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Sample records for twitch muscle fibers

  1. Regeneration of frog twitch and slow muscle fibers after mincing.

    Science.gov (United States)

    Schmidt, H; Emser, W

    1985-10-01

    Iliofibularis muscles of Rana temporaria were minced and allowed to regenerate in the iliofibularis or the sartorius bed of the same frog. Regenerated muscles were examined for the presence of slow muscle fibers using electrophysiologic, histochemical, and contractile parameters. Muscle regeneration from sartorius mince was also studied. Regeneration was more successful from iliofibularis than from sartorius mince, and the iliofibularis bed was more favorable for regeneration than the sartorius bed for both types of muscle. Twitch fibers regenerated within a few months, but slow fibers could not be identified earlier than 14 months after muscle destruction. Slow muscle fibers regenerated only from iliofibularis mince, both orthotopically and heterotopically. All regenerates capable of maintaining a K-contracture contained histochemically identified slow fibers; the membrane properties of electrophysiologically identified slow fibers were normal. It is concluded that slow muscle fibers regenerate only from the remnants of a muscle that contains slow fibers. The results are discussed with respect to the role of innervating nerve fibers.

  2. Adaptation of fibers in fast-twitch muscles of rats to spaceflight and hindlimb suspension

    Science.gov (United States)

    Jiang, Bian; Ohira, Yoshi; Roy, Roland R.; Nguyen, Quyet; Il'ina-Kakueva, E. I.; Oganov, V.; Edgerton, V. R.

    1992-01-01

    The adaptation of single fibers in medial gastrocnemius (MG), a fast-twitch extensor, and in tibialis anterior (TA), a fast-twitch flexor, was studied after 14 days of spaceflight onboard Cosmos 2044 or hindlimb suspension. Quantitative myosin ATPase activities of single fibers were measured in flight and suspended rats. Each of the enzyme and size measurements were directly correlated within each fiber with respect to its qualitative myosin ATPase staining properties and its expression of fast, slow, or both myosin heavy chains (MHC). The percentage of slow- and fast-twitch fibers of the MG and TA were found to be unchanged. Mean fiber size of all fibers was unaffected after flight or suspension. The ATPase activity in the MG was higher in flight than in control or suspended rats. In comparison to Cosmos 1887 spaceflight, the adaptations in the muscle fibers of the MG were more moderate.

  3. Comparison of myoplasmic calcium movements during excitation-contraction coupling in frog twitch and mouse fast-twitch muscle fibers.

    Science.gov (United States)

    Hollingworth, Stephen; Baylor, Stephen M

    2013-05-01

    Single twitch fibers from frog leg muscles were isolated by dissection and micro-injected with furaptra, a rapidly responding fluorescent Ca(2+) indicator. Indicator resting fluorescence (FR) and the change evoked by an action potential (ΔF) were measured at long sarcomere length (16°C); ΔF/FR was scaled to units of ΔfCaD, the change in fraction of the indicator in the Ca(2+)-bound form. ΔfCaD was simulated with a multicompartment model of the underlying myoplasmic Ca(2+) movements, and the results were compared with previous measurements and analyses in mouse fast-twitch fibers. In frog fibers, sarcoplasmic reticulum (SR) Ca(2+) release evoked by an action potential appears to be the sum of two components. The time course of the first component is similar to that of the entire Ca(2+) release waveform in mouse fibers, whereas that of the second component is severalfold slower; the fractional release amounts are ~0.8 (first component) and ~0.2 (second component). Similar results were obtained in frog simulations with a modified model that permitted competition between Mg(2+) and Ca(2+) for occupancy of the regulatory sites on troponin. An anatomical basis for two release components in frog fibers is the presence of both junctional and parajunctional SR Ca(2+) release channels (ryanodine receptors [RyRs]), whereas mouse fibers (usually) have only junctional RyRs. Also, frog fibers have two RyR isoforms, RyRα and RyRβ, whereas the mouse fibers (usually) have only one, RyR1. Our simulations suggest that the second release component in frog fibers functions to supply extra Ca(2+) to activate troponin, which, in mouse fibers, is not needed because of the more favorable location of their triadic junctions (near the middle of the thin filament). We speculate that, in general, parajunctional RyRs permit increased myofilament activation in fibers whose triadic junctions are located at the z-line.

  4. Calcium transients in single fibers of low-frequency stimulated fast-twitch muscle of rat.

    Science.gov (United States)

    Carroll, S; Nicotera, P; Pette, D

    1999-12-01

    Ca(2+) transients were investigated in single fibers isolated from rat extensor digitorum longus muscles exposed to chronic low-frequency stimulation for different time periods up to 10 days. Approximately 2.5-fold increases in resting Ca(2+) concentration ([Ca(2+)]) were observed 2 h after stimulation onset and persisted throughout the stimulation period. The elevated [Ca(2+)] levels were in the range characteristic of slow-twitch fibers from soleus muscle. In addition, we noticed a transitory elevation of the integral [Ca(2+)] per pulse with a maximum ( approximately 5-fold) after 1 day. Steep decreases in rate constant of [Ca(2+)] decay could be explained by an immediate impairment of Ca(2+) uptake and, with longer stimulation periods, by an additional loss of cytosolic Ca(2+) binding capacity resulting from a decay in parvalbumin content. A partial recovery of the rate constant of [Ca(2+)] decay in 10-day stimulated muscle could be explained by an increasing mitochondrial contribution to Ca(2+) sequestration.

  5. Reptilian skeletal muscle: contractile properties of identified, single fast-twitch and slow fibers from the lizard Dipsosaurus dorsalis.

    Science.gov (United States)

    Gleeson, T T; Johnston, I A

    1987-06-01

    Contractile properties and innervation patterns were determined in identified single fibers from the iliofibularis muscle of the desert iguana, Dipsosaurus dorsalis. Single fibers from both the red and white regions of the iliofibularis muscle were dissected along their length under oil and a portion was mounted on transducers for determination of maximum isometric tension (Po) and unloaded shortening velocity (Vmax) using the slack test method. Fibers were chemically skinned and activated by high Ca++. The remaining portion of the muscle fiber was mounted on a glass slide and histochemically treated to demonstrate myosin ATPase activity. Fibers studied functionally could therefore be classified as fast or slow according to their myosin ATPase activity, and they could also be classified metabolically according to the region of the muscle from which they were dissected. Fast-twitch glycolytic (FG) fibers from the white region and fast-twitch oxidative, glycolytic (FOG) and slow fibers from the red region had shortening velocities at 25 degrees C of 7.5, 4.4, and 1.5 l X s-1, respectively. Po did not differ in the three fiber types, averaging 279 kN X m-2. In a second experiment, 10 microns sections were examined every 30 microns through the proximal-most 7.5 mm of the iliofibularis muscle for motor endplates. Sections were stained to demonstrate regions of acetylcholinesterase activity. Fibers with visible endplates were classified in serial sections by histochemical treatment for myosin ATPase and succinic dehydrogenase. All slow fibers examined (n = 22) exhibited multiple endplates, averaging one every 725 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Transcriptional regulation of acetylcholinesterase-associated collagen ColQ in fast- and slow-twitch muscle fibers.

    Science.gov (United States)

    Ting, Annie K L; Siow, Nina L; Kong, L W; Tsim, Karl W K

    2005-12-15

    The presence of a collagenous protein (ColQ) characterizes the collagen-tailed forms of acetylcholinesterase (AChE) and butyrylcholinesterase at vertebrate neuromuscular junctions, which is tethered in the synaptic basal lamina. ColQ subunits, differing mostly by their signal sequences, are encoded by transcripts ColQ-1 and ColQ-1a, which are differentially expressed in slow- and fast-twitch muscles in mammals, respectively. Both ColQ transcripts are derived from a single COLQ gene. Transcripts encoding ColQ increased during myogenic differentiation of C2C12 cells; the increase was in parallel with AChE catalytic subunit. Quantitative PCR analysis indicated that the increase during the myotube formation was due to the up regulation of ColQ-1 transcript instead of ColQ-1a. In order to reveal the regulatory mechanism of ColQ transcripts, two distinct promoters, pColQ-1 and pColQ-1a, were isolated from human COLQ gene. The ColQ promoters showed a muscle fiber type-specific expression pattern, and which was in line with the expression of endogenous transcript. After in vivo DNA transfection, pColQ-1 showed strong activity in slow-twitch muscle (e.g. soleus), while pColQ-1a was preferably expressed in fast-twitch muscle (e.g. tibialis). Mutation analysis of the ColQ promoters suggested that the muscle fiber type-specific expression pattern of ColQ transcripts was regulated by a slow upsteam regulatory element (SURE) and a fast intronic regulatory element (FIRE). These results explain the specific expression patterns of collagen-tailed AChE in slow and fast muscle fibers.

  7. The effects of temperature on the mechanical performance in fatigued single muscle fibers of the frog induced by twitch and tetanus.

    Science.gov (United States)

    Inamura, N; Fujisige, A; Miyake, S; Ono, A; Tsuchiya, T

    2000-02-01

    Muscle fatigue induced by consecutive twitches or tetani was studied in single skeletal muscle fibers of the frog, Rana japonica. The fatigue by twitch appeared sooner after the start of stimulation at lower temperatures (2-5 degrees C) than at higher ones (15-20 degrees C), while the fatigue by tetanus appeared sooner at higher temperatures. When a twitch-fatigued fiber was bathed in a solution with caffeine (15 mM), the contracture force was much higher than the fatigued force, while in tetanus fatigue, the force by caffeine was not different from the fatigued force. The length-force relation in fatigued fibers was compared with that in pre-fatigue at low and high temperatures. It was noticed that the ascending limb of the length-force curve in fatigued fibers by twitch was lower than that in pre-fatigue at the low temperatures; namely, the fatigue by twitch was more marked in shorter muscle length, while no marked change in the length-force relation was detected in the tetanus fatigue at the low and high temperatures. The maximum shortening velocity, measured by the slack test, decreased in both types of fatigue. These results suggest that the fatigue by twitch may be mainly due to the failure of activation of the contractile system, while in the fatigue by tetanus, the rate of the interaction between actin and myosin may be impaired due to the change in intracellular chemical environment.

  8. Size and metabolic properties of fibers in rat fast-twitch muscles after hindlimb suspension

    Science.gov (United States)

    Roy, Roland R.; Bello, Maureen A.; Bouissou, Phillip; Edgerton, V. Reggie

    1987-01-01

    The effect of hind-limb suspension (HS) on single fibers of the medial gastrocnemius (MG) and the tibialis anterior (TA) muscles were studied in rats. Fiber area and the activities of succinate dehydrogenase (SDH) and alpha-glycerophosphate dehydrogenase (GPD) were determined in tissue sections using an image analysis system. After 28 days of HS, the MG atrophied 28 percent, whereas the TA weight was maintained. Both dark- and light-ATPase fibers in the deep region of the MG had decreased cross-sectional areas following HS, with the atrophic response being twice as great in the light-ATPase fibers than in the dark-ATPase fibers. Following HS, mean SDH activities of both fiber types were significantly lower in the MG and TA than in the CON; by contrast, mean GPD activities were either maintained at the CON level or were higher in both MG and TA muscles. The data suggest an independence of the mechanisms determining the muscle fiber size and the metabolic adaptations associated with HS.

  9. Regulation of ClC-1 and KATP channels in action potential-firing fast-twitch muscle fibers.

    Science.gov (United States)

    Pedersen, Thomas Holm; de Paoli, Frank Vincenzo; de Paoli, Frank Vinzenco; Flatman, John A; Nielsen, Ole Baekgaard

    2009-10-01

    Action potential (AP) excitation requires a transient dominance of depolarizing membrane currents over the repolarizing membrane currents that stabilize the resting membrane potential. Such stabilizing currents, in turn, depend on passive membrane conductance (G(m)), which in skeletal muscle fibers covers membrane conductances for K(+) (G(K)) and Cl(-) (G(Cl)). Myotonic disorders and studies with metabolically poisoned muscle have revealed capacities of G(K) and G(Cl) to inversely interfere with muscle excitability. However, whether regulation of G(K) and G(Cl) occur in AP-firing muscle under normal physiological conditions is unknown. This study establishes a technique that allows the determination of G(Cl) and G(K) with a temporal resolution of seconds in AP-firing muscle fibers. With this approach, we have identified and quantified a biphasic regulation of G(m) in active fast-twitch extensor digitorum longus fibers of the rat. Thus, at the onset of AP firing, a reduction in G(Cl) of approximately 70% caused G(m) to decline by approximately 55% in a manner that is well described by a single exponential function characterized by a time constant of approximately 200 APs (phase 1). When stimulation was continued beyond approximately 1,800 APs, synchronized elevations in G(K) ( approximately 14-fold) and G(Cl) ( approximately 3-fold) caused G(m) to rise sigmoidally to approximately 400% of its level before AP firing (phase 2). Phase 2 was often associated with a failure to excite APs. When AP firing was ceased during phase 2, G(m) recovered to its level before AP firing in approximately 1 min. Experiments with glibenclamide (K(ATP) channel inhibitor) and 9-anthracene carboxylic acid (ClC-1 Cl(-) channel inhibitor) revealed that the decreased G(m) during phase 1 reflected ClC-1 channel inhibition, whereas the massively elevated G(m) during phase 2 reflected synchronized openings of ClC-1 and K(ATP) channels. In conclusion, G(Cl) and G(K) are acutely regulated in AP

  10. Increased wheel-running activity in the genetically skeletal muscle fast-twitch fiber-dominant rats.

    Science.gov (United States)

    Suwa, Masataka; Nakano, Hiroshi; Higaki, Yasuki; Nakamura, Tomohiro; Katsuta, Shigeru; Kumagai, Shuzo

    2003-01-01

    The purpose of the present study was to investigate whether genetic differences in muscle histochemical characteristics were related to the voluntary wheel-running activity level by using genetically fast-twitch fiber-dominant rats (FFDR) and control rats (CR). The rats were divided into four groups; sedentary CR (Sed-CR), wheel-running CR (WR-CR), sedentary FFDR (Sed-FFDR), and wheel-running FFDR (WR-FFDR). Wheel access was started at age 9 wk and lasted for 7 days. The FFDR showed a lower percentage of type I fibers of the deep portion of gastrocnemius and soleus muscles and a higher percentage of both type IIX fibers of the gastrocnemius muscle and type IIA fibers of the soleus muscle compared with CR. A higher capillary density and smaller fiber cross-sectional area were also observed in FFDR. The daily running distance in WR-FFDR was higher than in WR-CR for each 7 days. The total running distance for 7 days in WR-FFDR was 3.2-fold higher than in WR-CR. On day 7 of the 7-day test, the total number of active 1-min intervals for 24 h, the average rpm when they were active, and the maximum rpm for any single 1-min period in the WR-FFDR were significantly higher than in the WR-CR (1.5-, 2.9-, and 2.0-fold, respectively). These results suggest that mechanical or physiological muscle characteristics may thus affect the wheel-running activity level.

  11. Fiber polymorphism in skeletal muscles of the American lobster, Homarus americanus: continuum between slow-twitch (S1) and slow-tonic (S2) fibers.

    Science.gov (United States)

    Medler, Scott; Lilley, Travis; Mykles, Donald L

    2004-07-01

    In recent years, an increasing number of studies has reported the existence of single fibers expressing more than one myosin heavy chain (MHC) isoform at the level of fiber proteins and/or mRNA. These mixed phenotype fibers, often termed hybrid fibers, are currently being recognized as the predominant fiber type in many muscles, and the implications of these findings are currently a topic of great interest. In a recent study, we reported single fibers from the cutter claw closer muscle of lobsters that demonstrated a gradation between the slow-twitch (S1) and slow-tonic (S2) muscle phenotype. In the present study, we focused on S1 and S2 fibers from the superficial abdominal muscles of the lobster as a model to study the continuum among muscle fiber types. Complementary DNAs (cDNA) encoding an S2 isoform of myosin heavy chain (MHC) and an S2 isoform of tropomyosin (Tm) were isolated from the superficial abdominal flexor muscles of adult lobsters. These identified sequences were used to design PCR primers used in conjunction with RT-PCR and real-time PCR to measure expression levels of these genes in small muscle samples and single fibers. The relative expression of the corresponding S1 MHC and S1 Tm isoforms was measured in the same samples with PCR primers designed according to previously identified sequences. In addition, we measured the relative proportions of MHC, troponin (Tn) T and I protein isoforms present in the same samples to examine the correlation of these proteins with one another and with the MHC and Tm mRNAs. These analyses revealed significant correlations among the different myofibrillar proteins, with the S1 and S2 fibers being characterized by a whole assemblage of myofibrillar isoforms. However, they also showed that small muscle samples, and more importantly single fibers, existed as a continuum from one phenotype to another. Most fibers possessed mixtures of mRNA for MHC isoforms that were unexpected based on protein analysis. These findings

  12. Diaphragm assessment in mice overexpressing phospholamban in slow-twitch type I muscle fibers.

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    Fajardo, Val Andrew; Smith, Ian Curtis; Bombardier, Eric; Chambers, Paige J; Quadrilatero, Joe; Tupling, Allan Russell

    2016-06-01

    Phospholamban (PLN) and sarcolipin (SLN) are small inhibitory proteins that regulate the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) pump. Previous work from our laboratory revealed that in the soleus and gluteus minimus muscles of mice overexpressing PLN (Pln (OE)), SERCA function was impaired, dynamin 2 (3-5 fold) and SLN (7-9 fold) were upregulated, and features of human centronuclear myopathy (CNM) were observed. Here, we performed structural and functional experiments to evaluate whether the diaphragm muscles of the Pln (OE) mouse would exhibit CNM pathology and muscle weakness. Diaphragm muscles from Pln (OE) and WT mice were subjected to histological/histochemical/immunofluorescent staining, Ca(2+)-ATPase and Ca(2+) uptake assays, Western blotting, and in vitro electrical stimulation. Our results demonstrate that PLN overexpression reduced SERCA's apparent affinity for Ca(2+) but did not reduce maximal SERCA activity or rates of Ca(2+) uptake. SLN was upregulated 2.5-fold, whereas no changes in dynamin 2 expression were found. With respect to CNM, we did not observe type I fiber predominance, central nuclei, or central aggregation of oxidative activity in diaphragm, although type I fiber hypotrophy was present. Furthermore, in vitro contractility assessment of Pln (OE) diaphragm strips revealed no reductions in force-generating capacity, maximal rates of relaxation or force development, but did indicate that ½ relaxation time was prolonged. Therefore, the effects of PLN overexpression on skeletal muscle phenotype differ between diaphragm and the postural soleus and gluteus minimus muscles. Our findings here point to differences in SLN expression and type I fiber distribution as potential contributing factors.

  13. Effect of Verapamil on Excitation-Contraction Coupling in Frog Single Twitch Muscle Fiber. I. Effect of Verapamil in Low Concentration

    OpenAIRE

    小原, 一男; 鈴木, 稔子; 永井, 寅男

    1981-01-01

    The effects of verapamil in low concentration (0.1 mM) on electrical and mechanical responses in single twitch muscle fiber of the frog were examined and the following results were obtained. 1) Twitch tension was potentiated by verapamil during the first 2 min after application and then declined little by little. 2) Resting and action potentials were not changed by verapamil except for an enhancement of a negative afterpotential. 3) The duration of the active state was prolonged by 1.5 times ...

  14. Effect of spaceflight on the maximal shortening velocity, morphology, and enzyme profile of fast- and slow-twitch skeletal muscle fibers in rhesus monkeys

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    Fitts, R. H.; Romatowski, J. G.; De La Cruz, L.; Widrick, J. J.; Desplanches, D.

    2000-01-01

    Weightlessness has been shown to cause limb muscle wasting and a reduced peak force and power in the antigravity soleus muscle. Despite a reduced peak power, Caiozzo et al. observed an increased maximal shortening velocity in the rat soleus muscle following a 14-day space flight. The major purpose of the present investigation was to determine if weightlessness induced an elevated velocity in the antigravity slow type I fibers of the rhesus monkey (Macaca mulatta), as well as to establish a cellular mechanism for the effect. Spaceflight or models of weightlessness have been shown to increase glucose uptake, elevate muscle glycogen content, and increase fatigability of the soleus muscle. The latter appears to be in part caused by a reduced ability of the slow oxidative fibers to oxidize fats. A second goal of this study was to establish the extent to which weightlessness altered the substrate profile and glycolytic and oxidative enzyme capacity of individual slow- and fast-twitch fibers.

  15. カエルの Single Twitch Muscle Fiber のカリウム拘縮に対する低温の効果

    OpenAIRE

    筒浦, 理正; 高氏, 昌

    1981-01-01

    The effect of low temperature (4℃) on potassium contracture in single twitch muscle fibers of the frog was studied and the following results were obtained. 1. The activation curve of potassium contracture was shifted toward the left at lower concentrations of potassium, and was shifted downward at higher concentrations of potassium by lowering the temperature from 24 to 4℃. 2. The time course (plateau and spontaneous relaxation phases) of potassium contracture was markedly prolonged at low te...

  16. Long-term, but not short-term high-fat diet induces fiber composition changes and impaired contractile force in mouse fast-twitch skeletal muscle.

    Science.gov (United States)

    Eshima, Hiroaki; Tamura, Yoshifumi; Kakehi, Saori; Kurebayashi, Nagomi; Murayama, Takashi; Nakamura, Kyoko; Kakigi, Ryo; Okada, Takao; Sakurai, Takashi; Kawamori, Ryuzo; Watada, Hirotaka

    2017-04-01

    In this study, we investigated the effects of a short-term and long-term high-fat diet (HFD) on morphological and functional features of fast-twitch skeletal muscle. Male C57BL/6J mice were fed a HFD (60% fat) for 4 weeks (4-week HFD) or 12 weeks (12-week HFD). Subsequently, the fast-twitch extensor digitorum longus muscle was isolated, and the composition of muscle fiber type, expression levels of proteins involved in muscle contraction, and force production on electrical stimulation were analyzed. The 12-week HFD, but not the 4-week HFD, resulted in a decreased muscle tetanic force on 100 Hz stimulation compared with control (5.1 ± 1.4 N/g in the 12-week HFD vs. 7.5 ± 1.7 N/g in the control group; P muscle weight and cross-sectional area were not altered after both HFD protocols. Morphological analysis indicated that the percentage of type IIx myosin heavy chain fibers, mitochondrial oxidative enzyme activity, and intramyocellular lipid levels increased in the 12-week HFD group, but not in the 4-week HFD group, compared with controls (P decreased in the 12-week HFD group, but not in the 4-week HFD group (P muscle fibers. Given that skeletal muscle strength largely depends on muscle fiber type, the impaired muscle contractile force by a HFD might result from morphological changes of fiber type composition. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  17. Differentiation of the intracellular structure of slow- versus fast-twitch muscle fibers through evaluation of the dielectric properties of tissue.

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    Sanchez, B; Li, J; Bragos, R; Rutkove, S B

    2014-05-21

    Slow-twitch (type 1) skeletal muscle fibers have markedly greater mitochondrial content than fast-twitch (type 2) fibers. Accordingly, we sought to determine whether the dielectric properties of these two fiber types differed, consistent with their distinct intracellular morphologies. The longitudinal and transverse dielectric spectrum of the ex vivo rat soleus (a predominantly type 1 muscle) and the superficial layers of rat gastrocnemius (predominantly type 2) (n = 15) were measured in the 1 kHz-10 MHz frequency range and modeled to a resistivity Cole-Cole function. Major differences were especially apparent in the dielectric spectrum in the 1 to 10 MHz range. Specifically, the gastrocnemius demonstrated a well-defined, higher center frequency than the soleus muscle, whereas the soleus muscle showed a greater difference in the modeled zero and infinite resistivities than the gastrocnemius. These findings are consistent with the fact that soleus tissue has larger and more numerous mitochondria than gastrocnemius. Evaluation of tissue at high frequency could provide a novel approach for assessing intracellular structure in health and disease.

  18. Differentiation of the intracellular structure of slow- versus fast-twitch muscle fibers through evaluation of the dielectric properties of tissue

    Science.gov (United States)

    Sanchez, B.; Li, J.; Bragos, R.; Rutkove, S. B.

    2014-05-01

    Slow-twitch (type 1) skeletal muscle fibers have markedly greater mitochondrial content than fast-twitch (type 2) fibers. Accordingly, we sought to determine whether the dielectric properties of these two fiber types differed, consistent with their distinct intracellular morphologies. The longitudinal and transverse dielectric spectrum of the ex vivo rat soleus (a predominantly type 1 muscle) and the superficial layers of rat gastrocnemius (predominantly type 2) (n = 15) were measured in the 1 kHz-10 MHz frequency range and modeled to a resistivity Cole-Cole function. Major differences were especially apparent in the dielectric spectrum in the 1 to 10 MHz range. Specifically, the gastrocnemius demonstrated a well-defined, higher center frequency than the soleus muscle, whereas the soleus muscle showed a greater difference in the modeled zero and infinite resistivities than the gastrocnemius. These findings are consistent with the fact that soleus tissue has larger and more numerous mitochondria than gastrocnemius. Evaluation of tissue at high frequency could provide a novel approach for assessing intracellular structure in health and disease.

  19. Denervation produces different single fiber phenotypes in fast- and slow-twitch hindlimb muscles of the rat.

    Science.gov (United States)

    Patterson, M F; Stephenson, G M M; Stephenson, D G

    2006-09-01

    Using a single, mechanically skinned fiber approach, we tested the hypothesis that denervation (0 to 50 days) of skeletal muscles that do not overlap in fiber type composition [extensor digitorum longus (EDL) and soleus (SOL) muscles of Long-Evans hooded rats] leads to development of different fiber phenotypes. Denervation (50 day) was accompanied by 1) a marked increase in the proportion of hybrid IIB/D fibers (EDL) and I/IIA fibers (SOL) from 30% to >75% in both muscles, and a corresponding decrease in the proportion of pure fibers expressing only one myosin heavy chain (MHC) isoform; 2) complex muscle- and fiber-type specific changes in sarcoplasmic reticulum Ca(2+)-loading level at physiological pCa approximately 7.1, with EDL fibers displaying more consistent changes than SOL fibers; 3) decrease by approximately 50% in specific force of all fiber types; 4) decrease in sensitivity to Ca(2+), particularly for SOL fibers (by approximately 40%); 5) decrease in the maximum steepness of the force-pCa curves, particularly for the hybrid I/IIA SOL fibers (by approximately 35%); and 6) increased occurrence of biphasic behavior with respect to Sr(2+) activation in SOL fibers, indicating the presence of both slow and fast troponin C isoforms. No fiber types common to the two muscles were detected at any time points (day 7, 21, and 50) after denervation. The results provide strong evidence that not only neural factors, but also the intrinsic properties of a muscle fiber, influence the structural and functional properties of a particular muscle cell and explain important functional changes induced by denervation at both whole muscle and single cell levels.

  20. Functional pools of fast and slow twitch fibers observed by /sup 31/P-NMR during exercise of flexor wrist muscles in man

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.H.; Park, C.R.; Brown, R.L.; Chance, B.

    1987-05-01

    Functional compartments of fast and slow twitch fibers have been observed by /sup 31/P-NMR spectroscopy during exercise of the wrist flexor muscles in a sedentary, young male subject. Values of Pi, phosphocreatine (PCr) and adenine nucleotides were determined at rest and during an exercise protocol. The subject flexed his wrist muscles at 20% of maximum strength every 5 sec for 6 min and then increased his effort in the next two 6 min intervals to 40% and 60% of maximum. With exercise, the Pi/PCr rose rapidly to the exceptionally high value of 2.2 at 60% effort. As the Pi increased, the initial single peak (pH 7.0-6.9) split into two distinct components with pH values of 6.8 and 6.3. Quantitatively, distribution of the Pi was 40% in the pH 6.8 peak and 60% in the pH 6.3 peak as determined by area estimation following curve fitting. This presumably reflects two pools of Pi corresponding to the oxidative (slow twitch, high pH) and glycolytic (fast twitch, low pH) fibers. In the second identical exercise sequence which followed immediately, only one Pi peak (pH 6.8-6.9) appeared. This suggested that the glycolytic contribution to energy production was largely exhausted and the residual energy was derived from oxidative metabolism. During exercise at high levels, total phosphate decreased due primarily to loss of NMR visible adenine nucleotides. Similar phenomena have been observed in three other sedentary individuals, but not in trained athletes.

  1. Unchanged content of oxidative enzymes in fast-twitch muscle fibers and V˙O2 kinetics after intensified training in trained cyclists

    DEFF Research Database (Denmark)

    Christensen, Peter Møller; Gunnarsson, Thomas Gunnar Petursson; Thomassen, Martin;

    2015-01-01

    The present study examined if high intensity training (HIT) could increase the expression of oxidative enzymes in fast-twitch muscle fibers causing a faster oxygen uptake (V˙O2) response during intense (INT), but not moderate (MOD), exercise and reduce the V˙O2 slow component and muscle metabolic...... perturbation during INT. Pulmonary V˙O2 kinetics was determined in eight trained male cyclists (V˙O2-max: 59 ± 4 (means ± SD) mL min(-1) kg(-1)) during MOD (205 ± 12 W ~65% V˙O2-max) and INT (286 ± 17 W ~85% V˙O2-max) exercise before and after a 7-week HIT period (30-sec sprints and 4-min intervals) with a 50...... between MOD and INT. Muscle creatine phosphate was lower (42 ± 15 vs. 66 ± 17 mmol kg DW(-1)) and muscle lactate was higher (40 ± 18 vs. 14 ± 5 mmol kg DW(-1)) at 6 min of INT (P training with a volume reduction did not increase the content...

  2. Cyclosporin A preferentially attenuates skeletal slow-twitch muscle regeneration

    Directory of Open Access Journals (Sweden)

    Miyabara E.H.

    2005-01-01

    Full Text Available Calcineurin, a Ca2+/calmodulin-dependent phosphatase, is associated with muscle regeneration via NFATc1/GATA2-dependent pathways. However, it is not clear whether calcineurin preferentially affects the regeneration of slow- or fast-twitch muscles. We investigated the effect of a calcineurin inhibitor, cyclosporin A (CsA, on the morphology and fiber diameter of regenerating slow- and fast-twitch muscles. Adult Wistar rats (259.5 ± 9 g maintained under standard conditions were treated with CsA (20 mg/kg body weight, ip for 5 days, submitted to cryolesion of soleus and tibialis anterior (TA muscles on the 6th day, and then treated with CsA for an additional 21 days. The muscles were removed, weighed, frozen, and stored in liquid nitrogen. Cryolesion did not alter the body weight gain of the animals after 21 days of regeneration (P = 0.001 and CsA significantly reduced the body weight gain (15.5%; P = 0.01 during the same period. All treated TA and soleus muscles showed decreased weights (17 and 29%, respectively, P < 0.05. CsA treatment decreased the cross-sectional area of both soleus and TA muscles of cryoinjured animals (TA: 2108 ± 930 vs 792 ± 640 µm²; soleus: 2209 ± 322 vs 764 ± 439 m²; P < 0.001. Histological sections of both muscles stained with Toluidine blue revealed similar regenerative responses after cryolesion. In addition, CsA was able to minimize these responses, i.e., centralized nuclei and split fibers, more efficiently so in TA muscle. These results indicate that calcineurin preferentially plays a role in regeneration of slow-twitch muscle.

  3. Fiber-type-specific sensitivities and phenotypic adaptations to dietary fat overload differentially impact fast- versus slow-twitch muscle contractile function in C57BL/6J mice.

    Science.gov (United States)

    Ciapaite, Jolita; van den Berg, Sjoerd A; Houten, Sander M; Nicolay, Klaas; van Dijk, Ko Willems; Jeneson, Jeroen A

    2015-02-01

    High-fat diets (HFDs) have been shown to interfere with skeletal muscle energy metabolism and cause peripheral insulin resistance. However, understanding of HFD impact on skeletal muscle primary function, i.e., contractile performance, is limited. Male C57BL/6J mice were fed HFD containing lard (HFL) or palm oil (HFP), or low-fat diet (LFD) for 5weeks. Fast-twitch (FT) extensor digitorum longus (EDL) and slow-twitch (ST) soleus muscles were characterized with respect to contractile function and selected biochemical features. In FT EDL muscle, a 30%-50% increase in fatty acid (FA) content and doubling of long-chain acylcarnitine (C14-C18) content in response to HFL and HFP feeding were accompanied by increase in protein levels of peroxisome proliferator-activated receptor-γ coactivator-1α, mitochondrial oxidative phosphorylation complexes and acyl-CoA dehydrogenases involved in mitochondrial FA β-oxidation. Peak force of FT EDL twitch and tetanic contractions was unaltered, but the relaxation time (RT) of twitch contractions was 30% slower compared to LFD controls. The latter was caused by accumulation of lipid intermediates rather than changes in the expression levels of proteins involved in calcium handling. In ST soleus muscle, no evidence for lipid overload was found in any HFD group. However, particularly in HFP group, the peak force of twitch and tetanic contractions was reduced, but RT was faster than LFD controls. The latter was associated with a fast-to-slow shift in troponin T isoform expression. Taken together, these data highlight fiber-type-specific sensitivities and phenotypic adaptations to dietary lipid overload that differentially impact fast- versus slow-twitch skeletal muscle contractile function. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Changes of macromolecular organizations in nonjunctional sarcolemmas after cross—innervation—a study of fast—and slow—twitch muscle fiberes in rats

    Institute of Scientific and Technical Information of China (English)

    LUJINANLI; TIEFENGZHANG; 等

    1995-01-01

    The purpose of the present study was to analyse the changes of macromolecular organizations in nonjunctional sarcolemmas of different types of skeletal muscle fibres after cross-innervation.In normal rate the mean density of square arrays(6nm particles organized in orthogonal of square arrays(6nm particles organized in othogonal arrays)was 9.02/μm2 for the nonjunctional sarcolemmas of fast-twitch extensor digitorum longus(control EDL,CE)muscle fibres and 0.34/μm2 for the nunjunctional sarcolemmas of slow-twitch soleus(control SOL,CS)muscle fibres.After cross-innervation between the fast-twitch EDL and slow-twitch SOL muscle fibres by slow and fast muscle nerves respectively for three months ,the mean density was 0.45/μm2 for the nonjunctional sarcolemmas of the operated EDL(OE)and 8.3/μm2 for the nonjunctional sarcolemmas of the operated SOL(OS).This indicates that the cross-innervation causes a reciprocal transformation of the number and distribution of such macromolecular organizations in the electrically excitable nonjunctional sarcolemmas.

  5. Fatigue and caffeine effects in fast-twitch and slow-twitch muscles of the mouse.

    Science.gov (United States)

    Brust, M

    1976-12-28

    In excised, curarized and massively stimulated fast-twitch mouse gastrocnemius muscles the early twitch tension enhancements (treppe) during 1/s activity between 10 and 36 degrees C increase and affect more contractions as temperature increases. Tension output eventually declines at a temperature-independent rate. Half-relaxation time lengthens below 25 degrees C and shortens above 25 degrees C. During 1/0.63s twitches half-relaxation time lengthens even at 25 degrees C. In slow-twitch soleus muscles activity decreases twitch tension and half-relaxation time regardless of temperature. Activity shortens contraction times in both muscles. Oxygen lack induced by NaN3 cannot account satisfactorily for these results. Activation is apparently more plastic in the gastrocnemius than in the soleus, and the relationship between the rates of their activation and relaxation processes and the temperature sensitivities of these rates also seem to differ. In both muscles caffeine can convert activity-induced shortened of half-relaxation times into prolongations. In the soleus this effect is more pronounced at 30 than at 25 degrees C. At high temperature and twitch rates caffeine reduces treppe amplitude and duration without affecting the eventual twitch tension decline in the gastrocnemius while it greatly accelerates twitch tension decline in the soleus. In both muscles intrafiber Ca2+ movements are apparently major determinants of fatigue behavior.

  6. Calcium buffering properties of sarcoplasmic reticulum and calcium-induced Ca(2+) release during the quasi-steady level of release in twitch fibers from frog skeletal muscle.

    Science.gov (United States)

    Fénelon, Karine; Lamboley, Cédric R H; Carrier, Nicole; Pape, Paul C

    2012-10-01

    Experiments were performed to characterize the properties of the intrinsic Ca(2+) buffers in the sarcoplasmic reticulum (SR) of cut fibers from frog twitch muscle. The concentrations of total and free calcium ions within the SR ([Ca(T)](SR) and [Ca(2+)](SR)) were measured, respectively, with the EGTA/phenol red method and tetramethylmurexide (a low affinity Ca(2+) indicator). Results indicate SR Ca(2+) buffering was consistent with a single cooperative-binding component or a combination of a cooperative-binding component and a linear binding component accounting for 20% or less of the bound Ca(2+). Under the assumption of a single cooperative-binding component, the most likely resting values of [Ca(2+)](SR) and [Ca(T)](SR) are 0.67 and 17.1 mM, respectively, and the dissociation constant, Hill coefficient, and concentration of the Ca-binding sites are 0.78 mM, 3.0, and 44 mM, respectively. This information can be used to calculate a variable proportional to the Ca(2+) permeability of the SR, namely d[Ca(T)](SR)/dt ÷ [Ca(2+)](SR) (denoted release permeability), in experiments in which only [Ca(T)](SR) or [Ca(2+)](SR) is measured. In response to a voltage-clamp step to -20 mV at 15°C, the release permeability reaches an early peak followed by a rapid decline to a quasi-steady level that lasts ~50 ms, followed by a slower decline during which the release permeability decreases by at least threefold. During the quasi-steady level of release, the release amplitude is 3.3-fold greater than expected from voltage activation alone, a result consistent with the recruitment by Ca-induced Ca(2+) release of 2.3 SR Ca(2+) release channels neighboring each channel activated by its associated voltage sensor. Release permeability at -60 mV increases as [Ca(T)](SR) decreases from its resting physiological level to ~0.1 of this level. This result argues against a release termination mechanism proposed in mammalian muscle fibers in which a luminal sensor of [Ca(2+)](SR) inhibits

  7. Differences between glycogen biogenesis in fast- and slow-twitch rabbit muscle

    DEFF Research Database (Denmark)

    Cussó, R; Lerner, L R; Cadefau, J;

    2003-01-01

    Skeletal muscle glycogen is an essential energy substrate for muscular activity. The biochemical properties of the enzymes involved in de novo synthesis of glycogen were analysed in two types of rabbit skeletal muscle fiber (fast- and slow-twitch). Glycogen concentration was higher in fast...

  8. Prolonged contraction-relaxation cycle of fast-twitch muscles in parvalbumin knockout mice.

    Science.gov (United States)

    Schwaller, B; Dick, J; Dhoot, G; Carroll, S; Vrbova, G; Nicotera, P; Pette, D; Wyss, A; Bluethmann, H; Hunziker, W; Celio, M R

    1999-02-01

    The calcium-binding protein parvalbumin (PV) occurs at high concentrations in fast-contracting vertebrate muscle fibers. Its putative role in facilitating the rapid relaxation of mammalian fast-twitch muscle fibers by acting as a temporary buffer for Ca2+ is still controversial. We generated knockout mice for PV (PV -/-) and compared the Ca2+ transients and the dynamics of contraction of their muscles with those from heterozygous (PV +/-) and wild-type (WT) mice. In the muscles of PV-deficient mice, the decay of intracellular Ca2+ concentration ([Ca2+]i) after 20-ms stimulation was slower compared with WT mice and led to a prolongation of the time required to attain peak twitch tension and to an extension of the half-relaxation time. The integral [Ca2+]i in muscle fibers of PV -/- mice was higher and consequently the force generated during a single twitch was approximately 40% greater than in PV +/- and WT animals. Acceleration of the contraction-relaxation cycle of fast-twitch muscle fibers by PV may confer an advantage in the performance of rapid, phasic movements.

  9. Twitch interpolation technique in testing of maximal muscle strength

    DEFF Research Database (Denmark)

    Bülow, P M; Nørregaard, J; Danneskiold-Samsøe, B

    1993-01-01

    The aim was to study the methodological aspects of the muscle twitch interpolation technique in estimating the maximal force of contraction in the quadriceps muscle utilizing commercial muscle testing equipment. Six healthy subjects participated in seven sets of experiments testing the effects on...

  10. Assessing voluntary muscle activation with the twitch interpolation technique.

    Science.gov (United States)

    Shield, Anthony; Zhou, Shi

    2004-01-01

    The twitch interpolation technique is commonly employed to assess the completeness of skeletal muscle activation during voluntary contractions. Early applications of twitch interpolation suggested that healthy human subjects could fully activate most of the skeletal muscles to which the technique had been applied. More recently, however, highly sensitive twitch interpolation has revealed that even healthy adults routinely fail to fully activate a number of skeletal muscles despite apparently maximal effort. Unfortunately, some disagreement exists as to how the results of twitch interpolation should be employed to quantify voluntary activation. The negative linear relationship between evoked twitch force and voluntary force that has been observed by some researchers implies that voluntary activation can be quantified by scaling a single interpolated twitch to a control twitch evoked in relaxed muscle. Observations of non-linear evoked-voluntary force relationships have lead to the suggestion that the single interpolated twitch ratio can not accurately estimate voluntary activation. Instead, it has been proposed that muscle activation is better determined by extrapolating the relationship between evoked and voluntary force to provide an estimate of true maximum force. However, criticism of the single interpolated twitch ratio typically fails to take into account the reasons for the non-linearity of the evoked-voluntary force relationship. When these reasons are examined, it appears that most are even more challenging to the validity of extrapolation than they are to the linear equation. Furthermore, several factors that contribute to the observed non-linearity can be minimised or even eliminated with appropriate experimental technique. The detection of small activation deficits requires high resolution measurement of force and careful consideration of numerous experimental details such as the site of stimulation, stimulation intensity and the number of interpolated

  11. Effects of caffeine at different temperatures on contractile properties of slow-twitch and fast-twitch rat muscles.

    Science.gov (United States)

    Wondmikun, Y; Soukup, T; Asmussen, G

    2006-01-01

    The slow-twitch soleus muscle (SOL) exhibits decreased twitch tension (cold depression) in response to a decreased temperature, whereas the fast-twitch extensor digitorum longus (EDL) muscle shows enhanced twitch tension (cold potentiation). On the other hand, the slow-twitch SOL muscle is more sensitive to twitch potentiation and contractures evoked by caffeine than the fast-twitch EDL muscle. In order to reveal the effects of these counteracting conditions (temperature and caffeine), we have studied the combined effects of temperature changes on the potentiation effects of caffeine in modulating muscle contractions and contractures in both muscles. Isolated muscles, bathed in a Tyrode solution containing 0.1-60 mM caffeine, were stimulated directly and isometric single twitches, fused tetanic contractions and contractures were recorded at 35 degrees C and 20 degrees C. Our results showed that twitches and tetani of both SOL and EDL were potentiated and prolonged in the presence of 0.3-10 mM caffeine. Despite the cold depression, the extent of potentiation of the twitch tension by caffeine in the SOL muscle at 20 degrees C was by 10-15 % higher than that at 35 degrees C, while no significant difference was noted in the EDL muscle between both temperatures. Since the increase of twitch tension was significantly higher than potentiation of tetani in both muscles, the twitch-tetanus ratio was enhanced. Higher concentrations of caffeine induced contractures in both muscles; the contracture threshold was, however, lower in the SOL than in the EDL muscle at both temperatures. Furthermore, the maximal tension was achieved at lower caffeine concentrations in the SOL muscle at both 35 degrees C and 20 degrees C compared to the EDL muscle. These effects of caffeine were rapidly and completely reversed in both muscles when the test solution was replaced by the Tyrode solution. The results have indicated that the potentiation effect of caffeine is both time- and temperature

  12. Mechanical tension and spontaneous muscle twitching precede the formation of cross-striated muscle in vivo.

    Science.gov (United States)

    Weitkunat, Manuela; Lindauer, Martina; Bausch, Andreas; Schnorrer, Frank

    2017-02-07

    Muscle forces are produced by repetitive stereotyped acto-myosin units called sarcomeres. Sarcomeres are chained into linear myofibrils spanning the entire muscle fiber. In mammalian body muscles, myofibrils are aligned laterally resulting in their typical cross-striated morphology. Despite this detailed textbook knowledge about the adult muscle structure, it is still unclear how cross-striated myofibrils are built in vivo Here, we investigate the morphogenesis of Drosophila abdominal muscles and establish them as in vivo model for cross-striated muscle development. Using live imaging, we find that long immature myofibrils lacking a periodic acto-myosin pattern are built simultaneously in the entire muscle fiber and then align laterally to mature cross-striated myofibrils. Interestingly, laser micro-lesion experiments demonstrate that mechanical tension precedes the formation of the immature myofibrils. Moreover, these immature myofibrils do generate spontaneous Ca(2+) dependent contractions in vivo, which when chemically blocked result in cross-striation defects. Together, these results suggest a myofibrillogenesis model, in which mechanical tension and spontaneous muscle twitchings synchronise the simultaneous self-organisation of different sarcomeric protein complexes to build highly regular cross-striated myofibrils spanning throughout large muscle fibers.

  13. Comparison of regulated passive membrane conductance in action potential-firing fast- and slow-twitch muscle.

    Science.gov (United States)

    Pedersen, Thomas Holm; Macdonald, William Alexander; de Paoli, Frank Vincenzo; de Paoli, Frank Vinzenco; Gurung, Iman Singh; Nielsen, Ole Baekgaard

    2009-10-01

    In several pathological and experimental conditions, the passive membrane conductance of muscle fibers (G(m)) and their excitability are inversely related. Despite this capacity of G(m) to determine muscle excitability, its regulation in active muscle fibers is largely unexplored. In this issue, our previous study (Pedersen et al. 2009. J. Gen. Physiol. doi:10.1085/jgp.200910291) established a technique with which biphasic regulation of G(m) in action potential (AP)-firing fast-twitch fibers of rat extensor digitorum longus muscles was identified and characterized with temporal resolution of seconds. This showed that AP firing initially reduced G(m) via ClC-1 channel inhibition but after approximately 1,800 APs, G(m) rose substantially, causing AP excitation failure. This late increase of G(m) reflected activation of ClC-1 and K(ATP) channels. The present study has explored regulation of G(m) in AP-firing slow-twitch fibers of soleus muscle and compared it to G(m) dynamics in fast-twitch fibers. It further explored aspects of the cellular signaling that conveyed regulation of G(m) in AP-firing fibers. Thus, in both fiber types, AP firing first triggered protein kinase C (PKC)-dependent ClC-1 channel inhibition that reduced G(m) by approximately 50%. Experiments with dantrolene showed that AP-triggered SR Ca(2+) release activated this PKC-mediated ClC-1 channel inhibition that was associated with reduced rheobase current and improved function of depolarized muscles, indicating that the reduced G(m) enhanced muscle fiber excitability. In fast-twitch fibers, the late rise in G(m) was accelerated by glucose-free conditions, whereas it was postponed when intermittent resting periods were introduced during AP firing. Remarkably, elevation of G(m) was never encountered in AP-firing slow-twitch fibers, even after 15,000 APs. These observations implicate metabolic depression in the elevation of G(m) in AP-firing fast-twitch fibers. It is concluded that regulation of G(m) is

  14. Increased postexercise insulin sensitivity is accompanied by increased AS160 phosphorylation in slow-twitch soleus muscle.

    Science.gov (United States)

    Iwabe, Maiko; Kawamoto, Emi; Koshinaka, Keiichi; Kawanaka, Kentaro

    2014-12-01

    A single bout of exercise can enhance insulin-stimulated glucose uptake in both fast-twitch (type II) and slow-twitch (type I) skeletal muscle for several hours postexercise. Akt substrate of 160 kDa (AS160) is most distal insulin signaling proteins that have been proposed to contribute to the postexercise enhancement of insulin action in fast-twitch muscle. In this study, we examined whether the postexercise increase in insulin action of glucose uptake in slow-twitch muscle is accompanied by increased phosphorylation of AS160 and its paralog TBC1D1. Male Wistar rats (~1-month-old) were exercised on a treadmill for 180 min (9 m/min). Insulin (50 μU/mL)-stimulated glucose uptake was increased at 2 h after cessation of exercise in soleus muscle composed of predominantly slow-twitch fibers. This postexercise increase in insulin action of glucose uptake was accompanied by increased phosphorylation of AS160 (detected by phospho-Thr642 and phospho-Ser588 antibody). On the other hand, prior exercise did not increase phosphorylation of TBC1D1 (detected by phospho-Thr590) at 2 h postexercise. These results suggest the possibility that an enhancement in AS160 phosphorylation but not TBC1D1 phosphorylation is involved with increased postexercise insulin action of glucose uptake in slow-twitch muscle.

  15. Impact of TIEG1 on the structural properties of fast- and slow-twitch skeletal muscle.

    Science.gov (United States)

    Kammoun, Malek; Meme, Sandra; Meme, William; Subramaniam, Malayannan; Hawse, John R; Canon, Francis; Bensamoun, Sabine F

    2017-03-01

    Transforming growth factor-beta (TGF-β)-inducible early gene-1 (TIEG1) is a transcription factor that is highly expressed in skeletal muscle. The purpose of this study was to characterize the structural properties of both fast-twitch (EDL) and slow-twitch (soleus) muscles in the hindlimb of TIEG1-deficient (TIEG1(-/-) ) mice. Ten slow and 10 fast muscles were analyzed from TIEG1(-/-) and wild-type (WT) mice using MRI texture (MRI-TA) and histological analyses. MRI-TA could discriminate between WT slow and fast muscles. Deletion of the TIEG1 gene led to changes in the texture profile within both muscle types. Specifically, muscle isolated from TIEG1(-/-) mice displayed hypertrophy, hyperplasia, and a modification of fiber area distribution. We demonstrated that TIEG1 plays an important role in the structural properties of skeletal muscle. This study further implicates important roles for TIEG1 in the development of skeletal muscle and suggests that defects in TIEG1 expression and/or function may be associated with muscle disease. Muscle Nerve 55: 410-416, 2017. © 2016 Wiley Periodicals, Inc.

  16. Single muscle fiber adaptations with marathon training.

    Science.gov (United States)

    Trappe, Scott; Harber, Matthew; Creer, Andrew; Gallagher, Philip; Slivka, Dustin; Minchev, Kiril; Whitsett, David

    2006-09-01

    The purpose of this investigation was to characterize the effects of marathon training on single muscle fiber contractile function in a group of recreational runners. Muscle biopsies were obtained from the gastrocnemius muscle of seven individuals (22 +/- 1 yr, 177 +/- 3 cm, and 68 +/- 2 kg) before, after 13 wk of run training, and after 3 wk of taper. Slow-twitch myosin heavy chain [(MHC) I] and fast-twitch (MHC IIa) muscle fibers were analyzed for size, strength (P(o)), speed (V(o)), and power. The run training program led to the successful completion of a marathon (range 3 h 56 min to 5 h 35 min). Oxygen uptake during submaximal running and citrate synthase activity were improved (P 60% increase (P twitch and fast-twitch muscle fiber size but that it maintained or improved the functional profile of these fibers. A taper period before the marathon further improved the functional profile of the muscle, which was targeted to the fast-twitch muscle fibers.

  17. Role of the JP45-Calsequestrin Complex on Calcium Entry in Slow Twitch Skeletal Muscles.

    Science.gov (United States)

    Mosca, Barbara; Eckhardt, Jan; Bergamelli, Leda; Treves, Susan; Bongianino, Rossana; De Negri, Marco; Priori, Silvia G; Protasi, Feliciano; Zorzato, Francesco

    2016-07-08

    We exploited a variety of mouse models to assess the roles of JP45-CASQ1 (CASQ, calsequestrin) and JP45-CASQ2 on calcium entry in slow twitch muscles. In flexor digitorum brevis (FDB) fibers isolated from JP45-CASQ1-CASQ2 triple KO mice, calcium transients induced by tetanic stimulation rely on calcium entry via La(3+)- and nifedipine-sensitive calcium channels. The comparison of excitation-coupled calcium entry (ECCE) between FDB fibers from WT, JP45KO, CASQ1KO, CASQ2KO, JP45-CASQ1 double KO, JP45-CASQ2 double KO, and JP45-CASQ1-CASQ2 triple KO shows that ECCE enhancement requires ablation of both CASQs and JP45. Calcium entry activated by ablation of both JP45-CASQ1 and JP45-CASQ2 complexes supports tetanic force development in slow twitch soleus muscles. In addition, we show that CASQs interact with JP45 at Ca(2+) concentrations similar to those present in the lumen of the sarcoplasmic reticulum at rest, whereas Ca(2+) concentrations similar to those present in the SR lumen after depolarization-induced calcium release cause the dissociation of JP45 from CASQs. Our results show that the complex JP45-CASQs is a negative regulator of ECCE and that tetanic force development in slow twitch muscles is supported by the dynamic interaction between JP45 and CASQs. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. Role of the JP45-Calsequestrin Complex on Calcium Entry in Slow Twitch Skeletal Muscles*

    Science.gov (United States)

    Mosca, Barbara; Eckhardt, Jan; Bergamelli, Leda; Treves, Susan; Bongianino, Rossana; De Negri, Marco; Priori, Silvia G.; Protasi, Feliciano; Zorzato, Francesco

    2016-01-01

    We exploited a variety of mouse models to assess the roles of JP45-CASQ1 (CASQ, calsequestrin) and JP45-CASQ2 on calcium entry in slow twitch muscles. In flexor digitorum brevis (FDB) fibers isolated from JP45-CASQ1-CASQ2 triple KO mice, calcium transients induced by tetanic stimulation rely on calcium entry via La3+- and nifedipine-sensitive calcium channels. The comparison of excitation-coupled calcium entry (ECCE) between FDB fibers from WT, JP45KO, CASQ1KO, CASQ2KO, JP45-CASQ1 double KO, JP45-CASQ2 double KO, and JP45-CASQ1-CASQ2 triple KO shows that ECCE enhancement requires ablation of both CASQs and JP45. Calcium entry activated by ablation of both JP45-CASQ1 and JP45-CASQ2 complexes supports tetanic force development in slow twitch soleus muscles. In addition, we show that CASQs interact with JP45 at Ca2+ concentrations similar to those present in the lumen of the sarcoplasmic reticulum at rest, whereas Ca2+ concentrations similar to those present in the SR lumen after depolarization-induced calcium release cause the dissociation of JP45 from CASQs. Our results show that the complex JP45-CASQs is a negative regulator of ECCE and that tetanic force development in slow twitch muscles is supported by the dynamic interaction between JP45 and CASQs. PMID:27189940

  19. Composition of Muscle Fiber Types in Rat Rotator Cuff Muscles.

    Science.gov (United States)

    Rui, Yongjun; Pan, Feng; Mi, Jingyi

    2016-10-01

    The rat is a suitable model to study human rotator cuff pathology owing to the similarities in morphological anatomy structure. However, few studies have reported the composition muscle fiber types of rotator cuff muscles in the rat. In this study, the myosin heavy chain (MyHC) isoforms were stained by immunofluorescence to show the muscle fiber types composition and distribution in rotator cuff muscles of the rat. It was found that rotator cuff muscles in the rat were of mixed fiber type composition. The majority of rotator cuff fibers labeled positively for MyHCII. Moreover, the rat rotator cuff muscles contained hybrid fibers. So, compared with human rotator cuff muscles composed partly of slow-twitch fibers, the majority of fast-twitch fibers in rat rotator cuff muscles should be considered when the rat model study focus on the pathological process of rotator cuff muscles after injury. Gaining greater insight into muscle fiber types in rotator cuff muscles of the rat may contribute to elucidate the mechanism of pathological change in rotator cuff muscles-related diseases. Anat Rec, 299:1397-1401, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  20. Impact of TIEG1 Deletion on the Passive Mechanical Properties of Fast and Slow Twitch Skeletal Muscles in Female Mice

    Science.gov (United States)

    Kammoun, Malek; Pouletaut, Philippe; Canon, Francis; Subramaniam, Malayannan; Hawse, John R.; Vayssade, Muriel; Bensamoun, Sabine F.

    2016-01-01

    As transforming growth factor (TGF)-β inducible early gene-1 is highly expressed in skeletal muscle, the effect of TIEG1 gene deletion on the passive mechanical properties of slow and fast twitch muscle fibers was analyzed. Twenty five muscle fibers were harvested from soleus (Sol) and extensor digitorum longus (EDL) muscles from TIEG1-/- (N = 5) and control (N = 5) mice. Mechanical tests were performed on fibers and the dynamic and static stresses were measured. A viscoelastic Hill model of 3rd order was used to fit the experimental relaxation test data. In parallel, immunohistochemical analyses were performed on three serial transverse sections to detect the myosin isoforms within the slow and fast muscles. The percentage and the mean cross sectional area of each fiber type were calculated. These tests revealed a significant increase in the mechanical stress properties for the TIEG1-/- Sol fibers while a significant decrease appeared for the TIEG1-/- EDL fibers. Hill model tracked the shape of the experimental relaxation curve for both genotypes and both fiber types. Immunohistochemical results showed hypertrophy of all fiber types for TIEG1-/- muscles with an increase in the percentage of glycolytic fibers (IIX, and IIB) and a decrease of oxidative fibers (I, and IIA). This study has provided new insights into the role of TIEG1, known as KLF10, in the functional (SoltypeI: more resistant, EDLtypeIIB: less resistant) and morphological (glycolytic hypertrophy) properties of fast and slow twitch skeletal muscles. Further investigation at the cellular level will better reveal the role of the TIEG1 gene in skeletal muscle tissue. PMID:27736981

  1. Unchanged content of oxidative enzymes in fast-twitch muscle fibers and V˙O2 kinetics after intensified training in trained cyclists

    DEFF Research Database (Denmark)

    Christensen, Peter Møller; Gunnarsson, Thomas Gunnar Petursson; Thomassen, Martin;

    2015-01-01

    DW(-1) min(-1)) of CS (56 ± 8 post-HIT vs. 59 ± 10 pre-HIT), HAD (27 ± 6 vs. 29 ± 3) and PFK (340 ± 69 vs. 318 ± 105) and the capillary to fiber ratio (2.30 ± 0.16 vs. 2.38 ± 0.20) was unaltered following HIT. V˙O2 kinetics was unchanged with HIT and the speed of the primary response did not differ...

  2. Twitch potentiation influences the time course of twitch depression in muscle relaxant studies : A pharmacokinetic-pharmacodynamic explanation

    NARCIS (Netherlands)

    Eleveld, Douglas J.; Proost, Johannes H.; Wierda, J. Mark K. H.

    2006-01-01

    The time course of twitch depression following neuromuscular blocking agent (NMBA) administration is influenced by the duration of control neuromuscular monitoring (twitch stabilization). The physiological mechanism for this interaction is not known. During twitch stabilization twitch response often

  3. Sarcomere length-dependence of activity-dependent twitch potentiation in mouse skeletal muscle

    Directory of Open Access Journals (Sweden)

    MacIntosh Brian R

    2002-12-01

    Full Text Available Abstract Background It has been reported that potentiation of a skeletal muscle twitch response is proportional to muscle length with a negative slope during staircase, and a positive slope during posttetanic potentiation. This study was done to directly compare staircase and posttetanic responses with measurement of sarcomere length to compare their length-dependence. Methods Mouse extensor digitorum longus (EDL muscles were dissected to small bundles of fibers, which permit measurement of sarcomere length (SL, by laser diffraction. In vitro fixed-end contractions of EDL fiber bundles were elicited at 22°C and 35°C at sarcomere lengths ranging from 2.35 μm to 3.85 μm. Twitch contractions were assessed before and after 1.5 s of 75 Hz stimulation at 22°C or during 10 s of 10 Hz stimulation at 22°C or 35°C. Results Staircase potentiation was greater at 35°C than 22°C, and the relative magnitude of the twitch contraction (Pt*/Pt was proportional to sarcomere length with a negative slope, over the range 2.3 μm – 3.7 μm. Linear regression yielded the following: Pt*/Pt = -0.59·SL+3.27 (r2 = 0.74; Pt*/Pt = -0.39·SL+2.34 (r2 = 0.48; and Pt*/Pt = -0.50·SL+2.45 (r2 = 0.80 for staircase at 35°C, and 22°C and posttetanic response respectively. Posttetanic depression rather than potentiation was present at long SL. This indicates that there may be two processes operating in these muscles to modulate the force: one that enhances and a second that depresses the force. Either or both of these processes may have a length-dependence of its mechanism. Conclusion There is no evidence that posttetanic potentiation is fundamentally different from staircase in these muscles.

  4. Molecular transformations in sarcoplasmic reticulum of fast-twitch muscle by electro-stimulation.

    Science.gov (United States)

    Heilmann, C; Pette, D

    1979-02-01

    Chronic electro-stimulation of fast-twitch rabbit muscle with the frequency pattern received by a slow-twitch muscle induces a progressive transformation of the sarcoplasmic reticulum. After 2 days stimulation activities of Ca2+-dependent ATPase and of Ca2+ transport begin to decrease, and are paralleled by a progressive decrease in Ca2+-dependent and Ca2+, Mg2+-dependent phosphoprotein formation, reduced rate of dephosphorylation and a rearrangement of the electrophoretic polypeptide and phosphoprotein patterns. These findings suggest a transformation of the sarcoplasmic reticulum to resemble that of a slow-twitch muscle. This transformation is paralleled by increase in time-to-peak of twitch contraction and half relaxation time and occurs before conversion of the myosin light chain pattern is observed. The parallel time course of changes in contractile properties of stimulated muscle and the molecular and functional properties of the sarcoplasmic reticulum emphasizes the definitive role of the latter in determining the twitch characteristics of fast and slow twitch muscles.

  5. Matching of sarcoplasmic reticulum and contractile properties in rat fast- and slow-twitch muscle fibres.

    Science.gov (United States)

    Trinh, Huong H; Lamb, Graham D

    2006-07-01

    1. The twitch characteristics (fast-twitch or slow-twitch) of skeletal muscle fibres are determined not only by the contractile apparatus properties of the fibre, but also by the time-course of Ca2+ release and re-uptake by the sarcoplasmic reticulum (SR). The present study examined, in individual fibres from non-transforming muscle of the rat, whether particular SR properties are matched to the contractile apparatus properties of the fibre, in particular in the case of fibres with fast-twitch contractile apparatus located in a slow-twitch muscle, namely the soleus. 2. Force was recorded in single, mechanically skinned fibres from extensor digitorum longus (EDL), gastrocnemius, peroneus longus and soleus muscles. Using repeated cycles in which the SR was emptied of all releasable Ca2+ and then reloaded, it was possible to determine the relative amount of Ca2+ present in the SR endogenously, the maximum SR capacity and the rate of Ca2+ loading. The sensitivity of the contractile apparatus to Ca2+ and Sr2+ was used to classify the fibres as fast-twitch (FT), slow-twitch (ST) or mixed (< 3% of the fibres examined) and thereby identify the likely troponin C and myosin heavy chain types present. 3. There was no significant difference in SR properties between the groups of FT fibres obtained from the four different muscles, including soleus. Despite some overlap in the SR properties of individual fibres between the FT and ST groups, the properties of the FT fibres in all four muscles studied were significantly different from those of the ST and mixed fibres. 4. In general, in FT fibres the SR had a larger capacity and the endogenous Ca2+ content was a relatively lower percentage of maximum compared with ST fibres. Importantly, in terms of their SR properties, FT fibres from soleus muscle more closely resembled FT fibres from other muscles than they did ST fibres from soleus muscle.

  6. An effective solution for capturing the single twitch of muscle: application to monitor muscle relaxation.

    Science.gov (United States)

    Colak, Omer H; Girard, Emmanuelle; Krejci, Eric

    2014-09-01

    In this study, a fast algorithm was developed to capture of train of four and to filter extra contraction and noises. A low pass filter created to filter extra contraction and high frequency noises. Then, a TCA algorithm designed to capturing of the single twitch of muscle. The algorithm updated to remove embedded extra contraction and to derive boundary values in this location from cubic spline interpolation. Efficiency of TCA and effect of extra contraction tested in time and frequency domain.

  7. Muscle twitch responses for shaping the multi-pad electrode for functional electrical stimulation

    OpenAIRE

    Malešević Nebojša; Popović Lana; Bijelić Goran; Kvaščev Goran

    2010-01-01

    In this paper we present a method for optimization of multi-pad electrode spatial selectivity during transcutaneous Functional Electrical Stimulation (FES) of hand. The presented method is based on measurement of individual muscle twitch responses during low frequency electrical stimulation via pads within multi-pad electrode. Twitch responses are recorded by Micro-Electro-Mechanical Systems (MEMS) accelerometers. The aim of this methodology is to substitute bulky sensors, torque sensor...

  8. Twitch and tetanic tension during culture of mature Xenopus laevis single muscle fibres.

    Science.gov (United States)

    Jaspers, R T; Feenstra, H M; Lee- de Groot, M B; Huijing, P A; van der Laarse, W J

    2001-12-01

    Investigation of the mechanisms of muscle adaptation requires independent control of the regulating factors. The aim of the present study was to develop a serum-free medium to culture mature single muscle fibres of Xenopus laevis. As an example, we used the culture system to study adaptation of twitch and tetanic force characteristics, number of sarcomeres in series and fibre cross-section. Fibres dissected from m. iliofibularis (n = 10) were kept in culture at a fibre mean sarcomere length of 2.3 microm in a culture medium without serum. Twitch and tetanic tension were determined daily. Before and after culture the number of sarcomeres was determined by laser diffraction and fibre cross-sectional area (CSA) was determined by microscopy. For five fibres twitch tension increased during culture and tetanic tension was stable for periods varying from 8 to 14 days ('stable fibres'), after which fibres were removed from culture for analysis. Fibre CSA and the number of sarcomeres in series remained constant during culture. Five other fibres showed a substantial reduction in twitch and tetanic tension within the first five days of culture ('unstable fibres'). After 7-9 days of culture, three of these fibres died. For two of the unstable fibres, after the substantial force reduction, twitch and tetanic tension increased again. Finally at day 14 and 18 of culture, respectively, the tensions attained values higher than their original values. For stable fibres, twitch contraction time, twitch half-relaxation time and tetanus 10%-relaxation time increased during culture. For unstable fibres these parameters fluctuated. For all fibres the stimulus threshold fluctuated during the first two days, and then remained constant, even for the fibres that were cultured for at least two weeks. It is concluded that the present culture system for mature muscle fibres allows long-term studies within a well-defined medium. Unfortunately, initial tetanic and twitch force are poor predictors

  9. Osteoprotegerin and β2-Agonists Mitigate Muscular Dystrophy in Slow- and Fast-Twitch Skeletal Muscles.

    Science.gov (United States)

    Dufresne, Sébastien S; Boulanger-Piette, Antoine; Frenette, Jérôme

    2017-03-01

    Our recent work showed that daily injections of osteoprotegerin (OPG)-immunoglobulin fragment complex (OPG-Fc) completely restore the function of fast-twitch extensor digitorum longus muscles in dystrophic mdx mice, a murine model of Duchenne muscular dystrophy. However, despite marked improvements, OPG-Fc was not as effective in preventing the loss of function of slow-twitch soleus and diaphragm muscles. Because β2-agonists enhance the function of slow- and fast-twitch dystrophic muscles and because their use is limited by their adverse effects on bone and cardiac tissues, we hypothesized that OPG-Fc, a bone and skeletal muscle protector, acts synergistically with β2-agonists and potentiates their positive effects on skeletal muscles. We observed that the content of β2-adrenergic receptors, which are mainly expressed in skeletal muscle, is significantly reduced in dystrophic muscles but is rescued by the injection of OPG-Fc. Most important, OPG-Fc combined with a low dose of formoterol, a member of a new generation of β2-agonists, histologically and functionally rescued slow-twitch dystrophic muscles. This combination of therapeutic agents, which have already been tested and approved for human use, may open up new therapeutic avenues for Duchenne muscular dystrophy and possibly other neuromuscular diseases. Copyright © 2017 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

  10. An experimental study on enzyme and twitch muscle fiber in spasmodic muscle after cervical perivalcular sympathectomy%颈总动脉周交感神经网剥脱切除术后痉挛肌肉内酶与肌纤维结构的研究

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    目的 探讨交感神经切断后,痉挛肌肉内酶与肌纤维结构的改变。方法 将20只wistar大白鼠作成痉挛性模型,分成两组,随机选择1组行颈总动脉周交感神经网剥脱切除术,另1组作为对照,于术后第20天切取两组大鼠部分肱三头肌组织,采用(Ellman)爱尔蒙法及AU1000检测仪测定肌组织内乙酰胆碱酯酶活性和肌酸激酶含量,在IBAS图像分析仪上观察两组肌组织内快收缩肌纤维与慢收缩肌纤维的改变情况。结果 交感神经切断后,乙酰胆碱酯酶活性和肌酸激酶含量明显下降,分别从(3.37±1.01) U/g降至(2.15±1.42) U/g(P<0.01);(3 582.90±1 561.7) IU/L降至(420.10±73.55) IU/L(P<0.01),快肌纤维明显减少,从(275 727.31±98 240.23) μm2降至(96 554.35±43 345.35) μm2(P<0.01);慢肌纤维显著增加,由(42 710.78±28 858.37) μm2增至(27 0764.02±66 642.46) μm2(P<0.01)。结论 交感神经切断后痉挛肌肉兴奋性下降。%Objective To investigate the change of enzyme and twitch muscle fiber in spasmodic muscle after sympathectomy.  Methods Spasmodic model was developed in 20 wistar rats. The rats were divided into 2 groups: one group received cervical perivalcular sympathectomy and the other group served as a control. The AchE and CK in musculsus triceps brachii of rats in the 2 groups were tested by using Ellman and AU 1000. The fast twitch muscle fibers and slow twitch muscle in musculsus triceps brachii were examined by using IBAS graph device at 20th day after sympathectomy. Results After sympathectomy, the AchE, CK and the fast muscle fibers were obviously decreased from (3.37±1.01) U/g to (2.15±1.42) U/g (P<0.01), (3 582.90±1 561.7) IU/L to (420.10±73.55) IU/L (P<0.01) and from (275 727.31±98 240.23) μm2 to (96 554.35±43 345.35) μm2 (P<0.01), respectively, while the slow twitch muscle fibers significantly increased from

  11. The twitch interpolation technique for study of fatigue of human quadriceps muscle

    DEFF Research Database (Denmark)

    Bülow, P M; Nørregaard, J; Mehlsen, J;

    1995-01-01

    technique. Then an endurance test was performed in which the subjects made repeated isometric contractions at 50% of the 'true' maximum torque for 4 s, separated by 6 s rest periods. During the test, the force response to single electrical stimulation (twitch amplitude) was measured at 50% and 25......The aim of the study was to examine if the twitch interpolation technique could be used to objectively measure fatigue in the quadriceps muscle in subjects performing submaximally. The 'true' maximum isometric quadriceps torque was determined in 21 healthy subject using the twitch interpolation......% of the estimated maximum torque. In 10 subjects, the test was repeated 2-4 weeks later. Twitch amplitudes at 50% of maximum torque declined exponentially with time in 20 of 21 subjects. The distribution of the exponential rate constant was skewed with a mean of 4.6 h-1 and range of 0.3-21.5 h-1. After...

  12. Increased postexercise insulin sensitivity is accompanied by increased AS160 phosphorylation in slow‐twitch soleus muscle

    OpenAIRE

    Iwabe, Maiko; Kawamoto, Emi; Koshinaka, Keiichi; Kawanaka, Kentaro

    2014-01-01

    Abstract A single bout of exercise can enhance insulin‐stimulated glucose uptake in both fast‐twitch (type II) and slow‐twitch (type I) skeletal muscle for several hours postexercise. Akt substrate of 160 kDa (AS160) is most distal insulin signaling proteins that have been proposed to contribute to the postexercise enhancement of insulin action in fast‐twitch muscle. In this study, we examined whether the postexercise increase in insulin action of glucose uptake in slow‐twitch muscle is accom...

  13. Regulatory light chain phosphorylation increases eccentric contraction-induced injury in skinned fast-twitch fibers.

    Science.gov (United States)

    Childers, Martin K; McDonald, Kerry S

    2004-02-01

    During contraction, activation of Ca(2+)/calmodulin-dependent myosin light chain kinase (MLCK) results in phosphorylation of myosin's regulatory light chain (RLC), which potentiates force and increases speed of force development over a wide range of [Ca(2+)]. We tested the hypothesis that RLC phosphorylation by MLCK mediates the extent of eccentric contraction-induced injury as measured by force deficit in skinned fast-twitch skeletal muscle fibers. Results indicated that RLC phosphorylation in single skinned rat psoas fibers significantly increased Ca(2+) sensitivity of isometric force; isometric force from 50 +/- 16 to 59 +/- 18 kN/m(2) during maximal Ca(2+) activation; peak absolute power output from 38 +/- 15 to 48 +/- 14 nW during maximal Ca(2+) activation; and the magnitude of contraction-induced force deficit during maximal (pCa 4.5) activation from 26 +/- 9.8 to 35 +/- 9.6%. We conclude that RLC phosphorylation increases force deficits following eccentric contractions, perhaps by increasing the number of force-generating cross-bridges.

  14. Interpolated twitches in fatiguing single mouse muscle fibres: implications for the assessment of central fatigue.

    Science.gov (United States)

    Place, Nicolas; Yamada, Takashi; Bruton, Joseph D; Westerblad, Håkan

    2008-06-01

    An electrically evoked twitch during a maximal voluntary contraction (twitch interpolation) is frequently used to assess central fatigue. In this study we used intact single muscle fibres to determine if intramuscular mechanisms could affect the force increase with the twitch interpolation technique. Intact single fibres from flexor digitorum brevis of NMRI mice were dissected and mounted in a chamber equipped with a force transducer. Free myoplasmic [Ca2+] ([Ca2+](i)) was measured with the fluorescent Ca2+ indicator indo-1. Seven fibres were fatigued with repeated 70 Hz tetani until 40% initial force with an interpolated pulse evoked every fifth tetanus. Results showed that the force generated by the interpolated twitch increased throughout fatigue, being 9 +/- 1% of tetanic force at the start and 19 +/- 1% at the end (P twitch during fatigue but rather to the fact that the force-[Ca2+](i) relationship is sigmoidal and fibres entered a steeper part of the relationship during fatigue. In another set of experiments, we observed that repeated tetani evoked at 150 Hz resulted in more rapid fatigue development than at 70 Hz and there was a decrease in force ('sag') during contractions, which was not observed at 70 Hz. In conclusion, the extent of central fatigue is difficult to assess and it may be overestimated when using the twitch interpolation technique.

  15. Calcium Release in Frog Cut Twitch Fibers Exposed to Different Ionic Environments under Voltage Clamp

    National Research Council Canada - National Science Library

    Hui, Chiu Shuen

    1999-01-01

    Calcium release was measured in highly stretched frog cut twitch fibers mounted in a double Vaseline-gap voltage clamp chamber, with the internal solution containing 20 mM EGTA plus 0.4 or 1.8 mM added calcium...

  16. Re-innervation of fast and slow twitch muscle following nerve crush at birth.

    Science.gov (United States)

    McArdle, J J; Sansone, F M

    1977-10-01

    1. The frequency of miniature end-plate potentials (m.e.p.p.s) was significantly greater in the fast twitch extensor digitorum longus muscle (extensor) than in the slow twitch soleus, even though end-plate surface area was greater for fibres in the latter muscle. 2. Crush of the sciatic nerve at birth did not prevent the appearance of this difference in m.e.p.p. frequency. However, the frequency of the potentials in the re-innervated muscles was less than normal, even though the regenerated neuromuscular junction was qualitatively normal in morphology. 3. Though the re-innevated muscles were differentiated with respect to twitch time course, the extensor muscle was more responsive than normal to the contracture-inducing action of caffeine. 4. The Z line of the re-innervated extensor muscle was similar to that of the normal soleus in thickness. 5. Resting potential, passive electrical properties and action potential generating mechanism of the sarcolemma were normal. 6. Since the re-innervated muscles lacked muscle spindles, a role of sensory feed-back in the function of the neuromuscular junction as well as the neutrotrophic regulation of muscle is discussed.

  17. Regenerating tail muscles in lizard contain Fast but not Slow Myosin indicating that most myofibers belong to the fast twitch type for rapid contraction.

    Science.gov (United States)

    Alibardi, L

    2015-10-01

    During tail regeneration in lizards a large mass of muscle tissue is formed in form of segmental myomeres of similar size located under the dermis of the new tail. These muscles accumulate glycogen and a fast form of myosin typical for twitch myofibers as it is shown by light and ultrastructural immunocytochemistry using an antibody directed against a Fast Myosin Heavy Chain. High resolution immunogold labeling shows that an intense labeling for fast myosin is localized over the thick filaments of the numerous myofibrils in about 70% of the regenerated myofibers while the labeling becomes less intense in the remaining muscle fibers. The present observations indicate that at least two subtypes of Fast Myosin containing muscle fibers are regenerated, the prevalent type was of the fast twitch containing few mitochondria, sparse glycogen, numerous smooth endoplasmic reticulum vesicles. The second, and less frequent type was a Fast-Oxidative-Glycolitic twitch fiber containing more mitochondria, a denser cytoplasm and myofibrils. Since their initial differentiation, myoblasts, myotubes and especially the regenerated myofibers do not accumulate any immuno-detectable Slow Myosin Heavy Chain. The study indicates that most of the segmental muscles of the regenerated tail serve for the limited bending of the tail during locomotion and trashing after amputation of the regenerated tail, a phenomenon that facilitates predator escape.

  18. Modeling of twitch fade based on slow interaction of nondepolarizing muscle relaxants with the presynaptic receptors.

    Science.gov (United States)

    Bhatt, Shashi B; Amann, Anton; Nigrovic, Vladimir

    2006-08-01

    Nondepolarizing muscle relaxants (MRs) diminish the indirectly evoked single twitch due to their binding to the postsynaptic receptors. Additionally, the MRs produce progressive diminution of successive twitches upon repetitive stimulation (fade). Our study addresses the generation of fade as observed under clinical situation. The study was conducted in two phases. In the clinical part, we have evaluated the time course of twitch depression and fade following the administration of several doses of three MRs (rocuronium, pancuronium, and cisatracurium). In the second part, we have modified our model of neuromuscular transmission to simulate the time course of twitch depression and fade. The MR was assumed to bind to a single site on the presynaptic receptor to produce fade. The rates of interaction with the presynaptic receptors were characterized in terms of the arbitrarily assigned equilibrium dissociation constant and the half-life for dissociation of the presynaptic complex. A method was developed to relate the release of acetylcholine to the occupancy of the presynaptic receptors. The strength of the first and the fourth twitch was calculated from the peak concentration of the activated postsynaptic receptors, i.e., of those receptors with both sites occupied by acetylcholine. Our results indicate that, while the affinity of the MR for the presynaptic receptor plays little role in the time course of fade, the rate of dissociation of the complex between the presynaptic receptors and the muscle relaxant may be critical in determining the time course of fade. Tentative estimates of this parameter are offered.

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

    Science.gov (United States)

    Morrissette, J; Xu, L; Nelson, A; Meissner, G; Block, B A

    2000-11-01

    Two distinct skeletal muscle ryanodine receptors (RyR1s) are expressed in a fiber type-specific manner in fish skeletal muscle (11). In this study, we compare [(3)H]ryanodine binding and single channel activity of RyR1-slow from fish slow-twitch skeletal muscle with RyR1-fast and RyR3 isolated from fast-twitch skeletal muscle. Scatchard plots indicate that RyR1-slow has a lower affinity for [(3)H]ryanodine when compared with RyR1-fast. In single channel recordings, RyR1-slow and RyR1-fast had similar slope conductances. However, the maximum open probability (P(o)) of RyR1-slow was threefold less than the maximum P(o) of RyR1-fast. Single channel studies also revealed the presence of two populations of RyRs in tuna fast-twitch muscle (RyR1-fast and RyR3). RyR3 had the highest P(o) of all the RyR channels and displayed less inhibition at millimolar Ca(2+). The addition of 5 mM Mg-ATP or 2.5 mM beta, gamma-methyleneadenosine 5'-triphosphate (AMP-PCP) to the channels increased the P(o) and [(3)H]ryanodine binding of both RyR1s but also caused a shift in the Ca(2+) dependency curve of RyR1-slow such that Ca(2+)-dependent inactivation was attenuated. [(3)H]ryanodine binding data also showed that Mg(2+)-dependent inhibition of RyR1-slow was reduced in the presence of AMP-PCP. These results indicate differences in the physiological properties of RyRs in fish slow- and fast-twitch skeletal muscle, which may contribute to differences in the way intracellular Ca(2+) is regulated in these muscle types.

  20. The twitch interpolation technique for the estimation of true quadriceps muscle strength.

    Science.gov (United States)

    Nørregaard, J; Lykkegaard, J J; Bülow, P M; Danneskiold-Samsøe, B

    1997-09-01

    The aim of this study was to examine the reliability of the twitch interpolation technique when used to estimate the true isometric knee extensor muscle strength. This included an examination of whether submaximal activation causes any bias in the estimation of the true muscle strength and an examination of the precision of the method. Twenty healthy subjects completed three contraction series, in which the subjects were told to perform as if their voluntary strength was 60%, 80% or 100% of that determined by a maximal voluntary contraction (MVC). Electrical muscle stimulations were given at each of five different contraction levels in each series. At torque levels above 25% of MVC the relationship between torque and twitch size could be approximated to be linear. The true muscle strength (TMS) could therefore be estimated using linear regression of the twitch-torque relationship to the torque point of no twitch in each of the three series, termed TMS60, TMS80 and TMS100. The TMS80 was slightly lower (P estimated central activation of below 40-50% were excluded. The only moderate precision and the slightly lower estimations in subjects applying submaximal does, however, limit its usefulness.

  1. Blood flow response to electrically induced twitch and tetanic lower-limb muscle contractions.

    NARCIS (Netherlands)

    Janssen, T.W.; Hopman, M.T.E.

    2003-01-01

    OBJECTIVES: To compare the effect of electric stimulation (ES)-induced twitch with tetanic leg muscle contractions on blood flow responses and to assess blood flow responses in the contralateral inactive leg. DESIGN: Intervention with within-subject comparisons. SETTING: University research laborato

  2. Stabilization and stability of twitch force during mechanomyography of the adductor pollicis muscle

    NARCIS (Netherlands)

    van Santen, G; Fidler, [No Value; Wierda, JMKH

    1998-01-01

    Objective. In order to study the stabilization time, the increase in twitch force during stabilization and the maintenance of stability during mechanomyography of the adductor pollicis muscle, neuromuscular function was monitored in 20 patients anaesthetized without the use of a neuromuscular blocki

  3. Age-related differences in twitch properties and muscle activation of the first dorsal interosseous.

    Science.gov (United States)

    Miller, Jonathan D; Herda, Trent J; Trevino, Michael A; Sterczala, Adam J; Ciccone, Anthony B; Nicoll, Justin X

    2017-06-01

    To examine twitch force potentiation and twitch contraction duration, as well as electromyographic amplitude (EMGRMS) and motor unit mean firing rates (MFR) at targeted forces between young and old individuals in the first dorsal interosseous (FDI). Ultrasonography was used to assess muscle quality. Twenty-two young (YG) (age=22.6±2.7years) and 14 older (OD) (age=62.1±4.7years) individuals completed conditioning contractions at 10% and 50% maximal voluntary contraction, (MVC) during which EMGRMS and MFRs were assessed. Evoked twitches preceded and followed the conditioning contractions. Ultrasound images were taken to quantify muscle quality (cross-sectional area [CSA] and echo intensity [EI]). No differences were found between young and old for CSA, pre-conditioning contraction twitch force, or MFRs (P>0.05). However, OD individuals exhibited greater EI and contraction duration (PMFRs. Ultrasonography suggested age-related changes in muscle structure contributed to altered contractile properties in the OD. Greater muscle activation requirements can have negative implications on fatigue resistance at low to moderate intensities in older individuals. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

  4. Differential microRNA Expression in Fast- and Slow-Twitch Skeletal Muscle of Piaractus mesopotamicus during Growth.

    Directory of Open Access Journals (Sweden)

    Bruno Oliveira da Silva Duran

    Full Text Available Pacu (Piaractus mesopotamicus is a Brazilian fish with a high economic value in pisciculture due to its rusticity and fast growth. Postnatal growth of skeletal muscle in fish occurs by hyperplasia and/or hypertrophy, processes that are dependent on the proliferation and differentiation of myoblasts. A class of small noncoding RNAs, known as microRNAs (miRNAs, represses the expression of target mRNAs, and many studies have demonstrated that miR-1, miR-133, miR-206 and miR-499 regulate different processes in skeletal muscle through the mRNA silencing of hdac4 (histone deacetylase 4, srf (serum response factor, pax7 (paired box 7 and sox6 ((sex determining region Y-box 6, respectively. The aim of our work was to evaluate the expression of these miRNAs and their putative target mRNAs in fast- and slow-twitch skeletal muscle of pacu during growth. We used pacus in three different development stages: larval (aged 30 days, juvenile (aged 90 days and 150 days and adult (aged 2 years. To complement our study, we also performed a pacu myoblast cell culture, which allowed us to investigate miRNA expression in the progression from myoblast proliferation to differentiation. Our results revealed an inverse correlation between the expression of the miRNAs and their target mRNAs, and there was evidence that miR-1 and miR-206 may regulate the differentiation of myoblasts, whereas miR-133 may regulate the proliferation of these cells. miR-499 was highly expressed in slow-twitch muscle, which suggests its involvement in the specification of the slow phenotype in muscle fibers. The expression of these miRNAs exhibited variations between different development stages and between distinct muscle twitch phenotypes. This work provides the first identification of miRNA expression profiles in pacu skeletal muscle and suggests an important role of these molecules in muscle growth and in the maintenance of the muscle phenotype.

  5. Differential microRNA Expression in Fast- and Slow-Twitch Skeletal Muscle of Piaractus mesopotamicus during Growth.

    Science.gov (United States)

    Duran, Bruno Oliveira da Silva; Fernandez, Geysson Javier; Mareco, Edson Assunção; Moraes, Leonardo Nazario; Salomão, Rondinelle Artur Simões; Gutierrez de Paula, Tassiana; Santos, Vander Bruno; Carvalho, Robson Francisco; Dal-Pai-Silva, Maeli; Dal-Pai-Silvca, Maeli

    2015-01-01

    Pacu (Piaractus mesopotamicus) is a Brazilian fish with a high economic value in pisciculture due to its rusticity and fast growth. Postnatal growth of skeletal muscle in fish occurs by hyperplasia and/or hypertrophy, processes that are dependent on the proliferation and differentiation of myoblasts. A class of small noncoding RNAs, known as microRNAs (miRNAs), represses the expression of target mRNAs, and many studies have demonstrated that miR-1, miR-133, miR-206 and miR-499 regulate different processes in skeletal muscle through the mRNA silencing of hdac4 (histone deacetylase 4), srf (serum response factor), pax7 (paired box 7) and sox6 ((sex determining region Y)-box 6), respectively. The aim of our work was to evaluate the expression of these miRNAs and their putative target mRNAs in fast- and slow-twitch skeletal muscle of pacu during growth. We used pacus in three different development stages: larval (aged 30 days), juvenile (aged 90 days and 150 days) and adult (aged 2 years). To complement our study, we also performed a pacu myoblast cell culture, which allowed us to investigate miRNA expression in the progression from myoblast proliferation to differentiation. Our results revealed an inverse correlation between the expression of the miRNAs and their target mRNAs, and there was evidence that miR-1 and miR-206 may regulate the differentiation of myoblasts, whereas miR-133 may regulate the proliferation of these cells. miR-499 was highly expressed in slow-twitch muscle, which suggests its involvement in the specification of the slow phenotype in muscle fibers. The expression of these miRNAs exhibited variations between different development stages and between distinct muscle twitch phenotypes. This work provides the first identification of miRNA expression profiles in pacu skeletal muscle and suggests an important role of these molecules in muscle growth and in the maintenance of the muscle phenotype.

  6. Myosin binding protein-C slow: a multifaceted family of proteins with a complex expression profile in fast and slow twitch skeletal muscles.

    Science.gov (United States)

    Ackermann, Maegen A; Kontrogianni-Konstantopoulos, Aikaterini

    2013-01-01

    Myosin Binding Protein-C slow (sMyBP-C) comprises a complex family of proteins expressed in slow and fast type skeletal muscles. Similar to its fast and cardiac counterparts, sMyBP-C functions to modulate the formation of actomyosin cross-bridges, and to organize and stabilize sarcomeric A- and M-bands. The slow form of MyBP-C was originally classified as a single protein, however several variants encoded by the single MYBPC1 gene have been recently identified. Alternative splicing of the 5' and 3' ends of the MYBPC1 transcript has led to the differential expression of small unique segments interspersed between common domains. In addition, the NH2-terminus of sMyBP-C undergoes complex phosphorylation. Thus, alternative splicing and phosphorylation appear to regulate the functional activities of sMyBP-C. sMyBP-C proteins are not restricted to slow twitch muscles, but they are abundantly expressed in fast twitch muscles, too. Using bioinformatic tools, we herein perform a systematic comparison of the known human and mouse sMyBP-C variants. In addition, using single fiber westerns and antibodies to a common region of all known sMyBP-C variants, we present a detailed and comprehensive characterization of the expression profile of sMyBP-C proteins in the slow twitch soleus and the fast twitch flexor digitorum brevis (FDB) mouse muscles. Our studies demonstrate for the first time that distinct sMyBP-C variants are co-expressed in the same fiber, and that their expression profile differs among fibers. Given the differential expression of sMyBP-C variants in single fibers, it becomes apparent that each variant or combination thereof may play unique roles in the regulation of actomyosin cross-bridges formation and the stabilization of thick filaments.

  7. Myosin Binding Protein-C Slow: a multifaceted family of proteins with a complex expression profile in fast and slow twitch skeletal muscles

    Directory of Open Access Journals (Sweden)

    Maegen A Ackermann

    2013-12-01

    Full Text Available Myosin Binding Protein-C slow (sMyBP-C comprises a complex family of proteins expressed in slow and fast type skeletal muscles. Similar to its fast and cardiac counterparts, sMyBP-C functions to modulate the formation of actomyosin cross-bridges, and to organize and stabilize sarcomeric A- and M-bands. The slow form of MyBP-C was originally classified as a single protein, however several variants encoded by the single MYBPC1 gene have been recently identified. Alternative splicing of the 5’ and 3’ ends of the MYBPC1 transcript has led to the differential expression of small unique segments interspersed between common domains. In addition, the NH2-terminus of sMyBP-C undergoes complex phosphorylation. Thus, alternative splicing and phosphorylation appear to regulate the functional activities of sMyBP-C. sMyBP-C proteins are not restricted to slow twitch muscles, but they are abundantly expressed in fast twitch muscles, too. Using bioinformatic tools, we herein perform a systematic comparison of the known human and mouse sMyBP-C variants. In addition, using single fiber westerns and antibodies to a common region of all known sMyBP-C variants, we present a detailed and comprehensive characterization of the expression profile of sMyBP-C proteins in the slow twitch soleus and the fast twitch flexor digitorum brevis (FDB mouse muscles. Our studies demonstrate for the first time that distinct sMyBP-C variants are co-expressed in the same fiber, and that their expression profile differs among fibers. Given the differential expression of sMyBP-C variants in single fibers, it becomes apparent that each variant or combination thereof may play unique roles in the regulation of actomyosin cross-bridges formation and the stabilization of thick filaments.

  8. Differential gene expression of muscle-specific ubiquitin ligase MAFbx/Atrogin-1 and MuRF1 in response to immobilization-induced atrophy of slow-twitch and fast-twitch muscles.

    Science.gov (United States)

    Okamoto, Takeshi; Torii, Suguru; Machida, Shuichi

    2011-11-01

    We examined muscle-specific ubiquitin ligases MAFbx/Atrogin-1 and MuRF1 gene expression resulting from immobilization-induced skeletal muscle atrophy of slow-twitch soleus and fast-twitch plantaris muscles. Male C57BL/6 mice were subjected to hindlimb immobilization, which induced similar percentage decreases in muscle mass in the soleus and plantaris muscles. Expression of MAFbx/Atrogin-1 and MuRF1 was significantly greater in the plantaris muscle than in the soleus muscle during the early stage of atrophy. After a 3-day period of atrophy, total FOXO3a protein level had increased in both muscles, while phosphorylated FOXO3a protein had decreased in the plantaris muscle, but not in the soleus muscle. PGC-1α protein expression did not change following immobilization in both muscles, but basal PGC-1α protein in the soleus was markedly higher than that in plantaris muscles. These data suggest that although soleus and plantaris muscles atrophied to a similar extent and that muscle-specific ubiquitin protein ligases (E3) may contribute more to the atrophy of fast-twitch muscle than to that of slow-twitch muscle during immobilization.

  9. An Active Learning Mammalian Skeletal Muscle Lab Demonstrating Contractile and Kinetic Properties of Fast- and Slow-Twitch Muscle

    Science.gov (United States)

    Head, S. I.; Arber, M. B.

    2013-01-01

    The fact that humans possess fast and slow-twitch muscle in the ratio of approximately 50% has profound implications for designing exercise training strategies for power and endurance activities. With the growth of exercise and sport science courses, we have seen the need to develop an undergraduate student laboratory that demonstrates the basic…

  10. An Active Learning Mammalian Skeletal Muscle Lab Demonstrating Contractile and Kinetic Properties of Fast- and Slow-Twitch Muscle

    Science.gov (United States)

    Head, S. I.; Arber, M. B.

    2013-01-01

    The fact that humans possess fast and slow-twitch muscle in the ratio of approximately 50% has profound implications for designing exercise training strategies for power and endurance activities. With the growth of exercise and sport science courses, we have seen the need to develop an undergraduate student laboratory that demonstrates the basic…

  11. Sarcoplasmic reticulum calcium release compared in slow-twitch and fast-twitch fibres of mouse muscle.

    Science.gov (United States)

    Baylor, S M; Hollingworth, S

    2003-08-15

    Experiments were carried out to compare the amplitude and time course of Ca2+ release from the sarcoplasmic reticulum (SR) in intact slow-twitch and fast-twitch mouse fibres. Individual fibres within small bundles were injected with furaptra, a low-affinity, rapidly responding Ca2+ indicator. In response to a single action potential at 16 degrees C, the peak amplitude and half-duration of the change in myoplasmic free [Ca2+] (Delta[Ca2+]) differed significantly between fibre types (slow-twitch: peak amplitude, 9.4 +/- 1.0 microM (mean +/- S.E.M.); half-duration, 7.7 +/- 0.6 ms; fast-twitch: peak amplitude 18.5 +/- 0.5 microM; half-duration, 4.9 +/- 0.3 ms). SR Ca2+ release was estimated from Delta[Ca2+] with a computational model that calculated Ca2+ binding to the major myoplasmic Ca2+ buffers (troponin, ATP and parvalbumin); buffer concentrations and reaction rate constants were adjusted to reflect fibre-type differences. In response to an action potential, the total concentration of released Ca2+ (Delta[CaT]) and the peak rate of Ca2+ release ((d/dt)Delta[CaT]) differed about 3-fold between the fibre types (slow-twitch: Delta[CaT], 127 +/- 7 microM; (d/dt)Delta[CaT], 70 +/- 6 microM ms-1; fast-twitch: Delta[CaT], 346 +/- 6 microM; (d/dt)Delta[CaT], 212 +/- 4 microM ms-1). In contrast, the half-duration of (d/dt)Delta[CaT] was very similar in the two fibre types (slow-twitch, 1.8 +/- 0.1 ms; fast-twitch, 1.6 +/- 0.0 ms). When fibres were stimulated with a 5-shock train at 67 Hz, the peaks of (d/dt)Delta[CaT] in response to the second and subsequent shocks were much smaller than that due to the first shock; the later peaks, expressed as a fraction of the amplitude of the first peak, were similar in the two fibre types (slow-twitch, 0.2-0.3; fast-twitch, 0.1-0.3). The results support the conclusion that individual SR Ca2+ release units function similarly in slow-twitch and fast-twitch mammalian fibres.

  12. In vivo behaviour of human muscle architecture and mechanomyographic response using the interpolated twitch technique.

    Science.gov (United States)

    Ohta, Yoichi; Shima, Norihiro; Yabe, Kyonosuke

    2009-06-01

    This study investigated the origin of curvilinear change in the superimposed mechanomyogram (MMG) amplitude of the human medial gastrocnemius muscle (MG) with increasing contraction intensity. The superimposed twitch amplitude, the superimposed MMG amplitude and the extent of fascicle shortening were measured using ultrasonic images of electrical stimulation during isometric plantar flexions at levels 20%, 40%, 60%, 80%, and 100% of the maximal voluntary contraction (MVC). The superimposed twitch amplitude, the superimposed MMG amplitude and the extent of fascicle shortening decreased with increasing contraction intensity. The superimposed MMG amplitude and the extent of fascicle shortening showed a curvilinear decrease, while the superimposed twitch amplitude showed a linear decrease at levels up to 80% of the MVC. There was a linear relationship between the superimposed MMG amplitude and the extent of fascicle shortening at different contraction intensities. These results indicate that the superimposed MMG amplitude reflects changes in the extent of fascicle shortening at different contraction intensities better than the superimposed twitch amplitude. Our study suggests that the origin of the curvilinear decrease of superimposed MMG amplitude is associated with a curvilinear decrease of the extent of fascicle shortening with increasing contraction intensity in the human MG.

  13. Effect of tibial bone resection on the development of fast- and slow-twitch skeletal muscles in foetal sheep.

    Science.gov (United States)

    West, J M; Williams, N A; Luff, A R; Walker, D W

    2000-04-01

    To determine if longitudinal bone growth affects the differentiation of fast- and slow-twitch muscles, the tibial bone was sectioned at 90 days gestation in foetal sheep so that the lower leg was permanently without structural support. At 140 days (term is approximately 147 days) the contractile properties of whole muscles, activation profiles of single fibres and ultrastructure of fast- and slow-twitch muscles from the hindlimbs were studied. The contractile and activation profiles of the slow-twitch soleus muscles were significantly affected by tibial bone resection (TIBX). The soleus muscles from the TIBX hindlimbs showed: (1) a decrease in the time to peak of the twitch responses from 106.2 +/- 10.7 ms (control, n = 4) to 65.1 +/- 2.48 ms (TIBX, n = 5); (2) fatigue profiles more characteristic of those observed in the fast-twitch muscles: and (3) Ca2+ - and Sr2+ -activation profiles of skinned fibres similar to those from intact hindlimbs at earlier stages of gestation. In the FDL, TIBX did not significantly change whole muscle twitch contraction time, the fatigue profile or the Ca2+ - and Sr2+ -activation profiles of skinned fibres. Electron microscopy showed an increased deposition of glycogen in both soleus and FDL muscles. This study shows that the development of the slow-twitch phenotype is impeded in the absence of the physical support normally provided by the tibial bone. We suggest that longitudinal stretch is an important factor in allowing full expression of the slow-twitch phenotype.

  14. Relation between equatorial x-ray intensities and isometric twitch forces in frog skeletal muscle

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Hidehiro; Tameyasu, Tsukasa; Sugi, Haruo (Teikyo Univ., Tokyo (Japan). Faculty of Medicine)

    1983-01-01

    The sartorius muscle of bullfrog (Rana catesbeiana) was mounted vertically in an experimental chamber. The muscle was continuously perfused with Ringer solution, and stimulated with single 2 msec supramaximal current pulses. The equatorial X-ray diffraction pattern (specimen to detector distance, 40 cm) during isometric twitches was recorded with a linear position-sensitive proportional counter, and the data were registered in a computer memory system. With an increase of temperature from 5 to 22/sup 0/C, the magnitude of peak twitch force was reduced by about 50% with a marked decrease in the duration of mechanical response, while the minimum value of Isub(1.0)/Isub(1.1) attained during a twitch increased by more than twofold. On the other hand, the equatorial reflection from resting and fully tetanized muscles showed no appreciable dependence on temperature, though the steady tetanic force P/sub 0/ increased by about 10% with an increase in temperature from 5 to 25/sup 0/C. The intensity ratio is not a linear function of isometric force developed.

  15. Catalase-positive microperoxisomes in rat soleus and extensor digitorum longus muscle fiber types

    Science.gov (United States)

    Riley, Danny A.; Bain, James L. W.; Ellis, Stanley

    1988-01-01

    The size, distribution, and content of catalase-reactive microperoxisomes were investigated cytochemically in three types of muscle fibers from the soleus and the extensor digitorum longus (EDL) of male rats. Muscle fibers were classified on the basis of the mitochondrial content and distribution, the Z-band widths, and the size and shape of myofibrils as the slow-twitch oxidative (SO), the fast-twitch oxidative glycolytic (FOG), and the fast-twitch glycolytic (FG) fibers. It was found that both the EDL and soleus SO fibers possessed the largest microperoxisomes. A comparison of microperoxisome number per muscle fiber area or the microperoxisome area per fiber area revealed following ranking, starting from the largest number and the area-ratio values: soleus SO, EDL SO, EDL FOG, and EDL FG.

  16. Developmental changes in the activation properties and ultrastructure of fast- and slow-twitch muscles from fetal sheep.

    Science.gov (United States)

    West, J M; Barclay, C J; Luff, A R; Walker, D W

    1999-04-01

    At early stages of muscle development, skeletal muscles contract and relax slowly, regardless of whether they are destined to become fast- or slow-twitch. In this study, we have characterised the activation profiles of developing fast- and slow-twitch muscles from a precocial species, the sheep, to determine if the activation profiles of the muscles are characteristically slow when both the fast- and slow-twitch muscles have slow isometric contraction profiles. Single skinned muscle fibres from the fast-twitch flexor digitorum longus (FDL) and slow-twitch soleus muscles from fetal (gestational ages 70, 90, 120 and 140 days; term 147 days) and neonatal (8 weeks old) sheep were used to determine the isometric force-pCa (pCa = -log10[Ca2+]) and force-pSr relations during development. Fast-twitch mammalian muscles generally have a greatly different sensitivity to Ca2+ and Sr2+ whereas slow-twitch muscles have a similar sensitivity to these divalent cations. At all ages studied, the force-pCa and force-pSr relations of the FDL muscle were widely separated. The mean separation of the mid-point of the curves (pCa50-pSr50) was approximately 1.1. This is typical of adult fast-twitch muscle. The force-pCa and force-pSr curves for soleus muscle were also widely separated at 70 and 90 days gestation (pCa50-pSr50 approximately 0.75); between 90 days and 140 days this separation decreased significantly to approximately 0.2. This leads to a paradoxical situation whereby at early stages of muscle development the fast muscles have contraction dynamics of slow muscles but the slow muscles have activation profiles more characteristic of fast muscles. The time course for development of the FDL and soleus is different, based on sarcomere structure with the soleus muscle developing clearly defined sarcomere structure earlier in gestation than the FDL. At 70 days gestation the FDL muscle had no clearly defined sarcomeres. Force (N cm-2) increased almost linearly between 70 and 140 days

  17. Blood vessels and desmin control the positioning of nuclei in skeletal muscle fibers

    DEFF Research Database (Denmark)

    Ralston, E; Lu, Z; Biscocho, N

    2006-01-01

    . Here we show that the nuclei are preferentially localized near blood vessels (BV), particularly in slow-twitch, oxidative fibers. Thus, in rat soleus muscle fibers, 81% of the nuclei appear next to BV. Lack of desmin markedly perturbs the distribution of nuclei along the fibers but does not prevent...

  18. Contractile function of single muscle fibers after hindlimb suspension

    Science.gov (United States)

    Gardetto, P. R.; Schluter, J. M.; Fitts, R. H.

    1989-01-01

    The effects of two weeks of hind-limb suspension (HS) on the functional properties of slow-twitch and fast-twitch single fibers isolated from the predominantly slow-twitch soleus and fast-twitch gastrocnemius of the suspended leg of rats were investigated. Single fibers were suspended between a motor arm and force transducer, and, after their functional properties were studied, the fiber type was established by the myosin heavy chain analysis. It was found that, after HS, the greatest decrease in diameter and a reduction in peak tension occurred in slow-twitch fibers from soleus, followed by slow-twitch fibers from gastrocnemius. Fast-twitch fibers from the red gastrocnemius showed a significant reduction in diameter but no change in peak tension. No effect of HS was observed on the diameter of the fast-twitch fibers from the white gastsrocnemius (which is known to contain 87 percent fast glycolytic fibers).

  19. Actions of lyotropic anions on the mechanical properties of fast and slow twitch rat muscles at different temperatures.

    Science.gov (United States)

    Wondmikun, Y; Soukup, T; Asmussen, G

    2003-01-01

    The effects of lyotropic (swelling) anions (Cl(-), Br(-), NO(3)(-) and I(-)) on contractile properties of fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles were investigated in vitro at 20 degrees C and 35 degrees C. Isolated muscles bathed in anionic Tyrode solution were stimulated directly and isometric single twitches and fused tetanic contractions were recorded. In a Cl(-)Tyrode solution a decrease of the bathing temperature led to a cold potentiation of the twitch tension (P(t)) in EDL muscles, however, to a cold depression in SOL muscles, in both muscles combined with a prolongation of contraction (CT) and half relaxation (HRT) times. The extent and order of the potentiating effect of lyotropic anions on the P(t), CT and HRT in EDL and SOL were quite similar and increased in the order: Cl(-)twitch-tetanus ratio (TTR) was increased in NO(3)(-) and I(-)solutions. All effects of the anions were rapidly and completely reversed in both muscles when the test solution was replaced by the normal one. The temperature decrease caused no significant alteration in the potentiation capacity of the anions or in the kinetics of their action and reversibility.

  20. Associations between force and fatigue in fast-twitch motor units of a cat hindlimb muscle.

    Science.gov (United States)

    Laouris, Y; Bevan, L; Reinking, R M; Stuart, D G

    2004-01-01

    Associations were quantified between the control force and fatigue-induced force decline in 22 single fast-twitch-fatigable motor units of 5 deeply anesthetized adult cats. The units were subjected to intermittent stimulation at 1 train/s for 360 s. Two stimulation patterns were delivered in a pseudo-random manner. The first was a 500-ms train with constant interpulse intervals. The second pattern had the same number of stimuli, mean stimulus rate, and stimulus duration, but the stimulus pulses were rearranged to increase the force produced by the units in the control (prefatigue) state. The associations among the control peak tetanic force of these units, 3 indices of fatigue, and total cumulative force during fatiguing contractions were dependent, in part, on the stimulation pattern used to produce fatigue. The associations were also dependent, albeit to a lesser extent, on the force measure (peak vs. integrated) and the fatigue index used to quantify fatigue. It is proposed that during high-force fatiguing contractions, neural mechanisms are potentially available to delay and reduce the fatigue of fast-twitch-fatigable units for brief, but functionally relevant, periods. In contrast, the fatigue of slow-twitch fatigue-resistant units seems more likely to be controlled largely, if not exclusively, by metabolic processes within their muscle cells.

  1. Decay of Ca2+ and force transients in fast- and slow-twitch skeletal muscles from the rat, mouse and Etruscan shrew.

    Science.gov (United States)

    Wetzel, P; Gros, G

    1998-02-01

    Isometric single-twitch force and intracellular Ca2+ transients were recorded simultaneously, using fura-2, from slow- and fast-twitch muscle fibres of the rat, mouse and Etruscan shrew Suncus etruscus. In the slow-twitch rat soleus, force half-relaxation time was three times longer than the 50% decay time of the fura-2 signal. In contrast, in the fast-twitch extensor digitorum longus muscles of all three animals, muscle relaxation preceded Ca2+ decay. It is proposed that this surprising property of fast-twitch muscles is due to their pCa-tension curve, which is shifted to the right compared with that of slow-twitch muscle.

  2. Fiber-type-specific sensitivities and phenotypic adaptations to dietary fat overload differentially impact fast- versus slow-twitch muscle contractile function in C57BL/6J mice

    NARCIS (Netherlands)

    Ciapaite, Jolita; van den Berg, Sjoerd A.; Houten, Sander M.; Nicolay, Klaas; van Dijk, Ko Willems; Jeneson, Jeroen

    2015-01-01

    High-fat diets (HFDs) have been shown to interfere with skeletal muscle energy metabolism and cause peripheral insulin resistance. However, understanding of HFD impact on skeletal muscle primary function, i.e., contractile performance, is limited. Male C57BL/6J mice were fed HFD containing lard (HFL

  3. Fiber-type-specific sensitivities and phenotypic adaptations to dietary fat overload differentially impact fast- versus slow-twitch muscle contractile function in C57BL/6J mice

    NARCIS (Netherlands)

    Ciapaite, Jolita; van den Berg, Sjoerd A.; Houten, Sander M.; Nicolay, Klaas; van Dijk, Ko Willems; Jeneson, Jeroen

    High-fat diets (HFDs) have been shown to interfere with skeletal muscle energy metabolism and cause peripheral insulin resistance. However, understanding of HFD impact on skeletal muscle primary function, i.e., contractile performance, is limited. Male C57BL/6J mice were fed HFD containing lard

  4. A persistent increase in insulin-stimulated glucose uptake by both fast-twitch and slow-twitch skeletal muscles after a single exercise session by old rats.

    Science.gov (United States)

    Xiao, Yuanyuan; Sharma, Naveen; Arias, Edward B; Castorena, Carlos M; Cartee, Gregory D

    2013-06-01

    Exercise has been demonstrated to enhance subsequent insulin-stimulated glucose uptake (GU) by predominantly type II (fast-twitch) muscle of old rats, but previous research has not evaluated exercise effects on GU by type I (slow-twitch) muscle from old rats. Accordingly, we studied male Fischer 344/Brown Norway rats (24 months old) and determined GU (0, 100, 200, and 5,000 μU/ml insulin) of isolated soleus (predominantly type I) and epitrochlearis (predominantly type II) muscles after one exercise session. Epitrochlearis (100, 200, and 5,000 μU/ml insulin) and soleus (100 and 200 μU/ml insulin) GU were greater at 3-h postexercise vs. age-matched sedentary controls. Insulin receptor tyrosine phosphorylation (Tyr1162/1163) was unaltered by exercise in either muscle. Akt phosphorylation (pAkt) was greater for exercised vs. sedentary rats in the epitrochlearis (Ser473 and Thr308 with 100 and 200 μU/ml, respectively) and soleus (Ser473 with 200 μU/ml). AS160 phosphorylation (pAS160) was greater for exercised vs. sedentary rats in the epitrochlearis (Thr642 with 100 μU/ml), but not the soleus. Exercised vs. sedentary rats did not differ for total protein abundance of insulin receptor, Akt, AS160, or GLUT4 in either muscle. These results demonstrate that both predominantly type I and type II muscles from old rats are susceptible to exercise-induced improvement in insulin-mediated GU by mechanisms that are independent of enhanced insulin receptor tyrosine phosphorylation or altered abundance of important signaling proteins or GLUT4. Exercise-induced elevation in pAkt, and possibly pAS160, may contribute to this effect in the epitrochlearis of old rats, but other mechanisms are likely important for the soleus.

  5. A multiscale chemo-electro-mechanical skeletal muscle model to analyze muscle contraction and force generation for different muscle fiber arrangements

    Directory of Open Access Journals (Sweden)

    Thomas eHeidlauf

    2014-12-01

    Full Text Available The presented chemo-electro-mechanical skeletal muscle model relies on a continuum mechanical formulation describing the muscle’s deformation and force generation on the macroscopic muscle level. Unlike other three-dimensional models, the description of the activation-induced behavior of the mechanical model is entirely based on chemo-electro-mechanical principles on the microscopic sarcomere level. Yet, the multiscale model reproduces key characteristics of skeletal muscles such as experimental force-length and force-velocity data on the macroscopic whole muscle level. The paper presents the methodological approaches required to obtain such a multiscale model, and demonstrates the feasibility of using such a model to analyze differences in the mechanical behavior of parallel-fibered muscles, in which the muscle fibers either span the entire length of the fascicles or terminate intrafascicularly. The presented results reveal that muscles, in which the fibers span the entire length of the fascicles, show lower peak forces, more dispersed twitches and fusion of twitches at lower stimulation frequencies. In detail, the model predicted twitch rise times of 38.2ms and 17.2ms for a 12 cm long muscle, in which the fibers span the entire length of the fascicles and with twelve fiber compartments in series, respectively. Further, the twelve-compartment model predicted peak twitch forces that were 19% higher than in the single-compartment model. The analysis of sarcomere lengths during fixed-end single twitch contractions at optimal length predicts rather small sarcomere length changes. The observed lengths range from 75 to 111% of the optimal sarcomere length, which corresponds to a region with maximum filament overlap. This result suggests that stability issues resulting from activation-induced stretches of non-activated sarcomeres are unlikely in muscles with passive forces appearing at short muscle length.

  6. Alterations in slow-twitch muscle phenotype in transgenic mice overexpressing the Ca2+ buffering protein parvalbumin.

    Science.gov (United States)

    Chin, Eva R; Grange, Robert W; Viau, Francois; Simard, Alain R; Humphries, Caroline; Shelton, John; Bassel-Duby, Rhonda; Williams, R Sanders; Michel, Robin N

    2003-03-01

    The purpose of this study was to determine whether induced expression of the Ca2+ buffering protein parvalbumin (PV) in slow-twitch fibres would lead to alterations in physiological, biochemical and molecular properties reflective of a fast fibre phenotype. Transgenic (TG) mice were generated that overexpressed PV in slow (type I) muscle fibres. In soleus muscle (SOL; 58 % type I fibres) total PV expression was 2- to 6-fold higher in TG compared to wild-type (WT) mice. Maximum twitch and tetanic tensions were similar in WT and TG but force at subtetanic frequencies (30 and 50 Hz) was reduced in TG SOL. Twitch time-to-peak tension and half-relaxation time were significantly decreased in TG SOL (time-to-peak tension: 39.3 +/- 2.6 vs. 55.1 +/- 4.7 ms; half-relaxation time: 42.1 +/- 3.5 vs. 68.1 +/- 9.6 ms, P single fibre glycerol-3-phosphate dehydrogenase activity was decreased in a subset of type IIa fibres. These differences were associated with a 64 % reduction in calcineurin activity in TG SOL. These data show that overexpression of PV, resulting in decreased calcineurin activity, can alter the functional and metabolic profile of muscle and influence the expression of key marker genes in a predominantly slow-twitch muscle with minimal effects on the expression of muscle contractile proteins.

  7. Properties of slow- and fast-twitch muscle fibres in a mouse model of amyotrophic lateral sclerosis.

    Science.gov (United States)

    Atkin, Julie D; Scott, Rachel L; West, Jan M; Lopes, Elizabeth; Quah, Alvin K J; Cheema, Surindar S

    2005-05-01

    This investigation was undertaken to determine if there are altered histological, pathological and contractile properties in presymptomatic or endstage diseased muscle fibres from representative slow-twitch and fast-twitch muscles of SOD1 G93A mice in comparison to wildtype mice. In presymptomatic SOD1 G93A mice, there was no detectable peripheral dysfunction, providing evidence that muscle pathology is secondary to motor neuronal dysfunction. At disease endstage however, single muscle fibre contractile analysis demonstrated that fast-twitch muscle fibres and neuromuscular junctions are preferentially affected by amyotrophic lateral sclerosis-induced denervation, being unable to produce the same levels of force when activated by calcium as muscle fibres from their age-matched controls. The levels of transgenic SOD1 expression, aggregation state and activity were also examined in these muscles but there no was no preference for muscle fibre type. Hence, there is no simple correlation between SOD1 protein expression/activity, and muscle fibre type vulnerability in SOD1 G93A mice.

  8. Double-sigmoid model for fitting fatigue profiles in mouse fast- and slow-twitch muscle.

    Science.gov (United States)

    Cairns, S P; Robinson, D M; Loiselle, D S

    2008-07-01

    We present a curve-fitting approach that permits quantitative comparisons of fatigue profiles obtained with different stimulation protocols in isolated slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles of mice. Profiles from our usual stimulation protocol (125 Hz for 500 ms, evoked once every second for 100-300 s) could be fitted by single-term functions (sigmoids or exponentials) but not by a double exponential. A clearly superior fit, as confirmed by the Akaiki Information Criterion, was achieved using a double-sigmoid function. Fitting accuracy was exceptional; mean square errors were typically 0.9995. The first sigmoid (early fatigue) involved approximately 10% decline of isometric force to an intermediate plateau in both muscle types; the second sigmoid (late fatigue) involved a reduction of force to a final plateau, the decline being 83% of initial force in EDL and 63% of initial force in soleus. The maximal slope of each sigmoid was seven- to eightfold greater in EDL than in soleus. The general applicability of the model was tested by fitting profiles with a severe force loss arising from repeated tetanic stimulation evoked at different frequencies or rest periods, or with excitation via nerve terminals in soleus. Late fatigue, which was absent at 30 Hz, occurred earlier and to a greater extent at 125 than 50 Hz. The model captured small changes in rate of late fatigue for nerve terminal versus sarcolemmal stimulation. We conclude that a double-sigmoid expression is a useful and accurate model to characterize fatigue in isolated muscle preparations.

  9. Single muscle fiber gene expression with run taper.

    Directory of Open Access Journals (Sweden)

    Kevin Murach

    Full Text Available This study evaluated gene expression changes in gastrocnemius slow-twitch myosin heavy chain I (MHC I and fast-twitch (MHC IIa muscle fibers of collegiate cross-country runners (n = 6, 20±1 y, VO₂max = 70±1 ml•kg-1•min-1 during two distinct training phases. In a controlled environment, runners performed identical 8 kilometer runs (30:18±0:30 min:s, 89±1% HRmax while in heavy training (∼72 km/wk and following a 3 wk taper. Training volume during the taper leading into peak competition was reduced ∼50% which resulted in improved race times and greater cross-section and improved function of MHC IIa fibers. Single muscle fibers were isolated from pre and 4 hour post run biopsies in heavily trained and tapered states to examine the dynamic acute exercise response of the growth-related genes Fibroblast growth factor-inducible 14 (FN14, Myostatin (MSTN, Heat shock protein 72 (HSP72, Muscle ring-finger protein-1 (MURF1, Myogenic factor 6 (MRF4, and Insulin-like growth factor 1 (IGF1 via qPCR. FN14 increased 4.3-fold in MHC IIa fibers with exercise in the tapered state (P<0.05. MSTN was suppressed with exercise in both fiber types and training states (P<0.05 while MURF1 and HSP72 responded to running in MHC IIa and I fibers, respectively, regardless of training state (P<0.05. Robust induction of FN14 (previously shown to strongly correlate with hypertrophy and greater overall transcriptional flexibility with exercise in the tapered state provides an initial molecular basis for fast-twitch muscle fiber performance gains previously observed after taper in competitive endurance athletes.

  10. Observation of the molecular organization of calcium release sites in fast- and slow-twitch skeletal muscle with nanoscale imaging.

    Science.gov (United States)

    Jayasinghe, Isuru D; Munro, Michelle; Baddeley, David; Launikonis, Bradley S; Soeller, Christian

    2014-10-06

    Localization microscopy is a fairly recently introduced super-resolution fluorescence imaging modality capable of achieving nanometre-scale resolution. We have applied the dSTORM variation of this method to image intracellular molecular assemblies in skeletal muscle fibres which are large cells that critically rely on nanoscale signalling domains, the triads. Immunofluorescence staining in fixed adult rat skeletal muscle sections revealed clear differences between fast- and slow-twitch fibres in the molecular organization of ryanodine receptors (RyRs; the primary calcium release channels) within triads. With the improved resolution offered by dSTORM, abutting arrays of RyRs in transverse view of fast fibres were observed in contrast to the fragmented distribution on slow-twitch muscle that were approximately 1.8 times shorter and consisted of approximately 1.6 times fewer receptors. To the best of our knowledge, for the first time, we have quantified the nanometre-scale spatial association between triadic proteins using multi-colour super-resolution, an analysis difficult to conduct with electron microscopy. Our findings confirm that junctophilin-1 (JPH1), which tethers the sarcoplasmic reticulum ((SR) intracellular calcium store) to the tubular (t-) system at triads, was present throughout the RyR array, whereas JPH2 was contained within much smaller nanodomains. Similar imaging of the primary SR calcium buffer, calsequestrin (CSQ), detected less overlap of the triad with CSQ in slow-twitch muscle supporting greater spatial heterogeneity in the luminal Ca2+ buffering when compared with fast twitch muscle. Taken together, these nanoscale differences can explain the fundamentally different physiologies of fast- and slow-twitch muscle.

  11. Reversal of TMS-induced motor twitch by training is associated with a reduction in excitability of the antagonist muscle

    Directory of Open Access Journals (Sweden)

    Fregni Felipe

    2011-08-01

    Full Text Available Abstract Background A single session of isolated repetitive movements of the thumb can alter the response to transcranial magnetic stimulation (TMS, such that the related muscle twitch measured post-training occurs in the trained direction. This response is attributed to transient excitability changes in primary motor cortex (M1 that form the early part of learning. We investigated; (1 whether this phenomenon might occur for movements at the wrist, and (2 how specific TMS activation patterns of opposing muscles underlie the practice-induced change in direction. Methods We used single-pulse suprathreshold TMS over the M1 forearm area, to evoke wrist movements in 20 healthy subjects. We measured the preferential direction of the TMS-induced twitch in both the sagittal and coronal plane using an optical goniometer fixed to the dorsum of the wrist, and recorded electromyographic (EMG activity from the flexor carpi radialis (FCR and extensor carpi radialis (ECR muscles. Subjects performed gentle voluntary movements, in the direction opposite to the initial twitch for 5 minutes at 0.2 Hz. We collected motor evoked potentials (MEPs elicited by TMS at baseline and for 10 minutes after training. Results Repetitive motor training was sufficient for TMS to evoke movements in the practiced direction opposite to the original twitch. For most subjects the effect of the newly-acquired direction was retained for at least 10 minutes before reverting to the original. Importantly, the direction change of the movement was associated with a significant decrease in MEP amplitude of the antagonist to the trained muscle, rather than an increase in MEP amplitude of the trained muscle. Conclusions These results demonstrate for the first time that a TMS-twitch direction change following a simple practice paradigm may result from reduced corticospinal drive to muscles antagonizing the trained direction. Such findings may have implications for training paradigms in

  12. The organization of the Golgi complex and microtubules in skeletal muscle is fiber type-dependent

    DEFF Research Database (Denmark)

    Ralston, E; Lu, Z; Ploug, Thorkil

    1999-01-01

    Skeletal muscle has a nonconventional Golgi complex (GC), the organization of which has been a subject of controversy in the past. We have now examined the distribution of the GC by immunofluorescence and immunogold electron microscopy in whole fibers from different rat muscles, both innervated...... of the hindlimb muscles, GC elements as well as microtubules converge toward a common pattern, that of the slow-twitch fibers, in all fibers. Our data suggest that innervation regulates the distribution of microtubules, which in turn organize the Golgi complex according to muscle fiber type....

  13. Measures of ''fastness'' : Force profiles of twitches and partly fused contractions in rat medial gastrocnemius and tibialis anterior muscle units

    NARCIS (Netherlands)

    Bakels, R; Kernell, D

    1995-01-01

    Recordings of isometric force were obtained for twitches and (sub)maximal tetani of gastrocnemius medialis (MG) and tibialis anterior (TA) muscle units in female Wistar rats. We assessed the relationships between unit properties that have all been associated with ''speed''. (1) the relative degree o

  14. Single muscle fiber gene expression with run taper.

    Science.gov (United States)

    Murach, Kevin; Raue, Ulrika; Wilkerson, Brittany; Minchev, Kiril; Jemiolo, Bozena; Bagley, James; Luden, Nicholas; Trappe, Scott

    2014-01-01

    This study evaluated gene expression changes in gastrocnemius slow-twitch myosin heavy chain I (MHC I) and fast-twitch (MHC IIa) muscle fibers of collegiate cross-country runners (n = 6, 20±1 y, VO₂max = 70±1 ml•kg-1•min-1) during two distinct training phases. In a controlled environment, runners performed identical 8 kilometer runs (30:18±0:30 min:s, 89±1% HRmax) while in heavy training (∼72 km/wk) and following a 3 wk taper. Training volume during the taper leading into peak competition was reduced ∼50% which resulted in improved race times and greater cross-section and improved function of MHC IIa fibers. Single muscle fibers were isolated from pre and 4 hour post run biopsies in heavily trained and tapered states to examine the dynamic acute exercise response of the growth-related genes Fibroblast growth factor-inducible 14 (FN14), Myostatin (MSTN), Heat shock protein 72 (HSP72), Muscle ring-finger protein-1 (MURF1), Myogenic factor 6 (MRF4), and Insulin-like growth factor 1 (IGF1) via qPCR. FN14 increased 4.3-fold in MHC IIa fibers with exercise in the tapered state (Ptwitch muscle fiber performance gains previously observed after taper in competitive endurance athletes.

  15. Multiple causes of fatigue during shortening contractions in rat slow twitch skeletal muscle.

    Science.gov (United States)

    Hortemo, Kristin Halvorsen; Munkvik, Morten; Lunde, Per Kristian; Sejersted, Ole M

    2013-01-01

    Fatigue in muscles that shorten might have other causes than fatigue during isometric contractions, since both cross-bridge cycling and energy demand are different in the two exercise modes. While isometric contractions are extensively studied, the causes of fatigue in shortening contractions are poorly mapped. Here, we investigate fatigue mechanisms during shortening contractions in slow twitch skeletal muscle in near physiological conditions. Fatigue was induced in rat soleus muscles with maintained blood supply by in situ shortening contractions at 37°C. Muscles were stimulated repeatedly (1 s on/off at 30 Hz) for 15 min against a constant load, allowing the muscle to shorten and perform work. Fatigue and subsequent recovery was examined at 20 s, 100 s and 15 min exercise. The effects of prior exercise were investigated in a second exercise bout. Fatigue developed in three distinct phases. During the first 20 s the regulatory protein Myosin Light Chain-2 (slow isoform, MLC-2s) was rapidly dephosphorylated in parallel with reduced rate of force development and reduced shortening. In the second phase there was degradation of high-energy phosphates and accumulation of lactate, and these changes were related to slowing of muscle relengthening and relaxation, culminating at 100 s exercise. Slowing of relaxation was also associated with increased leak of calcium from the SR. During the third phase of exercise there was restoration of high-energy phosphates and elimination of lactate, and the slowing of relaxation disappeared, whereas dephosphorylation of MLC-2s and reduced shortening prevailed. Prior exercise improved relaxation parameters in a subsequent exercise bout, and we propose that this effect is a result of less accumulation of lactate due to more rapid onset of oxidative metabolism. The correlation between dephosphorylation of MLC-2s and reduced shortening was confirmed in various experimental settings, and we suggest MLC-2s as an important regulator of

  16. Multiple causes of fatigue during shortening contractions in rat slow twitch skeletal muscle.

    Directory of Open Access Journals (Sweden)

    Kristin Halvorsen Hortemo

    Full Text Available Fatigue in muscles that shorten might have other causes than fatigue during isometric contractions, since both cross-bridge cycling and energy demand are different in the two exercise modes. While isometric contractions are extensively studied, the causes of fatigue in shortening contractions are poorly mapped. Here, we investigate fatigue mechanisms during shortening contractions in slow twitch skeletal muscle in near physiological conditions. Fatigue was induced in rat soleus muscles with maintained blood supply by in situ shortening contractions at 37°C. Muscles were stimulated repeatedly (1 s on/off at 30 Hz for 15 min against a constant load, allowing the muscle to shorten and perform work. Fatigue and subsequent recovery was examined at 20 s, 100 s and 15 min exercise. The effects of prior exercise were investigated in a second exercise bout. Fatigue developed in three distinct phases. During the first 20 s the regulatory protein Myosin Light Chain-2 (slow isoform, MLC-2s was rapidly dephosphorylated in parallel with reduced rate of force development and reduced shortening. In the second phase there was degradation of high-energy phosphates and accumulation of lactate, and these changes were related to slowing of muscle relengthening and relaxation, culminating at 100 s exercise. Slowing of relaxation was also associated with increased leak of calcium from the SR. During the third phase of exercise there was restoration of high-energy phosphates and elimination of lactate, and the slowing of relaxation disappeared, whereas dephosphorylation of MLC-2s and reduced shortening prevailed. Prior exercise improved relaxation parameters in a subsequent exercise bout, and we propose that this effect is a result of less accumulation of lactate due to more rapid onset of oxidative metabolism. The correlation between dephosphorylation of MLC-2s and reduced shortening was confirmed in various experimental settings, and we suggest MLC-2s as an

  17. Dynamic formation of microenvironments at the myotendinous junction correlates with muscle fiber morphogenesis in zebrafish.

    Science.gov (United States)

    Snow, Chelsi J; Henry, Clarissa A

    2009-01-01

    Muscle development involves the specification and morphogenesis of muscle fibers that attach to tendons. After attachment, muscles and tendons then function as an integrated unit to transduce force to the skeletal system and stabilize joints. The attachment site is the myotendinous junction, or MTJ, and is the primary site of force transmission. We find that attachment of fast-twitch myofibers to the MTJ correlates with the formation of novel microenvironments within the MTJ. The expression or activation of two proteins involved in anchoring the intracellular cytoskeleton to the extracellular matrix, Focal adhesion kinase (Fak) and beta-dystroglycan is up-regulated. Conversely, the extracellular matrix protein Fibronectin (Fn) is down-regulated. This degradation of Fn as fast-twitch fibers attach to the MTJ results in Fn protein defining a novel microenvironment within the MTJ adjacent to slow-twitch, but not fast-twitch, muscle. Interestingly, however, Fak, laminin, Fn and beta-dystroglycan concentrate at the MTJ in mutants that do not have slow-twitch fibers. Taken together, these data elucidate novel and dynamic microenvironments within the MTJ and indicate that MTJ morphogenesis is spatially and temporally complex.

  18. Ca2+_, Sr2+_force relationships and kinetic properties of fast-twitch rat leg muscle fibre subtypes.

    Science.gov (United States)

    Galler, S

    1999-10-01

    Force generation of fast-twitch and slow-twitch fibres exhibits large differences in its sensitivity to Ca2+ and Sr2+ (e.g. Fink et al. 1986). Little is known about fast-twitch fibre subtypes. Thus, a variety of mechanical measurements on segments of rehydrated freeze-dried fast-twitch rat leg muscle fibres were executed in this study. Among these, the Ca2+- and Sr2+-force relationship and the unloaded shortening velocity were determined. The fibres were classified into subtypes according to their kinetics of stretch activation (Galler et al. 1994). In all fibres, the maximal force under Sr2+ activation was about 0.9 of that under Ca2+ activation. The Ca2+- and Sr2+-force relationship exhibited a biphasic shape with a steeper part (Hill coefficient, n1) below 50% and a flatter part (Hill coefficient, n2) above 50% of maximal force. The difference between the Ca2+ - and Sr2+ -sensitivity was independent of the fibre subtypes. The Hill coefficients were only partially correlated with kinetic properties. The correlation was more pronounced for the unloaded shortening velocity than for the kinetics of stretch activation. The data are consistent with the idea that the Ca2+ and Sr2+ sensitivities of fast-twitch fibres are mainly determined by a single isoform of troponin C. Among several protein isoforms, the isoforms of the myosin light chains seem to be involved for determining the slope of the Ca2+- and Sr2+-force relationship of fast-twitch muscle fibres.

  19. Phosphorylation of anchoring protein by calmodulin protein kinase associated to the sarcoplasmic reticulum of rabbit fast-twitch muscle.

    Science.gov (United States)

    Damiani, E; Sacchetto, R; Margreth, A

    2000-12-09

    Regulatory phosphorylation of phospholamban and of SR Ca(2+)-ATPase SERCA2a isoform by endogenous CaM-K II in slow-twitch skeletal and cardiac sarcoplasmic reticulum (SR) is well documented, but much less is known of the exact functional role of CaM K II in fast-twitch muscle SR. Recently, it was shown that RNA splicing of brain-specific alpha CaM K II, gives rise to a truncated protein (alpha KAP), consisting mainly of the association domain, serving to anchor CaM K II to SR membrane in rat skeletal muscle [Bayer, K.-U., et al. (1998) EMBO J. 19, 5598-5605]. In the present study, we searched for the presence of alpha KAP in sucrose-density purified SR membrane fractions from representative fast-twitch and slow-twitch limb muscles, both of the rabbit and the rat, using immunoblot techniques and antibody directed against the association domain of alpha CaM K II. Putative alpha KAP was immunodetected as a 23-kDa electrophoretic component on SDS-PAGE of the isolated SR from fast-twitch but not from slow-twitch muscle, and was further identified as a specific substrate of endogenous CaM K II, in the rabbit. Immunodetected, (32)P-labeled, non-calmodulin binding protein, behaved as a single 23-kDa protein species under several electrophoretic conditions. The 23-kDa protein, with defined properties, was isolated as a complex with 60-kDa delta CaM K II isoform, by sucrose-density sedimentation analysis. Moreover, we show here that putative alphaKAP, in spite of its inability to bind CaM in ligand blot overlay, co-eluted with delta CaM K II from CaM-affinity columns. That raises the question of whether CaM K II-mediated phosphorylation of alpha KAP and triadin together might be involved in a molecular signaling pathway important for SR Ca(2+)-release in fast-twitch muscle SR.

  20. Attenuated fatigue in slow twitch skeletal muscle during isotonic exercise in rats with chronic heart failure.

    Directory of Open Access Journals (Sweden)

    Morten Munkvik

    Full Text Available During isometric contractions, slow twitch soleus muscles (SOL from rats with chronic heart failure (chf are more fatigable than those of sham animals. However, a muscle normally shortens during activity and fatigue development is highly task dependent. Therefore, we examined the development of skeletal muscle fatigue during shortening (isotonic contractions in chf and sham-operated rats. Six weeks following coronary artery ligation, infarcted animals were classified as failing (chf if left ventricle end diastolic pressure was >15 mmHg. During isoflurane anaesthesia, SOL with intact blood supply was stimulated (1s on 1s off at 30 Hz for 15 min and allowed to shorten isotonically against a constant afterload. Muscle temperature was maintained at 37°C. In resting muscle, maximum isometric force (F(max and the concentrations of ATP and CrP were not different in the two groups. During stimulation, F(max and the concentrations declined in parallel sham and chf. Fatigue, which was evident as reduced shortening during stimulation, was also not different in the two groups. The isometric force decline was fitted to a bi-exponential decay equation. Both time constants increased transiently and returned to initial values after approximately 200 s of the fatigue protocol. This resulted in a transient rise in baseline tension between stimulations, although this effect which was less prominent in chf than sham. Myosin light chain 2s phosphorylation declined in both groups after 100 s of isotonic contractions, and remained at this level throughout 15 min of stimulation. In spite of higher energy demand during isotonic than isometric contractions, both shortening capacity and rate of isometric force decline were as well or better preserved in fatigued SOL from chf rats than in sham. This observation is in striking contrast to previous reports which have employed isometric contractions to induce fatigue.

  1. Muscle Fiber Conduction Velocity, Muscle Fiber Composition, and Power Performance.

    Science.gov (United States)

    Methenitis, Spyridon; Karandreas, Nikolaos; Spengos, Konstantinos; Zaras, Nikolaos; Stasinaki, Angeliki-Nikoletta; Terzis, Gerasimos

    2016-09-01

    The aim of this study was to explore the relationship between muscle fiber conduction velocity (MFCV), fiber type composition, and power performance in participants with different training background. Thirty-eight young males with different training background participated: sedentary (n = 10), endurance runners (n = 9), power trained (n = 10), and strength trained (n = 9). They performed maximal countermovement jumps (CMJ) and maximal isometric leg press for the measurement of the rate of force development (RFD). Resting vastus lateralis MFCV was measured with intramuscular microelectrodes on a different occasion, whereas muscle fiber type and cross-sectional area (CSA) of vastus lateralis were evaluated through muscle biopsies 1wk later. MFCV, CMJ power, RFD, and % CSA of type II and type IIx fibers were higher for the power-trained group (P power participants. Close correlations were found between MFCV and fiber CSA as well as the % CSA of all fiber types as well as with RFD and CMJ power (r = 0.712-0.943, P power performance. Significant models for the prediction of the % CSA of type IIa and type II as well as the CSA of all muscle fibers based upon MFCV, RFD, and CMJ were revealed (P = 0.000). MFCV is closely associated with muscle fiber % CSA. RFD and jumping power are associated with the propagation of the action potentials along the muscle fibers. This link is regulated by the size and the distribution of type II, and especially type IIx muscle fibers.

  2. Effects of shakuyakukanzoto and its absorbed components on twitch contractions induced by physiological Ca2+ release in rat skeletal muscle.

    Science.gov (United States)

    Kaifuchi, Noriko; Omiya, Yuji; Kushida, Hirotaka; Fukutake, Miwako; Nishimura, Hiroaki; Kase, Yoshio

    2015-07-01

    Shakuyakukanzoto (SKT) is a kampo medicine composed of equal proportions of Glycyrrhizae radix (G. radix) and Paeoniae radix (P. radix). A double-blind study reported that SKT significantly ameliorated painful muscle cramp in cirrhosis patients without the typical severe side effects of muscle weakness and central nervous system (CNS) depression. Previous basic studies reported that SKT and its active components induced relaxation by a direct action on skeletal muscle and that SKT did not depress CNS functions; however, why SKT has a lower incidence of muscle weakness remains unknown. In the present study, we investigated which components are absorbed into the blood of rats after a single oral administration of SKT to identify the active components of SKT. We also investigated the effects of SKT and its components on the twitch contraction induced by physiological Ca(2+) release. Our study demonstrated that SKT and five G. radix isolates, which are responsible for the antispasmodic effect of SKT, did not inhibit the twitch contraction in contrast to dantrolene sodium, a direct-acting peripheral muscle relaxant, indicating that the mechanisms of muscle contraction of SKT and dantrolene in skeletal muscle differ. These findings suggest that SKT does not reduce the contractile force in skeletal muscle under physiological conditions, i.e., SKT may have a low risk of causing muscle weakness in clinical use. Considering that most muscle relaxants and anticonvulsants cause various harmful side effects such as weakness and CNS depression, SKT appears to have a benign safety profile.

  3. Can fast-twitch muscle fibres be selectively recruited during lengthening contractions? Review and applications to sport movements.

    Science.gov (United States)

    Chalmers, Gordon R

    2008-01-01

    Literature examining the recruitment order of motor units during lengthening (eccentric) contractions was reviewed to determine if fast-twitch motor units can be active while lower threshold slow-twitch motor units are not active. Studies utilizing surface electromyogram (EMG) amplitude, single motor unit activity, spike amplitude-frequency analyses, EMG power spectrum, mechanomyographic, and phosphocreatine-to-creatine ratio (PCr/Cr) techniques were reviewed. Only single motor unit and PCr/Cr data were found to be suitable to address the goals of this review. Nine of ten single motor unit studies, examining joint movement velocities up to 225 degrees/s and forces up to 53% of a maximum voluntary contraction, found that the size principle of motor unit recruitment applied during lengthening contractions. Deviation from the size principle was demonstrated by one study examining movements within a small range of low velocities and modest forces, although other studies examining similar low forces and lengthening velocities reported size-ordered recruitment. The PCr/Cr data demonstrated the activation of all fibre types in lengthening maximal contractions. Most evidence indicates that for lengthening contractions of a wide range of efforts and speeds, fast-twitch muscle fibres cannot be selectively recruited without activity of the slow-twitch fibres of the same muscle.

  4. Dynamic formation of microenvironments at the myotendinous junction correlates with muscle fiber morphogenesis in zebrafish

    OpenAIRE

    Snow, Chelsi J.; Henry, Clarissa A.

    2008-01-01

    Muscle development involves the specification and morphogenesis of muscle fibers that attach to tendons. After attachment, muscles and tendons then function as an integrated unit to transduce force to the skeletal system and stabilize joints. The attachment site is the myotendinous junction, or MTJ, and is the primary site of force transmission. We find that attachment of fast-twitch myofibers to the MTJ correlates with the formation of novel microenvironments within the MTJ. The expression o...

  5. Single-channel properties of the sarcoplasmic reticulum calcium-release channel in slow- and fast-twitch muscles of Rhesus monkeys.

    Science.gov (United States)

    Bastide, B; Mounier, Y

    1998-08-01

    RyR1 is the main isoform of ryanodine receptor expressed in fast- and slow-twitch mammalian skeletal muscles although differences in Ca2+-release kinetics and properties have been reported. Single-channel measurements reveal that a large proportion (82%) of Ca2+-release channels measured in slow-twitch muscle preparations have properties similar to those of the Ca2+-release channels of fast-twitch preparations, i.e. the same conductance, an identical sensitivity to caffeine and a bell-shaped Ca2+ activation curve for pCa (-log10[Ca2+]) 7 to 3. A low proportion (18%) of Ca2+-release channels observed in preparations from slow-twitch muscles were characterized by a very high activity level. These channels were not inhibited at a millimolar concentration of Ca2+. Our data suggest that the different properties of Ca2+ release in slow- and fast-twitch muscles might not be related to intrinsic properties of the Ca2+-release channels of each type of muscle but rather to the co-expression of two isoforms of ryanodine receptor and the lower amount of Ca2+-release channels expressed in slow- than in fast-twitch muscles.

  6. Decrease in sarcoplasmic reticulum calcium content, not myofilament function, contributes to muscle twitch force decline in isolated cardiac trabeculae

    Science.gov (United States)

    Milani-Nejad, Nima; Brunello, Lucia; Gyorke, Sándor; Janssen, Paul M.L.

    2014-01-01

    We set out to determine the factors responsible for twitch force decline in isolated intact rat cardiac trabeculae. The contractile force of trabeculae declined over extended periods of isometric twitch contractions. The force-frequency relationship within the frequency range of 4–8 Hz, at 37 °C, became more positive and the frequency optimum shifted to higher rates with this decline in baseline twitch tensions. The post-rest potentiation (37 °C), a phenomenon highly dependent on calcium handling mechanisms, became more pronounced with decrease in twitch tensions. We show that the main abnormality during muscle run-down was not due to a deficit in the myofilaments; maximal tension achieved using a K+ contracture protocol was either unaffected or only slightly decreased. Conversely, the sarcoplasmic reticulum (SR) calcium content, as assessed by rapid cooling contractures (from 27 °C to 0 °C), decreased, and had a close association with the declining twitch tensions (R2 ~ 0.76). SR Ca2+-ATPase, relative to Na+/Ca2+ exchanger activity, was not altered as there was no significant change in paired rapid cooling contracture ratios. Furthermore, confocal microscopy detected no abnormalities in the overall structure of the cardiomyocytes and t-tubules in the cardiac trabeculae (~23 °C). Overall, the data indicates that the primary mechanism responsible for force run-down in multi-cellular cardiac preparations is a decline in the SR calcium content and not the maximal tension generation capability of the myofilaments. PMID:25056841

  7. Adaptive responses of GLUT-4 and citrate synthase in fast-twitch muscle of voluntary running rats

    Science.gov (United States)

    Henriksen, E. J.; Halseth, A. E.

    1995-01-01

    Glucose transporter (GLUT-4) protein, hexokinase, and citrate synthase (proteins involved in oxidative energy production from blood glucose catabolism) increase in response to chronically elevated neuromuscular activity. It is currently unclear whether these proteins increase in a coordinated manner in response to this stimulus. Therefore, voluntary wheel running (WR) was used to chronically overload the fast-twitch rat plantaris muscle and the myocardium, and the early time courses of adaptative responses of GLUT-4 protein and the activities of hexokinase and citrate synthase were characterized and compared. Plantaris hexokinase activity increased 51% after just 1 wk of WR, whereas GLUT-4 and citrate synthase were increased by 51 and 40%, respectively, only after 2 wk of WR. All three variables remained comparably elevated (+50-64%) through 4 wk of WR. Despite the overload of the myocardium with this protocol, no substantial elevations in these variables were observed. These findings are consistent with a coordinated upregulation of GLUT-4 and citrate synthase in the fast-twitch plantaris, but not in the myocardium, in response to this increased neuromuscular activity. Regulation of hexokinase in fast-twitch muscle appears to be uncoupled from regulation of GLUT-4 and citrate synthase, as increases in the former are detectable well before increases in the latter.

  8. Neuromuscular control of a single twitch muscle in wild type and mutant Drosophila, measured with an ergometer.

    Science.gov (United States)

    Harvey, Jennifer; Brunger, Holly; Middleton, C Adam; Hill, Julia A; Sevdali, Maria; Sweeney, Sean T; Sparrow, John C; Elliott, Christopher J H

    2008-06-01

    How do deficits in neuronal growth, aging or synaptic function affect the final, mechanical output of a single muscle twitch? We address this in vivo (indeed in situ) with a novel ergometer that records the output of a large specialised muscle, the Drosophila jump muscle. Here, we describe in detail the ergometer, its construction and use. We evaluated the ergometer by showing that adult fly jump muscle output varies little between 3 h and 7 days; but newly eclosed flies produce only 65%. In a mutant with little octopamine (Tbetah), jump muscle performance is reduced by 28%. The initial responses of synaptic growth mutants (highwire and spinster) do not differ from wild type, as expected on the homeostatic hypothesis. However, responses in highwire mutations gradually decline following repeated stimuli, suggesting physiological as well as anatomical abnormalities. We conclude that the assay is robust, sensitive and reliable with a good throughput.

  9. Twitch potentiation induced by stimulated and voluntary isometric contractions at various torque levels in human knee extensor muscles.

    Science.gov (United States)

    Miyamoto, Naokazu; Yanai, Toshimasa; Kawakami, Yasuo

    2011-03-01

    The purpose of this study was to compare the extent of twitch potentiation (TP) after stimulated or voluntary contractions at identical intensities for the human knee extensor muscles. Isometric knee extensions of 10 s were performed at 20%, 40%, and 60% of maximal voluntary contraction (MVC) torque level, through percutaneous electrical stimulation of the quadriceps at 80 Hz or voluntary contraction. Twitch responses were evoked by stimulating the femoral nerve percutaneously with supramaximal intensity. The extent of TP after the stimulated contraction was greater than that after the voluntary contraction at the 20% MVC torque level, whereas a stimulated contraction induced a smaller extent of TP than did a voluntary contraction at contraction intensities higher than 40% MVC. We suggest that this contraction intensity dependence of differences in TP after stimulated and voluntary isometric conditioning contractions is responsible for differences in the recruitment pattern of motor units during the conditioning contractions.

  10. Potassium-induced contractures in crab (Callinectes danae) muscle fibers.

    Science.gov (United States)

    Leal-Cardoso, J H; Suarez-Kurtz, G

    1984-01-01

    The contractures induced by 20-200 mM [K+]o in single crab muscle fibers were resolved into two components. The first component, consisting of single twitches or brief tetanic contractions, was associated with electrogenic membrane responses. The second occurred after spiking subsided with an amplitude that increased linearly with the [K+]o between 20 and 90 mM. The amplitude and time course of the contractures elicited by a given [K+]o differed markedly between different fibers. Contracture reproducibility of a single fiber was best when 90 mM [K+]o was used. The K-induced contractures were abolished after brief (3 min) exposure of the fibers to a calcium-free solution and were greatly depressed by 8 mM procaine. The data suggest that the contractures require both Ca2+-influx across the sarcolemma and release of Ca2+ stored in the sarcoplasmic reticulum.

  11. Fnip1 regulates skeletal muscle fiber type specification, fatigue resistance, and susceptibility to muscular dystrophy.

    Science.gov (United States)

    Reyes, Nicholas L; Banks, Glen B; Tsang, Mark; Margineantu, Daciana; Gu, Haiwei; Djukovic, Danijel; Chan, Jacky; Torres, Michelle; Liggitt, H Denny; Hirenallur-S, Dinesh K; Hockenbery, David M; Raftery, Daniel; Iritani, Brian M

    2015-01-13

    Mammalian skeletal muscle is broadly characterized by the presence of two distinct categories of muscle fibers called type I "red" slow twitch and type II "white" fast twitch, which display marked differences in contraction strength, metabolic strategies, and susceptibility to fatigue. The relative representation of each fiber type can have major influences on susceptibility to obesity, diabetes, and muscular dystrophies. However, the molecular factors controlling fiber type specification remain incompletely defined. In this study, we describe the control of fiber type specification and susceptibility to metabolic disease by folliculin interacting protein-1 (Fnip1). Using Fnip1 null mice, we found that loss of Fnip1 increased the representation of type I fibers characterized by increased myoglobin, slow twitch markers [myosin heavy chain 7 (MyH7), succinate dehydrogenase, troponin I 1, troponin C1, troponin T1], capillary density, and mitochondria number. Cultured Fnip1-null muscle fibers had higher oxidative capacity, and isolated Fnip1-null skeletal muscles were more resistant to postcontraction fatigue relative to WT skeletal muscles. Biochemical analyses revealed increased activation of the metabolic sensor AMP kinase (AMPK), and increased expression of the AMPK-target and transcriptional coactivator PGC1α in Fnip1 null skeletal muscle. Genetic disruption of PGC1α rescued normal levels of type I fiber markers MyH7 and myoglobin in Fnip1-null mice. Remarkably, loss of Fnip1 profoundly mitigated muscle damage in a murine model of Duchenne muscular dystrophy. These results indicate that Fnip1 controls skeletal muscle fiber type specification and warrant further study to determine whether inhibition of Fnip1 has therapeutic potential in muscular dystrophy diseases.

  12. Correlation between histochemically assessed fiber type distribution and isomyosin and myosin heavy chain content in porcine skeletal muscles.

    Science.gov (United States)

    Bee, G; Solomon, M B; Czerwinski, S M; Long, C; Pursel, V G

    1999-08-01

    Highly sensitive enzyme assays developed to differentiate skeletal muscle fibers allow the recognition of three main fiber types: slow-twitch oxidative (SO), fast-twitch oxidative glycolytic (FOG), and fast-twitch glycolytic (FG). Myosin, the predominant contractile protein in mammalian skeletal muscle, can be separated based on the electrophoretic mobility under nondissociating conditions into SM2, SM1, IM, FM3, and FM2 isoforms, or under dissociating conditions into myosin heavy chain (MHC) I, IIb, IIx/d, and IIa. The purpose of the present study was to determine whether the histochemical method of differentiation of fiber types is consistent with the electrophoretically identified isomyosin and MHC isoforms. These comparisons were made using serratus ventralis (SV), gluteus medius (GM), and longissimus muscles (LM) from 13 pigs. Two calculation methods for the histochemical assessed fiber type distribution were adopted. The first method incorporated the number of fibers counted for each fiber type and calculated a percentage of the total fiber number (fiber number percentage: FNP). The second method expressed the cross-sectional area of each fiber type as a percentage of the total fiber area measured per muscle (fiber area percentage: FAP). Independent of the calculation methods, correlation analyses revealed in all muscles a strong relation between SO fibers, the slow isomyosin (SM1 and SM2), and MHCI, as well as between the FG fibers, the fast isomyosin (FM3 and FM2), and MHCIIx/b content (PFOG fiber population assessed by histochemical analysis and intermediate isoform (IM) or MHCIIa content. The present results did not provide conclusive evidence as to which of the calculation methods (FNP or FAP) was more closely related to myosin composition of skeletal muscles. Despite some incompatibility between the methods, the present study shows that histochemical as well as electrophoretic analyses yielded important information about the composition of porcine

  13. Hydrogen peroxide modulates Ca2+-activation of single permeabilized fibres from fast- and slow-twitch skeletal muscles of rats.

    Science.gov (United States)

    Plant, D R; Lynch, G S; Williams, D A

    2000-01-01

    We examined the effects of redox modulation on single membrane-permeabilized fibre segments from the fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus muscles of adult rats to determine whether the contractile apparatus was the redox target responsible for the increased contractility of muscles exposed to low concentrations of H2O2. The effects of H2O2 on maximum Ca2+-activated force were dose-dependent with 30 min exposure to 5 mM H2O2 causing a progressive decrease by 22+/-3 and 13+/-2% in soleus and EDL permeabilized muscle fibres, respectively. Lower concentrations of exogenous H2O2 (100 microM and 1 mM) had no effect on maximum Ca2+-activated force. Subsequent exposure to the reductant dithiothreitol (DTT, 10 mM, 10 min) fully reversed the H2O2-induced depression of force in EDL, but not in soleus muscle fibres. Incubation with DTT alone for 10 min did not alter Ca2+-activated force in either soleus or EDL muscle fibres. The sensitivity of the contractile filaments to Ca2+ (pCa50) was not altered by exposure to any concentration of exogenous H2O2. However, all concentrations of H2O2 diminished the Hill coefficient in permeabilized fibres from the EDL muscle, indicating that the cooperativity of Ca2+ binding to troponin is altered. H2O2 (5 mM) did not affect rigor force, which indicates that the number of crossbridges participating in contraction was not reduced. In conclusion, H2O2 may reduce the maximum Ca2+ activated force production in skinned muscle fibres by decreasing the force per crossbridge.

  14. cAMP levels in fast- and slow-twitch skeletal muscle after an acute bout of aerobic exercise

    Science.gov (United States)

    Sheldon, A.; Booth, F. W.; Kirby, C. R.

    1993-01-01

    The present study examined whether exercise duration was associated with elevated and/or sustained elevations of postexercise adenosine 3',5'-cyclic monophosphate (cAMP) by measuring cAMP levels in skeletal muscle for up to 4 h after acute exercise bouts of durations that are known to either produce (60 min) or not produce (10 min) mitochondrial proliferation after chronic training. Treadmill-acclimatized, but untrained, rats were run at 22 m/min for 0 (control), 10, or 60 min and were killed at various postexercise (0, 0.5, 1, 2, and 4 h) time points. Fast-twitch white and red (quadriceps) and slow-twitch (soleus) muscles were quickly excised, frozen in liquid nitrogen, and assayed for cAMP with a commercial kit. Unexpectedly, cAMP contents in all three muscles were similar to control (nonexercise) at most (21 of 30) time points after a single 10- or 60-min run. Values at 9 of 30 time points were significantly different from control (P single bout of endurance-type exercise is not, by itself, associated with exercise duration.

  15. Functional properties of slow and fast gastrocnemius muscle fibers after a 17-day spaceflight

    Science.gov (United States)

    Widrick, J. J.; Romatowski, J. G.; Norenberg, K. M.; Knuth, S. T.; Bain, J. L.; Riley, D. A.; Trappe, S. W.; Trappe, T. A.; Costill, D. L.; Fitts, R. H.

    2001-01-01

    The purpose of this investigation was to study the effects of a 17-day spaceflight on the contractile properties of individual fast- and slow-twitch fibers isolated from biopsies of the fast-twitch gastrocnemius muscle of four male astronauts. Single chemically skinned fibers were studied during maximal Ca2+-activated contractions with fiber myosin heavy chain (MHC) isoform expression subsequently determined by SDS gel electrophoresis. Spaceflight had no significant effect on the mean diameter or specific force of single fibers expressing type I, IIa, or IIa/IIx MHC, although a small reduction in average absolute force (P(o)) was observed for the type I fibers (0.68 +/- 0.02 vs. 0.64 +/- 0.02 mN, P twitch gastrocnemius muscle compared with slow and fast fibers obtained from the slow antigravity soleus [J. J. Widrick, S. K. Knuth, K. M. Norenberg, J. G. Romatowski, J. L. W. Bain, D. A. Riley, M. Karhanek, S. W. Trappe, T. A. Trappe, D. L. Costill, and R. H. Fitts. J Physiol (Lond) 516: 915-930, 1999].

  16. Quantifying Ca2+ release and inactivation of Ca2+ release in fast- and slow-twitch muscles.

    Science.gov (United States)

    Barclay, C J

    2012-12-01

    The aims of this study were to quantify the Ca(2+) release underlying twitch contractions of mammalian fast- and slow-twitch muscle and to comprehensively describe the transient inactivation of Ca(2+) release following a stimulus. Experiments were performed using bundles of fibres from mouse extensor digitorum longus (EDL) and soleus muscles. Ca(2+) release was quantified from the amount of ATP used to remove Ca(2+) from the myoplasm following stimulation. ATP turnover by crossbridges was blocked pharmacologically (N-benzyl-p-toluenesulphonamide for EDL, blebbistatin for soleus) and muscle heat production was used as an index of Ca(2+) pump ATP turnover. At 20°C, Ca(2+) release in response to a single stimulus was 34 and 84 μmol (kg muscle)(-1) for soleus and EDL, respectively, and increased with temperature (30°C: soleus, 61 μmol kg(-1); EDL, 168 μmol kg(-1)). Delivery of another stimulus within 100 ms of the first produced a smaller Ca(2+) release. The maximum magnitude of the decrease in Ca(2+) release was greater in EDL than soleus. Ca(2+) release recovered with an exponential time course which was faster in EDL (mean time constant at 20°C, 32.1 ms) than soleus (65.6 ms) and faster at 30°C than at 20°C. The amounts of Ca(2+) released and crossbridge cycles performed are consistent with a scheme in which Ca(2+) binding to troponin-C allowed an average of ∼1.7 crossbridge cycles in the two muscles.

  17. The twitch interpolation technique for study of fatigue of human quadriceps muscle

    DEFF Research Database (Denmark)

    Bülow, P M; Nørregaard, J; Mehlsen, J;

    1995-01-01

    technique. Then an endurance test was performed in which the subjects made repeated isometric contractions at 50% of the 'true' maximum torque for 4 s, separated by 6 s rest periods. During the test, the force response to single electrical stimulation (twitch amplitude) was measured at 50% and 25......% of the estimated maximum torque. In 10 subjects, the test was repeated 2-4 weeks later. Twitch amplitudes at 50% of maximum torque declined exponentially with time in 20 of 21 subjects. The distribution of the exponential rate constant was skewed with a mean of 4.6 h-1 and range of 0.3-21.5 h-1. After...... logarithmical transformation, the distribution of the exponential rate constant fitted closely to a normal distribution, and the inter-individual variation was SD = 1.15 compared to an intra-individual variation of 0.29. The coefficient of correlation for repeated determination was 0.91 (P

  18. Bion 11 Spaceflight Project: Effect of Weightlessness on Single Muscle Fiber Function in Rhesus Monkeys

    Science.gov (United States)

    Fitts, Robert H.; Romatowski, Janell G.; Widrick, Jeffrey J.; DeLaCruz, Lourdes

    1999-01-01

    Although it is well known that microgravity induces considerable limb muscle atrophy, little is known about how weightlessness alters cell function. In this study, we investigated how weightlessness altered the functional properties of single fast and slow striated muscle fibers. Physiological studies were carried out to test the hypothesis that microgravity causes fiber atrophy, a decreased peak force (Newtons), tension (Newtons/cross-sectional area) and power, an elevated peak rate of tension development (dp/dt), and an increased maximal shortening velocity (V(sub o)) in the slow type I fiber, while changes in the fast-twitch fiber are restricted to atrophy and a reduced peak force. For each fiber, we determined the peak force (P(sub o)), V(sub o), dp/dt, the force-velocity relationship, peak power, the power-force relationship, the force-pCa relationship, and fiber stiffness. Biochemical studies were carried out to assess the effects of weightlessness on the enzyme and substrate profile of the fast- and slow-twitch fibers. We predicted that microgravity would increase resting muscle glycogen and glycolytic metabolism in the slow fiber type, while the fast-twitch fiber enzyme profile would be unaltered. The increased muscle glycogen would in part result from an elevated hexokinase and glycogen synthase. The enzymes selected for study represent markers for mitochondrial function (citrate synthase and 0-hydroxyacyl-CoA dehydrogenase), glycolysis (Phosphofructokinase and lactate dehydrogenase), and fatty acid transport (Carnitine acetyl transferase). The substrates analyzed will include glycogen, lactate, adenosine triphosphate, and phosphocreatine.

  19. Dynamic Elbow Flexion Force Estimation Through a Muscle Twitch Model and sEMG in a Fatigue Condition.

    Science.gov (United States)

    Na, Youngjin; Kim, Jung

    2016-11-14

    We propose a joint force estimation method to compute elbow flexion force using surface electromyogram (sEMG) considering time-varying effects in a fatigue condition. Muscle fatigue is a major cause inducing sEMG changes with respect to time over long periods and repetitive contractions. The proposed method composed the muscle-twitch model representing the force generated by a single spike and the spikes extracted from sEMG. In this study, isometric contractions at six different joint angles (ten subjects) and dynamic contractions with constant velocity (six subjects) were performed under non-fatigue and fatigue conditions. Performance of the proposed method was evaluated and compared with that of previous methods using mean absolute value (MAV). The proposed method achieved average 6.7±2.8 %RMSE for isometric contraction and 15.6±24.7 %RMSE for isokinetic contraction under fatigue condition with more accurate results than the previous methods.

  20. Incubating Isolated Mouse EDL Muscles with Creatine Improves Force Production and Twitch Kinetics in Fatigue Due to Reduction in Ionic Strength

    Science.gov (United States)

    Head, Stewart I.; Greenaway, Bronwen; Chan, Stephen

    2011-01-01

    Background Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. Methods and Results The extensor digitorum longus muscle from mice aged 12–14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i) before fatigue; (ii) immediately after a fatigue protocol; and (iii) after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. Conclusion Acute creatine application improves force production in isolated fast-twitch EDL muscle, and these improvements are particularly apparent when the muscle is fatigued. One likely mechanism for this improvement is an increase in Ca2+ sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation. PMID:21850234

  1. Incubating isolated mouse EDL muscles with creatine improves force production and twitch kinetics in fatigue due to reduction in ionic strength.

    Directory of Open Access Journals (Sweden)

    Stewart I Head

    Full Text Available BACKGROUND: Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. METHODS AND RESULTS: The extensor digitorum longus muscle from mice aged 12-14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i before fatigue; (ii immediately after a fatigue protocol; and (iii after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. CONCLUSION: Acute creatine application improves force production in isolated fast-twitch EDL muscle, and these improvements are particularly apparent when the muscle is fatigued. One likely mechanism for this improvement is an increase in Ca(2+ sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation.

  2. Vestigial-like 2 contributes to normal muscle fiber type distribution in mice.

    Science.gov (United States)

    Honda, Masahiko; Hidaka, Kyoko; Fukada, So-Ichiro; Sugawa, Ryo; Shirai, Manabu; Ikawa, Masahito; Morisaki, Takayuki

    2017-08-02

    Skeletal muscle is composed of heterogeneous populations of myofibers that are classified as slow- and fast-twitch fibers. The muscle fiber-type is regulated in a coordinated fashion by multiple genes, including transcriptional factors and microRNAs (miRNAs). However, players involved in this regulation are not fully elucidated. One of the members of the Vestigial-like factors, Vgll2, is thought to play a pivotal role in TEA domain (TEAD) transcription factor-mediated muscle-specific gene expression because of its restricted expression in skeletal muscles of adult mice. Here, we generated Vgll2 null mice and investigated Vgll2 function in adult skeletal muscles. These mice presented an increased number of fast-twitch type IIb fibers and exhibited a down-regulation of slow type I myosin heavy chain (MyHC) gene, Myh7, which resulted in exercise intolerance. In accordance with the decrease in Myh7, down-regulation of miR-208b, encoded within Myh7 gene and up-regulation of targets of miR-208b, Sox6, Sp3, and Purβ, were observed in Vgll2 deficient mice. Moreover, we detected the physical interaction between Vgll2 and TEAD1/4 in neonatal skeletal muscles. These results suggest that Vgll2 may be both directly and indirectly involved in the programing of slow muscle fibers through the formation of the Vgll2-TEAD complex.

  3. Is functional hypertrophy and specific force coupled with the addition of myonuclei at the single muscle fiber level?

    Science.gov (United States)

    Qaisar, Rizwan; Renaud, Guillaume; Morine, Kevin; Barton, Elisabeth R; Sweeney, H Lee; Larsson, Lars

    2012-03-01

    Muscle force is typically proportional to muscle size, resulting in constant force normalized to muscle fiber cross-sectional area (specific force). Mice overexpressing insulin-like growth factor-1 (IGF-1) exhibit a proportional gain in muscle force and size, but not the myostatin-deficient mice. In an attempt to explore the role of the cytoplasmic volume supported by individual myonuclei [myonuclear domain (MND) size] on functional capacity of skeletal muscle, we have investigated specific force in relation to MND and the content of the molecular motor protein, myosin, at the single muscle fiber level from myostatin-knockout (Mstn(-/-)) and IGF-1-overexpressing (mIgf1(+/+)) mice. We hypothesize that the addition of extra myonuclei is a prerequisite for maintenance of specific force during muscle hypertrophy. A novel algorithm was used to measure individual MNDs in 3 dimensions along the length of single muscle fibers from the fast-twitch extensor digitorum longus and the slow-twitch soleus muscle. A significant effect of the size of individual MNDs in hypertrophic muscle fibers on both specific force and myosin content was observed. This effect was muscle cell type specific and suggested there is a critical volume individual myonuclei can support efficiently. The large MNDs found in fast muscles of Mstn(-/-) mice were correlated with the decrement in specific force and myosin content in Mstn(-/-) muscles. Thus, myostatin inhibition may not be able to maintain the appropriate MND for optimal function.

  4. In situ hybridisation of a large repertoire of muscle-specific transcripts in fish larvae: the new superficial slow-twitch fibres exhibit characteristics of fast-twitch differentiation.

    Science.gov (United States)

    Chauvigné, F; Ralliere, C; Cauty, C; Rescan, P Y

    2006-01-01

    Much of the present information on muscle differentiation in fish concerns the early embryonic stages. To learn more about the maturation and the diversification of the fish myotomal fibres in later stages of ontogeny, we investigated, by means of in situ hybridisation, the developmental expression of a large repertoire of muscle-specific genes in trout larvae from hatching to yolk resorption. At hatching, transcripts for fast and slow muscle protein isoforms, namely myosins, tropomyosins, troponins and myosin binding protein C were present in the deep fast and the superficial slow areas of the myotome, respectively. During myotome expansion that follows hatching, the expression of fast isoforms became progressively confined to the borders of the fast muscle mass, whereas, in contrast, slow muscle isoform transcripts were uniformly expressed in all the slow fibres. Transcripts for several enzymes involved in oxidative metabolism such as citrate synthase, cytochrome oxidase component IV and succinate dehydrogenase, were present throughout the whole myotome of hatching embryos but in later stages became concentrated in slow fibre as well as in lateral fast fibres. Surprisingly, the slow fibres that are added externally to the single superficial layer of the embryonic (original) slow muscle fibres expressed not only slow twitch muscle isoforms but also, transiently, a subset of fast twitch muscle isoforms including MyLC1, MyLC3, MyHC and myosin binding protein C. Taken together these observations show that the growth of the myotome of the fish larvae is associated with complex patterns of muscular gene expression and demonstrate the unexpected presence of fast muscle isoform-expressing fibres in the most superficial part of the slow muscle.

  5. A new method for non-invasive estimation of human muscle fiber type composition.

    Directory of Open Access Journals (Sweden)

    Audrey Baguet

    Full Text Available BACKGROUND: It has been established that excellence in sports with short and long exercise duration requires a high proportion of fast-twitch (FT or type-II fibers and slow-twitch (ST or type-I fibers, respectively. Until today, the muscle biopsy method is still accepted as gold standard to measure muscle fiber type composition. Because of its invasive nature and high sampling variance, it would be useful to develop a non-invasive alternative. METHODOLOGY: Eighty-three control subjects, 15 talented young track-and-field athletes, 51 elite athletes and 14 ex-athletes volunteered to participate in the current study. The carnosine content of all 163 subjects was measured in the gastrocnemius muscle by proton magnetic resonance spectroscopy ((1H-MRS. Muscle biopsies for fiber typing were taken from 12 untrained males. PRINCIPAL FINDINGS: A significant positive correlation was found between muscle carnosine, measured by (1H-MRS, and percentage area occupied by type II fibers. Explosive athletes had ∼30% higher carnosine levels compared to a reference population, whereas it was ∼20% lower than normal in typical endurance athletes. Similar results were found in young talents and ex-athletes. When active elite runners were ranked according to their best running distance, a negative sigmoidal curve was found between logarithm of running distance and muscle carnosine. CONCLUSIONS: Muscle carnosine content shows a good reflection of the disciplines of elite track-and-field athletes and is able to distinguish between individual track running distances. The differences between endurance and sprint muscle types is also observed in young talents and former athletes, suggesting this characteristic is genetically determined and can be applied in early talent identification. This quick method provides a valid alternative for the muscle biopsy method. In addition, this technique may also contribute to the diagnosis and monitoring of many conditions and

  6. Hexamethonium-induced augmentation of the electrical twitch response in the guinea-pig ileum longitudinal muscle-myenteric plexus strip.

    Science.gov (United States)

    Donnerer, Josef; Liebmann, Ingrid; Holzer-Petsche, Ulrike

    2014-08-08

    Longitudinal muscle-myenteric plexus strips of the guinea-pig ileum were used to investigate the nature of the hexamethonium-induced augmentation of the twitch response. All preparations were set up in Tyrode solution and intermittent longitudinal twitch contractions were evoked by single pulse electrical field stimulation. Hexamethonium, a blocker of nicotinic ganglionic transmission, at 300 μmol/l and 1 mmol/l augmented the twitch contractions by 21% and 35%, respectively. First we tested for a possible nicotinic drive onto an inhibitory neuronal component to the longitudinal smooth muscle cells. However, guanethidine (5 μmol/l), naloxone (1 μmol/l), or l-NAME (300 μmol/l) were without effect on the hexamethonium-induced augmentation. The P2 purinoceptor antagonist pyridoxalphosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS), 25-100 μmol/l, without altering the control twitch responses, dose-dependently reduced the hexamethonium-induced augmentation; at 100 μmol/l a statistically significantly inhibition was observed. Based on these functional experiments we found no evidence that blocking nicotinic transmission removed a tonic adrenergic, opioidergic or nitrergic inhibitory input to the longitudinal muscle. However, we provide evidence for a hexamethonium-induced augmentation of the P2 purinergic input to cholinergic motoneurons of the guinea-pig ileum longitudinal muscle. The P2-nicotinic receptor interaction presents a novel modulatory mechanism to cholinergic myenteric motor neurons.

  7. Monitoring the structural behavior of troponin and myoplasmic free Ca2+ concentration during twitch of frog skeletal muscle.

    Science.gov (United States)

    Matsuo, Tatsuhito; Iwamoto, Hiroyuki; Yagi, Naoto

    2010-07-07

    The interaction of troponin molecules on the thin filament with Ca(2+) plays a key role in regulating muscle contraction. To characterize the structural changes of troponin caused by Ca(2+) and crossbridge formation, we recorded the small-angle x-ray intensity and the myoplasmic free Ca(2+) concentration using fluo-3 AM in the same frog skeletal muscle during twitch elicited by a single electrical pulse at 16 degrees C. In an overstretched muscle, the intensity of the meridional reflection from troponin at 1/38.5 nm(-1) began to change at 4 ms after the stimulus, reached a peak at 10 ms, and returned to the resting level with a halftime of 25 ms. The concentration of troponin-bound Ca(2+) began to increase at 1-2 ms after the stimulus, reached a peak at 5 ms, and returned to the resting level with a halftime of 40 ms, indicating that troponin begins to change conformation only after a sizable amount of Ca(2+) has bound to it, and returns to the resting structure even when there is still some bound Ca(2+). In a muscle with a filament overlap, crossbridge formation appears to slow down Ca(2+) release from troponin and have a large effect on its conformation.

  8. The Expression of MMP-2 Following Immobilization and High-Intensity Running in Plantaris Muscle Fiber in Rats

    Directory of Open Access Journals (Sweden)

    Eli Carmeli

    2006-01-01

    Full Text Available The effect of 2-week, high-intensity running and a 2-week immobilization on muscle fiber type composition of the plantaris muscle from 18 female, 6-month-old Wistar rats (running, n = 6; immobilization, n = 6; sedentary control, n = 6 was bio- and histochemically investigated. The high-intensity treadmill running began with 20 min (32 m/min, 0% gradient, 75% VO2 max, up to 50 min/day. Right hind limbs were immobilized by an external fixation procedure for 13 days. Muscle mass of the plantaris muscle in the immobilized groups was reduced by 16% in comparison with the sedentary control group. High-intensity running and immobilization increased both mRNA and protein levels of matrix metalloproteinase type 2 (MMP-2 in plantaris. Running and immobilization decreased the percentages of transverse sectional area of fast-twitch glycolytic (FG type IIb fibers, running increased relative cross-sectional area of fast-twitch oxidative glycolytic (FOG type IIa muscle fibers, whereas immobilization increased relative cross-sectional area of slow-twitch oxidative (SO muscle fibers (type I. Our results suggest that both high-intensity running and immobilization are enough to induce overwhelming changes in plantaris.

  9. What are the stimulation parameters that affect the extent of twitch force potentiation in the adductor pollicis muscle?

    Science.gov (United States)

    Mettler, Joni A; Griffin, Lisa

    2010-12-01

    Muscle force potentiation affects force output during electrical stimulation. Few studies have examined stimulation train parameters that influence potentiation such as pulse number, stimulation frequency, train duration, and force-time integral and peak force produced during the train. Pulse-matched trains (100 pulses) at 7.5, 15, 25, 30, 50, and 100 Hz, and trains of varying pulse number (50, 100, and 200 pulses) at 30 and 50 Hz were delivered to the ulnar nerve of 10 (5 male, 5 female; 23.4 ± 0.9 years), healthy individuals in random order. Single twitches of the adductor pollicis muscle were elicited before and after each train with a rest interval of at least 5 min between each train. No differences in potentiation occurred across the pulse-matched trains at frequencies of 15-50 Hz (38.9 ± 5.4-44.6 ± 5.5%). Twitch force potentiation following the highest (100 Hz) and lowest (7.5 Hz) frequency trains were not significantly different and were lower than the other 100 pulse-matched trains. As pulse number increased, potentiation increased for both the 30 and 50-Hz trains. There was a significant positive correlation between force potentiation and force-time integral produced by the stimulation train, r = 0.70. The results indicate that potentiation magnitude is dependent on the force-time integral produced during the test train and the number of pulses delivered, independent of stimulation frequency.

  10. Effect of levosimendan on the contractility of muscle fibers from nemaline myopathy patients with mutations in the nebulin gene.

    Science.gov (United States)

    de Winter, Josine M; Joureau, Barbara; Sequeira, Vasco; Clarke, Nigel F; van der Velden, Jolanda; Stienen, Ger Jm; Granzier, Henk; Beggs, Alan H; Ottenheijm, Coen Ac

    2015-01-01

    Nemaline myopathy (NM), the most common non-dystrophic congenital myopathy, is characterized by generalized skeletal muscle weakness, often from birth. To date, no therapy exists that enhances the contractile strength of muscles of NM patients. Mutations in NEB, encoding the giant protein nebulin, are the most common cause of NM. The pathophysiology of muscle weakness in NM patients with NEB mutations (NEB-NM) includes a lower calcium-sensitivity of force generation. We propose that the lower calcium-sensitivity of force generation in NEB-NM offers a therapeutic target. Levosimendan is a calcium sensitizer that is approved for use in humans and has been developed to target cardiac muscle fibers. It exerts its effect through binding to slow skeletal/cardiac troponin C. As slow skeletal/cardiac troponin C is also the dominant troponin C isoform in slow-twitch skeletal muscle fibers, we hypothesized that levosimendan improves slow-twitch muscle fiber strength at submaximal levels of activation in patients with NEB-NM. To test whether levosimendan affects force production, permeabilized slow-twitch muscle fibers isolated from biopsies of NEB-NM patients and controls were exposed to levosimendan and the force response was measured. No effect of levosimendan on muscle fiber force in NEB-NM and control skeletal muscle fibers was found, both at a submaximal calcium level using incremental levosimendan concentrations, and at incremental calcium concentrations in the presence of levosimendan. In contrast, levosimendan did significantly increase the calcium-sensitivity of force in human single cardiomyocytes. Protein analysis confirmed that the slow skeletal/cardiac troponin C isoform was present in the skeletal muscle fibers tested. These findings indicate that levosimendan does not improve the contractility in human skeletal muscle fibers, and do not provide rationale for using levosimendan as a therapeutic to restore muscle weakness in NEB-NM patients. We stress the

  11. Microvascular oxygen pressures in muscles comprised of different fiber types: Impact of dietary nitrate supplementation

    Science.gov (United States)

    Ferguson, Scott K.; Holdsworth, Clark T.; Wright, Jennifer L.; Fees, Alex J.; Allen, Jason D.; Jones, Andrew M.; Musch, Timothy I.; Poole, David C.

    2014-01-01

    Nitrate (NO3−) supplementation via beetroot juice (BR) preferentially improves vascular conductance and O2 delivery to contracting skeletal muscles comprised predominantly of type IIb + d/x (i.e. highly glycolytic) fibers following its reduction to nitrite and nitric oxide (NO). To address the mechanistic basis for NO3− to improve metabolic control we tested the hypothesis that increased NO bioavailability via BR supplementation would elevate microvascular PO2 (PO2mv) in fast twitch but not slow twitch muscle. Twelve young adult male Sprague-Dawley rats were administered BR ([NO3−] 1 mmol/kg/day, n=6) or water (control, n=6) for 5 days. PO2mv (phosphorescence quenching) was measured at rest and during 180s of electrically induced 1-Hz twitch contractions (6–8 V) of the soleus (9% type IIb +d/x) and mixed portion of the gastrocnemius (MG, 91% type IIb + d/x) muscles. In the MG, but not the soleus, BR elevated contracting steady state PO2mv by ~43% (control: 13.7 ± 0.5, BR: 19 ± 1.6 mmHg, (P<0.05). This higher PO2mv represents a greater blood-myocyte O2 driving force during muscle contractions thus providing a potential mechanism by which NO3− supplementation via BR improves metabolic control in fast twitch muscle. Recruitment of higher order type II muscle fibers is thought to play a role in the development of the V.O2 slow component which is inextricably linked to the fatigue process. These data therefore provide a putative mechanism for the BR-induced improvements in high-intensity exercise performance seen in humans. PMID:25280991

  12. Enhancement of twitch force by stretch in a nerve-skeletal muscle preparation of the frog Rana porosa brevipoda and the effects of temperature on it.

    Science.gov (United States)

    Ishii, Yoshiki; Watari, Takashi; Tsuchiya, Teizo

    2004-12-01

    We investigated the mechanism of the enhancement of twitch force by stretch and the effects of temperature on it in nerve-skeletal muscle preparations of whole iliofibularis muscles isolated from the frog Rana brevipoda. When a preparation was stimulated indirectly and stretched, the twitch force after the stretch was enhanced remarkably in comparison to that observed before a stretch at low temperature. The enhanced force obtained by a stretch of 20% resting muscle length (l0) at low temperature was as high as the force obtained by direct stimulation. The phenomenon was not dependent on the velocity but on the amplitude of stretch. The enhanced force obeyed the length-force relationship when a stretch was long enough. The above results were observed when the frogs were kept at room temperature (20-22 degrees C). Measurements were also taken at low temperature (4 degrees C); when frogs were kept at low temperature for more than 2 months, twitch force obtained without stretch was considerably higher at l0. The amplitude of the action potential recorded extracellularly from the muscle surface increased remarkably after a stretch, but was same before and after a stretch when recorded from the nerve innervating muscle. The effects of temperature on twitch and tetanic force by direct or indirect stimulation without stretch were also studied as basic data of the stretch experiment. The results from this study suggest that stretch-induced force enhancement in a nerve-muscle preparation is caused by an increase in the transmission rate between nerve and muscle, and the amplitude of the enhanced force is determined by the length-force relationship of the muscle. The phenomenon is also strongly affected by the temperature at which the frogs are kept.

  13. Tubular system volume changes in twitch fibres from toad and rat skeletal muscle assessed by confocal microscopy.

    Science.gov (United States)

    Launikonis, Bradley S; Stephenson, D George

    2002-01-15

    The volume of the extracellular compartment (tubular system) within intact muscle fibres from cane toad and rat was measured under various conditions using confocal microscopy. Under physiological conditions at rest, the fractional volume of the tubular system (t-sys(Vol)) was 1.38 +/- 0.09 % (n = 17), 1.41 +/- 0.09 % (n = 12) and 0.83 +/- 0.07 % (n = 12) of the total fibre volume in the twitch fibres from toad iliofibularis muscle, rat extensor digitorum longus muscle and rat soleus muscle, respectively. In toad muscle fibres, the t-sys(Vol) decreased by 30 % when the tubular system was fully depolarized and decreased by 15 % when membrane cholesterol was depleted from the tubular system with methyl-beta-cyclodextrin but did not change as the sarcomere length was changed from 1.93 to 3.30 microm. There was also an increase by 30 % and a decrease by 25 % in t-sys(Vol) when toad fibres were equilibrated in solutions that were 2.5-fold hypertonic and 50 % hypotonic, respectively. When the changes in total fibre volume were taken into consideration, the t-sys(Vol) expressed as a percentage of the isotonic fibre volume did actually decrease as tonicity increased, revealing that the tubular system in intact fibres cannot be compressed below 0.9 % of the isotonic fibre volume. The results can be explained in terms of forces acting at the level of the tubular wall. These observations have important physiological implications showing that the tubular system is a dynamic membrane structure capable of changing its volume in response to the membrane potential, cholesterol depletion and osmotic stress but not when the sarcomere length is changed in resting muscle.

  14. Comparative analysis of fiber-type composition in the iliofibularis muscle of phrynosomatid lizards (Squamata).

    Science.gov (United States)

    Bonine, K E; Gleeson, T T; Garland, T

    2001-12-01

    The lizard family Phrynosomatidae comprises three subclades: the closely related sand and horned lizards, and their relatives the Sceloporus group. This family exhibits great variation in ecology, behavior, and general body plan. Previous studies also show that this family exhibits great diversity in locomotor performance abilities; as measured on a high-speed treadmill, sand lizards are exceptionally fast sprinters, members of the Sceloporus group are intermediate, and horned lizards are slowest. These differences are paralleled by differences in relative hindlimb span. To determine if muscle fiber-type composition also varies among the three subclades, we examined the iliofibularis (IF), a hindlimb muscle used in lizard locomotion, in 11 species of phrynosomatid lizards. Using histochemical assays for myosin ATPase, an indicator of fast-twitch capacity, and succinic dehydrogenase, denoting oxidative capacity, we classified fiber types into three categories based on existing nomenclature: fast-twitch glycolytic (FG), fast-twitch oxidative-glycolytic (FOG), and slow-twitch oxidative (SO). Sand lizards have a high proportion of FG fibers (64-70%) and a low proportion of FOG fibers (25-33%), horned lizards are the converse (FG fibers 25-31%, FOG fibers 56-66%), and members of the Sceloporus group are intermediate for both FG (41-48%) and FOG (42-45%) content. Hence, across all 11 species %FOG and %FG are strongly negatively correlated. Analysis with phylogenetically independent contrasts indicate that this negative relationship is entirely attributable to the divergence between sand and horned lizards. The %SO also varies among the three subclades. Results from conventional nested ANCOVA (with log body mass as a covariate) indicate that the log mean cross-sectional area of individual muscle fibers differs among species and is positively correlated with body mass across species, but does not differ significantly among subclades. The log cross-sectional area of the IF

  15. Single fiber analyses of glycogen-related proteins reveal their differential association with glycogen in rat skeletal muscle.

    Science.gov (United States)

    Murphy, Robyn M; Xu, Hongyang; Latchman, Heidy; Larkins, Noni T; Gooley, Paul R; Stapleton, David I

    2012-12-01

    To understand how glycogen affects skeletal muscle physiology, we examined enzymes essential for muscle glycogen synthesis and degradation using single fibers from quiescent and stimulated rat skeletal muscle. Presenting a shift in paradigm, we show these proteins are differentially associated with glycogen granules. Protein diffusibility and/or abundance of glycogenin, glycogen branching enzyme (GBE), debranching enzyme (GDE), phosphorylase (GP), and synthase (GS) were examined in fibers isolated from rat fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscle. GDE and GP proteins were more abundant (~10- to 100-fold) in fibers from EDL compared with SOL muscle. GS and glycogenin proteins were similar between muscles while GBE had an approximately fourfold greater abundance in SOL muscle. Mechanically skinned fibers exposed to physiological buffer for 10 min showed ~70% total pools of GBE and GP were diffusible (nonbound), whereas GDE and GS were considerably less diffusible. Intense in vitro stimulation, sufficient to elicit a ~50% decrease in intracellular glycogen, increased diffusibility of GDE, GP, and GS (~15-60%) and decreased GBE diffusibility (~20%). Amylase treatment, which breaks α-1,4 linkages of glycogen, indicated differential diffusibilities and hence glycogen associations of GDE and GS. Membrane solubilization (1% Triton-X-100) allowed a small additional amount of GDE and GS to diffuse from fibers, suggesting the majority of nonglycogen-associated GDE/GS is associated with myofibrillar/contractile network of muscle rather than membranes. Given differences in enzymes required for glycogen metabolism, the current findings suggest glycogen particles have fiber-type-dependent structures. The greater catabolic potential of glycogen breakdown in fast-twitch fibers may account for different contraction induced rates of glycogen utilization.

  16. Prevention of muscle fibers atrophy during gravitational unloading: The effect of L-arginine administration

    Science.gov (United States)

    Kartashkina, N.; Lomonosova, Y.; Shevchenko, T. F.; Bugrova, A. E.; Turtikova, O. V.; Kalamkarov, G. R.; Nemirovskaya, T. L.

    2011-05-01

    Gravitational unloading results in pronounced atrophy of m.soleus. Probably, the output of NO is controlled by the muscle activity. We hypothesized that NO may be involved in the protein metabolism and increase of its concentration in muscle can prevent atrophic changes induced by gravitational unloading. In order to test the hypothesis we applied NO donor L-arginine during gravitational unloading. 2.5-month-old male Wistar rats weighing 220-230g were divided into sedentary control group (CTR, n=7), 14-day hindlimb suspension (HS, n=7), 14 days of hindlimb suspension+ L-arginine (HSL, n=7) (with a daily supplementation of 500 mg/kg wt L-arginine) and 14 days of hindlimb suspension+ L-NAME (HSN, n=7) (90 mg/kg wt during 14 days). Cross sectional area (CSA) of slow twitch (ST) and fast twitch (FT) soleus muscle fibers decreased by 45% and 28% in the HS group ( patrophy of FT muscle fibers in the HSL group was completely prevented since FT fiber CSA had no significant differences from the CTR group. In HS group, the percentage of fibers revealing either gaps/disruption of the dystrophin layer of the myofiber surface membrane increased by 27% and 17%, respectively, as compared to the controls (CTR group, patrophy level under gravitational unloading.

  17. Twitch and tetanic tension during culture of mature xenopus laevis single muscle fibres

    NARCIS (Netherlands)

    Jaspers, R.T.; Feenstra, H.M.; Lee-de Groot, M.B.E.; Huijing, P.A.; Laarse, W.J.

    2001-01-01

    Investigation of the mechanisms of muscle adaptation requires independent control of the regulating factors. The aim of the present study was to develop a serum-free medium to culture mature single muscle fibres of Xenopus laevis. As an example, we used the culture system to study adaptation of twit

  18. Spaceflight effects on single skeletal muscle fiber function in the rhesus monkey

    Science.gov (United States)

    Fitts, R. H.; Desplanches, D.; Romatowski, J. G.; Widrick, J. J.

    2000-01-01

    The purpose of this investigation was to understand how 14 days of weightlessness alters the cellular properties of individual slow- and fast-twitch muscle fibers in the rhesus monkey. The diameter of the soleus (Sol) type I, medial gastrocnemius (MG) type I, and MG type II fibers from the vivarium controls averaged 60 +/- 1, 46 +/- 2, and 59 +/- 2 microm, respectively. Both a control 1-G capsule sit (CS) and spaceflight (SF) significantly reduced the Sol type I fiber diameter (20 and 13%, respectively) and peak force, with the latter declining from 0.48 +/- 0.01 to 0.31 +/- 0.02 (CS group) and 0.32 +/- 0.01 mN (SF group). When the peak force was expressed as kiloNewtons per square meter (kN/m(2)), only the SF group showed a significant decline. This group also showed a significant 15% drop in peak fiber stiffness that suggests that fewer cross bridges were contracting in parallel. In the MG, SF but not CS depressed the type I fiber diameter and force. Additionally, SF significantly depressed absolute (mN) and relative (kN/m(2)) force in the fast-twitch MG fibers by 30% and 28%, respectively. The Ca(2+) sensitivity of the type I fiber (Sol and MG) was significantly reduced by growth but unaltered by SF. Flight had no significant effect on the mean maximal fiber shortening velocity in any fiber type or muscle. The post-SF Sol type I fibers showed a reduced peak power and, at peak power, an elevated velocity and decreased force. In conclusion, CS and SF caused atrophy and a reduced force and power in the Sol type I fiber. However, only SF elicited atrophy and reduced force (mN) in the MG type I fiber and a decline in relative force (kN/m(2)) in the Sol type I and MG type II fibers.

  19. Fiber-type composition of hindlimb muscles in the turtle, Pseudemys (Trachemys) scripta elegans.

    Science.gov (United States)

    Laidlaw, D H; Callister, R J; Stuart, D G

    1995-08-01

    A description is provided of the fiber-type composition of several hindlimb muscles of the adult turtle, Pseudemys (Trachemys) scripta elegans. In addition, cross-section areas of each fiber type and an estimation of the relative (weighted) cross-section area (wCSA) occupied by the different fiber types are also provided. Seven muscles were selected for study, based on their suitability for future neurophysiological analysis as components of the segmental motor system, and on their homologies with muscles in other vertebrates. The test muscles were iliofibularis (ILF), ambiens (AMB), external gastrocnemius (EG), extensor digitorum communis (EDC), flexor digitorum longus (FDL), tibialis anterior (TA), and peroneus anterior (PA). Serial sections of these muscles were stained for myosin adenosine triphosphatase (ATPase), NADH-diaphorase, and alpha-glycerophosphate dehydrogenase (alpha-GPDH), thereby enabling fiber-type classification on the basis of indirect markers for contraction speed and oxidative (aerobic) vs. glycolytic (anaerobic) metabolism. All muscles contained three fiber types: slow oxidative (SO; possibly including some non-twitch tonic fibers); fast oxidative glycolytic (FOG); and fast glycolytic (Fg). There were at least 30% FOG and 50% FOG + Fg fibers in the seven muscles, the extreme distributions being the predominantly glycolytic ILF vs. the predominantly oxidative FDL muscle (ILF--15.5% SO, 35.2% FOG, 49.3% Fg vs. FDL--49.1% SO, 41.1% FOG, 9.8% Fg). As in other species, the test muscles exhibited varying degrees of regional concentration (compartmentalization) of the different fiber types. This feature was most striking in ILF. Pronounced compartmentalization was also observed in AMB, EG, PA, TA, and EDC, whereas the distribution of fiber types in the highly oxidative FDL was homogeneous. In five of the seven muscles, fiber size was ranked with Fg > FOG > SO. In terms of wCSA, which provides a coarse-grain measure of the different fiber types

  20. AMPK alpha1 activation is required for stimulation of glucose uptake by twitch contraction, but not by H2O2, in mouse skeletal muscle

    DEFF Research Database (Denmark)

    Jensen, Thomas Elbenhardt; Schjerling, Peter; Viollet, Benoit

    2008-01-01

    BACKGROUND: AMPK is a promising pharmacological target in relation to metabolic disorders partly due to its non-insulin dependent glucose uptake promoting role in skeletal muscle. Of the 2 catalytic alpha-AMPK isoforms, alpha(2) AMPK is clearly required for stimulation of glucose transport......, in wildtype and alpha-AMPK transgenic mouse muscles, this study aimed to define conditions where alpha(1) AMPK is required to increase muscle glucose uptake. METHODOLOGY/PRINCIPAL FINDINGS: Following stimulation with H(2)O(2) (3 mM, 20 min) or twitch-contraction (0.1 ms pulse, 2 Hz, 2 min), signaling and 2...

  1. Increase in twitch force of the adductor pollicis muscle with stabilized preload at constant thumb abduction before and after administration of muscle relaxant

    NARCIS (Netherlands)

    van Santen, G; Wierda, JMKH; Fidler, [No Value

    1999-01-01

    Objective. To determine whether the twitch force of the adductor pollicis remains stable when 0.1 Hz single twitch stimulation is started after stabilization of the thumb preload at a constant degree of thumb abduction; also to study any possible increase in twitch force before the onset of and afte

  2. In Vivo Imaging of Human Sarcomere Twitch Dynamics in Individual Motor Units.

    Science.gov (United States)

    Sanchez, Gabriel N; Sinha, Supriyo; Liske, Holly; Chen, Xuefeng; Nguyen, Viet; Delp, Scott L; Schnitzer, Mark J

    2015-12-16

    Motor units comprise a pre-synaptic motor neuron and multiple post-synaptic muscle fibers. Many movement disorders disrupt motor unit contractile dynamics and the structure of sarcomeres, skeletal muscle's contractile units. Despite the motor unit's centrality to neuromuscular physiology, no extant technology can image sarcomere twitch dynamics in live humans. We created a wearable microscope equipped with a microendoscope for minimally invasive observation of sarcomere lengths and contractile dynamics in any major skeletal muscle. By electrically stimulating twitches via the microendoscope and visualizing the sarcomere displacements, we monitored single motor unit contractions in soleus and vastus lateralis muscles of healthy individuals. Control experiments verified that these evoked twitches involved neuromuscular transmission and faithfully reported muscle force generation. In post-stroke patients with spasticity of the biceps brachii, we found involuntary microscopic contractions and sarcomere length abnormalities. The wearable microscope facilitates exploration of many basic and disease-related neuromuscular phenomena never visualized before in live humans.

  3. Differential effects of docoosahexaenoic and arachidonic acid on fatty acid composition and myosin heavy chain-related genes of slow- and fast-twitch skeletal muscle tissues.

    Science.gov (United States)

    Hashimoto, Michio; Inoue, Takayuki; Katakura, Masanori; Hossain, Shahdat; Mamun, Abdullah Al; Matsuzaki, Kentaro; Arai, Hiroyuki; Shido, Osamu

    2016-04-01

    Myosin heavy chain (MHC) mediates the metabolic and contractile responses of skeletal muscles. MHC displays different isoforms, each of which has different characteristics. To better understand the effect of polyunsaturated fatty acids in skeletal muscles, rats were fed with control-, docosahexaenoic acid (DHA)-, and arachidonic acid (ARA)-oil, and the effects on plasma and muscular fatty acid profile, oxidative stress, mRNA levels of myosin heavy chain isoforms MHC1 of slow-twitch muscle (SO) and MHC2A, MHC2X, and MHCB isoforms of extensor digitorum longus (EDL) of fast-twitch muscle were evaluated. Concomitantly, mRNA levels of anti-oxidative enzymes, such as, catalase, glutathione peroxidase (GPx) and superoxide dismutase (SOD were determined. The expressions of MHC1, MHC2A, MHC2X, and MHC2B were lower in the SO of the DHA-fed rats. In the EDL muscles of DHA-fed rats, the expressions of MHC1 and MHC2A increased; however, the expressions of MHC2X increased and that of the MHC2 were not altered. Oxidative stress, as indicated by the levels of LPO, was significantly higher in the plasma of the ARA-fed rats, when compared with that of the DHA-fed rats. The LPO levels were higher both in the SO and EDL muscles of ARA-fed rats. Compared with ARA oil intake, DHA oil showed higher mRNA levels of GPx and SOD. Catalase expression was higher only in the EDL but not in the SO-type muscles. Our studies finally indicate that DHA and ARA differentially affect the regulation of contractile and metabolic properties of slow- and fast-twitch skeletal muscles.

  4. Interaction of Mechanical Load with Growth Hormone (GH) and Insulin-Like Growth Factor I (IGF-I) on Slow-Twitch Skeletal Muscle and Bone

    Science.gov (United States)

    Linderman, Jon K.; Gosselink, Kristin L.; Wang, Tommy J.; Mukku, Venkat R.; Grindeland, Richard E.

    1994-01-01

    Exogenous humoral growth factors, combined with increased mechanical loading, reportedly induce hypertrophy of fast-, but not slow-twitch skeletal muscles, and have little effect in attenuating atrophy of slow-twitch muscle associated with exposure to microgravity in animals with intact neuroendocrine systems. These observations suggest that anabolic adjuvants and muscle tension do not interact to stimulate growth or maintenance of slow-twitch skeletal muscle. The purpose of the present study was to determine whether a chronic increase in mechanical loading (synergistic ablation) or hindlimb unweighting (hindlimb suspension) interact with exogenous GH and IGF-I (Genentech, So San Francisco, CA) in the slow-twitch soleus muscles of female rats (approx. 250 g). Bilateral ablation of the plantaris and gastrocnemius muscles induced 38% and 40% increases in the absolute (mg/pair) and relative (mg/100 g body weight) weights of the soleus, respectively (p less than or = 0.05), in ambulatory rats. GH and IGF-I interacted with chronic loading to increase absolute soleus mass an additional 20% (p less than or = 0.05), and mixed and myofibrillar protein contents an additional 12% and 7%, respectively (NS). In contrast, hindlimb suspension (HLS) resulted in 20% and 18% decreases in the absolute and relative weights of the soleus, respectively (p less than or = 0.05); GH and IGF-I did not spare loss of soleus mass or protein content in HLS rats. HLS decreased tibial plate thickness approx. 11% (p less than or = 0.05), but not weights of the tibia or femus. GH and IGF-I increased tibial plate thickness approx. 30% (p less than or = 0.05), in ambulatory and HLS rats, and increased femur and tibial weights 12% (p less than or = 0.05) and 8% (NS), respectively, in ambulatory rats, but had no effect in HLS rats. Results of the present investigation suggest that GH and IGF-I can stimulate hypertrophy of slow-twitch skeletal muscle when chronically overloaded, but can also stimulate

  5. Interaction of Mechanical Load with Growth Hormone (GH) and Insulin-Like Growth Factor I (IGF-I) on Slow-Twitch Skeletal Muscle and Bone

    Science.gov (United States)

    Linderman, Jon K.; Gosselink, Kristin L.; Wang, Tommy J.; Mukku, Venkat R.; Grindeland, Richard E.

    1994-01-01

    Exogenous humoral growth factors, combined with increased mechanical loading, reportedly induce hypertrophy of fast-, but not slow-twitch skeletal muscles, and have little effect in attenuating atrophy of slow-twitch muscle associated with exposure to microgravity in animals with intact neuroendocrine systems. These observations suggest that anabolic adjuvants and muscle tension do not interact to stimulate growth or maintenance of slow-twitch skeletal muscle. The purpose of the present study was to determine whether a chronic increase in mechanical loading (synergistic ablation) or hindlimb unweighting (hindlimb suspension) interact with exogenous GH and IGF-I (Genentech, So San Francisco, CA) in the slow-twitch soleus muscles of female rats (approx. 250 g). Bilateral ablation of the plantaris and gastrocnemius muscles induced 38% and 40% increases in the absolute (mg/pair) and relative (mg/100 g body weight) weights of the soleus, respectively (p less than or = 0.05), in ambulatory rats. GH and IGF-I interacted with chronic loading to increase absolute soleus mass an additional 20% (p less than or = 0.05), and mixed and myofibrillar protein contents an additional 12% and 7%, respectively (NS). In contrast, hindlimb suspension (HLS) resulted in 20% and 18% decreases in the absolute and relative weights of the soleus, respectively (p less than or = 0.05); GH and IGF-I did not spare loss of soleus mass or protein content in HLS rats. HLS decreased tibial plate thickness approx. 11% (p less than or = 0.05), but not weights of the tibia or femus. GH and IGF-I increased tibial plate thickness approx. 30% (p less than or = 0.05), in ambulatory and HLS rats, and increased femur and tibial weights 12% (p less than or = 0.05) and 8% (NS), respectively, in ambulatory rats, but had no effect in HLS rats. Results of the present investigation suggest that GH and IGF-I can stimulate hypertrophy of slow-twitch skeletal muscle when chronically overloaded, but can also stimulate

  6. Blood vessels and desmin control the positioning of nuclei in skeletal muscle fibers.

    Science.gov (United States)

    Ralston, E; Lu, Z; Biscocho, N; Soumaka, E; Mavroidis, M; Prats, C; Lømo, T; Capetanaki, Y; Ploug, T

    2006-12-01

    Skeletal muscle fibers contain hundreds to thousands of nuclei which lie immediately under the plasmalemma and are spaced out along the fiber, except for a small cluster of specialized nuclei at the neuromuscular junction. How the nuclei attain their positions along the fiber is not understood. Here we show that the nuclei are preferentially localized near blood vessels (BV), particularly in slow-twitch, oxidative fibers. Thus, in rat soleus muscle fibers, 81% of the nuclei appear next to BV. Lack of desmin markedly perturbs the distribution of nuclei along the fibers but does not prevent their close association with BV. Consistent with a role for desmin in the spacing of nuclei, we show that denervation affects the organization of desmin filaments as well as the distribution of nuclei. During chronic stimulation of denervated muscles, new BV form, along which muscle nuclei align themselves. We conclude that the positioning of nuclei along muscle fibers is plastic and that BV and desmin intermediate filaments each play a distinct role in the control of this positioning.

  7. Drug action of benzocaine on the sarcoplasmic reticulum Ca-ATPase from fast-twitch skeletal muscle.

    Science.gov (United States)

    Di Croce, D; Trinks, P W; Grifo, M B; Takara, D; Sánchez, G A

    2015-11-01

    The effect of the local anesthetic benzocaine on sarcoplasmic reticulum membranes isolated from fast-twitch muscles was tested. The effects on Ca-ATPase activity, calcium binding and uptake, phosphoenzyme accumulation and decomposition were assessed using radioisotopic methods. The calcium binding to the Ca-ATPase was noncompetitively inhibited, and the enzymatic activity decreased in a concentration-dependent manner (IC50 47.1 mM). The inhibition of the activity depended on the presence of the calcium ionophore calcimycin and the membrane protein concentration. The pre-exposure of the membranes to benzocaine enhanced the enzymatic activity in the absence of calcimycin, supporting the benzocaine permeabilizing effect, which was prevented by calcium. Benzocaine also interfered with the calcium transport capability by decreasing the maximal uptake (IC50 40.3 mM) without modification of the calcium affinity for the ATPase. It inhibited the phosphorylation of the enzyme, and at high benzocaine concentration, the dephosphorylation step became rate-limiting as suggested by the biphasic profile of phosphoenzyme accumulation at different benzocaine concentrations. The data reported in this paper revealed a complex pattern of inhibition involving two sites for interaction with low and high benzocaine concentrations. It is concluded that benzocaine not only exerts an indirect action on the membrane permeability to calcium but also affects key steps of the Ca-ATPase enzymatic cycle.

  8. Earliest mechanical evidence of cross-bridge activity after stimulation of single skeletal muscle fibers.

    Science.gov (United States)

    Claflin, D R; Morgan, D L; Julian, F J

    1990-03-01

    The stiffness of single fibers from frog skeletal muscle was measured by the application of small 2-kHz sinusoidal length oscillations during twitch and tetanic contractions at a range of initial sarcomere lengths. The earliest mechanical signs of activation were a fall in tension (latency relaxation) and a rise in stiffness. The earliest stiffness increase and the earliest tension fall occurred simultaneously at all sarcomere lengths. This suggests a cross-bridge origin for the latency relaxation. The lead of stiffness over tension seen during the rise of tension was substantially established during the latent period. Reducing the size of the twitch by reducing calcium release with D-600 (methoxyverapamil) reduced the latency relaxation and the stiffness development during latency much less than it reduced the twitch tension. For very small twitches the peak of the stiffness response occurred during the latent period and the times of onset of both latency relaxation and stiffness rise were delayed, but remained coincident. This suggests a strong connection between the latency relaxation and the rise of stiffness during the latent period, whereas the connection between these events and positive tension generation appears to be less strong.

  9. Emerin increase in regenerating muscle fibers

    Directory of Open Access Journals (Sweden)

    S Squarzoni

    2009-06-01

    Full Text Available The fate of emerin during skeletal muscle regeneration was investigated in an animal model by means of crush injury. Immunofluorescence, immunoblotting and mRNA analysis demonstrated that emerin level is increased in regenerating rat muscle fibers with respect to normal mature myofibers. This finding suggests an involvement of emerin during the muscle fiber regeneration process, in analogy with its reported involvement in muscle cell differentiation in vitro. The impairment of skeletal muscle physiological regeneration or reorganization could be a possible pathogenetic mechanism for Emery Dreifuss muscular dystrophy.

  10. Fiber type distribution in the shoulder muscles of the tree shrew, the cotton-top tamarin, and the squirrel monkey related to shoulder movements and forelimb loading.

    Science.gov (United States)

    Schmidt, Manuela; Schilling, Nadja

    2007-04-01

    Muscle fiber type composition of intrinsic shoulder muscles was examined in tree shrews, cotton-top tamarins, and squirrel monkeys with respect to their shoulder kinematics and forelimb loading during locomotion. Enzyme- and immunohistochemical techniques were applied to differentiate muscle fiber types on serial cross-sections of the shoulder. In the majority of the shoulder muscles, the proportions of fatigue resistant slow-twitch fibers (SO) and fatigable fast-twitch fibers (FG) were inversely related to each other, whereas the percentage of intermediate FOG-fibers varied independently. A segregation of fatigue resistant SO-fibers into deep muscle regions is indicative of differential activation of histochemically distinct muscle regions in which deep regions stabilize the joint against gravitational loading. In all three species, this antigravity function was demonstrated for both the supraspinatus and the cranial subscapularis muscle, which prevent passive joint flexion during the support phase of the limb. The infraspinatus muscle showed a high content of SO-fibers in the primate species but not in the tree shrew, which demonstrates the "new" role of the infraspinatus muscle in joint stabilization related to the higher degree of humeral protraction in primates. In the tree shrew and the cotton-top tamarin, a greater proportion of the body weight is carried on the forelimb, but the squirrel monkey exhibits a weight shift to the hind limbs. The lower amount of forelimb loading is reflected by an overall lower proportion of fatigue resistant muscle fibers in the shoulder muscles of the squirrel monkey. Several muscles such as the deltoid no longer function as joint stabilizers and allow the humerus to move beyond the scapular plane. These differences among species demonstrate the high plasticity of the internal muscle architecture and physiology which is suggested to be the underlying reason for different muscle activity patterns in homologous muscles

  11. Fiber architecture of canine abdominal muscles.

    Science.gov (United States)

    Boriek, Aladin M; Ortize, Jaime; Zhu, Deshen

    2002-02-01

    During respiration, abdominal muscles experience loads, not only in the muscle-fiber direction but also transverse to the fibers. We wondered whether the abdominal muscles exhibit a fiber architecture that is similar to the diaphragm muscle, and, therefore, we chose two adjacent muscles: the internal oblique (IO), with about the same muscle length as the diaphragm, and the transverse abdominis (TA), which is twice as long as the diaphragm. First, we used acetylcholinesterase staining to examine the distribution of neuromuscular junctions on both surfaces of the TA and IO muscles in six dogs. A maximum of four irregular bands of neuromuscular junctions crossed the IO, and as many as six bands crossed the TA, which is consistent with a discontinuous fiber architecture. In six additional dogs, we examined fiber architecture of these muscles by microdissecting 103 fascicles from the IO and 139 from the TA. Each fascicle contained between 20 and 30 muscle fibers. The mean length of nonspanning fibers (NSF) ranged from 2.8 +/- 0.3 cm in the IO to 4.3 +/- 0.5 cm in the TA, and the mean length of spanning fibers ranged from 4.3 +/- 0.5 cm in the IO to 7.6 +/- 1.4 cm in the TA. NSF accounted for 89.6 +/- 1.5% of all fibers dissected from the IO and 99.1 +/- 0.2% of all fibers dissected from the TA. The percentage of NSF with both ends tapered was 6.2 +/- 1.0 and 41.0 +/- 2.3% for IO and TA, respectively. These data show that fiber architecture in either IO or TA is discontinuous, with much more short-tapered fibers in the TA than in the IO. When abdominal muscles are submaximally activated, as during both normal expiration and maximal expiratory efforts, muscle force could be transmitted to the cell membrane and to the extracellular intramuscular connective tissue by shear linkage, presumably via structural transmembrane proteins.

  12. Accumulation of ceramide in slow-twitch muscle contributes to the development of insulin resistance in the obese JCR:LA-cp rat.

    Science.gov (United States)

    Fillmore, Natasha; Keung, Wendy; Kelly, Sandra E; Proctor, Spencer D; Lopaschuk, Gary D; Ussher, John R

    2015-06-01

    What is the central question of this study? The aim was to determine whether the accumulation of ceramide contributes to skeletal muscle insulin resistance in the JCR obese rat. What is the main finding and its importance? Our main new finding is that ceramides accumulate only in slow-twitch skeletal muscle in the JCR obese rat and that reducing ceramide content in this muscle type by inhibition of serine palmitoyl transferase-1 halts the progression of insulin resistance in this rat model predisposed to early development of type 2 diabetes. Our findings highlight the importance of assessing insulin signalling/sensitivity and lipid intermediate accumulation in different muscle fibre types. It has been postulated that insulin resistance results from the accumulation of cytosolic lipid metabolites (i.e. diacylglycerol/ceramide) that impede insulin signalling and impair glucose homeostasis. De novo ceramide synthesis is catalysed by serine palmitoyl transferase-1. Our aim was to determine whether de novo ceramide synthesis plays a role during development of insulin resistance in the JCR:LA-cp obese rat. Ten-week-old JCR:LA-cp obese rats were supplemented with either vehicle or the serine palmitoyl transferase-1 inhibitor l-cycloserine (360 mg l(-1) ) in their drinking water for a 2 week period, and glycaemia was assessed by meal tolerance testing. Treatment of JCR:LA-cp obese rats with l-cycloserine improved their plasma glucose and insulin levels during a meal tolerance test. Examination of muscle lipid metabolites and protein phosphorylation patterns revealed differential signatures in slow-twitch (soleus) versus fast-twitch muscle (gastrocnemius), in that ceramide levels were increased in soleus but not gastrocnemius muscles of JCR:LA-cp obese rats. Likewise, improved glycaemia in l-cycloserine-treated JCR:LA-cp obese rats was associated with enhanced Akt and pyruvate dehydrogenase signalling in soleus but not gastrocnemius muscles, probably as a result of l

  13. Alterations in intrinsic mitochondrial function with aging are fiber type-specific and do not explain differential atrophy between muscles.

    Science.gov (United States)

    Picard, Martin; Ritchie, Darmyn; Thomas, Melissa M; Wright, Kathryn J; Hepple, Russell T

    2011-12-01

    To determine whether mitochondrial dysfunction is causally related to muscle atrophy with aging, we examined respiratory capacity, H(2) O(2) emission, and function of the mitochondrial permeability transition pore (mPTP) in permeabilized myofibers prepared from four rat muscles that span a range of fiber type and degree of age-related atrophy. Muscle atrophy with aging was greatest in fast-twitch gastrocnemius (Gas) muscle (-38%), intermediate in both the fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (Sol) muscles (-21%), and non-existent in adductor longus (AL) muscle (+47%). In contrast, indices of mitochondrial dysfunction did not correspond to this differential degree of atrophy. Specifically, despite higher protein expression for oxidative phosphorylation (oxphos) system in fast Gas and EDL, state III respiratory capacity per myofiber wet weight was unchanged with aging, whereas the slow Sol showed proportional decreases in oxphos protein, citrate synthase activity, and state III respiration. Free radical leak (H(2) O(2) emission per O(2) flux) under state III respiration was higher with aging in the fast Gas, whereas state II free radical leak was higher in the slow AL. Only the fast muscles had impaired mPTP function with aging, with lower mitochondrial calcium retention capacity in EDL and shorter time to mPTP opening in Gas and EDL. Collectively, our results underscore that the age-related changes in muscle mitochondrial function depend largely upon fiber type and are unrelated to the severity of muscle atrophy, suggesting that intrinsic changes in mitochondrial function are unlikely to be causally involved in aging muscle atrophy. © 2011 The Authors. Aging Cell © 2011 Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland.

  14. FINE STRUCTURE OF RAT INTRAFUSAL MUSCLE FIBERS

    Science.gov (United States)

    Ovalle, William K.

    1972-01-01

    An ultrastructural study has been undertaken on the equatorial (sensory) region of the rat muscle spindle. Two kinds of intrafusal muscle fibers, a nuclear bag fiber and a nuclear chain fiber, have been identified in this region on the basis of fiber diameter, nuclear disposition, and M-band appearance. The large-diameter nuclear bag fiber contains an aggregation of tightly packed vesicular nuclei, while the small-diameter nuclear chain fiber contains a single row of elongated, well-separated nuclei. Both muscle fibers contain an attenuated peripheral cylinder of myofilaments surrounding a central core of sarcoplasm. Elements of the sarcotubular system, dilatations of the sarcoplasmic reticulum, and the presence of other sarcoplasmic organelles and inclusions are considerably more abundant in the nuclear chain fiber than in the nuclear bag fiber. Leptomeric organelles and membrane-bounded sarcoplasmic granules are present in both intrafusal fiber types and may be situated between the myofibrils or in intimate association with the sarcolemma. The functional significance of some of these structural findings is discussed. PMID:4257999

  15. Skeletal muscle fiber type composition and performance during repeated bouts of maximal, concentric contractions

    Science.gov (United States)

    Colliander, E. B.; Dudley, G. A.; Tesch, P. A.

    1988-01-01

    Force output and fatigue and recovery patterns were studied during intermittent short-term exercise. 27 men performed three bouts of 30 maximal unilateral knee extensions on 2 different occasions. Blood flow was maintained or occluded during recovery periods (60 s). Blood flow was restricted by inflating a pneumatic cuff placed around the proximal thigh. Muscle biopsies from vastus lateralis were analyzed for identification of fast twitch (FT) and slow twitch (ST) fibers and relative FT area. Peak torque decreased during each bout of exercise and more when blood flow was restricted during recovery. Initial peak torque (IPT) and average peak torque (APT) decreased over the three exercise bouts. This response was 3 fold greater without than with blood flow during recovery. IPT and APT decreased more in individuals with mainly FT fibers than in those with mainly ST fibers. It is suggested that performance during repeated bouts of maximal concentric contractions differs between individuals with different fiber type composition. Specifically, in high intensity, intermittent exercise with emphasis on anaerobic energy release a high FT composition may not necessarily be advantageous for performance.

  16. Effect of spaceflight on the isotonic contractile properties of single skeletal muscle fibers in the rhesus monkey

    Science.gov (United States)

    Fitts, R. H.; Romatowski, J. G.; Blaser, C.; De La Cruz, L.; Gettelman, G. J.; Widrick, J. J.

    2000-01-01

    Experiments from both Cosmos and Space Shuttle missions have shown weightlessness to result in a rapid decline in the mass and force of rat hindlimb extensor muscles. Additionally, despite an increased maximal shortening velocity, peak power was reduced in rat soleus muscle post-flight. In humans, declines in voluntary peak isometric ankle extensor torque ranging from 15-40% have been reported following long- and short-term spaceflight and prolonged bed rest. Complete understanding of the cellular events responsible for the fiber atrophy and the decline in force, as well as the development of effective countermeasures, will require detailed knowledge of how the physiological and biochemical processes of muscle function are altered by spaceflight. The specific purpose of this investigation was to determine the extent to which the isotonic contractile properties of the slow- and fast-twitch fiber types of the soleus and gastrocnemius muscles of rhesus monkeys (Macaca mulatta) were altered by a 14-day spaceflight.

  17. Effect of number of stimuli and timing of twitch application on variability in interpolated twitch torque.

    Science.gov (United States)

    Suter, E; Herzog, W

    2001-03-01

    Application of a supramaximal electrical twitch to the voluntarily contracted muscle is used to assess the level of muscle activation. Large variability in the interpolated twitch torque (ITT) has been observed when repeated stimulations are performed. It is hypothesized that this variability in ITT is caused by the stochastic nature of the timing of twitch application relative to pulses of voluntary excitation trains. Two experiments were performed on 12 subjects each to test this hypothesis. For the first experiment, a single twitch was superimposed on a train stimulation at different time intervals relative to the train pulses. For the second experiment, single, double, triple, or quadruple twitches were applied on a voluntarily contracted muscle. The ITT critically depended on the time point of twitch application: a single pulse applied 5 ms before a train pulse consistently evoked higher ITTs than all other stimulation conditions. Furthermore, variability of the ITT decreased as the number of applied twitches increased. The results support the hypothesis that a large part of the variability in the ITT may be caused by the timing of the superimposed twitch relative to the motor unit trains. The variability may be reduced by increasing the number of superimposed twitches.

  18. Optimal inter-stimulus interval for interpolated twitch technique when using double pulse stimulation

    OpenAIRE

    Karimpour, Rana

    2013-01-01

    Interpolated twitch technique is a method frequently used to assess voluntary activa- tion. This method uses electrically evoked twitch superimposed on the voluntary activi- ty and its comparison with the twitch in rested muscle i.e. control twitch, to evaluate completeness of muscle activation. The purpose of this study was to investigate the ef- fect of interval in paired stimulation on control twitch in young and elderly individuals with bent and flexed knee positions. Supramaximal electri...

  19. Expression of a dominant negative CELF protein in vivo leads to altered muscle organization, fiber size, and subtype.

    Directory of Open Access Journals (Sweden)

    Dara S Berger

    Full Text Available BACKGROUND: CUG-BP and ETR-3-like factor (CELF proteins regulate tissue- and developmental stage-specific alternative splicing in striated muscle. We previously demonstrated that heart muscle-specific expression of a nuclear dominant negative CELF protein in transgenic mice (MHC-CELFΔ effectively disrupts endogenous CELF activity in the heart in vivo, resulting in impaired cardiac function. In this study, transgenic mice that express the dominant negative protein under a skeletal muscle-specific promoter (Myo-CELFΔ were generated to investigate the role of CELF-mediated alternative splicing programs in normal skeletal muscle. METHODOLOGY/PRINCIPAL FINDINGS: Myo-CELFΔ mice exhibit modest changes in CELF-mediated alternative splicing in skeletal muscle, accompanied by a reduction of endomysial and perimysial spaces, an increase in fiber size variability, and an increase in slow twitch muscle fibers. Weight gain and mean body weight, total number of muscle fibers, and overall muscle strength were not affected. CONCLUSIONS/SIGNIFICANCE: Although these findings demonstrate that CELF activity contributes to the normal alternative splicing of a subset of muscle transcripts in vivo, the mildness of the effects in Myo-CELFΔ muscles compared to those in MHC-CELFΔ hearts suggests CELF activity may be less determinative for alternative splicing in skeletal muscle than in heart muscle. Nonetheless, even these small changes in CELF-mediated splicing regulation were sufficient to alter muscle organization and muscle fiber properties affected in myotonic dystrophy. This lends further evidence to the hypothesis that dysregulation of CELF-mediated alternative splicing programs may be responsible for the disruption of these properties during muscle pathogenesis.

  20. RNA sequencing reveals a slow to fast muscle fiber type transition after olanzapine infusion in rats.

    Directory of Open Access Journals (Sweden)

    Christopher J Lynch

    Full Text Available Second generation antipsychotics (SGAs, like olanzapine, exhibit acute metabolic side effects leading to metabolic inflexibility, hyperglycemia, adiposity and diabetes. Understanding how SGAs affect the skeletal muscle transcriptome could elucidate approaches for mitigating these side effects. Male Sprague-Dawley rats were infused intravenously with vehicle or olanzapine for 24h using a dose leading to a mild hyperglycemia. RNA-Seq was performed on gastrocnemius muscle, followed by alignment of the data with the Rat Genome Assembly 5.0. Olanzapine altered expression of 1347 out of 26407 genes. Genes encoding skeletal muscle fiber-type specific sarcomeric, ion channel, glycolytic, O2- and Ca2+-handling, TCA cycle, vascularization and lipid oxidation proteins and pathways, along with NADH shuttles and LDH isoforms were affected. Bioinformatics analyses indicate that olanzapine decreased the expression of slower and more oxidative fiber type genes (e.g., type 1, while up regulating those for the most glycolytic and least metabolically flexible, fast twitch fiber type, IIb. Protein turnover genes, necessary to bring about transition, were also up regulated. Potential upstream regulators were also identified. Olanzapine appears to be rapidly affecting the muscle transcriptome to bring about a change to a fast-glycolytic fiber type. Such fiber types are more susceptible than slow muscle to atrophy, and such transitions are observed in chronic metabolic diseases. Thus these effects could contribute to the altered body composition and metabolic disease olanzapine causes. A potential interventional strategy is implicated because aerobic exercise, in contrast to resistance exercise, can oppose such slow to fast fiber transitions.

  1. The effect of fiber-type heterogeneity on optimized work and power output of hindlimb muscles of the salamander Ambystoma tigrinum.

    Science.gov (United States)

    Ashley-Ross, M A; Barker, J U

    2002-09-01

    Most vertebrate muscles are composed of a mixture of fiber types. However, studies of muscle mechanics have concentrated on homogeneous bundles of fibers. Hindlimb muscles of the tiger salamander, Ambystoma tigrinum, present an excellent system to explore the consequences of fiber heterogeneity. Isometric twitches and work loops were obtained in vitro from two muscles, the m. iliotibialis pars posterior (heterogeneous, containing types I, IIa and IIb fibers) and the m. iliofibularis (nearly homogeneous for type IIa fibers). Maximal isometric twitch and tetanic stresses in m. iliotibialis posterior were significantly greater than in iliofibularis. Work loops were obtained over a range of frequencies (0.5-3.0 Hz) and strains (2-6% muscle length) that encompassed the observed ranges in vivo. Work per cycle from the homogeneous iliofibularis declined from 1.5-3.0 Hz, while that from the heterogeneous m. iliotibialis posterior increased from 0.5 Hz to 2.5 Hz and declined at 3.0 Hz. Power output from the iliofibularis rose with frequency to at least 3 Hz; power from the iliotibialis posterior rose with frequency to 2.5 Hz and declined thereafter. Mass-specific work per cycle and power output were higher in iliofibularis than iliotibialis posterior over most frequencies and strains tested.

  2. Muscle fiber-type variation in lizards (Squamata) and phylogenetic reconstruction of hypothesized ancestral states.

    Science.gov (United States)

    Bonine, Kevin E; Gleeson, Todd T; Garland, Theodore

    2005-12-01

    Previously, we found that phrynosomatid lizards, a diverse group common in the southwestern USA, vary markedly in fiber-type composition of the iliofibularis (a hindlimb muscle important in locomotion). Phrynosomatidae comprises three subclades: the closely related sand and horned lizards, and their relatives the Sceloporus group. The variation in muscle fiber-type composition for 11 phrynosomatid species is attributable mainly to differences between the sand- and horned-lizard subclades. Here, we expand the phrynosomatid database with three additional species and compare these results with data collected for 10 outgroup (distantly related) species. Our goal was to determine if the patterns found in Phrynosomatidae hold across a broader phylogenetic range of the extant lizards and to elucidate the evolution of muscle fiber-type composition and related traits. To allow for meaningful comparisons, data were collected from species that are primarily terrestrial and relatively small in size (3.5-65 g body mass). Results indicate that the fiber-type variation observed within the Phrynosomatidae almost spans the range of variation observed in our sample of 24 species from eight families. However, one species of Acanthodactylus (Lacertidae) had a consistent region of large tonic fibers (that did not stain darkly for either succinic dehydrogenase or myosin ATPase activity), a fiber-type only occasionally seen in the other 23 species examined. Many species have a large proportion of either fast-twitch glycolytic (FG; e.g. sand lizards and Aspidoscelis) or fast-twitch oxidative-glycolytic (FOG) fibers (e.g. horned lizards), with the slow-oxidative proportion occupying only 1-17% of the iliofibularis. Importantly, the negative relationship between FG and FOG composition observed in Phrynosomatidae appears to be a characteristic of lizards in general, and could lead to functional trade-offs in aspects of locomotor performance, as has previously been reported for Lacertidae

  3. Creatine loading elevates the intracellular phosphorylation potential and alters adaptive responses of rat fast-twitch muscle to chronic low-frequency stimulation.

    Science.gov (United States)

    Putman, Charles T; Gallo, Maria; Martins, Karen J B; MacLean, Ian M; Jendral, Michelle J; Gordon, Tessa; Syrotuik, Daniel G; Dixon, Walter T

    2015-07-01

    This study tested the hypothesis that elevating the intracellular phosphorylation potential (IPP = [ATP]/[ADP]free) within rat fast-twitch tibialis anterior muscles by creatine (Cr) loading would prevent fast-to-slow fibre transitions induced by chronic low-frequency electrical stimulation (CLFS, 10 Hz, 12 h/day). Creatine-control and creatine-CLFS groups drank a solution of 1% Cr + 5% dextrose, ad libitum, for 10 days before and during 10 days of CLFS; dextrose-control and dextrose-CLFS groups drank 5% dextrose. Cr loading increased total Cr (P creatine-CLFS than in dextrose-CLFS. Higher IPP was confirmed by a 58% reduction in phospho-AMP-activated protein kinase α (Thr172) (P creatine-CLFS, MyHC-I and MyHC-IIa mRNA were unchanged and MyHC-IIb mRNA decreased by 75% (P creatine-CLFS, but reciprocal reductions in glycolytic reference enzymes occurred only in dextrose-CLFS (P creatine-CLFS coincided with prolonged time to peak tension and half-rise time (P < 0.01). These results highlight the IPP as an important physiological regulator of muscle fibre plasticity and demonstrate that training-induced changes typically associated with improvements in muscular endurance or increased power output are not mutually exclusive in Cr-loaded muscles.

  4. Phenol increases intracellular [Ca2+] during twitch contractions in intact Xenopus skeletal myofibers.

    Science.gov (United States)

    Nogueira, Leonardo; Hogan, Michael C

    2010-11-01

    Phenol is a neurolytic agent used for management of spasticity in patients with either motoneuron lesions or stroke. In addition, compounds that enhance muscle contractility (i.e., polyphenols, etc.) may affect muscle function through the phenol group. However, the effects of phenol on muscle function are unknown, and it was, therefore, the purpose of the present investigation to examine the effects of phenol on tension development and Ca(2+) release in intact skeletal muscle fibers. Dissected intact muscle fibers from Xenopus laevis were electrically stimulated, and cytosolic Ca(2+) concentration ([Ca(2+)](c)) and tension development were recorded. During single twitches and unfused tetani, phenol significantly increased [Ca(2+)](c) and tension without affecting myofilament Ca(2+) sensitivity. To investigate the phenol effects on Ca(2+) channel/ryanodine receptors, single fibers were treated with different concentrations of caffeine in the presence and absence of phenol. Low concentrations of phenol significantly increased the caffeine sensitivity (P twitch contractions in muscle fibers without altering myofilament Ca(2+) sensitivity and may be used as a new agent to study skeletal muscle Ca(2+) handling.

  5. Adherent primary cultures of mouse intercostal muscle fibers for isolated fiber studies.

    Science.gov (United States)

    Robison, Patrick; Hernández-Ochoa, Erick O; Schneider, Martin F

    2011-01-01

    Primary culture models of single adult skeletal muscle fibers dissociated from locomotor muscles adhered to glass coverslips are routine and allow monitoring of functional processes in living cultured fibers. To date, such isolated fiber cultures have not been established for respiratory muscles, despite the fact that dysfunction of core respiratory muscles leading to respiratory arrest is the most common cause of death in many muscular diseases. Here we present the first description of an adherent culture system for single adult intercostal muscle fibers from the adult mouse. This system allows for monitoring functional properties of these living muscle fibers in culture with or without electrical field stimulation to drive muscle fiber contraction at physiological or pathological respiratory firing patterns. We also provide initial characterization of these fibers, demonstrating several common techniques in this new model system in the context of the established Flexor Digitorum Brevis muscle primary culture model.

  6. Adherent Primary Cultures of Mouse Intercostal Muscle Fibers for Isolated Fiber Studies

    Directory of Open Access Journals (Sweden)

    Patrick Robison

    2011-01-01

    Full Text Available Primary culture models of single adult skeletal muscle fibers dissociated from locomotor muscles adhered to glass coverslips are routine and allow monitoring of functional processes in living cultured fibers. To date, such isolated fiber cultures have not been established for respiratory muscles, despite the fact that dysfunction of core respiratory muscles leading to respiratory arrest is the most common cause of death in many muscular diseases. Here we present the first description of an adherent culture system for single adult intercostal muscle fibers from the adult mouse. This system allows for monitoring functional properties of these living muscle fibers in culture with or without electrical field stimulation to drive muscle fiber contraction at physiological or pathological respiratory firing patterns. We also provide initial characterization of these fibers, demonstrating several common techniques in this new model system in the context of the established Flexor Digitorum Brevis muscle primary culture model.

  7. Adherent Primary Cultures of Mouse Intercostal Muscle Fibers for Isolated Fiber Studies

    Science.gov (United States)

    Robison, Patrick; Hernández-Ochoa, Erick O.; Schneider, Martin F.

    2011-01-01

    Primary culture models of single adult skeletal muscle fibers dissociated from locomotor muscles adhered to glass coverslips are routine and allow monitoring of functional processes in living cultured fibers. To date, such isolated fiber cultures have not been established for respiratory muscles, despite the fact that dysfunction of core respiratory muscles leading to respiratory arrest is the most common cause of death in many muscular diseases. Here we present the first description of an adherent culture system for single adult intercostal muscle fibers from the adult mouse. This system allows for monitoring functional properties of these living muscle fibers in culture with or without electrical field stimulation to drive muscle fiber contraction at physiological or pathological respiratory firing patterns. We also provide initial characterization of these fibers, demonstrating several common techniques in this new model system in the context of the established Flexor Digitorum Brevis muscle primary culture model. PMID:21869860

  8. Regional heterogeneity in muscle fiber strain: The role of fiber architecture

    Directory of Open Access Journals (Sweden)

    E. eAzizi

    2014-08-01

    Full Text Available The force, mechanical work and power produced by muscle fibers are profoundly affected by the length changes they undergo during a contraction. These length changes are in turn affected by the spatial orientation of muscle fibers within a muscle (fiber architecture. Therefore any heterogeneity in fiber architecture within a single muscle has the potential to cause spatial variation in fiber strain. Here we examine how the architectural variation within a pennate muscle and within a fusiform muscle can result in regional fiber strain heterogeneity. We combine simple geometric models with empirical measures of fiber strain to better understand the effect of architecture on fiber strain heterogeneity. We show that variation in pennation angle throughout a muscle can result in differences in fiber strain with higher strains being observed at lower angles of pennation. We also show that in fusiform muscles, the outer/superficial fibers of the muscle experience lower strains than central fibers. These results show that regional variation in mechanical output of muscle fibers can arise solely from architectural features of the muscle without the presence of any spatial variation in motor recruitment.

  9. Myomaker is required for the fusion of fast-twitch myocytes in the zebrafish embryo.

    Science.gov (United States)

    Zhang, Weibin; Roy, Sudipto

    2017-03-01

    During skeletal muscle development, myocytes aggregate and fuse to form multinucleated muscle fibers. Inhibition of myocyte fusion is thought to significantly derail the differentiation of functional muscle fibers. Despite the purported importance of fusion in myogenesis, in vivo studies of this process in vertebrates are rather limited. Myomaker, a multipass transmembrane protein, has been shown to be the first muscle-specific fusion protein essential for myocyte fusion in the mouse. We have generated loss-of-function alleles in zebrafish myomaker, and found that fusion of myocytes into syncytial fast-twitch muscles was significantly compromised. However, mutant myocytes could be recruited to fuse with wild-type myocytes in chimeric embryos, albeit rather inefficiently. Conversely, overexpression of Myomaker was sufficient to induce hyperfusion among fast-twitch myocytes, and it also induced fusion among slow-twitch myocytes that are normally fusion-incompetent. In line with this, Myomaker overexpression also triggered fusion in another myocyte fusion mutant compromised in the function of the junctional cell adhesion molecule, Jam2a. We also provide evidence that Rac, a regulator of actin cytoskeleton, requires Myomaker activity to induce fusion, and that an approximately 3kb of myomaker promoter sequence, with multiple E-box motifs, is sufficient to direct expression within the fast-twitch muscle lineage. Taken together, our findings underscore a conserved role for Myomaker in vertebrate myocyte fusion. Strikingly, and in contrast to the mouse, homozygous myomaker mutants are viable and do not exhibit discernible locomotory defects. Thus, in the zebrafish, myocyte fusion is not an absolute requirement for skeletal muscle morphogenesis and function.

  10. Disodium cromoglycate protects dystrophin-deficient muscle fibers from leakiness.

    Science.gov (United States)

    Marques, Maria Julia; Ventura Machado, Rafael; Minatel, Elaine; Santo Neto, Humberto

    2008-01-01

    In dystrophin-deficient fibers of mdx mice and in Duchenne dystrophy, the lack of dystrophin leads to sarcolemma breakdown and muscle degeneration. We verified that cromolyn, a mast-cell stabilizer agent, stabilized dystrophic muscle fibers using Evans blue dye as a marker of sarcolemma leakiness. Mdx mice (n=8; 14 days of age) received daily intraperitoneal injections of cromolyn (50 mg/kg body weight) for 15 days. Untreated mdx mice (n=8) were injected with saline. Cryostat cross-sections of the sternomastoid, tibialis anterior, and diaphragm muscles were stained with hematoxylin and eosin. Cromolyn dramatically reduced Evans blue dye-positive fibers in all muscles (P<0.05; Student's t-test) and led to a significant increase in the percentage of fibers with peripheral nuclei. This study supports the protective effects of cromolyn in dystrophic muscles and further indicates its action against muscle fiber leakiness in muscles that are differently affected by the lack of dystrophin.

  11. Disturbances of the sarcoplasmic reticulum and transverse tubular system in 24-h electrostimulated fast-twitch skeletal muscle

    DEFF Research Database (Denmark)

    Frías, J A; Cadefau, J A; Prats, C;

    2005-01-01

    -migration of terminal cisternae and t-tubules from R3 to R4, indicating the presence of triads. This density change may be associated with calcium overload of the sarcoplasmic reticulum, since total calcium rose three- to fourfold in stimulated muscle homogenates. These changes correlate well with ultrastructural...... damage to longitudinal sarcoplasmic reticulum and swelling of t-tubules revealed by electron microscopy. The ultrastructural changes observed here reflect exercise-induced damage of membrane systems that might severely compromise muscle function. Since this process is reversible, we suggest that it may......Chronic low-frequency stimulation of rabbit tibialis anterior muscle over a 24-h period induces a conspicuous loss of isometric tension that is unrelated to muscle energy metabolism (J.A. Cadefau, J. Parra, R. Cusso, G. Heine, D. Pette, Responses of fatigable and fatigue-resistant fibres of rabbit...

  12. MUSCLE FIBER SPECIFIC ANTIOXIDATIVE SYSTEM ADAPTATION TO SWIM TRAINING IN RATS: INFLUENCE OF INTERMITTENT HYPOXIA

    Directory of Open Access Journals (Sweden)

    Olga Gonchar

    2005-06-01

    Full Text Available The aim of the present study was to examine the influence of intermittent hypoxia at rest and in combination with long-term high-intensity swimming exercise on lipid peroxidation and antioxidant defense system adaptation in skeletal muscles differing in fiber type composition. High-intensity chronic exercise was performed as swimming training with load that corresponded to ~ 75 % VO2max (30 min·day-1, 5 days·wk-1, for 4 wk. Intermittent hypoxic training (IHT consisted of repeated episodes of hypoxia (12%O2, 15 min, interrupted by equal periods of recovery (5 sessions/day, for 2 wk. Sessions of IHT were used during the first two weeks and during the last two weeks of chronic exercise. Oxidative (red gastrocnemius and soleus, mix and glycolytic (white gastrocnemius muscles were sampled. Our results indicated that high-intensity swim training in combination with sessions of IHT induced more profound antioxidative adaptations in skeletal muscles than the exercise training only. This adaptation has muscle fiber type specificity and is reflected in significantly elevated superoxide dismutase and catalase activities in highly oxidative muscle only. Training adaptation of GSH system (reduced glutathione content, activities of glutathione reductase, glutathione peroxidase, NADPH-supplying enzyme glucose-6-phosphate dehydrogenase occurred both in slow- and fast-twitch muscles. However, this process was more effective in oxidative muscles. IHT attenuated the increase in TBARS content induced by high-intensity swimming training. The test on exercise tolerance demonstrated a significant elevation of the swimming time to exhaustion after IHT at rest and after IHT in conjunction with high-intensity exercise in comparison with untrained and chronically exercised rats. These results confirmed that sessions of IHT might improve exercise tolerance and increase maximal work capacity

  13. Adherent Primary Cultures of Mouse Intercostal Muscle Fibers for Isolated Fiber Studies

    OpenAIRE

    2011-01-01

    Primary culture models of single adult skeletal muscle fibers dissociated from locomotor muscles adhered to glass coverslips are routine and allow monitoring of functional processes in living cultured fibers. To date, such isolated fiber cultures have not been established for respiratory muscles, despite the fact that dysfunction of core respiratory muscles leading to respiratory arrest is the most common cause of death in many muscular diseases. Here we present the first description of an ad...

  14. Properties of motor units of the frog iliofibularis muscle.

    Science.gov (United States)

    Luff, A R; Proske, U

    1979-01-01

    The tension developed by single motor units of the iliofibularis muscle of the frog Litoria aurea was recorded in response to single-shock and repetitive stimulation of motor axons. The majority of units in each muscle, 13 on the average, were of the twitch type; an additional 4 units were slow or tonic. It appeared that slow units comprised a single homogeneous population, but two types of twitch units could be recognized: small fatigue-resistant units with long twitch times to peak (20--40 ms) and larger, fatigable units with briefer times to peak (16--27 ms). Evidence from a comparison of unit tetanic tensions indicated the presence of polyneuronal innervation of both slow and twitch muscle fibers. The relatively low incidence of polyneuronal innervation of twitch fibers in iliofibularis, when compared with a muscle like sartorius (9), was attributed to the difference in lengths of muscle fibers in the two muscles. It was argued that slow muscle fibers probably receive a multiterminal as well as polyneuronal innervation, with the terminals of any one axon lying widely spaced along the muscle fiber.

  15. Glucose transporter expression in human skeletal muscle fibers

    DEFF Research Database (Denmark)

    Gaster, M; Handberg, A; Beck-Nielsen, H

    2000-01-01

    amplification (TSA) technique to detect the localization of glucose transporter expression in human skeletal muscle. We found expression of GLUT-1, GLUT-3, and GLUT-4 in developing human muscle fibers showing a distinct expression pattern. 1) GLUT-1 is expressed in human skeletal muscle cells during gestation......, but its expression is markedly reduced around birth and is further reduced to undetectable levels within the first year of life; 2) GLUT-3 protein expression appears at 18 wk of gestation and disappears after birth; and 3) GLUT-4 protein is diffusely expressed in muscle cells throughout gestation, whereas...... after birth, the characteristic subcellular localization is as seen in adult muscle fibers. Our results show that GLUT-1, GLUT-3, and GLUT-4 seem to be of importance during muscle fiber growth and development. GLUT-5 protein was undetectable in fetal and adult skeletal muscle fibers. In adult muscle...

  16. Ultrastructural organization of muscle fiber types and their distribution in the rat superior rectus extraocular muscle.

    Science.gov (United States)

    Rashed, Rashed M; El-Alfy, Sherif H

    2012-05-01

    Extraocular muscles (EOMs) are unique as they show greater variation in anatomical and physiological properties than any other skeletal muscles. To investigate the muscle fiber types and to understand better the structure-function correlation of the extraocular muscles, the present study examined the ultrastructural characteristics of the superior rectus muscle of rat. The superior rectus muscle is organized into two layers: a central global layer of mainly large-diameter fibers and an outer C-shaped orbital layer of principally small-diameter fibers. Six morphologically distinct fiber types were identified within the superior rectus muscle. Four muscle fiber types, three single innervated fibers (SIFs) and one multiple innervated fiber (MIF), were recognized in the global layer. The single innervated fibers included red, white and intermediate fibers. They differed from one another with respect to diameter, mitochondrial size and distribution, sarcoplasmic reticulum and myofibrillar size. The orbital layer contained two distinct MIFs in addition to the red and intermediate SIFs. The orbital MIFs were categorized into low oxidative and high oxidative types according to their mitochondrial content and distribution. The highly specialized function of the superior rectus extraocular muscle is reflected in the multiplicity of its fiber types, which exhibit unique structural features. The unique ultrastructural features of the extraocular muscles and their possible relation to muscle function are discussed. Copyright © 2011 Elsevier GmbH. All rights reserved.

  17. A temporary decrease in twitch response during reversal of rocuronium-induced muscle relaxation with a small dose of sugammadex

    NARCIS (Netherlands)

    Eleveld, Douglas J.; Kuizenga, Karel; Proost, Johannes H.; Wierda, J. Mark K. H.

    BACKGROUND: We present a case in which a temporary decrease in train-of-four (TOF) response was observed after reversal of muscle relaxation with a small dose (0.5 mg/kg) of sugammadex administered 42 min after 0.9 mg/kg of rocuronium. At the end of the operation, the TOF ratio was > 0.9, and the

  18. Force-dependent and force-independent heat production in single slow- and fast-twitch muscle fibres from Xenopus laevis.

    Science.gov (United States)

    Buschman, H P; van der Laarse, W J; Stienen, G J; Elzinga, G

    1996-10-15

    1. The origin of labile heat production, i.e. a heat component which rapidly decays after the onset of stimulation, and of stable (maintenance) heat production was investigated in intact single fast-twitch (type 1) and slow-twitch (type 3) iliofibularis muscle fibres from Xenopus laevis, at 20 degrees C, by varying stimulation frequency and by varying sarcomere length and the concentration of 2,3-butanedione 2-monoxime (BDM) added. 2. The labile heat produced consisted of a force-independent and a force-dependent part. The average parvalbumin (PA) content found in type 1 fibre bundles (0.84 +/- 0.08 mM; mean +/- S.E.M.; n = 5) and in type 3 fibre bundles (0.12 +/- 0.02 mM; n = 5) indicates that the force-independent labile heat is explained by Ca(2+)-Mg2+ exchange on PA, and amounts to a molar enthalpy change of -78 kJ (molPA)-1. 3. Force-dependent labile heat during fused contractions was similar to the calculated heat production resulting from the formation of force-generating cross-bridges, assuming an enthalpy change associated with cross-bridge formation of -30 kJ mol-1. 4. Activation heat, i.e. the part of the total stable heat that is not related to the contractile apparatus, and of which the calcium sequestration by the sarcoplasmic reticulum is the most important contributor, determined by varying sarcomere length or BDM concentration, was identical. For fused contractions the fraction activation heat of the stable maintenance rate of heat production was 34 +/- 4% (mean +/- S.E.M.; n = 13) in type 1 fibres, and 52 +/- 4% (n = 15) in type 3 fibres. In unfused contractions this was 48 +/- 5% (n = 13) in type 1 fibres, and 35 +/- 2% (n = 11) in type 3 fibres. 5. From the force-dependent stable rate of heat production the economy of cross-bridge cycling, expressed as the force-time integral for a single myosin head per ATP molecule hydrolysed, was calculated. It followed that cross-bridge interaction in type 3 fibres is more economical than in type 1 fibres

  19. Use and disuse and the control of acetylcholinesterase activity in fast and slow twitch muscle of rat

    Science.gov (United States)

    Dettbarn, W. D.; Groswald, D.; Gupta, R. C.; Misulis, K. E.

    1985-01-01

    The role of acetylcholinesterase (AChE) in neuromuscular transmission is relatively well established, little is known, however, of the mechanisms that regulate its synthesis and control its specific distribution in fast and slow muscle. Innervation plays an important role in the regulation of AChE and elimination of the influence of the nerve by surgical denervation results in a loss of AChE. The influences of the nerve and how they are mediated was investigated. It is suggested that muscle usage and other factors such as materials carried by axonal transport may participate in the regulation of this enzyme. The mechanisms that regulate AChE and its molecular forms in two functionally different forms are studied.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

  2. Thixotropy and rheopexy of muscle fibers probed using sinusoidal oscillations.

    Directory of Open Access Journals (Sweden)

    David Altman

    Full Text Available Length changes of muscle fibers have previously been shown to result in a temporary reduction in fiber stiffness that is referred to as thixotropy. Understanding the mechanism of this thixotropy is important to our understanding of muscle function since there are many instances in which muscle is subjected to repeated patterns of lengthening and shortening. By applying sinusoidal length changes to one end of single permeabilized muscle fibers and measuring the force response at the opposite end, we studied the history-dependent stiffness of both relaxed and activated muscle fibers. For length change oscillations greater than 1 Hz, we observed thixotropic behavior of activated fibers. Treatment of these fibers with EDTA and blebbistatin, which inhibits myosin-actin interactions, quashed this effect, suggesting that the mechanism of muscle fiber thixotropy is cross-bridge dependent. We modeled a half-sarcomere experiencing sinusoidal length changes, and our simulations suggest that thixotropy could arise from force-dependent cross-bridge kinetics. Surprisingly, we also observed that, for length change oscillations less than 1 Hz, the muscle fiber exhibited rheopexy. In other words, the stiffness of the fiber increased in response to the length changes. Blebbistatin and EDTA did not disrupt the rheopectic behavior, suggesting that a non-cross-bridge mechanism contributes to this phenomenon.

  3. MOTOR UNIT TERRITORIES AND FIBER TYPES IN RABBIT MASSETER MUSCLE

    NARCIS (Netherlands)

    WEIJS, WA; JUCH, PJW; KWA, SHS; KORFAGE, JAM

    1993-01-01

    The myosin heavy chain (MHC) content and spatial distribution of the fibers of 11 motor units (MUs) of the rabbit masseter muscle were determined. The fibers of single MUs were visualized in whole-muscle serial sections by a negative periodic acid/Schiff reaction for glycogen after they had been dep

  4. Mitochondrial specialization revealed by single muscle fiber proteomics

    DEFF Research Database (Denmark)

    Schiaffino, S; Reggiani, C; Kostrominova, T Y

    2015-01-01

    We have developed a highly sensitive mass spectrometry-based proteomic workflow to examine the proteome of single muscle fibers. This study revealed significant differences in the mitochondrial proteome of the four major fiber types present in mouse skeletal muscle. Here, we focus on Krebs cycle ...... scavenging capacity to cope with the higher levels of reactive oxygen species production....

  5. Impact of diaphragm muscle fiber atrophy on neuromotor control.

    Science.gov (United States)

    Mantilla, Carlos B; Sieck, Gary C

    2013-11-01

    In skeletal muscles, motor units comprise a motoneuron and the group of muscle fibers innervated by it, which are usually classified based on myosin heavy chain isoform expression. Motor units displaying diverse contractile and fatigue properties are important in determining the range of motor behaviors that can be accomplished by a muscle. Muscle fiber atrophy and weakness may disproportionately affect specific fiber types across a variety of diseases or clinical conditions, thus impacting neuromotor control. In this regard, fiber atrophy that affects a specific fiber type will alter the relative contribution of different motor units to overall muscle structure and function. For example, in various diseases there is fairly selective atrophy of type IIx and/or IIb fibers comprising the strongest yet most fatigable motor units. As a result, there is muscle weakness (i.e., reductions in force per cross-sectional area) associated with an apparent improvement in resistance to fatiguing contractions. This review will examine neuromotor control of respiratory muscles such as the diaphragm muscle and the impact of muscle fiber atrophy on motor performance. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Anisotropic Smoothing Improves DT-MRI-Based Muscle Fiber Tractography.

    Directory of Open Access Journals (Sweden)

    Amanda K W Buck

    Full Text Available To assess the effect of anisotropic smoothing on fiber tracking measures, including pennation angle, fiber tract length, and fiber tract number in the medial gastrocnemius (MG muscle in healthy subjects using diffusion-weighted magnetic resonance imaging (DW-MRI.3T DW-MRI data were used for muscle fiber tractography in the MG of healthy subjects. Anisotropic smoothing was applied at three levels (5%, 10%, 15%, and pennation angle, tract length, fiber tract number, fractional anisotropy, and principal eigenvector orientation were quantified for each smoothing level.Fiber tract length increased with pre-fiber tracking smoothing, and local heterogeneities in fiber direction were reduced. However, pennation angle was not affected by smoothing.Modest anisotropic smoothing (10% improved fiber-tracking results, while preserving structural features.

  7. Muscle organizers in Drosophila: the role of persistent larval fibers in adult flight muscle development

    Science.gov (United States)

    Farrell, E. R.; Fernandes, J.; Keshishian, H.

    1996-01-01

    In many organisms muscle formation depends on specialized cells that prefigure the pattern of the musculature and serve as templates for myoblast organization and fusion. These include muscle pioneers in insects and muscle organizing cells in leech. In Drosophila, muscle founder cells have been proposed to play a similar role in organizing larval muscle development during embryogenesis. During metamorphosis in Drosophila, following histolysis of most of the larval musculature, there is a second round of myogenesis that gives rise to the adult muscles. It is not known whether muscle founder cells organize the development of these muscles. However, in the thorax specific larval muscle fibers do not histolyze at the onset of metamorphosis, but instead serve as templates for the formation of a subset of adult muscles, the dorsal longitudinal flight muscles (DLMs). Because these persistent larval muscle fibers appear to be functioning in many respects like muscle founder cells, we investigated whether they were necessary for DLM development by using a microbeam laser to ablate them singly and in combination. We found that, in the absence of the larval muscle fibers, DLMs nonetheless develop. Our results show that the persistent larval muscle fibers are not required to initiate myoblast fusion, to determine DLM identity, to locate the DLMs in the thorax, or to specify the total DLM fiber volume. However, they are required to regulate the number of DLM fibers generated. Thus, while the persistent larval muscle fibers are not obligatory for DLM fiber formation and differentiation, they are necessary to ensure the development of the correct number of fibers.

  8. Nitric oxide synthase inhibition delays low-frequency stimulation-induced satellite cell activation in rat fast-twitch muscle.

    Science.gov (United States)

    Martins, Karen J B; MacLean, Ian; Murdoch, Gordon K; Dixon, Walter T; Putman, Charles T

    2011-12-01

    This study examined the effect of nitric oxide synthase (NOS) inhibition via N(ω)-nitro-l-arginine methyl ester (l-NAME) administration on low-frequency stimulation-induced satellite cell (SC) activation in rat skeletal muscle. l-NAME only delayed stimulation-induced increases in SC activity. Also, stimulation-induced increases in hepatocyte growth factor (HGF) mRNA and protein expression were only abrogated at the mRNA level in l-NAME-treated animals. Therefore, early stimulation-induced SC activation appears to be NOS-dependent, while continued activation may involve NOS-independent HGF translational control mechanisms.

  9. Voluntary activation of trapezius measured with twitch interpolation

    DEFF Research Database (Denmark)

    Taylor, Janet L; Olsen, Henrik Baare; Sjøgaard, Gisela

    2009-01-01

    This study investigated the feasibility of measuring voluntary activation of the trapezius muscle with twitch interpolation. Subjects (n=8) lifted the right shoulder or both shoulders against fixed force transducers. Stimulation of the accessory nerve in the neck was used to evoke maximal twitche...

  10. Acyl-CoA binding protein expression is fiber type- specific and elevated in muscles from the obese insulin-resistant Zucker rat.

    Science.gov (United States)

    Franch, Jesper; Knudsen, Jens; Ellis, Bronwyn A; Pedersen, Preben K; Cooney, Gregory J; Jensen, Jørgen

    2002-02-01

    Accumulation of acyl-CoA is hypothesized to be involved in development of insulin resistance. Acyl-CoA binds to acyl-CoA binding protein (ACBP) with high affinity, and therefore knowledge about ACBP concentration is important for interpreting acyl-CoA data. In the present study, we used a sandwich enzyme-linked immunosorbent assay to quantify ACBP concentration in different muscle fiber types. Furthermore, ACBP concentration was compared in muscles from lean and obese Zucker rats. Expression of ACBP was highest in the slow-twitch oxidative soleus muscle and lowest in the fast-twitch glycolytic white gastrocnemius (0.46 +/- 0.02 and 0.16 +/- 0.005 microg/mg protein, respectively). Expression of ACBP was soleus > red gastrocnemius > extensor digitorum longus > white gastrocnemius. Similar fiber type differences were found for carnitine palmitoyl transferase (CPT)-1, and a correlation was observed between ACBP and CPT-1. Muscles from obese Zucker rats had twice the triglyceride content, had approximately twice the long-chain acyl CoA content, and were severely insulin resistant. ACBP concentration was approximately 30% higher in all muscles from obese rats. Activities of CPT-1 and 3-hydroxy-acyl-CoA dehydrogenase were increased in muscles from obese rats, whereas citrate synthase activity was similar. In conclusion, ACBP expression is fiber type-specific with the highest concentration in oxidative muscles and the lowest in glycolytic muscles. The 90% increase in the concentration of acyl-CoA in obese Zucker muscle compared with only a 30% increase in the concentration of ACBP supports the hypothesis that an increased concentration of free acyl-CoA is involved in the development of insulin resistance.

  11. Effects Of treadmill training on hindlimb muscles of spinal cord–injured mice

    Science.gov (United States)

    Battistuzzo, Camila R.; Rank, Michelle M.; Flynn, Jamie R.; Morgan, David L.; Callister, Robin; Callister, Robert J.

    2016-01-01

    ABSTRACT Introduction: Treadmill training is known to prevent muscle atrophy after spinal cord injury (SCI), but the training duration required to optimize recovery has not been investigated. Methods: Hemisected mice were randomized to 3, 6, or 9 weeks of training or no training. Muscle fiber type composition and fiber cross‐sectional area (CSA) of medial gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA) were assessed using ATPase histochemistry. Results: Muscle fiber type composition of SCI animals did not change with training. However, 9 weeks of training increased the CSA of type IIB and IIX fibers in TA and MG muscles. Conclusions: Nine weeks of training after incomplete SCI was effective in preventing atrophy of fast‐twitch muscles, but there were limited effects on slow‐twitch muscles and muscle fiber type composition. These data provide important evidence of the benefits of exercising paralyzed limbs after SCI. Muscle Nerve, 2016 Muscle Nerve 55: 232–242, 2017 PMID:27273462

  12. Muscle fiber types composition and type identified endplate morphology of forepaw intrinsic muscles in the rat.

    Science.gov (United States)

    Pan, Feng; Mi, Jing-Yi; Zhang, Yan; Pan, Xiao-Yun; Rui, Yong-Jun

    2016-06-01

    The failure to accept reinnervation is considered to be one of the reasons for the poor motor functional recovery of intrinsic hand muscles (IHMs) after nerve injury. Rat could be a suitable model to be used in simulating motor function recovery of the IHMs after nerve injury as to the similarities in function and anatomy of the muscles between human and rat. However, few studies have reported the muscle fiber types composition and endplate morphologic characteristics of intrinsic forepaw muscles (IFMs) in the rat. In this study, the myosin heavy chain isoforms and acetylcholine receptors were stained by immunofluorescence to show the muscle fiber types composition and endplates on type-identified fibers of the lumbrical muscles (LMs), interosseus muscles (IMs), abductor digiti minimi (AM) and flexor pollicis brevis (FM) in rat forepaw. The majority of IFMs fibers were labeled positively for fast-switch fiber. However, the IMs were composed of only slow-switch fiber. With the exception of the IMs, the other IFMs had a part of hybrid fibers. Two-dimensional morphological characteristics of endplates on I and IIa muscle fiber had no significant differences among the IFMs. The LMs is the most suitable IFMs of rat to stimulate reinnervation of the IHMs after nerve injury. Gaining greater insight into the muscle fiber types composition and endplate morphology in the IFMs of rat may help understand the pathological and functional changes of IFMs in rat model stimulating reinnervation of IHMs after peripheral nerve injury.

  13. Caloric restriction induces energy-sparing alterations in skeletal muscle contraction, fiber composition and local thyroid hormone metabolism that persist during catch-up fat upon refeeding

    Directory of Open Access Journals (Sweden)

    Paula Bresciani M. De Andrade

    2015-09-01

    Full Text Available Weight regain after caloric restriction results in accelerated fat storage in adipose tissue. This catch-up fat phenomenon is postulated to result partly from suppressed skeletal muscle thermogenesis, but the underlying mechanisms are elusive. We investigated whether the reduced rate of skeletal muscle contraction-relaxation cycle that occurs after caloric restriction persists during weight recovery and could contribute to catch-up fat. Using a rat model of semistarvation-refeeding, in which fat recovery is driven by suppressed thermogenesis, we show that contraction and relaxation of leg muscles are slower after both semistarvation and refeeding. These effects are associated with (i higher expression of muscle deiodinase type 3 (DIO3 which inactivates tri-iodothyronine (T3, and lower expression of T3-activating enzyme, deiodinase type 2 (DIO2, (ii slower net formation of T3 from its T4 precursor in muscles, and (iii accumulation of slow fibers at the expense of fast fibers. These semistarvation-induced changes persisted during recovery and correlated with impaired expression of transcription factors involved in slow-twitch muscle development.We conclude that diminished muscle thermogenesis following caloric restriction results from reduced muscle T3 levels, alteration in muscle-specific transcription factors, and fast-to-slow fiber shift causing slower contractility. Energy-sparing effects persist during weight recovery and likely contribute to catch-up fat.

  14. The Effects of Ligustrazine on the Ca2+ Concentration of Soleus and Gastrocnemius Muscle Fibers in Hindlimb Unloaded Rat

    Science.gov (United States)

    Gao, Yunfang; Goswami, Nandu; Du, Bei; Hu, Huanxin; Wu, Xue

    Background:Spaceflight or inactivity (bed rest, limb immobilization, hindlimb unloading) causes skeletal muscle atrophy. Recent studies show that an increase in protein degradation is an important mechanism for disuse atrophy. Furthermore, the calcium overload of disuse-atrophied muscle fiber has been shown to initiate the skeletal muscle proteolysis in disuse atrophy. Ligustrazine (tetramethylpyrazine, TMP), one of the important active ingredient extracted from Chuanxiong, has been shown by our group to increase muscle fiber cross-sectional area in atrophied soleus induced by 14 days hindlimb unloading. However, the underlying mechanisms of ligustrazine effects on disuse-atrophied muscle fibers remain unknown. Objective: We investigated the effects of ligustrazine on the cytoplasmic calcium overloading in soleus and gastrocnemius in 14 days hindlimb unloaded (HU) rats. Methods: Adult female Sprague-Dawley rats were matched for body mass and randomly assigned to three groups (n=8, each group): 1) synchronous control (CON); HU + intragastric water instillation (HU+W); HU + intragastric 60.0 mg kg-1 ligustrazine instillation (HU+Tmp). Laser scanning confocal microscope assessed the concentrations of cytoplasmic calcium ions. Spaceflight disuse atrophy was simulated by hindlimb unloading, provided by tail suspension. Results: 1) Compared with CON, the concentration of soleus intracellular calcium ion in HU+W and HU+Tmp increased 330% and 86% respectively(P<0.01). Compared with HU+W, the concentration of soleus intracellular calcium ion in HU+Tmp decreased by 130%(P<0.01). 2) Compared with CON, the concentration of gastrocnemius intracellular calcium ion in HU+W and HU+Tmp increased 189.8% and 32.1% respectively(P<0.01). Compared with HU+W, the concentration of gastrocnemius intracellular calcium ion in HU+Tmp decreased by 119.3% (P<0.01). Conclusion: After 14 days of hindlimb unloading, cytoplasmic calcium of soleus (slow-twitch muscle) and gastrocnemius (fast-twitch

  15. Effective fiber hypertrophy in satellite cell-depleted skeletal muscle.

    Science.gov (United States)

    McCarthy, John J; Mula, Jyothi; Miyazaki, Mitsunori; Erfani, Rod; Garrison, Kelcye; Farooqui, Amreen B; Srikuea, Ratchakrit; Lawson, Benjamin A; Grimes, Barry; Keller, Charles; Van Zant, Gary; Campbell, Kenneth S; Esser, Karyn A; Dupont-Versteegden, Esther E; Peterson, Charlotte A

    2011-09-01

    An important unresolved question in skeletal muscle plasticity is whether satellite cells are necessary for muscle fiber hypertrophy. To address this issue, a novel mouse strain (Pax7-DTA) was created which enabled the conditional ablation of >90% of satellite cells in mature skeletal muscle following tamoxifen administration. To test the hypothesis that satellite cells are necessary for skeletal muscle hypertrophy, the plantaris muscle of adult Pax7-DTA mice was subjected to mechanical overload by surgical removal of the synergist muscle. Following two weeks of overload, satellite cell-depleted muscle showed the same increases in muscle mass (approximately twofold) and fiber cross-sectional area with hypertrophy as observed in the vehicle-treated group. The typical increase in myonuclei with hypertrophy was absent in satellite cell-depleted fibers, resulting in expansion of the myonuclear domain. Consistent with lack of nuclear addition to enlarged fibers, long-term BrdU labeling showed a significant reduction in the number of BrdU-positive myonuclei in satellite cell-depleted muscle compared with vehicle-treated muscle. Single fiber functional analyses showed no difference in specific force, Ca(2+) sensitivity, rate of cross-bridge cycling and cooperativity between hypertrophied fibers from vehicle and tamoxifen-treated groups. Although a small component of the hypertrophic response, both fiber hyperplasia and regeneration were significantly blunted following satellite cell depletion, indicating a distinct requirement for satellite cells during these processes. These results provide convincing evidence that skeletal muscle fibers are capable of mounting a robust hypertrophic response to mechanical overload that is not dependent on satellite cells.

  16. Effective fiber hypertrophy in satellite cell-depleted skeletal muscle

    Science.gov (United States)

    McCarthy, John J.; Mula, Jyothi; Miyazaki, Mitsunori; Erfani, Rod; Garrison, Kelcye; Farooqui, Amreen B.; Srikuea, Ratchakrit; Lawson, Benjamin A.; Grimes, Barry; Keller, Charles; Van Zant, Gary; Campbell, Kenneth S.; Esser, Karyn A.; Dupont-Versteegden, Esther E.; Peterson, Charlotte A.

    2011-01-01

    An important unresolved question in skeletal muscle plasticity is whether satellite cells are necessary for muscle fiber hypertrophy. To address this issue, a novel mouse strain (Pax7-DTA) was created which enabled the conditional ablation of >90% of satellite cells in mature skeletal muscle following tamoxifen administration. To test the hypothesis that satellite cells are necessary for skeletal muscle hypertrophy, the plantaris muscle of adult Pax7-DTA mice was subjected to mechanical overload by surgical removal of the synergist muscle. Following two weeks of overload, satellite cell-depleted muscle showed the same increases in muscle mass (approximately twofold) and fiber cross-sectional area with hypertrophy as observed in the vehicle-treated group. The typical increase in myonuclei with hypertrophy was absent in satellite cell-depleted fibers, resulting in expansion of the myonuclear domain. Consistent with lack of nuclear addition to enlarged fibers, long-term BrdU labeling showed a significant reduction in the number of BrdU-positive myonuclei in satellite cell-depleted muscle compared with vehicle-treated muscle. Single fiber functional analyses showed no difference in specific force, Ca2+ sensitivity, rate of cross-bridge cycling and cooperativity between hypertrophied fibers from vehicle and tamoxifen-treated groups. Although a small component of the hypertrophic response, both fiber hyperplasia and regeneration were significantly blunted following satellite cell depletion, indicating a distinct requirement for satellite cells during these processes. These results provide convincing evidence that skeletal muscle fibers are capable of mounting a robust hypertrophic response to mechanical overload that is not dependent on satellite cells. PMID:21828094

  17. Expression of the human fast-twitch skeletal muscle troponin I cDNA in a human ovarian carcinoma suppresses tumor growth

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To explore the efficiency and mechanism of ovarian carcinoma gene therapy with the human fast-twitch skeletal muscle troponin I gene (TnI-fast), TnI-fast cDNA was transferred into human ovarian adeno-carcinoma cell-line SK-OV-3. In vitro, the cell growth and cell cycle of TnI-fast-, vector-, and mock-transfected cells were determined by MTT and flow cytometry assay, respectively. The condi-tioned media of TnI-fast-, vector-, and mock-transfected SK-OV-3 cells were collected, and the cell pro-liferation inhibiting rates of human umbilical cord venous endothelial cells (HUVECs) by the three conditioned media were assayed. All the three cell lines were implanted into node mice, and the tumor growth, cell apoptosis, angiogenesis, and expression of TnI-fast were observed or analyzed, respec-tively. In vitro, expression of TnI-fast protein had no inhibiting effect on the growth of the dominant and stable transfectant cells, but endothelium, when compared with vector-transfected cells and nontrans-fected parental SK-OV-3 cells. Implantation of stable clone expressing TnI-fast in the female BALB/c nude mice inhibits primary tumor growth by an average of 73%. The nude mice grafts expressing TnI-fast exhibit a significant decrease of microvascular density, a higher rate of tumor cells apoptosis and a comparable proliferation rate as control. Our study, to our knowledge, shows the slowed down growth of the primary ovarian carcinoma, suggested that grafts were self-inhibitory by halting angio-genesis. Our data might also provide a novel useful strategy for cancer therapy by antiangiogenic gene therapy with a specific angiogenesis inhibitor TnI-fast.

  18. Muscle fiber and motor unit behavior in the longest human skeletal muscle.

    Science.gov (United States)

    Harris, A John; Duxson, Marilyn J; Butler, Jane E; Hodges, Paul W; Taylor, Janet L; Gandevia, Simon C

    2005-09-14

    The sartorius muscle is the longest muscle in the human body. It is strap-like, up to 600 mm in length, and contains five to seven neurovascular compartments, each with a neuromuscular endplate zone. Some of its fibers terminate intrafascicularly, whereas others may run the full length of the muscle. To assess the location and timing of activation within motor units of this long muscle, we recorded electromyographic potentials from multiple intramuscular electrodes along sartorius muscle during steady voluntary contraction and analyzed their activity with spike-triggered averaging from a needle electrode inserted near the proximal end of the muscle. Approximately 30% of sartorius motor units included muscle fibers that ran the full length of the muscle, conducting action potentials at 3.9 +/- 0.1 m/s. Most motor units were innervated within a single muscle endplate zone that was not necessarily near the midpoint of the fiber. As a consequence, action potentials reached the distal end of a unit as late as 100 ms after initiation at an endplate zone. Thus, contractile activity is not synchronized along the length of single sartorius fibers. We postulate that lateral transmission of force from fiber to endomysium and a wide distribution of motor unit endplates along the muscle are critical for the efficient transmission of force from sarcomere to tendon and for the prevention of muscle injury caused by overextension of inactive regions of muscle fibers.

  19. Muscle-specific Pikfyve gene disruption causes glucose intolerance, insulin resistance, adiposity, and hyperinsulinemia but not muscle fiber-type switching

    Science.gov (United States)

    Ikonomov, Ognian C.; Sbrissa, Diego; Delvecchio, Khortnal; Feng, Han-Zhong; Cartee, Gregory D.; Jin, Jian-Ping

    2013-01-01

    The evolutionarily conserved kinase PIKfyve that synthesizes PtdIns5P and PtdIns(3,5)P2 has been implicated in insulin-regulated GLUT4 translocation/glucose entry in 3T3-L1 adipocytes. To decipher PIKfyve's role in muscle and systemic glucose metabolism, here we have developed a novel mouse model with Pikfyve gene disruption in striated muscle (MPIfKO). These mice exhibited systemic glucose intolerance and insulin resistance at an early age but had unaltered muscle mass or proportion of slow/fast-twitch muscle fibers. Insulin stimulation of in vivo or ex vivo glucose uptake and GLUT4 surface translocation was severely blunted in skeletal muscle. These changes were associated with premature attenuation of Akt phosphorylation in response to in vivo insulin, as tested in young mice. Starting at 10–11 wk of age, MPIfKO mice progressively accumulated greater body weight and fat mass. Despite increased adiposity, serum free fatty acid and triglyceride levels were normal until adulthood. Together with the undetectable lipid accumulation in liver, these data suggest that lipotoxicity and muscle fiber switching do not contribute to muscle insulin resistance in MPIfKO mice. Furthermore, the 80% increase in total fat mass resulted from increased fat cell size rather than altered fat cell number. The observed profound hyperinsulinemia combined with the documented increases in constitutive Akt activation, in vivo glucose uptake, and gene expression of key enzymes for fatty acid biosynthesis in MPIfKO fat tissue suggest that the latter is being sensitized for de novo lipid anabolism. Our data provide the first in vivo evidence that PIKfyve is essential for systemic glucose homeostasis and insulin-regulated glucose uptake/GLUT4 translocation in skeletal muscle. PMID:23673157

  20. Diagnostic value of the muscle fiber conduction velocity for evaluation of muscle hypotrophy.

    Science.gov (United States)

    Gechev, Antonin G; Ilieva, Elena M; Marinkev, Marin D; Hadjigeorgiev, Georgi H

    2004-01-01

    To find an objective method of evaluation of the thigh muscle hypothrophy in gonarthrosis. The subjects of the study were 24 patients with gonarthrosis (mean age 58.4 +/- 2.6 years). Of these 8 (33%) were males and 16 (67%) females. The following methods of examination were used: computed tomography (CT) of the thigh musculature--linear measurement and area of the cross-section of the vastus medialis muscle; electromyography--muscle fiber conduction velocity; and measurement of thigh girth. Significant reduction of the cross-section area and linear measurement of the vastus medialis muscle and significant delay of the muscle fiber conduction velocity was found in the symptomatic side compared with the asymptomatic side. No correlation was found between the tape measure of the thigh and cross-section area of the muscle. A significant correlation was found between the cross-section area of the muscle and the fast fiber conduction velocity as well as between the linear measurement of the vastus medialis muscle cross-section and fast fiber conduction velocity. The correlation between the macromorphological changes of the vastus medialis muscle assessed by computed tomography and the functional changes detected by electromyography allows the conclusion that the muscle fiber conduction velocity can be used as an objective method of evaluation of muscle atrophy in degenerative joint diseases.

  1. Induction of GLUT-1 protein in adult human skeletal muscle fibers

    DEFF Research Database (Denmark)

    Gaster, M; Franch, J; Staehr, P

    2000-01-01

    fibers. Metabolic stress (obesity, non-insulin-dependent diabetes mellitus), contractile activity (training), and conditions of de- and reinnervation (amyotrophic lateral sclerosis) could not induce GLUT-1 expression in human muscle fibers. However, regenerating muscle fibers in polymyositis expressed...

  2. Repeated blood flow restriction induces muscle fiber hypertrophy.

    Science.gov (United States)

    Sudo, Mizuki; Ando, Soichi; Kano, Yutaka

    2017-02-01

    We recently developed an animal model to investigate the effects of eccentric contraction (ECC) and blood flow restriction (BFR) on muscle tissue at the cellular level. This study clarified the effects of repeated BFR, ECC, and BFR combined with ECC (BFR+ECC) on muscle fiber hypertrophy. Male Wistar rats were assigned to 3 groups: BFR, ECC, and BFR+ECC. The contralateral leg in the BFR group served as a control (CONT). Muscle fiber cross-sectional area (CSA) of the tibialis anterior was determined after the respective treatments for 6 weeks. CSA was greater in the BFR+ECC group than in the CONT (P muscle fiber hypertrophy at the cellular level. Muscle Nerve 55: 274-276, 2017. © 2016 Wiley Periodicals, Inc.

  3. Differential Responses of Soleus and Plantaris Muscle Fibers to Overloading

    Science.gov (United States)

    Kawano, Fuminori; Shibaguchi, Tsubasa; Ohira, Takashi; Nakai, Naoya; Ohira, Yoshinobu

    2013-02-01

    Responses of slow and fast fibers in soleus and plantaris muscles of adult rats to overloading by the tendon transection of synergists were studied. Overloading-related hypertrophy was noted in the slow fibers of plantaris and soleus, although the magnitude was greater in plantaris. Five genes with minor expression in slow soleus muscle were identified by microarray analysis. Base-line expressions of these genes in slow fibers of plantaris were also low. Further, repressive effects of overloading on these genes were seen in some fast fibers of plantaris, not in whole plantaris and soleus. The data suggested that the repression of particular genes might be related to the pronounced morphological response of fibers expressing type II, including I+II, myosin heavy chain (MyHC), although these genes with lower base-line expression in slow fibers did not respond to overloading.

  4. Muscle fiber-type distribution, fiber-type-specific damage, and the Pompe disease phenotype.

    Science.gov (United States)

    van den Berg, L E M; Drost, M R; Schaart, G; de Laat, J; van Doorn, P A; van der Ploeg, A T; Reuser, A J J

    2013-09-01

    Pompe disease is a lysosomal storage disorder caused by acid α-glucosidase deficiency and characterized by progressive muscle weakness. Enzyme replacement therapy (ERT) has ameliorated patients' perspectives, but reversal of skeletal muscle pathology remains a challenge. We studied pretreatment biopsies of 22 patients with different phenotypes to investigate to what extent fiber-type distribution and fiber-type-specific damage contribute to clinical diversity. Pompe patients have the same fiber-type distribution as healthy persons, but among nonclassic patients with the same GAA mutation (c.-32-13T>G), those with early onset of symptoms tend to have more type 2 muscle fibers than those with late-onset disease. Further, it seemed that the older, more severely affected classic infantile patients and the wheelchair-bound and ventilated nonclassic patients had a greater proportion of type 2x muscle fibers. However, as in other diseases, this may be caused by physical inactivity of those patients.

  5. The effects of inorganic phosphate and arsenate on both passive muscle visco-elasticity and maximum Ca2+ activated tension in chemically skinned rat fast and slow twitch muscle fibres.

    Science.gov (United States)

    Mutungi, Gabriel

    2003-01-01

    The effects of adding either 25 mM inorganic phosphate (Pi) or its structural analogue arsenate (ASi) on both the maximum Ca2+ activated tension (Po) and passive muscle visco-elasticity (P2 tension) were investigated at 10 degrees C, using segments of single, chemically skinned rat muscle fibres. Whilst the results confirmed some previous findings on the effects of Pi on Po, they also showed that the addition of 25 mM ASi led to a large (approximately 50%) but completely reversible depression of Po in both the fast and slow twitch rat muscle fibres. Moreover, the depression of Po by ASi was greater at low than at high pH values. Examined in the presence of Dextran T-500, the passive tension and sarcomere length responses to a ramp stretch were found to be qualitatively and quantitatively similar to those previously reported in intact rat muscle fibres. Thus, the tension response to a ramp stretch, in the presence and absence of either 25 mM Pi or ASi, consisted of a viscous (P1), a visco-elastic (P2) and an elastic (P3) tension. However, the addition of either 25 mM Pi or ASi led to approximately 15-18% increase in the amplitude of the visco-elastic (P2) tension but had little or no effect on the amplitudes of the other two tension components (viscous, P1 and elastic, P3 tensions). Furthermore, neither compound significantly altered the relaxation rate of the passive muscle visco-elasticity (P2 tension). These results show that Po (arising from cycling cross-bridges) and passive muscle visco-elasticity (P2 tension) are affected differently by both Pi and ASi and suggest that they may not share a common structural basis. The possibility that passive muscle visco-elasticity (P2 tension) arises from the gap-(titin) filament (as suggested previously by Mutungi and Ranatunga, 1996b J Physiol 496: 827-837) and that Pi and ASi increase its amplitude by interacting with the PEVK region of the filament are discussed.

  6. Incidence of centrally positioned nuclei in mouse masticatory muscle fibers

    DEFF Research Database (Denmark)

    Vilmann, A; Vilmann, H; Kirkeby, S

    1989-01-01

    Cross-sections of normal digastric, temporalis and masseter muscles from 7- and 30-week-old mice were studied for centrally positioned nuclei. Such nuclei were inhomogeneously distributed throughout each muscle and varied markedly between specimens. The incidence of centrally positioned nuclei......, the frequency in a given muscle was apparently age-independent. A connection between fiber type and centrally positioned nuclei is suggested....

  7. Functional sparing of intrafusal muscle fibers in muscular dystrophies.

    Science.gov (United States)

    Aimonetti, Jean-Marc; Ribot-Ciscar, Edith; Rossi-Durand, Christiane; Attarian, Shahram; Pouget, Jean; Roll, Jean-Pierre

    2005-07-01

    In a previous study, we showed that patients with muscular dystrophies (MDs) perceive passive movements, experience sensations of illusory movement induced by muscle tendon vibration, and have proprioceptive-regulated sways in response to vibratory stimulation applied to the neck and ankle muscle tendons. These findings argue for preserved proprioceptive functions of muscle spindles. However, it is unclear whether the function of intrafusal muscle fibers is spared, i.e., whether they retain their ability to contract when submitted to a fusimotor drive. To answer this question, we analyzed the effects of reinforcement maneuvers (mental computation and the Jendrassik maneuver) that are known to increase muscle spindle sensitivity via fusimotor drive in healthy subjects. Nine patients with different MDs participated in the study. Reinforcement maneuvers increased both the mean amplitude of the Achilles tendon reflex (187 +/- 52.9% of the mean control amplitude) and the sensitivity of muscle spindle afferents to imposed movements of the ankle. The same reinforcement maneuvers failed to alter the amplitude of the Hoffmann reflex in the triceps surae muscle. These results suggest that the intrafusal muscle fibers preserve their contractile abilities in slowly progressive MDs. The reasons for a differential impairment of intrafusal and extrafusal muscle fibers and the clinical implications of the present results are discussed.

  8. GLUT-3 expression in human skeletal muscle

    Science.gov (United States)

    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.

  9. Polylysine modification of adenoviral fiber protein enhances muscle cell transduction.

    Science.gov (United States)

    Bouri, K; Feero, W G; Myerburg, M M; Wickham, T J; Kovesdi, I; Hoffman, E P; Clemens, P R

    1999-07-01

    Adenoviral vectors (ADVs) are used widely for gene delivery to different tissues including muscle. One particularly promising use for ADVs is in the transfer of the dystrophin gene to the muscle of patients with Duchenne muscular dystrophy (DMD). However, studies in different animal models of DMD suggest that ADVs inefficiently transduce mature skeletal muscle. In this article we test whether AdZ.F(pK7), a genetically modified ADV that expresses a polylysine moiety on the end of the fiber protein, could enhance transduction of muscle cells and circumvent the maturation-dependent loss of muscle infectivity by ADVs. The efficiency of transduction was tested at different levels of muscle maturation. In vitro, AdZ.F(pK7) showed a higher level of transduction at all stages of differentiation including myoblasts, myotubes, and single muscle fibers. In vivo, mature skeletal muscle was transduced fourfold better by AdZ.F(pK7) than by the unmodifled vector (AdZ.F). Together, these observations demonstrate improved ADV transduction of skeletal muscle by modifying ADV tropism, and provide a proof-of-principle that modification of ADVs to target muscle-specific molecules could result in tissue-specific transfer of skeletal muscle tissue as well.

  10. The effects of short-term exercise training on peak-torque are time- and fiber-type dependent

    NARCIS (Netherlands)

    Ureczky, Dora; Vacz, Gabriella; Costa, Andreas; Kopper, Bence; Lacza, Zsombor; Hortobagyi, Tibor; Tihanyi, Jozsef

    We examined the susceptibility of fast and slow twitch muscle fibers in the quadriceps muscle to eccentric exercise-induced muscle damage. Nine healthy men (age: 22.5 +/- 1.6 years) performed maximal eccentric quadriceps contractions at 120 degrees.s(-1) over a 120 degrees of knee joint range of

  11. The effects of short-term exercise training on peak-torque are time- and fiber-type dependent

    NARCIS (Netherlands)

    Ureczky, Dora; Vacz, Gabriella; Costa, Andreas; Kopper, Bence; Lacza, Zsombor; Hortobagyi, Tibor; Tihanyi, Jozsef

    2014-01-01

    We examined the susceptibility of fast and slow twitch muscle fibers in the quadriceps muscle to eccentric exercise-induced muscle damage. Nine healthy men (age: 22.5 +/- 1.6 years) performed maximal eccentric quadriceps contractions at 120 degrees.s(-1) over a 120 degrees of knee joint range of mot

  12. The effects of short-term exercise training on peak-torque are time- and fiber-type dependent

    NARCIS (Netherlands)

    Ureczky, Dora; Vacz, Gabriella; Costa, Andreas; Kopper, Bence; Lacza, Zsombor; Hortobagyi, Tibor; Tihanyi, Jozsef

    2014-01-01

    We examined the susceptibility of fast and slow twitch muscle fibers in the quadriceps muscle to eccentric exercise-induced muscle damage. Nine healthy men (age: 22.5 +/- 1.6 years) performed maximal eccentric quadriceps contractions at 120 degrees.s(-1) over a 120 degrees of knee joint range of mot

  13. Size and metabolic properties of single muscle fibers in rat soleus after hindlimb suspension

    Science.gov (United States)

    Hauschka, Edward O.; Roy, Roland R.; Edgerton, V. Reggie

    1987-01-01

    The effect of 28-day-long hind-limb suspension (HS) combined with 10 daily forceful lengthening contractions of the limb on the morphological and metabolic properties of individual fibers of the soleus was studied in rats, using quantitative histochemical techniques. Compared with nonsuspended controls (CON), soleus wet weights of HS rats were decreased by 49 percent; the fibers staining lightly for myosin ATPase ('light-ATPase' fibers) atrophied more than the 'dark-ATPase' fibers. Single-fiber alpha-glycerophosphate dehydrogenase (GPD) and succinate dehydrogenase (SDH) activities were higher in HS than in CON rats. Daily forceful lengthening contractions did not prevent the HS-induced changes. The results support the view that the soleus fibers can change from a slow-twitch oxidative to a fast-twitch oxidative-glycolytic profile, but rarely to a fast-twitch glycolytic one, and that the SDH and GPD activities per volume of tissue can be increased even when there are severe losses of contractile proteins.

  14. Muscle fiber viability, a novel method for the fast detection of ischemic muscle injury in rats.

    Science.gov (United States)

    Turóczi, Zsolt; Arányi, Péter; Lukáts, Ákos; Garbaisz, Dávid; Lotz, Gábor; Harsányi, László; Szijártó, Attila

    2014-01-01

    Acute lower extremity ischemia is a limb- and life-threatening clinical problem. Rapid detection of the degree of injury is crucial, however at present there are no exact diagnostic tests available to achieve this purpose. Our goal was to examine a novel technique - which has the potential to accurately assess the degree of ischemic muscle injury within a short period of time - in a clinically relevant rodent model. Male Wistar rats were exposed to 4, 6, 8 and 9 hours of bilateral lower limb ischemia induced by the occlusion of the infrarenal aorta. Additional animals underwent 8 and 9 hours of ischemia followed by 2 hours of reperfusion to examine the effects of revascularization. Muscle samples were collected from the left anterior tibial muscle for viability assessment. The degree of muscle damage (muscle fiber viability) was assessed by morphometric evaluation of NADH-tetrazolium reductase reaction on frozen sections. Right hind limbs were perfusion-fixed with paraformaldehyde and glutaraldehyde for light and electron microscopic examinations. Muscle fiber viability decreased progressively over the time of ischemia, with significant differences found between the consecutive times. High correlation was detected between the length of ischemia and the values of muscle fiber viability. After reperfusion, viability showed significant reduction in the 8-hour-ischemia and 2-hour-reperfusion group compared to the 8-hour-ischemia-only group, and decreased further after 9 hours of ischemia and 2 hours of reperfusion. Light- and electron microscopic findings correlated strongly with the values of muscle fiber viability: lesser viability values represented higher degree of ultrastructural injury while similar viability results corresponded to similar morphological injury. Muscle fiber viability was capable of accurately determining the degree of muscle injury in our rat model. Our method might therefore be useful in clinical settings in the diagnostics of acute ischemic

  15. Age-related botulinum toxin effects on muscle fiber conduction velocity in non-injected muscles

    NARCIS (Netherlands)

    Lange, Fiete; van Weerden, Tiemen W.; van der Hoeven, Johannes H.

    2007-01-01

    Objective: We studied systemic effects of botulinum toxin (BTX) treatment on muscle fiber conduction velocity (MFCV) and possible effects of age. Methods: MFCV was determined by an invasive EMG method in the biceps brachii muscle. Seventeen BTX treated patients and 58 controls were investigated. BTX

  16. SUPERNORMAL MUSCLE-FIBER CONDUCTION-VELOCITY DURING INTERMITTENT ISOMETRIC-EXERCISE IN HUMAN MUSCLE

    NARCIS (Netherlands)

    VANDERHOEVEN, JH; LANGE, F

    1994-01-01

    Muscle fiber conduction velocity (MFCV) and surface electromyographic parameters were studied in the brachial biceps muscle of healthy males during voluntary intermittent isometric contractions at 50% of maximum force. Recovery in the following 15 min was then observed. The measurements were perform

  17. Relation of systemic and local muscle exercise capacity to skeletal muscle characteristics in men with congestive heart failure

    Science.gov (United States)

    Massie, B. M.; Simonini, A.; Sahgal, P.; Wells, L.; Dudley, G. A.

    1996-01-01

    OBJECTIVES. The present study was undertaken to further characterize changes in skeletal muscle morphology and histochemistry in congestive heart failure and to determine the relation of these changes to abnormalities of systemic and local muscle exercise capacity. BACKGROUND. Abnormalities of skeletal muscle appear to play a role in the limitation of exercise capacity in congestive heart failure, but information on the changes in muscle morphology and biochemistry and their relation to alterations in muscle function is limited. METHODS. Eighteen men with predominantly mild to moderate congestive heart failure (mean +/- SEM New York Heart Association functional class 2.6 +/- 0.2, ejection fraction 24 +/- 2%) and eight age- and gender-matched sedentary control subjects underwent measurements of peak systemic oxygen consumption (VO2) during cycle ergometry, resistance to fatigue of the quadriceps femoris muscle group and biopsy of the vastus lateralis muscle. RESULTS. Peak VO2 and resistance to fatigue were lower in the patients with heart failure than in control subjects (15.7 +/- 1.2 vs. 25.1 +/- 1.5 ml/min-kg and 63 +/- 2% vs. 85 +/- 3%, respectively, both p twitch, type I fibers than did control subjects (36 +/- 3% vs. 46 +/- 5%, p = 0.048) and a higher proportion of fast twitch, type IIab fibers (18 +/- 3% vs. 7 +/- 2%, p = 0.004). Fiber cross-sectional area was smaller, and single-fiber succinate dehydrogenase activity, a mitochondrial oxidative marker, was lower in patients (both p twitch to slow twitch fiber cross-sectional area was lower in patients (0.780 +/- 0.06 vs. 1.05 +/- 0.08, p = 0.019). Peak VO2 was strongly related to integrated succinate dehydrogenase activity in patients (r = 0.896, p = 0.001). Peak VO2, resistance to fatigue and strength also correlated significantly with several measures of fiber size, especially of fast twitch fibers, in patients. None of the skeletal muscle characteristics examined correlated with exercise capacity in control

  18. Satellite cell depletion prevents fiber hypertrophy in skeletal muscle.

    Science.gov (United States)

    Egner, Ingrid M; Bruusgaard, Jo C; Gundersen, Kristian

    2016-08-15

    The largest mammalian cells are the muscle fibers, and they have multiple nuclei to support their large cytoplasmic volumes. During hypertrophic growth, new myonuclei are recruited from satellite stem cells into the fiber syncytia, but it was recently suggested that such recruitment is not obligatory: overload hypertrophy after synergist ablation of the plantaris muscle appeared normal in transgenic mice in which most of the satellite cells were abolished. When we essentially repeated these experiments analyzing the muscles by immunohistochemistry and in vivo and ex vivo imaging, we found that overload hypertrophy was prevented in the satellite cell-deficient mice, in both the plantaris and the extensor digitorum longus muscles. We attribute the previous findings to a reliance on muscle mass as a proxy for fiber hypertrophy, and to the inclusion of a significant number of regenerating fibers in the analysis. We discuss that there is currently no model in which functional, sustainable hypertrophy has been unequivocally demonstrated in the absence of satellite cells; an exception is re-growth, which can occur using previously recruited myonuclei without addition of new myonuclei. © 2016. Published by The Company of Biologists Ltd.

  19. A Temporally Controlled Inhibitory Drive Coordinates Twitch Movements during REM Sleep.

    Science.gov (United States)

    Brooks, Patricia L; Peever, John

    2016-05-01

    During REM sleep, skeletal muscles are paralyzed in one moment but twitch and jerk in the next. REM sleep twitches are traditionally considered random motor events that result from momentary lapses in REM sleep paralysis [1-3]. However, recent evidence indicates that twitches are not byproducts of REM sleep, but are in fact self-generated events that could function to promote motor learning and development [4-6]. If REM twitches are indeed purposefully generated, then they should be controlled by a coordinated and definable mechanism. Here, we used behavioral, electrophysiological, pharmacological, and neuroanatomical methods to demonstrate that an inhibitory drive onto skeletal motoneurons produces a temporally coordinated pattern of muscle twitches during REM sleep. First, we show that muscle twitches in adult rats are not uniformly distributed during REM sleep, but instead follow a well-defined temporal trajectory. They are largely absent during REM initiation but increase steadily thereafter, peaking toward REM termination. Next, we identify the transmitter mechanism that controls the temporal nature of twitch activity. Specifically, we show that a GABA and glycine drive onto motoneurons prevents twitch activity during REM initiation, but progressive weakening of this drive functions to promote twitch activity during REM termination. These results demonstrate that REM twitches are not random byproducts of REM sleep, but are instead rather coherently generated events controlled by a temporally variable inhibitory drive.

  20. Severely atrophic human muscle fibers with nuclear misplacement survive many years of permanent denervation

    Directory of Open Access Journals (Sweden)

    Ugo Carraro

    2016-06-01

    Full Text Available Likewise in rodents, after complete spinal cord injury (SCI the lower motor neuron (LMN denervated human muscle fibers lose completely the myofibrillar apparatus and the coil distribution of myonuclei that are relocated in groups (nuclear clumps in the center of severely atrophic muscle fibers. Up to two years of LMN denervation the muscle fibers with nuclear clumps are very seldom, but in this cohort of patients the severely atrophic muscle fibers are frequent in muscle biopsies harvested three to six years after SCI. Indeed, the percentage increased to 27 ± 9% (p< 0.001, and then abruptly decreased from the 6th year onward, when fibrosis takes over to neurogenic muscle atrophy. Immunohistochemical analyses shown that nuclear misplacements occurred in both fast and slow muscle fibers. In conclusion, human muscle fibers survive permanent denervation much longer than generally accepted and relocation of nuclei is a general behavior in long term denervated muscle fibers.

  1. Common errors in textbook descriptions of muscle fiber size in nontrained humans.

    Science.gov (United States)

    Chalmers, Gordon R; Row, Brandi S

    2011-09-01

    Exercise science and human anatomy and physiology textbooks commonly report that type IIB muscle fibers have the largest cross-sectional area of the three fiber types. These descriptions of muscle fiber sizes do not match with the research literature examining muscle fibers in young adult nontrained humans. For men, most commonly type IIA fibers were significantly larger than other fiber types (six out of 10 cases across six different muscles). For women, either type I, or both I and IIA muscle fibers were usually significantly the largest (five out of six cases across four different muscles). In none of these reports were type IIB fibers significantly larger than both other fiber types. In 27 studies that did not include statistical comparisons of mean fiber sizes across fiber types, in no cases were type IIB or fast glycolytic fibers larger than both type I and IIA, or slow oxidative and fast oxidative glycolytic fibers. The likely reason for mistakes in textbook descriptions of human muscle fiber sizes is that animal data were presented without being labeled as such, and without any warning that there are interspecies differences in muscle fiber properties. Correct knowledge of muscle fiber sizes may facilitate interpreting training and aging adaptations.

  2. Biochemical adaptations of antigravity muscle fibers to disuse atrophy

    Science.gov (United States)

    Booth, F. W.

    1978-01-01

    Studies are presented in four parts of this report. The four parts include; (1) studies to gain information on the molecular basis of atrophy by antigravity muscle; (2) studies on the work capacity of antigravity muscles during atrophy and during recovery from atrophy; (3) studies on recovery of degenerated antigravity fibers after removal of hind-limb casts; and (4) studies on the atrophy and recovery of bone. The philosophy of these studies was to identify the time sequence of events in the soleus muscle of the rat following immobilization of the hind limbs, so that the length of the soleus muscle within the fixed limb is less than its resting length. In two separate studies, no decline in the weight of the soleus muscle could be detected during the first 72 hours of limb immobilization.

  3. Changes of contractile responses due to simulated weightlessness in rat soleus muscle

    Science.gov (United States)

    Elkhammari, A.; Noireaud, J.; Léoty, C.

    1994-08-01

    Some contractile and electrophysiological properties of muscle fibers isolated from the slow-twitch soleus (SOL) and fast-twitch extensor digitorum longus (EDL) muscles of rats were compared with those measured in SOL muscles from suspended rats. In suspendede SOL (21 days of tail-suspension) membrane potential (Em), intracellular sodium activity (aiNa) and the slope of the relationship between Em and log [K]o were typical of fast-twitch muscles. The relation between the maximal amplitude of K-contractures vs Em was steeper for control SOL than for EDL and suspended SOL muscles. After suspension, in SOL muscles the contractile threshold and the inactivation curves for K-contractures were shifted to more positive Em. Repriming of K-contractures was unaffected by suspencion. The exposure of isolated fibers to perchlorate (ClO4-)-containing (6-40 mM) solutions resulted ina similar concentration-dependent shift to more negative Em of activation curves for EDL and suspended SOL muscles. On exposure to a Na-free TEA solution, SOL from control and suspended rats, in contrast to EDL muscles, generated slow contractile responses. Suspended SOL showed a reduced sensitivity to the contracture-producing effect of caffeine compared to control muscles. These results suggested that the modification observed due to suspension could be encounted by changes in the characteristics of muscle fibers from slow to fast-twitch type.

  4. Fiber optic biofluorometer for physiological research on muscle slices

    Science.gov (United States)

    Belz, Mathias; Dendorfer, Andreas; Werner, Jan; Lambertz, Daniel; Klein, Karl-Friedrich

    2016-03-01

    A focus of research in cell physiology is the detection of Ca2+, NADH, FAD, ATPase activity or membrane potential, only to name a few, in muscle tissues. In this work, we report on a biofluorometer using ultraviolet light emitting diodes (UV-LEDs), optical fibers and two photomultipliers (PMTs) using synchronized fluorescence detection with integrated background correction to detect free calcium, Ca2+, in cardiac muscle tissue placed in a horizontal tissue bath and a microscope setup. Fiber optic probes with imaging optics have been designed to transport excitation light from the biofluorometer's light output to a horizontal tissue bath and to collect emission light from a tissue sample of interest to two PMTs allowing either single excitation / single emission or ratiometric, dual excitation / single emission or single excitation / dual emission fluorescence detection of indicator dyes or natural fluorophores. The efficient transport of light from the excitation LEDs to the tissue sample, bleaching effects of the excitation light in both, polymer and fused silica-based fibers will be discussed. Furthermore, a new approach to maximize light collection of the emission light using high NA fibers and high NA coupling optics will be shown. Finally, first results on Ca2+ measurements in cardiac muscle slices in a traditional microscope setup and a horizontal tissue bath using fiber optic probes will be introduced and discussed.

  5. Overexpression of SMPX in adult skeletal muscle does not change skeletal muscle fiber type or size.

    Directory of Open Access Journals (Sweden)

    Einar Eftestøl

    Full Text Available Mechanical factors such as stretch are thought to be important in the regulation of muscle phenotype. Small muscle protein X-linked (SMPX is upregulated by stretch in skeletal muscle and has been suggested to serve both as a transcription factor and a mechanosensor, possibly giving rise to changes in both fiber size and fiber type. We have used in vivo confocal imaging to study the subcellular localization of SMPX in skeletal muscle fibers of adult rats using a SMPX-EGFP fusion protein. The fusion protein was localized predominantly in repetitive double stripes flanking the Z-disc, and was excluded from all nuclei. This localization would be consistent with SMPX being a mechanoreceptor, but not with SMPX playing a role as a transcription factor. In vivo overexpression of ectopic SMPX in skeletal muscle of adult mice gave no significant changes in fiber type distribution or cross sectional area, thus a role of SMPX in regulating muscle phenotype remains unclear.

  6. Decreased Peak Expiratory Flow Associated with Muscle Fiber-Type Switching in Spinal and Bulbar Muscular Atrophy.

    Science.gov (United States)

    Yamada, Shinichiro; Hashizume, Atsushi; Hijikata, Yasuhiro; Inagaki, Tomonori; Suzuki, Keisuke; Kondo, Naohide; Kawai, Kaori; Noda, Seiya; Nakanishi, Hirotaka; Banno, Haruhiko; Hirakawa, Akihiro; Koike, Haruki; Halievski, Katherine; Jordan, Cynthia L; Katsuno, Masahisa; Sobue, Gen

    2016-01-01

    The aim of this study was to characterize the respiratory function profile of subjects with spinal and bulbar muscular atrophy (SBMA), and to explore the underlying pathological mechanism by comparing the clinical and biochemical indices of this disease with those of amyotrophic lateral sclerosis (ALS). We enrolled male subjects with SBMA (n = 40) and ALS (n = 25) along with 15 healthy control subjects, and assessed their respiratory function, motor function, and muscle strength. Predicted values of peak expiratory flow (%PEF) and forced vital capacity were decreased in subjects with SBMA compared with controls. In SBMA, both values were strongly correlated with the trunk subscores of the motor function tests and showed deterioration relative to disease duration. Compared with activities of daily living (ADL)-matched ALS subjects, %PEF, tongue pressure, and grip power were substantially decreased in subjects with SBMA. Both immunofluorescence and RT-PCR demonstrated a selective decrease in the expression levels of the genes encoding the myosin heavy chains specific to fast-twitch fibers in SBMA subjects. The mRNA levels of peroxisome proliferator-activated receptor gamma coactivator 1-alpha and peroxisome proliferator-activated receptor delta were up-regulated in SBMA compared with ALS and controls. In conclusion, %PEF is a disease-specific respiratory marker for the severity and progression of SBMA. Explosive muscle strength, including %PEF, was selectively affected in subjects with SBMA and was associated with activation of the mitochondrial biogenesis-related molecular pathway in skeletal muscles.

  7. Fresh muscle fiber fragments on a scaffold in rats-a new concept in urogynecology?

    DEFF Research Database (Denmark)

    Boennelycke, Marie; Christensen, Lise; Nielsen, Lene F

    2011-01-01

    To investigate if a synthetic, biodegradable scaffold with either autologous in vitro cultured muscle-derived cells or autologous fresh muscle fiber fragments could be used for tissue repair.......To investigate if a synthetic, biodegradable scaffold with either autologous in vitro cultured muscle-derived cells or autologous fresh muscle fiber fragments could be used for tissue repair....

  8. Fish protein intake induces fast-muscle hypertrophy and reduces liver lipids and serum glucose levels in rats.

    Science.gov (United States)

    Kawabata, Fuminori; Mizushige, Takafumi; Uozumi, Keisuke; Hayamizu, Kohsuke; Han, Li; Tsuji, Tomoko; Kishida, Taro

    2015-01-01

    In our previous study, fish protein was proven to reduce serum lipids and body fat accumulation by skeletal muscle hypertrophy and enhancing basal energy expenditure in rats. In the present study, we examined the precise effects of fish protein intake on different skeletal muscle fiber types and metabolic gene expression of the muscle. Fish protein increased fast-twitch muscle weight, reduced liver triglycerides and serum glucose levels, compared with the casein diet after 6 or 8 weeks of feeding. Furthermore, fish protein upregulated the gene expressions of a fast-twitch muscle-type marker and a glucose transporter in the muscle. These results suggest that fish protein induces fast-muscle hypertrophy, and the enhancement of basal energy expenditure by muscle hypertrophy and the increase in muscle glucose uptake reduced liver lipids and serum glucose levels. The present results also imply that fish protein intake causes a slow-to-fast shift in muscle fiber type.

  9. Myoglobin plasma level related to muscle mass and fiber composition: a clinical marker of muscle wasting?

    Science.gov (United States)

    Weber, Marc-André; Kinscherf, Ralf; Krakowski-Roosen, Holger; Aulmann, Michael; Renk, Hanna; Künkele, Annette; Edler, Lutz; Kauczor, Hans-Ulrich; Hildebrandt, Wulf

    2007-08-01

    Progressive muscle wasting is a central feature of cancer-related cachexia and has been recognized as a determinant of poor prognosis and quality of life. However, until now, no easily assessable clinical marker exists that allows to predict or to track muscle wasting. The present study evaluated the potential of myoglobin (MG) plasma levels to indicate wasting of large locomotor muscles and, moreover, to reflect the loss of MG-rich fiber types, which are most relevant for daily performance. In 17 cancer-cachectic patients (weight loss 22%) and 27 age- and gender-matched healthy controls, we determined plasma levels of MG and creatine kinase (CK), maximal quadriceps muscle cross-sectional area (CSA) by magnetic resonance imaging, muscle morphology and fiber composition in biopsies from the vastus lateralis muscle, body cell mass (BCM) by impedance technique as well as maximal oxygen uptake (VO(2)max). In cachectic patients, plasma MG, muscle CSA, BCM, and VO(2)max were 30-35% below control levels. MG showed a significant positive correlation to total muscle CSA (r = 0.65, p max as an important functional readout. CK plasma levels appear to be less reliable because prolonged increases are observed in even subclinical myopathies or after exercise. Notably, cancer-related muscle wasting was not associated with increases in plasma MG or CK in this study.

  10. Myriocin prevents muscle ceramide accumulation but not muscle fiber atrophy during short-term mechanical unloading.

    Science.gov (United States)

    Salaun, Erwann; Lefeuvre-Orfila, Luz; Cavey, Thibault; Martin, Brice; Turlin, Bruno; Ropert, Martine; Loreal, Olivier; Derbré, Frédéric

    2016-01-15

    Bedridden patients in intensive care unit or after surgery intervention commonly develop skeletal muscle weakness. The latter is promoted by a variety of prolonged hospitalization-associated conditions. Muscle disuse is the most ubiquitous and contributes to rapid skeletal muscle atrophy and progressive functional strength reduction. Disuse causes a reduction in fatty acid oxidation, leading to its accumulation in skeletal muscle. We hypothesized that muscle fatty acid accumulation could stimulate ceramide synthesis and promote skeletal muscle weakness. Therefore, the present study was designed to determine the effects of sphingolipid metabolism on skeletal muscle atrophy induced by 7 days of disuse. For this purpose, male Wistar rats were treated with myriocin, an inhibitor of de novo synthesis of ceramides, and subjected to hindlimb unloading (HU) for 7 days. Soleus muscles were assayed for fiber diameter, ceramide levels, protein degradation, and apoptosis signaling. Serum and liver were removed to evaluate the potential hepatoxicity of myriocin treatment. We found that HU increases content of saturated C16:0 and C18:0 ceramides and decreases soleus muscle weight and fiber diameter. HU increased the level of polyubiquitinated proteins and induced apoptosis in skeletal muscle. Despite a prevention of C16:0 and C18:0 muscle accumulation, myriocin treatment did not prevent skeletal muscle atrophy and concomitant induction of apoptosis and proteolysis. Moreover, myriocin treatment increased serum transaminases and induced hepatocyte necrosis. These data highlight that inhibition of de novo synthesis of ceramides during immobilization is not an efficient strategy to prevent skeletal muscle atrophy and exerts adverse effects like hepatotoxicity. Copyright © 2016 the American Physiological Society.

  11. Influence of exercise contraction mode and protein supplementation on human skeletal muscle satellite cell content and muscle fiber growth.

    Science.gov (United States)

    Farup, Jean; Rahbek, Stine Klejs; Riis, Simon; Vendelbo, Mikkel Holm; Paoli, Frank de; Vissing, Kristian

    2014-10-15

    Skeletal muscle satellite cells (SCs) are involved in remodeling and hypertrophy processes of skeletal muscle. However, little knowledge exists on extrinsic factors that influence the content of SCs in skeletal muscle. In a comparative human study, we investigated the muscle fiber type-specific association between emergence of satellite cells (SCs), muscle growth, and remodeling in response to 12 wk unilateral resistance training performed as eccentric (Ecc) or concentric (Conc) resistance training ± whey protein (Whey, 19.5 g protein + 19.5 g glucose) or placebo (Placebo, 39 g glucose) supplementation. Muscle biopsies (vastus lateralis) were analyzed for fiber type-specific SCs, myonuclei, and fiber cross-sectional area (CSA). Following training, SCs increased with Conc in both type I and type II fibers (P hypertrophy correlated with whole muscle hypertrophy exclusively following Conc training (P eccentric resistance training while type II fiber hypertrophy was accentuated when combining concentric resistance training with whey protein supplementation.

  12. Muscle fiber type specific induction of slow myosin heavy chain 2 gene expression by electrical stimulation

    Energy Technology Data Exchange (ETDEWEB)

    Crew, Jennifer R.; Falzari, Kanakeshwari [Department of Cell Biology and Anatomy, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064 (United States); DiMario, Joseph X., E-mail: joseph.dimario@rosalindfranklin.edu [Department of Cell Biology and Anatomy, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064 (United States)

    2010-04-01

    Vertebrate skeletal muscle fiber types are defined by a broad array of differentially expressed contractile and metabolic protein genes. The mechanisms that establish and maintain these different fiber types vary throughout development and with changing functional demand. Chicken skeletal muscle fibers can be generally categorized as fast and fast/slow based on expression of the slow myosin heavy chain 2 (MyHC2) gene in fast/slow muscle fibers. To investigate the cellular and molecular mechanisms that control fiber type formation in secondary or fetal muscle fibers, myoblasts from the fast pectoralis major (PM) and fast/slow medial adductor (MA) muscles were isolated, allowed to differentiate in vitro, and electrically stimulated. MA muscle fibers were induced to express the slow MyHC2 gene by electrical stimulation, whereas PM muscle fibers did not express the slow MyHC2 gene under identical stimulation conditions. However, PM muscle fibers did express the slow MyHC2 gene when electrical stimulation was combined with inhibition of inositol triphosphate receptor (IP3R) activity. Electrical stimulation was sufficient to increase nuclear localization of expressed nuclear-factor-of-activated-T-cells (NFAT), NFAT-mediated transcription, and slow MyHC2 promoter activity in MA muscle fibers. In contrast, both electrical stimulation and inhibitors of IP3R activity were required for these effects in PM muscle fibers. Electrical stimulation also increased levels of peroxisome-proliferator-activated receptor-{gamma} co-activator-1 (PGC-1{alpha}) protein in PM and MA muscle fibers. These results indicate that MA muscle fibers can be induced by electrical stimulation to express the slow MyHC2 gene and that fast PM muscle fibers are refractory to stimulation-induced slow MyHC2 gene expression due to fast PM muscle fiber specific cellular mechanisms involving IP3R activity.

  13. Muscle fatigue, nNOS and muscle fiber atrophy in limb girdle muscular dystrophy.

    Science.gov (United States)

    Angelini, Corrado; Tasca, Elisabetta; Nascimbeni, Anna Chiara; Fanin, Marina

    2014-12-01

    Muscle fatigability and atrophy are frequent clinical signs in limb girdle muscular dystrophy (LGMD), but their pathogenetic mechanisms are still poorly understood. We review a series of different factors that may be connected in causing fatigue and atrophy, particularly considering the role of neuronal nitric oxide synthase (nNOS) and additional factors such as gender in different forms of LGMD (both recessive and dominant) underlying different pathogenetic mechanisms. In sarcoglycanopathies, the sarcolemmal nNOS reactivity varied from absent to reduced, depending on the residual level of sarcoglycan complex: in cases with complete sarcoglycan complex deficiency (mostly in beta-sarcoglycanopathy), the sarcolemmal nNOS reaction was absent and it was always associated with early severe clinical phenotype and cardiomyopathy. Calpainopathy, dysferlinopathy, and caveolinopathy present gradual onset of fatigability and had normal sarcolemmal nNOS reactivity. Notably, as compared with caveolinopathy and sarcoglycanopathies, calpainopathy and dysferlinopathy showed a higher degree of muscle fiber atrophy. Males with calpainopathy and dysferlinopathy showed significantly higher fiber atrophy than control males, whereas female patients have similar values than female controls, suggesting a gender difference in muscle fiber atrophy with a relative protection in females. In female patients, the smaller initial muscle fiber size associated to endocrine factors and less physical effort might attenuate gender-specific muscle loss and atrophy.

  14. Treatment efficacy of eyelid twitch muscle transposition surgery in senile entropion%下睑缩肌转位术治疗老年性下睑内翻的疗效

    Institute of Scientific and Technical Information of China (English)

    黄瑞尧; 李万鹏; 蒋克非; 向小芳; 黄靓

    2015-01-01

    AlM:To explore treatment efficacy of the lower eyelid twitch muscle transposition surgery in senile entropion.METHODS:Fifty cases (86 eyes) of senile lower eyelid entropion patients underwent lower eyelid twitch muscle transposition correction surgery as the experimental group, and the other 42 cases (68 eyes) of senile lower eyelid entropion patients received orbicularis muscle shortening correction as controls group. The correction rate, double eyelid symmetry and overcorrection rate of patients were observed one week after surgery. The patients were followed up for 6~12mo to be observed the long-term recurrence rate, double eyelid symmetry and overcorrection rate.RESULTS: One week after operation, eyelid symmetry, overcorrection rate of experimental group and control group had significant difference (P<0. 05); After followed up for 6 ~12mo, eyelid symmetry, overcorrection rate of experimental group and control group had significant difference (P<0. 05). CONCLUSlON: Folding and orbicularis muscle shortening treatment of senile entropion was compared with the lower eyelid twitch muscle transposition surgery treatment of senile entropion, We can find that clinical results in double eyelid surgery symmetry and overcorrection rate are of obvious advantage.%目的::探讨下睑缩肌转位术治疗老年性下睑内翻的临床效果。方法:对50例86眼老年性下睑内翻患者采用下睑缩肌转位术矫正作为试验组,另42例68眼老年性下睑内翻患者采用眼轮匝肌折叠缩短术矫正作为对照组,观察术后1 wk患者的矫正率、双眼睑对称性、过矫率;并随访6~12mo,观察远期复发率、双眼睑对称性、过矫率。结果:术后1 wk双眼睑对称性、过矫率试验组与对照组差异有统计学意义(P<0.05);随访6~12mo,双眼睑对称性、过矫率试验组与对照组差异有统计学意义(P<0.05)。结论:与眼轮匝肌折叠缩短术治疗老年性下睑内翻相比,下睑缩肌转位术治

  15. Impact of weightlessness on muscle function

    Science.gov (United States)

    Tischler, M. E.; Slentz, M.

    1995-01-01

    The most studied skeletal muscles which depend on gravity, "antigravity" muscles, are located in the posterior portion of the legs. Antigravity muscles are characterized generally by a different fiber type composition than those which are considered nonpostural. The gravity-dependent function of the antigravity muscles makes them particularly sensitive to weightlessness (unweighting) resulting in a substantial loss of muscle protein, with a relatively greater loss of myofibrillar (structural) proteins. Accordingly alpha-actin mRNA decreases in muscle of rats exposed to microgravity. In the legs, the soleus seems particularly responsive to the lack of weight-bearing associated with space flight. The loss of muscle protein leads to a decreased cross-sectional area of muscle fibers, particularly of the slow-twitch, oxidative (SO) ones compared to fast-twitch glycolytic (FG) or oxidative-glycolytic (FOG) fibers. In some muscles, a shift in fiber composition from SO to FOG has been reported in the adaptation to spaceflight. Changes in muscle composition with spaceflight have been associated with decreased maximal isometric tension (Po) and increased maximal shortening velocity. In terms of fuel metabolism, results varied depending on the pathway considered. Glucose uptake, in the presence of insulin, and activities of glycolytic enzymes are increased by space flight. In contrast, oxidation of fatty acids may be diminished. Oxidation of pyruvate, activity of the citric acid cycle, and ketone metabolism in muscle seem to be unaffected by microgravity.

  16. Impact of weightlessness on muscle function

    Science.gov (United States)

    Tischler, M. E.; Slentz, M.

    1995-01-01

    The most studied skeletal muscles which depend on gravity, "antigravity" muscles, are located in the posterior portion of the legs. Antigravity muscles are characterized generally by a different fiber type composition than those which are considered nonpostural. The gravity-dependent function of the antigravity muscles makes them particularly sensitive to weightlessness (unweighting) resulting in a substantial loss of muscle protein, with a relatively greater loss of myofibrillar (structural) proteins. Accordingly alpha-actin mRNA decreases in muscle of rats exposed to microgravity. In the legs, the soleus seems particularly responsive to the lack of weight-bearing associated with space flight. The loss of muscle protein leads to a decreased cross-sectional area of muscle fibers, particularly of the slow-twitch, oxidative (SO) ones compared to fast-twitch glycolytic (FG) or oxidative-glycolytic (FOG) fibers. In some muscles, a shift in fiber composition from SO to FOG has been reported in the adaptation to spaceflight. Changes in muscle composition with spaceflight have been associated with decreased maximal isometric tension (Po) and increased maximal shortening velocity. In terms of fuel metabolism, results varied depending on the pathway considered. Glucose uptake, in the presence of insulin, and activities of glycolytic enzymes are increased by space flight. In contrast, oxidation of fatty acids may be diminished. Oxidation of pyruvate, activity of the citric acid cycle, and ketone metabolism in muscle seem to be unaffected by microgravity.

  17. An Overview of Laryngeal Muscle Single Fiber Electromyography.

    Science.gov (United States)

    Bertorini, Tulio E; Sharaf, Aboubakar G

    2015-08-01

    Needle electromyography is an important tool in the diagnosis of neuromuscular diseases and has also been applied successfully in the evaluation of the vocal cord paralysis. Laryngeal electromyography, initially described by Weddell, is used to determine the cause of vocal cord paralysis and to differentiate organic from nonorganic causes of speech disorders. This test allows the diagnosis of lower motor neuron and nerve paralysis as well as myopathies. Laryngeal electromyography also helps to determine the prognosis of paralysis caused by traumatic injury of the laryngeal nerves and is used for guidance during botulinum toxin injection in spasmodic dysphonias. Single fiber electromyography is used to diagnose abnormalities of neuromuscular transmission and is applied in the study the architecture of the motor unit in muscles. This article reviews the techniques of laryngeal muscles single fiber electromyography, provides limited informative data, and discusses its potential value in the evaluation of patients with dysphonia.

  18. Effect of one stretch a week applied to the immobilized soleus muscle on rat muscle fiber morphology

    Directory of Open Access Journals (Sweden)

    Gomes A.R.S.

    2004-01-01

    Full Text Available We determined the effect of stretching applied once a week to the soleus muscle immobilized in the shortened position on muscle fiber morphology. Twenty-six male Wistar rats weighing 269 ± 26 g were divided into three groups. Group I, the left soleus was immobilized in the shortened position for 3 weeks; group II, the soleus was immobilized in the shortened position and stretched once a week for 3 weeks; group III, the soleus was submitted only to stretching once a week for 3 weeks. The medial part of the soleus muscle was frozen for histology and muscle fiber area evaluation and the lateral part was used for the determination of number and length of serial sarcomeres. Soleus muscle submitted only to immobilization showed a reduction in weight (44 ± 6%, P = 0.002, in serial sarcomere number (23 ± 15% and in cross-sectional area of the fibers (37 ± 31%, P < 0.001 compared to the contralateral muscles. The muscle that was immobilized and stretched showed less muscle fiber atrophy than the muscles only immobilized (P < 0.05. Surprisingly, in the muscles submitted only to stretching, fiber area was decreased compared to the contralateral muscle (2548 ± 659 vs 2961 ± 806 µm², respectively, P < 0.05. In conclusion, stretching applied once a week for 40 min to the soleus muscle immobilized in the shortened position was not sufficient to prevent the reduction of muscle weight and of serial sarcomere number, but provided significant protection against muscle fiber atrophy. In contrast, stretching normal muscles once a week caused a reduction in muscle fiber area.

  19. Average but not continuous speed match between motoneurons and muscle units of rat tibialis anterior.

    Science.gov (United States)

    Bakels, R; Kernell, D

    1993-10-01

    1. Properties of single motoneuron/muscle-unit combinations were determined for tibialis anterior (TA) in rats anesthetized with pentobarbital. The TA observations were systematically compared with those obtained earlier by the use of the same techniques from rat medial gastrocnemius (MG). 2. TA motoneurons were investigated with regard to afterhyperpolarization (AHP; total duration 32-74 ms, amplitude 0.39-4.96 mV) and axonal conduction velocity (41-79 m/s). TA muscle-unit measurements included the time course of the isometric twitch (time-to-peak force 10.8-18.0 ms; total duration 42-92 ms), the maximum tetanic force (22-217 mN), and a measure of fatigue sensitivity (fatigue index 5-100%). The range of twitch and AHP durations ("speed range") was markedly smaller in the present TA material than for MG. 3. The mean duration of the TA motoneuronal AHP (49 +/- 8 ms, mean +/- SD) was close to that of its muscle-unit twitch (56 +/- 12 ms). Thus an "average" speed match existed between TA motoneurons and their muscle fibers. 4. For TA there was no correlation between the time courses of AHP and twitch. Thus there was for TA no "continuous" speed match between the motoneurons and their muscle fibers. 5. For TA twitches or AHPs studied separately, there was a significant correlation between different time course measures. Furthermore, compared with TA units having relatively fast twitches, those with slower twitches tended to show 1) a smaller maximum tetanic force and 2) a greater AHP amplitude. Fatigue-resistant units tended to have slower twitches than fatigue-sensitive ones.(ABSTRACT TRUNCATED AT 250 WORDS)

  20. Inhibition of platelet-derived growth factor signaling prevents muscle fiber growth during skeletal muscle hypertrophy.

    Science.gov (United States)

    Sugg, Kristoffer B; Korn, Michael A; Sarver, Dylan C; Markworth, James F; Mendias, Christopher L

    2017-03-01

    The platelet-derived growth factor receptors alpha and beta (PDGFRα and PDGFRβ) mark fibroadipogenic progenitor cells/fibroblasts and pericytes in skeletal muscle, respectively. While the role that these cells play in muscle growth and development has been evaluated, it was not known whether the PDGF receptors activate signaling pathways that control transcriptional and functional changes during skeletal muscle hypertrophy. To evaluate this, we inhibited PDGFR signaling in mice subjected to a synergist ablation muscle growth procedure, and performed analyses 3 and 10 days after induction of hypertrophy. The results from this study indicate that PDGF signaling is required for fiber hypertrophy, extracellular matrix production, and angiogenesis that occur during muscle growth. © 2017 Federation of European Biochemical Societies.

  1. Comparisons of different muscle metabolic enzymes and muscle fiber types in Jinhua and Landrace pigs.

    Science.gov (United States)

    Guo, J; Shan, T; Wu, T; Zhu, L N; Ren, Y; An, S; Wang, Y

    2011-01-01

    Western and indigenous Chinese pig breeds show obvious differences in muscle growth and meat quality, however, the underlying molecular mechanism remains unclear. The main objective of this study was to evaluate the breed-specific mechanisms controlling meat quality and postmortem muscle metabolism. The specific purpose was to investigate the variations in meat quality, muscle fiber type, and enzyme activity between local Jinhua and exotic Landrace pigs at the same age (180 d of age), as well as the same BW of 64 kg, respectively. We compared differentially expressed muscle fiber types such as types I and IIa (oxidative), type IIb (glycolytic), as well as type IIx (intermediate) fibers in LM and soleus muscles of Jinhua and Landrace pigs using real-time reverse-transcription PCR. Furthermore, the metabolic enzyme activities of lactate dehydrogenase, as well as succinic dehydrogenase and malate dehydrogenase, were used as markers of glycolytic and oxidative capacities, respectively. Results showed that Jinhua pigs exhibited greater intramuscular fat content and less drip loss compared with the Landrace (P Landrace (P Landrace (P Landrace pigs. These results may provide valuable information for understanding the molecular mechanism responsible for breed specific differences in growth performance and meat quality.

  2. Ultrastructure of striated muscle fibers in the middle third of the human esophagus

    OpenAIRE

    Faussone-Pellegrini, M.S; Cortesini, C.

    1986-01-01

    Striated muscle fibers and .their spatial relationship to smooth muscle cells have been studied in the middle third of human esophagus. Biopsies were obtained from 3 patients during surgery. In both the circular and longitudinal layers, the muscle coat of this transition zone was composed of fascicles of uniform dimensioi~ (100-200 pm of diameter); some of these bundles were made up of striated muscle fibers, others were pure bundles of smooth muscle cells and ...

  3. Dexmedetomidine controls twitch-convulsive syndrome in the course of uremic encephalopathy.

    Science.gov (United States)

    Nomoto, Koichi; Scurlock, Corey; Bronster, David

    2011-12-01

    An 85 year old man with a history of chronic renal insufficiency was admitted to the cardiothoracic intensive care unit after aortic valve replacement. His postoperative course was marked by acute oliguric renal failure for high blood urea nitrogen (BUN) and acute hyperactive delirium. At this time he also developed tremors with muscle twitching; he received no other form of sedatives. A neurology consult made the diagnosis of twitch-convulsive syndrome associated with uremic encephalopathy. While the patient was receiving the dexmedetomidine infusion, the signs of the twitch-convulsive syndrome, particularly the twitching and tremors, disappeared. Within 30 minutes of the end of the dexmedetomidine infusion, symptoms of the twitch-convulsive syndrome returned, manifesting as acute tremulousness. After several dialysis treatments, his BUN decreased and the dexmedetomidine was weaned, without return of the symptoms of twitch-convulsive syndrome. Published by Elsevier Inc.

  4. Fluctuations in tension during contraction of single muscle fibers.

    Science.gov (United States)

    Borejdo, J; Morales, M F

    1977-12-01

    We have searched for fluctuations in the steady-state tension developed by stimulated single muscle fibers. Such tension "noise" is expected to be present as a result of the statistical fluctuations in the number and/or state of myosin cross-bridges interacting with thin filament sites at any time. A sensitive electro-optical tension transducer capable of resolving the expected fluctuations in magnitude and frequency was constructed to search for the fluctuations. The noise was analyzed by computing the power spectra and amplitude of stochastic fluctuations in the photomultiplier counting rate, which was made proportional to muscle force. The optical system and electronic instrumentation together with the minicomputer software are described. Tensions were measured in single skinned glycerinated rabbit psoas muscle fibers in rigor and during contraction and relaxation. The results indicate the presence of fluctuations in contracting muscles and a complete absence of tension noise in eith rigor or relaxation. Also, a numerical method was developed to simulate the power spectra and amplitude of fluctuations, given the rate constants for association and dissociation of the cross-bridges and actin. The simulated power spectra and the frequency distributions observed experimentally are similar.

  5. Influence of exercise contraction mode and protein supplementation on human skeletal muscle satellite cell content and muscle fiber growth

    DEFF Research Database (Denmark)

    Farup, Jean; Rahbek, Stine Klejs; Riis, Simon

    2014-01-01

    -specific association between emergence of satellite cells (SCs), muscle growth, and remodeling in response to 12 wk unilateral resistance training performed as eccentric (Ecc) or concentric (Conc) resistance training ± whey protein (Whey, 19.5 g protein + 19.5 g glucose) or placebo (Placebo, 39 g glucose......Skeletal muscle satellite cells (SCs) are involved in remodeling and hypertrophy processes of skeletal muscle. However, little knowledge exists on extrinsic factors that influence the content of SCs in skeletal muscle. In a comparative human study, we investigated the muscle fiber type......) supplementation. Muscle biopsies (vastus lateralis) were analyzed for fiber type-specific SCs, myonuclei, and fiber cross-sectional area (CSA). Following training, SCs increased with Conc in both type I and type II fibers (P

  6. The α2Na+/K+-ATPase is critical for skeletal and heart muscle function in zebrafish

    DEFF Research Database (Denmark)

    Doganli, Canan; Kjaer-Sørensen, Kasper; Knoeckel, Christopher

    2012-01-01

    +/K+-ATPase associated with striated muscles and that α2Na+/K+-ATPase knockdown causes a significant depolarization of the resting membrane potential in slow-twitch fibers of skeletal muscles. Abrupt mechanosensory responses were observed in α2Na+/K+-ATPase deficient embryos, possibly linked to a postsynaptic defect...

  7. Fiber type effects on contraction-stimulated glucose uptake and GLUT4 abundance in single fibers from rat skeletal muscle.

    Science.gov (United States)

    Castorena, Carlos M; Arias, Edward B; Sharma, Naveen; Bogan, Jonathan S; Cartee, Gregory D

    2015-02-01

    To fully understand skeletal muscle at the cellular level, it is essential to evaluate single muscle fibers. Accordingly, the major goals of this study were to determine if there are fiber type-related differences in single fibers from rat skeletal muscle for: 1) contraction-stimulated glucose uptake and/or 2) the abundance of GLUT4 and other metabolically relevant proteins. Paired epitrochlearis muscles isolated from Wistar rats were either electrically stimulated to contract (E-Stim) or remained resting (No E-Stim). Single fibers isolated from muscles incubated with 2-deoxy-d-[(3)H]glucose (2-DG) were used to determine fiber type [myosin heavy chain (MHC) isoform protein expression], 2-DG uptake, and abundance of metabolically relevant proteins, including the GLUT4 glucose transporter. E-Stim, relative to No E-Stim, fibers had greater (P GLUT4, tethering protein containing a UBX domain for GLUT4 (TUG), cytochrome c oxidase IV (COX IV), and filamin C protein levels were significantly greater (P GLUT4 levels for MHC-IIax fibers exceeded MHC-IIxb fibers. GLUT4, COX IV, filamin C, and TUG abundance in single fibers was significantly (P GLUT4 abundance among the fiber types were not accompanied by significant differences in contraction-stimulated glucose uptake.

  8. Effects of Endurance Training on A12 Acetyl Cholinesterase Activity in Fast and Slow-Twitch Skeletal Muscles of Male Wistar Rats

    Directory of Open Access Journals (Sweden)

    Ali Gorzi

    2013-10-01

    Full Text Available Background: Endurance training improves the activity of G4 type acetylcholine esterase (AchE in muscle fibres. The purpose of this study was to investigate the effects of 8 weeks of endurance training (ET on activity of A12 type of AchE in Flexor Hallucis Longus (FHL and Soleus (SOL muscles of rats. Materials and Methods: 16 male wistar rats (age: 10 weeks and weight: 172.17±10.080 gr, were randomly divided in 2 groups (control; N=8 and ET; N=8. Training group carried out 8 weeks (5 session/week of endurance training on animal treadmill with speed of 10 m/min for 30 min at the first week which was gradually increased to 30 m/min for 60 min (70-80% of VO2max at the last week. Forty eight hours after last session of training, FHL and Sol muscles of animals were moved out under sterilized situation by cutting on posterio-lateral side of hind limb. For separating AchE subunits, homogenization and electrophoresis (0.06 non-denaturaing polyacrilamide methods were used. AchE activity was measured by Elisa kit.Results: The activity of this protein significantly (p=0.017 increased in SOL muscle of ET group by 119%, but did not changed in FHL. In both groups (ET and Con, FHL muscle had significantly (ET: p=0.028 and Con p=0.01 higher basic levels of AchE activity compared to SOL muscle. This significant increase in AchE of SOL might be indicative of responsiveness of AchE of this muscle following endurance training for improving acetylcholine (Ach cycle in neuromuscular junction.Conclusion: Endurance training might increase the A12 type AchE activity to improve the Ach cycle as part of the adaptation of neuromuscular junction to increased level of physical activity.

  9. Evidence for ACTN3 as a Speed Gene in Isolated Human Muscle Fibers.

    Directory of Open Access Journals (Sweden)

    Siacia Broos

    Full Text Available To examine the effect of α-actinin-3 deficiency due to homozygosity for the ACTN3 577X-allele on contractile and morphological properties of fast muscle fibers in non-athletic young men.A biopsy was taken from the vastus lateralis of 4 RR and 4 XX individuals to test for differences in morphologic and contractile properties of single muscle fibers. The cross-sectional area of the fiber and muscle fiber composition was determined using standard immunohistochemistry analyses. Skinned single muscle fibers were subjected to active tests to determine peak normalized force (P0, maximal unloading velocity (V0 and peak power. A passive stretch test was performed to calculate Young's Modulus and hysteresis to assess fiber visco-elasticity.No differences were found in muscle fiber composition. The cross-sectional area of type IIa and IIx fibers was larger in RR compared to XX individuals (P<0.001. P0 was similar in both groups over all fiber types. A higher V0 was observed in type IIa fibers of RR genotypes (P<0.001 but not in type I fibers. The visco-elasticity as determined by Young's Modulus and hysteresis was unaffected by fiber type or genotype.The greater V0 and the larger fast fiber CSA in RR compared to XX genotypes likely contribute to enhanced whole muscle performance during high velocity contractions.

  10. Striated muscle fiber size, composition and capillary density in diabetes in relation to neuropathy and muscle strength

    DEFF Research Database (Denmark)

    Andreassen, Christer Swan; Jensen, Jacob Malte; Jakobsen, Johannes

    2014-01-01

    study was to evaluate histologic properties and capillarization of diabetic skeletal muscle in relation to DPN and muscle strength. METHODS: Twenty type 1 and 20 type 2 diabetic (T1D and T2D, respectively) patients underwent biopsy of the gastrocnemic muscle, isokinetic dynamometry at the ankle......, electrophysiological studies, clinical examination, and quantitative sensory examinations. Muscle biopsies were stained immunohistochemically and muscle fiber diameter, fiber type distribution, and capillary density determined. Twenty control subjects were also included in the study. RESULTS: No relationship was found...

  11. Effects of a myosin-II inhibitor (N-benzyl-p-toluene sulphonamide, BTS) on contractile characteristics of intact fast-twitch mammalian muscle fibres.

    Science.gov (United States)

    Pinniger, G J; Bruton, J D; Westerblad, H; Ranatunga, K W

    2005-01-01

    We have examined the effects of N-benzyl-p-toluene sulphonamide (BTS), a potent and specific inhibitor of fast muscle myosin-II, using small bundles of intact fibres or single fibres from rat foot muscle. BTS decreased tetanic tension reversibly in a concentration-dependent manner with half-maximal inhibition at approximately approximately 2 microM at 20 degrees C. The inhibition of tension with 10 microM BTS was marked at the three temperatures examined (10, 20 and 30 degrees C), but greatest at 10 degrees C. BTS decreased active muscle stiffness to a lesser extent than tetanic tension indicating that not all of the tension inhibition was due to a reduced number of attached cross-bridges. BTS-induced inhibition of active tension was not accompanied by any change in the free myoplasmic Ca2+ transients. The potency and specificity of BTS make it a very suitable myosin inhibitor for intact mammalian fast muscle and should be a useful tool for the examination of outstanding questions in muscle contraction.

  12. The growth allometrically Mandalung and histological muscle fiber leg

    Directory of Open Access Journals (Sweden)

    Meisji Liana Sari

    2003-12-01

    Full Text Available This study was conducted to compare the growth alometrically performance especially rate of muscle growth microscopically of Mandalung offspring of Muscovy x Duck (MD and Duck x Muscovy (DM. Fifty-one Mandalung duck of IE and EI were used. They were fed with 2-type broiler commercial feed, which were starter type (day 1 – week 4 and finisher type (week 4 – week 12. Starter feed contained of 20% protein and 2800 kcal/kg energy while finisher feed contained of 18% protein and 3000 kcal/kg energy. Data on weights of slaughtered body and body parts (head, neck, fore back, rear back, breast, upper leg, lower leg, foot and its membrane were measured at week 1, 4, 8 and 12. Diameter of muscle fiber was measured at age 8, 10 and 12 weeks, and each slaughter was represented by 1, 2 and 3 ducks. The results showed The growth direction was similar in IE and EI, initiated from head, to the neck, fore back and rear back, and from foot, to the thigh, breast and wings. Diameter of muscle fibers of Mandalung duck offspring of EI were larger (14,49 vs 13,37; 20,02 vs. 15, 24 μm; 23,68 vs. 18, 08 μm than the IE.

  13. A comparative study of the membrane structure in different types of muscle fibers in the frog.

    Science.gov (United States)

    Verma, V

    1984-09-01

    The muscle membrane of slow and fast fibers in cruralis and iliofibularis muscles and of intermediate fibers in submaxillaris muscle of the frog is studied in freeze-fracture replicas. A comparison of membrane folds, number, size and distribution of caveolae and of intramembrane particles (IMP) is given. In slow muscle fibers, the membrane folds are systematically present at the level of the I zone with a transversal continuity, whereas in fast and intermediate types the membrane folds are small and are randomly distributed. In slow muscle the caveolae are more numerous at the I zone than in the part corresponding to the center of the sarcomere. In fast muscle, small groups of caveolae form linear patterns, and in intermediate fibers the distribution is random. The number of caveolae in slow muscle fibers is two times more than in fast and intermediate fibers. The mean area of caveolae opening is largest in fast and smallest in slow muscle fibers. The number of IMP is significantly different in the three types of fibers, being highest in slow and lowest in intermediate fibers. The different pattern of folds in slow fibers may correspond to the different contractile properties of this fiber type. The presence of double the number of caveolae in slow fibers correlated to the less elaborate T system in this fiber type shows the possibility that slow fibers may be the result of an arrest during development for the performance of a different function. The difference in IMP density in the three muscle fiber types may be interpreted as the difference in their electrical properties.

  14. How muscle fiber lengths and velocities affect muscle force generation as humans walk and run at different speeds.

    Science.gov (United States)

    Arnold, Edith M; Hamner, Samuel R; Seth, Ajay; Millard, Matthew; Delp, Scott L

    2013-06-01

    The lengths and velocities of muscle fibers have a dramatic effect on muscle force generation. It is unknown, however, whether the lengths and velocities of lower limb muscle fibers substantially affect the ability of muscles to generate force during walking and running. We examined this issue by developing simulations of muscle-tendon dynamics to calculate the lengths and velocities of muscle fibers from electromyographic recordings of 11 lower limb muscles and kinematic measurements of the hip, knee and ankle made as five subjects walked at speeds of 1.0-1.75 m s(-1) and ran at speeds of 2.0-5.0 m s(-1). We analyzed the simulated fiber lengths, fiber velocities and forces to evaluate the influence of force-length and force-velocity properties on force generation at different walking and running speeds. The simulations revealed that force generation ability (i.e. the force generated per unit of activation) of eight of the 11 muscles was significantly affected by walking or running speed. Soleus force generation ability decreased with increasing walking speed, but the transition from walking to running increased the force generation ability by reducing fiber velocities. Our results demonstrate the influence of soleus muscle architecture on the walk-to-run transition and the effects of muscle-tendon compliance on the plantarflexors' ability to generate ankle moment and power. The study presents data that permit lower limb muscles to be studied in unprecedented detail by relating muscle fiber dynamics and force generation to the mechanical demands of walking and running.

  15. Skeletal muscle fiber characteristics and oxidative capacity in hemiparetic stroke survivors

    DEFF Research Database (Denmark)

    Severinsen, Kaare; Dalgas, Ulrik; Overgaard, Kristian

    2016-01-01

    INTRODUCTION: Skeletal muscle is changed after stroke, but conflicting data exist concerning muscle morphology and oxidative enzymatic capacity. METHODS: In 36 chronic stroke patients bilateral muscle biopsies were analysed, and fiber type proportions and cross sectional areas were determined...... capacity (r=0.47, P=0.01). DISCUSSION: In stroke survivors there is a phenotypic shift towards more fatigable muscle fibers with reduced oxidative enzymatic capacity that relates to clinical outcomes. This article is protected by copyright. All rights reserved....

  16. The mechanism of spontaneous oscillatory contractions in skeletal muscle.

    Science.gov (United States)

    Smith, D A; Stephenson, D G

    2009-05-06

    Most striated muscles generate steady contractile tension when activated, but some preparations, notably cardiac myocytes and slow-twitch fibers, may show spontaneous oscillatory contractions (SPOC) at low levels of activation. We have provided what we believe is new evidence that SPOC is a property of the contractile system at low actin-myosin affinity, whether caused by a thin-filament regulatory system or by other means. We present a quantitative single-sarcomere model for isotonic SPOC in skeletal muscle with three basic ingredients: i), actin and myosin filaments initially in partial overlap, ii), stretch activation by length-dependent changes in the lattice spacing, and iii), viscoelastic passive tension. Modeling examples are given for slow-twitch and fast-twitch fibers, with periods of 10 s and 4 s respectively. Isotonic SPOC occurs in a narrow domain of parameter values, with small minimum and maximum values for actin-myosin affinity, a minimum amount of passive tension, and a maximum transient response rate that explains why SPOC is favored in slow-twitch fibers. The model also predicts the contractile, relaxed and SPOC phases as a function of phosphate and ADP levels. The single-sarcomere model can also be applied to a whole fiber under auxotonic and fixed-end conditions if the remaining sarcomeres are treated as a viscoelastic load. Here the model predicts an upper limit for the load stiffness that leads to SPOC; this limit lies above the equivalent loads expected from the rest of the fiber.

  17. Reduced muscle fiber force production and disrupted myofibril architecture in patients with chronic rotator cuff tears.

    Science.gov (United States)

    Mendias, Christopher L; Roche, Stuart M; Harning, Julie A; Davis, Max E; Lynch, Evan B; Sibilsky Enselman, Elizabeth R; Jacobson, Jon A; Claflin, Dennis R; Calve, Sarah; Bedi, Asheesh

    2015-01-01

    A persistent atrophy of muscle fibers and an accumulation of fat, collectively referred to as fatty degeneration, commonly occur in patients with chronic rotator cuff tears. The etiology of fatty degeneration and function of the residual rotator cuff musculature have not been well characterized in humans. We hypothesized that muscles from patients with chronic rotator cuff tears have reduced muscle fiber force production, disordered myofibrils, and an accumulation of fat vacuoles. The contractility of muscle fibers from biopsy specimens of supraspinatus muscles of 13 patients with chronic full-thickness posterosuperior rotator cuff tears was measured and compared with data from healthy vastus lateralis muscle fibers. Correlations between muscle fiber contractility, American Shoulder and Elbow Surgeons (ASES) scores, and tear size were analyzed. Histology and electron microscopy were also performed. Torn supraspinatus muscles had a 30% reduction in maximum isometric force production and a 29% reduction in normalized force compared with controls. Normalized supraspinatus fiber force positively correlated with ASES score and negatively correlated with tear size. Disordered sarcomeres were noted, along with an accumulation of lipid-laden macrophages in the extracellular matrix surrounding supraspinatus muscle fibers. Patients with chronic supraspinatus tears have significant reductions in muscle fiber force production. Force production also correlates with ASES scores and tear size. The structural and functional muscle dysfunction of the residual muscle fibers is independent of the additional area taken up by fibrotic tissue. This work may help establish future therapies to restore muscle function after the repair of chronically torn rotator cuff muscles. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  18. Constant Fiber Number During Skeletal Muscle Atrophy and Modified Arachidonate Metabolism During Hypertrophy

    Science.gov (United States)

    Templeton, G.

    1985-01-01

    A previously documented shift from Type I to IIA predominance of the soleus muscle during rat suspension was further investigated to determine if this shift was by selective reduction of a single fiber type, simultaneous reduction and formation of fibers with different fiber types, or a transformation of fiber type by individual fibers. By partial acid digestion and dissection, average total soleus fiber number was found to be 3022 + or - 80 (SE) and 3008 + or - 64 before and after four-week suspension (n=12). Another area of current research was based on previous studies which indicate that prostaglandins are biosynthesized by skeletal muscle and evoke protein synthesis and degradation.

  19. Constant Fiber Number During Skeletal Muscle Atrophy and Modified Arachidonate Metabolism During Hypertrophy

    Science.gov (United States)

    Templeton, G.

    1985-01-01

    A previously documented shift from Type I to IIA predominance of the soleus muscle during rat suspension was further investigated to determine if this shift was by selective reduction of a single fiber type, simultaneous reduction and formation of fibers with different fiber types, or a transformation of fiber type by individual fibers. By partial acid digestion and dissection, average total soleus fiber number was found to be 3022 + or - 80 (SE) and 3008 + or - 64 before and after four-week suspension (n=12). Another area of current research was based on previous studies which indicate that prostaglandins are biosynthesized by skeletal muscle and evoke protein synthesis and degradation.

  20. Hindlimb immobilization - Length-tension and contractile properties of skeletal muscle

    Science.gov (United States)

    Witzmann, F. A.; Kim, D. H.; Fitts, R. H.

    1982-01-01

    Casts were placed around rat feet in plantar flexion position to immobilize the soleus muscle in a shortened position, while the other foot was fixed in dorsal flexion to set the extensor digitorum longus in a shortened position. The total muscular atrophy and contractile properties were measured at 1, 2, 4, 7, 14, 21, 28, 35, and 42 days after immobilization, with casts being replaced every two weeks. The slow twitch soleus and the fast-twitch vastus lateralis and longus muscles were excised after termination of the experiment. The muscles were then stretched and subjected to electric shock to elicit peak tetanic tension and peak tetanic tension development. Force velocity features of the three muscles were assayed in a series of afterloaded contractions and fiber lengths were measured from subsequently macerated muscle. All muscles atrophied during immobilization, reaching a new steady state by day 21. Decreases in fiber and sarcomere lengths were also observed.

  1. Distinct muscle apoptotic pathways are activated in muscles with different fiber types a rat model of critical illness myopathy

    OpenAIRE

    Barnes, Benjamin T.; Confides, Amy L.; Rich, Mark M.; Dupont-Versteegden, Esther E.

    2015-01-01

    Critical illness myopathy (CIM) is associated with severe muscle atrophy and fatigue in affected patients. Apoptotic signaling is involved in atrophy and is elevated in muscles from patients with CIM. In this study we investigated underlying mechanisms of apoptosis-related pathways in muscles with different fiber type composition in a rat model of CIM using denervation and glucocorticoid administration (denervation and steroid-induced myopathy, DSIM). Soleus and tibialis anterior (TA) muscles...

  2. Fiber-type composition of the human jaw muscles--(part 2) role of hybrid fibers and factors responsible for inter-individual variation.

    Science.gov (United States)

    Korfage, J A M; Koolstra, J H; Langenbach, G E J; van Eijden, T M G J

    2005-09-01

    This is the second of two articles about fiber-type composition of the human jaw muscles. It reviews the functional relationship of hybrid fibers and the adaptive properties of jaw-muscle fibers. In addition, to explain inter-individual variation in fiber-type composition, we discuss these adaptive properties in relation to environmental stimuli or perturbations. The fiber-type composition of the human jaw muscles is very different from that of limb and trunk muscles. Apart from the presence of the usual type I, IIA, and IIX myosin heavy-chains (MyHC), human jaw-muscle fibers contain MyHCs that are typical for developing or cardiac muscle. In addition, much more frequently than in limb and trunk muscles, jaw-muscle fibers are hybrid, i.e., they contain more than one type of MyHC isoform. Since these fibers have contractile properties that differ from those of pure fibers, this relatively large quantity of hybrid fibers provides a mechanism that produces a very fine gradation of force and movement. The presence of hybrid fibers might also reflect the adaptive capacity of jaw-muscle fibers. The capacity for adaptation also explains the observed large inter-individual variability in fiber-type composition. Besides local influences, like the amount of muscle activation and/or stretch, more general influences, like aging and gender, also play a role in the composition of fiber types.

  3. Human muscle fiber type-specific insulin signaling: impact of obesity and type 2 diabetes.

    Science.gov (United States)

    Albers, Peter H; Pedersen, Andreas J T; Birk, Jesper B; Kristensen, Dorte E; Vind, Birgitte F; Baba, Otto; Nøhr, Jane; Højlund, Kurt; Wojtaszewski, Jørgen F P

    2015-02-01

    Skeletal muscle is a heterogeneous tissue composed of different fiber types. Studies suggest that insulin-mediated glucose metabolism is different between muscle fiber types. We hypothesized that differences are due to fiber type-specific expression/regulation of insulin signaling elements and/or metabolic enzymes. Pools of type I and II fibers were prepared from biopsies of the vastus lateralis muscles from lean, obese, and type 2 diabetic subjects before and after a hyperinsulinemic-euglycemic clamp. Type I fibers compared with type II fibers have higher protein levels of the insulin receptor, GLUT4, hexokinase II, glycogen synthase (GS), and pyruvate dehydrogenase-E1α (PDH-E1α) and a lower protein content of Akt2, TBC1 domain family member 4 (TBC1D4), and TBC1D1. In type I fibers compared with type II fibers, the phosphorylation response to insulin was similar (TBC1D4, TBC1D1, and GS) or decreased (Akt and PDH-E1α). Phosphorylation responses to insulin adjusted for protein level were not different between fiber types. Independently of fiber type, insulin signaling was similar (TBC1D1, GS, and PDH-E1α) or decreased (Akt and TBC1D4) in muscle from patients with type 2 diabetes compared with lean and obese subjects. We conclude that human type I muscle fibers compared with type II fibers have a higher glucose-handling capacity but a similar sensitivity for phosphoregulation by insulin.

  4. Changes in antioxidant enzymes and lipid peroxidation in extensor digitorum longus muscles of streptozotocin-diabetic rats may contribute to muscle atrophy.

    Science.gov (United States)

    Nonaka, Koji; Une, S; Tatsuta, N; Ito, K; Akiyama, J

    2014-12-01

    We investigated muscle atrophy, major antioxidant enzymes and lipid peroxidation in the extensor digitorum longus (EDL, predominantly fast fibers) and soleus (predominantly slow fibers) muscle of streptozotocin-diabetic rats. Female Wistar rats were divided into a control (n = 5) and streptozotocin-induced diabetic group (n = 5). Eight weeks after diabetes induction the EDL and soleus muscles were removed and catalase (CAT), glutathione peroxidase (GPX) and superoxide dismutase activity (SOD), and thiobarbituric acid reactive substances (TBARS) levels measured. The CAT activity increased in both the EDL and soleus muscles of the diabetic rats (p muscle (p muscle of the diabetic rats (p muscles showed significant atrophy but the EDL muscle elicited the greatest atrophy. In conclusion, it appears that adaptive responses to oxidative stress were adequate in the soleus muscle, but not in the EDL muscle, of diabetic rats. Thus fast twitch muscle fibers may be more susceptible to oxidative stress than slow twitch muscle fibers and this may contribute to muscle atrophy under diabetic conditions.

  5. Muscle-specific integrins in masseter muscle fibers of chimpanzees: an immunohistochemical study.

    Directory of Open Access Journals (Sweden)

    Gianluigi Vaccarino

    2010-05-01

    Full Text Available Most notably, recent comparative genomic analyses strongly indicate that the marked differences between modern human and chimpanzees are likely due more to changes in gene regulation than to modifications of the genes. The most peculiar aspect of hominoid karyotypes is that human have 46 chromosomes whereas gorillas and chimpanzees have 48. Interestingly, human and chimpanzees do share identical inversions on chromosome 7 and 9 that are not evident in the gorilla karyotype. Thus, the general phylogeny suggests that humans and chimpanzees are sister taxa; based on this, it seems that human-chimpanzee sequence similarity is an astonishing 99%. At this purpose, of particular interest is the inactivation of the myosin heavy chain 16 (MYH16 gene, most prominently expressed in the masticatory muscle of mammals. It has been showed that the loss of this gene in humans may have resulted in smaller masticatory muscle and consequential changes to cranio-facial morphology and expansion of the human brain case. Powerful masticatory muscles are found in most primates; contrarily, in both modern and fossil member Homo, these muscles are considerably smaller. The evolving hominid masticatory apparatus shifted towards a pattern of gracilization nearly simultaneously with accelerated encephalization in early Homo. To better comprehend the real role of the MYH16 gene, we studied the primary proteins present in the muscle fibers of humans and non-humans, in order to understand if they really can be influenced by MYH16 gene. At this aim we examined the muscle-specific integrins, alpha 7B and beta 1D-integrins, and their relative fetal isoforms, alpha 7A and beta 1A-integrins, analyzing, by immunohistochemistry, muscle biopsies of two components of a chimpanzee's group in captivity, an alpha male and a non-alpha male subjects; all these integrins participate in vital biological processes such as maintenance of tissue integrity, embryonic development, cell

  6. The single nucleotide polymorphism Gly482Ser in the PGC-1α gene impairs exercise-induced slow-twitch muscle fibre transformation in humans.

    Directory of Open Access Journals (Sweden)

    Peter Steinbacher

    Full Text Available PGC-1α (peroxisome proliferator-activated receptor γ co-activator 1α is an important regulator of mitochondrial biogenesis and a master regulator of enzymes involved in oxidative phosphorylation. Recent evidence demonstrated that the Gly482Ser single nucleotide polymorphism (SNP in the PGC-1α gene affects insulin sensitivity, blood lipid metabolism and binding to myocyte enhancer factor 2 (MEF2. Individuals carrying this SNP were shown to have a reduced cardiorespiratory fitness and a higher risk to develop type 2 diabetes. Here, we investigated the responses of untrained men with the Gly482Ser SNP to a 10 week programme of endurance training (cycling, 3 x 60 min/week, heart rate at 70-90% VO2peak. Quantitative data from analysis of biopsies from vastus lateralis muscle revealed that the SNP group, in contrast to the control group, lacked a training-induced increase in content of slow contracting oxidative fibres. Capillary supply, mitochondrial density, mitochondrial enzyme activities and intramyocellular lipid content increased similarly in both groups. These results indicate that the impaired binding of MEF2 to PGC-1α in humans with this SNP impedes exercise-induced fast-to-slow muscle fibre transformation.

  7. The single nucleotide polymorphism Gly482Ser in the PGC-1α gene impairs exercise-induced slow-twitch muscle fibre transformation in humans.

    Science.gov (United States)

    Steinbacher, Peter; Feichtinger, René G; Kedenko, Lyudmyla; Kedenko, Igor; Reinhardt, Sandra; Schönauer, Anna-Lena; Leitner, Isabella; Sänger, Alexandra M; Stoiber, Walter; Kofler, Barbara; Förster, Holger; Paulweber, Bernhard; Ring-Dimitriou, Susanne

    2015-01-01

    PGC-1α (peroxisome proliferator-activated receptor γ co-activator 1α) is an important regulator of mitochondrial biogenesis and a master regulator of enzymes involved in oxidative phosphorylation. Recent evidence demonstrated that the Gly482Ser single nucleotide polymorphism (SNP) in the PGC-1α gene affects insulin sensitivity, blood lipid metabolism and binding to myocyte enhancer factor 2 (MEF2). Individuals carrying this SNP were shown to have a reduced cardiorespiratory fitness and a higher risk to develop type 2 diabetes. Here, we investigated the responses of untrained men with the Gly482Ser SNP to a 10 week programme of endurance training (cycling, 3 x 60 min/week, heart rate at 70-90% VO2peak). Quantitative data from analysis of biopsies from vastus lateralis muscle revealed that the SNP group, in contrast to the control group, lacked a training-induced increase in content of slow contracting oxidative fibres. Capillary supply, mitochondrial density, mitochondrial enzyme activities and intramyocellular lipid content increased similarly in both groups. These results indicate that the impaired binding of MEF2 to PGC-1α in humans with this SNP impedes exercise-induced fast-to-slow muscle fibre transformation.

  8. Electrophysiological characteristics of motor units and muscle fibers in trained and untrained young male subjects

    DEFF Research Database (Denmark)

    Duez, Lene; Qerama, Erisela; Fuglsang-Frederiksen, Anders

    2010-01-01

    We hypothesized that the amplitudes of compound muscle action potentials (CMAPs) and interference pattern analysis (IPA) would be larger in trained subjects compared with untrained subjects, possibly due to hypertrophy of muscle fibers and/or increased central drive. Moreover, we hypothesized...... and untrained subjects in IPA power spectrum and turns per second or amplitude of the CMAPs obtained by DMS. Muscle fiber hypertrophy and/or altered central drive may account for our results, but there was no indication of changes in muscle fiber excitability. Muscle Nerve, 2010....... that the untrained muscle is less excitable compared with the trained muscle. An electromyographic (EMG) needle electrode was used to record the IPA at maximal voluntary effort. The CMAP was obtained by stimulating the musculocutaneous nerve and recording the brachial biceps muscle using surface electrodes. CMAPs...

  9. Evidence for ACTN3 as a Speed Gene in Isolated Human Muscle Fibers.

    Science.gov (United States)

    Broos, Siacia; Malisoux, Laurent; Theisen, Daniel; van Thienen, Ruud; Ramaekers, Monique; Jamart, Cécile; Deldicque, Louise; Thomis, Martine A; Francaux, Marc

    2016-01-01

    To examine the effect of α-actinin-3 deficiency due to homozygosity for the ACTN3 577X-allele on contractile and morphological properties of fast muscle fibers in non-athletic young men. A biopsy was taken from the vastus lateralis of 4 RR and 4 XX individuals to test for differences in morphologic and contractile properties of single muscle fibers. The cross-sectional area of the fiber and muscle fiber composition was determined using standard immunohistochemistry analyses. Skinned single muscle fibers were subjected to active tests to determine peak normalized force (P0), maximal unloading velocity (V0) and peak power. A passive stretch test was performed to calculate Young's Modulus and hysteresis to assess fiber visco-elasticity. No differences were found in muscle fiber composition. The cross-sectional area of type IIa and IIx fibers was larger in RR compared to XX individuals (PYoung's Modulus and hysteresis was unaffected by fiber type or genotype. The greater V0 and the larger fast fiber CSA in RR compared to XX genotypes likely contribute to enhanced whole muscle performance during high velocity contractions.

  10. Connectin filaments in stretched skinned fibers of frog skeletal muscle

    Science.gov (United States)

    1984-01-01

    Indirect immunofluorescence microscopy of highly stretched skinned frog semi-tendinous muscle fibers revealed that connectin, an elastic protein of muscle, is located in the gap between actin and myosin filaments and also in the region of myosin filaments except in their centers. Electron microscopic observations showed that there were easily recognizable filaments extending from the myosin filaments to the I band region and to Z lines in the myofibrils treated with antiserum against connectin. In thin sections prepared with tannic acid, very thin filaments connected myosin filaments to actin filaments. These filaments were also observed in myofibrils extracted with a modified Hasselbach-Schneider solution (0.6 M KCl, 0.1 M phosphate buffer, pH 6.5, 2 mM ATP, 2 mM MgCl2, and 1 mM EGTA) and with 0.6 M Kl. SDS PAGE revealed that connectin (also called titin) remained in extracted myofibrils. We suggest that connectin filaments play an important role in the generation of tension upon passive stretch. A scheme of the cytoskeletal structure of myofibrils of vertebrate skeletal muscle is presented on the basis of our present information of connectin and intermediate filaments. PMID:6384237

  11. Fiber-type differences in masseter muscle associated with different facial morphologies

    Science.gov (United States)

    Rowlerson, Anthea; Raoul, Gwénaël; Daniel, Yousif; Close, John; Maurage, Claude-Alain; Ferri, Joel; Sciote, James J.

    2013-01-01

    Background The influence of muscle forces and associated physiologic behaviors on dental and skeletal development is well recognized but difficult to quantify because of the limited understanding of the interrelationships between physiologic and other mechanisms during growth. Methods The purpose of this study was to characterize fiber-type composition of masseter muscle in 44 subjects during surgical correction of malocclusion. Four fiber types were identified after immunostaining of biopsy sections with myosin heavy chain-specific antibodies, and the average fiber diameter and percentage of muscle occupancy of the fiber types were determined in each of 6 subject groups (Class II or Class III and open bite, normal bite, or deepbite). A 2 × 3 × 4 analysis of variance was used to determine significant differences between mean areas for fiber types, vertical relationships, and sagittal relationships. Results There were significant differences in percentage of occupancy of fiber types in masseter muscle in bite groups with different vertical dimensions. Type I fiber occupancy increased in open bites, and conversely, type II fiber occupancy increased in deepbites. The association between sagittal jaw relationships and mean fiber area was less strong, but, in the Class III group, the average fiber area was significantly different between the open bite, normal bite, and deepbite subjects. In the Class III subjects, type I and I/II hybrid fiber areas were greatly increased in subjects with deepbite. Conclusions Given the variation between subjects in fiber areas and fiber numbers, larger subject populations will be needed to demonstrate more significant associations between sagittal relationships and muscle composition. However, the robust influence of jaw-closing muscles on vertical dimension allowed us to conclude that vertical bite characteristics vary according to the fiber type composition of masseter muscle. PMID:15643413

  12. [Comparison of force and shortening velocity in fast and slow rabbit muscle fibers at different temperatures].

    Science.gov (United States)

    Kochubeĭ, P V; Bershitskiĭ, S Iu

    2014-01-01

    The temperature dependence of force, maximal shortening velocity and power of maximally activated single permeabilized fibers from fast and slow muscles of the rabbit were recorded in a temperature range from 10 to 35 degrees C with 5 degrees C step. It was found that temperature dependence of force of both types of fibers is identical. Averaged maximal shortening velocity in the slow fibers, unlike the fast fibers, had no statistically significant temperature dependence that is not in agreement with the data obtained on intact rat muscle fibers and in an in vitro motility assay. However maximal shortening velocity in each individual slow fiber did depend on temperature. The temperature dependence of power of the slow fibers was lower than that of the fast ones. Because of large data scattering the average temperature dependence of power of the slow fibers was significantly lower than that in individual slow fibers.

  13. Mapping of intramuscular tenderness and muscle fiber orientation of muscles in the beef round.

    Science.gov (United States)

    Senaratne, L S; Calkins, C R; de Mello, A S; Pokharel, S; Hinkle, J B

    2010-09-01

    Intramuscular tenderness variation and muscle fiber orientation of beef M. adductor femoris (AF), M. biceps femoris (BF), M. gracilis (GL), M. pectineus (PT), M. sartorius (SR), M. semimembranosus (SM), M. semitendinosus (SO), M. vastus intermedius (VI), M. vastus medialis (VM), and M. vastus lateralis (VL) were investigated. The USDA Choice boxed beef subprimals were purchased and aged for 14 d from boxed date. The AF, BF, GL, PT, SR, SM, SO, VI, VM, and VL (n = 10 each) were fabricated from subprimals. Crust-frozen AF, BF, SO, SM, and VL were cut into 2.54-cm steaks perpendicular to the long axis and grilled (71 degrees C). The PT, SR, VI, and VM were grilled (71 degrees C) as whole muscles, whereas the GL was grilled after cutting into anterior and posterior regions. Grilled muscles were cut into equal size sections perpendicular to long axis of muscles. Location-specific cores were prepared from each steak/section, and Warner-Bratzler shear force (WBSF) was measured. The muscle fiber orientations of BF, PT, and VI were bipennate, SR and SO were fusiform, and AD, SM, VL, GL, and VM were unipennate. The overall mean WBSF values for BF, SO, AF, SM, PT, SR, GL, VI, VM, and VL were 5.62, 4.86, 4.18, 4.90, 3.76, 4.44, 4.75, 4.78, 4.24, and 6.53 kg, respectively. Based on WBSF values, PT was tender, BF and VL were tough, and VM, VI, SM, GL SR, AF, and SO were intermediate. The first 2 proximal steaks of long head BF were more tender than the rest (P Dry or moist heat oven roasting, as compared with grilling, significantly tenderized SO (P = 0.002) and VL (P beef round.

  14. Effect of endurance training on glucose transport capacity and glucose transporter expression in rat skeletal muscle

    Energy Technology Data Exchange (ETDEWEB)

    Ploug, T.; Stallknecht, B.M.; Pedersen, O.; Kahn, B.B.; Ohkuwa, T.; Vinten, J.; Galbo, H. (Panum Institute, Copenhagen (Denmark))

    1990-12-01

    The effect of 10 wk endurance swim training on 3-O-methylglucose (3-MG) uptake (at 40 mM 3-MG) in skeletal muscle was studied in the perfused rat hindquarter. Training resulted in an increase of approximately 33% for maximum insulin-stimulated 3-MG transport in fast-twitch red fibers and an increase of approximately 33% for contraction-stimulated transport in slow-twitch red fibers compared with nonexercised sedentary muscle. A fully additive effect of insulin and contractions was observed both in trained and untrained muscle. Compared with transport in control rats subjected to an almost exhaustive single exercise session the day before experiment both maximum insulin- and contraction-stimulated transport rates were increased in all muscle types in trained rats. Accordingly, the increased glucose transport capacity in trained muscle was not due to a residual effect of the last training session. Half-times for reversal of contraction-induced glucose transport were similar in trained and untrained muscles. The concentrations of mRNA for GLUT-1 (the erythrocyte-brain-Hep G2 glucose transporter) and GLUT-4 (the adipocyte-muscle glucose transporter) were increased approximately twofold by training in fast-twitch red muscle fibers. In parallel to this, Western blot demonstrated a approximately 47% increase in GLUT-1 protein and a approximately 31% increase in GLUT-4 protein. This indicates that the increases in maximum velocity for 3-MG transport in trained muscle is due to an increased number of glucose transporters.

  15. Hyperspectral deep ultraviolet autofluorescence of muscle fibers is affected by postmortem changes.

    Science.gov (United States)

    Chagnot, Caroline; Vénien, Annie; Jamme, Frédéric; Réfrégiers, Matthieu; Desvaux, Mickaël; Astruc, Thierry

    2015-05-20

    After slaughter, muscle cells undergo biochemical and physicochemical changes that may affect their autofluorescence characteristics. The autofluorescent response of different rat extensor digitorum longus (EDL) and soleus muscle fiber types was investigated by deep ultraviolet (UV) synchrotron microspectroscopy immediately after animal sacrifice and after 24 h of storage in a moist chamber at 20 °C. The glycogen content decreased from 23 to 18 μmol/g of fresh muscle in 24 h postmortem. Following a 275 nm excitation wavelength, the spectral muscle fiber autofluorescence response showed discrimination depending upon postmortem time (t0 versus t24 h) on both muscles at 346 and 302 nm and, to a lesser extent, at 408 and 325 nm. Taken individually, all fiber types were discriminated but with variable accuracy, with type IIA showing better separation of t0/t24 h than other fiber types. These results suggest the usefulness of the autofluorescent response of muscle cells for rapid meat-aging characterization.

  16. Human muscle fiber type-specific insulin signaling: Impact of obesity and type 2 diabetes

    DEFF Research Database (Denmark)

    Albers, Peter Hjorth; Pedersen, Andreas J T; Birk, Jesper Bratz

    2015-01-01

    /or metabolic enzymes. Pools of type I and II fibers were prepared from biopsies of the vastus lateralis muscles from lean, obese and type 2 diabetic subjects before and after a hyperinsulinemic-euglycemic clamp. Type I fibers compared to type II fibers have higher protein levels of the insulin receptor, GLUT4......-responses to insulin adjusted for protein level were not different between fiber types. Independently of fiber type, insulin signaling was similar (TBC1D1, GS and PDH-E1α) or decreased (Akt and TBC1D4) in muscle from patients with type 2 diabetes compared to lean and obese subjects. We conclude that human type I...

  17. Equations for estimating muscle fiber stress in the left ventricular wall.

    Science.gov (United States)

    Rabben, S I; Irgens, F; Angelsen, B

    1999-01-01

    Left ventricular muscle fiber stress is an important parameter in cardiac energetics. Hence, we developed equations for estimating regional fiber stresses in rotationally symmetric chambers, and equatorial and apical fiber stresses in prolate spheroidal chambers. The myocardium was modeled as a soft incompressible material embedding muscle fibers that support forces only in their longitudinal direction. A thin layer of muscle fibers then contributes with a pressure increment determined by the fiber stress and curvature. The fiber curvature depends on the orientation of the fibers, which varies continuously across the wall. However, by assuming rotational symmetry about the long axis of the ventricle and including a longitudinal force balance, we obtained equations where fiber stress is completely determined by the principal curvatures of the middle wall surface, wall thickness, and cavity pressure. The equations were validated against idealized prolate spheroidal chambers, whose wall thicknesses are such that the fiber stress is uniform from the equator to the apex. Because the apex is free to rotate, the resultant moment about the long axis of the LV must be zero. By using this constraint together with our fiber-stress equations, we were able to estimate a muscle fiber orientation distribution across the wall that was in qualitative agreement with published measurements.

  18. Direct evidence of fiber type-dependent GLUT-4 expression in human skeletal muscle

    DEFF Research Database (Denmark)

    Gaster, M; Poulsen, P; Handberg, A

    2000-01-01

    GLUT-4 expression in individual fibers of human skeletal muscles in younger and older adults was studied. Furthermore, the dependency of insulin-stimulated glucose uptake on fiber type distribution was investigated. Fiber type distribution was determined in cryosections of muscle biopsies from 8...... younger (29 yr) and 8 older (64 yr) healthy subjects, and estimates of GLUT-4 expression in individual fibers were obtained by combining immunohistochemistry and stereology. GLUT-4 was more abundantly expressed in slow compared with fast muscle fibers in both younger (P ...) subjects. A 25% reduction of GLUT-4 density in fast fibers (P GLUT-4 density in slow fibers were demonstrated in older compared with younger subjects. Insulin-stimulated glucose uptake rates measured by hyperinsulinemic, euglycemic clamp were not correlated with the fraction...

  19. Ablation of Protein Kinase CK2β in Skeletal Muscle Fibers Interferes with Their Oxidative Capacity

    Directory of Open Access Journals (Sweden)

    Nane Eiber

    2017-01-01

    Full Text Available The tetrameric protein kinase CK2 was identified playing a role at neuromuscular junctions by studying CK2β-deficient muscle fibers in mice, and in cultured immortalized C2C12 muscle cells after individual knockdown of CK2α and CK2β subunits. In muscle cells, CK2 activity appeared to be at least required for regular aggregation of nicotinic acetylcholine receptors, which serves as a hallmark for the presence of a postsynaptic apparatus. Here, we set out to determine whether any other feature accompanies CK2β-deficient muscle fibers. Hind limb muscles gastrocnemius, plantaris, and soleus of adult wildtype and CK2β-deficient mice were dissected, cross-sectioned, and stained histochemically by Gomori trichrome and for nicotinamide adenine dinucleotide (NADH dehydrogenase and succinate dehydrogenase (SDH enzymatic activities. A reduction of oxidative enzymatic activity was determined for CK2β-deficient muscle fibers in comparison with wildtype controls. Importantly, the CK2β-deficient fibers, muscle fibers that typically exhibit high NADH dehydrogenase and SDH activities, like slow-type fibers, showed a marked reduction in these activities. Altogether, our data indicate additional impairments in the absence of CK2β in skeletal muscle fibers, pointing to an eventual mitochondrial myopathy.

  20. Fiber type composition and maximum shortening velocity of muscles crossing the human shoulder.

    Science.gov (United States)

    Srinivasan, R C; Lungren, M P; Langenderfer, J E; Hughes, R E

    2007-03-01

    A study of the fiber type composition of fourteen muscles spanning the human glenohumeral joint was carried out with the purpose of determining the contribution of fiber types to overall muscle cross-sectional area (CSA) and to estimate the maximum shortening velocity (V(max)) of those muscles. Muscle biopsies were procured from 4 male cadavers (mean age 50) within 24 hr of death, snap frozen, mounted, and transversely sectioned (10 microm). Slides were stained for myofibrillar ATPase after alkaline preincubation. Photoimages were taken of defined areas (100 fibers) using the Bioquant system, and fiber type and CSA were measured from these images. Staining for mATPase produced three different fiber types: slow-oxidative (SO), fast-oxidative-glycolytic (FOG), and fast-glycolytic (FG). On average, the muscle fiber type composition ranged from 22 to 40% of FG, from 17 to 51% of FOG, and from 23 to 56% of SO. Twelve out of the 14 muscles had average SO proportions ranging from 35 to 50%. V(max) was calculated from the fiber type contribution relative to CSA and shortening velocity values taken from the literature. The maximum velocities of shortening presented here provide a physiological basis for the development of human shoulder musculoskeletal models suitable for predicting muscle forces for functionally relevant tasks encompassing conditions of muscle shortening and lengthening.

  1. Persistent muscle fiber regeneration in long term denervation. Past, present, future

    Directory of Open Access Journals (Sweden)

    Ugo Carraro

    2015-03-01

    Full Text Available Despite the ravages of long term denervation there is structural and ultrastructural evidence for survival of muscle fibers in mammals, with some fibers surviving at least ten months in rodents and 3-6 years in humans. Further, in rodents there is evidence that muscle fibers may regenerate even after repeated damage in the absence of the nerve, and that this potential is maintained for several months after denervation. While in animal models permanently denervated muscle sooner or later loses the ability to contract, the muscles may maintain their size and ability to function if electrically stimulated soon after denervation. Whether in mammals, humans included, this is a result of persistent de novo formation of muscle fibers is an open issue we would like to explore in this review. During the past decade, we have studied muscle biopsies from the quadriceps muscle of Spinal Cord Injury (SCI patients suffering with Conus and Cauda Equina syndrome, a condition that fully and irreversibly disconnects skeletal muscle fibers from their damaged innervating motor neurons. We have demonstrated that human denervated muscle fibers survive years of denervation and can be rescued from severe atrophy by home-based Functional Electrical Stimulation (h-bFES. Using immunohistochemistry with both non-stimulated and the h-bFES stimulated human muscle biopsies, we have observed the persistent presence of muscle fibers which are positive to labeling by an antibody which specifically recognizes the embryonic myosin heavy chain (MHCemb. Relative to the total number of fibers present, only a small percentage of these MHCemb positive fibers are detected, suggesting that they are regenerating muscle fibers and not pre-existing myofibers re-expressing embryonic isoforms. Although embryonic isoforms of acetylcholine receptors are known to be re-expressed and to spread from the end-plate to the sarcolemma of muscle fibers in early phases of muscle denervation, we suggest

  2. Influence of muscle fiber type composition on early fat accumulation under high-fat diet challenge.

    Science.gov (United States)

    Hua, Ning; Takahashi, Hirokazu; Yee, Grace M; Kitajima, Yoichiro; Katagiri, Sayaka; Kojima, Motoyasu; Anzai, Keizo; Eguchi, Yuichiro; Hamilton, James A

    2017-01-01

    To investigate whether differences in muscle fiber types affect early-stage fat accumulation, under high fat diet challenge in mice. Twelve healthy male C57BL/6 mice experienced with short-term (6 weeks) diet treatment for the evaluation of early pattern changes in muscular fat. The mice were randomly divided into two groups: high fat diet (n = 8) and normal control diet (n = 4). Extra- and intra-myocellular lipid (EMCL and IMCL) in lumbar muscles (type I fiber predominant) and tibialis anterior (TA) muscle (type II fiber predominant) were determined using magnetic resonance spectroscopy (MRS). Correlation of EMCL, IMCL and their ratio between TA and lumbar muscles was evaluated. EMCL increased greatly in both muscle types after high fat diet. IMCL in TA and lumbar muscles increased to a much lower extent, with a slightly greater increase in TA muscles. EMCLs in the 2 muscles were positively correlated (r = 0.84, p = 0.01), but IMCLs showed a negative relationship (r = -0.84, p = 0.01). In lumbar muscles, high fat diet significantly decreased type I fiber while it increased type II fiber (all p≤0.001). In TA muscle, there was no significant fiber type shifting (p>0.05). Under short-time high fat diet challenge, lipid tends to initially accumulate extra-cellularly. In addition, compared to type II dominant muscle, Type I dominant muscle was less susceptible to IMCL accumulation but more to fiber type shifting. These phenomena might reflect compensative responses of skeletal muscle to dietary lipid overload in order to regulate metabolic homeostasis.

  3. Effects of aging on muscle mechanical function and muscle fiber morphology during short-term immobilization and subsequent retraining

    DEFF Research Database (Denmark)

    Hvid, Lars; Aagaard, Per; Justesen, Lene;

    2010-01-01

    Very little attention has been given to the combined effects of aging and disuse as separate factors causing deterioration in muscle mechanical function. Thus the purpose of this study was to investigate the effects of 2 wk of immobilization followed by 4 wk of retraining on knee extensor muscle...... to the deleterious effects of short-term muscle disuse on muscle fiber size and rapid force capacity than YM. Furthermore, OM seems to require longer time to recover and regain rapid muscle force capacity, which may lead to a larger risk of falling in aged individuals after periods of short-term disuse....

  4. Function of longitudinal vs circular muscle fibers in esophageal peristalsis, deduced with mathematical modeling

    Institute of Scientific and Technical Information of China (English)

    James G Brasseur; Mark A Nicosia; Anupam Pal; Larr S Miller

    2007-01-01

    We summarize from previous works the functions of circular vs. longitudinal muscle in esophageal peristaltic bolus transport using a mix of experimental data, the conservation laws of mechanics and mathematical modeling. Whereas circular muscle tone generates radial closure pressure to create a local peristaltic closure wave, longitudinal muscle tone has two functions, one physiological with mechanical implications, and one purely mechanical. Each of these functions independently reduces the tension of individual circular muscle fibers to maintain closure as a consequence of shortening of longitudinal muscle locally coordinated with increasing circular muscle tone. The physiological function is deduced by combining basic laws of mechanics with concurrent measurements of intraluminal pressure from manometry, and changes in cross sectional muscle area from endoluminal ultrasound from which local longitudinal shortening (LLS) can be accurately obtained. The purely mechanical function of LLS was discovered from mathematical modeling of peristaltic esophageal transport with the axial wall motion generated by LLS. Physiologically, LLS concentrates circular muscle fibers where closure pressure is highest.However, the mechanical function of LLS is to reduce the level of pressure required to maintain closure. The combined physiological and mechanical consequences of LLS are to reduce circular muscle fiber tension and power by as much as 1/10 what would be required for peristalsis without the longitudinal muscle layer, a tremendous benefit that may explain the existence of longitudinal muscle fiber in the gut. We also review what is understood of the role of longitudinal muscle in esophageal emptying, reflux and pathology.

  5. Epaxial muscle fiber architecture favors enhanced excursion and power in the leaper Galago senegalensis.

    Science.gov (United States)

    Huq, Emranul; Wall, Christine E; Taylor, Andrea B

    2015-10-01

    Galago senegalensis is a habitual arboreal leaper that engages in rapid spinal extension during push-off. Large muscle excursions and high contraction velocities are important components of leaping, and experimental studies indicate that during leaping by G. senegalensis, peak power is facilitated by elastic storage of energy. To date, however, little is known about the functional relationship between epaxial muscle fiber architecture and locomotion in leaping primates. Here, fiber architecture of select epaxial muscles is compared between G. senegalensis (n = 4) and the slow arboreal quadruped, Nycticebus coucang (n = 4). The hypothesis is tested that G. senegalensis exhibits architectural features of the epaxial muscles that facilitate rapid and powerful spinal extension during the take-off phase of leaping. As predicted, G. senegalensis epaxial muscles have relatively longer, less pinnate fibers and higher ratios of tendon length-to-fiber length, indicating the capacity for generating relatively larger muscle excursions, higher whole-muscle contraction velocities, and a greater capacity for elastic energy storage. Thus, the relatively longer fibers and higher tendon length-to-fiber length ratios can be functionally linked to leaping performance in G. senegalensis. It is further predicted that G. senegalensis epaxial muscles have relatively smaller physiological cross-sectional areas (PCSAs) as a consequence of an architectural trade-off between fiber length (excursion) and PCSA (force). Contrary to this prediction, there are no species differences in relative PCSAs, but the smaller-bodied G. senegalensis trends towards relatively larger epaxial muscle mass. These findings suggest that relative increase in muscle mass in G. senegalensis is largely attributable to longer fibers. The relative increase in erector spinae muscle mass may facilitate sagittal flexibility during leaping. The similarity between species in relative PCSAs provides empirical support for

  6. Microintegrating smooth muscle cells into a biodegradable, elastomeric fiber matrix.

    Science.gov (United States)

    Stankus, John J; Guan, Jianjun; Fujimoto, Kazuro; Wagner, William R

    2006-02-01

    Electrospinning permits fabrication of biodegradable elastomers into matrices that can resemble the scale and mechanical behavior of the native extracellular matrix. However, achieving high-cellular density and infiltration with this technique remains challenging and time consuming. We have overcome this limitation by electrospraying vascular smooth muscle cells (SMCs) concurrently with electrospinning a biodegradable, elastomeric poly(ester urethane)urea (PEUU). Trypan blue staining revealed no significant decrease in cell viability from the fabrication process and electrosprayed SMCs spread and proliferated similar to control unprocessed SMCs. The resulting SMC microintegrated PEUU constructs were cultured under static conditions or transmural perfusion. Higher cell numbers resulted with perfusion culture with 131% and 98% more viable cells versus static culture at days 4 and 7 (pfibers after perfusion culture. SMC microintegrated PEUU was strong, flexible and anisotropic with tensile strengths ranging from 2.0 to 6.5 MPa and breaking strains from 850 to 1,700% dependent on the material axis. The ability to microintegrate smooth muscle or other cell types into a biodegradable elastomer fiber matrix embodies a novel tissue engineering approach that could be applied to fabricate high cell density elastic tissue mimetics, blood vessels or other cardiovascular tissues.

  7. Effect of passive stretching on the immobilized soleus muscle fiber morphology

    Directory of Open Access Journals (Sweden)

    Coutinho E.L.

    2004-01-01

    Full Text Available The aim of the present study was to determine the effect of stretching applied every 3 days to the soleus muscle immobilized in the shortened position on muscle fiber morphology. Eighteen 16-week-old Wistar rats were used and divided into three groups of 6 animals each: a the left soleus muscle was immobilized in the shortened position for 3 weeks; b during immobilization, the soleus was stretched for 40 min every 3 days; c the non-immobilized soleus was only stretched. Left and right soleus muscles were examined. One portion of the soleus was frozen for histology and muscle fiber area evaluation, while the other portion was used to identify the number and length of serial sarcomeres. Immobilized muscles (group A showed a significant decrease in weight (44 ± 6%, length (19 ± 7%, serial sarcomere number (23 ± 15%, and fiber area (37 ± 31% compared to the contralateral muscles (P < 0.05, paired Student t-test. The immobilized and stretched soleus (group B showed a similar reduction but milder muscle fiber atrophy compared to the only immobilized group (22 ± 40 vs 37 ± 31%, respectively; P < 0.001, ANOVA test. Muscles submitted only to stretching (group C significantly increased the length (5 ± 2%, serial sarcomere number (4 ± 4%, and fiber area (16 ± 44% compared to the contralateral muscles (P < 0.05, paired Student t-test. In conclusion, stretching applied every 3 days to immobilized muscles did not prevent the muscle shortening, but reduced muscle atrophy. Stretching sessions induced hypertrophic effects in the control muscles. These results support the use of muscle stretching in sports and rehabilitation.

  8. Effects of aging on muscle mechanical function and muscle fiber morphology during short-term immobilization and subsequent retraining

    DEFF Research Database (Denmark)

    Hvid, Lars; Aagaard, Per; Justesen, Lene

    2010-01-01

    (i.e., rate of force development, impulse) than YM (∼ 20-37 vs. ∼ 13-16%; P ... mechanical function (e.g., maximal strength and rapid force capacity) and muscle fiber morphology in 9 old (OM: 67.3 ± 1.3 yr) and 11 young healthy men (YM: 24.4 ± 0.5 yr) with comparable levels of physical activity. Following immobilization, OM demonstrated markedly larger decreases in rapid force capacity...... function and muscle fiber area in YM, whereas OM showed an attenuated recovery in muscle fiber area and rapid force capacity (tendency). Changes in maximal isometric and dynamic muscle strength were similar between OM and YM. In conclusion, the present data reveal that OM may be more susceptible...

  9. Is fast fiber innervation responsible for increased acetylcholinesterase activity in reinnervating soleus muscles?

    Science.gov (United States)

    Misulis, K. E.; Dettbarn, W. D.

    1985-01-01

    An investigation was conducted as to whether the predominantly slow SOL, which is low in AChE activity, is initially reinnervated by axons that originally innervated fast muscle fibers with high AChE activity, such as those of the EDL. Local denervation of the SOL in the guinea pig was performed because this muscle is composed solely of slow (type I) fibers; thereby virtually eliminating the possibility of homologous muscle fast fiber innervation. The overshoot in this preparation was qualitatively similar to that seen with distal denervation in the guinea pig and local and distal denervation in the rat. Thus, initial fast fiber innvervation is not responsible for the patterns of change in AChE activity seen with reinnervation in the SOL. It is concluded that the neural control of AChe is different in these two muscles and may reflect specific differences in the characteristics of AChE regulation in fast and slow muscle.

  10. Novel locomotor muscle design in extreme deep-diving whales.

    Science.gov (United States)

    Velten, B P; Dillaman, R M; Kinsey, S T; McLellan, W A; Pabst, D A

    2013-05-15

    Most marine mammals are hypothesized to routinely dive within their aerobic dive limit (ADL). Mammals that regularly perform deep, long-duration dives have locomotor muscles with elevated myoglobin concentrations that are composed of predominantly large, slow-twitch (Type I) fibers with low mitochondrial volume densities (V(mt)). These features contribute to extending ADL by increasing oxygen stores and decreasing metabolic rate. Recent tagging studies, however, have challenged the view that two groups of extreme deep-diving cetaceans dive within their ADLs. Beaked whales (including Ziphius cavirostris and Mesoplodon densirostris) routinely perform the deepest and longest average dives of any air-breathing vertebrate, and short-finned pilot whales (Globicephala macrorhynchus) perform high-speed sprints at depth. We investigated the locomotor muscle morphology and estimated total body oxygen stores of several species within these two groups of cetaceans to determine whether they (1) shared muscle design features with other deep divers and (2) performed dives within their calculated ADLs. Muscle of both cetaceans displayed high myoglobin concentrations and large fibers, as predicted, but novel fiber profiles for diving mammals. Beaked whales possessed a sprinter's fiber-type profile, composed of ~80% fast-twitch (Type II) fibers with low V(mt). Approximately one-third of the muscle fibers of short-finned pilot whales were slow-twitch, oxidative, glycolytic fibers, a rare fiber type for any mammal. The muscle morphology of beaked whales likely decreases the energetic cost of diving, while that of short-finned pilot whales supports high activity events. Calculated ADLs indicate that, at low metabolic rates, both beaked and short-finned pilot whales carry sufficient onboard oxygen to aerobically support their dives.

  11. Single skinned muscle fibers in Duchenne muscular dystrophy generate normal force.

    Science.gov (United States)

    Horowits, R; Dalakas, M C; Podolsky, R J

    1990-06-01

    We measured the intrinsic mechanical properties and protein content of single skinned muscle fibers obtained from patients who had Duchenne muscular dystrophy. To check for possible nonspecific changes caused by muscle disease per se, we also studied the properties of muscle fibers obtained from patients exhibiting severe muscle weakness due to polymyositis. Relative to control fibers obtained from 4 patients with normal or nonmyopathic muscle, we found no significant changes in the ability of muscle fibers from the patients with Duchenne muscular dystrophy or polymyositis to generate active tension in response to calcium or resting tension in response to stretch. In addition, we found no significant changes in the concentrations of the major contractile proteins myosin and actin, of the elastic protein titin, or of the structural proteins nebulin and alpha-actinin. In contrast, immunocytochemical studies showed that dystrophin was absent in the biopsy specimens from the patients with Duchenne muscular dystrophy, but localized at the cell membrane in all of the other muscle biopsy specimens used in this study. These results indicate that myofibrils assemble and function normally in Duchenne muscular dystrophy. Therefore, the absence of dystrophin, which is the primary biochemical defect in this disease, leads to clinical weakness by causing the breakdown of muscle fibers that were once capable of generating normal force, while the surviving fibers exhibit normal contractility.

  12. Rotator cuff tear reduces muscle fiber specific force production and induces macrophage accumulation and autophagy.

    Science.gov (United States)

    Gumucio, Jonathan P; Davis, Max E; Bradley, Joshua R; Stafford, Patrick L; Schiffman, Corey J; Lynch, Evan B; Claflin, Dennis R; Bedi, Asheesh; Mendias, Christopher L

    2012-12-01

    Full-thickness tears to the rotator cuff can cause severe pain and disability. Untreated tears progress in size and are associated with muscle atrophy and an infiltration of fat to the area, a condition known as "fatty degeneration." To improve the treatment of rotator cuff tears, a greater understanding of the changes in the contractile properties of muscle fibers and the molecular regulation of fatty degeneration is essential. Using a rat model of rotator cuff injury, we measured the force generating capacity of individual muscle fibers and determined changes in muscle fiber type distribution that develop after a full thickness rotator cuff tear. We also measured the expression of mRNA and miRNA transcripts involved in muscle atrophy, lipid accumulation, and matrix synthesis. We hypothesized that a decrease in specific force of rotator cuff muscle fibers, an accumulation of type IIb fibers, and an upregulation in fibrogenic, adipogenic, and inflammatory gene expression occur in torn rotator cuff muscles. Thirty days following rotator cuff tear, we observed a reduction in muscle fiber force production, an induction of fibrogenic, adipogenic, and autophagocytic mRNA and miRNA molecules, and a dramatic accumulation of macrophages in areas of fat accumulation. Copyright © 2012 Orthopaedic Research Society.

  13. Distinct muscle apoptotic pathways are activated in muscles with different fiber types a rat model of critical illness myopathy

    Science.gov (United States)

    Barnes, Benjamin T.; Confides, Amy L.; Rich, Mark M.; Dupont-Versteegden, Esther E.

    2015-01-01

    Critical illness myopathy (CIM) is associated with severe muscle atrophy and fatigue in affected patients. Apoptotic signaling is involved in atrophy and is elevated in muscles from patients with CIM. In this study we investigated underlying mechanisms of apoptosis-related pathways in muscles with different fiber type composition in a rat model of CIM using denervation and glucocorticoid administration (denervation and steroid-induced myopathy, DSIM). Soleus and tibialis anterior (TA) muscles showed severe muscle atrophy (40–60% of control muscle weight) and significant apoptosis in interstitial as well as myofiber nuclei that was similar between the two muscles with DSIM. Caspase-3 and −8 activities, but not caspase-9 and −12, were elevated in TA and not in soleus muscle, while the caspase-independent proteins endonuclease G (EndoG) and apoptosis inducing factor (AIF) were not changed in abundance nor differentially localized in either muscle. Anti-apoptotic proteins HSP70, −27, and apoptosis repressor with a caspase recruitment domain (ARC) were elevated in soleus compared to TA muscle and ARC was significantly decreased with induction of DSIM in soleus. Results indicate that apoptosis is a significant process associated with DSIM in both soleus and TA muscles, and that apoptosis-associated processes are differentially regulated in muscles of different function and fiber type undergoing atrophy due to DSIM. We conclude that interventions combating apoptosis with CIM may need to be directed towards inhibiting caspase-dependent as well as -independent mechanisms to be able to affect muscles of all fiber types. PMID:25740800

  14. Distinct muscle apoptotic pathways are activated in muscles with different fiber types in a rat model of critical illness myopathy.

    Science.gov (United States)

    Barnes, Benjamin T; Confides, Amy L; Rich, Mark M; Dupont-Versteegden, Esther E

    2015-06-01

    Critical illness myopathy (CIM) is associated with severe muscle atrophy and fatigue in affected patients. Apoptotic signaling is involved in atrophy and is elevated in muscles from patients with CIM. In this study we investigated underlying mechanisms of apoptosis-related pathways in muscles with different fiber type composition in a rat model of CIM using denervation and glucocorticoid administration (denervation and steroid-induced myopathy, DSIM). Soleus and tibialis anterior (TA) muscles showed severe muscle atrophy (40-60% of control muscle weight) and significant apoptosis in interstitial as well as myofiber nuclei that was similar between the two muscles with DSIM. Caspase-3 and -8 activities, but not caspase-9 and -12, were elevated in TA and not in soleus muscle, while the caspase-independent proteins endonuclease G (EndoG) and apoptosis inducing factor (AIF) were not changed in abundance nor differentially localized in either muscle. Anti-apoptotic proteins HSP70, -27, and apoptosis repressor with a caspase recruitment domain (ARC) were elevated in soleus compared to TA muscle and ARC was significantly decreased with induction of DSIM in soleus. Results indicate that apoptosis is a significant process associated with DSIM in both soleus and TA muscles, and that apoptosis-associated processes are differentially regulated in muscles of different function and fiber type undergoing atrophy due to DSIM. We conclude that interventions combating apoptosis with CIM may need to be directed towards inhibiting caspase-dependent as well as -independent mechanisms to be able to affect muscles of all fiber types.

  15. Distribution of tropomyosin isoforms in different types of single fibers isolated from bovine skeletal muscles.

    Science.gov (United States)

    Oe, M; Ojima, K; Nakajima, I; Chikuni, K; Shibata, M; Muroya, S

    2016-08-01

    To clarify the relationship between myosin heavy chain (MyHC) isoforms and tropomyosin (TPM) isoforms in single fibers, 64 single fibers were isolated from each of bovine three muscles (masseter, semispinalis and semitendinosus). mRNA expressions of MyHC and TPM isoforms were analyzed by real-time PCR. All single fibers from the masseter expressed MyHC-slow. The fibers from the semispinalis expressed both MyHC-slow and 2a. The fibers from the semitendinosus expressed MyHC-slow, 2a and 2x. TPM-1 and TPM-2 were co-expressed in 2a and 2x type fibers, and TPM-2 and TPM-3 were co-expressed in slow type fibers. The expression pattern of TPM isoforms in each fiber type was similar between fibers isolated from different muscles. These results suggest that TPM-1 and TPM-3 isoforms correspond to the function of 2a or 2x type fibers and slow type fibers, respectively, with TPM-2 in common. Furthermore, the patterns of MyHC and TPM isoform combinations did not vary among single fibers isolated from the individual muscles examined.

  16. Denervation causes fiber atrophy and myosin heavy chain co-expression in senescent skeletal muscle.

    Directory of Open Access Journals (Sweden)

    Sharon L Rowan

    Full Text Available Although denervation has long been implicated in aging muscle, the degree to which it is causes the fiber atrophy seen in aging muscle is unknown. To address this question, we quantified motoneuron soma counts in the lumbar spinal cord using choline acetyl transferase immunhistochemistry and quantified the size of denervated versus innervated muscle fibers in the gastrocnemius muscle using the in situ expression of the denervation-specific sodium channel, Nav₁.₅, in young adult (YA and senescent (SEN rats. To gain insights into the mechanisms driving myofiber atrophy, we also examined the myofiber expression of the two primary ubiquitin ligases necessary for muscle atrophy (MAFbx, MuRF1. MN soma number in lumbar spinal cord declined 27% between YA (638±34 MNs×mm⁻¹ and SEN (469±13 MNs×mm⁻¹. Nav₁.₅ positive fibers (1548±70 μm² were 35% smaller than Nav₁.₅ negative fibers (2367±78 μm²; P<0.05 in SEN muscle, whereas Nav₁.₅ negative fibers in SEN were only 7% smaller than fibers in YA (2553±33 μm²; P<0.05 where no Nav₁.₅ labeling was seen, suggesting denervation is the primary cause of aging myofiber atrophy. Nav₁.₅ positive fibers had higher levels of MAFbx and MuRF1 (P<0.05, consistent with involvement of the proteasome proteolytic pathway in the atrophy of denervated muscle fibers in aging muscle. In summary, our study provides the first quantitative assessment of the contribution of denervation to myofiber atrophy in aging muscle, suggesting it explains the majority of the atrophy we observed. This striking result suggests a renewed focus should be placed on denervation in seeking understanding of the causes of and treatments for aging muscle atrophy.

  17. Severe insulin-resistant diabetes mellitus in patients with congenital muscle fiber type disproportion myopathy

    DEFF Research Database (Denmark)

    Vestergaard, H; Klein, H H; Hansen, T

    1995-01-01

    Congenital muscle fiber type disproportion myopathy (CFTDM) is a chronic, nonprogressive muscle disorder characterized by universal muscle hypotrophy and growth retardation. Histomorphometric examination of muscle shows a preponderance of smaller than normal type 1 fibers and overall fiber size....... Insulin receptor function and glycogen synthase (GS) activity and expression were examined in biopsies of vastus lateralis muscle. Despite a 45-90-fold increase in both fasting and postprandial serum insulin levels, both CFTDM patients had diabetes mellitus. Clamp studies revealed that the oldest boy had...... severe insulin resistance of both liver and peripheral tissues. The impaired insulin-stimulated glucose disposal to peripheral tissues was primarily due to reduced nonoxidative glucose metabolism. These changes were paralleled by reduced basal values of muscle GS total activity, allosterical activation...

  18. The effect of resistance training combined with timed ingestion of protein on muscle fiber size and muscle strength

    DEFF Research Database (Denmark)

    Andersen, Lars L; Tufekovic, Goran; Zebis, Mette K

    2005-01-01

    of resistance training combined with timed ingestion of isoenergetic protein vs carbohydrate supplementation on muscle fiber hypertrophy and mechanical muscle performance. Supplementation was administered before and immediately after each training bout and, in addition, in the morning on nontraining days......) concentric and eccentric contractions of the knee extensor muscle was measured in an isokinetic dynamometer. After 14 weeks of resistance training, the protein group showed hypertrophy of type I (18% +/- 5%; P muscle fibers, whereas no change above baseline occurred......Acute muscle protein metabolism is modulated not only by resistance exercise but also by amino acids. However, less is known about the long-term hypertrophic effect of protein supplementation in combination with resistance training. The present study was designed to compare the effect of 14 weeks...

  19. Differences in muscle fiber size and associated energetic costs in phylogenetically paired tropical and temperate birds.

    Science.gov (United States)

    Jimenez, Ana Gabriela; Williams, Joseph B

    2014-01-01

    Tropical and temperate birds provide a unique system to examine mechanistic consequences of life-history trade-offs at opposing ends of the pace-of-life spectrum; tropical birds tend to have a slow pace of life whereas temperate birds the opposite. Birds in the tropics have a lower whole-animal basal metabolic rate and peak metabolic rate, lower rates of reproduction, and longer survival than birds in temperate regions. Although skeletal muscle has a relatively low tissue-specific metabolism at rest, it makes up the largest fraction of body mass and therefore contributes more to basal metabolism than any other tissue. A principal property of muscle cells that influences their rate of metabolism is fiber size. The optimal fiber size hypothesis attempts to link whole-animal basal metabolic rate to the cost of maintaining muscle mass by stating that larger fibers may be metabolically cheaper to maintain since the surface area∶volume ratio (SA∶V) is reduced compared with smaller fibers and thus the amount of area to transport ions is also reduced. Because tropical birds have a reduced whole-organism metabolism, we hypothesized that they would have larger muscle fibers than temperate birds, given that larger muscle fibers have reduced energy demand from membrane Na(+)-K(+) pumps. Alternatively, smaller muscle fibers could result in a lower capacity for shivering and exercise. To test this idea, we examined muscle fiber size and Na(+)-K(+)-ATPase activity in 16 phylogenetically paired species of tropical and temperate birds. We found that 3 of the 16 paired comparisons indicated that tropical birds had significantly larger fibers, contrary to our hypothesis. Our data show that SA∶V is proportional to Na(+)-K(+)-ATPase activity in muscles of birds.

  20. Effects of muscle fiber type and size on EMG median frequency and conduction velocity.

    Science.gov (United States)

    Kupa, E J; Roy, S H; Kandarian, S C; De Luca, C J

    1995-07-01

    This paper describes an in vitro method for comparing surface-detected electromyographic median frequency (MF) and conduction velocity (CV) parameters with histochemical measurements of muscle fiber type composition and cross-sectional area (CSA). Electromyographic signals were recorded during electrically elicited tetanic contractions from rat soleus, extensor digitorum longus, and diaphragm muscles placed in an oxygenated Krebs bath. Fibers were typed as slow oxidative, fast oxidative glycolytic, and fast glycolytic based on histochemical enzyme stains. Muscles with a greater percentage of fast glycolytic and fast oxidative glycolytic fibers exhibited greater initial values of MF and CV as well as a greater reduction in these variables over the course of the contraction. Regression indicated that fiber type composition could be predicted based on two MF parameters. A weighted measure of muscle fiber CSA was found to be linearly related to both initial MF and CV. The results of this study suggest that MF and CV parameters recorded during a muscular contraction are related to muscle fiber type composition and muscle fiber CSA.

  1. Myosin phosphorylation and force potentiation in skeletal muscle: evidence from animal models.

    Science.gov (United States)

    Vandenboom, Rene; Gittings, William; Smith, Ian C; Grange, Robert W; Stull, James T

    2013-12-01

    The contractile performance of mammalian fast twitch skeletal muscle is history dependent. The effect of previous or ongoing contractile activity to potentiate force, i.e. increase isometric twitch force, is a fundamental property of fast skeletal muscle. The precise manifestation of force potentiation is dependent upon a variety of factors with two general types being identified; staircase potentiation referring to the progressive increase in isometric twitch force observed during low frequency stimulation while posttetanic potentiation refers to the step-like increase in isometric twitch force observed following a brief higher frequency (i.e. tetanic) stimulation. Classic studies established that the magnitude and duration of potentiation depends on a number of factors including muscle fiber type, species, temperature, sarcomere length and stimulation paradigm. In addition to isometric twitch force, more recent work has shown that potentiation also influences dynamic (i.e. concentric and/or isotonic) force, work and power at a range of stimulus frequencies in situ or in vitro, an effect that may translate to enhanced physiological function in vivo. Early studies performed on both intact and permeabilized models established that the primary mechanism for this modulation of performance was phosphorylation of myosin, a modification that increased the Ca(2+) sensitivity of contraction. More recent work from a variety of muscle models indicates, however, the presence of a secondary mechanism for potentiation that may involve altered Ca(2+) handling. The primary purpose of this review is to highlight these recent findings relative to the physiological utility of force potentiation in vivo.

  2. Diaphragm muscle fiber function and structure in humans with hemidiaphragm paralysis.

    Science.gov (United States)

    Welvaart, W N; Paul, M A; van Hees, H W H; Stienen, G J M; Niessen, J W M; de Man, F S; Sieck, G C; Vonk-Noordegraaf, A; Ottenheijm, C A C

    2011-08-01

    Recent studies proposed that mechanical inactivity of the human diaphragm during mechanical ventilation rapidly causes diaphragm atrophy and weakness. However, conclusive evidence for the notion that diaphragm weakness is a direct consequence of mechanical inactivity is lacking. To study the effect of hemidiaphragm paralysis on diaphragm muscle fiber function and structure in humans, biopsies were obtained from the paralyzed hemidiaphragm in eight patients with hemidiaphragm paralysis. All patients had unilateral paralysis of known duration, caused by en bloc resection of the phrenic nerve with a tumor. Furthermore, diaphragm biopsies were obtained from three control subjects. The contractile performance of demembranated muscle fibers was determined, as well as fiber ultrastructure and morphology. Finally, expression of E3 ligases and proteasome activity was determined to evaluate activation of the ubiquitin-proteasome pathway. The force-generating capacity, as well as myofibrillar ultrastructure, of diaphragm muscle fibers was preserved up to 8 wk of paralysis. The cross-sectional area of slow fibers was reduced after 2 wk of paralysis; that of fast fibers was preserved up to 8 wk. The expression of the E3 ligases MAFbx and MuRF-1 and proteasome activity was not significantly upregulated in diaphragm fibers following paralysis, not even after 72 and 88 wk of paralysis, at which time marked atrophy of slow and fast diaphragm fibers had occurred. Diaphragm muscle fiber atrophy and weakness following hemidiaphragm paralysis develops slowly and takes months to occur.

  3. Muscle atrophy associated with microgravity in rat: Basic data for countermeasures

    Science.gov (United States)

    Falempin, M.; Mounier, Y.

    Morphological, contractile properties and myosin heavy chain (MHC) composition of rat soleus muscles were studied after 2 weeks of unloading (HS) and after 2 weeks of HS associated with selective deafferentation (HS + DEAF) at the level L4 and L5. The same significant reductions in muscle mass and tetanic tension were found after HS and HS + DEAF. However, the transformation of the slow-twitch soleus muscle towards a faster type characterized by a decrease in twitch time parameters and an increase in fast-twitch type MHC isoforms in HS did not appear in HS + DEAF conditions. Our results also showed that a pattern similar to firing rate of motoneurones innervating slow-twitch muscles inhibited the slow to fast fiber changes observed during HS. Nevertheless, neither the loss of mass or force output in the HS muscles were prevented by electrostimulation. Immobilization in a stretched position during HS maintained the muscle wet weight, mechanical and electrophoretical characteristics close to control values. We concluded that the decrease in mechanical strains imposed on the muscle during unloading was the main factor for the development of atrophy, while the kinetic changes might be predominantly modulated by the nervous command. These basic data suggested that some experimental conditions such as electrostimulation or stretching, could participate in countermeasure programmes.

  4. [New formation of elastic fiber material in aortic defects covered with muscle flaps].

    Science.gov (United States)

    Klima, G; Papp, C

    1985-01-01

    The examination of the coverage of vascular defects with intercostal muscles showed during an observation period of 7 weeks the development of cartilage tissue with thick elastic fiber nettings running between the chondroma.

  5. Effect of exercise at light loads with manipulative resistance on infraspinatus, trapezius (upper fiber) and deltoid (middle fiber) muscle activities in shoulder joint elevation

    National Research Council Canada - National Science Library

    Nanba, Yoshifumi; Miyamoto, Shigenori; Takemasa, Seiichi; Uesugi, Masayuki; Inoue, Yuri; Ootani, Yoshitaka; Fujii, Shun; Hirotsu, Takaaki; Tanaka, Hideki

    2015-01-01

    ...] To determine the effects of the closed kinetic chain exercise on the upper limb, we measured the surface EMG of the infraspinatus muscle, the trapezius (upper fiber) and the deltoid (middle fiber...

  6. Spermine oxidase maintains basal skeletal muscle gene expression and fiber size and is strongly repressed by conditions that cause skeletal muscle atrophy.

    Science.gov (United States)

    Bongers, Kale S; Fox, Daniel K; Kunkel, Steven D; Stebounova, Larissa V; Murry, Daryl J; Pufall, Miles A; Ebert, Scott M; Dyle, Michael C; Bullard, Steven A; Dierdorff, Jason M; Adams, Christopher M

    2015-01-15

    Skeletal muscle atrophy is a common and debilitating condition that remains poorly understood at the molecular level. To better understand the mechanisms of muscle atrophy, we used mouse models to search for a skeletal muscle protein that helps to maintain muscle mass and is specifically lost during muscle atrophy. We discovered that diverse causes of muscle atrophy (limb immobilization, fasting, muscle denervation, and aging) strongly reduced expression of the enzyme spermine oxidase. Importantly, a reduction in spermine oxidase was sufficient to induce muscle fiber atrophy. Conversely, forced expression of spermine oxidase increased muscle fiber size in multiple models of muscle atrophy (immobilization, fasting, and denervation). Interestingly, the reduction of spermine oxidase during muscle atrophy was mediated by p21, a protein that is highly induced during muscle atrophy and actively promotes muscle atrophy. In addition, we found that spermine oxidase decreased skeletal muscle mRNAs that promote muscle atrophy (e.g., myogenin) and increased mRNAs that help to maintain muscle mass (e.g., mitofusin-2). Thus, in healthy skeletal muscle, a relatively low level of p21 permits expression of spermine oxidase, which helps to maintain basal muscle gene expression and fiber size; conversely, during conditions that cause muscle atrophy, p21 expression rises, leading to reduced spermine oxidase expression, disruption of basal muscle gene expression, and muscle fiber atrophy. Collectively, these results identify spermine oxidase as an important positive regulator of muscle gene expression and fiber size, and elucidate p21-mediated repression of spermine oxidase as a key step in the pathogenesis of skeletal muscle atrophy.

  7. Spermine oxidase maintains basal skeletal muscle gene expression and fiber size and is strongly repressed by conditions that cause skeletal muscle atrophy

    Science.gov (United States)

    Bongers, Kale S.; Fox, Daniel K.; Kunkel, Steven D.; Stebounova, Larissa V.; Murry, Daryl J.; Pufall, Miles A.; Ebert, Scott M.; Dyle, Michael C.; Bullard, Steven A.; Dierdorff, Jason M.

    2014-01-01

    Skeletal muscle atrophy is a common and debilitating condition that remains poorly understood at the molecular level. To better understand the mechanisms of muscle atrophy, we used mouse models to search for a skeletal muscle protein that helps to maintain muscle mass and is specifically lost during muscle atrophy. We discovered that diverse causes of muscle atrophy (limb immobilization, fasting, muscle denervation, and aging) strongly reduced expression of the enzyme spermine oxidase. Importantly, a reduction in spermine oxidase was sufficient to induce muscle fiber atrophy. Conversely, forced expression of spermine oxidase increased muscle fiber size in multiple models of muscle atrophy (immobilization, fasting, and denervation). Interestingly, the reduction of spermine oxidase during muscle atrophy was mediated by p21, a protein that is highly induced during muscle atrophy and actively promotes muscle atrophy. In addition, we found that spermine oxidase decreased skeletal muscle mRNAs that promote muscle atrophy (e.g., myogenin) and increased mRNAs that help to maintain muscle mass (e.g., mitofusin-2). Thus, in healthy skeletal muscle, a relatively low level of p21 permits expression of spermine oxidase, which helps to maintain basal muscle gene expression and fiber size; conversely, during conditions that cause muscle atrophy, p21 expression rises, leading to reduced spermine oxidase expression, disruption of basal muscle gene expression, and muscle fiber atrophy. Collectively, these results identify spermine oxidase as an important positive regulator of muscle gene expression and fiber size, and elucidate p21-mediated repression of spermine oxidase as a key step in the pathogenesis of skeletal muscle atrophy. PMID:25406264

  8. Effects of cannabinoids on caffeine contractures in slow and fast skeletal muscle fibers of the frog.

    Science.gov (United States)

    Huerta, Miguel; Ortiz-Mesina, Mónica; Trujillo, Xóchitl; Sánchez-Pastor, Enrique; Vásquez, Clemente; Castro, Elena; Velasco, Raymundo; Montoya-Pérez, Rocío; Onetti, Carlos

    2009-05-01

    The effect of cannabinoids on caffeine contractures was investigated in slow and fast skeletal muscle fibers using isometric tension recording. In slow muscle fibers, WIN 55,212-2 (10 and 5 microM) caused a decrease in tension. These doses reduced maximum tension to 67.43 +/- 8.07% (P = 0.02, n = 5) and 79.4 +/- 14.11% (P = 0.007, n = 5) compared to control, respectively. Tension-time integral was reduced to 58.37 +/- 7.17% and 75.10 +/- 3.60% (P = 0.002, n = 5), respectively. Using the CB(1) cannabinoid receptor agonist ACPA (1 microM) reduced the maximum tension of caffeine contractures by 68.70 +/- 11.63% (P = 0.01, n = 5); tension-time integral was reduced by 66.82 +/- 6.89% (P = 0.02, n = 5) compared to controls. When the CB(1) receptor antagonist AM281 was coapplied with ACPA, it reversed the effect of ACPA on caffeine-evoked tension. In slow and fast muscle fibers incubated with the pertussis toxin, ACPA had no effect on tension evoked by caffeine. In fast muscle fibers, ACPA (1 microM) also decreased tension; the maximum tension was reduced by 56.48 +/- 3.4% (P = 0.001, n = 4), and tension-time integral was reduced by 57.81 +/- 2.6% (P = 0.006, n = 4). This ACPA effect was not statistically significant with respect to the reduction in tension in slow muscle fibers. Moreover, we detected the presence of mRNA for the cannabinoid CB(1) receptor on fast and slow skeletal muscle fibers, which was significantly higher in fast compared to slow muscle fiber expression. In conclusion, our results suggest that in the slow and fast muscle fibers of the frog cannabinoids diminish caffeine-evoked tension through a receptor-mediated mechanism.

  9. Systems Biology of Skeletal Muscle: Fiber Type as an Organizing Principle

    OpenAIRE

    Greising, Sarah M.; Gransee, Heather M.; Mantilla, Carlos B.; Sieck, Gary C.

    2012-01-01

    Skeletal muscle force generation and contraction are fundamental to countless aspects of human life. The complexity of skeletal muscle physiology is simplified by fiber type classification where differences are observed from neuromuscular transmission to release of intracellular Ca2+ from the sarcoplasmic reticulum and the resulting recruitment and cycling of cross-bridges. This review uses fiber type classification as an organizing and simplifying principle to explore the complex interaction...

  10. Contractile properties of muscle fibers from the deep and superficial digital flexors of horses.

    Science.gov (United States)

    Butcher, M T; Chase, P B; Hermanson, J W; Clark, A N; Brunet, N M; Bertram, J E A

    2010-10-01

    Equine digital flexor muscles have independent tendons but a nearly identical mechanical relationship to the main joint they act upon. Yet these muscles have remarkable diversity in architecture, ranging from long, unipennate fibers ("short" compartment of DDF) to very short, multipennate fibers (SDF). To investigate the functional relevance of the form of the digital flexor muscles, fiber contractile properties were analyzed in the context of architecture differences and in vivo function during locomotion. Myosin heavy chain (MHC) isoform fiber type was studied, and in vitro motility assays were used to measure actin filament sliding velocity (V(f)). Skinned fiber contractile properties [isometric tension (P(0)/CSA), velocity of unloaded shortening (V(US)), and force-Ca(2+) relationships] at both 10 and 30°C were characterized. Contractile properties were correlated with MHC isoform and their respective V(f). The DDF contained a higher percentage of MHC-2A fibers with myosin (heavy meromyosin) and V(f) that was twofold faster than SDF. At 30°C, P(0)/CSA was higher for DDF (103.5 ± 8.75 mN/mm(2)) than SDF fibers (81.8 ± 7.71 mN/mm(2)). Similarly, V(US) (pCa 5, 30°C) was faster for DDF (2.43 ± 0.53 FL/s) than SDF fibers (1.20 ± 0.22 FL/s). Active isometric tension increased with increasing Ca(2+) concentration, with maximal Ca(2+) activation at pCa 5 at each temperature in fibers from each muscle. In general, the collective properties of DDF and SDF were consistent with fiber MHC isoform composition, muscle architecture, and the respective functional roles of the two muscles in locomotion.

  11. TWITCH PARAMETERS IN TRANSVERSAL AND LONGITUDINAL BICEPS BRACHII RESPONSE

    Directory of Open Access Journals (Sweden)

    Boštjan Šimunič

    2010-01-01

    Full Text Available Assessment of the contractile properties of skeletal muscles is continuing to be an important issue and a difficult task methodologically. Longitudinal direction of skeletal muscle contraction blurs intrinsic muscle belly contractile properties with many factors. This study evaluates and explains contractile properties such as: delay time (Td, contraction time (Tc, half relaxation time (Tr and maximal amplitude (Dm extracted from twitch transversal response and compare them with torque response. In fifteen healthy males (age 23.7 ± 3.4 years isometric twitch transversal and torque responses were simultaneously recorded during graded electrically elicited contractions in the biceps brachii muscle. The amplitude of electrical stimulation was increased in 5 mA steps from a threshold up to a maximal response. The muscles’ belly transversal response was measured by a high precision mechanical displacement sensor while elbow joint torque was calculated from force readings. Results indicate a parabolic relation between the transversal displacement and the torque Dm. A significantly shorter Tc was found in transversal response without being correlated to torque Tc (r = -0.12; > 0.05. A significant correlation was found between torque Tc and the time occurrence of the second peak in the transversal response (r = 0.83; < 0.001. Electrical stimulation amplitude dependant variation of the Tc was notably different in transversal than in torque response. Td was similar at submaximal and maximal responses but larger in transversal at just above threshold contractions. Tr has a similar linear trend in both responses, however, the magnitude and the slope are much larger in the transversal response. We could conclude that different mechanisms affect longitudinal and transversal twitch skeletal muscle deformations. Contractile properties extracted from the transversal response enable alternative insights into skeletal muscle contraction mechanics.

  12. Two-weeks of elbow immobilization affects torque production but does not change muscle activation

    OpenAIRE

    Karolczak,Ana P. B.; Diefenthaeler, Fernando; Jeam M. Geremia; Vaz,Marco A.

    2009-01-01

    BACKGROUND: Limb immobilization has been extensively used during the recovery process of musculoskeletal injuries despite the fact that this technique causes functional deficits in the skeletal muscle. There is evidence showing strength reduction due to muscle hypotrophy and an increase in the percentage of fast-twitch fibers, however it is still unclear how the injuries and the immobilization contribute to these changes. OBJECTIVE: To verify the influence of elbow joint immobilization on the...

  13. Immunohistochemical detection of interleukin-6 in human skeletal muscle fibers following exercise.

    Science.gov (United States)

    Penkowa, Milena; Keller, Charlotte; Keller, Pernille; Jauffred, Sune; Pedersen, Bente Klarlund

    2003-11-01

    Interleukin-6 (IL-6) is produced by many different cell types. Human skeletal muscles produce and release high amounts of IL-6 during exercise; however, the cell source of origin in the muscle is not known. Therefore, we studied the protein expression of IL-6 by immunohistochemistry in human muscle tissue from biopsies obtained at time points 0, 3, 4.5, 6, 9, and 24 h in relation to 3 h of bicycle exercise performed by healthy young males (n=12) and in resting controls (n=6). The IL-6 expression was clearly increased after exercise and remained high even by 24 h, relative to pre-exercise or resting individuals. The IL-6 immunostainings of skeletal muscle cells were homogeneous and without difference between muscle fiber types. The IL-6 mRNA peaked immediately after the exercise, and, in accordance, the IL-6 protein expression within muscle cells was most pronounced around 3 h post-exercise. However, the finding that plasma IL-6 concentration peaked in the end of exercise indicates a high turnover of muscle-derived IL-6. In conclusion, the finding of marked IL-6 protein expression exclusively within skeletal muscle fibers following exercise demonstrates that skeletal muscle fibers of all types are the dominant cell source of exercise-induced release of IL-6 from working muscle.

  14. Elastic properties of relaxed, activated, and rigor muscle fibers measured with microsecond resolution.

    OpenAIRE

    Jung, D. W.; Blangé, T; van der Graaf, H.; Treijtel, B W

    1988-01-01

    Tension responses due to small and rapid length changes (completed within 40 microseconds) were obtained from skinned single-fiber segments (4- to 7-mm length) of the iliofibularis muscle of the frog incubated in relaxing, rigor, and activating solution. The fibers were skinned by freeze-drying. The first 500 microseconds of the responses for all three conditions could be described with a linear model, in which the fiber is regarded as a rod composed of infinitesimally small identical segment...

  15. Grb2-associated binder-1 is required for extrafusal and intrafusal muscle fiber development.

    Science.gov (United States)

    Park, So Y; Jang, So Y; Shin, Yoon K; Yoon, Byeol A; Lee, Hye J; Park, Hwan T

    2017-07-05

    The neuregulin-1 (NRG1) signaling pathway plays an important role in the development of the peripheral neuromuscular system, including in muscle spindle and postnatal myelination. We previously showed that NRG1 on the axonal membrane regulates peripheral nerve myelination through Grb2-associated binder 1 (Gab1), a scaffolding mediator of receptor tyrosine kinase signaling. Here, we determined the role of Gab1 in the development of muscles and the muscle spindle using muscle-specific conditional Gab1 knockout mice. The mutant mice showed general retardation in muscular growth and hypotrophy of extrafusal muscle fibers. In addition, the muscle-specific Gab1 knockout mutant exhibited significant underdevelopment of muscle spindles, which are normally regulated by NRG1, and abnormal proprioceptive behavior. Furthermore, the selective knockdown of Gab1 in C2C12 muscle cells reduced NRG1-induced expression of Egr3, a critical transcription factor for muscle spindle development. However, Gab2 knockout mice did not show any defects in the development of muscles or muscle spindles. Our findings suggest that Gab1 is an essential signaling molecule in mediating axonal NRG1 signaling for the development of both extrafusal and intrafusal muscle fibers.

  16. Skeletal muscle histology and biochemistry of an elite sprinter, the African cheetah.

    Science.gov (United States)

    Williams, T M; Dobson, G P; Mathieu-Costello, O; Morsbach, D; Worley, M B; Phillips, J A

    1997-11-01

    To establish a skeletal muscle profile for elite sprinters, we obtained muscle biopsy samples from the vastus lateralis, gastrocnemius and soleus of African cheetahs (Acinonyx jubatus). Muscle ultrastructure was characterized by the fiber type composition and mitochondrial volume density of each sample. Maximum enzyme activity, myoglobin content and mixed fiber metabolite content were used to assess the major biochemical pathways. The results demonstrate a preponderance of fast-twitch fibers in the locomotor muscles of cheetahs; 83% of the total number of fibers examined in the vastus lateralis and nearly 61% of the gastrocnemius were comprised of fast-twitch fibers. The total mitochondrial volume density of the limb muscles ranged from 2.0 to 3.9% for two wild cheetahs. Enzyme activities reflected the sprinting capability of the cheetah. Maximum activities for pyruvate kinase and lactate dehydrogenase in the vastus lateralis were 1519.00 +/- 203.60 and 1929.25 +/- 482.35 mumol min-1.g wet wt-1, respectively, and indicated a high capacity for glycolysis. This study demonstrates that the locomotor muscles of cheetahs are poised for anaerobically based exercise. Fiber type composition, mitochondrial content and glycolytic enzyme capacities in the locomotor muscles of these sprinting cats are at the extreme range of values for other sprinters bred or trained for this activity including greyhounds, thoroughbred horses and elite human athletes.

  17. A new surface electromyography analysis method to determine spread of muscle fiber conduction velocities

    NARCIS (Netherlands)

    Lange, F; Van Weerden, TW; Van der Hoeven, JH

    2002-01-01

    Muscle fiber conduction velocity (MFCV) estimation from surface signals is widely used to study muscle function, e. g., in neuromuscular disease and in fatigue studies. However, most analysis methods do not yield information about the velocity distribution of the various motor unit action potentials

  18. Effect of Quadriceps Exercise Training on Muscle Fiber Angle in Patients With Patellofemoral Pain Syndrome

    Directory of Open Access Journals (Sweden)

    Honarpishe

    2015-10-01

    Full Text Available Background Imbalance between the vastus medialis oblique (VMO muscle and the vastus lateralis oblique (VTO Vastus lateralis has been thought to be a primary cause of abnormal patellar tracking, possibly leading to patellofemoral pain syndrome (PFPS. Objectives The purpose of this study was to investigate the effect of quadriceps muscle strengthening exercises on the ratio of VMO to VL oblique and longus muscle fiber angles. Patients and Methods Thirty-five subjects (23 females and 12 males, mean age 26.6 years ± 1.1 SD with PFPS were randomized into an exercise group or a control group. The exercise group performed knee extension exercises for four weeks based on the Kaya exercise program (three times per week, while the control group received no treatment. Measurements included knee extensor concentric and eccentric muscle torque using a Biodex isokinetic machine and the fiber angle of the VMO, VL oblique and longus muscles using ultrasonography, all of which were evaluated at the time of the initial examination and at the end of the four-week period. Results There were no significant differences in the muscle strength and fiber angle of the VMO, VL oblique and longus muscles after training between the control and experimental groups (P > 0.05. Conclusions The study findings indicate that short-term exercises had no significant effect on the ratio of VMO to VL muscle fiber angles in patients with PFPS.

  19. Mechanical muscle function, morphology, and fiber type in lifelong trained elderly

    DEFF Research Database (Denmark)

    Aagaard, Per; Magnusson, Peter S; Larsson, Benny

    2007-01-01

    PURPOSE: Maximal muscle contraction force and muscle mass are both reduced during the natural aging process. Long-term training may be used to attenuate this age-related loss in muscle function and muscle size. METHODS: Maximum isometric quadriceps strength (MVC), rate of force development (RFD......), and muscle fiber composition and size (CSA) were studied in elderly individuals (68-78 yr) chronically exposed (> 50 yr) to either endurance (E) or strength (S) training, and in age-matched, untrained (U) elderly group. RESULTS: E and S showed greater MVC than did U. Contractile RFD was elevated in S...

  20. Jaw-muscle fiber architecture in tufted capuchins favors generating relatively large muscle forces without compromising jaw gape.

    Science.gov (United States)

    Taylor, Andrea B; Vinyard, Christopher J

    2009-12-01

    Tufted capuchins (sensu lato) are renowned for their dietary flexibility and capacity to exploit hard and tough objects. Cebus apella differs from other capuchins in displaying a suite of craniodental features that have been functionally and adaptively linked to their feeding behavior, particularly the generation and dissipation of relatively large jaw forces. We compared fiber architecture of the masseter and temporalis muscles between C. apella (n=12) and two "untufted" capuchins (C. capucinus, n=3; C. albifrons, n=5). These three species share broadly similar diets, but tufted capuchins occasionally exploit mechanically challenging tissues. We tested the hypothesis that tufted capuchins exhibit architectural properties of their jaw muscles that facilitate relatively large forces including relatively greater physiologic cross-sectional areas (PCSA), more pinnate fibers, and lower ratios of mass to tetanic tension (Mass/P(0)). Results show some evidence supporting these predictions, as C. apella has relatively greater superficial masseter and temporalis PCSAs, significantly so only for the temporalis following Bonferroni adjustment. Capuchins did not differ in pinnation angle or Mass/P(0). As an architectural trade-off between maximizing muscle force and muscle excursion/contraction velocity, we also tested the hypothesis that C. apella exhibits relatively shorter muscle fibers. Contrary to our prediction, there are no significant differences in relative fiber lengths between tufted and untufted capuchins. Therefore, we attribute the relatively greater PCSAs in tufted capuchins primarily to their larger muscle masses. These findings suggest that relatively large jaw-muscle PCSAs can be added to the suite of masticatory features that have been functionally linked to the exploitation of a more resistant diet by C. apella. By enlarging jaw-muscle mass to increase PCSA, rather than reducing fiber lengths and increasing pinnation, tufted capuchins appear to have

  1. Myasthenia gravis and myasthenic syndrome: simulation of twitch strength with or without therapy.

    Science.gov (United States)

    Nigrovic, Vladimir; Amann, Anton; Bhatt, Shashi

    2005-12-01

    To examine the quantitative relationship between indirectly evoked twitch and decreases in the number of either postsynaptic receptors or acetylcholine molecules released by a single stimulus, we studied these variables in a computer-simulated model of neuromuscular transmission. Twitch strength decreased if the number of receptors decreased to below 30% of normal or the number of acetylcholine molecules released by a stimulus decreased to below 80%. Inhibition of acetylcholine hydrolysis to 50% restored twitch strength in the presence of a decreased number of receptors. However, twitch strength was more easily restored to normalcy by augmenting the release of acetylcholine, if the release was diminished by disease. The simulations mimic the clinically known therapeutic outcomes in certain disorders of neuromuscular transmission. These results provide useful quantitative insights into the relationship between acetylcholine receptors or the stimulus-induced release of acetylcholine and muscle function in myasthenia gravis or Lambert-Eaton myasthenic syndrome.

  2. Fine-mapping of genes determining extrafusal fiber properties in murine soleus muscle.

    Science.gov (United States)

    Carroll, A M; Cheng, R; Collie-Duguid, E S R; Meharg, C; Scholz, M E; Fiering, S; Fields, J L; Palmer, A A; Lionikas, A

    2017-03-01

    Muscle fiber cross-sectional area (CSA) and proportion of different fiber types are important determinants of muscle function and overall metabolism. Genetic variation plays a substantial role in phenotypic variation of these traits; however, the underlying genes remain poorly understood. This study aimed to map quantitative trait loci (QTL) affecting differences in soleus muscle fiber traits between the LG/J and SM/J mouse strains. Fiber number, CSA, and proportion of oxidative type I fibers were assessed in the soleus of 334 genotyped female and male mice of the F34 generation of advanced intercross lines (AIL) derived from the LG/J and SM/J strains. To increase the QTL detection power, these data were combined with 94 soleus samples from the F2 intercross of the same strains. Transcriptome of the soleus muscle of LG/J and SM/J females was analyzed by microarray. Genome-wide association analysis mapped four QTL (genome-wide P < 0.05) affecting the properties of muscle fibers to chromosome 2, 3, 4, and 11. A 1.5-LOD QTL support interval ranged between 2.36 and 4.67 Mb. On the basis of the genomic sequence information and functional and transcriptome data, we identified candidate genes for each of these QTL. The combination of analyses in F2 and F34 AIL populations with transcriptome and genomic sequence data in the parental strains is an effective strategy for refining QTL and nomination of the candidate genes.

  3. Muscle fibers in the central nervous system of nemerteans: spatial organization and functional role.

    Science.gov (United States)

    Petrov, A A; Zaitseva, O V

    2012-08-01

    The system of muscle fibers associated with the brain and lateral nerve cords is present in all major groups of enoplan nemerteans. Unfortunately, very little is known about the functional role and spatial arrangement of these muscles of the central nervous system. This article examines the architecture of the musculature of the central nervous system in two species of monostiliferous nemerteans (Emplectonema gracile and Tetrastemma cf. candidum) using phalloidin staining and confocal microscopy. The article also briefly discusses the body-wall musculature and the muscles of the cephalic region. In both species, the lateral nerve cords possess two pairs of cardinal muscles that run the length of the nerve cords and pass through the ventral cerebral ganglia. A system of peripheral muscles forms a meshwork around the lateral nerve cords in E. gracile. The actin-rich processes that ramify within the nerve cords in E. gracile (transverse fibers) might represent a separate population of glia-like cells or sarcoplasmic projections of the peripheral muscles of the central nervous system. The lateral nerve cords in T. cf. candidum lack peripheral muscles but have muscles similar in their position and orientation to the transverse fibers. The musculature of the central nervous system is hypothesized to function as a support system for the lateral nerve cords and brain, preventing rupturing and herniation of the nervous tissue during locomotion. The occurrence of muscles of the central nervous system in nemerteans and other groups and their possible relevance in taxonomy are discussed.

  4. Nuclear receptor/microRNA circuitry links muscle fiber type to energy metabolism.

    Science.gov (United States)

    Gan, Zhenji; Rumsey, John; Hazen, Bethany C; Lai, Ling; Leone, Teresa C; Vega, Rick B; Xie, Hui; Conley, Kevin E; Auwerx, Johan; Smith, Steven R; Olson, Eric N; Kralli, Anastasia; Kelly, Daniel P

    2013-06-01

    The mechanisms involved in the coordinate regulation of the metabolic and structural programs controlling muscle fitness and endurance are unknown. Recently, the nuclear receptor PPARβ/δ was shown to activate muscle endurance programs in transgenic mice. In contrast, muscle-specific transgenic overexpression of the related nuclear receptor, PPARα, results in reduced capacity for endurance exercise. We took advantage of the divergent actions of PPARβ/δ and PPARα to explore the downstream regulatory circuitry that orchestrates the programs linking muscle fiber type with energy metabolism. Our results indicate that, in addition to the well-established role in transcriptional control of muscle metabolic genes, PPARβ/δ and PPARα participate in programs that exert opposing actions upon the type I fiber program through a distinct muscle microRNA (miRNA) network, dependent on the actions of another nuclear receptor, estrogen-related receptor γ (ERRγ). Gain-of-function and loss-of-function strategies in mice, together with assessment of muscle biopsies from humans, demonstrated that type I muscle fiber proportion is increased via the stimulatory actions of ERRγ on the expression of miR-499 and miR-208b. This nuclear receptor/miRNA regulatory circuit shows promise for the identification of therapeutic targets aimed at maintaining muscle fitness in a variety of chronic disease states, such as obesity, skeletal myopathies, and heart failure.

  5. Spaceflight and growth effects on muscle fibers in the rhesus monkey

    Science.gov (United States)

    Bodine-Fowler, Sue C.; Roy, Roland R.; Rudolph, William; Haque, Naz; Kozlovskaia, Inessa B.; Edgerton, V. R.

    1992-01-01

    The effect of a 14-day spaceflight onboard Cosmos 2044 on selected morphological and metabolic properties of single muscle fibers was investigated in a nonhuman primate, Macaca mulatta. It is concluded that the 14-day spaceflight had little impact on fiber size in the soleus (S) and medial gastrocnemius (MG) muscles, whereas it appeared to be a slight decrease in sized in the tibialis anterior (TA). The mean fiber size in the postflight biopsies increased relative to preflight values. The mean fiber succinate dehydrogenase activity was found to decrease in the MG, whereas there was no apparent effect of spaceflight on the s and ta muscles. The differences in response of the S, MG, and TA to spaceflight in monkeys vs rats may be related to a species responsiveness to spaceflight, the manner in which the animals were restrained, and/or the possibility that the ankle musculature was able to function against a load while in space.

  6. Spaceflight and growth effects on muscle fibers in the rhesus monkey

    Science.gov (United States)

    Bodine-Fowler, Sue C.; Roy, Roland R.; Rudolph, William; Haque, Naz; Kozlovskaia, Inessa B.; Edgerton, V. R.

    1992-01-01

    The effect of a 14-day spaceflight onboard Cosmos 2044 on selected morphological and metabolic properties of single muscle fibers was investigated in a nonhuman primate, Macaca mulatta. It is concluded that the 14-day spaceflight had little impact on fiber size in the soleus (S) and medial gastrocnemius (MG) muscles, whereas it appeared to be a slight decrease in sized in the tibialis anterior (TA). The mean fiber size in the postflight biopsies increased relative to preflight values. The mean fiber succinate dehydrogenase activity was found to decrease in the MG, whereas there was no apparent effect of spaceflight on the s and ta muscles. The differences in response of the S, MG, and TA to spaceflight in monkeys vs rats may be related to a species responsiveness to spaceflight, the manner in which the animals were restrained, and/or the possibility that the ankle musculature was able to function against a load while in space.

  7. Muscle fiber hypotrophy with intact neuromuscular junctions. A study of a patient with congenital neuromuscular disease and ophthalmoplegia.

    Science.gov (United States)

    Bender, A N; Bender, M B

    1977-03-01

    An infant born with severe but nonprogressive somatic and cranial muscle weakness including bilateral external ophthalmoplegia was studied with a motor-point muscle biopsy. There was a strinking generalized decrease in the size of muscle fibers (hypotrophy), most marked in the type I fibers. Many of the small fibers were immature, resembling myotubes. Neuromuscular junctions on severely hypotrophic fibers were normal with esterase staining and by ultrastructural criteria. Although these are unusual clinical and biopsy characteristics, this infant's condition bears a resemblance to two other congenital nonprogressive neuromuscular diseases:myotubular myopathy and congenital fiber type disproportion. In these conditions and in our patient, there is no primary degenerative process affecting nerve or muscle but, rather, an apparent lack of maturation of fetal muscle fibers, indicating a defective normal trophic interaction between nerve and muscle.

  8. Type II muscle fibers atrophy associated with silent corticotroph adenoma in a dog.

    Directory of Open Access Journals (Sweden)

    L Insabato

    2010-11-01

    Full Text Available The Silent Corticotroph Adenoma (SCA is a pituitary adenoma variant characterized by the immunoreactivity for adrenocorticotropic hormone (ACTH and related peptides, without the clinical signs of Cushing's disease. SCA has been postulated to either secrete structurally abnormal ACTH that is inactive but detectable by immunohistochemistry or radioimmunoassay, or to secrete ACTH intermittently or at low levels continuously. Excess of ACTH has been associated to type II muscle atrophy. We describe a case of type II muscle fibers atrophy associated with silent corticotroph adenoma in a dog. The dog showed moderate to severe proximal muscle wasting and weakness with normal levels of muscle-associated enzymes. In the limb muscle biopsies, type II fibers were uniformly smaller than type I fibers. In temporalis muscles, there were few atrophic fibers, and several irregular areas of loss of enzymatic activity observed in NADH, SDH and COX stains. The tumour showed a trabecular growth pattern and immunohistochemical analysis demonstrated the presence of cytoplasmic immunoreactivity for ACTH. The muscle atrophy was considered to be related to an excess of inactive ACTH. Studying spontaneous occurring rare diseases in animals could help to understand the mechanism of similar diseases in human has well.

  9. The Click and Twitch in Contemporary Poetry.

    Science.gov (United States)

    Meredith, Bernard

    It is the creative writing instructor's role to help the student turn "twitch" poems into "click" poems ("twitch" being a kind of verbal hypertension that takes shape in the absence of anything humanly important to say on the poet's part and "click" being the finished poem that makes a sound like the click of the lid on a perfectly made box).…

  10. Clustering of the human skeletal muscle fibers using linear programming and angular Hilbertian metrics.

    Science.gov (United States)

    Neji, Radhouène; Besbes, Ahmed; Komodakis, Nikos; Deux, Jean-François; Maatouk, Mezri; Rahmouni, Alain; Bassez, Guillaume; Fleury, Gilles; Paragios, Nikos

    2009-01-01

    In this paper, we present a manifold clustering method fo the classification of fibers obtained from diffusion tensor images (DTI) of the human skeletal muscle. Using a linear programming formulation of prototype-based clustering, we propose a novel fiber classification algorithm over manifolds that circumvents the necessity to embed the data in low dimensional spaces and determines automatically the number of clusters. Furthermore, we propose the use of angular Hilbertian metrics between multivariate normal distributions to define a family of distances between tensors that we generalize to fibers. These metrics are used to approximate the geodesic distances over the fiber manifold. We also discuss the case where only geodesic distances to a reduced set of landmark fibers are available. The experimental validation of the method is done using a manually annotated significant dataset of DTI of the calf muscle for healthy and diseased subjects.

  11. Mitochondrial specialization revealed by single muscle fiber proteomics: focus on the Krebs cycle.

    Science.gov (United States)

    Schiaffino, S; Reggiani, C; Kostrominova, T Y; Mann, M; Murgia, M

    2015-12-01

    We have developed a highly sensitive mass spectrometry-based proteomic workflow to examine the proteome of single muscle fibers. This study revealed significant differences in the mitochondrial proteome of the four major fiber types present in mouse skeletal muscle. Here, we focus on Krebs cycle enzymes and in particular on the differential distribution of the two mitochondrial isocitrate dehydrogenases, IDH2 and IDH3. Type 1/slow fibers contain high levels of IDH2 and relatively low levels of IDH3, whereas fast 2X and 2B fibers show an opposite expression pattern. The findings suggest that in skeletal muscle, IDH2 functions in the forward direction of the Krebs cycle and that substrate flux along the cycle occurs predominantly via IDH2 in type 1 fibers and via IDH3 in 2X and 2B fibers. IDH2-mediated conversion of isocitrate to α-ketoglutarate leads to the generation of NADPH, which is critical to buffering the H2O2 produced by the respiratory chain. Nicotinamide nucleotide transhydrogenase (NNT), the other major mitochondrial enzyme involved in NADPH generation, is also more abundant in type 1 fibers. We suggest that the continuously active type 1 fibers are endowed with a more efficient H2O2 scavenging capacity to cope with the higher levels of reactive oxygen species production.

  12. Fiber hypertrophy and increased oxidative capacity can occur simultaneously in pig glycolytic skeletal muscle.

    Science.gov (United States)

    Scheffler, T L; Scheffler, J M; Park, S; Kasten, S C; Wu, Y; McMillan, R P; Hulver, M W; Frisard, M I; Gerrard, D E

    2014-02-15

    An inverse relationship between skeletal muscle fiber cross-sectional area (CSA) and oxidative capacity suggests that muscle fibers hypertrophy at the expense of oxidative capacity. Therefore, our objective was to utilize pigs possessing mutations associated with increased oxidative capacity [AMP-activated protein kinase (AMPKγ3(R200Q))] or fiber hypertrophy [ryanodine receptor 1 (RyR1(R615C))] to determine if these events occur in parallel. Longissimus muscle was collected from wild-type (control), AMPKγ3(R200Q), RyR1(R615C), and AMPKγ3(R200Q)-RyR1(R615C) pigs. Regardless of AMPK genotype, RyR(R615C) increased fiber CSA by 35%. In contrast, AMPKγ3(R200Q) pig muscle exhibited greater citrate synthase and β-hydroxyacyl CoA dehydrogenase activity. Isolated mitochondria from AMPKγ3(R200Q) muscle had greater maximal, ADP-stimulated oxygen consumption rate. Additionally, AMPKγ3(R200Q) muscle contained more (∼50%) of the mitochondrial proteins succinate dehydrogenase and cytochrome c oxidase and more mitochondrial DNA. Surprisingly, RyR1(R615C) increased mitochondrial proteins and DNA, but this was not associated with improved oxidative capacity, suggesting that altered energy metabolism in RyR1(R615C) muscle influences mitochondrial proliferation and protein turnover. Thus pigs that possess both AMPKγ3(R200Q) and RyR(R615C) exhibit increased muscle fiber CSA as well as greater oxidative capacity. Together, our findings support the notion that hypertrophy and enhanced oxidative capacity can occur simultaneously in skeletal muscle and suggest that the signaling mechanisms controlling these events are independently regulated.

  13. Type ⅡB human skeletal muscle fibers positively correlate with bone mineral density irrespective to age

    Institute of Scientific and Technical Information of China (English)

    Wing-Hoi Cheung; Wing-Sze Lee; Ling Qin; Ning Tang; Vivian Wing-Yin Hung; Kwok-Sui Leung

    2010-01-01

    Background Age-associated decrease in type ⅡA/B human skeletal muscle fibers was detected in human biopsies in our previous study. The relationship between change in muscle fiber typing and bone mineral density (BMD) is, however,unknown either cross-sectionally or longitudinally. We therefore conducted a cross-sectional study to investigate their correlation using human muscle biopsies.Methods Forty human subjects aged (53.4±20.2) years were recruited. Histomorphometric parameters of their muscle biopsies were measured by ATPase staining and image analysis, including average area percentage, fiber number percentage, mean fiber area, and area percentage of connective tissues. Hip and spine BMD was measured by dual-energy X-ray absorptiometry. Partial correlation with adjusting age was performed.Results Type ⅡB muscle fiber was found positively correlated with hip BMD irrespective to age and demonstrated significantly stronger relationship with BMD among all fiber types, in terms of its cross-sectional area (r=0.380, P=0.029)and size (r=0.389, P=0.025). Type ⅡA muscle fibers associated with hip BMD in mean fiber area only (r=0.420, P=0.015).Conclusions Type ⅡB muscle fiber may play an important role in maintaining bone quality. This may also be a relatively more sensitive fiber type of sarcopenia and osteoporosis. These findings further consolidate the muscle-bone relationship.

  14. Twitch and tetanic properties of human thenar motor units paralyzed by chronic spinal cord injury.

    Science.gov (United States)

    Häger-Ross, C K; Klein, C S; Thomas, C K

    2006-07-01

    Little is known about how human motor units respond to chronic paralysis. Our aim was to record surface electromyographic (EMG) signals, twitch forces, and tetanic forces from paralyzed motor units in the thenar muscles of individuals (n = 12) with chronic (1.5-19 yr) cervical spinal cord injury (SCI). Each motor unit was activated by intraneural stimulation of its motor axon using single pulses and trains of pulses at frequencies between 5 and 100 Hz. Paralyzed motor units (n = 48) had small EMGs and weak tetanic forces (n = 32 units) but strong twitch forces, resulting in half-maximal force being achieved at a median of only 8 Hz. The distributions for cumulative twitch and tetanic forces also separated less for paralyzed units than for control units, indicating that increases in stimulation frequency made a smaller relative contribution to the total force output in paralyzed muscles. Paralysis also induced slowing of conduction velocities, twitch contraction times and EMG durations. However, the elevated ratios between the twitch and the tetanic forces, but not contractile speed, correlated significantly with the extent to which unit force summated in response to different frequencies of stimulation. Despite changes in the absolute values of many electrical and mechanical properties of paralyzed motor units, most of the distributions shifted uniformly relative to those of thenar units obtained from control subjects. Thus human thenar muscles paralyzed by SCI retain a population of motor units with heterogeneous contractile properties because chronic paralysis influenced all of the motor units similarly.

  15. A comparison of peripheral and rubrospinal synaptic input to slow and fast twitch motor units of triceps surae.

    Science.gov (United States)

    Burke, R E; Jankowska, E; ten Bruggencate, G

    1970-05-01

    1. Post-synaptic potentials (PSPs) evoked by electrical stimulation of a variety of input systems have been compared in triceps surae motoneurones innervating slow and fast muscle units, the speed of contraction of which was also determined.2. Stimulation of high threshold afferents in both flexor and extensor muscle nerves, and of joint afferents, evoked polysynaptic PSPs which were predominantly hyperpolarizing in both fast and slow twitch motor units.3. Volleys in cutaneous afferents in the sural and saphenous nerves evoked polysynaptic PSPs composed of mixtures of inhibitory and excitatory components. The inhibitory components were predominant in slow twitch motor units, while in fast twitch units there was a trend towards excitatory predominance.4. Repetitive stimulation of the red nucleus caused predominantly inhibitory PSPs in slow twitch units and mixed or predominantly excitatory PSPs in fast twitch units. There was a correlation in the excitatory/inhibitory balance between PSPs of cutaneous and rubrospinal origin in those motoneurones in which both types of PSPs were studied.5. The amplitudes of group Ia disynaptic inhibitory PSPs were found to be correlated with motor unit twitch type: IPSPs in slow twitch units were larger than those in fast twitch units. Rubrospinal conditioning volleys were found to facilitate group Ia IPSPs in both fast and slow twitch motor units.6. The results suggest that there may be several basic patterns of synaptic input organization to motoneurones within a given motor unit pool. In addition to quantitative variation in synaptic distribution, there is evidence that qualitative differences in excitatory to inhibitory balance also exist in the pathways conveying input from cutaneous afferents and rubrospinal systems to triceps surae motoneurones. These qualitative differences are correlated with the motor unit twitch type.

  16. Matrix metalloproteinase-2 ablation in dystrophin-deficient mdx muscles reduces angiogenesis resulting in impaired growth of regenerated muscle fibers.

    Science.gov (United States)

    Miyazaki, Daigo; Nakamura, Akinori; Fukushima, Kazuhiro; Yoshida, Kunihiro; Takeda, Shin'ichi; Ikeda, Shu-ichi

    2011-05-01

    Matrix metalloproteases (MMPs) are a family of endopeptidases classified into subgroups based on substrate preference in normal physiological processes such as embryonic development and tissue remodeling, as well as in various disease processes via degradation of extracellular matrix components. Among the MMPs, MMP-9 and MMP-2 have been reported to be up-regulated in skeletal muscles in the lethal X-linked muscle disorder Duchenne muscular dystrophy (DMD), which is caused by loss of dystrophin. A recent study showed that deletion of the MMP9 gene in mdx, a mouse model for DMD, improved skeletal muscle pathology and function; however, the role of MMP-2 in the dystrophin-deficient muscle is not well known. In this study, we aimed at verifying the role of MMP-2 in the dystrophin-deficient muscle by using mdx mice with genetic ablation of MMP-2 (mdx/MMP-2(-/-)). We found impairment of regenerated muscle fiber growth with reduction of angiogenesis in mdx/MMP-2(-/-) mice at 3 months of age. Expression of vascular endothelial growth factor-A (VEGF-A), an important angiogenesis-related factor, decreased in mdx/MMP-2(-/-) mice at 3 months of age. MMP-2 had not a critical role in the degradation of dystrophin-glycoprotein complex (DGC) components such as β-dystroglycan and β-sarcoglycan in the regeneration process of the dystrophic muscle. Accordingly, MMP-2 may be essential for growth of regenerated muscle fibers through VEGF-associated angiogenesis in the dystrophin-deficient skeletal muscle.

  17. Effects of fiber type on force depression after active shortening in skeletal muscle.

    Science.gov (United States)

    Joumaa, V; Power, G A; Hisey, B; Caicedo, A; Stutz, J; Herzog, W

    2015-07-16

    The aim of this study was to investigate force depression in Type I and Type II muscle fibers. Experiments were performed using skinned fibers from rabbit soleus and psoas muscles. Force depression was quantified after active fiber shortening from an average sarcomere length (SL) of 3.2µ m to an average SL of 2.6 µm at an absolute speed of 0.115f iber length/s and at a relative speed corresponding to 17% of the unloaded shortening velocity (V0) in each type of fibers. Force decay and mechanical work during shortening were also compared between fiber types. After mechanical testing, each fiber was subjected to myosin heavy chain (MHC) analysis in order to confirm its type (Type I expressing MHC I, and Type II expressing MHC IId). Type II fibers showed greater steady-state force depression after active shortening at a speed of 0.115 fiber length/s than Type I fibers (14.5±1.5% versus 7.8±1.7%). Moreover, at this absolute shortening speed, Type I fibers showed a significantly greater rate of force decay during shortening and produced less mechanical work than Type II fibers. When active shortening was performed at the same relative speed (17% V0), the difference in force depression between fiber types was abolished. These results suggest that no intrinsic differences were at the origin of the disparate force depressions observed in Type I and Type II fibers when actively shortened at the same absolute speed, but rather their distinct force-velocity relationships.

  18. Velocity, force, power, and Ca2+ sensitivity of fast and slow monkey skeletal muscle fibers

    Science.gov (United States)

    Fitts, R. H.; Bodine, S. C.; Romatowski, J. G.; Widrick, J. J.

    1998-01-01

    In this study, we determined the contractile properties of single chemically skinned fibers prepared from the medial gastrocnemius (MG) and soleus (Sol) muscles of adult male rhesus monkeys and assessed the effects of the spaceflight living facility known as the experiment support primate facility (ESOP). Muscle biopsies were obtained 4 wk before and immediately after an 18-day ESOP sit, and fiber type was determined by immunohistochemical techniques. The MG slow type I fiber was significantly smaller than the MG type II, Sol type I, and Sol type II fibers. The ESOP sit caused a significant reduction in the diameter of type I and type I/II (hybrid) fibers of Sol and MG type II and hybrid fibers but no shift in fiber type distribution. Single-fiber peak force (mN and kN/m2) was similar between fiber types and was not significantly different from values previously reported for other species. The ESOP sit significantly reduced the force (mN) of Sol type I and MG type II fibers. This decline was entirely explained by the atrophy of these fiber types because the force per cross-sectional area (kN/m2) was not altered. Peak power of Sol and MG fast type II fiber was 5 and 8.5 times that of slow type I fiber, respectively. The ESOP sit reduced peak power by 25 and 18% in Sol type I and MG type II fibers, respectively, and, for the former fiber type, shifted the force-pCa relationship to the right, increasing the Ca2+ activation threshold and the free Ca2+ concentration, eliciting half-maximal activation. The ESOP sit had no effect on the maximal shortening velocity (Vo) of any fiber type. Vo of the hybrid fibers was only slightly higher than that of slow type I fibers. This result supports the hypothesis that in hybrid fibers the slow myosin heavy chain would be expected to have a disproportionately greater influence on Vo.

  19. Differences in the Charge Distribution of Glycerol-Extracted Muscle Fibers in Rigor, Relaxation, and Contraction

    Science.gov (United States)

    Pemrick, Suzanne M.; Edwards, Charles

    1974-01-01

    Glycerol-extracted rabbit psoas muscle fibers were impaled with KCl-filled glass microelectrodes. For fibers at rest-length, the potentials were significantly more negative in solutions producing relaxation than in solutions producing either rigor or contraction; further the potentials in the latter two cases were not significantly different. For stretched fibers, with no overlap between thick and thin filaments, the potentials did not differ in the rigor, the relaxation, or the contraction solutions. The potentials measured from fibers in rigor did not vary significantly with the sarcomere length. For relaxed fibers, however, the potential magnitude decreased with increasing sarcomere length. The difference between the potentials measured for rigor and relaxed fibers exhibited a nonlinear relationship with sarcomere length. The potentials from calcium-insensitive fibers were less negative in both the rigor and the relaxation solutions than those from normal fibers. When calcium-insensitive fibers had been incubated in Hasselbach and Schneider's solution plus MgCl2 or Guba-Straub's solution plus MgATP the potentials recorded upon impalement were similar in the rigor and the relaxation solution to those obtained from normal fibers in the relaxed state. It is concluded that the increase in the negative potential as the glycerinated fiber goes from rigor to relaxation may be due to an alteration in the conformation of the contractile proteins in the relaxed state. PMID:4443791

  20. The fiber-type specific response of skeletal muscle satellite cells to high-intensity resistance training in dialysis patients

    DEFF Research Database (Denmark)

    Molsted, Stig; Andersen, Jesper Løvind; Harrison, Adrian Paul;

    2015-01-01

    weekly. SC and myonuclear number were determined by immunohistochemistry of vastus lateralis muscle biopsy cross-sections. Knee extension torque was tested in a dynamometer. Results. During training SCs/type I fibers increased by 15%, whereas SCs/type II fibers remained unchanged. Myonuclear content...... of type II, but not type I, fibers increased with training. Before the control period, the SC content of type II fibers was lower than type I fibers, whereas contents were comparable when normalized to fiber area. Torque increased after training. Discussion. Increased myonuclear content of type II muscle...

  1. Inhibition of FoxO transcriptional activity prevents muscle fiber atrophy during cachexia and induces hypertrophy

    Science.gov (United States)

    Reed, Sarah A.; Sandesara, Pooja B.; Senf, Sarah M.; Judge, Andrew R.

    2012-01-01

    Cachexia is characterized by inexorable muscle wasting that significantly affects patient prognosis and increases mortality. Therefore, understanding the molecular basis of this muscle wasting is of significant importance. Recent work showed that components of the forkhead box O (FoxO) pathway are increased in skeletal muscle during cachexia. In the current study, we tested the physiological significance of FoxO activation in the progression of muscle atrophy associated with cachexia. FoxO-DNA binding dependent transcription was blocked in the muscles of mice through injection of a dominant negative (DN) FoxO expression plasmid prior to inoculation with Lewis lung carcinoma cells or the induction of sepsis. Expression of DN FoxO inhibited the increased mRNA levels of atrogin-1, MuRF1, cathepsin L, and/or Bnip3 and inhibited muscle fiber atrophy during cancer cachexia and sepsis. Interestingly, during control conditions, expression of DN FoxO decreased myostatin expression, increased MyoD expression and satellite cell proliferation, and induced fiber hypertrophy, which required de novo protein synthesis. Collectively, these data show that FoxO-DNA binding-dependent transcription is necessary for normal muscle fiber atrophy during cancer cachexia and sepsis, and further suggest that basal levels of FoxO play an important role during normal conditions to depress satellite cell activation and limit muscle growth.—Reed, S. A., Sandesara, P. B., Senf, S. F., Judge, A. R. Inhibition of FoxO transcriptional activity prevents muscle fiber atrophy during cachexia and induces hypertrophy. PMID:22102632

  2. Nicotine-Induced Modulation of the Cholinergic Twitch Response in the Ileum of Guinea Pig.

    Science.gov (United States)

    Donnerer, Josef; Liebmann, Ingrid

    2015-01-01

    In the present study, the direct drug effects of nicotine and its effects on the cholinergic twitch responses of the electrically stimulated longitudinal muscle-myenteric plexus strip from the ileum of guinea pig were investigated. Nicotine dose-dependently (0.3-10 µmol/l) evoked the well-known contractile responses on its own. Whereas the interposed twitch responses remained present without a change in height at 1 µmol/l nicotine, a nicotine concentration of 3 µmol/l slightly and a concentration of 10 µmol/l markedly diminished the twitch during their presence. After the washout of 1-10 µmol/l nicotine, the height of the twitch response was also temporarily and significantly reduced by 30-77%. The P2X purinoceptor agonist αβ-methylene ATP (1-10 µmol/l) dose-dependently induced contractions on its own and reduced the twitch response during its presence in the organ bath; however, it did not diminish the twitch responses after washout of the drug as nicotine did. The P2X antagonist pyridoxalphosphate-6-azophenyl-2'-4'-disulphonic acid, the NMDA channel blocker MK-801 and the inhibitor of small conductance Ca(2+)-activated K(+) (SK) channels apamin reduced the contractile effect of 1 µmol/l nicotine. Apamin also significantly prevented the 'post-nicotine inhibition of the twitch' following the washout of 1-3 µmol/l nicotine. As a conclusion, we provide evidence for a functional interaction between nicotinic receptors and the P2X receptors in the ileum of the guinea pig. The 'post-nicotine inhibition of the twitch' is not due to nicotinic acetylcholine receptor desensitization or transmitter depletion, but most probably the secondary effects of nicotine on SK channels determine the reduced cholinergic motor neuron excitability.

  3. Intracellular calcium movements during relaxation and recovery of superfast muscle fibers of the toadfish swimbladder

    Science.gov (United States)

    Nelson, Frank E.; Hollingworth, Stephen; Rome, Lawrence C.

    2014-01-01

    The mating call of the Atlantic toadfish is generated by bursts of high-frequency twitches of the superfast twitch fibers that surround the swimbladder. At 16°C, a calling period can last several hours, with individual 80–100-Hz calls lasting ∼500 ms interleaved with silent periods (intercall intervals) lasting ∼10 s. To understand the intracellular movements of Ca2+ during the intercall intervals, superfast fibers were microinjected with fluo-4, a high-affinity fluorescent Ca2+ indicator, and stimulated by trains of 40 action potentials at 83 Hz, which mimics fiber activity during calling. The fluo-4 fluorescence signal was measured during and after the stimulus trains; the signal was also simulated with a kinetic model of the underlying myoplasmic Ca2+ movements, including the binding and transport of Ca2+ by the sarcoplasmic reticulum (SR) Ca2+ pumps. The estimated total amount of Ca2+ released from the SR during a first stimulus train is ∼6.5 mM (concentration referred to the myoplasmic water volume). At 40 ms after cessation of stimulation, the myoplasmic free Ca2+ concentration ([Ca2+]) is below the threshold for force generation (∼3 µM), yet the estimated concentration of released Ca2+ remaining in the myoplasm (Δ[CaM]) is large, ∼5 mM, with ∼80% bound to parvalbumin. At 10 s after stimulation, [Ca2+] is ∼90 nM (three times the assumed resting level) and Δ[CaM] is ∼1.3 mM, with 97% bound to parvalbumin. Ca2+ movements during the intercall interval thus appear to be strongly influenced by (a) the accumulation of Ca2+ on parvalbumin and (b) the slow rate of Ca2+ pumping that ensues when parvalbumin lowers [Ca2+] near the resting level. With repetitive stimulus trains initiated at 10-s intervals, Ca2+ release and pumping come quickly into balance as a result of the stability (negative feedback) supplied by the increased rate of Ca2+ pumping at higher [Ca2+]. PMID:24733838

  4. STRETCHY ELECTRONICS. Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles.

    Science.gov (United States)

    Liu, Z F; Fang, S; Moura, F A; Ding, J N; Jiang, N; Di, J; Zhang, M; Lepró, X; Galvão, D S; Haines, C S; Yuan, N Y; Yin, S G; Lee, D W; Wang, R; Wang, H Y; Lv, W; Dong, C; Zhang, R C; Chen, M J; Yin, Q; Chong, Y T; Zhang, R; Wang, X; Lima, M D; Ovalle-Robles, R; Qian, D; Lu, H; Baughman, R H

    2015-07-24

    Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson's ratio on torsional actuation and electronic properties.

  5. Myosin types and fiber types in cardiac muscle. II. Atrial myocardium.

    Science.gov (United States)

    Gorza, L; Sartore, S; Schiaffino, S

    1982-12-01

    Antibodies were produced against myosins isolated from the left atrial myocardium (anti-bAm) and the left ventricular myocardium (anti-bVm) of the bovine heart. Cross-reactive antibodies were removed by cross-absorption. Absorbed anti-bAm and anti-bVm were specific for the myosin heavy chains when tested by enzyme immunoassay combined with SDS gel electrophoresis. Indirect immunofluorescence was used to determine the reactivity of atrial muscle fibers to the two antibodies. Three populations of atrial muscle fibers were distinguished in the bovine heart: (a) fibers reactive with anti-bAm and unreactive with anti-bVm, like most fibers in the left atrium; (b) fibers reactive with both antibodies, especially numerous in the right atrium; (c) fibers reactive with anti-bVm and unreactive with anti-bAm, present only in the interatrial septum and in specific regions of the right atrium, such as the crista terminalis. These findings can be accounted for by postulating the existence of two distinct types of atrial myosin heavy chains, one of which is antigenically related to ventricular myosin. The tendency for fibers labeled by anti-bVm to occur frequently in bundles and their preferential distribution in the crista terminalis, namely along one of the main conduction pathways between the sinus node and the atrioventricular node, and in the interatrial septum, where different internodal tracts are known to converge, suggests that these fibers may be specialized for faster conduction.

  6. Muscle fiber velocity and electromyographic signs of fatigue in fibromyalgia

    NARCIS (Netherlands)

    Klaver-Krol, Ewa G.; Rasker, Johannes J.; Henriquez, Nizare R.; Verheijen, Wilma G.; Zwarts, Machiel J.

    2012-01-01

    Introduction: Fibromyalgia (FM) is a disorder of widespread muscular pain. We investigated possible differences in surface electromyography (sEMG) in clinically unaffected muscle between patients with FM and controls. Methods: sEMG was performed on the biceps brachii muscle of 13 women with FM and 1

  7. Muscle fiber velocity and electromyographic signs of fatigue in fibromyalgia

    NARCIS (Netherlands)

    Klaver-Krol, Ewa G.; Rasker, Johannes J.; Henriquez, Nizare R.; Verheijen, Wilma G.; Zwarts, Machiel J.

    2012-01-01

    Introduction: Fibromyalgia (FM) is a disorder of widespread muscular pain. We investigated possible differences in surface electromyography (sEMG) in clinically unaffected muscle between patients with FM and controls. Methods: sEMG was performed on the biceps brachii muscle of 13 women with FM and 1

  8. IP3-dependent, post-tetanic calcium transients induced by electrostimulation of adult skeletal muscle fibers

    Science.gov (United States)

    Casas, Mariana; Figueroa, Reinaldo; Jorquera, Gonzalo; Escobar, Matías; Molgó, Jordi

    2010-01-01

    Tetanic electrical stimulation induces two separate calcium signals in rat skeletal myotubes, a fast one, dependent on Cav 1.1 or dihydropyridine receptors (DHPRs) and ryanodine receptors and related to contraction, and a slow signal, dependent on DHPR and inositol trisphosphate receptors (IP3Rs) and related to transcriptional events. We searched for slow calcium signals in adult muscle fibers using isolated adult flexor digitorum brevis fibers from 5–7-wk-old mice, loaded with fluo-3. When stimulated with trains of 0.3-ms pulses at various frequencies, cells responded with a fast calcium signal associated with muscle contraction, followed by a slower signal similar to one previously described in cultured myotubes. Nifedipine inhibited the slow signal more effectively than the fast one, suggesting a role for DHPR in its onset. The IP3R inhibitors Xestospongin B or C (5 µM) also inhibited it. The amplitude of post-tetanic calcium transients depends on both tetanus frequency and duration, having a maximum at 10–20 Hz. At this stimulation frequency, an increase of the slow isoform of troponin I mRNA was detected, while the fast isoform of this gene was inhibited. All three IP3R isoforms were present in adult muscle. IP3R-1 was differentially expressed in different types of muscle fibers, being higher in a subset of fast-type fibers. Interestingly, isolated fibers from the slow soleus muscle did not reveal the slow calcium signal induced by electrical stimulus. These results support the idea that IP3R-dependent slow calcium signals may be characteristic of distinct types of muscle fibers and may participate in the activation of specific transcriptional programs of slow and fast phenotype. PMID:20837675

  9. Chronic treatment with 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside increases insulin-stimulated glucose uptake and GLUT4 translocation in rat skeletal muscles in a fiber type-specific manner.

    Science.gov (United States)

    Buhl, E S; Jessen, N; Schmitz, O; Pedersen, S B; Pedersen, O; Holman, G D; Lund, S

    2001-01-01

    Recent studies have demonstrated that chronic administration of AICAR (5-aminoimidazole-4-carboxamide- 1-beta-D-ribofuranoside), an activator of the AMP-activated protein kinase, increases hexokinase activity and the contents of total GLUT4 and glycogen in rat skeletal muscles. To explore whether AICAR also affects insulin-stimulated glucose transport and GLUT4 cell surface content, Wistar rats were subcutaneously injected with AICAR for 5 days in succession (1 mg/g body wt). Maximally insulin-stimulated (60 nmol/l) glucose uptake was markedly increased in epitrochlearis (EPI) muscle (average 63%, P fiber type-specific increase in insulin-stimulated glucose uptake and GLUT4 cell surface content in rat skeletal muscle with the greatest effect observed on white fast-twitch glycolytic muscles (EPI). These results are comparable with the effects of chronic exercise training, and it brings the AMP-activated protein kinase into focus as a new interesting target for future pharmacological intervention in insulin-resistant conditions.

  10. The Masticatory Contractile Load Induced Expression and Activation of Akt1/PKBα in Muscle Fibers at the Myotendinous Junction within Muscle-Tendon-Bone Unit

    Science.gov (United States)

    Korkmaz, Yüksel; Klinz, Franz J.; Moghbeli, Mehrnoush; Addicks, Klaus; Raab, Wolfgang H. -M.; Bloch, Wilhelm

    2010-01-01

    The cell specific detection of enzyme activation in response to the physiological contractile load within muscle-tendon-bone unit is essential for understanding of the mechanical forces transmission from muscle cells via tendon to the bone. The hypothesis that the physiological mechanical loading regulates activation of Akt1/PKBα at Thr308 and at Ser473 in muscle fibers within muscle-tendon-bone unit was tested using quantitative immunohistochemistry, confocal double fluorescence analysis, and immunoblot analysis. In comparison to the staining intensities in peripheral regions of the muscle fibers, Akt1/PKBα was detected with a higher staining intensity in muscle fibers at the myotendinous junction (MTJ) areas. In muscle fibers at the MTJ areas, Akt1/PKBα is dually phosphorylated at Thr308 and Ser473. The immunohistochemical results were confirmed by immunoblot analysis. We conclude that contractile load generated by masticatory muscles induces local domain-dependent expression of Akt1/PKBα as well as activation by dually phosphorylation at Thr308 and Ser473 in muscle fibers at the MTJ areas within muscle-tendon-bone unit. PMID:20454577

  11. The masticatory contractile load induced expression and activation of Akt1/PKBalpha in muscle fibers at the myotendinous junction within muscle-tendon-bone unit.

    Science.gov (United States)

    Korkmaz, Yüksel; Klinz, Franz J; Moghbeli, Mehrnoush; Addicks, Klaus; Raab, Wolfgang H-M; Bloch, Wilhelm

    2010-01-01

    The cell specific detection of enzyme activation in response to the physiological contractile load within muscle-tendon-bone unit is essential for understanding of the mechanical forces transmission from muscle cells via tendon to the bone. The hypothesis that the physiological mechanical loading regulates activation of Akt1/PKBalpha at Thr308 and at Ser473 in muscle fibers within muscle-tendon-bone unit was tested using quantitative immunohistochemistry, confocal double fluorescence analysis, and immunoblot analysis. In comparison to the staining intensities in peripheral regions of the muscle fibers, Akt1/PKBalpha was detected with a higher staining intensity in muscle fibers at the myotendinous junction (MTJ) areas. In muscle fibers at the MTJ areas, Akt1/PKBalpha is dually phosphorylated at Thr308 and Ser473. The immunohistochemical results were confirmed by immunoblot analysis. We conclude that contractile load generated by masticatory muscles induces local domain-dependent expression of Akt1/PKBalpha as well as activation by dually phosphorylation at Thr308 and Ser473 in muscle fibers at the MTJ areas within muscle-tendon-bone unit.

  12. The Masticatory Contractile Load Induced Expression and Activation of Akt1/PKBα in Muscle Fibers at the Myotendinous Junction within Muscle-Tendon-Bone Unit

    Directory of Open Access Journals (Sweden)

    Yüksel Korkmaz

    2010-01-01

    Full Text Available The cell specific detection of enzyme activation in response to the physiological contractile load within muscle-tendon-bone unit is essential for understanding of the mechanical forces transmission from muscle cells via tendon to the bone. The hypothesis that the physiological mechanical loading regulates activation of Akt1/PKBα at Thr308 and at Ser473 in muscle fibers within muscle-tendon-bone unit was tested using quantitative immunohistochemistry, confocal double fluorescence analysis, and immunoblot analysis. In comparison to the staining intensities in peripheral regions of the muscle fibers, Akt1/PKBα was detected with a higher staining intensity in muscle fibers at the myotendinous junction (MTJ areas. In muscle fibers at the MTJ areas, Akt1/PKBα is dually phosphorylated at Thr308 and Ser473. The immunohistochemical results were confirmed by immunoblot analysis. We conclude that contractile load generated by masticatory muscles induces local domain-dependent expression of Akt1/PKBα as well as activation by dually phosphorylation at Thr308 and Ser473 in muscle fibers at the MTJ areas within muscle-tendon-bone unit.

  13. Sexual dimorphism in the histologic organization of the muscle fibers in human tongue.

    Science.gov (United States)

    de Campos, Deivis; Jotz, Geraldo Pereira; Heck, Layana; Xavier, Léder Leal

    2014-07-01

    Tongue movements are critical for speech, swallowing, and respiration; and tongue dysfunction could lead to dysarthria, dysphagia, and obstructive sleep apnea, respectively. Our current understanding of the contributions of specific tongue muscles (TOs) to precise movement patterns is limited. Likewise, there is still little information regarding the orientation of histologic muscle fibers of the tongue in humans, especially between men and women. Thus, the aim of this study was to compare the histologic organization in the tongue of men and women. Ten tongues were studied in human specimens obtained from necropsies (five men and five women). The muscles were analyzed using histology, and the morphometric parameters were measured using Image Pro-Plus Software (Image Pro-Plus 6.0; Media Cybernetics, Silver Spring, MD). Slices were obtained from the anterior, median, and posterior parts of the tongue. We classified and estimated the percentages of transverse (T), oblique (O), and longitudinal (L) fibers in the tongue. To quantify the percentage of fibers in each category in the tongue, the shape coefficient (Shape Z) was estimated. Statistical differences were found between the orientation of the muscle fibers of men and women only for the middle region of the tongue. The middle region of the tongue in women compared with men has a smaller difference in the variation of the percentage of fibers T (P=0.0004), O (P=0.0006), and L (P=0.0013). These morphologic findings are probably related to physiological differences.

  14. Self-reinnervated cat medial gastrocnemius muscles. II. analysis of the mechanisms and significance of fiber type grouping in reinnervated muscles.

    Science.gov (United States)

    Rafuse, V F; Gordon, T

    1996-01-01

    1. The technique of glycogen depletion was used to determine whether regenerating motor axons reestablish the normal regionalization of motor units (MUs) in the cat medial gastrocnemius (MG) muscle, 2) whether the extent of clumping between MU fibers and/or type grouping of muscle fibers progressively increases with a decrease in reinnervated MU numbers, and 3) whether the pattern of innervation can explain why MUs fail to increase significantly in size when the cut nerve is sutured directly to the muscle, even when few axons make functional connections. 2. Distributions of MU fibers were analyzed in 5 normal and 14 reinnervated cat MG muscles 4.5-16 mo after sectioning of its nerve and suturing of the proximal end to the distal nerve sheaths (N-N suture) or directly to the muscle fascia (N-M suture). Muscle unit distributions were quantified according to location, territory size, density, and extent of clumping between fibers from the same MU. 3. Normal MU fibers were regionalized within five regions along the muscle's longitudinal and transverse axes. Reinnervated MUs were located within similar regions, indicating that regenerating axons follow the major proximal nerve branches to restore normal compartmentalization. 4. Muscle unit fibers were diffusely scattered within discrete MU territories in normal muscles. Territory size tended to increase with MU size, whereas density of muscle unit fibers within the territory decreased. 5. Territories increased with MU size after N-N suture but were smaller and showed little size variation after N-M suture. The extent of muscle unit fiber clumping was inversely related to the number of reinnervated MUs. On average, the extent of clumping was substantially higher in muscles reinnervated after N-M suture. These results indicate that distal nerve sheaths facilitate proximal axon branching, which establishes MU territory size. Once the territory is established, motor axons branch distally to increase MU size, which in turn

  15. Effect of endurance training on glucose transport capacity and glucose transporter expression in rat skeletal muscle

    DEFF Research Database (Denmark)

    Ploug, T; Stallknecht, B M; Pedersen, O

    1990-01-01

    session. Half-times for reversal of contraction-induced glucose transport were similar in trained and untrained muscles. The concentrations of mRNA for GLUT-1 (the erythrocyte-brain-Hep G2 glucose transporter) and GLUT-4 (the adipocyte-muscle glucose transporter) were increased approximately twofold...... by training in fast-twitch red muscle fibers. In parallel to this, Western blot demonstrated a approximately 47% increase in GLUT-1 protein and a approximately 31% increase in GLUT-4 protein. This indicates that the increases in maximum velocity for 3-MG transport in trained muscle is due to an increased...

  16. Lesions of rat skeletal muscle after local block of acetylcholinesterase and neuromuscular stimulation.

    Science.gov (United States)

    Mense, S; Simons, D G; Hoheisel, U; Quenzer, B

    2003-06-01

    In skeletal muscle, a local increase of acetylcholine (ACh) in a few end plates has been hypothesized to cause the formation of contraction knots that can be found in myofascial trigger points. To test this hypothesis in rats, small amounts of an acetylcholinesterase inhibitor [diisopropylfluorophosphate (DFP)] were injected into the proximal half of the gastrocnemius muscle, and the muscle nerve was electrically stimulated for 30-60 min for induction of muscle twitches. The distal half of the muscle, which performed the same contractions, served as a control to assess the effects of the twitches without DFP. Sections of the muscle were evaluated for morphological changes in relation to the location of blocked end plates. Compared with the distal half of the muscle, the DFP-injected proximal half exhibited significantly higher numbers of abnormally contracted fibers (local contractures), torn fibers, and longitudinal stripes. DFP-injected animals in which the muscle nerve was not stimulated and that were allowed to survive for 24 h exhibited the same lesions but in smaller numbers. The data indicate that an increased concentration of ACh in a few end plates causes damage to muscle fibers. The results support the assumption that a dysfunctional end plate exhibiting increased release of ACh may be the starting point for regional abnormal contractions, which are thought to be essential for the formation of myofascial trigger points.

  17. Eccentric contraction-induced injury to type I, IIa, and IIa/IIx muscle fibers of elderly adults

    Science.gov (United States)

    Muscles of old laboratory rodents experience exaggerated force losses after eccentric contractile activity. We extended this line of inquiry to humans and investigated the influence of fiber myosin heavy chain (MHC) isoform content on the injury process. Skinned muscle fiber segments, prepared from ...

  18. Function and position determine relative proportions of different fiber types in limb muscles of the lizard Tropidurus psammonastes.

    Science.gov (United States)

    Pereira, Anieli G; Abdala, Virginia; Kohlsdorf, Tiana

    2015-02-01

    Skeletal muscles can be classified as flexors or extensors according to their function, and as dorsal or ventral according to their position. The latter classification evokes their embryological origin from muscle masses initially divided during limb development, and muscles sharing a given position do not necessarily perform the same function. Here, we compare the relative proportions of different fiber types among six limb muscles in the lizard Tropidurus psammonastes. Individual fibers were classified as slow oxidative (SO), fast glycolytic (FG) or fast oxidative-glycolytic (FOG) based on mitochondrial content; muscles were classified according to position and function. Mixed linear models considering one or both effects were compared using likelihood ratio tests. Variation in the proportion of FG and FOG fibers is mainly explained by function (flexor muscles have on average lower proportions of FG and higher proportions of FOG fibers), while variation in SO fibers is better explained by position (they are less abundant in ventral muscles than in those developed from a dorsal muscle mass). Our results clarify the roles of position and function in determining the relative proportions of the various muscle fibers and provide evidence that these factors may differentially affect distinct fiber types. Copyright © 2014. Published by Elsevier GmbH.

  19. Fatigue accumulation and twitch potentiation during complex MVC-relative profiles.

    Science.gov (United States)

    Sonne, Michael W; Potvin, Jim R

    2015-08-01

    Fatigue accumulation can be significantly influenced by post-activation potentiation (PAP). This phenomenon leads to increased force generating capacity after a series of conditioning efforts. The purpose of our study was to examine how the order of force demands impacted muscle fatigue accumulation, and how fatigue was affected by potentiation. We had 33 participants complete one of four different force orders, consisting of 5 cycles of 12-s submaximal isometric "task plateaus". Every order consisted of 8 force plateaus of the different intensity, arranged in a different ways. A subset of 18 participants then received a stimulated muscle twitch, and all participants performed a brief MVC. Each task plateau was followed by a 12s long 10% MVC "reference plateau" also followed by twitch and MVC. Overall, the order of the force presentation only had an impact on fatigue levels and twitch potentiation during the first cycle. Maximum voluntary forces decreased, and twitch forces increased, at different rates between orders during the first cycle. At the end of each cycle, there was no difference between any of the orders in terms of twitch potentiation or decrease in MVC force. In a task that features identical force patterns, arranged in different orders, the order did not affect the final fatigue accumulation or potentiation level.

  20. X-linked recessive congenital muscle fiber hypotrophy with central nuclei: abnormalities of growth and adenylate cyclase in muscle tissue cultures.

    Science.gov (United States)

    Askanas, V; Engel, W K; Reddy, N B; Barth, P G; Bethlem, J; Krauss, D R; Hibberd, M E; Lawrence, J V; Carter, L S

    1979-10-01

    Muscle cells in cultures established from biopsy specimens of two children with an infantile-fatal form of X-linked recessive muscle fiber smallness with central nuclei showed an unusual ability to proliferate through numerous passages. Ultrastructurally, the cultured muscle fibers appeared very immature even after several weeks. The nuclei were large, the number of ribosomes was greatly increased, the myofibrils remained unstriated, and glycogen was accumulated in large lakes. The plasmalemma bound concanavalin A, alpha-bungarotoxin, and ruthenium red normally, but with tannic acid it did not show the dark binding of mature fibers. Biochemically, in the cultured muscle fibers, beta-adrenergic receptors were quantitatively normal. The level of adenylate cyclase in membranes was less than in cultured normal muscle; this defect could be responsible for impaired control mechanisms resulting in the other abnormalities observed.

  1. Identification and quantification in single muscle fibers of four isoforms of parvalbumin in the iliofibularis muscle of Xenopus laevis.

    Science.gov (United States)

    Simonides, W S; van Hardeveld, C

    1989-10-05

    The major parvalbumins present in the iliofibularis muscle of Xenopus laevis were identified and the total parvalbumin content of different types of single fibers of this muscle was determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS). The criteria used in the identification of proteins as parvalbumins were: a relative molecular mass (Mr) between 10,000 and 14,000, an isoelectric point (pI) between 4.0 and 5.0, and a Ca2+-dependent mobility when run on a polyacrylamide gel in the absence of SDS. Four proteins were thus identified as parvalbumins: PA1, Mr 14,000, pI 4.90; PA2, Mr 11,000, pI 4.90; PA3, Mr 11,000, pI 4.95; and PA4, Mr 11,000, pI 4.25. An ultraviolet absorbance spectrum characteristic of parvalbumins was recorded for a purified preparation of these four proteins. Because the apparent Mr of rabbit parvalbumin in the gel system used was 14,000, whereas the true value is 12,100, it is not excluded that the Mr of component PA1 of 14,000 is an overestimation. The total parvalbumin content of muscles and single muscle fibers was determined using the supernatant obtained after centrifugation of tissue homogenates. Analysis of the protein pattern after electrophoresis in the presence of SDS of this fraction indicated that the Mr 14,000 and 11,000 protein bands contained virtually only parvalbumin. Quantification of the total parvalbumin content of relatively fast (type 1) and slow (type 2) contracting and relaxing single muscle fibers, using laser densitometric analysis of minigels, yielded mean values (mg protein/g wet wt., +/- S.D.) of 5.2 +/- 0.8 for nine type 1 fibers, and 1.9 +/- 1.0 for five type 2 fibers. Both fiber types contained about 2.5-times as much of the Mr 14,000 isoform relative to the combined Mr 11,000 isoforms.

  2. Smooth muscle-like tissue constructs with circumferentially oriented cells formed by the cell fiber technology.

    Directory of Open Access Journals (Sweden)

    Amy Y Hsiao

    Full Text Available The proper functioning of many organs and tissues containing smooth muscles greatly depends on the intricate organization of the smooth muscle cells oriented in appropriate directions. Consequently controlling the cellular orientation in three-dimensional (3D cellular constructs is an important issue in engineering tissues of smooth muscles. However, the ability to precisely control the cellular orientation at the microscale cannot be achieved by various commonly used 3D tissue engineering building blocks such as spheroids. This paper presents the formation of coiled spring-shaped 3D cellular constructs containing circumferentially oriented smooth muscle-like cells differentiated from dedifferentiated fat (DFAT cells. By using the cell fiber technology, DFAT cells suspended in a mixture of extracellular proteins possessing an optimized stiffness were encapsulated in the core region of alginate shell microfibers and uniformly aligned to the longitudinal direction. Upon differentiation induction to the smooth muscle lineage, DFAT cell fibers self-assembled to coiled spring structures where the cells became circumferentially oriented. By changing the initial core-shell microfiber diameter, we demonstrated that the spring pitch and diameter could be controlled. 21 days after differentiation induction, the cell fibers contained high percentages of ASMA-positive and calponin-positive cells. Our technology to create these smooth muscle-like spring constructs enabled precise control of cellular alignment and orientation in 3D. These constructs can further serve as tissue engineering building blocks for larger organs and cellular implants used in clinical treatments.

  3. Smooth muscle-like tissue constructs with circumferentially oriented cells formed by the cell fiber technology.

    Science.gov (United States)

    Hsiao, Amy Y; Okitsu, Teru; Onoe, Hiroaki; Kiyosawa, Mahiro; Teramae, Hiroki; Iwanaga, Shintaroh; Kazama, Tomohiko; Matsumoto, Taro; Takeuchi, Shoji

    2015-01-01

    The proper functioning of many organs and tissues containing smooth muscles greatly depends on the intricate organization of the smooth muscle cells oriented in appropriate directions. Consequently controlling the cellular orientation in three-dimensional (3D) cellular constructs is an important issue in engineering tissues of smooth muscles. However, the ability to precisely control the cellular orientation at the microscale cannot be achieved by various commonly used 3D tissue engineering building blocks such as spheroids. This paper presents the formation of coiled spring-shaped 3D cellular constructs containing circumferentially oriented smooth muscle-like cells differentiated from dedifferentiated fat (DFAT) cells. By using the cell fiber technology, DFAT cells suspended in a mixture of extracellular proteins possessing an optimized stiffness were encapsulated in the core region of alginate shell microfibers and uniformly aligned to the longitudinal direction. Upon differentiation induction to the smooth muscle lineage, DFAT cell fibers self-assembled to coiled spring structures where the cells became circumferentially oriented. By changing the initial core-shell microfiber diameter, we demonstrated that the spring pitch and diameter could be controlled. 21 days after differentiation induction, the cell fibers contained high percentages of ASMA-positive and calponin-positive cells. Our technology to create these smooth muscle-like spring constructs enabled precise control of cellular alignment and orientation in 3D. These constructs can further serve as tissue engineering building blocks for larger organs and cellular implants used in clinical treatments.

  4. Functional imaging of skeletal muscle fiber in different physiological states by second harmonic generation

    Science.gov (United States)

    Nucciotti, V.; Stringari, C.; Sacconi, L.; Vanzi, F.; Tesi, C.; Piroddi, N.; Poggesi, C.; Castiglioni, C.; Milani, A.; Linari, M.; Piazzesi, G.; Lombardi, V.; Pavone, F. S.

    2007-07-01

    The intrinsically ordered arrays of proteins in skeletal muscle allows imaging of this tissue by Second Harmonic Generation (SHG). Biochemical and colocalization studies have gathered an increasing wealth of clues for the attribution of the molecular origin of the muscle SHG signal to the motor protein myosin. Thus, SHG represents a potentially very powerful tool in the investigation of structural dynamics occurring in muscle during active production of force. A full characterization of the polarization-dependence of the SHG signal represents a very selective information on the orientation of the emitting proteins and their dynamics during contraction, provided that different physiological states of muscle (relaxed, rigor and active) exhibit distinct patterns of SHG polarization dependence. Here polarization data are obtained from single frog muscle fibers at rest and during isometric contraction and interpreted, by means of a model, in terms of an average orientation of the SHG emitters which are structured with a cylindrical symmetry about the fiber axis. Optimizing the setup for accurate polarization measurements with SHG, we developed a line scan imaging method allowing measurement of SHG polarization curves in different physiological states. We demonstrate that muscle fiber displays a measurable variation of the orientation of SHG emitters with the transition from rest to isometric contraction.

  5. Selective cortical control of information flow through different intraspinal collaterals of the same muscle afferent fiber.

    Science.gov (United States)

    Eguibar, J R; Quevedo, J; Jiménez, I; Rudomin, P

    1994-04-18

    We have analyzed in the anesthetized cat the effects of electrical stimulation of the cerebral cortex on the intraspinal threshold of two collaterals belonging to the same muscle spindle or tendon organ afferent fiber. The results obtained provide, for the first time, direct evidence showing that the motor cortex is able to modify, in a highly selective manner, the synaptic effectiveness of individual collaterals of the same primary afferent fiber. This presynaptic control could function as a mechanism that allows funneling of information to specific groups of spinal neurons in the presence of extensive intraspinal branching of the afferent fibers.

  6. Fiber type specific expression of TNF-alpha, IL-6 and IL-18 in human skeletal muscles

    DEFF Research Database (Denmark)

    Plomgaard, Peter; Penkowa, Milena; Pedersen, Bente K

    2005-01-01

    Skeletal muscle is now recognized as an endocrine organ with the capacity to produce signal peptides in response to muscle contractions. Here we demonstrate that resting healthy human muscles express cytokines in a fiber type specific manner. Human muscle biopsies from seven healthy young males...... were obtained from m. triceps, m. quadriceps vastus lateralis and m. soleus. Type I fibers contributed (mean +/- SE) 24.0 +/- 2.5% in triceps of total fibers, 51.3 +/- 2.4% in vastus and 84.9 +/- 22% in soleus. As expected, differences in the fiber type composition were accompanied by marked...... differences between the three muscles with regard to MHC I and MHC IIa mRNA expression. Immunohistochemistry demonstrated that tumor necrosis factor (TNF)-alpha and interleukin (IL)-18 were solely expressed by type II fibers, whereas the expression of IL-6 was more prominent in type I compared to type II...

  7. Abnormalities in the Fiber Composition and Capillary Architecture in the Soleus Muscle of Type 2 Diabetic Goto-Kakizaki Rats

    Directory of Open Access Journals (Sweden)

    Shinichiro Murakami

    2012-01-01

    Full Text Available Type 2 diabetes mellitus is linked to impaired skeletal muscle glucose uptake and storage. This study aimed to investigate the fiber type distributions and the three-dimensional (3D architecture of the capillary network in the skeletal muscles of type 2 diabetic rats. Muscle fiber type transformation, succinate dehydrogenase (SDH activity, capillary density, and 3D architecture of the capillary network in the soleus muscle were determined in 36-week-old Goto-Kakizaki (GK rats as an animal model of nonobese type 2 diabetes and age-matched Wistar (Cont rats. Although the soleus muscle of Cont rats comprised both type I and type IIA fibers, the soleus muscle of GK rats had only type I fibers. In addition, total SDH activity in the soleus muscle of GK rats was significantly lower than that in Cont rats because GK rats had no high-SDH activity type IIA fiber in the soleus muscle. Furthermore, the capillary diameter, capillary tortuosity, and microvessel volume in GK rats were significantly lower than those in Cont rats. These results indicate that non-obese diabetic GK rats have muscle fiber type transformation, low SDH activity, and reduced skeletal muscle capillary content, which may be related to the impaired glucose metabolism characteristic of type 2 diabetes.

  8. Coenzyme Q10 Deficiency and Type 2C Muscle Fibers

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2013-12-01

    Full Text Available Investigators at Washington University School of Medicine, St Louis, MO, evaluated retrospectively clinical, laboratory, and muscle histochemistry and oxidative enzyme characteristics in 49 children with suspected mitochondrial disorders.

  9. Controlled chaos: three-dimensional kinematics, fiber histochemistry, and muscle contractile dynamics of autotomized lizard tails.

    Science.gov (United States)

    Higham, Timothy E; Lipsett, Kathryn R; Syme, Douglas A; Russell, Anthony P

    2013-01-01

    The ability to shed an appendage occurs in both vertebrates and invertebrates, often as a tactic to avoid predation. The tails of lizards, unlike most autotomized body parts of animals, exhibit complex and vigorous movements once disconnected from the body. Despite the near ubiquity of autotomy across groups of lizards and the fact that this is an extraordinary event involving the self-severing of the spinal cord, our understanding of why and how tails move as they do following autotomy is sparse. We herein explore the histochemistry and physiology of the tail muscles of the leopard gecko (Eublepharis macularius), a species that exhibits vigorous and variable tail movements following autotomy. To confirm that the previously studied tail movements of this species are generally representative of geckos and therefore suitable for in-depth muscle studies, we quantified the three-dimensional kinematics of autotomized tails in three additional species. The movements of the tails of all species were generally similar and included jumps, flips, and swings. Our preliminary analyses suggest that some species of gecko exhibit short but high-frequency movements, whereas others exhibit larger-amplitude but lower-frequency movements. We then compared the ATPase and oxidative capacity of muscle fibers and contractile dynamics of isolated muscle bundles from original tails, muscle from regenerate tails, and fast fibers from an upper limb muscle (iliofibularis) of the leopard gecko. Histochemical analysis revealed that more than 90% of the fibers in original and regenerate caudal muscles had high ATPase but possessed a superficial layer of fibers with low ATPase and high oxidative capacity. We found that contraction kinetics, isometric force, work, power output, and the oscillation frequency at which maximum power was generated were lowest in the original tail, followed by the regenerate tail and then the fast fibers of the iliofibularis. Muscle from the original tail exhibited

  10. Acute effects of passive stretching on the electromechanical delay and evoked twitch properties.

    Science.gov (United States)

    Costa, Pablo B; Ryan, Eric D; Herda, Trent J; Walter, Ashley A; Hoge, Katherine M; Cramer, Joel T

    2010-01-01

    The purpose of this study was to investigate the acute effects of passive stretching on the electromechanical delay (EMD), peak twitch force (PTF), rate of force development (RFD), and compound muscle action potential (M-wave) amplitude during evoked twitches of the plantar flexor muscles. 16 men (mean age +/- SD = 21.1 +/- 1.7 years; body mass = 75.9 +/- 11.4 kg; height = 176.5 +/- 8.6 cm) participated in this study. A single, square-wave, supramaximal transcutaneous electrical stimulus was delivered to the tibial nerve before and after passive stretching. The stretching protocol consisted of nine repetitions of passive assisted stretching designed to stretch the calf muscles. Each repetition was held for 135 s separated by 5-10 s of rest. Dependent-samples t tests (pre- vs. post-stretching) were used to analyze the EMD, PTF, RFD, and M-wave amplitude data. There were significant changes (P 0.05). These findings suggested that passively stretching the calf muscles affected the mechanical aspects of force production from the onset of the electrically evoked twitch to the peak twitch force. These results may help to explain the mechanisms underlying the stretching-induced force deficit that have been reported as either "mechanical" or "electrical" in origin.

  11. Continued twitching of the latissimus dorsi miniflap after breast conservation therapy: a case report

    Directory of Open Access Journals (Sweden)

    Huang Du-Ping

    2012-06-01

    Full Text Available Abstract We report a case of continued twitching of the latissimus dorsi muscle following breast conservation therapy, along with immediate reconstruction with a latissimus dorsi miniflap, which continued despite several attempts at control including BTX-A percutaneous local injection, and was finally cured by delayed division of the thoracodorsal nerve via a small well-tolerated axillary incision.

  12. Differential adenosine sensitivity of diaphragm and skeletal muscle arterioles.

    Science.gov (United States)

    Aaker, Aaron; Laughlin, M H

    2002-09-01

    The hyperemic response in exercising skeletal muscle is dependent on muscle fiber-type composition and fiber recruitment patterns, but the vascular control mechanisms producing exercise hyperemia in skeletal muscle remain poorly understood. The purpose of this study was to test the hypothesis that arterioles from white, low-oxidative skeletal muscle are less responsive to adenosine-induced dilation than are arterioles from diaphragm (Dia) and red, high-oxidative skeletal muscle. Second-order arterioles (2As) were isolated from the white portion of gastrocnemius muscle (WG; low-oxidative, fast-twitch muscle tissue) and two types of high-oxidative skeletal muscle [Dia and red portion of gastrocnemius muscle (RG)] of rats. Results reveal that 2As from all three types of muscle dilated in response to the endothelium-dependent dilator acetylcholine (WG: 48 +/- 3%, Dia: 51 +/- 3%, RG: 74 +/- 3%). In contrast, adenosine dilated only 2As from WG (48 +/- 4%) and Dia (46 +/- 5%) but not those from RG (5 +/- 5%). Thus adenosine-induced dilator responses differed among 2As of these different types of muscle tissue. However, the results do not support our hypothesis because 2As from Dia and WG dilated in response to adenosine, whereas 2As from RG did not. We conclude that the adenosine responsiveness of 2As from rat skeletal muscle cannot be predicted only by the fiber-type composition or oxidative capacity of the skeletal muscle tissue wherein the arteriole lies.

  13. Injection of duck recombinant follistatin fusion protein into duck muscle tissues stimulates satellite cell proliferation and muscle fiber hypertrophy.

    Science.gov (United States)

    Liu, He-he; Wang, Ji-wen; Yu, Hai-yue; Zhang, Rong-ping; Chen, Xi; Jin, Hai-bo; Dai, Fei; Li, Liang; Xu, Feng

    2012-06-01

    Follistatin (FST) can inhibit the expression of myostatin, which is a predominant inhibitor of muscle development. The potential application of myostatin-based technology has been prompted in different ways in agriculture. We previously constructed an expression vector of duck FST and isolated the FST fusion protein. After the protein was purified and refolded, it was added to the medium of duck myoblasts cultured in vitro. The results show that the 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide value of the myoblasts in the duck FST treatment group is higher than that in the control group, which indicates that the duck FST fusion protein exhibits the biological activities that can accelerate myoblast proliferation. To further investigate the roles of duck FST on muscle development, we injected the protein into the duck muscle tissues in vivo. The results show that both the duck muscle fiber cross-sectional area and the satellite cell activation frequency are influenced more in the FST treatment group than they are in the control group. In addition to these phenomena, expression of MyoD and Myf5 were increased, and the expression of myostatin was decreased. Together, these results suggest the potential for using duck FST fusion protein to inhibit myostatin activity and subsequently to enhance muscle growth in vivo. The mechanism by which FST regulates muscle development in the duck is similar to that in mammals and fishes.

  14. Fiber type specific expression of TNF-alpha, IL-6 and IL-18 in human skeletal muscles.

    Science.gov (United States)

    Plomgaard, Peter; Penkowa, Milena; Pedersen, Bente K

    2005-01-01

    Skeletal muscle is now recognized as an endocrine organ with the capacity to produce signal peptides in response to muscle contractions. Here we demonstrate that resting healthy human muscles express cytokines in a fiber type specific manner. Human muscle biopsies from seven healthy young males were obtained from m. triceps, m. quadriceps vastus lateralis and m. soleus. Type I fibers contributed (mean +/- SE) 24.0 +/- 2.5% in triceps of total fibers, 51.3 +/- 2.4% in vastus and 84.9 +/- 22% in soleus. As expected, differences in the fiber type composition were accompanied by marked differences between the three muscles with regard to MHC I and MHC IIa mRNA expression. Immunohistochemistry demonstrated that tumor necrosis factor (TNF)-alpha and interleukin (IL)-18 were solely expressed by type II fibers, whereas the expression of IL-6 was more prominent in type I compared to type II fibers. The fiber type specificity was found in triceps, vastus and soleus indicating that the level of daily muscle activity did not influence basal cytokine expression. The specificity of cytokine expression in different muscle fiber types in healthy young males suggests that cytokines may play specific regulatory roles in normal physiology.

  15. EXPERIMENTAL STUDY ON INFLUENCE OF MUSCLE TENSION TOWARDS THE FUNCTION OF THE SKELETAL MUSCLE FOLLOWING ITS REINNERVATION

    Institute of Scientific and Technical Information of China (English)

    Pramod DEVKOTA; ZENG Bing-fang(曾炳芳); FAN Cun-yi(范存义); TANG Jian-fei(唐剑飞); SHUI Shu-ping(眭述平); JIANG Pei-zhu(姜佩珠)

    2004-01-01

    Objective To investigate the influence of tension on the function of the denervated skeletal muscle after its reinnervation. Methods Fifty-four Sprague-Dawley (SD) rats were randomly divided into 3 groups. The left gastrocnemius muscles of the rats were dissected with only the neurovascular pedicles intact; the tibial nerves were cut and immediately repaired by epineurial suture. Then the Achilles tendons were isolated and treated accordingly; the Achilles tendon was lengthened by 0. 5cra in lengthened group, shortened by 0. 5cra in shortened group and left alone in normal (control) group. In the 2nd, 4th and 8th week after operation, the isometric twitch contractile force of both the right and the left gastrocnemius muscles were measured; specimens were taken from gastrocnemius muscle for histological study by light microscope. Results In comparison between the groups, the gastrocnemius muscles in the shortened group showed less severe muscle atrophy and connective tissue proliferation,bigger diameter and cross section dimension of the muscle fiber and greater isometric twitch contractile strength of the bilateral gastrocnemius muscles than those in the normal and lengthened groups in all the postoperative periods.Conclusion A proper high tension of the muscle may improve the function of the denervated skeletal muscle after its reinnervation.

  16. Effect of Tongue Exercise on Protrusive Force and Muscle Fiber Area in Aging Rats

    Science.gov (United States)

    Connor, Nadine P.; Russell, John A.; Wang, Hao; Jackson, Michelle A.; Mann, Laura; Kluender, Keith

    2009-01-01

    Purpose: Age-related changes in tongue function may contribute to dysphagia in elderly people. The authors' purpose was to investigate whether aged rats that have undergone tongue exercise would manifest increased protrusive tongue forces and increased genioglossus (GG) muscle fiber cross-sectional areas. Method: Forty-eight young adult,…

  17. An image processing pipeline to detect and segment nuclei in muscle fiber microscopic images.

    Science.gov (United States)

    Guo, Yanen; Xu, Xiaoyin; Wang, Yuanyuan; Wang, Yaming; Xia, Shunren; Yang, Zhong

    2014-08-01

    Muscle fiber images play an important role in the medical diagnosis and treatment of many muscular diseases. The number of nuclei in skeletal muscle fiber images is a key bio-marker of the diagnosis of muscular dystrophy. In nuclei segmentation one primary challenge is to correctly separate the clustered nuclei. In this article, we developed an image processing pipeline to automatically detect, segment, and analyze nuclei in microscopic image of muscle fibers. The pipeline consists of image pre-processing, identification of isolated nuclei, identification and segmentation of clustered nuclei, and quantitative analysis. Nuclei are initially extracted from background by using local Otsu's threshold. Based on analysis of morphological features of the isolated nuclei, including their areas, compactness, and major axis lengths, a Bayesian network is trained and applied to identify isolated nuclei from clustered nuclei and artifacts in all the images. Then a two-step refined watershed algorithm is applied to segment clustered nuclei. After segmentation, the nuclei can be quantified for statistical analysis. Comparing the segmented results with those of manual analysis and an existing technique, we find that our proposed image processing pipeline achieves good performance with high accuracy and precision. The presented image processing pipeline can therefore help biologists increase their throughput and objectivity in analyzing large numbers of nuclei in muscle fiber images.

  18. Effect of Tongue Exercise on Protrusive Force and Muscle Fiber Area in Aging Rats

    Science.gov (United States)

    Connor, Nadine P.; Russell, John A.; Wang, Hao; Jackson, Michelle A.; Mann, Laura; Kluender, Keith

    2009-01-01

    Purpose: Age-related changes in tongue function may contribute to dysphagia in elderly people. The authors' purpose was to investigate whether aged rats that have undergone tongue exercise would manifest increased protrusive tongue forces and increased genioglossus (GG) muscle fiber cross-sectional areas. Method: Forty-eight young adult,…

  19. Supramaximal stimuli do not evoke a maximal contraction in urinary bladder smooth muscle fibers

    NARCIS (Netherlands)

    J. Minekus (Joanne); A.J. Visser (Anna); R. van Mastrigt (Ron)

    2001-01-01

    textabstractBACKGROUND: Smooth muscle fibers can be stimulated with an electrical field, high potassium or carbachol. We studied the effect of combined, supramaximal stimulation on the isometric force and the maximum shortening velocity of the pig urinary bladder. MATERIALS AND METHODS: After determ

  20. The expression of HSP in human skeletal muscle. Effects of muscle fiber phenotype and training background

    DEFF Research Database (Denmark)

    Folkesson, Mattias; Mackey, Abigail L; Langberg, Henning;

    2013-01-01

    AIM: Exercise-induced adaptations of skeletal muscle are related to training mode and can be muscle fibre type specific. This study aimed to investigate heat shock protein expression in type I and type II muscle fibres in resting skeletal muscle of subjects with different training backgrounds...... HSPs in human skeletal muscle is influenced by muscle fibre phenotype. The fibre type specific expression of HSP70 is influenced by resistance and endurance training whereas those of αB-crystallin and HSP27 are influenced only by endurance training suggesting the existence of a training......-modality specific action on the adaptive processes including heat shock proteins in human skeletal muscle. This article is protected by copyright. All rights reserved....

  1. Contractile Properties of Single Permeabilized Muscle Fibers from Congenital Cleft Palates and Normal Palates of Spanish Goats

    Science.gov (United States)

    Hanes, Michael C.; Weinzweig, Jeffrey; Kuzon, William M.; Panter, Kip E.; Buchman, Steven R.; Faulkner, John A.; Yu, Deborah; Cederna, Paul S.; Larkin, Lisa M.

    2009-01-01

    Background Analysis of the composition of muscle fibers constituent to a cleft palate could provide significant insight into the cause of velopharyngeal inadequacy. The authors hypothesized that levator veli palatini muscle dysfunction inherent to cleft palates could affect the timing and outcome of cleft palate repair. Methods Single, permeabilized muscle fibers from levator veli palatini muscles of three normal (n = 19 fibers) and three chemically induced congenital cleft palates (n = 21 fibers) of 14-month-old goats were isolated, and contractile properties were evaluated. The maximum isometric force and rate constants of tension redevelopment (ktr) were measured, and the specific force and normalized power were calculated for each fiber. Results The ktr measures indicate that cleft fibers are predominantly fast-fatigable; normal fibers are slow fatigue-resistant: after a 10-minute isometric contraction, fibers from cleft palates had a loss of force 16 percent greater than that from normal palates (p = 0.0001). The cross-sectional areas of the fibers from cleft palates (2750 ± 209 μm2) were greater (p = 0.05) than those from normal palates (2226 ± 143 μm2). Specific forces did not differ between the two groups. Maximum normalized power of fibers from cleft palates (11.05 ± 1.82 W/l) was greater (p = 0.0001) than fibers from normal palates (1.60 ± 0.12 W/l). Conclusions There are clear physiologic differences in single muscle fibers from cleft palates and normal palates: cleft palate fibers are physiologically fast, have greater fatigability, and have greater power production. Detection of functional and/or fiber type differences in muscles of cleft palates may provide preoperative identification of a patient's susceptibility to velopharyngeal inadequacy and permit early surgical intervention to correct this clinical condition. PMID:17440342

  2. Newly formed skeletal muscle fibers are prone to false positive immunostaining by rabbit antibodies

    DEFF Research Database (Denmark)

    Andersen, Ditte C; Kliem, Anette; Schrøder, Henrik Daa

    2011-01-01

    Reports on muscle biology and regeneration often implicate immuno(cyto/histo)chemical protein characterization using rabbit polyclonal antibodies. In this study we demonstrate that newly formed myofibers are especially prone to false positive staining by rabbit antibodies and this unwanted staining...... is only recognized (1) by a negative muscle tissue control that does not harbor the protein to be examined (fx. from knockout mouse) or (2) by use of a nonsense rabbit antibody that has been prepared in the same way as the antibody of interest. However, many muscle immuno(cyto/histo)chemical studies only...... rely on controls that reveal non-specific binding by the secondary antibody and neglect that the primary rabbit antibody itself may cause false positive staining of the muscle. We suggest that reliable immuno-based protein detection in newly formed muscle fibers at least requires a nonsense rabbit...

  3. Glutamine deficiency in extracellular fluid exerts adverse effects on protein and amino acid metabolism in skeletal muscle of healthy, laparotomized, and septic rats.

    Science.gov (United States)

    Holecek, Milan; Sispera, Ludek

    2014-05-01

    Characteristic feature of critical illness, such as trauma and sepsis, is muscle wasting associated with activated oxidation of branched-chain amino acids (valine, leucine, isoleucine) and enhanced release of glutamine (GLN) to the blood. GLN consumption in visceral tissues frequently exceeds its release from muscle resulting in GLN deficiency that may exert adverse effects on the course of the disease. In the present study, we investigated the effects of GLN depletion in extracellular fluid on GLN production and protein and amino acid metabolism in skeletal muscle of healthy, laparotomized, and septic rats. Cecal ligation and puncture (CLP) was used as a model of sepsis. After 24 h, soleus muscle (SOL, slow-twitch, red muscle) and extensor digitorum longus (EDL, fast-twitch, white muscle) were isolated and incubated in a medium containing 0.5 mM GLN or without GLN. L-[1-(14)C]leucine was used to estimate protein synthesis and leucine oxidation, 3-methylhistidine release was used to evaluate myofibrillar protein breakdown. CLP increased GLN release from muscle, protein breakdown and leucine oxidation, and decreased protein synthesis. The effects were more pronounced in EDL. Alterations induced by laparotomy were similar to those observed in sepsis, but of a lower extent. GLN deficiency in medium enhanced GLN release and decreased intramuscular GLN concentration, decreased protein synthesis in muscles of intact and laparotomized rats, and enhanced leucine oxidation in SOL of intact and protein breakdown in SOL of laparotomized rats. It is concluded that (1) fast-twitch fibers are more sensitive to septic stimuli than slow-twitch fibers, (2) extracellular GLN deficiency may exert adverse effects on protein and amino acid metabolism in skeletal muscle, and (3) muscles of healthy and laparotomized animals are more sensitive to GLN deficiency than muscles of septic animals.

  4. Artificial muscles made of chiral two-way shape memory polymer fibers

    Science.gov (United States)

    Yang, Qianxi; Fan, Jizhou; Li, Guoqiang

    2016-10-01

    In this work, we demonstrate the unusual improvement of the tensile actuation of hierarchically chiral structured artificial muscle made of two-way shape memory polymer (2W-SMP) fiber. Experimental results show that the chemically cross-linked poly(ethylene-co-vinyl acetate) 2W-SMP fibers possess an average negative coefficient of thermal expansion (NCTE) that is at least one order higher than that of the polyethylene fiber used previously. As expected, the increase in axial thermal contraction of the precursor fiber leads to an increase in the recovered torque ( 4.4 Nmm ) of the chiral fiber and eventually in the tensile actuation of the twisted-then-coiled artificial muscle ( 67.81 ±1.82 % ). A mechanical model based on Castigliano's second theorem is proposed, and the calculated result is consistent with the experimental result (64.17% tensile stroke). The model proves the significance of the NCTE and the recovered torque on tensile actuation of the artificial muscle and can be used as a guidance for the future design.

  5. Mouse Skeletal Muscle Fiber-Type-Specific Macroautophagy and Muscle Wasting Are Regulated by a Fyn/STAT3/Vps34 Signaling Pathway

    Directory of Open Access Journals (Sweden)

    Eijiro Yamada

    2012-05-01

    Full Text Available Skeletal muscle atrophy induced by aging (sarcopenia, inactivity, and prolonged fasting states (starvation is predominantly restricted to glycolytic type II muscle fibers and typical spares oxidative type I fibers. However, the mechanisms accounting for muscle fiber-type specificity of atrophy have remained enigmatic. In the current study, although the Fyn tyrosine kinase activated the mTORC1 signaling complex, it also induced marked atrophy of glycolytic fibers with relatively less effect on oxidative muscle fibers. This was due to inhibition of macroautophagy via an mTORC1-independent but STAT3-dependent reduction in Vps34 protein levels and decreased Vps34/p150/Beclin1/Atg14 complex 1. Physiologically, in the fed state endogenous Fyn kinase activity was increased in glycolytic but not oxidative skeletal muscle. In parallel, Y705-STAT3 phosphorylation increased with decreased Vps34 protein levels. Moreover, fed/starved regulation of Y705-STAT3 phosphorylation and Vps34 protein levels was prevented in skeletal muscle of Fyn null mice. These data demonstrate a Fyn/STAT3/Vps34 pathway that is responsible for fiber-type-specific regulation of macroautophagy and skeletal muscle atrophy.

  6. An unusual myopathy: speckled muscle fibers due to enlarged mitochondria.

    Science.gov (United States)

    Jeffree, Rosalind L; Wills, Edward J; Harper, Clive

    2007-07-01

    We report a 52-year-old woman who presented with a 6-month history of proximal muscle weakness, elevated serum creatine kinase, and myopathic pattern on electromyography (EMG). Histology of the muscle shows a speckled pattern due to clustering of enlarged mitochondria. The pathology resembles that of selenium deficiency. The patient was found to have borderline low serum selenium and also low vitamin D and thyroid-stimulating hormone. The cause of this unusual myopathy is probably multifactorial. This case is important because the unusual pathological picture represents a potentially treatable myopathy. In addition, we hope that publication of the complex clinical and biochemical abnormalities of this case, in conjunction with other case reports, may facilitate future elucidation of muscle mitochondrial function and dysfunction.

  7. Tetranectin in slow intra- and extrafusal chicken muscle fibers

    DEFF Research Database (Denmark)

    Xu, X; Gilpin, B; Iba, K

    2001-01-01

    Tetranectin is a C-type lectin that occurs in the mammalian musculoskeletal system. In the present report we describe the first studies on an avian tetranectin. A full-length chicken tetranectin cDNA was isolated. Comparison of the deduced amino acid sequence of chicken tetranectin with mouse...... and human tetranectin showed an identity of 67 and 68%, respectively. Northern blot analysis demonstrated broad expression of chicken tetranectin mRNA, which was first detected on embryonic day 4. Tetranectin protein was detected in chicken serum and egg yolk. Since muscle is one of few tissues in which...... tetranectin protein is retained, we examined the distribution of tetranectin in various muscle types in chicken. Myofibers strongly positive for tetranectin were observed in several muscles including m. tibialis ant. and m. sartorius (from embryonic day 10 to adult). Using antibodies to fast and slow myosin...

  8. Severe insulin-resistant diabetes mellitus in patients with congenital muscle fiber type disproportion myopathy.

    Science.gov (United States)

    Vestergaard, H; Klein, H H; Hansen, T; Müller, J; Skovby, F; Bjørbaek, C; Røder, M E; Pedersen, O

    1995-04-01

    Congenital muscle fiber type disproportion myopathy (CFTDM) is a chronic, nonprogressive muscle disorder characterized by universal muscle hypotrophy and growth retardation. Histomorphometric examination of muscle shows a preponderance of smaller than normal type 1 fibers and overall fiber size heterogeneity. Concomitant endocrine dysfunctions have not been described. We report the findings of altered insulin secretion and insulin action in two brothers affected with CFTDM and glucose intolerance as well as in their nonconsanguineous glucose-tolerant parents. Results are compared with those of six normoglycemic control subjects. All study participants underwent an oral glucose tolerance test to estimate insulin secretion. The oldest boy and his parents volunteered for studies of whole-body insulin sensitivity consisting of a 4-h euglycemic hyperinsulinemic clamp in combination with indirect calorimetry. Insulin receptor function and glycogen synthase (GS) activity and expression were examined in biopsies of vastus lateralis muscle. Despite a 45-90-fold increase in both fasting and postprandial serum insulin levels, both CFTDM patients had diabetes mellitus. Clamp studies revealed that the oldest boy had severe insulin resistance of both liver and peripheral tissues. The impaired insulin-stimulated glucose disposal to peripheral tissues was primarily due to reduced nonoxidative glucose metabolism. These changes were paralleled by reduced basal values of muscle GS total activity, allosterical activation of GS by glucose-6-phosphate, GS protein, and GS mRNA. The father expressed a lesser degree of insulin resistance, and studies of muscle insulin receptor function showed a severe impairment of receptor kinase activity. In conclusion, CFTDM is a novel form of severe hyperinsulinemia and insulin resistance. Whether insulin resistance is causally related to the muscle disorder awaits to be clarified.

  9. MUSCLE-FIBER CONDUCTION-VELOCITY IN THE DIAGNOSIS OF FAMILIAL HYPOKALEMIC PERIODIC PARALYSIS - INVASIVE VERSUS SURFACE DETERMINATION

    NARCIS (Netherlands)

    VANDERHOEVEN, JH; LINKS, TP; ZWARTS, MJ; VANWEERDEN, TW

    1994-01-01

    Muscle fiber conduction velocity (MFCV) in the brachial biceps muscle was determined in a large family of patients with hypokalemic periodic paralysis (HOPP) by both a surface and an invasive method. Other surface EMG parameters and the muscle force were also determined. Both the surface and the inv

  10. Changes in human muscle oxygen saturation and mean fiber conduction velocity during intense dynamic exercise - effect of muscular training status

    DEFF Research Database (Denmark)

    Kilen, Anders; Gizzi, Leonardo; Jensen, Bente Rona

    2012-01-01

    Introduction: In this study we investigated whether an association exists between muscle fiber conduction velocity (MFCV) and local muscle oxygen saturation (StO(2) ) in the superficial part of the latissimus dorsi muscle of runners and swimmers during exhaustive dynamic exercise. Methods: Partic...

  11. [Familial spastic paraplegia with syndrome of continuous muscle fiber activity (Isaacs)].

    Science.gov (United States)

    Yokota, T; Matsunaga, T; Furukawa, T; Tsukagoshi, H

    1989-06-01

    A woman aged fifty-three developed paraparesis at the age of 4, which progressed slowly and required crutches by the age of 30. At the age of 51, muscle stiffness involved bilateral hands and arms gradually. At the age of 53, she suffered from painful spasms in right deltoid muscle. Her two brothers had spastic paraplegia without other neurological deficits. Her paternal grandfather and maternal grandmother were cousins. Slight dementia was noted (WAIS: IQ, 79). Her posture was stiff and muscles of upper limbs were in a persistent contraction; Subcutaneous tissue was thin, and muscles were well-defined and firm. There was moderate muscle weakness of legs and hands. Continuous fasciculations and myokymias were recognized in muscles of the arms and the limb girdles. Muscle tone was considerably increased especially in the bilateral arms. The deep tendon reflexes were exaggerated with extensor plantar responses. Profuse sweating affected palms, soles and backs. No sensory disturbance was appreciated. There was no myotonic responses to percussion of muscles. Following laboratory data were normal; thyroid functions, CSF studies, anti HTLV-I antibody and long chain fatty acid in red blood cells, myelography and brain CT except for increased basal metabolic rate (53%). Electromyographic study in the arms and hands revealed spontaneous motor unit activities including doublets at rest and increased proportion of polyphasic potentials and high amplitude potentials in voluntary contraction. Biopsy of right quadriceps femoris muscle showed hypertrophy of type I fibers and angulated atrophy of type II fibers. Continuous muscle activities in upper limbs did not change at sleep or with intravenous administration of 7 mg diazepam.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Role of aerobic and anaerobic circular mantle muscle fibers in swimming squid: electromyography.

    Science.gov (United States)

    Bartol, I K

    2001-02-01

    Circular mantle muscle of squids and cuttlefishes consists of distinct zones of aerobic and anaerobic muscle fibers that are thought to have functional roles analogous to red and white muscle in fishes. To test predictions of the functional role of the circular muscle zones during swimming, electromyograms (EMGs) in conjunction with video footage were recorded from brief squid Lolliguncula brevis (5.0-6.8 cm dorsal mantle length, 10.9-18.3 g) swimming in a flume at speeds of 3-27 cm s(-1). In one set of experiments, in which EMGs were recorded from electrodes intersecting both the central anaerobic and peripheral aerobic circular mantle muscles, electrical activity was detected during each mantle contraction at all swimming speeds, and the amplitude and frequency of responses increased with speed. In another set of experiments, in which EMGs were recorded from electrodes placed in the central anaerobic circular muscle fibers alone, electrical activity was not detected during mantle contraction until speeds of about 15 cm s(-1), when EMG activity was sporadic. At speeds greater than 15 cm s(-1), the frequency of central circular muscle activity subsequently increased with swimming speed until maximum speeds of 21-27 cm s(-1), when muscular activity coincided with the majority of mantle contractions. These results indicate that peripheral aerobic circular muscle is used for low, intermediate, and probably high speeds, whereas central anaerobic circular muscle is recruited at intermediate speeds and used progressively more with speed for powerful, unsteady jetting. This is significant because it suggests that there is specialization and efficient use of locomotive muscle in squids.

  13. Dosing schedule-dependent attenuation of dexamethasone-induced muscle atrophy in mice.

    Science.gov (United States)

    Nakao, Reiko; Yamamoto, Saori; Yasumoto, Yuki; Oishi, Katsutaka

    2014-05-01

    Many inflammatory and autoimmune diseases are treated using synthetic glucocorticoids. However, excessive glucocorticoid can often cause unpredictable effects including muscle atrophy. Endogenous glucocorticoid levels robustly fluctuate in a circadian manner and peak just before the onset of the active phase in both humans and nocturnal rodents. The present study determines whether muscle atrophy induced by exogenous glucocorticoid can be avoided by optimizing dosing times. We administered single daily doses of the glucocorticoid analog dexamethasone (Dex) to mice for 10 days at the times of day corresponding to peak (early night) or trough (early morning) endogenous glucocorticoid levels. Administration at the acrophase of endogenous glucocorticoids significantly attenuated Dex-induced wasting of the gastrocnemius (Ga) and tibialis anterior (TA) muscles that comprise mostly fast-twitch muscle fibers. Real-time RT-PCR revealed that the Dex-induced mRNA expression of genes encoding the atrophy-related ubiquitin ligases Muscle Atrophy F-box (Fbxo32, also known as MAFbx/Atrogin-1) and Muscle RING finger 1 (Trim63, also known as MuRF1) in the Ga and TA muscles was significantly attenuated by Dex when administered during the early night. Dex negligibly affected the weight of the soleus (So) muscle that mostly comprises slow-twitch muscle fibers, but significantly and similarly decreased the weight of the spleen at both dosing times. These results suggest that glucocorticoid-induced muscle atrophy can be attenuated by optimizing the dosing schedule.

  14. Segmental distribution of myosin heavy chain isoforms within single muscle fibers.

    Science.gov (United States)

    Zhang, Ming; Gould, Maree

    2017-02-18

    Despite many studies looking at the distribution of myosin heavy chain (MHC) isoforms across a transverse section of muscle, knowledge of MHC distribution along the longitudinal axis of a single skeletal muscle fiber has been relatively overlooked. Immunocytochemistry was performed on serial sections of rat extensor digitorum longus (EDL) muscle to identify MHC types I, IIA, IIX, IIY and IIB. Sixteen fascicles which contained a total of 362 fibers were randomly and systematically sampled from the 3 EDL muscles. All MHC type I and type II isoforms were expressed. Segmental expression occurred within a very limited segment. MHC isoform expression followed the accepted traditional order from I&cenveo_unknown_entity_wingdings_F0F3;IIA&cenveo_unknown_entity_wingdings_F0F3;IIX&cenveo_unknown_entity_wingdings_F0F3;IIB, however in some samples expression of an isoform was circumvented from IIB to I or from I to IIB directly. Segmental distribution of MHC isoforms along a single muscle fiber may be due to the myonuclear domain. This article is protected by copyright. All rights reserved.

  15. The influence of training status, age, and muscle fiber type on cycling efficiency and endurance performance.

    Science.gov (United States)

    Hopker, James G; Coleman, Damian A; Gregson, Hannah C; Jobson, Simon A; Von der Haar, Tobias; Wiles, Jonathan; Passfield, Louis

    2013-09-01

    The purpose of this study was to assess the influence of age, training status, and muscle fiber-type distribution on cycling efficiency. Forty men were recruited into one of four groups: young and old trained cyclists, and young and old untrained individuals. All participants completed an incremental ramp test to measure their peak O2 uptake, maximal heart rate, and maximal minute power output; a submaximal test of cycling gross efficiency (GE) at a series of absolute and relative work rates; and, in trained participants only, a 1-h cycling time trial. Finally, all participants underwent a muscle biopsy of their right vastus lateralis muscle. At relative work rates, a general linear model found significant main effects of age and training status on GE (P 0.05). Power output in the 1-h performance trial was predicted by average O2 uptake and GE, with standardized β-coefficients of 0.94 and 0.34, respectively, although some mathematical coupling is evident. These data demonstrate that muscle fiber type does not affect cycling efficiency and was not influenced by the aging process. Cycling efficiency and the percentage of type I muscle fibers were influenced by training status, but only GE at 120 revolutions/min was seen to predict cycling performance.

  16. Decrease of muscle fiber conduction velocity correlates with strength loss after an endurance run.

    Science.gov (United States)

    Boccia, Gennaro; Dardanello, Davide; Tarperi, Cantor; Rosso, Valeria; Festa, Luca; La Torre, Antonio; Pellegrini, Barbara; Schena, Federico; Rainoldi, Alberto

    2017-02-01

    Monitoring surface electromyographic (EMG) signals can provide useful insights for characterizing muscle fatigue, which is defined as an exercise-induced strength loss. This experiment investigated the muscle fiber conduction velocity (CV) changes induced by an endurance run. The day before and immediately after a half-marathon run (21.097 km) 11 amateur runners performed maximum voluntary contractions (MVCs) of knee extensor muscles. During the MVC, multichannel EMG was recorded from the vastus lateralis and EMG amplitude and CV were calculated. After the run, knee extensors showed a decreased strength (-13  ±  9%, p  =  0.001) together with a reduction in EMG amplitude (-13  ±  10%, p  =  0.003) and in CV (-6  ±  8%, p  =  0.032). Knee extensor strength loss positively correlated with vastus lateralis CV differences (r  =  0.76, p  =  0.006). Thus, the exercises-induced muscle fatigue was associated not only with a decrease in EMG amplitude, but also with a reduction in CV. This finding suggests that muscle fibers with higher CV (i.e. those with greater fiber size) were the most impaired during strength production after an endurance run.

  17. Effects of diltiazem on skinned skeletal muscle fibers of the African clawed toad.

    Science.gov (United States)

    Ishizuka, T; Endo, M

    1983-02-01

    To examine the effects of diltiazem and its l-cis isomer (which possesses only a weak Ca++-antagonistic action) on the contractile system and the sarcoplasmic reticulum of skeletal muscle, we used skinned fibers isolated from iliofibularis muscle of the African clawed toad, Xenopus laevis. Diltiazem showed the following effects: an increase in the Ca++ sensitivity of the contractile system, a decrease in the maximal tension developed in a saturating concentration of Ca++, an inhibition of Ca++ uptake by the sarcoplasmic reticulum, an inhibition of Ca++ release from the sarcoplasmic reticulum by caffeine, and an increase in the Ca++ permeability of the sarcoplasmic reticulum membrane. The effects of the l-cis isomer were similar to those of diltiazem, and the potencies of the two substances were nearly equal, except with respect to the effect on the Ca++ release induced by caffeine: the l-cis isomer potentiated this type of Ca++ release. Diltiazem's effects on amphibian skinned skeletal muscle fibers may not be related qualitatively or quantitatively to the Ca++-antagonistic actions of the drug on mammalian cardiac and smooth muscles. The pharmacological spectrum of diltiazem on skinned skeletal muscle fibers is similar to that of some local anesthetics.

  18. Fiber-type susceptibility to eccentric contraction-induced damage of hindlimb-unloaded rat AL muscles

    Science.gov (United States)

    Vijayan, K.; Thompson, J. L.; Norenberg, K. M.; Fitts, R. H.; Riley, D. A.

    2001-01-01

    Slow oxidative (SO) fibers of the adductor longus (AL) were predominantly damaged during voluntary reloading of hindlimb unloaded (HU) rats and appeared explainable by preferential SO fiber recruitment. The present study assessed damage after eliminating the variable of voluntary recruitment by tetanically activating all fibers in situ through the motor nerve while applying eccentric (lengthening) or isometric contractions. Muscles were aldehyde fixed and resin embedded, and semithin sections were cut. Sarcomere lesions were quantified in toluidine blue-stained sections. Fibers were typed in serial sections immunostained with antifast myosin and antitotal myosin (which highlights slow fibers). Both isometric and eccentric paradigms caused fatigue. Lesions occurred only in eccentrically contracted control and HU muscles. Fatigue did not cause lesions. HU increased damage because lesioned- fiber percentages within fiber types and lesion sizes were greater than control. Fast oxidative glycolytic (FOG) fibers were predominantly damaged. In no case did damaged SO fibers predominate. Thus, when FOG, SO, and hybrid fibers are actively lengthened in chronically unloaded muscle, FOG fibers are intrinsically more susceptible to damage than SO fibers. Damaged hybrid-fiber proportions ranged between these extremes.

  19. The combined influence of stretch, mobility and electrical stimulation in the prevention of muscle fiber atrophy caused hypokinesia and hypodynamia

    Science.gov (United States)

    Goldspink, G.; Goldspink, D.; Loughna, P.

    1984-01-01

    The morphological and biochemical changes which occur in the hind limb muscles of the rat in response to hypokinesia and hypodynamia were investigated. Hind limb cast fixation and suspension techniques were employed to study the musclar atrophy after five days of hypokinesia and hypodynamia induced by suspension, appreciable muscular atrophy was apparent, particularly in the anti-gravity muscles. The effect of passive stretching and electrical stimulation on muscle atrophy was studied. Changes in muscle protein mass were assessed with spectrophotometric and radioactive techniques. Passive stretch is shown to counteract muscle disuse atrophy. The change in the numbers of specific muscle fibers in atrophied muscles is discussed.

  20. X-ray diffraction analysis of the effects of myosin regulatory light chain phosphorylation and butanedione monoxime on skinned skeletal muscle fibers

    Science.gov (United States)

    Kimura, Masako; Li, Zhao-bo; Ohno, Tetsuo; Takemori, Shigeru; Hoh, Joseph F. Y.; Yagi, Naoto

    2016-01-01

    The phosphorylation of the myosin regulatory light chain (RLC) is an important modulator of skeletal muscle performance and plays a key role in posttetanic potentiation and staircase potentiation of twitch contractions. The structural basis for these phenomena within the filament lattice has not been thoroughly investigated. Using a synchrotron radiation source at SPring8, we obtained X-ray diffraction patterns from skinned rabbit psoas muscle fibers before and after phosphorylation of myosin RLC in the presence of myosin light chain kinase, calmodulin, and calcium at a concentration below the threshold for tension development ([Ca2+] = 10−6.8 M). After phosphorylation, the first myosin layer line slightly decreased in intensity at ∼0.05 nm−1 along the equatorial axis, indicating a partial loss of the helical order of myosin heads along the thick filament. Concomitantly, the (1,1/1,0) intensity ratio of the equatorial reflections increased. These results provide a firm structural basis for the hypothesis that phosphorylation of myosin RLC caused the myosin heads to move away from the thick filaments towards the thin filaments, thereby enhancing the probability of interaction with actin. In contrast, 2,3-butanedione monoxime (BDM), known to inhibit contraction by impeding phosphate release from myosin, had exactly the opposite effects on meridional and equatorial reflections to those of phosphorylation. We hypothesize that these antagonistic effects are due to the acceleration of phosphate release from myosin by phosphorylation and its inhibition by BDM, the consequent shifts in crossbridge equilibria leading to opposite changes in abundance of the myosin-ADP-inorganic phosphate complex state associated with helical order of thick filaments. PMID:26911280

  1. Skeletal muscle signature of a champion sprint runner.

    Science.gov (United States)

    Trappe, Scott; Luden, Nicholas; Minchev, Kiril; Raue, Ulrika; Jemiolo, Bozena; Trappe, Todd A

    2015-06-15

    We had the unique opportunity to study the skeletal muscle characteristics, at the single fiber level, of a world champion sprint runner who is the current indoor world record holder in the 60-m hurdles (7.30 s) and former world record holder in 110-m hurdles (12.91 s). Muscle biopsies were obtained from the vastus lateralis at rest and 4 h after a high-intensity exercise challenge (4 × 7 repetitions of resistance exercise). Single muscle fiber analyses were conducted for fiber type distribution (myosin heavy chain, MHC), fiber size, contractile function (strength, speed, and power) and mRNA expression (before and after the exercise bout). The world-class sprinter's leg muscle had a high abundance (24%) of the pure MHC IIx muscle fibers with a total fast-twitch fiber population of 71%. Power output of the MHC IIx fibers (35.1 ± 1.4 W/l) was 2-fold higher than MHC IIa fibers (17.1 ± 0.5 W/l) and 14-fold greater than MHC I fibers (2.5 ± 0.1 W/l). Additionally, the MHC IIx fibers were highly responsive to intense exercise at the transcriptional level for genes involved with muscle growth and remodeling (Fn14 and myostatin). To our knowledge, the abundance of pure MHC IIx muscle fibers is the highest observed in an elite sprinter. Further, the power output of the MHC IIa and MHC IIx muscle fibers was greater than any human values reported to date. These data provide a myocellular basis for the high level of sprinting success achieved by this individual.

  2. Potentiation increases peak twitch torque by enhancing rates of torque development and relaxation.

    Science.gov (United States)

    Froyd, Christian; Beltrami, Fernando Gabe; Jensen, Jørgen; Noakes, Timothy David

    2013-01-01

    The aim of this study was to measure the extent to which potentiation changes in response to an isometric maximal voluntary contraction. Eleven physically active subjects participated in two separate studies. Single stimulus of electrical stimulation of the femoral nerve was used to measure torque at rest in unpotentiated quadriceps muscles (study 1 and 2), and potentiated quadriceps muscles torque in a 10 min period after a 5 s isometric maximal voluntary contraction of the quadriceps muscles (study 1). Additionally, potentiated quadriceps muscles torque was measured every min after a further 10 maximal voluntary contractions repeated every min (study 2). Electrical stimulation repeated several times without previous maximal voluntary contraction showed similar peak twitch torque. Peak twitch torque 4 s after a 5 s maximal voluntary contraction increased by 45±13% (study 1) and by 56±10% (study 2), the rate of torque development by 53±13% and 82±29%, and the rate of relaxation by 50±17% and 59±22%, respectively, but potentiation was lost already two min after a 5 s maximal voluntary contraction. There was a tendency for peak twitch torque to increase for the first five repeated maximal voluntary contractions, suggesting increased potentiation with additional maximal voluntary contractions. Correlations for peak twitch torque vs the rate of torque development and for the rate of relaxation were r(2)= 0.94 and r(2)=0.97. The correlation between peak twitch torque, the rate of torque development and the rate of relaxation suggests that potentiation is due to instantaneous changes in skeletal muscle contractility and relaxation.

  3. Recovery of skeletal muscle after 3 mo of hindlimb immobilization in rats

    Science.gov (United States)

    Booth, F. W.; Seider, M. J.

    1979-01-01

    During immobilization, skeletal muscle undergoes decreases in size and strength with concomitant atrophic and degenerative changes in slow-twitch muscle fibers. Currently there are no objective data in slow-twitch muscle demonstrating recovery of biochemical or physiological indices following termination of immobilization. The purpose of this study was to determine whether the soleus, a slow-twitch muscle, could recover normal biochemical or physiological levels following termination of immobilization. Adenosine triphosphate, glycogen, and protein concentration (mg/g wet wt) all significantly decreased following 90 days of hindlimb immobilization, but these three values returned to control levels by the 60th recovery day. Similarly, soleus muscle wet weight and protein content (mg protein/muscle) returned to control levels by the 14th recovery day. In contrast, maximal isometric tension did not return to normal until the 120th day. These results indicate that following muscular atrophy, which was achieved through 90 days of hindlimb immobilization, several biochemical and physiological values in skeletal muscle are recovered at various times after the end of immobilization.

  4. Chronic intrinsic transient tracheal occlusion elicits diaphragmatic muscle fiber remodeling in conscious rodents.

    Directory of Open Access Journals (Sweden)

    Barbara K Smith

    Full Text Available BACKGROUND: Although the prevalence of inspiratory muscle strength training has increased in clinical medicine, its effect on diaphragm fiber remodeling is not well-understood and no relevant animal respiratory muscle strength training-rehabilitation experimental models exist. We tested the postulate that intrinsic transient tracheal occlusion (ITTO conditioning in conscious animals would provide a novel experimental model of respiratory muscle strength training, and used significant increases in diaphragmatic fiber cross-sectional area (CSA as the primary outcome measure. We hypothesized that ITTO would increase costal diaphragm fiber CSA and further hypothesized a greater duration and magnitude of occlusions would amplify remodeling. METHODOLOGY/PRINCIPAL FINDINGS: Sprague-Dawley rats underwent surgical placement of a tracheal cuff and were randomly assigned to receive daily either 10-minute sessions of ITTO, extended-duration, 20-minute ITTO (ITTO-20, partial obstruction with 50% of cuff inflation pressure (ITTO-PAR or observation (SHAM over two weeks. After the interventions, fiber morphology, myosin heavy chain composition and CSA were examined in the crural and ventral, medial, and dorsal costal regions. In the medial costal diaphragm, with ITTO, type IIx/b fibers were 26% larger in the medial costal diaphragm (p<0.01 and 24% larger in the crural diaphragm (p<0.05. No significant changes in fiber composition or morphology were detected. ITTO-20 sessions also yielded significant increases in medial costal fiber cross-sectional area, but the effects were not greater than those elicited by 10-minute sessions. On the other hand, ITTO-PAR resulted in partial airway obstruction and did not generate fiber hypertrophy. CONCLUSIONS/SIGNIFICANCE: The results suggest that the magnitude of the load was more influential in altering fiber cross-sectional area than extended-duration conditioning sessions. The results also indicated that ITTO was

  5. Alteration of inflammatory cytokines, energy metabolic regulators, and muscle fiber type in the skeletal muscle of postweaning piglets.

    Science.gov (United States)

    Li, F; Li, Y; Tan, B; Wang, J; Duan, Y; Guo, Q; Liu, Y; Kong, X; Li, T; Tang, Y; Yin, Y

    2016-03-01

    This study was conducted to determine the alterations of inflammatory cytokines, energy metabolic regulators, and muscle fiber type in the LM of the piglets postweaning. Crossbred piglets (Landrace × Large White) weaned at 14 d age were randomly selected from 8 litters and slaughtered at 0 (W0), 1 (W1), 3 (W3), 5 (W5), or 7 (W7) days postweaning. The glycogen content, free glucose concentration, and enzyme activities, including ATPase (Na/K, Ca/Mg), creatine kinase, and lactic dehydrogenase (LDH), were detected in the skeletal muscle tissue. Concentrations of proinflammatory cytokines, including IL-1β, IL-6, and tumor necrosis factor-α (TNF-α), and anti-inflammatory cytokines, including IL-10 and transforming growth factor-β1 (TGF-β1), were measured in serum. The mRNA abundance of the above cytokines, energy metabolic regulators, and muscle fiber type related genes were determined via real-time quantitative PCR analysis. The adenosine monophosphate-activated protein kinase α (AMPKα) signaling was measured by Western blot analysis. Our results showed ATPase activities were lower on W7 d but LDH activity was higher on W3 d after weaning ( cytokines were reduced to a low point on W5 d after weaning. Additionally, the IL-6 mRNA abundance was upregulated during W3 to W7 d, but cytokine TNF-α was upregulated just on W7 d ( cytokines, which then stimulated the AMPKα and UCP involved in energy metabolism events, accompanied by significant alterations in muscle fiber type.

  6. Intracellular localization of markers within injected or cut frog muscle fibers.

    Science.gov (United States)

    Eisenberg, B R; Mathias, R T; Gilai, A

    1979-07-01

    Many experimental procedures require drastic alterations of muscle fibers, such as cutting the fiber or injecting molecular probes through microelectrodes. We report the ultrastructure of similarly altered muscle fibers and the intracellular distribution of injected horseradish peroxidase (HRP). Cut fibers appear structurally normal at distances greater than 500 microM from the cut end, however, the structure deteriorates nearer to the cut. HRP diffuses longitudinally about 2,000 micrometer from the cut end and the concentration is uniform over the fiber's cross section. If HRP is introduced intracellularly either by pressure injection or through a nick in the sarcolemma, it distributes in a C-shaped annulus extending approximately 2,000 micrometer longitudinally and 1-20 micrometer radially. The ultrastructure of injected or nicked fibers appears normal. The HRP freely entered the junctional gap between T-system and sarcoplasmic reticulum (SR) but was excluded from either structure. Occasionally, a light pillar could be seen between T-system and SR; the space of these pillars suggest they are the central area of the "feet" appearing light against the dark marker.

  7. Quantitative PCR Analysis of Laryngeal Muscle Fiber Types

    Science.gov (United States)

    Van Daele, Douglas J.

    2010-01-01

    Voice and swallowing dysfunction as a result of recurrent laryngeal nerve paralysis can be improved with vocal fold injections or laryngeal framework surgery. However, denervation atrophy can cause late-term clinical failure. A major determinant of skeletal muscle physiology is myosin heavy chain (MyHC) expression, and previous protein analyses…

  8. Quantitative PCR Analysis of Laryngeal Muscle Fiber Types

    Science.gov (United States)

    Van Daele, Douglas J.

    2010-01-01

    Voice and swallowing dysfunction as a result of recurrent laryngeal nerve paralysis can be improved with vocal fold injections or laryngeal framework surgery. However, denervation atrophy can cause late-term clinical failure. A major determinant of skeletal muscle physiology is myosin heavy chain (MyHC) expression, and previous protein analyses…

  9. Muscle fiber conduction abnormalities in early diabetic polyneuropathy

    NARCIS (Netherlands)

    Meijer, J. W. G.; Lange, F.; Links, T. P.; van der Hoeven, J. H.

    2008-01-01

    Objective: Diabetic polyneuropathy (PNP) has been proposed to be a primary disorder of sensory nerves. At an early stage motor nerve conduction velocity (MNCV) and muscle strength remain preserved due to compensatory mechanisms (axonal sprouting, reinnervation). We evaluated the use of invasive musc

  10. Postnatal development and plasticity of specialized muscle fiber characteristics in the hindlimb.

    Science.gov (United States)

    Garry, D J; Bassel-Duby, R S; Richardson, J A; Grayson, J; Neufer, P D; Williams, R S

    1996-01-01

    Recent progress in defining molecular components of pathways controlling early stages of myogenesis has been substantial, but regulatory factors that govern the striking functional specialization of adult skeletal muscle fibers in vertebrate organisms have not yet been identified. A more detailed understanding of the temporal and spatial patterns by which specialized fiber characteristics arise may provide clues to the identity of the relevant regulatory factors. In this study, we used immunohistochemical, in situ hybridization, and Northern blot analyses to examine the time course and spatial characteristics of expression of myoglobin protein and mRNA during development of the distal hindlimb in the mouse. In adult animals, myoglobin is expressed selectively in oxidative, mitochondria-rich, fatigue-resistant myofibers, and it provides a convenient marker for this particular subset of specialized fibers. We observed only minimal expression of myoglobin in the hindlimb prior to the second day after birth, but a rapid and large (50-fold) induction of this gene in the ensuing neonatal period. Myoglobin expression was limited, however, to fibers located centrally within the limb which coexpress myosin isoforms characteristic of type I, IIA, and IIX fibers. This induction of myoglobin expression within the early postnatal period was accompanied by increased expression of nuclear genes encoding mitochondrial proteins, and exhibited a time course similar to the upregulation of myoglobin and mitochondrial proteins, and exhibited a time course similar to the upregulation of myoglobin and mitochondrial protein expression that can be induced in adult muscle fibers by continuous motor nerve stimulation. This comparison suggests that progressive locomotor activity of neonatal animals may provide signals which trigger the development of the specialized features of oxidative, fatigue-resistant skeletal muscle fibers.

  11. MicroRNA-206 is highly expressed in newly formed muscle fibers: implications regarding potential for muscle regeneration and maturation in muscular dystrophy.

    Science.gov (United States)

    Yuasa, Katsutoshi; Hagiwara, Yasuko; Ando, Masanori; Nakamura, Akinori; Takeda, Shin'ichi; Hijikata, Takao

    2008-01-01

    miR-1, miR-133a, and miR-206 are muscle-specific microRNAs expressed in skeletal muscles and have been shown to contribute to muscle development. To gain insight into the pathophysiological roles of these three microRNAs in dystrophin-deficient muscular dystrophy, their expression in the tibialis anterior (TA) muscles of mdx mice and CXMD(J) dogs were evaluated by semiquantitative RT-PCR and in situ hybridization. Their temporal and spatial expression patterns were also analyzed in C2C12 cells during muscle differentiation and in cardiotoxin (CTX)-injured TA muscles to examine how muscle degeneration and regeneration affect their expression. In dystrophic TA muscles of mdx mice, miR-206 expression was significantly elevated as compared to that in control TA muscles of age-matched B10 mice, whereas there were no differences in miR-1 or miR-133a expression between B10 and mdx TA muscles. On in situ hybridization analysis, intense signals for miR-206 probes were localized in newly formed myotubes with centralized nuclei, or regenerating muscle fibers, but not in intact pre-degenerated fibers or numerous small mononucleated cells, possibly proliferating myoblasts and inflammatory infiltrates. Similar increased expression of miR-206 was also found in C2C12 differentiation and CTX-induced regeneration, in which differentiated myotubes or regenerating fibers showed abundant expression of miR-206. However, CXMD(J) TA muscles contained smaller amounts of miR-206, miR-1, and miR-133a than controls. They exhibited more severe and more progressive degenerative alterations than mdx TA muscles. Taken together, these observations indicated that newly formed myotubes showed markedly increased expression of miR-206, which might reflect active regeneration and efficient maturation of skeletal muscle fibers.

  12. One-dimensional chain of quantum molecule motors as a mathematical physics model for muscle fibers

    Science.gov (United States)

    Si, Tie-Yan

    2015-12-01

    A quantum chain model of multiple molecule motors is proposed as a mathematical physics theory for the microscopic modeling of classical force-velocity relation and tension transients in muscle fibers. The proposed model was a quantum many-particle Hamiltonian to predict the force-velocity relation for the slow release of muscle fibers, which has not yet been empirically defined and was much more complicated than the hyperbolic relationships. Using the same Hamiltonian model, a mathematical force-velocity relationship was proposed to explain the tension observed when the muscle was stimulated with an alternative electric current. The discrepancy between input electric frequency and the muscle oscillation frequency could be explained physically by the Doppler effect in this quantum chain model. Further more, quantum physics phenomena were applied to explore the tension time course of cardiac muscle and insect flight muscle. Most of the experimental tension transient curves were found to correspond to the theoretical output of quantum two- and three-level models. Mathematical modeling electric stimulus as photons exciting a quantum three-level particle reproduced most of the tension transient curves of water bug Lethocerus maximus. Project supported by the Fundamental Research Foundation for the Central Universities of China.

  13. Structural dynamics of the skeletal muscle fiber by second harmonic generation

    Science.gov (United States)

    Nucciotti, V.; Stringari, C.; Sacconi, L.; Vanzi, F.; Linari, M.; Piazzesi, G.; Lombardi, V.; Pavone, F. S.

    2008-02-01

    The high degree of structural order in skeletal muscle allows imaging of this tissue by Second Harmonic Generation (SHG). As previously found (Vanzi et al., J. Muscle Cell Res. Motil. 2006) by fractional extraction of proteins, myosin is the source of SHG signal. A full characterization of the polarization-dependence of the SHG signal can provide very selective information on the orientation of the emitting proteins and their dynamics during contraction. We developed a line scan polarization method, allowing measurements of a full polarization curve in intact muscle fibers from skeletal muscle of the frog to characterize the SHG polarization dependence on different physiological states (resting, rigor and isometric tetanic contraction). The polarization data have been interpreted by means of a model in terms of the average orientation of SHG emitters.The different physiological states are characterized by distinct patterns of SHG polarization. The variation of the orientation of emitting molecules in relation to the physiological state of the muscle demonstrates that one part of SHG signal arises from the globular head of the myosin molecule that cross-links actin and myosin filaments. The dependence of the SHG modulation on the degree of overlap between actin and myosin filaments during an isometric contraction, provides the constraints to estimate the fraction of myosin heads generating the isometric force in the active muscle fiber.

  14. [Ultrastructure of the blood vessels and muscle fibers in the skeletal muscle of rats flown on the Kosmos-605 and Kosmos-782 biosatellites].

    Science.gov (United States)

    Savik, Z F; Rokhlenko, K D

    1981-01-01

    Electron microscopy was used to study ultrastructures of the wall of blood vessels and muscle fibers of the red (soleus) and mixed (gastrocnemius) muscles of rats flown on Cosmos-605 for 22.5 days and on Cosmos-782 for 19,5 days and sacrificed 4-6 hours, 48 hours and 25-27 days postflight. It was demonstrated that the orbital flight did not induce significant changes in the ultrastructure of blood vessels of the soleus and gastrocnemius muscles but caused atrophy of muscle fibers and reduction of the number of functioning capillaries. Readaptation of the soleus vascular system to 1 g led to degradation of permeability of capillary and venular walls and development of edema of the perivascular connective tissue. This may be one of the factors responsible for dystrophic changes in muscle fibers.

  15. Repeated high-intensity exercise modulates Ca(2+) sensitivity of human skeletal muscle fibers

    DEFF Research Database (Denmark)

    Gejl, K D; Hvid, L G; Willis, S J;

    2016-01-01

    The effects of short-term high-intensity exercise on single fiber contractile function in humans are unknown. Therefore, the purposes of this study were: (a) to access the acute effects of repeated high-intensity exercise on human single muscle fiber contractile function; and (b) to examine whether...... the fourth sprint with respect to Ca(2+) sensitivity and maximal Ca(2+) -activated force. To investigate the oxidative effects of exercise on single fiber contractile function, a subset of fibers was incubated with dithiothreitol (DTT) before analysis. Ca(2+) sensitivity was enhanced by exercise in both MHC...... I (17%, P exercise. In conclusion, repeated high-intensity exercise increased Ca(2+) sensitivity in both MHC I and MHC II...

  16. GLUT4 is reduced in slow muscle fibers of type 2 diabetic patients: is insulin resistance in type 2 diabetes a slow, type 1 fiber disease?

    DEFF Research Database (Denmark)

    Gaster, M; Staehr, P; Beck-Nielsen, H

    2001-01-01

    To gain further insight into the mechanisms underlying muscle insulin resistance, the influence of obesity and type 2 diabetes on GLUT4 immunoreactivity in slow and fast skeletal muscle fibers was studied. Through a newly developed, very sensitive method using immunohistochemistry combined...... with morphometry, GLUT4 density was found to be significantly higher in slow compared with fast fibers in biopsy specimens from lean and obese subjects. In contrast, in type 2 diabetic subjects, GLUT4 density was significantly lower in slow compared with fast fibers. GLUT4 density in slow fibers from diabetic...... patients was reduced by 9% compared with the weight-matched obese subjects and by 18% compared with the lean control group. The slow-fiber fraction was reduced to 86% in the obese subjects and to 75% in the diabetic subjects compared with the control group. Estimated GLUT4 contribution from slow fibers...

  17. Effects of muscle activity and fiber composition on glucose transport and GLUT-4.

    Science.gov (United States)

    Megeney, L A; Neufer, P D; Dohm, G L; Tan, M H; Blewett, C A; Elder, G C; Bonen, A

    1993-04-01

    We examined glucose uptake and GLUT-4 in rat muscles [soleus (Sol), plantaris (PL), extensor digitorum longus (EDL), tibialis anterior, and the red and white gastrocnemius (WG)]. In the normally innervated perfused rat hindlimb muscles the proportion of oxidative fibers was highly correlated with the muscle's insulin-stimulated 3-O-methyl-D-glucose (3-MG) uptake (R2 = 0.78) and GLUT-4 content (r = 0.94). Insulin-stimulated 3-MG uptake and GLUT-4 were also highly correlated (R2 = 0.996). In 3-day denervated muscles, insulin-stimulated 3-MG uptake was reduced in all six muscles (-41 to -14.6%, P 0.05). A very high correlation was observed between the decrements in GLUT-4 (%) and the decrements in 3-MG uptake (%; r = 0.99). The relatively greater loss in muscle activity (%) due to denervation in the Sol compared with the PL coincided with the reductions (%) in GLUT-4 and 3-MG uptake. These studies demonstrate that glucose uptake and GLUT-4 are regulated by insulin-independent means, namely the oxidative capacity of the muscle and the normal activity level of the muscle.

  18. Relation between muscle fiber conduction velocity and exerted dynamic characteristics of muscular tension in patients with hemiplegia caused by stroke.

    Science.gov (United States)

    Murakami, Kenichi; Fujisawa, Hiroyuki; Suzuki, Makoto; Sato, Yoichiro; Sakurai, Kentaro; Abe, Chie

    2016-10-01

    [Purpose] The aim of this study was to clarify the relationships among muscle fiber conduction velocity, time-force characteristics of muscle force production, and voluntary movement in patients with hemiplegia. [Subjects and Methods] The participants in the present study were 13 patients with hemiplegia. Muscle fiber conduction velocity, deep temperature of muscles and muscle thickness were measured for the tibialis anterior, and a time force curve was obtained from dorsiflexion of the ankle and lower thigh girth (maximum, minimum) for both sides. The maximum torque rate of change and maximum torque were calculated from the force-time curve. In addition, Brunnstrom Recovery Stage was used to evaluate the function of the hemiplegic side. [Results] In all the measurement items, significant differences were observed between the hemiplegic side and the healthy side. The maximum torque rate of change and Brunnstrom Recovery Stage showed a high degree of correlation. The muscle fiber conduction velocity and maximum torque rate of change or maximum torque showed a medium degree of correlation. However, muscle fiber conduction velocity was not significantly correlated with Brunnstrom Recovery Stage. [Conclusion] Brunnstrom Recovery Stage was good as a determination factor for the maximum torque rate of change. In addition, in patients with hemiplegia, it became clear that relationship is between muscle fiber conduction velocity and time-force characteristics of muscle force production as in healthy persons.

  19. Distinct Fiber Type Signature in Mouse Muscles Expressing a Mutant Lamin A Responsible for Congenital Muscular Dystrophy in a Patient

    Directory of Open Access Journals (Sweden)

    Alice Barateau

    2017-04-01

    Full Text Available Specific mutations in LMNA, which encodes nuclear intermediate filament proteins lamins A/C, affect skeletal muscle tissues. Early-onset LMNA myopathies reveal different alterations of muscle fibers, including fiber type disproportion or prominent dystrophic and/or inflammatory changes. Recently, we identified the p.R388P LMNA mutation as responsible for congenital muscular dystrophy (L-CMD and lipodystrophy. Here, we asked whether viral-mediated expression of mutant lamin A in murine skeletal muscles would be a pertinent model to reveal specific muscle alterations. We found that the total amount and size of muscle fibers as well as the extent of either inflammation or muscle regeneration were similar to wildtype or mutant lamin A. In contrast, the amount of fast oxidative muscle fibers containing myosin heavy chain IIA was lower upon expression of mutant lamin A, in correlation with lower expression of genes encoding transcription factors MEF2C and MyoD. These data validate this in vivo model for highlighting distinct muscle phenotypes associated with different lamin contexts. Additionally, the data suggest that alteration of muscle fiber type identity may contribute to the mechanisms underlying physiopathology of L-CMD related to R388P mutant lamin A.

  20. Atrophy of type I and II muscle fibers is reversible in the case of grade >2 fatty degeneration of the supraspinatus muscle: an experimental study in rabbits.

    Science.gov (United States)

    Fabis, Jaroslaw; Danilewicz, Marian; Zwierzchowski, Jacek T; Niedzielski, Kryspin

    2016-03-01

    Although clinical investigations indicate that the limit of reversibility of rotator cuff muscles fibers type I and II atrophy is grade 2 of fatty degeneration (FD) according to the Goutallier computed tomography classification, little is known about the morphometric verification of these findings. The supraspinatus tendon was detached from the greater tubercle and the infraspinatus and subscapularis in 12 rabbits, and a 12-week observation period followed. This proved to be sufficient for development of grade >2 FD of the supraspinatus tendon. The tendon was then reinserted. The animals were euthanized 24 weeks after tendon reconstruction. The sections of middle part of supraspinatus were stained for adenosine triphosphatase reaction, and morphometric measurements were taken of type I and II muscle fiber diameters. The contralateral shoulders served as controls. The macroscopic inspection of the supraspinatus tendons revealed complete healing in all cases. No statistically significant differences were found between controls and operated-on shoulders for type I (P = .13) and type II (P = .55) muscle fibers. Atrophy of type I and II muscle fibers in rabbit supraspinatus muscle, characterized by grade >2 fatty degeneration according to the Goutallier computed tomography classification, is reversible after 24 weeks from reattachment of its tendon. A requirement for type I and II muscle fibers hypertrophy is a change in the biomechanical and functional conditions of the muscle after its tendon is reconstructed. Copyright © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  1. The effects of PGC-1α on control of microvascular P(O2) kinetics following onset of muscle contractions.

    Science.gov (United States)

    Kano, Yutaka; Miura, Shinji; Eshima, Hiroaki; Ezaki, Osamu; Poole, David C

    2014-07-15

    During contractions, regulation of microvascular oxygen partial pressure (Pmv(O2)), which drives blood-myocyte O2 flux, is a function of skeletal muscle fiber type and oxidative capacity and can be altered by exercise training. The kinetics of Pmv(O2) during contractions in predominantly fast-twitch muscles evinces a more rapid fall to far lower levels compared with slow-twitch counterparts. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) improves endurance performance, in part, due to mitochondrial biogenesis, a fiber-type switch to oxidative fibers, and angiogenesis in skeletal muscle. We tested the hypothesis that improvement of exercise capacity by genetic overexpression of PGC-1α would be associated with an altered Pmv(O2) kinetics profile of the fast-twitch (white) gastrocnemius during contractions toward that seen in slow-twitch muscles (i.e., slowed response kinetics and elevated steady-state Pmv(O2)). Phosphorescence quenching techniques were used to measure Pmv(O2) at rest and during separate bouts of twitch (1 Hz) and tetanic (100 Hz) contractions in gastrocnemius muscles of mice with overexpression of PGC-1α and wild-type littermates (WT) mice under isoflurane anesthesia. Muscles of PGC-1α mice exhibited less fatigue than WT (P contractions, WT and PGC-1α mice demonstrated similar Pmv(O2) kinetics. Specifically, the time delay of the Pmv(O2) response was shortened in PGC-1α mice compared with WT (1 Hz: WT, 6.6 ± 2.4 s; PGC-1α, 2.9 ± 0.8 s; 100 Hz: WT, 3.3 ± 1.1 s, PGC-1α, 0.9 ± 0.3 s, both P contractions in PGC-1α mice. Slower dynamics and maintenance of higher Pmv(O2) following muscle contractions is not obligatory for improved fatigue resistance in fast-twitch muscle of PGC-1α mice. Moreover, overexpression of PGC-1α may accelerate O2 utilization kinetics to a greater extent than O2 delivery kinetics.

  2. Na+-K+-ATPase in rat skeletal muscle: muscle fiber-specific differences in exercise-induced changes in ion affinity and maximal activity

    DEFF Research Database (Denmark)

    Juel, Carsten

    2008-01-01

    other muscles tested. In conclusion, muscle activity induces fiber type-specific changes both in Na(+) affinity and maximal in vitro activity of the Na(+)-K(+)-ATPase. The underlying mechanisms may involve translocation of subunits and increased association between PLM units and the alphabeta complex...

  3. Co-expression of SERCA isoforms, phospholamban and sarcolipin in human skeletal muscle fibers.

    Directory of Open Access Journals (Sweden)

    Val A Fajardo

    Full Text Available Sarcolipin (SLN and phospholamban (PLN inhibit the activity of sarco(endoplasmic reticulum Ca(2+-ATPases (SERCAs by reducing their apparent affinity for Ca(2+. A ternary complex between SLN, PLN, and SERCAs results in super-inhibition of SERCA activity. Analysis of skeletal muscle homogenate has limited our current understanding of whether SLN and PLN regulate SERCA1a, SERCA2a, or both in skeletal muscle and whether SLN and PLN are co-expressed in skeletal muscle fibers. Biopsies from human vastus lateralis were analyzed through single fiber Western blotting and immunohisto/fluorescence staining to circumvent this limitation. With a newly generated SLN antibody, we report for the first time that SLN protein is present in human skeletal muscle. Addition of the SLN antibody (50 µg to vastus lateralis homogenates increased the apparent Ca(2+ affinity of SERCA (K Ca, pCa units (-Ab, 5.85 ± 0.02 vs. +Ab, 5.95 ± 0.02 and maximal SERCA activity (μmol/g protein/min (-Ab, 122 ± 6.4 vs. +Ab, 159 ± 11 demonstrating a functional interaction between SLN and SERCAs in human vastus lateralis. Specifically, our results suggest that although SLN and PLN may preferentially regulate SERCA1a, and SERCA2a, respectively, physiologically they both may regulate either SERCA isoform. Furthermore, we show that SLN and PLN co-immunoprecipitate in human vastus lateralis homogenate and are simultaneously expressed in 81% of the fibers analyzed with Western blotting which implies that super-inhibition of SERCA may exist in human skeletal muscle. Finally, we demonstrate unequivocally that mouse soleus contains PLN protein suggesting that super-inhibition of SERCA may also be important physiologically in rodent skeletal muscle.

  4. Muscle Fiber Characteristics, Satellite Cells and Soccer Performance in Young Athletes

    Directory of Open Access Journals (Sweden)

    Thomas I. Metaxas, Athanasios Mandroukas, Efstratios Vamvakoudis, Kostas Kotoglou, Björn Ekblom, Konstantinos Mandroukas

    2014-09-01

    Full Text Available This study is aimed to examine the muscle fiber type, composition and satellite cells in young male soccer players and to correlate them to cardiorespiratory indices and muscle strength. The participants formed three Groups: Group A (n = 13, 11.2 ± 0.4yrs, Group B (n=10, 13.1 ± 0.5yrs and Group C (n = 9, 15.2 ± 0.6yrs. Muscle biopsies were obtained from the vastus lateralis. Peak torque values of the quadriceps and hamstrings were recorded and VO2max was measured on the treadmill. Group C had lower type I percentage distribution compared to A by 21.3% (p < 0.01, while the type IIA relative percentage was higher by 18.1% and 18.4% than in Groups A and B (p < 0.05. Groups B and C had higher cross-sectional area (CSA values in all fiber types than in Group A (0.05 < p < 0.001. The number of satellite cells did not differ between the groups. Groups B and C had higher peak torque at all angular velocities and absolute VO2max in terms of ml·min-1 than Group A (0.05 < p < 0.001. It is concluded that the increased percentage of type IIA muscle fibers noticed in Group C in comparison to the Groups A and B should be mainly attributed to the different workload exercise and training programs. The alteration of myosin heavy chain (MHC isoforms composition even in children is an important mechanism for skeletal muscle characteristics. Finally, CSA, isokinetic muscle strength and VO2max values seems to be expressed according to age.

  5. Effects of resistance training on endurance capacity and muscle fiber composition in young top-level cyclists

    DEFF Research Database (Denmark)

    Aagaard, P; Andersen, J L; Bennekou, M

    2011-01-01

    Equivocal findings exist on the effect of concurrent strength (S) and endurance (E) training on endurance performance and muscle morphology. Further, the influence of concurrent SE training on muscle fiber-type composition, vascularization and endurance capacity remains unknown in top......-level endurance athletes. The present study examined the effect of 16 weeks of concurrent SE training on maximal muscle strength (MVC), contractile rate of force development (RFD), muscle fiber morphology and composition, capillarization, aerobic power (VO2max), cycling economy (CE) and long/short-term endurance...... capacity in young elite competitive cyclists (n=14). MVC and RFD increased 12-20% with SE (P...

  6. Effects of resistance training on endurance capacity and muscle fiber composition in young top-level cyclists

    DEFF Research Database (Denmark)

    Aagaard, P; Andersen, J L; Bennekou, M

    2011-01-01

    Equivocal findings exist on the effect of concurrent strength (S) and endurance (E) training on endurance performance and muscle morphology. Further, the influence of concurrent SE training on muscle fiber-type composition, vascularization and endurance capacity remains unknown in top......-level endurance athletes. The present study examined the effect of 16 weeks of concurrent SE training on maximal muscle strength (MVC), contractile rate of force development (RFD), muscle fiber morphology and composition, capillarization, aerobic power (VO(2max) ), cycling economy (CE) and long....../short-term endurance capacity in young elite competitive cyclists (n=14). MVC and RFD increased 12-20% with SE (P...

  7. Mechanical, electrical, and morphological characteristics of skeletal muscle fibers from Xenopus and other species of frogs.

    Science.gov (United States)

    Oba, T; Yamamoto, M; Aoki, T; Hotta, K

    1983-01-01

    Mechanical, electrical, and morphological properties of iliofibularis or semitendinosus of Xenopus laevis, Rana catesbeiana, and Rana nigromaculata were investigated in an attempt to find out the differences between them which will give the basic knowledge for the study of excitation-contraction coupling. With application of electrical stimulation, a single muscle fiber from Xenopus contracted at a faster rate of rise than did the other muscles tested. The maximum rate of rise (Tmax) of tension was in the order of Xenopus, R. catesbeiana, and R. nigromaculata. Ca2+ sensitivity and Tmax of mechanically skinned fibers of Xenopus resembled those of R. catesbeiana. Xenopus muscle had a small cross-sectional area of T-tubule compared with that in other species and the action potential exhibited a small positive-going hump. The volume density of the terminal cisternae of sarcoplasmic reticulum (SR) to the myofibril was the largest in the Xenopus muscle, with a statistically significant difference. Therefore, the Xenopus muscle appears to be good material for investigation of mechanisms related to Ca2+ release from SR, as elicited by the excitation of T-tubules.

  8. Effects of microgravity and tail suspension on enzymes of individual soleus and tibialis anterior fibers

    Science.gov (United States)

    Chi, Maggie M.-Y.; Choski, Rati; Nemeth, Patti; Krasnov, Igor'; Il'ina-Kakueva, E. I.; Manchester, Jill K.; Lowry, Oliver H.

    1992-01-01

    Selected enzymes of energy metabolism were measured in random individual fibers of soleus and tibialis anterior (TA) muscles from rats exposed for 2 wk to spaceflight (F) aboard Cosmos 2044 or tail suspension (T) and from synchronous controls. Average size of soleus fibers (dry weight per unit length) was reduced 37 percent in F and T fibers; there was little change in Ta fibers. Enzyme changes were more pronounced in soleus than in TA fibers. Three enzymes characteristic of fast-twitch muscles, pyruvate kinase, glycerol-3-phosphate dehydrogenase, and 1-phosphofructokinase, were elevated in F and T soleus fibers, but changes in phosphofructokinase were not statistically significant. In TA fibers analyzed for hexokinase, malate dehydrogenase, phosphohexoisomerase, and pyruvate kinase, only hexokinase and malate dehydrogenase showed significant changes. Hexokinase incresed 83 percent in one of two T muscles. Enzyme data for TA fibers typed by myosin adenosinetriphosphatase were more informative: phosphofructokinase, phosphorylase, and glycerol-3-phosphate dehydrogenase were increased in type IIn fibers of either F or T muscles or both. Malate dehydrogenase was not changed in fibers of any type in either F or T muscle.

  9. Distinctive genes determine different intramuscular fat and muscle fiber ratios of the longissimus dorsi muscles in Jinhua and landrace pigs.

    Directory of Open Access Journals (Sweden)

    Ting Wu

    Full Text Available Meat quality is determined by properties such as carcass color, tenderness and drip loss. These properties are closely associated with meat composition, which includes the types of muscle fiber and content of intramuscular fat (IMF. Muscle fibers are the main contributors to meat mass, while IMF not only contributes to the sensory properties but also to the plethora of physical, chemical and technological properties of meat. However, little is known about the molecular mechanisms that determine meat composition in different pig breeds. In this report we show that Jinhua pigs, a Chinese breed, contains much higher levels of IMF than do Landrace pigs, a Danish breed. We analyzed global gene expression profiles in the longissimus dorsi muscles in Jinhua and Landrace breeds at the ages of 30, 90 and 150 days. Cross-comparison analysis revealed that genes that regulate fatty acid biosynthesis (e.g., fatty acid synthase and stearoyl-CoA desaturase are expressed at higher levels in Jinhua pigs whereas those that regulate myogenesis (e.g., myogenic factor 6 and forkhead box O1 are expressed at higher levels in Landrace pigs. Among those genes which are highly expressed in Jinhua pigs at 90 days (d90, we identified a novel gene porcine FLJ36031 (pFLJ, which functions as a positive regulator of fat deposition in cultured intramuscular adipocytes. In summary, our data showed that the up-regulation of fatty acid biosynthesis regulatory genes such as pFLJ and myogenesis inhibitory genes such as myostatin in the longissimus dorsi muscles of Jinhua pigs could explain why this local breed produces meat with high levels of IMF.

  10. Distinctive genes determine different intramuscular fat and muscle fiber ratios of the longissimus dorsi muscles in Jinhua and landrace pigs.

    Science.gov (United States)

    Wu, Ting; Zhang, Zhenhai; Yuan, Zhangqin; Lo, Li Jan; Chen, Jun; Wang, Yizhen; Peng, Jinrong

    2013-01-01

    Meat quality is determined by properties such as carcass color, tenderness and drip loss. These properties are closely associated with meat composition, which includes the types of muscle fiber and content of intramuscular fat (IMF). Muscle fibers are the main contributors to meat mass, while IMF not only contributes to the sensory properties but also to the plethora of physical, chemical and technological properties of meat. However, little is known about the molecular mechanisms that determine meat composition in different pig breeds. In this report we show that Jinhua pigs, a Chinese breed, contains much higher levels of IMF than do Landrace pigs, a Danish breed. We analyzed global gene expression profiles in the longissimus dorsi muscles in Jinhua and Landrace breeds at the ages of 30, 90 and 150 days. Cross-comparison analysis revealed that genes that regulate fatty acid biosynthesis (e.g., fatty acid synthase and stearoyl-CoA desaturase) are expressed at higher levels in Jinhua pigs whereas those that regulate myogenesis (e.g., myogenic factor 6 and forkhead box O1) are expressed at higher levels in Landrace pigs. Among those genes which are highly expressed in Jinhua pigs at 90 days (d90), we identified a novel gene porcine FLJ36031 (pFLJ), which functions as a positive regulator of fat deposition in cultured intramuscular adipocytes. In summary, our data showed that the up-regulation of fatty acid biosynthesis regulatory genes such as pFLJ and myogenesis inhibitory genes such as myostatin in the longissimus dorsi muscles of Jinhua pigs could explain why this local breed produces meat with high levels of IMF.

  11. The contribution of the deep fibers of the masseter muscle to selected tooth-clenching and chewing tasks.

    Science.gov (United States)

    Belser, U C; Hannam, A G

    1986-11-01

    Anatomically, the human masseter muscle consists of at least two portions (pars superficialis, pars profunda) with distinctly different fiber directions. The purpose of this study was to describe functional behavior in the deep fibers of the masseter muscle and to define any differences in its behavior from that of the superficial fibers. In 20 subjects, EMG activity of the superficial and the deep portions of the masseter muscle was recorded during specific parafunctional (intercuspal and eccentric tooth clenching) and functional (unilateral chewing) tests. Superficial and deep activity was measured with bipolar surface electrodes and intramuscular fine-wire electrodes. Simultaneously, displacement of a lower incisor point was recorded in three dimensions. The data were collected and stored for analysis by a disk-based computer system. The results indicated that changes in the direction of effort, in mandibular position, and in the side used for chewing all influenced activity in both parts of the muscle to different extents. The most distinct separation of activity occurred when intercuspal clenching was directed retrusively; the deep fibers of the masseter muscle response reduced to 47.5% of its maximum value while that of the superficial fibers of the masseter muscle fell to 5.5%. During chewing, activity in the deep fibers of masseter muscle was distributed evenly bilaterally, whereas that in the superficial fibers of the masseter muscle was biased significantly toward the chewing side. Differentiation of activity within the masseter muscle may be relevant to the distribution of regional tenderness in the muscle when it is involved in parafunctional activity.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Regulation of the muscle fiber microenvironment by activated satellite cells during hypertrophy.

    Science.gov (United States)

    Fry, Christopher S; Lee, Jonah D; Jackson, Janna R; Kirby, Tyler J; Stasko, Shawn A; Liu, Honglu; Dupont-Versteegden, Esther E; McCarthy, John J; Peterson, Charlotte A

    2014-04-01

    Our aim in the current study was to determine the necessity of satellite cells for long-term muscle growth and maintenance. We utilized a transgenic Pax7-DTA mouse model, allowing for the conditional depletion of > 90% of satellite cells with tamoxifen treatment. Synergist ablation surgery, where removal of synergist muscles places functional overload on the plantaris, was used to stimulate robust hypertrophy. Following 8 wk of overload, satellite cell-depleted muscle demonstrated an accumulation of extracellular matrix (ECM) and fibroblast expansion that resulted in reduced specific force of the plantaris. Although the early growth response was normal, an attenuation of hypertrophy measured by both muscle wet weight and fiber cross-sectional area occurred in satellite cell-depleted muscle. Isolated primary myogenic progenitor cells (MPCs) negatively regulated fibroblast ECM mRNA expression in vitro, suggesting a novel role for activated satellite cells/MPCs in muscle adaptation. These results provide evidence that satellite cells regulate the muscle environment during growth.

  13. Simulation of propagation in a bundle of skeletal muscle fibers: Modulation effects of passive fibers

    DEFF Research Database (Denmark)

    Henneberg, Kaj-åge; F.A., Roberge

    1997-01-01

    source current (I-ma) enters the passive tissue as a radial load current (I-ep) while the rest flows longitudinally in the cleft between the active and adjacent passive fibers. The conduction velocity of 1.32 m/s was about 30% lower than on an isolated fiber in a Ringer bath, in close agreement...... rate of rise of the action potential upstroke (V-max) from 512 to 503 V/s. Increasing the phase angle of the passive fiber membrane impedence (Z(m)) increases the phase delay between I-ma and I-ep, thereby increasing phi(epp) which in turn slows down propagation and increases V-max....

  14. Morphology of nerve fiber regeneration along a biodegradable poly (DLLA-epsilon-CL) nerve guide filled with fresh skeletal muscle.

    Science.gov (United States)

    Varejão, Artur S P; Cabrita, António M; Meek, Marcel F; Fornaro, Michele; Geuna, Stefano; Giacobini-Robecchi, Maria G

    2003-01-01

    Previous morphological and morphometrical studies showed that fresh-skeletal-muscle-enriched vein segments are good conduits for leading peripheral nerve regeneration. In the present study, we investigated the morphological features of peripheral nerve fibers regenerated along a 10-mm-long biodegradable poly (DLLA-epsilon-CL) nerve guide enriched with fresh skeletal muscle, comparing them to nerve fiber regeneration along 10-mm-long phosphate-buffered saline (PBS)-enriched poly (DLLA-epsilon-CL) tubes. Repaired nerves were analyzed at weeks 6 and 24 postoperatively. Structural and ultrastructural observation showed that good nerve fiber regeneration occurred in both PBS-enriched and fresh-skeletal-muscle-enriched nerve guides, and histomorphometrical analysis of regenerated myelinated fibers revealed no statistically significant differences between the two experimental groups at week 24 after surgery. The employment of fresh-muscle-enriched conduits for the repair of nerve defects is critically discussed in the light of these results.

  15. Micro-RNA expression in muscle and fiber morphometry in myotonic dystrophy type 1.

    Science.gov (United States)

    Fritegotto, Chiara; Ferrati, Chiara; Pegoraro, Valentina; Angelini, Corrado

    2017-04-01

    We aimed to explore the cellular action of micro-RNAs that are non-coding-RNAs modulating gene expression, whose expression is dysregulated in myotonic dystrophy (DM1). Basic procedure was to measure the levels of muscle-specific myo-miRNAs (miR-1, miR-133a/b, miR-206) in muscle of 12 DM1 patients. Muscle fiber morphometry and a new grading of histopathological severity score were used to compare specific myo-miRNA level and fiber atrophy. We found that the levels of miR-1 and miR-133a/b were significantly decreased, while miR-206 was significantly increased as compared to controls. The histopathological score did not significantly correlate with the levels of myo-miRNAs, even if the lowest levels of miRNA-1 and miRNA-133a/b, and the highest levels of miRNA-206 were observed in patients with either severe histopathological scores or long disease duration. The histopathological score was inversely correlated with disease duration. Nowadays that DM1 muscle biopsies are scanty, since patients are usually diagnosed by genetic analysis, our study offers a unique opportunity to present miRNA expression profiles in muscle and correlate them to muscle morphology in this rare multisystem disorder. Our molecular and morphologic data suggest a post-transcriptional regulatory action of myo-miRNA in DM1, highlighting their potential role as biomarkers of muscle plasticity.

  16. Using spike-triggered averaging to characterize motor unit twitch vectors in the first dorsal interosseous.

    Science.gov (United States)

    Suresh, Nina; Kuo, Art; Heckman, C J; Rymer, William Zev

    2012-01-01

    Earlier studies in multifunctional muscles such as the first dorsal interosseous (FDI) have demonstrated that the selection and control of motor units (MUs) can vary as a function of generated force direction. While directionally dependent motor unit recruitment and rate properties imply that there may also be differential mechanical action, this has yet to be directly demonstrated. Our objective was to determine whether there exists a range of force vectors from different motor units in the FDI muscle within individual subjects. We utilized the spike-triggered averaging (STA) method to derive force twitch estimates from single motor units. We derived MU twitch direction from the ratio of individual twitch estimates recorded concurrently from the load cell. Fifteen units from 2 subjects were used to determine MU force vectors. We were able to estimate force twitch vectors from 7-8 different MUs in each subject. The results of our study suggest that there is varied mechanical action of motor units in the FDI. It is thus possible that differential activation of individual MUs in the FDI is a function of varied mechanical action.

  17. Myosin types and fiber types in cardiac muscle. II. Atrial myocardium

    OpenAIRE

    1982-01-01

    Antibodies were produced against myosins isolated from the left atrial myocardium (anti-bAm) and the left ventricular myocardium (anti-bVm) of the bovine heart. Cross-reactive antibodies were removed by cross- absorption. Absorbed anti-bAm and anti-bVm were specific for the myosin heavy chains when tested by enzyme immunoassay combined with SDS gel electrophoresis. Indirect immunofluorescence was used to determine the reactivity of atrial muscle fibers to the two antibodies. Three populations...

  18. A case of adult Pompe disease presenting with severe fatigue and selective involvement of type 1 muscle fibers.

    Science.gov (United States)

    van den Berg, Linda E M; de Vries, Juna M; Verdijk, Robert M; van der Ploeg, Ans T; Reuser, Arnold J J; van Doorn, Pieter A

    2011-03-01

    We present a case of adult Pompe disease (acid maltase deficiency) with an uncommon clinical presentation characterized by severe fatigue and myalgia prior to the onset of limb girdle weakness. Remarkably, the muscle biopsy demonstrated selective involvement of type 1 muscle fibers. The cause and clinical effects of fiber type specific involvement are currently unknown, but the phenomenon might contribute to the clinical heterogeneity in Pompe disease and the variable response to enzyme replacement therapy.

  19. Direct observation of failing fibers in muscles of dystrophic mice provides mechanistic insight into muscular dystrophy.

    Science.gov (United States)

    Claflin, Dennis R; Brooks, Susan V

    2008-02-01

    Duchenne muscular dystrophy is caused by the absence of the protein dystrophin. Dystrophin's function is not known, but its cellular location and associations with both the force-generating contractile core and membrane-spanning entities suggest a role in mechanically coupling force from its intracellular origins to the fiber membrane and beyond. We report here the presence of destructive contractile activity in lumbrical muscles from dystrophin-deficient (mdx) mice during nominally quiescent periods following exposure to mechanical stress. The ectopic activity, which was observable microscopically, resulted in longitudinal separation and clotting of fiber myoplasm and was absent when calcium (Ca(2+)) was removed from the bathing medium. Separation and clotting of myoplasm were also produced in dystrophin-deficient muscles by local application of a Ca(2+) ionophore to create membrane breaches in the absence of mechanical stress, whereas muscles from control mice tolerated ionophore-induced entry of Ca(2+) without damage. These observations suggest a failure cascade in dystrophin-deficient fibers that 1) is initiated by a stress-induced influx of extracellular Ca(2+), causing localized activation to continue after cessation of stimulation, and 2) proceeds as the persistent local activation, combined with reduced lateral mechanical coupling between the contractile core and the extracellular matrix, results in longitudinal separation of myoplasm in nonactivated regions of the fiber. This mechanism invokes both the membrane stabilization and the mechanical coupling functions frequently proposed for dystrophin and suggests that, whereas the absence of either function alone is not sufficient to cause fiber failure, their combined absence is catastrophic.

  20. Optical polarization tractography revealed significant fiber disarray in skeletal muscles of a mouse model for Duchenne muscular dystrophy.

    Science.gov (United States)

    Wang, Y; Zhang, K; Wasala, N B; Duan, D; Yao, G

    2015-02-01

    Optical polarization tractography (OPT) was recently developed to visualize tissue fiber architecture with cellular-level resolution and accuracy. In this study, we explored the feasibility of using OPT to study muscle disease in the mdx4cv mouse model of Duchenne muscular dystrophy. The freshly dissected tibialis anterior muscles of mdx4cv and normal mice were imaged. A "fiber disarray index" (FDI) was developed to quantify the myofiber disorganization. In necrotic muscle regions of the mdx4cv mice, the FDI was significantly elevated and can be used to segment the 3D necrotic regions for assessing the overall muscle damage. These results demonstrated the OPT's capability for imaging microscopic fiber alternations in muscle research.

  1. Use of a fiber glass optical system to measure the contractile characteristics of a single isolated muscle cell

    Science.gov (United States)

    Chen, Chulung; Yin, Shizhuo; Li, Jiang; Yu, Francis T. S.; Cheung, Joseph Y.; Zhang, Xueqian; Lei, Xiaoxiao; Wu, Zhongkong

    1998-05-01

    Cell is the basic structural and fundamental unit of all organisms; the smallest structure capable of performing all the activities vital to life. One goal of current research interest is to learn how the muscle varies the strength of its contraction in response to electric stimuli. A wide variety of techniques have been developed to monitor the mechanical response of isolated cardiac myocytes. Some success has been reported either with the use of intact rat myocytes supported by suction micropipettes or in guinea pig myocytes adhering to glass beams. However, the usual measuring techniques exhibit destructive contact performance on live cells. They could not solve the problem, since the cell may die during or after the time-consuming attachment process at the beginning of each experiment. In contrast, a novel optical system, which consists of a microglass tube with an inner diameter the same size of a real cardiac cell, is proposed to simulate real cell's twitch process. the physical parameters of synthetic cell are well known. By comparing the dynamics of the real cell with that of the simulated cell, the twitch characteristics of the real cell can be measured.

  2. Fiber type and metabolic characteristics of lion (Panthera leo), caracal (Caracal caracal) and human skeletal muscle.

    Science.gov (United States)

    Kohn, Tertius Abraham; Burroughs, Richard; Hartman, Marthinus Jacobus; Noakes, Timothy David

    2011-06-01

    Lion (Panthera leo) and caracal (Caracal caracal) skeletal muscle samples from Vastus lateralis, Longissimus dorsi and Gluteus medius were analyzed for fiber type and citrate synthase (CS; EC 2.3.3.1), 3-hydroxyacyl Co A dehydrogenase (3HAD; EC 1.1.1.35), phosphofructokinase-1 (PFK; EC 2.7.1.11), creatine kinase (CK; EC 2.7.3.2), phosphorylase (PHOS; EC 2.4.1.1) and lactate dehydrogenase (LDH; EC 1.1.1.27) activities and compared to human runners, the latter also serving as validation of methodology. Both felids had predominantly type IIx fibers (range 50-80%), whereas human muscle had more types I and IIa. Oxidative capacity of both felids (CS: 5-9 μmol/min/g ww and 3HAD: 1.4-2.6 μmol/min/g ww)