satellite cells and their consequent incorporation and fusion with the parent fiber. This way focal damage is repaired often without visible reminders. We would run out of satellite cells were they not stem cells: After division one daughter remains a satellite cell while the other is free to divide. Divide how often? Important for the human cells since the cell ages and proliferates slower and slower till it stops to divide at all, at least in culture. The same is true for the new satellite cell. This we know from recent experiments in which human biopsies derived myogenic cells were grown in vitro and in vivo (by implanting them into skeletal muscles of immunoincompetent mice): Growth correlates negatively with age of the donor. Between age 2 and some 70 years, about two divisions are performed by each satellite cell in human vastus lateralis and biceps brachii muscle in 10 years in the average. Most important for the older among us: at age 76 there are still some 13 divisions left before complete exhaustion. However, there are diseases like Duchenne Muscular Dystrophy (DMD) in which muscle fibers lack a structural protein with the effect of enhanced vulnerability to mechanical stress. There the enhanced use of the satellite cell pool makes the remaining growth capacity in an 8-years-old child as low as otherwise found at age 80. Some time ago, implantation of genetically intact myoblasts obtained from healthy relatives has been proposed as a treatment of DMD. Every logic would have predicted that some local implantation of whatever numbers of cells was bound to fail rescue the complete masculature or at least the muscles for breathing. The human as guinea pig? Now, even years later, we still collect the basic information on growth of human myoblasts and start thinking of ways for systemic application and quantitatively relevant incorporation of the myogenic stem cell or other--possibly pluripotent--stem cells derived from bone marrow. PMID:12956031

  9. Aging of Skeletal Muscle Fibers

    PubMed Central

    Miljkovic, Natasa; Lim, Jae-Young; Miljkovic, Iva

    2015-01-01

    Aging has become an important topic for scientific research because life expectancy and the number of men and women in older age groups have increased dramatically in the last century. This is true in most countries of the world including the Republic of Korea and the United States. From a rehabilitation perspective, the most important associated issue is a progressive decline in functional capacity and independence. Sarcopenia is partly responsible for this decline. Many changes underlying the loss of muscle mass and force-generating capacity of skeletal muscle can be understood at the cellular and molecular levels. Muscle size and architecture are both altered with advanced adult age. Further, changes in myofibers include impairments in several physiological domains including muscle fiber activation, excitation-contraction coupling, actin-myosin cross-bridge interaction, energy production, and repair and regeneration. A thorough understanding of these alterations can lead to the design of improved preventative and rehabilitative interventions, such as personalized exercise training programs. PMID:25932410

  10. Skeletal muscle-smooth muscle interaction: an unusual myoelastic system.

    PubMed

    Hikida, R S; Peterson, W J

    1983-09-01

    The serratus superficialis metapatagialis (SSM) of pigeons is a skeletal muscle with unusual properties. It lies between the ribs and the trailing edge of the wing, where it is attached to the skin by a system of smooth muscles having elastic tendons. Wing movements during flight induce marked changes in this muscle's length. The SSM inserts onto the deep fascia, and at its termination the skeletal muscle contains large numbers of microtubules. Many myofibrils attach to leptomeric organelles, which then attach to the terminal end of the skeletal muscle fiber. The deep fascia next connects to the dermis of the skin by bundles of smooth muscles that have elastic tendons at both ends. This system allows large movements of the muscle while preventing its fibers from overstretching. The movements and presumed forces acting at this muscle make the presence of sensory receptors such as muscle spindles unlikely. Spindles are absent in this muscle. PMID:6227753

  11. STRUCTURE OF SKELETAL MUSCLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 Structure of an Individual Muscle Fiber . . . . . . . . . . . . . . . . . . . . .

    E-print Network

    Cooper, Robin L.

    STRUCTURE OF SKELETAL MUSCLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 Structure of an Individual Muscle Fiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 The Connective Tissue System within the Muscle Belly

  12. Regulation of skeletal muscle perfusion during exercise

    NASA Technical Reports Server (NTRS)

    Delp, M. D.; Laughlin, M. H.

    1998-01-01

    For exercise to be sustained, it is essential that adequate blood flow be provided to skeletal muscle. The local vascular control mechanisms involved in regulating muscle perfusion during exercise include metabolic control, endothelium-mediated control, propagated responses, myogenic control, and the muscle pump. The primary determinant of muscle perfusion during sustained exercise is the metabolic rate of the muscle. Metabolites from contracting muscle diffuse to resistance arterioles and act directly to induce vasodilation, or indirectly to inhibit noradrenaline release from sympathetic nerve endings and oppose alpha-adrenoreceptor-mediated vasoconstriction. The vascular endothelium also releases vasodilator substances (e.g., prostacyclin and nitric oxide) that are prominent in establishing basal vascular tone, but these substances do not appear to contribute to the exercise hyperemia in muscle. Endothelial and smooth muscle cells may also be involved in propagating vasodilator signals along arterioles to parent and daughter vessels. Myogenic autoregulation does not appear to be involved in the exercise hyperemia in muscle, but the rhythmic propulsion of blood from skeletal muscle veins facilitates venous return to the heart and muscle perfusion. It appears that the primary determinants of sustained exercise hyperemia in skeletal muscle are metabolic vasodilation and increased vascular conductance via the muscle pump. Additionally, sympathetic neural control is important in regulating muscle blood flow during exercise.

  13. Enhanced skeletal muscle for effective glucose homeostasis.

    PubMed

    Yang, Jinzeng

    2014-01-01

    As the single largest organ in the body, the skeletal muscle is the major site of insulin-stimulated glucose uptake in the postprandial state. Skeletal muscles provide the physiological foundation for physical activities and fitness. Reduced muscle mass and strength is commonly associated with many chronic diseases, including obesity and insulin resistance. The complications of diabetes on skeletal muscle mass and physiology, resulting from either insulin deprivation or insulin resistance, may not be life-threatening, but accelerate the lost physiological functions of glucose homeostasis. The formation of skeletal muscle commences in the embryonic developmental stages at the time of mesoderm generation, where somites are the developmental milestone in musculoskeletal formation. Dramatic skeletal muscle growth occurs during adolescence as a result of muscle fiber hypertrophy since muscle fiber formation is mostly completed before birth. The rate of growth rapidly decelerates in the late stages of adulthood as adipose tissue gradually accumulates more fat when energy intake exceeds expenditure. Physiologically, the key to effective glucose homeostasis is the hormone insulin and insulin sensitivity of target tissues. Enhanced skeletal muscle, by either intrinsic mechanism or physical activity, offers great advantages and benefits in facilitating glucose regulation. One key protein factor named myostatin is a dominant inhibitor of muscle mass. Depression of myostatin by its propeptide or mutated receptor enhances muscle mass effectively. The muscle tissue utilizes a large portion of metabolic energy for its growth and maintenance. We demonstrated that transgenic overexpression of myostatin propeptide in mice fed with a high-fat diet enhanced muscle mass and circulating adiponectin, while the wild-type mice developed obesity and insulin resistance. Enhanced muscle growth has positive effects on fat metabolism through increasing adiponectin expression and its regulations. Molecular studies of the exercise-induced glucose uptake in skeletal muscle also provide insights on auxiliary substances that mimic the plastic adaptations of muscle to exercise so that the body may amplify the effects of exercise in contending physical activity limitations or inactivity. The recent results from the peroxisome proliferator-activated receptor ? coactivator 1? provide a promising therapeutic approach for future metabolic drug development. In summary, enhanced skeletal muscle and fundamental understanding of the biological process are critical for effective glucose homeostasis in metabolic disorders. PMID:24373237

  14. Sumoylated ?-skeletal muscle actin in the skeletal muscle of adult rats.

    PubMed

    Uda, Munehiro; Kawasaki, Hiroaki; Iizumi, Kyoichi; Shigenaga, Ayako; Baba, Takeshi; Naito, Hisashi; Yoshioka, Toshitada; Yamakura, Fumiyuki

    2015-11-01

    Skeletal muscles are composed of two major muscle fiber types: slow-twitch oxidative fibers and fast-twitch glycolytic fibers. The proteins in these muscle fibers are known to differ in their expression, relative abundance, and post-translational modifications. In this study, we report a previously unreported post-translational modification of ?-skeletal muscle actin in the skeletal muscles of adult male F344 rats in vivo. Using two-dimensional electrophoresis (2D-PAGE), we first examined the differences in the protein expression profiles between the soleus and plantaris muscles. We found higher intensity protein spots at approximately 60 kDa and pH 9 on 2D-PAGE for the soleus muscle compared with the plantaris muscle. These spots were identified as ?-skeletal muscle actin by liquid chromatography-nanoelectrospray ionization-tandem mass spectrometry and western blot analyses. In addition, we found that the 60 kDa ?-skeletal muscle actin is modified by small ubiquitin-like modifier (SUMO) 1, using 2D-PAGE and western blot analyses. Furthermore, we found that ?-skeletal muscle actin with larger molecular weight was localized in the nuclear and cytosol of the skeletal muscle, but not in the myofibrillar fraction by the combination of subcellular fractionation and western blot analyses. These results suggest that ?-skeletal muscle actin is modified by SUMO-1 in the skeletal muscles, localized in nuclear and cytosolic fractions, and the extent of this modification is much higher in the slow muscles than in the fast muscles. This is the first study to show the presence of SUMOylated actin in animal tissues. PMID:26169987

  15. Space travel directly induces skeletal muscle atrophy

    NASA Technical Reports Server (NTRS)

    Vandenburgh, H.; Chromiak, J.; Shansky, J.; Del Tatto, M.; Lemaire, J.

    1999-01-01

    Space travel causes rapid and pronounced skeletal muscle wasting in humans that reduces their long-term flight capabilities. To develop effective countermeasures, the basis of this atrophy needs to be better understood. Space travel may cause muscle atrophy indirectly by altering circulating levels of factors such as growth hormone, glucocorticoids, and anabolic steroids and/or by a direct effect on the muscle fibers themselves. To determine whether skeletal muscle cells are directly affected by space travel, tissue-cultured avian skeletal muscle cells were tissue engineered into bioartificial muscles and flown in perfusion bioreactors for 9 to 10 days aboard the Space Transportation System (STS, i.e., Space Shuttle). Significant muscle fiber atrophy occurred due to a decrease in protein synthesis rates without alterations in protein degradation. Return of the muscle cells to Earth stimulated protein synthesis rates of both muscle-specific and extracellular matrix proteins relative to ground controls. These results show for the first time that skeletal muscle fibers are directly responsive to space travel and should be a target for countermeasure development.

  16. RESEARCH Open Access Dystrophin deficiency exacerbates skeletal muscle

    E-print Network

    Campbell, Kevin P.

    RESEARCH Open Access Dystrophin deficiency exacerbates skeletal muscle pathology in dysferlin globular domains. The absence of dystrophin disrupts this link, leading to compromised muscle sarcolemmal of damaged sarcolemma in skeletal muscle. Because dysferlin and dystrophin play different roles

  17. Skeletal muscle weakness in osteogeneis imperfecta mice

    PubMed Central

    Gentry, Bettina A; Ferreira, J. Andries; McCambridge, Amanda J.; Brown, Marybeth; Phillips, Charlotte L.

    2010-01-01

    Exercise intolerance, muscle fatigue and weakness are often-reported, little-investigated concerns of patients with osteogenesis imperfecta (OI). OI is a heritable connective tissue disorder hallmarked by bone fragility resulting primarily from dominant mutations in the pro?1(I) or pro?2(I) collagen genes and the recently discovered recessive mutations in post-translational modifying proteins of type I collagen. In this study we examined the soleus (S), plantaris (P), gastrocnemius (G), tibialis anterior (TA) and quadriceps (Q) muscles of mice expressing mild (+/oim) and moderately severe (oim/oim) OI for evidence of inherent muscle pathology. In particular, muscle weight, fiber cross-sectional area (CSA), fiber type, fiber histomorphology, fibrillar collagen content, absolute, relative and specific peak tetanic force (Po, Po/mg and Po/CSA respectively) of individual muscles were evaluated. Oim/oim mouse muscles were generally smaller, contained less fibrillar collagen, had decreased Po and an inability to sustain Po for the 300 ms testing duration for specific muscles; +/oim mice had a similar but milder skeletal muscle phenotype. +/oim mice had mild weakness of specific muscles but were less affected than their oim/oim counterparts which demonstrated readily apparent skeletal muscle pathology. Therefore muscle weakness in oim mice reflects inherent skeletal muscle pathology. PMID:20619344

  18. Do inflammatory cells influence skeletal muscle hypertrophy?

    PubMed

    Koh, Timothy J; Pizza, Francis X

    2009-01-01

    Most research on muscle hypertrophy has focused on the responses of muscle cells to mechanical loading; however, a number of studies also suggest that inflammatory cells may influence muscle hypertrophy. Neutrophils and macrophages accumulate in skeletal muscle following increased mechanical loading, and we have demonstrated that macrophages are essential for hypertrophy following synergist ablation. Whether neutrophils are required remains to be determined. Non-steroidal anti-inflammatory drugs impair adaptive responses of skeletal muscle in both human and animal experiments suggesting that the routine use of such drugs could impair muscle performance. Much remains to be learned about the role of inflammatory cells in muscle hypertrophy, including the molecular signals involved in calling neutrophils and macrophages to skeletal muscle as well as those that regulate their function in muscle. In addition, although we have demonstrated that macrophages produce growth promoting factors during muscle hypertrophy, the full range of functional activities involved in muscle hypertrophy remains to be determined. Further investigation should provide insight into the intriguing hypothesis that inflammatory cells play integral roles in regulating muscle hypertrophy. PMID:19482625

  19. Aspects of skeletal muscle modelling.

    PubMed Central

    Epstein, Marcelo; Herzog, Walter

    2003-01-01

    The modelling of skeletal muscle raises a number of philosophical questions, particularly in the realm of the relationship between different possible levels of representation and explanation. After a brief incursion into this area, a list of desiderata is proposed as a guiding principle for the construction of a viable model, including: comprehensiveness, soundness, experimental consistency, predictive ability and refinability. Each of these principles is illustrated by means of simple examples. The presence of internal constraints, such as incompressibility, may lead to counterintuitive results. A one-panel example is exploited to advocate the use of the principle of virtual work as the ideal tool to deal with these situations. The question of stability in the descending limb of the force-length relation is addressed and a purely mechanical analogue is suggested. New experimental results confirm the assumption that fibre stiffness is positive even in the descending limb. The indeterminacy of the force-sharing problem is traditionally resolved by optimizing a, presumably, physically meaningful target function. After presenting some new results in this area, based on a separation theorem, it is suggested that a more fundamental approach to the problem is the abandoning of optimization criteria in favour of an explicit implementation of activation criteria. PMID:14561335

  20. Inactivity amplifies the catabolic response of skeletal muscle to cortisol

    NASA Technical Reports Server (NTRS)

    Ferrando, A. A.; Stuart, C. A.; Sheffield-Moore, M.; Wolfe, R. R.

    1999-01-01

    Severe injury or trauma is accompanied by both hypercortisolemia and prolonged inactivity or bed rest (BR). Trauma and BR alone each result in a loss of muscle nitrogen, albeit through different metabolic alterations. Although BR alone can result in a 2-3% loss of lean body mass, the effects of severe trauma can be 2- to 3-fold greater. We investigated the combined effects of hypercortisolemia and prolonged inactivity on muscle protein metabolism in healthy volunteers. Six males were studied before and after 14 days of strict BR using a model based on arteriovenous sampling and muscle biopsy. Fractional synthesis and breakdown rates of skeletal muscle protein were also directly calculated. Each assessment of protein metabolism was conducted during a 12-h infusion of hydrocortisone sodium succinate (120 microg/kg x h), resulting in blood cortisol concentrations that mimic severe injury (approximately 31 microg/dL). After 14 days of strict BR, hypercortisolemia increased phenylalanine efflux from muscle by 3-fold (P < 0.05). The augmented negative amino acid balance was the result of an increased muscle protein breakdown (P < 0.05) without a concomitant change in muscle protein synthesis. Muscle efflux of glutamine and alanine increased significantly after bed rest due to a significant increase in de novo synthesis (P < 0.05). Thus, inactivity sensitizes skeletal muscle to the catabolic effects of hypercortisolemia. Furthermore, these effects on healthy volunteers are analogous to those seen after severe injury.

  1. d-Amino Acid Substitution of Peptide-Mediated NF-?B Suppression in mdx Mice Preserves Therapeutic Benefit in Skeletal Muscle, but Causes Kidney Toxicity

    PubMed Central

    Reay, Daniel P; Bastacky, Sheldon I; Wack, Kathryn E; Stolz, Donna B; Robbins, Paul D; Clemens, Paula R

    2015-01-01

    In Duchenne muscular dystrophy (DMD) patients and the mdx mouse model of DMD, chronic activation of the classical nuclear factor-?B (NF-?B) pathway contributes to the pathogenesis that causes degeneration of muscle fibers, inflammation and fibrosis. Prior studies demonstrate that inhibition of inhibitor of ?B kinase (IKK)-mediated NF-?B activation using l-isomer NF-?B essential modulator (NEMO)-binding domain (NBD) peptide-based approaches reduce muscle pathology in the mdx mouse. For our studies, the NBD peptide is synthesized as a fusion peptide with an eight-lysine (8K) protein transduction domain to facilitate intracellular delivery. We hypothesized that the d-isoform peptide could have a greater effect than the naturally occurring l-isoform peptide due to the longer persistence of the d-isoform peptide in vivo. In this study, we compared systemic treatment with low (1 mg/kg) and high (10 mg/kg) doses of l- and d-isomer 8K-wild-type-NBD peptide in mdx mice. Treatment with both l- or d-isoform 8K-wild-type-NBD peptide resulted in decreased activation of NF-?B and improved histology in skeletal muscle of the mdx mouse. However, we observed kidney toxicity (characterized by proteinuria), increased serum creatinine, activation of NF-?B and pathological changes in kidney cortex that were most severe with treatment with the d-isoform of 8K-wild-type-NBD peptide. The observed toxicity was also seen in normal mice. PMID:26018805

  2. The benefits of coffee on skeletal muscle.

    PubMed

    Dirks-Naylor, Amie J

    2015-12-15

    Coffee is consumed worldwide with greater than a billion cups of coffee ingested every day. Epidemiological studies have revealed an association of coffee consumption with reduced incidence of a variety of chronic diseases as well as all-cause mortality. Current research has primarily focused on the effects of coffee or its components on various organ systems such as the cardiovascular system, with relatively little attention on skeletal muscle. Summary of current literature suggests that coffee has beneficial effects on skeletal muscle. Coffee has been shown to induce autophagy, improve insulin sensitivity, stimulate glucose uptake, slow the progression of sarcopenia, and promote the regeneration of injured muscle. Much more research is needed to reveal the full scope of benefits that coffee consumption may exert on skeletal muscle structure and function. PMID:26546720

  3. Optimizing skeletal muscle reinnervation with nerve transfer.

    PubMed

    Lien, Samuel C; Cederna, Paul S; Kuzon, William M

    2008-11-01

    Denervation as a consequence of nerve injury causes profound structural and functional changes within skeletal muscle and can lead to a marked impairment in function of the affected limb. Prompt reinnervation of a muscle with a sufficient number of motion-specific motor axons generally results in good structural and functional recovery, whereas long-term denervation or insufficient or improper axonal recruitment uniformly results in poor functional recovery. Only nerve transfer has been highly efficacious in changing the clinical outcomes of patients with skeletal muscle denervation, especially in the case of proximal limb nerve injuries. Rapid reinnervation with an abundant number of motor axons remains the only clinically effective means to restore function to denervated skeletal muscles. PMID:18928892

  4. HIF-1-driven skeletal muscle adaptations to chronic hypoxia: molecular insights into muscle physiology.

    PubMed

    Favier, F B; Britto, F A; Freyssenet, D G; Bigard, X A; Benoit, H

    2015-12-01

    Skeletal muscle is a metabolically active tissue and the major body protein reservoir. Drop in ambient oxygen pressure likely results in a decrease in muscle cells oxygenation, reactive oxygen species (ROS) overproduction and stabilization of the oxygen-sensitive hypoxia-inducible factor (HIF)-1?. However, skeletal muscle seems to be quite resistant to hypoxia compared to other organs, probably because it is accustomed to hypoxic episodes during physical exercise. Few studies have observed HIF-1? accumulation in skeletal muscle during ambient hypoxia probably because of its transient stabilization. Nevertheless, skeletal muscle presents adaptations to hypoxia that fit with HIF-1 activation, although the exact contribution of HIF-2, I kappa B kinase and activating transcription factors, all potentially activated by hypoxia, needs to be determined. Metabolic alterations result in the inhibition of fatty acid oxidation, while activation of anaerobic glycolysis is less evident. Hypoxia causes mitochondrial remodeling and enhanced mitophagy that ultimately lead to a decrease in ROS production, and this acclimatization in turn contributes to HIF-1? destabilization. Likewise, hypoxia has structural consequences with muscle fiber atrophy due to mTOR-dependent inhibition of protein synthesis and transient activation of proteolysis. The decrease in muscle fiber area improves oxygen diffusion into muscle cells, while inhibition of protein synthesis, an ATP-consuming process, and reduction in muscle mass decreases energy demand. Amino acids released from muscle cells may also have protective and metabolic effects. Collectively, these results demonstrate that skeletal muscle copes with the energetic challenge imposed by O2 rarefaction via metabolic optimization. PMID:26298291

  5. Human Skeletal Muscle Health with Spaceflight

    NASA Astrophysics Data System (ADS)

    Trappe, Scott

    2012-07-01

    This lecture will overview the most recent aerobic and resistance exercise programs used by crewmembers while aboard the International Space Station (ISS) for six months and examine its effectiveness for protecting skeletal muscle health. Detailed information on the exercise prescription program, whole muscle size, whole muscle performance, and cellular data obtained from muscle biopsy samples will be presented. Historically, detailed information on the exercise program while in space has not been available. These most recent exercise and muscle physiology findings provide a critical foundation to guide the exercise countermeasure program forward for future long-duration space missions.

  6. Adult Stem Cells and Skeletal Muscle Regeneration.

    PubMed

    Costamagna, Domiziana; Berardi, Emanuele; Ceccarelli, Gabriele; Sampaolesi, Maurilio

    2015-01-01

    Satellite cells are unipotent stem cells involved in muscle regeneration. However, the skeletal muscle microenvironment exerts a dominant influence over stem cell function. The cell intrinsic complexity of the skeletal muscle niche located within the connective tissue between fibers includes motor neurons, tendons, blood vessels, immune response mediators and interstitial cells. All these cell types modulate the trafficking of stimuli responsible of muscle fiber regeneration. In addition, several stem cell types have been discovered in skeletal muscle tissue, mainly located in the interstitium. The majority of these stem cells appears to directly contribute to myogenic differentiation, although some of them are mainly implicated in paracrine effects. This review focuses on adult stem cells, which have been used for therapeutic purposes, mainly in animal models of chronic muscle degeneration. Emerging literature identifies other myogenic progenitors generated from pluripotent stem cells as potential candidates for the treatment of skeletal muscle degeneration. However, adult stem cells still represent the gold standard for future comparative studies. PMID:26122100

  7. Gene Regions Responding to Skeletal Muscle Atrophy

    NASA Technical Reports Server (NTRS)

    Booth, Frank W.

    1997-01-01

    Our stated specific aims for this project were: 1) Identify the region(s) of the mouse IIb myosin heavy chain (MHC) promoter necessary for in vivo expression in mouse fast-twitch muscle, and 2) Identify the region(s) of the mouse IIb MHC promoter responsive to immobilization in mouse slow-twitch muscle in vivo. We sought to address these specific aims by introducing various MHC IIb promoter/reporter gene constructs directly into the tibialis anterior and gastrocnemius muscles of living mice. Although the method of somatic gene transfer into skeletal muscle by direct injection has been successfully used in our laboratory to study the regulation of the skeletal alpha actin gene in chicken skeletal muscle, we had many difficulties utilizing this procedure in the mouse. Because of the small size of the mouse soleus and the difficulty in obtaining consistent results, we elected not to study this muscle as first proposed. Rather, our MHC IIb promoter deletion experiments were performed in the gastrocnemius. Further, we decided to use hindlimb unloading via tail suspension to induce an upregulation of the MHC IIb gene, rather than immobilization of the hindlimbs via plaster casts. This change was made because tail suspension more closely mimics spaceflight, and this procedure in our lab results in a smaller loss of overall body mass than the mouse hindlimb immobilization procedure. This suggests that the stress level during tail suspension is less than during immobilization. This research has provided an important beginning point towards understanding the molecular regulation of the MHC lIb gene in response to unweighting of skeletal muscle Future work will focus on the regulation of MHC IIb mRNA stability in response to altered loading of skeletal muscle

  8. Ultrastructural Localization of Calsequestrin in Rat Skeletal Muscle by

    E-print Network

    Campbell, Kevin P.

    Ultrastructural Localization of Calsequestrin in Rat Skeletal Muscle by Immunoferritin Labeling. ABSTRACT The ultrastructural localization of calsequestrin in rat skeletal muscle (gracilis) was determined. The sarcoplasmic reticulum is the intracellular membrane system that, together with the transverse tubular system

  9. Satellite cells in human skeletal muscle plasticity

    PubMed Central

    Snijders, Tim; Nederveen, Joshua P.; McKay, Bryon R.; Joanisse, Sophie; Verdijk, Lex B.; van Loon, Luc J. C.; Parise, Gianni

    2015-01-01

    Skeletal muscle satellite cells are considered to play a crucial role in muscle fiber maintenance, repair and remodeling. Our knowledge of the role of satellite cells in muscle fiber adaptation has traditionally relied on in vitro cell and in vivo animal models. Over the past decade, a genuine effort has been made to translate these results to humans under physiological conditions. Findings from in vivo human studies suggest that satellite cells play a key role in skeletal muscle fiber repair/remodeling in response to exercise. Mounting evidence indicates that aging has a profound impact on the regulation of satellite cells in human skeletal muscle. Yet, the precise role of satellite cells in the development of muscle fiber atrophy with age remains unresolved. This review seeks to integrate recent results from in vivo human studies on satellite cell function in muscle fiber repair/remodeling in the wider context of satellite cell biology whose literature is largely based on animal and cell models. PMID:26557092

  10. Satellite cells in human skeletal muscle plasticity.

    PubMed

    Snijders, Tim; Nederveen, Joshua P; McKay, Bryon R; Joanisse, Sophie; Verdijk, Lex B; van Loon, Luc J C; Parise, Gianni

    2015-01-01

    Skeletal muscle satellite cells are considered to play a crucial role in muscle fiber maintenance, repair and remodeling. Our knowledge of the role of satellite cells in muscle fiber adaptation has traditionally relied on in vitro cell and in vivo animal models. Over the past decade, a genuine effort has been made to translate these results to humans under physiological conditions. Findings from in vivo human studies suggest that satellite cells play a key role in skeletal muscle fiber repair/remodeling in response to exercise. Mounting evidence indicates that aging has a profound impact on the regulation of satellite cells in human skeletal muscle. Yet, the precise role of satellite cells in the development of muscle fiber atrophy with age remains unresolved. This review seeks to integrate recent results from in vivo human studies on satellite cell function in muscle fiber repair/remodeling in the wider context of satellite cell biology whose literature is largely based on animal and cell models. PMID:26557092

  11. AMINO ACIDS AUGMENT MUSCLE PROTEIN SYNTHESIS IN NEONATAL PIGS DURING ENDOTOXEMIA BY MODULATING TRANSLATION INITIATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In adults, sepsis reduces protein synthesis in skeletal muscle by restraining translation. The effect of sepsis on amino acid-stimulated muscle protein synthesis has not been determined in neonates, a population who is highly anabolic and whose muscle protein synthesis rates are uniquely sensitive ...

  12. Skeletal muscle metabolism in hypokinetic rats

    NASA Technical Reports Server (NTRS)

    Tischler, M. E.

    1984-01-01

    Muscle growth, protein metabolism, and amino acid metabolism were studied in various groups of rats. Certain groups were adrenaliectomized; some rats were suspended while others (the controls) were weight bearing. Results show that: (1) metabolic changes in the extensor digitorum longus muscle of suspended rats are due primarily to increased circulating glucocorticoids; (2) metabolic changes in the soleus muscle due to higher steroid levels are probably potentiated by greater numbers of steroid receptors; and (3) not all metabolic responses of the soleus muscle to unloading are due to the elevated levels of glucocorticoids or the increased sensitivity of this muscle to these hormones.

  13. Redox Characterization of Functioning Skeletal Muscle

    PubMed Central

    Zuo, Li; Pannell, Benjamin K.

    2015-01-01

    Skeletal muscle physiology is influenced by the presence of chemically reactive molecules such as reactive oxygen species (ROS). These molecules regulate multiple redox-sensitive signaling pathways that play a critical role in cellular processes including gene expression and protein modification. While ROS have gained much attention for their harmful effects in muscle fatigue and dysfunction, research has also shown ROS to facilitate muscle adaptation after stressors such as physical exercise. This manuscript aims to provide a comprehensive review of the current understanding of redox signaling in skeletal muscle. ROS-induced oxidative stress and its role in the aging process are discussed. Mitochondria have been shown to generate large amounts of ROS during muscular contractions, and thus are susceptible to oxidative stress. ROS can modify proteins located in the mitochondrial membrane leading to cell death and osmotic swelling. ROS also contribute to the necrosis and inflammation of muscle fibers that is associated with muscular diseases including Duchenne muscular dystrophy. It is imperative that future research continues to investigate the exact role of ROS in normal skeletal muscle function as well as muscular dysfunction and disease. PMID:26635624

  14. Oxidative proteome alterations during skeletal muscle ageing

    PubMed Central

    Lourenço dos Santos, Sofia; Baraibar, Martin A.; Lundberg, Staffan; Eeg-Olofsson, Orvar; Larsson, Lars; Friguet, Bertrand

    2015-01-01

    Sarcopenia corresponds to the degenerative loss of skeletal muscle mass, quality, and strength associated with ageing and leads to a progressive impairment of mobility and quality of life. However, the cellular and molecular mechanisms involved in this process are not completely understood. A hallmark of cellular and tissular ageing is the accumulation of oxidatively modified (carbonylated) proteins, leading to a decreased quality of the cellular proteome that could directly impact on normal cellular functions. Although increased oxidative stress has been reported during skeletal muscle ageing, the oxidized protein targets, also referred as to the ‘oxi-proteome’ or ‘carbonylome’, have not been characterized yet. To better understand the mechanisms by which these damaged proteins build up and potentially affect muscle function, proteins targeted by these modifications have been identified in human rectus abdominis muscle obtained from young and old healthy donors using a bi-dimensional gel electrophoresis-based proteomic approach coupled with immunodetection of carbonylated proteins. Among evidenced protein spots, 17 were found as increased carbonylated in biopsies from old donors comparing to young counterparts. These proteins are involved in key cellular functions such as cellular morphology and transport, muscle contraction and energy metabolism. Importantly, impairment of these pathways has been described in skeletal muscle during ageing. Functional decline of these proteins due to irreversible oxidation may therefore impact directly on the above-mentioned pathways, hence contributing to the generation of the sarcopenic phenotype. PMID:26073261

  15. Dysregulation of skeletal muscle protein metabolism by alcohol.

    PubMed

    Steiner, Jennifer L; Lang, Charles H

    2015-05-01

    Alcohol abuse, either by acute intoxication or prolonged excessive consumption, leads to pathological changes in many organs and tissues including skeletal muscle. As muscle protein serves not only a contractile function but also as a metabolic reserve for amino acids, which are used to support the energy needs of other tissues, its content is tightly regulated and dynamic. This review focuses on the etiology by which alcohol perturbs skeletal muscle protein balance and thereby over time produces muscle wasting and weakness. The preponderance of data suggest that alcohol primarily impairs global protein synthesis, under basal conditions as well as in response to several anabolic stimuli including growth factors, nutrients, and muscle contraction. This inhibitory effect of alcohol is mediated, at least in part, by a reduction in mTOR kinase activity via a mechanism that remains poorly defined but likely involves altered protein-protein interactions within mTOR complex 1. Furthermore, alcohol can exacerbate the decrement in mTOR and/or muscle protein synthesis present in other catabolic states. In contrast, alcohol-induced changes in muscle protein degradation, either global or via specific modulation of the ubiquitin-proteasome or autophagy pathways, are relatively inconsistent and may be model dependent. Herein, changes produced by acute intoxication versus chronic ingestion are contrasted in relation to skeletal muscle metabolism, and limitations as well as opportunities for future research are discussed. As the proportion of more economically developed countries ages and chronic illness becomes more prevalent, a better understanding of the etiology of biomedical consequences of alcohol use disorders is warranted. PMID:25759394

  16. Nutritional regulation of mTOR signaling in skeletal muscle of neonates in vivo

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The post-prandial rise in both amino acids and insulin independently stimulate protein synthesis in the rapidly growing skeletal muscle of the neonate. Leucine, in particular, is important in mediating the response to amino acids. We have shown that a physiological rise in leucine, but not isoleuc...

  17. Tissue engineering skeletal muscle for orthopaedic applications

    NASA Technical Reports Server (NTRS)

    Payumo, Francis C.; Kim, Hyun D.; Sherling, Michael A.; Smith, Lee P.; Powell, Courtney; Wang, Xiao; Keeping, Hugh S.; Valentini, Robert F.; Vandenburgh, Herman H.

    2002-01-01

    With current technology, tissue-engineered skeletal muscle analogues (bioartificial muscles) generate too little active force to be clinically useful in orthopaedic applications. They have been engineered genetically with numerous transgenes (growth hormone, insulinlike growth factor-1, erythropoietin, vascular endothelial growth factor), and have been shown to deliver these therapeutic proteins either locally or systemically for months in vivo. Bone morphogenetic proteins belonging to the transforming growth factor-beta superfamily are osteoinductive molecules that drive the differentiation pathway of mesenchymal cells toward the chondroblastic or osteoblastic lineage, and stimulate bone formation in vivo. To determine whether skeletal muscle cells endogenously expressing bone morphogenetic proteins might serve as a vehicle for systemic bone morphogenetic protein delivery in vivo, proliferating skeletal myoblasts (C2C12) were transduced with a replication defective retrovirus containing the gene for recombinant human bone morphogenetic protein-6 (C2BMP-6). The C2BMP-6 cells constitutively expressed recombinant human bone morphogenetic protein-6 and synthesized bioactive recombinant human bone morphogenetic protein-6, based on increased alkaline phosphatase activity in coincubated mesenchymal cells. C2BMP-6 cells did not secrete soluble, bioactive recombinant human bone morphogenetic protein-6, but retained the bioactivity in the cell layer. Therefore, genetically-engineered skeletal muscle cells might serve as a platform for long-term delivery of osteoinductive bone morphogenetic proteins locally.

  18. Development of Sensory Receptors in Skeletal Muscle

    NASA Technical Reports Server (NTRS)

    DeSantis, Mark

    2000-01-01

    The two major goals for this project is to (1) examine the hindlimb walking pattern of offspring from the Flight dams as compared with offspring of the ground control groups from initiation of walking up to two months thereafter; and (2) examine skeletal muscle.

  19. Skeletal muscle fibre types in the dog.

    PubMed Central

    Latorre, R; Gil, F; Vázquez, J M; Moreno, F; Mascarello, F; Ramirez, G

    1993-01-01

    Using a variety of histochemical methods we have investigated the mATPase reaction of skeletal muscle fibres in the dog. Types I, IIA, IIDog (peculiar to the dog) and IIC fibres were identified. The results reveal that the interpretation of the fibre type composition depends on the methods used. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:8226288

  20. Amino acid residues 489-503 of dihydropyridine receptor (DHPR) ?1a subunit are critical for structural communication between the skeletal muscle DHPR complex and type 1 ryanodine receptor.

    PubMed

    Eltit, Jose M; Franzini-Armstrong, Clara; Perez, Claudio F

    2014-12-26

    The ?1a subunit is a cytoplasmic component of the dihydropyridine receptor (DHPR) complex that plays an essential role in skeletal muscle excitation-contraction (EC) coupling. Here we investigate the role of the C-terminal end of this auxiliary subunit in the functional and structural communication between the DHPR and the Ca(2+) release channel (RyR1). Progressive truncation of the ?1a C terminus showed that deletion of amino acid residues Gln(489) to Trp(503) resulted in a loss of depolarization-induced Ca(2+) release, a severe reduction of L-type Ca(2+) currents, and a lack of tetrad formation as evaluated by freeze-fracture analysis. However, deletion of this domain did not affect expression/targeting or density (Qmax) of the DHPR-?1S subunit to the plasma membrane. Within this motif, triple alanine substitution of residues Leu(496), Leu(500), and Trp(503), which are thought to mediate direct ?1a-RyR1 interactions, weakened EC coupling but did not replicate the truncated phenotype. Therefore, these data demonstrate that an amino acid segment encompassing sequence (489)QVQVLTSLRRNLSFW(503) of ?1a contains critical determinant(s) for the physical link of DHPR and RyR1, further confirming a direct correspondence between DHPR positioning and DHPR/RyR functional interactions. In addition, our data strongly suggest that the motif Leu(496)-Leu(500)-Trp(503) within the ?1a C-terminal tail plays a nonessential role in the bidirectional DHPR/RyR1 signaling that supports skeletal-type EC coupling. PMID:25384984

  1. Cellular Players in Skeletal Muscle Regeneration

    PubMed Central

    Ceafalan, Laura Cristina; Popescu, Bogdan Ovidiu; Hinescu, Mihail Eugen

    2014-01-01

    Skeletal muscle, a tissue endowed with remarkable endogenous regeneration potential, is still under focused experimental investigation mainly due to treatment potential for muscle trauma and muscular dystrophies. Resident satellite cells with stem cell features were enthusiastically described quite a long time ago, but activation of these cells is not yet controlled by any medical interventions. However, after thorough reports of their existence, survival, activation, and differentiation there are still many questions to be answered regarding the intimate mechanism of tissue regeneration. This review delivers an up-to-date inventory of the main known key players in skeletal muscle repair, revealed by various models of tissue injuries in mechanical trauma, toxic lesions, and muscular dystrophy. A better understanding of the spatial and temporal relationships between various cell populations, with different physical or paracrine interactions and phenotype changes induced by local or systemic signalling, might lead to a more efficient approach for future therapies. PMID:24779022

  2. Interactive effects of glutamine and gamma-aminobutyric acid on growth performance and skeletal muscle amino acid metabolism of 22-42-day-old broilers exposed to hot environment

    NASA Astrophysics Data System (ADS)

    Hu, Hong; Bai, Xi; Shah, Assar Ali; Dai, Sifa; Wang, Like; Hua, Jinling; Che, Chuanyan; He, Shaojun; Wen, Aiyou; Jiang, Jinpeng

    2015-10-01

    The present experiment was conducted to investigate the interactive effects between dietary glutamine (Gln, 0 and 5 g/kg) and gamma-aminobutyric acid (GABA, 0 and 100 mg/kg) on growth performance and amino acid (AA) metabolism of broilers under hot environment. A total of 360 22-day-old Arbor Acres male chickens were randomly assigned to five treatment groups under thermoneutral chamber (PC, 23 °C) and cyclic heat stress (HS, 30-34 °C cycling) conditions. Compared with the PC group, cyclic HS decreased (P < 0.05) daily weight gain (DWG), daily feed consumption (DFC), the concentrations of Gln, glutamate (Glu), and GABA, and the activities of glutaminase and glutamic acid decarboxylase (GAD) in breast muscle at 28, 35, and 42 days, while it increased (P < 0.05) the activities of glutamine synthetase (GS) and gamma-aminobutyric acid transaminase (GABA-T) at 28, 35, and 42 days. Dietary Gln and GABA improved (P < 0.05) DWG and DFC of broilers under cyclic HS during 28-42 days. In breast muscle, the Gln supplementation increased (P < 0.05) the concentrations of Gln (28, 35, and 42 days), Glu (28, 35, and 42 days), and GABA (42 days) and the activities of glutaminase (28, 35, and 42 days) and GAD (28, 35, and 42 days) but decreased (P < 0.05) GS activities at 28, 35, and 42 days and GABA-T activities at 28 days. The addition of GABA increased (P < 0.05) the concentrations of Gln and Glu and activities of glutaminase and GAD, while it decreased (P < 0.05) GABA-T activities at 28, 35, and 42 days. Significant interactions (P < 0.05) between Gln and GABA were found on breast skeletal muscle Gln concentrations, glutaminase activities, GS activities at 28 and 35 days, and DWG, GABA concentrations, and GABA-T activities at 28, 35, and 42 days in broilers under cyclic HS. In conclusion, the present results indicated that the interactions of exogenous Gln and GABA could offer a potential nutritional strategy to prevent HS-related depression in skeletal muscle Gln and GABA metabolism of broilers.

  3. Androgen Receptor Immunoreactivity in Skeletal Muscle: Enrichment at the

    E-print Network

    Breedlove, Marc

    that ARs within LA muscle fibers mediate the androgen-dependent survival and growth of the LA muscleAndrogen Receptor Immunoreactivity in Skeletal Muscle: Enrichment at the Neuromuscular Junction of androgen action within skeletal muscle of the rat were determined by comparing the cellular distribution

  4. Role of skeletal muscle in mandible development.

    PubMed

    Rot, Irena; Mardesic-Brakus, Snjezana; Costain, Willard J; Saraga-Babic, Mirna; Kablar, Boris

    2014-11-01

    As a continuation of the previous study on palate development (Rot and Kablar, 2013), here we explore the relationship between the secondary cartilage mandibular condyles (parts of the temporomandibular joint) and the contributions (mechanical and secretory) from the adjacent skeletal musculature. Previous analysis of Myf5-/-:MyoD-/- mouse fetuses lacking skeletal muscle demonstrated the importance of muscle contraction and static loading in mouse skeletogenesis. Among abnormal skeletal features, micrognathia (mandibular hypoplasia) was detected: small, bent and posteriorly displaced mandible. As an example of Waddingtonian epigenetics, we suggest that muscle, in addition to acting via mechanochemical signal transduction pathways, networks and promoters, also exerts secretory stimuli on skeleton. Our goal is to identify candidate molecules at that muscle-mandible interface. By employing Systematic Subtractive Microarray Analysis approach, we compared gene expression between mandibles of amyogenic and wild type mouse fetuses and we identified up- and down-regulated genes. This step was followed by a bioinformatics approach and consultation of web-accessible mouse databases. We searched for individual tissue-specific gene expression and distribution, and for the functional effects of mutations in a particular gene. The database search tools allowed us to generate a set of candidate genes with involvement in mandibular development: Cacna1s, Ckm, Des, Mir300, Myog and Tnnc1. We also performed mouse-to-human translational experiments and found analogies. In the light of our findings we discuss various players in mandibular morphogenesis and make an argument for the need to consider mandibular development as a consequence of reciprocal epigenetic interactions of both skeletal and non-skeletal compartments. PMID:24867377

  5. Skeletal Muscle Tissue Engineering: Methods to Form Skeletal Myotubes and Their Applications

    PubMed Central

    Ostrovidov, Serge; Hosseini, Vahid; Ahadian, Samad; Fujie, Toshinori; Parthiban, Selvakumar Prakash; Ramalingam, Murugan; Bae, Hojae; Kaji, Hirokazu

    2014-01-01

    Skeletal muscle tissue engineering (SMTE) aims to repair or regenerate defective skeletal muscle tissue lost by traumatic injury, tumor ablation, or muscular disease. However, two decades after the introduction of SMTE, the engineering of functional skeletal muscle in the laboratory still remains a great challenge, and numerous techniques for growing functional muscle tissues are constantly being developed. This article reviews the recent findings regarding the methodology and various technical aspects of SMTE, including cell alignment and differentiation. We describe the structure and organization of muscle and discuss the methods for myoblast alignment cultured in vitro. To better understand muscle formation and to enhance the engineering of skeletal muscle, we also address the molecular basics of myogenesis and discuss different methods to induce myoblast differentiation into myotubes. We then provide an overview of different coculture systems involving skeletal muscle cells, and highlight major applications of engineered skeletal muscle tissues. Finally, potential challenges and future research directions for SMTE are outlined. PMID:24320971

  6. Dietary lysine affected the expression of genes related to lipid metabolism in skeletal muscle of finishing pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It has been reported that some amino acids can function as signaling molecules to regulate skeletal muscle growth in mammals. This study was conducted to identify those genes that may be regulated by amino acid lysine and responsible for muscle growth and meat quality of pigs. Nine crossbred barrows...

  7. Development of Sensory Receptors in Skeletal Muscle

    NASA Technical Reports Server (NTRS)

    DeSantis, Mark

    2000-01-01

    There were two major goals for my project. One was to examine the hindlimb walking pattern of offspring from the Flight dams as compared with offspring of the ground control groups from initiation of walking up to two months thereafter. This initial goal was subsequently modified so that additional developmental measures were taken (e.g. body weight, eye opening) as the progeny developed, and the study period was lengthened to eighty days. Also videotapes taken shortly after the pregnant Flight dams returned to Earth were scored for locomotor activity and compared to those for the Synchronous control dams at the same stage of pregnancy. The second goal was to examine skeletal muscle. Selected hindlimb skeletal muscles were to be identified, weighed, and examined for the presence and integrity of muscle receptors, (both muscle spindles and tendon organs), at the level of the light and electron microscope. Muscles were examined from rats that were at fetal (G20), newborn (postnatal day 1 or P1, where P1 = day of birth), and young adult (approx. P100) stages. At the present time data from only the last group of rats (i.e. P100) has been completely examined.

  8. Prolonged stimulation of muscle protein synthesis by leucine in neonates is dependent on amino acid availability

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rise in amino acids and insulin after a meal independently stimulate protein synthesis in skeletal muscle of neonates by activating the intracellular signalling pathways that regulate mRNA translation. Leucine, in particular, is important in mediating the response to amino acids. Previously, w...

  9. Skeletal Muscle Basement Membrane-Sarcolemma-Cytoskeleton Interaction Minireview Series*

    E-print Network

    Campbell, Kevin P.

    Skeletal Muscle Basement Membrane-Sarcolemma-Cytoskeleton Interaction Minireview Series* Published Center, Dallas, Texas 75390 The sarcolemma (muscle plasma membrane) plays a central role in skeletal muscle structure and function (1). In addition to the housekeeping functions of a cell plasma membrane

  10. Phosphorylation of human skeletal muscle myosin

    SciTech Connect

    Houston, M.E.; Lingley, M.D.; Stuart, D.S.; Hoffman-Goetz, L.

    1986-03-01

    Phosphorylation of the P-light chains (phosphorylatable light chains) in human skeletal muscle myosin was studied in vitro and in vivo under resting an d contracted conditions. biopsy samples from rested vastus lateralis muscle of male and female subjects were incubated in oxygenated physiological solution at 30/sup 0/C. Samples frozen following a quiescent period showed the presence of only unphosphorylated P-light chains designated LC2f (light chain two of fast myosin) CL2s and LC2s'(light chains two of slow myosin). Treatment with caffeine (10 mM) or direct electrical stimulation resulted in the appearance of three additional bands which were identified as the phosphorylated forms of the P-light chains i.e. LC2f-P, LC2s-P and LC2s'-P. The presence of phosphate was confirmed by prior incubation with (/sup 30/P) orthophosphate. Muscle samples rapidly frozen from resting vastus lateralis muscle revealed the presence of unphosphorylated and phosphorylated P-light chains in approximately equal ratios. Muscle samples rapidly frozen following a maximal 10 second isometric contraction showed virtually only phosphorylated fast and slow P-light chains. These results reveal that the P-light chains in human fast and slow myosin may be rapidly phosphorylated, but the basal level of phosphorylation in rested human muscle considerably exceeds that observed in animal muscles studied in vitro or in situ.

  11. GLUT-3 expression in human skeletal muscle

    NASA Technical Reports Server (NTRS)

    Stuart, C. A.; Wen, G.; Peng, B. H.; Popov, V. L.; Hudnall, S. D.; Campbell, G. A.

    2000-01-01

    Muscle biopsy homogenates contain GLUT-3 mRNA and protein. Before these studies, it was unclear where GLUT-3 was located in muscle tissue. In situ hybridization using a midmolecule probe demonstrated GLUT-3 within all muscle fibers. Fluorescent-tagged antibody reacting with affinity-purified antibody directed at the carboxy-terminus demonstrated GLUT-3 protein in all fibers. Slow-twitch muscle fibers, identified by NADH-tetrazolium reductase staining, possessed more GLUT-3 protein than fast-twitch fibers. Electron microscopy using affinity-purified primary antibody and gold particle-tagged second antibody showed that the majority of GLUT-3 was in association with triads and transverse tubules inside the fiber. Strong GLUT-3 signals were seen in association with the few nerves that traversed muscle sections. Electron microscopic evaluation of human peripheral nerve demonstrated GLUT-3 within the axon, with many of the particles related to mitochondria. GLUT-3 protein was found in myelin but not in Schwann cells. GLUT-1 protein was not present in nerve cells, axons, myelin, or Schwann cells but was seen at the surface of the peripheral nerve in the perineurium. These studies demonstrated that GLUT-3 mRNA and protein are expressed throughout normal human skeletal muscle, but the protein is predominantly found in the triads of slow-twitch muscle fibers.

  12. Effects of regular exercise training on skeletal muscle contractile function

    NASA Technical Reports Server (NTRS)

    Fitts, Robert H.

    2003-01-01

    Skeletal muscle function is critical to movement and one's ability to perform daily tasks, such as eating and walking. One objective of this article is to review the contractile properties of fast and slow skeletal muscle and single fibers, with particular emphasis on the cellular events that control or rate limit the important mechanical properties. Another important goal of this article is to present the current understanding of how the contractile properties of limb skeletal muscle adapt to programs of regular exercise.

  13. Inferring crossbridge properties from skeletal muscle energetics.

    PubMed

    Barclay, C J; Woledge, R C; Curtin, N A

    2010-01-01

    Work is generated in muscle by myosin crossbridges during their interaction with the actin filament. The energy from which the work is produced is the free energy change of ATP hydrolysis and efficiency quantifies the fraction of the energy supplied that is converted into work. The purpose of this review is to compare the efficiency of frog skeletal muscle determined from measurements of work output and either heat production or chemical breakdown with the work produced per crossbridge cycle predicted on the basis of the mechanical responses of contracting muscle to rapid length perturbations. We review the literature to establish the likely maximum crossbridge efficiency for frog skeletal muscle (0.4) and, using this value, calculate the maximum work a crossbridge can perform in a single attachment to actin (33 x 10(-21) J). To see whether this amount of work is consistent with our understanding of crossbridge mechanics, we examine measurements of the force responses of frog muscle to fast length perturbations and, taking account of filament compliance, determine the crossbridge force-extension relationship and the velocity dependences of the fraction of crossbridges attached and average crossbridge strain. These data are used in combination with a Huxley-Simmons-type model of the thermodynamics of the attached crossbridge to determine whether this type of model can adequately account for the observed muscle efficiency. Although it is apparent that there are still deficiencies in our understanding of how to accurately model some aspects of ensemble crossbridge behaviour, this comparison shows that crossbridge energetics are consistent with known crossbridge properties. PMID:19836411

  14. The abundance and activation of mTORC1 regulators in skeletal muscle of neonatal pigs are modulated by insulin, amino acids, and age

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previously we demonstrated that the insulin (INS) and amino acid (AA) -induced activation of the mammalian target of rapamycin complex 1 (mTORC1) is developmentally regulated in neonatal pigs. This study aimed to determine the effects of the post-prandial rise in INS and AA on the activation and abu...

  15. Abundance of amino acid transporters involved in mTORC1 activation in skeletal muscle of neonatal pigs is developmentally regulated

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previously we demonstrated that the insulinand amino acid-induced activation of the mammalian target of rapamycin complex 1 (mTORC1) is developmentally regulated in neonatal pigs. Recent studies have indicated that members of the System A transporter (SNAT2), the System N transporter (SNAT3), the Sy...

  16. Skeletal muscle biomechanics drives intramuscular transport of locally delivered drugs

    E-print Network

    Wu, Peter I-Kung

    2007-01-01

    Introduction: Effective local drug delivery to contractile tissues such as skeletal muscle requires a thorough understanding of the impact of mechanical loads on intramuscular pharmacokinetics. Current preparations for ...

  17. Amino acids augment muscle protein synthesis in neonatal pigs during acute endotoxemia by stimulating mTOR-dependent translation initiation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In skeletal muscle of adults, sepsis reduces protein synthesis by depressing translation initiation and induces resistance to branched-chain amino acid stimulation. Normal neonates maintain a high basal muscle protein synthesis rate that is sensitive to amino acid stimulation. In the present study...

  18. Modeling of the Skeletal Muscle Microcirculation

    NASA Astrophysics Data System (ADS)

    Jacobitz, Frank; Beth, Christophe; Salado, Jerome

    2004-11-01

    Numerical simulations of blood flow in a microvascular network require extensive modeling. This contribution focuses on the reconstruction of a complete network topology from microscopic images of rat skeletal muscle and skeletal muscle fascia. The bifurcating network is composed of a feeding arterial network, a collecting venous network, and bundles of capillaries. Multiple topologies of each network component are recontructed and statistical properties of the network, such as distributions of vessel diameters, vessel lengths, and branching patters are determined. Particular attention has been paid to venous vessel loops that are observed only in the muscle fascia. The flow in the microvessel network is then computed. In the simulations, the microvessels are distensible by pressure, and the arterioles are actively contractile. The blood has non-Newtonian apparent viscosity. Models of each of these properties have previously been determined and are used in the computations. The method of indefinite admittances is used to compute the flow in the network. The apparent viscosity is computed from the local hematocrit, which is found using a combination of breadth first search and Dykstra's algorithms. The computations allow the determination of additional properties of the network, such as flow velocities, shear stresses, and hematocrit.

  19. Osmoregulatory processes and skeletal muscle metabolism

    NASA Astrophysics Data System (ADS)

    Boschmann, Michael; Gottschalk, Simone; Adams, Frauke; Luft, Friedrich C.; Jordan, Jens

    Prolonged microgravity during space flight is associated with a decrease in blood and extracellular volume. These changes in water and electrolyte balance might activate catabolic processes which contribute finally to the loss of muscle and bone mass and strength. Recently, we found a prompt increase that energy expenditure by about 30% in both normal and overweight men and women after drinking 500 ml water. This effect is mediated by an increased sympathetic nervous system activity, obviously secondary to stimulation of osmosensitive afferent neurons in the liver, and skeletal muscle is possibly one effector organ. Therefore, we tested the hypothesis that this thermogenic response to water is accompanied by a stimulation of aerobic glucose metabolism in skeletal muscle. To this end, 16 young healthy volunteers (8 men) were studied. After an overnight fast (12h), a microdialysis probe was implanted into the right M. quadriceps femoris vastus lateralis and subsequently perfused with Ringer's solution (+50 mM ethanol). After 1h, volunteers were asked to drink 500 ml water (22° C) followed by continuing microdialysis for another 90 min. Dialysates (15 min fractions) were analyzed for [ethanol], [glucose], [lactate], [pyruvate], and [glycerol] in order to assess changes in muscle tissue perfusion (ethanol dilution technique), glycolysis and lipolysis. Blood samples were taken and heart rate (HR) and blood pressure (BP) were monitored. Neither HR and systolic and diastolic BP, nor plasma [glucose], [lactate], [insulin], and [C peptide] changed significantly after water drinking. Also, tissue perfusion and dialysate [glucose] did not change significantly. However, dialysate [lactate] increased by about 10 and 20% and dialysate [pyruvate] by about 100 and 200% in men and women, respectively. In contrast, dialysate [glycerol] decreased by about 30 and 20% in men and women, respectively. Therefore, drinking of 500 ml water stimulates aerobic glucose metabolism and inhibits lipolysis in skeletal muscle and this to a greater extent in women than men. These insulin-like effects after water drinking originate possibly from regulatory cell volume swelling in osmosensitive organs such as muscle. Therefore, a well-balanced water homeostasis might be important for preventing catabolic processes during long-term space expeditions.

  20. Optical anisotropy characteristics of skeletal muscle tissues

    NASA Astrophysics Data System (ADS)

    Sun, Chia-Wei; Yang, Chih Chung; Kiang, Yean-Woei

    2002-06-01

    To explore the polarization-dependent optical properties of skeletal muscle tissues, we calibrated the extinction coefficients of the polarization components parallel with and perpendicular to chicken breast tissue filaments and the cross-polarized intensity coupling coefficients between the two polarization components, based on the measured quasi- coherent photons. The calibrated values of these coefficients were quite consistent with previously reported. The extinction coefficient in the polarization along tissue filaments was significantly higher than that of the other polarization. Also, the cross-polarized coupling coefficient of the coupling from the polarization of tissue filaments into the other was stronger than that of inverse coupling.

  1. Structure-function relationship of skeletal muscle provides inspiration for design of new artificial muscle

    NASA Astrophysics Data System (ADS)

    Gao, Yingxin; Zhang, Chi

    2015-03-01

    A variety of actuator technologies have been developed to mimic biological skeletal muscle that generates force in a controlled manner. Force generation process of skeletal muscle involves complicated biophysical and biochemical mechanisms; therefore, it is impossible to replace biological muscle. In biological skeletal muscle tissue, the force generation of a muscle depends not only on the force generation capacity of the muscle fiber, but also on many other important factors, including muscle fiber type, motor unit recruitment, architecture, structure and morphology of skeletal muscle, all of which have significant impact on the force generation of the whole muscle or force transmission from muscle fibers to the tendon. Such factors have often been overlooked, but can be incorporated in artificial muscle design, especially with the discovery of new smart materials and the development of innovative fabrication and manufacturing technologies. A better understanding of the physiology and structure-function relationship of skeletal muscle will therefore benefit the artificial muscle design. In this paper, factors that affect muscle force generation are reviewed. Mathematical models used to model the structure-function relationship of skeletal muscle are reviewed and discussed. We hope the review will provide inspiration for the design of a new generation of artificial muscle by incorporating the structure-function relationship of skeletal muscle into the design of artificial muscle.

  2. Measurement of insulin sensitivity in skeletal muscle in vitro.

    PubMed

    Sell, Henrike; Jensen, Jørgen; Eckel, Juergen

    2012-01-01

    Glucose disposal in skeletal muscle is a major target for insulin action and assessment of insulin-regulated glucose uptake under in vitro conditions allows the direct determination of insulin sensitivity in this organ. For this purpose, a variety of muscle preparations from different parts of the body can be used. We describe here a detailed protocol for using epitrochlearis muscle strips and additionally for using primary skeletal muscle cells. PMID:22893412

  3. Skeletal muscle responses to unloading in humans

    NASA Technical Reports Server (NTRS)

    Dudley, G.; Tesch, P.; Hather, B.; Adams, G.; Buchanan, P.

    1992-01-01

    This study examined the effects of unloading on skeletal muscle structure. Method: Eight subjects walked on crutches for six weeks with a 110 cm elevated sole on the right shoe. This removed weight bearing by the left lower limb. Magnetic resonance imaging of both lower limbs and biopsies of the left m. vastus laterallis (VL) were used to study muscle structure. Results: Unloading decreased (P less than 0.05) muscle cross-sectional areas (CSA) of the knee extensors 16 percent. The knee flexors showed about 1/2 of this response (-7 percent, P less than 0.05). The three vasti muscles each showed decreases (P less than 0.05) of about 15 percent. M. rectus femoris did not change. Mean fiber CSA in VL decreased (P less than 0.05) 14 percent with type 2 and type 1 fibers showing reductions of 15 and 11 percent respectively. The ankle extensors showed a 20 percent decrease (P less than 0.05) in CSA. The reduction for the 'fast' m. gastrocnemius was 27 percent compared to the 18 percent decrease for the 'slow' soleus. Summary: The results suggest that decreases in muscle CSA are determined by the relative change in impact loading history because atrophy was (1) greater in extensor than flexor muscles, (2) at least as great in fast as compared to slow muscles or fibers, and (3) not dependent on single or multi-joint function. They also suggest that the atrophic responses to unloading reported for lower mammals are quantitatively but not qualitatively similar to those of humans.

  4. Molecular mechanisms of skeletal muscle development, regeneration, and osteogenic conversion.

    PubMed

    Endo, Takeshi

    2015-11-01

    Both skeletal muscle and bone are of mesodermal origin and derived from somites during embryonic development. Somites differentiate into the dorsal dermomyotome and the ventral sclerotome, which give rise to skeletal muscle and bone, respectively. Extracellular signaling molecules, such as Wnt and Shh, secreted from the surrounding environment, determine the developmental fate of skeletal muscle. Dermomyotome cells are specified as trunk muscle progenitor cells by transcription factor networks involving Pax3. These progenitor cells delaminate and migrate to form the myotome, where they are determined as myoblasts that differentiate into myotubes or myofibers. The MyoD family of transcription factors plays pivotal roles in myogenic determination and differentiation. Adult skeletal muscle regenerates upon exercise, muscle injury, or degeneration. Satellite cells are muscle-resident stem cells and play essential roles in muscle growth and regeneration. Muscle regeneration recapitulates the process of muscle development in many aspects. In certain muscle diseases, ectopic calcification or heterotopic ossification, as well as fibrosis and adipogenesis, occurs in skeletal muscle. Muscle-resident mesenchymal progenitor cells, which may be derived from vascular endothelial cells, are responsible for the ectopic osteogenesis, fibrogenesis, and adipogenesis. The small GTPase M-Ras is likely to participate in the ectopic calcification and ossification, as well as in osteogenesis during development. This article is part of a Special Issue entitled "Muscle Bone Interactions". PMID:26453493

  5. Three-dimensionally printed biological machines powered by skeletal muscle

    E-print Network

    Bashir, Rashid

    muscle was characterized. Electrical stimulation triggered contraction of cells in the muscle strip of electrical signals and synchro- nous contraction of engineered muscle (14). This advantageous property hasThree-dimensionally printed biological machines powered by skeletal muscle Caroline Cvetkovica,b,1

  6. 3D Structure of the Skeletal Muscle Dihydropyridine Receptor

    E-print Network

    Dolphin, Annette C.

    , in response to changes in membrane poten- tial. In excitable cells such as neurons, heart and skeletal muscle such as secretion, neurotrans- mitter release, and muscle contraction.1 One group of drugs binding to these calcium of muscle excitation­contraction (E­C) coupling.3 However, as yet the exact mecha- nism of muscle E

  7. Growth factor involvement in tension-induced skeletal muscle growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman W.

    1987-01-01

    New muscle tissue culture techniques were developed to grow embryonic skeletal myofibers which are able to differentiate into more adultlike myofibers. Studies on mechanical simulation of cultured muscle cell growth will now be more directly applicable to mechanically-induced growth in adult muscle, and lead to better models for understanding muscle tissue atrophy caused by disuse in the microgravity of space.

  8. Skeletal muscle stem cells from animals I. Basic cell biology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Skeletal muscle stem cells from food-producing animals have been of interest to agricultural life scientists seeking to develop a better understanding of the molecular regulation of lean tissue (skeletal muscle protein hypertrophy) and intramuscular fat (marbling) development. Enhanced understanding...

  9. Satellite cell proliferation in adult skeletal muscle

    NASA Technical Reports Server (NTRS)

    Booth, Frank W. (Inventor); Thomason, Donald B. (Inventor); Morrison, Paul R. (Inventor); Stancel, George M. (Inventor)

    1995-01-01

    Novel methods of retroviral-mediated gene transfer for the in vivo corporation and stable expression of eukaryotic or prokaryotic foreign genes in tissues of living animals is described. More specifically, methods of incorporating foreign genes into mitotically active cells are disclosed. The constitutive and stable expression of E. coli .beta.-galactosidase gene under the promoter control of the Moloney murine leukemia virus long terminal repeat is employed as a particularly preferred embodiment, by way of example, establishes the model upon which the incorporation of a foreign gene into a mitotically-active living eukaryotic tissue is based. Use of the described methods in therapeutic treatments for genetic diseases, such as those muscular degenerative diseases, is also presented. In muscle tissue, the described processes result in genetically-altered satellite cells which proliferate daughter myoblasts which preferentially fuse to form a single undamaged muscle fiber replacing damaged muscle tissue in a treated animal. The retroviral vector, by way of example, includes a dystrophin gene construct for use in treating muscular dystrophy. The present invention also comprises an experimental model utilizable in the study of the physiological regulation of skeletal muscle gene expression in intact animals.

  10. Motor force homeostasis in skeletal muscle contraction.

    PubMed

    Chen, Bin; Gao, Huajian

    2011-07-20

    In active biological contractile processes such as skeletal muscle contraction, cellular mitosis, and neuronal growth, an interesting common observation is that multiple motors can perform coordinated and synchronous actions, whereas individual myosin motors appear to randomly attach to and detach from actin filaments. Recent experiment has demonstrated that, during skeletal muscle shortening at a wide range of velocities, individual myosin motors maintain a force of ~6 pN during a working stroke. To understand how such force-homeostasis can be so precisely regulated in an apparently chaotic system, here we develop a molecular model within a coupled stochastic-elastic theoretical framework. The model reveals that the unique force-stretch relation of myosin motor and the stochastic behavior of actin-myosin binding cause the average number of working motors to increase in linear proportion to the filament load, so that the force on each working motor is regulated at ~6 pN, in excellent agreement with experiment. This study suggests that it might be a general principle to use catch bonds together with a force-stretch relation similar to that of myosin motors to regulate force homeostasis in many biological processes. PMID:21767492

  11. Omega-3 Fatty Acids and Skeletal Muscle Health.

    PubMed

    Jeromson, Stewart; Gallagher, Iain J; Galloway, Stuart D R; Hamilton, D Lee

    2015-01-01

    Skeletal muscle is a plastic tissue capable of adapting and mal-adapting to physical activity and diet. The response of skeletal muscle to adaptive stimuli, such as exercise, can be modified by the prior nutritional status of the muscle. The influence of nutrition on skeletal muscle has the potential to substantially impact physical function and whole body metabolism. Animal and cell based models show that omega-3 fatty acids, in particular those of marine origin, can influence skeletal muscle metabolism. Furthermore, recent human studies demonstrate that omega-3 fatty acids of marine origin can influence the exercise and nutritional response of skeletal muscle. These studies show that the prior omega-3 status influences not only the metabolic response of muscle to nutrition, but also the functional response to a period of exercise training. Omega-3 fatty acids of marine origin therefore have the potential to alter the trajectory of a number of human diseases including the physical decline associated with aging. We explore the potential molecular mechanisms by which omega-3 fatty acids may act in skeletal muscle, considering the n-3/n-6 ratio, inflammation and lipidomic remodelling as possible mechanisms of action. Finally, we suggest some avenues for further research to clarify how omega-3 fatty acids may be exerting their biological action in skeletal muscle. PMID:26610527

  12. Omega-3 Fatty Acids and Skeletal Muscle Health

    PubMed Central

    Jeromson, Stewart; Gallagher, Iain J.; Galloway, Stuart D. R.; Hamilton, D. Lee

    2015-01-01

    Skeletal muscle is a plastic tissue capable of adapting and mal-adapting to physical activity and diet. The response of skeletal muscle to adaptive stimuli, such as exercise, can be modified by the prior nutritional status of the muscle. The influence of nutrition on skeletal muscle has the potential to substantially impact physical function and whole body metabolism. Animal and cell based models show that omega-3 fatty acids, in particular those of marine origin, can influence skeletal muscle metabolism. Furthermore, recent human studies demonstrate that omega-3 fatty acids of marine origin can influence the exercise and nutritional response of skeletal muscle. These studies show that the prior omega-3 status influences not only the metabolic response of muscle to nutrition, but also the functional response to a period of exercise training. Omega-3 fatty acids of marine origin therefore have the potential to alter the trajectory of a number of human diseases including the physical decline associated with aging. We explore the potential molecular mechanisms by which omega-3 fatty acids may act in skeletal muscle, considering the n-3/n-6 ratio, inflammation and lipidomic remodelling as possible mechanisms of action. Finally, we suggest some avenues for further research to clarify how omega-3 fatty acids may be exerting their biological action in skeletal muscle. PMID:26610527

  13. Growth factor involvement in tension-induced skeletal muscle growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, H. H.

    1987-01-01

    Muscle tissue culture techniques were developed to grow skeletal myofibers which differentiate into more adult-like myofibers. Mechanical simulation studies of these muscle cells in a newly developed mechanical cell simulator can now be performed to study growth processes in skeletal muscle. Conditions in the mechanical cell simulator were defined where mechanical activity can either prevent muscle wasting or stimulate muscle growth. The role of endogenous and exogenous growth factors in tension-induced muscle growth is being investigated under the defined conditions of tissue culture.

  14. Strategies for functional bioscaffold-based skeletal muscle reconstruction

    PubMed Central

    Sicari, Brian M.; Dziki, Jenna L.

    2015-01-01

    Tissue engineering and regenerative medicine-based strategies for the reconstruction of functional skeletal muscle tissue have included cellular and acellular approaches. The use of acellular biologic scaffold material as a treatment for volumetric muscle loss (VML) in five patients has recently been reported with a generally favorable outcome. Further studies are necessary for a better understanding of the mechanism(s) behind acellular bioscaffold-mediated skeletal muscle repair, and for combination cell-based/bioscaffold based approaches. The present overview highlights the current thinking on bioscaffold-based remodeling including the associated mechanisms and the future of scaffold-based skeletal muscle reconstruction. PMID:26605302

  15. Physiology and Metabolism of Tissue Engineered Skeletal Muscle

    PubMed Central

    Cheng, Cindy S.; Davis, Brittany N.J.; Madden, Lauran; Bursac, Nenad; Truskey, George A.

    2014-01-01

    Skeletal muscle is a major target for tissue engineering, given its relative size in the body, fraction of cardiac output that passes through muscle beds, as well as its key role in energy metabolism and diabetes, and the need for therapies for muscle diseases such as muscular dystrophy and sarcopenia. To date, most studies with tissue-engineered skeletal muscle have utilized murine and rat cell sources. On the other hand, successful engineering of functional human muscle would enable different applications including improved methods for preclinical testing of drugs and therapies. Some of the requirements for engineering functional skeletal muscle include expression of adult forms of muscle proteins, comparable contractile forces to those produced by native muscle, and physiological force-length and force-frequency relations. This review discusses the various strategies and challenges associated with these requirements, specific applications with cultured human myoblasts, and future directions. PMID:24912506

  16. The activation of nutrient signaling components leading to mRNA translation in skeletal muscle of neonatal pigs is developmentally regulated

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Insulin and amino acids (AA) can act independently to stimulate skeletal muscle protein synthesis in neonatal pigs. To elucidate the role of development in the AA-induced activation of nutrient signaling components leading to translation in skeletal muscle, a balanced AA mixture was infused into fa...

  17. The activation of insulin signaling components leading to mRNA translation in skeletal muscle of neonatal pigs is developmentally regulated

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Insulin and amino acids can act independently to stimulate skeletal muscle protein synthesis in neonatal pigs. The purpose of this study was to elucidate the developmental regulation of the activation of signaling components leading to protein synthesis in skeletal muscle that is induced by insulin...

  18. Glucose stimulates protein synthesis in skeletal muscle of neonatal pigs through an AMPK- and mTOR-independent process

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Skeletal muscle protein synthesis is elevated in neonates in part due to an enhanced response to the rise in insulin and amino acids after eating. In vitro studies suggest that glucose plays a role in protein synthesis regulation. To determine whether glucose, independently of insulin and amino acid...

  19. Skeletal muscle metabolism in hypokinetic rats

    NASA Technical Reports Server (NTRS)

    Tischler, Marc E.

    1993-01-01

    This grant focused on the mechanisms of metabolic changes associated with unweighting atrophy and reduced growth of hind limb muscles of juvenile rats. Metabolic studies included a number of different areas. Amino acid metabolic studies placed particular emphasis on glutamine and branched-chain amino acid metabolism. These studies were an outgrowth of understanding stress effects and the role of glucocorticoids in these animals. Investigations on protein metabolism were largely concerned with selective loss of myofibrillar proteins and the role of muscle proteolysis. These investigations lead to finding important differences from denervation and atrophy and to define the roles of cytosolic versus lysosomal proteolysis in these atrophy models. A major outgrowth of these studies was demonstrating an ability to prevent atrophy of the unweighted muscle for at least 24 hours. A large amount of work concentrated on carbohydrate metabolism and its regulation by insulin and catecholamines. Measurements focused on glucose transport, glycogen metabolism, and glucose oxidation. The grant was used to develop an important new in situ approach for studying protein metabolism, glucose transport, and hormonal effects which involves intramuscular injection of various agents for up to 24 hours. Another important consequence of this project was the development and flight of Physiological-Anatomical Rodent Experiment-1 (PARE-1), which was launched aboard Space Shuttle Discovery in September 1991. Detailed descriptions of these studies can be found in the 30 peer-reviewed publications, 15 non-reviewed publications, 4 reviews and 33 abstracts (total 82 publications) which were or are scheduled to be published as a result of this project. A listing of these publications grouped by area (i.e. amino acid metabolism, protein metabolism, carbohydrate metabolism, and space flight studies) are included.

  20. Leucine stimulates protein synthesis in skeletal muscle of neonatal pigs by enhancing mTORC1 activation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Skeletal muscle in the neonate grows at a rapid rate due in part to an enhanced sensitivity to the postprandial rise in amino acids, particularly leucine. To elucidate the molecular mechanism by which leucine stimulates protein synthesis in neonatal muscle, overnight-fasted 7-day-old piglets were tr...

  1. Rapamycin blocks leucine-induced protein synthesis by suppressing mTORC1 activation in skeletal muscle of neonatal pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Skeletal muscle in the neonate grows at a rapid rate due in part to an enhanced sensitivity to the postprandial rise in amino acids, particularly leucine (Leu). To elucidate the molecular mechanism by which Leu stimulates protein synthesis in neonatal muscle, overnight fasted 7-day-old piglets were...

  2. Tissue Triage and Freezing for Models of Skeletal Muscle Disease

    PubMed Central

    Meng, Hui; Janssen, Paul M.L.; Grange, Robert W.; Yang, Lin; Beggs, Alan H.; Swanson, Lindsay C.; Cossette, Stacy A.; Frase, Alison; Childers, Martin K.; Granzier, Henk; Gussoni, Emanuela; Lawlor, Michael W.

    2014-01-01

    Skeletal muscle is a unique tissue because of its structure and function, which requires specific protocols for tissue collection to obtain optimal results from functional, cellular, molecular, and pathological evaluations. Due to the subtlety of some pathological abnormalities seen in congenital muscle disorders and the potential for fixation to interfere with the recognition of these features, pathological evaluation of frozen muscle is preferable to fixed muscle when evaluating skeletal muscle for congenital muscle disease. Additionally, the potential to produce severe freezing artifacts in muscle requires specific precautions when freezing skeletal muscle for histological examination that are not commonly used when freezing other tissues. This manuscript describes a protocol for rapid freezing of skeletal muscle using isopentane (2-methylbutane) cooled with liquid nitrogen to preserve optimal skeletal muscle morphology. This procedure is also effective for freezing tissue intended for genetic or protein expression studies. Furthermore, we have integrated our freezing protocol into a broader procedure that also describes preferred methods for the short term triage of tissue for (1) single fiber functional studies and (2) myoblast cell culture, with a focus on the minimum effort necessary to collect tissue and transport it to specialized research or reference labs to complete these studies. Overall, this manuscript provides an outline of how fresh tissue can be effectively distributed for a variety of phenotypic studies and thereby provides standard operating procedures (SOPs) for pathological studies related to congenital muscle disease. PMID:25078247

  3. Microfluidic devices for construction of contractile skeletal muscle microtissues.

    PubMed

    Shimizu, Kazunori; Araki, Hiroyuki; Sakata, Kohei; Tonomura, Wataru; Hashida, Mitsuru; Konishi, Satoshi

    2015-02-01

    Cell-culture microchips mimicking tissue/organ-specific functions are required as alternatives to animal testing for drug discovery and disease models. Although three-dimensional (3D) cell culture microfluidic devices can create more biologically relevant cellular microenvironments and higher throughput analysis platforms of cell behavior than conventional techniques, devices for skeletal muscle cells have not been developed. In the present study, we aimed to develop microfluidic devices for 3D cultures of skeletal muscle cells. Skeletal muscle cells mixed with a collagen type-I solution was introduced into the microchannel for cells (MC-C) and was gelated. Then, the medium was introduced into the microchannel for medium (MC-M). During this process, connecting microchannels (Con-MCs) prevented leakage of the collagen solution mixed with cells from MC-C to MC-M and supplied the nutrients from the medium in MC-M to the cells in MC-C. Skeletal muscle microtissues cultured in the microchannel for a week consisted of myotubes were confirmed by histological analysis and immunofluorescence staining. The skeletal muscle microtissues in the microchannel contracted in response to externally applied electrical stimulation (1 and 50 Hz). These results indicate that the functional skeletal muscle microtissues were constructed in the microchannel. Thus, the microfluidic device for culturing 3D skeletal muscle microtissues presented in this study has a potential to be used for drug discovery and toxicological tests. PMID:25085533

  4. Skeletal Muscle Stem Cells from Animals I. Basic Cell Biology

    PubMed Central

    Dodson, Michael V.; Hausman, Gary J.; Guan, LeLuo; Du, Min; Rasmussen, Theodore P.; Poulos, Sylvia P.; Mir, Priya; Bergen, Werner G.; Fernyhough, Melinda E.; McFarland, Douglas C.; Rhoads, Robert P.; Soret, Beatrice; Reecy, James M.; Velleman, Sandra G.; Jiang, Zhihua

    2010-01-01

    Skeletal muscle stem cells from food-producing animals are of interest to agricultural life scientists seeking to develop a better understanding of the molecular regulation of lean tissue (skeletal muscle protein hypertrophy) and intramuscular fat (marbling) development. Enhanced understanding of muscle stem cell biology and function is essential for developing technologies and strategies to augment the metabolic efficiency and muscle hypertrophy of growing animals potentially leading to greater efficiency and reduced environmental impacts of animal production, while concomitantly improving product uniformity and consumer acceptance and enjoyment of muscle foods. PMID:20827399

  5. Skeletal muscle stem cells from animals I. Basic cell biology.

    PubMed

    Dodson, Michael V; Hausman, Gary J; Guan, Leluo; Du, Min; Rasmussen, Theodore P; Poulos, Sylvia P; Mir, Priya; Bergen, Werner G; Fernyhough, Melinda E; McFarland, Douglas C; Rhoads, Robert P; Soret, Beatrice; Reecy, James M; Velleman, Sandra G; Jiang, Zhihua

    2010-01-01

    Skeletal muscle stem cells from food-producing animals are of interest to agricultural life scientists seeking to develop a better understanding of the molecular regulation of lean tissue (skeletal muscle protein hypertrophy) and intramuscular fat (marbling) development. Enhanced understanding of muscle stem cell biology and function is essential for developing technologies and strategies to augment the metabolic efficiency and muscle hypertrophy of growing animals potentially leading to greater efficiency and reduced environmental impacts of animal production, while concomitantly improving product uniformity and consumer acceptance and enjoyment of muscle foods. PMID:20827399

  6. Lifting the nebula: novel insights into skeletal muscle contractility.

    PubMed

    Ottenheijm, Coen A C; Granzier, Henk

    2010-10-01

    Nebulin is a giant protein and a constituent of the skeletal muscle sarcomere. The name of this protein refers to its unknown (i.e., nebulous) function. However, recent rapid advances reveal that nebulin plays important roles in the regulation of muscle contraction. When these functions of nebulin are compromised, muscle weakness ensues, as is the case in patients with nemaline myopathy. PMID:20940435

  7. Postnatal ontogeny of skeletal muscle protein synthesis in pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The neonatal period is characterized by rapid growth and elevated rates of synthesis and accretion of skeletal muscle proteins. The fractional rate of muscle protein synthesis is very high at birth and declines rapidly with age. The elevated capacity for muscle protein synthesis in the neonatal pig ...

  8. INTRODUCTION In mammalian skeletal muscle, increases in exercise intensity are

    E-print Network

    Saltzman, Wendy

    238 INTRODUCTION In mammalian skeletal muscle, increases in exercise intensity are sustained, including increased rates of glucose transport into muscle cells, increased activation of pyruvate dehydrogenase (PDH) and an enhanced recruitment of type 2B muscle fibers, partially mediated by increased

  9. Molecular events in skeletal muscle during disuse atrophy

    NASA Technical Reports Server (NTRS)

    Kandarian, Susan C.; Stevenson, Eric J.

    2002-01-01

    This review summarizes the current knowledge of the molecular processes underlying skeletal muscle atrophy due to disuse. Because the processes involved with muscle wasting due to illness are similar to disuse, this literature is used for comparison. Areas that are ripe for further study and that will advance our understanding of muscle atrophy are suggested.

  10. Long-term leucine induced stimulation of muscle protein synthesis is amino acid dependent

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Infusing leucine for 1 h increases skeletal muscle protein synthesis in the neonate, but this is not sustained for 2 h unless the corresponding fall in amino acids is prevented. This study aimed to determine whether a continuous leucine infusion can stimulate protein synthesis for a prolonged period...

  11. Purification of Progenitors from Skeletal Muscle

    PubMed Central

    Yi, Lin; Rossi, Fabio

    2011-01-01

    Skeletal muscle contains multiple progenitor populations of distinct embryonic origins and developmental potential. Myogenic progenitors, usually residing in a "satellite cell position" between the myofiber plasma membrane and the laminin-rich basement membrane that ensheaths it, are self-renewing cells that are solely committed to the myogenic lineage1,2. We have recently described a second class of vessel associated progenitors that can generate myofibroblasts and white adipocytes, which responds to damage by efficiently entering proliferation and provides trophic support to myogenic cells during tissue regeneration3,4. One of the most trusted assays to determine the developmental and regenerative potential of a given cell population relies on their isolation and transplantation5-7. To this end we have optimized protocols for their purification by flow cytometry from enzymatically dissociated muscle, which we will outline in this article. The populations obtained using this method will contain either myogenic or fibro/adipogenic colony forming cells: no other cell types are capable of expanding in vitro or surviving in vivo delivery. However, when these populations are used immediately after the sort for molecular analysis (e.g qRT-PCR) one must keep in mind that the freshly sorted subsets may contain other contaminant cells that lack the ability of forming colonies or engrafting recipients. PMID:21445045

  12. Leucine degradation in cell-free extracts of skeletal muscle.

    PubMed Central

    Odessey, R; Goldberg, A L

    1979-01-01

    Since skeletal muscle is the major site in the body for oxidation of leucine, isoleucine and valine, the pathway and control of leucine oxidation were investigated in cell-free preparations of rat muscle. Leucine was found to be transaminated to 4-methyl-2-oxopentanoate, which was then oxidatively decarboxylated. On differential centrifugation 70--80% of the transaminase activity was recovered in the soluble fraction of the cell, and the remaining amount in the mitochondrial fraction. The transaminase, from both fractions had similar pH optima and both were markedly inhibited by Ca2+. Thus changes in cellular Ca2+ concentration may regulate transaminase activity. Both transaminases had a much higher affinity for 2-oxoglutarate than for pyruvate. Therefore the utilization of amino groups from leucine for the biosynthesis of alanine in muscle [Odessey, Khairallah & Goldberg (1974) J. Biol. Chem. 249, 7623--7629] in vivo involves transamination with 2-oxoglutarate to produce glutamate, which is then transaminated with pyruvate to produce alanine. The dehydrogenase activity assayed by the decarboxylation of methyl-2-oxo[1-14C]pentanoate was localized exclusively in the fraction containing mitochondria and required NAD+, CoA and thiamin pyrophosphate for optimal activity. Measurements of competitive inhibition suggested that the oxo acids of leucine, isoleucine and valine are all decarboxylated by the same enzyme. The enzyme activity was decreased by 90% upon freezing or sonication and was stimulated severalfold by Mg2+, K+ and phosphate ions. In addition, it was markedly inhibited by ATP, but not by non-metabolizable analogues. This observation suggests that splitting of ATP is required for inhibition. The oxidative decarboxylation of 4-methyl-2-oxopentanoate by the dehydrogenase appears to be the rate-limiting step for leucine oxidation in muscle homogenates and also in intact tissues. In fact, rat muscles incubated with [1-14C]leucine release 1-14C-labelled oxo acid into the medium at rates comparable with the rate of decarboxylation. Intact muscles also released the oxo acids of [1-14C]valine or [1-14C]isoleucine, but not of other amino acids. These findings suggest that muscle is the primary source of the branched-chain oxo acids found in the blood. PMID:444223

  13. Heparan sulfate in skeletal muscle development

    SciTech Connect

    Noonan, D.M.

    1985-01-01

    In this study, chick breast skeletal muscle cells developing in vitro from myoblasts to myotubes were found to synthesize heparan sulfate (HS), chrondroitin-6-sulfate, chrondroitin-4-sulfate, dermatan sulfate, unsulfated chrondroitin and hyaluronic acid in both the substratum attached material (SAM) and the cellular fraction. SAM was found to contain predominantly chrondroitin-6-sulfate and relatively little HS whereas the cellular fraction contained relatively higher levels of HS and lower levels of chrondroitin-6-sulfate. Hyaluronic acid was also a major component in both fractions with the other glycosaminoglycan isomers present as minor components. Muscle derived fibroblast cultures had higher levels of dermatan sulfate in the cell layer and higher levels of HS in the SAM fraction than did muscle cultures. The structure of the proteoglycans were partially characterized in /sup 35/SO/sub 4//sup 2 -/ radio-labeled cultures which indicated an apparent increase in the hydrodynamic size of the cell fraction heparan sulfate proteoglycan (HS PG). Myotubes incorporated /sup 35/SO/sub 4//sup 2 -/ into HS PG at a rate 3 times higher than myoblasts. The turnover rate of HS in the cellular fraction was the same for myoblasts and myotubes, with a t/sub 1/2/ of approximately 5 hours. Fibroblasts in culture synthesized the smallest HS PG, and incorporated /sup 35/SO/sub 4//sup 2 -/ into HS PG at a rate lower than that of myotubes. Studies in which fusion was reversibly inhibited with decreased medium (Ca/sup + +/) closely linked the increased synthesis of cell fraction, but not SAM fraction, HS with myotube formation. However, decreasing medium calcium appeared to cause significant alterations in the metabolism of inorganic sulfate.

  14. Migration of Dendritic Cells from Murine Skeletal Muscle

    PubMed Central

    Wang, Lei; Eghtesad, Saman; Clemens, Paula R.

    2010-01-01

    To better understand the role of dendritic cells (DCs) in skeletal muscle, we investigated the migration of DCs from murine skeletal muscle and compared that to previously studied footpad (FP) DC trafficking. We adoptively transferred carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled mature DCs to syngeneic mice and followed them in various lymphatic tissues at different time points. Injection of DCs into the tibialis anterior muscle resulted in the peak number of CFSE+ DCs recovered in spleen at 12h, not at 24h, when the largest number of these cells appeared in the draining lymph nodes. Interestingly, this result for adoptive transfer of DCs to skeletal muscle differs with what is previously reported for adoptive transfer to the FP, a result that we also confirmed in parallel studies. These findings could have a significant impact on 1) understanding muscle diseases with immunological complications such as muscular dystrophies and 2) the immunologic effects of treatments for muscle diseases. PMID:20580121

  15. Dissemination of Walker 256 carcinoma cells to rat skeletal muscle

    SciTech Connect

    Ueoka, H.; Hayashi, K.; Namba, T.; Grob, D.

    1986-03-05

    After injection of 10/sup 6/ Walker 256 carcinoma cells labelled with /sup 125/I-5-iodo-2'-deoxyuridine into the tail vein, peak concentration in skeletal muscle was 46 cells/g at 60 minutes, which was lower than 169202, 1665, 555, 198 and 133 cells/g, respectively, at 30 or 60 minutes in lung, liver, spleen, kidney and heart. Because skeletal muscle constitutes 37.4% of body weight, the total number of tumor cells was 2323 cells, which was much greater than in spleen, kidney and heart with 238, 271, and 85 cells, respectively, and only less than in lung and liver, at 222857 and 11700 cells, respectively. The total number in skeletal muscle became greater than in liver at 4 hours and than in lung at 24 hours. Ten minutes after injection of 7.5 x 10/sup 6/ Walker 256 carcinoma cells into the abdominal aorta of rats, a mean of 31 colony-forming cells were recovered from the gastrocnemius, while 106 cells were recovered from the lung after injection into the tail vein. These results indicate that a large number of viable tumor cells can be arrested in skeletal muscle through circulation. The rare remote metastasis of malignancies into skeletal muscle despite constantly circulating tumor cells does not appear to be due to poor dissemination of tumor cells into muscle but due to unhospitable environment of skeletal muscle.

  16. Skeletal muscle proteomics: current approaches, technical challenges and emerging techniques

    PubMed Central

    2011-01-01

    Background Skeletal muscle fibres represent one of the most abundant cell types in mammals. Their highly specialised contractile and metabolic functions depend on a large number of membrane-associated proteins with very high molecular masses, proteins with extensive posttranslational modifications and components that exist in highly complex supramolecular structures. This makes it extremely difficult to perform conventional biochemical studies of potential changes in protein clusters during physiological adaptations or pathological processes. Results Skeletal muscle proteomics attempts to establish the global identification and biochemical characterisation of all members of the muscle-associated protein complement. A considerable number of proteomic studies have employed large-scale separation techniques, such as high-resolution two-dimensional gel electrophoresis or liquid chromatography, and combined them with mass spectrometry as the method of choice for high-throughput protein identification. Muscle proteomics has been applied to the comprehensive biochemical profiling of developing, maturing and aging muscle, as well as the analysis of contractile tissues undergoing physiological adaptations seen in disuse atrophy, physical exercise and chronic muscle transformation. Biomedical investigations into proteome-wide alterations in skeletal muscle tissues were also used to establish novel biomarker signatures of neuromuscular disorders. Importantly, mass spectrometric studies have confirmed the enormous complexity of posttranslational modifications in skeletal muscle proteins. Conclusions This review critically examines the scientific impact of modern muscle proteomics and discusses its successful application for a better understanding of muscle biology, but also outlines its technical limitations and emerging techniques to establish new biomarker candidates. PMID:21798084

  17. The effects of obesity on skeletal muscle regeneration

    PubMed Central

    Akhmedov, Dmitry; Berdeaux, Rebecca

    2013-01-01

    Obesity and metabolic disorders such as type 2 diabetes mellitus are accompanied by increased lipid deposition in adipose and non-adipose tissues including liver, pancreas, heart and skeletal muscle. Recent publications report impaired regenerative capacity of skeletal muscle following injury in obese mice. Although muscle regeneration has not been thoroughly studied in obese and type 2 diabetic humans and mechanisms leading to decreased muscle regeneration in obesity remain elusive, the initial findings point to the possibility that muscle satellite cell function is compromised under conditions of lipid overload. Elevated toxic lipid metabolites and increased pro-inflammatory cytokines as well as insulin and leptin resistance that occur in obese animals may contribute to decreased regenerative capacity of skeletal muscle. In addition, obesity-associated alterations in the metabolic state of skeletal muscle fibers and satellite cells may directly impair the potential for satellite cell-mediated repair. Here we discuss recent studies that expand our understanding of how obesity negatively impacts skeletal muscle maintenance and regeneration. PMID:24381559

  18. Exercise Training Reverses Skeletal Muscle Atrophy in an Experimental Model of VCP Disease

    E-print Network

    2013-01-01

    that exercise increased the muscle strength and endurance inincreased oxidative capacity and attenuation of exercise-induced ultrastructural damage in skeletal muscles [increased antioxidant capacity. However, the molecular mechanisms by which exercise may delay or reverse skeletal muscle

  19. Renal function alterations during skeletal muscle disuse in simulated microgravity

    NASA Technical Reports Server (NTRS)

    Tucker, Bryan J.

    1992-01-01

    This project was to examine the alterations in renal functions during skeletal muscle disuse in simulated microgravity. Although this area could cover a wide range of investigative efforts, the limited funding resulted in the selection of two projects. These projects would result in data contributing to an area of research deemed high priority by NASA and would address issues of the alterations in renal response to vasoactive stimuli during conditions of skeletal muscle disuse as well as investigate the contribution of skeletal muscle disuse, conditions normally found in long term human exposure to microgravity, to the balance of fluid and macromolecules within the vasculature versus the interstitium. These two projects selected are as follows: investigate the role of angiotensin 2 on renal function during periods of simulated microgravity and skeletal muscle disuse to determine if the renal response is altered to changes in circulating concentrations of angiotensin 2 compared to appropriate controls; and determine if the shift of fluid balance from vasculature to the interstitium, the two components of extracellular fluid volume, that occur during prolonged exposure to microgravity and skeletal muscle disuse is a result, in part, to alterations in the fluid and macromolecular balance in the peripheral capillary beds, of which the skeletal muscle contains the majority of recruitment capillaries. A recruitment capillary bed would be most sensitive to alterations in Starling forces and fluid and macromolecular permeability.

  20. Circadian Rhythms, the Molecular Clock, and Skeletal Muscle

    PubMed Central

    Lefta, Mellani; Wolff, Gretchen; Esser, Karyn A.

    2015-01-01

    Almost all organisms ranging from single cell bacteria to humans exhibit a variety of behavioral, physiological, and biochemical rhythms. In mammals, circadian rhythms control the timing of many physiological processes over a 24-h period, including sleep-wake cycles, body temperature, feeding, and hormone production. This body of research has led to defined characteristics of circadian rhythms based on period length, phase, and amplitude. Underlying circadian behaviors is a molecular clock mechanism found in most, if not all, cell types including skeletal muscle. The mammalian molecular clock is a complex of multiple oscillating networks that are regulated through transcriptional mechanisms, timed protein turnover, and input from small molecules. At this time, very little is known about circadian aspects of skeletal muscle function/metabolism but some progress has been made on understanding the molecular clock in skeletal muscle. The goal of this chapter is to provide the basic terminology and concepts of circadian rhythms with a more detailed review of the current state of knowledge of the molecular clock, with reference to what is known in skeletal muscle. Research has demonstrated that the molecular clock is active in skeletal muscles and that the muscle-specific transcription factor, MyoD, is a direct target of the molecular clock. Skeletal muscle of clock-compromised mice, Bmal1?/? and Clock?19 mice, are weak and exhibit significant disruptions in expression of many genes required for adult muscle structure and metabolism. We suggest that the interaction between the molecular clock, MyoD, and metabolic factors, such as PGC-1, provide a potential system of feedback loops that may be critical for both maintenance and adaptation of skeletal muscle. PMID:21621073

  1. Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    BACKGROUND: The effects of essential amino acid (EAA) supplementation during moderate steady state (ie, endurance) exercise on postexercise skeletal muscle metabolism are not well described, and the potential role of supplemental leucine on muscle protein synthesis (MPS) and associated molecular re...

  2. Bex1 knock out mice show altered skeletal muscle regeneration

    SciTech Connect

    Koo, Jae Hyung Smiley, Mark A.; Lovering, Richard M.; Margolis, Frank L.

    2007-11-16

    Bex1 and Calmodulin (CaM) are upregulated during skeletal muscle regeneration. We confirm this finding and demonstrate the novel finding that they interact in a calcium-dependent manner. To study the role of Bex1 and its interaction with CaM in skeletal muscle regeneration, we generated Bex1 knock out (Bex1-KO) mice. These mice appeared to develop normally and are fertile, but displayed a functional deficit in exercise performance compared to wild type (WT) mice. After intramuscular injection of cardiotoxin, which causes extensive and reproducible myotrauma followed by recovery, regenerating muscles of Bex1-KO mice exhibited elevated and prolonged cell proliferation, as well as delayed cell differentiation, compared to WT mice. Thus, our results provide the first evidence that Bex1-KO mice show altered muscle regeneration, and allow us to propose that the interaction of Bex1 with Ca{sup 2+}/CaM may be involved in skeletal muscle regeneration.

  3. Anabolic and catabolic pathways regulating skeletal muscle mass

    PubMed Central

    McCarthy, John J.; Esser, Karyn A.

    2010-01-01

    Purpose of review the purpose of this review is to discuss recent findings as they pertain to anabolic and catabolic signaling pathways involved in the regulation of adult skeletal muscle mass. Recent findings research conducted over the past few years has continued to refine our understanding of the pathways that govern skeletal muscle mass, in particular the mTOR, FoxO and NF-?B pathways. Alternative signaling pathways have also emerged as important regulators of muscle mass such as the ?-catenin pathway. Summary a better understanding of the anabolic and catabolic processes which regulate skeletal muscle mass is critical for the development of more effective therapeutics to prevent the loss of muscle with disuse, aging and disease. PMID:20154608

  4. Estimation of skeletal muscle mass from body creatine content

    NASA Technical Reports Server (NTRS)

    Pace, N.; Rahlmann, D. F.

    1982-01-01

    Procedures have been developed for studying the effect of changes in gravitational loading on skeletal muscle mass through measurements of the body creatine content. These procedures were developed for studies of gravitational scale effects in a four-species model, comprising the hamster, rat, guinea pig, and rabbit, which provides a sufficient range of body size for assessment of allometric parameters. Since intracellular muscle creatine concentration varies among species, and with age within a given species, the concentration values for metabolically mature individuals of these four species were established. The creatine content of the carcass, skin, viscera, smooth muscle, and skeletal muscle was determined for each species. In addition, the skeletal muscle mass of the major body components was determined, as well as the total and fat-free masses of the body and carcass, and the percent skeletal muscle in each. It is concluded that these procedures are particularly useful for studying the effect of gravitational loading on the skeletal muscle content of the animal carcass, which is the principal weight-bearing organ of the body.

  5. No-dependent signaling pathways in unloaded skeletal muscle

    PubMed Central

    Shenkman, Boris S.; Nemirovskaya, Tatiana L.; Lomonosova, Yulia N.

    2015-01-01

    The main focus of the current review is the nitric oxide (NO)-mediated signaling mechanism in unloaded skeletal. Review of the published data describing muscles during physical activity and inactivity demonstrates that NO is an essential trigger of signaling processes, which leads to structural and metabolic changes of the muscle fibers. The experiments with modulation of NO-synthase (NOS) activity during muscle unloading demonstrate the ability of an activated enzyme to stabilize degradation processes and prevent development of muscle atrophy. Various forms of muscle mechanical activity, i.e., plantar afferent stimulation, resistive exercise and passive chronic stretch increase the content of neural NOS (nNOS) and thus may facilitate an increase in NO production. Recent studies demonstrate that NO-synthase participates in the regulation of protein and energy metabolism in skeletal muscle by fine-tuning and stabilizing complex signaling systems which regulate protein synthesis and degradation in the fibers of inactive muscle. PMID:26582991

  6. Naturally derived and synthetic scaffolds for skeletal muscle reconstruction.

    PubMed

    Wolf, Matthew T; Dearth, Christopher L; Sonnenberg, Sonya B; Loboa, Elizabeth G; Badylak, Stephen F

    2015-04-01

    Skeletal muscle tissue has an inherent capacity for regeneration following injury. However, severe trauma, such as volumetric muscle loss, overwhelms these natural muscle repair mechanisms prompting the search for a tissue engineering/regenerative medicine approach to promote functional skeletal muscle restoration. A desirable approach involves a bioscaffold that simultaneously acts as an inductive microenvironment and as a cell/drug delivery vehicle to encourage muscle ingrowth. Both biologically active, naturally derived materials (such as extracellular matrix) and carefully engineered synthetic polymers have been developed to provide such a muscle regenerative environment. Next generation naturally derived/synthetic "hybrid materials" would combine the advantageous properties of these materials to create an optimal platform for cell/drug delivery and possess inherent bioactive properties. Advances in scaffolds using muscle tissue engineering are reviewed herein. PMID:25174309

  7. Low intrinsic running capacity is associated with reduced skeletal muscle substrate oxidation and lower mitochondrial content in white skeletal muscle.

    PubMed

    Rivas, Donato A; Lessard, Sarah J; Saito, Misato; Friedhuber, Anna M; Koch, Lauren G; Britton, Steven L; Yaspelkis, Ben B; Hawley, John A

    2011-04-01

    Chronic metabolic diseases develop from the complex interaction of environmental and genetic factors, although the extent to which each contributes to these disorders is unknown. Here, we test the hypothesis that artificial selection for low intrinsic aerobic running capacity is associated with reduced skeletal muscle metabolism and impaired metabolic health. Rat models for low- (LCR) and high- (HCR) intrinsic running capacity were derived from genetically heterogeneous N:NIH stock for 20 generations. Artificial selection produced a 530% difference in running capacity between LCR/HCR, which was associated with significant functional differences in glucose and lipid handling by skeletal muscle, as assessed by hindlimb perfusion. LCR had reduced rates of skeletal muscle glucose uptake (?30%; P = 0.04), glucose oxidation (?50%; P = 0.04), and lipid oxidation (?40%; P = 0.02). Artificial selection for low aerobic capacity was also linked with reduced molecular signaling, decreased muscle glycogen, and triglyceride storage, and a lower mitochondrial content in skeletal muscle, with the most profound changes to these parameters evident in white rather than red muscle. We show that a low intrinsic aerobic running capacity confers reduced insulin sensitivity in skeletal muscle and is associated with impaired markers of metabolic health compared with high intrinsic running capacity. Furthermore, selection for high running capacity, in the absence of exercise training, endows increased skeletal muscle insulin sensitivity and oxidative capacity in specifically white muscle rather than red muscle. These data provide evidence that differences in white muscle may have a role in the divergent aerobic capacity observed in this generation of LCR/HCR. PMID:21270346

  8. A novel calcium current in dysgenic skeletal muscle.

    PubMed

    Adams, B A; Beam, K G

    1989-09-01

    The whole-cell patch-clamp technique was used to study voltage-dependent calcium currents in primary cultures of myotubes and in freshly dissociated skeletal muscle from normal and dysgenic mice. In addition to the transient, dihydropyridine (DHP)-insensitive calcium current previously described, a maintained DHP-sensitive calcium current was found in dysgenic skeletal muscle. This current, here termed ICa-dys, is largest in acutely dissociated fetal or neonatal dysgenic muscle and also in dysgenic myotubes grown on a substrate of killed fibroblasts. In dysgenic myotubes grown on untreated plastic culture dishes, ICa-dys is usually so small that it cannot be detected. In addition, ICa-dys is apparently absent from normal skeletal muscle. From a holding potential of -80 mV. ICa-dys becomes apparent for test pulses to approximately -20 mV and peaks at approximately +20 mV. The current activates rapidly (rise time approximately 5 ms at 20 degrees C) and with 10 mM Ca as charge carrier inactivates little or not at all during a 200-ms test pulse. Thus, ICa-dys activates much faster than the slowly activating calcium current of normal skeletal muscle and does not display Ca-dependent inactivation like the cardiac L-type calcium current. Substituting Ba for Ca as the charge carrier doubles the size of ICa-dys without altering its kinetics. ICa-dys is approximately 75% blocked by 100 nM (+)-PN 200-110 and is increased about threefold by 500 nM racemic Bay K 8644. The very high sensitivity of ICa-dys to these DHP compounds distinguishes it from neuronal L-type calcium current and from the calcium currents of normal skeletal muscle. ICa-dys may represent a calcium channel that is normally not expressed in skeletal muscle, or a mutated form of the skeletal muscle slow calcium channel. PMID:2558151

  9. Oxidants, antioxidants and alcohol: implications for skeletal and cardiac muscle.

    PubMed

    Preedy, V R; Patel, V B; Reilly, M E; Richardson, P J; Falkous, G; Mantle, D

    1999-08-01

    The chronic form of alcoholic skeletal myopathy is characterized by selective atrophy of Type II fibers and affects up to two thirds of all alcohol misusers. Plasma selenium and alpha-tocopherol are reduced in myopathic alcoholics compared to alcoholic patients without myopathy. Plasma carnosinase is also reduced in myopathic alcoholics, implicating a mechanism related to reduced intramuscular carnosine, an imidazole dipeptide with putative antioxidant properties. Together with the observation that alcoholic patients have increased indices of lipid peroxidation, there is evidence suggestive of free radical (i.e., unpaired electrons or reactive oxygen species) mediated damage in the pathogenesis of alcohol-induced muscle disease. Protein synthesis is a multi-step process that encompasses amino acid transport, signal transduction, translation and transcription. Any defect in one or more of the innumerable components of each process will have an impact on protein synthesis, as determined by radiolabelling of constituent proteins. Both acute and chronic alcohol exposure are associated with a reduction in skeletal muscle protein synthesis. Paradoxically, alcohol-feeding studies in rats have shown that the imidazole dipeptide concentrations are increased in myopathic muscles though alpha-tocopherol contents are not significantly altered. In acutely dosed rats, where protein synthesis is reduced, protein carbonyl concentrations (an index of oxidative damage to muscle) also decline slightly or are unaltered, contrary to the expected increase. Alcoholic cardiomyopathy can ensue from heavy consumption of alcohol over a long period of time. The clinical features include poor myocardial contractility with reduced left ventricular ejection volume, raised tissue enzymes, dilation of the left ventricle, raised auto- antibodies and defects in mitochondrial function. Whilst oxidant damage occurs in experimental models, however this issues remains to be confirmed in the clinical setting. In the rat, circulating troponin-T release increases in the presence of ethanol, a mechanism ascribed to free radical mediated damage, as it is prevented with the xanthine oxidase inhibitor and beta-blocker, propranolol. However, whilst propranolol prevents the release of troponin-T, it does not prevent the fall in whole cardiac protein synthesis, suggestive of localized ischemic damage due to ethanol. PMID:10430553

  10. Acylcarnitines: potential implications for skeletal muscle insulin resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Insulin resistance is linked to increased acylcarnitine species in a number of tissues including skeletal muscle, due to incomplete fatty acid oxidation (FAO). It is not known if acylcarnitines participate in muscle insulin resistance or simply reflect dysregulated metabolism. The aim of this stud...

  11. Skeletal Muscle as a Peripheral Modifier of Behavior

    ERIC Educational Resources Information Center

    Jenkins, Robert R.

    1978-01-01

    Discusses how muscle can exert an influence on the behavioral potential of an organism and attempts to refute the "all or none law" by demonstrating that skeletal muscle is not merely a slave of the central nervous system. (Author/MA)

  12. Vitamin D and its role in skeletal muscle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This review discusses the clinical and laboratory studies that have examined a role of vitamin D in skeletal muscle. Many observational studies, mainly in older populations, indicate that vitamin D status is positively associated with muscle strength and physical performance and inversely associated...

  13. The impact of vitamin D on skeletal muscle function

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This review discusses the clinical and laboratory studies that have examined a role of vitamin D in skeletal muscle. Many observational studies, mainly in older populations, indicate that vitamin D status is positively associated with muscle strength and physical performance and inversely associated...

  14. Molecular responses to moderate endurance exercise in skeletal muscle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study examined alterations in skeletal-muscle growth and atrophy-related molecular events after a single bout of moderate-intensity endurance exercise. Muscle biopsies were obtained from 10 men (23 +/- 1 yr, body mass 80 +/- 2 kg, and VO(2peak) 45 +/- 1 ml x kg'¹ x min'¹) immediately (0 hr) and...

  15. Glutamine metabolism in skeletal muscles from the broiler chick (Gallus domesticus) and the laboratory rat (Rattus norvegicus)

    PubMed Central

    Wu, G Y; Thompson, J R; Baracos, V E

    1991-01-01

    Oxidative decarboxylation of L-[1-14C]glutamine was studied in isolated chick and rat skeletal muscles incubated in the presence of glucose, insulin and plasma concentrations of amino acids. (1) The rate of oxidative decarboxylation of L-[1-14C]glutamine was high, and exceeded that of L-[1-14C]leucine in all muscles. (2) The rate of oxidative decarboxylation of L-[1-14C]glutamine increased with increasing intracellular concentrations of glutamine. (3) The activities of glutamine aminotransferases K and L were more than 10-fold greater in rat than in chick skeletal muscles. (4) Mitochondrial phosphate-activated glutaminase activity was approx. 10-fold greater in chick than in rat skeletal muscles and increased with increasing glutamine concentrations. (5) An inhibitor of glutaminase, 6-diazo-5-oxo-L-norleucine, inhibited the rate of glutamine decarboxylation in chick, but not in rat, skeletal muscle. These findings suggest that glutamine degradation in skeletal muscle may be substantial and may make an important contribution to the regulation of intramuscular glutamine concentrations. A species difference in the pathways and the subcellular location for the conversion of glutamine into 2-oxoglutarate in rat and chick skeletal muscles is implied by the relative activities of glutamine-degrading enzymes. PMID:2012604

  16. A method for preparing skeletal muscle fiber basal laminae

    SciTech Connect

    Carlson, E.C.; Carlson, B.M. )

    1991-07-01

    Previous attempts to prepare skeletal muscle basal laminae (BL) for ultrastructural analyses have been hampered by difficulties in successfully removing skeletal muscle proteins and cellular debris from BL tubes. In the present study the authors describe a two phase method which results in an acellular muscle preparation, the BL of which are examined by light, transmission electron, and scanning electron microscopy. In the first phase, excised rat extensor digitorum longus muscles are subjected to x-radiation and then soaked in Marcaine to inhibit muscle regeneration and to destroy peripheral muscle fibers. The muscles are then grafted back into their original sites and allowed to remain in place 7-14 days to allow for maximal removal of degenerating muscle tissue with minimal scar tissue formation. In the second phase, the muscle grafts are subjected sequentially to EDTA, triton X-100, DNAase, and sodium deoxycholate to remove phagocytizing cells and associated degenerating muscle tissue. These procedures result in translucent, acellular muscle grafts which show numerous empty tubes of BL backed by endomysial collagenous fibers. These preparations should be useful for morphological analyses of isolated muscle BL and for possible in vitro studies by which the biological activity of muscle BL can be examined.

  17. Obesity, insulin resistance, and skeletal muscle nitric oxide synthase

    PubMed Central

    Kraus, Raymond M.; Houmard, Joseph A.; Kraus, William E.; Tanner, Charles J.; Pierce, Joseph R.; Choi, Myung Dong

    2012-01-01

    The molecular mechanisms responsible for impaired insulin action have yet to be fully identified. Rodent models demonstrate a strong relationship between insulin resistance and an elevation in skeletal muscle inducible nitric oxide synthase (iNOS) expression; the purpose of this investigation was to explore this potential relationship in humans. Sedentary men and women were recruited to participate (means ± SE: nonobese, body mass index = 25.5 ± 0.3 kg/m2, n = 13; obese, body mass index = 36.6 ± 0.4 kg/m2, n = 14). Insulin sensitivity was measured using an intravenous glucose tolerance test with the subsequent modeling of an insulin sensitivity index (SI). Skeletal muscle was obtained from the vastus lateralis, and iNOS, endothelial nitric oxide synthase (eNOS), and neuronal nitric oxide synthase (nNOS) content were determined by Western blot. SI was significantly lower in the obese compared with the nonobese group (?43%; P < 0.05), yet skeletal muscle iNOS protein expression was not different between nonobese and obese groups. Skeletal muscle eNOS protein was significantly higher in the nonobese than the obese group, and skeletal muscle nNOS protein tended to be higher (P = 0.054) in the obese compared with the nonobese group. Alternative analysis based on SI (high and low tertile) indicated that the most insulin-resistant group did not have significantly more skeletal muscle iNOS protein than the most insulin-sensitive group. In conclusion, human insulin resistance does not appear to be associated with an elevation in skeletal muscle iNOS protein in middle-aged individuals under fasting conditions. PMID:22797309

  18. Mechanically induced alterations in cultured skeletal muscle growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, H. H.; Hatfaludy, S.; Karlisch, P.; Shansky, J.

    1991-01-01

    Model systems are available for mechanically stimulating cultured skeletal muscle cells by passive tensile forces which simulate those found in vivo. When applied to embryonic muscle cells in vitro these forces induce tissue organogenesis, metabolic adaptations, and muscle cell growth. The mechanical stimulation of muscle cell growth correlates with stretch-induced increases in the efflux of prostaglandins PGE2 and PGF2(alpha) in a time and frequency dependent manner. These prostaglandins act as mechanical 'second messengers' regulating skeletal muscle protein turnover rates. Since they also effect bone remodelling in response to tissue loading and unloading, secreted prostaglandins may serve as paracrine growth factors, coordinating the growth rates of muscle and bone in response to external mechanical forces. Cell culture model systems will supplement other models in understanding mechanical transduction processes at the molecular level.

  19. Dystrophin-associated Proteins Are Greatly Reduced in Skeletal Muscle from mdx Mice

    E-print Network

    Campbell, Kevin P.

    accompanied by skeletal muscle necrosis makes the mdx mouse an excellent model system to study how muscleDystrophin-associated Proteins Are Greatly Reduced in Skeletal Muscle from mdx Mice Kay- man Duchenne muscular dystrophy gene, exists in skeletal muscle as a large oligomeric complex

  20. Decellularized Human Skeletal Muscle as Biologic Scaffold for Reconstructive Surgery

    PubMed Central

    Porzionato, Andrea; Sfriso, Maria Martina; Pontini, Alex; Macchi, Veronica; Petrelli, Lucia; Pavan, Piero G.; Natali, Arturo N.; Bassetto, Franco; Vindigni, Vincenzo; De Caro, Raffaele

    2015-01-01

    Engineered skeletal muscle tissues have been proposed as potential solutions for volumetric muscle losses, and biologic scaffolds have been obtained by decellularization of animal skeletal muscles. The aim of the present work was to analyse the characteristics of a biologic scaffold obtained by decellularization of human skeletal muscles (also through comparison with rats and rabbits) and to evaluate its integration capability in a rabbit model with an abdominal wall defect. Rat, rabbit and human muscle samples were alternatively decellularized with two protocols: n.1, involving sodium deoxycholate and DNase I; n.2, trypsin-EDTA and Triton X-NH4OH. Protocol 2 proved more effective, removing all cellular material and maintaining the three-dimensional networks of collagen and elastic fibers. Ultrastructural analyses with transmission and scanning electron microscopy confirmed the preservation of collagen, elastic fibres, glycosaminoglycans and proteoglycans. Implantation of human scaffolds in rabbits gave good results in terms of integration, although recellularization by muscle cells was not completely achieved. In conclusion, human skeletal muscles may be effectively decellularized to obtain scaffolds preserving the architecture of the extracellular matrix and showing mechanical properties suitable for implantation/integration. Further analyses will be necessary to verify the suitability of these scaffolds for in vitro recolonization by autologous cells before in vivo implantation. PMID:26140375

  1. In vivo calcium regulation in diabetic skeletal muscle.

    PubMed

    Eshima, Hiroaki; Poole, David C; Kano, Yutaka

    2014-11-01

    In skeletal muscle, dysfunctional contractile activity has been linked to impaired intracellular Ca(2+) concentration ([Ca(2+)]i) regulation. Muscle force production is impaired and fatigability and muscle fragility deteriorate with diabetes. Use of a novel in vivo model permits investigation of [Ca(2+)]i homeostasis in diabetic skeletal muscle. Within this in vivo environment we have shown that diabetes perturbs the Ca(2+) regulatory system such that resting [Ca(2+)]i homeostasis following muscle contractions is compromised and elevations of [Ca(2+)]i are exacerbated. This review considers the impact of diabetes on the capacity of skeletal muscle to regulate [Ca(2+)]i, following muscle contractions and, in particular, the relationship between muscle fatigue and elevated [Ca(2+)]i in a highly ecologically relevant circulation-intact environment. Importantly, the role of mitochondria in calcium sequestration and the possibility that diabetes impacts this process is explored. Given the profound microcirculatory dysfunction in diabetes this preparation offers the unique opportunity to study the interrelationships among microvascular function, blood-myocyte oxygen flux and [Ca(2+)]i as they relate to enhanced muscle fatigability and exercise intolerance. PMID:25224503

  2. COX-2 inhibitor reduces skeletal muscle hypertrophy in mice.

    PubMed

    Novak, Margaret L; Billich, William; Smith, Sierra M; Sukhija, Kunal B; McLoughlin, Thomas J; Hornberger, Troy A; Koh, Timothy J

    2009-04-01

    Anti-inflammatory strategies are often used to reduce muscle pain and soreness that can result from high-intensity muscular activity. However, studies indicate that components of the acute inflammatory response may be required for muscle repair and growth. The hypothesis of this study was that cyclooxygenase (COX)-2 activity is required for compensatory hypertrophy of skeletal muscle. We used the synergist ablation model of skeletal muscle hypertrophy, along with the specific COX-2 inhibitor NS-398, to investigate the role of COX-2 in overload-induced muscle growth in mice. COX-2 was expressed in plantaris muscles during compensatory hypertrophy and was localized mainly in or near muscle cell nuclei. Treatment with NS-398 blunted the increases in mass and protein content in overloaded muscles compared with vehicle-treated controls. Additionally, the COX-2 inhibitor decreased activity of the urokinase type plasminogen activator, macrophage accumulation, and cell proliferation, all of which are required for hypertrophy after synergist ablation. Expression of insulin-like growth factor-1 and phosphorylation of Akt, mammalian target of rapamycin, and p70S6K were increased following synergist ablation, but were not affected by NS-398. Additionally, expression of atrogin-1 was reduced during hypertrophy, but was also not affected by NS-398. These results demonstrate that COX-2 activity is required for skeletal muscle hypertrophy, possibly through facilitation of extracellular protease activity, macrophage accumulation, and cell proliferation. PMID:19176887

  3. Compensatory Hypertrophy of Skeletal Muscle: Contractile Characteristics

    ERIC Educational Resources Information Center

    Ianuzzo, C. D.; Chen, V.

    1977-01-01

    Describes an experiment using rats that demonstrates contractile characteristics of normal and hypertrophied muscle. Compensatory hypertrophy of the plantaris muscle is induced by surgical removal of the synergistic gastrocnemium muscle. Includes methods for determination of contractile properties of normal and hypertrophied muscle and…

  4. Hypodynamic and hypokinetic condition of skeletal muscles

    NASA Technical Reports Server (NTRS)

    Katinas, G. S.; Oganov, V. S.; Potapov, A. N.

    1980-01-01

    Data are presented in regard to the effect of unilateral brachial amputation on the physiological characteristics of two functionally different muscles, the brachial muscle (flexor of the brachium) and the medial head of the brachial triceps muscle (extensor of the brachium), which in rats represents a separate muscle. Hypokinesia and hypodynamia were studied.

  5. The adipokine leptin increases skeletal muscle mass and significantly alters skeletal muscle miRNA expression profile in aged mice

    SciTech Connect

    Hamrick, Mark W.; Herberg, Samuel; Arounleut, Phonepasong; Department of Orthopaedic Surgery, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA ; He, Hong-Zhi; Department of Dermatology, Henry Ford Health System, Detroit, MI ; Shiver, Austin; Department of Orthopaedic Surgery, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA ; Qi, Rui-Qun; Department of Dermatology, Henry Ford Health System, Detroit, MI ; Zhou, Li; Department of Dermatology, Henry Ford Health System, Detroit, MI; Department of Internal Medicine, Henry Ford Health System, Detroit, MI ; Isales, Carlos M.; Department of Orthopaedic Surgery, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA ; and others

    2010-09-24

    Research highlights: {yields} Aging is associated with muscle atrophy and loss of muscle mass, known as the sarcopenia of aging. {yields} We demonstrate that age-related muscle atrophy is associated with marked changes in miRNA expression in muscle. {yields} Treating aged mice with the adipokine leptin significantly increased muscle mass and the expression of miRNAs involved in muscle repair. {yields} Recombinant leptin therapy may therefore be a novel approach for treating age-related muscle atrophy. -- Abstract: Age-associated loss of muscle mass, or sarcopenia, contributes directly to frailty and an increased risk of falls and fractures among the elderly. Aged mice and elderly adults both show decreased muscle mass as well as relatively low levels of the fat-derived hormone leptin. Here we demonstrate that loss of muscle mass and myofiber size with aging in mice is associated with significant changes in the expression of specific miRNAs. Aging altered the expression of 57 miRNAs in mouse skeletal muscle, and many of these miRNAs are now reported to be associated specifically with age-related muscle atrophy. These include miR-221, previously identified in studies of myogenesis and muscle development as playing a role in the proliferation and terminal differentiation of myogenic precursors. We also treated aged mice with recombinant leptin, to determine whether leptin therapy could improve muscle mass and alter the miRNA expression profile of aging skeletal muscle. Leptin treatment significantly increased hindlimb muscle mass and extensor digitorum longus fiber size in aged mice. Furthermore, the expression of 37 miRNAs was altered in muscles of leptin-treated mice. In particular, leptin treatment increased the expression of miR-31 and miR-223, miRNAs known to be elevated during muscle regeneration and repair. These findings suggest that aging in skeletal muscle is associated with marked changes in the expression of specific miRNAs, and that nutrient-related hormones such as leptin may be able to reverse muscle atrophy and alter the expression of atrophy-related miRNAs in aging skeletal muscle.

  6. Assessment of calcium sparks in intact skeletal muscle fibers.

    PubMed

    Park, Ki Ho; Weisleder, Noah; Zhou, Jingsong; Gumpper, Kristyn; Zhou, Xinyu; Duann, Pu; Ma, Jianjie; Lin, Pei-Hui

    2014-01-01

    Maintaining homeostatic Ca(2+) signaling is a fundamental physiological process in living cells. Ca(2+) sparks are the elementary units of Ca(2+) signaling in the striated muscle fibers that appear as highly localized Ca(2+) release events mediated by ryanodine receptor (RyR) Ca(2+) release channels on the sarcoplasmic reticulum (SR) membrane. Proper assessment of muscle Ca(2+) sparks could provide information on the intracellular Ca(2+) handling properties of healthy and diseased striated muscles. Although Ca(2+) sparks events are commonly seen in resting cardiomyocytes, they are rarely observed in resting skeletal muscle fibers; thus there is a need for methods to generate and analyze sparks in skeletal muscle fibers. Detailed here is an experimental protocol for measuring Ca(2+) sparks in isolated flexor digitorm brevis (FDB) muscle fibers using fluorescent Ca(2+) indictors and laser scanning confocal microscopy. In this approach, isolated FDB fibers are exposed to transient hypoosmotic stress followed by a return to isotonic physiological solution. Under these conditions, a robust Ca(2+) sparks response is detected adjacent to the sarcolemmal membrane in young healthy FDB muscle fibers. Altered Ca(2+) sparks response is detected in dystrophic or aged skeletal muscle fibers. This approach has recently demonstrated that membrane-delimited signaling involving cross-talk between inositol (1,4,5)-triphosphate receptor (IP3R) and RyR contributes to Ca(2+) spark activation in skeletal muscle. In summary, our studies using osmotic stress induced Ca(2+) sparks showed that this intracellular response reflects a muscle signaling mechanism in physiology and aging/disease states, including mouse models of muscle dystrophy (mdx mice) or amyotrophic lateral sclerosis (ALS model). PMID:24638093

  7. Growth Factors and Tension-Induced Skeletal Muscle Growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.

    1994-01-01

    The project investigated biochemical mechanisms to enhance skeletal muscle growth, and developed a computer based mechanical cell stimulator system. The biochemicals investigated in this study were insulin/(Insulin like Growth Factor) IGF-1 and Steroids. In order to analyze which growth factors are essential for stretch-induced muscle growth in vitro, we developed a defined, serum-free medium in which the differentiated, cultured avian muscle fibers could be maintained for extended periods of time. The defined medium (muscle maintenance medium, MM medium) maintains the nitrogen balance of the myofibers for 3 to 7 days, based on myofiber diameter measurements and myosin heavy chain content. Insulin and IGF-1, but not IGF-2, induced pronounced myofiber hypertrophy when added to this medium. In 5 to 7 days, muscle fiber diameters increase by 71 % to 98% compared to untreated controls. Mechanical stimulation of the avian muscle fibers in MM medium increased the sensitivity of the cells to insulin and IGF-1, based on a leftward shift of the insulin dose/response curve for protein synthesis rates. (54). We developed a ligand binding assay for IGF-1 binding proteins and found that the avian skeletal muscle cultures produced three major species of 31, 36 and 43 kD molecular weight (54) Stretch of the myofibers was found to have no significant effect on the efflux of IGF-1 binding proteins, but addition of exogenous collagen stimulated IGF-1 binding protein production 1.5 to 5 fold. Steroid hormones have a profound effect on muscle protein turnover rates in vivo, with the stress-related glucocorticoids inducing rapid skeletal muscle atrophy while androgenic steroids induce skeletal muscle growth. Exercise in humans and animals reduces the catabolic effects of glucocorticoids and may enhance the anabolic effects of androgenic steroids on skeletal muscle. In our continuing work on the involvement of exogenrus growth factors in stretch-induced avian skeletal muscle growth, we have performed experiments to determine whether mechanical stimulation of cultured avian muscle cells alters their response to anabolic steroids or glucocorticoids. In static cultures, testosterone had no effect on muscle cell growth, but 5alpha-dihydrotestosterone and the synthetic steroid stanozolol increased cell growth by up to 18% and 30%, respectively, after a three day exposure. We completed development of a new IBM-based mechanical cell stimulator system to provide greater flexibility in operating and monitoring our experiments. Our previous long term studies on myofiber growth were designed around a perfusion system of our own design. We have recently changed to performing these studies using a modified CELLCO cartridge bioreactor system Z since it has been certified as the ground-based model for the Shuttle's Space Tissue Loss (STL) F= Cell Culture Module. The current goals of this aspect of the project are three fold: 1) to design a Z cell culture system for studying avian skeletal myofiber atrophy on the Shuttle and Space Station; 0 2) to expand the use of bioreactors to cells which do not grow in either suspension or attached to the hollow fibers; and 3) to combine the bioreactor system with our computerized mechanical cell stimulator to have a better in vitro model to study tension/gravity/stretch regulation of skeletal muscle size. Preliminary studies also reported on involved : (1) how release of tension can induce rapid atrophy of tissues cultured avian skeletal muscle cells, and (2) a mechanism to transfer and maintain avian skeletal muscle organoids in modified cartridges in the Space Tissue Loss Module.

  8. Bone marrow mesenchymal cells improve muscle function in a skeletal muscle re-injury model.

    PubMed

    Andrade, Bruno M; Baldanza, Marcelo R; Ribeiro, Karla C; Porto, Anderson; Peçanha, Ramon; Fortes, Fabio S A; Zapata-Sudo, Gisele; Campos-de-Carvalho, Antonio C; Goldenberg, Regina C S; Werneck-de-Castro, João Pedro

    2015-01-01

    Skeletal muscle injury is the most common problem in orthopedic and sports medicine, and severe injury leads to fibrosis and muscle dysfunction. Conventional treatment for successive muscle injury is currently controversial, although new therapies, like cell therapy, seem to be promise. We developed a model of successive injuries in rat to evaluate the therapeutic potential of bone marrow mesenchymal cells (BMMC) injected directly into the injured muscle. Functional and histological assays were performed 14 and 28 days after the injury protocol by isometric tension recording and picrosirius/Hematoxilin & Eosin staining, respectively. We also evaluated the presence and the fate of BMMC on treated muscles; and muscle fiber regeneration. BMMC treatment increased maximal skeletal muscle contraction 14 and 28 days after muscle injury compared to non-treated group (4.5 ± 1.7 vs 2.5 ± 0.98 N/cm2, p<0.05 and 8.4 ± 2.3 vs. 5.7 ± 1.3 N/cm2, p<0.05 respectively). Furthermore, BMMC treatment increased muscle fiber cross-sectional area and the presence of mature muscle fiber 28 days after muscle injury. However, there was no difference in collagen deposition between groups. Immunoassays for cytoskeleton markers of skeletal and smooth muscle cells revealed an apparent integration of the BMMC within the muscle. These data suggest that BMMC transplantation accelerates and improves muscle function recovery in our extensive muscle re-injury model. PMID:26039243

  9. Regulation of skeletal muscle oxidative capacity and muscle mass by SIRT3

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We have previously reported that the expression of mitochondrial deacetylase SIRT3 is high in the slow oxidative muscle and that the expression of muscle SIRT3 level is increased by dietary restriction or exercise training. To explore the function of SIRT3 in skeletal muscle, we report here the esta...

  10. X-ray recordings reveal how a human disease-linked skeletal muscle ?-actin mutation leads to contractile dysfunction.

    PubMed

    Ochala, Julien; Ravenscroft, Gianina; McNamara, Elyshia; Nowak, Kristen J; Iwamoto, Hiroyuki

    2015-12-01

    In humans, mutant skeletal muscle ?-actin proteins are associated with contractile dysfunction, skeletal muscle weakness and a wide range of primarily skeletal muscle diseases. Despite this knowledge, the exact molecular mechanisms triggering the contractile dysfunction remain unknown. Here, we aimed to unravel these. Hence, we used a transgenic mouse model expressing a well-described D286G mutant skeletal muscle ?-actin protein and recapitulating the human condition of contractile deregulation and severe skeletal muscle weakness. We then recorded and analyzed the small-angle X-ray diffraction patterns of isolated membrane-permeabilized myofibers. Results showed that upon addition of Ca(2+), the intensity changes of the second (1/19nm(-1)) and sixth (1/5.9nm(-1)) actin layer lines and of the first myosin meridional reflection (1/14.3nm(-1)) were disrupted when the thin-thick filament overlap was optimal (sarcomere length of 2.5-2.6?m). However these reflections were normal when the thin and thick filaments were not interacting (sarcomere length>3.6?m). These findings demonstrate, for the first time, that the replacement of just one amino acid in the skeletal muscle ?-actin protein partly prevents actin conformational changes during activation, disrupting the strong binding of myosin molecules. This leads to a limited myosin-related tropomyosin movement over the thin filaments, further affecting the amount of cross-bridges, explaining the contractile dysfunction. PMID:26407659

  11. Response and function of skeletal muscle heat shock protein 70.

    PubMed

    Liu, Yuefei; Gampert, Larissa; Nething, Katja; Steinacker, Jürgen M

    2006-01-01

    In response to stress, cells produce a series of heat shock proteins (Hsps). One of the most prominent Hsps, is the 70 kDa Hsp (Hsp70). Hsp70 is a highly conserved and essential protein against stress. The skeletal muscle responds to a diverse group of stress signals namely, muscle contraction linked energy and milieu challenges, ischemia and exercise by producing Hsp70. The extent of this Hsp70 response in skeletal muscle depends on the type and intensity of the signal, and is characterized in a muscle fiber specific manner by a special time course. Hsp70 in the skeletal muscle is regulated at transcriptional, translational and posttranslational levels. Hsp70 serves as an indicator for cellular stress as a molecular chaperone, plays pivotal role in maintaining cellular homeostasis by preventing apoptosis, influences energy metabolism, facilitates cellular processes in terms of muscular adaptation and interacts with other signalling pathways. This review summarizes our current knowledge on the skeletal muscle Hsp70 response. PMID:16720354

  12. Kelch proteins: emerging roles in skeletal muscle development and diseases

    PubMed Central

    2014-01-01

    Our understanding of genes that cause skeletal muscle disease has increased tremendously over the past three decades. Advances in approaches to genetics and genomics have aided in the identification of new pathogenic mechanisms in rare genetic disorders and have opened up new avenues for therapeutic interventions by identification of new molecular pathways in muscle disease. Recent studies have identified mutations of several Kelch proteins in skeletal muscle disorders. The Kelch superfamily is one of the largest evolutionary conserved gene families. The 66 known family members all possess a Kelch-repeat containing domain and are implicated in diverse biological functions. In skeletal muscle development, several Kelch family members regulate the processes of proliferation and/or differentiation resulting in normal functioning of mature muscles. Importantly, many Kelch proteins function as substrate-specific adaptors for Cullin E3 ubiquitin ligase (Cul3), a core component of the ubiquitin-proteasome system to regulate the protein turnover. This review discusses the emerging roles of Kelch proteins in skeletal muscle function and disease. PMID:24959344

  13. Growth factor involvement in tension-induced skeletal muscle growth

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.

    1993-01-01

    Long-term manned space travel will require a better understanding of skeletal muscle atrophy which results from microgravity. Astronaut strength and dexterity must be maintained for normal mission operations and for emergency situations. Although exercise in space slows the rate of muscle loss, it does not prevent it. A biochemical understanding of how gravity/tension/exercise help to maintain muscle size by altering protein synthesis and/or degradation rate should ultimately allow pharmacological intervention to prevent muscle atrophy in microgravity. The overall objective is to examine some of the basic biochemical processes involved in tension-induced muscle growth. With an experimental in vitro system, the role of exogenous and endogenous muscle growth factors in mechanically stimulated muscle growth are examined. Differentiated avian skeletal myofibers can be 'exercised' in tissue culture using a newly developed dynamic mechanical cell stimulator device which simulates different muscle activity patterns. Patterns of mechanical activity which significantly affect muscle growth and metabolic characteristics were found. Both exogenous and endogenous growth factors are essential for tension-induced muscle growth. Exogenous growth factors found in serum, such as insulin, insulin-like growth factors, and steroids, are important regulators of muscle protein turnover rates and mechanically-induced muscle growth. Endogenous growth factors are synthesized and released into the culture medium when muscle cells are mechanically stimulated. At least one family of mechanically induced endogenous factors, the prostaglandins, help to regulate the rates of protein turnover in muscle cells. Endogenously synthesized IGF-1 is another. The interaction of muscle mechanical activity and these growth factors in the regulation of muscle protein turnover rates with our in vitro model system is studied.

  14. Protein synthesis in skeletal muscle of neonatal pigs is enhanced by administration of beta-hydroxy-beta-methylbutyrate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many low-birth-weight infants experience failure to thrive. The amino acid leucine stimulates protein synthesis in skeletal muscle of the neonate, but less is known about the effects of the leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB). To determine the effects of HMB on protein synthesi...

  15. Protein synthesis in skeletal muscle of neonatal pigs is enhanced by administration of beta-hydroxy-beta-methylbutyrate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many low-birth-weight infants experience failure to thrive. The amino acid leucine stimulates protein synthesis in skeletal muscle of the neonate, but less is known about the effects of the leucine metabolite ß-hydroxy-ß-methylbutyrate (HMB). To determine the effects of HMB on protein synthesis and ...

  16. Protein synthesis in skeletal muscle of neonatal pigs is enhanced by administration of Beta-hydroxy-Beta-methylbutyrate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many low-birth-weight infants experience failure to thrive. The amino acid leucine stimulates protein synthesis in skeletal muscle of the neonate, but less is known about the effects of the leucine metabolite Beta-hydroxy-Beta-methylbutyrate (HMB). To determine the effects of HMB on protein synthesi...

  17. Fast Skeletal Muscle Troponin Activation Increases Force of Mouse Fast Skeletal Muscle and Ameliorates Weakness Due to Nebulin-Deficiency

    PubMed Central

    Lee, Eun-Jeong; De Winter, Josine M.; Buck, Danielle; Jasper, Jeffrey R.; Malik, Fady I.; Labeit, Siegfried; Ottenheijm, Coen A.; Granzier, Henk

    2013-01-01

    The effect of the fast skeletal muscle troponin activator, CK-2066260, on calcium-induced force development was studied in skinned fast skeletal muscle fibers from wildtype (WT) and nebulin deficient (NEB KO) mice. Nebulin is a sarcomeric protein that when absent (NEB KO mouse) or present at low levels (nemaline myopathy (NM) patients with NEB mutations) causes muscle weakness. We studied the effect of fast skeletal troponin activation on WT muscle and tested whether it might be a therapeutic mechanism to increase muscle strength in nebulin deficient muscle. We measured tension–pCa relations with and without added CK-2066260. Maximal active tension in NEB KO tibialis cranialis fibers in the absence of CK-2066260 was ?60% less than in WT fibers, consistent with earlier work. CK-2066260 shifted the tension-calcium relationship leftwards, with the largest relative increase (up to 8-fold) at low to intermediate calcium levels. This was a general effect that was present in both WT and NEB KO fiber bundles. At pCa levels above ?6.0 (i.e., calcium concentrations <1 µM), CK-2066260 increased tension of NEB KO fibers to beyond that of WT fibers. Crossbridge cycling kinetics were studied by measuring ktr (rate constant of force redevelopment following a rapid shortening/restretch). CK-2066260 greatly increased ktr at submaximal activation levels in both WT and NEB KO fiber bundles. We also studied the sarcomere length (SL) dependence of the CK-2066260 effect (SL 2.1 µm and 2.6 µm) and found that in the NEB KO fibers, CK-2066260 had a larger effect on calcium sensitivity at the long SL. We conclude that fast skeletal muscle troponin activation increases force at submaximal activation in both wildtype and NEB KO fiber bundles and, importantly, that this troponin activation is a potential therapeutic mechanism for increasing force in NM and other skeletal muscle diseases with loss of muscle strength. PMID:23437068

  18. The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption.

    PubMed

    van Vliet, Stephan; Burd, Nicholas A; van Loon, Luc J C

    2015-09-01

    Clinical and consumer market interest is increasingly directed toward the use of plant-based proteins as dietary components aimed at preserving or increasing skeletal muscle mass. However, recent evidence suggests that the ingestion of the plant-based proteins in soy and wheat results in a lower muscle protein synthetic response when compared with several animal-based proteins. The possible lower anabolic properties of plant-based protein sources may be attributed to the lower digestibility of plant-based sources, in addition to greater splanchnic extraction and subsequent urea synthesis of plant protein-derived amino acids compared with animal-based proteins. The latter may be related to the relative lack of specific essential amino acids in plant- as opposed to animal-based proteins. Furthermore, most plant proteins have a relatively low leucine content, which may further reduce their anabolic properties when compared with animal proteins. However, few studies have actually assessed the postprandial muscle protein synthetic response to the ingestion of plant proteins, with soy and wheat protein being the primary sources studied. Despite the proposed lower anabolic properties of plant vs. animal proteins, various strategies may be applied to augment the anabolic properties of plant proteins. These may include the following: 1) fortification of plant-based protein sources with the amino acids methionine, lysine, and/or leucine; 2) selective breeding of plant sources to improve amino acid profiles; 3) consumption of greater amounts of plant-based protein sources; or 4) ingesting multiple protein sources to provide a more balanced amino acid profile. However, the efficacy of such dietary strategies on postprandial muscle protein synthesis remains to be studied. Future research comparing the anabolic properties of a variety of plant-based proteins should define the preferred protein sources to be used in nutritional interventions to support skeletal muscle mass gain or maintenance in both healthy and clinical populations. PMID:26224750

  19. On the Importance of Exchangeable NH Protons in Creatine for the Magnetic Coupling of Creatine Methyl Protons in Skeletal Muscle

    NASA Astrophysics Data System (ADS)

    Kruiskamp, M. J.; Nicolay, K.

    2001-03-01

    The methyl protons of creatine in skeletal muscle exhibit a strong off-resonance magnetization transfer effect. The mechanism of this process is unknown. We previously hypothesized that the exchangeable amide/amino protons of creatine might be involved. To test this the characteristics of the creatine magnetization transfer effect were investigated in excised rat hindleg skeletal muscle that was equilibrated in either H2O or D2O solutions containing creatine. The efficiency of off-resonance magnetization transfer to the protons of mobile creatine in excised muscle was similar to that previously reported in intact muscle in vivo. Equilibrating the isolated muscle in D2O solution had no effect on the magnetic coupling to the immobile protons. It is concluded that exchangeable protons play a negligible role in the magnetic coupling of creatine methyl protons in muscle.

  20. Exercise-Induced Skeletal Muscle Damage.

    ERIC Educational Resources Information Center

    Evans, William J.

    1987-01-01

    Eccentric exercise, in which the muscles exert force by lengthening, is associated with delayed onset muscle soreness. How soreness occurs, how recovery proceeds, and what precautions athletes should take are described. (Author/MT)

  1. Functional heterogeneity of side population cells in skeletal muscle

    SciTech Connect

    Uezumi, Akiyoshi; Ojima, Koichi; Fukada, So-ichiro; Ikemoto, Madoka; Masuda, Satoru; Miyagoe-Suzuki, Yuko; Takeda, Shin'ichi . E-mail: takeda@ncnp.go.jp

    2006-03-17

    Skeletal muscle regeneration has been exclusively attributed to myogenic precursors, satellite cells. A stem cell-rich fraction referred to as side population (SP) cells also resides in skeletal muscle, but its roles in muscle regeneration remain unclear. We found that muscle SP cells could be subdivided into three sub-fractions using CD31 and CD45 markers. The majority of SP cells in normal non-regenerating muscle expressed CD31 and had endothelial characteristics. However, CD31{sup -}CD45{sup -} SP cells, which are a minor subpopulation in normal muscle, actively proliferated upon muscle injury and expressed not only several regulatory genes for muscle regeneration but also some mesenchymal lineage markers. CD31{sup -}CD45{sup -} SP cells showed the greatest myogenic potential among three SP sub-fractions, but indeed revealed mesenchymal potentials in vitro. These SP cells preferentially differentiated into myofibers after intramuscular transplantation in vivo. Our results revealed the heterogeneity of muscle SP cells and suggest that CD31{sup -}CD45{sup -} SP cells participate in muscle regeneration.

  2. Suppression of muscle protein turnover and amino acid degradation by dietary protein deficiency

    NASA Technical Reports Server (NTRS)

    Tawa, N. E. Jr; Goldberg, A. L.

    1992-01-01

    To define the adaptations that conserve amino acids and muscle protein when dietary protein intake is inadequate, rats (60-70 g final wt) were fed a normal or protein-deficient (PD) diet (18 or 1% lactalbumin), and their muscles were studied in vitro. After 7 days on the PD diet, both protein degradation and synthesis fell 30-40% in skeletal muscles and atria. This fall in proteolysis did not result from reduced amino acid supply to the muscle and preceded any clear decrease in plasma amino acids. Oxidation of branched-chain amino acids, glutamine and alanine synthesis, and uptake of alpha-aminoisobutyrate also fell by 30-50% in muscles and adipose tissue of PD rats. After 1 day on the PD diet, muscle protein synthesis and amino acid uptake decreased by 25-40%, and after 3 days proteolysis and leucine oxidation fell 30-45%. Upon refeeding with the normal diet, protein synthesis also rose more rapidly (+30% by 1 day) than proteolysis, which increased significantly after 3 days (+60%). These different time courses suggest distinct endocrine signals for these responses. The high rate of protein synthesis and low rate of proteolysis during the first 3 days of refeeding a normal diet to PD rats contributes to the rapid weight gain ("catch-up growth") of such animals.

  3. Revascularization of Ischemic Skeletal Muscle by Estrogen-Related Receptor-?

    PubMed Central

    Matsakas, Antonios; Yadav, Vikas; Lorca, Sabina; Evans, Ronald M.; Narkar, Vihang A.

    2013-01-01

    Rationale Oxidative myofibers in the skeletal muscles express high levels of angiogenic factors, have dense vasculature, and promptly revascularize during ischemia. Estrogen-related receptor-gamma (ERR?) activates genes that govern metabolic and vascular features typical to oxidative myofibers. Therefore, ERR?-dependent remodeling of the myofibers may promote neoangiogenesis and restoration of blood perfusion in skeletal muscle ischemia. Objective To investigate the muscle fiber type remodeling by ERR? and its role in the vascular recovery of ischemic muscle. Methods and Results Using immunohistology, we show that skeletal muscle-specific transgenic overexpression of ERR? increases the proportions of oxidative and densely vascularized type IIA and IIX myofibers and decreases glycolytic and less vascularized type IIB myofibers. This myofiber remodeling results in a higher basal blood flow in the transgenic skeletal muscle. By applying unilateral hind limb ischemia to transgenic and wild-type mice, we found accelerated revascularization (fluorescent microangiography), restoration of blood perfusion (laser Doppler flowmetry), and muscle repair (Evans blue dye exclusion) in transgenic compared to wild-type ischemic muscles. This ameliorative effect is linked to enhanced neoangiogenesis (CD31 staining and microfil perfusion) by ERR?. Using cultured muscle cells in which ERR? is inactivated, we show that the receptor is dispensable for the classical hypoxic response of transcriptional upregulation and secretion of vascular endothelial growth factor A. Rather, the ameliorative effect of ERR? is linked to the receptor-mediated increase in oxidative myofibers that inherently express and secrete high levels of angiogenic factors. Conclusions The ERR? is a hypoxia-independent inducer of neoangiogenesis that can promote reparative revascularization. PMID:22415017

  4. Adenosine A3 receptor stimulation induces protection of skeletal muscle from eccentric exercise-mediated injury

    E-print Network

    Campbell, Kevin P.

    of exercise. In the vehicle-treated WT animals, eccentric exercise in- creased serum creatine kinase (CK injury. -sarcoglycan; muscle force; creatine kinase; inflammation SKELETAL MUSCLE IS SUSCEPTIBLE

  5. Human skeletal muscle responses to spaceflight and possible countermeasures

    NASA Technical Reports Server (NTRS)

    Gollnick, Philip D.; Edgerton, V. Reggie; Saltin, Bengt

    1990-01-01

    The current status of knowledge concerning the effects of unweighting skeletal muscle is summarized. The results of both ground-based and space-based animal studies are reviewed which show that there is rapid loss in muscle mass, primarily in slow-twitch muscle, of the rat during unweighting of muscle. There is also a shift in the myosin isoforms with muscles such that slow-twitch muscles take on many of the characteristics of fast-twitch muscles. Ground-based studies in human suggest that programs of electrical stimulation can be developed to simulate normal muscular contractions. Attempts to develop countermeasures to the adverse effects of space travel on muscular functions in humans have not been successful to date.

  6. Prospective heterotopic ossification progenitors in adult human skeletal muscle.

    PubMed

    Downey, Jennifer; Lauzier, Dominique; Kloen, Peter; Klarskov, Klaus; Richter, Martin; Hamdy, Reggie; Faucheux, Nathalie; Scimè, Anthony; Balg, Frédéric; Grenier, Guillaume

    2015-02-01

    Skeletal muscle has strong regenerative capabilities. However, failed regeneration can lead to complications where aberrant tissue forms as is the case with heterotopic ossification (HO), in which chondrocytes, osteoblasts and white and brown adipocytes can arise following severe trauma. In humans, the various HO cell types likely originate from multipotent mesenchymal stromal cells (MSCs) in skeletal muscle, which have not been identified in humans until now. In the present study, adherent cells from freshly digested skeletal muscle tissue were expanded in defined culture medium and were FACS-enriched for the CD73(+)CD105(+)CD90(-) population, which displayed robust multilineage potential. Clonal differentiation assays confirmed that all three lineages originated from a single multipotent progenitor. In addition to differentiating into typical HO lineages, human muscle resident MSCs (hmrMSCs) also differentiated into brown adipocytes expressing uncoupling protein 1 (UCP1). Characterizing this novel multipotent hmrMSC population with a brown adipocyte differentiation capacity has enhanced our understanding of the contribution of non-myogenic progenitor cells to regeneration and aberrant tissue formation in human skeletal muscle. PMID:25445454

  7. Avoidance of skeletal muscle atrophy in spontaneous and facultative hibernators.

    PubMed

    Cotton, Clark J; Harlow, Henry J

    2010-01-01

    Smooth and skeletal muscle changes were compared from overwintering white-tailed prairie dogs, spontaneous hibernators that undergo regular, low-temperature torpor bouts, and black-tailed prairie dogs, facultative hibernators that use sporadic, moderate-temperature torpor bouts. The objectives were to assess the abilities of these two species with dramatically different torpor patterns (1) to conserve skeletal muscle morphology, protein, and strength and (2) to use labile protein in the small intestine and liver during the winter season of reduced activity and food intake. Mass and protein concentration of the extensor digitorum longus (EDL), soleus, liver, and small intestine, as well as skeletal muscle strength and fiber morphology for the EDL and soleus, were compared before and after hibernation in both species. Both species appeared to be similar to overwintering black bears and underwent very little strength and protein loss, as compared with euthermic models of immobility and long-term fasting. Although the two species used vastly different hibernation strategies, none of the changes in parameters related to muscle atrophy and labile-protein use during the hibernation season differed significantly between them. Therefore, it appears that regardless of the phenotypic expressions of hibernation, the outcome is the conservation of skeletal muscle. PMID:20337528

  8. Functional classification of skeletal muscle networks. II. Applications to pathophysiology

    PubMed Central

    Wang, Yu; Winters, Jack

    2012-01-01

    In our preceding companion paper (Wang Y, Winters J, Subramaniam S. J Appl Physiol. doi: 10.1152/japplphysiol.01514.2011), we used extensive expression profile data on normal human subjects, in combination with legacy knowledge to classify skeletal muscle function into four models, namely excitation-activation, mechanical, metabolic, and signaling-production model families. In this paper, we demonstrate how this classification can be applied to study two well-characterized myopathies: amyotrophic lateral sclerosis (ALS) and Duchenne muscular dystrophy (DMD). Using skeletal muscle profile data from ALS and DMD patients compared with that from normal subjects, normal young in the case of DMD, we delineate molecular mechanisms that are causative and consequential to skeletal muscle dysfunction. In ALS, our analysis establishes the metabolic role and specifically identifies the mechanisms of calcium dysregulation and defects in mitochondrial transport of materials as important for muscle dysfunction. In DMD, we illustrate how impaired mechanical function is strongly coordinated with other three functional networks, resulting in transformation of the skeletal muscle into hybrid forms as a compensatory mechanism. Our functional models also provide, in exquisite detail, the mechanistic role of myriad proteins in these four families in normal and disease function. PMID:23085957

  9. Metformin Protects Skeletal Muscle from Cardiotoxin Induced Degeneration

    PubMed Central

    Langone, Francesca; Cannata, Stefano; Fuoco, Claudia; Lettieri Barbato, Daniele; Testa, Stefano; Nardozza, Aurelio Pio; Ciriolo, Maria Rosa; Castagnoli, Luisa; Gargioli, Cesare; Cesareni, Gianni

    2014-01-01

    The skeletal muscle tissue has a remarkable capacity to regenerate upon injury. Recent studies have suggested that this regenerative process is improved when AMPK is activated. In the muscle of young and old mice a low calorie diet, which activates AMPK, markedly enhances muscle regeneration. Remarkably, intraperitoneal injection of AICAR, an AMPK agonist, improves the structural integrity of muscles of dystrophin-deficient mdx mice. Building on these observations we asked whether metformin, a powerful anti-hyperglycemic drug, which indirectly activates AMPK, affects the response of skeletal muscle to damage. In our conditions, metformin treatment did not significantly influence muscle regeneration. On the other hand we observed that the muscles of metformin treated mice are more resilient to cardiotoxin injury displaying lesser muscle damage. Accordingly myotubes, originated in vitro from differentiated C2C12 myoblast cell line, become more resistant to cardiotoxin damage after pre-incubation with metformin. Our results indicate that metformin limits cardiotoxin damage by protecting myotubes from necrosis. Although the details of the molecular mechanisms underlying the protective effect remain to be elucidated, we report a correlation between the ability of metformin to promote resistance to damage and its capacity to counteract the increment of intracellular calcium levels induced by cardiotoxin treatment. Since increased cytoplasmic calcium concentrations characterize additional muscle pathological conditions, including dystrophies, metformin treatment could prove a valuable strategy to ameliorate the conditions of patients affected by dystrophies. PMID:25461598

  10. Leucine supplementation improves regeneration of skeletal muscles from old rats.

    PubMed

    Pereira, Marcelo G; Silva, Meiricris T; da Cunha, Fernanda M; Moriscot, Anselmo S; Aoki, Marcelo S; Miyabara, Elen H

    2015-12-01

    The decreased regenerative capacity of old skeletal muscles involves disrupted turnover of proteins. This study investigated whether leucine supplementation in old rats could improve muscle regenerative capacity. Young and old male Wistar rats were supplemented with leucine; then, the muscles were cryolesioned and examined after 3 and 10days. Leucine supplementation attenuated the decrease in the expression of eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1) and eukaryotic translation initiation factor 4E (eIF4E) in young and old muscles on day 3 post-injury and promoted an increase in the cross-sectional area of regenerating myofibers from both young and old soleus muscles on day 10 post-injury. This supplementation decreased the levels of ubiquitinated proteins and increased the proteasome activity in young regenerating muscles, but the opposite effect was observed in old regenerating muscles. Moreover, leucine decreased the inflammation area and induced an increase in the number of proliferating satellite cells in both young and old muscles. Our results suggest that leucine supplementation improves the regeneration of skeletal muscles from old rats, through the preservation of certain biological responses upon leucine supplementation. Such responses comprise the decrease in the inflammation area, increase in the number of proliferating satellite cells and size of regenerating myofibers, combined with the modulation of components of the phosphoinositide 3-kinase/Akt-protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway and ubiquitin-proteasome system. PMID:26481769

  11. Transcriptional regulation of decreased protein synthesis during skeletal muscle unloading

    NASA Technical Reports Server (NTRS)

    Howard, G.; Steffen, J. M.; Geoghegan, T. E.

    1989-01-01

    The regulatory role of transcriptional alterations in unloaded skeletal muscles was investigated by determining levels of total muscle RNA and mRNA fractions in soleus, gastrocnemius, and extensor digitorum longus (EDL) of rats subjected to whole-body suspension for up to 7 days. After 7 days, total RNA and mRNA contents were lower in soleus and gastrocnemius, compared with controls, but the concentrations of both RNAs per g muscle were unaltered. Alpha-actin mRNA (assessed by dot hybridization) was significantly reduced in soleus after 1, 3, and 7 days of suspension and in gastrocnemius after 3 and 7 days, but was unchanged in EDL. Protein synthesis directed by RNA extracted from soleus and EDL indicated marked alteration in mRNAs coding for several small proteins. Results suggest that altered transcription and availability of specific mRNAs contribute significantly to the regulation of protein synthesis during skeletal muscle unloading.

  12. The influence of skeletal muscle on systemic aging and lifespan

    PubMed Central

    Demontis, Fabio; Piccirillo, Rosanna; Goldberg, Alfred L.; Perrimon, Norbert

    2013-01-01

    SUMMARY Epidemiological studies in humans suggest that skeletal muscle aging is a risk factor for the development of several age-related diseases such as metabolic syndrome, cancer, Alzheimer’s disease, and Parkinson’s disease. Here we review recent studies in mammals and Drosophila highlighting how nutrient- and stress-sensing in skeletal muscle can influence lifespan and overall aging of the organism. In addition to exercise and indirect effects of muscle metabolism, growing evidence suggests that muscle-derived growth factors and cytokines, known as myokines, modulate systemic physiology. Myokines may influence the progression of age-related diseases and contribute to the inter-tissue communication that underlies systemic aging. PMID:23802635

  13. Biomaterial-based delivery for skeletal muscle repair.

    PubMed

    Cezar, Christine A; Mooney, David J

    2015-04-01

    Skeletal muscle possesses a remarkable capacity for regeneration in response to minor damage, but severe injury resulting in a volumetric muscle loss can lead to extensive and irreversible fibrosis, scarring, and loss of muscle function. In early clinical trials, the intramuscular injection of cultured myoblasts was proven to be a safe but ineffective cell therapy, likely due to rapid death, poor migration, and immune rejection of the injected cells. In recent years, appropriate therapeutic cell types and culturing techniques have improved progenitor cell engraftment upon transplantation. Importantly, the identification of several key biophysical and biochemical cues that synergistically regulate satellite cell fate has paved the way for the development of cell-instructive biomaterials that serve as delivery vehicles for cells to promote in vivo regeneration. Material carriers designed to spatially and temporally mimic the satellite cell niche may be of particular importance for the complete regeneration of severely damaged skeletal muscle. PMID:25271446

  14. Is Visfatin an Adipokine or Myokine? Evidence for Greater Visfatin Expression in Skeletal Muscle than

    E-print Network

    Ramachandran, Ramesh

    skeletal muscle growth and visceral fat accretion occurring in broiler chickens during this period. However skeletal muscle growth and metabolism. (Endocrinology 149: 1543­1550, 2008) THE GROWING OBESITY epidemicIs Visfatin an Adipokine or Myokine? Evidence for Greater Visfatin Expression in Skeletal Muscle

  15. Ultrastructural alterations in skeletal muscle fibers of rats after exercise

    NASA Technical Reports Server (NTRS)

    Akuzawa, M.; Hataya, M.

    1982-01-01

    Ultrastructural alterations in skeletal muscle fibers were electron microscopically studied in rats forced to run on the treadmill until all-out. When they were mild and limited to relatively small areas, the reconstruction of filaments ensued within 10 days without infiltration of cells. When they were severe and extensive, phagocytes infiltrated in the lesions and removed degenerative sacroplasmic debris from muscle fibers. A little later, myoblasts appeared and regeneration was accomplished in 30 days in much the same manner as in myogenesis.

  16. Myopathic changes in murine skeletal muscle lacking synemin.

    PubMed

    García-Pelagio, Karla P; Muriel, Joaquin; O'Neill, Andrea; Desmond, Patrick F; Lovering, Richard M; Lund, Linda; Bond, Meredith; Bloch, Robert J

    2015-03-15

    Diseases of striated muscle linked to intermediate filament (IF) proteins are associated with defects in the organization of the contractile apparatus and its links to costameres, which connect the sarcomeres to the cell membrane. Here we study the role in skeletal muscle of synemin, a type IV IF protein, by examining mice null for synemin (synm-null). Synm-null mice have a mild skeletal muscle phenotype. Tibialis anterior (TA) muscles show a significant decrease in mean fiber diameter, a decrease in twitch and tetanic force, and an increase in susceptibility to injury caused by lengthening contractions. Organization of proteins associated with the contractile apparatus and costameres is not significantly altered in the synm-null. Elastimetry of the sarcolemma and associated contractile apparatus in extensor digitorum longus myofibers reveals a reduction in tension consistent with an increase in sarcolemmal deformability. Although fatigue after repeated isometric contractions is more marked in TA muscles of synm-null mice, the ability of the mice to run uphill on a treadmill is similar to controls. Our results suggest that synemin contributes to linkage between costameres and the contractile apparatus and that the absence of synemin results in decreased fiber size and increased sarcolemmal deformability and susceptibility to injury. Thus synemin plays a moderate but distinct role in fast twitch skeletal muscle. PMID:25567810

  17. Characterization of a 6K oligonucleotide turkey skeletal muscle microarray.

    PubMed

    Sporer, K R B; Chiang, W; Tempelman, R J; Ernst, C W; Reed, K M; Velleman, S G; Strasburg, G M

    2011-02-01

    Consumer demand for lean, inexpensive meat products has driven the domestic turkey (Meleagris gallopavo) industry to unprecedented production; however, this has coincided with an increase in growth-induced myopathies and meat quality defects. With the aim of developing a new tool for the study of turkey growth and development at the muscle transcriptome level, a 6K oligonucleotide microarray was constructed, the Turkey Skeletal Muscle Long Oligo (TSKMLO) microarray. Skeletal muscle samples were collected at three critical stages in muscle development: 18-day embryo (hyperplasia), 1-day post-hatch (hypertrophy), and 16-week (market age) from two genetic lines of turkeys: RBC2, a line maintained without selection pressure, and F, a line selected from the RBC2 line for increased 16-week body weight. Oligonucleotides were designed from sequences obtained from skeletal muscle cDNA libraries from the three developmental stages. Several unique controls, including mismatch and distance controls and scrambled sequences, were designed for 30 genes. Quality control hybridizations were completed, confirming the validity and repeatability of the array. Control features were evaluated across two larger experiments comparing developmental stage within genetic line or genetic line within each developmental stage, totaling 70 arrays. Mismatch and scrambled sequences appeared to be useful controls of specific hybridization for most genes. In addition, quantitative real-time RT-PCR confirmed microarray results. This creation and assessment of the TSKMLO array provides a valuable community resource for the study of gene expression changes related to turkey muscle growth and development. PMID:20528844

  18. Regulation of skeletal muscle capillary growth in exercise and disease.

    PubMed

    Haas, Tara L; Nwadozi, Emmanuel

    2015-12-01

    Capillaries, which are the smallest and most abundant type of blood vessel, form the primary site of gas, nutrient, and waste transfer between the vascular and tissue compartments. Skeletal muscle exhibits the capacity to generate new capillaries (angiogenesis) as an adaptation to exercise training, thus ensuring that the heightened metabolic demand of the active muscle is matched by an improved capacity for distribution of gases, nutrients, and waste products. This review summarizes the current understanding of the regulation of skeletal muscle capillary growth. The multi-step process of angiogenesis is coordinated through the integration of a diverse array of signals associated with hypoxic, metabolic, hemodynamic, and mechanical stresses within the active muscle. The contributions of metabolic and mechanical factors to the modulation of key pro- and anti-angiogenic molecules are discussed within the context of responses to a single aerobic exercise bout and short-term and long-term training. Finally, the paradoxical lack of angiogenesis in peripheral artery disease and diabetes and the implications for disease progression and muscle health are discussed. Future studies that emphasize an integrated analysis of the mechanisms that control skeletal muscle capillary growth will enable development of targeted exercise programs that effectively promote angiogenesis in healthy individuals and in patient populations. PMID:26554747

  19. Advancements in stem cells treatment of skeletal muscle wasting

    PubMed Central

    Meregalli, Mirella; Farini, Andrea; Sitzia, Clementina; Torrente, Yvan

    2014-01-01

    Muscular dystrophies (MDs) are a heterogeneous group of inherited disorders, in which progressive muscle wasting and weakness is often associated with exhaustion of muscle regeneration potential. Although physiological properties of skeletal muscle tissue are now well known, no treatments are effective for these diseases. Muscle regeneration was attempted by means transplantation of myogenic cells (from myoblast to embryonic stem cells) and also by interfering with the malignant processes that originate in pathological tissues, such as uncontrolled fibrosis and inflammation. Taking into account the advances in the isolation of new subpopulation of stem cells and in the creation of artificial stem cell niches, we discuss how these emerging technologies offer great promises for therapeutic approaches to muscle diseases and muscle wasting associated with aging. PMID:24575052

  20. Leucine supplementation of a low-protein meal increases skeletal muscle and visceral tissue protein synthesis in neonatal pigs by stimulating mTOR-dependent translation initiation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Protein synthesis and eukaryotic initiation factor (eIF) activation are increased in skeletal muscle of neonatal pigs parenterally infused with amino acids. Leucine appears to be the most effective single amino acid to trigger these effects. To examine the response to enteral leucine supplementation...

  1. Differential global gene expression in red and white skeletal muscle

    NASA Technical Reports Server (NTRS)

    Campbell, W. G.; Gordon, S. E.; Carlson, C. J.; Pattison, J. S.; Hamilton, M. T.; Booth, F. W.

    2001-01-01

    The differences in gene expression among the fiber types of skeletal muscle have long fascinated scientists, but for the most part, previous experiments have only reported differences of one or two genes at a time. The evolving technology of global mRNA expression analysis was employed to determine the potential differential expression of approximately 3,000 mRNAs between the white quad (white muscle) and the red soleus muscle (mixed red muscle) of female ICR mice (30-35 g). Microarray analysis identified 49 mRNA sequences that were differentially expressed between white and mixed red skeletal muscle, including newly identified differential expressions between muscle types. For example, the current findings increase the number of known, differentially expressed mRNAs for transcription factors/coregulators by nine and signaling proteins by three. The expanding knowledge of the diversity of mRNA expression between white and mixed red muscle suggests that there could be quite a complex regulation of phenotype between muscles of different fiber types.

  2. Role of PKC? in Insulin Sensitivity and Skeletal Muscle Metabolism.

    PubMed

    Li, Mengyao; Vienberg, Sara G; Bezy, Olivier; O'Neill, Brian T; Kahn, C Ronald

    2015-12-01

    Protein kinase C (PKC)? has been shown to be increased in liver in obesity and plays an important role in the development of hepatic insulin resistance in both mice and humans. In the current study, we explored the role of PKC? in skeletal muscle in the control of insulin sensitivity and glucose metabolism by generating mice in which PKC? was deleted specifically in muscle using Cre-lox recombination. Deletion of PKC? in muscle improved insulin signaling in young mice, especially at low insulin doses; however, this did not change glucose tolerance or insulin tolerance tests done with pharmacological levels of insulin. Likewise, in young mice, muscle-specific deletion of PKC? did not rescue high-fat diet-induced insulin resistance or glucose intolerance. However, with an increase in age, PKC? levels in muscle increased, and by 6 to 7 months of age, muscle-specific deletion of PKC? improved whole-body insulin sensitivity and muscle insulin resistance and by 15 months of age improved the age-related decline in whole-body glucose tolerance. At 15 months of age, M-PKC?KO mice also exhibited decreased metabolic rate and lower levels of some proteins of the OXPHOS complex suggesting a role for PKC? in the regulation of mitochondrial mass at older age. These data indicate an important role of PKC? in the regulation of insulin sensitivity and mitochondrial homeostasis in skeletal muscle with aging. PMID:26307588

  3. Adipose tissue and skeletal muscle blood flow during mental stress

    SciTech Connect

    Linde, B.; Hjemdahl, P.; Freyschuss, U.; Juhlin-Dannfelt, A.

    1989-01-01

    Mental stress (a modified Stroop color word conflict test (CWT)) increased adipose tissue blood flow (ATBF; 133Xe clearance) by 70% and reduced adipose tissue vascular resistance (ATR) by 25% in healthy male volunteers. The vasculatures of adipose tissue (abdomen as well as thigh), skeletal muscle of the calf (133Xe clearance), and the entire calf (venous occlusion plethysmography) responded similarly. Arterial epinephrine (Epi) and glycerol levels were approximately doubled by stress. Beta-Blockade by metoprolol (beta 1-selective) or propranolol (nonselective) attenuated CWT-induced tachycardia similarly. Metoprolol attenuated stress-induced vasodilation in the calf and tended to do so in adipose tissue. Propranolol abolished vasodilation in the calf and resulted in vasoconstriction during CWT in adipose tissue. Decreases in ATR, but not in skeletal muscle or calf vascular resistances, were correlated to increases in arterial plasma glycerol (r = -0.42, P less than 0.05), whereas decreases in skeletal muscle and calf vascular resistances, but not in ATR, were correlated to increases in arterial Epi levels (r = -0.69, P less than 0.01; and r = -0.43, P less than 0.05, respectively). The results suggest that mental stress increases nutritive blood flow in adipose tissue and skeletal muscle considerably, both through the elevation of perfusion pressure and via vasodilatation. Withdrawal of vasoconstrictor nerve activity, vascular beta 2-adrenoceptor stimulation by circulating Epi, and metabolic mechanisms (in adipose tissue) may contribute to the vasodilatation.

  4. Physical injuries, contractures and rigidity of skeletal muscle

    SciTech Connect

    Korenyi-Both, A.L.; Korenyi-Both, I.

    1986-01-01

    The authors condensed their knowledge of physical injuries of skeletal muscle, particularly injuries caused by mechanical energy, atmospheric pressure, radiation, extremes of temperature and electricity. The possible perils, outcomes and consequences are discussed. Special attention is given to the military medical projections.

  5. Neural Regulation of -Dystroglycan Biosynthesis and Glycosylation in Skeletal Muscle

    E-print Network

    Campbell, Kevin P.

    that muscular dystrophies might result from a primary defect in mo- toneurons (Bradley, 1974). More recently dystrophies (reviewed by Campbell, 1995). Although these studies have revealed that Duchenne and related, extensive progress has been made in our understanding of the degeneration of skeletal muscle in muscular

  6. MicroRNA Transcriptome Profiles During Swine Skeletal Muscle Development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    MicroRNA (miR) are a class of small RNAs that regulate gene expression by inhibiting translation of protein encoding transcripts. To evaluate the role of miR in skeletal muscle of swine, global microRNA abundance was measured at specific developmental stages including proliferating satellite cells,...

  7. Acylated and unacylated ghrelin impair skeletal muscle atrophy in mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cachexia is a wasting syndrome associated with cancer, AIDS, multiple sclerosis, and several other disease states. It is characterized by weight loss, fatigue, loss of appetite, and skeletal muscle atrophy and is associated with poor patient prognosis, making it an important treatment target. Ghreli...

  8. Redox Signaling in Skeletal Muscle: Role of Aging and Exercise

    ERIC Educational Resources Information Center

    Ji, Li Li

    2015-01-01

    Skeletal muscle contraction is associated with the production of ROS due to altered O[subscript 2] distribution and flux in the cell. Despite a highly efficient antioxidant defense, a small surplus of ROS, such as hydrogen peroxide and nitric oxide, may serve as signaling molecules to stimulate cellular adaptation to reach new homeostasis largely…

  9. Noncoding RNAs, Emerging Regulators of Skeletal Muscle Development and Diseases

    PubMed Central

    Nie, Mao; Deng, Zhong-Liang; Liu, Jianming; Wang, Da-Zhi

    2015-01-01

    A healthy and independent life requires skeletal muscles to maintain optimal function throughout the lifespan, which is in turn dependent on efficient activation of processes that regulate muscle development, homeostasis, and metabolism. Thus, identifying mechanisms that modulate these processes is of crucial priority. Noncoding RNAs (ncRNAs), including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), have emerged as a class of previously unrecognized transcripts whose importance in a wide range of biological processes and human disease is only starting to be appreciated. In this review, we summarize the roles of recently identified miRNAs and lncRNAs during skeletal muscle development and pathophysiology. We also discuss several molecular mechanisms of these noncoding RNAs. Undoubtedly, further systematic understanding of these noncoding RNAs' functions and mechanisms will not only greatly expand our knowledge of basic skeletal muscle biology, but also significantly facilitate the development of therapies for various muscle diseases, such as muscular dystrophies, cachexia, and sarcopenia. PMID:26258142

  10. Skeletal muscle responses to lower limb suspension in humans

    NASA Technical Reports Server (NTRS)

    Hather, Bruce M.; Adams, Gregory R.; Tesch, Per A.; Dudley, Gary A.

    1992-01-01

    The morphological responses of human skeletal muscle to unweighting were assessed by analyzing multiple transaxial magnetic resonance (MR) images of both lower limbs and skeletal muscle biopsies of the unweighted lower limb before and after six weeks of unilaterial (left) lower limb suspension (ULLS). Results indicated that, as a results of 6 weeks of unweighting (by the subjects walking on crutches using only one limb), the cross sectional area (CSA) of the thigh muscle of the unweighted left limb decreased 12 percent, while the CSA of the right thigh muscle did not change. The decrease was due to a twofold greater response of the knee extensors than the knee flexors. The pre- and post-ULLS biopsies of the left vastus lateralis showed a 14 percent decrease in average fiber CSA due to unweighting. The number of capillaries surrounding the different fiber types was unchanged after ULLS. Results showed that the adaptive responses of human skeletal muscle to unweighting are qualitatively, but not quantitatively, similar to those of lower mammals and not necessarily dependent on the fiber-type composition.

  11. [Concentration of macroergic phosphates and oxidative potential of skeletal muscles].

    PubMed

    Nemirovskaia, T L; Shenkman, B S; Mazin, M G; Koshelev, V B; Maevski?, E I; Grishina, E

    2000-01-01

    It is known that a long-duration decline of high-energy phosphate (HP) level in skeletal muscles, induced by administration of beta-guanidinpropionic acid (beta-GPA), is followed by an increase in mitochondrial enzyme activities (MEA). The same increase in MEA was observed in the course of physical exercise training. Under gravitational inloading decrease in MEA and increase in the level of high-energy phosphates occurred. If changes in (HP) level are believed to trigger the alterations in MEA, the increase in high-energy phosphate levels in muscles is to lead to a decline in MEA as well. The present work was purposed to reveal if changes in HP level under different contractile activity levels may be associated with changes in oxidative potential in the skeletal muscles. PMID:10709257

  12. Improved Cell Culture Method for Growing Contracting Skeletal Muscle Models

    NASA Technical Reports Server (NTRS)

    Marquette, Michele L.; Sognier, Marguerite A.

    2013-01-01

    An improved method for culturing immature muscle cells (myoblasts) into a mature skeletal muscle overcomes some of the notable limitations of prior culture methods. The development of the method is a major advance in tissue engineering in that, for the first time, a cell-based model spontaneously fuses and differentiates into masses of highly aligned, contracting myotubes. This method enables (1) the construction of improved two-dimensional (monolayer) skeletal muscle test beds; (2) development of contracting three-dimensional tissue models; and (3) improved transplantable tissues for biomedical and regenerative medicine applications. With adaptation, this method also offers potential application for production of other tissue types (i.e., bone and cardiac) from corresponding precursor cells.

  13. Compartmentalization of NO signaling cascade in skeletal muscles

    SciTech Connect

    Buchwalow, Igor B. . E-mail: buchwalo@uni-muenster.de; Minin, Evgeny A.; Samoilova, Vera E.; Boecker, Werner; Wellner, Maren; Schmitz, Wilhelm; Neumann, Joachim

    2005-05-06

    Skeletal muscle functions regulated by NO are now firmly established. However, the literature on the compartmentalization of NO signaling in myocytes is highly controversial. To address this issue, we examined localization of enzymes engaged in L-arginine-NO-cGMP signaling in the rat quadriceps muscle. Employing immunocytochemical labeling complemented with tyramide signal amplification and electron microscopy, we found NO synthase expressed not only in the sarcolemma, but also along contractile fibers, in the sarcoplasmic reticulum and mitochondria. The expression pattern of NO synthase in myocytes showed striking parallels with the enzymes engaged in L-arginine-NO-cGMP signaling (arginase, phosphodiesterase, and soluble guanylyl cyclase). Our findings are indicative of an autocrine fashion of NO signaling in skeletal muscles at both cellular and subcellular levels, and challenge the notion that the NO generation is restricted to the sarcolemma.

  14. Multinucleation of Skeletal Muscle in vitro

    PubMed Central

    Capers, Charles R.

    1960-01-01

    Healthy, mature, spontaneously contracting muscle was cultivated from explants of 13-day chick embryos for periods up to 4 months in the multipurpose chamber (Rose, 1954) using cellophane-strip technique (Rose et al., 1958) with silicone gaskets, Eagle's medium including 10 per cent horse serum reinforced with 300 mg-per cent of glucose, and the teased type of explant. This method provided optically ideal conditions for the study of muscle fibers with oil immersion, phase contrast time-lapse cinematography at 1 frame per minute without apparent damage for periods as long as 10 days. In no case was mitosis, amitosis, or nuclear "budding" observed in the course of muscle development. Multinuclear muscle fibers have been shown with cine technique to result from both myoblast fusion and polar extension of preformed (explanted) muscle tissue. Myoblast fusion was the only demonstrable way of giving rise to multinucleation. Nuclear membrane "wrinkling" was shown to be merely a temporary distortion that occurred during nuclear migration and rotation. It is suggested that this phenomenon may be responsible for numerous reports of amitosis in the genesis of muscle fibers. The histological development of new straps resulted from an orderly sequence of events. Included in these were polar extension, nuclear migration, rotation, and fixation. Following these events there was increased mitochondrial activity, myofibril formation, and cross-banding. Spontaneous contractions were seen throughout the entire course of differentiation in vitro but became more regular and stronger in the later stages. PMID:13807523

  15. Enhanced Myogenesis in adult skeletal muscle by transgenic expression of Myostatin Propeptide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Skeletal muscle growth and maintenance are essential for human health. One of the muscle regulatory genes, namely myostatin, a member of transforming growth factor-ß, plays a dominant role in the genetic control of muscle mass. Transgenic expression of myostatin propeptide in skeletal muscle showed ...

  16. Optimizing IGF-I for skeletal muscle therapeutics

    PubMed Central

    Philippou, Anastassios; Barton, Elisabeth R.

    2015-01-01

    It is virtually undisputed that IGF-I promotes cell growth and survival. However, the presence of several IGF-I isoforms, vast numbers of intracellular signaling components, and multiple receptors results in a complex and highly regulated system by which IGF-I actions are mediated. IGF-I has long been recognized as one of the critical factors for coordinating muscle growth, enhancing muscle repair, and increasing muscle mass and strength. How to optimize this panoply of pathways to drive anabolic processes in muscle as opposed to aberrant growth in other tissues is an area that deserves focus. This review will address how advances in the bioavailability, potency, and tissue response of IGF-I can provide new potential directions for skeletal muscle therapeutics. PMID:25002025

  17. Prolonged bed rest decreases skeletal muscle and whole body protein synthesis

    NASA Technical Reports Server (NTRS)

    Ferrando, A. A.; Lane, H. W.; Stuart, C. A.; Davis-Street, J.; Wolfe, R. R.

    1996-01-01

    We sought to determine the extent to which the loss of lean body mass and nitrogen during inactivity was due to alterations in skeletal muscle protein metabolism. Six male subjects were studied during 7 days of diet stabilization and after 14 days of stimulated microgravity (-6 degrees bed rest). Nitrogen balance became more negative (P < 0.03) during the 2nd wk of bed rest. Leg and whole body lean mass decreased after bed rest (P < 0.05). Serum cortisol, insulin, insulin-like growth factor I, and testosterone values did not change. Arteriovenous model calculations based on the infusion of L-[ring-13C6]-phenylalanine in five subjects revealed a 50% decrease in muscle protein synthesis (PS; P < 0.03). Fractional PS by tracer incorporation into muscle protein also decreased by 46% (P < 0.05). The decrease in PS was related to a corresponding decrease in the sum of intracellular amino acid appearance from protein breakdown and inward transport. Whole body protein synthesis determined by [15N]alanine ingestion on six subjects also revealed a 14% decrease (P < 0.01). Neither model-derived nor whole body values for protein breakdown change significantly. These results indicate that the loss of body protein with inactivity is predominantly due to a decrease in muscle PS and that this decrease is reflected in both whole body and skeletal muscle measures.

  18. Neuromuscular Electrical Stimulation for Skeletal Muscle Function

    PubMed Central

    Doucet, Barbara M.; Lam, Amy; Griffin, Lisa

    2012-01-01

    Lack of neural innervation due to neurological damage renders muscle unable to produce force. Use of electrical stimulation is a medium in which investigators have tried to find a way to restore movement and the ability to perform activities of daily living. Different methods of applying electrical current to modify neuromuscular activity are electrical stimulation (ES), neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS), and functional electrical stimulation (FES). This review covers the aspects of electrical stimulation used for rehabilitation and functional purposes. Discussed are the various parameters of electrical stimulation, including frequency, pulse width/duration, duty cycle, intensity/amplitude, ramp time, pulse pattern, program duration, program frequency, and muscle group activated, and how they affect fatigue in the stimulated muscle. PMID:22737049

  19. Muscle contraction controls skeletal morphogenesis through regulation of chondrocyte convergent extension

    E-print Network

    chondrocyte intercalation in growth plates of muscle-less Spd mouse embryos, implying the evolutionaryMuscle contraction controls skeletal morphogenesis through regulation of chondrocyte convergent 2012 Keywords: Chondrocyte intercalation Convergent extension Muscle contraction Mechanical load

  20. The creation of a measurable contusion injury in skeletal muscle.

    PubMed

    Deane, Margaret N; Gregory, Michael; Mars, Maurice

    2014-01-01

    The effect that compressed air massage (CAM) has on skeletal muscle has been ascertained by the morphological and morphometric evaluation of healthy vervet monkey and rabbit skeletal muscle. How CAM may influence the process of healing following a contusion injury is not known. To determine how CAM or other physiotherapeutic modalities may influence healing, it is necessary to create a minor injury that is both reproducible and quantifiable at the termination of a pre-determined healing period. An earlier study described changes in the morphology of skeletal muscle following a reproducible contusion injury. This study extended that work in that it attempted to quantify the 'severity' of such an injury. A 201 g, elongated oval-shaped weight was dropped seven times through a 1 m tube onto the left vastus lateralis muscle of four New Zealand white rabbits. Biopsies were obtained 6 days after injury from the left healing juxta-bone and sub-dermal muscle and uninjured (control) right vastus lateralis of each animal. The tissue was fixed in formal saline, embedded in wax, cut and stained with haematoxylin and phosphotungstic haematoxylin. The muscle was examined by light microscopy and quantification of the severity of injury made using a modified, 'in-house' morphological index and by the comparative morphometric measurement of the cross-sectioned epimysium and myofibres in injured and control muscle. The results showed that a single contusion causes multiple, quantifiable degrees of injury from skin to bone - observations of particular importance to others wishing to investigate contusion injury in human or animal models. PMID:25686259

  1. Defining skeletal muscle resident progenitors and their cell fate potentials.

    PubMed

    Pannérec, Alice; Formicola, Luigi; Besson, Vanessa; Marazzi, Giovanna; Sassoon, David A

    2013-07-01

    The satellite cell is the major tissue-resident stem cell underlying muscle regeneration; however, multiple non-satellite myogenic progenitors as well as non-myogenic populations that support the muscle regenerative process have been identified. PW1 is expressed in satellite cells as well as in a subset of interstitial cells with myogenic potential termed PICs (PW1+ interstitial cells). Microarray profiling revealed that PICs express a broad range of genes common to mesenchymal stem cells, whereas satellite cells express genes consistent with a committed myogenic progenitor. Isolated PICs from both young and adult muscles can differentiate into smooth and skeletal muscle and fat whereas satellite cells are restricted to a skeletal muscle fate. We demonstrate that the adipogenic potential of PICs corresponds to a subpopulation that expresses platelet derived growth factor receptor alpha (PDGFR?) and overlaps with the recently described interstitial adipogenic progenitors. By contrast, PICs with myogenic potential do not express PDGFR?. Moreover, we observe a discrete and transient population of juvenile PICs based upon SCA1 expression that disappears by 3 weeks of postnatal development coincident with a switch in the cellular and genetic mechanisms underlying postnatal muscle growth. PMID:23739133

  2. Neurofibromin (Nf1) is required for skeletal muscle development

    PubMed Central

    Kossler, Nadine; Stricker, Sigmar; Rödelsperger, Christian; Robinson, Peter N.; Kim, Johnny; Dietrich, Carola; Osswald, Monika; Kühnisch, Jirko; Stevenson, David A.; Braun, Thomas; Mundlos, Stefan; Kolanczyk, Mateusz

    2011-01-01

    Neurofibromatosis type 1 (NF1) is a multi-system disease caused by mutations in the NF1 gene encoding a Ras-GAP protein, neurofibromin, which negatively regulates Ras signaling. Besides neuroectodermal malformations and tumors, the skeletal system is often affected (e.g. scoliosis and long bone dysplasia) demonstrating the importance of neurofibromin for development and maintenance of the musculoskeletal system. Here, we focus on the role of neurofibromin in skeletal muscle development. Nf1 gene inactivation in the early limb bud mesenchyme using Prx1-cre (Nf1Prx1) resulted in muscle dystrophy characterized by fibrosis, reduced number of muscle fibers and reduced muscle force. This was caused by an early defect in myogenesis affecting the terminal differentiation of myoblasts between E12.5 and E14.5. In parallel, the muscle connective tissue cells exhibited increased proliferation at E14.5 and an increase in the amount of connective tissue as early as E16.5. These changes were accompanied by excessive mitogen-activated protein kinase pathway activation. Satellite cells isolated from Nf1Prx1 mice showed normal self-renewal, but their differentiation was impaired as indicated by diminished myotube formation. Our results demonstrate a requirement of neurofibromin for muscle formation and maintenance. This previously unrecognized function of neurofibromin may contribute to the musculoskeletal problems in NF1 patients. PMID:21478499

  3. Effect of insulin on human skeletal muscle mitochondrial ATP production, protein synthesis, and mRNA transcripts

    NASA Astrophysics Data System (ADS)

    Stump, Craig S.; Short, Kevin R.; Bigelow, Maureen L.; Schimke, Jill M.; Sreekumaran Nair, K.

    2003-06-01

    Mitochondria are the primary site of skeletal muscle fuel metabolism and ATP production. Although insulin is a major regulator of fuel metabolism, its effect on mitochondrial ATP production is not known. Here we report increases in vastus lateralis muscle mitochondrial ATP production capacity (32-42%) in healthy humans (P < 0.01) i.v. infused with insulin (1.5 milliunits/kg of fat-free mass per min) while clamping glucose, amino acids, glucagon, and growth hormone. Increased ATP production occurred in association with increased mRNA levels from both mitochondrial (NADH dehydrogenase subunit IV) and nuclear [cytochrome c oxidase (COX) subunit IV] genes (164-180%) encoding mitochondrial proteins (P < 0.05). In addition, muscle mitochondrial protein synthesis, and COX and citrate synthase enzyme activities were increased by insulin (P < 0.05). Further studies demonstrated no effect of low to high insulin levels on muscle mitochondrial ATP production for people with type 2 diabetes mellitus, whereas matched nondiabetic controls increased 16-26% (P < 0.02) when four different substrate combinations were used. In conclusion, insulin stimulates mitochondrial oxidative phosphorylation in skeletal muscle along with synthesis of gene transcripts and mitochondrial protein in human subjects. Skeletal muscle of type 2 diabetic patients has a reduced capacity to increase ATP production with high insulin levels. cytochrome c oxidase | NADH dehydrogenase subunit IV | amino acids | citrate synthase

  4. Skeletal muscle microvascular function in girls with Turner syndrome

    PubMed Central

    West, Sarah L.; O'Gorman, Clodagh S.; Elzibak, Alyaa H.; Caterini, Jessica; Noseworthy, Michael D.; Rayner, Tammy; Hamilton, Jill; Wells, Greg D.

    2014-01-01

    Background Exercise intolerance is prevalent in individuals with Turner Syndrome (TS). We recently demonstrated that girls with TS have normal aerobic but altered skeletal muscle anaerobic metabolism compared to healthy controls (HC). The purpose of this study was to compare peripheral skeletal muscle microvascular function in girls with TS to HC after exercise. We hypothesized that girls with TS would have similar muscle blood-oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) signal responses during recovery from exercise compared to HC. Methods Thirteen TS participants and 8 HC completed testing. BOLD MRI was used to measure skeletal muscle microvascular response during 60 second recovery, following 60 s of exercise at 65% of maximal workload. Exercise and recovery were repeated four times, and the BOLD signal time course was fit to a four-parameter sigmoid function. Results Participants were 13.7 ± 3.1 years old and weighed 47.9 ± 14.6 kg. The mean change in BOLD signal intensity following exercise at the end of recovery, the mean response time of the function/the washout of deoxyhemoglobin, and the mean half-time of recovery were similar between the TS and HC groups. Conclusions Our results demonstrate that compared to HC, peripheral skeletal muscle microvascular function following exercise in girls with TS is not impaired. General significance This study supports the idea that the aerobic energy pathway is not impaired in children with TS in response to submaximal exercise. Other mechanisms are likely responsible for exercise intolerance in TS; this needs to be further investigated. PMID:26676172

  5. The Effect of Statins on Skeletal Muscle Function

    PubMed Central

    Parker, Beth A.; Capizzi, Jeffrey A.; Grimaldi, Adam S.; Clarkson, Priscilla M.; Cole, Stephanie M.; Keadle, Justin; Chipkin, Stuart; Pescatello, Linda S.; Simpson, Kathleen; White, C. Michael; Thompson, Paul D.

    2015-01-01

    Background Many clinicians believe that statins cause muscle pain, but this has not been observed in clinical trials and the effect of statins on muscle performance has not been carefully studied. Methods and Results The Effect of STatins On Skeletal Muscle Function and Performance (STOMP) study assessed symptoms and measured creatine kinase (CK), exercise capacity, and muscle strength before and after atorvastatin 80 mg or placebo were administered for 6 months to 420 healthy, statin-naive subjects. No individual CK value exceeded 10 times normal, but average CK increased 20.8 ± 141.1 U/L (p<0.0001) with atorvastatin. There were no significant changes in several measures of muscle strength or exercise capacity with atorvastatin, but more atorvastatin than placebo subjects developed myalgia (19 vs 10; p = 0.05). Myalgic subjects on atorvastatin or placebo decreased muscle strength in 5 of 14 and 4 of 14 variables respectively (p = 0.69). Conclusions These results indicate that high-dose atorvastatin for 6 months does not decrease average muscle strength or exercise performance in healthy, previously untreated subjects. Nevertheless, this blinded, controlled trial confirms the undocumented impression that statins increase muscle complaints. Atorvastatin also increased average CK suggesting that statins produce mild muscle injury even among asymptomatic subjects. This increase in CK should prompt studies examining the effects of more prolonged, high-dose statin treatment on muscular performance. Clinical Trial Registration Information: www.clinicaltrials.gov; Identifier: NCT00609063. PMID:23183941

  6. Skeletal muscle calcineurin: influence of phenotype adaptation and atrophy

    NASA Technical Reports Server (NTRS)

    Spangenburg, E. E.; Williams, J. H.; Roy, R. R.; Talmadge, R. J.; Spangenberg, E. E. (Principal Investigator)

    2001-01-01

    Calcineurin (CaN) has been implicated as a signaling molecule that can transduce physiological stimuli (e.g., contractile activity) into molecular signals that initiate slow-fiber phenotypic gene expression and muscle growth. To determine the influence of muscle phenotype and atrophy on CaN levels in muscle, the levels of soluble CaN in rat muscles of varying phenotype, as assessed by myosin heavy chain (MHC)-isoform proportions, were determined by Western blotting. CaN levels were significantly greater in the plantaris muscle containing predominantly fast (IIx and IIb) MHC isoforms, compared with the soleus (predominantly type I MHC) or vastus intermedius (VI, contains all 4 adult MHC isoforms). Three months after a complete spinal cord transection (ST), the CaN levels in the VI muscle were significantly reduced, despite a significant increase in fast MHC isoforms. Surprisingly, the levels of CaN in the VI were highly correlated with muscle mass but not MHC isoform proportions in ST and control rats. These data demonstrate that CaN levels in skeletal muscle are highly correlated to muscle mass and that the normal relationship with phenotype is lost after ST.

  7. Activity Dependent Signal Transduction in Skeletal Muscle

    NASA Technical Reports Server (NTRS)

    Hamilton, Susan L.

    1999-01-01

    The overall goals of this project are: 1) to define the initial signal transduction events whereby the removal of gravitational load from antigravity muscles, such as the soleus, triggers muscle atrophy, and 2) to develop countermeasures to prevent this from happening. Our rationale for this approach is that, if countermeasures can be developed to regulate these early events, we could avoid having to deal with the multiple cascades of events that occur downstream from the initial event. One of our major findings is that hind limb suspension causes an early and sustained increase in intracellular Ca(2+) concentration ([Ca (2+)](sub i)). In most cells the consequences of changes in ([Ca (2+)](sub i))depend on the amplitude, frequency and duration of the Ca(2+) signal and on other factors in the intracellular environment. We propose that muscle remodeling in microgravity represents a change in the balance among several CA(2+) regulated signal transduction pathways, in particular those involving the transcription factors NFAT and NFkB and the pro-apoptotic protein BAD. Other Ca(2+) sensitive pathways involving PKC, ras, rac, and CaM kinase II may also contribute to muscle remodeling.

  8. Complexity of age-related change in skeletal muscle.

    PubMed

    Brown, M; Hasser, E M

    1996-03-01

    Age-related changes in skeletal muscle mass, fiber area, and contractile function were examined in pathogen-free rats at 6, 12, 28 and 36 mos of age. The intent of this study was to clarify age-related decline, particularly in contractile force, and to determine if the decline in contractile tension with age is due to alterations at the neuromuscular junction. A variable amount of age-associated reduction in muscle mass was noted for the soleus (18%), extensor digitorum longus (EDL-16%), plantaris (37%), and gastrocnemius (38%) muscles. The decline in fiber area for these four muscles was between 5 and 16% greater than the loss in muscle wet weight. A variable amount of change in peak contractile force between 6 and 36 mos was observed for the soleus (62%), EDL (48%), and plantaris (34%). For soleus and EDL, the decline in peak tetanic tension exceeded the decline in muscle mass and fiber area. Most of the declines for the animals used in this study did not become significant until after the age of 28 mo. The marked reduction in peak tetanic tension, fiber area, and muscle mass between 28 and 36 mos indicates an accelerated age-related decline in this time period. The reduced peak twitch and peak tetanic tension in the oldest animals was not due to likely age-related changes at the neuromuscular junction. Peak values for tetanic tension were similar, whether tension was elicited via direct muscle stimulation or through stimulation of the nerve. Results underscore the complexity of age-related change and suggest that multiple mechanisms contribute to the decline of skeletal muscle. PMID:8612095

  9. Increasing mitochondrial muscle fatty acid oxidation induces skeletal muscle remodeling toward an oxidative phenotype.

    PubMed

    Hénique, Carole; Mansouri, Abdelhak; Vavrova, Eliska; Lenoir, Véronique; Ferry, Arnaud; Esnous, Catherine; Ramond, Elodie; Girard, Jean; Bouillaud, Frédéric; Prip-Buus, Carina; Cohen, Isabelle

    2015-06-01

    Adult skeletal muscle is a dynamic, remarkably plastic tissue, which allows myofibers to switch from fast/glycolytic to slow/oxidative types and to increase mitochondrial fatty acid oxidation (mFAO) capacity and vascularization in response to exercise training. mFAO is the main muscle energy source during endurance exercise, with carnitine palmitoyltransferase 1 (CPT1) being the key regulatory enzyme. Whether increasing muscle mFAO affects skeletal muscle physiology in adulthood actually remains unknown. To investigate this, we used in vivo electrotransfer technology to express in mouse tibialis anterior (TA), a fast/glycolytic muscle, a mutated CPT1 form (CPT1mt) that is active but insensitive to malonyl-CoA, its physiologic inhibitor. In young (2-mo-old) adult mice, muscle CPT1mt expression enhanced mFAO (+40%), but also increased the percentage of oxidative fibers (+28%), glycogen content, and capillary-to-fiber density (+45%). This CPT1mt-induced muscle remodeling, which mimicked exercise-induced oxidative phenotype, led to a greater resistance to muscle fatigue. In the context of aging, characterized by sarcopenia and reduced oxidative capacity, CPT1mt expression in TAs from aged (20-mo-old) mice partially reversed aging-associated sarcopenia and fiber-type transition, and increased muscle capillarity. These findings provide evidence that mFAO regulates muscle phenotype and may be a potential target to combat age-related decline in muscle function. PMID:25713059

  10. Direct optical activation of skeletal muscle fibres efficiently controls muscle contraction and attenuates denervation atrophy

    PubMed Central

    Magown, Philippe; Shettar, Basavaraj; Zhang, Ying; Rafuse, Victor F.

    2015-01-01

    Neural prostheses can restore meaningful function to paralysed muscles by electrically stimulating innervating motor axons, but fail when muscles are completely denervated, as seen in amyotrophic lateral sclerosis, or after a peripheral nerve or spinal cord injury. Here we show that channelrhodopsin-2 is expressed within the sarcolemma and T-tubules of skeletal muscle fibres in transgenic mice. This expression pattern allows for optical control of muscle contraction with comparable forces to nerve stimulation. Force can be controlled by varying light pulse intensity, duration or frequency. Light-stimulated muscle fibres depolarize proportionally to light intensity and duration. Denervated triceps surae muscles transcutaneously stimulated optically on a daily basis for 10 days show a significant attenuation in atrophy resulting in significantly greater contractile forces compared with chronically denervated muscles. Together, this study shows that channelrhodopsin-2/H134R can be used to restore function to permanently denervated muscles and reduce pathophysiological changes associated with denervation pathologies. PMID:26460719

  11. Diffraction Ellipsometry Studies of Skeletal Muscle Structure

    NASA Astrophysics Data System (ADS)

    Kerr, William Lloyd

    Many of the techniques used to study the structure and contraction mechanism of muscle rely on the interaction of light or other electromagnetic radiation with the muscle. Some of the most important of these techniques are light and electron microscopy, x-ray diffraction, spectroscopy of muscle fibers "labelled" with spin or fluorescent probes, visible spectrum diffraction, and transmission birefringence. Chapter I of this dissertation reviews these techniques, focussing on what they have to tell us about muscle structure. In Chapter II, we discuss experiments in which the microstructural features of relaxed, skinned fibers compressed with polyvinylpyrollidone were examined by optical diffraction ellipsometry. The change in polarization state of light after interacting with the muscle is described by the differential field ratio (DFR) and birefringence (Deltan). Compression of single fibers with 0%-21% PVP caused an increase in up to 23% and 31% for DFR and Deltan, respectively. Theoretical modelling suggests that the average S-1 tilt angle may be reduced upon compression of the filament lattice. This is supported by experiments in which S-1 was cleaved with alpha-chymotrypsin. Experiments comparing fibers with intact membranes and skinned fibers compressed to an equivalent lattice spacing showed little difference in DFR or Deltan. Chapter III deals with experiments on contracting, intact fibers. The differential field ratio (DFR) was monitored for tetanically contracting muscle fibers subject to rapid (<0.4 msec) release or stretch. Upon stimulation, DFR decreases 14% from its resting value; the half-time for the decrease leads that of tension rise by 10 msecs. This suggests that the movement of cross -bridges precedes tension development and that the average cross-bridge angle is more perpendicular in the contracting state. Upon rapid release of 0.5% of the fiber length, DFR decreases 9.5% further simultaneous with the length step. Rapid and slow recovery phases were observed. A smaller decrease in DFR was seen upon 0.5% rapid stretch, but a rapid recovery phase was not observed. Our discussion of these results suggests that a crossbridge has internal flexibility, and that an undamped elastic element may reside somewhere in the crossbridge itself.

  12. Muscle metaboreflex activation during dynamic exercise vasoconstricts ischemic active skeletal muscle.

    PubMed

    Kaur, Jasdeep; Machado, Tiago M; Alvarez, Alberto; Krishnan, Abhinav C; Hanna, Hanna W; Altamimi, Yasir H; Senador, Danielle; Spranger, Marty D; O'Leary, Donal S

    2015-12-15

    Metabolite accumulation due to ischemia of active skeletal muscle stimulates group III/IV chemosensitive afferents eliciting reflex increases in arterial blood pressure and sympathetic activity, termed the muscle metaboreflex. We and others have previously demonstrated sympathetically mediated vasoconstriction of coronary, renal, and forelimb vasculatures with muscle metaboreflex activation (MMA). Whether MMA elicits vasoconstriction of the ischemic muscle from which it originates is unknown. We hypothesized that the vasodilation in active skeletal muscle with imposed ischemia becomes progressively restrained by the increasing sympathetic vasoconstriction during MMA. We activated the metaboreflex during mild dynamic exercise in chronically instrumented canines via graded reductions in hindlimb blood flow (HLBF) before and after ?1-adrenergic blockade [prazosin (50 ?g/kg)], ?-adrenergic blockade [propranolol (2 mg/kg)], and ?1 + ?-blockade. Hindlimb resistance was calculated as femoral arterial pressure/HLBF. During mild exercise, HLBF must be reduced below a threshold level before the reflex is activated. With initial reductions in HLBF, vasodilation occurred with the imposed ischemia. Once the muscle metaboreflex was elicited, hindlimb resistance increased. This increase in hindlimb resistance was abolished by ?1-adrenergic blockade and exacerbated after ?-adrenergic blockade. We conclude that metaboreflex activation during submaximal dynamic exercise causes sympathetically mediated ?-adrenergic vasoconstriction in ischemic skeletal muscle. This limits the ability of the reflex to improve blood flow to the muscle. PMID:26475591

  13. Inhibition of skeletal muscle protein synthesis in septic intra-abdominal abscess

    SciTech Connect

    Vary, T.C.; Siegel, J.H.; Tall, B.D.; Morris, J.G.; Smith, J.A.

    1988-07-01

    Chronic sepsis is always associated with profound wasting leading to increased release of amino acids from skeletal muscle. Net protein catabolism may be due to decreased rate of synthesis, increased rate of degradation, or both. To determine whether protein synthesis is altered in chronic sepsis, the rate of protein synthesis in vivo was estimated by measuring the incorporation of (/sup 3/H)-phenylalanine in skeletal muscle protein in a chronic (5-day) septic rat model induced by creation of a stable intra-abdominal abscess using an E. coli + B. fragilis-infected sterile fecal-agar pellet as foreign body nidus. Septic rats failed to gain weight at rates similar to control animals, therefore control animals were weight matched to the septic animals. The skeletal muscle protein content in septic animals was significantly reduced relative to control animals (0.18 +/- 0.01 vs. 0.21 +/- 0.01 mg protein/gm wet wt; p less than 0.02). The rate of incorporation of (/sup 3/H)-phenylalanine into skeletal muscle protein from control animals was 39 +/- 4 nmole/gm wet wt/hr or a fractional synthetic rate of 5.2 +/- 0.5%/day. In contrast to control animals, the fractional synthetic rate in septic animals (2.6 +/- 0.2%/day) was reduced by 50% compared to control animals (p less than 0.005). The decreased rate of protein synthesis in sepsis was not due to an energy deficit, as high-energy phosphates and ATP/ADP ratio were not altered. This decrease in protein synthesis occurred even though septic animals consumed as much food as control animals.

  14. Skeletal muscle programming and re-programming

    PubMed Central

    Fong, Abraham P.; Tapscott, Stephen J.

    2013-01-01

    The discovery of the transcription factor MyoD and its ability to induce muscle differentiation was the first demonstration of genetically programmed cell transdifferentiation. MyoD functions by activating a feed-forward circuit to regulate muscle gene expression. This requires binding to specific E-boxes throughout the genome, followed by recruitment of chromatin modifying complexes and transcription machinery. MyoD binding can be modified by both cooperative factors and inhibitors, including microRNAs that may serve as important developmental switches. Recent studies indicate that epigenetic regulation of MyoD binding sites is another important mechanism for controlling MyoD activity, which may ultimately limit its ability to induce transdifferentiation to cells with permissive epigenetic ‘landscapes.’ PMID:23756045

  15. Skeletal muscle programming and re-programming.

    PubMed

    Fong, Abraham P; Tapscott, Stephen J

    2013-10-01

    The discovery of the transcription factor MyoD and its ability to induce muscle differentiation was the first demonstration of genetically programmed cell transdifferentiation. MyoD functions by activating a feed-forward circuit to regulate muscle gene expression. This requires binding to specific E-boxes throughout the genome, followed by recruitment of chromatin modifying complexes and transcription machinery. MyoD binding can be modified by both cooperative factors and inhibitors, including microRNAs that may serve as important developmental switches. Recent studies indicate that epigenetic regulation of MyoD binding sites is another important mechanism for controlling MyoD activity, which may ultimately limit its ability to induce transdifferentiation to cells with permissive epigenetic 'landscapes.' PMID:23756045

  16. Optical NIR monitoring of skeletal muscle contraction

    NASA Astrophysics Data System (ADS)

    Lago, Paolo; Gelmetti, Andrea; Pavesi, Roberta; Zambarbieri, Daniela

    1996-12-01

    NIR spectroscopy allows monitoring of muscle oxygenation and perfusion during contraction. The knowledge of modifications of blood characteristics in body tissues has relevant clinical interest. A compact and reliable device, which makes use of two laser diodes at 750 and 810 nm coupled with the skin surface through optical fibers, was tested. NIR and surface EMG signals during isometric contractions both in normal and ischaemic conditions were analyzed. A set of parameters from the 750/810 spectroscopic curve was analyzed. Two different categories depending on the recovery rate from maximal voluntary contraction to basal oxygenation conditions were found. This behavior can give information about metabolic modifications during muscle fatigue. Interesting results in testing isokinetic rehabilitation training were also obtained.

  17. Fragility fracture risk and skeletal muscle function.

    PubMed

    Pérez-López, F R; Ara, I

    2016-02-01

    Low-intensity fractures are closely related with age-related musculoskeletal disorders, including osteoporosis, muscle dysfunction and sarcopenia, age-related chronic diseases, and pharmacological treatments. During the last years, a huge amount of information and recommendations has been released in relation to bone metabolism and mineral content. Muscle dysfunction and sarcopenia are highly prevalent during the second half of life, especially in older subjects. The development of sarcopenia may be slowed through healthy lifestyle changes, which include adequate dietary protein, vitamin D and mineral intakes, and regular physical activity. Prevention of falls should be integral, including correction in major involved factors in order to reduce fragility fracture, improve quality of life and appropriately focus clinical and economic resources. Therefore, to obtain better results a global approach is needed to prevent age-related fractures in frail patients that is not only centered on bone metabolism and antiresorptive drugs. PMID:26588486

  18. cap alpha. -skeletal and. cap alpha. -cardiac actin genes are coexpressed in adult human skeletal muscle and heart

    SciTech Connect

    Gunning, P.; Ponte, P.; Blau, H.; Kedes, L.

    1983-11-01

    The authors determined the actin isotypes encoded by 30 actin cDNA clones previously isolated from an adult human muscle cDNA library. Using 3' untranslated region probes, derived from ..cap alpha.. skeletal, ..beta..- and ..gamma..-actin cDNAs and from an ..cap alpha..-cardiac actin genomic clone, they showed that 28 of the cDNAs correspond to ..cap alpha..-skeletal actin transcripts. Unexpectedly, however, the remaining two cDNA clones proved to derive from ..cap alpha..-cardiac actin mRNA. Sequence analysis confirmed that the two skeletal muscle ..cap alpha..-cardiac actin cDNAs are derived from transcripts of the cloned ..cap alpha..-cardiac actin gene. Comparison of total actin mRNA levels in adult skeletal muscle and adult heart revealed that the steady-state levels in skeletal muscle are about twofold greater, per microgram of total cellular RNA, than those in heart. Thus, in skeletal muscle and in heart, both of the sarcomeric actin mRNA isotypes are quite abundant transcripts. They conclude that ..cap alpha..-skeletal and ..cap alpha..-cardiac actin genes are coexpressed as an actin pair in human adult striated muscles. Since the smooth-muscle actins (aortic and stomach) and the cytoplasmic actins (..beta.. and ..gamma..) are known to be coexpressed in smooth muscle and nonmuscle cells, respectively, they postulate that coexpression of actin pairs may be a common feature of mammalian actin gene expression in all tissues.

  19. Methods for the Organogenesis of Skeletal Muscle in Tissue Culture

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman; Shansky, Janet; DelTatto, Michael; Chromiak, Joseph

    1997-01-01

    Skeletal muscle structure is regulated by many factors, including nutrition, hormones, electrical activity, and tension. The muscle cells are subjected to both passive and active mechanical forces at all stages of development and these forces play important but poorly understood roles in regulating muscle organogenesis and growth. For example, during embryogenesis, the rapidly growing skeleton places large passive mechanical forces on the attached muscle tissue. These forces not only help to organize the proliferating mononucleated myoblasts into the oriented, multinucleated myofibers of a functional muscle but also tightly couple the growth rate of muscle to that of bone. Postnatally, the actively contracting, innervated muscle fibers are subjected to different patterns of active and passive tensions which regulate longitudinal and cross sectional myofiber growth. These mechanically-induced organogenic processes have been difficult to study under normal tissue culture conditions, resulting in the development of numerous methods and specialized equipment to simulate the in vivo mechanical environment.These techniques have led to the "engineering" of bioartificial muscles (organoids) which display many of the characteristics of in vivo muscle including parallel arrays of postmitotic fibers organized into fascicle-like structures with tendon-like ends. They are contractile, express adult isoforms of contractile proteins, perform directed work, and can be maintained in culture for long periods. The in vivo-like characteristics and durability of these muscle organoids make them useful for long term in vitro studies on mechanotransduction mechanisms and on muscle atrophy induced by decreased tension. In this report, we described a simple method for generating muscle organoids from either primary embrionic avain or neonatal rodent myoblasts.

  20. Developmental programming of fetal skeletal muscle and adipose tissue development.

    PubMed

    Yan, Xu; Zhu, Mei-Jun; Dodson, Michael V; Du, Min

    2013-01-01

    All important developmental milestones are accomplished during the fetal stage, and nutrient fluctuation during this stage produces lasting effects on offspring health, so called fetal programming or developmental programming. The fetal stage is critical for skeletal muscle development, as well as adipose and connective tissue development. Maternal under-nutrition at this stage affects the proliferation of myogenic precursor cells and reduces the number of muscle fibers formed. Maternal over-nutrition results in impaired myogenesis and elevated adipogenesis. Because myocytes, adipocytes and fibrocytes are all derived from mesenchymal stem cells, molecular events which regulate the commitment of stem cells to different lineages directly impact fetal muscle and adipose tissue development. Recent studies indicate that microRNA is intensively involved in myogenic and adipogenic differentiation from mesenchymal stem cells, and epigenetic changes such as DNA methylation are expected to alter cell lineage commitment during fetal muscle and adipose tissue development. PMID:25031653

  1. Detyrosinated microtubules modulate mechanotransduction in heart and skeletal muscle.

    PubMed

    Kerr, Jaclyn P; Robison, Patrick; Shi, Guoli; Bogush, Alexey I; Kempema, Aaron M; Hexum, Joseph K; Becerra, Natalia; Harki, Daniel A; Martin, Stuart S; Raiteri, Roberto; Prosser, Benjamin L; Ward, Christopher W

    2015-01-01

    In striated muscle, X-ROS is the mechanotransduction pathway by which mechanical stress transduced by the microtubule network elicits reactive oxygen species. X-ROS tunes Ca(2+) signalling in healthy muscle, but in diseases such as Duchenne muscular dystrophy (DMD), microtubule alterations drive elevated X-ROS, disrupting Ca(2+) homeostasis and impairing function. Here we show that detyrosination, a post-translational modification of ?-tubulin, influences X-ROS signalling, contraction speed and cytoskeletal mechanics. In the mdx mouse model of DMD, the pharmacological reduction of detyrosination in vitro ablates aberrant X-ROS and Ca(2+) signalling, and in vivo it protects against hallmarks of DMD, including workload-induced arrhythmias and contraction-induced injury in skeletal muscle. We conclude that detyrosinated microtubules increase cytoskeletal stiffness and mechanotransduction in striated muscle and that targeting this post-translational modification may have broad therapeutic potential in muscular dystrophies. PMID:26446751

  2. Turning terminally differentiated skeletal muscle cells into regenerative progenitors.

    PubMed

    Wang, Heng; Lööf, Sara; Borg, Paula; Nader, Gustavo A; Blau, Helen M; Simon, András

    2015-01-01

    The ability to repeatedly regenerate limbs during the entire lifespan of an animal is restricted to certain salamander species among vertebrates. This ability involves dedifferentiation of post-mitotic cells into progenitors that in turn form new structures. A long-term enigma has been how injury leads to dedifferentiation. Here we show that skeletal muscle dedifferentiation during newt limb regeneration depends on a programmed cell death response by myofibres. We find that programmed cell death-induced muscle fragmentation produces a population of 'undead' intermediate cells, which have the capacity to resume proliferation and contribute to muscle regeneration. We demonstrate the derivation of proliferating progeny from differentiated, multinucleated muscle cells by first inducing and subsequently intercepting a programmed cell death response. We conclude that cell survival may be manifested by the production of a dedifferentiated cell with broader potential and that the diversion of a programmed cell death response is an instrument to achieve dedifferentiation. PMID:26243583

  3. Detyrosinated microtubules modulate mechanotransduction in heart and skeletal muscle

    PubMed Central

    Kerr, Jaclyn P.; Robison, Patrick; Shi, Guoli; Bogush, Alexey I.; Kempema, Aaron M.; Hexum, Joseph K.; Becerra, Natalia; Harki, Daniel A.; Martin, Stuart S.; Raiteri, Roberto; Prosser, Benjamin L.; Ward, Christopher W.

    2015-01-01

    In striated muscle, X-ROS is the mechanotransduction pathway by which mechanical stress transduced by the microtubule network elicits reactive oxygen species. X-ROS tunes Ca2+ signalling in healthy muscle, but in diseases such as Duchenne muscular dystrophy (DMD), microtubule alterations drive elevated X-ROS, disrupting Ca2+ homeostasis and impairing function. Here we show that detyrosination, a post-translational modification of ?-tubulin, influences X-ROS signalling, contraction speed and cytoskeletal mechanics. In the mdx mouse model of DMD, the pharmacological reduction of detyrosination in vitro ablates aberrant X-ROS and Ca2+ signalling, and in vivo it protects against hallmarks of DMD, including workload-induced arrhythmias and contraction-induced injury in skeletal muscle. We conclude that detyrosinated microtubules increase cytoskeletal stiffness and mechanotransduction in striated muscle and that targeting this post-translational modification may have broad therapeutic potential in muscular dystrophies. PMID:26446751

  4. Proteomic profiling of the contractile apparatus from skeletal muscle.

    PubMed

    Holland, Ashling; Ohlendieck, Kay

    2013-06-01

    In skeletal muscle fibers, the excitation-contraction-relaxation cycle is a highly evolved process that is mediated by the contractile proteins - myosin and actin - and the regulatory elements - troponin and tropomyosin. Contractile fibers exhibit enormous complexity and heterogeneity on the molecular level, which is reflected by the diversity of protein isoforms that constitute the actomyosin apparatus. The main components of the contractile apparatus exist in high abundance and are relatively soluble, making them ideal candidates for a systematic analysis by liquid chromatography or gel electrophoresis-based proteomics. This review discusses the proteomic profiling of contractile components in adapting, degenerating and aging skeletal muscle tissues. The proteomic identification of altered contractile proteins may be useful for the establishment of biomarker signatures that can be applied in the examination of the physiological adaptability, cellular plasticity and pathological susceptibility of the neuromuscular system. PMID:23777215

  5. Mechanical stimulation improves tissue-engineered human skeletal muscle

    NASA Technical Reports Server (NTRS)

    Powell, Courtney A.; Smiley, Beth L.; Mills, John; Vandenburgh, Herman H.

    2002-01-01

    Human bioartificial muscles (HBAMs) are tissue engineered by suspending muscle cells in collagen/MATRIGEL, casting in a silicone mold containing end attachment sites, and allowing the cells to differentiate for 8 to 16 days. The resulting HBAMs are representative of skeletal muscle in that they contain parallel arrays of postmitotic myofibers; however, they differ in many other morphological characteristics. To engineer improved HBAMs, i.e., more in vivo-like, we developed Mechanical Cell Stimulator (MCS) hardware to apply in vivo-like forces directly to the engineered tissue. A sensitive force transducer attached to the HBAM measured real-time, internally generated, as well as externally applied, forces. The muscle cells generated increasing internal forces during formation which were inhibitable with a cytoskeleton depolymerizer. Repetitive stretch/relaxation for 8 days increased the HBAM elasticity two- to threefold, mean myofiber diameter 12%, and myofiber area percent 40%. This system allows engineering of improved skeletal muscle analogs as well as a nondestructive method to determine passive force and viscoelastic properties of the resulting tissue.

  6. Receptor Expression in Rat Skeletal Muscle Cell Cultures

    NASA Technical Reports Server (NTRS)

    Young, Ronald B.

    1996-01-01

    One on the most persistent problems with long-term space flight is atrophy of skeletal muscles. Skeletal muscle is unique as a tissue in the body in that its ability to undergo atrophy or hypertrophy is controlled exclusively by cues from the extracellular environment. The mechanism of communication between muscle cells and their environment is through a group of membrane-bound and soluble receptors, each of which carries out unique, but often interrelated, functions. The primary receptors include acetyl choline receptors, beta-adrenergic receptors, glucocorticoid receptors, insulin receptors, growth hormone (i.e., somatotropin) receptors, insulin-like growth factor receptors, and steroid receptors. This project has been initiated to develop an integrated approach toward muscle atrophy and hypertrophy that takes into account information on the populations of the entire group of receptors (and their respective hormone concentrations), and it is hypothesized that this information can form the basis for a predictive computer model for muscle atrophy and hypertrophy. The conceptual basis for this project is illustrated in the figure below. The individual receptors are shown as membrane-bound, with the exception of the glucocorticoid receptor which is a soluble intracellular receptor. Each of these receptors has an extracellular signalling component (e.g., innervation, glucocorticoids, epinephrine, etc.), and following the interaction of the extracellular component with the receptor itself, an intracellular signal is generated. Each of these intracellular signals is unique in its own way; however, they are often interrelated.

  7. Prioritization of skeletal muscle growth for emergence from hibernation.

    PubMed

    Hindle, Allyson G; Otis, Jessica P; Epperson, L Elaine; Hornberger, Troy A; Goodman, Craig A; Carey, Hannah V; Martin, Sandra L

    2015-01-15

    Mammalian hibernators provide an extreme example of naturally occurring challenges to muscle homeostasis. The annual hibernation cycle is characterized by shifts between summer euthermy with tissue anabolism and accumulation of body fat reserves, and winter heterothermy with fasting and tissue catabolism. The circannual patterns of skeletal muscle remodelling must accommodate extended inactivity during winter torpor, the motor requirements of transient winter active periods, and sustained activity following spring emergence. Muscle volume in thirteen-lined ground squirrels (Ictidomys tridecemlineatus) calculated from MRI upper hindlimb images (n=6 squirrels, n=10 serial scans) declined from hibernation onset, reaching a nadir in early February. Paradoxically, mean muscle volume rose sharply after February despite ongoing hibernation, and continued total body mass decline until April. Correspondingly, the ratio of muscle volume to body mass was steady during winter atrophy (October-February) but increased (+70%) from February to May, which significantly outpaced changes in liver or kidney examined by the same method. Generally stable myocyte cross-sectional area and density indicated that muscle remodelling is well regulated in this hibernator, despite vastly altered seasonal fuel and activity levels. Body composition analysis by echo MRI showed lean tissue preservation throughout hibernation amid declining fat mass by the end of winter. Muscle protein synthesis was 66% depressed in early but not late winter compared with a summer fasted baseline, while no significant changes were observed in the heart, liver or intestine, providing evidence that could support a transition in skeletal muscle regulation between early and late winter, prior to spring emergence and re-feeding. PMID:25452506

  8. Leukemia inhibitory factor increases glucose uptake in mouse skeletal muscle.

    PubMed

    Brandt, Nina; O'Neill, Hayley M; Kleinert, Maximilian; Schjerling, Peter; Vernet, Erik; Steinberg, Gregory R; Richter, Erik A; Jørgensen, Sebastian B

    2015-07-15

    Members of the IL-6 family, IL-6 and ciliary neurotrophic factor (CNTF), have been shown to increase glucose uptake and fatty acid oxidation in skeletal muscle. However, the metabolic effects of another family member, leukemia inhibitory factor (LIF), are not well characterized. Effects of LIF on skeletal muscle glucose uptake and palmitate oxidation and signaling were investigated in ex vivo incubated mouse soleus and EDL muscles from muscle-specific AMPK?2 kinase-dead, muscle-specific SOCS3 knockout, and lean and high-fat-fed mice. Inhibitors were used to investigate involvement of specific signaling pathways. LIF increased muscle glucose uptake in dose (50-5,000 pM/l) and time-dependent manners with maximal effects at the 30-min time point. LIF increased Akt Ser(473) phosphorylation (P) in soleus and EDL, whereas AMPK Thr(172) P was unaffected. Incubation with parthenolide abolished LIF-induced glucose uptake and STAT3 Tyr(705) P, whereas incubation with LY-294002 and wortmannin suppressed both basal and LIF-induced glucose uptake and Akt Ser(473) P, indicating that JAK and PI 3-kinase signaling is required for LIF-stimulated glucose uptake. Incubation with rapamycin and AZD8055 indicated that mammalian target of rapamycin complex (mTORC)2, but not mTORC1, also is required for LIF-stimulated glucose uptake. In contrast to CNTF, LIF stimulation did not alter palmitate oxidation. LIF-stimulated glucose uptake was maintained in EDL from obese insulin-resistant mice, whereas soleus developed LIF resistance. Lack of SOCS3 and AMPK?2 did not affect LIF-stimulated glucose uptake. In conclusion, LIF acutely increased muscle glucose uptake by a mechanism potentially involving the PI 3-kinase/mTORC2/Akt pathway and is not impaired in EDL muscle from obese insulin-resistant mice. PMID:25968579

  9. An In Vitro Model of Skeletal Muscle Volume Regulation

    PubMed Central

    Wibberley, Anna; Staunton, Caroline A.; Feetham, Claire H.; Vereninov, Alexey A.; Barrett-Jolley, Richard

    2015-01-01

    Introduction Hypertonic media causes cells to shrink due to water loss through aquaporin channels. After acute shrinkage, cells either regulate their volume or, alternatively, undergo a number of metabolic changes which ultimately lead to cell death. In many cell types, hypertonic shrinkage is followed by apoptosis. Due to the complex 3D morphology of skeletal muscle and the difficulty in obtaining isolated human tissue, we have begun skeletal muscle volume regulation studies using the human skeletal muscle cell line TE671RD. In this study we investigated whether hypertonic challenge of the human skeletal muscle cell line TE671RD triggered cell death or evoked a cell volume recovery response. Methods The cellular volume of TE671RD cells was calculated from the 2D surface area. Cell death was assessed by both the trypan blue live/dead assay and the TUNEL assay. Results Medium osmolality was increased by addition of up to 200mM sucrose. Addition of 200mM sucrose resulted in mean cell shrinkage of 44±1% after 30mins. At later time points (2 and 4 hrs) two separate cell subpopulations with differing mean cell volume became apparent. The first subpopulation (15±2% of the total cell number) continued to shrink whereas the second subpopulation had an increased cell volume. Cell death was observed in a small proportion of cells (approximately 6-8%). Conclusion We have established that a substantial proportion of TE671RD cells respond to hypertonic challenge with RVI, but that these cells are resistant to hypertonicity triggered cell death. PMID:26029913

  10. Low Intensity Exercise Training Improves Skeletal Muscle Regeneration Potential

    PubMed Central

    Pietrangelo, Tiziana; Di Filippo, Ester S.; Mancinelli, Rosa; Doria, Christian; Rotini, Alessio; Fanò-Illic, Giorgio; Fulle, Stefania

    2015-01-01

    Purpose: The aim of this study was to determine whether 12 days of low-to-moderate exercise training at low altitude (598 m a.s.l.) improves skeletal muscle regeneration in sedentary adult women. Methods: Satellite cells were obtained from the vastus lateralis skeletal muscle of seven women before and after this exercise training at low altitude. They were investigated for differentiation aspects, superoxide anion production, antioxidant enzymes, mitochondrial potential variation after a depolarizing insult, intracellular Ca2+ concentrations, and micro (mi)RNA expression (miR-1, miR-133, miR-206). Results: In these myogenic populations of adult stem cells, those obtained after exercise training, showed increased Fusion Index and intracellular Ca2+ concentrations. This exercise training also generally reduced superoxide anion production in cells (by 12–67%), although not in two women, where there was an increase of ~15% along with a reduced superoxide dismutase activity. miRNA expression showed an exercise-induced epigenetic transcription profile that was specific according to the reduced or increased superoxide anion production of the cells. Conclusions: The present study shows that low-to-moderate exercise training at low altitude improves the regenerative capacity of skeletal muscle in adult women. The differentiation of cells was favored by increased intracellular calcium concentration and increased the fusion index. This low-to-moderate training at low altitude also depicted the epigenetic signature of cells.

  11. Signalling and the control of skeletal muscle size

    SciTech Connect

    Otto, Anthony; Patel, Ketan

    2010-11-01

    Skeletal muscle is highly adaptive to environmental stimuli and can alter its mass accordingly. This tissue is almost unique in that it can increase its size through two distinct mechanisms. It can grow through a cellular process mediated by cell fusion, or it can increase its size simply by increasing its protein content. Understanding how these processes are regulated is crucial for the development of potential therapies against debilitating skeletal muscle wasting diseases. Two key signalling molecules, Insulin like Growth Factor (IGF) and GDF-8/myostatin, have emerged in recent years to be potent regulators of skeletal muscle size. In this review we bring together recent data highlighting the important and novel aspects of both molecules and their signalling pathways, culminating in a discussion of the cellular and tissue phenotypic outcomes of their stimulation or antagonism. We emphasise the complex regulatory mechanisms and discuss the temporal and spatial differences that control their action, understanding of which is crucial to further their use as potential therapeutic targets.

  12. Optical reflectance in fibrous tissues and skeletal muscles

    NASA Astrophysics Data System (ADS)

    Ranasinghesagara, Janaka C.

    We studied two biological tissues with optically anisotropic structures: high moisture soy protein extrudates and skeletal muscles. High moisture extrusion has been used to produce vegetable meat analogs that resemble real animal meat and have significant health benefits. Since visual and textural properties are key factors for consumer acceptance, assessing fiber formation in the extruded soy protein product is important for quality control purpose. A non-destructive method based on photon migration was developed to measure fiber formation in extruded soy proteins. The measured fiber formation index in intact samples showed good agreement with that obtained from image analysis on peeled samples. By implementing this new method in a fast laser scanning system, we have acquired two dimensional mappings of fiber formation and orientation in the entire sample in real time. In addition to fibrous structures, skeletal muscles have a unique periodic sarcomere structure which produces strong light diffractions. However, inconsistent experimental results have been reported in single fiber diffraction studies. By applying the three-dimensional coupled wave theory in a physical sarcomere model, we found that a variety of experimental observations can be explained if inhomogeneous muscle morphological profiles are considered. We also discovered that the sarcomere structure produced a unique optical reflectance pattern in whole muscle. None of the existing light propagation theories are able to describe this pattern. We developed a Monte Carlo model incorporating the sarcomere diffraction effect. The simulated results quantitatively resemble the unique patterns observed in experiments. We used a set of parameters to quantify the optical reflectance profiles produced by a point incident light in whole muscle. Two parameters, q and B, were obtained by numerically fitting the equi-intensity contours of the reflectance pattern. Two spatial gradients were calculated along the directions parallel and perpendicular to muscle fibers. The mean diffuse intensity was obtained by excluding the specular reflectance. These five parameters provide a comprehensive and complete description of the diffuse reflectance in muscle. In a study of 336 muscle samples, we found these optical parameters were subject to the effects of different muscle physical and biochemical factors. Different types of muscle have significantly different diffuse intensities. Aging shows different effects on the q parameter in different muscles. In addition, the mean diffuse intensity is significantly different (p<0.05) in different animal breeds. Optical parameters showed good correlations with Warner-Bratzler shear force. Further studies on a large sample group are necessary to develop a statistical model to predict muscle physical and chemical properties using these non-destructive optical measurements.

  13. Formation and optogenetic control of engineered 3D skeletal muscle bioactuators

    E-print Network

    Sakar, Mahmut Selman

    Densely arrayed skeletal myotubes are activated individually and as a group using precise optical stimulation with high spatiotemporal resolution. Skeletal muscle myoblasts are genetically encoded to express a light-activated ...

  14. Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles

    PubMed Central

    Park, Ki Ho; Brotto, Leticia; Lehoang, Oanh; Brotto, Marco; Ma, Jianjie; Zhao, Xiaoli

    2012-01-01

    Described here is a method to measure contractility of isolated skeletal muscles. Parameters such as muscle force, muscle power, contractile kinetics, fatigability, and recovery after fatigue can be obtained to assess specific aspects of the excitation-contraction coupling (ECC) process such as excitability, contractile machinery and Ca2+ handling ability. This method removes the nerve and blood supply and focuses on the isolated skeletal muscle itself. We routinely use this method to identify genetic components that alter the contractile property of skeletal muscle though modulating Ca2+ signaling pathways. Here, we describe a newly identified skeletal muscle phenotype, i.e., mechanic alternans, as an example of the various and rich information that can be obtained using the in vitro muscle contractility assay. Combination of this assay with single cell assays, genetic approaches and biochemistry assays can provide important insights into the mechanisms of ECC in skeletal muscle. PMID:23149471

  15. Fluorescence Polarization Transients from Rhodamine Isomers on the Myosin Regulatory Light Chain in Skeletal Muscle Fibers

    E-print Network

    Croquette, Vincent

    in Skeletal Muscle Fibers Seth C. Hopkins,* Cibele Sabido-David,# John E.T. Corrie,§ Malcolm Irving,# and Yale E. Goldman* *Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, Pennsylvania to examine orientation changes of two rhodamine probes bound to myosin heads in skeletal muscle fibers

  16. Impact of Oxidative Stress on Exercising Skeletal Muscle

    PubMed Central

    Steinbacher, Peter; Eckl, Peter

    2015-01-01

    It is well established that muscle contractions during exercise lead to elevated levels of reactive oxygen species (ROS) in skeletal muscle. These highly reactive molecules have many deleterious effects, such as a reduction of force generation and increased muscle atrophy. Since the discovery of exercise-induced oxidative stress several decades ago, evidence has accumulated that ROS produced during exercise also have positive effects by influencing cellular processes that lead to increased expression of antioxidants. These molecules are particularly elevated in regularly exercising muscle to prevent the negative effects of ROS by neutralizing the free radicals. In addition, ROS also seem to be involved in the exercise-induced adaptation of the muscle phenotype. This review provides an overview of the evidences to date on the effects of ROS in exercising muscle. These aspects include the sources of ROS, their positive and negative cellular effects, the role of antioxidants, and the present evidence on ROS-dependent adaptations of muscle cells in response to physical exercise. PMID:25866921

  17. Fetal Stem Cells and Skeletal Muscle Regeneration: A Therapeutic Approach

    PubMed Central

    Pozzobon, Michela; Franzin, Chiara; Piccoli, Martina; De Coppi, Paolo

    2014-01-01

    More than 40% of the body mass is represented by muscle tissue, which possesses the innate ability to regenerate after damage through the activation of muscle-specific stem cells, namely satellite cells. Muscle diseases, in particular chronic degenerative states of skeletal muscle such as dystrophies, lead to a perturbation of the regenerative process, which causes the premature exhaustion of satellite cell reservoir due to continuous cycles of degeneration/regeneration. Nowadays, the research is focused on different therapeutic approaches, ranging from gene and cell to pharmacological therapy, but still there is no definitive cure in particular for genetic muscle disease. Keeping this in mind, in this article, we will give special consideration to muscle diseases and the use of fetal derived stem cells as a new approach for therapy. Cells of fetal origin, from cord blood to placenta and amniotic fluid, can be easily obtained without ethical concern, expanded and differentiated in culture, and possess immune-modulatory properties. The in vivo approach in animal models can be helpful to study the mechanism underneath the operating principle of the stem cell reservoir, namely the niche, which holds great potential to understand the onset of muscle pathologies. PMID:25221507

  18. Activated Protein Synthesis and Suppressed Protein Breakdown Signaling in Skeletal Muscle of Critically Ill Patients

    PubMed Central

    Jespersen, Jakob G.; Nedergaard, Anders; Reitelseder, Søren; Mikkelsen, Ulla R.; Dideriksen, Kasper J.; Agergaard, Jakob; Kreiner, Frederik; Pott, Frank C.; Schjerling, Peter; Kjaer, Michael

    2011-01-01

    Background Skeletal muscle mass is controlled by myostatin and Akt-dependent signaling on mammalian target of rapamycin (mTOR), glycogen synthase kinase 3? (GSK3?) and forkhead box O (FoxO) pathways, but it is unknown how these pathways are regulated in critically ill human muscle. To describe factors involved in muscle mass regulation, we investigated the phosphorylation and expression of key factors in these protein synthesis and breakdown signaling pathways in thigh skeletal muscle of critically ill intensive care unit (ICU) patients compared with healthy controls. Methodology/Principal Findings ICU patients were systemically inflamed, moderately hyperglycemic, received insulin therapy, and showed a tendency to lower plasma branched chain amino acids compared with controls. Using Western blotting we measured Akt, GSK3?, mTOR, ribosomal protein S6 kinase (S6k), eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), and muscle ring finger protein 1 (MuRF1); and by RT-PCR we determined mRNA expression of, among others, insulin-like growth factor 1 (IGF-1), FoxO 1, 3 and 4, atrogin1, MuRF1, interleukin-6 (IL-6), tumor necrosis factor ? (TNF-?) and myostatin. Unexpectedly, in critically ill ICU patients Akt-mTOR-S6k signaling was substantially higher compared with controls. FoxO1 mRNA was higher in patients, whereas FoxO3, atrogin1 and myostatin mRNAs and MuRF1 protein were lower compared with controls. A moderate correlation (r2?=?0.36, p<0.05) between insulin infusion dose and phosphorylated Akt was demonstrated. Conclusions/Significance We present for the first time muscle protein turnover signaling in critically ill ICU patients, and we show signaling pathway activity towards a stimulation of muscle protein synthesis and a somewhat inhibited proteolysis. PMID:21483870

  19. Metabolomic Analysis of the Skeletal Muscle of Mice Overexpressing PGC-1?

    PubMed Central

    Tadaishi, Miki; Ogawa, Yoshihiro; Ezaki, Osamu; Kamei, Yasutomi; Miura, Shinji

    2015-01-01

    Peroxisome proliferator-activated receptor (PPAR) ? coactivator 1? (PGC-1?) is a coactivator of various nuclear receptors and other transcription factors whose expression increases in the skeletal muscle during exercise. We have previously made transgenic mice overexpressing PGC-1? in the skeletal muscle (PGC-1?-Tg mice). PGC-1? upregulates the expression of genes associated with red fibers, mitochondrial function, fatty acid oxidation, and branched chain amino acid (BCAA) degradation. However, global analyses of the actual metabolic products have not been investigated. In this study, we conducted metabolomic analysis of the skeletal muscle in PGC-1?-Tg mice by capillary electrophoresis with electrospray ionization time-of-flight mass spectrometry. Principal component analysis and hierarchical cluster analysis showed clearly distinguishable changes in the metabolites between PGC-1?-Tg and wild-type control mice. Changes were observed in metabolite levels of various metabolic pathways such as the TCA cycle, pentose phosphate pathway, nucleotide synthesis, purine nucleotide cycle, and amino acid metabolism, including BCAA and ?-alanine. Namely, metabolic products of the TCA cycle increased in PGC-1?-Tg mice, with increased levels of citrate (2.3-fold), succinate (2.2-fold), fumarate (2.8-fold), and malate (2.3-fold) observed. Metabolic products associated with the pentose phosphate pathway and nucleotide biosynthesis also increased in PGC-1?-Tg mice. Meanwhile, BCAA levels decreased (Val, 0.7-fold; Leu, 0.8-fold; and Ile, 0.7-fold), and Glu (3.1-fold) and Asp (2.2-fold) levels increased. Levels of ?-alanine and related metabolites were markedly decreased in PGC-1?-Tg mice. Coordinated regulation of the TCA cycle and amino acid metabolism, including BCAA, suggests that PGC-1? plays important roles in energy metabolism. Moreover, our metabolomics data showing the activation of the purine nucleotide pathway, malate–aspartate shuttle, as well as creatine metabolism, which are known to be active during exercise, further suggests that PGC-1? regulates metabolism in exercise. Thus, we demonstrated the roles of PGC-1? in the skeletal muscle at the metabolite level. PMID:26114427

  20. Defective Homocysteine Metabolism: Potential Implications for Skeletal Muscle Malfunction

    PubMed Central

    Veeranki, Sudhakar; Tyagi, Suresh C.

    2013-01-01

    Hyperhomocysteinemia (HHcy) is a systemic medical condition and has been attributed to multi-organ pathologies. Genetic, nutritional, hormonal, age and gender differences are involved in abnormal homocysteine (Hcy) metabolism that produces HHcy. Homocysteine is an intermediate for many key processes such as cellular methylation and cellular antioxidant potential and imbalances in Hcy production and/or catabolism impacts gene expression and cell signaling including GPCR signaling. Furthermore, HHcy might damage the vagus nerve and superior cervical ganglion and affects various GPCR functions; therefore it can impair both the parasympathetic and sympathetic regulation in the blood vessels of skeletal muscle and affect long-term muscle function. Understanding cellular targets of Hcy during HHcy in different contexts and its role either as a primary risk factor or as an aggravator of certain disease conditions would provide better interventions. In this review we have provided recent Hcy mediated mechanistic insights into different diseases and presented potential implications in the context of reduced muscle function and integrity. Overall, the impact of HHcy in various skeletal muscle malfunctions is underappreciated; future studies in this area will provide deeper insights and improve our understanding of the association between HHcy and diminished physical function. PMID:23873298

  1. Skeletal muscle hydatid cysts presenting as soft tissue masses

    PubMed Central

    Gougoulias, N E; Varitimidis, S E; Bargiotas, K A; Dovas, T N; Karydakis, G; Dailiana, Z H

    2010-01-01

    Muscle hydatidosis is rare, accounting only for 3–5% of all cases. We present a case series of 9 patients (8 male, one female, mean age 59.3 years, range 48-75 years) with primary echinococcosis of skeletal muscles. The cysts presented as soft tissue masses in 8 patients, whereas in one, the cyst was an incidental finding on a CT scan performed for investigation of a lung problem. All hydatid cysts were confined into muscles, without affecting the bone. The location was the thigh region in 6 patients (quadriceps in 4, biceps in 2), the popliteal fossa (gastrocnemius) in one, the humerus (triceps branchii) in one and the shoulder (infraspinatus) in one patient. MRI showed multi-vesicular cysts in all patients. Indirect hemagglutination serological test was positive in 6 out of 9 cases. En block surgical excision of the cysts was undertaken in all patients. Two patients received antihelminthic chemotherapy preoperatively. Histopathologic findings confirmed the diagnosis. No recurrence occurred during the follow-up period (1-8 years). Skeletal muscle echinococcosis should be considered in the differential diagnosis of limb masses, especially in endemic countries. A meticulous history taking and MRI imaging are essential, while pericystectomy is an effective method of treatment. PMID:20596270

  2. Glutamine metabolism in rat skeletal muscle wounded with lambda-carrageenan

    SciTech Connect

    Albina, J.E.; Henry, W.; King, P.A.; Shearer, J.; Mastrofrancesco, B.; Goldstein, L.; Caldwell, M.D.

    1987-01-01

    Wounding with lambda-carrageenan results in a marked decrease in the intracellular-free glutamine content of rat skeletal muscle. The potential mechanisms for this finding, including alterations in glutamine release, glutamine utilization, and glutamine synthesis, were investigated in rats under pentobarbitol anesthesia. Wounding did not increase glutamine release from muscle during incubation or isolated hindlimb perfusion. Wounded muscle utilized more glutamine than nonwounded muscle, as measured both by the production of (/sup 14/C)O/sub 2/ and of -glutamate from labeled glutamine. Maximal glutamine synthetase activity was increased by wounding. The increase in glutamine synthetase activity in wounded muscle was prevented by adrenalectomy and restored by replacement doses of corticosterone in wounded adrenalectomized animals. The decrease in muscle free glutamine induced by wounding is therefore not mediated by an increase in the release of this amino acid, nor by a reduction in the tissue capacity for glutamine synthesis, but by an increase in glutamine utilization at the site of injury. This difference is apparently determined by the utilization of glutamine by the cellular components of the inflammatory infiltrate, which were shown to be capable of active glutaminolysis.

  3. Essential amino acid ingestion as an efficient nutritional strategy for the preservation of muscle mass following gastric bypass surgery.

    PubMed

    Katsanos, Christos S; Madura, James A; Roust, Lori R

    2016-01-01

    Loss of skeletal muscle in patients who have undergone gastric bypass is a consistent observation. Skeletal muscle constitutes the largest protein/amino acid pool in the body, and loss of skeletal muscle has important implications in health and disease. Sustaining a given level of muscle protein requires a balance between the rates of muscle protein synthesis and breakdown. Current evidence suggests that reduced rate of protein synthesis is implicated in the loss of muscle after gastric bypass. This is not surprising given a less than optimal dietary protein intake after the procedure and because, unlike other macronutrients, protein/amino acids are not stored in the body. Ingesting essential amino acids (EAAs), which cannot be synthesized de novo and have the primary role in the regulation of muscle protein synthesis, can potentially ameliorate loss of muscle protein after gastric bypass. At the same time, ingestion of EAAs provides a more efficient nutritional approach (i.e., greater stimulation of protein synthesis relative to the amount of amino acids ingested) to enhance muscle protein synthesis compared with the ingestion of intact protein. Changing current dietary practices toward increasing ingestion of EAAs provides an approach that can potentially prevent loss of lean body tissue and ultimately achieve a more sustained level of health in patients who have undergone gastric bypass. PMID:26456190

  4. The pentose phosphate pathway in regenerating skeletal muscle.

    PubMed

    Wagner, K R; Kauffman, F C; Max, S R

    1978-01-15

    1. The activities of the oxidative enzymes (glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase) and of the non-oxidative enzymes (transaldolase, tranketolase, ribose 5 phosphate isomerase and ribulose 5-phosphate 3-epimerase) of the pentose phosphate pathway were measured at various times during the first 24h of skeletal-muscle regeneration after administration of Marcaine, a mytoxic local anesthetic. 2. The activities of the oxidative enzymes increased after Marcaine injection and rose to 9 times control activities by 24h. 3. The activities of all non-oxidative enzymes were increased after Marcaine administration, but to a much smaller extent than the oxidative enzymes (1.1-1.7-fold). 4. Histochemical analysis localized glucose 6-phosphate dehydrogenase activity within muscle fibres of control and Marcaine-treated muscles. 5. Cycloheximide or actinomycin D prevented the increase in oxidative enzyme activities, suggesting a requirement for synthesis of protein and RNA. PMID:629775

  5. Biosynthesis of titin in cultured skeletal muscle cells

    SciTech Connect

    Isaacs, W.B.; Kim, I.S.; Struve, A.; Fulton, A.B. )

    1989-11-01

    Although significant progress has been made regarding the structure and function of titin, little data exist on the biosynthesis of this large protein in developing muscle. Using pulse-labeling with ({sup 35}S)methionine and immunoprecipitation with an anti-titin mAb, we have examined the biosynthesis of titin in synchronized cultures of skeletal muscle cells derived from day 12 chicken embryos. We find that: (a) titin synthesis increases greater than 4-fold during the first week in culture and during this same time period, synthesis of muscle-specific myosin heavy chain increases greater than 12-fold; (b) newly synthesized titin has a t1/2 of approximately 70 h; (c) titin is resistant to extraction with Triton X-100 both during and immediately after its synthesis. These observations suggest that newly synthesized titin molecules are stable proteins that rapidly associate with the cytoskeleton of developing myotubes.

  6. A Small Volatile Bacterial Molecule Triggers Mitochondrial Dysfunction in Murine Skeletal Muscle

    PubMed Central

    Tzika, A. Aria; Constantinou, Caterina; Bandyopadhaya, Arunava; Psychogios, Nikolaos; Lee, Sangseok; Mindrinos, Michael; Martyn, J. A. Jeevendra; Tompkins, Ronald G.; Rahme, Laurence G.

    2013-01-01

    Mitochondria integrate distinct signals that reflect specific threats to the host, including infection, tissue damage, and metabolic dysfunction; and play a key role in insulin resistance. We have found that the Pseudomonas aeruginosa quorum sensing infochemical, 2-amino acetophenone (2-AA), produced during acute and chronic infection in human tissues, including in the lungs of cystic fibrosis (CF) patients, acts as an interkingdom immunomodulatory signal that facilitates pathogen persistence, and host tolerance to infection. Transcriptome results have led to the hypothesis that 2-AA causes further harm to the host by triggering mitochondrial dysfunction in skeletal muscle. As normal skeletal muscle function is essential to survival, and is compromised in many chronic illnesses, including infections and CF-associated muscle wasting, we here determine the global effects of 2-AA on skeletal muscle using high-resolution magic-angle-spinning (HRMAS), proton (1H) nuclear magnetic resonance (NMR) metabolomics, in vivo 31P NMR, whole-genome expression analysis and functional studies. Our results show that 2-AA when injected into mice, induced a biological signature of insulin resistance as determined by 1H NMR analysis-, and dramatically altered insulin signaling, glucose transport, and mitochondrial function. Genes including Glut4, IRS1, PPAR-?, PGC1 and Sirt1 were downregulated, whereas uncoupling protein UCP3 was up-regulated, in accordance with mitochondrial dysfunction. Although 2-AA did not alter high-energy phosphates or pH by in vivo 31P NMR analysis, it significantly reduced the rate of ATP synthesis. This affect was corroborated by results demonstrating down-regulation of the expression of genes involved in energy production and muscle function, and was further validated by muscle function studies. Together, these results further demonstrate that 2-AA, acts as a mediator of interkingdom modulation, and likely effects insulin resistance associated with a molecular signature of mitochondrial dysfunction in skeletal muscle. Reduced energy production and mitochondrial dysfunctional may further favor infection, and be an important step in the establishment of chronic and persistent infections. PMID:24098655

  7. Membrane glycoproteins of differentiating skeletal muscle cells

    SciTech Connect

    Miller, K.R.; Remy, C.N.; Smith, P.B.

    1987-05-01

    The composition of N-linked glycoprotein oligosaccharides was studied in myoblasts and myotubes of the C2 muscle cell line. Oligosaccharides were radioactively labelled for 15 hr with (TH) mannose and plasma membranes isolated. Ten glycopeptides were detected by SDS-PAGE and fluorography. The extent of labelling was 4-6 fold greater in myoblasts vs myotubes. A glycopeptide of Mr > 100,000 was found exclusively in myoblast membranes. Lectin chromatography revealed that the proportion of tri-, tetranntenary, biantennary and high mannose chains was similar throughout differentiation. The high mannose chain fraction was devoid of hybrid chains. The major high mannose chain contained nine mannose residues. The higher level of glycopeptide labelling in myoblasts vs myotubes corresponded to a 5-fold greater rate of protein synthesis. Pulse-chase experiments were used to follow the synthesis of the Dol-oligosaccharides. Myoblasts and myotubes labelled equivalently the glucosylated tetradecasaccharide but myoblasts labelled the smaller intermediates 3-4 greater than myotubes. Myoblasts also exhibited a 2-3 fold higher Dol-P dependent glycosyl transferase activity for chain elongation and Dol-sugar synthesis. Together these results show that the degree of protein synthesis and level of Dol-P are contributing factors in the higher capacity of myoblasts to produce N-glycoproteins compared to myotubes.

  8. Chronic muscle stimulation increases lactate transport in rat skeletal muscle.

    PubMed

    McCullagh, K J; Juel, C; O'Brien, M; Bonen, A

    1996-03-01

    The aim of this study was to examine the effects of chronic low frequency stimulation on the lactate transport across the plasma membrane of the tibialis anterior (TA) muscle of the rat. Stimulating electrodes were implanted on either side of the peroneal nerve in one hindlimb. Chronic stimulation (10 Hz, 50 microsecond bursts, 24h/day) commenced 7 days after surgery, and were continued for 7 days. Animals were then left for 24 h, and thereafter muscles were obtained. Cytochrome C-oxidase activity was increased 1.9-fold in the stimulated TA compared to the control TA (p < 0.05). Lactate transport (zero-trans) was measured in giant sarcolemmal vesicles obtained from the chronically stimulated TA and the control TA. At each of the concentrations used in these studies a significant increase in lactate transport was observed; 2.8-fold increase at 1 mM lactate p < 0.05); 2-fold increases at both 30 mM and 50 mM lactate p < 0.05). These studies have shown that lactate transport capacity is markedly increased in response to chronic muscle contraction. PMID:8709976

  9. Three-dimensionally printed biological machines powered by skeletal muscle

    PubMed Central

    Cvetkovic, Caroline; Raman, Ritu; Chan, Vincent; Williams, Brian J.; Tolish, Madeline; Bajaj, Piyush; Sakar, Mahmut Selman; Asada, H. Harry; Saif, M. Taher A.; Bashir, Rashid

    2014-01-01

    Combining biological components, such as cells and tissues, with soft robotics can enable the fabrication of biological machines with the ability to sense, process signals, and produce force. An intuitive demonstration of a biological machine is one that can produce motion in response to controllable external signaling. Whereas cardiac cell-driven biological actuators have been demonstrated, the requirements of these machines to respond to stimuli and exhibit controlled movement merit the use of skeletal muscle, the primary generator of actuation in animals, as a contractile power source. Here, we report the development of 3D printed hydrogel “bio-bots” with an asymmetric physical design and powered by the actuation of an engineered mammalian skeletal muscle strip to result in net locomotion of the bio-bot. Geometric design and material properties of the hydrogel bio-bots were optimized using stereolithographic 3D printing, and the effect of collagen I and fibrin extracellular matrix proteins and insulin-like growth factor 1 on the force production of engineered skeletal muscle was characterized. Electrical stimulation triggered contraction of cells in the muscle strip and net locomotion of the bio-bot with a maximum velocity of ?156 ?m s?1, which is over 1.5 body lengths per min. Modeling and simulation were used to understand both the effect of different design parameters on the bio-bot and the mechanism of motion. This demonstration advances the goal of realizing forward-engineered integrated cellular machines and systems, which can have a myriad array of applications in drug screening, programmable tissue engineering, drug delivery, and biomimetic machine design. PMID:24982152

  10. Dexamethasone regulates glutamine synthetase expression in rat skeletal muscles

    NASA Technical Reports Server (NTRS)

    Max, Stephen R.; Konagaya, Masaaki; Konagaya, Yoko; Thomas, John W.; Banner, Carl; Vitkovic, Ljubisa

    1986-01-01

    The regulation of glutamine synthetase by glucocorticoids in rat skeletal muscles was studied. Administration of dexamethasone strikingly enhanced glutamine synthetase activity in plantaris and soleus muscles. The dexamethasone-mediated induction of glutamine synthetase activity was blocked to a significant extent by orally administered RU38486, a glucocorticoid antagonist, indicating the involvement of intracellular glucocorticoid receptors in the induction. Northern blot analysis revealed that dexamethasone-mediated enhancement of glutamine synthetase activity involves dramatically increased levels of glutamine synthetase mRNA. The induction of glutamine synthetase was selective in that glutaminase activity of soleus and plantaris muscles was not increased by dexamethasone. Furthermore, dexamethasone treatment resulted in only a small increase in glutamine synthetase activity in the heart. Accordingly, there was only a slight change in glutamine synthetase mRNA level in this tissue. Thus, glucocorticoids regulate glutamine synthetase gene expression in rat muscles at the transcriptional level via interaction with intracellular glutamine production by muscle and to mechanisms underlying glucocorticoid-induced muscle atrophy.

  11. Muscle-specific Drp1 overexpression impairs skeletal muscle growth via translational attenuation

    PubMed Central

    Touvier, T; De Palma, C; Rigamonti, E; Scagliola, A; Incerti, E; Mazelin, L; Thomas, J-L; D'Antonio, M; Politi, L; Schaeffer, L; Clementi, E; Brunelli, S

    2015-01-01

    Mitochondrial fission and fusion are essential processes in the maintenance of the skeletal muscle function. The contribution of these processes to muscle development has not been properly investigated in vivo because of the early lethality of the models generated so far. To define the role of mitochondrial fission in muscle development and repair, we have generated a transgenic mouse line that overexpresses the fission-inducing protein Drp1 specifically in skeletal muscle. These mice displayed a drastic impairment in postnatal muscle growth, with reorganisation of the mitochondrial network and reduction of mtDNA quantity, without the deficiency of mitochondrial bioenergetics. Importantly we found that Drp1 overexpression activates the stress-induced PKR/eIF2?/Fgf21 pathway thus leading to an attenuated protein synthesis and downregulation of the growth hormone pathway. These results reveal for the first time how mitochondrial network dynamics influence muscle growth and shed light on aspects of muscle physiology relevant in human muscle pathologies. PMID:25719247

  12. Hyperinsulinemia and skeletal muscle fatty acid trafficking.

    PubMed

    Kanaley, Jill A; Shadid, Samyah; Sheehan, Michael T; Guo, ZengKui; Jensen, Michael D

    2013-08-15

    We hypothesized that insulin alters plasma free fatty acid (FFA) trafficking into intramyocellular (im) long-chain acylcarnitines (imLCAC) and triglycerides (imTG). Overnight-fasted adults (n = 41) received intravenous infusions of [U-¹³C]palmitate (0400-0900 h) and [U-¹³C]oleate (0800-1400 h) to label imTG and imLCAC. A euglycemic-hyperinsulinemic (1.0 mU·kg fat-free mass?¹·min?¹) clamp (0800-1400 h) and two muscle biopsies (0900 h, 1400 h) were performed. The patterns of [U-¹³C]palmitate incorporation into imTG-palmitate and palmitoylcarnitine were similar to those we reported in overnight postabsorptive adults (saline control); the intramyocellular palmitoylcarnitine enrichment was not different from and correlated with imTG-palmitate enrichment for both the morning (r = 0.38, P = 0.02) and afternoon (r = 0.44, P = 0.006) biopsy samples. Plasma FFA concentrations, flux, and the incorporation of plasma oleate into imTG-oleate during hyperinsulinemia were ~1/10th of that observed in the previous saline control studies (P < 0.001). At the time of the second biopsy, the enrichment in oleoylcarnitine was <25% of that in imTG-oleate and was not correlated with imTG-oleate enrichment. The intramyocellular nonesterified fatty acid-palmitate-to-imTG-palmitate enrichment ratio was greater (P < 0.05) in women than men, suggesting that sex differences in intramyocellular palmitate trafficking may occur under hyperinsulinemic conditions. We conclude that plasma FFA trafficking into imTG during hyperinsulinemia is markedly suppressed, and these newly incorporated FFA fatty acids do not readily enter the LCAC preoxidative pools. Hyperinsulinemia does not seem to inhibit the entry of fatty acids from imTG pools that were labeled under fasting conditions, possibly reflecting the presence of two distinct imTG pools that are differentially regulated by insulin. PMID:23820622

  13. Bioactives from Artemisia dracunculus L. Enhance Insulin Sensitivity via Modulation of Skeletal Muscle Protein Phosphorylation

    PubMed Central

    Kheterpal, Indu; Scherp, Peter; Kelley, Lauren; Wang, Zhong; Johnson, William; Ribnicky, David; Cefalu, William T.

    2014-01-01

    A botanical extract from Artemisia dracunculus L., termed PMI 5011, has been shown previously to improve insulin sensitivity by increasing cellular insulin signaling in in vitro and in vivo studies. These studies suggest that PMI 5011 effects changes in phosphorylation levels of proteins involved in insulin signaling. To explore effects of this promising botanical extract on the human skeletal muscle phosphoproteome, changes in site-specific protein phosphorylation levels in primary skeletal muscle cultures from obese, insulin resistant individuals were evaluated with and without insulin stimulation. Insulin resistance is a condition in which a normal or elevated insulin level results in an abnormal biologic response, e.g., glucose uptake. Using isobaric tagging for relative and absolute quantification (iTRAQ™) followed by phosphopeptide enrichment and liquid chromatography – tandem mass spectrometry, 125 unique phosphopeptides and 159 unique phosphorylation sites from 80 unique proteins were identified and quantified. Insulin stimulation of primary cultured muscle cells from insulin resistant individuals resulted in minimal increase in phosphorylation, demonstrating impaired insulin action in this condition. Treatment with PMI 5011 resulted in significant up regulation of 35 phosphopeptides that were mapped to proteins participating in the regulation of transcription, translation, actin cytoskeleton signaling, caveolae translocation and GLUT4 transport. These data further showed that PMI 5011 increased phosphorylation levels of specific amino acids in proteins in the insulin resistant state that are normally phosphorylated by insulin (thus, increasing cellular insulin signaling) and PMI 5011 also increased the abundance of phosphorylation sites of proteins regulating anti-apoptotic effects. Thus, the phosphoproteomics analysis demonstrated conclusively that PMI 5011 effects changes in phosphorylation levels of proteins and identified novel pathways by which PMI 5011 exerts its insulin sensitizing effects in skeletal muscle. PMID:24985106

  14. MicroRNAs in skeletal muscle: their role and regulation in development, disease and function.

    PubMed

    Güller, Isabelle; Russell, Aaron P

    2010-11-01

    Maintaining skeletal muscle function throughout the lifespan is a prerequisite for good health and independent living. For skeletal muscle to consistently function at optimal levels, the efficient activation of processes that regulate muscle development, growth, regeneration and metabolism is required. Numerous conditions including neuromuscular disorders, physical inactivity, chronic disease and ageing are associated with perturbations in skeletal muscle function. A loss or reduction in skeletal muscle function often leads to increased morbidity and mortality either directly, or indirectly, via the development of secondary diseases such as diabetes, obesity, cardiovascular and respiratory disease. Identifying mechanisms which influence the processes regulating skeletal muscle function is a key priority. The discovery of microRNAs (miRNAs) provides a new avenue that will extend our knowledge of factors controlling skeletal muscle function. miRNAs may also improve our understanding and application of current therapeutic approaches as well as enable the identification of new therapeutic strategies and targets aimed at maintaining and/or improving skeletal muscle health. This review brings together the latest developments in skeletal muscle miRNA biology and focuses on their role and regulation under physiological and patho-physiological conditions with an emphasis on: myogenesis, hypertrophy, atrophy and regeneration; exercise and nutrition; muscle disease, ageing, diabetes and obesity. PMID:20724363

  15. Time-dependent behavior of passive skeletal muscle

    NASA Astrophysics Data System (ADS)

    Ahamed, T.; Rubin, M. B.; Trimmer, B. A.; Dorfmann, L.

    2015-07-01

    An isotropic three-dimensional nonlinear viscoelastic model is developed to simulate the time-dependent behavior of passive skeletal muscle. The development of the model is stimulated by experimental data that characterize the response during simple uniaxial stress cyclic loading and unloading. Of particular interest is the rate-dependent response, the recovery of muscle properties from the preconditioned to the unconditioned state and stress relaxation at constant stretch during loading and unloading. The model considers the material to be a composite of a nonlinear hyperelastic component in parallel with a nonlinear dissipative component. The strain energy and the corresponding stress measures are separated additively into hyperelastic and dissipative parts. In contrast to standard nonlinear inelastic models, here the dissipative component is modeled using an evolution equation that combines rate-independent and rate-dependent responses smoothly with no finite elastic range. Large deformation evolution equations for the distortional deformations in the elastic and in the dissipative component are presented. A robust, strongly objective numerical integration algorithm is used to model rate-dependent and rate-independent inelastic responses. The constitutive formulation is specialized to simulate the experimental data. The nonlinear viscoelastic model accurately represents the time-dependent passive response of skeletal muscle.

  16. Nrf2 Protects Against TWEAK-mediated Skeletal Muscle Wasting

    NASA Astrophysics Data System (ADS)

    Al-Sawaf, Othman; Fragoulis, Athanassios; Rosen, Christian; Kan, Yuet Wai; Sönmez, Tolga Taha; Pufe, Thomas; Wruck, Christoph Jan

    2014-01-01

    Skeletal muscle (SM) regeneration after injury is impaired by excessive inflammation. Particularly, the inflammatory cytokine tumour necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a potent inducer of skeletal muscle wasting and fibrosis. In this study we investigated the role of Nrf2, a major regulator of oxidative stress defence, in SM ischemia/reperfusion (I/R) injury and TWEAK induced atrophy. We explored the time-dependent expression of TWEAK after I/R in SM of Nrf2-wildtype (WT) and knockout (KO) mice. Nrf2-KO mice expressed significant higher levels of TWEAK as compared to WT mice. Consequently, Nrf2-KO mice present an insufficient regeneration as compared to Nrf2-WT mice. Moreover, TWEAK stimulation activates Nrf2 in the mouse myoblast cell line C2C12. This Nrf2 activation inhibits TWEAK induced atrophy in C2C12 differentiated myotubes. In summary, we show that Nrf2 protects SM from TWEAK-induced cell death in vitro and that Nrf2-deficient mice therefore have poorer muscle regeneration.

  17. Optogenetic control of contractile function in skeletal muscle.

    PubMed

    Bruegmann, Tobias; van Bremen, Tobias; Vogt, Christoph C; Send, Thorsten; Fleischmann, Bernd K; Sasse, Philipp

    2015-01-01

    Optogenetic stimulation allows activation of cells with high spatial and temporal precision. Here we show direct optogenetic stimulation of skeletal muscle from transgenic mice expressing the light-sensitive channel Channelrhodopsin-2 (ChR2). Largest tetanic contractions are observed with 5-ms light pulses at 30?Hz, resulting in 84% of the maximal force induced by electrical stimulation. We demonstrate the utility of this approach by selectively stimulating with a light guide individual intralaryngeal muscles in explanted larynges from ChR2-transgenic mice, which enables selective opening and closing of the vocal cords. Furthermore, systemic injection of adeno-associated virus into wild-type mice provides sufficient ChR2 expression for optogenetic opening of the vocal cords. Thus, direct optogenetic stimulation of skeletal muscle generates large force and provides the distinct advantage of localized and cell-type-specific activation. This technology could be useful for therapeutic purposes, such as restoring the mobility of the vocal cords in patients suffering from laryngeal paralysis. PMID:26035411

  18. Optogenetic control of contractile function in skeletal muscle

    PubMed Central

    Bruegmann, Tobias; van Bremen, Tobias; Vogt, Christoph C.; Send, Thorsten; Fleischmann, Bernd K.; Sasse, Philipp

    2015-01-01

    Optogenetic stimulation allows activation of cells with high spatial and temporal precision. Here we show direct optogenetic stimulation of skeletal muscle from transgenic mice expressing the light-sensitive channel Channelrhodopsin-2 (ChR2). Largest tetanic contractions are observed with 5-ms light pulses at 30?Hz, resulting in 84% of the maximal force induced by electrical stimulation. We demonstrate the utility of this approach by selectively stimulating with a light guide individual intralaryngeal muscles in explanted larynges from ChR2-transgenic mice, which enables selective opening and closing of the vocal cords. Furthermore, systemic injection of adeno-associated virus into wild-type mice provides sufficient ChR2 expression for optogenetic opening of the vocal cords. Thus, direct optogenetic stimulation of skeletal muscle generates large force and provides the distinct advantage of localized and cell-type-specific activation. This technology could be useful for therapeutic purposes, such as restoring the mobility of the vocal cords in patients suffering from laryngeal paralysis. PMID:26035411

  19. Photoengineering of tissue repair in skeletal and cardiac muscles.

    PubMed

    Oron, Uri

    2006-04-01

    This review discusses the application of He-Ne laser irradiation to injured muscles at optimal power densities and optimal timing, which was found to significantly enhance (twofold) muscle regeneration in rats and, even more, in the cold-blooded toads. Multiple and frequent (daily) application of the laser in the toad model was found to be less effective than irradiation on alternate days. It was found that in the ischemia/reperfusion type of injury in the skeletal leg muscles (3 h of ischemia), infrared Ga-Al-As laser irradiation reduced muscle degeneration, increased the cytoprotective heat shock proteins (HSP-70i) content, and produced a twofold increase in total antioxidants. In vitro studies on myogenic satellite cells (SC) revealed that phototherapy restored their proliferation. Phototherapy induced mitogen-activated protein kinase/extracellular signal-regulated protein kinase (MAPK/ERK) phosphorylation in these cells, probably by specific receptor phosphorylation. Cell cycle entry and the accumulation of satellite cells around isolated single myofibers cultured in vitro was also stimulated by phototherapy. Phototherapy also had beneficial effects on mouse, rat, dog and pig ischemic heart models. In these models, it was found that phototherapy markedly and significantly reduced (50-70%) the scar tissue formed after induction of myocardial infarction (MI). The phototherapeutic effect was associated with reduction of ventricular dilatation, preservation of mitochondria and elevation of HSP- 70i and ATP in the infarcted zone. It is concluded that phototherapy using the correct parameters and timing has a markedly beneficial effect on repair processes after injury or ischemia in skeletal and heart muscles. This phenomenon may have clinical applications. PMID:16706689

  20. Effect of spaceflight on skeletal muscle: Mechanical properties and myosin isoform content of a slow muscle

    NASA Technical Reports Server (NTRS)

    Caiozzo, Vincent J.; Baker, Michael J.; Herrick, Robert E.; Tao, Ming; Baldwin, Kenneth M.

    1994-01-01

    This study examined changes in contractile, biochemical, and histochemical properties of slow antigravity skeletal muscle after a 6-day spaceflight mission. Twelve male Sprague-Dawley rats were randomly divided into two groups: flight and ground-based control. Approximately 3 h after the landing, in situ contractile measurements were made on the soleus muscles of the flight animals. The control animals were studied 24 h later. The contractile measurements included force-velocity relationship, force-frequency relationship, and fatigability. Biochemical measurements focused on the myosin heavy chain (MHC) and myosin light chain profiles. Adenosinetriphosphatase histochemistry was performed to identify cross-sectional area of slow and fast muscle fibers and to determine the percent fiber type distribution. The force-velocity relationships of the flight muscles were altered such that maximal isometric tension P(sub o) was decreased by 24% and maximal shortening velocity was increased by 14% (P less than 0.05). The force-frequency relationship of the flight muscles was shifted to the right of the control muscles. At the end of the 2-min fatigue test, the flight muscles generated only 34% of P(sub o), whereas the control muscles generated 64% of P(sub o). The flight muscles exhibited de novo expression of the type IIx MHC isoform as well as a slight decrease in the slow type I and fast type IIa MHC isoforms. Histochemical analyses of flight muscles demonstrated a small increase in the percentage of fast type II fibers and a greater atrophy of the slow type I fibers. The results demonstrate that contractile properties of slow antigravity skeletal muscle are sensitive to the microgravity environment and that changes begin to occur within the 1st wk. These changes were at least, in part, associated with changes in the amount and type of contractile protein expressed.

  1. Skeletal Muscle Lipid Deposition and Insulin Resistance: Impact of Dietary Fatty Acids and Exercise

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evidence has mounted indicating that elevated intramuscular triacylglycerol levels are associated with diminished insulin sensitivity in skeletal muscle. This lipid accumulation is most likely due to enhanced fatty acid uptake into the muscle coupled with diminished mitochondrial lipid oxidation. Th...

  2. The STARS signaling pathway: a key regulator of skeletal muscle function.

    PubMed

    Lamon, Séverine; Wallace, Marita A; Russell, Aaron P

    2014-09-01

    During the last decade, the striated muscle activator of Rho signaling (STARS), a muscle-specific protein, has been proposed to play an increasingly important role in skeletal muscle growth, metabolism, regeneration and stress adaptation. STARS influences actin dynamics and, as a consequence, regulates the myocardin-related transcription factor A/serum response factor (MRTF-A/SRF) transcriptional program, a well-known pathway controlling skeletal muscle development and function. Muscle-specific stress conditions, such as exercise, positively regulates, while disuse and degenerative muscle diseases are associated with a downregulation of STARS and its downstream partners, suggesting a pivotal role for STARS in skeletal muscle health. This review provides a comprehensive overview of the known role and regulation of STARS and the members of its signaling pathway, RhoA, MRTF-A and SRF, in skeletal muscle. PMID:24557714

  3. Procedures for rat in situ skeletal muscle contractile properties.

    PubMed

    MacIntosh, Brian R; Esau, Shane P; Holash, R John; Fletcher, Jared R

    2011-01-01

    There are many circumstances where it is desirable to obtain the contractile response of skeletal muscle under physiological circumstances: normal circulation, intact whole muscle, at body temperature. This includes the study of contractile responses like posttetanic potentiation, staircase and fatigue. Furthermore, the consequences of disease, disuse, injury, training and drug treatment can be of interest. This video demonstrates appropriate procedures to set up and use this valuable muscle preparation. To set up this preparation, the animal must be anesthetized, and the medial gastrocnemius muscle is surgically isolated, with the origin intact. Care must be taken to maintain the blood and nerve supplies. A long section of the sciatic nerve is cleared of connective tissue, and severed proximally. All branches of the distal stump that do not innervate the medial gastrocnemius muscle are severed. The distal nerve stump is inserted into a cuff lined with stainless steel stimulating wires. The calcaneus is severed, leaving a small piece of bone still attached to the Achilles tendon. Sonometric crystals and/or electrodes for electromyography can be inserted. Immobilization by metal probes in the femur and tibia prevents movement of the muscle origin. The Achilles tendon is attached to the force transducer and the loosened skin is pulled up at the sides to form a container that is filled with warmed paraffin oil. The oil distributes heat evenly and minimizes evaporative heat loss. A heat lamp is directed on the muscle, and the muscle and rat are allowed to warm up to 37°C. While it is warming, maximal voltage and optimal length can be determined. These are important initial conditions for any experiment on intact whole muscle. The experiment may include determination of standard contractile properties, like the force-frequency relationship, force-length relationship, and force-velocity relationship. With care in surgical isolation, immobilization of the origin of the muscle and alignment of the muscle-tendon unit with the force transducer, and proper data analysis, high quality measurements can be obtained with this muscle preparation. PMID:22025076

  4. Autocrine and/or paracrine insulin-like growth factor-I activity in skeletal muscle

    NASA Technical Reports Server (NTRS)

    Adams, Gregory R.

    2002-01-01

    Similar to bone, skeletal muscle responds and adapts to changes in loading state via mechanisms that appear to be intrinsic to the muscle. One of the mechanisms modulating skeletal muscle adaptation it thought to involve the autocrine and/or paracrine production of insulinlike growth factor-I. This brief review outlines components of the insulinlike growth factor-I system as it relates to skeletal muscle and provides the rationale for the theory that insulinlike growth factor-I is involved with muscle adaptation.

  5. Tissue-Engineered Skeletal Muscle Organoids for Reversible Gene Therapy

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman; DelTatto, Michael; Shansky, Janet; Lemaire, Julie; Chang, Albert; Payumo, Francis; Lee, Peter; Goodyear, Amy; Raven, Latasha

    1996-01-01

    Genetically modified murine skeletal myoblasts were tissue engineered in vitro into organ-like structures (organoids) containing only postmitotic myofibers secreting pharmacological levels of recombinant human growth hormone (rhGH). Subcutaneous organoid Implantation under tension led to the rapid and stable appearance of physiological sera levels of rhGH for up to 12 weeks, whereas surgical removal led to its rapid disappearance. Reversible delivery of bioactive compounds from postimtotic cells in tissue engineered organs has several advantages over other forms of muscle gene therapy.

  6. Tissue-Engineered Skeletal Muscle Organoids for Reversible Gene Therapy

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman; DelTatto, Michael; Shansky, Janet; Lemaire, Julie; Chang, Albert; Payumo, Francis; Lee, Peter; Goodyear, Amy; Raven, Latasha

    1996-01-01

    Genetically modified murine skeletal myoblasts were tissue engineered in vitro into organ-like structures (organoids) containing only postmitotic myoribers secreting pharmacological levels of recombinant human growth hormone (rhGH). Subcutaneous organoid implantation under tension led to the rapid and stable appearance of physiological sera levels of rhGH for up to 12 weeks, whereas surgical removal led to its rapid disappearance. Reversible delivery of bioactive compounds from postmitotic cells in tissue engineered organs has several advantages over other forms of muscle gene therapy.

  7. Computer-aided mechanogenesis of skeletal muscle organs from single cells in vitro

    NASA Technical Reports Server (NTRS)

    Vanderburgh, Herman H.; Swasdison, Somporn; Karlisch, Patricia

    1991-01-01

    Complex mechanical forces generated in the growing embryo play an important role in organogenesis. Computerized application of similar forces to differentiating skeletal muscle myoblasts in vitro generate three dimensional artificial muscle organs. These organs contain parallel networks of long unbranched myofibers organized into fascicle-like structures. Tendon development is initiated and the muscles are capable of performing directed, functional work. Kinetically engineered organs provide a new method for studying the growth and development of normal and diseased skeletal muscle.

  8. Computer aided mechanogenesis of skeletal muscle organs from single cells in vitro

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.; Swasdison, Somporn; Karlisch, Patricia

    1990-01-01

    Complex mechanical forces generated in the growing embryo play an important role in organogenesis. Computerized application of similar forces to differentiating skeletal muscle myoblasts in vitro generate three dimensional artificial muscle organs. These organs contain parallel networks of long unbranched myofibers organized into fascicle-like structures. Tendon development is initiated and the muscles are capable of performing directed, functional work. Kinetically engineered organs provide a new method for studying the growth and development of normal and diseased skeletal muscle.

  9. Tbx15 controls skeletal muscle fibre-type determination and muscle metabolism

    PubMed Central

    Lee, Kevin Y.; Singh, Manvendra K.; Ussar, Siegfried; Wetzel, Petra; Hirshman, Michael F.; Goodyear, Laurie J.; Kispert, Andreas; Kahn, C. Ronald

    2015-01-01

    Skeletal muscle is composed of both slow-twitch oxidative myofibers and fast-twitch glycolytic myofibers that differentially impact muscle metabolism, function and eventually whole-body physiology. Here we show that the mesodermal transcription factor T-box 15 (Tbx15) is highly and specifically expressed in glycolytic myofibers. Ablation of Tbx15 in vivo leads to a decrease in muscle size due to a decrease in the number of glycolytic fibres, associated with a small increase in the number of oxidative fibres. This shift in fibre composition results in muscles with slower myofiber contraction and relaxation, and also decreases whole-body oxygen consumption, reduces spontaneous activity, increases adiposity and glucose intolerance. Mechanistically, ablation of Tbx15 leads to activation of AMPK signalling and a decrease in Igf2 expression. Thus, Tbx15 is one of a limited number of transcription factors to be identified with a critical role in regulating glycolytic fibre identity and muscle metabolism. PMID:26299309

  10. Skeletal muscle satellite cells cultured in simulated microgravity

    NASA Technical Reports Server (NTRS)

    Molnar, Greg; Hartzell, Charles R.; Schroedl, Nancy A.; Gonda, Steve R.

    1993-01-01

    Satellite cells are postnatal myoblasts responsible for providing additional nuclei to growing or regenerating muscle cells. Satellite cells retain the capacity to proliferate and differentiate in vitro and therefore provide a useful model to study postnatal muscle development. Most culture systems used to study postnatal muscle development are limited by the two-dimensional (2-D) confines of the culture dish. Limiting proliferation and differentiation of satellite cells in 2-D could potentially limit cell-cell contacts important for developing the level of organization in skeletal muscle obtained in vivo. Culturing satellite cells on microcarrier beads suspended in the High-Aspect-Ratio-Vessel (HARV) designed by NASA provides a low shear, three-dimensional (3-D) environment to study muscle development. Primary cultures established from anterior tibialis muscles of growing rats (approximately 200 gm) were used for all studies and were composed of greater than 75 % satellite cells. Different inoculation densities did not affect the proliferative potential of satellite cells in the HARV. Plating efficiency, proliferation, and glucose utilization were compared between 2-D flat culture and 3-D HARV culture. Plating efficiency (cells attached - cells plated x 100) was similar between the two culture systems. Proliferation was reduced in HARV cultures and this reduction was apparent for both satellite cells and non-satellite cells. Furthermore, reduction in proliferation within the HARV could not be attributed to reduced substrate availability since glucose levels in media from HARV and 2-D cell culture were similar. Morphologically, microcarrier beads within the HARVS were joined together by cells into three-dimensional aggregates composed of greater than 10 beads/aggregate. Aggregation of beads did not occur in the absence of cells. Myotubes were often seen on individual beads or spanning the surface of two beads. In summary, proliferation and differentiation of satellite cells on microcarrier beads within the HARV bioreactor results in a three dimensional level of organization that could provide a more suitable model to study postnatal muscle development.

  11. Structural dynamics of troponin during activation of skeletal muscle.

    PubMed

    Fusi, Luca; Brunello, Elisabetta; Sevrieva, Ivanka R; Sun, Yin-Biao; Irving, Malcolm

    2014-03-25

    Time-resolved changes in the conformation of troponin in the thin filaments of skeletal muscle were followed during activation in situ by photolysis of caged calcium using bifunctional fluorescent probes in the regulatory and the coiled-coil (IT arm) domains of troponin. Three sequential steps in the activation mechanism were identified. The fastest step (1,100 s(-1)) matches the rate of Ca(2+) binding to the regulatory domain but also dominates the motion of the IT arm. The second step (120 s(-1)) coincides with the azimuthal motion of tropomyosin around the thin filament. The third step (15 s(-1)) was shown by three independent approaches to track myosin head binding to the thin filament, but is absent in the regulatory head. The results lead to a four-state structural kinetic model that describes the molecular mechanism of muscle activation in the thin filament-myosin head complex under physiological conditions. PMID:24616505

  12. Role of the occult insulin receptors in the regulation of atrophy and hypertrophy of skeletal muscles

    SciTech Connect

    McLeod, M.J.

    1980-10-01

    Insulin levels in the plasma are variable, as are insulin receptor numbers on the surface of skeletal muscles. Increased blood supply to the muscle during exercise delivers more insulin to the muscles even though insulin levels are suppressed by epinephrine. Increasing muscle temperatures result in an increased insulin effect, if enough receptors are available for binding. In exhaustive exercise, insulin levels are minimal but the movement of glucose across the cell membrane increases. Since insulin-receptor affinity decreases at high temperature, the only way this increased movement of glucose can be accomplished is by increased insulin binding. Thus more receptors must be available to capture the insulin. Epinephrine levels drop drastically after exercise. Insulin levels increase and the cell can import glucose, amino acids, and nucleotides. As the cell temperature decreases after exercise, insulin binding increases but the total effect decreases because the many surface receptors disappear again over a period of time. If the muscle is immobilized, the number of surface receptors decreases. There is less insulin effect and as a result the muscle atrophies. Acetylcholine (ACh) causes the proper arrangement of the myofibrils in the foetus, and has some effect on the rate of atrophy in an immobilized muscle. It also appears to maintain the cell membrane organization. Disuse atrophy is caused by a decrease in cell size, while exercise hypertrophy is caused by an increase in cell size. Growth hormone (STH) is therefore ruled out as the exercise hypertrophy controlling factor, since STH causes cell division and not hypertrophy. Testosterone can also be ruled out as the controlling factor in the development of hypertrophy and atrophy of muscles. Estrogen can likewise be ruled out. (ERB)

  13. Regulatory circuitry of TWEAK-Fn14 system and PGC-1? in skeletal muscle atrophy program.

    PubMed

    Hindi, Sajedah M; Mishra, Vivek; Bhatnagar, Shephali; Tajrishi, Marjan M; Ogura, Yuji; Yan, Zhen; Burkly, Linda C; Zheng, Timothy S; Kumar, Ashok

    2014-03-01

    Skeletal muscle wasting attributed to inactivity has significant adverse functional consequences. Accumulating evidence suggests that peroxisome proliferator-activated receptor ? coactivator 1? (PGC-1?) and TNF-like weak inducer of apoptosis (TWEAK)-Fn14 system are key regulators of skeletal muscle mass in various catabolic states. While the activation of TWEAK-Fn14 signaling causes muscle wasting, PGC-1? preserves muscle mass in several conditions, including functional denervation and aging. However, it remains unknown whether there is any regulatory interaction between PGC-1? and TWEAK-Fn14 system during muscle atrophy. Here we demonstrate that TWEAK significantly reduces the levels of PGC-1? and mitochondrial content (?50%) in skeletal muscle. Levels of PGC-1? are significantly increased in skeletal muscle of TWEAK-knockout (KO) and Fn14-KO mice compared to wild-type mice on denervation. Transgenic (Tg) overexpression of PGC-1? inhibited progressive muscle wasting in TWEAK-Tg mice. PGC-1? inhibited the TWEAK-induced activation of NF-?B (?50%) and dramatically reduced (?90%) the expression of atrogenes such as MAFbx and MuRF1. Intriguingly, muscle-specific overexpression of PGC-1? also prevented the inducible expression of Fn14 in denervated skeletal muscle. Collectively, our study demonstrates that TWEAK induces muscle atrophy through repressing the levels of PGC-1?. Overexpression of PGC-1? not only blocks the TWEAK-induced atrophy program but also diminishes the expression of Fn14 in denervated skeletal muscle. PMID:24327607

  14. Skeletal Muscle Loss is Associated with TNF Mediated Insufficient Skeletal Myogenic Activation After Burn.

    PubMed

    Song, Juquan; Saeman, Melody R; De Libero, Jana; Wolf, Steven E

    2015-11-01

    Muscle loss accompanies severe burn; in this hyper-catabolic state, muscle undergoes atrophy through protein degradation and disuse. Muscle volume is related to the relative rates of cellular degradation and myogenesis. We hypothesize that muscle atrophy after injury is in part because of insufficient myogenesis associated with the hyper-inflammatory response. The aim of this study was to investigate the role of skeletal myogenesis and muscle cell homeostasis in response to severe burn. Twenty-eight male C57BL6 mice received 25% TBSA scald. Gluteus muscle from these animals was analyzed at days 1, 3, 7, and 14 after injury. Six additional animals without burn served as controls. We showed muscle wet weight and protein content decreased at days 3 and 7 after burn, with elevated tumor necrosis factor (TNF) mRNA expression (P?muscle lysate at day 3 (P?

  15. The calcineurin-NFAT pathway controls activity-dependent circadian gene expression in slow skeletal muscle

    PubMed Central

    Dyar, Kenneth A.; Ciciliot, Stefano; Tagliazucchi, Guidantonio Malagoli; Pallafacchina, Giorgia; Tothova, Jana; Argentini, Carla; Agatea, Lisa; Abraham, Reimar; Ahdesmäki, Miika; Forcato, Mattia; Bicciato, Silvio; Schiaffino, Stefano; Blaauw, Bert

    2015-01-01

    Objective Physical activity and circadian rhythms are well-established determinants of human health and disease, but the relationship between muscle activity and the circadian regulation of muscle genes is a relatively new area of research. It is unknown whether muscle activity and muscle clock rhythms are coupled together, nor whether activity rhythms can drive circadian gene expression in skeletal muscle. Methods We compared the circadian transcriptomes of two mouse hindlimb muscles with vastly different circadian activity patterns, the continuously active slow soleus and the sporadically active fast tibialis anterior, in the presence or absence of a functional skeletal muscle clock (skeletal muscle-specific Bmal1 KO). In addition, we compared the effect of denervation on muscle circadian gene expression. Results We found that different skeletal muscles exhibit major differences in their circadian transcriptomes, yet core clock gene oscillations were essentially identical in fast and slow muscles. Furthermore, denervation caused relatively minor changes in circadian expression of most core clock genes, yet major differences in expression level, phase and amplitude of many muscle circadian genes. Conclusions We report that activity controls the oscillation of around 15% of skeletal muscle circadian genes independently of the core muscle clock, and we have identified the Ca2+-dependent calcineurin-NFAT pathway as an important mediator of activity-dependent circadian gene expression, showing that circadian locomotor activity rhythms drive circadian rhythms of NFAT nuclear translocation and target gene expression. PMID:26629406

  16. Early parenteral nutrition evokes a phenotype of autophagy deficiency in liver and skeletal muscle of critically ill rabbits.

    PubMed

    Derde, Sarah; Vanhorebeek, Ilse; Güiza, Fabian; Derese, Inge; Gunst, Jan; Fahrenkrog, Birthe; Martinet, Wim; Vervenne, Hilke; Ververs, Eric-Jan; Larsson, Lars; Van den Berghe, Greet

    2012-05-01

    Muscular and hepatic abnormalities observed in artificially fed critically ill patients strikingly resemble the phenotype of autophagy-deficient mice. Autophagy is the only pathway to clear damaged organelles and large ubiquitinated proteins and aggregates. Fasting is its strongest physiological trigger. Severity of autophagy deficiency in critically ill patients correlated with the amount of infused amino acids. We hypothesized that impaired autophagy in critically ill patients could partly be evoked by early provision of parenteral nutrition enriched with amino acids in clinically used amounts. In a randomized laboratory investigation, we compared the effect of isocaloric moderate-dose iv feeding with fasting during illness on the previously studied markers of autophagy deficiency in skeletal muscle and liver. Critically ill rabbits were allocated to fasting or to iv nutrition (220 kcal/d, 921 kJ/d) supplemented with 50 kcal/d (209 kJ/d) of either glucose, amino acids, or lipids, while maintaining normoglycemia, and were compared with healthy controls. Fasted critically ill rabbits revealed weight loss and activation of autophagy. Feeding abolished these responses, with most impact of amino acid-enriched nutrition. Accumulation of p62 and ubiquitinated proteins in muscle and liver, indicative of insufficient autophagy, occurred with parenteral feeding enriched with amino acids and lipids. In liver, this was accompanied by fewer autophagosomes, fewer intact mitochondria, suppressed respiratory chain activity, and an increase in markers of liver damage. In muscle, early parenteral nutrition enriched with amino acids or lipids aggravated vacuolization of myofibers. In conclusion, early parenteral nutrition during critical illness evoked a phenotype of autophagy deficiency in liver and skeletal muscle. PMID:22396453

  17. Three-dimensional optical coherence micro-elastography of skeletal muscle tissue.

    PubMed

    Chin, Lixin; Kennedy, Brendan F; Kennedy, Kelsey M; Wijesinghe, Philip; Pinniger, Gavin J; Terrill, Jessica R; McLaughlin, Robert A; Sampson, David D

    2014-09-01

    In many muscle pathologies, impairment of skeletal muscle function is closely linked to changes in the mechanical properties of the muscle constituents. Optical coherence micro-elastography (OCME) uses optical coherence tomography (OCT) imaging of tissue under a quasi-static, compressive mechanical load to map variations in tissue mechanical properties on the micro-scale. We present the first study of OCME on skeletal muscle tissue. We show that this technique can resolve features of muscle tissue including fibers, fascicles and tendon, and can also detect necrotic lesions in skeletal muscle from the mdx mouse model of Duchenne muscular dystrophy. In many instances, OCME provides better or additional contrast complementary to that provided by OCT. These results suggest that OCME could provide new understanding and opportunity for assessment of skeletal muscle pathologies. PMID:25401023

  18. Alterations in skeletal muscle arteriolar vasoreactivity during the progression of type 2 diabetes in the Zucker Diabetic Fatty rat 

    E-print Network

    Lesniewski, Lisa AnnMarie

    2004-09-30

    and passive properties of low-oxidative glycolytic skeletal muscle arterioles are present during prediabetes, and precede the development of type 2 diabetes, and that although endothelial dysfunction does not become manifest in these skeletal muscle arterioles...

  19. Nuclear genetic control of mitochondrial translation in skeletal muscle revealed in patients

    E-print Network

    Shoubridge, Eric

    Nuclear genetic control of mitochondrial translation in skeletal muscle revealed in patients in a developmentally regulated nuclear factor important for mitochondrial translation in skeletal muscle. INTRODUCTION The enzymatic system responsible for the generation of ATP by oxidative phosphorylation of ADP, located

  20. ORIGINAL ARTICLE Gene Transfer to Mouse Heart and Skeletal Muscles Using

    E-print Network

    Kay, Mark A.

    ORIGINAL ARTICLE Gene Transfer to Mouse Heart and Skeletal Muscles Using a Minicircle Expressing to be improved. A novel vector system that shows great promise is the minicircle (MC) vector being smaller than, expressing the human vascular endothelial growth factor (hVEGF), to mouse heart and skeletal muscles

  1. Histochemical, enzymatic, and contractile properties of skeletal muscles of three anuran amphibians

    E-print Network

    Bennett, Albert F.

    Histochemical, enzymatic, and contractile properties of skeletal muscles of three anuran amphibians, and contractile properties of skeletal muscles of three anuran amphibians. Am. J. Physiol. 244 (Regulatory with organismal metabolic capacity and behavioral pattern. Anuran amphibians were chosen as the model system

  2. Lower physical activity is associated with fat infiltration within skeletal muscle in young girls

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fat infiltration within skeletal muscle is strongly associated with obesity, type 2 diabetes mellitus, and metabolic syndrome. Lower physical activity may be a risk factor for greater fat infiltration within skeletal muscle, although whether lower physical activity is associated with fat infiltrati...

  3. Genetic selection of mice for high voluntary wheel running: effect on skeletal muscle glucose uptake

    E-print Network

    Saltzman, Wendy

    Genetic selection of mice for high voluntary wheel running: effect on skeletal muscle glucose: effect on skeletal muscle glucose uptake. J Appl Physiol 91: 1289­1297, 2001.--Effects of genetic glucose uptake were stud- ied in mice with the following treatments for 8 wk: 1) access to unlocked wheels

  4. ADIPOCYTE DIFFERENTIATION-RELATED PROTEIN IN HUMAN SKELETAL MUSCLE: RELATIONSHIP TO INSULIN SENSITIVITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To determine whether adipocyte differentiation-related protein (ADRP), a lipid droplet-associated protein that binds to and sequesters intracellular fatty acids, is 1) expressed in human skeletal muscle and 2) differentially regulated in human skeletal muscle obtained from obese non-diabetic (OND) a...

  5. Contrast Agent-Enhanced Magnetic Resonance Imaging of Skeletal Muscle Damage in Animal Models

    E-print Network

    Campbell, Kevin P.

    in the degeneration of skeletal muscle fibers in Duchenne muscular dystrophy patients is the breakdown of the sar of Muscular Dystrophy Volker Straub,1 Kathleen M. Donahue,2,3 Vale´rie Allamand,1 Robin L. Davisson,4 Young R for muscular dystrophy was studied by MRI. Intravenously injected MS-325 does not enter skeletal muscle

  6. Skeletal Muscle-Specific Ablation of ccyto-Actin Does Not Exacerbate the mdx Phenotype

    E-print Network

    Ervasti, James M.

    -deficient skeletal muscle and hypothesized that increased ccyto-actin expression may participate in an adaptiveSkeletal Muscle-Specific Ablation of ccyto-Actin Does Not Exacerbate the mdx Phenotype Kurt W of America Abstract We previously documented a ten-fold increase in ccyto-actin expression in dystrophin

  7. Exercise and Type 2 Diabetes: Molecular Mechanisms Regulating Glucose Uptake in Skeletal Muscle

    ERIC Educational Resources Information Center

    Stanford, Kristin I.; Goodyear, Laurie J.

    2014-01-01

    Exercise is a well-established tool to prevent and combat type 2 diabetes. Exercise improves whole body metabolic health in people with type 2 diabetes, and adaptations to skeletal muscle are essential for this improvement. An acute bout of exercise increases skeletal muscle glucose uptake, while chronic exercise training improves mitochondrial…

  8. Cloning and characterization of fiber type-specific ryanodine receptor isoforms in skeletal muscles of fish

    E-print Network

    Block, Barbara A.

    Cloning and characterization of fiber type-specific ryanodine receptor isoforms in skeletal muscles. Block. Cloning and characterization of fiber type-specific ryanodine receptor isoforms in skeletal muscles of fish. Am. J. Physiol. 275 (Cell Physiol. 44): C401­C415, 1998.--We have cloned a group of c

  9. p53 Improves Aerobic Exercise Capacity and Augments Skeletal Muscle Mitochondrial DNA Content

    E-print Network

    Leary, Scot

    p53 Improves Aerobic Exercise Capacity and Augments Skeletal Muscle Mitochondrial DNA Content Joon: The purpose of this study was to understand the genetic mechanism by which p53 regulates aerobic exercise / compared to p53 / mice was more marked in aerobic versus glycolytic skeletal muscle groups

  10. CYTOCHEMICAL LOCALIZATION OF LACTIC DEHYDROGENASE IN WHITE SKELETAL MUSCLE

    PubMed Central

    Fahimi, H. Dariush; Amarasingham, Chandra Raj

    1964-01-01

    The limitations of the conventional histochemical methods for localization of lactic dehydrogenase (LDH) in white skeletal muscle have been analyzed quantitatively. It is demonstrated that more than 80 per cent of LDH diffuses into the incubation medium within the first 10 minutes of incubation. Furthermore, it is confirmed that the addition of phenazine methosulfate (PMS) to the ingredients of the histochemical reaction for LDH increases substantially the capacity of the white muscle extract to reduce Nitro-BT. Based on these observations, a modified method of cytochemical localization of LDH has been developed. This method prevents the leakage of LDH from tissue sections by the application of all the ingredients of the histochemical reaction to tissue sections in a thin gelatin film. The incubation mixture contains PMS so that the staining system is independent of tissue diaphorase. The application of this method to the adductor magnus muscle of the rabbit revealed a fine reticulum in the sarcoplasm of all muscle fibers, in addition to the staining of mitochondria. The distribution of the staining suggests that LDH is localized in the sarcoplasmic reticulum. PMID:14195619

  11. Therapeutic strategies for preventing skeletal muscle fibrosis after injury

    PubMed Central

    Garg, Koyal; Corona, Benjamin T.; Walters, Thomas J.

    2015-01-01

    Skeletal muscle repair after injury includes a complex and well-coordinated regenerative response. However, fibrosis often manifests, leading to aberrant regeneration and incomplete functional recovery. Research efforts have focused on the use of anti-fibrotic agents aimed at reducing the fibrotic response and improving functional recovery. While there are a number of mediators involved in the development of post-injury fibrosis, TGF-?1 is the primary pro-fibrogenic growth factor and several agents that inactivate TGF-?1 signaling cascade have emerged as promising anti-fibrotic therapies. A number of these agents are FDA approved for other conditions, clearing the way for rapid translation into clinical treatment. In this article, we provide an overview of muscle's host response to injury with special emphasis on the cellular and non-cellular mediators involved in the development of fibrosis. This article also reviews the findings of several pre-clinical studies that have utilized anti-fibrotic agents to improve muscle healing following most common forms of muscle injuries. Although some studies have shown positive results with anti-fibrotic treatment, others have indicated adverse outcomes. Some concerns and questions regarding the clinical potential of these anti-fibrotic agents have also been presented. PMID:25954202

  12. The role of mitochondria in aging of skeletal muscle.

    PubMed

    Figueiredo, Pedro Alexandre; Mota, Maria P; Appell, Hans Joachim; Duarte, José Alberto

    2008-04-01

    Aging can be characterized as a time dependent decline of maximal functionality that affects tissues and organs of the whole body. Such is induced by the progressive loss of redundant components and leads to an increased susceptibility to disease and risk of death. Regarding the aging of skeletal muscle, it has been pointed out that mitochondria is a key factor behind the loss of redundancy and functionality, since this organelle has a major role in cellular homeostasis particularly at the level of the bioenergetic status. Decreased activities of the mitochondrial electron transport chain complexes and an increased release of reactive oxygen species from mitochondria are well documented with age; it is suggested that the mitochondrial loss of function results from the increased oxidative damage to proteins, lipids, and DNA of this organelle. However, it is important to be aware that the mitochondrial loss of function could also be a consequence, rather than a cause, of the cellular deterioration with age, which compromises mitochondrial biogenesis, mitochondrial protein turnover and autophagocytosis of damaged mitochondria. In this review several topics will be addressed regarding the age-related loss of skeletal muscle redundancy associated with mitochondrial dysfunction, emphasizing hypotheses for underlying mechanisms. In addition, we discuss some of the cellular mechanisms that can be pointed out as being responsible for the age-related mitochondrial dysfunction. PMID:18175203

  13. Genomic organization of the human skeletal muscle sodium channel gene

    SciTech Connect

    George, A.L. Jr.; Iyer, G.S.; Kleinfield, R.; Kallen, R.G.; Barchi, R.L. )

    1993-03-01

    Voltage-dependent sodium channels are essential for normal membrane excitability and contractility in adult skeletal muscle. The gene encoding the principal sodium channel [alpha]-subunit isoform in human skeletal muscle (SCN4A) has recently been shown to harbor point mutations in certain hereditary forms of periodic paralysis. The authors have carried out an analysis of the detailed structure of this gene including delination of intron-exon boundaries by genomic DNA cloning and sequence analysis. The complete coding region of SCN4A is found in 32.5 kb of genomic DNA and consists of 24 exons (54 to >2.2 kb) and 23 introns (97 bp-4.85 kb). The exon organization of the gene shows no relationship to the predicted functional domains of the channel protein and splice junctions interrupt many of the transmembrane segments. The genomic organization of sodium channels may have been partially conserved during evolution as evidenced by the observation that 10 of the 24 splice junctions in SCN4A are positioned in homologous locations in a putative sodium channel gene in Drosophila (para). The information presented here should be extremely useful both for further identifying sodium channel mutations and for gaining a better understanding of sodium channel evolution. 39 refs., 5 figs., 2 tabs.

  14. Dynamics of myosin replacement in skeletal muscle cells.

    PubMed

    Ojima, Koichi; Ichimura, Emi; Yasukawa, Yuya; Wakamatsu, Jun-Ichi; Nishimura, Takanori

    2015-11-15

    Highly organized thick filaments in skeletal muscle cells are formed from ?300 myosin molecules. Each thick-filament-associated myosin molecule is thought to be constantly exchanged. However, the mechanism of myosin replacement remains unclear, as does the source of myosin for substitution. Here, we investigated the dynamics of myosin exchange in the myofibrils of cultured myotubes by fluorescent recovery after photobleaching and found that myofibrillar myosin is actively replaced with an exchange half-life of ?3 h. Myosin replacement was not disrupted by the absence of the microtubule system or by actomyosin interactions, suggesting that known cytoskeletal systems are dispensable for myosin substitution. Intriguingly, myosin replacement was independent of myosin binding protein C, which links myosin molecules together to form thick filaments. This implies that an individual myosin molecule rather than a thick filament functions as an exchange unit. Furthermore, the myosin substitution rate was decreased by the inhibition of protein synthesis, suggesting that newly synthesized myosin, as well as preexisting cytosolic myosin, contributes to myosin replacement in myofibrils. Notably, incorporation and release of myosin occurred simultaneously in myofibrils, but rapid myosin release from myofibrils was observed without protein synthesis. Collectively, our results indicate that myosin shuttles between myofibrils and the nonmyofibrillar cytosol to maintain a dynamic equilibrium in skeletal muscle cells. PMID:26377314

  15. Lysophosphatidic acid mediates pleiotropic responses in skeletal muscle cells

    SciTech Connect

    Jean-Baptiste, Gael; Yang Zhao; Khoury, Chamel; Greenwood, Michael T.; E-mail: michael.greenwood@mcgill.ca

    2005-10-07

    Lysophosphatidic acid (LPA) is a potent modulator of growth, cell survival, and apoptosis. Although all four LPA receptors are expressed in skeletal muscle, very little is known regarding the role they play in this tissue. We used RT-PCR to demonstrate that cultured skeletal muscle C2C12 cells endogenously express multiple LPA receptor subtypes. The demonstration that LPA mediates the activation of ERK1/2 MAP kinase and Akt/PKB in C2C12 cells is consistent with the widely observed mitogenic properties of LPA. In spite of these observations, LPA did not induce proliferation in C2C12 cells. Paradoxically, we found that prolonged treatment of C2C12 cells with LPA led to caspase 3 and PARP cleavage as well as the activation of stress-associated MAP kinases JNK and p38. In spite of these typically pro-apoptotic responses, LPA did not induce cell death. Blocking ERK1/2 and Akt/PKB activation with specific pharmacological inhibitors, nevertheless, stimulated LPA-mediated apoptosis. Taken together, these results suggest that both mitogenic and apoptotic responses serve to counterbalance the effects of LPA in cultured C2C12 cells.

  16. Module-based multiscale simulation of angiogenesis in skeletal muscle

    PubMed Central

    2011-01-01

    Background Mathematical modeling of angiogenesis has been gaining momentum as a means to shed new light on the biological complexity underlying blood vessel growth. A variety of computational models have been developed, each focusing on different aspects of the angiogenesis process and occurring at different biological scales, ranging from the molecular to the tissue levels. Integration of models at different scales is a challenging and currently unsolved problem. Results We present an object-oriented module-based computational integration strategy to build a multiscale model of angiogenesis that links currently available models. As an example case, we use this approach to integrate modules representing microvascular blood flow, oxygen transport, vascular endothelial growth factor transport and endothelial cell behavior (sensing, migration and proliferation). Modeling methodologies in these modules include algebraic equations, partial differential equations and agent-based models with complex logical rules. We apply this integrated model to simulate exercise-induced angiogenesis in skeletal muscle. The simulation results compare capillary growth patterns between different exercise conditions for a single bout of exercise. Results demonstrate how the computational infrastructure can effectively integrate multiple modules by coordinating their connectivity and data exchange. Model parameterization offers simulation flexibility and a platform for performing sensitivity analysis. Conclusions This systems biology strategy can be applied to larger scale integration of computational models of angiogenesis in skeletal muscle, or other complex processes in other tissues under physiological and pathological conditions. PMID:21463529

  17. Large fiber size in skeletal muscle is metabolically advantageous

    PubMed Central

    Jimenez, Ana Gabriela; Dillaman, Richard M.; Kinsey, Stephen T.

    2013-01-01

    Skeletal muscle fiber size is highly variable, and while diffusion appears to limit maximal fiber size, there is no paradigm for the control of minimal size. The optimal fiber size hypothesis posits that the reduced surface area to volume (SA:V) in larger fibers reduces the metabolic cost of maintaining the membrane potential, and so fibers attain an optimal size that minimizes metabolic cost while avoiding diffusion limitation. Here we examine changes during hypertrophic fiber growth in metabolic cost and activity of the Na+-K+-ATPase in white skeletal muscle from crustaceans and fishes. We provide evidence for a major tenet of the optimal fiber size hypothesis by demonstrating that larger fibers are metabolically cheaper to maintain, and the cost of maintaining the membrane potential is proportional to fiber SA:V. The influence of SA:V on metabolic cost is apparent during growth in 16 species spanning a 20-fold range in fiber size, suggesting that this principle may apply widely. PMID:23851638

  18. Skeletal Muscle Fascicle Arrangements Can Be Reconstructed Using a Laplacian Vector Field Simulation

    PubMed Central

    Choi, Hon Fai; Blemker, Silvia S.

    2013-01-01

    Skeletal muscles are characterized by a large diversity in anatomical architecture and function. Muscle force and contraction are generated by contractile fiber cells grouped in fascicle bundles, which transmit the mechanical action between origin and insertion attachments of the muscle. Therefore, an adequate representation of fascicle arrangements in computational models of skeletal muscles is important, especially when investigating three-dimensional muscle deformations in finite element models. However, obtaining high resolution in vivo measurements of fascicle arrangements in skeletal muscles is currently still challenging. This motivated the development of methods in previous studies to generate numerical representations of fascicle trajectories using interpolation templates. Here, we present an alternative approach based on the hypothesis of a rotation and divergence free (Laplacian) vector field behavior which reflects observed physical characteristics of fascicle trajectories. To obtain this representation, the Laplace equation was solved in anatomical reconstructions of skeletal muscle shapes based on medical images using a uniform flux boundary condition on the attachment areas. Fascicle tracts were generated through a robust flux based tracing algorithm. The concept of this approach was demonstrated in two-dimensional synthetic examples of typical skeletal muscle architectures. A detailed evaluation was performed in an example of the anatomical human tibialis anterior muscle which showed an overall agreement with measurements from the literature. The utility and capability of the proposed method was further demonstrated in other anatomical examples of human skeletal muscles with a wide range of muscle shapes and attachment morphologies. PMID:24204878

  19. Heart failure alters MyoD and MRF4 expressions in rat skeletal muscle

    PubMed Central

    Carvalho, Robson Francisco; Cicogna, Antonio Carlos; Campos, Gerson Eduardo Rocha; da Silva Lopes, Francis; Sugizaki, Mário Mateus; Nogueira, Célia Regina; Pai-Silva, Maeli Dal

    2006-01-01

    Heart failure (HF) is characterized by a skeletal muscle myopathy with increased expression of fast myosin heavy chains (MHCs). The skeletal muscle-specific molecular regulatory mechanisms controlling MHC expression during HF have not been described. Myogenic regulatory factors (MRFs), a family of transcriptional factors that control the expression of several skeletal muscle-specific genes, may be related to these alterations. This investigation was undertaken in order to examine potential relationships between MRF mRNA expression and MHC protein isoforms in Wistar rat skeletal muscle with monocrotaline-induced HF. We studied soleus (Sol) and extensor digitorum longus (EDL) muscles from both HF and control Wistar rats. MyoD, myogenin and MRF4 contents were determined using reverse transcription-polymerase chain reaction while MHC isoforms were separated using polyacrylamide gel electrophoresis. Despite no change in MHC composition of Wistar rat skeletal muscles with HF, the mRNA relative expression of MyoD in Sol and EDL muscles and that of MRF4 in Sol muscle were significantly reduced, whereas myogenin was not changed in both muscles. This down-regulation in the mRNA relative expression of MRF4 in Sol was associated with atrophy in response to HF while these alterations were not present in EDL muscle. Taken together, our results show a potential role for MRFs in skeletal muscle myopathy during HF. PMID:16709230

  20. Optimized dietary strategies to protect skeletal muscle mass during periods of unavoidable energy deficit.

    PubMed

    Pasiakos, Stefan M; Margolis, Lee M; Orr, Jeb S

    2015-04-01

    Interactions between dietary protein and energy balance on the regulation of human skeletal muscle protein turnover are not well described. A dietary protein intake above the recommended dietary allowance during energy balance typically enhances nitrogen retention and up-regulates muscle protein synthesis, which in turn may promote positive protein balance and skeletal muscle accretion. Recent studies show that during energy deficit, muscle protein synthesis is down-regulated with concomitant increases in ubiquitin proteasome-mediated muscle proteolysis and nitrogen excretion, reflecting the loss of skeletal muscle mass. However, consuming high-protein diets (1.6-2.4 g/kg per day), or high-quality, protein-based meals (15-30 g whey) during energy deficit attenuates intracellular proteolysis, restores muscle protein synthesis, and mitigates skeletal muscle loss. These findings are particularly important for physically active, normal-weight individuals because attenuating the extent to which skeletal muscle mass is lost during energy deficit could prevent decrements in performance, reduce injury risk, and facilitate recovery. This article reviews the relationship between energy status, protein intake, and muscle protein turnover, and explores future research directives designed to protect skeletal muscle mass in physically active, normal-weight adults. PMID:25550460

  1. Mitochondrial dysfunction in skeletal muscle during experimental Chagas disease.

    PubMed

    Báez, Alejandra L; Reynoso, María N; Lo Presti, María S; Bazán, Paola C; Strauss, Mariana; Miler, Noemí; Pons, Patricia; Rivarola, Héctor W; Paglini-Oliva, Patricia

    2015-06-01

    Trypanosoma cruzi invasion and replication in cardiomyocytes and other tissues induce cellular injuries and cytotoxic reactions, with the production of inflammatory cytokines and nitric oxide, both sources of reactive oxygen species. The myocyte response to oxidative stress involves the progression of cellular changes primarily targeting mitochondria. Similar alterations could be taking place in mitochondria from the skeletal muscle; if that is the case, a simple skeletal muscle biopsy would give information about the cardiac energetic production that could be used as a predictor of the chagasic cardiopathy evolution. Therefore, in the present paper we studied skeletal muscle mitochondrial structure and the enzymatic activity of citrate synthase and respiratory chain complexes I to IV (CI-CIV), in Albino Swiss mice infected with T. cruzi, Tulahuen strain and SGO Z12 and Lucky isolates, along the infection. Changes in the mitochondrial structure were detected in 100% of the mitochondria analyzed from the infected groups: they all presented at least 1 significant abnormality such as increase in their matrix or disorganization of their cristae, which are probably related to the enzymatic dysfunction. When we studied the Krebs cycle functionality through the measurement of the specific citrate synthase activity, we found it to be significantly diminished during the acute phase of the infection in Tulahuen and SGO Z12 infected groups with respect to the control one; citrate synthase activity from the Lucky group was significantly increased (p<0.05). The activity of this enzyme was reduced in all the infected groups during the chronic asymptomatic phase (p<0.001) and return to normal values (Tulahuen and SGO Z12) or increased its activity (Lucky) by day 365 post-infection (p.i.). When the mitochondrial respiratory chain was analyzed from the acute to the chronic phase of the infection through the measurement of the activity of complexes I to IV, the activity of CI remained similar to control in Tulahuen and Lucky groups, but was significantly augmented in the SGO Z12 one in the acute and chronic phases (p<0.05). CII increased its activity in Tulahuen and Lucky groups by day 75 p.i. and in SGO Z12 by day 365 p.i. (p<0.05). CIII showed a similar behavior in the 3 infected groups, remaining similar to control values in the first two stages of the infection and significantly increasing later on (p<0.0001). CIV showed an increase in its activity in Lucky throughout all stages of infection (p<0.0001) and an increase in Tulahuen by day 365days p.i. (p<0.0001); SGO Z12 on the other hand, showed a decreased CIV activity at the same time. The structural changes in skeletal muscle mitochondria and their altered enzyme activity began in the acute phase of infection, probably modifying the ability of mitochondria to generate energy; these changes were not compensated in the rest of the phases of the infection. Chagas is a systemic disease, which produces not only heart damage but also permanent skeletal muscle alterations. PMID:25835781

  2. Age-dependent capacity to accelerate protein synthesis dictates the extent of compensatory growth in skeletal muscle following undernutrition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In both humans and animals, impaired growth during early life compromises adult lean body mass and muscle strength despite skeletal muscle’s large regenerative capacity. To identify the significance of developmental age on skeletal muscle’s capacity for catch-up growth following an episode of under ...

  3. Induction of functional tissue-engineered skeletal muscle constructs by defined electrical stimulation

    PubMed Central

    Ito, Akira; Yamamoto, Yasunori; Sato, Masanori; Ikeda, Kazushi; Yamamoto, Masahiro; Fujita, Hideaki; Nagamori, Eiji; Kawabe, Yoshinori; Kamihira, Masamichi

    2014-01-01

    Electrical impulses are necessary for proper in vivo skeletal muscle development. To fabricate functional skeletal muscle tissues in vitro, recapitulation of the in vivo niche, including physical stimuli, is crucial. Here, we report a technique to engineer skeletal muscle tissues in vitro by electrical pulse stimulation (EPS). Electrically excitable tissue-engineered skeletal muscle constructs were stimulated with continuous electrical pulses of 0.3?V/mm amplitude, 4?ms width, and 1?Hz frequency, resulting in a 4.5-fold increase in force at day 14. In myogenic differentiation culture, the percentage of peak twitch force (%Pt) was determined as the load on the tissue constructs during the artificial exercise induced by continuous EPS. We optimized the stimulation protocol, wherein the tissues were first subjected to 24.5%Pt, which was increased to 50–60%Pt as the tissues developed. This technique may be a useful approach to fabricate tissue-engineered functional skeletal muscle constructs. PMID:24759171

  4. Responses of skeletal muscle to unloading - A review

    NASA Technical Reports Server (NTRS)

    Tischler, M. E.; Jaspers, S. R.; Henriksen, E. J.; Jacob, S.

    1985-01-01

    Suspension models were used to study muscle response to reduced activity. During 6 days of tail casting, the soleus (SOL) atrophies while the extensor digitorum longus grows relatively normally. After discounting those changes in both muscles due primarily to increased secretion of adrenal hormones, the following conclusions regarding the specific responses of the SOL could be drawn: (1) Atrophy is probably due primarily to increased protein degradation; (2) Decreased synthesis of glutamine may result from reduced availability of ammonia due to diminished use of ATP; (3) Greater muscle glycogen seems to reflect an increased response to insulin of glucose uptake which leads to greater glucose metabolism; and (4) Faster catabolism of branched-chain amino acids can be attributed to enhanced flux through ketoacid dehydrogenase. Studies by others using tail casted suspended rats showed in the SOL: (1) a gradual switch from type 1 to type 2 fibers; (2) increased acid protease activity; and (3) altered muscle function and contractile duration. Using harness suspended rats, others showed in the SOL: (1) significant atrophy; (2) increased numbers of glucocorticoid receptors; and (3) no change in muscle fatigability.

  5. Responses of skeletal muscle to unloading, a review

    NASA Technical Reports Server (NTRS)

    Tischler, M. E.; Jaspers, S. R.; Henriksen, E. J.; Jacob, S.

    1985-01-01

    Suspension models were used to study muscle response to reduced activity. During 6 days of tail casting, the soleus (SOL) atrophies while the extensor digitorum longus grows relatively normally. After discounting those changes in both muscles due primarily to increased secretion of adrenal hormones, the following conclusions regarding the specific responses of the SOL could be drawn: (1) Atrophy is probably due primarily to increased protein degradation; (2) Decreased synthesis of glutamine may result from reduced availability of ammonia due to diminished use of ATP; (3) Greater muscle glycogen seems to reflect an increased response to insulin of glucose uptake which leads to greater glucose metabolism; and (4) Faster catabolism of branched-chain amino acids can be attributed to enhanced flux through ketoacid dehydrogenase. Studies by others using tail casted suspended rats showed in the SOL: (1) a gradual switch from type 1 to type 2 fibers; (2) increased acid protease activity; and (3) altered muscle function and contractile duration. Using harness suspended rats, others showed in the SOL: (1) significant atrophy; (2) increased numbers of glucocorticoid receptors; and (3) no change in muscle fatigability.

  6. Microcurrent Electrical Neuromuscular Stimulation Facilitates Regeneration of Injured Skeletal Muscle in Mice

    PubMed Central

    Fujiya, Hiroto; Ogura, Yuji; Ohno, Yoshitaka; Goto, Ayumi; Nakamura, Ayane; Ohashi, Kazuya; Uematsu, Daiki; Aoki, Haruhito; Musha, Haruki; Goto, Katsumasa

    2015-01-01

    Conservative therapies, mainly resting care for the damaged muscle, are generally used as a treatment for skeletal muscle injuries (such as muscle fragmentation). Several past studies reported that microcurrent electrical neuromuscular stimulation (MENS) facilitates a repair of injured soft tissues and shortens the recovery period. However, the effects of MENS on the regeneration in injured skeletal muscle are still unclear. The purpose of this study was to investigate the effect of MENS on the regenerative process of injured skeletal muscle and to elucidate whether satellite cells in injured skeletal muscle are activated by MENS by using animal models. Male C57BL/6J mice, aged 7 weeks old, were used (n = 30). Mice were randomly divided into two groups: (1) cardiotoxin (CTX)-injected (CX, n = 15) and (2) CTX-injected with MENS treatment (MX, n=15) groups. CTX was injected into tibialis anterior muscle (TA) of mice in CX and MX groups to initiate the necrosis-regeneration cycle of the muscle. TA was dissected 1, 2, and 3 weeks after the injection. Muscle weight, muscle protein content, the mean cross-sectional areas of muscle fibers, the relative percentage of fibers having central nuclei, and the number of muscle satellite cells were evaluated. MENS facilitated the recovery of the muscle dry weight and protein content relative to body weight, and the mean cross-sectional areas of muscle fibers in CTX-induced injured TA muscle. The number of Pax7-positive muscle satellite cells was increased by MENS during the regenerating period. Decrease in the percentages of fibers with central nuclei after CTX-injection was facilitated by MENS. MENS may facilitate the regeneration of injured skeletal muscles by activating the regenerative potential of skeletal muscles. Key points Microcurrent electrical neuromuscular stimulation (MENS) facilitated the recovery of the relative muscle dry weight, the relative muscle protein content, and the mean cross-sectional areas of muscle fibers of injured TA muscle in mice. The number of satellite cells was increased by MENS during the regenerating phase of injured skeletal muscle. Decrease in the percentages of fibers with central nuclei was facilitated by MENS. MENS may facilitate the regeneration of injured skeletal muscles. PMID:25983578

  7. Human skeletal muscle xenograft as a new preclinical model for muscle disorders

    PubMed Central

    Zhang, Yuanfan; King, Oliver D.; Rahimov, Fedik; Jones, Takako I.; Ward, Christopher W.; Kerr, Jaclyn P.; Liu, Naili; Emerson, Charles P.; Kunkel, Louis M.; Partridge, Terence A.; Wagner, Kathryn R.

    2014-01-01

    Development of novel therapeutics requires good animal models of disease. Disorders for which good animal models do not exist have very few drugs in development or clinical trial. Even where there are accepted, albeit imperfect models, the leap from promising preclinical drug results to positive clinical trials commonly fails, including in disorders of skeletal muscle. The main alternative model for early drug development, tissue culture, lacks both the architecture and, usually, the metabolic fidelity of the normal tissue in vivo. Herein, we demonstrate the feasibility and validity of human to mouse xenografts as a preclinical model of myopathy. Human skeletal muscle biopsies transplanted into the anterior tibial compartment of the hindlimbs of NOD-Rag1null IL2r?null immunodeficient host mice regenerate new vascularized and innervated myofibers from human myogenic precursor cells. The grafts exhibit contractile and calcium release behavior, characteristic of functional muscle tissue. The validity of the human graft as a model of facioscapulohumeral muscular dystrophy is demonstrated in disease biomarker studies, showing that gene expression profiles of xenografts mirror those of the fresh donor biopsies. These findings illustrate the value of a new experimental model of muscle disease, the human muscle xenograft in mice, as a feasible and valid preclinical tool to better investigate the pathogenesis of human genetic myopathies and to more accurately predict their response to novel therapeutics. PMID:24452336

  8. Roles of nonmyogenic mesenchymal progenitors in pathogenesis and regeneration of skeletal muscle

    PubMed Central

    Uezumi, Akiyoshi; Ikemoto-Uezumi, Madoka; Tsuchida, Kunihiro

    2014-01-01

    Adult skeletal muscle possesses a remarkable regenerative ability that is dependent on satellite cells. However, skeletal muscle is replaced by fatty and fibrous connective tissue in several pathological conditions. Fatty and fibrous connective tissue becomes a major cause of muscle weakness and leads to further impairment of muscle function. Because the occurrence of fatty and fibrous connective tissue is usually associated with severe destruction of muscle, the idea that dysregulation of the fate switch in satellite cells may underlie this pathological change has emerged. However, recent studies identified nonmyogenic mesenchymal progenitors in skeletal muscle and revealed that fatty and fibrous connective tissue originates from these progenitors. Later, these progenitors were also demonstrated to be the major contributor to heterotopic ossification in skeletal muscle. Because nonmyogenic mesenchymal progenitors represent a distinct cell population from satellite cells, targeting these progenitors could be an ideal therapeutic strategy that specifically prevents pathological changes of skeletal muscle, while preserving satellite cell-dependent regeneration. In addition to their roles in pathogenesis of skeletal muscle, nonmyogenic mesenchymal progenitors may play a vital role in muscle regeneration by regulating satellite cell behavior. Conversely, muscle cells appear to regulate behavior of nonmyogenic mesenchymal progenitors. Thus, these cells regulate each other reciprocally and a proper balance between them is a key determinant of muscle integrity. Furthermore, nonmyogenic mesenchymal progenitors have been shown to maintain muscle mass in a steady homeostatic condition. Understanding the nature of nonmyogenic mesenchymal progenitors will provide valuable insight into the pathophysiology of skeletal muscle. In this review, we focus on nonmyogenic mesenchymal progenitors and discuss their roles in muscle pathogenesis, regeneration, and homeostasis. PMID:24605102

  9. Characterization of RyR1-slow, a ryanodine receptor specific to slow-twitch skeletal muscle

    E-print Network

    Block, Barbara A.

    Characterization of RyR1-slow, a ryanodine receptor specific to slow-twitch skeletal muscle JEFFERY, a ryanodine receptor specific to slow-twitch skeletal muscle. Am J Physiol Regulatory Integrative Comp Physiol 279: R1889­R1898, 2000.--Two distinct skeletal muscle ryanodine receptors (RyR1s) are expressed

  10. Generation of skeletal muscle from transplanted embryonic stem cells in dystrophic mice

    SciTech Connect

    Bhagavati, Satyakam . E-mail: satyakamb@hotmail.com; Xu Weimin

    2005-07-29

    Embryonic stem (ES) cells have great therapeutic potential because of their capacity to proliferate extensively and to form any fully differentiated cell of the body, including skeletal muscle cells. Successful generation of skeletal muscle in vivo, however, requires selective induction of the skeletal muscle lineage in cultures of ES cells and following transplantation, integration of appropriately differentiated skeletal muscle cells with recipient muscle. Duchenne muscular dystrophy (DMD), a severe progressive muscle wasting disease due to a mutation in the dystrophin gene and the mdx mouse, an animal model for DMD, are characterized by the absence of the muscle membrane associated protein, dystrophin. Here, we show that co-culturing mouse ES cells with a preparation from mouse muscle enriched for myogenic stem and precursor cells, followed by injection into mdx mice, results occasionally in the formation of normal, vascularized skeletal muscle derived from the transplanted ES cells. Study of this phenomenon should provide valuable insights into skeletal muscle development in vivo from transplanted ES cells.

  11. Making Skeletal Muscle from Progenitor and Stem Cells: Development versus Regeneration

    PubMed Central

    Li, Lydia; Rozo, Michelle E.; Lepper, Christoph

    2012-01-01

    For locomotion, vertebrate animals use the force generated by contractile skeletal muscles. These muscles form an actin/myosin-based bio-machinery that is attached to skeletal elements to effect body movement and maintain posture. The mechanics, physiology, and homeostasis of skeletal muscles in normal and disease states are of significant clinical interest. How muscles originate from progenitors during embryogenesis has attracted considerable attention from developmental biologists. How skeletal muscles regenerate and repair themselves after injury by the use of stem cells is an important process to maintain muscle homeostasis throughout lifetime. In recent years, much progress has been made towards uncovering the origins of myogenic progenitors and stem cells as well as the regulation of these cells during development and regeneration. PMID:22737183

  12. Sarcopenia and the Common Mental Disorders: a Potential Regulatory Role of Skeletal Muscle on Brain Function?

    PubMed

    Pasco, Julie A; Williams, Lana J; Jacka, Felice N; Stupka, Nicole; Brennan-Olsen, Sharon L; Holloway, Kara L; Berk, Michael

    2015-10-01

    While it is understood that body composition impacts on physical conditions, such as diabetes and cardiovascular disease, it is only now apparent that body composition might play a role in the genesis of common mental disorders, depression and anxiety. Sarcopenia occurs in ageing and comprises a progressive decline in muscle mass, strength and function, leading to frailty, decreased independence and poorer quality of life. This review presents an emerging body of evidence to support the hypothesis that shared pathophysiological pathways for sarcopenia and the common mental disorders constitute links between skeletal muscle and brain function. Contracting skeletal muscle secretes neurotrophic factors that are known to play a role in mood and anxiety, and have the dual role of nourishing neuronal growth and differentiation, while protecting the size and number of motor units in skeletal muscle. Furthermore, skeletal muscle activity has important immune and redox effects that impact behaviour and reduce muscle catabolism. PMID:26228522

  13. Deep Proteomics of Mouse Skeletal Muscle Enables Quantitation of Protein Isoforms, Metabolic Pathways, and Transcription Factors*

    PubMed Central

    Deshmukh, Atul S.; Murgia, Marta; Nagaraj, Nagarjuna; Treebak, Jonas T.; Cox, Jürgen; Mann, Matthias

    2015-01-01

    Skeletal muscle constitutes 40% of individual body mass and plays vital roles in locomotion and whole-body metabolism. Proteomics of skeletal muscle is challenging because of highly abundant contractile proteins that interfere with detection of regulatory proteins. Using a state-of-the art MS workflow and a strategy to map identifications from the C2C12 cell line model to tissues, we identified a total of 10,218 proteins, including skeletal muscle specific transcription factors like myod1 and myogenin and circadian clock proteins. We obtain absolute abundances for proteins expressed in a muscle cell line and skeletal muscle, which should serve as a valuable resource. Quantitation of protein isoforms of glucose uptake signaling pathways and in glucose and lipid metabolic pathways provides a detailed metabolic map of the cell line compared with tissue. This revealed unexpectedly complex regulation of AMP-activated protein kinase and insulin signaling in muscle tissue at the level of enzyme isoforms. PMID:25616865

  14. Mechanisms of nascent fiber formation during avian skeletal muscle hypertrophy

    NASA Technical Reports Server (NTRS)

    McCormick, K. M.; Schultz, E.

    1992-01-01

    This study examined two putative mechanisms of new fiber formation in postnatal skeletal muscle, namely longitudinal fragmentation of existing fibers and de novo formation. The relative contributions of these two mechanisms to fiber formation in hypertrophying anterior latissimus dorsi (ALD) muscle were assessed by quantitative analysis of their nuclear populations. Muscle hypertrophy was induced by wing-weighting for 1 week. All nuclei formed during the weighting period were labeled by continuous infusion of 5-bromo-2'-deoxyuridine (BrdU), a thymidine analog, and embryonic-like fibers were identified using an antibody to ventricular-like embryonic (V-EMB) myosin. The number of BrdU-labeled and unlabeled nuclei in V-EMB-positive fibers were counted. Wing-weighting resulted in significant muscle enlargement and the appearance of many V-EMB+ fibers. The majority of V-EMB+ fibers were completely independent of mature fibers and had a nuclear density characteristics of developing fibers. Furthermore, nearly 100% of the nuclei in independent V-EMB+ fibers were labeled. These findings strongly suggest that most V-EMB+ fibers were nascent fibers formed de novo during the weighting period by satellite cell activation and fusion. Nascent fibers were found primarily in the space between fascicles where they formed a complex anastomosing network of fibers running at angles to one another. Although wing-weighting induced an increase in the number of branched fibers, there was no evidence that V-EMB+ fibers were formed by longitudinal fragmentation. The location of newly formed fibers in wing-weighted and regenerating ALD muscle was compared to determine whether satellite cells in the ALD muscle were unusual in that, if stimulated to divide, they would form fibers in the inter- and intrafascicular space. In contrast to wing-weighted muscle, nascent fibers were always found closely associated with necrotic fibers. These results suggest that wing-weighting is not simply another model of regeneration, but rather produces a unique environment which induces satellite cell migration and subsequent fiber formation in the interfascicular space. De novo fiber formation is apparently the principal mechanism for the hyperplasia reported to occur in the ALD muscle undergoing hypertrophy induced by wing-weighting.

  15. Xin is a marker of skeletal muscle damage severity in myopathies.

    PubMed

    Nilsson, Mats I; Nissar, Aliyah A; Al-Sajee, Dhuha; Tarnopolsky, Mark A; Parise, Gianni; Lach, Boleslav; Fürst, Dieter O; van der Ven, Peter F M; Kley, Rudolf A; Hawke, Thomas J

    2013-12-01

    Xin is a striated muscle-specific protein that is localized to the myotendinous junction in skeletal muscle. However, in injured mouse muscle, Xin expression is up-regulated and observed throughout skeletal muscle fibers and within satellite cells. In this study, Xin was analyzed by immunofluorescent staining in skeletal muscle samples from 47 subjects with various forms of myopathy, including muscular dystrophies, inflammatory myopathies, mitochondrial/metabolic myopathy, and endocrine myopathy. Results indicate that Xin immunoreactivity is positively and significantly correlated (rs = 0.6175, P = <0.0001) with the severity of muscle damage, regardless of myopathy type. Other muscle damage measures also showed a correlation with severity [Xin actin-binding repeat-containing 2 (rs = -0.7108, P = 0.0006) and collagen (rs = 0.4683, P = 0.0783)]. However, because only Xin lacked immunoreactivity within the healthy muscle belly, any detectable immunoreactivity for Xin was indicative of muscle damage. We also investigated the expression of Xin within the skeletal muscle of healthy individuals subjected to damaging eccentric exercise. Consistent with our previously mentioned results, Xin immunoreactivity was increased 24 hours after exercise in damaged muscle fibers and within the activated muscle satellite cells. Taken together, these data demonstrate Xin as a useful biomarker of muscle damage in healthy individuals and in patients with myopathy. The strong correlation between the degree of muscle damage and Xin immunoreactivity suggests that Xin may be a suitable outcome measure to evaluate disease progression and treatment effects in clinical trials. PMID:24225086

  16. Skeletal muscle wasting with disuse atrophy is multi-dimensional: the response and interaction of myonuclei, satellite cells and signaling pathways

    PubMed Central

    Brooks, Naomi E.; Myburgh, Kathryn H.

    2014-01-01

    Maintenance of skeletal muscle is essential for health and survival. There are marked losses of skeletal muscle mass as well as strength and physiological function under conditions of low mechanical load, such as space flight, as well as ground based models such as bed rest, immobilization, disuse, and various animal models. Disuse atrophy is caused by mechanical unloading of muscle and this leads to reduced muscle mass without fiber attrition. Skeletal muscle stem cells (satellite cells) and myonuclei are integrally involved in skeletal muscle responses to environmental changes that induce atrophy. Myonuclear domain size is influenced differently in fast and slow twitch muscle, but also by different models of muscle wasting, a factor that is not yet understood. Although the myonuclear domain is 3-dimensional this is rarely considered. Apoptosis as a mechanism for myonuclear loss with atrophy is controversial, whereas cell death of satellite cells has not been considered. Molecular signals such as myostatin/SMAD pathway, MAFbx, and MuRF1 E3 ligases of the ubiquitin proteasome pathway and IGF1-AKT-mTOR pathway are 3 distinctly different contributors to skeletal muscle protein adaptation to disuse. Molecular signaling pathways activated in muscle fibers by disuse are rarely considered within satellite cells themselves despite similar exposure to unloading or low mechanical load. These molecular pathways interact with each other during atrophy and also when various interventions are applied that could alleviate atrophy. Re-applying mechanical load is an obvious method to restore muscle mass, however how nutrient supplementation (e.g., amino acids) may further enhance recovery (or reduce atrophy despite unloading or ageing) is currently of great interest. Satellite cells are particularly responsive to myostatin and to growth factors. Recently, the hibernating squirrel has been identified as an innovative model to study resistance to atrophy. PMID:24672488

  17. SKELETAL MUSCLE CAPILLARY FUNCTION: CONTEMPORARY OBSERVATIONS AND NOVEL HYPOTHESES

    PubMed Central

    Poole, David C.; Copp, Steven W.; Ferguson, Scott K.; Musch, Timothy I.

    2014-01-01

    The capillary bed constitutes a vast surface facilitating exchange of O2, substrates and metabolites between blood and organs. In contracting skeletal muscle capillary blood flow and O2 diffusing capacity as well as O2 flux may increase two orders of magnitude above resting. Chronic diseases such as heart failure, diabetes and also sepsis impair these processes leading to compromised energetic, metabolic and ultimately contractile function. Among researchers seeking to understand blood-myocyte exchange in health and the bases for dysfunction in disease there is a fundamental disconnect between microcirculation specialists and many physiologists and physiologist clinicians. Whereas the former observe capillaries and capillary function directly (muscle intravital microscopy) the latter generally use indirect methodologies (e.g., post-mortem tissue analysis, 1-methyl xanthine, contrast enhanced ultrasound, permeability surface area product) and interpret their findings based upon August Krogh’s observations made nearly a century ago. “Kroghian” theory holds that only a small fraction of capillaries support red blood cell (RBC) flux in resting muscle leaving the vast majority to be “recruited” (i.e., initiate RBC flux) during contractions which would constitute the basis for increasing capillary exchange surface area and reducing capillary-mitochondrial diffusion distances. Experimental techniques each have their strengths and weaknesses and often the correct or complete answer to a problem emerges from integration across multiple technologies. Today Krogh’s entrenched “capillary recruitment” hypothesis is challenged by direct observations of capillaries in contracting muscle; something that he and his colleagues could not do. Moreover, in the peer-reviewed scientific literature, application of a range of contemporary physiological technologies including intravital microscopy of contracting muscle, magnetic resonance and near infrared spectroscopy and phosphorescence quenching combined with elegant in situ and in vivo models suggest that the role of the capillary bed, at least in contracting muscle, is subserved without the necessity for de novo capillary recruitment of previously non-flowing capillaries. When viewed within the context of the capillary recruitment hypothesis, this evidence casts serious doubt on the interpretation of those data that are based upon Kroghian theory and indirect methodologies. Thus today a wealth of evidence calls for a radical revision of blood-muscle exchange theory to one in which most capillaries support RBC flux at rest and, during contractions, capillary surface area is “recruited” along the length of previously flowing capillaries. This occurs, in part, by elevating capillary hematocrit and extending the length of the capillary available for blood-myocyte exchange (i.e., longitudinal recruitment). Our understanding of blood-myocyte O2 and substrate/metabolite exchange in health and the mechanistic bases for dysfunction in disease demands no less. PMID:23995101

  18. Functional and structural adaptations of skeletal muscle to microgravity

    NASA Technical Reports Server (NTRS)

    Fitts, R. H.; Riley, D. R.; Widrick, J. J.

    2001-01-01

    Our purpose is to summarize the major effects of space travel on skeletal muscle with particular emphasis on factors that alter function. The primary deleterious changes are muscle atrophy and the associated decline in peak force and power. Studies on both rats and humans demonstrate a rapid loss of cell mass with microgravity. In rats, a reduction in muscle mass of up to 37% was observed within 1 week. For both species, the antigravity soleus muscle showed greater atrophy than the fast-twitch gastrocnemius. However, in the rat, the slow type I fibers atrophied more than the fast type II fibers, while in humans, the fast type II fibers were at least as susceptible to space-induced atrophy as the slow fiber type. Space flight also resulted in a significant decline in peak force. For example, the maximal voluntary contraction of the human plantar flexor muscles declined by 20-48% following 6 months in space, while a 21% decline in the peak force of the soleus type I fibers was observed after a 17-day shuttle flight. The reduced force can be attributed both to muscle atrophy and to a selective loss of contractile protein. The former was the primary cause because, when force was expressed per cross-sectional area (kNm(-2)), the human fast type II and slow type I fibers of the soleus showed no change and a 4% decrease in force, respectively. Microgravity has been shown to increase the shortening velocity of the plantar flexors. This increase can be attributed both to an elevated maximal shortening velocity (V(0)) of the individual slow and fast fibers and to an increased expression of fibers containing fast myosin. Although the cause of the former is unknown, it might result from the selective loss of the thin filament actin and an associated decline in the internal drag during cross-bridge cycling. Despite the increase in fiber V(0), peak power of the slow type I fiber was reduced following space flight. The decreased power was a direct result of the reduced force caused by the fiber atrophy. In addition to fiber atrophy and the loss of force and power, weightlessness reduces the ability of the slow soleus to oxidize fats and increases the utilization of muscle glycogen, at least in rats. This substrate change leads to an increased rate of fatigue. Finally, with return to the 1g environment of earth, rat studies have shown an increased occurrence of eccentric contraction-induced fiber damage. The damage occurs with re-loading and not in-flight, but the etiology has not been established.

  19. Engineered skeletal muscle tissue for soft robotics: fabrication strategies, current applications, and future challenges.

    PubMed

    Duffy, Rebecca M; Feinberg, Adam W

    2014-01-01

    Skeletal muscle is a scalable actuator system used throughout nature from the millimeter to meter length scales and over a wide range of frequencies and force regimes. This adaptability has spurred interest in using engineered skeletal muscle to power soft robotics devices and in biotechnology and medical applications. However, the challenges to doing this are similar to those facing the tissue engineering and regenerative medicine fields; specifically, how do we translate our understanding of myogenesis in vivo to the engineering of muscle constructs in vitro to achieve functional integration with devices. To do this researchers are developing a number of ways to engineer the cellular microenvironment to guide skeletal muscle tissue formation. This includes understanding the role of substrate stiffness and the mechanical environment, engineering the spatial organization of biochemical and physical cues to guide muscle alignment, and developing bioreactors for mechanical and electrical conditioning. Examples of engineered skeletal muscle that can potentially be used in soft robotics include 2D cantilever-based skeletal muscle actuators and 3D skeletal muscle tissues engineered using scaffolds or directed self-organization. Integration into devices has led to basic muscle-powered devices such as grippers and pumps as well as more sophisticated muscle-powered soft robots that walk and swim. Looking forward, current, and future challenges include identifying the best source of muscle precursor cells to expand and differentiate into myotubes, replacing cardiomyocytes with skeletal muscle tissue as the bio-actuator of choice for soft robots, and vascularization and innervation to enable control and nourishment of larger muscle tissue constructs. PMID:24319010

  20. Frizzled-9 impairs acetylcholine receptor clustering in skeletal muscle cells

    PubMed Central

    Avilés, Evelyn C.; Pinto, Cristina; Hanna, Patricia; Ojeda, Jorge; Pérez, Viviana; De Ferrari, Giancarlo V.; Zamorano, Pedro; Albistur, Miguel; Sandoval, Daniel; Henríquez, Juan P.

    2014-01-01

    Cumulative evidence indicates that Wnt pathways play crucial and diverse roles to assemble the neuromuscular junction (NMJ), a peripheral synapse characterized by the clustering of acetylcholine receptors (AChR) on postsynaptic densities. The molecular determinants of Wnt effects at the NMJ are still to be fully elucidated. We report here that the Wnt receptor Frizzled-9 (Fzd9) is expressed in developing skeletal muscles during NMJ synaptogenesis. In cultured myotubes, gain- and loss-of-function experiments revealed that Fzd9-mediated signaling impairs the AChR-clustering activity of agrin, an organizer of postsynaptic differentiation. Overexpression of Fzd9 induced the cytosolic accumulation of ?-catenin, a key regulator of Wnt signaling. Consistently, Fzd9 and ?-catenin localize in the postsynaptic domain of embryonic NMJs in vivo. Our findings represent the first evidence pointing to a crucial role of a Fzd-mediated, ?-catenin-dependent signaling on the assembly of the vertebrate NMJ. PMID:24860427

  1. Heart and Skeletal Muscle Are Targets of Dengue Virus Infection

    PubMed Central

    Salgado, Doris Martha; Eltit, José Miguel; Mansfield, Keith; Panqueba, César; Castro, Dolly; Vega, Martha Rocio; Xhaja, Kris; Schmidt, Diane; Martin, Katherine J.; Allen, Paul D.; Rodriguez, Jairo Antonio; Dinsmore, Jonathan H.; López, José Rafael; Bosch, Irene

    2010-01-01

    Background Dengue fever is one of the most significant re-emerging tropical diseases, despite our expanding knowledge of the disease, viral tropism is still not known to target heart tissues or muscle. Methods A prospective pediatric clinical cohort of 102 dengue hemorrhagic fever patients from Colombia, South America, was followed for 1 year. Clinical diagnosis of myocarditis was routinely performed. Electrocardiograph and echocardiograph analysis were performed to confirm those cases. Immunohistochemistry for detection of dengue virus and inflammatory markers was performed on autopsied heart tissue. In vitro studies of human striated skeletal fibers (myotubes) infected with dengue virus were used as a model for myocyte infection. Measurements of intracellular Ca2+ concentration as well as immunodetection of dengue virus and inflammation markers in infected myotubes were performed. Results Eleven children with dengue hemorrhagic fever presented with symptoms of myocarditis. Widespread viral infection of the heart, myocardial endothelium, and cardiomyocytes, accompanied by inflammation was observed in 1 fatal case. Immunofluorescence confocal microscopy showed that myotubes were infected by dengue virus and had increased expression of the inflammatory genes and protein IP-10. The infected myotubes also had increases in intracellular Ca2+ concentration. Conclusions Vigorous infection of heart tissues in vivo and striated skeletal cells in vitro are demonstrated. Derangements of Ca2+ storage in the infected cells may directly contribute to the presentation of myocarditis in pediatric patients. PMID:20032806

  2. The determinants of transverse tubular volume in resting skeletal muscle

    PubMed Central

    Sim, Jingwei; Fraser, James A

    2014-01-01

    The transverse tubular (t)-system of skeletal muscle couples sarcolemmal electrical excitation with contraction deep within the fibre. Exercise, pathology and the composition of the extracellular fluid (ECF) can alter t-system volume (t-volume). T-volume changes are thought to contribute to fatigue, rhabdomyolysis and disruption of excitation–contraction coupling. However, mechanisms that underlie t-volume changes are poorly understood. A multicompartment, history-independent computer model of rat skeletal muscle was developed to define the minimum conditions for t-volume stability. It was found that the t-system tends to swell due to net ionic fluxes from the ECF across the access resistance. However, a stable t-volume is possible when this is offset by a net efflux from the t-system to the cell and thence to the ECF, forming a net ion cycle ECF?t-system?sarcoplasm?ECF that ultimately depends on Na+/K+-ATPase activity. Membrane properties that maximize this circuit flux decrease t-volume, including PNa(t) > PNa(s), PK(t) < PK(s) and N(t) < N(s) [P, permeability; N, Na+/K+-ATPase density; (t), t-system membrane; (s), sarcolemma]. Hydrostatic pressures, fixed charges and/or osmoles in the t-system can influence the magnitude of t-volume changes that result from alterations in this circuit flux. Using a parameter set derived from literature values where possible, this novel theory of t-volume was tested against data from previous experiments where t-volume was measured during manipulations of ECF composition. Predicted t-volume changes correlated satisfactorily. The present work provides a robust, unifying theoretical framework for understanding the determinants of t-volume. PMID:25384782

  3. Prevalence study of genetically defined skeletal muscle channelopathies in England

    PubMed Central

    Horga, Alejandro; Raja Rayan, Dipa L.; Matthews, Emma; Sud, Richa; Fialho, Doreen; Durran, Siobhan C.M.; Burge, James A.; Portaro, Simona; Davis, Mary B.; Haworth, Andrea

    2013-01-01

    Objectives: To obtain minimum point prevalence rates for the skeletal muscle channelopathies and to evaluate the frequency distribution of mutations associated with these disorders. Methods: Analysis of demographic, clinical, electrophysiologic, and genetic data of all patients assessed at our national specialist channelopathy service. Only patients living in the United Kingdom with a genetically defined diagnosis of nondystrophic myotonia or periodic paralysis were eligible for the study. Prevalence rates were estimated for England, December 2011. Results: A total of 665 patients fulfilled the inclusion criteria, of which 593 were living in England, giving a minimum point prevalence of 1.12/100,000 (95% confidence interval [CI] 1.03–1.21). Disease-specific prevalence figures were as follows: myotonia congenita 0.52/100,000 (95% CI 0.46–0.59), paramyotonia congenita 0.17/100,000 (95% CI 0.13–0.20), sodium channel myotonias 0.06/100,000 (95% CI 0.04–0.08), hyperkalemic periodic paralysis 0.17/100,000 (95% CI 0.13–0.20), hypokalemic periodic paralysis 0.13/100,000 (95% CI 0.10–0.17), and Andersen-Tawil syndrome (ATS) 0.08/100,000 (95% CI 0.05–0.10). In the whole sample (665 patients), 15 out of 104 different CLCN1 mutations accounted for 60% of all patients with myotonia congenita, 11 out of 22 SCN4A mutations for 86% of paramyotonia congenita/sodium channel myotonia pedigrees, and 3 out of 17 KCNJ2 mutations for 42% of ATS pedigrees. Conclusion: We describe for the first time the overall prevalence of genetically defined skeletal muscle channelopathies in England. Despite the large variety of mutations observed in patients with nondystrophic myotonia and ATS, a limited number accounted for a large proportion of cases. PMID:23516313

  4. Exercise, Skeletal Muscle and Circulating microRNAs.

    PubMed

    Russell, Aaron P; Lamon, Séverine

    2015-01-01

    Regular exercise stimulates numerous structural, metabolic, and morphological adaptations in skeletal muscle. These adaptations are vital to maintain human health over the life span. Exercise is therefore seen as a primary intervention to reduce the risk of chronic disease. Advances in molecular biology, biochemistry, and bioinformatics, combined with exercise physiology, have identified many key signaling pathways as well as transcriptional and translational processes responsible for exercise-induced adaptations. Noncoding RNAs, and specifically microRNAs (miRNAs), constitute a new regulatory component that may play a role in these adaptations. The short single-stranded miRNA sequences bind to the 3' untranslated region of specific messenger RNAs (mRNAs) on the basis of sequence homology. This results in the degradation of the target mRNA or the inhibition of protein translation causing repression of the corresponding protein. While tissue specificity or enrichment of certain miRNAs makes them ideal targets to manipulate and understand tissue development, function, health, and disease, other miRNAs are ubiquitously expressed; however, it is uncertain whether their mRNA/protein targets are conserved across different tissues. miRNAs are stable in plasma and serum and their altered circulating expression levels in disease conditions may provide important biomarker information. The emerging research into the role that miRNAs play in exercise-induced adaptations has predominantly focused on the miRNA species that are regulated in skeletal muscle or in circulation. This chapter provides an overview of these current research findings, highlights the strengths and weaknesses identified to date, and suggests where the exercise-miRNA field may move into the future. PMID:26477927

  5. Niacin supplementation induces type II to type I muscle fiber transition in skeletal muscle of sheep

    PubMed Central

    2013-01-01

    Background It was recently shown that niacin supplementation counteracts the obesity-induced muscle fiber transition from oxidative type I to glycolytic type II and increases the number of type I fibers in skeletal muscle of obese Zucker rats. These effects were likely mediated by the induction of key regulators of fiber transition, PPAR? (encoded by PPARD), PGC-1? (encoded by PPARGC1A) and PGC-1? (encoded by PPARGC1B), leading to type II to type I fiber transition and upregulation of genes involved in oxidative metabolism. The aim of the present study was to investigate whether niacin administration also influences fiber distribution and the metabolic phenotype of different muscles [M. longissimus dorsi (LD), M. semimembranosus (SM), M. semitendinosus (ST)] in sheep as a model for ruminants. For this purpose, 16 male, 11 wk old Rhoen sheep were randomly allocated to two groups of 8 sheep each administered either no (control group) or 1 g niacin per day (niacin group) for 4 wk. Results After 4 wk, the percentage number of type I fibers in LD, SM and ST muscles was greater in the niacin group, whereas the percentage number of type II fibers was less in niacin group than in the control group (P?muscles were greater (P?muscle fiber transition from type II to type I, and thereby an oxidative metabolic phenotype of skeletal muscle in sheep as a model for ruminants. The enhanced capacity of skeletal muscle to utilize fatty acids in ruminants might be particularly useful during metabolic states in which fatty acids are excessively mobilized from adipose tissue, such as during the early lactating period in high producing cows. PMID:24267720

  6. Engineering skeletal muscle tissue – new perspectives in vitro and in vivo

    PubMed Central

    Klumpp, Dorothee; Horch, Raymund E; Kneser, Ulrich; Beier, Justus P

    2010-01-01

    Abstract Muscle tissue engineering (TE) has not yet been clinically applied because of several problems. However, the field of skeletal muscle TE has been developing tremendously and new approaches and techniques have emerged. This review will highlight recent developments in the field of nanotechnology, especially electrospun nanofibre matrices, as well as potential cell sources for muscle TE. Important developments in cardiac muscle TE and clinical studies on Duchenne muscular dystrophy (DMD) will be included to show their implications on skeletal muscle TE. PMID:21091904

  7. Skeletal muscle adiposity is associated with physical activity, exercise capacity and fibre shift in COPD

    PubMed Central

    Maddocks, Matthew; Shrikrishna, Dinesh; Vitoriano, Simone; Natanek, Samantha A.; Tanner, Rebecca J.; Hart, Nicholas; Kemp, Paul R.; Moxham, John; Polkey, Michael I.; Hopkinson, Nicholas S.

    2014-01-01

    Quadriceps muscle phenotype varies widely between patients with chronic obstructive pulmonary disease (COPD) and cannot be determined without muscle biopsy. We hypothesised that measures of skeletal muscle adiposity could provide noninvasive biomarkers of muscle quality in this population. In 101 patients and 10 age-matched healthy controls, mid-thigh cross-sectional area, percentage intramuscular fat and skeletal muscle attenuation were calculated using computed tomography images and standard tissue attenuation ranges: fat -190– -30 HU; skeletal muscle -29–150 HU. Mean±sd percentage intramuscular fat was higher in the patient group (6.7±3.5% versus 4.3±1.2%, p = 0.03). Both percentage intramuscular fat and skeletal muscle attenuation were associated with physical activity level, exercise capacity and type I fibre proportion, independent of age, mid-thigh cross-sectional area and quadriceps strength. Combined with transfer factor of the lung for carbon monoxide, these variables could identify >80% of patients with fibre type shift with >65% specificity (area under the curve 0.83, 95% CI 0.72–0.95). Skeletal muscle adiposity assessed by computed tomography reflects multiple aspects of COPD related muscle dysfunction and may help to identify patients for trials of interventions targeted at specific muscle phenotypes. PMID:24993908

  8. Isolation and characterization of a novel gene sfig in rat skeletal muscle up-regulated by spaceflight (STS-90)

    NASA Technical Reports Server (NTRS)

    Kano, Mihoko; Kitano, Takako; Ikemoto, Madoka; Hirasaka, Katsuya; Asanoma, Yuki; Ogawa, Takayuki; Takeda, Shinichi; Nonaka, Ikuya; Adams, Gregory R.; Baldwin, Kenneth M.; Oarada, Motoko; Kishi, Kyoichi; Nikawa, Takeshi

    2003-01-01

    We obtained the skeletal muscle of rats exposed to weightless conditions during a 16-day-spaceflight (STS-90). By using a differential display technique, we identified 6 up-regulated and 3 down-regulated genes in the gastrocnemius muscle of the spaceflight rats, as compared to the ground control. The up-regulated genes included those coding Casitas B-lineage lymphoma-b, insulin growth factor binding protein-1, titin and mitochondrial gene 16 S rRNA and two novel genes (function unknown). The down-regulated genes included those encoding RNA polymerase II elongation factor-like protein, NADH dehydrogenase and one novel gene (function unknown). In the present study, we isolated and characterized one of two novel muscle genes that were remarkably up-regulated by spaceflight. The deduced amino acid sequence of the spaceflight-induced gene (sfig) comprises 86 amino acid residues and is well conserved from Drosophila to Homo sapiens. A putative leucine-zipper structure located at the N-terminal region of sfig suggests that this gene may encode a transcription factor. The up-regulated expression of this gene, confirmed by Northern blot analysis, was observed not only in the muscles of spaceflight rats but also in the muscles of tail-suspended rats, especially in the early stage of tail-suspension when gastrocnemius muscle atrophy initiated. The gene was predominantly expressed in the kidney, liver, small intestine and heart. When rat myoblastic L6 cells were grown to 100% confluence in the cell culture system, the expression of sfig was detected regardless of the cell differentiation state. These results suggest that spaceflight has many genetic effects on rat skeletal muscle.

  9. A practical approach to in vivo quantification of physiological cross-sectional area for human skeletal muscle

    E-print Network

    Toronto, University of

    skeletal muscle Dongwoon Leea , Soo Kimb , Ken Jacksona , Eugene Fiumea , Anne Agurc a of skeletal muscle. A common approach to estimate PCSA uses an algebraic formula based on muscle volume (MV) and ultrasono- graphic assessments. Due to the limited capability of assessing architecturally complex muscles

  10. Microarchitecture Is Severely Compromised but Motor Protein Function Is Preserved in Dystrophic mdx Skeletal Muscle

    E-print Network

    Garbe, Christoph S.

    Skeletal Muscle O. Friedrich,§ * M. Both, C. Weber, S. Schu¨rmann, M. D. H. Teichmann, F. von Wegner,{ R. H/regeneration cycles and fibrosis. Disease progression may involve structural remodeling of muscle tissue. An effect vastly altered subcellular sarcomere microarch- itecture in intact single dystrophic mdx muscle cells (~1

  11. PGC-1?-mediated changes in phospholipid profiles of exercise-trained skeletal muscle.

    PubMed

    Senoo, Nanami; Miyoshi, Noriyuki; Goto-Inoue, Naoko; Minami, Kimiko; Yoshimura, Ryoji; Morita, Akihito; Sawada, Naoki; Matsuda, Junichiro; Ogawa, Yoshihiro; Setou, Mitsutoshi; Kamei, Yasutomi; Miura, Shinji

    2015-12-01

    Exercise training influences phospholipid fatty acid composition in skeletal muscle and these changes are associated with physiological phenotypes; however, the molecular mechanism of this influence on compositional changes is poorly understood. Peroxisome proliferator-activated receptor ? coactivator 1? (PGC-1?), a nuclear receptor coactivator, promotes mitochondrial biogenesis, the fiber-type switch to oxidative fibers, and angiogenesis in skeletal muscle. Because exercise training induces these adaptations, together with increased PGC-1?, PGC-1? may contribute to the exercise-mediated change in phospholipid fatty acid composition. To determine the role of PGC-1?, we performed lipidomic analyses of skeletal muscle from genetically modified mice that overexpress PGC-1? in skeletal muscle or that carry KO alleles of PGC-1?. We found that PGC-1? affected lipid profiles in skeletal muscle and increased several phospholipid species in glycolytic muscle, namely phosphatidylcholine (PC) (18:0/22:6) and phosphatidylethanolamine (PE) (18:0/22:6). We also found that exercise training increased PC (18:0/22:6) and PE (18:0/22:6) in glycolytic muscle and that PGC-1? was required for these alterations. Because phospholipid fatty acid composition influences cell permeability and receptor stability at the cell membrane, these phospholipids may contribute to exercise training-mediated functional changes in the skeletal muscle. PMID:26438561

  12. Mineralocorticoid receptors are present in skeletal muscle and represent a potential therapeutic target.

    PubMed

    Chadwick, Jessica A; Hauck, J Spencer; Lowe, Jeovanna; Shaw, Jeremiah J; Guttridge, Denis C; Gomez-Sanchez, Celso E; Gomez-Sanchez, Elise P; Rafael-Fortney, Jill A

    2015-11-01

    Early treatment with heart failure drugs lisinopril and spironolactone improves skeletal muscle pathology in Duchenne muscular dystrophy (DMD) mouse models. The angiotensin converting enzyme inhibitor lisinopril and mineralocorticoid receptor (MR) antagonist spironolactone indirectly and directly target MR. The presence and function of MR in skeletal muscle have not been explored. MR mRNA and protein are present in all tested skeletal muscles from both wild-type mice and DMD mouse models. MR expression is cell autonomous in both undifferentiated myoblasts and differentiated myotubes from mouse and human skeletal muscle cultures. To test for MR function in skeletal muscle, global gene expression analysis was conducted on human myotubes treated with MR agonist (aldosterone; EC50 1.3 nM) or antagonist (spironolactone; IC50 1.6 nM), and 53 gene expression differences were identified. Five differences were conserved in quadriceps muscles from dystrophic mice treated with spironolactone plus lisinopril (IC50 0.1 nM) compared with untreated controls. Genes down-regulated more than 2-fold by MR antagonism included FOS, ANKRD1, and GADD45B, with known roles in skeletal muscle, in addition to NPR3 and SERPINA3, bona fide targets of MR in other tissues. MR is a novel drug target in skeletal muscle and use of clinically safe antagonists may be beneficial for muscle diseases.-Chadwick, J. A., Hauck, J. S., Lowe, J. , Shaw, J. J., Guttridge, D. C., Gomez-Sanchez, C. E., Gomez-Sanchez, E. P., Rafael-Fortney, J. A. Mineralocorticoid receptors are present in skeletal muscle and represent a potential therapeutic target. PMID:26178166

  13. Measurement of Maximum Isometric Force Generated by Permeabilized Skeletal Muscle Fibers

    PubMed Central

    Roche, Stuart M.; Gumucio, Jonathan P.; Brooks, Susan V.; Mendias, Christopher L.; Claflin, Dennis R.

    2015-01-01

    Analysis of the contractile properties of chemically skinned, or permeabilized, skeletal muscle fibers offers a powerful means by which to assess muscle function at the level of the single muscle cell. Single muscle fiber studies are useful in both basic science and clinical studies. For basic studies, single muscle fiber contractility measurements allow investigation of fundamental mechanisms of force production, and analysis of muscle function in the context of genetic manipulations. Clinically, single muscle fiber studies provide useful insight into the impact of injury and disease on muscle function, and may be used to guide the understanding of muscular pathologies. In this video article we outline the steps required to prepare and isolate an individual skeletal muscle fiber segment, attach it to force-measuring apparatus, activate it to produce maximum isometric force, and estimate its cross-sectional area for the purpose of normalizing the force produced. PMID:26131687

  14. Determinants of Skeletal Muscle Catabolism After Severe Burn

    PubMed Central

    Hart, David W.; Wolf, Steven E.; Chinkes, David L.; Gore, Dennis C.; Mlcak, Ronald P.; Beauford, Robert B.; Obeng, Michael K.; Lal, Sophia; Gold, Warren F.; Wolfe, Robert R.; Herndon, David N.

    2000-01-01

    Objective To determine which patient factors affect the degree of catabolism after severe burn. Summary Background Data Catabolism is associated with severe burn and leads to erosion of lean mass, impaired wound healing, and delayed rehabilitation. Methods From 1996 to 1999, 151 stable-isotope protein kinetic studies were performed in 102 pediatric and 21 adult subjects burned over 20–99.5% of their total body surface area (TBSA). Patient demographics, burn characteristics, and hospital course variables were correlated with the net balance of skeletal muscle protein synthesis and breakdown across the leg. Data were analyzed sequentially and cumulatively through univariate and cross-sectional multiple regression. Results Increasing age, weight, and delay in definitive surgical treatment predict increased catabolism (P < .05). Body surface area burned increased catabolism until 40% TBSA was reached; catabolism did not consistently increase thereafter. Resting energy expenditure and sepsis were also strong predictors of net protein catabolism. Among factors that did not significantly correlate were burn type, pneumonia, wound contamination, and time after burn. From these results, the authors also infer that gross muscle mass correlates independently with protein wasting after burn. Conclusions Heavier, more muscular subjects, and subjects whose definitive surgical treatment is delayed are at the greatest risk for excess catabolism after burn. Sepsis and excessive hypermetabolism are also associated with protein catabolism. PMID:10998644

  15. Diffusion characteristics of ethylene glycol in skeletal muscle.

    PubMed

    Oliveira, Luís M; Carvalho, Maria Inês; Nogueira, Elisabete M; Tuchin, Valery V

    2015-05-01

    Part of the optical clearing study in biological tissues concerns the determination of the diffusion characteristics of water and optical clearing agents in the subject tissue. Such information is sufficient to characterize the time dependence of the optical clearing mechanisms—tissue dehydration and refractive index (RI) matching. We have used a simple method based on collimated optical transmittance measurements made from muscle samples under treatment with aqueous solutions containing different concentrations of ethylene glycol (EG), to determine the diffusion time values of water and EG in skeletal muscle. By representing the estimated mean diffusion time values from each treatment as a function of agent concentration in solution, we could identify the real diffusion times for water and agent. These values allowed for the calculation of the correspondent diffusion coefficients for those fluids. With these results, we have demonstrated that the dehydration mechanism is the one that dominates optical clearing in the first minute of treatment, while the RI matching takes over the optical clearing operations after that and remains for a longer time of treatment up to about 10 min, as we could see for EG and thin tissue samples of 0.5 mm. PMID:25525766

  16. Muscle-derived stem cells isolated as non-adherent population give rise to cardiac, skeletal muscle and neural lineages

    SciTech Connect

    Arsic, Nikola; Mamaeva, Daria; Lamb, Ned J.; Fernandez, Anne

    2008-04-01

    Stem cells with the ability to differentiate in specialized cell types can be extracted from a wide array of adult tissues including skeletal muscle. Here we have analyzed a population of cells isolated from skeletal muscle on the basis of their poor adherence on uncoated or collagen-coated dishes that show multi-lineage differentiation in vitro. When analysed under proliferative conditions, these cells express stem cell surface markers Sca-1 (65%) and Bcrp-1 (80%) but also MyoD (15%), Neuronal {beta} III-tubulin (25%), GFAP (30%) or Nkx2.5 (1%). Although capable of growing as non-attached spheres for months, when given an appropriate matrix, these cells adhere giving rise to skeletal muscle, neuronal and cardiac muscle cell lineages. A similar cell population could not be isolated from either bone marrow or cardiac tissue suggesting their specificity to skeletal muscle. When injected into damaged muscle, these non-adherent muscle-derived cells are retrieved expressing Pax7, in a sublaminar position characterizing satellite cells and participate in forming new myofibers. These data show that a non-adherent stem cell population can be specifically isolated and expanded from skeletal muscle and upon attachment to a matrix spontaneously differentiate into muscle, cardiac and neuronal lineages in vitro. Although competing with resident satellite cells, these cells are shown to significantly contribute to repair of injured muscle in vivo supporting that a similar muscle-derived non-adherent cell population from human muscle may be useful in treatment of neuromuscular disorders.

  17. Selected Contribution: Skeletal muscle focal adhesion kinase, paxillin, and serum response factor are loading dependent

    NASA Technical Reports Server (NTRS)

    Gordon, S. E.; Fluck, M.; Booth, F. W.

    2001-01-01

    This investigation examined the effect of mechanical loading state on focal adhesion kinase (FAK), paxillin, and serum response factor (SRF) in rat skeletal muscle. We found that FAK concentration and tyrosine phosphorylation, paxillin concentration, and SRF concentration are all lower in the lesser load-bearing fast-twitch plantaris and gastrocnemius muscles compared with the greater load-bearing slow-twitch soleus muscle. Of these three muscles, 7 days of mechanical unloading via tail suspension elicited a decrease in FAK tyrosine phosphorylation only in the soleus muscle and decreases in FAK and paxillin concentrations only in the plantaris and gastrocnemius muscles. Unloading decreased SRF concentration in all three muscles. Mechanical overloading (via bilateral gastrocnemius ablation) for 1 or 8 days increased FAK and paxillin concentrations in the soleus and plantaris muscles. Additionally, whereas FAK tyrosine phosphorylation and SRF concentration were increased by < or =1 day of overloading in the soleus muscle, these increases did not occur until somewhere between 1 and 8 days of overloading in the plantaris muscle. These data indicate that, in the skeletal muscles of rats, the focal adhesion complex proteins FAK and paxillin and the transcription factor SRF are generally modulated in association with the mechanical loading state of the muscle. However, the somewhat different patterns of adaptation of these proteins to altered loading in slow- vs. fast-twitch skeletal muscles indicate that the mechanisms and time course of adaptation may partly depend on the prior loading state of the muscle.

  18. Skeletal Muscle Expression of the Adhesion-GPCR CD97: CD97 Deletion Induces an Abnormal Structure of the Sarcoplasmatic Reticulum but Does Not Impair Skeletal Muscle Function

    PubMed Central

    Zyryanova, Tatiana; Schneider, Rick; Adams, Volker; Sittig, Doreen; Kerner, Christiane; Gebhardt, Claudia; Ruffert, Henrik; Glasmacher, Stefan; Hepp, Pierre; Punkt, Karla; Neuhaus, Jochen; Hamann, Jörg; Aust, Gabriela

    2014-01-01

    CD97 is a widely expressed adhesion class G-protein-coupled receptor (aGPCR). Here, we investigated the presence of CD97 in normal and malignant human skeletal muscle as well as the ultrastructural and functional consequences of CD97 deficiency in mice. In normal human skeletal muscle, CD97 was expressed at the peripheral sarcolemma of all myofibers, as revealed by immunostaining of tissue sections and surface labeling of single myocytes using flow cytometry. In muscle cross-sections, an intracellular polygonal, honeycomb-like CD97-staining pattern, typical for molecules located in the T-tubule or sarcoplasmatic reticulum (SR), was additionally found. CD97 co-localized with SR Ca2+-ATPase (SERCA), a constituent of the longitudinal SR, but not with the receptors for dihydropyridine (DHPR) or ryanodine (RYR), located in the T-tubule and terminal SR, respectively. Intracellular expression of CD97 was higher in slow-twitch compared to most fast-twitch myofibers. In rhabdomyosarcomas, CD97 was strongly upregulated and in part more N-glycosylated compared to normal skeletal muscle. All tumors were strongly CD97-positive, independent of the underlying histological subtype, suggesting high sensitivity of CD97 for this tumor. Ultrastructural analysis of murine skeletal myofibers confirmed the location of CD97 in the SR. CD97 knock-out mice had a dilated SR, resulting in a partial increase in triad diameter yet not affecting the T-tubule, sarcomeric, and mitochondrial structure. Despite these obvious ultrastructural changes, intracellular Ca2+ release from single myofibers, force generation and fatigability of isolated soleus muscles, and wheel-running capacity of mice were not affected by the lack of CD97. We conclude that CD97 is located in the SR and at the peripheral sarcolemma of human and murine skeletal muscle, where its absence affects the structure of the SR without impairing skeletal muscle function. PMID:24949957

  19. Robust conversion of marrow cells to skeletal muscle with formation of marrow-derived muscle cell colonies: A multifactorial process

    SciTech Connect

    Abedi, Mehrdad; Greer, Deborah A.; Colvin, Gerald A.; Demers, Delia A.; Dooner, Mark S.; Harpel, Jasha A.; Weier, Heinz-Ulrich G.; Lambert, Jean-Francois; Quesenberry, Peter J.

    2004-01-10

    Murine marrow cells are capable of repopulating skeletal muscle fibers. A point of concern has been the robustness of such conversions. We have investigated the impact of type of cell delivery, muscle injury, nature of delivered cell, and stem cell mobilizations on marrow to muscle conversion. We transplanted GFP transgenic marrow into irradiated C57BL/6 mice and then injured anterior tibialis muscle by cardiotoxin. One month after injury, sections were analyzed by standard and deconvolutional microscopy for expression of muscle and hematopietic markers. Irradiation was essential to conversion although whether by injury or induction of chimerism is not clear. Cardiotoxin and to a lesser extent PBS injected muscles showed significant number of GFP+ muscle fibers while uninjected muscles showed only rare GFP+ cells. Marrow conversion to muscle was increased by two cycles of G-CSF mobilization and to a lesser extent with G-CSF and steel or GM-CSF. Transplantation of female GFP to male C57 BL/6 and GFP to Rosa26 mice showed fusion of donor cells to recipient muscle. High numbers of donor derived muscle colonies and up to12 percent GFP positive muscle cells were seen after mobilization or direct injection. These levels of donor muscle chimerism approach levels which could be clinically significant in developing strategies for the treatment of muscular dystrophies. In summary, the conversion of marrow to skeletal muscle cells is based on cell fusion and is critically dependent on injury. This conversion is also numerically significant and increases with mobilization.

  20. Mesodermal iPSC-derived progenitor cells functionally regenerate cardiac and skeletal muscle.

    PubMed

    Quattrocelli, Mattia; Swinnen, Melissa; Giacomazzi, Giorgia; Camps, Jordi; Barthélemy, Ines; Ceccarelli, Gabriele; Caluwé, Ellen; Grosemans, Hanne; Thorrez, Lieven; Pelizzo, Gloria; Muijtjens, Manja; Verfaillie, Catherine M; Blot, Stephane; Janssens, Stefan; Sampaolesi, Maurilio

    2015-12-01

    Conditions such as muscular dystrophies (MDs) that affect both cardiac and skeletal muscles would benefit from therapeutic strategies that enable regeneration of both of these striated muscle types. Protocols have been developed to promote induced pluripotent stem cells (iPSCs) to differentiate toward cardiac or skeletal muscle; however, there are currently no strategies to simultaneously target both muscle types. Tissues exhibit specific epigenetic alterations; therefore, source-related lineage biases have the potential to improve iPSC-driven multilineage differentiation. Here, we determined that differential myogenic propensity influences the commitment of isogenic iPSCs and a specifically isolated pool of mesodermal iPSC-derived progenitors (MiPs) toward the striated muscle lineages. Differential myogenic propensity did not influence pluripotency, but did selectively enhance chimerism of MiP-derived tissue in both fetal and adult skeletal muscle. When injected into dystrophic mice, MiPs engrafted and repaired both skeletal and cardiac muscle, reducing functional defects. Similarly, engraftment into dystrophic mice of canine MiPs from dystrophic dogs that had undergone TALEN-mediated correction of the MD-associated mutation also resulted in functional striatal muscle regeneration. Moreover, human MiPs exhibited the same capacity for the dual differentiation observed in murine and canine MiPs. The findings of this study suggest that MiPs should be further explored for combined therapy of cardiac and skeletal muscles. PMID:26571398

  1. MicroRNAs in skeletal muscle and their regulation with exercise, ageing, and disease.

    PubMed

    Zacharewicz, Evelyn; Lamon, Séverine; Russell, Aaron P

    2013-01-01

    Skeletal muscle makes up approximately 40% of the total body mass, providing structural support and enabling the body to maintain posture, to control motor movements and to store energy. It therefore plays a vital role in whole body metabolism. Skeletal muscle displays remarkable plasticity and is able to alter its size, structure and function in response to various stimuli; an essential quality for healthy living across the lifespan. Exercise is an important stimulator of extracellular and intracellular stress signals that promote positive adaptations in skeletal muscle. These adaptations are controlled by changes in gene transcription and protein translation, with many of these molecules identified as potential therapeutic targets to pharmacologically improve muscle quality in patient groups too ill to exercise. MicroRNAs (miRNAs) are recently identified regulators of numerous gene networks and pathways and mainly exert their effect by binding to their target messenger RNAs (mRNAs), resulting in mRNA degradation or preventing protein translation. The role of exercise as a regulatory stimulus of skeletal muscle miRNAs is now starting to be investigated. This review highlights our current understanding of the regulation of skeletal muscle miRNAs with exercise and disease as well as how they may control skeletal muscle health. PMID:24137130

  2. MicroRNAs in skeletal muscle and their regulation with exercise, ageing, and disease

    PubMed Central

    Zacharewicz, Evelyn; Lamon, Séverine; Russell, Aaron P.

    2013-01-01

    Skeletal muscle makes up approximately 40% of the total body mass, providing structural support and enabling the body to maintain posture, to control motor movements and to store energy. It therefore plays a vital role in whole body metabolism. Skeletal muscle displays remarkable plasticity and is able to alter its size, structure and function in response to various stimuli; an essential quality for healthy living across the lifespan. Exercise is an important stimulator of extracellular and intracellular stress signals that promote positive adaptations in skeletal muscle. These adaptations are controlled by changes in gene transcription and protein translation, with many of these molecules identified as potential therapeutic targets to pharmacologically improve muscle quality in patient groups too ill to exercise. MicroRNAs (miRNAs) are recently identified regulators of numerous gene networks and pathways and mainly exert their effect by binding to their target messenger RNAs (mRNAs), resulting in mRNA degradation or preventing protein translation. The role of exercise as a regulatory stimulus of skeletal muscle miRNAs is now starting to be investigated. This review highlights our current understanding of the regulation of skeletal muscle miRNAs with exercise and disease as well as how they may control skeletal muscle health. PMID:24137130

  3. Identification of the Acetylation and Ubiquitin-Modified Proteome during the Progression of Skeletal Muscle Atrophy

    PubMed Central

    Ryder, Daniel J.; Judge, Sarah M.; Beharry, Adam W.; Farnsworth, Charles L.; Silva, Jeffrey C.; Judge, Andrew R.

    2015-01-01

    Skeletal muscle atrophy is a consequence of several physiological and pathophysiological conditions including muscle disuse, aging and diseases such as cancer and heart failure. In each of these conditions, the predominant mechanism contributing to the loss of skeletal muscle mass is increased protein turnover. Two important mechanisms which regulate protein stability and degradation are lysine acetylation and ubiquitination, respectively. However our understanding of the skeletal muscle proteins regulated through acetylation and ubiquitination during muscle atrophy is limited. Therefore, the purpose of the current study was to conduct an unbiased assessment of the acetylation and ubiquitin-modified proteome in skeletal muscle during a physiological condition of muscle atrophy. To induce progressive, physiologically relevant, muscle atrophy, rats were cast immobilized for 0, 2, 4 or 6 days and muscles harvested. Acetylated and ubiquitinated peptides were identified via a peptide IP proteomic approach using an anti-acetyl lysine antibody or a ubiquitin remnant motif antibody followed by mass spectrometry. In control skeletal muscle we identified and mapped the acetylation of 1,326 lysine residues to 425 different proteins and the ubiquitination of 4,948 lysine residues to 1,131 different proteins. Of these proteins 43, 47 and 50 proteins were differentially acetylated and 183, 227 and 172 were differentially ubiquitinated following 2, 4 and 6 days of disuse, respectively. Bioinformatics analysis identified contractile proteins as being enriched among proteins decreased in acetylation and increased in ubiquitination, whereas histone proteins were enriched among proteins increased in acetylation and decreased in ubiquitination. These findings provide the first proteome-wide identification of skeletal muscle proteins exhibiting changes in lysine acetylation and ubiquitination during any atrophy condition, and provide a basis for future mechanistic studies into how the acetylation and ubiquitination status of these identified proteins regulates the muscle atrophy phenotype. PMID:26302492

  4. Creating and Simulating Skeletal Muscle from the Visible Human Data Set

    E-print Network

    Varadarajan, Veeravalli S.

    Creating and Simulating Skeletal Muscle from the Visible Human Data Set Joseph Teran, Eftychios--Simulation of the musculoskeletal system has important applications in biomechanics, biomedical engineering, surgery simulation

  5. Regulation of skeletal muscle mitochondrial function by nuclear receptors: implications for health and disease.

    PubMed

    Perez-Schindler, Joaquin; Philp, Andrew

    2015-10-01

    Skeletal muscle metabolism is highly dependent on mitochondrial function, with impaired mitochondrial biogenesis associated with the development of metabolic diseases such as insulin resistance and type 2 diabetes. Mitochondria display substantial plasticity in skeletal muscle, and are highly sensitive to levels of physical activity. It is thought that physical activity promotes mitochondrial biogenesis in skeletal muscle through increased expression of genes encoded in both the nuclear and the mitochondrial genome; however, how this process is co-ordinated at the cellular level is poorly understood. Nuclear receptors (NRs) are key signalling proteins capable of integrating environmental factors and mitochondrial function, thereby providing a potential link between exercise and mitochondrial biogenesis. The aim of this review is to highlight the function of NRs in skeletal muscle mitochondrial biogenesis and discuss the therapeutic potential of NRs for the management and treatment of chronic metabolic disease. PMID:26186742

  6. Protein Degradative Processes Associated with Anabolic Dysregulation in Diabetic Skeletal Muscle 

    E-print Network

    Perticone, Jacqueline Ilene

    2014-05-19

    Skeletal muscle of obese Zucker rats function at higher rates of anabolism when compared to lean littermates, and are resistant to the anabolic effect of exercise. We recently determined that DEP domain containing mammalian target of rapamycin (m...

  7. Protein Diffusion in Living Skeletal Muscle Fibers: Dependence on Protein Size, Fiber Type, and Contraction

    E-print Network

    Voigt, Chris

    Protein Diffusion in Living Skeletal Muscle Fibers: Dependence on Protein Size, Fiber Type Hochschule Hannover, 30623 Hannover, Germany ABSTRACT Sarcoplasmic protein diffusion was studied under different conditions, using microinjection in combination with microspectrophotometry. Six globular proteins

  8. A role for nephrin, a renal protein, in vertebrate skeletal muscle cell fusion

    E-print Network

    Kalluri, Raghu

    Skeletal muscle is formed via fusion of myoblasts, a well-studied process in Drosophila. In vertebrates however, this process is less well understood, and whether there is evolutionary conservation with the proteins studied ...

  9. Perilipin 4 in human skeletal muscle: localization and effect of physical activity

    PubMed Central

    Pourteymour, Shirin; Lee, Sindre; Langleite, Torgrim M; Eckardt, Kristin; Hjorth, Marit; Bindesbøll, Christian; Dalen, Knut T; Birkeland, Kåre I; Drevon, Christian A; Holen, Torgeir; Norheim, Frode

    2015-01-01

    Perilipins (PLINs) coat the surface of lipid droplets and are important for the regulation of lipid turnover. Knowledge about the physiological role of the individual PLINs in skeletal muscle is limited although lipid metabolism is very important for muscle contraction. To determine the effect of long-term exercise on PLINs expression, 26 middle-aged, sedentary men underwent 12 weeks combined endurance and strength training intervention. Muscle biopsies from m. vastus lateralis and subcutaneous adipose tissue were taken before and after the intervention and total gene expression was measured with deep mRNA sequencing. PLIN4 mRNA exhibited the highest expression of all five PLINs in both tissues, and the expression was significantly reduced after long-term exercise in skeletal muscle. Moreover, PLIN4 mRNA expression levels in muscle correlated with the expression of genes involved in de novo phospholipid biosynthesis, with muscular content of phosphatidylethanolamine and phosphatidylcholine, and with the content of subsarcolemmal lipid droplets. The PLIN4 protein was mainly located at the periphery of skeletal muscle fibers, with higher levels in slow-twitch as compared to fast-twitch skeletal muscle fibers. In summary, we report reduced expression of PLIN4 after long-term physical activity, and preferential slow-twitch skeletal muscle fibers and plasma membrane-associated PLIN4 location. PMID:26265748

  10. Perilipin 4 in human skeletal muscle: localization and effect of physical activity.

    PubMed

    Pourteymour, Shirin; Lee, Sindre; Langleite, Torgrim M; Eckardt, Kristin; Hjorth, Marit; Bindesbøll, Christian; Dalen, Knut T; Birkeland, Kåre I; Drevon, Christian A; Holen, Torgeir; Norheim, Frode

    2015-08-01

    Perilipins (PLINs) coat the surface of lipid droplets and are important for the regulation of lipid turnover. Knowledge about the physiological role of the individual PLINs in skeletal muscle is limited although lipid metabolism is very important for muscle contraction. To determine the effect of long-term exercise on PLINs expression, 26 middle-aged, sedentary men underwent 12 weeks combined endurance and strength training intervention. Muscle biopsies from m. vastus lateralis and subcutaneous adipose tissue were taken before and after the intervention and total gene expression was measured with deep mRNA sequencing. PLIN4 mRNA exhibited the highest expression of all five PLINs in both tissues, and the expression was significantly reduced after long-term exercise in skeletal muscle. Moreover, PLIN4 mRNA expression levels in muscle correlated with the expression of genes involved in de novo phospholipid biosynthesis, with muscular content of phosphatidylethanolamine and phosphatidylcholine, and with the content of subsarcolemmal lipid droplets. The PLIN4 protein was mainly located at the periphery of skeletal muscle fibers, with higher levels in slow-twitch as compared to fast-twitch skeletal muscle fibers. In summary, we report reduced expression of PLIN4 after long-term physical activity, and preferential slow-twitch skeletal muscle fibers and plasma membrane-associated PLIN4 location. PMID:26265748

  11. Role of IGF-I in follistatin-induced skeletal muscle hypertrophy.

    PubMed

    Barbé, Caroline; Kalista, Stéphanie; Loumaye, Audrey; Ritvos, Olli; Lause, Pascale; Ferracin, Benjamin; Thissen, Jean-Paul

    2015-09-15

    Follistatin, a physiological inhibitor of myostatin, induces a dramatic increase in skeletal muscle mass, requiring the type 1 IGF-I receptor/Akt/mTOR pathway. The aim of the present study was to investigate the role of IGF-I and insulin, two ligands of the IGF-I receptor, in the follistatin hypertrophic action on skeletal muscle. In a first step, we showed that follistatin increases muscle mass while being associated with a downregulation of muscle IGF-I expression. In addition, follistatin retained its full hypertrophic effect toward muscle in hypophysectomized animals despite very low concentrations of circulating and muscle IGF-I. Furthermore, follistatin did not increase muscle sensitivity to IGF-I in stimulating phosphorylation of Akt but, surprisingly, decreased it once hypertrophy was present. Taken together, these observations indicate that increased muscle IGF-I production or sensitivity does not contribute to the muscle hypertrophy caused by follistatin. Unlike low IGF-I, low insulin, as obtained by streptozotocin injection, attenuated the hypertrophic action of follistatin on skeletal muscle. Moreover, the full anabolic response to follistatin was restored in this condition by insulin but also by IGF-I infusion. Therefore, follistatin-induced muscle hypertrophy requires the activation of the insulin/IGF-I pathway by either insulin or IGF-I. When insulin or IGF-I alone is missing, follistatin retains its full anabolic effect, but when both are deficient, as in streptozotocin-treated animals, follistatin fails to stimulate muscle growth. PMID:26219865

  12. Elevated levels of TWEAK in skeletal muscle promote visceral obesity, insulin resistance, and metabolic dysfunction.

    PubMed

    Sato, Shuichi; Ogura, Yuji; Tajrishi, Marjan M; Kumar, Ashok

    2015-03-01

    Skeletal muscle is responsible for the majority of glucose disposal in body. Impairment in skeletal muscle glucose handling capacity leads to the state of insulin resistance. The TNF-like weak inducer of apoptosis (TWEAK) cytokine has now emerged as a major regulator of skeletal muscle mass and function. However, the role of TWEAK in skeletal muscle metabolic function remains less understood. Here, we demonstrate that with progressive age, skeletal muscle-specific TWEAK-transgenic (TWEAK-Tg) mice gain increased body weight (?16%) and fat mass (?64%) and show glucose intolerance and insulin insensitivity. TWEAK-Tg mice also exhibit adipocyte hypertrophy in the epididymal fat. Oxygen uptake, voluntary physical activity, and exercise capacity were significantly reduced in TWEAK-Tg mice compared with controls. Overexpression of TWEAK inhibited (?31%) 5' AMP-activated protein kinase (AMPK) and reduced (?31%) the levels of glucose transporter type 4 (GLUT4) without affecting the Akt pathway. TWEAK also inhibited insulin-stimulated glucose uptake (?32%) and repressed the levels of GLUT4 (?50%) in cultured myotubes from C57BL6 mice. TWEAK represses the levels of Krüppel-like factor 15; myocyte enhancer factor 2, and peroxisome proliferator-activated receptor-? coactivator-1?, which are required for the activation of the GLUT4 locus. Collectively our study demonstrates that elevated levels of TWEAK in skeletal muscle cause metabolic abnormalities. Inhibition of TWEAK could be a potential approach to prevent weight gain and type 2 diabetes. PMID:25466899

  13. Constitutively active calcineurin in skeletal muscle increases endurance performance and mitochondrial respiratory capacity.

    PubMed

    Jiang, Lake Q; Garcia-Roves, Pablo M; de Castro Barbosa, Thais; Zierath, Juleen R

    2010-01-01

    Expression of an activated form of calcineurin in skeletal muscle selectively up-regulates slow-fiber-specific gene expression. Here, we tested the hypothesis that expression of activated calcineurin in skeletal muscle influences body composition, energy homeostasis, and exercise performance. Using transgenic mice expressing activated calcineurin (CnA*) in skeletal muscle (MCK-CnA* transgenic mice), we determined whether skeletal muscle reprogramming by calcineurin activation affects exercise performance and skeletal muscle mitochondrial function. Body weight and extensor digitorum longus (EDL) skeletal muscle weight were reduced 10% in MCK-CnA* mice compared with wild-type littermates. Basal oxygen consumption, food intake, and voluntary exercise behavior were unchanged between MCK-CnA* and wild-type mice. However, when total energy expenditure was normalized by fat-free mass, energy expenditure was increased in MCK-CnA* mice. An endurance performance treadmill running test revealed MCK-CnA* mice are fatigue resistant and run 50% farther before exhaustion. After a standardized exercise bout, glycogen and triglyceride content in EDL muscle was higher in MCK-CnA* vs. wild-type mice. Mitochondrial respiratory capacity was increased 35% in EDL muscle from resting MCK-CnA* mice. In conclusion, our results provide evidence to support the hypothesis that calcineurin activation in skeletal muscle increases mitochondrial oxidative function and energy substrate storage, which contributes to enhanced endurance exercise performance. These adaptive changes occur as a consequence of a lifelong expression of a constitutively active calcineurin and mimic the response to chronic endurance training. PMID:19861587

  14. Decreased hydrogen peroxide production and mitochondrial respiration in skeletal muscle but not cardiac muscle of the green-striped burrowing frog, a natural model of muscle disuse.

    PubMed

    Reilly, Beau D; Hickey, Anthony J R; Cramp, Rebecca L; Franklin, Craig E

    2014-04-01

    Suppression of disuse-induced muscle atrophy has been associated with altered mitochondrial reactive oxygen species (ROS) production in mammals. However, despite extended hindlimb immobility, aestivating animals exhibit little skeletal muscle atrophy compared with artificially immobilised mammalian models. Therefore, we studied mitochondrial respiration and ROS (H2O2) production in permeabilised muscle fibres of the green-striped burrowing frog, Cyclorana alboguttata. Mitochondrial respiration within saponin-permeabilised skeletal and cardiac muscle fibres was measured concurrently with ROS production using high-resolution respirometry coupled to custom-made fluorometers. After 4 months of aestivation, C. alboguttata had significantly depressed whole-body metabolism by ~70% relative to control (active) frogs, and mitochondrial respiration in saponin-permeabilised skeletal muscle fibres decreased by almost 50% both in the absence of ADP and during oxidative phosphorylation. Mitochondrial ROS production showed up to an 88% depression in aestivating skeletal muscle when malate, succinate and pyruvate were present at concentrations likely to reflect those in vivo. The percentage ROS released per O2 molecule consumed was also ~94% less at these concentrations, indicating an intrinsic difference in ROS production capacities during aestivation. We also examined mitochondrial respiration and ROS production in permeabilised cardiac muscle fibres and found that aestivating frogs maintained respiratory flux and ROS production at control levels. These results show that aestivating C. alboguttata has the capacity to independently regulate mitochondrial function in skeletal and cardiac muscles. Furthermore, this work indicates that ROS production can be suppressed in the disused skeletal muscle of aestivating frogs, which may in turn protect against potential oxidative damage and preserve skeletal muscle structure during aestivation and following arousal. PMID:24311816

  15. Cardiomyoplasty: treatment of the failing heart using the skeletal muscle wrap.

    PubMed

    Stewart, J V; Hicks, S L; Leflar, K M; Kaempf, G; Bove, L A; DiMarzio, D

    1993-01-01

    Surgical methods of augmenting cardiac function are gaining credibility among researchers as animal and human clinical trials continue around the world. The procedures themselves may vary slightly depending upon protocol and surgeon preference, but generally involve the use of skeletal muscle such as the latissimus dorsi. The muscle may be wrapped around the heart or the aorta, or fashioned into a separate pumping chamber. The muscle is then stimulated with specialized burst pacing, the resultant contractions providing circulatory support. This article describes preoperative, intraoperative, postoperative, and follow-up patient and family care for those undergoing skeletal muscle wrap procedures. If trials continue to produce positive results, these interventions may become an important bridge to transplant. Moreover, with the scarcity of donor hearts, the implications for skeletal muscle wrapping as a long-term alternative to transplant are promising. PMID:7679437

  16. Fatigue mechanisms in patients with cancer: effects of tumor necrosis factor and exercise on skeletal muscle

    NASA Technical Reports Server (NTRS)

    St Pierre, B. A.; Kasper, C. E.; Lindsey, A. M.

    1992-01-01

    Fatigue is a common adverse effect of cancer and its therapy. However, the specific mechanisms underlying cancer fatigue are unclear. One physiologic mechanism may involve changes in skeletal muscle protein stores or metabolite concentration. A reduction in skeletal muscle protein stores may result from endogenous tumor necrosis factor (TNF) or from TNF administered as antineoplastic therapy. This muscle wasting would require patients to exert an unusually high amount of effort to generate adequate contractile force during exercise performance or during extended periods of sitting or standing. This additional effort could result in the onset of fatigue. Additionally, cancer fatigue may develop or become exacerbated during exercise as a consequence of changes in the concentration of skeletal muscle metabolites. These biochemical alterations may interfere with force that is produced by the muscle contractile proteins. These physiologic changes may play a role in the decision to include exercise in the rehabilitation plans of patients with cancer. They also may affect ideas about fatigue.

  17. Effect of hindlimb suspension and clenbuterol treatment on polyamine levels in skeletal muscle

    NASA Technical Reports Server (NTRS)

    Abukhalaf, Imad K.; von Deutsch, Daniel A.; Wineski, Lawrence E.; Silvestrov, Natalia A.; Abera, Saare A.; Sahlu, Sinafikish W.; Potter, David E.; Thierry-Palmer, M. (Principal Investigator)

    2002-01-01

    Polyamines are unbiquitous, naturally occurring small aliphatic, polycationic, endogenous compounds. They are involved in many cellular processes and may serve as secondary or tertiary messengers to hormonal regulation. The relationship of polyamines and skeletal muscle mass of adductor longus, extensor digitorum longus, and gastrocnemius under unloading (hindlimb suspension) conditions was investigated. Unloading significantly affected skeletal muscle polyamine levels in a fiber-type-specific fashion. Under loading conditions, clenbuterol treatment increased all polyamine levels, whereas under unloading conditions, only the spermidine levels were consistently increased. Unloading attenuated the anabolic effects of clenbuterol in predominately slow-twitch muscles (adductor longus), but had little impact on clenbuterol's action as a countermeasure in fast- twitch muscles such as the extensor digitorum longus. Spermidine appeared to be the primary polyamine involved in skeletal muscle atrophy/hypertrophy. Copyright 2002 S. Karger AG, Basel.

  18. Effect of leucine uptake on hepatic and skeletal muscle gene expression in rats: a microarray analysis

    PubMed Central

    Cheon, Wookwang

    2015-01-01

    [Purpose] This study was performed to explore the physiological functions of leucine by exploring genes with leucine-dependent variability using DNA microarray. [Methods] Sprague-Dawley rats (n = 20) were separated into a HPD (30% High Protein Diet, n = 10) group and a NPD (0% Non Protein Diet, n = 10) group and fed a protein diet for 2 weeks. At the end of the 2-week period, the rats were fasted for 12-16 hours, further separated into subgroups within the HPD (Saline, n = 5, Leucine, n = 5) and NPD (Saline, n = 5, Leucine, n = 5) groups and administered with a leucine solution. The liver and muscles were harvested after 2 hours for RNA extraction. RNA purification from the isolated muscles and target gene identification using DNA chip were performed. The target gene was determined based on the results of the DNA chip experiment, and mRNA expression of the target gene was analyzed using Real-Time PCR. [Results] In the skeletal muscle, 27 genes were upregulated while 52 genes were down regulated after leucine administration in the NPD group. In the liver, 160 genes were up-regulated while 126 were down-regulated. The per2 gene was one of the genes with leucine-dependent induction in muscles and liver. [Conclusion] This study was performed to explore the physiological functions of leucine, however, a large number of genes showed variability. Therefore, it was difficult to definitively identify the genes linked with a particular physiological function. Various nutritional effects of leucine were observed. High variability in cytokines, receptors, and various membrane proteins were observed, which suggests that leucine functions as more than a nutrient. The interpretation may depend on investigators’ perspectives, therefore, discussion with relevant experts and the BCAA (Branched-Chain Amino Acids) society may be needed for effective utilization of this data. PMID:26244133

  19. Adaptive skeletal muscle action requires anticipation and "conscious broadcasting".

    PubMed

    Poehlman, T Andrew; Jantz, Tiffany K; Morsella, Ezequiel

    2012-01-01

    Historically, the conscious and anticipatory processes involved in voluntary action have been associated with the loftiest heights of nervous function. Concepts like mental time travel, "theory of mind," and the formation of "the self" have been at the center of many attempts to determine the purpose of consciousness. Eventually, more reductionistic accounts of consciousness emerged, proposing rather that conscious states play a much more basic role in nervous function. Though the widely held integration consensus proposes that conscious states integrate information-processing structures and events that would otherwise be independent, Supramodular Interaction Theory (SIT) argues that conscious states are necessary for the integration of only certain kinds of information. As revealed in this selective review, this integration is related to what is casually referred to as "voluntary" action, which is intimately related to the skeletal muscle output system. Through a peculiar form of broadcasting, conscious integration often controls and guides action via "ideomotor" mechanisms, where anticipatory processes play a central role. Our selective review covers evidence (including findings from anesthesia research) for the integration consensus, SIT, and ideomotor theory. PMID:23264766

  20. Adaptive Skeletal Muscle Action Requires Anticipation and “Conscious Broadcasting”

    PubMed Central

    Poehlman, T. Andrew; Jantz, Tiffany K.; Morsella, Ezequiel

    2012-01-01

    Historically, the conscious and anticipatory processes involved in voluntary action have been associated with the loftiest heights of nervous function. Concepts like mental time travel, “theory of mind,” and the formation of “the self” have been at the center of many attempts to determine the purpose of consciousness. Eventually, more reductionistic accounts of consciousness emerged, proposing rather that conscious states play a much more basic role in nervous function. Though the widely held integration consensus proposes that conscious states integrate information-processing structures and events that would otherwise be independent, Supramodular Interaction Theory (SIT) argues that conscious states are necessary for the integration of only certain kinds of information. As revealed in this selective review, this integration is related to what is casually referred to as “voluntary” action, which is intimately related to the skeletal muscle output system. Through a peculiar form of broadcasting, conscious integration often controls and guides action via “ideomotor” mechanisms, where anticipatory processes play a central role. Our selective review covers evidence (including findings from anesthesia research) for the integration consensus, SIT, and ideomotor theory. PMID:23264766

  1. Skeletal muscle tissue engineering: strategies for volumetric constructs

    PubMed Central

    Cittadella Vigodarzere, Giorgio; Mantero, Sara

    2014-01-01

    Skeletal muscle tissue is characterized by high metabolic requirements, defined structure and high regenerative potential. As such, it constitutes an appealing platform for tissue engineering to address volumetric defects, as proven by recent works in this field. Several issues common to all engineered constructs constrain the variety of tissues that can be realized in vitro, principal among them the lack of a vascular system and the absence of reliable cell sources; as it is, the only successful tissue engineering constructs are not characterized by active function, present limited cellular survival at implantation and possess low metabolic requirements. Recently, functionally competent constructs have been engineered, with vascular structures supporting their metabolic requirements. In addition to the use of biochemical cues, physical means, mechanical stimulation and the application of electric tension have proven effective in stimulating the differentiation of cells and the maturation of the constructs; while the use of co-cultures provided fine control of cellular developments through paracrine activity. This review will provide a brief analysis of some of the most promising improvements in the field, with particular attention to the techniques that could prove easily transferable to other branches of tissue engineering. PMID:25295011

  2. Evidence for the contribution of muscle stem cells to nonhypertrophic skeletal muscle remodeling in humans

    PubMed Central

    Joanisse, Sophie; Gillen, Jenna B.; Bellamy, Leeann M.; McKay, Bryon R.; Tarnopolsky, Mark A.; Gibala, Martin. J.; Parise, Gianni

    2013-01-01

    The purpose of this study was to explore the possible role of muscle stem cells, also referred to as satellite cells (SCs), in adaptation and remodeling following a nonhypertrophic stimulus in humans. Muscle biopsies were obtained from the vastus lateralis of previously untrained women (n=15; age: 27±8 yr, BMI: 29±6 kg/m2) before and after 6 wk of aerobic interval training. The fiber type-specific SC response to training was analyzed using immunofluorescent microscopy of muscle cross sections. Following training, the number of SCs associated with fibers expressing myosin heavy-chain type I and II isoforms (hybrid fibers) increased (pre: 0.062±0.035 SC/hybrid fiber; post: 0.38±0.063 SC/hybrid fiber; P<0.01). In addition, there was a greater number of MyoD+/Pax7? SCs, indicative of differentiating SCs, associated with hybrid fibers (0.18±0.096 MyoD+/Pax7? SC/hybrid fiber) compared to type I (0.015±0.00615 MyoD+/Pax7? SC/type I fiber) or II (0.012±0.00454 MyoD+/Pax7? SC/type II fiber) fibers (P<0.05). There was also a training-induced increase in the number of hybrid fibers containing centrally located nuclei (15.1%) compared to either type I (3.4%) or II fibers (3.6%) (P<0.01). These data are consistent with the hypothesis that SCs contribute to the remodeling of muscle fibers even in the absence of hypertrophy.—Joanisse, S., Gillen, J. B., Bellamy, L. M., McKay, B. R., Tarnopolsky, M. A., Gibala, M. J., Parise, G. Evidence for the contribution of muscle stem cells to nonhypertrophic skeletal muscle remodeling in humans. PMID:23928822

  3. Cellular Mechanisms of Tissue Fibrosis. 4. Structural and functional consequences of skeletal muscle fibrosis

    PubMed Central

    Ward, Samuel R.

    2013-01-01

    Skeletal muscle fibrosis can be a devastating clinical problem that arises from many causes, including primary skeletal muscle tissue diseases, as seen in the muscular dystrophies, or it can be secondary to events that include trauma to muscle or brain injury. The cellular source of activated fibroblasts (myofibroblasts) may include resident fibroblasts, adult muscle stem cells, or inflammatory or perivascular cells, depending on the model studied. Even though it is likely that there is no single source for all myofibroblasts, a common mechanism for the production of fibrosis is via the transforming growth factor-?/phosphorylated Smad3 pathway. This pathway and its downstream targets thus provide loci for antifibrotic therapies, as do methods for blocking the transdifferentiation of progenitors into activated fibroblasts. A structural model for the extracellular collagen network of skeletal muscle is needed so that measurements of collagen content, morphology, and gene expression can be related to mechanical properties. Approaches used to study fibrosis in tissues, such as lung, kidney, and liver, need to be applied to studies of skeletal muscle to identify ways to prevent or even cure the devastating maladies of skeletal muscle. PMID:23761627

  4. Constitutive Expression of Yes-Associated Protein (Yap) in Adult Skeletal Muscle Fibres Induces Muscle Atrophy and Myopathy

    PubMed Central

    Judson, Robert N.; Gray, Stuart R.; Walker, Claire; Carroll, Andrew M.; Itzstein, Cecile; Lionikas, Arimantas; Zammit, Peter S.; De Bari, Cosimo; Wackerhage, Henning

    2013-01-01

    The aim of this study was to investigate the function of the Hippo pathway member Yes-associated protein (Yap, gene name Yap1) in skeletal muscle fibres in vivo. Specifically we bred an inducible, skeletal muscle fibre-specific knock-in mouse model (MCK-tTA-hYAP1 S127A) to test whether the over expression of constitutively active Yap (hYAP1 S127A) is sufficient to drive muscle hypertrophy or stimulate changes in fibre type composition. Unexpectedly, after 5–7 weeks of constitutive hYAP1 S127A over expression, mice suddenly and rapidly lost 20–25% body weight and suffered from gait impairments and kyphosis. Skeletal muscles atrophied by 34–40% and the muscle fibre cross sectional area decreased by ?40% when compared to control mice. Histological analysis revealed evidence of skeletal muscle degeneration and regeneration, necrotic fibres and a NADH-TR staining resembling centronuclear myopathy. In agreement with the histology, mRNA expression of markers of regenerative myogenesis (embryonic myosin heavy chain, Myf5, myogenin, Pax7) and muscle protein degradation (atrogin-1, MuRF1) were significantly elevated in muscles from transgenic mice versus control. No significant changes in fibre type composition were detected using ATPase staining. The phenotype was largely reversible, as a cessation of hYAP1 S127A expression rescued body and muscle weight, restored muscle morphology and prevented further pathological progression. To conclude, high Yap activity in muscle fibres does not induce fibre hypertrophy nor fibre type changes but instead results in a reversible atrophy and deterioration. PMID:23544078

  5. Aging Affects the Transcriptional Regulation of Human Skeletal Muscle Disuse Atrophy

    PubMed Central

    Jensen, Line; Jensen, Mette Munk; Jespersen, Jakob G.; Hvid, Lars G.; Bayer, Monika; Petersson, Stine J.; Schrøder, Henrik D.; Andersen, Jesper L.; Heinemeier, Katja M.; Aagaard, Per; Schjerling, Peter; Kjaer, Michael

    2012-01-01

    Important insights concerning the molecular basis of skeletal muscle disuse-atrophy and aging related muscle loss have been obtained in cell culture and animal models, but these regulatory signaling pathways have not previously been studied in aging human muscle. In the present study, muscle atrophy was induced by immobilization in healthy old and young individuals to study the time-course and transcriptional factors underlying human skeletal muscle atrophy. The results reveal that irrespectively of age, mRNA expression levels of MuRF-1 and Atrogin-1 increased in the very initial phase (2–4 days) of human disuse-muscle atrophy along with a marked reduction in PGC-1? and PGC-1? (1–4 days) and a ?10% decrease in myofiber size (4 days). Further, an age-specific decrease in Akt and S6 phosphorylation was observed in young muscle within the first days (1–4 days) of immobilization. In contrast, Akt phosphorylation was unchanged in old muscle after 2 days and increased after 4 days of immobilization. Further, an age-specific down-regulation of MuRF-1 and Atrogin-1 expression levels was observed following 2 weeks of immobilization, along with a slowing atrophy response in aged skeletal muscle. Neither the immediate loss of muscle mass, nor the subsequent age-differentiated signaling responses could be explained by changes in inflammatory mediators, apoptosis markers or autophagy indicators. Collectively, these findings indicate that the time-course and regulation of human skeletal muscle atrophy is age dependent, leading to an attenuated loss in aging skeletal muscle when exposed to longer periods of immobility-induced disuse. PMID:23284670

  6. A truncated Wnt7a retains full biological activity in skeletal muscle

    NASA Astrophysics Data System (ADS)

    von Maltzahn, Julia; Zinoviev, Radoslav; Chang, Natasha C.; Bentzinger, C. Florian; Rudnicki, Michael A.

    2013-11-01

    Wnt signaling has essential roles during embryonic development and tissue homoeostasis. Wnt proteins are post-translationally modified and the attachment of a palmitate moiety at two conserved residues is believed to be a prerequisite for the secretion and function of Wnt proteins. Here we demonstrate that a mammalian Wnt protein can be fully functional without palmitoylation. We generate a truncated Wnt7a variant, consisting of the C-terminal 137 amino acids lacking the conserved palmitoylation sites and show that it retains full biological activity in skeletal muscle. This includes binding to and signaling through its receptor Fzd7 to stimulate symmetric expansion of satellite stem cells by activating the planar-cell polarity pathway and inducing myofibre hypertrophy by signaling through the AKT/mTOR pathway. Furthermore, this truncated Wnt7a shows enhanced secretion and dispersion compared with the full-length protein. Together, these findings open important new avenues for the development of Wnt7a as a treatment for muscle-wasting diseases and have broad implications for the therapeutic use of Wnts as biologics.

  7. Effects of prior exercise on the action of insulin-like growth factor I in skeletal muscle

    NASA Technical Reports Server (NTRS)

    Henriksen, E. J.; Louters, L. L.; Stump, C. S.; Tipton, C. M.

    1992-01-01

    Prior exercise increases insulin sensitivity for glucose and system A neutral amino acid transport activities in skeletal muscle. Insulin-like growth factor I (IGF-I) also activates these transport processes in resting muscle. It is not known, however, whether prior exercise increases IGF-I action in muscle. Therefore we determined the effect of a single exhausting bout of swim exercise on IGF-I-stimulated glucose transport activity [assessed by 2-deoxy-D-glucose (2-DG) uptake] and system A activity [assessed by alpha-(methylamino)isobutyric acid (MeAIB) uptake] in the isolated rat epitrochlearis muscle. When measured 3.5 h after exercise, the responses to a submaximal concentration (0.2 nM), but not a maximal concentration (13.3 nM), of insulin for activation of 2-DG uptake and MeAIB uptake were enhanced. In contrast, prior exercise increased markedly both the submaximal (5 nM) and maximal (20 nM) responses to IGF-I for activation of 2-DG uptake, whereas only the submaximal response to IGF-I (3 nM) for MeAIB uptake was enhanced after exercise. We conclude that 1) prior exercise significantly enhances the response to a submaximal concentration of IGF-I for activation of the glucose transport and system A neutral amino acid transport systems in skeletal muscle and 2) the enhanced maximal response for IGF-I action after exercise is restricted to the signaling pathway for activation of the glucose transport system.

  8. Biochemical characterization, integrity, and sidedness of purified skeletal muscle triads.

    PubMed

    Mitchell, R D; Volpe, P; Palade, P; Fleischer, S

    1983-08-25

    The release of Ca2+ from the terminal cisternae of sarcoplasmic reticulum in muscle fiber triggers muscle contraction. The signal for Ca2+ release is mediated via the triad junction, i.e. the junctional association of terminal cisternae and transverse tubule. Recently, highly purified morphologically intact triads were isolated from rabbit skeletal muscle (Mitchell, R. D., Palade, P., and Fleischer, S. (1983) J. Cell Biol. 96, 1008-1016). In this study, biochemical characterization of two variants of purified triad preparations (Pyrophosphate and Standard) is provided. Terminal cisternae of triads sequester Ca2+ at rates comparable to those of purified heavy sarcoplasmic reticulum which is referable to terminal cisternae (Meissner, G. (1975) Biochim. Biophys. Acta 389, 51-68). The permeability for calcium ions, as reflected by a 2-3-fold stimulation of (Ca2+, Mg2+)-ATPase activity in the presence of the Ca2+ ionophore A23187, and by the Ca2+ leak rate, is comparable in triads and heavy sarcoplasmic reticulum. Several transverse tubule characteristics are present in triads. Four of them, i.e. cholesterol content, ouabain binding, dihydroalprenolol binding (beta-adrenergic receptor), and ouabain-sensitive (Na+, K+)-ATPase activity, are comparably enriched in the Pyrophosphate triads and therefore appear to be quantitative indices of the amount of transverse tubule. Adenylate cyclase and basal ATPase are unreliable in this regard. Methodology for analyzing membrane integrity and sidedness was applied (adenylate cyclase activity) and modified (ouabain-sensitive (Na+, K+)-ATPase activity) to characterize the transverse tubule of the triad. In addition, a new method was developed making use of ouabain binding to study sidedness. These studies show that the transverse tubule is largely sealed and inside out in orientation, i.e. with the cytoplasmic face exposed. This report indicates that the t-tubule and sarcoplasmic reticulum components of the triads possess transport capability and retain permeability barriers for ions. Therefore, the isolated triads appear to be suitable for studying the physiological Ca2+ release process in vitro. PMID:6136506

  9. Skeletal Muscle Function Deficit: A New Terminology to Embrace the Evolving Concepts of Sarcopenia and Age-Related Muscle Dysfunction

    PubMed Central

    Hadley, Evan

    2014-01-01

    Background. Concerns remain as to the best terminology to embrace sarcopenia’s evolving conceptualization. Many of these concerns stem from the fact that age-related decrements in muscle performance associated with physical impairment are only partially explained by decreases in muscle mass and that other pathophysiologic factors contribute to age-related impairments in muscle performance. Methods. Review of literature on the evolving conceptualization of sarcopenia since its early definition in 1989 and concerns with terminology. Results. Early definitions of sarcopenia were based solely on muscle mass in relationship to the range of muscle within a reference population. Subsequent definitions added performance criteria to muscle mass alone. The Foundation for the National Institutes of Health Sarcopenia Project identified criteria for clinically relevant low muscle strength (weakness) and low lean mass. Progress on the sarcopenia’s evolving definitions has not been accompanied by recommendations on specific terminologies that address the lack of sufficient specificity from the use of an anatomic term to define a functional condition with numerous now known nonanatomic contributory factors. Skeletal Muscle Function Deficit is a broader construct that accommodates a set of diagnoses that includes both sarcopenia and other age-related muscle dysfunctions. Conclusions. Skeletal Muscle Function Deficit is proposed as a new terminology to embrace the evolving conceptualization of sarcopenia and other age-related muscle dysfunctions. It comprises a variety of contributory etiologies and has the potential to provide a framework for developing diagnostic categories that are useful for both clinical practice and research. PMID:24737562

  10. Tissue Engineered Skeletal Muscle Using Recellularized Whole Muscle INTRODUCTION: For the reconstructive surgeon, tissue engineered skeletal muscle may offer

    E-print Network

    Dennis, Robert G.

    . These acellular muscles were placed in a bath of 20% fetal bovine serum in DMEM and 100 U/mL penicillin for one. The resulting constructs were placed in growth medium (DMEM, 20% fetal bovine serum, and 100 U/mL penicillin in differentiation medium (DMEM, 6.5% horse serum, and 100 U/mL penicillin) for one week, with media changes every 48

  11. Nitric oxide availability is increased in contracting skeletal muscle from aged mice, but does not differentially decrease muscle superoxide.

    PubMed

    Pearson, T; McArdle, A; Jackson, M J

    2015-01-01

    Reactive oxygen and nitrogen species have been implicated in the loss of skeletal muscle mass and function that occurs during aging. Nitric oxide (NO) and superoxide are generated by skeletal muscle and where these are generated in proximity their chemical reaction to form peroxynitrite can compete with the superoxide dismutation to hydrogen peroxide. Changes in NO availability may therefore theoretically modify superoxide and peroxynitrite activities in tissues, but published data are contradictory regarding aging effects on muscle NO availability. We hypothesised that an age-related increase in NO generation might increase peroxynitrite generation in muscles from old mice, leading to an increased nitration of muscle proteins and decreased superoxide availability. This was examined using fluorescent probes and an isolated fiber preparation to examine NO content and superoxide in the cytosol and mitochondria of muscle fibers from adult and old mice both at rest and following contractile activity. We also examined the 3-nitrotyrosine (3-NT) and peroxiredoxin 5 (Prx5) content of muscles from mice as markers of peroxynitrite activity. Data indicate that a substantial age-related increase in NO levels occurred in muscle fibers during contractile activity and this was associated with an increase in muscle eNOS. Muscle proteins from old mice also showed an increased 3-NT content. Inhibition of NOS indicated that NO decreased superoxide bioavailability in muscle mitochondria, although this effect was not age related. Thus increased NO in muscles of old mice was associated with an increased 3-NT content that may potentially contribute to age-related degenerative changes in skeletal muscle. PMID:25462644

  12. Identification of MicroRNAs Linked to Regulators of Muscle Protein Synthesis and Regeneration in Young and Old Skeletal Muscle

    PubMed Central

    Zacharewicz, Evelyn; Della Gatta, Paul; Reynolds, John; Garnham, Andrew; Crowley, Tamsyn; Russell, Aaron P.; Lamon, Séverine

    2014-01-01

    Background Over the course of ageing there is a natural and progressive loss of skeletal muscle mass. The onset and progression of age-related muscle wasting is associated with an attenuated activation of Akt-mTOR signalling and muscle protein synthesis in response to anabolic stimuli such as resistance exercise. MicroRNAs (miRNAs) are novel and important post-transcriptional regulators of numerous cellular processes. The role of miRNAs in the regulation of muscle protein synthesis following resistance exercise is poorly understood. This study investigated the changes in skeletal muscle miRNA expression following an acute bout of resistance exercise in young and old subjects with a focus on the miRNA species predicted to target Akt-mTOR signalling. Results Ten young (24.2±0.9 years) and 10 old (66.6±1.1 years) males completed an acute resistance exercise bout known to maximise muscle protein synthesis, with muscle biopsies collected before and 2 hours after exercise. We screened the expression of 754 miRNAs in the muscle biopsies and found 26 miRNAs to be regulated with age, exercise or a combination of both factors. Nine of these miRNAs are highly predicted to regulate targets within the Akt-mTOR signalling pathway and 5 miRNAs have validated binding sites within the 3? UTRs of several members of the Akt-mTOR signalling pathway. The miR-99/100 family of miRNAs notably emerged as potentially important regulators of skeletal muscle mass in young and old subjects. Conclusion This study has identified several miRNAs that were regulated with age or with a single bout of resistance exercise. Some of these miRNAs were predicted to influence Akt-mTOR signalling, and therefore potentially skeletal muscle mass. These miRNAs should be considered as candidate targets for in vivo modulation. PMID:25460913

  13. Attenuation of skeletal muscle wasting with recombinant human growth hormone secreted from a tissue-engineered bioartificial muscle

    NASA Technical Reports Server (NTRS)

    Vandenburgh, H.; Del Tatto, M.; Shansky, J.; Goldstein, L.; Russell, K.; Genes, N.; Chromiak, J.; Yamada, S.

    1998-01-01

    Skeletal muscle wasting is a significant problem in elderly and debilitated patients. Growth hormone (GH) is an anabolic growth factor for skeletal muscle but is difficult to deliver in a therapeutic manner by injection owing to its in vivo instability. A novel method is presented for the sustained secretion of recombinant human GH (rhGH) from genetically modified skeletal muscle implants, which reduces host muscle wasting. Proliferating murine C2C12 skeletal myoblasts stably transduced with the rhGH gene were tissue engineered in vitro into bioartificial muscles (C2-BAMs) containing organized postmitotic myofibers secreting 3-5 microg of rhGH/day in vitro. When implanted subcutaneously into syngeneic mice, C2-BAMs delivered a sustained physiologic dose of 2.5 to 11.3 ng of rhGH per milliliter of serum. rhGH synthesized and secreted by the myofibers was in the 22-kDa monomeric form and was biologically active, based on downregulation of a GH-sensitive protein synthesized in the liver. Skeletal muscle disuse atrophy was induced in mice by hindlimb unloading, causing the fast plantaris and slow soleus muscles to atrophy by 21 to 35% ( < 0.02). This atrophy was significantly attenuated 41 to 55% (p < 0.02) in animals that received C2-BAM implants, but not in animals receiving daily injections of purified rhGH (1 mg/kg/day). These data support the concept that delivery of rhGH from BAMs may be efficacious in treating muscle-wasting disorders.

  14. Growth and development of skeletal muscle in mu-calpain knockout mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The calpain system has been identified as a potential candidate in muscle growth and development due to its role in a variety of cellular processes such as cytoskeletal remodeling and myogenesis. The objective of this study was to evaluate growth and development of skeletal muscle in mu-calpain kno...

  15. Proto-oncogene expression during terminal differentiation of cardiac and skeletal muscle

    SciTech Connect

    Claycomb, W.C.; Lanson, N.A. Jr.; Springhorn, J.P.

    1986-05-01

    The authors have examined the expression of 17 different protooncogenes in proliferating and terminally differentiating cardiac and skeletal muscle cells. Cardiac muscle cells at various periods during differentiation were obtained from the rat. The L6 skeletal muscle cell line and a primary culture of human skeletal muscle satellite cells were the source of skeletal muscle cells. Total cellular RNA was isolated by the quanidinium procedure and purified by CsCl. RNA was separated on 1.2% agarose-formaldehyde gels and blotted onto Zeta-Probe nylon membranes. DNA probes, labeled with /sup 32/P, were generated by nick translation of purified DNA fragments or recombinant plasmid DNA. Northern blots were hybridized with /sup 32/P-DNA in 50% formamide, 1 mM EDTA, 7% SDS, 0.5 M NaHPO/sub 4/, 0.5 mg/ml denatured herring testes DNA and washed in 1 mM EDTA, 40 mM NaHPO/sub 4/ and 5% SDS. As positive controls, to assess DNA synthesis and cell proliferation, human histone H/sub 4/ and thymidine kinase were used as probes; rat cardiac muscle myosin heavy chain and M creatine kinase served to assess muscle cell differentiation. Results of these studies indicate that several of these oncogenes may be involved with the regulation of cell proliferation and terminal cell differentiation in striated muscle.

  16. Protein kinase D controls voluntary-running-induced skeletal muscle remodelling

    PubMed Central

    Ellwanger, Kornelia; Kienzle, Christine; Lutz, Sylke; Jin, Zheng-Gen; Wiekowski, Maria T.; Pfizenmaier, Klaus; Hausser, Angelika

    2014-01-01

    Skeletal muscle responds to exercise by activation of signalling pathways that co-ordinate gene expression to sustain muscle performance. MEF2 (myocyte enhancer factor 2)-dependent transcriptional activation of MHC (myosin heavy chain) genes promotes the transformation from fast-twitch into slow-twitch fibres, with MEF2 activity being tightly regulated by interaction with class IIa HDACs (histone deacetylases). PKD (protein kinase D) is known to directly phosphorylate skeletal muscle class IIa HDACs, mediating their nuclear export and thus derepression of MEF2. In the present study, we report the generation of transgenic mice with inducible conditional expression of a dominant-negative PKD1kd (kinase-dead PKD1) protein in skeletal muscle to assess the role of PKD in muscle function. In control mice, long-term voluntary running experiments resulted in a switch from type IIb + IId/x to type IIa plantaris muscle fibres as measured by indirect immunofluorescence of MHCs isoforms. In mice expressing PKD1kd, this fibre type switch was significantly impaired. These mice exhibited altered muscle fibre composition and decreased running performance compared with control mice. Our findings thus indicate that PKD activity is essential for exercise-induced MEF2-dependent skeletal muscle remodelling in vivo. PMID:21848513

  17. Protein kinase D controls voluntary-running-induced skeletal muscle remodelling.

    PubMed

    Ellwanger, Kornelia; Kienzle, Christine; Lutz, Sylke; Jin, Zheng-Gen; Wiekowski, Maria T; Pfizenmaier, Klaus; Hausser, Angelika

    2011-12-15

    Skeletal muscle responds to exercise by activation of signalling pathways that co-ordinate gene expression to sustain muscle performance. MEF2 (myocyte enhancer factor 2)-dependent transcriptional activation of MHC (myosin heavy chain) genes promotes the transformation from fast-twitch into slow-twitch fibres, with MEF2 activity being tightly regulated by interaction with class IIa HDACs (histone deacetylases). PKD (protein kinase D) is known to directly phosphorylate skeletal muscle class IIa HDACs, mediating their nuclear export and thus derepression of MEF2. In the present study, we report the generation of transgenic mice with inducible conditional expression of a dominant-negative PKD1kd (kinase-dead PKD1) protein in skeletal muscle to assess the role of PKD in muscle function. In control mice, long-term voluntary running experiments resulted in a switch from type IIb+IId/x to type IIa plantaris muscle fibres as measured by indirect immunofluorescence of MHCs isoforms. In mice expressing PKD1kd, this fibre type switch was significantly impaired. These mice exhibited altered muscle fibre composition and decreased running performance compared with control mice. Our findings thus indicate that PKD activity is essential for exercise-induced MEF2-dependent skeletal muscle remodelling in vivo. PMID:21848513

  18. Formation and optogenetic control of engineered 3D skeletal muscle bioactuators{

    E-print Network

    Chen, Christopher S.

    ) technology with skeletal muscle tissue engineering to open up opportunities to generate soft robots actuated- istics of their in vivo counterparts and serve as powering units for soft robotic devices, demonstrating activity.1 Muscle is an efficient actuator having a superior power-to-weight ratio, force-to-weight ratio

  19. A Simplified Method for Tissue Engineering Skeletal Muscle Organoids in Vitro

    NASA Technical Reports Server (NTRS)

    Shansky, Janet; DelTatto, Michael; Chromiak, Joseph; Vandenburgh, Herman

    1996-01-01

    Tissue-engineered three dimensional skeletal muscle organ-like structures have been formed in vitro from primary myoblasts by several different techniques. This report describes a simplified method for generating large numbers of muscle organoids from either primary embryonic avian or neonatal rodent myoblasts, which avoids the requirements for stretching and other mechanical stimulation.

  20. DEVELOPMENTAL REGULATION OF PROTEIN KINASE B ACTIVATION IS ISOFORM SPECIFIC IN SKELETAL MUSCLE OF NEONATAL PIGS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The postprandial activation of the insulin signaling pathway that leads to translation initiation is enhanced in skeletal muscle of the neonate and decreases with development in parallel with the developmental decline in muscle protein synthesis. Our previous study showed that the activity of protei...

  1. Mechanical ventilation induces myokine expression and catabolism in peripheral skeletal muscle in pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Endotoxin (LPS)-induced sepsis increases circulating cytokines which have been associated with skeletal muscle catabolism. During critical illness, it has been postulated that muscle wasting associated with mechanical ventilation (MV) occurs due to inactivity. We hypothesize that MV and sepsis promo...

  2. Mechanical ventilation and sepsis induce skeletal muscle catabolism in neonatal pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reduced rates of skeletal muscle accretion are a prominent feature of the metabolic response to sepsis in infants and children. Septic neonates often require medical support with mechanical ventilation (MV). The combined effects of MV and sepsis in muscle have not been examined in neonates, in whom ...

  3. Mechanical ventilation alone, and in the presence sepsis, induces peripheral skeletal muscle catabolism in neonatal pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reduced rates of skeletal muscle accretion are a prominent feature of the metabolic response to sepsis in infants and children. Septic neonates often require medical support with mechanical ventilation (MV). The combined effects of MV and sepsis in muscle have not been examined in neonates, in whom ...

  4. [Cases of Three Patients with Gastric Cancer and Metastasis to the Skeletal Muscle].

    PubMed

    Sugitani, Yoshihiko; Inatomi, Osamu; Tanabe, Rie; Kanda, Toshihiro; Sonoda, Ayano; Hasegawa, Hiroshi; Osaki, Rie; Imaeda, Hirotsugu; Ban, Hiromitsu; Nishida, Atsushi; Shioya, Makoto; Bamba, Shigeki; Sugimoto, Mitsushige; Tsujikawa, Tomoyuki; Andoh, Akira

    2015-11-01

    Metastasis to the skeletal muscle from gastric cancer is relatively rare. We report cases of 3 patients undergoing chemotherapy for gastric cancer with metastasis to the skeletal muscle. Case 1: A man in his 70s was diagnosed with advanced gastric cancer(cT4N3M1P0, stage IV), with metastasis to the lung, brain, lymph node, and iliopsoas muscle. Case 2: A man in his 60s was diagnosed with advanced gastric cancer(cT3N3M1P0, stage IV), with metastasis to the brain, lung, lymph node, and iliopsoas muscle. Case 3: A man in his 50s was diagnosed with advanced gastric cancer(cT4N3M1P0, stage IV), with metastasis to the urinary duct, lymph node, back muscle, and iliopsoas muscle. All 3 patients died within 7-8 months after the diagnosis due to progressive disease despite chemotherapy. The prognosis of these 3 patients was significantly poorer than that of patients in our hospital with metastasis not involving the skeletal muscle(p<0.01). Accordingly, metastasis to the skeletal muscle may be an adverse prognostic factor in gastric cancer. PMID:26602403

  5. A 3-day EGCG-supplementation reduces interstitial lactate concentration in skeletal muscle of overweight subjects

    PubMed Central

    Most, Jasper; van Can, Judith G P; van Dijk, Jan-Willem; Goossens, Gijs H.; Jocken, Johan; Hospers, Jeannette J.; Bendik, Igor; Blaak, Ellen E.

    2015-01-01

    Green tea, particularly epigallocatechin-3-gallate (EGCG), may affect body weight and composition, possibly by enhancing fat oxidation. The aim of this double-blind, randomized placebo-controlled cross-over study was to investigate whether 3-day supplementation with EGCG (282mg/day) stimulates fat oxidation and lipolysis in 24 overweight subjects (age?=?30?±?2yrs, BMI?=?27.7?±?0.3?kg/m2). Energy expenditure, substrate metabolism and circulating metabolites were determined during fasting and postprandial conditions. After 6?h, a fat biopsy was collected to examine gene expression. In 12 subjects, skeletal muscle glycerol, glucose and lactate concentrations were determined using microdialysis. EGCG-supplementation did not alter energy expenditure and substrate oxidation compared to placebo. Although EGCG reduced postprandial circulating glycerol concentrations (P?=?0.015), no difference in skeletal muscle lipolysis was observed. Fasting (P?=?0.001) and postprandial (P?=?0.003) skeletal muscle lactate concentrations were reduced after EGCG-supplementation compared to placebo, despite similar tissue blood flow. Adipose tissue leptin (P?=?0.05) and FAT/CD36 expression (P?=?0.08) were increased after EGCG compared to placebo. In conclusion, 3-day EGCG-supplementation decreased postprandial plasma glycerol concentrations, but had no significant effects on skeletal muscle lipolysis and whole-body fat oxidation in overweight individuals. Furthermore, EGCG decreased skeletal muscle lactate concentrations, which suggest a shift towards a more oxidative muscle phenotype. PMID:26647963

  6. Effect of spaceflight on the functional, biochemical, and metabolic properties of skeletal muscle

    NASA Technical Reports Server (NTRS)

    Baldwin, K. M.

    1996-01-01

    This paper summarizes the effects of spaceflight on the functional, morphological, and biochemical properties of human and rodent skeletal muscle. The findings suggest that following as little as 5-6 in space there are deficits in both human and rodent motor capacity, strength, and endurance properties of skeletal muscle. The reduced strength is associated, in part, with a reduction in muscle mass as reflected in smaller cross-sectional areas of both fast- and slow-twitch fibers. Available evidence in animal models suggests that slow-twitch fibers are more sensitive to the atrophying process. Accompanying the atrophy is a transformation of slow to fast protein phenotype involving myosin heavy chain and sarcoplasmic reticulum protein isoforms. These transformations appear to be regulated, in part, by pretranslational processes. Data on the oxidative capacity of rodent skeletal muscle suggest a bias toward preferential utilization of carbohydrate as the primary substrate. These collective findings suggest that skeletal muscles comprised chiefly of slow fibers are highly dependent on gravity for the normal expression of protein mass and slow phenotype. Future studies need to focus on elucidating the mechanisms associated with the atrophy response, as well as identifying suitable exercise and other countermeasures capable of preserving the structural and functional integrity of skeletal muscle.

  7. In Vitro Effects of Beta-2 Agonists on Skeletal Muscle Differentiation, Hypertrophy, and Atrophy

    PubMed Central

    2012-01-01

    Background Beta-2 agonists are widely used in the treatment of asthma and chronic obstructive pulmonary disease for their effect on airway smooth muscle relaxation. They also act on skeletal muscle, although their reported ergogenic effect is controversial. Aim To evaluate the in vitro effects of short-acting and long-acting beta-2 agonists on adrenergic receptor (ADR) expression, hypertrophy, and atrophy markers, in a skeletal muscle cell line. Methods The C2C12 cell line was used as a model of skeletal muscle differentiation. ADR messenger RNA expression was evaluated in proliferating myoblasts, committed cells, and differentiated myotubes, in basal conditions and after treatment with 10-6 M clenbuterol, salbutamol, salmeterol, and formoterol. Effect of beta-2 agonists on gene and protein expression of hypertrophy and atrophy markers was assessed in differentiated myotubes. Results Our study shows that beta-2 ADR messenger RNA was expressed and progressively increased during cell differentiation. Beta-2 agonist treatment did not affect its expression. Skeletal muscle hypertrophy markers (fast and slow myosin, myogenin) were not modulated by any of the beta-2 agonists evaluated. However, clenbuterol induced a significant, dose-dependent downregulation of skeletal muscle atrophy genes (atrogin-1, MuRF-1, and cathepsin L). Conclusions The reported ergogenic effect of beta-2 agonists, if any, should be considered as drug-specific and not class-specific and that of clenbuterol is mediated by the inhibition of the atrophic pathway. PMID:23283108

  8. Interaction between vestibulosympathetic and skeletal muscle reflexes on sympathetic activity in humans

    NASA Technical Reports Server (NTRS)

    Ray, C. A.

    2001-01-01

    Evidence from animals indicates that skeletal muscle afferents activate the vestibular nuclei and that both vestibular and skeletal muscle afferents have inputs to the ventrolateral medulla. The purpose of the present study was to investigate the interaction between the vestibulosympathetic and skeletal muscle reflexes on muscle sympathetic nerve activity (MSNA) and arterial pressure in humans. MSNA, arterial pressure, and heart rate were measured in 17 healthy subjects in the prone position during three experimental trials. The three trials were 2 min of 1) head-down rotation (HDR) to engage the vestibulosympathetic reflex, 2) isometric handgrip (IHG) at 30% maximal voluntary contraction to activate skeletal muscle afferents, and 3) HDR and IHG performed simultaneously. The order of the three trials was randomized. HDR and IHG performed alone increased total MSNA by 46 +/- 16 and 77 +/- 24 units, respectively (P < 0.01). During the HDR plus IHG trial, MSNA increased 142 +/- 38 units (P < 0.01). This increase was not significantly different from the sum of the individual trials (130 +/- 41 units). This finding was also observed with mean arterial pressure (sum = 21 +/- 2 mmHg and HDR + IHG = 22 +/- 2 mmHg). These findings suggest that there is an additive interaction for MSNA and arterial pressure when the vestibulosympathetic and skeletal muscle reflexes are engaged simultaneously in humans. Therefore, no central modulation exists between these two reflexes with regard to MSNA output in humans.

  9. A 3-day EGCG-supplementation reduces interstitial lactate concentration in skeletal muscle of overweight subjects.

    PubMed

    Most, Jasper; van Can, Judith G P; van Dijk, Jan-Willem; Goossens, Gijs H; Jocken, Johan; Hospers, Jeannette J; Bendik, Igor; Blaak, Ellen E

    2015-01-01

    Green tea, particularly epigallocatechin-3-gallate (EGCG), may affect body weight and composition, possibly by enhancing fat oxidation. The aim of this double-blind, randomized placebo-controlled cross-over study was to investigate whether 3-day supplementation with EGCG (282mg/day) stimulates fat oxidation and lipolysis in 24 overweight subjects (age?=?30?±?2yrs, BMI?=?27.7?±?0.3?kg/m(2)). Energy expenditure, substrate metabolism and circulating metabolites were determined during fasting and postprandial conditions. After 6?h, a fat biopsy was collected to examine gene expression. In 12 subjects, skeletal muscle glycerol, glucose and lactate concentrations were determined using microdialysis. EGCG-supplementation did not alter energy expenditure and substrate oxidation compared to placebo. Although EGCG reduced postprandial circulating glycerol concentrations (P?=?0.015), no difference in skeletal muscle lipolysis was observed. Fasting (P?=?0.001) and postprandial (P?=?0.003) skeletal muscle lactate concentrations were reduced after EGCG-supplementation compared to placebo, despite similar tissue blood flow. Adipose tissue leptin (P?=?0.05) and FAT/CD36 expression (P?=?0.08) were increased after EGCG compared to placebo. In conclusion, 3-day EGCG-supplementation decreased postprandial plasma glycerol concentrations, but had no significant effects on skeletal muscle lipolysis and whole-body fat oxidation in overweight individuals. Furthermore, EGCG decreased skeletal muscle lactate concentrations, which suggest a shift towards a more oxidative muscle phenotype. PMID:26647963

  10. Pericytes: multitasking cells in the regeneration of injured, diseased, and aged skeletal muscle

    PubMed Central

    Birbrair, Alexander; Zhang, Tan; Wang, Zhong-Min; Messi, Maria L.; Mintz, Akiva; Delbono, Osvaldo

    2014-01-01

    Pericytes are perivascular cells that envelop and make intimate connections with adjacent capillary endothelial cells. Recent studies show that they may have a profound impact in skeletal muscle regeneration, innervation, vessel formation, fibrosis, fat accumulation, and ectopic bone formation throughout life. In this review, we summarize and evaluate recent advances in our understanding of pericytes' influence on adult skeletal muscle pathophysiology. We also discuss how further elucidating their biology may offer new approaches to the treatment of conditions characterized by muscle wasting. PMID:25278877

  11. Measurement of calcium release due to inositol trisphosphate receptors in skeletal muscle.

    PubMed

    Casas, Mariana; Altamirano, Francisco; Jaimovich, Enrique

    2012-01-01

    Calcium transients elicited by IP(3) receptors upon electrical stimulation of skeletal muscle cells (slow calcium signals) are often hard to visualize due to their relatively small amplitude compared to the large transient originated from ryanodine receptors associated to excitation-contraction coupling. The study of slow calcium transients, however, is relevant due to their function in regulation of muscle gene expression and in the process of excitation-transcription coupling. Discussed here are the procedures used to record slow calcium signals from both cultured mouse myotubes and from cultured adult skeletal muscle fibers. PMID:22130849

  12. Piecing together the puzzle of perilipin proteins and skeletal muscle lipolysis.

    PubMed

    MacPherson, Rebecca E K; Peters, Sandra J

    2015-07-01

    The regulation of skeletal muscle lipolysis and fat oxidation is a complex process involving multiple proteins and enzymes. Emerging work indicates that skeletal muscle PLIN proteins likely play a role in the hydrolysis of triglycerides stored in lipid droplets and the passage of fatty acids to the mitochondria for oxidation. In adipocytes, PLIN1 regulates lipolysis by interacting with comparative gene identification-58 (CGI-58), an activator of adipose triglyceride lipase (ATGL). Upon lipolytic stimulation, PLIN1 is phosphorylated, releasing CGI-58 to activate ATGL and initiate triglyceride breakdown. The absence of PLIN1 in skeletal muscle leads us to believe that other PLIN family members undertake this role. The focus of this review is on the PLIN family proteins expressed in skeletal muscle: PLIN2, PLIN3, and PLIN5. To date, most studies involving these PLIN proteins have used nonmuscle tissues and cell cultures to determine their potential roles. Results from work in these models support a role for PLIN proteins in sequestering lipases during basal conditions and in potentially working together for lipase translocation and activity during lipolysis. In skeletal muscle, PLIN2 tends to mirror the lipid content and may play a role in lipid droplet growth and stability through lipase interactions on the lipid droplet surface, whereas the skeletal muscle roles of both PLIN3 and PLIN5 seem to be more complex because they are found not only on the lipid droplet, but also at the mitochondria. Clearly, further work is needed to fully understand the intricate mechanisms by which PLIN proteins contribute to skeletal muscle lipid metabolism. PMID:25971423

  13. Disruption of skeletal muscle mitochondrial network genes and miRNAs in amyotrophic lateral sclerosis.

    PubMed

    Russell, Aaron P; Wada, Shogo; Vergani, Lodovica; Hock, M Benjamin; Lamon, Séverine; Léger, Bertrand; Ushida, Takashi; Cartoni, Romain; Wadley, Glenn D; Hespel, Peter; Kralli, Anastasia; Soraru, Gianni; Angelini, Corrado; Akimoto, Takayuki

    2013-01-01

    Skeletal muscle mitochondrial dysfunction is believed to play a role in the progression and severity of amyotrophic lateral sclerosis (ALS). The regulation of transcriptional co-activators involved in mitochondrial biogenesis and function in ALS is not well known. When compared with healthy control subjects, patients with ALS, but not neurogenic disease (ND), had lower levels of skeletal muscle peroxisome proliferator-activated receptor ? coactivator-1? (PGC-1?) mRNA and protein and estrogen-related receptor-? (ERR?) and mitofusin-2 (Mfn2) mRNA. PGC-1?, nuclear respiratory factor-1 (NRF-1) and Mfn1 mRNA as well as cytochrome C oxidase subunit IV (COXIV) mRNA and protein were lower in patients with ALS and ND. Both patient groups had reductions in citrate synthase and cytochrome c oxidase activity. Similar observations were made in skeletal muscle from transgenic ALS G93A transgenic mice. In vitro, PGC-1? and PGC-1? regulated Mfn1 and Mfn2 in an ERR?-dependent manner. Compared to healthy controls, miRNA 23a, 29b, 206 and 455 were increased in skeletal muscle of ALS patients. miR-23a repressed PGC-1? translation in a 3' UTR dependent manner. Transgenic mice over expressing miR-23a had a reduction in PGC-1?, cytochome-b and COXIV protein levels. These results show that skeletal muscle mitochondrial dysfunction in ALS patients is associated with a reduction in PGC-1? signalling networks involved in mitochondrial biogenesis and function, as well as increases in several miRNAs potentially implicated in skeletal muscle and neuromuscular junction regeneration. As miR-23a negatively regulates PGC-1? signalling, therapeutic inhibition of miR-23a may be a strategy to rescue PGC-1? activity and ameliorate skeletal muscle mitochondrial function in ALS. PMID:22975021

  14. Activation of serum/glucocorticoid-induced kinase 1 (SGK1) is important to maintain skeletal muscle homeostasis and prevent atrophy

    PubMed Central

    Andres-Mateos, Eva; Brinkmeier, Heinrich; Burks, Tyesha N; Mejias, Rebeca; Files, Daniel C; Steinberger, Martin; Soleimani, Arshia; Marx, Ruth; Simmers, Jessica L; Lin, Benjamin; Finanger Hedderick, Erika; Marr, Tom G; Lin, Brian M; Hourdé, Christophe; Leinwand, Leslie A; Kuhl, Dietmar; Föller, Michael; Vogelsang, Silke; Hernandez-Diaz, Ivan; Vaughan, Dana K; Alvarez de la Rosa, Diego; Lang, Florian; Cohn, Ronald D

    2013-01-01

    Maintaining skeletal muscle mass is essential for general health and prevention of disease progression in various neuromuscular conditions. Currently, no treatments are available to prevent progressive loss of muscle mass in any of these conditions. Hibernating mammals are protected from muscle atrophy despite prolonged periods of immobilization and starvation. Here, we describe a mechanism underlying muscle preservation and translate it to non-hibernating mammals. Although Akt has an established role in skeletal muscle homeostasis, we find that serum- and glucocorticoid-inducible kinase 1 (SGK1) regulates muscle mass maintenance via downregulation of proteolysis and autophagy as well as increased protein synthesis during hibernation. We demonstrate that SGK1 is critical for the maintenance of skeletal muscle homeostasis and function in non-hibernating mammals in normal and atrophic conditions such as starvation and immobilization. Our results identify a novel therapeutic target to combat loss of skeletal muscle mass associated with muscle degeneration and atrophy. PMID:23161797

  15. Nutrient Excess and AMPK Downregulation in Incubated Skeletal Muscle and Muscle of Glucose Infused Rats

    PubMed Central

    Valentine, Rudy J.; Petrocelli, Robert; Schultz, Vera; Brandon, Amanda; Cooney, Gregory J.; Kraegen, Edward W.; Ruderman, Neil B.; Saha, Asish K.

    2015-01-01

    We have previously shown that incubation for 1h with excess glucose or leucine causes insulin resistance in rat extensor digitorum longus (EDL) muscle by inhibiting AMP-activated protein kinase (AMPK). To examine the events that precede and follow these changes, studies were performed in rat EDL incubated with elevated levels of glucose or leucine for 30min-2h. Incubation in high glucose (25mM) or leucine (100?M) significantly diminished AMPK activity by 50% within 30min, with further decreases occurring at 1 and 2h. The initial decrease in activity at 30min coincided with a significant increase in muscle glycogen. The subsequent decreases at 1h were accompanied by phosphorylation of ?AMPK at Ser485/491, and at 2h by decreased SIRT1 expression and increased PP2A activity, all of which have previously been shown to diminish AMPK activity. Glucose infusion in vivo, which caused several fold increases in plasma glucose and insulin, produced similar changes but with different timing. Thus, the initial decrease in AMPK activity observed at 3h was associated with changes in Ser485/491 phosphorylation and SIRT1 expression and increased PP2A activity was a later event. These findings suggest that both ex vivo and in vivo, multiple factors contribute to fuel-induced decreases in AMPK activity in skeletal muscle and the insulin resistance that accompanies it. PMID:25996822

  16. Effects of microgravity on myogenic factor expressions during postnatal development of rat skeletal muscle

    NASA Technical Reports Server (NTRS)

    Inobe, Manabu; Inobe, Ikuko; Adams, Gregory R.; Baldwin, Kenneth M.; Takeda, Shin'Ichi

    2002-01-01

    To clarify the role of gravity in the postnatal development of skeletal muscle, we exposed neonatal rats at 7 days of age to microgravity. After 16 days of spaceflight, tibialis anterior, plantaris, medial gastrocnemius, and soleus muscles were removed from the hindlimb musculature and examined for the expression of MyoD-family transcription factors such as MyoD, myogenin, and MRF4. For this purpose, we established a unique semiquantitative method, based on RT-PCR, using specific primers tagged with infrared fluorescence. The relative expression of MyoD in the tibialis anterior and plantaris muscles and that of myogenin in the plantaris and soleus muscles were significantly reduced (P < 0.001) in the flight animals. In contrast, MRF4 expression was not changed in any muscle. These results suggest that MyoD and myogenin, but not MRF4, are sensitive to gravity-related stimuli in some skeletal muscles during postnatal development.

  17. Insights into the molecular mechanism of glucose metabolism regulation under stress in chicken skeletal muscle tissues.

    PubMed

    Liu, Wuyi; Zhao, Jingpeng

    2014-07-01

    As substantial progress has been achieved in modern poultry production with large-scale and intensive feeding and farming in recent years, stress becomes a vital factor affecting chicken growth, development, and production yield, especially the quality and quantity of skeletal muscle mass. The review was aimed to outline and understand the stress-related genetic regulatory mechanism, which significantly affects glucose metabolism regulation in chicken skeletal muscle tissues. Progress in current studies was summarized relevant to the molecular mechanism and regulatory pathways of glucose metabolism regulation under stress in chicken skeletal muscle tissues. Particularly, the elucidation of those concerned pathways promoted by insulin and insulin receptors would give key clues to the understanding of biological processes of stress response and glucose metabolism regulation under stress, as well as their later effects on chicken muscle development. PMID:24955006

  18. Stretch-induced prostaglandins and protein turnover in cultured skeletal muscle

    NASA Technical Reports Server (NTRS)

    Vandenburgh, Herman H.; Hatfaludy, Sophia; Sohar, Istvan; Shansky, Janet

    1990-01-01

    The purpose of the study is to determine whether mechanical stimulation of cultured muscle cells influences prostaglandin efflux rates and whether they are related to stretch-induced alterations in protein turnover rates. The materials and methods of the experiment, including cell cultures, mechanical stimulation, protein synthesis, and degradation assays are outlined, and emphasis is placed on the effect of short-term mechanical stimulation in basal medium prostaglandin efflux from cultured skeletal muscle and stretch-induced alterations in prostaglandins efflux in complete medium. The major finding of the study is that mechanical stimulation of tissue-cultured skeletal-muscle cells under conditions inducing skeletal-muscle hypertropy increases the efflux of PGE(2) and PGE(2-alpha) but not 6-keto-PGF(1-alpha), the prostacyclin product.

  19. Transcriptional regulation of IGF-I expression in skeletal muscle

    NASA Technical Reports Server (NTRS)

    McCall, G. E.; Allen, D. L.; Haddad, F.; Baldwin, K. M.

    2003-01-01

    The present study investigated the role of transcription in the regulation of insulin-like growth factor (IGF)-I expression in skeletal muscle. RT-PCR was used to determine endogenous expression of IGF-I pre-mRNA and mRNA in control (Con) and functionally overloaded (FO) rat plantaris. The transcriptional activities of five different-length IGF-I promoter fragments controlling transcription of a firefly luciferase (FLuc) reporter gene were tested in vitro by transfection of myoblasts or in vivo during FO by direct gene transfer into the plantaris. Increased endogenous IGF-I gene transcription during 7 days of plantaris FO was evidenced by an approximately 140-160% increase (P < 0.0001) in IGF-I pre-mRNA (a transcriptional marker). IGF-I mRNA expression also increased by approximately 90% (P < 0.0001), and it was correlated (R = 0.93; P < 0.0001) with the pre-mRNA increases. The three longest IGF-I exon 1 promoters induced reporter gene expression in proliferating C2C12 and L6E9 myoblasts. In differentiated L6E9 myotubes, promoter activity increased approximately two- to threefold over myoblasts. Overexpression of calcineurin and MyoD increased the activity of the -852/+192 promoter in C2C12 myotubes by approximately 5- and approximately 18-fold, respectively. However, FO did not induce these exogenous promoter fragments. Nevertheless, the present findings are consistent with the hypothesis that the IGF-I gene is transcriptionally regulated during muscle hypertrophy in vivo as evidenced by the induction of the endogenous IGF-I pre-mRNA during plantaris FO. The exon 1 promoter region of the IGF-I gene is sufficient to direct inducible expression in vitro; however, an in vivo response to FO may require elements outside the -852/+346 region of the exon 1 IGF-I promoter or features inherent to the endogenous IGF-I gene.

  20. Study of Muscle Cell Dedifferentiation after Skeletal Muscle Injury of Mice with a Cre-Lox System

    PubMed Central

    Mu, Xiaodong; Peng, Hairong; Pan, Haiying; Huard, Johnny; Li, Yong

    2011-01-01

    Background Dedifferentiation of muscle cells in the tissue of mammals has yet to be observed. One of the challenges facing the study of skeletal muscle cell dedifferentiation is the availability of a reliable model that can confidentially distinguish differentiated cell populations of myotubes and non-fused mononuclear cells, including stem cells that can coexist within the population of cells being studied. Methodology/Principal Findings In the current study, we created a Cre/Lox-?-galactosidase system, which can specifically tag differentiated multinuclear myotubes and myotube-generated mononuclear cells based on the activation of the marker gene, ?-galactosidase. By using this system in an adult mouse model, we found that ?-galactosidase positive mononuclear cells were generated from ?-galactosidase positive multinuclear myofibers upon muscle injury. We also demonstrated that these mononuclear cells can develop into a variety of different muscle cell lineages, i.e., myoblasts, satellite cells, and muscle derived stem cells. Conclusions/Significance These novel findings demonstrated, for the first time, that cellular dedifferentiation of skeletal muscle cells actually occurs in mammalian skeletal muscle following traumatic injury in vivo. PMID:21304901

  1. Gene expression changes controlling distinct adaptations in the heart and skeletal muscle of a hibernating mammal.

    PubMed

    Vermillion, Katie L; Anderson, Kyle J; Hampton, Marshall; Andrews, Matthew T

    2015-03-01

    Throughout the hibernation season, the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) experiences extreme fluctuations in heart rate, metabolism, oxygen consumption, and body temperature, along with prolonged fasting and immobility. These conditions necessitate different functional requirements for the heart, which maintains contractile function throughout hibernation, and the skeletal muscle, which remains largely inactive. The adaptations used to maintain these contractile organs under such variable conditions serves as a natural model to study a variety of medically relevant conditions including heart failure and disuse atrophy. To better understand how two different muscle tissues maintain function throughout the extreme fluctuations of hibernation we performed Illumina HiSeq 2000 sequencing of cDNAs to compare the transcriptome of heart and skeletal muscle across the circannual cycle. This analysis resulted in the identification of 1,076 and 1,466 differentially expressed genes in heart and skeletal muscle, respectively. In both heart and skeletal muscle we identified a distinct cold-tolerant mechanism utilizing peroxisomal metabolism to make use of elevated levels of unsaturated depot fats. The skeletal muscle transcriptome also shows an early increase in oxidative capacity necessary for the altered fuel utilization and increased oxygen demand of shivering. Expression of the fetal gene expression profile is used to maintain cardiac tissue, either through increasing myocyte size or proliferation of resident cardiomyocytes, while skeletal muscle function and mass are protected through transcriptional regulation of pathways involved in protein turnover. This study provides insight into how two functionally distinct muscles maintain function under the extreme conditions of mammalian hibernation. PMID:25572546

  2. Ursolic acid ameliorates aging-metabolic phenotype through promoting of skeletal muscle rejuvenation.

    PubMed

    Bakhtiari, Nuredin; Hosseinkhani, Saman; Tashakor, Amin; Hemmati, Roohullah

    2015-07-01

    Ursolic acid (UA) is a lipophilic compound, which highly found in apple peels. UA has some certain features, of the most important is its anabolic effects on skeletal muscles, which in turn plays a prominent role in the aging process, encouraged us to evaluate skeletal muscle rejuvenation. This study seeks to address the two following questions: primarily, we wonder to know if UA increases anti-aging biomarkers (SIRT1 and PGC-1?) in the isolated satellite cells, to pave the way for satellite cells proliferation. The results revealed that UA elevated the expression of SIRT1 (? 35 folds) and PGC-1? (? 175 folds) genes. The other question that needs to be asked, however, is to understand whether it is possible to generalize the in vitro findings to in vivo. For this, a study was designed to investigate the effects of UA on the cellular energy status in the animal models (C57BL/6 mice). We found that UA decreased cellular energy charges such as ATP (? 3 times) and ADP (? 18 times). With respect to the role of UA in energy expenditure and as an anti-aging biomarker, one might wonder to elucidate skeletal muscle rejuvenation as well as satellite cells proliferation and neomyogenesis. The results illustrated that UA boosted neomyogenesis through enhancing the number of satellite cells. In addition, rejuvenation effects of UA on the skeletal muscle promptly encouraged us to reexamine the performance of skeletal muscles. The results indicated that UA through increasing myoglobin expression (? 2 folds) accompanied with transforming of glycolytic to fast oxidative status chiefly and slow-twitch muscle fibers. To the best of our knowledge, it seems that UA might be considered as a potential candidate for treatment of pathological conditions associated with muscular atrophy and dysfunction, including skeletal muscle atrophy, amyotrophic lateral sclerosis (ALS), sarcopenia and metabolic diseases of the muscles. PMID:25976755

  3. Endothelial, cardiac muscle and skeletal muscle exhibit different viscous and elastic properties as determined by atomic force microscopy

    NASA Technical Reports Server (NTRS)

    Mathur, A. B.; Collinsworth, A. M.; Reichert, W. M.; Kraus, W. E.; Truskey, G. A.

    2001-01-01

    This study evaluated the hypothesis that, due to functional and structural differences, the apparent elastic modulus and viscous behavior of cardiac and skeletal muscle and vascular endothelium would differ. To accurately determine the elastic modulus, the contribution of probe velocity, indentation depth, and the assumed shape of the probe were examined. Hysteresis was observed at high indentation velocities arising from viscous effects. Irreversible deformation was not observed for endothelial cells and hysteresis was negligible below 1 microm/s. For skeletal muscle and cardiac muscle cells, hysteresis was negligible below 0.25 microm/s. Viscous dissipation for endothelial and cardiac muscle cells was higher than for skeletal muscle cells. The calculated elastic modulus was most sensitive to the assumed probe geometry for the first 60 nm of indentation for the three cell types. Modeling the probe as a blunt cone-spherical cap resulted in variation in elastic modulus with indentation depth that was less than that calculated by treating the probe as a conical tip. Substrate contributions were negligible since the elastic modulus reached a steady value for indentations above 60 nm and the probe never indented more than 10% of the cell thickness. Cardiac cells were the stiffest (100.3+/-10.7 kPa), the skeletal muscle cells were intermediate (24.7+/-3.5 kPa), and the endothelial cells were the softest with a range of elastic moduli (1.4+/-0.1 to 6.8+/-0.4 kPa) depending on the location of the cell surface tested. Cardiac and skeletal muscle exhibited nonlinear elastic behavior. These passive mechanical properties are generally consistent with the function of these different cell types.

  4. Bone and skeletal muscle: Key players in mechanotransduction and potential overlapping mechanisms.

    PubMed

    Goodman, Craig A; Hornberger, Troy A; Robling, Alexander G

    2015-11-01

    The development and maintenance of skeletal muscle and bone mass is critical for movement, health and issues associated with the quality of life. Skeletal muscle and bone mass are regulated by a variety of factors that include changes in mechanical loading. Moreover, bone mass is, in large part, regulated by muscle-derived mechanical forces and thus by changes in muscle mass/strength. A thorough understanding of the cellular mechanism(s) responsible for mechanotransduction in bone and skeletal muscle is essential for the development of effective exercise and pharmaceutical strategies aimed at increasing, and/or preventing the loss of, mass in these tissues. Thus, in this review we will attempt to summarize the current evidence for the major molecular mechanisms involved in mechanotransduction in skeletal muscle and bone. By examining the differences and similarities in mechanotransduction between these two tissues, it is hoped that this review will stimulate new insights and ideas for future research and promote collaboration between bone and muscle biologists.(1). PMID:26453495

  5. Defective Natriuretic Peptide Receptor Signaling in Skeletal Muscle Links Obesity to Type 2 Diabetes.

    PubMed

    Coué, Marine; Badin, Pierre-Marie; Vila, Isabelle K; Laurens, Claire; Louche, Katie; Marquès, Marie-Adeline; Bourlier, Virginie; Mouisel, Etienne; Tavernier, Geneviève; Rustan, Arild C; Galgani, Jose E; Joanisse, Denis R; Smith, Steven R; Langin, Dominique; Moro, Cedric

    2015-12-01

    Circulating natriuretic peptide (NP) levels are reduced in obesity and predict the risk of type 2 diabetes (T2D). Since skeletal muscle was recently shown as a key target tissue of NP, we aimed to investigate muscle NP receptor (NPR) expression in the context of obesity and T2D. Muscle NPRA correlated positively with whole-body insulin sensitivity in humans and was strikingly downregulated in obese subjects and recovered in response to diet-induced weight loss. In addition, muscle NP clearance receptor (NPRC) increased in individuals with impaired glucose tolerance and T2D. Similar results were found in obese diabetic mice. Although no acute effect of brain NP (BNP) on insulin sensitivity was observed in lean mice, chronic BNP infusion improved blood glucose control and insulin sensitivity in skeletal muscle of obese and diabetic mice. This occurred in parallel with a reduced lipotoxic pressure in skeletal muscle due to an upregulation of lipid oxidative capacity. In addition, chronic NP treatment in human primary myotubes increased lipid oxidation in a PGC1?-dependent manner and reduced palmitate-induced lipotoxicity. Collectively, our data show that activation of NPRA signaling in skeletal muscle is important for the maintenance of long-term insulin sensitivity and has the potential to treat obesity-related metabolic disorders. PMID:26253614

  6. Skeletal muscle mass and quality: evolution of modern measurement concepts in the context of sarcopenia.

    PubMed

    Heymsfield, Steven B; Gonzalez, M Cristina; Lu, Jianhua; Jia, Guang; Zheng, Jolene

    2015-11-01

    The first reports of accurate skeletal muscle mass measurement in human subjects appeared at about the same time as introduction of the sarcopenia concept in the late 1980s. Since then these methods, computed tomography and MRI, have been used to gain insights into older (i.e. anthropometry and urinary markers) and more recently developed and refined methods (ultrasound, bioimpedance analysis and dual-energy X-ray absorptiometry) of quantifying regional and total body skeletal muscle mass. The objective of this review is to describe the evolution of these methods and their continued development in the context of sarcopenia evaluation and treatment. Advances in these technologies are described with a focus on additional quantifiable measures that relate to muscle composition and 'quality'. The integration of these collective evaluations with strength and physical performance indices is highlighted with linkages to evaluation of sarcopenia and the spectrum of related disorders such as sarcopenic obesity, cachexia and frailty. Our findings show that currently available methods and those in development are capable of non-invasively extending measures from solely 'mass' to quality evaluations that promise to close the gaps now recognised between skeletal muscle mass and muscle function, morbidity and mortality. As the largest tissue compartment in most adults, skeletal muscle mass and aspects of muscle composition can now be evaluated by a wide array of technologies that provide important new research and clinical opportunities aligned with the growing interest in the spectrum of conditions associated with sarcopenia. PMID:25851205

  7. Minimally invasive approach to the repair of injured skeletal muscle with a shape-memory scaffold.

    PubMed

    Wang, Lin; Cao, Lan; Shansky, Janet; Wang, Zheng; Mooney, David; Vandenburgh, Herman

    2014-08-01

    Repair of injured skeletal muscle by cell therapies has been limited by poor survival of injected cells. Use of a carrier scaffold delivering cells locally, may enhance in vivo cell survival, and promote skeletal muscle regeneration. Biomaterial scaffolds are often implanted into muscle tissue through invasive surgeries, which can result in trauma that delays healing. Minimally invasive approaches to scaffold implantation are thought to minimize these adverse effects. This hypothesis was addressed in the context of a severe mouse skeletal muscle injury model. A degradable, shape-memory alginate scaffold that was highly porous and compressible was delivered by minimally invasive surgical techniques to injured tibialis anterior muscle. The scaffold controlled was quickly rehydrated in situ with autologous myoblasts and growth factors (either insulin-like growth factor-1 (IGF-1) alone or IGF-1 with vascular endothelial growth factor (VEGF)). The implanted scaffolds delivering myoblasts and IGF-1 significantly reduced scar formation, enhanced cell engraftment, and improved muscle contractile function. The addition of VEGF to the scaffold further improved functional recovery likely through increased angiogenesis. Thus, the delivery of myoblasts and dual local release of VEGF and IGF-1 from degradable scaffolds implanted through a minimally invasive procedure effectively promoted the functional regeneration of injured skeletal muscle. PMID:24769909

  8. Magnetic resonance imaging of mouse skeletal muscle to measure denervation atrophy

    PubMed Central

    Zhang, Jiangyang; Zhang, Gang; Morrison, Brett; Mori, Susumu; Sheikh, Kazim A.

    2008-01-01

    We assessed the potential of different MRI measures to detect and quantify skeletal muscle changes with denervation in two mouse models of denervation/neurogenic atrophy. Acute complete denervation and chronic partial denervation were examined in calf muscles after sciatic nerve axotomy and in transgenic SOD1G93A mice, respectively. Serial T2, diffusion tensor, and high resolution anatomical images were acquired, and compared to behavioral, histological, and electrophysiological data. Increase in muscle T2 signal was first detected after sciatic nerve axotomy. Progressive muscle atrophy could be monitored with MRI-based volume measurements, which correlated strongly with postmortem muscle mass measurements. Significant increase in muscle fractional anisotropy and decreases in secondary and tertiary eigenvalues obtained from diffusion tensor imaging (DTI) were observed after denervation. In SOD1G93A animals, muscle denervation was detected by elevated muscle T2 and atrophy in the medial gastrocnemius at 10 weeks. Changes in T2 and muscle volume were first observed in medial gastrocnemius and later in other calf muscles. Alterations in secondary and tertiary eigenvalues obtained from DTI were first observed in tibialis anterior and medial gastrocnemius muscles at age 12 weeks. We propose that MRI of skeletal muscle is a sensitive surrogate outcome measure of denervation atrophy in animal models of neuromuscular disorders, with potential applicability in preclinical therapeutic screening studies in rodents. PMID:18571650

  9. Endurance training enhances skeletal muscle interleukin-15 in human male subjects.

    PubMed

    Rinnov, Anders; Yfanti, Christina; Nielsen, Søren; Akerström, Thorbjörn C A; Peijs, Lone; Zankari, Alaa; Fischer, Christian P; Pedersen, Bente K

    2014-03-01

    Regular endurance exercise promotes metabolic and oxidative changes in skeletal muscle. Overexpression of interleukin-15 (IL-15) in mice exerts similar metabolic changes in muscle as seen with endurance exercise. Muscular IL-15 production has been shown to increase in mice after weeks of regular endurance running. With the present study we aimed to determine if muscular IL-15 production would increase in human male subjects following 12 weeks of endurance training. In two different studies we obtained plasma and muscle biopsies from young healthy subjects performing: (1) 12 weeks of ergometer cycling exercise five times per week with plasma and biopsies before and after the intervention, and (2) 3 h of ergometer cycling exercise with plasma and biopsies before and after the exercise bout and well into recovery. We measured changes in plasma IL-15, muscle IL-15 mRNA and IL-15 protein. Twelve weeks of regular endurance training induced a 40% increase in basal skeletal muscle IL-15 protein content (p < 0.01), but with no changes in either muscle IL-15 mRNA or plasma IL-15 levels. However, an acute bout of 3-h exercise did not show significant changes in muscle IL-15 or plasma IL-15 levels. The induction of muscle IL-15 protein in humans following a regular training period supports previous findings in mice and emphasizes the hypothesis of IL-15 taking part in skeletal muscle adaptation during training. PMID:23649460

  10. Skeletal Muscle Satellite Cells: Background and Methods for Isolation and Analysis in a Primary Culture System

    PubMed Central

    Danoviz, Maria Elena; Yablonka-Reuveni, Zipora

    2012-01-01

    Summary Repair of adult skeletal muscle depends on satellite cells, myogenic stem cells located between the basal lamina and the plasmalemma of the myofiber. Standardized protocols for the isolation and culture of satellite cells are key tools for understanding cell autonomous and extrinsic factors that regulate their performance. Knowledge gained from such studies can contribute important insights to developing strategies for the improvement of muscle repair following trauma and in muscle wasting disorders. This chapter provides an introduction to satellite cell biology and further describes the basic protocol used in our laboratory to isolate and culture satellite cells from adult skeletal muscle. The cell culture conditions detailed herein support proliferation and differentiation of satellite cell progeny and the development of reserve cells, which are thought to reflect the in vivo self-renewal ability of satellite cells. Additionally, this chapter describes our standard immunostaining protocol that allows the characterization of satellite cell progeny by the temporal expression of characteristic transcription factors and structural proteins associated with different stages of myogenic progression. While emphasis is given here to the isolation and characterization of satellite cells from mouse hindlimb muscles, the protocols are suitable for other muscle types (such as diaphragm and extraocular muscles) and for muscles from other species, including chicken and rat. Altogether, the basic protocols described are straightforward and facilitate the study of diverse aspects of skeletal muscle stem cells. PMID:22130829

  11. Diacylglycerol kinase-? regulates AMPK signaling, lipid metabolism, and skeletal muscle energetics.

    PubMed

    Jiang, Lake Q; de Castro Barbosa, Thais; Massart, Julie; Deshmukh, Atul S; Löfgren, Lars; Duque-Guimaraes, Daniella E; Ozilgen, Arda; Osler, Megan E; Chibalin, Alexander V; Zierath, Juleen R

    2016-01-01

    Decrease of AMPK-related signal transduction and insufficient lipid oxidation contributes to the pathogenesis of obesity and type 2 diabetes. Previously, we identified that diacylglycerol kinase-? (DGK?), an enzyme involved in triglyceride biosynthesis, is reduced in skeletal muscle from type 2 diabetic patients. Here, we tested the hypothesis that DGK? plays a role in maintaining appropriate AMPK action in skeletal muscle and energetic aspects of contraction. Voluntary running activity was reduced in DGK?(+/-) mice, but glycogen content and mitochondrial markers were unaltered, suggesting that DGK? deficiency affects skeletal muscle energetics but not mitochondrial protein abundance. We next determined the role of DGK? in AMPK-related signal transduction and lipid metabolism in isolated skeletal muscle. AMPK activation and signaling were reduced in DGK?(+/-) mice, concomitant with impaired lipid oxidation and elevated incorporation of free fatty acids into triglycerides. Strikingly, DGK? deficiency impaired work performance, as evident by altered force production and relaxation dynamics in response to repeated contractions. In conclusion, DGK? deficiency impairs AMPK signaling and lipid metabolism, thereby highlighting the deleterious role of excessive lipid metabolites in the development of peripheral insulin resistance and type 2 diabetes pathogenesis. DGK? deficiency also influences skeletal muscle energetics, which may lead to low physical activity levels in type 2 diabetes. PMID:26530149

  12. Protein kinase C? promotes proliferation and induces malignant transformation in skeletal muscle

    PubMed Central

    Czifra, Gabriella; Szöll?si, Attila; Nagy, Zsuzsanna; Boros, Miklós; Juhász, István; Kiss, Andrea; Erd?di, Ferenc; Szabó, Tamás; Kovács, Ilona; Török, Miklós; Kovács, László; Blumberg, Peter M; Bíró, Tamás

    2015-01-01

    In this paper, we investigated the isoform-specific roles of certain protein kinase C (PKC) isoforms in the regulation of skeletal muscle growth. Here, we provide the first intriguing functional evidence that nPKC? (originally described as an inhibitor of proliferation in various cells types) is a key player in promoting both in vitro and in vivo skeletal muscle growth. Recombinant overexpression of a constitutively active nPKC? in C2C12 myoblast increased proliferation and inhibited differentiation. Conversely, overexpression of kinase-negative mutant of nPKC? (DN-nPKC?) markedly inhibited cell growth. Moreover, overexpression of nPKC? also stimulated in vivo tumour growth and induced malignant transformation in immunodeficient (SCID) mice whereas that of DN-nPKC? suppressed tumour formation. The role of nPKC? in the formation of rhabdomyosarcoma was also investigated where recombinant overexpression of nPKC? in human rhabdomyosarcoma RD cells also increased cell proliferation and enhanced tumour formation in mouse xenografts. The other isoforms investigated (PKC?, ?, ?) exerted only minor (mostly growth-inhibitory) effects in skeletal muscle cells. Collectively, our data introduce nPKC? as a novel growth-promoting molecule in skeletal muscles and invite further trials to exploit its therapeutic potential in the treatment of skeletal muscle malignancies. PMID:25283340

  13. Protein kinase C? promotes proliferation and induces malignant transformation in skeletal muscle.

    PubMed

    Czifra, Gabriella; Szöll?si, Attila; Nagy, Zsuzsanna; Boros, Miklós; Juhász, István; Kiss, Andrea; Erd?di, Ferenc; Szabó, Tamás; Kovács, Ilona; Török, Miklós; Kovács, László; Blumberg, Peter M; Bíró, Tamás

    2015-02-01

    In this paper, we investigated the isoform-specific roles of certain protein kinase C (PKC) isoforms in the regulation of skeletal muscle growth. Here, we provide the first intriguing functional evidence that nPKC? (originally described as an inhibitor of proliferation in various cells types) is a key player in promoting both in vitro and in vivo skeletal muscle growth. Recombinant overexpression of a constitutively active nPKC? in C2C12 myoblast increased proliferation and inhibited differentiation. Conversely, overexpression of kinase-negative mutant of nPKC? (DN-nPKC?) markedly inhibited cell growth. Moreover, overexpression of nPKC? also stimulated in vivo tumour growth and induced malignant transformation in immunodeficient (SCID) mice whereas that of DN-nPKC? suppressed tumour formation. The role of nPKC? in the formation of rhabdomyosarcoma was also investigated where recombinant overexpression of nPKC? in human rhabdomyosarcoma RD cells also increased cell proliferation and enhanced tumour formation in mouse xenografts. The other isoforms investigated (PKC?, ?, ?) exerted only minor (mostly growth-inhibitory) effects in skeletal muscle cells. Collectively, our data introduce nPKC? as a novel growth-promoting molecule in skeletal muscles and invite further trials to exploit its therapeutic potential in the treatment of skeletal muscle malignancies. PMID:25283340

  14. Cytokine expression and secretion by skeletal muscle cells: regulatory mechanisms and exercise effects.

    PubMed

    Peake, Jonathan M; Della Gatta, Paul; Suzuki, Katsuhiko; Nieman, David C

    2015-01-01

    Cytokines are important mediators of various aspects of health and disease, including appetite, glucose and lipid metabolism, insulin sensitivity, skeletal muscle hypertrophy and atrophy. Over the past decade or so, considerable attention has focused on the potential for regular exercise to counteract a range of disease states by modulating cytokine production. Exercise stimulates moderate to large increases in the circulating concentrations of interleukin (IL)-6, IL-8, IL- 10, IL-1 receptor antagonist, granulocyte-colony stimulating factor, and smaller increases in tumor necrosis factor-?, monocyte chemotactic protein-1, IL-1?, brain-derived neurotrophic factor, IL-12p35/p40 and IL-15. Although many of these cytokines are also expressed in skeletal muscle, not all are released from skeletal muscle into the circulation during exercise. Conversely, some cytokines that are present in the circulation are not expressed in skeletal muscle after exercise. The reasons for these discrepant cytokine responses to exercise are unclear. In this review, we address these uncertainties by summarizing the capacity of skeletal muscle cells to produce cytokines, analyzing other potential cellular sources of circulating cytokines during exercise, and discussing the soluble factors and intracellular signaling pathways that regulate cytokine synthesis (e.g., RNA-binding proteins, microRNAs, suppressor of cytokine signaling proteins, soluble receptors). PMID:25826432

  15. Triennial Growth Symposium--A role for vitamin D in skeletal muscle development and growth.

    PubMed

    Starkey, J D

    2014-03-01

    Although well known for its role in bone development and mineral homeostasis, there is emerging evidence that vitamin D is capable of functioning as a regulator of skeletal muscle development and hypertrophic growth. This review will focus on the relatively limited body of evidence regarding the impact of vitamin D on prenatal development and postnatal growth of skeletal muscle in meat animal species. Recent evidence indicating that improvement of maternal vitamin D status through dietary 25-hydroxycholecalciferol supplementation can positively affect fetal skeletal muscle fiber number and myoblast activity in swine as well as work demonstrating that posthatch vitamin D status enhancement stimulates a satellite cell-mediated skeletal muscle hypertrophy response in broiler chickens is discussed. The relative lack of information regarding how and when to best supply dietary vitamin D to promote optimal prenatal development and postnatal growth of skeletal muscle provides an exciting field of research. Expansion of knowledge in this area will ultimately improve our ability to efficiently and effectively produce the livestock required to meet the increasing worldwide demand for meat products. PMID:24243904

  16. Tetracycline-inducible system for regulation of skeletal muscle-specific gene expression in transgenic mice

    NASA Technical Reports Server (NTRS)

    Grill, Mischala A.; Bales, Mark A.; Fought, Amber N.; Rosburg, Kristopher C.; Munger, Stephanie J.; Antin, Parker B.

    2003-01-01

    Tightly regulated control of over-expression is often necessary to study one aspect or time point of gene function and, in transgenesis, may help to avoid lethal effects and complications caused by ubiquitous over-expression. We have utilized the benefits of an optimized tet-on system and a modified muscle creatine kinase (MCK) promoter to generate a skeletal muscle-specific, doxycycline (Dox) controlled over-expression system in transgenic mice. A DNA construct was generated in which the codon optimized reverse tetracycline transactivator (rtTA) was placed under control of a skeletal muscle-specific version of the mouse MCK promoter. Transgenic mice containing this construct expressed rtTA almost exclusively in skeletal muscles. These mice were crossed to a second transgenic line containing a bi-directional promoter centered on a tet responder element driving both a luciferase reporter gene and a tagged gene of interest; in this case the calpain inhibitor calpastatin. Compound hemizygous mice showed high level, Dox dependent muscle-specific luciferase activity often exceeding 10,000-fold over non-muscle tissues of the same mouse. Western and immunocytochemical analysis demonstrated similar Dox dependent muscle-specific induction of the tagged calpastatin protein. These findings demonstrate the effectiveness and flexibility of the tet-on system to provide a tightly regulated over-expression system in adult skeletal muscle. The MCKrtTA transgenic lines can be combined with other transgenic responder lines for skeletal muscle-specific over-expression of any target gene of interest.

  17. Characterising skeletal muscle under large strain using eccentric and Fourier Transform-rheology.

    PubMed

    Tan, Kristy; Cheng, Shaokoon; Jugé, Lauriane; Bilston, Lynne E

    2015-11-01

    Characterising the passive anisotropic properties of soft tissues has been largely limited to the linear viscoelastic regime and shear loading is rarely done in the large deformation regime, despite the physiological significance of such properties. This paper demonstrates the use of eccentric rheology, which allows the anisotropy of skeletal muscle to be investigated. The large amplitude oscillatory strain properties of skeletal muscle were also investigated using Fourier Transform-rheology. Histology was used to qualitatively assess the microstructure changes induced by large strain. Results showed that skeletal muscle was strongly anisotropic in the linear regime. The storage and loss moduli were found to be significantly different (p<0.05) between the three fibre alignment groups; for the group tested with fibres perpendicular to plane of shear was 12.3±1.3kPa and 3.0±0.35kPa, parallel to shear direction was 10.6±1.2kPa and 2.4±0.23kPa, and perpendicular to shear direction was 5.5±0.90kPa and 1.3±0.21kPa. The appearance and growth of higher order harmonics at large strain was different in the three testing directions indicating that the anisotropy of muscle affects skeletal muscle behaviour in the nonlinear regime. Histological analysis showed an increasing destruction of extracellular matrix and the rearrangement of fibres with increasing strain indicating mechanical damage at strains of larger than 10%. These microstructural changes could contribute to the complex nonlinear behaviour in skeletal muscle. This paper demonstrates a method of characterising the anisotropic properties in skeletal muscle under large strain whilst giving meaningful information on the physical response of tissue at various strains. PMID:26433920

  18. A Mathematical Model of Oxygen Transport in Skeletal Muscle During Hindlimb Unloading

    NASA Technical Reports Server (NTRS)

    Causey, Laura; Lewandowski, Beth E.; Weinbaum, Sheldon

    2014-01-01

    During hindlimb unloading (HU) dramatic fluid shifts occur within minutes of the suspension, leading to a less precise matching of blood flow to O2 demands of skeletal muscle. Vascular resistance directs blood away from certain muscles, such as the soleus (SOL). The muscle volume gradually reduces in these muscles so that eventually the relative blood flow returns to normal. It is generally believed that muscle volume change is not due to O2 depletion, but a consequence of disuse. However, the volume of the unloaded rat muscle declines over the course of weeks, whereas the redistribution of blood flow occurs immediately. Using a Krogh Cylinder Model, the distribution of O2 was predicted in two skeletal muscles: SOL and gastrocnemius (GAS). Effects of the muscle blood flow, volume, capillary density, and O2 uptake, are included to calculate the pO2 at rest and after 10 min and 15 days of unloading. The model predicts that 32 percent of the SOL muscle tissue has a pO2 1.25 mm Hg within 10 min, whereas the GAS maintains normal O2 levels, and that equilibrium is reached only as the SOL muscle cells degenerate. The results provide evidence that there is an inadequate O2 supply to the mitochondria in the SOL muscle after 10 min HU.

  19. The Pleiotropic Effect of Physical Exercise on Mitochondrial Dynamics in Aging Skeletal Muscle

    PubMed Central

    Barbieri, Elena; Agostini, Deborah; Polidori, Emanuela; Potenza, Lucia; Guescini, Michele; Lucertini, Francesco; Annibalini, Giosuè; Stocchi, Laura; De Santi, Mauro; Stocchi, Vilberto

    2015-01-01

    Decline in human muscle mass and strength (sarcopenia) is one of the principal hallmarks of the aging process. Regular physical exercise and training programs are certain powerful stimuli to attenuate the physiological skeletal muscle alterations occurring during aging and contribute to promote health and well-being. Although the series of events that led to these muscle adaptations are poorly understood, the mechanisms that regulate these processes involve the “quality” of skeletal muscle mitochondria. Aerobic/endurance exercise helps to maintain and improve cardiovascular fitness and respiratory function, whereas strength/resistance-exercise programs increase muscle strength, power development, and function. Due to the different effect of both exercises in improving mitochondrial content and quality, in terms of biogenesis, dynamics, turnover, and genotype, combined physical activity programs should be individually prescribed to maximize the antiaging effects of exercise. PMID:25945152

  20. Macrophage Plasticity and the Role of Inflammation in Skeletal Muscle Repair

    PubMed Central

    Kharraz, Yacine; Guerra, Joana; Mann, Christopher J.; Serrano, Antonio L.; Muñoz-Cánoves, Pura

    2013-01-01

    Effective repair of damaged tissues and organs requires the coordinated action of several cell types, including infiltrating inflammatory cells and resident cells. Recent findings have uncovered a central role for macrophages in the repair of skeletal muscle after acute damage. If damage persists, as in skeletal muscle pathologies such as Duchenne muscular dystrophy (DMD), macrophage infiltration perpetuates and leads to progressive fibrosis, thus exacerbating disease severity. Here we discuss how dynamic changes in macrophage populations and activation states in the damaged muscle tissue contribute to its efficient regeneration. We describe how ordered changes in macrophage polarization, from M1 to M2 subtypes, can differently affect muscle stem cell (satellite cell) functions. Finally, we also highlight some of the new mechanisms underlying macrophage plasticity and briefly discuss the emerging implications of lymphocytes and other inflammatory cell types in normal versus pathological muscle repair. PMID:23509419

  1. Absolute quantitative profiling of the key metabolic pathways in slow and fast skeletal muscle.

    PubMed

    Rakus, Dariusz; Gizak, Agnieszka; Deshmukh, Atul; Wi?niewski, Jacek R

    2015-03-01

    Slow and fast skeletal muscles are composed of, respectively, mainly oxidative and glycolytic muscle fibers, which are the basic cellular motor units of the motility apparatus. They largely differ in excitability, contraction mechanism, and metabolism. Because of their pivotal role in body motion and homeostasis, the skeletal muscles have been extensively studied using biochemical and molecular biology approaches. Here we describe a simple analytical and computational approach to estimate titers of enzymes of basic metabolic pathways and proteins of the contractile machinery in the skeletal muscles. Proteomic analysis of mouse slow and fast muscles allowed estimation of the titers of enzymes involved in the carbohydrate, lipid, and energy metabolism. Notably, we observed that differences observed between the two muscle types occur simultaneously for all proteins involved in a specific process such as glycolysis, free fatty acid catabolism, Krebs cycle, or oxidative phosphorylation. These differences are in a good agreement with the well-established biochemical picture of the muscle types. We show a correlation between maximal activity and the enzyme titer, suggesting that change in enzyme concentration is a good proxy for its catalytic potential in vivo. As a consequence, proteomic profiling of enzyme titers can be used to monitor metabolic changes in cells. Additionally, quantitative data of structural proteins allowed studying muscle type specific cell architecture and its remodeling. The presented proteomic approach can be applied to study metabolism in any other tissue or cell line. PMID:25597705

  2. Pointed-end capping by tropomodulin modulates actomyosin crossbridge formation in skeletal muscle fibers

    PubMed Central

    Ochala, Julien; Gokhin, David S.; Iwamoto, Hiroyuki; Fowler, Velia M.

    2014-01-01

    In skeletal muscle, thick and thin filaments are arranged in a myofibrillar lattice. Tropomodulin 1 (Tmod1) is a pointed-end capping and tropomyosin-binding protein that controls thin-filament assembly, stability, and lengths. It remains unknown whether Tmods have other functional roles, such as regulating muscle contractility. To investigate this, we recorded and analyzed the mechanical properties and X-ray diffraction patterns of single membrane-permeabilized skeletal muscle fibers from mice lacking Tmod1. Results show that absence of Tmod1 and its replacement by Tmod3 and Tmod4 may impair initial tropomyosin movement over actin subunits during thin-filament activation, thus reducing both the fraction of actomyosin crossbridges in the strongly bound state (?29%) and fiber force-generating capacity (?31%). Therefore, Tmods are novel regulators of actomyosin crossbridge formation and muscle contractility, and future investigations and models of skeletal muscle force production must incorporate Tmods.—Ochala, J., Gokhin, D. S., Iwamoto, H., Fowler, V. M. Pointed-end capping by tropomodulin modulates actomyosin crossbridge formation in skeletal muscle fibers. PMID:24072783

  3. Skeletal Muscle an Active Compartment in the Sequestering and Metabolism of Doxorubicin Chemotherapy

    PubMed Central

    Fabris, Sergio; MacLean, David A.

    2015-01-01

    Doxorubicin remains one of the most widely used chemotherapeutic agents however its effect on healthy tissue, such as skeletal muscle, remains poorly understood. The purpose of the current study was to examine the accumulation of doxorubicin (DOX) and its metabolite doxorubicinol (DOXol) in skeletal muscle of the rat up to 8 days after the administration of a 1.5 or 4.5 mg kg-1 i.p. dose. Subsequent to either dose, DOX and DOXol were observed in skeletal muscle throughout the length of the experiment. Interestingly an efflux of DOX was examined after 96 hours, followed by an apparent re-uptake of the drug which coincided with a spike and rapid decrease of plasma DOX concentrations. The interstitial space within the muscle did not appear to play a significant rate limiting compartment for the uptake or release of DOX or DOXol from the tissue to the circulation. Furthermore, there was no evidence that DOX preferentially accumulated in a specific muscle group with either dose. It appears that the sequestering of drug in skeletal muscle plays an acute and important role in the systemic availability and metabolism of DOX which may have a greater impact on the clinical outcome than previously considered. PMID:26401619

  4. Cardiac assistance from skeletal muscle: a critical appraisal of the various approaches

    PubMed Central

    Salmons, Stanley; Jarvis, Jonathan C

    1992-01-01

    We review here various ways in which cardiac assistance might be derived from a patient's own skeletal muscle. Calculations based on experimental data and optimistic estimates of the efficiency of the energy conversions involved suggest that the continuous assist available would be limited to about 2 litres a minute if a muscle were used to energise an electromechanical device. It would be more efficient to couple the energy mechanically or hydraulically, but these approaches still pose problems of anatomical placement, muscle attachment, fluid leakage, and cost. Unless these issues can be addressed, the use of skeletal muscle as an internal power source for mechanical circulatory assist devices will remain an unworkable concept. Configurations that couple skeletal muscle contraction directly to the circulation would be more efficient and less costly. In terms of the energy available, a skeletal muscle ventricle could be designed to provide a continuous partial assist of 1–21/min, with flows of up to 8 1/min sustainable for limited periods. Such an approach offers new possibilities for the surgical treatment of chronic cardiac failure. PMID:1389770

  5. Glucose-dependent insulinotropic polypeptide directly induces glucose transport in rat skeletal muscle.

    PubMed

    Snook, Laelie A; Nelson, Emery M; Dyck, David J; Wright, David C; Holloway, Graham P

    2015-08-01

    Several gastrointestinal proteins have been identified to have insulinotropic effects, including glucose-dependent insulinotropic polypeptide (GIP); however, the direct effects of incretins on skeletal muscle glucose transport remain largely unknown. Therefore, the purpose of the current study was to examine the role of GIP on skeletal muscle glucose transport and insulin signaling in rats. Relative to a glucose challenge, a mixed glucose+lipid oral challenge increased circulating GIP concentrations, skeletal muscle Akt phosphorylation, and improved glucose clearance by ?35% (P < 0.05). These responses occurred without alterations in serum insulin concentrations. In an incubated soleus muscle preparation, GIP directly stimulated glucose transport and increased GLUT4 accumulation on the plasma membrane in the absence of insulin. Moreover, the ability of GIP to stimulate glucose transport was mitigated by the addition of the PI 3-kinase (PI3K) inhibitor wortmannin, suggesting that signaling through PI3K is required for these responses. We also provide evidence that the combined stimulatory effects of GIP and insulin on soleus muscle glucose transport are additive. However, the specific GIP receptor antagonist (Pro(3))GIP did not attenuate GIP-stimulated glucose transport, suggesting that GIP is not signaling through its classical receptor. Together, the current data provide evidence that GIP regulates skeletal muscle glucose transport; however, the exact signaling mechanism(s) remain unknown. PMID:26041107

  6. Use It or Lose It: Skeletal Muscle Function and Performance Results from Space Shuttle

    NASA Technical Reports Server (NTRS)

    Ryder, Jeffrey

    2011-01-01

    The Space Shuttle Program provided a wealth of valuable information regarding the adaptations of skeletal muscle to weightlessness. Studies conducted during the Extended Duration Orbiter Medical Project (EDOMP) represented ground breaking work on the effects of spaceflight on muscle form and function from applied human research to cellular adaptations. Results from detailed supplementary objective (DSO) 477 demonstrated that muscle strength losses could occur rapidly in response to short-duration spaceflight. The effects of spaceflight-induced unloading were primarily restricted to postural muscles such as those of the back as well as the knee extensors. DSO 606 provided evidence from MRI that the observed strength losses were partially accounted for by a reduction in the size of the individual muscles. Muscle biopsy studies conducted during DSO 475 were able to show muscle atrophy in individual muscle fibers from the quadriceps muscles. Reduced quadriceps muscle size and strength was also observed during the 17-d Life and Microgravity Spacelab mission aboard STS-78. Multiple maximal strength tests were conducted in flight on the calf muscles and it has been hypothesized that these high force contractions may have acted as a countermeasure. Muscle fiber mechanics were studied on calf muscle samples pre- and postflight. While some responses were crewmember specific, the general trend was that muscle fiber force production dropped and shortening velocity increased. The increased shortening velocity helped to maintain muscle fiber power. Numerous rodent studies performed during Shuttle missions suggest that many of the effects reported in Shuttle crewmembers could be due to lesions in the cellular signaling pathways that stimulate protein synthesis as well as an increase in the mechanisms that up-regulate protein breakdown. The results have important implications regarding the overall health and performance capabilities of future crewmembers that will venture beyond low-Earth orbit. Learning Objective: Overview of the Space Shuttle Program regarding adaptive changes in skeletal muscle function and performance, including what was learned from research and what was implemented for countermeasures.

  7. Implications of skeletal muscle loss for public health nutrition messages: a brief report.

    PubMed

    Levy, Louis B; Welch, Ailsa A

    2015-11-01

    Age-related skeletal muscle loss, sarcopenia, cachexia and wider malnutrition (under nutrition) are complex in aetiology with interaction of clinical, social and economic factors. Weight loss and loss of skeletal muscle mass in older people are associated with increased morbidity and mortality with implications for increasing health and social care costs. There is insufficient evidence to identify the ideal treatment options. However, preventing weight loss and loss of skeletal muscle in older age will be keys to reducing morbidity and mortality. This will require all those coming into contact with older people to identify and address weight loss early, including through diet, improving physical activity and increasing social interaction. Public health messages on diet should, in the main, continue to focus on older people achieving current UK dietary recommendations for their age as visually depicted in the eatwell plate together with associated messages regarding dietary supplements where appropriate. PMID:26062652

  8. Molecular mechanisms for mitochondrial adaptation to exercise training in skeletal muscle.

    PubMed

    Drake, Joshua C; Wilson, Rebecca J; Yan, Zhen

    2016-01-01

    Exercise training enhances physical performance and confers health benefits, largely through adaptations in skeletal muscle. Mitochondrial adaptation, encompassing coordinated improvements in quantity (content) and quality (structure and function), is increasingly recognized as a key factor in the beneficial outcomes of exercise training. Exercise training has long been known to promote mitochondrial biogenesis, but recent work has demonstrated that it has a profound impact on mitochondrial dynamics (fusion and fission) and clearance (mitophagy), as well. In this review, we discuss the various mechanisms through which exercise training promotes mitochondrial quantity and quality in skeletal muscle.-Drake, J. C., Wilson, R. J., Yan, Z. Molecular mechanisms for mitochondrial adaptation to exercise training in skeletal muscle. PMID:26370848

  9. Fate choice of post-natal mesoderm progenitors: skeletal versus cardiac muscle plasticity.

    PubMed

    Costamagna, Domiziana; Quattrocelli, Mattia; Duelen, Robin; Sahakyan, Vardine; Perini, Ilaria; Palazzolo, Giacomo; Sampaolesi, Maurilio

    2014-02-01

    Regenerative medicine for skeletal and cardiac muscles still constitutes a fascinating and ambitious frontier. In this perspective, understanding the possibilities of intrinsic cell plasticity, present in post-natal muscles, is vital to define and improve novel therapeutic strategies for acute and chronic diseases. In addition, many somatic stem cells are now crossing the boundaries of basic/translational research to enter the first clinical trials. However, it is still an open question whether a lineage switch between skeletal and cardiac adult myogenesis is possible. Therefore, this review focuses on resident somatic stem cells of post-natal skeletal and cardiac muscles and their plastic potential toward the two lineages. Furthermore, examples of myogenic lineage switch in adult stem cells are also reported and discussed. PMID:23949444

  10. AHNAK1 and AHNAK2 are costameric proteins: AHNAK1 affects transverse skeletal muscle fiber stiffness

    SciTech Connect

    Marg, Andreas; Haase, Hannelore; Neumann, Tanja; Kouno, Michiyoshi; Morano, Ingo; University Medicine Charite, Berlin

    2010-10-08

    Research highlights: {yields} AHNAK1 and AHNAK2 are costameric proteins. {yields} Intact membrane repair in AHNAK1-deficient mice. {yields} AHNAK1{sup -/-} single fibers have a higher transverse stiffness. -- Abstract: The AHNAK scaffold PDZ-protein family is implicated in various cellular processes including membrane repair; however, AHNAK function and subcellular localization in skeletal muscle are unclear. We used specific AHNAK1 and AHNAK2 antibodies to analyzed the detailed localization of both proteins in mouse skeletal muscle. Co-localization of AHNAK1 and AHNAK2 with vinculin clearly demonstrates that both proteins are components of the costameric network. In contrast, no AHNAK expression was detected in the T-tubule system. A laser wounding assay with AHNAK1-deficient fibers suggests that AHNAK1 is not involved in membrane repair. Using atomic force microscopy (AFM), we observed a significantly higher transverse stiffness of AHNAK1{sup -/-} fibers. These findings suggest novel functions of AHNAK proteins in skeletal muscle.

  11. Effects of Nandrolone in the Counteraction of Skeletal Muscle Atrophy in a Mouse Model of Muscle Disuse: Molecular Biology and Functional Evaluation

    PubMed Central

    Camerino, Giulia Maria; Desaphy, Jean-François; De Bellis, Michela; Capogrosso, Roberta Francesca; Cozzoli, Anna; Dinardo, Maria Maddalena; Caloiero, Roberta; Musaraj, Kejla; Fonzino, Adriano; Conte, Elena; Jagerschmidt, Catherine; Namour, Florence; Liantonio, Antonella; De Luca, Annamaria; Conte Camerino, Diana; Pierno, Sabata

    2015-01-01

    Muscle disuse produces severe atrophy and a slow-to-fast phenotype transition in the postural Soleus (Sol) muscle of rodents. Antioxidants, amino-acids and growth factors were ineffective to ameliorate muscle atrophy. Here we evaluate the effects of nandrolone (ND), an anabolic steroid, on mouse skeletal muscle atrophy induced by hindlimb unloading (HU). Mice were pre-treated for 2-weeks before HU and during the 2-weeks of HU. Muscle weight and total protein content were reduced in HU mice and a restoration of these parameters was found in ND-treated HU mice. The analysis of gene expression by real-time PCR demonstrates an increase of MuRF-1 during HU but minor involvement of other catabolic pathways. However, ND did not affect MuRF-1 expression. The evaluation of anabolic pathways showed no change in mTOR and eIF2-kinase mRNA expression, but the protein expression of the eukaryotic initiation factor eIF2 was reduced during HU and restored by ND. Moreover we found an involvement of regenerative pathways, since the increase of MyoD observed after HU suggests the promotion of myogenic stem cell differentiation in response to atrophy. At the same time, Notch-1 expression was down-regulated. Interestingly, the ND treatment prevented changes in MyoD and Notch-1 expression. On the contrary, there was no evidence for an effect of ND on the change of muscle phenotype induced by HU, since no effect of treatment was observed on the resting gCl, restCa and contractile properties in Sol muscle. Accordingly, PGC1? and myosin heavy chain expression, indexes of the phenotype transition, were not restored in ND-treated HU mice. We hypothesize that ND is unable to directly affect the phenotype transition when the specialized motor unit firing pattern of stimulation is lacking. Nevertheless, through stimulation of protein synthesis, ND preserves protein content and muscle weight, which may result advantageous to the affected skeletal muscle for functional recovery. PMID:26066046

  12. Analysis of MicroRNA Expression Profiles in Weaned Pig Skeletal Muscle after Lipopolysaccharide Challenge

    PubMed Central

    Zhang, Jing; Fu, Shu-Lin; Liu, Yan; Liu, Yu-Lan; Wang, Wen-Jun

    2015-01-01

    MicroRNAs (miRNAs) constitute a class of non-coding RNAs that play a crucial regulatory role in skeletal muscle development and disease. Several acute inflammation conditions including sepsis and cancer are characterized by a loss of skeletal muscle due primarily to excessive muscle catabolism. As a well-known inducer of acute inflammation, a lipopolysaccharide (LPS) challenge can cause serious skeletal muscle wasting. However, knowledge of the role of miRNAs in the course of inflammatory muscle catabolism is still very limited. In this study, RNA extracted from the skeletal muscle of pigs injected with LPS or saline was subjected to small RNA deep sequencing. We identified 304 conserved and 114 novel candidate miRNAs in the pig. Of these, four were significantly increased in the LPS-challenged samples and five were decreased. The expression of five miRNAs (ssc-miR-146a-5p, ssc-miR-221-5p, ssc-miR-148b-3p, ssc-miR-215 and ssc-miR-192) were selected for validation by quantitative polymerase chain reaction (qPCR), which found that ssc-miR-146a-5p and ssc-miR-221-5p were significantly upregulated in LPS-challenged pig skeletal muscle. Moreover, we treated mouse C2C12 myotubes with 1000 ng/mL LPS as an acute inflammation cell model. Expression of TNF-?, IL-6, muscle atrophy F-box (MAFbx) and muscle RING finger 1 (MuRF1) mRNA was strongly induced by LPS. Importantly, miR-146a-5p and miR-221-5p also showed markedly increased expression in LPS-treated C2C12 myotubes, suggesting the two miRNAs may be involved in muscle catabolism systems in response to acute inflammation caused by a LPS challenge. To our knowledge, this study is the first to examine miRNA expression profiles in weaned pig skeletal muscle challenged with LPS, and furthers our understanding of miRNA function in the regulation of inflammatory muscle catabolism. PMID:26389897

  13. Statin-induced Myopathy in Skeletal Muscle: the Role of Exercise

    PubMed Central

    Kwak, Hyo-Bum

    2014-01-01

    Statins are widely used drugs to lower cholesterol levels and to reduce the risk of cardiovascular disease. However, it has been reported that statins are associated with adverse side effects of skeletal myopathy. Statin treatment can impair mitochondrial function and induce apoptosis in skeletal muscle in both human and animal models. Ubiquinone plays an essential role in transferring electrons in the mitochondrial electron transfer chain for oxidative phosphorylation. However, statin treatment reduces ubiquinone levels in the cholesterol synthesis pathway, which may be associated with mitochondrial dysfunction. In addition, reactive oxygen species (ROS) production and apoptosis induced by statins may provide cellular and molecular mechanisms in skeletal myopathy. Exercise is the most effective therapy to prevent metabolic and cardiovascular diseases. However, whether exercise provides a benefit to or exacerbation of statin-induced myopathy in skeletal muscle remains poorly investigated. This review will briefly provide a comprehensive summary regarding the effects of statins on skeletal myopathy, and discuss the potential mechanisms of statin-induced myopathy and the role of exercise in statin-induced myopathy in skeletal muscle. PMID:26064857

  14. Modulation of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. Effects of dietary protein and meal consumption.

    PubMed Central

    Block, K P; Aftring, R P; Mehard, W B; Buse, M G

    1987-01-01

    The effects of dietary protein on the activity of skeletal muscle branched-chain alpha-keto acid dehydrogenase (BCKAD) were investigated. BCKAD is rate-limiting for branched-chain amino acid (BCAA) catabolism by muscle; its activity is modulated by phosphorylation-dephosphorylation. In rats fed an adequate protein (25% casein) diet, BCKAD was approximately 2% active postabsorptively and increased to 10% or 16% active after a 25% or 50% protein meal, respectively. Prolonged feeding of a 50% protein diet increased postabsorptive BCKAD activity to 7% with further increases to 40% active postprandially. On a low protein (9% casein) diet BCKAD remained approximately 2% active regardless of meal-feeding. Dose-dependent activation of BCKAD by intravenous leucine in postabsorptive rats was blunted by a low protein diet. We conclude that excesses of dietary protein enhance the capacity of skeletal muscle to oxidize BCAA, muscle conserves BCAA when protein intake is inadequate, and skeletal muscle may play an important role in whole-body BCAA homeostasis. Images PMID:3571490

  15. Defects of Vps15 in skeletal muscles lead to autophagic vacuolar myopathy and lysosomal disease

    PubMed Central

    Nemazanyy, Ivan; Blaauw, Bert; Paolini, Cecilia; Caillaud, Catherine; Protasi, Feliciano; Mueller, Amelie; Proikas-Cezanne, Tassula; Russell, Ryan C; Guan, Kun-Liang; Nishino, Ichizo; Sandri, Marco; Pende, Mario; Panasyuk, Ganna

    2013-01-01

    The complex of Vacuolar Protein Sorting 34 and 15 (Vps34 and Vps15) has Class III phosphatidylinositol 3-kinase activity and putative roles in nutrient sensing, mammalian Target Of Rapamycin (mTOR) activation by amino acids, cell growth, vesicular trafficking and autophagy. Contrary to expectations, here we show that Vps15-deficient mouse tissues are competent for LC3-positive autophagosome formation and maintain mTOR activation. However, an impaired lysosomal function in mutant cells is traced by accumulation of adaptor protein p62, LC3 and Lamp2 positive vesicles, which can be reverted to normal levels after ectopic overexpression of Vps15. Mice lacking Vps15 in skeletal muscles, develop a severe myopathy. Distinct from the autophagy deficient Atg7?/? mutants, pathognomonic morphological hallmarks of autophagic vacuolar myopathy (AVM) are observed in Vps15?/? mutants, including elevated creatine kinase plasma levels, accumulation of autophagosomes, glycogen and sarcolemmal features within the fibres. Importantly, Vps34/Vps15 overexpression in myoblasts of Danon AVM disease patients alleviates the glycogen accumulation. Thus, the activity of the Vps34/Vps15 complex is critical in disease conditions such as AVMs, and possibly a variety of other lysosomal storage diseases. PMID:23630012

  16. Human skeletal muscle-derived stem cells retain stem cell properties after expansion in myosphere culture

    SciTech Connect

    Wei, Yan; Department of Otolaryngology, Head and Neck Surgery, The Third Affiliated Hospital of Sun Yat-sen University, Guang Zhou ; Li, Yuan; Chen, Chao; Stoelzel, Katharina; Kaufmann, Andreas M.

    2011-04-15

    Human skeletal muscle contains an accessible adult stem-cell compartment in which differentiated myofibers are maintained and replaced by a self-renewing stem cell pool. Previously, studies using mouse models have established a critical role for resident stem cells in skeletal muscle, but little is known about this paradigm in human muscle. Here, we report the reproducible isolation of a population of cells from human skeletal muscle that is able to proliferate for extended periods of time as floating clusters of rounded cells, termed 'myospheres' or myosphere-derived progenitor cells (MDPCs). The phenotypic characteristics and functional properties of these cells were determined using reverse transcription-polymerase chain reaction (RT-PCR), flow cytometry and immunocytochemistry. Our results showed that these cells are clonogenic, express skeletal progenitor cell markers Pax7, ALDH1, Myod, and Desmin and the stem cell markers Nanog, Sox2, and Oct3/4 significantly elevated over controls. They could be maintained proliferatively active in vitro for more than 20 weeks and passaged at least 18 times, despite an average donor-age of 63 years. Individual clones (4.2%) derived from single cells were successfully expanded showing clonogenic potential and sustained proliferation of a subpopulation in the myospheres. Myosphere-derived cells were capable of spontaneous differentiation into myotubes in differentiation media and into other mesodermal cell lineages in induction media. We demonstrate here that direct culture and expansion of stem cells from human skeletal muscle is straightforward and reproducible with the appropriate technique. These cells may provide a viable resource of adult stem cells for future therapies of disease affecting skeletal muscle or mesenchymal lineage derived cell types.

  17. Effect of extraluminal ATP application on vascular tone and blood flow in skeletal muscle: implications for exercise hyperemia

    PubMed Central

    Al-Khazraji, Baraa K.; Mortensen, Stefan P.; Jackson, Dwayne N.; Ellis, Christopher G.; Hellsten, Ylva

    2013-01-01

    During skeletal muscle contractions, the concentration of ATP increases in muscle interstitial fluid as measured by microdialysis probes. This increase is associated with the magnitude of blood flow, suggesting that interstitial ATP may be important for contraction-induced vasodilation. However, interstitial ATP has solely been described to induce vasoconstriction in skeletal muscle. To examine whether interstitial ATP induces vasodilation in skeletal muscle and to what extent this vasoactive effect is mediated by formation of nitric oxide (NO) and prostanoids, three different experimental models were studied. The rat gluteus maximus skeletal muscle model was used to study changes in local skeletal muscle hemodynamics. Superfused ATP at concentrations found during muscle contractions (1–10 ?M) increased blood flow by up to 400%. In this model, the underlying mechanism was also examined by inhibition of NO and prostanoid formation. Inhibition of these systems abolished the vasodilator effect of ATP. Cell-culture experiments verified ATP-induced formation of NO and prostacyclin in rat skeletal muscle microvascular endothelial cells, and ATP-induced formation of NO in rat skeletal muscle cells. To confirm these findings in humans, ATP was infused into skeletal muscle interstitium of healthy subjects via microdialysis probes and found to increase muscle interstitial concentrations of NO and prostacyclin by ?60% and ?40%, respectively. Collectively, these data suggest that a physiologically relevant elevation in interstitial ATP concentrations increases muscle blood flow, indicating that the contraction-induced increase in skeletal muscle interstitial [ATP] is important for exercise hyperemia. The vasodilator effect of ATP application is mediated by NO and prostanoid formation. PMID:23761642

  18. The TWEAK–Fn14 dyad is involved in age-associated pathological changes in skeletal muscle

    SciTech Connect

    Tajrishi, Marjan M.; Sato, Shuichi; Shin, Jonghyun; Zheng, Timothy S.; Burkly, Linda C.; Kumar, Ashok

    2014-04-18

    Highlights: • The levels of TWEAK receptor Fn14 are increased in skeletal muscle during aging. • Deletion of Fn14 attenuates age-associated skeletal muscle fiber atrophy. • Deletion of Fn14 inhibits proteolysis in skeletal muscle during aging. • TWEAK–Fn14 signaling activates transcription factor NF-?B in aging skeletal muscle. • TWEAK–Fn14 dyad is involved in age-associated fibrosis in skeletal muscle. - Abstract: Progressive loss of skeletal muscle mass and strength (sarcopenia) is a major clinical problem in the elderly. Recently, proinflammatory cytokine TWEAK and its receptor Fn14 were identified as key mediators of muscle wasting in various catabolic states. However, the role of the TWEAK–Fn14 pathway in pathological changes in skeletal muscle during aging remains unknown. In this study, we demonstrate that the levels of Fn14 are increased in skeletal muscle of 18-month old (aged) mice compared with adult mice. Genetic ablation of Fn14 significantly increased the levels of specific muscle proteins and blunted the age-associated fiber atrophy in mice. While gene expression of two prominent muscle-specific E3 ubiquitin ligases MAFBx and MuRF1 remained comparable, levels of ubiquitinated proteins and the expression of autophagy-related molecule Atg12 were significantly reduced in Fn14-knockout (KO) mice compared with wild-type mice during aging. Ablation of Fn14 significantly diminished the DNA-binding activity of transcription factor nuclear factor-kappa B (NF-?B), gene expression of various inflammatory molecules, and interstitial fibrosis in skeletal muscle of aged mice. Collectively, our study suggests that the TWEAK–Fn14 signaling axis contributes to age-associated muscle atrophy and fibrosis potentially through its local activation of proteolytic systems and inflammatory pathways.

  19. In vivo alterations in skeletal muscle form and function after disuse atrophy.

    PubMed

    Clark, Brian C

    2009-10-01

    Prolonged reductions in muscle activity and mechanical loading (e.g., bed rest, cast immobilization) result in alterations in skeletal muscle form and function. The purpose of this review article was to synthesize recent findings from several studies on the dramatic effects of disuse on skeletal muscle morphology and muscle performance in humans. Specifically, the following are discussed: 1) how the antigravity muscles are most susceptible to atrophy and how the degree of atrophy varies between muscle groups; 2) how disuse alters muscle composition by increasing intermuscular adipose tissue; 3) the influence of different disuse models on regulating the loss of muscle mass and strength, with immobilization causing greater reductions than bed rest and limb suspension do; 4) the observation that disuse decreases strength to a greater extent than muscle mass and the role of adaptations in both neural and contractile properties that influences this excessive loss of strength; 5) the equivocal findings on the effect of disuse on muscle fatigue resistance; and 6) the reduction in motor control after prolonged disuse. Lastly, emerging data warranting further inquiry into the modulating role of biological sex on disuse-induced adaptations are also discussed. PMID:19727027

  20. Skeletal muscle fiber, nerve, and blood vessel breakdown in space-flown rats

    NASA Technical Reports Server (NTRS)

    Riley, D. A.; Ilyina-Kakueva, E. I.; Ellis, S.; Bain, J. L.; Slocum, G. R.; Sedlak, F. R.

    1990-01-01

    Histochemical and ultrastructural analyses were performed postflight on hind limb skeletal muscles of rats orbited for 12.5 days aboard the unmanned Cosmos 1887 biosatellite and returned to Earth 2 days before sacrifice. The antigravity adductor longus (AL), soleus, and plantaris muscles atrophied more than the non-weight-bearing extensor digitorum longus, and slow muscle fibers were more atrophic than fast fibers. Muscle fiber segmental necrosis occurred selectively in the AL and soleus muscles; primarily, macrophages and neutrophils infiltrated and phagocytosed cellular debris. Granule-rich mast cells were diminished in flight AL muscles compared with controls, indicating the mast cell secretion contributed to interstitial tissue edema. Increased ubiquitination of disrupted myofibrils implicated ubiquitin in myofilament degradation. Mitochondrial content and succinic dehydrogenase activity were normal, except for subsarcolemmal decreases. Myofibrillar ATPase activity of flight AL muscle fibers shifted toward the fast type. Absence of capillaries and extravasation of red blood cells indicated failed microcirculation. Muscle fiber regeneration from activated satellite cells was detected. About 17% of the flight AL end plates exhibited total or partial denervation. Thus, skeletal muscle weakness associated with spaceflight can result from muscle fiber atrophy and segmental necrosis, partial motor denervation, and disruption of the microcirculation.

  1. ANG II is required for optimal overload-induced skeletal muscle hypertrophy

    NASA Technical Reports Server (NTRS)

    Gordon, S. E.; Davis, B. S.; Carlson, C. J.; Booth, F. W.

    2001-01-01

    ANG II mediates the hypertrophic response of overloaded cardiac muscle, likely via the ANG II type 1 (AT(1)) receptor. To examine the potential role of ANG II in overload-induced skeletal muscle hypertrophy, plantaris and/or soleus muscle overload was produced in female Sprague-Dawley rats (225-250 g) by the bilateral surgical ablation of either the synergistic gastrocnemius muscle (experiment 1) or both the gastrocnemius and plantaris muscles (experiment 2). In experiment 1 (n = 10/group), inhibiting endogenous ANG II production by oral administration of an angiotensin-converting enzyme (ACE) inhibitor during a 28-day overloading protocol attenuated plantaris and soleus muscle hypertrophy by 57 and 96%, respectively (as measured by total muscle protein content). ACE inhibition had no effect on nonoverloaded (sham-operated) muscles. With the use of new animals (experiment 2; n = 8/group), locally perfusing overloaded soleus muscles with exogenous ANG II (via osmotic pump) rescued the lost hypertrophic response in ACE-inhibited animals by 71%. Furthermore, orally administering an AT(1) receptor antagonist instead of an ACE inhibitor produced a 48% attenuation of overload-induced hypertrophy that could not be rescued by ANG II perfusion. Thus ANG II may be necessary for optimal overload-induced skeletal muscle hypertrophy, acting at least in part via an AT(1) receptor-dependent pathway.

  2. BIOLOGICAL FRAMEWORKS FOR ENGINEERS Laboratory Experience #3 [Skeletal Muscle Biomechanics

    E-print Network

    Sniadecki, Nathan J.

    for muscle contraction, make up the myofibrils. Each myofibril is made up of ~1,500 myosin filaments and 3 contraction through a ratcheting mechanism. There are two main determinants of muscle strength. The first is held at a constant length and the force generated by the muscle during contraction is recorded

  3. BIOLOGICAL FRAMEWORKS FOR ENGINEERS Laboratory Experience #3 [Skeletal Muscle Biomechanics

    E-print Network

    Sniadecki, Nathan J.

    units called myofibrils. Actin and myosin filaments, the components responsible for muscle contraction and myosin are polymerized proteins; their interaction produces muscle contraction through a ratcheting is held at a constant length and the force generated by the muscle during contraction is recorded

  4. Obesity Impairs Skeletal Muscle Regeneration Through Inhibition of AMPK.

    PubMed

    Fu, Xing; Zhu, Meijun; Zhang, Shuming; Foretz, Marc; Viollet, Benoit; Du, Min

    2016-01-01

    Obesity is increasing rapidly worldwide and is accompanied by many complications, including impaired muscle regeneration. The obese condition is known to inhibit AMPK activity in multiple tissues. We hypothesized that the loss of AMPK activity is a major reason for hampered muscle regeneration in obese subjects. We found that obesity inhibits AMPK activity in regenerating muscle, which was associated with impeded satellite cell activation and impaired muscle regeneration. To test the mediatory role of AMPK?1, we knocked out AMPK?1 and found that both proliferation and differentiation of satellite cells are reduced after injury and that muscle regeneration is severely impeded, reminiscent of hampered muscle regeneration seen in obese subjects. Transplanted satellite cells with AMPK?1 deficiency had severely impaired myogenic capacity in regenerating muscle fibers. We also found that attenuated muscle regeneration in obese mice is rescued by AICAR, a drug that specifically activates AMPK, but AICAR treatment failed to improve muscle regeneration in obese mice with satellite cell-specific AMPK?1 knockout, demonstrating the importance of AMPK?1 in satellite cell activation and muscle regeneration. In summary, AMPK?1 is a key mediator linking obesity and impaired muscle regeneration, providing a convenient drug target to facilitate muscle regeneration in obese populations. PMID:26384382

  5. SKELETAL MUSCLE SODIUM GLUCOSE CO-TRANSPORTERS IN OLDER ADULTS WITH TYPE 2 DIABETES UNDERGOING RESISTANCE TRAINING

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We examined the expression of the sodium-dependent glucose co-transporter system (SGLT3) in skeletal muscle of Hispanic older adults with type 2 diabetes. Subjects (65+/-8 yr) were randomized to resistance training (3x/wk, n=13) or standard of care (controls, n=5) for 16 weeks. Skeletal muscle SGL...

  6. ABSTRACT: Neuromuscular electrical stimulation (NMES) involves the use of electrical current to facilitate contraction of skeletal muscle. However,

    E-print Network

    Dixon, Warren

    to facilitate contraction of skeletal muscle. However, little is known concerning the effects of varying skeletal muscle in vivo. Ten subjects under- went NMES-elicited contractions of varying pulse frequencies Brain Rehabilitation Research Center, North Florida / South Georgia Veterans Health System

  7. 1 Age-dependent regulation of skeletal muscle mitochondria by the thrombospondin-1 2 receptor CD47

    E-print Network

    Frazier, William A.

    1 Age-dependent regulation of skeletal muscle mitochondria by the thrombospondin-1 2 receptor CD47 biogenesis 21 Skeletal muscles 22 Mitochondria 23 CD47 receptor 24 Fast twitch fibers 25 Slow-twitch fibers null mice. 29We further assessed the mitochondria status of CD47-null vs WT mice. Quantitative RT

  8. EXPRESSION OF THE TGF-BETA FAMILY OF LIGANDS IS DEVELOPMENTALLY REGULATED IN SKELETAL MUSCLE OF NEONATAL RATS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To dissect the possible role of the transforming growth factor-beta (TGF-beta) family in the regulation of skeletal muscle growth during the early postnatal period, the protein abundances of the TGF-beta family and their correlation with protein synthesis were determined in skeletal muscle of neonat...

  9. In utero glucocorticoid (GLC) exposure and maternal undernutrition reduce fetal skeletal muscle mass by different mechanisms in rats

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Both maternal undernutrition and exposure of the fetus to above normal levels of GLC impair skeletal muscle growth. The degree to which the effects of maternal undernutrition on fetal skeletal muscle growth are a direct result of nutrient deficit or secondary to the presence of above normal GLC leve...

  10. Long-term Skeletal Muscle Protection After Gene Transfer in a Mouse Model of LGMD-2D

    E-print Network

    Campbell, Kevin P.

    Long-term Skeletal Muscle Protection After Gene Transfer in a Mouse Model of LGMD-2D Christina of Physiology, Biophysics, University of Iowa, Iowa City, Iowa, USA Limb girdle muscular dystrophy (LGMD in maintaining skeletal muscle membrane stability. LGMD type-2D is caused by mutations in alpha-sarcoglycan (sgca

  11. Metabogenic and Nutriceutical Approaches to Address Energy Dysregulation and Skeletal Muscle Wasting in Duchenne Muscular Dystrophy

    PubMed Central

    Rybalka, Emma; Timpani, Cara A.; Stathis, Christos G.; Hayes, Alan; Cooke, Matthew B.

    2015-01-01

    Duchenne Muscular Dystrophy (DMD) is a fatal genetic muscle wasting disease with no current cure. A prominent, yet poorly treated feature of dystrophic muscle is the dysregulation of energy homeostasis which may be associated with intrinsic defects in key energy systems and promote muscle wasting. As such, supplementative nutriceuticals that target and augment the bioenergetical expansion of the metabolic pathways involved in cellular energy production have been widely investigated for their therapeutic efficacy in the treatment of DMD. We describe the metabolic nuances of dystrophin-deficient skeletal muscle and review the potential of various metabogenic and nutriceutical compounds to ameliorate the pathological and clinical progression of the disease. PMID:26703720

  12. Myogenic regulatory factor (MRF) expression is affected by exercise in postnatal chicken skeletal muscles.

    PubMed

    Yin, Huadong; Li, Diyan; Wang, Yan; Zhao, Xiaoling; Liu, Yiping; Yang, Zhiqin; Zhu, Qing

    2015-05-01

    The MyoD1, MyoG, Myf5, and Mrf4 proteins belong to the family of muscle regulatory factors (MRFs) and play important roles in skeletal muscle hyperplasia and hypertrophy. We hypothesized that exercise would affect MRF mRNA and protein abundance in postnatal chicken skeletal muscle driving molecular changes that could ultimately lead to increased muscle fiber diameter. At day (d) 43, twelve hundred chickens with similar body weight were randomly assigned to cage, pen, and free-range groups. The MRF mRNA abundance was measured in the pectoralis major and thigh muscle at d56, d70, and d84, and the protein levels of MRFs were determined from the thigh muscle at d84. The results showed no significant difference in mRNA of the MRFs among the three groups at d56 (P>0.05). At d84, chicken in the pen and free-range group showed higher MyoD1, MyoG, Myf5, and Mrf4 mRNA abundance compared to the caged chickens (P<0.05). Free-range chickens had higher Mrf4 and MyoG expression than those in penned ones (P<0.05). Protein abundances of all four factors were lowest in the caged group, and Mrf4 and MyoG protein quantities were greatest in free-range chickens (P<0.05), but Myf5 and MyoD1 protein abundance did not differ between penned and caged groups. The results suggested that exercise up-regulated MRF expression in the postnatal skeletal muscles, which led to an increase in muscle fiber diameter, and eventually affected the meat quality of the skeletal muscles in adult chickens. PMID:25701607

  13. Raman spectroscopic study of acute oxidative stress induced changes in mice skeletal muscles

    NASA Astrophysics Data System (ADS)

    Sriramoju, Vidyasagar; Alimova, Alexandra; Chakraverty, Rahul; Katz, A.; Gayen, S. K.; Larsson, L.; Savage, H. E.; Alfano, R. R.

    2008-02-01

    The oxidative stress due to free radicals is implicated in the pathogenesis of tissue damage in diseases such as muscular dystrophy, Alzheimer dementia, diabetes mellitus, and mitochrondrial myopathies. In this study, the acute oxidative stress induced changes in nicotinamide adenine dinucleotides in mouse skeletal muscles are studied in vitro using Raman spectroscopy. Mammalian skeletal muscles are rich in nicotinamide adenine dinucleotides in both reduced (NADH) and oxidized (NAD) states, as they are sites of aerobic and anaerobic respiration. The relative levels of NAD and NADH are altered in certain physiological and pathological conditions of skeletal muscles. In this study, near infrared Raman spectroscopy is used to identify the molecular fingerprints of NAD and NADH in five-week-old mice biceps femoris muscles. A Raman vibrational mode of NADH is identified in fresh skeletal muscle samples suspended in buffered normal saline. In the same samples, when treated with 1% H IIO II for 5 minutes and 15 minutes, the Raman spectrum shows molecular fingerprints specific to NAD and the disappearance of NADH vibrational bands. The NAD bands after 15 minutes were more intense than after 5 minutes. Since NADH fluoresces and NAD does not, fluorescence spectroscopy is used to confirm the results of the Raman measurements. Fluorescence spectra exhibit an emission peak at 460 nm, corresponding to NADH emission wavelength in fresh muscle samples; while the H IIO II treated muscle samples do not exhibit NADH fluorescence. Raman spectroscopy may be used to develop a minimally invasive, in vivo optical biopsy method to measure the relative NAD and NADH levels in muscle tissues. This may help to detect diseases of muscle, including mitochondrial myopathies and muscular dystrophies.

  14. Nutritional interventions to augment resistance training-induced skeletal muscle hypertrophy

    PubMed Central

    Morton, Robert W.; McGlory, Chris; Phillips, Stuart M.

    2015-01-01

    Skeletal muscle mass is regulated by a balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). In healthy humans, MPS is more sensitive (varying 4–5 times more than MPB) to changes in protein feeding and loading rendering it the primary locus determining gains in muscle mass. Performing resistance exercise (RE) followed by the consumption of protein results in an augmentation of MPS and, over time, can lead to muscle hypertrophy. The magnitude of the RE-induced increase in MPS is dictated by a variety of factors including: the dose of protein, source of protein, and possibly the distribution and timing of post-exercise protein ingestion. In addition, RE variables such as frequency of sessions, time under tension, volume, and training status play roles in regulating MPS. This review provides a brief overview of our current understanding of how RE and protein ingestion can influence gains in skeletal muscle mass in young, healthy individuals. It is the goal of this review to provide nutritional recommendations for optimal skeletal muscle adaptation. Specifically, we will focus on how the manipulation of protein intake during the recovery period following RE augments the adaptive response. PMID:26388782

  15. A hormone-encoding gene identifies a pathway for cardiac but not skeletal muscle gene transcription.

    PubMed Central

    Grépin, C; Dagnino, L; Robitaille, L; Haberstroh, L; Antakly, T; Nemer, M

    1994-01-01

    In contrast to skeletal muscle, the mechanisms responsible for activation and maintenance of tissue-specific transcription in cardiac muscle remain poorly understood. A family of hormone-encoding genes is expressed in a highly specific manner in cardiac but not skeletal myocytes. This includes the A- and B-type natriuretic peptide (ANP and BNP) genes, which encode peptide hormones with crucial roles in the regulation of blood volume and pressure. Since these genes are markers of cardiac cells, we have used them to probe the mechanisms for cardiac muscle-specific transcription. Cloning and functional analysis of the rat BNP upstream sequences revealed unexpected structural resemblance to erythroid but not to muscle-specific promoters and enhancers, including a requirement for regulatory elements containing GATA motifs. A cDNA clone corresponding to a member of the GATA family of transcription factors was isolated from a cardiomyocyte cDNA library. Transcription of this GATA gene is restricted mostly to the heart and is undetectable in skeletal muscle. Within the heart, GATA transcripts are localized in ANP- and BNP-expressing myocytes, and forced expression of the GATA protein in heterologous cells markedly activates transcription from the natural cardiac muscle-specific ANP and BNP promoters. This GATA-dependent pathway defines the first mechanism for cardiac muscle-specific transcription. Moreover, the present findings reveal striking similarities between the mechanisms controlling gene expression in hematopoietic and cardiac cells and may have important implications for studies of cardiogenesis. Images PMID:8164667

  16. Lysosomal Two-pore Channel Subtype 2 (TPC2) Regulates Skeletal Muscle Autophagic Signaling*

    PubMed Central

    Lin, Pei-Hui; Duann, Pu; Komazaki, Shinji; Park, Ki Ho; Li, Haichang; Sun, Mingzhai; Sermersheim, Mathew; Gumpper, Kristyn; Parrington, John; Galione, Antony; Evans, A. Mark; Zhu, Michael X.; Ma, Jianjie

    2015-01-01

    Postnatal skeletal muscle mass is regulated by the balance between anabolic protein synthesis and catabolic protein degradation, and muscle atrophy occurs when protein homeostasis is disrupted. Autophagy has emerged as critical in clearing dysfunctional organelles and thus in regulating protein turnover. Here we show that endolysosomal two-pore channel subtype 2 (TPC2) contributes to autophagy signaling and protein homeostasis in skeletal muscle. Muscles derived from Tpcn2?/? mice exhibit an atrophic phenotype with exacerbated autophagy under starvation. Compared with wild types, animals lacking TPC2 demonstrated an enhanced autophagy flux characterized by increased accumulation of autophagosomes upon combined stress induction by starvation and colchicine treatment. In addition, deletion of TPC2 in muscle caused aberrant lysosomal pH homeostasis and reduced lysosomal protease activity. Association between mammalian target of rapamycin and TPC2 was detected in skeletal muscle, allowing for appropriate adjustments to cellular metabolic states and subsequent execution of autophagy. TPC2 therefore impacts mammalian target of rapamycin reactivation during the process of autophagy and contributes to maintenance of muscle homeostasis. PMID:25480788

  17. Aging related ER stress is not responsible for anabolic resistance in mouse skeletal muscle.

    PubMed

    Chalil, Sreeda; Pierre, Nicolas; Bakker, Astrid D; Manders, Ralph J; Pletsers, Annelies; Francaux, Marc; Klein-Nulend, Jenneke; Jaspers, Richard T; Deldicque, Louise

    2015-12-25

    Anabolic resistance reflects the inability of skeletal muscle to maintain protein mass by appropriate stimulation of protein synthesis. We hypothesized that endoplasmic reticulum (ER) stress contributes to anabolic resistance in skeletal muscle with aging. Muscles were isolated from adult (8 mo) and old (26 mo) mice and weighed. ER stress markers in each muscle were quantified, and the anabolic response to leucine was assessed by measuring the phosphorylation state of S6K1 in soleus and EDL using an ex vivo muscle model. Aging reduced the muscle-to-body weight ratio in soleus, gastrocnemius, and plantaris, but not in EDL and tibialis anterior. Compared to adult mice, the expression of ER stress markers BiP and IRE1? was higher in EDL, and phospho-eIF2? was higher in soleus and EDL of old mice. S6K1 response to leucine was impaired in soleus, but not in EDL, suggesting that anabolic resistance contributes to soleus weight loss in old mice. Pre-incubation with ER stress inducer tunicamycin before leucine stimulation increased S6K1 phosphorylation beyond the level reached by leucine alone. Since tunicamycin did not impair leucine-induced S6K1 response, and based on the different ER stress marker regulation patterns, ER stress is probably not involved in anabolic resistance in skeletal muscle with aging. PMID:26551463

  18. Lysosomal two-pore channel subtype 2 (TPC2) regulates skeletal muscle autophagic signaling.

    PubMed

    Lin, Pei-Hui; Duann, Pu; Komazaki, Shinji; Park, Ki Ho; Li, Haichang; Sun, Mingzhai; Sermersheim, Mathew; Gumpper, Kristyn; Parrington, John; Galione, Antony; Evans, A Mark; Zhu, Michael X; Ma, Jianjie

    2015-02-01

    Postnatal skeletal muscle mass is regulated by the balance between anabolic protein synthesis and catabolic protein degradation, and muscle atrophy occurs when protein homeostasis is disrupted. Autophagy has emerged as critical in clearing dysfunctional organelles and thus in regulating protein turnover. Here we show that endolysosomal two-pore channel subtype 2 (TPC2) contributes to autophagy signaling and protein homeostasis in skeletal muscle. Muscles derived from Tpcn2(-/-) mice exhibit an atrophic phenotype with exacerbated autophagy under starvation. Compared with wild types, animals lacking TPC2 demonstrated an enhanced autophagy flux characterized by increased accumulation of autophagosomes upon combined stress induction by starvation and colchicine treatment. In addition, deletion of TPC2 in muscle caused aberrant lysosomal pH homeostasis and reduced lysosomal protease activity. Association between mammalian target of rapamycin and TPC2 was detected in skeletal muscle, allowing for appropriate adjustments to cellular metabolic states and subsequent execution of autophagy. TPC2 therefore impacts mammalian target of rapamycin reactivation during the process of autophagy and contributes to maintenance of muscle homeostasis. PMID:25480788

  19. Hindlimb unloading increases oxidative stress and disrupts antioxidant capacity in skeletal muscle

    NASA Technical Reports Server (NTRS)

    Lawler, John M.; Song, Wook; Demaree, Scott R.; Bloomfield, S. A. (Principal Investigator)

    2003-01-01

    Skeletal muscle disuse with space-flight and ground-based models (e.g., hindlimb unloading) results in dramatic skeletal muscle atrophy and weakness. Pathological conditions that cause muscle wasting (i.e., heart failure, muscular dystrophy, sepsis, COPD, cancer) are characterized by elevated "oxidative stress," where antioxidant defenses are overwhelmed by oxidant production. However, the existence, cellular mechanisms, and ramifications of oxidative stress in skeletal muscle subjected to hindlimb unloading are poorly understood. Thus we examined the effects of hindlimb unloading on hindlimb muscle antioxidant enzymes (e.g., superoxide dismutase, catalase, glutathione peroxidase), nonenzymatic antioxidant scavenging capacity (ASC), total hydroperoxides, and dichlorohydrofluorescein diacetate (DCFH-DA) oxidation, a direct indicator of oxidative stress. Twelve 6 month old Sprague Dawley rats were divided into two groups: 28 d of hindlimb unloading (n = 6) and controls (n = 6). Hindlimb unloading resulted in a small decrease in Mn-superoxide dismutase activity (10.1%) in the soleus muscle, while Cu,Zn-superoxide dismutase increased 71.2%. In contrast, catalase and glutathione peroxidase, antioxidant enzymes that remove hydroperoxides, were significantly reduced in the soleus with hindlimb unloading by 54.5 and 16.1%, respectively. Hindlimb unloading also significantly reduced ASC. Hindlimb unloading increased soleus lipid hydroperoxide levels by 21.6% and hindlimb muscle DCFH-DA oxidation by 162.1%. These results indicate that hindlimb unloading results in a disruption of antioxidant status, elevation of hydroperoxides, and an increase in oxidative stress.

  20. Suppression of macrophage functions impairs skeletal muscle regeneration with severe fibrosis

    SciTech Connect

    Segawa, Masashi; Fukada, So-ichiro Yamamoto, Yukiko; Yahagi, Hiroshi; Kanematsu, Masanori; Sato, Masaki; Ito, Takahito; Uezumi, Akiyoshi; Hayashi, Shin'ichi; Miyagoe-Suzuki, Yuko; Takeda, Shin'ichi; Tsujikawa, Kazutake; Yamamoto, Hiroshi

    2008-10-15

    When damaged, skeletal muscle regenerates. In the early phases of regeneration, inflammatory cells such as neutrophils/granulocytes and macrophages infiltrate damaged muscle tissue. To reveal the roles of macrophages during skeletal muscle regeneration, we injected an antibody, AFS98 that blocks the binding of M-CSF to its receptor into normal mice that received muscle damages. Anti-M-CSF receptor administration suppressed macrophage but not neutrophil infiltration. Histological study indicated that suppression of macrophages function leads to the incomplete muscle regeneration. In addition FACS and immunohistochemical study showed that the acute lack of macrophages delayed proliferation and differentiation of muscle satellite cells in vivo. Furthermore, mice injected with the anti-M-CSF receptor antibody exhibited not only adipogenesis, but also significant collagen deposition, i.e., fibrosis and continuous high expression of connective tissue growth factor. Finally we indicate that these fibrosis markers were strongly enriched in CD90(+) cells that do not include myogenic cells. These results indicate that macrophages directly affect satellite cell proliferation and that a macrophage deficiency severely impairs skeletal muscle regeneration and causes fibrosis.

  1. Nutritional interventions to augment resistance training-induced skeletal muscle hypertrophy.

    PubMed

    Morton, Robert W; McGlory, Chris; Phillips, Stuart M

    2015-01-01

    Skeletal muscle mass is regulated by a balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). In healthy humans, MPS is more sensitive (varying 4-5 times more than MPB) to changes in protein feeding and loading rendering it the primary locus determining gains in muscle mass. Performing resistance exercise (RE) followed by the consumption of protein results in an augmentation of MPS and, over time, can lead to muscle hypertrophy. The magnitude of the RE-induced increase in MPS is dictated by a variety of factors including: the dose of protein, source of protein, and possibly the distribution and timing of post-exercise protein ingestion. In addition, RE variables such as frequency of sessions, time under tension, volume, and training status play roles in regulating MPS. This review provides a brief overview of our current understanding of how RE and protein ingestion can influence gains in skeletal muscle mass in young, healthy individuals. It is the goal of this review to provide nutritional recommendations for optimal skeletal muscle adaptation. Specifically, we will focus on how the manipulation of protein intake during the recovery period following RE augments the adaptive response. PMID:26388782

  2. Acute heat treatment improves insulin-stimulated glucose uptake in aged skeletal muscle

    PubMed Central

    Gupte, Anisha A.; Bomhoff, Gregory L.; Touchberry, Chad D.

    2011-01-01

    Aging is associated with insulin resistance and decreased insulin-stimulated glucose uptake into skeletal muscle. Although the mechanisms underlying age-related insulin resistance are not clearly defined, impaired defense against inflammation and tissue oxidative stress are likely causes. Heat shock proteins (HSPs) have been shown to protect tissue from oxidative stress and inhibit the activation of stress kinases such as JNK, known to interfere with the insulin signaling pathway. While the induction of HSPs via chronic heat treatment has been shown to protect skeletal muscle from obesity-related insulin resistance, the ability of heat treatment to improve insulin action in aged skeletal muscle is not known. In the present study, one bout of in vivo heat treatment applied to 24-mo-old Fischer 344 rats improved insulin-stimulated glucose uptake after 24 h in slow-twitch soleus muscles. In vitro heat treatment applied to young (3-mo-old) and aged (24-mo-old) soleus muscles increased expression of HSP72 and inhibited anisomycin-induced activation of JNK. In contrast, heat treatment had no effect on p38 MAPK, a MAPK strongly activated with anisomycin. Prior inhibition of HSP72 transcription with the pharmacological inhibitor KNK437 eliminated the ability of heat treatment to blunt JNK activation. This suggests that the ability of heat treatment to inhibit JNK activation in skeletal muscle is dependent on increased HSP72 expression. In conclusion, an acute bout of heat treatment can increase insulin-stimulated glucose uptake in aged skeletal muscle, with the underlying mechanism likely to be HSP72-mediated JNK inhibition. PMID:21148343

  3. Dissecting human skeletal muscle troponin proteoforms by top-down mass spectrometry.

    PubMed

    Chen, Yi-Chen; Sumandea, Marius P; Larsson, Lars; Moss, Richard L; Ge, Ying

    2015-04-01

    Skeletal muscles are the most abundant tissues in the human body. They are composed of a heterogeneous collection of muscle fibers that perform various functions. Skeletal muscle troponin (sTn) regulates skeletal muscle contraction and relaxation. sTn consists of 3 subunits, troponin I (TnI), troponin T (TnT), and troponin C (TnC). TnI inhibits the actomyosin Mg(2+)-ATPase, TnC binds Ca(2+), and TnT is the tropomyosin (Tm)-binding subunit. The cardiac and skeletal isoforms of Tn share many similarities but the roles of modifications of Tn in the two muscles may differ. The modifications of cardiac Tn are known to alter muscle contractility and have been well-characterized. However, the modification status of sTn remains unclear. Here, we have employed top-down mass spectrometry (MS) to decipher the modifications of human sTnT and sTnI. We have extensively characterized sTnT and sTnI proteoforms, including alternatively spliced isoforms and post-translationally modified forms, found in human skeletal muscle with high mass accuracy and comprehensive sequence coverage. Moreover, we have localized the phosphorylation site of slow sTnT isoform III to Ser1 by tandem MS with electron capture dissociation. This is the first study to comprehensively characterize human sTn and also the first to identify the basal phosphorylation site for human sTnT by top-down MS. PMID:25613324

  4. Intracellular MMP-2 activity in skeletal muscle is associated with type II fibers.

    PubMed

    Hadler-Olsen, Elin; Solli, Ann Iren; Hafstad, Anne; Winberg, Jan-Olof; Uhlin-Hansen, Lars

    2015-01-01

    Matrix metalloproteinase 2 (MMP-2) is a proteolytic enzyme implicated in motility, differentiation, and regeneration of skeletal muscle fibers through processing of extracellular substrates. Although MMP-2 has been found to be localized intracellularly in cardiomyocytes where the enzyme is thought to contribute to post-ischemic loss of contractility, little is known about intracellular MMP-2 activity in skeletal muscle fibers. In the present study we demonstrate intracellular MMP-2 in normal skeletal muscle by immunohistochemical staining. Immunogold electron microscopic analyses indicated that the enzyme was concentrated in Z-lines of the sarcomers, in the nuclear membrane, and in mitochondria. By use of in situ zymography, we found that gelatinolytic activity in muscle fibers was co-localized with immunofluorecent staining for MMP-2. Staining for MMP-9, the other member of the gelatinase group of the MMPs, was negative. The broad-spectrum metalloprotease inhibitor EDTA and the selective gelatinase inhibitor CTT2, but not the cysteine inhibitor E64, strongly reduced the gelatinolytic activity. The intracellular gelatinolytic activity was much more prominent in fast twitch type II fibers than in slow twitch type I fibers, and there was a decrease in intracellular gelatinolytic activity and MMP-2 expression in muscles from mice exposed to high intensity interval training. Together our results indicate that MMP-2 is part of the intracellular proteolytic network in normal skeletal muscle, especially in fast twitch type II fibers. Further, the results suggest that intracellular MMP-2 in skeletal muscle fibers is active during normal homeostasis, and affected by the level of physical activity. PMID:24905939

  5. Ca2+/calmodulin-dependent transcriptional pathways: potential mediators of skeletal muscle growth and development.

    PubMed

    Al-Shanti, Nasser; Stewart, Claire E

    2009-11-01

    The loss of muscle mass with age and disuse has a significant impact on the physiological and social well-being of the aged; this is an increasingly important problem as the population becomes skewed towards older age. Exercise has psychological benefits but it also impacts on muscle protein synthesis and degradation, increasing muscle tissue volume in both young and older individuals. Skeletal muscle hypertrophy involves an increase in muscle mass and cross-sectional area and associated increased myofibrillar protein content. Attempts to understand the molecular mechanisms that underlie muscle growth, development and maintenance, have focused on characterising the molecular pathways that initiate, maintain and regenerate skeletal muscle. Such understanding may aid in improving targeted interventional therapies for age-related muscle loss and muscle wasting associated with diseases. Two major routes through which skeletal muscle development and growth are regulated are insulin-like growth factor I (IGF-I) and Ca(2+)/calmodulin-dependent transcriptional pathways. Many reviews have focused on understanding the signalling pathways of IGF-I and its receptor, which govern skeletal muscle hypertrophy. However, alternative molecular signalling pathways such as the Ca(2+)/calmodulin-dependent transcriptional pathways should also be considered as potential mediators of muscle growth. These latter pathways have received relatively little attention and the purpose herein is to highlight the progress being made in the understanding of these pathways and associated molecules: calmodulin, calmodulin kinases (CaMKs), calcineurin and nuclear factor of activated T-cell (NFAT), which are involved in skeletal muscle regulation. We describe: (1) how conformational changes in the Ca(2+) sensor calmodulin result in the exposure of binding pockets for the target proteins (CaMKs and calcineurin). (2) How Calmodulin consequently activates either the Ca(2+)/calmodulin-dependent kinases pathways (via CaMKs) or calmodulin-dependent serine/threonine phosphatases (via calcineurin). (3) How calmodulin kinases alter transcription in the nucleus through the phosphorylation, deactivation and translocation of histone deacetylase 4 (HDAC4) from the nucleus to the cytoplasm. (4) How calcineurin transmits signals to the nucleus through the dephosphorylation and translocation of NFAT from the cytoplasm to the nucleus. PMID:19725819

  6. Synergizing Engineering and Biology to Treat and Model Skeletal Muscle Injury and Disease.

    PubMed

    Bursac, Nenad; Juhas, Mark; Rando, Thomas A

    2015-12-01

    Although skeletal muscle is one of the most regenerative organs in our body, various genetic defects, alterations in extrinsic signaling, or substantial tissue damage can impair muscle function and the capacity for self-repair. The diversity and complexity of muscle disorders have attracted much interest from both cell biologists and, more recently, bioengineers, leading to concentrated efforts to better understand muscle pathology and develop more efficient therapies. This review describes the biological underpinnings of muscle development, repair, and disease, and discusses recent bioengineering efforts to design and control myomimetic environments, both to study muscle biology and function and to aid in the development of new drug, cell, and gene therapies for muscle disorders. The synergy between engineering-aided biological discovery and biology-inspired engineering solutions will be the path forward for translating laboratory results into clinical practice. PMID:26643021

  7. Journal of Biomechanical Engineering, Vol. 130, no. 6, article 061017 (2008), pp. 1-9 Constitutive Modeling of Skeletal Muscle Tissue with an Explicit

    E-print Network

    Odegard, Gregory M.

    2008-01-01

    in the muscle [7] or curvature of muscle during contraction. More recently, continuum-mechanics muscle models Modeling of Skeletal Muscle Tissue with an Explicit Strain-Energy Function G.M. Odegard T.L. Haut Donahue in the modeling of skeletal muscle, no model has, to date, been developed that describes the mechanical behavior

  8. Telomeres shorten in response to oxidative stress in mouse skeletal muscle fibers.

    PubMed

    Ludlow, Andrew T; Spangenburg, Espen E; Chin, Eva R; Cheng, Wen-Hsing; Roth, Stephen M

    2014-07-01

    Aging phenotypes are dictated by myriad cellular changes including telomere shortening. In most tissues, telomere shortening is accelerated during replication if unrepaired oxidative damage to telomere sequences is present. However, the effect of reactive oxygen species exposure on skeletal muscle telomeres is unknown. We sought to determine if oxidative stress shortens telomeres in isolated adult rodent skeletal muscle fibers. Flexor digitorum brevis muscles were dissected from male mice (C57BL/6, long telomere and CAST/Ei, wild-derived, short telomere) and dissociated into single fibers. Fibers were cultured at an oxygen tension of 2%-5% for 5 days in control, hydrogen peroxide (oxidant), or a combination of N-acetylcysteine (antioxidant) and oxidant containing media. Telomere length, telomerase enzyme activity, and protein content of TRF1 and TRF2 were subsequently measured. In both strains, oxidative stress resulted in significant telomere shortening in isolated skeletal muscle fibers, likely by different mechanisms. Telomerase activity was not altered by oxidative stress treatment but was significantly different between strains, with greater telomerase activity in long-telomere-bearing C57BL/6 mice. These results provide important insights into mechanisms by which oxidative stress could shorten skeletal muscle telomeres. PMID:24418792

  9. MiR-206, a Key Modulator of Skeletal Muscle Development and Disease

    PubMed Central

    Ma, Guoda; Wang, Yajun; Li, You; Cui, Lili; Zhao, Yujuan; Zhao, Bin; Li, Keshen

    2015-01-01

    MicroRNAs (miRNAs) have recently emerged as fundamental post-transcriptional regulators inhibit gene expression linked to various biological processes. MiR-206 is one of the most studied and best characterized miRNA to date, which specifically expressed in skeletal muscle. In this review, we summarized the results of studies of miR-206 with emphasis on its function in skeletal muscle development. Importantly, dysregulation of miR-206 has been linked to many disorders in skeletal muscle such as Duchenne muscular dystrophy (DMD) and amyotrophic lateral sclerosis (ALS), and circulating miR-206 has highlighted its potential as a diagnose biomarker. In addition, a mutation in the 3' untranslated region (3'-UTR) of the myostatin gene in the Texel sheep creating a target site for the miR-206 and miR-1 leads to inhibition of myostatin expression, which likely to cause the muscular hypertrophy phenotype of this breed of sheep. Therefore, miR-206 may become novel target for ameliorating skeletal muscle-related disorders and optimization of muscle quantity of domestic animals. PMID:25678853

  10. Characterization of skeletal muscle in the synemin knock-out mouse

    NASA Astrophysics Data System (ADS)

    García-Pelagio, Karla P.; Muriel, Joaquin; Lovering, Richard M.; Lund, Linda; Bond, Meredith; Bloch, Robert J.

    2014-11-01

    Diseases linked to intermediate filament (IF) proteins are associated with defects in the organization of the contractile apparatus of skeletal and cardiac muscle and its links to costameres, which connect the sarcomeres to the cell membrane. Synemin is a large IF protein that associates with dystrobrevin, vinculin, and talin at costameres of the cell membrane of striated muscle, as well as with ?-actinin and desmin at the Z disks. Synemin can be expressed in either 210 kDa ?- or 180 kDa ?- alternatively spliced forms. We generated mice null for synemin by homologous recombination to study synemin's function in skeletal muscle. Skeletal muscle in the knock out (syn KO) mouse does not make synemin mRNA or protein. Preliminary characterization of the syn KO mouse suggests that it has a mild skeletal muscle phenotype. The organization of costameres appears to be normal. Treadmill running uphill test results was not significantly affected when compared to controls at any age. More notably, the biomechanical properties of the cell membrane are different in the syn KO, though they are less affected than by the absence of desmin or dystrophin. These results suggest that the viscoelastic properties of the cell membrane-costamere-myofibril complex are significantly influenced by synemin.

  11. Treatment of Dyslipidemia with Statins and Physical Exercises: Recent Findings of Skeletal Muscle Responses

    PubMed Central

    Bonfim, Mariana Rotta; Oliveira, Acary Souza Bulle; do Amaral, Sandra Lia; Monteiro, Henrique Luiz

    2015-01-01

    Statin treatment in association with physical exercise practice can substantially reduce cardiovascular mortality risk of dyslipidemic individuals, but this practice is associated with myopathic event exacerbation. This study aimed to present the most recent results of specific literature about the effects of statins and its association with physical exercise on skeletal musculature. Thus, a literature review was performed using PubMed and SciELO databases, through the combination of the keywords “statin” AND “exercise” AND “muscle”, restricting the selection to original studies published between January 1990 and November 2013. Sixteen studies evaluating the effects of statins in association with acute or chronic exercises on skeletal muscle were analyzed. Study results indicate that athletes using statins can experience deleterious effects on skeletal muscle, as the exacerbation of skeletal muscle injuries are more frequent with intense training or acute eccentric and strenuous exercises. Moderate physical training, in turn, when associated to statins does not increase creatine kinase levels or pain reports, but improves muscle and metabolic functions as a consequence of training. Therefore, it is suggested that dyslipidemic patients undergoing statin treatment should be exposed to moderate aerobic training in combination to resistance exercises three times a week, and the provision of physical training prior to drug administration is desirable, whenever possible. PMID:25993596

  12. Mechanical load induces sarcoplasmic wounding and FGF release in differentiated human skeletal muscle cultures

    NASA Technical Reports Server (NTRS)

    Clarke, M. S.; Feeback, D. L.

    1996-01-01

    The transduction mechanism (or mechanisms) responsible for converting a mechanical load into a skeletal muscle growth response are unclear. In this study we have used a mechanically active tissue culture model of differentiated human skeletal muscle cells to investigate the relationship between mechanical load, sarcolemma wounding, fibroblast growth factor release, and skeletal muscle cell growth. Using the Flexcell Strain Unit we demonstrate that as mechanical load increases, so too does the amount of sarcolemma wounding. A similar relationship was also observed between the level of mechanical load inflicted on the cells and the amount of bFGF (FGF2) released into the surrounding medium. In addition, we demonstrate that the muscle cell growth response induced by chronic mechanical loading in culture can be inhibited by the presence of an antibody capable of neutralizing the biological activity of FGF. This study provides direct evidence that mechanically induced, sarcolemma wound-mediated FGF release is an important autocrine mechanism for transducing the stimulus of mechanical load into a skeletal muscle growth response.

  13. Exercise sensitizes skeletal muscle to extracellular ATP for IL-6 expression in mice.

    PubMed

    Fernández-Verdejo, R; Casas, M; Galgani, J E; Jaimovich, E; Buvinic, S

    2014-04-01

    Active skeletal muscle synthesizes and releases interleukin-6 (IL-6), which plays important roles in the organism's adaptation to exercise. Autocrine/paracrine ATP signaling has been shown to modulate IL-6 expression. The aim of this study was to determine whether a period of physical activity modifies the ATP-induced IL-6 expression. BalbC mice were either subject to 5 weeks voluntary wheel running (VA) or kept sedentary (SED). Flexor digitorum brevis muscles were dissected, stimulated with different ATP concentrations (0-100 ?M) and IL-6 mRNA levels were measured using qPCR. ATP evoked a concentration-dependent rise in IL-6 mRNA in both SED and VA mice. VA mice however, had significantly higher ATP sensitivity (pD2 pharmacological values: VA=5.58±0.02 vs. SED=4.95±0.04, p<0.05). Interestingly, in VA mice we observed a positive correlation between the level of physical activity and the IL-6 mRNA increase following fiber stimulation with 10??M ATP. In addition, there were lower P2Y2- and higher P2Y14-receptor mRNA levels in skeletal muscles of VA compared to SED mice, showing plasticity of nucleotide receptors with exercise. These results suggest that exercise increases skeletal muscle ATP sensitivity, a response dependent on the level of physical activity performed. This could have an important role in the mechanisms controlling skeletal muscle adaptation to exercise and training. PMID:24022572

  14. Quantitative measurement of Ca²(+) in the sarcoplasmic reticulum lumen of mammalian skeletal muscle.

    PubMed

    Ziman, Andrew P; Ward, Christopher W; Rodney, George G; Lederer, W Jonathan; Bloch, Robert J

    2010-10-20

    Skeletal muscle stores Ca²(+) in the sarcoplasmic reticulum (SR) and releases it to initiate contraction, but the concentration of luminal Ca²(+) in the SR ([Ca²(+)](SR)) and the amount that is released by physiological or pharmacological stimulation has been difficult to measure. Here we present a novel, yet simple and direct, method that provides the first quantitative estimates of static content and dynamic changes in [Ca²(+)](SR) in mammalian skeletal muscle, to our knowledge. The method uses fluo-5N loaded into the SR of single, mammalian skeletal muscle cells (murine flexor digitorum brevis myofibers) and confocal imaging to detect and calibrate the signals. Using this method, we have determined that [Ca²(+)](SR, free) is 390 ?M. 4-Chloro-m-cresol, an activator of the skeletal muscle ryanodine receptor, reduces [Ca²(+)](SR, free) to ?8 ?M, when values are corrected for background fluorescence from cytoplasmic pools of dye. Prolonged electrical stimulation (10 s) at 50 Hz releases 88% of the SR Ca²(+) content, whereas stimulation at 1 Hz (10 s) releases only 20%. Our results lay the foundation for molecular modeling of the dynamics of luminal SR Ca²(+) and for future studies of the role of SR Ca²(+) in healthy and diseased mammalian muscle. PMID:20959112

  15. Membrane-stabilizing copolymers confer marked protection to dystrophic skeletal muscle in vivo

    PubMed Central

    Houang, Evelyne M; Haman, Karen J; Filareto, Antonio; Perlingeiro, Rita C; Bates, Frank S; Lowe, Dawn A; Metzger, Joseph M

    2015-01-01

    Duchenne muscular dystrophy (DMD) is a fatal disease of striated muscle deterioration. A unique therapeutic approach for DMD is the use of synthetic membrane stabilizers to protect the fragile dystrophic sarcolemma against contraction-induced mechanical stress. Block copolymer-based membrane stabilizer poloxamer 188 (P188) has been shown to protect the dystrophic myocardium. In comparison, the ability of synthetic membrane stabilizers to protect fragile DMD skeletal muscles has been less clear. Because cardiac and skeletal muscles have distinct structural and functional features, including differences in the mechanism of activation, variance in sarcolemma phospholipid composition, and differences in the magnitude and types of forces generated, we speculated that optimized membrane stabilization could be inherently different. Our objective here is to use principles of pharmacodynamics to evaluate membrane stabilization therapy for DMD skeletal muscles. Results show a dramatic differential effect of membrane stabilization by optimization of pharmacodynamic-guided route of poloxamer delivery. Data show that subcutaneous P188 delivery, but not intravascular or intraperitoneal routes, conferred significant protection to dystrophic limb skeletal muscles undergoing mechanical stress in vivo. In addition, structure-function examination of synthetic membrane stabilizers further underscores the importance of copolymer composition, molecular weight, and dosage in optimization of poloxamer pharmacodynamics in vivo. PMID:26623440

  16. Isolation, Culture and Identification of Porcine Skeletal Muscle Satellite Cells

    PubMed Central

    Li, Bo-jiang; Li, Ping-hua; Huang, Rui-hua; Sun, Wen-xing; Wang, Han; Li, Qi-fa; Chen, Jie; Wu, Wang-jun; Liu, Hong-lin

    2015-01-01

    The objective of this study was to establish the optimum protocol for the isolation and culture of porcine muscle satellite cells. Mononuclear muscle satellite cells are a kind of adult stem cell, which is located between the basal lamina and sarcolemma of muscle fibers and is the primary source of myogenic precursor cells in postnatal muscle. Muscle satellite cells are a useful model to investigate the mechanisms of muscle growth and development. Although the isolation and culture protocols of muscle satellite cells in some species (e.g. mouse) have been established successfully, the culture system for porcine muscle satellite cells is very limited. In this study, we optimized the isolation procedure of porcine muscle satellite cells and elaborated the isolation and culture process in detail. Furthermore, we characterized the porcine muscle satellite cells using the immunofluorecence. Our study provides a reference for the isolation of porcine muscle satellite cells and will be useful for studying the molecular mechanisms in these cells. PMID:26104526

  17. External physical and biochemical stimulation to enhance skeletal muscle bioengineering

    PubMed Central

    Plock, Jan; Eberli, Daniel

    2015-01-01

    Purpose of review Cell based muscle tissue engineering carries the potential to revert the functional loss of muscle tissue caused by disease and trauma. Although muscle tissue can be bioengineered using various precursor cells, major limitations still remain. Recent findings In the last decades several cellular pathways playing a crucial role in muscle tissue regeneration have been described. These pathways can be influenced by external stimuli and they not only orchestrate the regenerative process after physiologic wear and muscle trauma, but they also play an important part in aging and maintaining the stem cell niche, which is required to maintain long-term muscle function. Summary In this review article we will highlight possible new avenues using external physical and biochemical stimulation in order to optimize muscle bioengineering. PMID:25453267

  18. Increased skeletal muscle-specific microRNA in the blood of patients with COPD

    PubMed Central

    Donaldson, Anna; Natanek, Samantha A; Lewis, Amy; Man, William D-C; Hopkinson, Nicholas S; Polkey, Michael I; Kemp, Paul R

    2013-01-01

    Background Skeletal muscle weakness in chronic obstructive pulmonary disease (COPD) carries a poor prognosis, therefore a non-invasive marker of this process could be useful. Reduced expression of muscle-specific microRNA (myomiRs) in quadriceps muscle in patients with COPD is associated with skeletal muscle weakness and changes in muscle fibre composition. Circulating exosomal miRNAs can be measured in blood, making them candidate biomarkers of biopsy phenotype. To determine whether plasma myomiR levels were associated with fibre size or fibre proportion, we measured myomiRs in plasma from patients with COPD and healthy controls. Methods and results 103 patients with COPD and 25 age-matched controls were studied. Muscle-specific miRNA was elevated in the plasma of patients with COPD and showed distinct patterns. Specifically, miR-1 was inversely associated with fat-free mass in the cohort, whereas levels of miR-499 were more directly associated with strength and quadriceps type I fibre proportion. Two miRs not restricted to muscle in origin (miR-16 and miR-122) did not differ between patients and controls. Plasma miR-499 was also associated with muscle nuclear factor ?B p50 but not p65 in patients with early COPD whereas plasma inflammatory cytokines were associated with miR-206 in patients with more advanced disease. Conclusions Plasma levels of individual myomiRs are altered in patients with COPD but alone do not predict muscle fibre size or proportion. Our findings are consistent with an increase in muscle wasting and turnover associated with the development of skeletal muscle dysfunction and fibre-type shift in patients with stable COPD. PMID:23814167

  19. Voltage clamp methods for the study of membrane currents and SR Ca2+ release in adult skeletal muscle fibres

    PubMed Central

    Hernández-Ochoa, Erick O.; Schneider, Martin F.

    2012-01-01

    Skeletal muscle excitation-contraction (E-C)1 coupling is a process composed of multiple sequential stages, by which an action potential triggers sarcoplasmic reticulum (SR)2 Ca2+ release and subsequent contractile activation. The various steps in the E-C coupling process in skeletal muscle can be studied using different techniques. The simultaneous recordings of sarcolemmal electrical signals and the accompanying elevation in myoplasmic Ca2+, due to depolarization-initiated SR Ca2+ release in skeletal muscle fibres, have been useful to obtain a better understanding of muscle function. In studying the origin and mechanism of voltage dependency of E-C coupling a variety of different techniques have been used to control the voltage in adult skeletal fibres. Pioneering work in muscles isolated from amphibians or crustaceans used microelectrodes or ‘high resistance gap’ techniques to manipulate the voltage in the muscle fibres. The develo