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Sample records for fiber muscle types

  1. Muscle Fiber Types and Training.

    ERIC Educational Resources Information Center

    Karp, Jason R.

    2001-01-01

    The specific types of fibers that make up individual muscles greatly influence how people will adapt to their training programs. This paper explains the complexities of skeletal muscles, focusing on types of muscle fibers (slow-twitch and fast-twitch), recruitment of muscle fibers to perform a motor task, and determining fiber type. Implications…

  2. Muscle Fiber Types and Training.

    ERIC Educational Resources Information Center

    Karp, Jason R.

    2001-01-01

    The specific types of fibers that make up individual muscles greatly influence how people will adapt to their training programs. This paper explains the complexities of skeletal muscles, focusing on types of muscle fibers (slow-twitch and fast-twitch), recruitment of muscle fibers to perform a motor task, and determining fiber type. Implications…

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

    PubMed

    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.

  4. Single Muscle Fiber Proteomics Reveals Fiber-Type-Specific Features of Human Muscle Aging.

    PubMed

    Murgia, Marta; Toniolo, Luana; Nagaraj, Nagarjuna; Ciciliot, Stefano; Vindigni, Vincenzo; Schiaffino, Stefano; Reggiani, Carlo; Mann, Matthias

    2017-06-13

    Skeletal muscle is a key tissue in human aging, which affects different muscle fiber types unequally. We developed a highly sensitive single muscle fiber proteomics workflow to study human aging and show that the senescence of slow and fast muscle fibers is characterized by diverging metabolic and protein quality control adaptations. Whereas mitochondrial content declines with aging in both fiber types, glycolysis and glycogen metabolism are upregulated in slow but downregulated in fast muscle fibers. Aging mitochondria decrease expression of the redox enzyme monoamine oxidase A. Slow fibers upregulate a subset of actin and myosin chaperones, whereas an opposite change happens in fast fibers. These changes in metabolism and sarcomere quality control may be related to the ability of slow, but not fast, muscle fibers to maintain their mass during aging. We conclude that single muscle fiber analysis by proteomics can elucidate pathophysiology in a sub-type-specific manner. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  5. Muscle fiber type diversification during exercise and regeneration.

    PubMed

    Qaisar, Rizwan; Bhaskaran, Shylesh; Van Remmen, Holly

    2016-09-01

    The plasticity of skeletal muscle can be traced down to extensive metabolic, structural and molecular remodeling at the single fiber level. Skeletal muscle is comprised of different fiber types that are the basis of muscle plasticity in response to various functional demands. Resistance and endurance exercises are two external stimuli that differ in their duration and intensity of contraction and elicit markedly different responses in muscles adaptation. Further, eccentric contractions that are associated with exercise-induced injuries, elicit varied muscle adaptation and regenerative responses. Most adaptive changes are fiber type-specific and are highly influenced by diverse structural, metabolic and functional characteristics of individual fiber types. Regulation of signaling pathways by reactive oxygen species (ROS) and oxidative stress also plays an important role in muscle fiber adaptation during exercise. This review focuses on cellular and molecular responses that regulate the adaptation of skeletal muscle to exercise and exercise-related injuries.

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

    PubMed

    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.

  7. Intermuscular relationship of human muscle fiber type proportions: slow leg muscles predict slow neck muscles.

    PubMed

    Vikne, Harald; Gundersen, Kristian; Liestøl, Knut; Maelen, Jan; Vøllestad, Nina

    2012-04-01

    Our aim in this study was to examine whether the muscle fiber type proportions in different muscles from the same individual are interrelated. Samples were excised from five skeletal muscles in each of 12 human autopsy cases, and the fiber type proportions were determined by immunohistochemistry. We further examined the intermuscular relationship in fiber type proportion by reanalyzing three previously published data sets involving other muscles. Subjects demonstrated a predominantly high or low proportion of type 1 fibers in all examined muscles, and the overall difference between individuals was statistically significant (P < 0.001). Accordingly, the type 1 fiber proportions in most muscles were positively correlated (median r = 0.42, range -0.03-0.80). Similar results were also obtained from the three reanalyzed data sets. We suggest the existence of an across-muscle phenotype with respect to fiber type proportions; some individuals display generally faster muscles and some individuals slower muscles when compared with others. Copyright © 2011 Wiley Periodicals, Inc.

  8. Preferential Type II Muscle Fiber Damage From Plyometric Exercise

    PubMed Central

    Macaluso, Filippo; Isaacs, Ashwin W.; Myburgh, Kathryn H.

    2012-01-01

    Context Plyometric training has been successfully used in different sporting contexts. Studies that investigated the effect of plyometric training on muscle morphology are limited, and results are controversial with regard to which muscle fiber type is mainly affected. Objective To analyze the skeletal muscle structural and ultrastructural change induced by an acute bout of plyometric exercise to determine which type of muscle fibers is predominantly damaged. Design Descriptive laboratory study. Setting Research laboratory. Patients or Other Participants Eight healthy, untrained individuals (age = 22 ± 1 years, height = 179.2 ± 6.4 cm, weight = 78.9 ± 5.9 kg). Intervention(s) Participants completed an acute bout of plyometric exercise (10 sets of 10 squat-jumps with a 1-minute rest between sets). Main Outcome Measure(s) Blood samples were collected 9 days and immediately before and 6 hours and 1, 2, and 3 days after the acute intervention. Muscle samples were collected 9 days before and 3 days after the exercise intervention. Blood samples were analyzed for creatine kinase activity. Muscle biopsies were analyzed for damage using fluorescent and electron transmission microscopy. Results Creatine kinase activity peaked 1 day after the exercise bout (529.0 ± 317.8 U/L). Immunofluorescence revealed sarcolemmal damage in 155 of 1616 fibers analyzed. Mainly fast-twitch fibers were damaged. Within subgroups, 7.6% of type I fibers, 10.3% of type IIa fibers, and 14.3% of type IIx fibers were damaged as assessed by losses in dystrophin staining. Similar damage was prevalent in IIx and IIa fibers. Electron microscopy revealed clearly distinguishable moderate and severe sarcomere damage, with damage quantifiably predominant in type II muscle fibers of both the glycolytic and oxidative subtypes (86% and 84%, respectively, versus only 27% of slow-twitch fibers). Conclusions We provide direct evidence that a single bout of plyometric exercise affected mainly type II muscle

  9. Preferential type II muscle fiber damage from plyometric exercise.

    PubMed

    Macaluso, Filippo; Isaacs, Ashwin W; Myburgh, Kathryn H

    2012-01-01

    Plyometric training has been successfully used in different sporting contexts. Studies that investigated the effect of plyometric training on muscle morphology are limited, and results are controversial with regard to which muscle fiber type is mainly affected. To analyze the skeletal muscle structural and ultrastructural change induced by an acute bout of plyometric exercise to determine which type of muscle fibers is predominantly damaged. Descriptive laboratory study. Research laboratory. Eight healthy, untrained individuals (age = 22 ± 1 years, height = 179.2 ± 6.4 cm, weight = 78.9 ± 5.9 kg). Participants completed an acute bout of plyometric exercise (10 sets of 10 squat-jumps with a 1-minute rest between sets). Blood samples were collected 9 days and immediately before and 6 hours and 1, 2, and 3 days after the acute intervention. Muscle samples were collected 9 days before and 3 days after the exercise intervention. Blood samples were analyzed for creatine kinase activity. Muscle biopsies were analyzed for damage using fluorescent and electron transmission microscopy. Creatine kinase activity peaked 1 day after the exercise bout (529.0 ± 317.8 U/L). Immunofluorescence revealed sarcolemmal damage in 155 of 1616 fibers analyzed. Mainly fast-twitch fibers were damaged. Within subgroups, 7.6% of type I fibers, 10.3% of type IIa fibers, and 14.3% of type IIx fibers were damaged as assessed by losses in dystrophin staining. Similar damage was prevalent in IIx and IIa fibers. Electron microscopy revealed clearly distinguishable moderate and severe sarcomere damage, with damage quantifiably predominant in type II muscle fibers of both the glycolytic and oxidative subtypes (86% and 84%, respectively, versus only 27% of slow-twitch fibers). We provide direct evidence that a single bout of plyometric exercise affected mainly type II muscle fibers.

  10. Muscle Histology Characterization Using H&E Staining and Muscle Fiber Type Classification Using Immunofluorescence Staining

    PubMed Central

    Wang, Chao; Yue, Feng; Kuang, Shihuan

    2017-01-01

    Muscle function is determined by its structure and fiber type composition. Here we describe a protocol to examine muscle histology and myofiber types using hematoxylin and eosin (H&E) and immunofluorescence staining, respectively. H&E stain nucleus in blue and cytoplasm in red, therefore allowing for morphological analyses, such as myofiber diameter, the presence of degenerated and regenerated myofibers, and adipocytes and fibrotic cells. Muscle fibers in adult skeletal muscles of rodents are classified into 4 subtypes based on the expression of myosin heavy chain proteins: Myh7 (type I fiber), Myh2 (type IIA fiber), Myh1 (type IIX fiber), Myh4 (type IIB fiber). A panel of monoclonal antibodies can be used to specifically label these muscle fiber subtypes. These protocols are commonly used in the study of muscle development, growth and regeneration (for example: Wang et al., 2015; Nie et al., 2016; Yue et al., 2016; Wang et al., 2017). PMID:28752107

  11. Regulation of muscle fiber type and running endurance by PPARdelta.

    PubMed

    Wang, Yong-Xu; Zhang, Chun-Li; Yu, Ruth T; Cho, Helen K; Nelson, Michael C; Bayuga-Ocampo, Corinne R; Ham, Jungyeob; Kang, Heonjoong; Evans, Ronald M

    2004-10-01

    Endurance exercise training can promote an adaptive muscle fiber transformation and an increase of mitochondrial biogenesis by triggering scripted changes in gene expression. However, no transcription factor has yet been identified that can direct this process. We describe the engineering of a mouse capable of continuous running of up to twice the distance of a wild-type littermate. This was achieved by targeted expression of an activated form of peroxisome proliferator-activated receptor delta (PPARdelta) in skeletal muscle, which induces a switch to form increased numbers of type I muscle fibers. Treatment of wild-type mice with PPARdelta agonist elicits a similar type I fiber gene expression profile in muscle. Moreover, these genetically generated fibers confer resistance to obesity with improved metabolic profiles, even in the absence of exercise. These results demonstrate that complex physiologic properties such as fatigue, endurance, and running capacity can be molecularly analyzed and manipulated.

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

    PubMed

    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.

  13. Experimental comparisons between McKibben type artificial muscles and straight fibers type artificial muscles

    NASA Astrophysics Data System (ADS)

    Nakamura, Taro

    2007-01-01

    This paper describes experimental comparison between a conventional McKibben type artificial muscle and a straight fibers type artificial muscle developed by the authors. A wearable device and a rehabilitation robot which assists a human muscle should have characteristics similar to those of human muscle. In addition, because the wearable device and the rehabilitation robot should be light, an actuator with a high power/weight ratio is needed. At present, the McKibben type is widely used as an artificial muscle, but in fact its physical model is highly nonlinear. Further, the heat and mechanical loss of this actuator are large because of the friction caused by the expansion and contraction of the sleeve. Therefore, the authors have developed an artificial muscle tube in which high strength glass fibers have been built into the tube made from natural latex rubber. As results, experimental results demonstrated that the developed artificial muscle is more effective regarding its fundamental characteristics than that of the McKibben type; the straight fibers types of artificial muscle have more contraction ratio and power, longer lifetime than the McKibben types. And it has almost same characteristics of human muscle for isotonic and isometric that evaluate it dynamically.

  14. Hybrid fibers transform into distinct fiber types in maturing mouse muscles.

    PubMed

    Brummer, Hannah; Zhang, Min Yi; Piddoubny, Maria; Medler, Scott

    2013-01-01

    The role of hybrid fibers as intermediates in fiber type transformations is not completely understood. In some cases hybrids are clearly transitional fibers changing from one type to another, but in others they represent phenotypically stable fibers in normal muscles. In the current study, our goal was to understand the fate of hybrid fibers in fiber type transitions that take place during muscle maturation. Previous studies have reported high proportions of hybrid fibers during postnatal development, but few have followed the fate of these fibers past the time of weaning. We quantified proportions of hybrid fibers in three different mouse skeletal muscles from newly weaned to 6-month-old mice. Hybrid fibers were very prevalent in the brachioradialis (BR) and tibialis anterior (TA) muscles from newly weaned mice, where they constituted 50 and 40% of the fibers, respectively. These hybrids declined steadily to about 15-30% over the next several months. In the soleus muscle the proportion of hybrids did not change, but constituted approximately 20% of fibers. The reduction in IIX/IIB hybrids resulted from different processes in the BR and the TA. In the BR, the reduction was coincident with an increase in type IIX fibers. In the TA, the number of IIX/IIB hybrids was inversely correlated with the proportion of IIB fibers. These patterns reveal that the role of hybrid fibers as intermediates in muscle development is complex. Some hybrid fibers in maturing muscles represent transitional fiber types, while others are phenotypically stable. Moreover, the fate of transitional fibers may be distinct among similar fiber types within different muscles.

  15. Mechanical properties and fiber type composition of chronically inactive muscles

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Monti, R. J.; Vallance, K. A.; Kim, J. A.; Edgerton, V. R.

    2000-01-01

    A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

  16. Mechanical properties and fiber type composition of chronically inactive muscles

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Monti, R. J.; Vallance, K. A.; Kim, J. A.; Edgerton, V. R.

    2000-01-01

    A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

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

    PubMed Central

    2013-01-01

    Background It was recently shown that niacin supplementation counteracts the obesity-induced muscle fiber transition from oxidative type I to glycolytic type II and increases the number of type I fibers in skeletal muscle of obese Zucker rats. These effects were likely mediated by the induction of key regulators of fiber transition, PPARδ (encoded by PPARD), PGC-1α (encoded by PPARGC1A) and PGC-1β (encoded by PPARGC1B), leading to type II to type I fiber transition and upregulation of genes involved in oxidative metabolism. The aim of the present study was to investigate whether niacin administration also influences fiber distribution and the metabolic phenotype of different muscles [M. longissimus dorsi (LD), M. semimembranosus (SM), M. semitendinosus (ST)] in sheep as a model for ruminants. For this purpose, 16 male, 11 wk old Rhoen sheep were randomly allocated to two groups of 8 sheep each administered either no (control group) or 1 g niacin per day (niacin group) for 4 wk. Results After 4 wk, the percentage number of type I fibers in LD, SM and ST muscles was greater in the niacin group, whereas the percentage number of type II fibers was less in niacin group than in the control group (P < 0.05). The mRNA levels of PPARGC1A, PPARGC1B, and PPARD and the relative mRNA levels of genes involved in mitochondrial fatty acid uptake (CPT1B, SLC25A20), tricarboxylic acid cycle (SDHA), mitochondrial respiratory chain (COX5A, COX6A1), and angiogenesis (VEGFA) in LD, SM and ST muscles were greater (P < 0.05) or tended to be greater (P < 0.15) in the niacin group than in the control group. Conclusions The study shows that niacin supplementation induces muscle fiber transition from type II to type I, and thereby an oxidative metabolic phenotype of skeletal muscle in sheep as a model for ruminants. The enhanced capacity of skeletal muscle to utilize fatty acids in ruminants might be particularly useful during metabolic states in which fatty acids are

  18. Functional characteristics of the rat jaw muscles: daily muscle activity and fiber type composition

    PubMed Central

    Kawai, Nobuhiko; Sano, Ryota; Korfage, Joannes A M; Nakamura, Saika; Tanaka, Eiji; van Wessel, Tim; Langenbach, Geerling E J; Tanne, Kazuo

    2009-01-01

    Skeletal muscles have a heterogeneous fiber type composition, which reflects their functional demand. The daily muscle use and the percentage of slow-type fibers have been shown to be positively correlated in skeletal muscles of larger animals but for smaller animals there is no information. The examination of this relationship in adult rats was the purpose of this study. We hypothesized a positive relationship between the percentage of fatigue-resistant fibers in each muscle and its total duration of use per day. Fourteen Wistar strain male rats (410–450 g) were used. A radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter, deep masseter, anterior belly of digastric and anterior temporalis muscles. The degree of daily muscle use was quantified by the total duration of muscle activity per day (duty time) exceeding specified levels of the peak activity (2, 5, 20 and 50%). The fiber type composition of the muscles was examined by the myosin heavy chain content of the fibers by means of immunohistochemical staining. At lower activity levels (exceeding 2 and 5% of the peak activity), the duty time of the anterior belly of digastric muscle was significantly (P < 0.01) longer than those of the other muscles. The anterior belly of digastric muscle also contained the highest percentage of slow-type fibers (type I fiber and hybrid fiber co-expressing myosin heavy chain I + IIA) (ca. 11%; P < 0.05). By regression analysis for all four muscles, an inter-muscular comparison showed a positive relationship between the duty time (exceeding 50% of the peak activity) and the percentage of type IIX fibers (P < 0.05), which demonstrate intermediate physiological properties relative to type IIA and IIB fibers. For the jaw muscles of adult male rats, the variations of fiber type composition and muscle use suggest that the muscle containing the largest amounts of slow-type fibers (the anterior belly of digastric muscle) is mainly

  19. Functional characteristics of the rat jaw muscles: daily muscle activity and fiber type composition.

    PubMed

    Kawai, Nobuhiko; Sano, Ryota; Korfage, Joannes A M; Nakamura, Saika; Tanaka, Eiji; van Wessel, Tim; Langenbach, Geerling E J; Tanne, Kazuo

    2009-12-01

    Skeletal muscles have a heterogeneous fiber type composition, which reflects their functional demand. The daily muscle use and the percentage of slow-type fibers have been shown to be positively correlated in skeletal muscles of larger animals but for smaller animals there is no information. The examination of this relationship in adult rats was the purpose of this study. We hypothesized a positive relationship between the percentage of fatigue-resistant fibers in each muscle and its total duration of use per day. Fourteen Wistar strain male rats (410-450 g) were used. A radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter, deep masseter, anterior belly of digastric and anterior temporalis muscles. The degree of daily muscle use was quantified by the total duration of muscle activity per day (duty time) exceeding specified levels of the peak activity (2, 5, 20 and 50%). The fiber type composition of the muscles was examined by the myosin heavy chain content of the fibers by means of immunohistochemical staining. At lower activity levels (exceeding 2 and 5% of the peak activity), the duty time of the anterior belly of digastric muscle was significantly (P < 0.01) longer than those of the other muscles. The anterior belly of digastric muscle also contained the highest percentage of slow-type fibers (type I fiber and hybrid fiber co-expressing myosin heavy chain I + IIA) (ca. 11%; P < 0.05). By regression analysis for all four muscles, an inter-muscular comparison showed a positive relationship between the duty time (exceeding 50% of the peak activity) and the percentage of type IIX fibers (P < 0.05), which demonstrate intermediate physiological properties relative to type IIA and IIB fibers. For the jaw muscles of adult male rats, the variations of fiber type composition and muscle use suggest that the muscle containing the largest amounts of slow-type fibers (the anterior belly of digastric muscle) is mainly

  20. Muscle growth and fiber type composition in hind limb muscles during postnatal development in pigs.

    PubMed

    Wank, Veit; Fischer, Martin S; Walter, Bernd; Bauer, Reinhard

    2006-01-01

    Rapid postnatal development in pigs is reflected by differentiation in skeletal muscle. This process depends on muscle function and demands, but a comprehensive overview of individual developmental characteristics of quickly growing leg muscles in pigs is still missing. This study focused on the development of 10 hind limb muscles in pigs. To determine these changes in mass, fiber type patterns and fiber diameters were analyzed 0, 2, 4, 7, 14, 28, 42, 56 and 400 days after birth. Generally, the proportion of slow fibers increased from birth to 8 weeks. Thereafter, only minor changes in muscle fiber type composition were observed. The majority of the muscles contained less then 10% slow-twitch fibers at birth, increasing to between 12 (Musculus vastus lateralis) and 38% (M. gastrocnemius medialis) in adult pigs. By contrast, postural muscles already had 20-30% slow fibers at birth, and this contribution increased up to 65% in adults (i.e. M. vastus intermedius). From birth to the 2nd week, only in slow fibers could activity of oxidative enzymes be detected. A differentiation of fast-twitch fibers into subtypes with high (comparable to type IIA) and low oxidative metabolism (equivalent to type IIB) occurred between the 2nd and 4th week of life. The ratio between type II fibers with high and low oxidative enzyme activity did not change markedly through development in any muscle, although there was a trend towards an increasing proportion of type IIA fibers in the soleus. In the majority of the muscles investigated, the fast-twitch fibers with low oxidative metabolism (IIB) obtained the largest cross-sectional area. In contrast, at birth no remarkable differences in the diameter of fast and slow fibers were found. The rapid increase in muscle mass compared to body mass reflects the high performance in meat production of the cross pig investigated.

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

    PubMed

    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.

  2. CYTOLOGICAL STUDIES OF FIBER TYPES IN SKELETAL MUSCLE

    PubMed Central

    Gauthier, Geraldine F.; Padykula, Helen A.

    1966-01-01

    A comparative investigation of the mammalian diaphragm has revealed a correlation between certain cytological aspects of red and white muscle fibers and functional activity. This skeletal muscle presents the advantage of a similar and constant function among the mammals, but its functional activity varies in a quantitative manner. Both the rate of breathing (and hence the rate of contraction of the diaphragm) and metabolic activity are known to be inversely related to body size; and this study has demonstrated a relationship between cytological characteristics of the diaphragm and body size of the animal. Small fibers rich in mitochondria (red fibers) are characteristic of small mammals, which have high metabolic activity and fast breathing rates; and large fibers with relatively low mitochondrial content predominate in large mammals, which have lower metabolic activity and slower breathing rates. In mammals with body size intermediate between these two groups (including the laboratory rat), the diaphragm consists of varying mixtures of fiber types. In general, the mitochondrial content of diaphragm fibers is inversely related to body size. It appears, then, that the red fiber reflects a high degree of metabolic activity or a relatively high rate of contraction within the range exhibited by this muscle. PMID:5950272

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

    PubMed

    Eftestøl, Einar; Alver, Tine Norman; Gundersen, Kristian; Bruusgaard, Jo C

    2014-01-01

    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.

  4. Human Masseter Muscle Fiber Type Properties, Skeletal Malocclusions, and Muscle Growth Factor Expression

    PubMed Central

    Sciote, James Joseph; Horton, Michael J.; Rowlerson, Anthea M.; Ferri, Joel; Close, John M.; Raoul, Gwenael

    2013-01-01

    Purpose We identified masseter muscle fiber type property differences in subjects with dentofacial deformities. Patients and Methods Samples of masseter muscle were collected from 139 young adults during mandibular osteotomy procedures to assess mean fiber areas and percent tissue occupancies for the 4 fiber types that comprise the muscle. Subjects were classified into 1 of 6 malocclusion groups based on the presence of a skeletal Class II or III sagittal dimension malocclusion and either a skeletal open, deep, or normal bite vertical dimension malocclusion. In a subpopulation, relative quantities of the muscle growth factors IGF-I and GDF-8 gene expression were quantified by real-time polymerase chain reaction. Results Fiber properties were not different in the sagittal malocclusion groups, but were very different in the vertical malocclusion groups (P ≤ .0004). There were significant mean fiber area differences for type II (P ≤ .0004) and type neonatal—atrial (P = .001) fiber types and for fiber percent occupancy differences for both type I–II hybrid fibers and type II fibers (P ≤ .0004). Growth factor expression differed by gender for IGF-I (P = .02) and GDF-8 (P < .01). The ratio of IGF-I:GDF-8 expression associates with type I and II mean fiber areas. Conclusion Fiber type properties are very closely associated with variations in vertical growth of the face, with statistical significance for overall comparisons at P ≤ .0004. An increase in masseter muscle type II fiber mean fiber areas and percent tissue occupancies is inversely related to increases in vertical facial dimension. PMID:21821327

  5. Energetic aspects of skeletal muscle contraction: implications of fiber types.

    PubMed

    Rall, J A

    1985-01-01

    In this chapter fundamental energetic properties of skeletal muscles as elucidated from isolated muscle preparations are described. Implications of these intrinsic properties for the energetic characterization of different fiber types and for the understanding of locomotion have been considered. Emphasis was placed on the myriad of physical and chemical techniques that can be employed to understand muscle energetics and on the interrelationship of results from different techniques. The anaerobic initial processes which liberate energy during contraction and relaxation are discussed in detail. The high-energy phosphate (approximately P) utilized during contraction and relaxation can be distributed between actomyosin ATPase or cross-bridge cycling (70%) and the Ca2+ ATPase of the sacroplasmic reticulum (30%). Muscle shortening increases the rate of approximately P hydrolysis, and stretching a muscle during contraction suppresses the rate of approximately P hydrolysis. The economy of an isometric contraction is defined as the ratio of isometric mechanical response to energetic cost and is shown to be a fundamental intrinsic parameter describing muscle energetics. Economy of contraction varies across the animal kingdom by over three orders of magnitude and is different in different mammalian fiber types. In mammalian skeletal muscles differences in economy of contraction can be attributed mainly to differences in the specific actomyosin and Ca2+ ATPase of muscles. Furthermore, there is an inverse relationship between economy of contraction and maximum velocity of muscle shortening (Vmax) and maximum power output. This is a fundamental relationship. Muscles cannot be economical at developing and maintaining force and also exhibit rapid shortening. Interestingly, there appears to be a subtle system of unknown nature that modulates the Vmax and economy of contraction. Efficiency of a work-producing contraction is defined and contrasted to the economy of contraction

  6. MOUSE TRANSGENIC LINES THAT SELECTIVELY LABEL TYPE I, TYPE IIA AND TYPES IIX+B SKELETAL MUSCLE FIBERS

    PubMed Central

    Chakkalakal, Joe V.; Kuang, Shihuan; Buffelli, Mario; Lichtman, Jeff W.; Sanes, Joshua R.

    2014-01-01

    Skeletal muscle fibers vary in contractile and metabolic properties. Four main fiber types are present in mammalian trunk and limb muscles; they are called I, IIA, IIX and IIB, ranging from slowest- to fastest-contracting. Individual muscles contain stereotyped proportions of two or more fiber types. Fiber type is determined by a combination of nerve-dependent and –independent influences, leading to formation of “homogeneous motor units” in which all branches of a single motor neuron form synapses on fibers of a single type. Fiber type composition of muscles can be altered in adulthood by multiple factors including exercise, denervation, hormones and aging. To facilitate analysis of muscle development, plasticity and innervation, we generated transgenic mouse lines in which Type I, Type IIA, and Type IIX+B fibers can be selectively labeled with distinguishable fluorophores. We demonstrate their use for motor unit reconstruction and live imaging of nerve-dependent alterations in fiber type. PMID:21898764

  7. Effects of aging on Type II muscle fibers: a systematic review of the literature.

    PubMed

    Brunner, Florian; Schmid, Annina; Sheikhzadeh, Ali; Nordin, Margareta; Yoon, Jangwhon; Frankel, Victor

    2007-07-01

    The authors conducted a systematic review of the literature for scientific articles in selected databases to determine the effects of aging on Type II muscle fibers in human skeletal muscles. They found that aging of Type II muscle fibers is primarily associated with a loss of fibers and a decrease in fiber size. Morphological changes with increasing age particularly included Type II fiber grouping. There is conflicting evidence regarding the change of proportion of Type II fibers. Type II muscle fibers seem to play an important role in the aging process of human skeletal muscles. According to this literature review, loss of fibers, decrease in size, and fiber-type grouping represent major quantitative changes. Because the process of aging involves various complex phenomena such as fiber-type coexpression, however, it seems difficult to assign those changes solely to a specific fiber type.

  8. Postnatal development of fiber type composition in rabbit jaw and leg muscles.

    PubMed

    Korfage, J A M; Helmers, R; Matignon, M de Goüyon; van Wessel, T; Langenbach, G E J; van Eijden, T M G J

    2009-01-01

    We examined the difference in fiber type composition and cross-sectional areas during postnatal development in male rabbit jaw muscles and compared these with changes in leg muscles. The myosin heavy chain (MyHC) content of the fibers was determined by immunohistochemistry. No fiber type difference was found between the jaw muscles in 20-week-old rabbits. However, the way this adult fiber type composition was reached differed between the muscles. The deep temporalis, medial pterygoid, and superficial masseter displayed an increase in alpha fibers during early and a decrease during late postnatal development. Other jaw muscles displayed an increase in alpha fibers during early development only. In contrast, alpha fibers were not found in the soleus, in which fiber type changes were completed at week 4. The gastrocnemius muscle did not change its fiber type composition. Initially, fibers in jaw-opening muscles had larger cross-sectional areas than in other muscles, but they increased less during development. Although there were no large differences in the fiber type composition of muscles in young adult rabbits, large differences were found in the jaw muscles, but not in the leg muscles, during development. In part, these developmental changes in fiber percentages within the jaw muscles can be explained by functional modifications in this muscle group. In the present study, the deep temporalis, medial pterygoid, and superficial masseter showed the most dramatic percent changes in fibers during postnatal development. (c) 2008 S. Karger AG, Basel.

  9. Skeletal muscle: energy metabolism, fiber types, fatigue and adaptability.

    PubMed

    Westerblad, Håkan; Bruton, Joseph D; Katz, Abram

    2010-11-01

    Skeletal muscles cope with a large range of activities, from being able to support the body weight during long periods of upright standing to perform explosive movements in response to an unexpected threat. This requires systems for energy metabolism that can provide energy during long periods of moderately increased energy consumption as well as being able to rapidly increasing the rate of energy production more than 100-fold in response to explosive contractions. In this short review we discuss how muscles can deal with these divergent demands. We first outline the major energy metabolism pathways in skeletal muscle. Next we describe metabolic differences between different muscle fiber types. Contractile performance declines during intense activation, i.e. fatigue develops, and we discuss likely underlying mechanisms. Finally, we discuss the ability of muscle fibers to adapt to altered demands, and mechanisms behind these adaptations. The accumulated experimental evidence forces us to conclude that most aspects of energy metabolism involve multiple and overlapping signaling pathways, which indicates that the control of energy metabolism is too important to depend on one single molecule or mechanism. Copyright © 2010 Elsevier Inc. All rights reserved.

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

    PubMed

    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 < 0.01). Meanwhile, the mRNA abundance of oxidative and intermediate fibers was increased in Jinhua pigs, whereas the glycolytic fibers were more highly expressed in the Landrace (P < 0.01). In addition, Jinhua pigs possessed greater oxidative capacity than that of the Landrace (P < 0.05). These results suggested that the increased expression of the oxidative and intermediate fibers and greater activities of oxidative enzymes in Jinhua pigs were related to meat quality as indicated by a greater intramuscular fat and reduced drip loss. Based on these results, we conclude that muscle fiber composition and postmortem muscle metabolism can explain, in part, the variation of meat quality in Jinhua and Landrace pigs. These results may provide valuable information for understanding the molecular mechanism responsible for breed specific differences in growth performance

  11. Fiber type characterization of striated muscles related to micturition in female rabbits.

    PubMed

    López-García, Kenia; Mariscal-Tovar, Silvia; Martínez-Gómez, Margarita; Jiménez-Estrada, Ismael; Castelán, Francisco

    2014-04-01

    Pelvic and perineal striated muscles are relevant for reproduction and micturition in female mammals. Damage to these muscles is associated with pelvic organ prolapse and stress urinary incontinence. The fiber type composition of skeletal muscle influences the susceptibility for damage and/or regeneration. The aim of the present study was to determine the fiber type composition of a perineal muscle, the bulbospongiosus, and a pelvic muscle, the pubococcygeus. Both muscles were harvested from adult female rabbits (8-10 months old). NADH-TR (nicotinamide adenine dinucleotide tetrazolium reductase) histochemistry was undertaken to identify oxidative and glycolytic muscle fibers. Alkaline (pH 9.4) ATP-ase (actomyosin adenosine triphosphatase) histochemistry was used to classify type I, type IIb or type IIa/IId muscle fibers. Results showed that the content of glycolytic fibers in the bulbospongiosus muscle was higher than that of oxidative fibers. Meanwhile, the opposite was true for the pubococcygeus. In the bulbospongiosus muscle, the content of type IIb muscle fibers was higher than that of type I, but was similar to that of type IIa/IId. In contrast, the content of each fiber type was similar in the pubococcygeus muscle. The relative proportion of fibers in bulbospongiosus and pubococcygeus muscles is consistent with their function during voiding and storage phases of micturition.

  12. Prostaglandin E2/cyclooxygenase pathway in human skeletal muscle: influence of muscle fiber type and age.

    PubMed

    Liu, Sophia Z; Jemiolo, Bozena; Lavin, Kaleen M; Lester, Bridget E; Trappe, Scott W; Trappe, Todd A

    2016-03-01

    Prostaglandin E2 (PGE2) produced by the cyclooxygenase (COX) pathway regulates skeletal muscle protein turnover and exercise training adaptations. The purpose of this study was twofold: 1) define the PGE2/COX pathway enzymes and receptors in human skeletal muscle, with a focus on type I and II muscle fibers; and 2) examine the influence of aging on this pathway. Muscle biopsies were obtained from the soleus (primarily type I fibers) and vastus lateralis (proportionally more type II fibers than soleus) of young men and women (n = 8; 26 ± 2 yr), and from the vastus lateralis of young (n = 8; 25 ± 1 yr) and old (n = 12; 79 ± 2 yr) men and women. PGE2/COX pathway proteins [COX enzymes (COX-1 and COX-2), PGE2 synthases (cPGES, mPGES-1, and mPGES-2), and PGE2 receptors (EP1, EP2, EP3, and EP4)] were quantified via Western blot. COX-1, cPGES, mPGES-2, and all four PGE2 receptors were detected in all skeletal muscle samples examined. COX-1 (P < 0.1) and mPGES-2 were ∼20% higher, while EP3 was 99% higher and EP4 57% lower in soleus compared with vastus lateralis (P < 0.05). Aging did not change the level of skeletal muscle COX-1, while cPGES increased 45% and EP1 (P < 0.1), EP3, and EP4 decreased ∼33% (P < 0.05). In summary, PGE2 production capacity and receptor levels are different in human skeletal muscles with markedly different type I and II muscle fiber composition. In aging skeletal muscle, PGE2 production capacity is elevated and receptor levels are downregulated. These findings have implications for understanding the regulation of skeletal muscle adaptations to exercise and aging by the PGE2/COX pathway and related inhibitors. Copyright © 2016 the American Physiological Society.

  13. Fiber type composition of pubococcygeus and bulbospongiosus striated muscles is modified by multiparity in the rabbit.

    PubMed

    López-García, Kenia; Mariscal-Tovar, Silvia; Serrano-Meneses, Martín Alejandro; Castelán, Francisco; Martínez-Gómez, Margarita; Jiménez-Estrada, Ismael

    2017-08-01

    We analyzed the effect of multiparity on the fiber type composition of two skeletal muscles involved in the maintenance of the micturition process, the pelvic pubococcygeus (Pc) and perineal bulbospongiosus (Bs) muscles in nulliparous and multiparous rabbits (Oryctolagus cuniculus). We used the basic ATPase and NADH-TR techniques to identify and characterize slow, intermediate, and fast fiber types and glycolitic and oxidative fibers in muscles, respectively. Pc muscles of multiparous rabbits present relatively high percentages of slow and intermediate fibers but a low percentage of fast fibers (P < 0.05) as compared to Pc muscles from nulliparous rabbits, while percentages of glycolytic and oxidative fibers were similar (P > 0.05). Bs muscles of multiparous rabbits had a higher proportion of intermediate and glycolytic fibers (P < 0.05) than muscles of nulliparous. Both, Pc and Bs muscles of nulliparous and multiparous rabbits contain slow fibers with similar large cross sectional area, but fast fibers in multiparous muscles showed small cross sectional area than in nulliparous. Multiparity modified the fiber type composition of Pc and Bs muscles in female rabbits. We propose that the contractile force and the physiological role of both muscles during micturition are affected because of the observed changes in the relative composition of muscle fiber types. © 2016 Wiley Periodicals, Inc.

  14. Change in fiber type in partially-denervated soleus muscle of the rat.

    PubMed

    Narusawa, M

    1985-10-01

    In 30% or less partially denervated muscle, the reinnervation of denervated muscle fiber may give rise to a change in motor unit size or number of muscle fibers innervated by a single motor neuron. This study was designed to evaluate changes in fiber type and contractibility of partially denervated rat soleus muscle. Partial denervation (by 30% or less) of the soleus nerve does not cause a decrease in the number of muscle fibers. A histochemical study was performed on frozen sections of the muscle. The total number of muscle fibers, atrophied fibers and type II fibers were counted. In the muscle 4 weeks after partial denervation, the number of type II fibers was fewer with a decrease of about 40% which was not significant. The twitch time to peak and half-relaxation time were not changed. The number of type II fibers was significantly decreased (p less than 0.01) after 8 weeks. There was a prolongation of contraction time. The decrease of type II fibers was extensive involving not only the denervated area but also the rest of the muscle area. The transformation of fiber type observed in partially denervated muscle may be attributed to a possible diminution of neurotrophic substances in intact motor neurons.

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

    SciTech Connect

    Crew, Jennifer R.; Falzari, Kanakeshwari; DiMario, Joseph X.

    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.

  16. Myosin types and fiber types in cardiac muscle. I. Ventricular myocardium

    PubMed Central

    1981-01-01

    Antisera against bovine atrial myosin were raised in rabbits, purified by affinity chromatography, and absorbed with insolubilized ventricular myosin. Specific anti-bovine atrial myosin (anti-bAm) antibodies reacted selectively with atrial myosin heavy chains, as determined by enzyme immunoassay combined with SDS-gel electrophoresis. In direct and indirect immunofluorescence assay, anti-bAm was found to stain all atrial muscle fibers and a minor proportion of ventricular muscle fibers in the right ventricle of the bovine heart. In contrast, almost all muscle fibers in the left ventricle were unreactive. Purkinje fibers showed variable reactivity. In the rabbit heart, all atrial muscle fibers were stained by anti-bAm, whereas ventricular fibers showed a variable response in both the right and left ventricle, with a tendency for reactive fibers to be more numerous in the right ventricle and in subepicardial regions. Diversification of fiber types with respect to anti-bAm reactivity was found to occur during late stages of postnatal development in the rabbit heart and to be influenced by thyroid hormone. All ventricular muscle fibers became strongly reactive after thyroxine treatment, whereas they became unreactive or poorly reactive after propylthiouracil treatment. These findings are consistent with the existence of different ventricular isomyosins whose relative proportions can vary according to the thyroid state. Variations in ventricular isomyosin composition can account for the changes in myosin Ca2+-activated ATPase activity previously observed in cardiac muscle from hyper- and hypothyroid animals and may be responsible for the changes in the velocity of contraction of ventricular myocardium that occur under these conditions. The differential distribution of ventricular isomyosins in the normal heart suggests that fiber types with different contractile properties may coexist in the ventricular myocardium. PMID:7009623

  17. Type IIB human skeletal muscle fibers positively correlate with bone mineral density irrespective to age.

    PubMed

    Cheung, Wing-Hoi; Lee, Wing-Sze; Qin, Ling; Tang, Ning; Hung, Vivian Wing-Yin; Leung, Kwok-Sui

    2010-11-01

    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. 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. 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). 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.

  18. Extensive Type II Muscle Fiber Atrophy in Elderly Female Hip Fracture Patients.

    PubMed

    Kramer, Irene Fleur; Snijders, Tim; Smeets, Joey S J; Leenders, Marika; van Kranenburg, Janneau; den Hoed, Marcel; Verdijk, Lex B; Poeze, Martijn; van Loon, Luc J C

    2017-10-01

    Sarcopenia, or the loss of muscle mass and strength, is known to increase the risk for falls and (hip) fractures in older people. The objective of this study was to assess the skeletal muscle fiber characteristics in elderly female hip fracture patients. Percutaneous needle biopsies were collected from the vastus lateralis muscle in 15 healthy young women (20 ± 0.4 years), 15 healthy elderly women (79 ± 1.7 years), and 15 elderly women with a fall-related hip fracture (82 ± 1.5 years). Immunohistochemical analyses were performed to assess Type I and Type II muscle fiber size, and myonuclear and satellite cell content. Type II muscle fiber size was significantly different between all groups (p < .05), with smaller Type II muscle fibers in the hip fracture patients (2,609 ± 185 µm2) compared with healthy elderly group (3,723 ± 322 µm2) and the largest Type II muscle fibers in the healthy young group (4,755 ± 335 µm2). Furthermore, Type I muscle fiber size was significantly lower in the hip fracture patients (4,684 ± 211 µm2) compared with the healthy elderly group (5,842 ± 316 µm2, p = .02). The number of myonuclei per Type II muscle fiber was significantly lower in the healthy elderly and hip fracture group compared with the healthy young group (p = .011 and p = .002, respectively). Muscle fiber satellite cell content did not differ between groups. Elderly female hip fracture patients show extensive Type II muscle fiber atrophy when compared with healthy young or age-matched healthy elderly controls. Type II muscle fiber atrophy is an important hallmark of sarcopenia and may predispose to falls and (hip) fractures in the older population.

  19. Administration of a soluble activin type IIB receptor promotes skeletal muscle growth independent of fiber type.

    PubMed

    Cadena, Samuel M; Tomkinson, Kathleen N; Monnell, Travis E; Spaits, Matthew S; Kumar, Ravindra; Underwood, Kathryn W; Pearsall, R Scott; Lachey, Jennifer L

    2010-09-01

    This is the first report that inhibition of negative regulators of skeletal muscle by a soluble form of activin type IIB receptor (ACE-031) increases muscle mass independent of fiber-type expression. This finding is distinct from the effects of selective pharmacological inhibition of myostatin (GDF-8), which predominantly targets type II fibers. In our study 8-wk-old C57BL/6 mice were treated with ACE-031 or vehicle control for 28 days. By the end of treatment, mean body weight of the ACE-031 group was 16% greater than that of the control group, and wet weights of soleus, plantaris, gastrocnemius, and extensor digitorum longus muscles increased by 33, 44, 46 and 26%, respectively (P<0.05). Soleus fiber-type distribution was unchanged with ACE-031 administration, and mean fiber cross-sectional area increased by 22 and 28% (P<0.05) in type I and II fibers, respectively. In the plantaris, a predominantly type II fiber muscle, mean fiber cross-sectional area increased by 57% with ACE-031 treatment. Analysis of myosin heavy chain (MHC) isoform transcripts by real-time PCR indicated no change in transcript levels in the soleus, but a decline in MHC I and IIa in the plantaris. In contrast, electrophoretic separation of total soleus and plantaris protein indicated that there was no change in the proportion of MHC isoforms in either muscle. Thus these data provide optimism that ACE-031 may be a viable therapeutic in the treatment of musculoskeletal diseases. Future studies should be undertaken to confirm that the observed effects are not age dependent or due to the relatively short study duration.

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

    PubMed Central

    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

  1. Changes in skeletal muscle biochemistry and histology relative to fiber type in rats with heart failure

    NASA Technical Reports Server (NTRS)

    Delp, M. D.; Duan, C.; Mattson, J. P.; Musch, T. I.

    1997-01-01

    One of the primary consequences of left ventricular dysfunction (LVD) after myocardial infarction is a decrement in exercise capacity. Several factors have been hypothesized to account for this decrement, including alterations in skeletal muscle metabolism and aerobic capacity. The purpose of this study was to determine whether LVD-induced alterations in skeletal muscle enzyme activities, fiber composition, and fiber size are 1) generalized in muscles or specific to muscles composed primarily of a given fiber type and 2) related to the severity of the LVD. Female Wistar rats were divided into three groups: sham-operated controls (n = 13) and rats with moderate (n = 10) and severe (n = 7) LVD. LVD was surgically induced by ligating the left main coronary artery and resulted in elevations (P < 0.05) in left ventricular end-diastolic pressure (sham, 5 +/- 1 mmHg; moderate LVD, 11 +/- 1 mmHg; severe LVD, 25 +/- 1 mmHg). Moderate LVD decreased the activities of phosphofructokinase (PFK) and citrate synthase in one muscle composed of type IIB fibers but did not modify fiber composition or size of any muscle studied. However, severe LVD diminished the activity of enzymes involved in terminal and beta-oxidation in muscles composed primarily of type I fibers, type IIA fibers, and type IIB fibers. In addition, severe LVD induced a reduction in the activity of PFK in type IIB muscle, a 10% reduction in the percentage of type IID/X fibers, and a corresponding increase in the portion of type IIB fibers. Atrophy of type I fibers, type IIA fibers, and/or type IIB fibers occurred in soleus and plantaris muscles of rats with severe LVD. These data indicate that rats with severe LVD after myocardial infarction exhibit 1) decrements in mitochondrial enzyme activities independent of muscle fiber composition, 2) a reduction in PFK activity in type IIB muscle, 3) transformation of type IID/X to type IIB fibers, and 4) atrophy of type I, IIA, and IIB fibers.

  2. Changes in skeletal muscle biochemistry and histology relative to fiber type in rats with heart failure

    NASA Technical Reports Server (NTRS)

    Delp, M. D.; Duan, C.; Mattson, J. P.; Musch, T. I.

    1997-01-01

    One of the primary consequences of left ventricular dysfunction (LVD) after myocardial infarction is a decrement in exercise capacity. Several factors have been hypothesized to account for this decrement, including alterations in skeletal muscle metabolism and aerobic capacity. The purpose of this study was to determine whether LVD-induced alterations in skeletal muscle enzyme activities, fiber composition, and fiber size are 1) generalized in muscles or specific to muscles composed primarily of a given fiber type and 2) related to the severity of the LVD. Female Wistar rats were divided into three groups: sham-operated controls (n = 13) and rats with moderate (n = 10) and severe (n = 7) LVD. LVD was surgically induced by ligating the left main coronary artery and resulted in elevations (P < 0.05) in left ventricular end-diastolic pressure (sham, 5 +/- 1 mmHg; moderate LVD, 11 +/- 1 mmHg; severe LVD, 25 +/- 1 mmHg). Moderate LVD decreased the activities of phosphofructokinase (PFK) and citrate synthase in one muscle composed of type IIB fibers but did not modify fiber composition or size of any muscle studied. However, severe LVD diminished the activity of enzymes involved in terminal and beta-oxidation in muscles composed primarily of type I fibers, type IIA fibers, and type IIB fibers. In addition, severe LVD induced a reduction in the activity of PFK in type IIB muscle, a 10% reduction in the percentage of type IID/X fibers, and a corresponding increase in the portion of type IIB fibers. Atrophy of type I fibers, type IIA fibers, and/or type IIB fibers occurred in soleus and plantaris muscles of rats with severe LVD. These data indicate that rats with severe LVD after myocardial infarction exhibit 1) decrements in mitochondrial enzyme activities independent of muscle fiber composition, 2) a reduction in PFK activity in type IIB muscle, 3) transformation of type IID/X to type IIB fibers, and 4) atrophy of type I, IIA, and IIB fibers.

  3. Regional variations in intramyocellular lipid concentration correlate with muscle fiber type distribution in rat tibialis anterior muscle.

    PubMed

    De Feyter, Henk M M L; Schaart, Gert; Hesselink, Matthijs K; Schrauwen, Patrick; Nicolay, Klaas; Prompers, Jeanine J

    2006-07-01

    1H MR spectroscopy (MRS) has proved to be a valuable noninvasive tool to measure intramyocellular lipids (IMCL) in research focused on insulin resistance and type II diabetes in both humans and rodents. An important determinant of IMCL is the muscle fiber type, since oxidative type I fibers can contain up to three times more IMCL than glycolytic type II muscle fibers. Because these different muscle fiber types are inhomogeneously distributed in rodent muscle, in the present study we investigated the distribution of IMCL within the rat tibialis anterior muscle (TA) in vivo using single-voxel 1H MRS along with the muscle fiber distribution in the TA ex vivo determined from immunohistological assays. IMCL levels in the TA differed by up to a factor of 3 depending on the position of the voxel. The distribution of IMCL over the TA cross section was not random, but emerged in a pattern similar to the distribution of the predominantly oxidative muscle fiber types. Dietary interventions, such as high-fat feeding and 15 hr of fasting, did not significantly change this typical fiber type-dependent pattern of IMCL content. These results stress the importance of voxel positioning when single-voxel 1H MRS is used to study IMCL in rodent muscle. Copyright (c) 2006 Wiley-Liss, Inc.

  4. Muscle fiber-type changes induced by botulinum toxin injection in the rat larynx.

    PubMed

    Inagi, K; Connor, N P; Schultz, E; Ford, C N; Cook, C H; Heisey, D M

    1999-06-01

    This study examined muscle fiber-type alterations after single or multiple botulinum toxin (BT) injections to better understand possible morphologic changes induced by therapeutic BT injections in patients with spasmodic dysphonia. Muscle fiber staining was accomplished in rat intrinsic laryngeal muscles with antibodies to specific myosin heavy chains. Results indicated that the typical baseline distributions of type II muscle fibers (ie, types IIa, IIb, IIx, and IIL) were altered by BT injection, while no change was observed in type I fibers. Embryonic fibers were observed only along the needle insertion site at 7 days post BT injection. Although inferences from these animal data to human neuromuscular function must be made with caution, our findings provide insight into the possible cellular and molecular changes characterizing BT-injected muscles.

  5. Eccentric exercise increases satellite cell content in type II muscle fibers.

    PubMed

    Cermak, Naomi M; Snijders, Tim; McKay, Bryon R; Parise, Gianni; Verdijk, Lex B; Tarnopolsky, Mark A; Gibala, Martin J; Van Loon, Luc J C

    2013-02-01

    Satellite cells (SCs) are of key importance in skeletal muscle tissue growth, repair, and regeneration. A single bout of high-force eccentric exercise has been demonstrated to increase mixed muscle SC content after 1-7 d of postexercise recovery. However, little is known about fiber type-specific changes in SC content and their activation status within 24 h of postexercise recovery. Nine recreationally active young men (23 ± 1 yr) performed 300 eccentric actions of the knee extensors on an isokinetic dynamometer. Skeletal muscle biopsies from the vastus lateralis were collected preexercise and 24 h postexercise. Muscle fiber type-specific SC content and the number of activated SCs were determined by immunohistochemical analyses. There was no difference between Type I and Type II muscle fiber SC content before exercise. SC content significantly increased 24 h postexercise in Type II muscle fibers (from 0.085 ± 0.012 to 0.133 ± 0.016 SCs per fiber, respectively; P < 0.05), whereas there was no change in Type I fibers. In accordance, activation status increased from preexercise to 24 h postexercise as demonstrated by the increase in the number of DLK1+ SCs in Type II muscle fibers (from 0.027 ± 0.008 to 0.070 ± 0.017 SCs per muscle fiber P < 0.05). Although no significant changes were observed in the number of Ki-67+ SCs, we did observe an increase in the number of proliferating cell nuclear antigen-positive SCs after 24 h of postexercise recovery. A single bout of high-force eccentric exercise increases muscle fiber SC content and activation status in Type II but not Type I muscle fibers.

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

    PubMed

    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.

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

    PubMed Central

    Castorena, Carlos M.; Arias, Edward B.; Sharma, Naveen; Bogan, Jonathan S.

    2014-01-01

    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-[3H]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 < 0.05) 2-DG uptake for each of the isolated fiber types (MHC-IIa, MHC-IIax, MHC-IIx, MHC-IIxb, and MHC-IIb). However, 2-DG uptake for E-Stim fibers was not significantly different among these five fiber types. 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 < 0.05) in MHC-IIa vs. MHC-IIx, MHC-IIxb, or MHC-IIb fibers. TUG and COX IV in either MHC-IIax or MHC-IIx fibers exceeded values for MHC-IIxb or MHC-IIb fibers. GLUT4 levels for MHC-IIax fibers exceeded MHC-IIxb fibers. GLUT4, COX IV, filamin C, and TUG abundance in single fibers was significantly (P < 0.05) correlated with each other. Differences in GLUT4 abundance among the fiber types were not accompanied by significant differences in contraction-stimulated glucose uptake. PMID:25491725

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

    PubMed

    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 < 0.05) 2-DG uptake for each of the isolated fiber types (MHC-IIa, MHC-IIax, MHC-IIx, MHC-IIxb, and MHC-IIb). However, 2-DG uptake for E-Stim fibers was not significantly different among these five fiber types. 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 < 0.05) in MHC-IIa vs. MHC-IIx, MHC-IIxb, or MHC-IIb fibers. TUG and COX IV in either MHC-IIax or MHC-IIx fibers exceeded values for MHC-IIxb or MHC-IIb fibers. GLUT4 levels for MHC-IIax fibers exceeded MHC-IIxb fibers. GLUT4, COX IV, filamin C, and TUG abundance in single fibers was significantly (P < 0.05) correlated with each other. Differences in GLUT4 abundance among the fiber types were not accompanied by significant differences in contraction-stimulated glucose uptake.

  9. Immobilization induces carbonic anhydrase III in type II fibers of rat skeletal muscle.

    PubMed

    Laurila, A L; Jeffery, S; Savolainen, J; Takala, T E; Carter, N D; Väänänen, H K

    1991-05-01

    The amount and fiber distribution of carbonic anhydrase III (CA III), a major soluble protein in Type I muscle fibers, were studied during cast immobilization of rat hindlimb with the ankle in plantar or dorsiflexion. The concentration of CA III increased two- (p less than 0.05) and three- (p less than 0.01) fold in the shortened and lengthened tibialis anterior muscle during a 3-weeks immobilization period, respectively. After 6 weeks of immobilization the increase was even greater (p less than 0.001). Concomitantly, the number of CA III positive fibers in the lengthened muscle increased so that almost all fibers were positive. In the soleus muscle no significant change in the CA III concentration was seen. On the basis of actomyosin ATPase staining, the transition of Type IIb fibers towards Type IIa occurred in the tibialis anterior muscle, whereas in the soleus muscle a transformation of Type I fibers towards Type IIa fibers occurred. Therefore, the increase in the muscle CA III concentration seems to be associated with a cell transformation of the muscle towards a more oxidative type.

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

    PubMed

    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.

  11. Myosin types and fiber types in cardiac muscle. II. Atrial myocardium

    PubMed Central

    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 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. PMID:6218175

  12. Mitochondrial Dynamics is a Distinguishing Feature of Skeletal Muscle Fiber Types and Regulates Organellar Compartmentalization.

    PubMed

    Mishra, Prashant; Varuzhanyan, Grigor; Pham, Anh H; Chan, David C

    2015-12-01

    Skeletal muscle fibers differentiate into specific fiber types with distinct metabolic properties determined by their reliance on oxidative phosphorylation (OXPHOS). Using in vivo approaches, we find that OXPHOS-dependent fibers, compared to glycolytic fibers, contain elongated mitochondrial networks with higher fusion rates that are dependent on the mitofusins Mfn1 and Mfn2. Switching of a glycolytic fiber to an oxidative IIA type is associated with elongation of mitochondria, suggesting that mitochondrial fusion is linked to metabolic state. Furthermore, we reveal that mitochondrial proteins are compartmentalized to discrete domains centered around their nuclei of origin. The domain dimensions are dependent on fiber type and are regulated by the mitochondrial dynamics proteins Mfn1, Mfn2, and Mff. Our results indicate that mitochondrial dynamics is tailored to fiber type physiology and provides a rationale for the segmental defects characteristic of aged and diseased muscle fibers.

  13. Effects of fiber type and training on beta-adrenoceptor density in human skeletal muscle.

    PubMed

    Martin, W H; Coggan, A R; Spina, R J; Saffitz, J E

    1989-11-01

    The density and distribution of beta-adrenergic receptors in type I and II fibers of human gastrocnemius and quadriceps muscles were characterized in ten healthy sedentary subjects and in a subgroup of six subjects before and after 12 wk of endurance exercise training. Total tissue content of beta-receptors was measured in frozen sections of skeletal muscle biopsies incubated with 125I-labeled cyanopindolol in the presence and absence of 10(-5) M L-propranolol. The relative beta-receptor densities of type I and II fibers were delineated autoradiographically. Muscle fiber types were identified in adjacent serial sections by histochemical staining of myofibrillar adenosine-triphosphatase (ATPase) activity. Type I fibers had a threefold greater beta-receptor density than type II fibers of the same muscle [P less than 0.001; type I-to-type II fiber ratio of beta-receptor density was 3.06 +/- 0.43 (SD)]. Exercise training elicited a change in muscle fiber subtype composition (+34% type IIa and -42% type IIb; P less than 0.05 and P = 0.066, respectively), a 40% increase in citrate synthase activity of skeletal muscle (P = 0.01), and a 23% rise in peak oxygen uptake (P less than 0.001). However, no change in total tissue content of beta-receptors was observed after exercise training, even when receptor density was adjusted for preconditioning fiber type composition. Thus beta-receptor density of type I fibers of human skeletal muscle is threefold greater than that of type II fibers. Enhanced capacity for aerobic metabolism after endurance exercise training is not associated with upregulation of total beta-receptor density.

  14. Contractile properties of rat, rhesus monkey, and human type I muscle fibers

    NASA Technical Reports Server (NTRS)

    Widrick, J. J.; Romatowski, J. G.; Karhanek, M.; Fitts, R. H.

    1997-01-01

    It is well known that skeletal muscle intrinsic maximal shortening velocity is inversely related to species body mass. However, there is uncertainty regarding the relationship between the contractile properties of muscle fibers obtained from commonly studied laboratory animals and those obtained from humans. In this study we determined the contractile properties of single chemically skinned fibers prepared from rat, rhesus monkey, and human soleus and gastrocnemius muscle samples under identical experimental conditions. All fibers used for analysis expressed type I myosin heavy chain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Allometric coefficients for type I fibers from each muscle indicated that there was little change in peak tension (force/fiber cross-sectional area) across species. In contrast, both soleus and gastrocnemius type I fiber maximal unloaded shortening velocity (Vo), the y-intercept of the force-velocity relationship (Vmax), peak power per unit fiber length, and peak power normalized for fiber length and cross-sectional area were all inversely related to species body mass. The present allometric coefficients for soleus fiber Vo (-0.18) and Vmax (-0.11) are in good agreement with published values for soleus fibers obtained from common laboratory and domesticated mammals. Taken together, these observations suggest that the Vo of slow fibers from quadrupeds and humans scale similarly and can be described by the same quantitative relationships. These findings have implications in the design and interpretation of experiments, especially those that use small laboratory mammals as a model of human muscle function.

  15. Contractile properties of rat, rhesus monkey, and human type I muscle fibers

    NASA Technical Reports Server (NTRS)

    Widrick, J. J.; Romatowski, J. G.; Karhanek, M.; Fitts, R. H.

    1997-01-01

    It is well known that skeletal muscle intrinsic maximal shortening velocity is inversely related to species body mass. However, there is uncertainty regarding the relationship between the contractile properties of muscle fibers obtained from commonly studied laboratory animals and those obtained from humans. In this study we determined the contractile properties of single chemically skinned fibers prepared from rat, rhesus monkey, and human soleus and gastrocnemius muscle samples under identical experimental conditions. All fibers used for analysis expressed type I myosin heavy chain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Allometric coefficients for type I fibers from each muscle indicated that there was little change in peak tension (force/fiber cross-sectional area) across species. In contrast, both soleus and gastrocnemius type I fiber maximal unloaded shortening velocity (Vo), the y-intercept of the force-velocity relationship (Vmax), peak power per unit fiber length, and peak power normalized for fiber length and cross-sectional area were all inversely related to species body mass. The present allometric coefficients for soleus fiber Vo (-0.18) and Vmax (-0.11) are in good agreement with published values for soleus fibers obtained from common laboratory and domesticated mammals. Taken together, these observations suggest that the Vo of slow fibers from quadrupeds and humans scale similarly and can be described by the same quantitative relationships. These findings have implications in the design and interpretation of experiments, especially those that use small laboratory mammals as a model of human muscle function.

  16. Skeletal muscle fiber types in the ghost crab, Ocypode quadrata: implications for running performance.

    PubMed

    Perry, Michael J; Tait, Jennifer; Hu, John; White, Scott C; Medler, Scott

    2009-03-01

    Ghost crabs possess rapid running capabilities, which make them good candidates for comparing invertebrate exercise physiology with that of more extensively studied vertebrates. While a number of studies have examined various aspects of running physiology and biomechanics in terrestrial crabs, none to date have defined the basic skeletal muscle fiber types that power locomotion. In the current study, we investigated skeletal muscle fiber types comprising the extensor and flexor carpopodite muscles in relation to running performance in the ghost crab. We used kinematic analyses to determine stride frequency and muscle shortening velocity and found that both parameters are similar to those of comparably sized mammals but slower than those observed in running lizards. Using several complementary methods, we found that the muscles are divided into two primary fiber types: those of the proximal and distal regions possess long sarcomeres (6.2+/-2.3 microm) observed in crustacean slow fibers and have characteristics of aerobic fibers whereas those of the muscle mid-region have short sarcomeres (3.5+/-0.4 microm) characteristic of fast fibers and appear to be glycolytic. Each fiber type is characterized by several different myofibrillar protein isoforms including multiple isoforms of myosin heavy chain (MHC), troponin I (TnI), troponin T (TnT) and a crustacean fast muscle protein, P75. Three different isoforms of MHC are differentially expressed in the muscles, with fibers of the mid-region always co-expressing two isoforms at a 1:1 ratio within single fibers. Based on our analyses, we propose that these muscles are functionally divided into a two-geared system, with the aerobic fibers used for slow sustained activities and the glycolytic mid-region fibers being reserved for explosive sprints. Finally, we identified subtle differences in myofibrillar isoform expression correlated with crab body size, which changes by several orders of magnitude during an animal's lifetime.

  17. Ontogenetic changes in skeletal muscle fiber type, fiber diameter and myoglobin concentration in the Northern elephant seal (Mirounga angustirostris).

    PubMed

    Moore, Colby D; Crocker, Daniel E; Fahlman, Andreas; Moore, Michael J; Willoughby, Darryn S; Robbins, Kathleen A; Kanatous, Shane B; Trumble, Stephen J

    2014-01-01

    Northern elephant seals (Mirounga angustirostris) (NES) are known to be deep, long-duration divers and to sustain long-repeated patterns of breath-hold, or apnea. Some phocid dives remain within the bounds of aerobic metabolism, accompanied by physiological responses inducing lung compression, bradycardia, and peripheral vasoconstriction. Current data suggest an absence of type IIb fibers in pinniped locomotory musculature. To date, no fiber type data exist for NES, a consummate deep diver. In this study, NES were biopsied in the wild. Ontogenetic changes in skeletal muscle were revealed through succinate dehydrogenase (SDH) based fiber typing. Results indicated a predominance of uniformly shaped, large type I fibers and elevated myoglobin (Mb) concentrations in the longissimus dorsi (LD) muscle of adults. No type II muscle fibers were detected in any adult sampled. This was in contrast to the juvenile animals that demonstrated type II myosin in Western Blot analysis, indicative of an ontogenetic change in skeletal muscle with maturation. These data support previous hypotheses that the absence of type II fibers indicates reliance on aerobic metabolism during dives, as well as a depressed metabolic rate and low energy locomotion. We also suggest that the lack of type IIb fibers (adults) may provide a protection against ischemia reperfusion (IR) injury in vasoconstricted peripheral skeletal muscle.

  18. Ontogenetic changes in skeletal muscle fiber type, fiber diameter and myoglobin concentration in the Northern elephant seal (Mirounga angustirostris)

    PubMed Central

    Moore, Colby D.; Crocker, Daniel E.; Fahlman, Andreas; Moore, Michael J.; Willoughby, Darryn S.; Robbins, Kathleen A.; Kanatous, Shane B.; Trumble, Stephen J.

    2014-01-01

    Northern elephant seals (Mirounga angustirostris) (NES) are known to be deep, long-duration divers and to sustain long-repeated patterns of breath-hold, or apnea. Some phocid dives remain within the bounds of aerobic metabolism, accompanied by physiological responses inducing lung compression, bradycardia, and peripheral vasoconstriction. Current data suggest an absence of type IIb fibers in pinniped locomotory musculature. To date, no fiber type data exist for NES, a consummate deep diver. In this study, NES were biopsied in the wild. Ontogenetic changes in skeletal muscle were revealed through succinate dehydrogenase (SDH) based fiber typing. Results indicated a predominance of uniformly shaped, large type I fibers and elevated myoglobin (Mb) concentrations in the longissimus dorsi (LD) muscle of adults. No type II muscle fibers were detected in any adult sampled. This was in contrast to the juvenile animals that demonstrated type II myosin in Western Blot analysis, indicative of an ontogenetic change in skeletal muscle with maturation. These data support previous hypotheses that the absence of type II fibers indicates reliance on aerobic metabolism during dives, as well as a depressed metabolic rate and low energy locomotion. We also suggest that the lack of type IIb fibers (adults) may provide a protection against ischemia reperfusion (IR) injury in vasoconstricted peripheral skeletal muscle. PMID:24959151

  19. Fiber type composition of the sternomastoid and diaphragm muscles of dystrophin-deficient mdx mice.

    PubMed

    Guido, Anderson Neri; Campos, Gerson Eduardo Rocha; Neto, Humberto Santo; Marques, Maria Julia; Minatel, Elaine

    2010-10-01

    The muscle fiber phenotype is mainly determined by motoneuron innervation and changes in neuromuscular interaction alter the muscle fiber type. In dystrophin-deficient mdx mice, changes in the molecular assembly of the neuromuscular junction and in nerve terminal sprouting occur in the sternomastoid (STN) muscle during early stages of the disease. In this study, we were interested to see whether early changes in neuromuscular assembly are correlated with alterations in fiber type in dystrophic STN at 2 months of age. A predominance of hybrid fast myofibers (about 52% type IIDB) was observed in control (C57Bl/10) STN. In mdx muscle, the lack of dystrophin did not change this profile (about 54% hybrid type IIDB). Pure fast type IID fibers predominated in normal and dystrophic diaphragm (DIA; about 39% in control and 30% in mdx muscle) and a population of slow Type I fibers was also present (about 10% in control and 13% in mdx muscle). In conclusion, early changes in neuromuscular assembly do not affect the fiber type composition of dystrophic STN. In contrast to the pure fast fibers of the more affected DIA, the hybrid phenotype of the STN may permit dynamic adaptations during progression of the disease.

  20. Effects of fiber type and size on the heterogeneity of oxygen distribution in exercising skeletal muscle.

    PubMed

    Liu, Gang; Mac Gabhann, Feilim; Popel, Aleksander S

    2012-01-01

    The process of oxygen delivery from capillary to muscle fiber is essential for a tissue with variable oxygen demand, such as skeletal muscle. Oxygen distribution in exercising skeletal muscle is regulated by convective oxygen transport in the blood vessels, oxygen diffusion and consumption in the tissue. Spatial heterogeneities in oxygen supply, such as microvascular architecture and hemodynamic variables, had been observed experimentally and their marked effects on oxygen exchange had been confirmed using mathematical models. In this study, we investigate the effects of heterogeneities in oxygen demand on tissue oxygenation distribution using a multiscale oxygen transport model. Muscles are composed of different ratios of the various fiber types. Each fiber type has characteristic values of several parameters, including fiber size, oxygen consumption, myoglobin concentration, and oxygen diffusivity. Using experimentally measured parameters for different fiber types and applying them to the rat extensor digitorum longus muscle, we evaluated the effects of heterogeneous fiber size and fiber type properties on the oxygen distribution profile. Our simulation results suggest a marked increase in spatial heterogeneity of oxygen due to fiber size distribution in a mixed muscle. Our simulations also suggest that the combined effects of fiber type properties, except size, do not contribute significantly to the tissue oxygen spatial heterogeneity. However, the incorporation of the difference in oxygen consumption rates of different fiber types alone causes higher oxygen heterogeneity compared to control cases with uniform fiber properties. In contrast, incorporating variation in other fiber type-specific properties, such as myoglobin concentration, causes little change in spatial tissue oxygenation profiles.

  1. Effects of Fiber Type and Size on the Heterogeneity of Oxygen Distribution in Exercising Skeletal Muscle

    PubMed Central

    Liu, Gang; Mac Gabhann, Feilim; Popel, Aleksander S.

    2012-01-01

    The process of oxygen delivery from capillary to muscle fiber is essential for a tissue with variable oxygen demand, such as skeletal muscle. Oxygen distribution in exercising skeletal muscle is regulated by convective oxygen transport in the blood vessels, oxygen diffusion and consumption in the tissue. Spatial heterogeneities in oxygen supply, such as microvascular architecture and hemodynamic variables, had been observed experimentally and their marked effects on oxygen exchange had been confirmed using mathematical models. In this study, we investigate the effects of heterogeneities in oxygen demand on tissue oxygenation distribution using a multiscale oxygen transport model. Muscles are composed of different ratios of the various fiber types. Each fiber type has characteristic values of several parameters, including fiber size, oxygen consumption, myoglobin concentration, and oxygen diffusivity. Using experimentally measured parameters for different fiber types and applying them to the rat extensor digitorum longus muscle, we evaluated the effects of heterogeneous fiber size and fiber type properties on the oxygen distribution profile. Our simulation results suggest a marked increase in spatial heterogeneity of oxygen due to fiber size distribution in a mixed muscle. Our simulations also suggest that the combined effects of fiber type properties, except size, do not contribute significantly to the tissue oxygen spatial heterogeneity. However, the incorporation of the difference in oxygen consumption rates of different fiber types alone causes higher oxygen heterogeneity compared to control cases with uniform fiber properties. In contrast, incorporating variation in other fiber type-specific properties, such as myoglobin concentration, causes little change in spatial tissue oxygenation profiles. PMID:23028531

  2. Muscle fiber type distribution in climbing Hawaiian gobioid fishes: ontogeny and correlations with locomotor performance.

    PubMed

    Cediel, Roberto A; Blob, Richard W; Schrank, Gordon D; Plourde, Robert C; Schoenfuss, Heiko L

    2008-01-01

    Three species of Hawaiian amphidromous gobioid fishes are remarkable in their ability to climb waterfalls up to several hundred meters tall. Juvenile Lentipes concolor and Awaous guamensis climb using rapid bursts of axial undulation, whereas juvenile Sicyopterus stimpsoni climb using much slower movements, alternately attaching oral and pelvic sucking disks to the substrate during prolonged bouts of several cycles. Based on these differing climbing styles, we hypothesized that propulsive musculature in juvenile L. concolor and A. guamensis would be dominated by white muscle fibers, whereas S. stimpsoni would exhibit a greater proportion of red muscle fibers than other climbing species. We further predicted that, because adults of these species shift from climbing to burst swimming as their main locomotor behavior, muscle from adult fish of all three species would be dominated by white fibers. To test these hypotheses, we used ATPase assays to evaluate muscle fiber type distribution in Hawaiian climbing gobies for three anatomical regions (midbody, anal, and tail). Axial musculature was dominated by white muscle fibers in juveniles of all three species, but juvenile S. stimpsoni had a significantly greater proportion of red fibers than the other two species. Fiber type proportions of adult fishes did not differ significantly from those of juveniles. Thus, muscle fiber type proportions in juveniles appear to help accommodate differences in locomotor demands among these species, indicating that they overcome the common challenge of waterfall climbing through both diverse behaviors and physiological specializations.

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

    PubMed

    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.

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

    PubMed

    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.

  5. Diet‐induced obesity alters skeletal muscle fiber types of male but not female mice

    PubMed Central

    DeNies, Maxwell S.; Johnson, Jordan; Maliphol, Amanda B.; Bruno, Michael; Kim, Annabelle; Rizvi, Abbas; Rustici, Kevyn; Medler, Scott

    2014-01-01

    Abstract Skeletal muscles are highly plastic tissues capable dramatic remodeling in response to use, disuse, disease, and other factors. Growing evidence suggests that adipose tissues exert significant effects on the basic fiber‐type composition of skeletal muscles. In the current study, we investigated the long‐term effects of a high‐fat diet and subsequent obesity on the muscle fiber types in C57 BLK/6J mice. Litters of mice were randomly assigned to either a high‐fat diet or a control group at the time of weaning, and were maintained on this diet for approximately 1 year. Single fibers were harvested from the soleus and plantaris muscles, and fiber types were determined using SDS‐PAGE. The high‐fat diet mice were significantly heavier than the control mice (39.17 ± 2.7 g vs. 56.87 ± 3.4 g; P < 0.0003), but muscle masses were not different. In male mice, the high‐fat diet was associated with a significantly lower proportion of slow, type I fibers in the soleus muscle (40.4 ± 3.5% vs. 29.33 ± 2.6%; P < 0.0165). Moreover, the proportion of type I fibers in the soleus of male mice was inversely proportional to the relative fatness of the male mice (P < 0.003; r2 = 0.65), but no association was observed in female mice. In male mice, the decline in type I fibers was correlated with an increase in type I/IIA hybrid fibers, suggesting that the type I fibers were transformed primarily into these hybrids. The reported trends indicate that type I fibers are most susceptible to the effects of obesity, and that these fiber‐type changes can be sex specific. PMID:24744883

  6. A One-Step Immunostaining Method to Visualize Rodent Muscle Fiber Type within a Single Specimen

    PubMed Central

    Sawano, Shoko; Komiya, Yusuke; Ichitsubo, Riho; Ohkawa, Yasuyuki; Nakamura, Mako; Tatsumi, Ryuichi; Ikeuchi, Yoshihide; Mizunoya, Wataru

    2016-01-01

    In this study, we present a quadruple immunostaining method for rapid muscle fiber typing of mice and rats using antibodies specific to the adult myosin heavy chain (MyHC) isoforms MyHC1, 2A, 2X, and 2B, which are common marker proteins of distinct muscle fiber types. We developed rat monoclonal antibodies specific to each MyHC isoform and conjugated these four antibodies to fluorophores with distinct excitation and emission wavelengths. By mixing the four types of conjugated antibodies, MyHC1, 2A, 2X, and 2B could be distinguished within a single specimen allowing for facile delineation of skeletal muscle fiber types. Furthermore, we could observe hybrid fibers expressing MyHC2X and MyHC2B together in single longitudinal muscle sections from mice and rats, that was not attained in previous techniques. This staining method is expected to be applied to study muscle fiber type transition in response to environmental factors, and to ultimately develop techniques to regulate animal muscle fiber types. PMID:27814384

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

    PubMed

    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.

  8. Muscle Fiber Type-Predominant Promoter Activity in Lentiviral-Mediated Transgenic Mouse

    PubMed Central

    Suga, Tomohiro; Kimura, En; Morioka, Yuka; Ikawa, Masahito; Li, Sheng; Uchino, Katsuhisa; Uchida, Yuji; Yamashita, Satoshi; Maeda, Yasushi; Chamberlain, Jeffrey S.; Uchino, Makoto

    2011-01-01

    Variations in gene promoter/enhancer activity in different muscle fiber types after gene transduction was noticed previously, but poorly analyzed. The murine stem cell virus (MSCV) promoter drives strong, stable gene expression in hematopoietic stem cells and several other cells, including cerebellar Purkinje cells, but it has not been studied in muscle. We injected a lentiviral vector carrying an MSCV-EGFP cassette (LvMSCV-EGFP) into tibialis anterior muscles and observed strong EGFP expression in muscle fibers, primary cultured myoblasts, and myotubes isolated from injected muscles. We also generated lentiviral-mediated transgenic mice carrying the MSCV-EGFP cassette and detected transgene expression in striated muscles. LvMSCV-EGFP transgenic mice showed fiber type-dependent variations in expression: highest in types I and IIA, intermediate in type IID/X, and lowest in type IIB fibers. The soleus and diaphragm muscles, consisting mainly of types I and IIA, are most severely affected in the mdx mouse model of muscular dystrophy. Further analysis of this promoter may have the potential to achieve certain gene expression in severely affected muscles of mdx mice. The Lv-mediated transgenic mouse may prove a useful tool for assessing the enhancer/promoter activities of a variety of different regulatory cassettes. PMID:21445245

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  11. Effects of fiber type on force depression after active shortening in skeletal muscle.

    PubMed

    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.

  12. Early changes in muscle atrophy and muscle fiber type conversion after spinal cord transection and peripheral nerve transection in rats.

    PubMed

    Higashino, Kosaku; Matsuura, Tetsuya; Suganuma, Katsuyoshi; Yukata, Kiminori; Nishisho, Toshihiko; Yasui, Natsuo

    2013-05-20

    Spinal cord transection and peripheral nerve transection cause muscle atrophy and muscle fiber type conversion. It is still unknown how spinal cord transection and peripheral nerve transection each affect the differentiation of muscle fiber type conversion mechanism and muscle atrophy. The aim of our study was to evaluate the difference of muscle weight change, muscle fiber type conversion, and Peroxisome proliferator-activated receptor-γ coactivatior-1α (PGC-1α) expression brought about by spinal cord transection and by peripheral nerve transection. Twenty-four Wistar rats underwent surgery, the control rats underwent a laminectomy; the spinal cord injury group underwent a spinal cord transection; the denervation group underwent a sciatic nerve transection. The rats were harvested of the soleus muscle and the TA muscle at 0 week, 1 week and 2 weeks after surgery. Histological examination was assessed using hematoxylin and eosin (H&E) staining and immunofluorescent staing. Western blot was performed with 3 groups. Both sciatic nerve transection and spinal cord transection caused muscle atrophy with the effect being more severe after sciatic nerve transection. Spinal cord transection caused a reduction in the expression of both sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection produced an increase in expression of sMHC protein and PGC-1α protein in the soleus muscle. The results of the expression of PGC-1α were expected in other words muscle atrophy after sciatic nerve transection is less than after spinal cord transection, however muscle atrophy after sciatic nerve transection was more severe than after spinal cord transection. In the conclusion, spinal cord transection diminished the expression of sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection enhanced the expression of sMHC protein and PGC-1α protein in the soleus muscle.

  13. Early changes in muscle atrophy and muscle fiber type conversion after spinal cord transection and peripheral nerve transection in rats

    PubMed Central

    2013-01-01

    Background Spinal cord transection and peripheral nerve transection cause muscle atrophy and muscle fiber type conversion. It is still unknown how spinal cord transection and peripheral nerve transection each affect the differentiation of muscle fiber type conversion mechanism and muscle atrophy. The aim of our study was to evaluate the difference of muscle weight change, muscle fiber type conversion, and Peroxisome proliferator-activated receptor-γ coactivatior-1α (PGC-1α) expression brought about by spinal cord transection and by peripheral nerve transection. Methods Twenty-four Wistar rats underwent surgery, the control rats underwent a laminectomy; the spinal cord injury group underwent a spinal cord transection; the denervation group underwent a sciatic nerve transection. The rats were harvested of the soleus muscle and the TA muscle at 0 week, 1 week and 2 weeks after surgery. Histological examination was assessed using hematoxylin and eosin (H&E) staining and immunofluorescent staing. Western blot was performed with 3 groups. Results Both sciatic nerve transection and spinal cord transection caused muscle atrophy with the effect being more severe after sciatic nerve transection. Spinal cord transection caused a reduction in the expression of both sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection produced an increase in expression of sMHC protein and PGC-1α protein in the soleus muscle. The results of the expression of PGC-1α were expected in other words muscle atrophy after sciatic nerve transection is less than after spinal cord transection, however muscle atrophy after sciatic nerve transection was more severe than after spinal cord transection. Conclusion In the conclusion, spinal cord transection diminished the expression of sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection enhanced the expression of sMHC protein and PGC-1α protein in the soleus

  14. Effects of fiber type and diet on nuclear magnetic resonance (NMR) relaxation times of skeletal muscle

    SciTech Connect

    Mardini, I.A.; McCarter, R.J.; Fullerton, G.D.

    1986-03-01

    NMR studies of muscle have typically used muscles of mixed fiber composition and have not taken into account the metabolic state of the host. Samples of psoas (type IIB fibers) and soleus (type I fibers) muscles were obtained from 3 groups of rabbits: group C, fed regular chow; group DK fed a potassium deficient diet; and group HC fed a high cholesterol diet. The T/sub 1/ and T/sub 2/ relaxation times of psoas and soleus muscles were not significantly different for group C. Following dietary manipulation, (groups KD and HC), however, the relaxation times of the psoas and soleus muscles were significantly different. There was also a significant difference in water content of psoas muscles in groups KD and HC vs. group C but the observed differences in NMR results could be only partially accounted for by the shift in water content. The authors results suggest that (1) changes in ion or cholesterol concentration are capable of inducing changes in water bonding and structuring in muscle tissues; (2) diet must be added to the growing list of environmental factors that can cause NMR contrast changes; (3) selective use of muscles rich in one fiber type or another for NMR measurements could provide either control or diagnostic information, related to changes in body composition.

  15. Thyroid hormone regulates muscle fiber type conversion via miR-133a1

    PubMed Central

    Zhang, Duo; Wang, Xiaoyun; Li, Yuying; Zhao, Lei; Lu, Minghua; Yao, Xuan; Xia, Hongfeng; Wang, Yu-cheng; Liu, Mo-Fang; Jiang, Jingjing; Li, Xihua

    2014-01-01

    It is known that thyroid hormone (TH) is a major determinant of muscle fiber composition, but the molecular mechanism by which it does so remains unclear. Here, we demonstrated that miR-133a1 is a direct target gene of TH in muscle. Intriguingly, miR-133a, which is enriched in fast-twitch muscle, regulates slow-to-fast muscle fiber type conversion by targeting TEA domain family member 1 (TEAD1), a key regulator of slow muscle gene expression. Inhibition of miR-133a in vivo abrogated TH action on muscle fiber type conversion. Moreover, TEAD1 overexpression antagonized the effect of miR-133a as well as TH on muscle fiber type switch. Additionally, we demonstrate that TH negatively regulates the transcription of myosin heavy chain I indirectly via miR-133a/TEAD1. Collectively, we propose that TH inhibits the slow muscle phenotype through a novel epigenetic mechanism involving repression of TEAD1 expression via targeting by miR-133a1. This identification of a TH-regulated microRNA therefore sheds new light on how TH achieves its diverse biological activities. PMID:25512392

  16. Fiber type composition of the muscle responsible for throat fan extension in green anole lizards.

    PubMed

    Rosen, G J; O'Bryant, E L; Swender, D; Wade, J

    2004-01-01

    Throat fan (dewlap) extension is sexually dimorphic in green anole lizards (Anolis carolinensis). Males have larger dewlaps which they display more frequently than females. Correlated with the behavior, sexual dimorphisms occur in the skeletal, muscular and neural structures responsible for dewlap extension in green anoles. We used histochemical techniques to stain for myosin ATPase and succinate dehydrogenase (SDH) to determine whether sex differences also exist in fiber type composition of the ceratohyoideus, the muscle that extends the dewlap. Based on the staining pattern for the two enzymes, four fiber types were identified: fast-oxidative-glycolytic (FOG), fast-glycolytic (FG), slow-oxidative (SO), and tonic. In the ceratohyoideus of both sexes, the predominate fiber types were FOG (approximately 43%) and FG (approximately 34%). Also in both males and females, the FOG and FG fibers had approximately twice the cross-sectional area of the SO and tonic fibers. No sex differences occurred in the percentages of FOG and FG fibers. However, males had a greater percentage of tonic fibers than females, whereas females had a greater percentage of SO fibers than males. The high proportion of FOG fibers in the anole ceratohyoideus makes it similar to other relatively fatigue-resistant muscles used in movements of moderate speed and duration. Although the precise role of tonic fibers in dewlap extension is not known, the greater percentage of these fibers in the male ceratohyoideus might be required to stabilize or maintain extension of the large dewlap apparatus in males.

  17. Niacin supplementation increases the number of oxidative type I fibers in skeletal muscle of growing pigs.

    PubMed

    Khan, Muckta; Ringseis, Robert; Mooren, Frank-Christoph; Krüger, Karsten; Most, Erika; Eder, Klaus

    2013-09-09

    A recent study showed that niacin supplementation counteracts the obesity-induced muscle fiber switching from oxidative type I to glycolytic type II and increases the number of type I fibers in skeletal muscle of obese Zucker rats. These effects were likely mediated by the induction of key regulators of fiber transition, PGC-1α and PGC-1β, leading to muscle fiber switching and up-regulation of genes involved in mitochondrial fatty acid import and oxidation, citrate cycle, oxidative phosphorylation, mitochondrial biogenesis. The aim of the present study was to investigate whether niacin supplementation causes type II to type I muscle and changes the metabolic phenotype of skeletal muscles in growing pigs. 25 male, 11 wk old crossbred pigs (Danzucht x Pietrain) with an average body weight of 32.8 ± 1.3 (mean ± SD) kg were randomly allocated to two groups of 12 (control group) and 13 pigs (niacin group) which were fed either a control diet or a diet supplemented with 750 mg niacin/kg diet. After 3 wk, the percentage number of type I fibers in three different muscles (M. longissismus dorsi, M. quadriceps femoris, M. gastrocnemius) was greater in the niacin group and the percentage number of type II fibers was lower in the niacin group than in the control group (P < 0.05). The mRNA levels of PGC-1β and genes involved in mitochondrial fatty acid catabolism (CACT, FATP1, OCTN2), citrate cycle (SDHA), oxidative phosphorylation (COX4/1, COX6A1), and thermogenesis (UCP3) in M. longissimus dorsi were greater in the niacin group than in the control group (P < 0.05). The study demonstrates that niacin supplementation induces type II to type I muscle fiber switching, and thereby an oxidative metabolic phenotype of skeletal muscle in pigs. Given that oxidative muscle types tend to develop dark, firm and dry pork in response to intense physical activity and/or high psychological stress levels preslaughter, a niacin-induced change in the muscle´s fiber type distribution may

  18. Niacin supplementation increases the number of oxidative type I fibers in skeletal muscle of growing pigs

    PubMed Central

    2013-01-01

    Background A recent study showed that niacin supplementation counteracts the obesity-induced muscle fiber switching from oxidative type I to glycolytic type II and increases the number of type I fibers in skeletal muscle of obese Zucker rats. These effects were likely mediated by the induction of key regulators of fiber transition, PGC-1α and PGC-1β, leading to muscle fiber switching and up-regulation of genes involved in mitochondrial fatty acid import and oxidation, citrate cycle, oxidative phosphorylation, mitochondrial biogenesis. The aim of the present study was to investigate whether niacin supplementation causes type II to type I muscle and changes the metabolic phenotype of skeletal muscles in growing pigs. Results 25 male, 11 wk old crossbred pigs (Danzucht x Pietrain) with an average body weight of 32.8 ± 1.3 (mean ± SD) kg were randomly allocated to two groups of 12 (control group) and 13 pigs (niacin group) which were fed either a control diet or a diet supplemented with 750 mg niacin/kg diet. After 3 wk, the percentage number of type I fibers in three different muscles (M. longissismus dorsi, M. quadriceps femoris, M. gastrocnemius) was greater in the niacin group and the percentage number of type II fibers was lower in the niacin group than in the control group (P < 0.05). The mRNA levels of PGC-1β and genes involved in mitochondrial fatty acid catabolism (CACT, FATP1, OCTN2), citrate cycle (SDHA), oxidative phosphorylation (COX4/1, COX6A1), and thermogenesis (UCP3) in M. longissimus dorsi were greater in the niacin group than in the control group (P < 0.05). Conclusions The study demonstrates that niacin supplementation induces type II to type I muscle fiber switching, and thereby an oxidative metabolic phenotype of skeletal muscle in pigs. Given that oxidative muscle types tend to develop dark, firm and dry pork in response to intense physical activity and/or high psychological stress levels preslaughter, a niacin

  19. Electrically and Hybrid-Induced Muscle Activations: Effects of Muscle Size and Fiber Type

    PubMed Central

    Stratton, Kelly; Faghri, Pouran D.

    2016-01-01

    The effect of three electrical stimulation (ES) frequencies (10, 35, and 50 Hz) on two muscle groups with different proportions of fast and slow twitch fibers (abductor pollicis brevis (APB) and vastus lateralis (VL)) was explored. We evaluated the acute muscles’ responses individually and during hybrid activations (ES superimposed by voluntary activations). Surface electromyography (sEMG) and force measurements were evaluated as outcomes. Ten healthy adults (mean age: 24.4 ± 2.5 years) participated after signing an informed consent form approved by the university Institutional Review Board. Protocols were developed to: 1) compare EMG activities during each frequency for each muscle when generating 25% Maximum Voluntary Contraction (MVC) force, and 2) compare EMG activities during each frequency when additional voluntary activation was superimposed over ES-induced 25% MVC to reach 50% and 75% MVC. Empirical mode decomposition (EMD) was utilized to separate ES artifacts from voluntary muscle activation. For both muscles, higher stimulation frequency (35 and 50Hz) induced higher electrical output detected at 25% of MVC, suggesting more recruitment with higher frequencies. Hybrid activation generated proportionally less electrical activity than ES alone. ES and voluntary activations appear to generate two different modes of muscle recruitment. ES may provoke muscle strength by activating more fatiguing fast acting fibers, but voluntary activation elicits more muscle coordination. Therefore, during the hybrid activation, less electrical activity may be detected due to recruitment of more fatigue-resistant deeper muscle fibers, not reachable by surface EMG. PMID:27990244

  20. Nuclear receptor/microRNA circuitry links muscle fiber type to energy metabolism.

    PubMed

    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.

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

    PubMed

    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.

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

    PubMed Central

    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

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

    PubMed

    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.

  4. The influence of training status, age, and muscle fiber type on cycling efficiency and endurance performance.

    PubMed

    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 < 0.01). The percentage of type I muscle fibers was higher in the trained groups (P < 0.01), with no difference between age groups. There was no relationship between fiber type and cycling efficiency at any work rate or cadence combination. Stepwise multiple regression indicated that muscle fiber type did not influence cycling performance (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.

  5. Changes in triacylglycerol-accumulated fiber type, fiber type composition, and biogenesis in the mitochondria of the soleus muscle in obese rats.

    PubMed

    Kaneko, Syuhei; Iida, Ryo-Hei; Suga, Takeo; Fukui, Tadayoshi; Morito, Mitsuhiko; Yamane, Akira

    2011-11-01

    Little is known about the effects of obesity on skeletal muscle consisting of approximately 80% type I (slow) fibers, such as that in the soleus muscle, although type I fibers have an enhanced capacity for mitochondrial respiration and fatty acid oxidation. We investigated the effects of obesity on the soleus muscle in the rat. Rats were fed a high-fat diet (protein:fat:carbohydrate = 20:57:23; 508 kcal/100 g) or a control diet (protein:fat:carbohydrate = 20:10:70; 366 kcal/100 g) for 10 weeks. We analyzed the accumulation of intramyocellular triacylglycerol (IMTG), fiber type composition, and the biogenesis and function of the mitochondria in the soleus muscle of the rat during 10 weeks of feeding, using histochemical and real-time polymerase chain reaction analyses. Obesity increased body weight and markedly elevated IMTG levels in type I, but not in type II, fibers of the soleus muscle throughout the feeding period. Obesity also inhibited the biogenesis and function in the mitochondria and altered the fiber type composition in the soleus muscle. The suppression of biogenesis and function in the mitochondria, and the alteration in the fiber type composition may be attributable to the marked IMTG accumulation in the soleus muscle of the rat.

  6. Regeneration and change of muscle fiber types after injury induced by a hemorrhagic fraction isolated from Agkistrodon contortrix laticinctus venom.

    PubMed

    Salvini, T F; Belluzzo, S S; Selistre de Araújo, H S; Souza, D H

    2001-05-01

    Tibialis anterior (TA) muscles of rats were evaluated 3h, 3 and 30days after intramuscular injection of ACL hemorrhagic toxin I (ACLHT-I, 5mg/kg), partially purified from the venom of Agkistrodon contortrix laticinctus. Contralateral muscles were injected with saline. Three hours after ACLHT-1 injection: presence of hemorrhagic areas and myonecrotic muscle fibers. Three days: injured muscles showed areas in regeneration, some regions with delay of regeneration and bundles of normal fibers. An increased TA muscle weight was found when compared with the contralateral (0.45+/-0.03g versus 0.36+/-0.04g, p=0.04). Thirty days: areas of regenerated muscle fibers presented splits and centralized nuclei. Some regions were replaced by connective tissue. All muscle fiber types were injured but only the incidence of type IIC increased (3.4+/-2.0% versus 0.2+/-0.2%, p=0.0005). Regenerated areas of muscles were exclusively composed by fiber types II and IIC. Regenerated muscles decreased the muscle weight (0.49+/-0.1g versus 0.66+/-0.05g, p=0. 03). In conclusion, ACLHT-I: (a) caused hemorrhage and muscle fiber injury; (b) injured both fiber types I and II; (c) increased the incidence of fiber type IIC and; (d) some muscle regions were replaced by connective tissue.

  7. Effect of physical training on the proportion of slow-twitch type I muscle fibers, a novel nonimmune-mediated mechanism for muscle impairment in polymyositis or dermatomyositis.

    PubMed

    Dastmalchi, Maryam; Alexanderson, Helene; Loell, Ingela; Ståhlberg, Marcus; Borg, Kristian; Lundberg, Ingrid E; Esbjörnsson, Mona

    2007-10-15

    To compare muscle fiber type composition and muscle fiber area in patients with chronic polymyositis or dermatomyositis and healthy controls, and to determine whether physical training for 12 weeks could alter these muscle characteristics. Muscle fiber type composition and muscle fiber area were investigated by biochemical and immunohistochemistry techniques in repeated muscle biopsy samples obtained from 9 patients with chronic myositis before and after a 12-week exercise program and in healthy controls. Muscle performance was evaluated by the Functional Index (FI) in myositis and by the Short Form 36 (SF-36) quality of life instrument. Before exercise, the proportion of type I fibers was lower (mean +/- SD 32% +/- 10%) and the proportion of type IIC fibers was higher (3% +/- 3%) in patients compared with healthy controls. After exercise, percentage of type I fiber increased to 42% +/- 13% (P < 0.05), and type IIC decreased to 1% +/- 1%. An exercise-induced 20% increase of the mean fiber area was also observed. The functional capacity measured by the FI in myositis and the physical functioning subscale of the SF-36 increased significantly. Improved physical functioning was positively correlated with the proportion of type I fibers (r = 0.88, P < 0.01) and type II muscle fiber area (r = 0.70, P < 0.05). Low muscle endurance in chronic polymyositis or dermatomyositis may be related to a low proportion of oxidative, slow-twitch type I fibers. Change in fiber type composition and increased muscle fiber area may contribute to improved muscle endurance and decreased muscle fatigue after a moderate physical training program.

  8. Intermittent Cold Exposure Causes a Muscle-Specific Shift in the Fiber Type Composition in Rats

    DTIC Science & Technology

    1993-01-01

    A69 ,,.765MU.𔃼rn ~AV!ON PAG[ .... ,er 1992 Intermittent cold exposure causes a muscle-specific shift in the fiber type composition in rats PR-212PR...the older report. blank, the abstract is assumed to be unlimited.Standard Form 298 Back (Rev. 2-89) 93-223A Intermittent cold exposure causes a... causes a muscle-specific shift in the fiber type composi- therefore, results in a much greater loss of heat, thus tion in rats. J. Appl. Physiol. 75

  9. Regulation of exercise-induced fiber type transformation, mitochondrial biogenesis, and angiogenesis in skeletal muscle

    PubMed Central

    Okutsu, Mitsuharu; Akhtar, Yasir N.; Lira, Vitor A.

    2011-01-01

    Skeletal muscle exhibits superb plasticity in response to changes in functional demands. Chronic increases of skeletal muscle contractile activity, such as endurance exercise, lead to a variety of physiological and biochemical adaptations in skeletal muscle, including mitochondrial biogenesis, angiogenesis, and fiber type transformation. These adaptive changes are the basis for the improvement of physical performance and other health benefits. This review focuses on recent findings in genetically engineered animal models designed to elucidate the mechanisms and functions of various signal transduction pathways and gene expression programs in exercise-induced skeletal muscle adaptations. PMID:21030673

  10. Effect of 23-day muscle disuse on sarcoplasmic reticulum Ca2+ properties and contractility in human type I and type II skeletal muscle fibers.

    PubMed

    Lamboley, C R; Wyckelsma, V L; Perry, B D; McKenna, M J; Lamb, G D

    2016-08-01

    Inactivity negatively impacts on skeletal muscle function mainly through muscle atrophy. However, recent evidence suggests that the quality of individual muscle fibers is also altered. This study examined the effects of 23 days of unilateral lower limb suspension (ULLS) on specific force and sarcoplasmic reticulum (SR) Ca(2+) content in individual skinned muscle fibers. Muscle biopsies of the vastus lateralis were taken from six young healthy adults prior to and following ULLS. After disuse, the endogenous SR Ca(2+) content was ∼8% lower in type I fibers and maximal SR Ca(2+) capacity was lower in both type I and type II fibers (-11 and -5%, respectively). The specific force, measured in single skinned fibers from three subjects, decreased significantly after ULLS in type II fibers (-23%) but not in type I fibers (-9%). Western blot analyses showed no significant change in the amounts of myosin heavy chain (MHC) I and MHC IIa following the disuse, whereas the amounts of sarco(endo)plasmic reticulum Ca(2+)-ATPase 1 (SERCA1) and calsequestrin increased by ∼120 and ∼20%, respectively, and the amount of troponin I decreased by ∼21%. These findings suggest that the decline in force and power occurring with muscle disuse is likely to be exacerbated in part by reductions in maximum specific force in type II fibers, and in the amount of releasable SR Ca(2+) in both fiber types, the latter not being attributable to a reduced calsequestrin level. Furthermore, the ∼3-wk disuse in human elicits change in SR properties, in particular a more than twofold upregulation in SERCA1 density, before any fiber-type shift.

  11. The Regulation of Skeletal Muscle Active Hyperemia: The Differential Role of Adenosine in Muscles of Varied Fiber Types

    DTIC Science & Technology

    1986-04-21

    0.2 Hz and three mnscles ~;timulated to contract at 0.4 Hz during BADA infuston. These m~tabolites were also mea~•1red in two muscles contractin ~ at...APR 1986 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE The Regulation of Skeletal Muscle Active Hyperemia: The Differential...Role of Adenosine in Muscles of Varied Fiber Types 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER

  12. Effects of disuse by limb immobilization on different muscle fiber types

    NASA Technical Reports Server (NTRS)

    Booth, F. W.; Seider, M. J.; Hugman, G. R.

    1980-01-01

    The effects of disuse by limb immobilization on different muscle fiber types are reviewed. It is demonstrated that many changes occurring in atrophying skeletal muscles of young rats can be explained by the duration of the half-lives of muscle proteins. Differences are found to exist in responses of fast- and slow-twitch muscles due to disuse atrophy, and the appearance of plasticity in skeletal muscle begins to occur very soon after changes in the level of contractile activity. Rates of protein degradation increase in slow-twitch muscles at rapidly growing rates after approximately one day of limb immobilization; however, no change in the rates of protein degradation is noted in fast-twitch muscles of young rats.

  13. Effects of disuse by limb immobilization on different muscle fiber types

    NASA Technical Reports Server (NTRS)

    Booth, F. W.; Seider, M. J.; Hugman, G. R.

    1980-01-01

    The effects of disuse by limb immobilization on different muscle fiber types are reviewed. It is demonstrated that many changes occurring in atrophying skeletal muscles of young rats can be explained by the duration of the half-lives of muscle proteins. Differences are found to exist in responses of fast- and slow-twitch muscles due to disuse atrophy, and the appearance of plasticity in skeletal muscle begins to occur very soon after changes in the level of contractile activity. Rates of protein degradation increase in slow-twitch muscles at rapidly growing rates after approximately one day of limb immobilization; however, no change in the rates of protein degradation is noted in fast-twitch muscles of young rats.

  14. Skeletal muscle architecture and fiber-type distribution with the multiple bellies of the mouse extensor digitorum longus muscle.

    PubMed

    Chleboun, G S; Patel, T J; Lieber, R L

    1997-01-01

    The purpose of this study was to describe the extent to which architectural and fiber-type characteristics of the four bellies of the mouse extensor digitorum longus (EDL) suggest specialization of the digits, and to mathematically model the functional effects of the structural properties. Six mice were perfused in situ with glutaraldehyde while the lower limb was positioned approximately in the neutral position. After perfusion, lower limbs were removed and placed in glutaraldehyde until the EDL was dissected from the limb and separated into individual muscle bellies corresponding to each digit for architectural determination. The results showed that the muscle belly of digit 5 tended to be different from the muscle bellies of digits 2-4 for many architectural characteristics. Muscle mass, physiological cross-sectional area, muscle length, and fiber length were all significantly greater in digit 5. Proximal tendon length was also significantly longer in digit 5, and distal tendon length, as well as total tendon length, were significantly shorter in digit 5. Sarcomere length was shortest at the proximal end of the muscle and longest, 60-80%, toward the distal end. Fiber type distribution was about 60% FOG, 39% FG with only 1% SO fibers in all muscle bellies. Muscle-tendon modeling illustrated that peak force and maximal shortening velocity were greatest in digit 5. Inclusion of the tendon in the model resulted in a 10% shift of the force-length curve to longer lengths. Assuming muscle structure is matched to function, we speculate that digit 5 of the mouse EDL bears higher loads over a greater excursion during locomotion compared to the remaining digits.

  15. Automated muscle fiber type population analysis with ImageJ of whole rat muscles using rapid myosin heavy chain immunohistochemistry.

    PubMed

    Bergmeister, Konstantin D; Gröger, Marion; Aman, Martin; Willensdorfer, Anna; Manzano-Szalai, Krisztina; Salminger, Stefan; Aszmann, Oskar C

    2016-08-01

    Skeletal muscle consists of different fiber types which adapt to exercise, aging, disease, or trauma. Here we present a protocol for fast staining, automatic acquisition, and quantification of fiber populations with ImageJ. Biceps and lumbrical muscles were harvested from Sprague-Dawley rats. Quadruple immunohistochemical staining was performed on single sections using antibodies against myosin heavy chains and secondary fluorescent antibodies. Slides were scanned automatically with a slide scanner. Manual and automatic analyses were performed and compared statistically. The protocol provided rapid and reliable staining for automated image acquisition. Analyses between manual and automatic data indicated Pearson correlation coefficients for biceps of 0.645-0.841 and 0.564-0.673 for lumbrical muscles. Relative fiber populations were accurate to a degree of ± 4%. This protocol provides a reliable tool for quantification of muscle fiber populations. Using freely available software, it decreases the required time to analyze whole muscle sections. Muscle Nerve 54: 292-299, 2016. © 2016 Wiley Periodicals, Inc.

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

    PubMed

    Lynch, Christopher J; Xu, Yuping; Hajnal, Andras; Salzberg, Anna C; Kawasawa, Yuka Imamura

    2015-01-01

    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.

  17. RNA Sequencing Reveals a Slow to Fast Muscle Fiber Type Transition after Olanzapine Infusion in Rats

    PubMed Central

    Lynch, Christopher J.; Xu, Yuping; Hajnal, Andras; Salzberg, Anna C.; Kawasawa, Yuka Imamura

    2015-01-01

    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. PMID:25893406

  18. Changes in types of muscle fibers induced by transcutaneous electrical stimulation of the diaphragm of rats.

    PubMed

    Costa, D; Cancelliero, K M; Campos, G E R; Salvini, T F; Silva, C A da

    2008-09-01

    The objective of the present study was to assess the effect of transcutaneous electrical diaphragmatic stimulation (TEDS) on different types of diaphragm muscle fibers. Male Wistar rats (8-12 weeks old) were divided into 2 experimental groups (N = 8 in each group): 1) control, 2) animals submitted to TEDS [frequency = 50 Hz; T(ON)/T(OFF) (contraction/relaxation time) = 2/2 s; pulse duration = 0.4 ms, intensity = 5 mA with a 1 mA increase every 3 min for 20 min] for 7 days. After completing this treatment period, the I, IIA, IIB, and IID diaphragm muscle fibers were identified using the mATPase technique. Statistical analysis consisted of the normality, homoscedasticity and t-tests (P < 0.05). There was a 19.6% (P < 0.05) reduction in the number of type I fibers and a 49.7% increase (P < 0.05) in type IID fibers in the TEDS group compared with the control group. An important result of the present study was that electrical stimulation with surface electrodes was efficient in altering the distribution of fibers in diaphragm muscle. This therapeutic resource could be used in the treatment of respiratory muscle alterations.

  19. Androgen dependent seasonal changes in muscle fiber type in the dewlap neuromuscular system of green anoles.

    PubMed

    Holmes, Melissa M; Bartrem, Casey L; Wade, Juli

    2007-08-15

    Green anoles (Anolis carolinensis) possess two sexually dimorphic neuromuscular systems involved in reproductive behaviors. One controls extension of a red throat fan (dewlap), which males employ during courtship, and the other controls intromission of copulatory organs (hemipenes). Although seasonal changes in circulating androgens mediate both courtship and copulatory behaviors, testosterone has differential effects on the underlying neuromuscular morphology. The present experiments were designed to test whether changes in muscle fiber type correspond to seasonal and androgenic regulation of reproductive behaviors in gonadally intact males (Experiment 1) or castrated males treated with either testosterone propionate or vehicle (Experiment 2). Gonadally intact males housed in breeding environmental conditions had a higher percentage of fast oxidative glycolytic fibers in the dewlap muscle than non-breeding males, but no effect of season on copulatory fibers was detected. Interestingly, testosterone treatment increased the percentage of fast oxidative glycolytic dewlap fibers independent of season, suggesting that routine changes in this hormone may mediate fiber type in gonadally intact males. In contrast, testosterone manipulation had little to no effect on copulatory muscle fiber type, demonstrating that a change in this feature is not the primary mediator for seasonal changes in male copulatory behaviors.

  20. Exercise type and muscle fiber specific induction of caveolin-1 expression for insulin sensitivity of skeletal muscle.

    PubMed

    Oh, Yoon Sin; Kim, Hyo Jeong; Ryu, Sung Jin; Cho, Kyung A; Park, Young Sik; Park, Hyon; Kim, MiJung; Kim, Chang Keun; Park, Sang Chul

    2007-06-30

    It is well known that exercise can have beneficial effects on insulin resistance by activation of glucose transporter. Following up our previous report that caveolin-1 plays an important role in glucose uptake in L6 skeletal muscle cells, we examined whether exercise alters the expression of caveolin-1, and whether exercise-caused changes are muscle fiber and exercise type specific. Fifty week-old Sprague Dawley (SD) rats were trained to climb a ladder and treadmill for 8 weeks and their soleus muscles (SOL) and extensor digitorum longus muscles (EDL) were removed after the last bout of exercise and compared with those from non-exercised animals. We found that the expression of insulin related proteins and caveolins did not change in SOL muscles after exercise. However, in EDL muscles, the expression of insulin receptor beta (IR beta) and glucose transporter-4 (GLUT-4) as well as phosphorylation of AKT and AMPK increased with resistance exercise but not with aerobic exercise. Also, caveolin-1 and caveolin-3 increased along with insulin related proteins only in EDL muscles by resistance exercise. These results suggest that upregulation of caveolin-1 in the skeletal muscle is fiber specific and exercise type specific, implicating the requirement of the specific mode of exercise to improve insulin sensitivity.

  1. De novo synthesis of adenine nucleotides in different skeletal muscle fiber types

    SciTech Connect

    Tullson, P.C.; John-Alder, H.B.; Hood, D.A.; Terjung, R.L.

    1988-09-01

    Management of adenine nucleotide catabolism differs among skeletal muscle fiber types. This study evaluated whether there are corresponding differences in the rates of de novo synthesis of adenine nucleotide among fiber type sections of skeletal muscle using an isolated perfused rat hindquarter preparation. Label incorporation into adenine nucleotides from the (1-14C)glycine precursor was determined and used to calculate synthesis rates based on the intracellular glycine specific radioactivity. Results show that intracellular glycine is closely related to the direct precursor pool. Rates of de novo synthesis were highest in fast-twitch red muscle (57.0 +/- 4.0, 58.2 +/- 4.4 nmol.h-1.g-1; deep red gastrocnemius and vastus lateralis), relatively high in slow-twitch red muscle (47.0 +/- 3.1; soleus), and low in fast-twitch white muscle (26.1 +/- 2.0 and 21.6 +/- 2.3; superficial white gastrocnemius and vastus lateralis). Rates for four mixed muscles were intermediate, ranging between 32.3 and 37.3. Specific de novo synthesis rates exhibited a strong correlation (r = 0.986) with muscle section citrate synthase activity. Turnover rates (de novo synthesis rate/adenine nucleotide pool size) were highest in high oxidative muscle (0.82-1.06%/h), lowest in low oxidative muscle (0.30-0.35%/h), and intermediate in mixed muscle (0.44-0.55%/h). Our results demonstrate that differences in adenine nucleotide management among fiber types extends to the process of de novo adenine nucleotide synthesis.

  2. Canine muscle fiber types and susceptibility of masticatory muscles to myositis.

    PubMed

    Orvis, J S; Cardinet, G H

    1981-01-01

    The myofiber type composition was studied in 42 different muscles of the dog to determine if there are unique features that might explain the preferential involvement of the muscles of mastication by inflammatory myopathies. The principal myofiber types for most muscles studied were type 1 and type 2A and, to a lesser extent, type 2C, whereas the dorsal group of muscles innervated by the mandibular nerve (Mm. temporalis, and tensor veli palatini) was composed only of type 2C myofibers and a variant of the type 1 myofiber whose staining intensity was not fully reversed after preincubation in acid media. The distribution of this myofiber type composition was associated with the innervation and embryologic development of the dorsal muscles innervated by the mandibular nerve. This unique myofiber type composition could provide the basis for the preferential susceptibility of these muscles to agents (e.g., immune and/or infectious) that produce myositis; however, further studies are required to assess that possibility.

  3. Histochemical study, morphometric analysis and systematic distribution of fiber types in the rectus femoris muscle of the albino rats.

    PubMed

    Vega-Alvarez, J A; Pena, C; Bengoechea, M P; Perez-Casas, A

    1989-06-01

    The histochemical and morphometric characteristics as well as the systematic distribution of fiber types in the muscle rectus femoris (RF) of adult male rats were studied from ATPase (pre-incubated at pH 9'4, 4'6 and 4'2) and NADH stained sections. The muscle fiber types were classified as I type, IIA type and IIB-type. In 20 RF muscles 90-95% of total fibers were sampled and the mean diameter, length and irregularity-degree analysed. The data were grouped in four quadrants and the percent of fiber types was determined. The type IIB fibers predominate in all quadrants. The largest fibers were the IIB type and the smallest ones the type I, for all the quadrants. Our findings support a functional compartmentalization as proposed by many authors.

  4. The effect of dietary fat content on phospholipid fatty acid profile is muscle fiber type dependent.

    PubMed

    Janovská, Alena; Hatzinikolas, George; Mano, Mark; Wittert, Gary A

    2010-04-01

    A high-saturated-fat diet (HFD) induces obesity and insulin resistance (IR). IR has been linked to alterations and increased saturation in the phospholipid composition of skeletal muscles. We aimed to determine whether HFD feeding affects fatty acid (FA) membrane profile in a muscle fiber type-specific manner. We measured phospholipid FAs and expression of FA synthesis genes in oxidative soleus (SOL) and glycolytic extensor digitorum longus (EDL) muscles from rats fed either standard chow (standard laboratory diet, SLD) or a HFD. The HFD increased fat mass, plasma insulin, and leptin levels. Compared with EDL, SOL muscles preferentially accumulated C18 over C16 FAs and n-6 over n-3 polyunsaturated FAs (PUFAs) on either diet. With the HFD, SOL muscles contained more n-9 monounsaturated FAs (MUFAs) and n-6 PUFAs and less n-7 MUFAs and n-3 PUFAs than EDL muscles and had lower unsaturation index, a pattern known to be associated with IR. Stearoyl-CoA desaturase-1 expression was approximately 13-fold greater in EDL than in SOL muscles but did not change with the HFD in either muscle. The expression of Elongase-5 was higher, and that of Elongase-6 (Elovl6) was lower in EDL compared with SOL muscles with both diets. In EDL muscles, the expression of Elovl6 was lower in the HFD than in the SLD. The pattern of FA uptake, expression, and diet-induced changes in FA desaturating and elongating enzymes maintained higher FA unsaturation in EDL muscles. Accordingly, the fiber type composition of skeletal muscles and their distribution may be important in the development and progression of obesity and IR.

  5. Fiber-type distribution in insect leg muscles parallels similarities and differences in the functional role of insect walking legs.

    PubMed

    Godlewska-Hammel, Elzbieta; Büschges, Ansgar; Gruhn, Matthias

    2017-06-08

    Previous studies have demonstrated that myofibrillar ATPase (mATPase) enzyme activity in muscle fibers determines their contraction properties. We analyzed mATPase activities in muscles of the front, middle and hind legs of the orthopteran stick insect (Carausius morosus) to test the hypothesis that differences in muscle fiber types and distributions reflected differences in their behavioral functions. Our data show that all muscles are composed of at least three fiber types, fast, intermediate and slow, and demonstrate that: (1) in the femoral muscles (extensor and flexor tibiae) of all legs, the number of fast fibers decreases from proximal to distal, with a concomitant increase in the number of slow fibers. (2) The swing phase muscles protractor coxae and levator trochanteris, have smaller percentages of slow fibers compared to the antagonist stance muscles retractor coxae and depressor trochanteris. (3) The percentage of slow fibers in the retractor coxae and depressor trochanteris increases significantly from front to hind legs. These results suggest that fiber-type distribution in leg muscles of insects is not identical across leg muscles but tuned towards the specific function of a given muscle in the locomotor system.

  6. Association of blood glucose, blood lactate, serum cortisol levels, muscle metabolites, muscle fiber type composition, and pork quality traits.

    PubMed

    Choe, J H; Kim, B C

    2014-06-01

    The objective of this study was to investigate the relationship of blood glucose levels with blood lactate, serum cortisol levels, postmortem muscle glycogen and lactate content, muscle fiber type composition, and pork quality traits. Compared to pigs with lower blood glucose levels, pigs with higher blood glucose levels showed higher blood lactate and serum cortisol levels at exsanguination, and they had lower residual glycogen and higher lactate content in the muscle at 45min postmortem. In addition, pigs with higher blood glucose levels had higher type IIB and lower type I area composition and finally exhibited lower muscle pH, paler color, and excessive loss of fluid on surface. These results imply that measuring blood glucose levels at exsanguination can be useful to indicate early glycolytic rates during postmortem and thus may be of value in the identification of pork with undesirable quality traits.

  7. Thin filament diversity and physiological properties of fast and slow fiber types in astronaut leg muscles

    NASA Technical Reports Server (NTRS)

    Riley, Danny A.; Bain, James L W.; Thompson, Joyce L.; Fitts, Robert H.; Widrick, Jeffrey J.; Trappe, Scott W.; Trappe, Todd A.; Costill, David L.

    2002-01-01

    Slow type I fibers in soleus and fast white (IIa/IIx, IIx), fast red (IIa), and slow red (I) fibers in gastrocnemius were examined electron microscopically and physiologically from pre- and postflight biopsies of four astronauts from the 17-day, Life and Microgravity Sciences Spacelab Shuttle Transport System-78 mission. At 2.5-microm sarcomere length, thick filament density is approximately 1,012 filaments/microm(2) in all fiber types and unchanged by spaceflight. In preflight aldehyde-fixed biopsies, gastrocnemius fibers possess higher percentages (approximately 23%) of short thin filaments than soleus (9%). In type I fibers, spaceflight increases short, thin filament content from 9 to 24% in soleus and from 26 to 31% in gastrocnemius. Thick and thin filament spacing is wider at short sarcomere lengths. The Z-band lattice is also expanded, except for soleus type I fibers with presumably stiffer Z bands. Thin filament packing density correlates directly with specific tension for gastrocnemius fibers but not soleus. Thin filament density is inversely related to shortening velocity in all fibers. Thin filament structural variation contributes to the functional diversity of normal and spaceflight-unloaded muscles.

  8. Thin filament diversity and physiological properties of fast and slow fiber types in astronaut leg muscles

    NASA Technical Reports Server (NTRS)

    Riley, Danny A.; Bain, James L W.; Thompson, Joyce L.; Fitts, Robert H.; Widrick, Jeffrey J.; Trappe, Scott W.; Trappe, Todd A.; Costill, David L.

    2002-01-01

    Slow type I fibers in soleus and fast white (IIa/IIx, IIx), fast red (IIa), and slow red (I) fibers in gastrocnemius were examined electron microscopically and physiologically from pre- and postflight biopsies of four astronauts from the 17-day, Life and Microgravity Sciences Spacelab Shuttle Transport System-78 mission. At 2.5-microm sarcomere length, thick filament density is approximately 1,012 filaments/microm(2) in all fiber types and unchanged by spaceflight. In preflight aldehyde-fixed biopsies, gastrocnemius fibers possess higher percentages (approximately 23%) of short thin filaments than soleus (9%). In type I fibers, spaceflight increases short, thin filament content from 9 to 24% in soleus and from 26 to 31% in gastrocnemius. Thick and thin filament spacing is wider at short sarcomere lengths. The Z-band lattice is also expanded, except for soleus type I fibers with presumably stiffer Z bands. Thin filament packing density correlates directly with specific tension for gastrocnemius fibers but not soleus. Thin filament density is inversely related to shortening velocity in all fibers. Thin filament structural variation contributes to the functional diversity of normal and spaceflight-unloaded muscles.

  9. Fiber type specific expression of TNF-alpha, IL-6 and IL-18 in human skeletal muscles.

    PubMed

    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.

  10. Quantitative PCR Analysis of Laryngeal Muscle Fiber Types

    ERIC Educational Resources Information Center

    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…

  11. Quantitative PCR Analysis of Laryngeal Muscle Fiber Types

    ERIC Educational Resources Information Center

    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…

  12. Histochemical fiber type alterations secondary to exercise training of reinnervating adult rat muscle.

    PubMed

    Herbison, G J; Jaweed, M M; Ditunno, J F

    1980-06-01

    The purpose of this study was to evaluate the effect of exercise training on reinnervating rat muscle histochemistry. Adult female Wistar rats in 5 groups (1 control and 4 experimental) underwent bilateral sciatic nerve crush. The 4 experimental groups were exercised on a motorized treadmill at 35% grade and a speed of 27m/min once (groups J and L) or twice (groups K and M) daily, 5 days/week from the 2nd (groups J and K), and 3rd (groups L and M), to the 6th week after the crush. The exercise sessions lasted 1 hour. The fiber diameter and percent of type I and II fibers (weak and strong myosin ATPase reaction, pH .94) were evaluated in the soleus and superficial and deep regions of the plantaris muscles. Exercise training did not affect the fiber diameters. There was no change in the fiber type distribution in the soleus and superficial region of the plantaris. However, the percent of type II fibers increased significantly (p less than 0.05) in the deep region of the plantaris groups J, K, L and M bu 12%, 7%, 15% and 10%, respectively. This study indicated that exercise did not interfere with reinnervation and that there was an increase in the proportion of fibers with a strong myosin ATPase reaction in the deep region of the plantaris.

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

    PubMed

    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 (P<.05). There were no correlations between FOG 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

  14. Skeletal fiber types and spindle distribution in limb and jaw muscles of the adult and neonatal opossum, Monodelphis domestica.

    PubMed

    Sciote, J J; Rowlerson, A

    1998-08-01

    The South American opossum, Monodelphis domestica, is very immature at birth, and we wished to assess its potential for studies of jaw muscle development. Given the lack of prior information about any Monodelphis fiber types or spindles, our study aimed to identify for the first time fiber types in both adult and neonatal muscles and the location of spindles in the jaw muscles. Fiber types were identified in frozen sections of adult and 6-day-old jaw and limb muscles by using myosin ATPase and metabolic enzyme histochemistry and by immunostaining for myosin isoforms. The distribution of fiber types and muscle spindles throughout the jaw-closer muscles was identified by immunostaining of sections of methacarnoy-fixed, wax-embedded heads. Most muscles contained one slow (type I) and two fast fiber types (equivalent to types IIA and IIX), which were similar to those in eutherian muscle, and an additional (non-IIB) fast type. In jaw-closer muscles, the main extrafusal fiber type was IIM (characteristic of these muscles in some eutherians), and almost all spindles were concentrated in four restricted areas: one in masseter and three in temporalis. Six-day neonatal muscles were very immature, but future spindle-rich areas were revealed by immunostaining and corresponded in position to the adult areas. Extrafusal and spindle fiber types in Monodelphis share many similarities with eutherian mammalian muscle. This finding, along with the immaturity of myosin isoform expression observed 6 days postnatally, indicates that Monodelphis could provide a valuable model for studying early developmental events in the jaw-closer muscles and their spindles.

  15. Fiber type-specific muscle glycogen sparing due to carbohydrate intake before and during exercise.

    PubMed

    De Bock, K; Derave, W; Ramaekers, M; Richter, E A; Hespel, P

    2007-01-01

    The effect of carbohydrate intake before and during exercise on muscle glycogen content was investigated. According to a randomized crossover study design, eight young healthy volunteers (n = 8) participated in two experimental sessions with an interval of 3 wk. In each session subjects performed 2 h of constant-load bicycle exercise ( approximately 75% maximal oxygen uptake). On one occasion (CHO), they received carbohydrates before ( approximately 150 g) and during (1 g.kg body weight(-1).h(-1)) exercise. On the other occasion they exercised after an overnight fast (F). Fiber type-specific relative glycogen content was determined by periodic acid Schiff staining combined with immunofluorescence in needle biopsies from the vastus lateralis muscle before and immediately after exercise. Preexercise glycogen content was higher in type IIa fibers [9.1 +/- 1 x 10(-2) optical density (OD)/microm(2)] than in type I fibers (8.0 +/- 1 x 10(-2) OD/microm(2); P < 0.0001). Type IIa fiber glycogen content decreased during F from 9.6 +/- 1 x 10(-2) OD/microm(2) to 4.5 +/- 1 x 10(-2) OD/microm(2) (P = 0.001), but it did not significantly change during CHO (P = 0.29). Conversely, in type I fibers during CHO and F the exercise bout decreased glycogen content to the same degree. We conclude that the combination of carbohydrate intake both before and during moderate- to high-intensity endurance exercise results in glycogen sparing in type IIa muscle fibers.

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

    PubMed

    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.

  17. Fiber number and type composition in extensor digitorum longus, soleus, and diaphragm muscles with aging in Fisher 344 rats.

    PubMed

    Eddinger, T J; Moss, R L; Cassens, R G

    1985-10-01

    Histochemical (M-ATPase) fiber typing was done on extensor digitorum longus, (EDL), soleus (SOL), and diaphragm (DIA) muscles of barrier-reared Fisher 344 rats obtained at four different ages (3, 9, 28, and 30 months) from the colonies of the National Institute of Aging. In the EDL there are no differences in the percent of type I fibers among the four age groups. The percent of type IIa and IIb fibers also showed no difference between the 3 and 30 month age groups. There was no apparent trend for an increase or decrease in the percent of type IIa or IIb fibers between the four age groups. In both the SOL and DIA muscles the percent of type I fibers was greater in the aged than in the young groups. The percent of type IIa fibers was lower in the 30 month group than in the younger groups for both muscles. The percent of type IIb (DIA) and IIc (SOL) fibers did not change between groups. Total fiber number per cross section of muscle showed no change in the EDL over this age range or in the SOL after 9 months of age. These findings bring into question published results that imply that decreasing fiber number and preferential loss of type II (a and b) fibers are typical aging phenomena.

  18. Some properties of different skeletal muscle fiber types: comparison of reference bases.

    PubMed

    Kelso, T B; Hodgson, D R; Visscher, A R; Gollnick, P D

    1987-04-01

    Several biochemical components of the white portion of the gastrocnemius (WGM), plantaris (PM), and soleus (SM) muscles of the rat and middle gluteal (MGM) muscle of the horse were compared based on wet and dry weight, protein, and total creatine concentrations ([TCr]). The water content was similar for the rat hindlimb muscles, however, the concentrations of protein, ATP, phosphocreatine (PCr), creatine, and glycogen ranked as SM less than PM less than WGM for all reference bases except total creatine. In contrast, concentrations of ATP, creatine, and PCr were similar in all muscles studied when expressed as ratios of [TCr]. Horse MGM had the lowest percent of water and protein per gram wet or dry weight but highest glycogen concentration of the muscles studied, irrespective of the reference base used to express concentrations. Coefficients of variation were lowest when muscle constituents were related to [TCr]. It is concluded that expressing muscle constituents relative to total creatine results in the smallest variation and is a good method for making comparisons between muscles of similar fiber composition. However, essential information concerning different types of muscle may be lost when this reference base is used.

  19. Histoenzymatic and Morphometric Analysis of Muscle Fiber Type Transformation during the Postnatal Development of the Chronically Food-Deprived Rat

    PubMed Central

    Ruiz-Rosado, Azucena; Fernández-Valverde, Francisca; Mariscal-Tovar, Silvia; Hinojosa-Rodriguez, Cindy Xilonen; Hernández-Valencia, Jorge Arturo; Anzueto-Rios, Álvaro; Guadarrama-Olmos, José Carlos; Segura-Alegría, Bertha

    2013-01-01

    We analyze the effect of chronic undernourishment on extensor digitorum longus (EDL) muscle maturation in the rat. Cytochrome c oxidase (COX) and alkaline ATPase histoenzymatic techniques were used to determine the relative proportion of different fiber types (oxidative/glycolytic and type I, IIa/IId, or IIb, respectively) and their cross-sectional area in control and undernourished EDL muscles at several postnatal (PN) ages. From PN days 15 to 45, undernourished EDL muscles showed predominance of oxidative and type IIa/IId fibers, but from PN days 60 to 90, there were a larger proportion of oxidative fibers and an equal proportion of type IIa/IId and IIb fibers. Meanwhile, in adult stages (from PN days 130–365), the relative proportion of fiber types in control and undernourished EDL muscles showed no significant differences. In addition, from PN days 15 to 90, there was a significant reduction in the cross-sectional area of all fibers (slow: 13–53%; intermediate: 24–74%; fast: 9–80%) but no differences from PN days 130 to 365. It is suggested that chronic undernourishment affects the maturation of fast-type muscle fibers only at juvenile stages (from PN days 15–45) and the probable occurrence of adaptive mechanisms in muscle fibers, allowing adult rats to counterbalance the alterations provoked by chronic food deprivation. PMID:23392735

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

    PubMed

    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 < 0.001). No difference was found between sedentary participants and endurance runners in these variables, but both of these groups performed worse than strength/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 < 0.005). Partial correlations revealed that the % CSA of IIx fibers dictates a large part of the correlation between MFCV and RFD, 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.

  1. Carnitine supplementation to obese Zucker rats prevents obesity-induced type II to type I muscle fiber transition and favors an oxidative phenotype of skeletal muscle

    PubMed Central

    2013-01-01

    Background In the present study, we tested the hypothesis that carnitine supplementation counteracts obesity-induced muscle fiber transition from type I to type II. Methods 24 obese Zucker rats were randomly divided into two groups of 12 rats each (obese control, obese carnitine) and 12 lean Zucker rats were selected for lean control group. A control diet was given to both control groups and a carnitine supplemented diet (3 g/kg diet) was given to obese carnitine group for 4 wk. Components of the muscle fiber transformation in skeletal muscle were examined. Results The plasma level of carnitine were lower in the obese control group compared to the lean control group and higher in the obese carnitine group than in the other groups (P < 0.05). Plasma concentrations of triglycerides and non-esterified fatty acids were increased in obese animals compared to lean animals and the obese carnitine group had lower level compared to the obese control group (P < 0.05). The obese carnitine group had an increased number of type I muscle fibers and higher mRNA levels of type I fiber-specific myosin heavy chain, regulators of muscle fiber transition and of genes involved in carnitine uptake, fatty acid transport, β-oxidation, angiogenesis, tricarboxylic acid cycle and thermo genesis in M. rectus femoris compared to the other groups (P < 0.05). Conclusion The results demonstrate that carnitine supplementation to obese Zucker a rat counteracts the obesity-induced muscle fiber transition and restores the muscle oxidative metabolic phenotype. Carnitine supplementation is supposed to be beneficial for the treatment of elevated levels of plasma lipids during obesity or diabetes. PMID:23842456

  2. Hindlimb muscle fiber types in two frogs (Rana catesbeiana and Litoria caerulea) with different locomotor behaviors: histochemical and enzymatic comparison.

    PubMed

    Crockett, Christy J; Peters, Susan E

    2008-03-01

    To test how differences in locomotor behaviors may be reflected in muscle fiber-type diversity within anurans, a comparison of hindlimb muscles between the powerful terrestrial hopper, Rana catesbeiana, and the tree frog, Litoria caerulea, was done. One postural muscle (tibialis posticus, TP) and one primary hopping muscle (plantaris longus, PL), were characterized to identify muscle fiber types using standard histochemical methods. In addition, spectophotometric analysis of activity levels of the oxidative enzyme citrate synthase (CS) and the glycolytic enzyme lactate dehydrogenase (LDH) were done in each muscle. In spite of presumed differences in behavior between the species, we found no significant differences in the proportions of the identified fiber types when the muscles were compared across species. In addition, there were no significant differences in the proportions of the different fiber types between the postural versus phasic muscles within species. Within Rana, the postural muscle (TP) had greater oxidative capacity (as measured by CS activity) than did the phasic muscle (PL). Both muscles had equivalent LDH activities. Within Litoria, PL and TP did not differ in either LDH or CS activities. Both PL and TP of Litoria had less LDH activity and greater CS activity than their homologs in Rana. Thus, in spite of the uniform populations of fiber types between muscles and species, the metabolic diversity based on enzyme activity is consistent with behavioral differences between the species. These results suggest that the range of functional diversity within fiber types may be very broad in anurans, and histochemical fiber typing alone is not a clear indicator of their metabolic or functional properties.

  3. Fiber type and metabolic characteristics of lion (Panthera leo), caracal (Caracal caracal) and human skeletal muscle.

    PubMed

    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) was lower than humans, whereas the glycolytic capacity was elevated. LDH activity of caracal (346 ± 81) was higher than lion (227 ± 62 μmol/min/g ww), with human being the lowest (55 ± 17). CK and PHOS activities were also higher in caracal and lion compared to human, but PFK was lower in both felid species. The current data and past research are illustrated graphically showing a strong relationship between type II fibers and sprinting ability in various species. These data on caracal and lion muscles confirm their sprinting behavior.

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

    PubMed

    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.

  5. Self-reinnervated cat medial gastrocnemius muscles. II. analysis of the mechanisms and significance of fiber type grouping in reinnervated muscles.

    PubMed

    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

  6. Function and position determine relative proportions of different fiber types in limb muscles of the lizard Tropidurus psammonastes.

    PubMed

    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.

  7. Cycling exercise-induced myofiber transitions in skeletal muscle depend on basal fiber type distribution.

    PubMed

    Gehlert, Sebastian; Weber, Sebastian; Weidmann, Bente; Gutsche, Katrin; Platen, Petra; Graf, Christine; Kappes-Horn, Karin; Bloch, Wilhelm

    2012-07-01

    The link between specific changes in myofiber type proportions and modulation of training in human skeletal muscle has yet to be unraveled. We investigated whether a defined increase in training volume induces a corresponding change of myofiber shifting in human skeletal muscle with distinct basal myofiber distribution. Twenty-one male cyclists (Age 26 ± 4 years) with different performance levels were exposed to increased cycling training volume with reduced power output for 3 months. Biopsies were taken from vastus lateralis muscle PRE-POST and the proportions of type I, IIa, IIx and IIc myofibers were determined. Total training time did not correlate to the degree of fiber type shifting of any type. In the entire sample of subjects, the proportion of type I myofibers tended to increase (P = 0.14) while IIa fibers decreased significantly (P < 0.05). Subgroups of subjects possessing higher (HPS) and lower proportions (LPS) of type I myofibers at baseline showed a distinct pattern in changing myofiber distribution. Subjects in HPS offered no change in myofiber proportions of any type. In contrast, subjects in LPS showed marked increases in type I (P = 0.06) and a significant reduction in IIa myofibers (P = 0.01). An inverse correlation between baseline proportion of type I and IIa myofibers and its change was observed. We conclude that individual myofiber composition constitutes a modulating factor for exercise-induced changes in its distribution. This might be influenced by altered demands of myofiber recruitment in relation to the intensity of muscle contraction but also by its relative abundance in contracting muscle.

  8. Nitrate Intake Promotes Shift in Muscle Fiber Type Composition during Sprint Interval Training in Hypoxia

    PubMed Central

    De Smet, Stefan; Van Thienen, Ruud; Deldicque, Louise; James, Ruth; Sale, Craig; Bishop, David J.; Hespel, Peter

    2016-01-01

    Purpose: We investigated the effect of sprint interval training (SIT) in normoxia, vs. SIT in hypoxia alone or in conjunction with oral nitrate intake, on buffering capacity of homogenized muscle (βhm) and fiber type distribution, as well as on sprint and endurance performance. Methods: Twenty-seven moderately-trained participants were allocated to one of three experimental groups: SIT in normoxia (20.9% FiO2) + placebo (N), SIT in hypoxia (15% FiO2) + placebo (H), or SIT in hypoxia + nitrate supplementation (HN). All participated in 5 weeks of SIT on a cycle ergometer (30-s sprints interspersed by 4.5 min recovery-intervals, 3 weekly sessions, 4–6 sprints per session). Nitrate (6.45 mmol NaNO3) or placebo capsules were administered 3 h before each session. Before and after SIT participants performed an incremental VO2max-test, a 30-min simulated cycling time-trial, as well as a 30-s cycling sprint test. Muscle biopsies were taken from m. vastus lateralis. Results: SIT decreased the proportion of type IIx muscle fibers in all groups (P < 0.05). The relative number of type IIa fibers increased (P < 0.05) in HN (P < 0.05 vs. H), but not in the other groups. SIT had no significant effect on βhm. Compared with H, SIT tended to enhance 30-s sprint performance more in HN than in H (P = 0.085). VO2max and 30-min time-trial performance increased in all groups to a similar extent. Conclusion: SIT in hypoxia combined with nitrate supplementation increases the proportion of type IIa fibers in muscle, which may be associated with enhanced performance in short maximal exercise. Compared with normoxic training, hypoxic SIT does not alter βhm or endurance and sprinting exercise performance. PMID:27378942

  9. Extracellular MCT4 is a possible indicator for skeletal muscle MHC fiber type change.

    PubMed

    Iizuka, Kenji; Machida, Takuji; Hirafuji, Masahiko

    2014-01-01

    Biochemical markers that indicate fiber type rearrangement in myosin heavy chain (MHC) have been used to evaluate the effectiveness of exercise and/or rehabilitation therapy. The aim of this study was to investigate whether measures of extracellular monocarboxylate transporter 4 (MCT4) protein can help in the detection of MHC fiber type variation. Human skeletal muscle cells (HSkMCs) were succumbed to high atmospheric pressure. Immunoblot analyses were performed to evaluate MHC fiber type change, and an enzyme-linked immunosorbent assay system was developed for the quantification of MCT4 concentration. Static pressurization to HSkMCs resulted in an increase in cells of median diameter (18 μm). The proportion of MHC Type I fiber was increased by pressurization, and MCT4 protein concentration in the culture medium was also increased in the pressurized sample. We conclude that the amount of MCT4 in culture medium released from HSkMCs reflects fiber type changes in MHC. © 2014 by the Association of Clinical Scientists, Inc.

  10. Alteration of inflammatory cytokines, energy metabolic regulators, and muscle fiber type in the skeletal muscle of postweaning piglets.

    PubMed

    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 ( < 0.05). Serum TNF-α concentration was markedly increased on W1 d, then returned to the value of preweaning ( < 0.05), and almost all the values of inflammatory 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 ( < 0.05). The mRNA abundance of AMPKα and uncoupling protein (UCP) 3 were both higher on W1 and W3 d, and UCP2 was higher on W7 d postweaning ( < 0.05). Myosin heavy chain (MyHC) I and MyHC IIx-type fibers were enhanced on W1 d, then returned to the value of preweaning, and the MyHC IIb-type fiber was significantly increased on W5 and W7 d ( < 0.05). Meanwhile, the value of P-AMPKα/T-AMPKα increased on W3 d postweaning ( < 0.05) compared with that on W0 d. These results indicate

  11. The miRNA Transcriptome Directly Reflects the Physiological and Biochemical Differences between Red, White, and Intermediate Muscle Fiber Types

    PubMed Central

    Ma, Jideng; Wang, Hongmei; Liu, Rui; Jin, Long; Tang, Qianzi; Wang, Xun; Jiang, Anan; Hu, Yaodong; Li, Zongwen; Zhu, Li; Li, Ruiqiang; Li, Mingzhou; Li, Xuewei

    2015-01-01

    MicroRNAs (miRNAs) are small non-coding RNAs that can regulate their target genes at the post-transcriptional level. Skeletal muscle comprises different fiber types that can be broadly classified as red, intermediate, and white. Recently, a set of miRNAs was found expressed in a fiber type-specific manner in red and white fiber types. However, an in-depth analysis of the miRNA transcriptome differences between all three fiber types has not been undertaken. Herein, we collected 15 porcine skeletal muscles from different anatomical locations, which were then clearly divided into red, white, and intermediate fiber type based on the ratios of myosin heavy chain isoforms. We further illustrated that three muscles, which typically represented each muscle fiber type (i.e., red: peroneal longus (PL), intermediate: psoas major muscle (PMM), white: longissimus dorsi muscle (LDM)), have distinct metabolic patterns of mitochondrial and glycolytic enzyme levels. Furthermore, we constructed small RNA libraries for PL, PMM, and LDM using a deep sequencing approach. Results showed that the differentially expressed miRNAs were mainly enriched in PL and played a vital role in myogenesis and energy metabolism. Overall, this comprehensive analysis will contribute to a better understanding of the miRNA regulatory mechanism that achieves the phenotypic diversity of skeletal muscles. PMID:25938964

  12. Abnormal Skeletal Muscle Regeneration plus Mild Alterations in Mature Fiber Type Specification in Fktn-Deficient Dystroglycanopathy Muscular Dystrophy Mice

    PubMed Central

    Foltz, Steven J.; Modi, Jill N.; Melick, Garrett A.; Abousaud, Marin I.; Luan, Junna; Fortunato, Marisa J.; Beedle, Aaron M.

    2016-01-01

    Glycosylated α-dystroglycan provides an essential link between extracellular matrix proteins, like laminin, and the cellular cytoskeleton via the dystrophin-glycoprotein complex. In secondary dystroglycanopathy muscular dystrophy, glycosylation abnormalities disrupt a complex O-mannose glycan necessary for muscle structural integrity and signaling. Fktn-deficient dystroglycanopathy mice develop moderate to severe muscular dystrophy with skeletal muscle developmental and/or regeneration defects. To gain insight into the role of glycosylated α-dystroglycan in these processes, we performed muscle fiber typing in young (2, 4 and 8 week old) and regenerated muscle. In mice with Fktn disruption during skeletal muscle specification (Myf5/Fktn KO), newly regenerated fibers (embryonic myosin heavy chain positive) peaked at 4 weeks old, while total regenerated fibers (centrally nucleated) were highest at 8 weeks old in tibialis anterior (TA) and iliopsoas, indicating peak degeneration/regeneration activity around 4 weeks of age. In contrast, mature fiber type specification at 2, 4 and 8 weeks old was relatively unchanged. Fourteen days after necrotic toxin-induced injury, there was a divergence in muscle fiber types between Myf5/Fktn KO (skeletal-muscle specific) and whole animal knockout induced with tamoxifen post-development (Tam/Fktn KO) despite equivalent time after gene deletion. Notably, Tam/Fktn KO retained higher levels of embryonic myosin heavy chain expression after injury, suggesting a delay or abnormality in differentiation programs. In mature fiber type specification post-injury, there were significant interactions between genotype and toxin parameters for type 1, 2a, and 2x fibers, and a difference between Myf5/Fktn and Tam/Fktn study groups in type 2b fibers. These data suggest that functionally glycosylated α-dystroglycan has a unique role in muscle regeneration and may influence fiber type specification post-injury. PMID:26751696

  13. Fiber-type susceptibility to eccentric contraction-induced damage of hindlimb-unloaded rat AL muscles

    NASA Technical Reports Server (NTRS)

    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.

  14. Fiber-type susceptibility to eccentric contraction-induced damage of hindlimb-unloaded rat AL muscles

    NASA Technical Reports Server (NTRS)

    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.

  15. Myostatin regulates fiber-type composition of skeletal muscle by regulating MEF2 and MyoD gene expression.

    PubMed

    Hennebry, Alex; Berry, Carole; Siriett, Victoria; O'Callaghan, Paul; Chau, Linda; Watson, Trevor; Sharma, Mridula; Kambadur, Ravi

    2009-03-01

    Myostatin (Mstn) is a secreted growth factor belonging to the tranforming growth factor (TGF)-beta superfamily. Inactivation of murine Mstn by gene targeting, or natural mutation of bovine or human Mstn, induces the double muscling (DM) phenotype. In DM cattle, Mstn deficiency increases fast glycolytic (type IIB) fiber formation in the biceps femoris (BF) muscle. Using Mstn null ((-/-)) mice, we suggest a possible mechanism behind Mstn-mediated fiber-type diversity. Histological analysis revealed increased type IIB fibers with a concomitant decrease in type IIA and type I fibers in the Mstn(-/-) tibialis anterior and BF muscle. Functional electrical stimulation of Mstn(-/-) BF revealed increased fatigue susceptibility, supporting increased type IIB fiber content. Given the role of myocyte enhancer factor 2 (MEF2) in oxidative type I fiber formation, MEF2 levels in Mstn(-/-) tissue were quantified. Results revealed reduced MEF2C protein in Mstn(-/-) muscle and myoblast nuclear extracts. Reduced MEF2-DNA complex was also observed in electrophoretic mobility-shift assay using Mstn(-/-) nuclear extracts. Furthermore, reduced expression of MEF2 downstream target genes MLC1F and calcineurin were found in Mstn(-/-) muscle. Conversely, Mstn addition was sufficient to directly upregulate MLC promoter-enhancer activity in cultured myoblasts. Since high MyoD levels are seen in fast fibers, we analyzed MyoD levels in the muscle. In contrast to MEF2C, MyoD levels were increased in Mstn(-/-) muscle. Together, these results suggest that while Mstn positively regulates MEF2C levels, it negatively regulates MyoD expression in muscle. We propose that Mstn could regulate fiber-type composition by regulating the expression of MEF2C and MyoD during myogenesis.

  16. Differential Expression of NADPH Oxidases Depends on Skeletal Muscle Fiber Type in Rats

    PubMed Central

    Loureiro, Adriano César Carneiro; do Rêgo-Monteiro, Igor Coutinho; Louzada, Ruy A.; Ortenzi, Victor Hugo; de Aguiar, Angélica Ponte; de Abreu, Ewerton Sousa; Cavalcanti-de-Albuquerque, João Paulo Albuquerque; Hecht, Fabio; de Oliveira, Ariclécio Cunha; Ceccatto, Vânia Marilande; Fortunato, Rodrigo S.

    2016-01-01

    NADPH oxidases (NOX) are important sources of reactive oxygen species (ROS) in skeletal muscle, being involved in excitation-contraction coupling. Thus, we aimed to investigate if NOX activity and expression in skeletal muscle are fiber type specific and the possible contribution of this difference to cellular oxidative stress. Oxygen consumption rate, NOX activity and mRNA levels, and the activity of catalase (CAT), glutathione peroxidase (GPX), and superoxide dismutase (SOD), as well as the reactive protein thiol levels, were measured in the soleus (SOL), red gastrocnemius (RG), and white gastrocnemius (WG) muscles of rats. RG showed higher oxygen consumption flow than SOL and WG, while SOL had higher oxygen consumption than WG. SOL showed higher NOX activity, as well as NOX2 and NOX4 mRNA levels, antioxidant enzymatic activities, and reactive protein thiol contents when compared to WG and RG. NOX activity and NOX4 mRNA levels as well as antioxidant enzymatic activities were higher in RG than in WG. Physical exercise increased NOX activity in SOL and RG, specifically NOX2 mRNA levels in RG and NOX4 mRNA levels in SOL. In conclusion, we demonstrated that NOX activity and expression differ according to the skeletal muscle fiber type, as well as antioxidant defense. PMID:27847553

  17. Differential Expression of NADPH Oxidases Depends on Skeletal Muscle Fiber Type in Rats.

    PubMed

    Loureiro, Adriano César Carneiro; do Rêgo-Monteiro, Igor Coutinho; Louzada, Ruy A; Ortenzi, Victor Hugo; de Aguiar, Angélica Ponte; de Abreu, Ewerton Sousa; Cavalcanti-de-Albuquerque, João Paulo Albuquerque; Hecht, Fabio; de Oliveira, Ariclécio Cunha; Ceccatto, Vânia Marilande; Fortunato, Rodrigo S; Carvalho, Denise P

    2016-01-01

    NADPH oxidases (NOX) are important sources of reactive oxygen species (ROS) in skeletal muscle, being involved in excitation-contraction coupling. Thus, we aimed to investigate if NOX activity and expression in skeletal muscle are fiber type specific and the possible contribution of this difference to cellular oxidative stress. Oxygen consumption rate, NOX activity and mRNA levels, and the activity of catalase (CAT), glutathione peroxidase (GPX), and superoxide dismutase (SOD), as well as the reactive protein thiol levels, were measured in the soleus (SOL), red gastrocnemius (RG), and white gastrocnemius (WG) muscles of rats. RG showed higher oxygen consumption flow than SOL and WG, while SOL had higher oxygen consumption than WG. SOL showed higher NOX activity, as well as NOX2 and NOX4 mRNA levels, antioxidant enzymatic activities, and reactive protein thiol contents when compared to WG and RG. NOX activity and NOX4 mRNA levels as well as antioxidant enzymatic activities were higher in RG than in WG. Physical exercise increased NOX activity in SOL and RG, specifically NOX2 mRNA levels in RG and NOX4 mRNA levels in SOL. In conclusion, we demonstrated that NOX activity and expression differ according to the skeletal muscle fiber type, as well as antioxidant defense.

  18. Fiber size, type, and myosin heavy chain content in rhesus hindlimb muscles after 2 weeks at 2 G

    NASA Technical Reports Server (NTRS)

    Tavakol, Morteza; Roy, Roland R.; Kim, Jung A.; Zhong, Hui; Hodgson, John A.; Hoban-Higgins, Tana M.; Fuller, Charles A.; Edgerton, V. Reggie

    2002-01-01

    BACKGROUND: Fiber atrophy and an increase in the percentage of fast fibers have been observed in Rhesus leg muscles after spaceflight. Hypothesis: Hypergravity will result in muscle fiber hypertrophy and an increase in the percentage of slow fibers. METHODS: Open muscle biopsies were obtained from Rhesus soleus, medial gastrocnemius (MG), and tibialis anterior (TA) muscles before and after 14 d of centrifugation (2 G) and in time-matched controls. Cage activity levels were measured by telemetry. RESULTS: Based on monoclonal antibody binding for myosin heavy chains (MHC), the fastest region of soleus contained a higher proportion of type I+II (27 vs. 13%) and had a tendency for a lower proportion of type I (38 vs. 61%, p = 0.10) fibers after than before centrifugation. There was a higher proportion of type I+II fibers in post- vs. pre-2 G (10 vs. 0.6%) MG biopsies. Fiber type distribution and MHC composition were unaffected in the TA. Overall, mean fiber sizes were unaffected by centrifugation. Average cage activity levels were 36% lower during than before 2 G. CONCLUSIONS: Our hypothesis was rejected. The changes in the proportion of fibers expressing type I MHC are the reverse of that expected with chronic loading of extensors and, paradoxically, are similar to changes observed with chronic unloading, such as occurs during spaceflight, in this primate model. The data are consistent with the observed decrease in total daily activity levels.

  19. Fiber size, type, and myosin heavy chain content in rhesus hindlimb muscles after 2 weeks at 2 G

    NASA Technical Reports Server (NTRS)

    Tavakol, Morteza; Roy, Roland R.; Kim, Jung A.; Zhong, Hui; Hodgson, John A.; Hoban-Higgins, Tana M.; Fuller, Charles A.; Edgerton, V. Reggie

    2002-01-01

    BACKGROUND: Fiber atrophy and an increase in the percentage of fast fibers have been observed in Rhesus leg muscles after spaceflight. Hypothesis: Hypergravity will result in muscle fiber hypertrophy and an increase in the percentage of slow fibers. METHODS: Open muscle biopsies were obtained from Rhesus soleus, medial gastrocnemius (MG), and tibialis anterior (TA) muscles before and after 14 d of centrifugation (2 G) and in time-matched controls. Cage activity levels were measured by telemetry. RESULTS: Based on monoclonal antibody binding for myosin heavy chains (MHC), the fastest region of soleus contained a higher proportion of type I+II (27 vs. 13%) and had a tendency for a lower proportion of type I (38 vs. 61%, p = 0.10) fibers after than before centrifugation. There was a higher proportion of type I+II fibers in post- vs. pre-2 G (10 vs. 0.6%) MG biopsies. Fiber type distribution and MHC composition were unaffected in the TA. Overall, mean fiber sizes were unaffected by centrifugation. Average cage activity levels were 36% lower during than before 2 G. CONCLUSIONS: Our hypothesis was rejected. The changes in the proportion of fibers expressing type I MHC are the reverse of that expected with chronic loading of extensors and, paradoxically, are similar to changes observed with chronic unloading, such as occurs during spaceflight, in this primate model. The data are consistent with the observed decrease in total daily activity levels.

  20. Reduction of type IIb myosin and IIB fibers in tibialis anterior muscle of mini-muscle mice from high-activity lines.

    PubMed

    Bilodeau, Geneviève M; Guderley, Helga; Joanisse, Denis R; Garland, Theodore

    2009-03-01

    Selective breeding of laboratory house mice (Mus domesticus) for high voluntary wheel running has generated four replicate lines that show an almost threefold increase in daily wheel-running distances as compared with four nonselected control lines. An unusual hindlimb "mini-muscle" phenotype (small muscles, increased mitochondrial enzyme levels, disorganized fiber distribution) has increased in frequency in two of the four replicate selected lines. The gene of major effect that accounts for this phenotype is an autosomal recessive that has been mapped to a 2.6335 Mb interval on MMU11, but not yet identified. This study examined the tibialis anterior muscle to determine whether changes in muscle fiber types could explain such modifications in muscle size and properties. Although selected and control lines did not exhibit systematic differences in the fiber types present in the tibialis anterior muscle, as assessed by electrophoresis of myosin heavy chains (MHC) and by histochemistry, mini-muscle mice lacked type IIB fibers and the corresponding MHCs. Mini-muscle tibialis show increased activities of hexokinase and citrate synthase compared with the normally sized muscles, likely the result of the modified fiber types in the muscle. The mini-muscle phenotype is the major means through which selective breeding for high wheel running has modified the functional capacities of the hindlimb muscles, as normally sized tibialis anterior muscles from control and selected lines did not show general differences in their enzymatic capacities, MHC profiles or fiber type composition, with the exception of an elevated hexokinase activity and a reduced GPa activity in the selected lines.

  1. Distinct Fiber Type Signature in Mouse Muscles Expressing a Mutant Lamin A Responsible for Congenital Muscular Dystrophy in a Patient.

    PubMed

    Barateau, Alice; Vadrot, Nathalie; Agbulut, Onnik; Vicart, Patrick; Batonnet-Pichon, Sabrina; Buendia, Brigitte

    2017-04-24

    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.

  2. Mouse skeletal muscle fiber-type specific macroautophagy and muscle wasting is regulated by a Fyn/STAT3/Vps34 signaling pathway

    PubMed Central

    Yamada, Eijiro; Bastie, Claire C.; Koga, Hiroshi; Wang, Yichen; Cuervo, Ana Maria; Pessin, Jeffrey E.

    2012-01-01

    SUMMARY 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, we that 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 complexes. Physiologically, in the fed sate 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 novel Fyn/STAT3/Vps34 pathway that is responsible for fiber type specific regulation of macroautophagy and skeletal muscle atrophy. PMID:22745922

  3. 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.

    PubMed

    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.

  4. Muscle enzyme and fiber type-specific sarcomere protein increases in serum after inertial concentric-eccentric exercise.

    PubMed

    Carmona, G; Guerrero, M; Cussó, R; Padullés, J M; Moras, G; Lloret, M; Bedini, J L; Cadefau, J A

    2015-12-01

    Muscle damage induced by inertial exercise performed on a flywheel device was assessed through the serum evolution of muscle enzymes, interleukin 6, and fiber type-specific sarcomere proteins such as fast myosin (FM) and slow myosin (SM). We hypothesized that a model of muscle damage could be constructed by measuring the evolution of serum concentration of muscle proteins following inertial exercise, according to their molecular weight and the fiber compartment in which they are located. Moreover, by measuring FM and SM, the type of fibers that are affected could be assessed. Serum profiles were registered before and 24, 48, and 144 h after exercise in 10 healthy and recreationally active young men. Creatine kinase (CK) and CK-myocardial band isoenzyme increased in serum early (24 h) and returned to baseline values after 48 h. FM increased in serum late (48 h) and remained elevated 144 h post-exercise. The increase in serum muscle enzymes suggests increased membrane permeability of both fast and slow fibers, and the increase in FM reveals sarcomere disruption as well as increased membrane permeability of fast fibers. Consequently, FM could be adopted as a fiber type-specific biomarker of muscle damage. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  5. NFATc1 controls skeletal muscle fiber type and is a negative regulator of MyoD activity.

    PubMed

    Ehlers, Melissa L; Celona, Barbara; Black, Brian L

    2014-09-25

    Skeletal muscle comprises a heterogeneous population of fibers with important physiological differences. Fast fibers are glycolytic and fatigue rapidly. Slow fibers utilize oxidative metabolism and are fatigue resistant. Muscle diseases such as sarcopenia and atrophy selectively affect fast fibers, but the molecular mechanisms regulating fiber type-specific gene expression remain incompletely understood. Here, we show that the transcription factor NFATc1 controls fiber type composition and is required for fast-to-slow fiber type switching in response to exercise in vivo. Moreover, MyoD is a crucial transcriptional effector of the fast fiber phenotype, and we show that NFATc1 inhibits MyoD-dependent fast fiber gene promoters by physically interacting with the N-terminal activation domain of MyoD and blocking recruitment of the essential transcriptional coactivator p300. These studies establish a molecular mechanism for fiber type switching through direct inhibition of MyoD to control the opposing roles of MyoD and NFATc1 in fast versus slow fiber phenotypes. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Types of muscle tissue (image)

    MedlinePlus

    The 3 types of muscle tissue are cardiac, smooth, and skeletal. Cardiac muscle cells are located in ... heart, appear striated, and are under involuntary control. Smooth muscle fibers are located in walls of hollow ...

  7. Relationship between short-range stiffness and yielding in type-identified, chemically skinned muscle fibers from the cat triceps surae muscles.

    PubMed

    Malamud, J G; Godt, R E; Nichols, T R

    1996-10-01

    1. Transient, stretch-evoked force responses of chemically skinned muscle fibers from the cat hindlimb were investigated. The purpose of these experiments was to determine the exent to which short-range stiffness, the apparent stiffness exerted by the fiber over the first 0.5% of length change, is higher in type I than type II muscle fibers. Fibers were obtained from soleus and vastus intermedius muscles, which contain predominantly type I fibers, the LGm, a compartment of the lateral gastrocnemius muscle that contains predominantly type II fibers, and LG3, a compartment of mixed type. 2. Beyond a short range of approximately 1% of muscle length during a 0.5 muscle length/s (ML/s) stretch, most fibers exhibited an abrupt decrease in apparent stiffness or yield. Fibers from the muscles containing predominantly type S (slow twitch, or type I) fibers, soleus and vastus intermedius, exhibited such a pronounced decline in apparent stiffness that force declined as well during continued stretch. Most of the fibers from the LG3 compartment could be divided into two distinct groups depending upon whether or not they showed a force yield at the stretch velocity of 0.5 ML/s. 3. The short-range stiffness measured over the first 0.5% of stretch was greater for fibers showing force yield than for those that did not at matched initial forces and normalized stretch amplitudes. This result is consistent with the hypothesis that the same mechanism that endows the fiber with high short-range stiffness is also responsible for a greater extent of yielding. 4. Fibers from soleus were found to exhibit a force yield over a 200-fold range of velocities (0.01-2 ML/s). In contrast, most fibers from the LGm compartment showed only an increase in extent of yield with stretch velocity. Some of these fibers eventually yielded in force, but only when they were stretched at velocities > 2 ML/s. The proposed relationship between high short-range stiffness and yielding was supported by the finding

  8. Continuous contractile activity induces fiber type specific expression of HSP70 in skeletal muscle.

    PubMed

    Neufer, P D; Ordway, G A; Hand, G A; Shelton, J M; Richardson, J A; Benjamin, I J; Williams, R S

    1996-12-01

    Continuous contractile activity of skeletal muscle elicits an early and dramatic increase in ribosomal RNA, suggesting that translational efficiency and/or capacity is enhanced during the adaptive response to increased metabolic demand. In view of the important role heat shock or stress proteins (HSPs) play as molecular chaperones during protein synthesis, we examined whether expression of the inducible 70-kDa HSP (HSP70) and/or mitochondrial 60-kDa HSP (HSP60) is altered in rabbit tibialis anterior muscle during continuous low-frequency motor nerve stimulation. Induction of the HSP70 gene was evident within 24 h after the onset of stimulation as reflected by increases in HSP70 transcription (> 20-fold) and mRNA (> 50-fold). HSP70 protein levels were significantly elevated (10- to 12-fold) after 14 and 21 days of stimulation. Mitochondrial HSP60 mRNA and protein also increased during stimulation (> 18- and > 5-fold after 21 days, respectively). In situ hybridization and immunohistochemistry coupled with myosin ATPase staining revealed that expression of HSP70 was restricted to oxidative type I and IIa fibers during the first 3 days of stimulation but shifted to primarily type II fibers after 21 days of stimulation. These findings demonstrate that induction of HSP70 during the adaptive response to chronic motor nerve stimulation proceeds from type I/IIa to type IId(x)/b fibers, suggesting that the expression of HSPs may be required to support the folding and compartmentalization of nascent proteins during the transformation process.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  11. Running for your life or running for your dinner: what drives fiber-type evolution in lizard locomotor muscles?

    PubMed

    Scales, Jeffrey A; King, Aaron A; Butler, Marguerite A

    2009-05-01

    Despite its role in whole-animal performance, the adaptation of muscle physiology related to terrestrial locomotion remains underexplored. We tested evolutionary models based on predator escape and foraging strategies of lizards to assess whether fiber-type composition of a leg muscle is adaptive for behavior. The best-fitting model for fast-twitch fiber-type evolution was one based on predator-escape strategy, while the foraging-mode model fared poorly (Akaike Information Criterion with small sample size correction; DeltaAICc=29.7). According to the predator-escape model, lizards relying on sprints to avoid predators are predicted to have relatively higher proportions of fast glycolytic (FG) fibers (70%), while cryptic lizards are predicted to have relatively higher fast oxidative glycolytic (FOG) fiber proportions (77%). This pattern suggests an evolutionary trend toward greater FG (FOG) fiber composition among lizards that specialize in sprinting (crypsis). The best-fitting model for slow-twitch fibers had a single optimum, suggesting a common selective pressure across these lizards. The second-best model explaining slow-twitch fiber-type evolution was Brownian motion (DeltaAICc=0.80), indicating some support for neutral evolution. We find evidence suggesting that different fiber types occurring in the same muscle can evolve under different evolutionary pressures.

  12. Unexpected dependence of RyR1 splice variant expression in human lower limb muscles on fiber-type composition.

    PubMed

    Willemse, Hermia; Theodoratos, Angelo; Smith, Paul N; Dulhunty, Angela F

    2016-02-01

    The skeletal muscle ryanodine receptor Ca(2+) release channel (RyR1), essential for excitation-contraction (EC) coupling, demonstrates a known developmentally regulated alternative splicing in the ASI region. We now find unexpectedly that the expression of the splice variants is closely related to fiber type in adult human lower limb muscles. We examined the distribution of myosin heavy chain isoforms and ASI splice variants in gluteus minimus, gluteus medius and vastus medialis from patients aged 45 to 85 years. There was a strong positive correlation between ASI(+)RyR1 and the percentage of type 2 fibers in the muscles (r = 0.725), and a correspondingly strong negative correlation between the percentages of ASI(+)RyR1 and percentage of type 1 fibers. When the type 2 fiber data were separated into type 2X and type 2A, the correlation with ASI(+)RyR1 was stronger in type 2X fibers (r = 0.781) than in type 2A fibers (r = 0.461). There was no significant correlation between age and either fiber-type composition or ASI(+)RyR1/ASI(-)RyR1 ratio. The results suggest that the reduced expression of ASI(-)RyR1 during development may reflect a reduction in type 1 fibers during development. Preferential expression of ASI(-) RyR1, having a higher gain of in Ca(2+) release during EC coupling than ASI(+)RyR1, may compensate for the reduced terminal cisternae volume, fewer junctional contacts and reduced charge movement in type 1 fibers.

  13. Black and White race differences in aerobic capacity, muscle fiber type, and their influence on metabolic processes.

    PubMed

    Ceaser, Tyrone; Hunter, Gary

    2015-05-01

    Obesity is a known risk factor for cardiometabolic disease. Increasing aerobic capacity (VO2max) reduces adiposity, maintains weight, and reduces the risk of developing obesity and cardiometabolic disease. Two major determinants of aerobic capacity are the metabolic properties specific to a particular muscle fiber type and the capacity of the cardiorespiratory system to deliver nutrient-rich content to the muscle. Recent research suggests that some race/ethnic groups, particularly non-Hispanic Black subjects, are predisposed to a reduced VO2max by way of muscle fiber type. Combined with insufficient physical activity, these characteristics place non-Hispanic Black subjects at an increased risk for obesity and other adverse health outcomes when compared with other race/ethnic groups. The purpose of this review was to suggest a model for explaining how skeletal muscle fiber type may contribute to reduced aerobic capacity and obesity among non-Hispanic Black subjects. Our review indicates that metabolic properties of type II skeletal muscle (e.g. reduced oxidative capacity, capillary density) are related to various cardiometabolic diseases. Based on the review, non-Hispanic Black subjects appear to have a lower maximal aerobic capacity and a greater percentage of type II skeletal muscle fibers. Combined with reduced energy expenditure and reduced hemoglobin concentration, non-Hispanic Black subjects may be inherently predisposed to a reduced maximal aerobic capacity compared with non-Hispanic White subjects, thereby increasing the risk for obesity and related metabolic diseases.

  14. Eccentric contraction-induced injury to type I, IIa, and IIa/IIx muscle fibers of elderly adults.

    PubMed

    Choi, Seung Jun; Lim, Jae-Young; Nibaldi, Eva G; Phillips, Edward M; Frontera, Walter R; Fielding, Roger A; Widrick, Jeffrey J

    2012-02-01

    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 vastus lateralis biopsies of elderly men and women (78 ± 2 years, N = 8), were subjected to a standardized eccentric contraction (strain, 0.25 fiber length; velocity, 0.50 unloaded shortening velocity). Injury was assessed by evaluating pre- and post-eccentric peak Ca(2+)-activated force per fiber cross-sectional area (F (max)). Over 90% of the variability in post-eccentric F (max) could be explained by a multiple linear regression model consisting of an MHC-independent slope, where injury was directly related to pre-eccentric F (max), and MHC-dependent y-intercepts, where the susceptibility to injury could be described as type IIa/IIx fibers > type IIa fibers > type I fibers. We previously reported that fiber type susceptibility to the same standardized eccentric protocol was type IIa/IIx > type IIa = type I for vastus lateralis fibers of 25-year-old adults (Choi and Widrick, Am J Physiol Cell Physiol 299:C1409-C1417, 2010). Modeling combined data sets revealed significant age by fiber type interactions, with post-eccentric F (max) deficits greater for type IIa and type IIa/IIx fibers from elderly vs. young subjects at constant pre-eccentric F (max). We conclude that the resistance of the myofilament lattice to mechanical strain has deteriorated for type IIa and type IIa/IIx, but not for type I, vastus lateralis fibers of elderly adults.

  15. Heart failure increases atrogin-1 and MuRF1 gene expression in skeletal muscle with fiber type-specific atrophy.

    PubMed

    Carvalho, Robson Francisco; Castan, Eduardo Paulino; Coelho, Cesar Augusto; Lopes, Francis Silva; Almeida, Fernanda Losi Alves; Michelin, Aline; de Souza, Rodrigo Wagner Alves; Araújo, João Pessoa; Cicogna, Antonio Carlos; Dal Pai-Silva, Maeli

    2010-02-01

    Heart failure (HF) is characterized by a reduced tolerance to exercise due to early fatigue and dyspnea; this may be due in part to skeletal muscle myopathy with a shift from slow to fast fibers and loss of muscle mass. Muscle wasting does not occur similarly in all types of muscle fiber, thus we tested the hypothesis that HF induces skeletal muscle atrophy in a fiber type-specific manner altering the expression of atrogin-1 and MuRF1 in a fast muscle of rats with monocrotaline-induced heart failure. We studied extensor digitorum longus (EDL) muscle from both HF and control Wistar rats. Atrogin-1 and MuRF1 mRNA content were determined using Real-Time RT-qPCR while muscle fiber cross-sectional area (CSA) from sections stained histochemically for myofibrillar ATPase were used as an index of type-specific fiber atrophy. The measurement of gene expression by RT-qPCR revealed that EDL muscle mRNA expression of MuRF1 and atrogin-1 was significantly increased in the HF group. Muscle fiber type IIB CSA decreased in the HF group compared to the CT group; there was no significant difference in muscle fiber types I and IIA/D CSA between the HF and CT groups. In conclusion, we showed that HF induces fiber type IIB specific atrophy, up-regulating atrogin-1 and MuRF1 mRNA expression in EDL muscle of monocrotaline treated rats.

  16. Effects of muscle fiber type on glycolytic potential and meat quality traits in different Tibetan pig muscles and their association with glycolysis-related gene expression.

    PubMed

    Shen, L Y; Luo, J; Lei, H G; Jiang, Y Z; Bai, L; Li, M Z; Tang, G Q; Li, X W; Zhang, S H; Zhu, L

    2015-11-13

    The myosin heavy chain (MyHC) composition, glycolytic potential, mitochondrial content, and gene expression related to energy metabolism were analyzed in eight muscles from Tibetan pigs, to study how meat quality develops in different muscle tissues. The muscles were classified into three clusters, based on MyHC composition: masseter, trapezius, and latissimus dorsi as 'slow-oxidative-type'; psoas major and semimembranosus as 'intermediate-type'; and longissimus dorsi, obliquus externus abdominis, and semitendinosus as 'fast-glycolytic-type'. The 'slow-oxidative-type' muscles had the highest MyHC I and MyHC IIA content (P < 0.01); 'intermediate-type' muscles, the highest MyHC IIx content (P < 0.01); and 'fast-glycolytic-type' muscles, the highest MyHC IIb content (P < 0.01). The pH values measured in 'slow-oxidative-type' muscles were higher than those in the other clusters were; however, the color of 'fast-glycolytic-type' muscles was palest (P < 0.01). Mitochondrial content increased in the order: fast-glycolytic-type < intermediate-type < slow-oxidative-type. In the 'slow-oxidative-type' muscles, the expression levels of genes related to ATP synthesis were higher, but were lower for those related to glycogen synthesis and glycolysis. Mitochondrial content was significantly positively correlated with MyHC I content, but negatively correlated with MyHC IIb content. MyHC I and mitochondrial content were both negatively correlated with glycolytic potential. Overall, muscles used frequently in exercise had a higher proportion of type I fibers. 'Slow-oxidative-type' muscles, rich in type I fibers with higher mitochondrial and lower glycogen and glucose contents, had a higher ATP synthesis efficiency and lower glycolytic capacity, which contributed to their superior meat quality.

  17. Skeletal muscle capillary density and fiber type are possible determinants of in vivo insulin resistance in man.

    PubMed Central

    Lillioja, S; Young, A A; Culter, C L; Ivy, J L; Abbott, W G; Zawadzki, J K; Yki-Järvinen, H; Christin, L; Secomb, T W; Bogardus, C

    1987-01-01

    We have compared the capillary density and muscle fiber type of musculus vastus lateralis with in vivo insulin action determined by the euglycemic clamp (M value) in 23 Caucasians and 41 Pima Indian nondiabetic men. M value was significantly correlated with capillary density (r = 0.63; P less than or equal to 0.0001), percent type I fibers (r = 0.29; P less than 0.02), and percent type 2B fibers (r = -0.38; P less than 0.003). Fasting plasma glucose and insulin concentrations were significantly negatively correlated with capillary density (r = -0.46, P less than or equal to 0.0001; r = -0.47, P less than or equal to 0.0001, respectively). Waist circumference/thigh circumference ratio was correlated with percent type 1 fibers (r = -0.39; P less than 0.002). These results suggest that diffusion distance from capillary to muscle cells or some associated biochemical change, and fiber type, could play a role in determining in vivo insulin action. The association of muscle fiber type with body fat distribution may indicate that central obesity is only one aspect of a more generalized metabolic syndrome. The data may provide at least a partial explanation for the insulin resistance associated with obesity and for the altered kinetics of insulin action in the obese. PMID:3301899

  18. The effect of nutritional status and muscle fiber type on myogenic satellite cell fate and apoptosis.

    PubMed

    Powell, D J; McFarland, D C; Cowieson, A J; Muir, W I; Velleman, S G

    2014-01-01

    Satellite cells (SC) are multipotential stem cells that can be induced by nutrition to alter their cellular developmental fate, which may vary depending on their fiber type origin. The objective of the current study was to determine the effect of restricting protein synthesis on inducing adipogenic transdifferentiation and apoptosis of SC originating from fibers of the fast glycolytic pectoralis major (p. major) and fast oxidative and glycolytic biceps femoris (b. femoris) muscles of the chicken. The availability of the essential sulfur amino acids Met and Cys was restricted to regulate protein synthesis during SC proliferation and differentiation. The SC were cultured and treated with 1 of 6 Met/Cys concentrations: 60/192, 30/96 (control), 7.5/24, 3/9.6, 1/3.2, or 0/0 mg/L. Reductions in Met/Cys concentrations from the control level resulted in increased lipid staining and expression of the adipogenic marker genes peroxisome proliferator-activated receptor gamma and stearoyl-CoA desaturase during differentiation in the p. major SC. Although b. femoris SC had increased lipid staining at lower Met/Cys concentrations, there was no increase in expression of either adipogenic gene. For both muscle types, SC Met/Cys, concentration above the control increased the expression of peroxisome proliferator-activated receptor gamma and stearoyl-CoA desaturase during differentiation. As Met/Cys concentration was decreased during proliferation, a dose-dependent decline in all apoptotic cells occurred except for early apoptotic cells in the p. major, which had no treatment effect (P < 0.05). During differentiation, decreasing Met/Cys concentration caused an increase in early apoptotic cells in both fiber types and no effect on late apoptotic cells except for an increase in the p. major 7.5/24 mg/L of Met/Cys treatment. In general, the viability of the SC was unaffected by the Met/Cys concentration except during proliferation in the p. major 0/0 mg/L of Met/Cys treatment, which

  19. Multiple isoforms of myofibrillar proteins in crustacean muscle: evidence for two slow fiber types

    SciTech Connect

    Mykles, D.L.

    1986-01-01

    Four distinct patterns of myofibrillar proteins, extracted from fast and slow muscles of the lobster, Homarus americanus, are distinguished by different assemblages of regulatory and contractile protein variants. Multiple isoforms of troponin-T, -I, and -C, paramyosin, and myosin light chains occur in six muscles of the claws and abdomen. Analysis of glycerinated fibers from the claws of lobster and land crab, Gecarcinus lateralis, show that more than one isoform is expressed in a single fiber, forming unique assemblages by which subgroups can be discriminated within the broader categories of fast and slow fibers. 9 refs., 3 figs.

  20. Specific muscle adaptations in type II fibers after high-intensity interval training of well-trained runners.

    PubMed

    Kohn, T A; Essén-Gustavsson, B; Myburgh, K H

    2011-12-01

    High-intensity interval training (HIIT) forms an important component of endurance athletes' training, but little is known on intramuscular metabolic and fiber type adaptations. This study investigated physiological and skeletal muscle adaptations in endurance runners subjected to 6 weeks HIIT. Eighteen well-trained endurance athletes were subjected to 6 weeks HIIT. Maximal and submaximal exercise tests and muscle biopsies were performed before and after training. Results indicated that peak treadmill speed (PTS) increased (21.0 ± 0.8 vs 22.1 ± 1.2 km/h, P<0.001) and plasma lactate decreased at 64% and 80% PTS (P<0.05) after HIIT. Cross-sectional area of type II fibers tended to have decreased (P=0.06). No changes were observed in maximal oxygen consumption, muscle fiber type, capillary supply, citrate synthase and 3-hydroxyacetyl CoA dehydrogenase activities. Lactate dehydrogenase (LDH) activity increased in homogenate (P<0.05) and type IIa fiber pools (9.3%, P<0.05). The change in the latter correlated with an absolute interval training speed (r=0.65; P<0.05). In conclusion, HIIT in trained endurance runners causes no adaptations in muscle oxidative capacity but increased LDH activity, especially in type IIa fibers and in relation to absolute HIIT speed. © 2010 John Wiley & Sons A/S.

  1. Skeletal muscle myostatin mRNA expression is fiber-type specific and increases during hindlimb unloading

    NASA Technical Reports Server (NTRS)

    Carlson, C. J.; Booth, F. W.; Gordon, S. E.

    1999-01-01

    Transgenic mice lacking a functional myostatin (MSTN) gene demonstrate greater skeletal muscle mass resulting from muscle fiber hypertrophy and hyperplasia (McPherron, A. C., A. M. Lawler, and S. -J. Lee. Nature 387: 83-90, 1997). Therefore, we hypothesized that, in normal mice, MSTN may act as a negative regulator of muscle mass. Specifically, we hypothesized that the predominately slow (type I) soleus muscle, which demonstrates greater atrophy than the fast (type II) gastrocnemius-plantaris complex (Gast/PLT), would show more elevation in MSTN mRNA abundance during hindlimb unloading (HU). Surprisingly, MSTN mRNA was not detectable in weight-bearing or HU soleus muscle, which atrophied 42% by the 7th day of HU in female ICR mice. In contrast, MSTN mRNA was present in weight-bearing Gast/PLT muscle and was significantly elevated (67%) at 1 day but not at 3 or 7 days of HU. However, the Gast/PLT muscle had only atrophied 17% by the 7th day of HU. Because the soleus is composed only of type I and IIa fibers, whereas the Gast/PLT expresses type IId/x and IIb in addition to type I and IIa, it was necessary to perform a more careful analysis of the relationship between MSTN mRNA levels and myosin heavy-chain (MHC) isoform expression (as a marker of fiber type). A significant correlation (r = 0.725, P < 0. 0005) was noted between the percentage of MHC isoform IIb expression and MSTN mRNA abundance in several muscles of the mouse hindlimb. These results indicate that MSTN expression is not strongly associated with muscle atrophy induced by HU; however, it is strongly associated with MHC isoform IIb expression in normal muscle.

  2. Skeletal muscle myostatin mRNA expression is fiber-type specific and increases during hindlimb unloading

    NASA Technical Reports Server (NTRS)

    Carlson, C. J.; Booth, F. W.; Gordon, S. E.

    1999-01-01

    Transgenic mice lacking a functional myostatin (MSTN) gene demonstrate greater skeletal muscle mass resulting from muscle fiber hypertrophy and hyperplasia (McPherron, A. C., A. M. Lawler, and S. -J. Lee. Nature 387: 83-90, 1997). Therefore, we hypothesized that, in normal mice, MSTN may act as a negative regulator of muscle mass. Specifically, we hypothesized that the predominately slow (type I) soleus muscle, which demonstrates greater atrophy than the fast (type II) gastrocnemius-plantaris complex (Gast/PLT), would show more elevation in MSTN mRNA abundance during hindlimb unloading (HU). Surprisingly, MSTN mRNA was not detectable in weight-bearing or HU soleus muscle, which atrophied 42% by the 7th day of HU in female ICR mice. In contrast, MSTN mRNA was present in weight-bearing Gast/PLT muscle and was significantly elevated (67%) at 1 day but not at 3 or 7 days of HU. However, the Gast/PLT muscle had only atrophied 17% by the 7th day of HU. Because the soleus is composed only of type I and IIa fibers, whereas the Gast/PLT expresses type IId/x and IIb in addition to type I and IIa, it was necessary to perform a more careful analysis of the relationship between MSTN mRNA levels and myosin heavy-chain (MHC) isoform expression (as a marker of fiber type). A significant correlation (r = 0.725, P < 0. 0005) was noted between the percentage of MHC isoform IIb expression and MSTN mRNA abundance in several muscles of the mouse hindlimb. These results indicate that MSTN expression is not strongly associated with muscle atrophy induced by HU; however, it is strongly associated with MHC isoform IIb expression in normal muscle.

  3. High-fat diet induces skeletal muscle oxidative stress in a fiber type-dependent manner in rats.

    PubMed

    Pinho, Ricardo A; Sepa-Kishi, Diane M; Bikopoulos, George; Wu, Michelle V; Uthayakumar, Abinas; Mohasses, Arta; Hughes, Meghan C; Perry, Christopher G R; Ceddia, Rolando B

    2017-09-01

    This study investigated the effects of high-fat (HF) diet on parameters of oxidative stress among muscles with distinct fiber type composition and oxidative capacities. To accomplish that, male Wistar rats were fed either a low-fat standard chow (SC) or a HF diet for 8 weeks. Soleus, extensor digitorum longus (EDL), and epitrochlearis muscles were collected and mitochondrial H2O2 (mtH2O2) emission, palmitate oxidation, and gene expression and antioxidant system were measured. Chronic HF feeding enhanced fat oxidation in oxidative and glycolytic muscles. It also caused a significant reduction in mtH2O2 emission in the EDL muscle, although a tendency towards a reduction was also found in the soleus and epitrochlearis muscles. In the epitrochlearis, HF diet increased mRNA expression of the NADPH oxidase complex; however, this muscle also showed an increase in the expression of antioxidant proteins, suggesting a higher capacity to generate and buffer ROS. The soleus muscle, despite being highly oxidative, elicited H2O2 emission rates equivalent to only 20% and 35% of the values obtained for EDL and epitrochlearis muscles, respectively. Furthermore, the Epi muscle with the lowest oxidative capacity was the second highest in H2O2 emission. In conclusion, it appears that intrinsic differences related to the distribution of type I and type II fibers, rather than oxidative capacity, drove the activity of the anti- and pro-oxidant systems and determine ROS production in different skeletal muscles. This also suggests that the impact of potentially deleterious effects of ROS production on skeletal muscle metabolism/function under lipotoxic conditions is fiber type-specific. Copyright © 2017. Published by Elsevier Inc.

  4. Fiber-type composition in the perivertebral musculature of lizards: Implications for the evolution of the diapsid trunk muscles.

    PubMed

    Moritz, Sabine; Schilling, Nadja

    2013-03-01

    The perivertebral musculature of lizards is critical for the stabilization and the mobilization of the trunk during locomotion. Some trunk muscles are also involved in ventilation. This dual function of trunk muscles in locomotion and ventilation leads to a biomechanical conflict in many lizards and constrains their ability to breathe while running ("axial constraint") which likely is reflected by their high anaerobic scope. Furthermore, different foraging and predator-escape strategies were shown to correlate with the metabolic profile of locomotor muscles in lizards. Because knowledge of muscle's fiber-type composition may help to reveal a muscle's functional properties, we investigated the distribution pattern of muscle fiber types in the perivertebral musculature in two small lizard species with a generalized body shape and subjected to the axial constraint (Dipsosaurus dorsalis, Acanthodactylus maculatus) and one species that circumvents the axial constraint by means of gular pumping (Varanus exanthematicus). Additionally, these species differ in their predator-escape and foraging behaviors. Using refined enzyme-histochemical protocols, muscle fiber types were differentiated in serial cross-sections through the trunk, maintaining the anatomical relationships between the skeleton and the musculature. The fiber composition in Dipsosaurus and Acanthodactylus showed a highly glycolytic profile, consistent with their intermittent locomotor style and reliance on anaerobic metabolism during activity. Because early representatives of diapsids resemble these two species in several postcranial characters, we suggest that this glycolytic profile represents the plesiomorphic condition for diapsids. In Varanus, we found a high proportion of oxidative fibers in all muscles, which is in accordance with its high aerobic scope and capability of sustained locomotion. Copyright © 2012 Wiley Periodicals, Inc.

  5. Transgenic mice expressing mutant Pinin exhibit muscular dystrophy, nebulin deficiency and elevated expression of slow-type muscle fiber genes

    SciTech Connect

    Wu, Hsu-Pin; Hsu, Shu-Yuan; Wu, Wen-Ai; Hu, Ji-Wei; Ouyang, Pin

    2014-01-03

    Highlights: •Pnn CCD domain functions as a dominant negative mutant regulating Pnn expression and function. •Pnn CCD mutant Tg mice have a muscle wasting phenotype during development and show dystrophic histological features. •Pnn mutant muscles are susceptible to slow fiber type gene transition and NEB reduction. •The Tg mouse generated by overexpression of the Pnn CCD domain displays many characteristics resembling NEB{sup +/−} mice. -- Abstract: Pinin (Pnn) is a nuclear speckle-associated SR-like protein. The N-terminal region of the Pnn protein sequence is highly conserved from mammals to insects, but the C-terminal RS domain-containing region is absent in lower species. The N-terminal coiled-coil domain (CCD) is, therefore, of interest not only from a functional point of view, but also from an evolutionarily standpoint. To explore the biological role of the Pnn CCD in a physiological context, we generated transgenic mice overexpressing Pnn mutant in skeletal muscle. We found that overexpression of the CCD reduces endogenous Pnn expression in cultured cell lines as well as in transgenic skeletal muscle fibers. Pnn mutant mice exhibited reduced body mass and impaired muscle function during development. Mutant skeletal muscles show dystrophic histological features with muscle fibers heavily loaded with centrally located myonuclei. Expression profiling and pathway analysis identified over-representation of genes in gene categories associated with muscle contraction, specifically those related to slow type fiber. In addition nebulin (NEB) expression level is repressed in Pnn mutant skeletal muscle. We conclude that Pnn downregulation in skeletal muscle causes a muscular dystrophic phenotype associated with NEB deficiency and the CCD domain is incapable of replacing full length Pnn in terms of functional capacity.

  6. Adrenergic control of vascular resistance varies in muscles composed of different fiber types: influence of the vascular endothelium.

    PubMed

    Behnke, Bradley J; Armstrong, Robert B; Delp, Michael D

    2011-09-01

    The influence of the sympathetic nervous system (SNS) upon vascular resistance is more profound in muscles comprised predominately of low-oxidative type IIB vs. high-oxidative type I fiber types. However, within muscles containing high-oxidative type IIA and IIX fibers, the role of the SNS on vasomotor tone is not well established. The purpose of this study was to examine the influence of sympathetic neural vasoconstrictor tone in muscles composed of different fiber types. In adult male rats, blood flow to the red and white portions of the gastrocnemius (Gast(Red) and Gast(White), respectively) and the soleus muscle was measured pre- and postdenervation. Resistance arterioles from these muscles were removed, and dose responses to α₁-phenylephrine or α₂-clonidine adrenoreceptor agonists were determined with and without the vascular endothelium. Denervation resulted in a 2.7-fold increase in blood flow to the soleus and Gast(Red) and an 8.7-fold increase in flow to the Gast(White). In isolated arterioles, α₂-mediated vasoconstriction was greatest in Gast(White) (∼50%) and less in Gast(Red) (∼31%) and soleus (∼17%); differences among arterioles were abolished with the removal of the endothelium. There was greater sensitivity to α(1)-mediated vasoconstriction in the Gast(White) and Gast(Red) vs. the soleus, which was independent of whether the endothelium was present. These data indicate that 1) control of vascular resistance by the SNS in high-oxidative, fast-twitch muscle is intermediate to that of low-oxidative, fast-twitch and high-oxidative, slow-twitch muscles; and 2) the ability of the SNS to control blood flow to low-oxidative type IIB muscle appears to be mediated through postsynaptic α₁- and α₂-adrenoreceptors on the vascular smooth muscle.

  7. Adrenergic control of vascular resistance varies in muscles composed of different fiber types: influence of the vascular endothelium

    PubMed Central

    Armstrong, Robert B.; Delp, Michael D.

    2011-01-01

    The influence of the sympathetic nervous system (SNS) upon vascular resistance is more profound in muscles comprised predominately of low-oxidative type IIB vs. high-oxidative type I fiber types. However, within muscles containing high-oxidative type IIA and IIX fibers, the role of the SNS on vasomotor tone is not well established. The purpose of this study was to examine the influence of sympathetic neural vasoconstrictor tone in muscles composed of different fiber types. In adult male rats, blood flow to the red and white portions of the gastrocnemius (GastRed and GastWhite, respectively) and the soleus muscle was measured pre- and postdenervation. Resistance arterioles from these muscles were removed, and dose responses to α1-phenylephrine or α2-clonidine adrenoreceptor agonists were determined with and without the vascular endothelium. Denervation resulted in a 2.7-fold increase in blood flow to the soleus and GastRed and an 8.7-fold increase in flow to the GastWhite. In isolated arterioles, α2-mediated vasoconstriction was greatest in GastWhite (∼50%) and less in GastRed (∼31%) and soleus (∼17%); differences among arterioles were abolished with the removal of the endothelium. There was greater sensitivity to α1-mediated vasoconstriction in the GastWhite and GastRed vs. the soleus, which was independent of whether the endothelium was present. These data indicate that 1) control of vascular resistance by the SNS in high-oxidative, fast-twitch muscle is intermediate to that of low-oxidative, fast-twitch and high-oxidative, slow-twitch muscles; and 2) the ability of the SNS to control blood flow to low-oxidative type IIB muscle appears to be mediated through postsynaptic α1- and α2-adrenoreceptors on the vascular smooth muscle. PMID:21677269

  8. Human Muscle Fiber

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The stimulus of gravity affects RNA production, which helps maintain the strength of human muscles on Earth (top), as seen in this section of muscle fiber taken from an astronaut before spaceflight. Astronauts in orbit and patients on Earth fighting muscle-wasting diseases need countermeasures to prevent muscle atrophy, indicated here with white lipid droplets (bottom) in the muscle sample taken from the same astronaut after spaceflight. Kerneth Baldwin of the University of California, Irvine, is conducting research on how reducing the stimulus of gravity affects production of the RNA that the body uses as a blueprint for making muscle proteins. Muscle proteins are what give muscles their strength, so when the RNA blueprints aren't available for producing new proteins to replace old ones -- a situation that occurs in microgravity -- the muscles atrophy. When the skeletal muscle system is exposed to microgravity during spaceflight, the muscles undergo a reduced mass that translates to a reduction in strength. When this happens, muscle endurance decreases and the muscles are more prone to injury, so individuals could have problems in performing extravehicular activity [space walks] or emergency egress because their bodies are functionally compromised.

  9. Human Muscle Fiber

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The stimulus of gravity affects RNA production, which helps maintain the strength of human muscles on Earth (top), as seen in this section of muscle fiber taken from an astronaut before spaceflight. Astronauts in orbit and patients on Earth fighting muscle-wasting diseases need countermeasures to prevent muscle atrophy, indicated here with white lipid droplets (bottom) in the muscle sample taken from the same astronaut after spaceflight. Kerneth Baldwin of the University of California, Irvine, is conducting research on how reducing the stimulus of gravity affects production of the RNA that the body uses as a blueprint for making muscle proteins. Muscle proteins are what give muscles their strength, so when the RNA blueprints aren't available for producing new proteins to replace old ones -- a situation that occurs in microgravity -- the muscles atrophy. When the skeletal muscle system is exposed to microgravity during spaceflight, the muscles undergo a reduced mass that translates to a reduction in strength. When this happens, muscle endurance decreases and the muscles are more prone to injury, so individuals could have problems in performing extravehicular activity [space walks] or emergency egress because their bodies are functionally compromised.

  10. Sprint training effects on muscle myoglobin, enzymes, fiber types, and blood lactate.

    PubMed

    Jacobs, I; Esbjörnsson, M; Sylvén, C; Holm, I; Jansson, E

    1987-08-01

    The purpose of this study was to determine if changes in intra-muscular myoglobin concentration accompany histochemical and enzymatic adaptations to supra-maximal exercise training. Subjects were assigned to either a training group (N = 11), who trained 2 to 3 times weekly for 6 wk, or a control group (N = 6). Training progressed from two 15-s and two 30-s "all-out" sprints on a cycle ergometer during week 1 to six 15-s and six 30-s bouts per session during week 6. The Wingate test was performed before and after the 6 wk, but performance variables were not changed in either group. In the training group, peak lactate after the Wingate test was significantly higher after training. No significant changes in enzyme activities, myoglobin concentration, or fiber-type frequency were observed in the control group. In contrast, in the training group, the percent fast twitch oxidative fibers increased, myoglobin decreased, and both citrate synthase and phosphofructokinase activities increased (P less than 0.05). The results suggest that muscle myoglobin concentration is not increased by 6 wk of supra-maximal exercise training and that such training induces cellular adaptations without accompanying performance changes. Alternatively, the Wingate test is not a sensitive test of adaptations to the training.

  11. Lack of correspondence between histochemical and structural fiber typing in antennal muscles of the rock lobster Palinurus vulgaris.

    PubMed

    Rossi-Durand, C

    1991-01-01

    1. Sarcomere lengths and fine structure were examined in three histochemical fiber types of antennal muscles of the rock lobster. 2. Sarcomere lengths are distributed over a continuum of values from 6.5 to 19 microns. 3. Although a correlation between ATPase activity and sarcomere length is demonstrated, fibers with high ATPase activity do not have the sarcomere length typical of fast contracting fibers. 4. These fibers deviated from the typical fast structure in having long sarcomeres (greater than 6.5 microns) and in having some unusual ultrastructural characteristics (absence of the H-band, presence of Z-tubules, high thin to thick ratio, 5:1) associated with other more classical features. 5. This finding demonstrates that sarcomere length measurements do not always accurately predict the physiological performance of a single muscle fiber. 6. The fiber type composition of two antagonistic antennal muscles is compared and the functional significance of the results is discussed with respect to their role in behavior.

  12. Early detection of denervated muscle fibers in hindlimb muscles after sciatic nerve transection in wild type mice and in the G93A mouse model of amyotrophic lateral sclerosis.

    PubMed

    Gordon, T; Ly, V; Hegedus, J; Tyreman, N

    2009-02-01

    The cell adhesion molecule N-CAM is localized to the adult neuromuscular junction but is also expressed in the extrajunctional membrane of denervated muscles concurrent with extrajunctional acetylcholine receptors. Here we used N-CAM immunohistochemistry to determine whether we could detect early denervation in hindlimb muscles of the G93A transgenic mouse model of amyotrophic lateral sclerosis (ALS). In denervated wild type mouse muscles, N-CAM immunoreactivity on the sarcolemma of all fiber types and within the sarcoplasm of only type IIA fibers was detected at day 2: approximately 30% of the muscle fibers in cross-section were fully circumscribed by N-CAM immunoreactivity and approximately 25% of fibers were incompletely circumscribed. The proportion of the latter fibers remained constant over the next 8 days as the proportions of the former fibers increased exponentially. Thereafter, fully circumscribed muscle fibers increased to a maximum by 30 days with a concomitant fall in the incompletely circumscribed fibers. Hence, early muscle denervation was detected by the incomplete circumscription of fiber membranes by N-CAM immunoreactivity with full circumscription and intracellular localization indicating more long-term denervation. In the G93A transgenic mouse, rapid denervation of fast-twitch muscles was readily detected by a corresponding proportion of muscle fibers in cross-section with positive N-CAM immunoreactivity. The proportions of incompletely and completely circumscribed muscle fibers corresponded well with the rate of decline in intact motor units and reduced muscle contractile forces. Progressively more fully circumscribed muscle fibers became evident with age. We conclude that the N-CAM immunoreactivity on muscle fiber membranes in muscle cross-sections provides a sensitive means of detecting early muscle fiber denervation.

  13. Reduced Appendicular Lean Body Mass, Muscle Strength, and Size of Type II Muscle Fibers in Patients with Spondyloarthritis versus Healthy Controls: A Cross-Sectional Study

    PubMed Central

    2016-01-01

    Introduction. The purpose of this study was to investigate body composition, muscle function, and muscle morphology in patients with spondyloarthritis (SpA). Methods. Ten male SpA patients (mean ± SD age 39 ± 4.1 years) were compared with ten healthy controls matched for sex, age, body mass index, and self-reported level of physical exercise. Body composition was measured by dual energy X-ray absorptiometry. Musculus quadriceps femoris (QF) strength was assessed by maximal isometric contractions prior to test of muscular endurance. Magnetic resonance imaging of QF was used to measure muscle size and calculate specific muscle strength. Percutaneous needle biopsy samples were taken from m. vastus lateralis. Results. SpA patients presented with significantly lower appendicular lean body mass (LBM) (p = 0.02), but there was no difference in bone mineral density, fat mass, or total LBM. Absolute QF strength was significantly lower in SpA patients (p = 0.03) with a parallel trend for specific strength (p = 0.08). Biopsy samples from the SpA patients revealed significantly smaller cross-sectional area (CSA) of type II muscle fibers (p = 0.04), but no difference in CSA type I fibers. Conclusions. Results indicate that the presence of SpA disease is associated with reduced appendicular LBM, muscle strength, and type II fiber CSA. PMID:27672678

  14. Reduced Appendicular Lean Body Mass, Muscle Strength, and Size of Type II Muscle Fibers in Patients with Spondyloarthritis versus Healthy Controls: A Cross-Sectional Study.

    PubMed

    Røren Nordén, Kristine; Dagfinrud, Hanne; Løvstad, Amund; Raastad, Truls

    Introduction. The purpose of this study was to investigate body composition, muscle function, and muscle morphology in patients with spondyloarthritis (SpA). Methods. Ten male SpA patients (mean ± SD age 39 ± 4.1 years) were compared with ten healthy controls matched for sex, age, body mass index, and self-reported level of physical exercise. Body composition was measured by dual energy X-ray absorptiometry. Musculus quadriceps femoris (QF) strength was assessed by maximal isometric contractions prior to test of muscular endurance. Magnetic resonance imaging of QF was used to measure muscle size and calculate specific muscle strength. Percutaneous needle biopsy samples were taken from m. vastus lateralis. Results. SpA patients presented with significantly lower appendicular lean body mass (LBM) (p = 0.02), but there was no difference in bone mineral density, fat mass, or total LBM. Absolute QF strength was significantly lower in SpA patients (p = 0.03) with a parallel trend for specific strength (p = 0.08). Biopsy samples from the SpA patients revealed significantly smaller cross-sectional area (CSA) of type II muscle fibers (p = 0.04), but no difference in CSA type I fibers. Conclusions. Results indicate that the presence of SpA disease is associated with reduced appendicular LBM, muscle strength, and type II fiber CSA.

  15. Kinetic effects of fiber type on the two subcomponents of the Huxley-Simmons phase 2 in muscle.

    PubMed

    Davis, Julien S; Epstein, Neal D

    2003-07-01

    The Huxley-Simmons phase 2 controls the kinetics of the first stages of tension recovery after a step-change in fiber length and is considered intimately associated with tension generation. It had been shown that phase 2 is comprised of two distinct unrelated phases. This is confirmed here by showing that the properties of phase 2(fast) are independent of fiber type, whereas those of phase 2(slow) are fiber type dependent. Phase 2(fast) has a rate of 1000-2000 s(-1) and is temperature insensitive (Q(10) approximately 1.16) in fast, medium, and slow speed fibers. Regardless of fiber type and temperature, the amplitude of phase 2(fast) is half (approximately 0.46) that of phase 1 (fiber instantaneous stiffness). Consequently, fiber compliance (cross-bridge and thick/thin filament) appears to be the common source of both phase 1 elasticity and phase 2(fast) viscoelasticity. In fast fibers, stiffness increases in direct proportion to tension from an extrapolated positive origin at zero tension. The simplest explanation is that tension generation can be approximated by two-state transition from attached preforce generating (moderate stiffness) to attached force generating (high stiffness) states. Phase 2(slow) is quite different, progressively slowing in concert with fiber type. An interesting interpretation of the amplitude and rate data is that reverse coupling of phase 2(slow) back to P(i) release and ATP hydrolysis appears absent in fast fibers, detectable in medium speed fibers, and marked in slow fibers contracting isometrically. Contracting slow and heart muscles stretched under load could employ this enhanced reversibility of the cross-bridge cycle as a mechanism to conserve energy.

  16. Effects of immunological challenge induced by lipopolysaccharide on skeletal muscle fiber type conversion of piglets.

    PubMed

    Jia, A F; Feng, J H; Zhang, M H; Chang, Y; Li, Z Y; Hu, C H; Zhen, L; Zhang, S S; Peng, Q Q

    2015-11-01

    The objective of this study was to investigate the effects of immunological challenge on the skeletal muscle fiber type conversion of piglets. Sixteen Large White weaned barrows (28 ± 3 d, 8.22 ± 0.89 kg BW) were allotted by weight and litter to 2 groups: the control group and the lipopolysaccharide (LPS) group. Saline (control) or LPS was injected intravenously via a jugular catheter on d 1, 3, 5, 7, 9, 11, 13, and 15 at an initial dosage of 80 μg/kg BW, which was increased by 30% at each subsequent injection. Blood samples were collected via the jugular catheter 3 h after the LPS challenge on d -1, 1, 5, 9, and 13. Muscle tissue samples were collected from the LM after exsanguination on d 15. The LPS challenge increased the plasma IL-6, tumor necrosis factor-α (TNF-α), cortisol, IL-1β, and haptoglobin concentrations on d 1 and 5 ( < 0.01) and increased the plasma IL-6 ( < 0.05), TNF-α ( < 0.05), and haptoglobin ( < 0.01) levels on d 9. Compared with that of the control group, the ADG of the LPS group decreased by 40.00% ( < 0.01), 29.52% ( < 0.05), and 19.30% ( < 0.05), and the ADFI decreased by 25.09% ( < 0.01), 23.15% ( < 0.05), and 19.47% ( < 0.05) during d 1 to 4, d 5 to 8, and d 9 to 15, respectively. In the LM of LPS-challenged piglets, myosin heavy chain 1 (MyHC1) mRNA and protein expression tended to be reduced ( = 0.08, 0.09), whereas mRNA, mRNA, and MyHC2 protein expression increased ( < 0.05). The LPS challenge reduced succinic dehydrogenase (SDH) activity ( < 0.05) and increased lactate dehydrogenase (LDH) activity ( < 0.05) in the LM of piglets. Compared with those in the control group, transcriptional peroxisome proliferator-activated receptor coactivator-α () mRNA ( < 0.05), calcineurin (CaN) mRNA, and protein expression were reduced ( < 0.05), and PGC-α protein expression tended to be reduced ( = 0.08) in the LM of LPS-challenged piglets. These results show that immunological challenge induced by LPS resulted in a shift from type I to

  17. Transcriptome signature of resistance exercise adaptations: mixed muscle and fiber type specific profiles in young and old adults

    PubMed Central

    Raue, Ulrika; Trappe, Todd A.; Estrem, Shawn T.; Qian, Hui-Rong; Helvering, Leah M.; Smith, Rosamund C.

    2012-01-01

    This investigation examined the effects of acute resistance exercise (RE), progressive resistance training (PRT), and age on the human skeletal muscle Transcriptome. Two cohorts of young and old adults [study A: 24 yr, 84 yr (n = 28); study B: 25 yr, 78 yr (n = 36)] were studied. Vastus lateralis biopsies were obtained pre- and 4 h post-RE in conjunction with the 1st and 36th (last) training session as part of a 12-wk PRT program in study A, whereas biopsies were obtained in the basal untrained state in study B. Additionally, the muscle fiber type specific (MHC I and MHC IIa) Transcriptome response to RE was examined in a subset of young and old women from study A. Transcriptome profiling was performed using HG U133 Plus 2.0 Arrays. The main findings were 1) there were 661 genes affected by RE during the 1st and 36th training bout that correlated with gains in muscle size and strength with PRT (termed the Transcriptome signature of resistance exercise adaptations); 2) the RE gene response was most pronounced in fast-twitch (MHC IIa) muscle fibers and provided additional insight into the skeletal muscle biology affected by RE; 3) skeletal muscle of young adults is more responsive to RE at the gene level compared with old adults and age also affected basal level skeletal muscle gene expression. These skeletal muscle Transcriptome findings provide further insight into the molecular basis of sarcopenia and the impact of resistance exercise at the mixed muscle and fiber type specific level. PMID:22302958

  18. FoxO1 regulates muscle fiber-type specification and inhibits calcineurin signaling during C2C12 myoblast differentiation.

    PubMed

    Yuan, Yuan; Shi, Xin-e; Liu, Yue-guang; Yang, Gong-she

    2011-02-01

    Adult skeletal muscle fibers can be categorized into slow-oxidative and fast-glycolytic subtypes based on specialized metabolic and contractile properties. The Forkhead box O1 (FoxO1) transcription factor governs muscle growth, metabolism, and cell differentiation, and has been shown to be involved in regulating muscle fiber type specification. However, to date, the mechanism behind FoxO1-mediated fiber type diversity is still unclear. In this article, FoxO1 being expressed preferentially in fast twitch fiber enriched muscles is reported. Moreover, the autors also detected that FoxO1 expression decreased in both fast and slow muscles from mice undergoing endurance exercise which induced a fast-to-slow fiber type transition. Using C2C12 myoblast, constitutively active FoxO1 mutant altered the proportion of muscle fiber type composition toward a fast-glycolytic phenotype and attenuated calcineurin phosphatase activity. In addition, a transcriptionally inactive FoxO1 by resveratrol triggered the expression of genes related to slow-oxidative muscle but not sufficient to induce a complete slow fiber transformation. Taken together, these results suggest that FoxO1 up-regulates fast fiber-type formation and down-regulates muscle oxidative capacity at least in part through inhibition of the calcineurin pathway.

  19. Physiologic, metabolic, and muscle fiber type characteristics of musculus uvulae in sleep apnea hypopnea syndrome and in snorers.

    PubMed Central

    Sériès, F; Côté, C; Simoneau, J A; Gélinas, Y; St Pierre, S; Leclerc, J; Ferland, R; Marc, I

    1995-01-01

    Upper airway dilator muscles play an important role in the pathophysiology of sleep apnea hypopnea syndrome (SAHS). The mechanical and structural characteristics of these muscles remain unknown. The aim of this study was to compare the physiologic, metabolic, and fiber type characteristics of one upper airway dilator muscle (musculus uvulae, MU) in 11 SAHS and in seven nonapneic snorers. The different analyses were done on MU obtained during uvulo-palato-pharyngoplasty. Snorers and SAHS differed only in their apnea + hypopnea indices (11.5 +/- 5.9 and 34.2 +/- 14.6/h, respectively, mean +/- SD). Absolute twitch and tetanic tension production of MU was significantly greater in SAHS than in snorers while the fatigability index was similar in the two groups. Protein content and anaerobic enzyme activities of MU were significantly greater in SAHS than in snorers; no difference was observed for aerobic enzyme activities. The total muscle fiber cross-sectional area of MU was significantly higher in SAHS (2.2 +/- 0.9 mm2) than in snorers (1.1 +/- 0.7 mm2). The surface occupied by type IIA muscle fibers of MU was larger in SAHS (2.00 +/- 0.96) than in snorers (0.84 +/- 0.63 mm2). We conclude that the capacity for tension production and the anaerobic metabolic activity of MU are greater in SAHS than in snorers. PMID:7814616

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

    PubMed

    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.

  1. Use it or Lose It: Tonic Activity of Slow Motoneurons Promotes Their Survival and Preferentially Increases Slow Fiber-Type Groupings in Muscles of Old Lifelong Recreational Sportsmen

    PubMed Central

    Mosole, Simone; Carraro, Ugo; Kern, Helmut; Loefler, Stefan; Zampieri, Sandra

    2016-01-01

    Histochemistry, immuno-histochemistry, gel electrophoresis of single muscle fibers and electromyography of aging muscles and nerves suggest that: i) denervation contributes to muscle atrophy, ii) impaired mobility accelerates the process, and iii) lifelong running protects against loss of motor units. Recent corroborating results on the muscle effects of Functional Electrical Stimulation (FES) of aged muscles will be also mentioned, but we will in particular discuss how and why a lifelong increased physical activity sustains reinnervation of muscle fibers. By analyzing distribution and density of muscle fibers co-expressing fast and slow Myosin Heavy Chains (MHC) we are able to distinguish the transforming muscle fibers due to activity related plasticity, to those that adapt muscle fiber properties to denervation and reinnervation. In muscle biopsies from septuagenarians with a history of lifelong high-level recreational activity we recently observed in comparison to sedentary seniors: 1. decreased proportion of small-size angular myofibers (denervated muscle fibers); 2. considerable increase of fiber-type groupings of the slow type (reinnervated muscle fibers); 3. sparse presence of muscle fibers co-expressing fast and slow MHC. Immuno-histochemical characteristics fluctuate from those with scarce fiber-type modulation and groupings to almost complete transformed muscles, going through a process in which isolated fibers co-expressing fast and slow MHC fill the gaps among fiber groupings. Data suggest that lifelong high-level exercise allows the body to adapt to the consequences of the age-related denervation and that it preserves muscle structure and function by saving otherwise lost muscle fibers through recruitment to different slow motor units. This is an opposite behavior of that described in long term denervated or resting muscles. These effects of lifelong high level activity seems to act primarily on motor neurons, in particular on those always more active

  2. Single muscle fiber adaptations with marathon training.

    PubMed

    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 < 0.05) with the training program. Muscle fiber size declined (P < 0.05) by approximately 20% in both fiber types after training. P(o) was maintained in both fiber types with training and increased (P < 0.05) by 18% in the MHC IIa fibers after taper. This resulted in >60% increase (P < 0.05) in force per cross-sectional area in both fiber types. Fiber V(o) increased (P < 0.05) by 28% in MHC I fibers with training and was unchanged in MHC IIa fibers. Peak power increased (P < 0.05) in MHC I and IIa fibers after training with a further increase (P < 0.05) in MHC IIa fiber power after taper. These data show that marathon training decreased slow-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.

  3. Acute antioxidant supplementation and skeletal muscle vascular conductance in aged rats: role of exercise and fiber type.

    PubMed

    Hirai, Daniel M; Copp, Steven W; Schwagerl, Peter J; Haub, Mark D; Poole, David C; Musch, Timothy I

    2011-04-01

    Age-related increases in oxidative stress contribute to impaired skeletal muscle vascular control. However, recent evidence indicates that antioxidant treatment with tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) attenuates flow-mediated vasodilation in isolated arterioles from the highly oxidative soleus muscle of aged rats. Whether antioxidant treatment with tempol evokes similar responses in vivo at rest and during exercise in senescent individuals and whether this effect varies based on muscle fiber type composition are unknown. We tested the hypothesis that redox modulation via acute systemic tempol administration decreases vascular conductance (VC) primarily in oxidative hindlimb locomotor muscles at rest and during submaximal whole body exercise (treadmill running at 20 m/min, 5% grade) in aged rats. Eighteen old (25-26 mo) male Fischer 344 x Brown Norway rats were assigned to either rest (n = 8) or exercise (n = 10) groups. Regional VC was determined via radiolabeled microspheres before and after intra-arterial administration of tempol (302 μmol/kg). Tempol decreased mean arterial pressure significantly by 9% at rest and 16% during exercise. At rest, similar VC in 26 out of 28 individual hindlimb muscles or muscle parts following tempol administration compared with control resulted in unchanged total hindlimb muscle VC (control: 0.18 ± 0.02; tempol: 0.17 ± 0.05 ml·min(-1)·100 g(-1)·mmHg(-1); P > 0.05). During exercise, all individual hindlimb muscles or muscle parts irrespective of fiber type composition exhibited either an increase or no change in VC with tempol (i.e., ↑11 and ↔17 muscles or muscle parts), such that total hindlimb VC increased by 25% (control: 0.93 ± 0.04; tempol: 1.15 ± 0.09 ml·min(-1)·100 g(-1)·mmHg(-1); P ≤ 0.05). These results demonstrate that acute systemic administration of the antioxidant tempol significantly impacts the control of regional vascular tone in vivo presumably via redox modulation and improves

  4. Block of single L-type Ca2+ channels in skeletal muscle fibers by aminoglycoside antibiotics

    PubMed Central

    1996-01-01

    The activity of single L-type Ca2+ channels was recorded from cell- attached patches on acutely isolated skeletal muscle fibers from the mouse. The experiments were concerned with the mechanism by which aminoglycoside antibiotics inhibit ion flow through the channel. Aminoglycosides produced discrete fluctuations in the single-channel current when added to the external solution. The blocking kinetics could be described as a simple bimolecular reaction between an aminoglycoside molecule and the open channel. The blocking rate was found to be increased when either the membrane potential was made more negative or the concentration of external permeant ion was reduced. Both of these effects are consistent with a blocking site that is located within the channel pore. Other features of block, however, were incompatible with a simple pore blocking mechanism. Hyperpolarization enhanced the rate of unblocking, even though an aminoglycoside molecule must dissociate from its binding site in the channel toward the external solution against the membrane field. Raising the external permeant ion concentration also enhanced the rate of unblocking. This latter finding suggests that aminglycoside affinity is modified by repulsive interactions that arise when the pore is simultaneously occupied by a permeant ion and an aminoglycoside molecule. PMID:8868052

  5. 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.

    PubMed

    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

  6. Micro-RNA expression in muscle and fiber morphometry in myotonic dystrophy type 1.

    PubMed

    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.

  7. Ca2+ release in muscle fibers expressing R4892W and G4896V type 1 ryanodine receptor disease mutants.

    PubMed

    Lefebvre, Romain; Legrand, Claude; Groom, Linda; Dirksen, Robert T; Jacquemond, Vincent

    2013-01-01

    The large and rapidly increasing number of potentially pathological mutants in the type 1 ryanodine receptor (RyR1) prompts the need to characterize their effects on voltage-activated sarcoplasmic reticulum (SR) Ca(2+) release in skeletal muscle. Here we evaluated the function of the R4892W and G4896V RyR1 mutants, both associated with central core disease (CCD) in humans, in myotubes and in adult muscle fibers. For both mutants expressed in RyR1-null (dyspedic) myotubes, voltage-gated Ca(2+) release was absent following homotypic expression and only partially restored following heterotypic expression with wild-type (WT) RyR1. In muscle fibers from adult WT mice, both mutants were expressed in restricted regions of the fibers with a pattern consistent with triadic localization. Voltage-clamp-activated confocal Ca(2+) signals showed that fiber regions endowed with G4896V-RyR1s exhibited an ∼30% reduction in the peak rate of SR Ca(2+) release, with no significant change in SR Ca(2+) content. Immunostaining revealed no associated change in the expression of either α1S subunit (Cav1.1) of the dihydropyridine receptor (DHPR) or type 1 sarco(endo)plasmic reticulum Ca(2+) ATPase (SERCA1), indicating that the reduced Ca(2+) release resulted from defective RyR1 function. Interestingly, in spite of robust localized junctional expression, the R4892W mutant did not affect SR Ca(2+) release in adult muscle fibers, consistent with a low functional penetrance of this particular CCD-associated mutant.

  8. Increase in S6K1 phosphorylation in human skeletal muscle following resistance exercise occurs mainly in type II muscle fibers.

    PubMed

    Koopman, René; Zorenc, Antoine H G; Gransier, Rudy J J; Cameron-Smith, David; van Loon, Luc J C

    2006-06-01

    To investigate the in vivo effects of resistance exercise on translational control in human skeletal muscle, we determined the phosphorylation of AMP-activated kinase (AMPK), eukaryotic initiation factor 4E-binding protein (4E-BP1), p70/p85-S6 protein kinase (S6K1), and ribosomal S6 protein (S6). Furthermore, we investigated whether changes in the phosphorylation of S6K1 are muscle fiber type specific. Eight male subjects performed a single high-intensity resistance exercise session. Muscle biopsies were collected before and immediately after exercise and after 30 and 120 min of postexercise recovery. The phosphorylation statuses of AMPK, 4E-BP1, S6K1, and S6 were determined by Western blotting with phospho-specific and pan antibodies. To determine fiber type-specific changes in the phosphorylation status of S6K1, immunofluorescence microscopy was applied. AMPK phosphorylation was increased approximately threefold immediately after resistance exercise, whereas 4E-BP1 phosphorylation was reduced to 27 +/- 6% of preexercise values. Phosphorylation of S6K1 at Thr421/Ser424 was increased 2- to 2.5-fold during recovery but did not induce a significant change in S6 phosphorylation. Phosphorylation of S6K1 was more pronounced in the type II vs. type I muscle fibers. Before exercise, phosphorylated S6K1 was predominantly located in the nuclei. After 2 h of postexercise recovery, phospho-S6K1 was primarily located in the cytosol of type II muscle fibers. We conclude that resistance exercise effectively increases the phosphorylation of S6K1 on Thr421/Ser424, which is not associated with a substantial increase in S6 phosphorylation in a fasted state.

  9. Eight weeks of ballistic exercise improves power independently of changes in strength and muscle fiber type expression.

    PubMed

    Winchester, Jason B; McBride, Jeffrey M; Maher, Margaret A; Mikat, Richard P; Allen, Brian K; Kline, Dennis E; McGuigan, Michael R

    2008-11-01

    This study investigated the effects of ballistic resistance training and strength training on muscle fiber composition, peak force (PF), maximal strength, and peak power (PP). Fourteen males (age = 21.3 +/- 2.9, body mass = 77.8 +/- 10.1 kg) with 3 months of resistance training experience completed the study. Subjects were tested pre and post for their squat one-repetition maximum (1RM) and PP in the jump squat (JS). Peak force and rate of force development (RFD) were tested during an isometric midthigh pull. Muscle biopsies were obtained from the vastus lateralis for analysis of muscle fiber type expression. Subjects were matched for strength and then randomly selected into either training (T) or control (C) groups. Group T performed 8 weeks of JS training using a periodized program with loading between 26 and 48% of 1RM, 3 days per week. Group T showed significant improvement in PP from 4088.9 +/- 520.6 to 5737.6 +/- 651.8 W. Rate of force development improved significantly in group T from 12687.5 +/- 4644.0 to 25343.8 +/- 12614.4 N x s(-1). PV improved significantly from 1.59 +/- 0.41 to 2.11 +/- 0.75 m x s(-1). No changes occurred in PF, 1RM, or muscle fiber type expression for group T. No changes occurred in any variables in group C. The results of this study indicate that using ballistic resistance exercise is an effective method for increasing PP and RFD independently of changes in maximum strength (1RM, PF), and those increases are a result of factors other than changes in muscle fiber type expression.

  10. Phenotype plasticity in postural muscles of the crayfish Orconectes limosus Raf.: correlation of myofibrillar ATPase-based fiber typing with electrophysiological fiber properties and the effect of chronic nerve stimulation.

    PubMed

    Gruhn, Matthias; Rathmayer, Werner

    2002-07-01

    The characteristics of the medial and lateral superficial extensor muscles (sem and sel) in the crayfish Orconectes limosus abdomen and their developmental and activity-dependent plasticity were studied. It was shown that both muscles are innervated by at least five excitatory and one inhibitory motor neuron in a nonuniform pattern. The muscles are composed of at least three different mATPase histochemistry-based fiber types that are all different from a fourth type in the uniform deep extensor muscles. sem and sel are composed of different ratios of these fiber types but do not show a constant fiber type pattern between segments and even between hemisegments. The three histochemically defined superficial extensor-fiber types have characteristic electrophysiological properties. The fiber types were shown to develop successively during the first postembryonic stages of development without a change in the number of muscle fibers. Based on histochemical ATPase staining after 21 days of chronic stimulation by means of an implantable, double-hook electrode, we show preliminary evidence that the fiber composition in the sem can switch from the presumably fast fiber type III to an intermediate type II. Repeated axotomy up to 53 days had no effect on the fiber type composition of the muscles. Copyright 2002 Wiley-Liss, Inc.

  11. The Relationship between Muscle Fiber Type-Specific PGC-1α Content and Mitochondrial Content Varies between Rodent Models and Humans

    PubMed Central

    Gouspillou, Gilles; Sgarioto, Nicolas; Norris, Brandon; Barbat-Artigas, Sébastien; Aubertin-Leheudre, Mylène; Morais, Jose A.; Burelle, Yan; Taivassalo, Tanja; Hepple, Russell T.

    2014-01-01

    PGC-1α regulates critical processes in muscle physiology, including mitochondrial biogenesis, lipid metabolism and angiogenesis. Furthermore, PGC-1α was suggested as an important regulator of fiber type determination. However, whether a muscle fiber type-specific PGC-1α content exists, whether PGC-1α content relates to basal levels of mitochondrial content, and whether such relationships are preserved between humans and classically used rodent models are all questions that have been either poorly addressed or never investigated. To address these issues, we investigated the fiber type-specific content of PGC-1α and its relationship to basal mitochondrial content in mouse, rat and human muscles using in situ immunolabeling and histochemical methods on muscle serial cross-sections. Whereas type IIa fibers exhibited the highest PGC-1α in all three species, other fiber types displayed a hierarchy of type IIx>I>IIb in mouse, type I = IIx> IIb in rat, and type IIx>I in human. In terms of mitochondrial content, we observed a hierarchy of IIa>IIx>I>IIb in mouse, IIa >I>IIx> IIb in rat, and I>IIa> IIx in human skeletal muscle. We also found in rat skeletal muscle that type I fibers displayed the highest capillarization followed by type IIa >IIx>IIb. Finally, we found in human skeletal muscle that type I fibers display the highest lipid content, followed by type IIa>IIx. Altogether, our results reveal that (i) the fiber type-specific PGC-1α and mitochondrial contents were only matched in mouse, (ii) the patterns of PGC-1α and mitochondrial contents observed in mice and rats do not correspond to that seen in humans in several respects, and (iii) the classical phenotypes thought to be regulated by PGC-1α do not vary exclusively as a function of PGC-1α content in rat and human muscles. PMID:25121500

  12. Effect of heart transplantation on skeletal muscle metabolic enzyme reserve and fiber type in end-stage heart failure patients.

    PubMed

    Pierce, Gary L; Magyari, Peter M; Aranda, Juan M; Edwards, David G; Hamlin, Scott A; Hill, James A; Braith, Randy W

    2007-01-01

    Skeletal muscle myopathy is a hallmark of chronic heart failure (HF). Phenotypic changes involve shift in myosin heavy chain (MHC) fiber type from oxidative, MHC type I, towards more glycolytic MHC IIx fibers, reductions in oxidative enzyme activity, and increase in glycolytic enzyme activity. However, it is unknown if muscle myopathy is reversed following heart transplantation. The purpose of this study was to determine the effect of heart transplantation on skeletal muscle metabolic enzyme reserve and MHC fiber type in end-stage HF patients. Thirteen HF subjects were prospectively studied before and two months after heart transplantation and a subgroup (n = 6) at eight months after transplantation. Skeletal muscle biopsy of the vastus lateralis was performed and relative MHC composition was determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Lactate dehydrogenase (LDH), citrate synthase (CS), and 3-hydroxyacyl-CoA-dehydrogenase (HACoA) enzyme activity assays were performed to assess glycolytic, oxidative, and beta-oxidative metabolic enzyme reserves, respectively. Lactate dehydrogenase activity (130.5 +/- 13.3 vs. 106.1 +/- 13.2 micromol/g wet wt/min, p < 0.05), CS activity (14.0 +/- 1.2 vs. 9 +/- 0.9 micromol/g wet wt/min, p < 0.05), and HACoA activity (4.5 +/- 0.48 vs. 3.6 +/- 0.3 micromol/g wet wt/min, p < 0.05) decreased two months after heart transplantation. At eight months, LDH activity was restored (139.0 +/- 11 micromol/g wet wt/min), but not CS or HACoA activity compared with before transplantation. There was no significant change in muscle %MHC type I (28.7 +/- 3.5% vs. 25.3 +/- 3.0%, p = NS), %MHC type IIa (33.2 +/- 2.0% vs. 34.6 +/- 1.9%, p = NS), or %MHC type IIx (38.1 +/- 2.8% vs. 40.1 +/- 3.7%, p = NS) fiber type two months after heart transplantation. However, %MHC type I (19.3 +/- 6.6%) was decreased and %MHC type IIx (51.0 +/- 6.5%) was increased at eight months after (p < 0.05) compared with before transplantation

  13. Aging affects different human muscles in various ways. An image analysis of the histomorphometric characteristics of fiber types in human masseter and vastus lateralis muscles from young adults and the very old.

    PubMed

    Kirkeby, S; Garbarsch, C

    2000-01-01

    This study is an attempt to objectively evaluate age-related changes in human muscles by use of histomorphometric methods. Aging in humans induces dramatic transformations in the skeletal muscles but little is known as to whether or not the aging processes per se may affect all muscles equally. In this study aging of two human muscles with different functions, origin and nerve supply is compared. Sections were cut from masseter and vastus lateralis muscles obtained from young adults aged 18-24 years and from the very old aged 90-102 years. Muscle fiber types were classified with the traditional myofibrillar ATPase staining. Various histomorphometric parameters of the different fiber types in human masseter and vastus lateralis muscle sections were obtained by image analyses to evaluate the age-related changes in the muscle fibers. The following variables were calculated: the number of each fiber type per photographed area; the area of each fiber and two indicators for the shape of the muscle fibers. In the aging muscles there was no relative preferential loss of a fiber type. High numbers of intermediate ATPase-stained fibers (IM fibers) were found in some old vastus muscles but were only sporadic in young vastus muscles. However, there was no change in the percentage distribution of intermediate ATPase-stained fibers when young and very old human masseter muscles were compared. Incubation of the sections with antimyosin antibodies showed that the IM fibers in old masseter and old vastus contained different myosin heavy chains. Thus ATPase activity and anti-myosin staining displayed a somewhat different pattern of fiber type distribution. The main changes in the shape and area indicated that type I fibers in the masseter became more circular while in the vastus they decreased significantly in size. The type II fibers in the vastus became very small and deviated significantly from circularity whereas the type II fibers in the masseter only exhibited a decrease in

  14. Effects of Mechanical Overloading on the Properties of Soleus Muscle Fibers, with or without Damage in MDX and Wild Type Mice

    NASA Astrophysics Data System (ADS)

    Terada, Masahiro; Kawano, Fuminori; Ohira, Takashi; Oke, Yoshihiko; Nakai, Naoya; Ohira, Yoshinobu

    2008-06-01

    Effects of mechanical overloading on the characteristics of regenerating or not-regenerating soleus muscle fibers were studied. The muscle fibers of mdx mice were characterized by the localization of myonuclei. Muscle damage was also induced in wild type (WT) mice by injection of cardiotoxin (CTX) into soleus muscle. Overloading was applied for 14 days to the left soleus muscle in mdx and intact and CTX-injected WT mice by removing the distal tendons of plantaris and gastrocnemius muscles. The contralateral muscle served as the normal control. These animals were then allowed ambulation recovery in the cage. Central myonuclei were noted in many fibers of mdx and CTX-injected mice with or without overloading. In general, the fibers with central nuclei were considered as regenerating fibers. The fibers with more central nuclei were increased in mdx mice, but the fibers with more peripheral nuclei were increased in CTX-injected WT mice by overloading. The muscle satellite cells, neuromuscular junctions (NMJ), and myonuclei were stained. Most of the properties, such as number of myonuclei and satellite cells, size of NMJ, and fiber length, were not influenced by mechanical overloading in all mice. Approximately 0.6% branched fibers were seen in the intact soleus of mdx mice, although these fibers were not detected in WT mice. However, the percentage of these fibers was increased by overloading especially in mdx mice (~50% vs. ~2.5% in WT). In CTX-injected WT mice, these fibers were ~15% with or without overloading. The fiber cross sectional area in normal WT, but not in mdx and CTX-injected WT mice, was increased by overloading (p<0.05). These results suggested that the functional overload induced muscle damage in mdx mice, but promoted the regeneration in CTX-injected WT mice.

  15. Improvement of Endurance Based on Muscle Fiber-Type Composition by Treatment with Dietary Apple Polyphenols in Rats

    PubMed Central

    Okamoto, Shinpei; Akahoshi, Mariko; Suzuki, Takahiro; Do, Mai-Khoi Q.; Ohtsubo, Hideaki; Komiya, Yusuke; Lan, Mu; Waga, Toshiaki; Iwata, Akira; Nakazato, Koichi; Ikeuchi, Yoshihide; Anderson, Judy E.; Tatsumi, Ryuichi

    2015-01-01

    A recent study demonstrated a positive effect of apple polyphenol (APP) intake on muscle endurance of young-adult animals. While an enhancement of lipid metabolism may be responsible, in part, for the improvement, the contributing mechanisms still need clarification. Here we show that an 8-week intake of 5% (w/w) APP in the diet, up-regulates two features related to fiber type: the ratio of myosin heavy chain (MyHC) type IIx/IIb and myoglobin protein expression in plantaris muscle of 9-week-old male Fischer F344 rats compared to pair-fed controls (P < 0.05). Results were demonstrated by our SDS-PAGE system specialized for MyHC isoform separation and western blotting of whole muscles. Animal-growth profiles (food intake, body-weight gain, and internal-organ weights) did not differ between the control and 5% APP-fed animals (n = 9/group). Findings may account for the increase in fatigue resistance of lower hind limb muscles, as evidenced by a slower decline in the maximum isometric planter-flexion torque generated by a 100-s train of electrical stimulation of the tibial nerve. Additionally, the fatigue resistance was lower after 8 weeks of a 0.5% APP diet than after 5% APP, supporting an APP-dose dependency of the shift in fiber-type composition. Therefore, the present study highlights a promising contribution of dietary APP intake to increasing endurance based on fiber-type composition in rat muscle. Results may help in developing a novel strategy for application in animal sciences, and human sports and age-related health sciences. PMID:26222548

  16. Improvement of Endurance Based on Muscle Fiber-Type Composition by Treatment with Dietary Apple Polyphenols in Rats.

    PubMed

    Mizunoya, Wataru; Miyahara, Hideo; Okamoto, Shinpei; Akahoshi, Mariko; Suzuki, Takahiro; Do, Mai-Khoi Q; Ohtsubo, Hideaki; Komiya, Yusuke; Lan, Mu; Waga, Toshiaki; Iwata, Akira; Nakazato, Koichi; Ikeuchi, Yoshihide; Anderson, Judy E; Tatsumi, Ryuichi

    2015-01-01

    A recent study demonstrated a positive effect of apple polyphenol (APP) intake on muscle endurance of young-adult animals. While an enhancement of lipid metabolism may be responsible, in part, for the improvement, the contributing mechanisms still need clarification. Here we show that an 8-week intake of 5% (w/w) APP in the diet, up-regulates two features related to fiber type: the ratio of myosin heavy chain (MyHC) type IIx/IIb and myoglobin protein expression in plantaris muscle of 9-week-old male Fischer F344 rats compared to pair-fed controls (P < 0.05). Results were demonstrated by our SDS-PAGE system specialized for MyHC isoform separation and western blotting of whole muscles. Animal-growth profiles (food intake, body-weight gain, and internal-organ weights) did not differ between the control and 5% APP-fed animals (n = 9/group). Findings may account for the increase in fatigue resistance of lower hind limb muscles, as evidenced by a slower decline in the maximum isometric planter-flexion torque generated by a 100-s train of electrical stimulation of the tibial nerve. Additionally, the fatigue resistance was lower after 8 weeks of a 0.5% APP diet than after 5% APP, supporting an APP-dose dependency of the shift in fiber-type composition. Therefore, the present study highlights a promising contribution of dietary APP intake to increasing endurance based on fiber-type composition in rat muscle. Results may help in developing a novel strategy for application in animal sciences, and human sports and age-related health sciences.

  17. De novo synthesis of purine nucleotides in different fiber types of rat skeletal muscle

    SciTech Connect

    Tullson, P.C.; John-Alder, H.; Hood, D.A.; Terjung, R.L.

    1986-03-01

    The contribution of de novo purine nucleotide synthesis to nucleotide metabolism in skeletal muscles is not known. The authors have determined rates of de novo synthesis in soleus (slow-twitch red), red gastrocnemius (fast-twitch red), and white gastrocnemius (fast-twitch white) using the perfused rat hindquarter. /sup 14/C glycine incorporation into ATP was linear after 1 and 2 hours of perfusion with 0.2 mM added glycine. The intracellular (I) and extracellular (E) specific activity of /sup 14/C glycine was determined by HPLC of phenylisothiocyanate derivatives of neutralized PCA extracts. The rates of de novo synthesis when expressed relative to muscle ATP content show slow and fast-twitch red muscles to be similar and about twice as great as fast-twitch white muscles. This could represent a greater turnover of the adenine nucleotide pool in more oxidative red muscle types.

  18. Relation between α-isoform and phosphatase activity of Na+,K+-ATPase in rat skeletal muscle fiber types.

    PubMed

    Chaillou, M; Rigoard, P; Fares, M; Francois, C; Sottejeau, Y; Maixent, J M

    2011-07-25

    In skeletal muscle the relationship between Na+,K+-ATPase activity and isoform content remains controversial (9,6). It could be due to the fiber-type content, membrane isolation and analytical methods. We investigated the distribution of subunit α1 and α2 Na+,K+-ATPase catalytic isoforms and the Na+,K+-ATPase activity in isolated membranes from white ( type I and glycolitic fibers) and red (type II and oxidative fibers) skeletal muscles. Red Gastrocnemius and White Gastrocnemius muscles were sampled from 8 week-old female Wistar rats and crude membranes were performed. The Na+,K+-ATPase activity and membrane distribution of Na+,K+-ATPase α1 and α2 isoforms were assessed by ouabain sensitive K-phosphatase (Kpase) measurements and Western Blot respectively. The Na+,K+-ATPase activity was 6 fold lower in White Gastrocnemius membranes than in Red Gastrocnemius membranes. The α1 and α2-isoform levels are higher in RG than in White Gastrocnemius. The α1 and α2-subunit Red Gastrocnemius content was significantly higher than in WG. The correlation between crude membrane Kpase activity and both catalytic α-subunit of the Na+,K+-ATPase exist.These data suggest that the Na+,K+-ATPase phosphatase activity correlates with the α1 and α2 isoforms levels in Red Gastrocnemius and White Gastrocnemius and confirms the fiber-specific Na+,K+-ATPase catalytic α-subunits and α2-isoform as the major catalytic isoform in rat skeletal muscle.

  19. Long-term delivery of FGF-6 changes the fiber type and fatigability of muscle reinnervated from embryonic neurons transplanted into adult rat peripheral nerve.

    PubMed

    Grumbles, Robert M; Casella, Gizelda T B; Rudinsky, Michelle J; Wood, Patrick M; Sesodia, Sanjay; Bent, Melissa; Thomas, Christine K

    2007-07-01

    Motoneuron death leads to muscle denervation and atrophy. Transplantation of embryonic neurons into peripheral nerves results in reinnervation and provides a strategy to rescue muscles from atrophy independent of neuron replacement in a damaged or diseased spinal cord. But the count of regenerating axons always exceeds the number of motor units in this model, so target-derived trophic factor levels may limit reinnervation. Our aim was to examine whether long-term infusion of fibroblast growth factor-6 (FGF-6) into denervated medial gastrocnemius muscles improved the function of muscles reinnervated from neurons transplanted into nerve of adult Fischer rats. Factor delivery (10 microg, 4 weeks) began after sciatic nerve transection. After a week of nerve degeneration, 1 million embryonic day 14-15 ventral spinal cord cells were transplanted into the distal tibial stump as a neuron source. Ten weeks later, neurons that expressed motoneuron markers survived in the nerves. More myelinated axons were in nerves to saline-treated muscles than in FGF-6-treated muscles. However, each group showed comparable reductions in muscle fiber atrophy because of reinnervation. Mean reinnervated fiber area was 43%-51% of non-denervated fibers. Denervated fiber area averaged 11%. FGF-6-treated muscles were more fatigable than other reinnervated muscles but had stronger motor units and fewer type I fibers than did saline-treated muscles. FGF-6 thus influenced function by changing the type of fiber reinnervated by transplanted neurons. Deficits in FGF-6 may also contribute to the increase in type I fibers in muscles reinnervated from peripheral axons, suggesting that the effects of FGF-6 on fiber type are independent of the neuron source used for reinnervation.

  20. Effect of ractopamine-hydrochloride on the fiber type distribution and shelf-life of six muscles of steers.

    PubMed

    Gonzalez, J M; Johnson, S E; Thrift, T A; Savell, J D; Ouellette, S E; Johnson, D D

    2009-05-01

    The goal of this study was to evaluate the effects of ractopamine-hydrochloride (RAC) supplementation on the myosin heavy chain isoform distribution and shelf-life properties of muscles from beef top round, knuckle, and loin. Thirty-four steer carcasses were selected from 4 separate slaughter groups. Within each slaughter group (3 groups, n = 8; 1 group, n = 10), steers were separated into pens (n = 8) and fed 0 or 200 mg x animal(-1) x d(-1) of RAC for the final 28 d of feeding. Seventy-two hours postmortem, the longissimus lumborum, semimembranosus (SM), adductor, gracilis, vastus lateralis (VL), and rectus femoris were removed from each carcass. A subsample of each muscle was collected for immunohistochemical analysis. Whole muscles were vacuum packaged and wet aged at 1 +/- 2 degrees C for 13 d before processing into steaks for a 5-d simulated retail display study. Daily, steaks were analyzed for reduction of nitric oxide metmyoglobin, lean color, fat color, and surface discoloration. Objective measures of metmyoglobin, oxymyoglobin, L*, a*, and b* values were recorded daily. Ractopamine significantly (P < 0.05) changed the fiber type isoform distribution in all muscles except the SM. The VL and gracilis presented the greatest fiber type switch with approximately 21% of type I fibers switching to type IIA fibers. However, the fiber type shifts induced by RAC supplementation had little to no effect on subjective and objective color measurements during the 5-d retail display period. Metmyoglobin and oxymyoglobin accumulation, L*, a*, and b*-values were not affected (P > 0.05) by RAC supplementation. Percent nitric oxide metmyoglobin reduction data indicate that reducing ability of RAC-treated steaks from the adductor and longissimus lumborum were significantly affected (P < 0.05). Visual panel data suggest that RAC tended (P < 0.10) to have the most detrimental effect on the lean color and surface discoloration scores of steaks from the VL during the last 3 d of

  1. Prolonged C2 spinal hemisection-induced inactivity reduces diaphragm muscle specific force with modest, selective atrophy of type IIx and/or IIb fibers.

    PubMed

    Mantilla, Carlos B; Greising, Sarah M; Zhan, Wen-Zhi; Seven, Yasin B; Sieck, Gary C

    2013-02-01

    The diaphragm muscle (DIAm) is critically responsible for sustaining ventilation. Previously we showed in a commonly used model of spinal cord injury, unilateral spinal cord hemisection at C(2) (SH), that there are minimal changes to muscle fiber cross-sectional area (CSA) and fiber type distribution following 14 days of SH-induced ipsilateral DIAm inactivity. In the present study, effects of long-term SH-induced inactivity on DIAm fiber size and force were examined. We hypothesized that prolonged inactivity would not result in substantial DIAm atrophy or force loss. Adult rats were randomized to control or SH groups (n = 34 total). Chronic bilateral DIAm electromyographic (EMG) activity was monitored during resting breathing. Minimal levels of spontaneous recovery of ipsilateral DIAm EMG activity were evident in 42% of SH rats (<25% of preinjury root mean square amplitude). Following 42 days of SH, DIAm specific force was reduced 39%. There was no difference in CSA for type I or IIa DIAm fibers in SH rats compared with age, weight-matched controls (classification based on myosin heavy chain isoform expression). Type IIx and/or IIb DIAm fibers displayed a modest 20% reduction in CSA (P < 0.05). Overall, there were no differences in the distribution of fiber types or the contribution of each fiber type to the total DIAm CSA. These data indicate that reduced specific force following prolonged inactivity of the DIAm is associated with modest, fiber type selective adaptations in muscle fiber size and fiber type distribution.

  2. Myofiber androgen receptor promotes maximal mechanical overload-induced muscle hypertrophy and fiber type transition in male mice.

    PubMed

    Ferry, Arnaud; Schuh, Mélanie; Parlakian, Ara; Mgrditchian, Takouhie; Valnaud, Nicolas; Joanne, Pierre; Butler-Browne, Gillian; Agbulut, Onnik; Metzger, Daniel

    2014-12-01

    The first aim of this study was to examine the role of myofiber androgen receptor (AR) in male mice on muscle performance gain and remodeling-induced muscle mechanical overloading (OVL) that mimics resistance training. The response of OVL in mice in which AR is selectively ablated in myofibers (AR(skm-/y)) was compared with that of wild-type (WT) mice. In addition, we determined whether the synthetic anabolic androgen nandrolone administration affects the OVL response. We found that OVL increased absolute maximal force and fatigue resistance in both mouse genotypes (P < .05). However, the absolute maximal force increased more in AR(skm-/y) mice as compared with WT mice (+88% vs +63%) (P < .05). Muscle weight increased less in response to OVL in AR(skm-/y) mice (+54%) than in WT mice (+115%) (P < .05). The fiber number per cross-section similarly increased in both mouse genotypes after OVL (P < .05). In contrast to WT mice, the diameter of the fibers expressing myosin heavy chain (MHC)-2x decreased after OVL in AR(skm-/y) mice (P < .05). The MHC-2b to MHC-2a fiber type transition in response to OVL was reduced in AR(skm-/y) mice as compared with WT mice (P < .05). Finally, nandrolone administration during OVL did not further improve absolute maximal force and fatigue resistance and markedly alter muscle remodeling in both mouse genotypes. Together, our results indicate that myofiber AR is required for a complete response to OVL and that exogenous androgens do not increase muscle performance during intensive remodeling in male mice.

  3. Effects of mechanical over-loading on the properties of soleus muscle fibers, with or without damage, in wild type and mdx mice.

    PubMed

    Terada, Masahiro; Kawano, Fuminori; Ohira, Takashi; Nakai, Naoya; Nishimoto, Norihiro; Ohira, Yoshinobu

    2012-01-01

    Effects of mechanical over-loading on the characteristics of regenerating or normal soleus muscle fibers were studied in dystrophin-deficient (mdx) and wild type (WT) mice. Damage was also induced in WT mice by injection of cardiotoxin (CTX) into soleus muscle. Over-loading was applied for 14 days to the left soleus muscle in mdx and intact and CTX-injected WT mouse muscles by ablation of the distal tendons of plantaris and gastrocnemius muscles. All of the myonuclei in normal muscle of WT mice were distributed at the peripheral region. But, central myonuclei were noted in all fibers of WT mice regenerating from CTX-injection-related injury. Further, many fibers of mdx mice possessed central myonuclei and the distribution of such fibers was increased in response to over-loading, suggesting a shift of myonuclei from peripheral to central region. Approximately 1.4% branched fibers were seen in the intact muscle of mdx mice, although these fibers were not detected in WT mice. The percentage of these fibers in mdx, not in WT, mice was increased by over-loading (∼51.2%). The fiber CSA in normal WT mice was increased by over-loading (p<0.05), but not in mdx and CTX-injected WT mice. It was suggested that compensatory hypertrophy is induced in normal muscle fibers of WT mice following functional over-loading. But, it was also indicated that muscle fibers in mdx mice are susceptible to mechanical over-loading and fiber splitting and shift of myonuclei from peripheral to central region are induced.

  4. The I4895T Mutation in the Type 1 Ryanodine Receptor Induces Fiber-Type Specific Alterations in Skeletal Muscle that Mimic Premature Aging

    PubMed Central

    Boncompagni, Simona; Loy, Ryan E.; Dirksen, Robert T.; Franzini-Armstrong, Clara

    2010-01-01

    SUMMARY The I4898T (IT) mutation in type 1 ryanodine receptor (RyR1), the Ca2+ release channel of the sarcoplasmic reticulum (SR) is linked to a form of central core disease (CCD) in humans and results in a non leaky channel and excitation-contraction uncoupling. We characterized age- and fiber type-dependent alterations in muscle ultrastructure, as well as the magnitude and spatiotemporal properties of evoked Ca2+ release in heterozygous Ryr1I4895T/WT (IT/+) knock-in mice on a mixed genetic background. The results indicate a classical but mild CCD phenotype that includes muscle weakness and the presence of mitochondrial-deficient areas in type I fibers. Electrically-evoked Ca2+ release is significantly reduced in single FDB fibers from young and old IT/+ mice. Structural changes are strongly fiber type-specific, affecting type I and IIB/IIX fibers in very distinct ways, and sparing type IIA fibers. Ultrastructural alterations in our IT/+ mice are also present in wild type, but at a lower frequency and older ages, suggesting that the disease mutation on the mixed background promotes an acceleration of normal age-dependent changes. The observed functional and structural alterations and their similarity to age-associated changes are entirely consistent with the known properties of the mutated channel, which result in reduced calcium release as is also observed in normal aging muscle. In strong contrast to these observations, a subset of patients with the analogous human heterozygous mutation and IT/+ mice on an inbred 129S2/SvPasCrl background exhibit a more severe disease phenotype, which is not directly consistent with the mutated channel properties. PMID:20961389

  5. Acute effects of taurine on sarcoplasmic reticulum Ca2+ accumulation and contractility in human type I and type II skeletal muscle fibers.

    PubMed

    Dutka, T L; Lamboley, C R; Murphy, R M; Lamb, G D

    2014-10-01

    Taurine occurs in high concentrations in muscle and is implicated in numerous physiological processes, yet its effects on many aspects of contractility remain unclear. Using mechanically skinned segments of human vastus lateralis muscle fibers, we characterized the effects of taurine on sarcoplasmic reticulum (SR) Ca2+ accumulation and contractile apparatus properties in type I and type II fibers. Prolonged myoplasmic exposure (>10 min) to taurine substantially increased the rate of accumulation of Ca2+ by the SR in both fiber types, with no change in the maximum amount accumulated; no such effect was found with carnosine. SR Ca2+ accumulation was similar with 10 or 20 mM taurine, but was significantly slower at 5 mM taurine. Cytoplasmic taurine (20 mM) had no detectable effects on the responsiveness of the Ca2+ release channels in either fiber type. Taurine caused a small increase in Ca2+ sensitivity of the contractile apparatus in type I fibers, but type II fibers were unaffected; maximum Ca(2+)-activated force was unchanged in both cases. The effects of taurine on SR Ca2+ accumulation (1) only became apparent after prolonged cytoplasmic exposure, and (2) persisted for some minutes after complete removal of taurine from the cytoplasm, consistent with the hypothesis that the effects were due to an action of taurine from inside the SR. In summary, taurine potentiates the rate of SR Ca2+ uptake in both type I and type II human fibers, possibly via an action from within the SR lumen, with the degree of potentiation being significantly reduced at low physiological taurine levels. Copyright © 2014 the American Physiological Society.

  6. The Preventive Effects of 8 Weeks of Resistance Training on Glucose Tolerance and Muscle Fiber Type Composition in Zucker Rats.

    PubMed

    Kim, Ji-Yeon; Choi, Mi Jung; So, Byunghun; Kim, Hee-Jae; Seong, Je Kyung; Song, Wook

    2015-10-01

    We investigated the therapeutic effects of resistance training on Zucker rats before and after the onset of diabetes to understand the importance of the timing of exercise intervention. We assessed whether 8 weeks of resistance training ameliorated impaired glucose tolerance and altered muscle fiber type composition in Zucker rats. Five-week-old male Zucker rats were divided into Zucker lean control (ZLC-Con), non-exercised Zucker diabetic fatty (ZDF-Con), and exercised Zucker diabetic fatty (ZDF-Ex) groups. The ZDF-Ex rats climbed a ladder three times a week for 8 weeks. Intraperitoneal glucose tolerance tests (IPGTT) were performed on the 1st and 8th weeks of training, and grip strength was measured during the last week. We also measured glucose transporter 4 (GLUT4) expression by Western blot and immunofluorescence. Moreover, immunohistochemistry was performed to assess muscle fiber type composition. Fasting glucose levels and area under the curve responses to IPGTTs gradually increased as diabetes progressed in the ZDF-Con rats but decreased in the ZDF-Ex rats. Grip strength decreased in the ZDF-Con rats. However, resistance training did not improve grip strength in the ZDF-Ex rats. GLUT4 expression in the ZLC-Con and the ZDF-Con rats did not differ, but it increased in the ZDF-Ex rats. The proportions of myosin heavy chain I and II were lower and higher, respectively, in the ZDF-Con rats compared to the ZLC-Con rats. Muscle fiber type composition did not change in the ZDF-Ex rats. Our results suggest that regular resistance training initiated at the onset of diabetes can improve glucose tolerance and GLUT4 expression without changing muscle morphology in Zucker rats.

  7. In vivo Ca2+ buffering capacity and microvascular oxygen pressures following muscle contractions in diabetic rat skeletal muscles: fiber-type specific effects.

    PubMed

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

    2015-07-15

    In Type 1 diabetes, skeletal muscle resting intracellular Ca(2+) concentration ([Ca(2+)]i) homeostasis is impaired following muscle contractions. It is unclear to what degree this behavior is contingent upon fiber type and muscle oxygenation conditions. We tested the hypotheses that: 1) the rise in resting [Ca(2+)]i evident in diabetic rat slow-twitch (type I) muscle would be exacerbated in fast-twitch (type II) muscle following contraction; and 2) these elevated [Ca(2+)]i levels would relate to derangement of microvascular partial pressure of oxygen (PmvO2 ) rather than sarcoplasmic reticulum dysfunction per se. Adult male Wistar rats were divided randomly into diabetic (DIA: streptozotocin ip) and healthy (CONT) groups. Four weeks later extensor digitorum longus (EDL, predominately type II fibers) and soleus (SOL, predominately type I fibers) muscle contractions were elicited by continuous electrical stimulation (120 s, 100 Hz). Ca(2+) imaging was achieved using fura 2-AM in vivo (i.e., circulation intact). DIA increased fatigability in EDL (P < 0.05) but not SOL. In recovery, SOL [Ca(2+)]i either returned to its resting baseline within 150 s (CONT 1.00 ± 0.02 at 600 s) or was not elevated in recovery at all (DIA 1.03 ± 0.02 at 600 s, P > 0.05). In recovery, EDL CONT [Ca(2+)]i also decreased to values not different from baseline (1.06 ± 0.01, P > 0.05) at 600 s. In marked contrast, EDL DIA [Ca(2+)]i remained elevated for the entire recovery period (i.e., 1.23 ± 0.03 at 600 s, P < 0.05). The inability of [Ca(2+)]i to return to baseline in EDL DIA was not associated with any reduction of SR Ca(2+)-ATPase (SERCA) 1 or SERCA2 protein levels (both increased 30-40%, P < 0.05). However, Pmv(O2) recovery kinetics were markedly slowed in EDL such that mean Pmv(O2) was substantially depressed (CONT 27.9 ± 2.0 vs. DIA 18.4 ± 2.0 Torr, P < 0.05), and this behavior was associated with the elevated [Ca(2+)]i. In contrast, this was not the case for SOL (P > 0.05) in that

  8. Comparison of mean frequency and median frequency in evaluating muscle fiber type selection in varying gait speed across healthy young adult individuals.

    PubMed

    Chan, C K; Timothy, G Fu; Yeow, C H

    2016-08-01

    The preferential slow and fast twitches fiber involvement in varying gait speed has not been thoroughly investigated. Attempt to classify fiber type in changing speed should be closely investigated and scrutinized as the histochemical-related experiments are cumbersome and time consuming. In addressing this issue, electromyography (EMG) is utilized to extract the muscle fiber type features by altering the muscle fatigue indices, namely mean frequency (MNF) and median frequency (MDF). Recently, there are no universal indices to determine the muscle type. In this paper, the MNF and MDF are employed in discovering the muscle type variation as the speed changes. Besides drawing the potential of MNF and MDF in unveiling the muscle type, both the parameters are applied to investigate the muscles that are recruited and which muscle type are involved as the gait velocity changes. In this study, six healthy and young participants are recruited, whereby the EMG sensors are placed on twelve lower extremity muscles. The EMG signals are then processed via Matlab software to deduce MNF and MDF. The MNF and MDF are determined from every of the phase gait, namely stance and swing. From the results obtained, it reveals that the superiority of the MNF over the MDF in determining and interpreting the muscle recruitment in both gait phases as the speed increases. The MNF, moreover, is able to show an apparent difference in muscle type selection compared to MDF. Interestingly, it is discovered that as the speed increases from slow to fast, the MNF decreases, which indicates that more muscle fiber type I is recruited. Contrarily, the MNF increases as the speed intensity decreases, which indicates that the distribution of muscle type II is prominent.

  9. Eccentric contraction-induced injury to type I, IIa, and IIa/IIx muscle fibers of elderly adults

    USDA-ARS?s Scientific Manuscript database

    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 ...

  10. G(s)alpha deficiency in skeletal muscle leads to reduced muscle mass, fiber-type switching, and glucose intolerance without insulin resistance or deficiency.

    PubMed

    Chen, Min; Feng, Han-Zhong; Gupta, Divakar; Kelleher, James; Dickerson, Kathryn E; Wang, Jie; Hunt, Desmond; Jou, William; Gavrilova, Oksana; Jin, Jian-Ping; Weinstein, Lee S

    2009-04-01

    The ubiquitously expressed G protein alpha-subunit G(s)alpha is required for receptor-stimulated intracellular cAMP responses and is an important regulator of energy and glucose metabolism. We have generated skeletal muscle-specific G(s)alpha-knockout (KO) mice (MGsKO) by mating G(s)alpha-floxed mice with muscle creatine kinase-cre transgenic mice. MGsKO mice had normal body weight and composition, and their serum glucose, insulin, free fatty acid, and triglyceride levels were similar to that of controls. However, MGsKO mice were glucose intolerant despite the fact that insulin sensitivity and glucose-stimulated insulin secretion were normal, suggesting an insulin-independent mechanism. Isolated muscles from MGsKO mice had increased basal glucose uptake and normal responses to a stimulator of AMP-activated protein kinase (AMPK), which indicates that AMPK and its downstream pathways are intact. Compared with control mice, MGsKO mice had reduced muscle mass with decreased cross-sectional area and force production. In addition, adult MGsKO mice showed an increased proportion of type I (slow-twitch, oxidative) fibers based on kinetic properties and myosin heavy chain isoforms, despite the fact that these muscles had reduced expression of peroxisome proliferator-activated receptor coactivator protein-1alpha (PGC-1alpha) and reduced mitochondrial content and oxidative capacity. Therefore G(s)alpha deficiency led to fast-to-slow fiber-type switching, which appeared to be dissociated from the expected change in oxidative capacity. MGsKO mice are a valuable model for future studies of the role of G(s)alpha signaling pathways in skeletal muscle adaptation and their effects on whole body metabolism.

  11. Improved VO2 uptake kinetics and shift in muscle fiber type in high-altitude trekkers.

    PubMed

    Doria, C; Toniolo, L; Verratti, V; Cancellara, P; Pietrangelo, T; Marconi, V; Paoli, A; Pogliaghi, S; Fanò, G; Reggiani, C; Capelli, C

    2011-12-01

    The study investigated the effect of prolonged hypoxia on central [i.e., cardiovascular oxygen delivery (Q(a)O(2))] and peripheral (i.e., O(2) utilization) determinants of oxidative metabolism response during exercise in humans. To this aim, seven male mountaineers were examined before and immediately after the Himalayan Expedition Interamnia 8000-Manaslu 2008, lasting 43 days, among which, 23 days were above 5,000 m. The subjects showed a decrease in body weight (P < 0.05) and of power output during a Wingate Anaerobic test (P < 0.05) and an increase of thigh cross-sectional area (P < 0.05). Absolute maximal O(2) uptake (VO(2max)) did not change. The mean response time of VO(2) kinetics at the onset of step submaximal cycling exercise was reduced significantly from 53.8 s ± 10.9 to 39.8 s ± 10.9 (P < 0.05), whereas that of Q(a)O(2) was not. Analysis of single fibers dissected from vastus lateralis biopsies revealed that the expression of slow isoforms of both heavy and light myosin subunits increased, whereas that of fast isoforms decreased. Unloaded shortening velocity of fibers was decreased significantly. In summary, independent findings converge in indicating that adaptation to chronic hypoxia brings about a fast-to-slow transition of muscle fibers, resulting in a faster activation of the mitochondrial oxidative metabolism. These results indicate that a prolonged and active sojourn in hypoxia may induce muscular ultrastructural and functional changes similar to those observed after aerobic training.

  12. Hydrostatic compression in glycerinated rabbit muscle fibers.

    PubMed

    Ranatunga, K W; Fortune, N S; Geeves, M A

    1990-12-01

    Glycerinated muscle fibers isolated from rabbit psoas muscle, and a number of other nonmuscle elastic fibers including glass, rubber, and collagen, were exposed to hydrostatic pressures of up to 10 MPa (100 Atm) to determine the pressure sensitivity of their isometric tension. The isometric tension of muscle fibers in the relaxed state (passive tension) was insensitive to increased pressure, whereas the muscle fiber tension in rigor state increased linearly with pressure. The tension of all other fiber types (except rubber) also increased with pressure; the rubber tension was pressure insensitive. The pressure sensitivity of rigor tension was 2.3 kN/m2/MPa and, in comparison with force/extension relation determined at atmospheric pressure, the hydrostatic compression in rigor muscle fibers was estimated to be 0.03% Lo/MPa. As reported previously, the active muscle fiber tension is depressed by increased pressure. The possible underlying basis of the different pressure-dependent tension behavior in relaxed, rigor, and active muscle is discussed.

  13. Age-related changes in rat intrinsic laryngeal muscles: analysis of muscle fibers, muscle fiber proteins, and subneural apparatuses.

    PubMed

    Nishida, Naoya; Taguchi, Aki; Motoyoshi, Kazumi; Hyodo, Masamitsu; Gyo, Kiyofumi; Desaki, Junzo

    2013-03-01

    We compared age-related changes in the intrinsic laryngeal muscles of aged and young adult rats by determining the number and diameter of muscle fibers, contractile muscle protein (myosin heavy chain isoforms, MHC) composition, and the morphology of the subneural apparatuses. In aged rats, both the numbers and the diameters of muscle fibers decreased in the cricothyroid (CT) muscle. The number of fibers, but not diameter, decreased in the thyroarytenoid (TA) muscle. In the posterior cricoarytenoid (PCA) muscle, neither the number nor the diameter of fibers changed significantly. Aging was associated with a decrease in type IIB and an increase in type IIA MHC isoform levels in CT muscle, but no such changes were observed in the TA or PCA muscles. Morphological examination of primary synaptic clefts of the subneural apparatus revealed that aging resulted in decreased labyrinthine and increased depression types in only the CT muscle. In the aged group, morphologically immature subneural apparatuses were found infrequently in the CT muscle, indicating continued tissue remodeling. We suggest, therefore, that age-related changes in the intrinsic laryngeal muscles primarily involve the CT muscle, whereas the structures of the TA and PCA muscles may better resist aging processes and therefore are less vulnerable to functional impairment. This may reflect differences in their roles; the CT muscle controls the tone of the vocal folds, while the TA and PCA muscles play an essential role in vital activities such as respiration and swallowing.

  14. Gene regulation mediating fiber-type transformation in skeletal muscle cells is partly glucose- and ChREBP-dependent.

    PubMed

    Hanke, Nina; Scheibe, Renate J; Manukjan, Georgi; Ewers, David; Umeda, Patrick K; Chang, Kin-Chow; Kubis, Hans-Peter; Gros, Gerolf; Meissner, Joachim D

    2011-03-01

    Adaptations in the oxidative capacity of skeletal muscle cells can occur under several physiological or pathological conditions. We investigated the effect of increasing extracellular glucose concentration on the expression of markers of energy metabolism in primary skeletal muscle cells and the C2C12 muscle cell line. Growth of myotubes in 25mM glucose (high glucose, HG) compared with 5.55mM led to increases in the expression and activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a marker of glycolytic energy metabolism, while oxidative markers peroxisome proliferator-activated receptor γ coactivator 1α and citrate synthase decreased. HG induced metabolic adaptations as are seen during a slow-to-fast fiber transformation. Furthermore, HG increased fast myosin heavy chain (MHC) IId/x but did not change slow MHCI/β expression. Protein phosphatase 2A (PP2A) was shown to mediate the effects of HG on GAPDH and MHCIId/x. Carbohydrate response element-binding protein (ChREBP), a glucose-dependent transcription factor downstream of PP2A, partially mediated the effects of glucose on metabolic markers. The glucose-induced increase in PP2A activity was associated with an increase in p38 mitogen-activated protein kinase activity, which presumably mediates the increase in MHCIId/x promoter activity. Liver X receptor, another possible mediator of glucose effects, induced only an incomplete metabolic shift, mainly increasing the expression of the glycolytic marker. Taken together, HG induces a partial slow-to-fast transformation comprising metabolic enzymes together with an increased expression of MHCIId/x. This work demonstrates a functional role for ChREBP in determining the metabolic type of muscle fibers and highlights the importance of glucose as a signaling molecule in muscle. Copyright © 2011 Elsevier B.V. All rights reserved.

  15. Intramyocellular lipid dependence on skeletal muscle fiber type and orientation characterized by diffusion tensor imaging and 1H-MRS

    NASA Astrophysics Data System (ADS)

    Valaparla, Sunil K.; Gao, Feng; Abdul-Ghani, Muhammad; Clarke, Geoffrey D.

    2014-03-01

    When muscle fibers are aligned with the B0 field, intramyocellular lipids (IMCL), important for providing energy during physical activity, can be resolved in proton magnetic resonance spectra (1H-MRS). Various muscles of the leg differ significantly in their proportion of fibers and angular distribution. This study determined the influence of muscle fiber type and orientation on IMCL using 1H-MRS and diffusion tensor imaging (DTI). Muscle fiber orientation relative to B0 was estimated by pennation angle (PA) measurements from DTI, providing orientation-specific extramyocellular lipid (EMCL) chemical shift data that were used for subject-specific IMCL quantification. Vastus lateralis (VL), tibialis anterior (TA) and soleus (SO) muscles of 6 healthy subjects (21-40 yrs) were studied on a Siemens 3T MRI system with a flex 4-channel coil. 1H-MRS were acquired using stimulated echo acquisition mode (STEAM, TR=3s, TE=270ms). DTI was performed using single shot EPI (b=600s/mm2, 30 directions, TR=4.5s, TE=82ms, and ten×5mm slices) with center slice indexed to the MRS voxel. The average PA's measured from ROI analysis of primary eigenvectors were PA=19.46+/-5.43 for unipennate VL, 15.65+/-3.73 for multipennate SO, and 7.04+/-3.34 for bipennate TA. Chemical shift (CS) was calculated using [3cos2θ-1] dependence: 0.17+/-0.02 for VL, 0.18+/-0.01 for SO and 0.19+/-0.004 ppm for TA. IMCL-CH2 concentrations from spectral analysis were 12.77+/-6.3 for VL, 3.07+/-1.63 for SO and 0.27+/-0.08 mmol/kg ww for TA. Small PA's were measured in TA and large CS with clear separation between EMCL and IMCL peaks were observed. Larger variations in PA were measured VL and SO resulting in an increased overlap of the EMCL on IMCL peaks.

  16. Protein Supplementation Augments Muscle Fiber Hypertrophy but Does Not Modulate Satellite Cell Content During Prolonged Resistance-Type Exercise Training in Frail Elderly.

    PubMed

    Dirks, Marlou L; Tieland, Michael; Verdijk, Lex B; Losen, Mario; Nilwik, Rachel; Mensink, Marco; de Groot, Lisette C P G M; van Loon, Luc J C

    2017-07-01

    Protein supplementation increases gains in lean body mass following prolonged resistance-type exercise training in frail older adults. We assessed whether the greater increase in lean body mass can be attributed to muscle fiber type specific hypertrophy with concomitant changes in satellite cell (SC) content. A total of 34 frail elderly individuals (77 ± 1 years, n = 12 male adults) participated in this randomized, double-blind, placebo-controlled trial with 2 arms in parallel. Participants performed 24 weeks of progressive resistance-type exercise training (2 sessions per week) during which they were supplemented twice-daily with milk protein (2 × 15 g) or a placebo. Muscle biopsies were taken at baseline, and after 12 and 24 weeks of intervention, to determine type I and type II muscle fiber specific cross-sectional area (CSA), SC content, and myocellular characteristics. In the placebo group, a trend for a 20% ± 11% increase in muscle fiber CSA was observed in type II fibers only (P = .051), with no increase in type I muscle fiber CSA. In the protein group, type I and II muscle fiber CSA increased by 23% ± 7% and 34% ± 10% following 6 months of training, respectively (P < .01). Myonuclear domain size increased over time in both groups and fiber types (P < .001), with no significant differences between groups (P > .05). No changes in myonuclear content and SC contents were observed over time in either group (both P > .05). Regression analysis showed that changes in myonuclear content and domain size are predictive of muscle fiber hypertrophy. Protein supplementation augments muscle fiber hypertrophy following prolonged resistance-type exercise training in frail older people, without changes in myonuclear and SC content. Copyright © 2017 AMDA – The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.

  17. An ultrastructural and histochemical study of the flexor tibialis muscle fiber types in male and female stick insects (Eurycantha calcarata, L).

    PubMed

    Pilehvarian, Ali Asghar

    2015-10-01

    In this study the ultrastructural and histochemical characteristics of the flexor tibialis muscle fibers of the specialized metathoracic legs in the male and those of homologous and unspecialized ones in the female stick insects, Eurycantha calcarata, L, were examined. For the ultrastructural analysis, the muscle was divided longitudinally and vertically to produce a total of 12 sample parts e.g., anterior-dorsal-distal (ADD), posterior-ventral-medial (PVM) and so on. Light and electron microscopes were used to observe the muscle tissue. The methods for myosin adenosine triphosphatase (mATPase) and nicotine adenine dinucleotide- tetrazolium (NADH-TR) staining were modified from the methods of (Stokes et al., '79; Anttila et al., 2009; Anttila and Manttari, 2009). Sections with thickness of 22 μm, were cut from the anterior and the posterior surfaces of the muscle, using a cryostat. The histochemical and ultrastructural results showed that the muscles of both the male and the female were mixtures of physiological fiber types, with predominantly fast fibers. The muscles were composed of fibers with different staining properties for both mATPase and NADH-TR activities. The population of fibers within the muscles was heterogeneous. The differences between the population of the male and that of the female were significant. The means of most criteria e.g., mitochondrial amount and sarcoplasmic reticulum area predicted that the muscle of the male contained more fast fibers than the female. The histochemical examination also showed that the muscle of the male contained more fibers stained darkly for mATPase and lightly for NADH-TR. © 2015 Wiley Periodicals, Inc.

  18. Bovine sire selection based on maintenance energy affects muscle fiber type and meat color of F1 progeny.

    PubMed

    Thornton, K J; Welch, C M; Davis, L C; Doumit, M E; Hill, R A; Murdoch, G K

    2012-05-01

    proportion of type IIa fibers (r = -0.42 and P = 0.03) in the steers. This indicates that relative mRNA expression of glyc may serve as a marker of muscle glycogen storage capacity in steers. Thus, selection for efficient Red Angus beef cattle based on sire ME(M) EPD does not adversely affect meat quality in F(1) progeny, based on the variables assessed in this study. Furthermore, selection for progeny from low-ME(M) EPD sires may improve fresh meat quality within Red Angus beef cattle.

  19. Carbonic Anhydrase III Is Expressed in Mouse Skeletal Muscles Independent of Fiber Type-Specific Myofilament Protein Isoforms and Plays a Role in Fatigue Resistance

    PubMed Central

    Feng, Han-Zhong; Jin, J.-P.

    2016-01-01

    Carbonic anhydrase III (CAIII) is a metabolic enzyme and a regulator for intracellular pH. CAIII has been reported with high level expression in slow twitch skeletal muscles. Here we demonstrate that CAIII is expressed in multiple slow and fast twitch muscles of adult mouse independent of the expression of myosin isoforms. Expressing similar fast type of myofilament proteins, CAIII-positive tibial anterior (TA) muscle exhibits higher tolerance to fatigue than that of CAIII-negative fast twitch extensor digitorum longus (EDL) muscle in in situ contractility studies. We further studied the muscles of CAIII knockout (Car3-KO) mice. The loss of CAIII in soleus and TA muscles in Car3-KO mice did not change muscle mass, sarcomere protein isoform contents, and the baseline twitch and tetanic contractility as compared with age-matched wild type (WT) controls. On the other hand, Car3-KO TA muscle showed faster force reduction at the beginning but higher resistance at the end during a fatigue test, followed by slower post fatigue recovery than that of WT TA muscle. Superfused Car3-KO soleus muscle also had faster total force reduction during fatigue test than that of WT soleus. However, it showed a less elevation of resting tension followed by a better post fatigue recovery under acidotic stress. CAIII was detected in neonatal TA and EDL muscle, downregulated during development, and then re-expressed in adult TA but not EDL muscles. The expression of CAIII in Tnnt1-KO myopathy mouse soleus muscle that has diminished slow fiber contents due to the loss of slow troponin T remained high. Car3-KO EDL, TA, and soleus muscles showed no change in the expression of mitochondria biomarker proteins. The data suggest a fiber type independent expression of CAIII with a role in the regulation of intracellular pH in skeletal muscle and may be explored as a target for improving fatigue resistance and for the treatment of TNNT1 myopathies. PMID:28018233

  20. Carbonic Anhydrase III Is Expressed in Mouse Skeletal Muscles Independent of Fiber Type-Specific Myofilament Protein Isoforms and Plays a Role in Fatigue Resistance.

    PubMed

    Feng, Han-Zhong; Jin, J-P

    2016-01-01

    Carbonic anhydrase III (CAIII) is a metabolic enzyme and a regulator for intracellular pH. CAIII has been reported with high level expression in slow twitch skeletal muscles. Here we demonstrate that CAIII is expressed in multiple slow and fast twitch muscles of adult mouse independent of the expression of myosin isoforms. Expressing similar fast type of myofilament proteins, CAIII-positive tibial anterior (TA) muscle exhibits higher tolerance to fatigue than that of CAIII-negative fast twitch extensor digitorum longus (EDL) muscle in in situ contractility studies. We further studied the muscles of CAIII knockout (Car3-KO) mice. The loss of CAIII in soleus and TA muscles in Car3-KO mice did not change muscle mass, sarcomere protein isoform contents, and the baseline twitch and tetanic contractility as compared with age-matched wild type (WT) controls. On the other hand, Car3-KO TA muscle showed faster force reduction at the beginning but higher resistance at the end during a fatigue test, followed by slower post fatigue recovery than that of WT TA muscle. Superfused Car3-KO soleus muscle also had faster total force reduction during fatigue test than that of WT soleus. However, it showed a less elevation of resting tension followed by a better post fatigue recovery under acidotic stress. CAIII was detected in neonatal TA and EDL muscle, downregulated during development, and then re-expressed in adult TA but not EDL muscles. The expression of CAIII in Tnnt1-KO myopathy mouse soleus muscle that has diminished slow fiber contents due to the loss of slow troponin T remained high. Car3-KO EDL, TA, and soleus muscles showed no change in the expression of mitochondria biomarker proteins. The data suggest a fiber type independent expression of CAIII with a role in the regulation of intracellular pH in skeletal muscle and may be explored as a target for improving fatigue resistance and for the treatment of TNNT1 myopathies.

  1. Impact of maximal strength training on work efficiency and muscle fiber type in the elderly: Implications for physical function and fall prevention.

    PubMed

    Wang, Eivind; Nyberg, Stian Kwak; Hoff, Jan; Zhao, Jia; Leivseth, Gunnar; Tørhaug, Tom; Husby, Otto Schnell; Helgerud, Jan; Richardson, Russell S

    2017-02-21

    Although aging is typically associated with a decreased efficiency of locomotion, somewhat surprisingly, there is also a reduction in the proportion of less efficient fast-twitch Type II skeletal muscle fibers and subsequently a greater propensity for falls. Maximal strength training (MST), with an emphasis on velocity in the concentric phase, improves maximal strength, the rate of force development (RFD), and work efficiency, but the impact on muscle morphology in the elderly is unknown. Therefore we evaluated force production, walking work efficiency, and muscle morphology in 11 old (72±3years) subjects before and after MST of the legs. Additionally, for reference, the MST-induced morphometric changes were compared with 7 old (74±6years) subjects who performed conventional strength training (CST), with focus on hypertrophy, as well as 13 young (24±2years) controls. As expected, MST in the old improved maximal strength (68%), RFD (48%), and work efficiency (12%), restoring each to a level similar to the young. However, of importance, these MST-induced functional changes were accompanied by a significant increase in the size (66%) and shift toward a larger percentage (56%) of Type II skeletal muscle fibers, mirroring the adaptations in the hypertrophy trained old subjects, with muscle composition now being similar to the young. In conclusion, MST can increase both work efficiency and Type II skeletal muscle fiber size and percentage in the elderly, supporting the potential role of MST as a countermeasure to maintain both physical function and fall prevention in this population.

  2. Muscles Susceptibility to Ischemia-Reperfusion Injuries Depends on Fiber Type Specific Antioxidant Level

    PubMed Central

    Charles, Anne-Laure; Guilbert, Anne-Sophie; Guillot, Max; Talha, Samy; Lejay, Anne; Meyer, Alain; Kindo, Michel; Wolff, Valérie; Bouitbir, Jamal; Zoll, Joffrey; Geny, Bernard

    2017-01-01

    Muscle injury resulting from ischemia-reperfusion largely aggravates patient prognosis but whether and how muscle phenotype modulates ischemia-reperfusion-induced mitochondrial dysfunction remains to be investigated. We challenged the hypothesis that glycolytic muscles are more prone to ischemia-reperfusion-induced injury than oxidative skeletal muscles. We therefore determined simultaneously the effect of 3 h of ischemia induced by aortic clamping followed by 2 h of reperfusion (IR, n = 11) on both gastrocnemius and soleus muscles, as compared to control animals (C, n = 11). Further, we investigated whether tempol, an antioxidant mimicking superoxide dismutase, might compensate a reduced defense system, likely characterizing glycolytic muscles (IR-Tempol, n = 7). In the glycolytic gastrocnemius muscle, as compared to control, ischemia-reperfusion significantly decreased mitochondrial respiration (−30.28 ± 6.16%, p = 0.003), increased reactive oxygen species production (+79.15 ± 28.72%, p = 0.04), and decreased reduced glutathione (−28.19 ± 6.80%, p = 0.011). Less deleterious effects were observed in the oxidative soleus muscle (−6.44 ± 6.30%, +4.32 ± 16.84%, and −8.07 ± 10.84%, respectively), characterized by enhanced antioxidant defenses (0.63 ± 0.05 in gastrocnemius vs. 1.24 ± 0.08 μmol L−1 g−1 in soleus). Further, when previously treated with tempol, glycolytic muscle was largely protected against the deleterious effects of ischemia-reperfusion. Thus, oxidative skeletal muscles are more protected than glycolytic ones against ischemia-reperfusion, thanks to their antioxidant pool. Such pivotal data support that susceptibility to ischemia-reperfusion-induced injury differs between organs, depending on their metabolic phenotypes. This suggests a need to adapt therapeutic strategies to the specific antioxidant power of the target organ to be protected. PMID:28220081

  3. Downhill Running Excessive Training Inhibits Hypertrophy in Mice Skeletal Muscles with Different Fiber Type Composition.

    PubMed

    da Rocha, Alisson L; Pereira, Bruno C; Pauli, José R; de Souza, Claudio T; Teixeira, Giovana R; Lira, Fábio S; Cintra, Dennys E; Ropelle, Eduardo R; Júnior, Carlos R B; da Silva, Adelino S R

    2016-05-01

    The aim of this study was to verify the effects of running overtraining protocols performed in downhill, uphill, and without inclination on the proteins related to hypertrophy signaling pathway in extensor digitorum longus (EDL) and soleus of C57BL/6 mice. We also performed histological and stereological analyses. Rodents were divided into control (CT; sedentary mice), overtrained by downhill running (OTR/down), overtrained by uphill running (OTR/up), and overtrained by running without inclination (OTR). The incremental load, exhaustive, and grip force tests were used as performance evaluation parameters. 36 h after the grip force test, EDL and soleus were removed and immediately used for immunoblotting analysis or stored at -80°C for histological and stereological analyses. For EDL, OTR/down decreased the protein kinase B (Akt) and tuberous sclerosis protein 2 (TSC2) phosphorylation (p), and increased myostatin, receptor-activated Smads (pSMAD2-3), and insulin receptor substrate-1 (pIRS-1; Ser307/636). OTR/down also presented low and high relative proportions of cytoplasm and connective tissue, respectively. OTR/up increased the mammalian target of rapamycin (pmTOR), 70-kDa ribosomal protein S6 kinase 1 (pS6K1) and pSMAD2-3, and decreased pTSC2. OTR decreased pTSC2 and increased pIRS-1 (Ser636). For soleus, OTR/down increased S6 ribosomal protein (pS6RP) and pSMAD2-3, and decreased pIRS-1 (Ser639). OTR/up decreased pS6K1, pS6RP and pIRS-1 (Ser639), and increased pTSC2 (Ser939), and pSMAD2-3. OTR increased pS6RP, 4E-binding protein-1 (p4E-BP1), pTSC2 (Ser939), and pSMAD2-3, and decreased pIRS-1 (Ser639). In summary, OTR/down inhibited the skeletal muscle hypertrophy with concomitant signs of atrophy in EDL. The effects of OTR/up and OTR depended on the analyzed skeletal muscle type. © 2015 Wiley Periodicals, Inc.

  4. Fiber Type Conversion by PGC-1α Activates Lysosomal and Autophagosomal Biogenesis in Both Unaffected and Pompe Skeletal Muscle

    PubMed Central

    Takikita, Shoichi; Schreiner, Cynthia; Baum, Rebecca; Xie, Tao; Ralston, Evelyn; Plotz, Paul H.; Raben, Nina

    2010-01-01

    PGC-1α is a transcriptional co-activator that plays a central role in the regulation of energy metabolism. Our interest in this protein was driven by its ability to promote muscle remodeling. Conversion from fast glycolytic to slow oxidative fibers seemed a promising therapeutic approach in Pompe disease, a severe myopathy caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA) which is responsible for the degradation of glycogen. The recently approved enzyme replacement therapy (ERT) has only a partial effect in skeletal muscle. In our Pompe mouse model (KO), the poor muscle response is seen in fast but not in slow muscle and is associated with massive accumulation of autophagic debris and ineffective autophagy. In an attempt to turn the therapy-resistant fibers into fibers amenable to therapy, we made transgenic KO mice expressing PGC-1α in muscle (tgKO). The successful switch from fast to slow fibers prevented the formation of autophagic buildup in the converted fibers, but PGC-1α failed to improve the clearance of glycogen by ERT. This outcome is likely explained by an unexpected dramatic increase in muscle glycogen load to levels much closer to those observed in patients, in particular infants, with the disease. We have also found a remarkable rise in the number of lysosomes and autophagosomes in the tgKO compared to the KO. These data point to the role of PGC-1α in muscle glucose metabolism and its possible role as a master regulator for organelle biogenesis - not only for mitochondria but also for lysosomes and autophagosomes. These findings may have implications for therapy of lysosomal diseases and other disorders with altered autophagy. PMID:21179212

  5. Endurance training induces fiber type-specific revascularization in hindlimb skeletal muscles of rats with chronic heart failure.

    PubMed

    Ranjbar, Kamal; Ardakanizade, Malihe; Nazem, Farzad

    2017-01-01

    Previous studies showed that skeletal muscle microcirculation was reduced in chronic heart failure. The aim of this study was to investigate the effects of endurance training on capillary and arteriolar density of fast and slow twitch muscles in rats with chronic heart failure. Four weeks after surgeries (left anterior descending (LAD) artery occlusion), chronic heart failure rats were divided into 3 groups: Sham (Sham, n=10); Sedentary (Sed, n=10); Exercise training (Ex, n=10). Ex group rats were subjected to endurance training in the form of treadmill running with moderate intensity for 10 weeks. Exercise training significantly increased capillary density and capillary to fiber ratio (P<0.05) in slow twitch muscle, but didn't change fast twitch muscle capillary density and capillary to fiber ratio. Furthermore, arteriolar density in fast twitch muscle increased remarkably (P<0.05) in response to training, but slow twitch muscle arteriolar density did not change in response to exercise in chronic heart failure rats. HIF-1 increased (P<0.01) but VEGF and FGF-2 mRNA did not change in slow twitch muscle after training. In fast twitch muscle, HIF-1 mRNA increased (P<0.05), and VEGF and angiostatin decreased (P<0.01) significantly after training. Endurance training ameliorates fast and slow twitch muscle revascularization non-uniformly in chronic heart failure rats by increasing capillary density in slow twitch muscle and arteriolar density in fast twitch muscle. The difference in revascularization at slow and fast twitch muscles may be induced by the difference in angiogenic and angiostatic gene expression response to endurance training.

  6. Endurance training induces fiber type-specific revascularization in hindlimb skeletal muscles of rats with chronic heart failure

    PubMed Central

    Ranjbar, Kamal; Ardakanizade, Malihe; Nazem, Farzad

    2017-01-01

    Objective(s): Previous studies showed that skeletal muscle microcirculation was reduced in chronic heart failure. The aim of this study was to investigate the effects of endurance training on capillary and arteriolar density of fast and slow twitch muscles in rats with chronic heart failure. Materials and Methods: Four weeks after surgeries (left anterior descending (LAD) artery occlusion), chronic heart failure rats were divided into 3 groups: Sham (Sham, n=10); Sedentary (Sed, n=10); Exercise training (Ex, n=10). Ex group rats were subjected to endurance training in the form of treadmill running with moderate intensity for 10 weeks. Results: Exercise training significantly increased capillary density and capillary to fiber ratio (P<0.05) in slow twitch muscle, but didn’t change fast twitch muscle capillary density and capillary to fiber ratio. Furthermore, arteriolar density in fast twitch muscle increased remarkably (P<0.05) in response to training, but slow twitch muscle arteriolar density did not change in response to exercise in chronic heart failure rats. HIF-1 increased (P<0.01) but VEGF and FGF-2 mRNA did not change in slow twitch muscle after training. In fast twitch muscle, HIF-1 mRNA increased (P<0.05), and VEGF and angiostatin decreased (P<0.01) significantly after training. Conclusion: Endurance training ameliorates fast and slow twitch muscle revascularization non-uniformly in chronic heart failure rats by increasing capillary density in slow twitch muscle and arteriolar density in fast twitch muscle. The difference in revascularization at slow and fast twitch muscles may be induced by the difference in angiogenic and angiostatic gene expression response to endurance training. PMID:28133530

  7. PGC-1α plays a functional role in exercise-induced mitochondrial biogenesis and angiogenesis but not fiber-type transformation in mouse skeletal muscle

    PubMed Central

    Geng, Tuoyu; Li, Ping; Okutsu, Mitsuharu; Yin, Xinhe; Kwek, Jyeyi; Zhang, Mei

    2010-01-01

    Endurance exercise stimulates peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) expression in skeletal muscle, and forced expression of PGC-1α changes muscle metabolism and exercise capacity in mice. However, it is unclear if PGC-1α is indispensible for endurance exercise-induced metabolic and contractile adaptations in skeletal muscle. In this study, we showed that endurance exercise-induced expression of mitochondrial enzymes (cytochrome oxidase IV and cytochrome c) and increases of platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31)-positive endothelial cells in skeletal muscle, but not IIb-to-IIa fiber-type transformation, were significantly attenuated in muscle-specific Pgc-1α knockout mice. Interestingly, voluntary running effectively restored the compromised mitochondrial integrity and superoxide dismutase 2 (SOD2) protein expression in skeletal muscle in Pgc-1α knockout mice. Thus, PGC-1α plays a functional role in endurance exercise-induced mitochondrial biogenesis and angiogenesis, but not IIb-to-IIa fiber-type transformation in mouse skeletal muscle, and the improvement of mitochondrial morphology and antioxidant defense in response to endurance exercise may occur independently of PGC-1α function. We conclude that PGC-1α is required for complete skeletal muscle adaptations induced by endurance exercise in mice. PMID:20032509

  8. PGC-1alpha plays a functional role in exercise-induced mitochondrial biogenesis and angiogenesis but not fiber-type transformation in mouse skeletal muscle.

    PubMed

    Geng, Tuoyu; Li, Ping; Okutsu, Mitsuharu; Yin, Xinhe; Kwek, Jyeyi; Zhang, Mei; Yan, Zhen

    2010-03-01

    Endurance exercise stimulates peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) expression in skeletal muscle, and forced expression of PGC-1alpha changes muscle metabolism and exercise capacity in mice. However, it is unclear if PGC-1alpha is indispensible for endurance exercise-induced metabolic and contractile adaptations in skeletal muscle. In this study, we showed that endurance exercise-induced expression of mitochondrial enzymes (cytochrome oxidase IV and cytochrome c) and increases of platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31)-positive endothelial cells in skeletal muscle, but not IIb-to-IIa fiber-type transformation, were significantly attenuated in muscle-specific Pgc-1alpha knockout mice. Interestingly, voluntary running effectively restored the compromised mitochondrial integrity and superoxide dismutase 2 (SOD2) protein expression in skeletal muscle in Pgc-1alpha knockout mice. Thus, PGC-1alpha plays a functional role in endurance exercise-induced mitochondrial biogenesis and angiogenesis, but not IIb-to-IIa fiber-type transformation in mouse skeletal muscle, and the improvement of mitochondrial morphology and antioxidant defense in response to endurance exercise may occur independently of PGC-1alpha function. We conclude that PGC-1alpha is required for complete skeletal muscle adaptations induced by endurance exercise in mice.

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

    PubMed

    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.

  10. Differential effect of chronic undernutrition on the fiber type composition of fascicles in the extensor digitorum longus muscles of the rat.

    PubMed

    Vázquez-Mendoza, Enrique; Rodríguez-Torres, Erika Elizabeth; López-García, Kenia; Hinojosa-Rodríguez, Cindy Xilonen; Jiménez-Estrada, Ismael

    2017-03-31

    Several studies have shown that chronic low food consumption alters the composition and metabolism of the extensor digitorum longus muscle (EDLm) fiber types. EDLm is constituted by four independent fascicles (F2-F5) of different sizes; their constitution and metabolism, however, as well as how chronic undernourishment affects these is virtually unknown. Thus, the aim of this study is to evaluate the relative fiber type composition and metabolism of each independent fascicle in the EDLm, using control and chronically undernourished young male rats by using the alkaline ATPase and NADH-TR histochemical techniques. Our results indicate that all control fascicles showed a higher percentage of intermediate fibers (P<0.001), except for F5, which had a higher percentage of fast fibers (P<0.001). After chronic undernutrition, the proportion of intermediate fibers decreased in F4 (P<0.05) and increased in F5 (P<0.001), whereas fast fibers decreased in F3 (P<0.05) and F5 (P<0.001). When we investigated fiber metabolism we found that F3 and F4 had a similar composition (mainly glycolytic), whereas F2 and F5 predominantly contained oxidative fibers. All fascicles of chronic undernourished rats showed a general decrease in oxidative fibers (P>0.05), except for F3, in which oxidative fibers increased (P<0.05). After determining the possible predominant metabolism expressed in intermediate fibers, we propose that chronic undernutrition induces the transformation of fast-glycolytic to intermediate-oxidative/glycolytic fibers, mainly in F3 and F5. Our observations confirm that chronic undernourishment differentially affects the fiber types of each fascicle in the EDLm, which could alter their individual physiological contractile properties.

  11. Effect of dietary zinc and ractopamine hydrochloride on pork chop muscle fiber type distribution, tenderness, and color characteristics.

    PubMed

    Paulk, C B; Tokach, M D; Nelssen, J L; Burnett, D D; Vaughn, M A; Phelps, K J; Dritz, S S; Derouchey, J M; Goodband, R D; Woodworth, J C; Houser, T A; Haydon, K D; Gonzalez, J M

    2014-05-01

    A total of 320 finishing pigs (PIC 327 × 1050; initially 98 kg) were used to determine the effects of adding Zn to diets containing ractopamine HCl (RAC) on muscle fiber type distribution, fresh chop color, and cooked meat characteristics. Dietary treatments were fed for approximately 35 d and consisted of a corn-soybean meal-based negative control (CON), a positive control diet with 10 mg/kg of RAC (RAC+), and the RAC+ diet plus 75, 150, or 225 mg/kg added Zn from either ZnO or Availa-Zn. Loins randomly selected from each treatment (n = 20) were evaluated using contrasts: CON vs. RAC+, interaction of Zn level × source, Zn level linear and quadratic polynomials, and Zn source. There were no Zn source effects or Zn source × level interactions throughout the study (P > 0.10). Pigs fed RAC+ had increased (P < 0.02) percentage type IIX and a tendency for increased (P = 0.10) percent type IIB muscle fibers. Increasing added Zn decreased (linear, P = 0.01) percentage type IIA and tended to increase (P = 0.09) IIX muscle fibers. On d 1, 2, 3, 4, and 5 of display, pork chops from pigs fed the RAC+ treatment had greater (P < 0.03) L* values compared to the CON. On d 0 and 3 of display, increasing added Zn tended to decrease (quadratic, P = 0.10) L* values and decreased (quadratic, P < 0.03) L* values on d 1, 2, 4, and 5. Pigs fed RAC+ had decreased (P < 0.05) a* values on d 1 and 4 of display and tended to have decreased (P < 0.10) a* values on d 0 and 2 compared to CON pork chops. Pork chops from the RAC+ treatment had a tendency for increased (P < 0.08) oxymyoglobin percentage compared to CON pork chops on d 1, 2, 4, and 5. On d 0, as dietary Zn increased in RAC+ diets, there was a decrease (linear, P < 0.01) in the formation of pork chop surface oxymyoglobin percentage. Metmyoglobin reducing ability (MRA) of pork chops on d 5 was decreased in the RAC+ group. Chops from pigs fed added Zn had increased (quadratic, P < 0.03) MRA on d 3 and 5 of the display period. There

  12. Experiment K-6-21. Effect of microgravity on 1) metabolic enzymes of type 1 and type 2 muscle fibers and on 2) metabolic enzymes, neutransmitter amino acids, and neurotransmitter associated enzymes in motor and somatosensory cerebral cortex. Part 1: Metabolic enzymes of individual muscle fibers; part 2: metabolic enzymes of hippocampus and spinal cord

    NASA Technical Reports Server (NTRS)

    Lowry, O.; Mcdougal, D., Jr.; Nemeth, Patti M.; Maggie, M.-Y. Chi; Pusateri, M.; Carter, J.; Manchester, J.; Norris, Beverly; Krasnov, I.

    1990-01-01

    The individual fibers of any individual muscle vary greatly in enzyme composition, a fact which is obscured when enzyme levels of a whole muscle are measured. The purpose of this study was therefore to assess the changes due to weightless on the enzyme patterns composed by the individual fibers within the flight muscles. In spite of the limitation in numbers of muscles examined, it is apparent that: (1) that the size of individual fibers (i.e., their dry weight) was reduced about a third, (2) that this loss in dry mass was accompanied by changes in the eight enzymes studied, and (3) that these changes were different for the two muscles, and different for the two enzyme groups. In the soleus muscle the absolute amounts of the three enzymes of oxidative metabolism decreased about in proportion to the dry weight loss, so that their concentration in the atrophic fibers was almost unchanged. In contrast, there was little loss among the four enzymes of glycogenolysis - glycolysis so that their concentrations were substantially increased in the atrophic fibers. In the TA muscle, these seven enzymes were affected in just the opposite direction. There appeared to be no absolute loss among the oxidative enzymes, whereas the glycogenolytic enzymes were reduced by nearly half, so that the concentrations of the first metabolic group were increased within the atrophic fibers and the concentrations of the second group were only marginally decreased. The behavior of hexokinase was exceptional in that it did not decrease in absolute terms in either type of muscle and probably increased as much as 50 percent in soleus. Thus, their was a large increase in concentration of this enzyme in the atrophied fibers of both muscles. Another clear-cut finding was the large increase in the range of activities of the glycolytic enzymes among individual fibers of TA muscles. This was due to the emergence of TA fibers with activities for enzymes of this group extending down to levels as low as

  13. Haplotype diversity in the equine myostatin gene with focus on variants associated with race distance propensity and muscle fiber type proportions

    PubMed Central

    Petersen, Jessica L; Valberg, Stephanie J; Mickelson, James R; McCue, Molly E

    2014-01-01

    Summary Two variants in the equine myostatin gene (MSTN), including a T/C SNP substitution in the first intron and a 227-bp SINE insertion in the promoter, are associated with muscle fiber type proportions in the Quarter Horse (QH) and with the prediction of race distance propensity in the Thoroughbred (TB). Genotypes from these loci, along with 18 additional variants surrounding MSTN, were examined in 301 horses of 14 breeds to evaluate haplotype relationships and diversity. The C allele of intron 1 was found in 12 of 14 breeds at a frequency of 0.27; the SINE was observed in five breeds, but common in only the TB and QH (0.73 and 0.48 respectively). Haplotype data suggest the SINE insertion is contemporary to and arose upon a haplotype containing the intron 1 C allele. Gluteal muscle biopsies of TBs showed a significant association of the intron 1 C allele and SINE with a higher proportion of Type 2B and lower proportion of Type 1 fibers. However, in the Belgian horse, in which the SINE is not present, the intron 1 SNP was not associated with fiber type proportions, and evaluation of fiber type proportions across the Belgian, TB and QH breeds shows the significant effect of breed on fiber type proportions is negated when evaluating horses without the SINE variant. These data suggest the SINE, rather than the intron 1 SNP, is driving the observed muscle fiber type characteristics and is the variant targeted by selection for short-distance racing. PMID:25160752

  14. Haplotype diversity in the equine myostatin gene with focus on variants associated with race distance propensity and muscle fiber type proportions.

    PubMed

    Petersen, Jessica L; Valberg, Stephanie J; Mickelson, James R; McCue, Molly E

    2014-12-01

    Two variants in the equine myostatin gene (MSTN), including a T/C SNP in the first intron and a 227-bp SINE insertion in the promoter, are associated with muscle fiber type proportions in the Quarter Horse (QH) and with the prediction of race distance propensity in the Thoroughbred (TB). Genotypes from these loci, along with 18 additional variants surrounding MSTN, were examined in 301 horses of 14 breeds to evaluate haplotype relationships and diversity. The C allele of intron 1 was found in 12 of 14 breeds at a frequency of 0.27; the SINE was observed in five breeds, but common in only the TB and QH (0.73 and 0.48 respectively). Haplotype data suggest the SINE insertion is contemporary to and arose upon a haplotype containing the intron 1 C allele. Gluteal muscle biopsies of TBs showed a significant association of the intron 1 C allele and SINE with a higher proportion of Type 2B and lower proportion of Type 1 fibers. However, in the Belgian horse, in which the SINE is not present, the intron 1 SNP was not associated with fiber type proportions, and evaluation of fiber type proportions across the Belgian, TB and QH breeds shows the significant effect of breed on fiber type proportions is negated when evaluating horses without the SINE variant. These data suggest the SINE, rather than the intron 1 SNP, is driving the observed muscle fiber type characteristics and is the variant targeted by selection for short-distance racing.

  15. Effect of acute and chronic eccentric exercise on FOXO1 mRNA expression as fiber type transition factor in rat skeletal muscles.

    PubMed

    Azad, Milad; Khaledi, Neda; Hedayati, Mehdi

    2016-06-15

    Skeletal muscle is a highly elastic tissue which can respond to various functional demands by altering fiber-type composition. Exercise affects muscle fiber phenotype. One of the transcription factors that induce fiber-type transition is forkhead box O1 (FOXO1). Since eccentric contraction considered an essential part of exercise, so we are interested to see the effects of eccentric exercise (acute/chronic) on FOXO1 as an important factor of fiber-type transition in rat skeletal muscles. Twenty-four Sprague-Dawley rats (190-235g) were divided to 3 groups of 8 rats: 1) chronic eccentric exercise (CEE), 2) acute eccentric exercise (AEE), and 3) control (C). The exercise groups underwent downhill running protocol. CEE was running on treadmill in 3 days of week for 9 weeks, that slope and duration gradually managed from -4° to -16° and 15 to 90 min, respectively. AEE group was running with 16 m/min on -16° slope for 3 consecutive days that included 18 sets of 5 min with rest interval of 2 min in between. Soleus and super vastus lateralis (SVL) muscles mRNA were analyzed by real-time RT-PCR. SVL FOXO1 mRNA levels increased by 3.92-fold in the AEE and decreased 0.56-fold in the CEE group and were not significant in soleus muscle. In soleus muscle, myosin heavy chain (MHC) IIa, IIx, and IIb decreased in the AEE group and MHC IIa and IIx decreased in the CEE group. In SVL muscle, MHC I, IIa, and IIx increased in the AEE group and MHC IIa and IIX increased in the CEE group. In summary, both acute and chronic eccentric exercise could lead to change in FOXO1 mRNA only in fast SVL muscle of rat and so could induce fiber-type transition in both muscles regardless of changes in expression of FOXO1. So, oxidative stress can play important role in change of FOXO1.

  16. The reproducibility of different metabolic markers for muscle fiber type distributions investigated by functional (31)P-MRS during dynamic exercise.

    PubMed

    Rzanny, Reinhard; Stutzig, Norman; Hiepe, Patrick; Gussew, Alexander; Thorhauer, Hans-Alexander; Reichenbach, Jürgen R

    2016-12-01

    The objective of the study was to investigate the reproducibility of exercise induced pH-heterogeneity by splitting of the inorganic phosphate (Pi) signal in the corresponding (31)P-MRS spectra and to compare results of this approach with other fiber-type related markers, like phosphocreatine/adenosine triphosphate (PCr/ATP) ratio, and PCr-recovery parameters. Subjects (N=3) with different sportive background were tested in 10 test sessions separated by at least 3 days. A MR-compatible pedal ergometer was used to perform the exercise and to induce a pH-based splitting of the Pi-signal in (31)P-MR spectra of the medial gastrocnemius muscle. The PCr recovery was analyzed using a non-negative least square algorithm (NNLS) and multi-exponential regression analysis to estimate the number of non-exponential components as well as their amplitude and time constant. The reproducibility of the estimated metabolic marker and the resulting fiber-type distributions between the 10 test sessions were compared. The reproducibility (standard deviation between measurements) based on (1) Pi components varied from 2% to 4%, (2) PCr recovery time components varied from 10% to 12% and (3) phosphate concentrations at rest varied from 8% to 11% between test sessions. Due to the sportive activity differences between the 3 subjects were expected in view of fiber type distribution. All estimated markers indicate the highest type I percentage for volunteer 3 medium for volunteer 2 and the lowest for volunteer 1. The relative high reproducibility of pH dependent Pi components during exercise indicates a high potential of this method to estimate muscle fiber-type distributions in vivo. To make this method usable not only to detect differences in muscle fiber distributions but also to determine individual fiber-type volume contents it is therefore recommended to validate this marker by histological methods and to reveal the effects of muscle fiber recruitments and fiber-type specific Pi

  17. Glycolytic-to-oxidative fiber-type switch and mTOR signaling activation are early-onset features of SBMA muscle modified by high-fat diet.

    PubMed

    Rocchi, Anna; Milioto, Carmelo; Parodi, Sara; Armirotti, Andrea; Borgia, Doriana; Pellegrini, Matteo; Urciuolo, Anna; Molon, Sibilla; Morbidoni, Valeria; Marabita, Manuela; Romanello, Vanina; Gatto, Pamela; Blaauw, Bert; Bonaldo, Paolo; Sambataro, Fabio; Robins, Diane M; Lieberman, Andrew P; Sorarù, Gianni; Vergani, Lodovica; Sandri, Marco; Pennuto, Maria

    2016-07-01

    Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by the expansion of a polyglutamine tract in the androgen receptor (AR). The mechanism by which expansion of polyglutamine in AR causes muscle atrophy is unknown. Here, we investigated pathological pathways underlying muscle atrophy in SBMA knock-in mice and patients. We show that glycolytic muscles were more severely affected than oxidative muscles in SBMA knock-in mice. Muscle atrophy was associated with early-onset, progressive glycolytic-to-oxidative fiber-type switch. Whole genome microarray and untargeted lipidomic analyses revealed enhanced lipid metabolism and impaired glycolysis selectively in muscle. These metabolic changes occurred before denervation and were associated with a concurrent enhancement of mechanistic target of rapamycin (mTOR) signaling, which induced peroxisome proliferator-activated receptor γ coactivator 1 alpha (PGC1α) expression. At later stages of disease, we detected mitochondrial membrane depolarization, enhanced transcription factor EB (TFEB) expression and autophagy, and mTOR-induced protein synthesis. Several of these abnormalities were detected in the muscle of SBMA patients. Feeding knock-in mice a high-fat diet (HFD) restored mTOR activation, decreased the expression of PGC1α, TFEB, and genes involved in oxidative metabolism, reduced mitochondrial abnormalities, ameliorated muscle pathology, and extended survival. These findings show early-onset and intrinsic metabolic alterations in SBMA muscle and link lipid/glucose metabolism to pathogenesis. Moreover, our results highlight an HFD regime as a promising approach to support SBMA patients.

  18. Long-Term Effects of Botulinum Toxin Complex Type A Injection on Mechano- and Metabo-Sensitive Afferent Fibers Originating from Gastrocnemius Muscle

    PubMed Central

    Caron, Guillaume; Marqueste, Tanguy; Decherchi, Patrick

    2015-01-01

    The aim of the present study was to investigate long term effects of motor denervation by botulinum toxin complex type A (BoNT/A) from Clostridium Botulinum, on the afferent fibers originating from the gastrocnemius muscle of rats. Animals were divided in 2 experimental groups: 1) untreated animals acting as control and 2) treated animals in which the toxin was injected in the left muscle, the latter being itself divided into 3 subgroups according to their locomotor recovery with the help of a test based on footprint measurements of walking rats: i) no recovery (B0), ii) 50% recovery (B50) and iii) full recovery (B100). Then, muscle properties, metabosensitive afferent fiber responses to potassium chloride (KCl) and lactic acid injections and Electrically-Induced Fatigue (EIF), and mechanosensitive responses to tendon vibrations were measured. At the end of the experiment, rats were killed and the toxin injected muscles were weighted. After toxin injection, we observed a complete paralysis associated to a loss of force to muscle stimulation and a significant muscle atrophy, and a return to baseline when the animals recover. The response to fatigue was only decreased in the B0 group. The responses to KCl injections were only altered in the B100 groups while responses to lactic acid were altered in the 3 injected groups. Finally, our results indicated that neurotoxin altered the biphasic pattern of response of the mechanosensitive fiber to tendon vibrations in the B0 and B50 groups. These results indicated that neurotoxin injection induces muscle afferent activity alterations that persist and even worsen when the muscle has recovered his motor activity. PMID:26485650

  19. Long-Term Effects of Botulinum Toxin Complex Type A Injection on Mechano- and Metabo-Sensitive Afferent Fibers Originating from Gastrocnemius Muscle.

    PubMed

    Caron, Guillaume; Marqueste, Tanguy; Decherchi, Patrick

    2015-01-01

    The aim of the present study was to investigate long term effects of motor denervation by botulinum toxin complex type A (BoNT/A) from Clostridium Botulinum, on the afferent fibers originating from the gastrocnemius muscle of rats. Animals were divided in 2 experimental groups: 1) untreated animals acting as control and 2) treated animals in which the toxin was injected in the left muscle, the latter being itself divided into 3 subgroups according to their locomotor recovery with the help of a test based on footprint measurements of walking rats: i) no recovery (B0), ii) 50% recovery (B50) and iii) full recovery (B100). Then, muscle properties, metabosensitive afferent fiber responses to potassium chloride (KCl) and lactic acid injections and Electrically-Induced Fatigue (EIF), and mechanosensitive responses to tendon vibrations were measured. At the end of the experiment, rats were killed and the toxin injected muscles were weighted. After toxin injection, we observed a complete paralysis associated to a loss of force to muscle stimulation and a significant muscle atrophy, and a return to baseline when the animals recover. The response to fatigue was only decreased in the B0 group. The responses to KCl injections were only altered in the B100 groups while responses to lactic acid were altered in the 3 injected groups. Finally, our results indicated that neurotoxin altered the biphasic pattern of response of the mechanosensitive fiber to tendon vibrations in the B0 and B50 groups. These results indicated that neurotoxin injection induces muscle afferent activity alterations that persist and even worsen when the muscle has recovered his motor activity.

  20. Aging of skeletal muscle fibers.

    PubMed

    Miljkovic, Natasa; Lim, Jae-Young; Miljkovic, Iva; Frontera, Walter R

    2015-04-01

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

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

    PubMed Central

    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

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

    PubMed

    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.

  3. Role of estrogen on skeletal muscle mitochondrial function in ovariectomized rats: a time course study in different fiber types.

    PubMed

    Cavalcanti-de-Albuquerque, J P A; Salvador, I C; Martins, Eduarda Lopes; Jardim-Messeder, D; Werneck-de-Castro, J P S; Galina, A; Carvalho, D P

    2014-04-01

    Postmenopausal women are prone to develop obesity and insulin resistance, which might be related to skeletal muscle mitochondrial dysfunction. In a rat model of ovariectomy (OVX), skeletal muscle mitochondrial function was examined at short- and long-term periods after castration. Mitochondrial parameters in the soleus and white gastrocnemius muscle fibers were analyzed. Three weeks after surgery, there were no differences in coupled mitochondrial respiration (ATP synthesis) with pyruvate, malate, and succinate; proton leak respiration; or mitochondrial reactive oxygen species production. However, after 3 wk of OVX, the soleus and white gastrocnemius muscles of the OVX animals showed a lower use of palmitoyl-carnitine and glycerol-phosphate substrates, respectively, and decreased peroxisome proliferator-activated receptor-γ coactivator-1α expression. Estrogen replacement reverted all of these phenotypes. Eight weeks after OVX, ATP synthesis was lower in the soleus and white gastrocnemius muscles of the OVX animals than in the sham-operated and estrogen-treated animals; however, when normalized by citrate synthase activity, these differences disappeared, indicating a lower muscle mitochondria content. No differences were observed in the proton leak parameter. Mitochondrial alterations did not impair the treadmill exercise capacity of the OVX animals. However, blood lactate levels in the OVX animals were higher after the physical test, indicating a compensatory extramitochondrial ATP synthesis system, but this phenotype was reverted by estrogen replacement. These results suggest early mitochondrial dysfunction related to lipid substrate use, which could be associated with the development of the overweight phenotype of ovariectomized animals.

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

    PubMed

    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.

  5. Effects of Two Different Weight Training Programs on Swimming Performance and Muscle Enzyme Activities and Fiber Type.

    PubMed

    Belfry, Glen R; Noble, Earl G; Taylor, Albert W

    2016-02-01

    The effects of 2 different weight training programs incorporating bench press (BP) and pullover (PO) exercises on swimming performance, power, enzyme activity, and fiber type distribution were studied on 16 men (age = 23 ± 4 years). A 30-second group (n = 6) performed up to 20 repetitions of BP and PO in 30 seconds. The 2-minute group (n = 6) performed a maximum of 80 repetitions of BP and PO in 2 minutes. As participants reached the prescribed 20 or 80 repetitions, the weight was increased 4.5 kg. A third group (n = 4) served as nontraining controls. Exercise groups trained 3 times per week for 6 weeks. Maximal effort swims of 50 and 200 yd were performed before and after training. Training resulted in increases in work on both exercises in both groups pre- to post-training (BP 30 seconds, 722 ± 236-895 ± 250 kg; PO 30 seconds, 586 ± 252-1,090 ± 677 kg; and BP 2 minutes, 1,530 ± 414-1,940 ± 296; PO 2 minutes, 1,212 ± 406-2,348 ± 194, p ≤ 0.05). Swim performances of the 30-second group improved for both the 50-yd (32.0 ± 6.9 seconds, 30.0 ± 5.9 seconds, p ≤ 0.05) and 200-yd swims 200.0 ± 54 seconds, 182 ± 45.1 seconds (p ≤ 0.05), whereas 2-minute training improved only the 200-yd swim (198.3 ± 32.3 seconds, 186.2 ± 32.2 seconds). No changes in swim performance were observed for the control group. Triceps muscle succinate dehydrogenase activities increased (pre 3.48 ± 1.1 μmol · g(-1) wet weight per minute, post 6.25 ± 1.5 μmoles · g(-1) wet weight per minute, p ≤ 0.05) in only the 30-second training group, whereas phosphofructokinase activities and fiber type distribution did not change in either training group. This study has demonstrated that a 30-second 20-repetition weight training program, specific to the swimming musculature without concurrent swim training, improves swimming performances at both 50- and 200-yd distances.

  6. Aged Muscle Demonstrates Fiber-Type Adaptations in Response to Mechanical Overload, in the Absence of Myofiber Hypertrophy, Independent of Satellite Cell Abundance.

    PubMed

    Lee, Jonah D; Fry, Christopher S; Mula, Jyothi; Kirby, Tyler J; Jackson, Janna R; Liu, Fujun; Yang, Lin; Dupont-Versteegden, Esther E; McCarthy, John J; Peterson, Charlotte A

    2016-04-01

    Although sarcopenia, age-associated loss of muscle mass and strength, is neither accelerated nor exacerbated by depletion of muscle stem cells, satellite cells, we hypothesized that adaptation in sarcopenic muscle would be compromised. To test this hypothesis, we depleted satellite cells with tamoxifen treatment of Pax7(CreER)-DTA mice at 4 months of age, and 20 months later subjected the plantaris muscle to 2 weeks of mechanical overload. We found myofiber hypertrophy was impaired in aged mice regardless of satellite cell content. Even in the absence of growth, vehicle-treated mice mounted a regenerative response, not apparent in tamoxifen-treated mice. Further, myonuclear accretion occurred in the absence of growth, which was prevented by satellite cell depletion, demonstrating that myonuclear addition is insufficient to drive myofiber hypertrophy. Satellite cell depletion increased extracellular matrix content of aged muscle that was exacerbated by overload, potentially limiting myofiber growth. These results support the idea that satellite cells regulate the muscle environment, and that their loss during aging may contribute to fibrosis, particularly during periods of remodeling. Overload induced a fiber-type composition improvement, independent of satellite cells, suggesting that aged muscle is very responsive to exercise-induced enhancement in oxidative capacity, even with an impaired hypertrophic response. © The Author 2015. Published by Oxford University Press on behalf of the Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  7. Aged Muscle Demonstrates Fiber-Type Adaptations in Response to Mechanical Overload, in the Absence of Myofiber Hypertrophy, Independent of Satellite Cell Abundance

    PubMed Central

    Lee, Jonah D.; Fry, Christopher S.; Mula, Jyothi; Kirby, Tyler J.; Jackson, Janna R.; Liu, Fujun; Yang, Lin; Dupont-Versteegden, Esther E.; McCarthy, John J.

    2016-01-01

    Although sarcopenia, age-associated loss of muscle mass and strength, is neither accelerated nor exacerbated by depletion of muscle stem cells, satellite cells, we hypothesized that adaptation in sarcopenic muscle would be compromised. To test this hypothesis, we depleted satellite cells with tamoxifen treatment of Pax7CreER-DTA mice at 4 months of age, and 20 months later subjected the plantaris muscle to 2 weeks of mechanical overload. We found myofiber hypertrophy was impaired in aged mice regardless of satellite cell content. Even in the absence of growth, vehicle-treated mice mounted a regenerative response, not apparent in tamoxifen-treated mice. Further, myonuclear accretion occurred in the absence of growth, which was prevented by satellite cell depletion, demonstrating that myonuclear addition is insufficient to drive myofiber hypertrophy. Satellite cell depletion increased extracellular matrix content of aged muscle that was exacerbated by overload, potentially limiting myofiber growth. These results support the idea that satellite cells regulate the muscle environment, and that their loss during aging may contribute to fibrosis, particularly during periods of remodeling. Overload induced a fiber-type composition improvement, independent of satellite cells, suggesting that aged muscle is very responsive to exercise-induced enhancement in oxidative capacity, even with an impaired hypertrophic response. PMID:25878030

  8. Longitudinal impedance of single frog muscle fibers

    PubMed Central

    1975-01-01

    The longitudinal impedance of single skeletal muscle fibers has been measured from1 to 10,000 Hz in an oil gap apparatus which forces current to flow longitudinally down the fiber. The impedance observed is purely resistive in some fibers from the semitendinosus muscle and in two fibers from the sartorius muscle. In other fibers from the semitendinosus muscle a small phase shift is observed. The mean value of the maximum phase shift observed from all fibers is 1.07 degrees. The artifacts associated with the apparatus and method are examined theoretically and it is shown that one of the likely artifacts could account for the small phase observed. It is concluded that the longitudinal impedance of skeletal muscle fibers is essentially resistive and that little, if any, longitudinal current crosses the membranes of the sarcoplasmic reticulum. PMID:1078575

  9. Effect of swim taper on whole muscle and single muscle fiber contractile properties.

    PubMed

    Trappe, S; Costill, D; Thomas, R

    2001-01-01

    To examine the changes in whole muscle function and single cell contractile properties of Type I and II muscle fibers from the deltoid muscle of highly trained swimmers before and after a 21-d reduction in training volume (taper). Six college male swimmers (age, 20+/-1 yr; height, 187+/-2 cm, weight, 79+/-3 kg, fat, 7+/-1%) who had been, on average, swimming 6200 m x d(-1) for 5 months before the taper participated in this investigation. Whole muscle power increased (P < 0.05) 17% and 13% on the swim bench and swim power tests, respectively. Swim times improved by 4% (range: 3.0-4.7%; P < 0.05). There was no change in Type I fiber diameter, whereas Type IIa fibers were 11% larger (P < 0.05) after taper. Peak force (Po) of the Type I fibers was unaffected by the taper but increased (P < 0.05) from 0.63+/-0.02 to 0.82+/-0.05 mN in the IIa fibers. However, the specific force (Po/CSA) of the IIa fibers was unchanged. Shortening velocity (Vo) was 32% and 67% faster (P < 0.05) in the Type I and IIa fibers, respectively. Although Type I fiber power was unaltered, the IIa fibers increased 2.5-fold from 24.6+/-2.8 to 56.2+/-3.9 microN x FL x s(-1). When power was normalized for cell size, the power was still elevated twofold. These data suggest that tapering induces alterations in the contractile properties of single muscle fibers. Further, it appears that the Type IIa fibers are more affected than the Type I fibers by the taper. The increased size, strength, velocity, and power of the IIa fibers may be responsible for the improvements in whole muscle strength and power after the taper.

  10. Molecular Mechanisms Regulating Muscle Fiber Composition Under Microgravity

    NASA Technical Reports Server (NTRS)

    Rosenthal, Nadia A.

    1999-01-01

    The overall goal of this project is to reveal the molecular mechanisms underlying the selective and debilitating atrophy of specific skeletal muscle fiber types that accompanies sustained conditions of microgravity. Since little is currently known about the regulation of fiber-specific gene expression programs in mammalian muscle, elucidation of the basic mechanisms of fiber diversification is a necessary prerequisite to the generation of therapeutic strategies for attenuation of muscle atrophy on earth or in space. Vertebrate skeletal muscle development involves the fusion of undifferentiated mononucleated myoblasts to form multinucleated myofibers, with a concomitant activation of muscle-specific genes encoding proteins that form the force-generating contractile apparatus. The regulatory circuitry controlling skeletal muscle gene expression has been well studied in a number of vertebrate animal systems. The goal of this project has been to achieve a similar level of understanding of the mechanisms underlying the further specification of muscles into different fiber types, and the role played by innervation and physical activity in the maintenance and adaptation of different fiber phenotypes into adulthood. Our recent research on the genetic basis of fiber specificity has focused on the emergence of mature fiber types and have implicated a group of transcriptional regulatory proteins, known as E proteins, in the control of fiber specificity. The restriction of E proteins to selected muscle fiber types is an attractive hypothetical mechanism for the generation of muscle fiber-specific patterns of gene expression. To date our results support a model wherein different E proteins are selectively expressed in muscle cells to determine fiber-restricted gene expression. These studies are a first step to define the molecular mechanisms responsible for the shifts in fiber type under conditions of microgravity, and to determine the potential importance of E proteins as

  11. Single muscle fiber properties in aging and disuse.

    PubMed

    Canepari, M; Pellegrino, M A; D'Antona, G; Bottinelli, R

    2010-02-01

    Since the middle of the 1980s, it was understood that myosin, the motor of contraction, can be expressed in several isoforms. The isoforms of the myosin heavy-chain (MHC) portion of the molecule were found to be mostly responsible for the diversity in the contractile and energetic properties of muscle fibers. In humans, three MHC isoforms are expressed in limb muscles (MHC-1, MHC-2A and MHC-2X) and they generate three pure fiber types (types 1, 2A and 2X) and two hybrid types (types 1-2A and -2AX). Type 1, 2A and 2X fibers widely differ with respect to most of their contractile and energetic properties, and a change in their relative distribution within muscles is known to modulate their functional properties in vivo through a "qualitative" mechanism. On the basis of the MHC regulation of muscle fibers properties, it is expected that a given fiber type develops the same force and shortens at the same speed regardless of the physiologic and pathologic conditions under which the muscle works. Surprisingly, several evidences have been accumulating to show that in aging and disuse, the properties of a muscle fiber type can change with no change in its myosin isoform content. This short review considers the latter phenomenon and the possible underlying mechanisms.

  12. Fiber type dependent upregulation of human skeletal muscle UCP2 and UCP3 mRNA expression by high-fat diet.

    PubMed

    Schrauwen, P; Hoppeler, H; Billeter, R; Bakker, A H; Pendergast, D R

    2001-04-01

    To test the hypothesis that consumption of a high-fat diet leads to an increase in UCP mRNA expression in human skeletal muscle. In a group of endurance athletes, with a range in fiber type distribution, we hypothesized that the effect of the high-fat diet on UCP2 and UCP3 mRNA expression is more pronounced in muscle fibers which are known to have a high capacity to shift from carbohydrate to fat oxidation (type IIA fibers). Ten healthy trained athletes (five males, five females) consumed a low-fat diet (17+/-0.9 en% of fat) and high-fat diet (41.4+/-1.4 en% fat) for 4 weeks, separated by a 4 week wash-out period. Muscle biopsies were collected at the end of both dietary periods. Using RT-PCR, levels of UCP2 and UCP3 mRNA expression were measured and the percentage of type I, IIA and IIB fibers were determined using the myofibrillar ATPase method in all subjects. UCP3L mRNA expression tended to be higher on the high-fat diet, an effect which reached significance when only males were considered (P=0.037). Furthermore, diet-induced change in mRNA expression of UCP3T (r: 0.66, P=0.037), UCP3L (r: 0.61, P=0.06) and UCP2 (r: 0.70, P=0.025), but not UCP3S, correlated significantly with percentage dietary fat on the high-fat diet. Plasma FFA levels were not different during the two diets. Finally, the percentage of type IIA fibers was positively correlated with the diet-induced change in mRNA expression for UCP2 (r: 0.7, P=0.03), UCP3L (r: 0.73, P=0.016) and UCP3T (r: 0.68, P=0.03) but not with UCP3S (r: 0.06, NS). UCP2 and UCP3 mRNAs are upregulated by a high-fat diet. This upregulation is more pronounced in humans with high proportions of type IIA fibers, suggesting a role for UCPs in lipid utilization.

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

    PubMed

    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.

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

    PubMed Central

    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. PMID:28005993

  15. Effects of myogenin on muscle fiber types and key metabolic enzymes in gene transfer mice and C2C12 myoblasts.

    PubMed

    Zhu, Lin-Na; Ren, Yang; Chen, Jing-Qing; Wang, Yi-Zhen

    2013-12-15

    Skeletal muscle fiber type composition is one of the important factors influencing muscle growth and meat quality. As a member of the myogenic transcription factors, myogenin (MyoG) is required for embryonic myoblast differentiation, but the expression of MyoG continues in mature muscle tissue of adult animals, especially in oxidative metabolic muscle, which suggests that MyoG may play a more extended role. Therefore, using MyoG gene transfer mice and C2C12 myoblasts as in vivo and in vitro models, respectively, we elected to study the role of MyoG in muscle fiber types and oxidative metabolism by using overexpression and siRNA suppression strategies. The overexpression of MyoG by DNA electroporation in mouse gastrocnemius muscle had no significant effect on fiber type composition but upregulated the mRNA expression (P<0.01) and enzyme activity (P<0.05) of oxidative succinic dehydrogenase (SDH). In addition, downregulation of the activity of the glycolytic enzymes lactate dehydrogenase (LDH, P<0.05) and pyruvate kinase (PK, P<0.05) was observed in MyoG gene transfer mice. In vitro experiments verified the results obtained in mice. Stable MyoG-transfected differentiating C2C12 cells showed higher mRNA expression levels of myosin heavy chain (MyHC) isoform IIX (P<0.01) and SDH (P<0.05), while the LDH mRNA was attenuated. The enzyme activities of SDH (P<0.01) and LDH (P<0.05) were similarly altered at the mRNA level. When MyoG was knocked down in C2C12 cells, MyHC IIX expression (P<0.05) was decreased, but the mRNA level (P<0.05) and the enzyme activity (P<0.05) of SDH were increased. Downregulating MyoG also increased the activity of the glycolytic enzymes PK (P<0.05) and hexokinase (HK, P<0.05). Based on those results, we concluded that MyoG barely changes the MyHC isoforms, except MyHC IIX, in differentiating myoblasts but probably influences the shift from glycolytic metabolism towards oxidative metabolism both in vivo and in vitro. These results contribute to

  16. Computational Model of Cellular Metabolic Dynamics in Skeletal Muscle Fibers during Moderate Intensity Exercise

    PubMed Central

    Li, Yanjun; Lai, Nicola; Kirwan, John P.; Saidel, Gerald M.

    2012-01-01

    Human skeletal muscles have different fiber types with distinct metabolic functions and physiological properties. The quantitative metabolic responses of muscle fibers to exercise provide essential information for understanding and modifying the regulatory mechanisms of skeletal muscle. Since in vivo data from skeletal muscle during exercise is limited, a computational, physiologically based model has been developed to quantify the dynamic metabolic responses of many key chemical species. This model distinguishes type I and II muscle fibers, which share the same blood supply. An underlying hypothesis is that the recruitment and metabolic activation of the two main types of muscle fibers differ depending on the pre-exercise state and exercise protocols. Here, activation measured by metabolic response (or enzymatic activation) in single fibers is considered linked but distinct from fiber recruitment characterized by the number (or mass) of each fiber type involved during a specific exercise. The model incorporates species transport processes between blood and muscle fibers and most of the important reactions/pathways in cytosol and mitochondria within each fiber type. Model simulations describe the dynamics of intracellular species concentrations and fluxes in muscle fibers during moderate intensity exercise according to various experimental protocols and conditions. This model is validated by comparing model simulations with experimental data in single muscle fibers and in whole muscle. Model simulations demonstrate that muscle-fiber recruitment and metabolic activation patterns in response to exercise produce significantly distinctive effects depending on the exercise conditions. PMID:22942911

  17. miR-30e is negatively regulated by myostatin in skeletal muscle and is functionally related to fiber-type composition.

    PubMed

    Jia, Haixue; Zhao, Yixia; Li, Tingting; Zhang, Yong; Zhu, Dahai

    2017-03-17

    Myostatin (MSTN) negatively regulates skeletal myogenesis in which microRNAs (miRNAs) also play critical roles. Using miRNA microarrays of skeletal muscle from MSTN-knockout (MSTN-/-) mice, we recently showed that miR-431 is regulated by MSTN signaling. To identify additional miRNAs regulated by MSTN, we re-analyzed these miRNA arrays and validated their expression by quantitative RT-PCR. Herein, we demonstrated that miR-30e was significantly upregulated in skeletal muscle of MSTN-/- mice compared with that of the wild-type littermates. Importantly, the predicted targets of miR-30e are functionally involved in myocyte differentiation and fiber-type formation. Using luciferase reporter gene assays, we further showed that peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (Pgc1α), is a direct target of miR-30e. Overexpression of miR-30e in C2C12 cells significantly decreased Pgc1α and increased type II form of myosin heavy chain gene expression, suggesting that miR-30e functionally associates with glycolytic myofiber formation. Thus, our data indicate that the altered fiber-type composition in MSTN-/- mice are attributable in part to deregulated expression of miR-30e.

  18. Staining of Human Thyroarytenoid Muscle with Myosin Antibodies Reveals Some Unique Extrafusal Fibers, but no Muscle Spindles

    PubMed Central

    Brandon, Carla A.; Rosen, Clark; Georgelis, George; Horton, Michael J.; Mooney, Mark P.; Sciote, James J.

    2013-01-01

    Summary This study describes the myosin composition of extrafusal and intrafusal muscle fibers found in the human thyroarytenoid (TA) and sternohyoid (control) muscles. We sought to determine the presence of muscle spindles in the TA muscle, and to identify unusual extrafusal fiber types, using the commonly accepted approach of tissue stainng with myosin isoform specific antibodies. Extrafusal fibers are organized into motor units, which subsequently produce muscle movement, whereas intrafusal fibers compose muscle spindles, the primary stretch receptor that provides afferent (feed back) information to the nervous system for regulation of motor unit length and tonicity. Immunohistochemical identification of muscle spindles was confirmed in sternohyoid, but not in TA samples; however, some extrafusal fibers contained tonic myosin. These results indicate that human TA muscle functions similar to some mammalian extraocular muscle, performing unloaded (non-weight bearing) contractions without afferent information from native muscle spindles. PMID:12825656

  19. Change in the contractile behavior of muscle fibers in subjects with primary muscle dysfunction.

    PubMed

    Back, Claudio Gregório Nuernberg; Benedini-Elias, Priscila C O; Mattiello, Stela M; Sobreira, Claudia; Martinez, Edson Z; Mattiello-Sverzut, Ana Claudia

    2013-01-01

    The mechanical and metabolic characteristics of skeletal muscle fibers can interfere with muscle contractile performance in healthy subjects. Few studies have investigated the degree of association between muscle function and muscle fiber morphology in patients with myopathy. A biopsy was obtained from the left biceps brachii muscle of 12 subjects with myopathic disorders. The relative cross-sectional area of type 2 fibers and their subtypes was determined by the ATPase technique. Relative torque (RT) was calculated by dividing isokinetic elbow flexion peak torque (PT) values (90 and 180° s-1) by isometric PT values. Correlations were analyzed using Spearman's coefficient (r). The relative cross-sectional area of type 2b fibers was positively correlated with RT90 (r = 0.71, P = 0.009) and RT180 (r = 0.73, P = 0.007). The relative cross-sectional area of type 2a fibers showed a moderate and negative correlation with RT180 (r = -0.62, P = 0.03) and a low correlation with RT90 (r = -0.57, P = 0.05). In contrast to healthy subjects, patients with myopathy presented changes in the contractile behavior of type 2a fibers and compensatory adaptations in type 2b fibers. The results suggest that RT in combination with morphometric parameters provides data regarding muscle function in patients with myopathic disorders and can contribute to the establishment of therapeutic exercises.

  20. From single muscle fiber to whole muscle mechanics: a finite element model of a muscle bundle with fast and slow fibers.

    PubMed

    Marcucci, Lorenzo; Reggiani, Carlo; Natali, Arturo N; Pavan, Piero G

    2017-06-05

    Muscles exhibit highly complex, multi-scale architecture with thousands of muscle fibers, each with different properties, interacting with each other and surrounding connective structures. Consequently, the results of single-fiber experiments are scarcely linked to the macroscopic or whole muscle behavior. This is especially true for human muscles where it would be important to understand of how skeletal muscles disorders affect patients' life. In this work, we developed a mathematical model to study how fast and slow muscle fibers, well characterized in single-fiber experiments, work and generate together force and displacement in muscle bundles. We characterized the parameters of a Hill-type model, using experimental data on fast and slow single human muscle fibers, and comparing experimental data with numerical simulations obtained from finite element (FE) models of single fibers. Then, we developed a FE model of a bundle of 19 fibers, based on an immunohistochemically stained cross section of human diaphragm and including the corresponding properties of each slow or fast fiber. Simulations of isotonic contractions of the bundle model allowed the generation of its apparent force-velocity relationship. Although close to the average of the force-velocity curves of fast and slow fibers, the bundle curve deviates substantially toward the fast fibers at low loads. We believe that the present model and the characterization of the force-velocity curve of a fiber bundle represents the starting point to link the single-fiber properties to those of whole muscle with FE application in phenomenological models of human muscles.

  1. SOD1-G93A mice exhibit muscle-fiber-type-specific decreases in glucose uptake in the absence of whole-body changes in metabolism.

    PubMed

    Smittkamp, Susan E; Morris, Jill K; Bomhoff, Gregory L; Chertoff, Mark E; Geiger, Paige C; Stanford, John A

    2014-01-01

    Skeletal muscles play an important role in systemic glucose homeostasis and are purported to be the origin of the altered metabolic state observed in amyotrophic lateral sclerosis (ALS). The purpose of this study was to evaluate whole-body and muscle-specific glucose metabolism in the SOD1-G93A mouse model of ALS. We assessed glucose tolerance in early-, middle-, and late-stage SOD1-G93A and control mice using an intraperitoneal glucose tolerance test. We then measured the respiratory exchange ratio (CO2 production/O2 consumption) as a function of fasting and feeding using indirect calorimetry in a subset of male mice at these time points. Finally, muscles from all mice were harvested to evaluate basal and insulin-stimulated glucose transport in fast- and slow-twitch muscles. No changes in systemic glucose clearance were observed in SOD1-G93A mice at any stage, nor were there changes in fasting insulin levels. Indirect calorimetry revealed an increase in the respiratory exchange ratio during the fed state at middle, but not at early or late stages of disease. Middle-stage SOD1-G93A mice exhibited decreased insulin-stimulated glucose uptake in fast-twitch, but not slow-twitch, skeletal muscle. Late-stage SOD1-G93A mice exhibited decreased insulin-stimulated glucose uptake in both fast- and slow-twitch muscle, as well as increased basal (non-insulin-stimulated) glucose uptake. These results suggest that alterations in muscle metabolism occur in a fiber-type-specific manner in ALS, but do not necessarily lead to whole-body metabolic changes in SOD1-G93A mice. Copyright © 2013 S. Karger AG, Basel

  2. Heterogeneity of fiber characteristics in the rat masseter and digastric muscles.

    PubMed

    Sano, R; Tanaka, E; Korfage, J A M; Langenbach, G E J; Kawai, Nobuhiko; van Eijden, T M G J; Tanne, K

    2007-10-01

    The functional requirements in muscle use are related to the fiber type composition of the muscles and the cross-sectional area of the individual fibers. We investigated the heterogeneity in the fiber type composition and fiber cross-sectional area in two muscles with an opposing function, namely the digastric and masseter muscles (n = 5 for each muscle) of adult male rats, by means of immunohistochemical staining according to their myosin heavy chain (MyHC) content. The digastric and masseter muscles were taken from Wistar strain male rats 10 weeks old. In the masseter six predefined sample locations were examined; in the digastric four. Most regions showed dominant proportions of type IIA and IIX fibers. However, both muscles also revealed a regional heterogeneity in their fiber type distribution. In the digastric, type I fibers were detected only at the central and deep areas of the anterior and posterior belly, respectively. Meanwhile, the peripheral area of the anterior belly contained a higher proportion of type IIB fibers. In the masseter, the type I fibers were absent. In the superficial masseter the distribution of IIA and IIB fibers was significantly different between the superior and inferior regions. In the deep masseter, regional differences were observed among all four examined areas, of which the posterolateral region contained the highest proportion of type IIB fibers. The cross-sectional areas of type IIB fibers were always the largest, followed by the type IIX and IIA fibers. Only a few differences in cross-sectional area of corresponding fiber types were detected between the various sites. In conclusion, the masseter and digastric muscles showed an obvious heterogeneity of fiber type composition and fiber cross-sectional area. Their heterogeneity reflects the complex role of the both muscles during function. This detailed description of the fiber type composition can serve as a reference for future studies examining the muscular adaptations after

  3. Changes in oxygenation and phosphocreatine during exercise and recovery in relation to fiber types and capillary supply in human skeletal muscle

    NASA Astrophysics Data System (ADS)

    Hamaoka, Takatumi; Mizuno, Masano; Osada, Takuya; Ratkevicius, Aivaras; Nielsen, Alexander N.; Nakagawa, Yoshinao; Katsumura, Toshihito; Shimomitsu, Teruichi; Quistorff, Bjorn

    1997-12-01

    The purpose of this study was to examine the relationship between histochemical characteristics obtained from the gastrocnemius and changes in muscle energetics. Muscle oxygenation was determined by near infrared spectroscopy, and phosphocreatine (PCr) by 31-phosphorus magnetic resonance spectroscopy (31P-MRS) during a submaximal plantar flexion exercise and recovery. The relative occurrence (%) of slow-twitch fibers (ST), fast-twitch oxidative fibers (FTa), fast-twitch glycolytic fibers (FTb), and the number of capillaries per fiber (Cap/Fiber) were also determined. The sum of %ST and %FTa (%ST + %FTa) was 85.8 +/- 8.74% (mean +/- SD), while the number of Cap/Fiber was 2.52 +/- 0.63. The initial rate of deoxygenation (Ratedeoxy) at the beginning of the exercise was 2.43 +/- 0.95 %(DOT)sec-1. The time constants (Tc) for the recovery of PCr and muscle oxygenation after exercise were 22.1 +/- 6.3 sec. and 20.3 +/- 13.6 sec., respectively. The %ST + FTa, and the number of Cap/Fiber were each positively correlated to the Ratedeoxy (P < 0.05). The %ST + %FTa, and the number of Cap/Fiber were negatively correlated to the Tc for PCr recovery (P < 0.05), but not correlated to that for muscle oxygenation recovery. In conclusion, the Ratedeoxy during localized submaximal exercise, and the Tc for PCr recovery are indicators of the muscle's oxidative capacity.

  4. Changes in oxygenation and phosphocreatine during exercise and recovery in relation to fiber types and capillary supply in human skeletal muscle

    NASA Astrophysics Data System (ADS)

    Hamaoka, Takatumi; Mizuno, Masano; Osada, Takuya; Ratkevicius, Aivaras; Nielsen, Alexander N.; Nakagawa, Yoshinao; Katsumura, Toshihito; Shimomitsu, Teruichi; Quistorff, Bjorn

    1998-01-01

    The purpose of this study was to examine the relationship between histochemical characteristics obtained from the gastrocnemius and changes in muscle energetics. Muscle oxygenation was determined by near infrared spectroscopy, and phosphocreatine (PCr) by 31-phosphorus magnetic resonance spectroscopy (31P-MRS) during a submaximal plantar flexion exercise and recovery. The relative occurrence (%) of slow-twitch fibers (ST), fast-twitch oxidative fibers (FTa), fast-twitch glycolytic fibers (FTb), and the number of capillaries per fiber (Cap/Fiber) were also determined. The sum of %ST and %FTa (%ST + %FTa) was 85.8 +/- 8.74% (mean +/- SD), while the number of Cap/Fiber was 2.52 +/- 0.63. The initial rate of deoxygenation (Ratedeoxy) at the beginning of the exercise was 2.43 +/- 0.95 %(DOT)sec-1. The time constants (Tc) for the recovery of PCr and muscle oxygenation after exercise were 22.1 +/- 6.3 sec. and 20.3 +/- 13.6 sec., respectively. The %ST + FTa, and the number of Cap/Fiber were each positively correlated to the Ratedeoxy (P < 0.05). The %ST + %FTa, and the number of Cap/Fiber were negatively correlated to the Tc for PCr recovery (P < 0.05), but not correlated to that for muscle oxygenation recovery. In conclusion, the Ratedeoxy during localized submaximal exercise, and the Tc for PCr recovery are indicators of the muscle's oxidative capacity.

  5. Effect of swim taper on whole muscle and single muscle fiber contractile properties.

    PubMed

    Trappe, SCOTT; Costill, DAVID; Thomas, ROBERT

    2000-12-01

    TRAPPE, S., D. COSTILL, and R. THOMAS. Effect of swim taper on whole muscle and single muscle fiber contractile properties. Med. Sci. Sports Exerc., Vol. 32, No. 12, 2000, pp. 48-56. Purpose: To examine the changes in whole muscle function and single cell contractile properties of Type I and II muscle fibers from the deltoid muscle of highly trained swimmers before and after a 21-d reduction in training volume (taper). Methods: Six college male swimmers (age, 20 +/- 1 yr; height, 187 +/- 2 cm, weight, 79 +/- 3 kg, fat, 7 +/- 1%) who had been, on average, swimming 6200 m.d-1 for 5 months before the taper participated in this investigation. Results: Whole muscle power increased (P < 0.05) 17% and 13% on the swim bench and swim power tests, respectively. Swim times improved by 4% (range: 3.0-4.7%; P < 0.05). There was no change in Type I fiber diameter, whereas Type IIa fibers were 11% larger (P < 0.05) after taper. Peak force (Po) of the Type I fibers was unaffected by the taper but increased (P < 0.05) from 0.63 +/- 0.02 to 0.82 +/- 0.05 mN in the IIa fibers. However, the specific force (Po/CSA) of the IIa fibers was unchanged. Shortening velocity (Vo) was 32% and 67% faster (P < 0.05) in the Type I and IIa fibers, respectively. Although Type I fiber power was unaltered, the IIa fibers increased 2.5-fold from 24.6 +/- 2.8 to 56.2 +/- 3.9 µN.FL.s-1. When power was normalized for cell size, the power was still elevated twofold. Conclusions: These data suggest that tapering induces alterations in the contractile properties of single muscle fibers. Further, it appears that the Type IIa fibers are more affected than the Type I fibers by the taper. The increased size, strength, velocity, and power of the IIa fibers may be responsible for the improvements in whole muscle strength and power after the taper.

  6. Muscle-fiber transdifferentiation in an experimental model of respiratory chain myopathy.

    PubMed

    Venhoff, Nils; Lebrecht, Dirk; Pfeifer, Dietmar; Venhoff, Ana C; Bissé, Emmanuel; Kirschner, Janbernd; Walker, Ulrich A

    2012-10-29

    Skeletal muscle fiber composition and muscle energetics are not static and change in muscle disease. This study was performed to determine whether a mitochondrial myopathy is associated with adjustments in skeletal muscle fiber-type composition. Ten rats were treated with zidovudine, an antiretroviral nucleoside reverse transcriptase inhibitor that induces a myopathy by interfering with mitochondrial functions. Soleus muscles were examined after 21 weeks of treatment. Ten untreated rats served as controls. Zidovudine induced a myopathy with mitochondrial DNA depletion, abnormalities in mitochondrial ultrastructure, and reduced cytochrome c oxidase activity. Mitochondrial DNA was disproportionally more diminished in type I compared with type II fibers, whereas atrophy predominated in type II fibers. Compared with those of controls, zidovudine-exposed soleus muscles contained an increased proportion (256%) of type II fibers, whereas neonatal myosin heavy chains remained repressed, indicating fiber-type transformation in the absence of regeneration. Microarray gene-expression analysis confirmed enhanced fast-fiber isoforms, repressed slow-fiber transcripts, and reduced neonatal fiber transcripts in the mitochondrial myopathy. Respiratory chain transcripts were diminished, whereas the enzymes of glycolysis and glycogenolysis were enhanced, indicating a metabolic adjustment from oxidative to glycolytic capacities. A coordinated regulation was found of transcription factors known to orchestrate type II fiber formation (upregulation of MyoD, Six1, Six2, Eya1, and Sox6, and downregulation of myogenin and ERRγ). The type I to type II fiber transformation in mitochondrial myopathy implicates mitochondrial function as a new regulator of skeletal muscle fiber type.

  7. Adaptations of human skeletal muscle fibers to spaceflight

    NASA Technical Reports Server (NTRS)

    Day, M. Kathleen; Allen, David L.; Mohajerani, Laleh; Greenisen, Michael C.; Roy, Roland R.; Edgerton, V. Reggie

    1995-01-01

    Human skeletal muscle fibers seem to share most of the same interrelationships among myosin ATPase activity, myosin heavy chain (MHC) phenotype, mitochondrial enzyme activities, glycolytic enzyme activities, and cross-sectional area (CSA) as found in rat, cat, and other species. One difference seems to be that fast fibers with high mitochrondrial content occur less frequently in humans than in the rat or cat. Recently, we have reported that the type of MHC expressed and the size of the muscle fibers in humans that have spent 11 days in space change significantly. Specifically, about 8% more fibers express fast MHCs and all phenotypes atrophy in the vastus lateralis (VL) post compared to preflight. In the present paper we examine the relationships among the population of myonuclei, MHC type, and CSA of single human muscle fibers before and after spaceflight. These are the first data that define the relationship among the types of MHC expressed, myonuclei number, and myonuclei domain of single fibers in human muscle. We then compare these data to similar measures in the cat. In addition, the maximal torque that can be generated by the knee extensors and their fatigability before and after spaceflight are examined. These data provide some indication of the potential physiologica consequences of the muscle adaptations that occur in humans in response to spaceflight.

  8. Adaptations of human skeletal muscle fibers to spaceflight

    NASA Technical Reports Server (NTRS)

    Day, M. Kathleen; Allen, David L.; Mohajerani, Laleh; Greenisen, Michael C.; Roy, Roland R.; Edgerton, V. Reggie

    1995-01-01

    Human skeletal muscle fibers seem to share most of the same interrelationships among myosin ATPase activity, myosin heavy chain (MHC) phenotype, mitochondrial enzyme activities, glycolytic enzyme activities, and cross-sectional area (CSA) as found in rat, cat, and other species. One difference seems to be that fast fibers with high mitochrondrial content occur less frequently in humans than in the rat or cat. Recently, we have reported that the type of MHC expressed and the size of the muscle fibers in humans that have spent 11 days in space change significantly. Specifically, about 8% more fibers express fast MHCs and all phenotypes atrophy in the vastus lateralis (VL) post compared to preflight. In the present paper we examine the relationships among the population of myonuclei, MHC type, and CSA of single human muscle fibers before and after spaceflight. These are the first data that define the relationship among the types of MHC expressed, myonuclei number, and myonuclei domain of single fibers in human muscle. We then compare these data to similar measures in the cat. In addition, the maximal torque that can be generated by the knee extensors and their fatigability before and after spaceflight are examined. These data provide some indication of the potential physiologica consequences of the muscle adaptations that occur in humans in response to spaceflight.

  9. Experiment K-7-21: Effect of Microgravity on 1: Metabolic Enzymes of Type 1 and Type 2 Muscle Fibers, and on 2: Metabolic Enzymes, Neurotransmitter Amino Acids, and Neurotransmitter Associated Enzymes in Selected Regions of the Central Nervous System. Part 1; Metabolic Enzymes of Individual Muscle Fibers

    NASA Technical Reports Server (NTRS)

    Lowry, O. H.; Ilyina-Kakueva, E. I.; Krasnov, I. B.; Carter, J. G.; Chi, M. M.-Y.; Choksi, R.; Manchester, J. K.; McDougal, D. B.; Nemeth, P. M.; Pusateri, M. E.

    1994-01-01

    Individual fibers of any given muscle vary widely in enzyme composition, a fact obscured when enzyme levels of whole muscle are measured. Therefore, the purpose of this part of the study was to assess the effects of microgravity and hind limb suspension on the enzyme patterns within a slow twitch muscle (soleus) and a fast twitch muscle (tibialis anterior).

  10. Experiment K-7-21: Effect of Microgravity on 1: Metabolic Enzymes of Type 1 and Type 2 Muscle Fibers, and on 2: Metabolic Enzymes, Neurotransmitter Amino Acids, and Neurotransmitter Associated Enzymes in Selected Regions of the Central Nervous System. Part 1; Metabolic Enzymes of Individual Muscle Fibers

    NASA Technical Reports Server (NTRS)

    Lowry, O. H.; Ilyina-Kakueva, E. I.; Krasnov, I. B.; Carter, J. G.; Chi, M. M.-Y.; Choksi, R.; Manchester, J. K.; McDougal, D. B.; Nemeth, P. M.; Pusateri, M. E.

    1994-01-01

    Individual fibers of any given muscle vary widely in enzyme composition, a fact obscured when enzyme levels of whole muscle are measured. Therefore, the purpose of this part of the study was to assess the effects of microgravity and hind limb suspension on the enzyme patterns within a slow twitch muscle (soleus) and a fast twitch muscle (tibialis anterior).

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Fiber architecture of canine abdominal muscles.

    PubMed

    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.

  13. Endurance training in humans leads to fiber type-specific increases in levels of peroxisome proliferator-activated receptor-gamma coactivator-1 and peroxisome proliferator-activated receptor-alpha in skeletal muscle.

    PubMed

    Russell, Aaron P; Feilchenfeldt, Jonas; Schreiber, Sylvia; Praz, Manu; Crettenand, Antoinette; Gobelet, Charles; Meier, Christoph A; Bell, David R; Kralli, Anastasia; Giacobino, Jean-Paul; Dériaz, Olivier

    2003-12-01

    The peroxisome proliferator-activated receptor (PPAR)-gamma coactivator-1 (PGC-1) can induce mitochondria biogenesis and has been implicated in the development of oxidative type I muscle fibers. The PPAR isoforms alpha, beta/delta, and gamma control the transcription of genes involved in fatty acid and glucose metabolism. As endurance training increases skeletal muscle mitochondria and type I fiber content and fatty acid oxidative capacity, our aim was to determine whether these increases could be mediated by possible effects on PGC-1 or PPAR-alpha, -beta/delta, and -gamma. Seven healthy men performed 6 weeks of endurance training and the expression levels of PGC-1 and PPAR-alpha, -beta/delta, and -gamma mRNA as well as the fiber type distribution of the PGC-1 and PPAR-alpha proteins were measured in biopsies from their vastus lateralis muscle. PGC-1 and PPAR-alpha mRNA expression increased by 2.7- and 2.2-fold (P < 0.01), respectively, after endurance training. PGC-1 expression was 2.2- and 6-fold greater in the type IIa than in the type I and IIx fibers, respectively. It increased by 2.8-fold in the type IIa fibers and by 1.5-fold in both the type I and IIx fibers after endurance training (P < 0.015). PPAR-alpha was 1.9-fold greater in type I than in the II fibers and increased by 3.0-fold and 1.5-fold in these respective fibers after endurance training (P < 0.001). The increases in PGC-1 and PPAR-alpha levels reported in this study may play an important role in the changes in muscle mitochondria content, oxidative phenotype, and sensitivity to insulin known to be induced by endurance training.

  14. Muscle Transcriptional Profile Based on Muscle Fiber, Mitochondrial Respiratory Activity, and Metabolic Enzymes

    PubMed Central

    Liu, Xuan; Du, Yang; Trakooljul, Nares; Brand, Bodo; Muráni, Eduard; Krischek, Carsten; Wicke, Michael; Schwerin, Manfred; Wimmers, Klaus; Ponsuksili, Siriluck

    2015-01-01

    Skeletal muscle is a highly metabolically active tissue that both stores and consumes energy. Important biological pathways that affect energy metabolism and metabolic fiber type in muscle cells may be identified through transcriptomic profiling of the muscle, especially ante mortem. Here, gene expression was investigated in malignant hyperthermia syndrome (MHS)-negative Duroc and Pietrian (PiNN) pigs significantly differing for the muscle fiber types slow-twitch-oxidative fiber (STO) and fast-twitch-oxidative fiber (FTO) as well as mitochondrial activity (succinate-dependent state 3 respiration rate). Longissimus muscle samples were obtained 24 h before slaughter and profiled using cDNA microarrays. Differential gene expression between Duroc and PiNN muscle samples were associated with protein ubiquitination, stem cell pluripotency, amyloid processing, and 3-phosphoinositide biosynthesis and degradation pathways. In addition, weighted gene co-expression network analysis within both breeds identified several co-expression modules that were associated with the proportion of different fiber types, mitochondrial respiratory activity, and ATP metabolism. In particular, Duroc results revealed strong correlations between mitochondrion-associated co-expression modules and STO (r = 0.78), fast-twitch glycolytic fiber (r = -0.98), complex I (r=0.72) and COX activity (r = 0.86). Other pathways in the protein-kinase-activity enriched module were positively correlated with STO (r=0.93), while negatively correlated with FTO (r = -0.72). In contrast to PiNN, co-expression modules enriched in macromolecule catabolic process, actin cytoskeleton, and transcription activator activity were associated with fiber types, mitochondrial respiratory activity, and metabolic enzyme activities. Our results highlight the importance of mitochondria for the oxidative capacity of porcine muscle and for breed-dependent molecular pathways in muscle cell fibers. PMID:26681915

  15. SCA28: Novel Mutation in the AFG3L2 Proteolytic Domain Causes a Mild Cerebellar Syndrome with Selective Type-1 Muscle Fiber Atrophy.

    PubMed

    Svenstrup, Kirsten; Nielsen, Troels Tolstrup; Aidt, Frederik; Rostgaard, Nina; Duno, Morten; Wibrand, Flemming; Vinther-Jensen, Tua; Law, Ian; Vissing, John; Roos, Peter; Hjermind, Lena Elisabeth; Nielsen, Jørgen Erik

    2017-02-01

    The spinocerebellar ataxias (SCA) are a group of rare inherited neurodegenerative diseases characterized by slowly progressive cerebellar ataxia, resulting in unsteady gait, clumsiness, and dysarthria. The disorders are predominantly inherited in an autosomal dominant manner. Mutations in the gene AFG3L2 that encodes a subunit of the mitochondrial m-AAA protease have previously been shown to cause spinocerebellar ataxia type 28 (SCA28). Here, we present the clinical phenotypes of three patients from a family with autosomal dominant cerebellar ataxia and show by molecular genetics and in silico modelling that this is caused by a novel missense mutation in the AFG3L2 gene. Furthermore, we show, for the first time, fluorodeoxyglucose-positron emission tomography (FDG-PET) scans of the brain and selective type I fiber atrophy of skeletal muscle of SCA28 patients indicating non-nervous-system involvement in SCA28 as well.

  16. An evaluation of the reliability of muscle fiber cross-sectional area and fiber number measurements in rat skeletal muscle

    USDA-ARS?s Scientific Manuscript database

    Background: The reliability of estimating muscle fiber cross-sectional area (measure of muscle fiber size) and fiber number from only a subset of fibers in rat hindlimb muscle cross-sections has not been systematically evaluated. This study examined the variability in mean estimates of fiber cross-s...

  17. Proportions of myosin heavy chain mRNAs, protein isoforms and fiber types in the slow and fast skeletal muscles are maintained after alterations of thyroid status in rats.

    PubMed

    Soukup, T; Diallo, M

    2015-01-01

    Recently, we have established that slow soleus (SOL) and fast extensor digitorum longus (EDL) muscles of euthyroid (EU) Lewis rats posses the same proportions between their four myosin heavy chain (MyHC) mRNAs, protein isoforms and fiber types as determined by real time RT-PCR, SDS-PAGE and 2-D stereological fiber type analysis, respectively. In the present paper we investigated if these proportions are maintained in adult Lewis rats with hyperthyroid (HT) and hypothyroid (HY) status. Although HT and HY states change MyHC isoform expression, results from all three methods showed that proportion between MyHC mRNA-1, 2a, -2x/d, -2b, protein isoforms MyHC-1, -2a, -2x/d, -2b and to lesser extent also fiber types 1, 2A, 2X/D, 2B were preserved in both SOL and EDL muscles. Furthermore, in the SOL muscle mRNA expression of slow MyHC-1 remained up to three orders higher compared to fast MyHC transcripts, which explains the predominance of MyHC-1 isoform and fiber type 1 even in HT rats. Although HT status led in the SOL to increased expression of MyHC-2a mRNA, MyHC-2a isoform and 2A fibers, it preserved extremely low expression of MyHC-2x and -2b mRNA and protein isoforms, which explains the absence of pure 2X/D and 2B fibers. HY status, on the other hand, almost completely abolished expression of all three fast MyHC mRNAs, MyHC protein isoforms and fast fiber types in the SOL muscle. Our data present evidence that a correlation between mRNA, protein content and fiber type composition found in EU status is also preserved in HT and HY rats.

  18. Molecular Mechanisms Regulating Muscle Fiber Composition Under Microgravity

    NASA Technical Reports Server (NTRS)

    Rosenthal, Nadia A.

    1999-01-01

    The overall goal of this project is to reveal the molecular mechanisms underlying the selective and debilitating atrophy of specific skeletal muscle fiber types that accompanies sustained conditions of microgravity. Since little is currently known about the regulation of fiber-specific gene expression programs in mammalian muscle, elucidation of the basic mechanisms of fiber diversification is a necessary prerequisite to the generation of therapeutic strategies for attenuation of muscle atrophy on earth or in space. Vertebrate skeletal muscle development involves the fusion of undifferentiated mononucleated myoblasts to form multinucleated myofibers, with a concomitant activation of muscle-specific genes encoding proteins that form the force-generating contractile apparatus. The regulatory circuitry controlling skeletal muscle gene expression has been well studied in a number of vertebrate animal systems. The goal of this project has been to achieve a similar level of understanding of the mechanisms underlying the further specification of muscles into different fiber types, and the role played by innervation and physical activity in the maintenance and adaptation of different fiber phenotypes into adulthood. Our recent research on the genetic basis of fiber specificity has focused on the emergence of mature fiber types and have implicated a group of transcriptional regulatory proteins, known as E proteins, in the control of fiber specificity. The restriction of E proteins to selected muscle fiber types is an attractive hypothetical mechanism for the generation of muscle fiber-specific patterns of gene expression. To date our results support a model wherein different E proteins are selectively expressed in muscle cells to determine fiber-restricted gene expression. These studies are a first step to define the molecular mechanisms responsible for the shifts in fiber type under conditions of microgravity, and to determine the potential importance of E proteins as

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

    NASA Technical Reports Server (NTRS)

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

    NASA Technical Reports Server (NTRS)

    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.

  1. Polarization of Tryptophan Fluorescence from Single Striated Muscle Fibers

    PubMed Central

    dos Remedios, C. G.; Millikan, R. G. C.; Morales, M. F.

    1972-01-01

    Instrumentation has been developed to detect rapidly the polarization of tryptophan fluorescence from single muscle fibers in rigor, relaxation, and contraction. The polarization parameter (P⊥) obtained by exiciting the muscle tryptophans with light polarized perpendicular to the long axis of the muscle fiber had a magnitude P⊥ (relaxation) > P⊥ (contraction) > P⊥ (rigor) for the three types of muscle fibers examined (glycerinated rabbit psoas, glycerinated dorsal longitudinal flight muscle of Lethocerus americanus, and live semitendinosus of Rana pipiens). P⊥ from single psoas fibers in rigor was found to increase as the sarcomere length increased but in relaxed fibers P⊥ was independent of sarcomere length. After rigor, pyrophosphate produced little or no change in P⊥, but following an adenosine triphosphate (ATP)-containing solution, pyrophosphate produced a value of P⊥ that fell between the contraction and relaxation values. Sinusoidal or square wave oscillations of the muscle of amplitude 0.5–2.0% of the sarcomere length and frequency 1, 2, or 5 Hz were applied in rigor when the myosin cross-bridges are considered to be firmly attached to the thin filaments. No significant changes in P⊥ were observed in either rigor or relaxation. The preceding results together with our present knowledge of tryptophan distribution in the contractile proteins has led us to the conclusion that the parameter P⊥ is a probe of the contractile state of myosin which is probably sensitive to the orientation of the myosin S1 subfragment. PMID:4332133

  2. Muscle fiber size and function in elderly humans: a longitudinal study.

    PubMed

    Frontera, Walter R; Reid, Kieran F; Phillips, Edward M; Krivickas, Lisa S; Hughes, Virginia A; Roubenoff, Ronenn; Fielding, Roger A

    2008-08-01

    Cross-sectional studies are likely to underestimate age-related changes in skeletal muscle strength and mass. The purpose of this longitudinal study was to assess whole muscle and single muscle fiber alterations in the same cohort of 12 older (mean age: start of study 71.1+/-5.4 yr and end of study 80+/-5.3 yr) volunteers (5 men) evaluated 8.9 yr apart. No significant changes were noted at follow-up in body weight, body mass index, and physical activity. Muscle strength, evaluated using isokinetic dynamometry, and whole muscle specific force of the knee extensors were significantly lower at follow-up. This was accompanied by a significant reduction (5.7%) in cross-sectional area of the total anterior muscle compartment of the thigh as evaluated by computed tomography. Muscle histochemistry showed no significant changes in fiber type distribution or fiber area. Experiments with chemically skinned single muscle fibers (n=411) demonstrated no change in type I fiber size but an increase in IIA fiber diameter. A trend toward an increase in maximal force in both fiber types was observed. Maximum unloaded shortening velocity did not change. In conclusion, single muscle fiber contractile function may be preserved in older humans in the presence of significant alterations at the whole muscle level. This suggests that surviving fibers compensate to partially correct muscle size deficits in an attempt to maintain optimal force-generating capacity.

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

    PubMed Central

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

    2016-01-01

    Purpose 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. Methods 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. Results 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. Conclusion 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. PMID:26930663

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

    PubMed

    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 (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.

  5. Muscle fiber size increases following resistance training in multiple sclerosis.

    PubMed

    Dalgas, U; Stenager, E; Jakobsen, J; Petersen, T; Overgaard, K; Ingemann-Hansen, T

    2010-11-01

    To test the hypothesis that lower body progressive resistance training (PRT) leads to an increase of the muscle fiber cross-sectional area (CSA) and a shift in the proportion of fiber types in patients with multiple sclerosis (MS). The present study was a two-arm, randomized controlled trial (RCT). Thirty-eight MS patients (Expanded Disability Status Scale (EDSS) 3-5.5) were randomized to a PRT group (Exercise, n = 19) or a control group (Control, n = 19). The Exercise group performed a biweekly 12-week lower body PRT program [five exercises progressing from 15RM (Repetition Maximum) towards 8RM], whereas the Control group maintained their usual daily activity level during the trial period. Muscle biopsies from vastus lateralis were taken before (pre) and after the trial (post). Thigh volume (TV) was estimated from anthropometric measurements. Isokinetic muscle strength of the knee extensors (KE) and flexors (KF) were evaluated at slow (90(°)/s) and fast (180(°)/s) angular velocities. In the Exercise group the mean CSA of all muscle fibers (7.9 ± 15.4% vs. -3.5 ± 9.0%, p = 0.03) and of type II muscle fibers (14.0 ± 19.4% vs. -2.6 ± 15.5%, p = 0.02) increased in comparison with the Control group. No changes occurred in the proportion of fiber types in the Exercise group. Neither was there any change in total TV. Isokinetic strength at KE180, KF90 and KF180 improved significantly after PRT when compared with the control group (10.2-21.3%, p ≤ 0.02). We conclude that progressive resistance training induces a compensatory increase of muscle fiber size in patients with the central nervous system disorder, multiple sclerosis.

  6. Effect of swim exercise training on human muscle fiber function

    NASA Technical Reports Server (NTRS)

    Fitts, R. H.; Costill, D. L.; Gardetto, P. R.

    1989-01-01

    The effect of swim exercise training on the human muscle fiber function was investigated in swimmers trained in a typical collegiate swim-training program followed by an intensified 10-day training period. The measured parameters included the peak tension (P0), negative log molar Ca(2+) concentration (pCa)-force, and maximal shortening speed (Vmax) of the slow-twitch type I and fast-twitch type II fibers obtained by biopsy from the deltoid muscle. The P0 values were found to be not altered after either the training or the 10-day intensive program. The type I fibers from the trained swimmers showed pCa-force curves shifted to the right, such that higher free Ca(2+) levels were required to elicit a given percent of P0. The training program significantly increased the Vmax in the type I fibers and decreased that of the type II fibers, and the 10-day intensive training produced a further significant decrease of the type II fibers.

  7. Effect of swim exercise training on human muscle fiber function

    NASA Technical Reports Server (NTRS)

    Fitts, R. H.; Costill, D. L.; Gardetto, P. R.

    1989-01-01

    The effect of swim exercise training on the human muscle fiber function was investigated in swimmers trained in a typical collegiate swim-training program followed by an intensified 10-day training period. The measured parameters included the peak tension (P0), negative log molar Ca(2+) concentration (pCa)-force, and maximal shortening speed (Vmax) of the slow-twitch type I and fast-twitch type II fibers obtained by biopsy from the deltoid muscle. The P0 values were found to be not altered after either the training or the 10-day intensive program. The type I fibers from the trained swimmers showed pCa-force curves shifted to the right, such that higher free Ca(2+) levels were required to elicit a given percent of P0. The training program significantly increased the Vmax in the type I fibers and decreased that of the type II fibers, and the 10-day intensive training produced a further significant decrease of the type II fibers.

  8. Measuring mitochondrial respiration in intact single muscle fibers

    PubMed Central

    Schuh, Rosemary A.; Jackson, Kathryn C.; Khairallah, Ramzi J.; Ward, Christopher W.

    2012-01-01

    Measurement of mitochondrial function in skeletal muscle is a vital tool for understanding regulation of cellular bioenergetics. Currently, a number of different experimental approaches are employed to quantify mitochondrial function, with each involving either mechanically or chemically induced disruption of cellular membranes. Here, we describe a novel approach that allows for the quantification of substrate-induced mitochondria-driven oxygen consumption in intact single skeletal muscle fibers isolated from adult mice. Specifically, we isolated intact muscle fibers from the flexor digitorum brevis muscle and placed the fibers in culture conditions overnight. We then quantified oxygen consumption rates using a highly sensitive microplate format. Peak oxygen consumption rates were significantly increased by 3.4-fold and 2.9-fold by simultaneous stimulation with the uncoupling agent, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), and/or pyruvate or palmitate exposure, respectively. However, when calculating the total oxygen consumed over the entire treatment, palmitate exposure resulted in significantly more oxygen consumption compared with pyruvate. Further, as proof of principle for the procedure, we isolated fibers from the mdx mouse model, which has known mitochondrial deficits. We found significant reductions in initial and peak oxygen consumption of 51% and 61% compared with fibers isolated from the wild-type (WT) animals, respectively. In addition, we determined that fibers isolated from mdx mice exhibited less total oxygen consumption in response to the FCCP + pyruvate stimulation compared with the WT mice. This novel approach allows the user to make mitochondria-specific measures in a nondisrupted muscle fiber that has been isolated from a whole muscle. PMID:22160545

  9. Measuring mitochondrial respiration in intact single muscle fibers.

    PubMed

    Schuh, Rosemary A; Jackson, Kathryn C; Khairallah, Ramzi J; Ward, Christopher W; Spangenburg, Espen E

    2012-03-15

    Measurement of mitochondrial function in skeletal muscle is a vital tool for understanding regulation of cellular bioenergetics. Currently, a number of different experimental approaches are employed to quantify mitochondrial function, with each involving either mechanically or chemically induced disruption of cellular membranes. Here, we describe a novel approach that allows for the quantification of substrate-induced mitochondria-driven oxygen consumption in intact single skeletal muscle fibers isolated from adult mice. Specifically, we isolated intact muscle fibers from the flexor digitorum brevis muscle and placed the fibers in culture conditions overnight. We then quantified oxygen consumption rates using a highly sensitive microplate format. Peak oxygen consumption rates were significantly increased by 3.4-fold and 2.9-fold by simultaneous stimulation with the uncoupling agent, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), and/or pyruvate or palmitate exposure, respectively. However, when calculating the total oxygen consumed over the entire treatment, palmitate exposure resulted in significantly more oxygen consumption compared with pyruvate. Further, as proof of principle for the procedure, we isolated fibers from the mdx mouse model, which has known mitochondrial deficits. We found significant reductions in initial and peak oxygen consumption of 51% and 61% compared with fibers isolated from the wild-type (WT) animals, respectively. In addition, we determined that fibers isolated from mdx mice exhibited less total oxygen consumption in response to the FCCP + pyruvate stimulation compared with the WT mice. This novel approach allows the user to make mitochondria-specific measures in a nondisrupted muscle fiber that has been isolated from a whole muscle.

  10. Contractile properties of single permeabilized muscle fibers from congenital cleft palates and normal palates of Spanish goats

    USDA-ARS?s Scientific Manuscript database

    A goat model in which cleft palate is induced by the plant alkaloid, anabasine was used to determine muscle fiber integrity of the levator veli palatine muscle. It was determined that the muscle fibers of the cleft palate-induced goats were primarily of the type 2 (fast fibers) which fatigue easil...

  11. Effects of chronic heart disease on skeletal muscle fiber size.

    PubMed

    Mattiello-Sverzut, A C; Chimelli, L; Teixeira, S; Pierre, M; Oliveira, L

    2005-02-01

    Size changes in muscle fibers of subjects with chronic heart disease (CHD) have been reported, although a consensus has not been achieved. The aims of the present study were to investigate a possible association between CHD and fiber size changes in the brachial biceps compared to subjects without heart disease. Forty-six muscle samples were obtained in autopsies of individuals (13 to 84 years) without neuromuscular disorders, 19 (10 males and 9 females) with, and 27 (14 males and 13 females) without CHD. In all cases muscle sections were stained with hematoxylin and eosin and processed for the visualization of myofibrillar ATPase activity. The lesser diameter of type 1 and type 2 fibers was obtained tracing their outlines (at least 150 fibers of each type per sample) onto an image analyzer connected to a computer. The results were analyzed statistically comparing males and females with and without CHD. Type 1 fiber mean lesser diameters were 51.51 and 54.52 microm in males (normal range 34-71 microm) and 45.65 and 55.42 microm in females (normal range 34-65 microm) without and with CHD, respectively; type 2 fibers measured 54.31, 58.23, 41.15, and 49.57 microm, respectively (normal range 36-79 microm for males and 32-59 microm for females). No significant difference in fiber size was detected in 24 males with and without CHD, while in 22 females there was a significant increase in size in those with cardiomyopathy. We concluded that CHD does not determine significant changes in fiber size. However, in females, there is some hypertrophy which, despite within normal range, may reflect morphologic heterogeneity of the sample, or the daily life activities in the upper limbs as a compensatory mechanism to fatigability that affect predominantly the lower limbs in subjects with CHD.

  12. Influence of Fiber-Type Composition on Recovery from Tourniquet-Induced Skeletal Muscle Ischemia-Reperfusion Injury

    DTIC Science & Technology

    2008-03-11

    secousse rapide ; la typologie des deux muscles est établie d’après l’éva- luation des propriétés contractiles en isométrie. Des rats mâles...par l’application de la technique du tourniquet varie beaucoup selon la typologie du muscle. Mots-clés : atrophie, propriétés contractiles, œdème...J., Kragh J. F., Baer D. G., 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) United

  13. Prenatal muscle fiber development and bundle structure in beef and dairy cattle.

    PubMed

    Albrecht, E; Lembcke, C; Wegner, J; Maak, S

    2013-08-01

    Muscle fiber development during gestation determines the muscle structure at birth and establishes the conditions for muscle development in growing cattle. Differences in muscle structure among beef cattle breeds and between beef and dairy cattle are obvious already shortly after birth. The objective of the study was to investigate the development of muscle fibers and muscle fiber bundle structure in semitendinosus muscle of divergent cattle breeds from 3 mo of gestation until birth. Fetuses of German Angus (GA), Galloway (GW), Belgian Blue (BB), and Holstein Friesian (HF) were harvested at 3, 4.5, 6, or 9 mo of gestation. Muscle sections were analyzed for fiber size and types as well as for bundle structure. The results confirmed that primary muscle fiber development occurs mainly during the first trimester of gestation. All fibers were initially positive for fetal fast myosin. Slow myosin as a marker for fiber maturation was detected in primary fibers at 3 mo of gestation showing a weak immunostaining. During the second trimester, the intensity of immunostaining strongly increased indicating increased slow myosin protein expression. Concurrently, the shape of primary fibers changed from myotubes to myofibers whereas the size stayed nearly constant. The main increase in muscle mass during the second trimester was caused by secondary fiber development. As an example, the ratio between secondary and primary fibers increased in Holstein Friesian fetuses from 5.9 at 4.5 mo of gestation to 21.6 at 6 mo of gestation. Primary and secondary fibers continued to growth during the third trimester. Regional differences in the density of slow muscle fibers were detected leading to greater variation within the muscle than among breeds. Structural organization of muscle fibers in muscle fiber bundles developed early in fetal life. At first, large main bundles were visible. Smaller structural units defined as primary bundles were measurable at 6 mo of gestation when most fibers

  14. Skeletal muscle fiber analysis by atmospheric pressure scanning microprobe matrix-assisted laser desorption/ionization mass spectrometric imaging at high mass and high spatial resolution.

    PubMed

    Tsai, Yu-Hsuan; Bhandari, Dhaka Ram; Garrett, Timothy J; Carter, Christy S; Spengler, Bernhard; Yost, Richard A

    2016-06-01

    Skeletal muscles are composed of heterogeneous muscle fibers with various fiber types. These fibers can be classified into different classes based on their different characteristics. MALDI mass spectrometric imaging (MSI) has been applied to study and visualize different metabolomics profiles of different fiber types. Here, skeletal muscles were analyzed by atmospheric pressure scanning microprobe MALDI-MSI at high spatial and high mass resolution.

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

    PubMed Central

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

    2014-01-01

    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 < 0.01) and exhibited a group difference from Ecc (P < 0.05), which did not increase. Myonuclei content in type I fibers increased in all groups (P < 0.01), while a specific accretion of myonuclei in type II fibers was observed in the Whey-Conc (P < 0.01) and Placebo-Ecc (P < 0.01) groups. Similarly, whereas type I fiber CSA increased independently of intervention (P < 0.001), type II fiber CSA increased exclusively with Whey-Conc (P < 0.01) and type II fiber hypertrophy correlated with whole muscle hypertrophy exclusively following Conc training (P < 0.01). In conclusion, isolated concentric knee extensor resistance training appears to constitute a stronger driver of SC content than eccentric resistance training while type II fiber hypertrophy was accentuated when combining concentric resistance training with whey protein supplementation. PMID:25103976

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

    PubMed

    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 < 0.01) and exhibited a group difference from Ecc (P < 0.05), which did not increase. Myonuclei content in type I fibers increased in all groups (P < 0.01), while a specific accretion of myonuclei in type II fibers was observed in the Whey-Conc (P < 0.01) and Placebo-Ecc (P < 0.01) groups. Similarly, whereas type I fiber CSA increased independently of intervention (P < 0.001), type II fiber CSA increased exclusively with Whey-Conc (P < 0.01) and type II fiber hypertrophy correlated with whole muscle hypertrophy exclusively following Conc training (P < 0.01). In conclusion, isolated concentric knee extensor resistance training appears to constitute a stronger driver of SC content than eccentric resistance training while type II fiber hypertrophy was accentuated when combining concentric resistance training with whey protein supplementation.

  17. Calcium-activated force of human muscle fibers following a standardized eccentric contraction.

    PubMed

    Choi, Seung Jun; Widrick, Jeffrey J

    2010-12-01

    Peak Ca(2+)-activated specific force (force/fiber cross-sectional area) of human chemically skinned vastus lateralis muscle fiber segments was determined before and after a fixed-end contraction or an eccentric contraction of standardized magnitude (+0.25 optimal fiber length) and velocity (0.50 unloaded shortening velocity). Fiber myosin heavy chain (MHC) isoform content was assayed by SDS-PAGE. Posteccentric force deficit, a marker of damage, was similar for type I and IIa fibers but threefold greater for type IIa/IIx hybrid fibers. A fixed-end contraction had no significant effect on force. Multiple linear regression revealed that posteccentric force was explained by a model consisting of a fiber type-independent and a fiber type-specific component (r(2) = 0.91). Preeccentric specific force was directly associated with a greater posteccentric force deficit. When preeccentric force was held constant, type I and IIa fibers showed identical susceptibility to damage, while type IIa/IIx fibers showed a significantly greater force loss. This heightened sensitivity to damage was directly related to the amount of type IIx MHC in the hybrid fiber. Our model reveals a fiber-type sensitivity of the myofilament lattice or cytoskeleton to mechanical strain that can be described as follows: type IIa/IIx > type IIa = type I. If these properties extend to fibers in vivo, then alterations in the number of type IIa/IIx fibers may modify a muscle's susceptibility to eccentric damage.

  18. 20-Hydroxyecdysone increases fiber size in a muscle-specific fashion in rat.

    PubMed

    Tóth, Noémi; Szabó, András; Kacsala, Péter; Héger, Júlia; Zádor, Ernö

    2008-09-01

    20-Hydroxyecdysone (20E) is an ecdysteroid hormone that regulates moulting in insects. Interestingly, 20E is also found most abundantly in plant species and has anabolic effects in vertebrates, i.e. increasing muscle size without androgen influence. The effect of 20E on slow and fast fiber types of skeletal muscle has not been reported yet. Here we present that 20E affects the size (cross-sectional area, CSA) of the different fiber types in a muscle-specific manner. The effect on fiber size was modified by the distance from the site of the treatment and the presence of a regenerating soleus muscle in the animal. Besides the fiber size, 20E also increased the myonuclear number in the fibers of normal and regenerating muscles, suggesting the activation of satellite cells. According to our results 20E may provide an alternative for substitution of anabolic-androgenic steroids in therapeutic treatments against muscle atrophy.

  19. Possible roles of myostatin and PGC-1alpha in the increase of skeletal muscle and transformation of fiber type in cold-exposed chicks: expression of myostatin and PGC-1alpha in chicks exposed to cold.

    PubMed

    Ijiri, Daichi; Kanai, Yukio; Hirabayashi, Miho

    2009-07-01

    This study examined the hypothesis that myostatin and PGC-1alpha are involved in the increase in skeletal muscle mass and transformation of fiber type in cold-exposed chicks. One-week-old chicks were exposed to acute (24h) or long-term (8d) cold at 4 degrees C or kept warm at 30 degrees C. Acute cold exposure induced a significant increase in the skeletal muscle weight and the ratio of slow- to fast-fiber specific troponin I expression (sTnI/fTnI), accompanied by a significant decrease in lactate dehydrogenase activity. Expression of myostatin mRNA in the muscle was significantly lower in cold-exposed chicks than in the controls, whereas PGC-1alpha mRNA expression was significantly enhanced. These changes in the gene expression rapidly returned to the levels of the control chicks after the end of cold exposure, whereas the changes in fiber type and enzymatic activity were not resumed within 24h after removal of cold exposure. On the other hand, long-term exposure to cold resulted in a remarkable increase in skeletal muscle weight, accompanied by a significant increase in the ratio of sTnI/fTnI and the enzymatic activities of cytochrome oxidase and lactate dehydrogenase. However, the expression level of myostatin mRNA in cold-exposed chicks was not different from that in their age-matched control chicks and that of PGC-1alpha mRNA was significantly lower than in the controls. These results indicate that myostatin and PGC-1alpha expression in the skeletal muscle rapidly change in response to acute cold, suggesting the possibility that these two genes could be involved in the increase in muscle mass and transformation of fiber type, respectively, at the initial stage of adaptation in cold-exposed chicks.

  20. Metabolic and morphometric profile of muscle fibers in chronic hemodialysis patients

    PubMed Central

    Fournier, Mario; Wang, Huiyuan; Storer, Thomas W.; Casaburi, Richard; Cohen, Arthur H.; Kopple, Joel D.

    2012-01-01

    Muscle weakness and effort intolerance are common in maintenance hemodialysis (MHD) patients. This study characterized morphometric, histochemical, and biochemical properties of limb muscle in MHD patients compared with controls (CTL) with similar age, gender, and ethnicity. Vastus lateralis muscle biopsies were obtained from 60 MHD patients, 1 day after dialysis, and from 21 CTL. Muscle fiber types and capillaries were identified immunohistochemically. Individual muscle fiber cross-sectional areas (CSA) were quantified. Individual fiber oxidative capacities were determined (microdensitometric assay) to measure succinate dehydrogenase (SDH) activity. Mean CSAs of type I, IIA, and IIX fibers were 33, 26, and 28% larger in MHD patients compared with CTL. SDH activities for type I, IIA, and IIX fibers were reduced by 29, 40, and 47%, respectively, in MHD. Capillary to fiber ratio was increased by 11% in MHD. The number of capillaries surrounding individual fiber types were also increased (type I: 9%; IIA: 10%; IIX: 23%) in MHD patients. However, capillary density (capillaries per unit muscle fiber area) was reduced by 34% in MHD patients, compared with CTL. Ultrastuctural analysis revealed swollen mitochondria with dense matrix in MHD patients. These results highlight impaired oxidative capacity and capillarity in MHD patients. This would be expected to impair energy production as well as substrate and oxygen delivery and exchange and contribute to exercise intolerance. The enlarged CSA of muscle fibers may, in part, be accounted for by edema. We speculate that these changes contribute to reduce limb strength in MHD patients by reducing specific force. PMID:22016372

  1. Electrophysiology and dye-coupling are sexually dimorphic characteristics of individual laryngeal muscle fibers in Xenopus laevis.

    PubMed

    Tobias, M L; Kelley, D B

    1988-07-01

    Sex differences at the laryngeal neuromuscular junction of Xenopus laevis were examined by recording intracellularly from muscle fibers in response to nerve stimulation. Male laryngeal muscle contains 2 physiologically distinct fiber types. Type I fibers generate postsynaptic potentials in response to low-magnitude stimulus pulses and action potentials in response to higher-magnitude stimulus pulses. Type II muscle fibers require repetitive stimulation for action potential production, probably because of facilitation. Subthreshold events in type I and II fibers suggest that these neuromuscular synapses have low safety factor junctions. Female laryngeal muscle contains one fiber type (III), which is physiologically distinct from those found in the male. Type III fibers produce an action potential in response to a single-stimulus pulse of suprathreshold voltage delivered to the laryngeal nerve; subthreshold events were not observed. Iontophoretic injection of Lucifer yellow into a single female muscle fiber resulted in as many as 43 labeled fibers. In males, only one fiber was labeled. Dye-coupling was not observed in adult females treated with the androgenic steroid hormone, testosterone. We have previously reported that laryngeal muscle fibers are recruited throughout a stimulus train presented to the laryngeal nerve in males, but are not recruited in females (Tobias and Kelly, 1987). Sex differences in the frequency of electrophysiological fiber types described here may account for sex differences in fiber recruitment. Synchronous activity of dye-coupled fibers may increase the effectiveness of muscle contraction in females.

  2. Respiratory muscle fiber remodeling in chronic hyperinflation: dysfunction or adaptation?

    PubMed

    Clanton, Thomas L; Levine, Sanford

    2009-07-01

    The diaphragm and other respiratory muscles undergo extensive remodeling in both animal models of emphysema and in human chronic obstructive pulmonary disease, but the nature of the remodeling is different in many respects. One common feature is a shift toward improved endurance characteristics and increased oxidative capacity. Furthermore, both animals and humans respond to chronic hyperinflation by diaphragm shortening. Although in rodent models this clearly arises by deletion of sarcomeres in series, the mechanism has not been proven conclusively in human chronic obstructive pulmonary disease. Unique characteristics of the adaptation in human diaphragms include shifts to more predominant slow, type I fibers, expressing slower myosin heavy chain isoforms, and type I and type II fiber atrophy. Although some laboratories report reductions in specific force, this may be accounted for by decreases in myosin heavy chain content as the muscles become more oxidative and more efficient. More recent findings have reported reductions in Ca(2+) sensitivity and reduced myofibrillar elastic recoil. In contrast, in rodent models of disease, there is no consistent evidence for loss of specific force, no consistent shift in fiber populations, and atrophy is predominantly seen only in fast, type IIX fibers. This review challenges the hypothesis that the adaptations in human diaphragm represent a form of dysfunction, secondary to systemic disease, and suggest that most findings can as well be attributed to adaptive processes of a complex muscle responding to unique alterations in its working environment.

  3. Gene transcripts encoding hypoxia-inducible factor (HIF) exhibit tissue- and muscle fiber type-dependent responses to hypoxia and hypercapnic hypoxia in the Atlantic blue crab, Callinectes sapidus.

    PubMed

    Hardy, Kristin M; Follett, Chandler R; Burnett, Louis E; Lema, Sean C

    2012-09-01

    Hypoxia inducible factor (HIF) is a transcription factor that under low environmental oxygen regulates the expression of suites of genes involved in metabolism, angiogenesis, erythropoiesis, immune function, and growth. Here, we isolated and sequenced partial cDNAs encoding hif-α and arnt/hif-β from the Atlantic blue crab, Callinectes sapidus, an estuarine species that frequently encounters concurrent hypoxia (low O(2)) and hypercapnia (elevated CO(2)). We then examined the effects of acute exposure (1h) to hypoxia (H) and hypercapnic hypoxia (HH) on relative transcript abundance for hif-α and arnt/hif-β in different tissues (glycolytic muscle, oxidative muscle, hepatopancreas, gill, and gonads) using quantitative real-time RT-PCR. Our results indicate that hif-α and arnt/hif-β mRNAs were constitutively present under well-aerated normoxia (N) conditions in all tissues examined. Further, H and HH exposure resulted in both tissue-specific and muscle fiber type-specific effects on relative hif-α transcript abundance. In the gill and glycolytic muscle, relative hif-α mRNA levels were significantly lower under H and HH, compared to N, while no change (or a slight increase) was detected in oxidative muscle, hepatopancreas and gonadal tissues. H and HH did not affect relative transcript abundance for arnt/hif-β in any tissue or muscle fiber type. Thus, in crustaceans the HIF response to H and HH appears to involve changes in hif transcript abundance, with variation in hif-α and arnt/hif-β transcriptional dynamics occurring in both a tissue- and muscle fiber type-dependent manner.

  4. Intense interval training in healthy older adults increases skeletal muscle [(3)H]ouabain-binding site content and elevates Na(+),K(+)-ATPase α2 isoform abundance in Type II fibers.

    PubMed

    Wyckelsma, Victoria L; Levinger, Itamar; Murphy, Robyn M; Petersen, Aaron C; Perry, Ben D; Hedges, Christopher P; Anderson, Mitchell J; McKenna, Michael J

    2017-04-01

    Young adults typically adapt to intense exercise training with an increased skeletal muscle Na(+),K(+)-ATPase (NKA) content, concomitant with reduced extracellular potassium concentration [K(+)] during exercise and enhanced exercise performance. Whether these changes with longitudinal training occur in older adults is unknown and was investigated here. Fifteen older adults (69.4 ± 3.5 years, mean ± SD) were randomized to either 12 weeks of intense interval training (4 × 4 min at 90-95% peak heart rate), 3 days/week (IIT, n = 8); or no exercise controls (n = 7). Before and after training, participants completed an incremental cycle ergometer exercise test until a rating of perceived exertion of 17 (very hard) on a 20-point scale was attained, with measures of antecubital venous [K(+)]v Participants underwent a resting muscle biopsy prior to and at 48-72 h following the final training session. After IIT, the peak exercise work rate (25%), oxygen uptake (16%) and heart rate (6%) were increased (P < 0.05). After IIT, the peak exercise plasma [K(+)]v tended to rise (P = 0.07), while the rise in plasma [K(+)]v relative to work performed (nmol.L(-1)J(-1)) was unchanged. Muscle NKA content increased by 11% after IIT (P < 0.05). Single fiber measurements, increased in NKA α2 isoform in Type II fibers after IIT (30%, P < 0.05), with no changes to the other isoforms in single fibers or homogenate. Thus, intense exercise training in older adults induced an upregulation of muscle NKA, with a fiber-specific increase in NKA α2 abundance in Type II fibers, coincident with increased muscle NKA content and enhanced exercise performance.

  5. Muscle-fiber transdifferentiation in an experimental model of respiratory chain myopathy

    PubMed Central

    2012-01-01

    Introduction Skeletal muscle fiber composition and muscle energetics are not static and change in muscle disease. This study was performed to determine whether a mitochondrial myopathy is associated with adjustments in skeletal muscle fiber-type composition. Methods Ten rats were treated with zidovudine, an antiretroviral nucleoside reverse transcriptase inhibitor that induces a myopathy by interfering with mitochondrial functions. Soleus muscles were examined after 21 weeks of treatment. Ten untreated rats served as controls. Results Zidovudine induced a myopathy with mitochondrial DNA depletion, abnormalities in mitochondrial ultrastructure, and reduced cytochrome c oxidase activity. Mitochondrial DNA was disproportionally more diminished in type I compared with type II fibers, whereas atrophy predominated in type II fibers. Compared with those of controls, zidovudine-exposed soleus muscles contained an increased proportion (256%) of type II fibers, whereas neonatal myosin heavy chains remained repressed, indicating fiber-type transformation in the absence of regeneration. Microarray gene-expression analysis confirmed enhanced fast-fiber isoforms, repressed slow-fiber transcripts, and reduced neonatal fiber transcripts in the mitochondrial myopathy. Respiratory chain transcripts were diminished, whereas the enzymes of glycolysis and glycogenolysis were enhanced, indicating a metabolic adjustment from oxidative to glycolytic capacities. A coordinated regulation was found of transcription factors known to orchestrate type II fiber formation (upregulation of MyoD, Six1, Six2, Eya1, and Sox6, and downregulation of myogenin and ERRγ). Conclusions The type I to type II fiber transformation in mitochondrial myopathy implicates mitochondrial function as a new regulator of skeletal muscle fiber type. PMID:23107834

  6. Radial forces within muscle fibers in rigor.

    PubMed

    Maughan, D W; Godt, R E

    1981-01-01

    Considering the widely accepted cross-bridge model of muscle contraction (Huxley. 1969. Science [Wash. D. C.]. 164:1356-1366), one would expect that attachment of angled cross-bridges would give rise to radial as well as longitudinal forces in the muscle fiber. These forces would tend, in most instances, to draw the myofilaments together and to cause the fiber to decrease in width. Using optical techniques, we have observed significant changes in the width of mechanically skinned frog muscle fibers when the fibers are put into rigor by deleting ATP from the bathing medium. Using a high molecular weight polymer polyvinylpyrrolidone (PVP-40; number average mol. wt. (Mn) = 40,000) in the bathing solution, we were able to estimate the magnitude of the radial forces by shrinking the relaxed fiber to the width observed with rigor induction. With rigor, fiber widths decreased up to approximately 10%, with shrinking being greater at shorter sarcomere spacing and at lower PVP concentrations. At higher PVP concentrations, some fibers actually swelled slightly. Radial pressures seen with rigor in 2 and 4% PVP ranged up to 8.9 x 10(3) N/m2. Upon rigor induction, fibers exerted a longitudinal force of approximately 1 x 10(5) N/m2 that was inhibited by high PVP concentrations (greater than or equal to 13%). In very high PVP concentrations (greater than or equal to 20%), fibers exerted an anomalous force, independent of ATP, which ranged up to 6 x 10(4) N/m2 at 60% PVP. Assuming that all the radial force is the result of cross-bridge attachment, we calculated that rigor cross-bridges exert a radial force of 0.2 x 1.2 x 10(-9) N per thick filament in sarcomeres near rest length. This force is of roughly the same order of magnitude as the longitudinal force per thick filament in rigor contraction or in maximal (calcium-activated) contraction of skinned fibers in ATP-containing solutions. Inasmuch as widths of fibers stretched well beyond overlap of thick and thin filaments

  7. Congenital fiber type disproportion--30 years on.

    PubMed

    Clarke, Nigel F; North, Kathryn N

    2003-10-01

    Thirty years ago, M. H. Brooke coined the term "congenital fiber type disproportion" (CFTD) to describe 12 children who had clinical features of a congenital myopathy and relative type 1 fiber hypotrophy on muscle biopsy. It is now clear that this histological pattern can accompany a wide range of neurological disorders, leading to disillusionment with CFTD as a distinct nosological entity. To determine whether the CFTD has clinical utility as a diagnostic entity, we have reviewed the literature for cases of type 1 fiber hypotrophy and have used strict exclusion criteria to identify 67 cases of CFTD. Most patients presented at birth with weakness and hypotonia, had normal intelligence, and followed a static or improving clinical course. In 43% of families, more than 1 individual was affected. Failure to thrive was common and 25% of patients had contractures or spinal deformities. Bulbar weakness and ophthalmoplegia were less common and cardiac involvement was rare. Twenty-five percent followed a severe course and 10% had died at the time of reporting, all from respiratory failure. Ophthalmoplegia and facial and bulbar weakness were significantly associated with a poorer prognosis. The relatively homogeneous phenotype supports the retention of CFTD as a distinct diagnostic entity and familial occurrence suggests a genetic basis. Regarding the diagnosis of CFTD, we found no strong evidence that the minimum difference between type 1 and type 2 fiber sizes should be increased from 12% to 25%. We also list the other reported causes of relative type 1 fiber hypotrophy to aid their exclusion from CFTD.

  8. Can proinflammatory cytokine gene expression explain multifidus muscle fiber changes after an intervertebral disc lesion?

    PubMed

    Hodges, Paul W; James, Gregory; Blomster, Linda; Hall, Leanne; Schmid, Annina B; Shu, Cindy; Little, Chris; Melrose, James

    2014-06-01

    Longitudinal case-controlled animal study. To investigate the effect of an intervertebral disc (IVD) lesion on the proportion of slow, fast, and intermediate muscle fiber types in the multifidus muscle in sheep, and whether muscle fiber changes were paralleled by local gene expression of the proinflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin 1-β. Structure and behavior of the multifidus muscle change in acute and chronic back pain, but the mechanisms are surprisingly poorly understood and the link between structure and behavior is tenuous. Although changes in muscle fiber types have the potential to unify the observations, the effect of injury on muscle fiber distribution has not been adequately tested, and understanding of possible mechanisms is limited. The L1-L2, L3-L4, and L5-L6 IVDs of 11 castrated male sheep received anterolateral lesions. Six control sheep underwent no surgical procedures. Multifidus muscle tissue was harvested at L4 for muscle fiber analysis using immunohistochemistry and L2 for cytokine analysis with polymerase chain reaction for local gene expression of TNF-α and interleukin-1β. The proportion of slow muscle fibers in multifidus was significantly less in the lesioned animals both ipsilateral and contralateral to the IVD lesion. The greatest reduction in slow fibers was in the deep medial muscle region. A greater prevalence of intermediate fibers on the uninjured side implies a delayed fiber-type transformation on that side. TNF-α gene expression in multifidus was greater on both sides in the lesion animals than in the muscle of control animals. Interleukin-1β was increased only on the injured side. These data provide evidence of muscle fiber changes after induction of an IVD lesion and a parallel increase in TNF-α expression. Proinflammatory cytokine changes provide a novel mechanism to explain behavioral and structural changes in multifidus. N/A.

  9. Single muscle fiber gene expression with run taper.

    PubMed

    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 (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. Distribution of slow muscle fiber of muscle spindle in postnatal rat masseter muscle.

    PubMed

    Sato, Iwao; Imura, Kosuke; Miwa, Yoko; Ide, Yoshiaki; Murata, Megumi; Sunohara, Masataka

    2007-11-01

    We investigated the properties of the muscle spindle in the masseter muscle at an immunohistochemical level in rats fed for 6 weeks. Slow myosin heavy chain (MyHC) isoforms were measured and intrafusal fibers in the muscle spindle were studied to determine the relationship between the superficial and deep regions of rat masseter muscle after alternated feeding pattern. However, muscle spindles were found in both regions, mainly in the deep region of the posterior superficial region of masseter muscle. The total number of the slow fiber in the intrafusal fiber and number of muscle spindle in the deep region were high from 5 to 8 weeks old in spite of various dimensions of data such as diameter and the compositions of the intrafusal fiber. The relationship of the protein expression of slow MyHC in the two regions at 5 weeks old reversed five weeks later (10 weeks old). This period is an important stage because the mastication system in masseter muscle with muscle spindle may be changed during the alternated feeding pattern of suckling to mastication. The changes may be a marker of the feeding system and of the control by the tension receptor of muscle spindle in this stage of masseter muscle after postnatal development.

  11. Polarization-sensitive optical projection tomography for muscle fiber imaging

    PubMed Central

    Fang, Mengjie; Dong, Di; Zeng, Chaoting; Liang, Xiao; Yang, Xin; Arranz, Alicia; Ripoll, Jorge; Hui, Hui; Tian, Jie

    2016-01-01

    Optical projection tomography (OPT) is a tool used for three-dimensional imaging of millimeter-scale biological samples, with the advantage of exhibiting isotropic resolution typically in the micron range. OPT can be divided into two types: transmission OPT (tOPT) and emission OPT (eOPT). Compared with eOPT, tOPT discriminates different tissues based on their absorption coefficient, either intrinsic or after specific staining. However, it fails to distinguish muscle fibers whose absorption coefficients are similar to surrounding tissues. To circumvent this problem, in this article we demonstrate a polarization sensitive OPT system which improves the detection and 3D imaging of muscle fibers by using polarized light. We also developed image acquisition and processing protocols that, together with the system, enable the clear visualization of muscles. Experimental results show that the muscle fibers of diaphragm and stomach, difficult to be distinguished in regular tOPT, were clearly displayed in our system, proving its potential use. Moreover, polarization sensitive OPT was fused with tOPT to investigate the stomach tissue comprehensively. Future applications of polarization sensitive OPT could be imaging other fiber-like structures such as myocardium or other tissues presenting high optical anisotropy. PMID:26752330

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

    PubMed

    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 < 0.001) and to the CSA fraction formed by type 1 and 2a fibers (r = 0.80, p < 0.001). However, when adjusted for body height and age by multiple regression, MG yielded a largely improved prediction of total CSA (multiple r = 0.83, p < 0.001) and of fiber type 1 and 2a CSA (multiple r = 0.89, p < 0.001). The correlations between CK and these muscle parameters were weaker, and elevated CK values were observed in 20% of control subjects despite a prior abstinence from exercise for 5 days. In conclusion, plasma MG, when adjusted for anthropometric parameters unaffected by weight, may be considered as a novel marker of muscle mass (CSA) indicating best the mass of MG-rich type 1 and 2a fibers as well as VO(2)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

  13. Glycogen synthesis in muscle fibers during active recovery from intense exercise.

    PubMed

    Fairchild, Timothy J; Armstrong, Alex A; Rao, Arjun; Liu, Hawk; Lawrence, Steve; Fournier, Paul A

    2003-04-01

    There is evidence that active recovery impairs glycogen repletion in skeletal muscles of fasted individuals. Our main goal was to examine the impact of active recovery on the glycogen stores of the different muscle fiber types. Eight endurance-trained individuals cycled for 2.5 min at 130% [OV0312]O(2peak) followed by a 30-s all-out cycling sprint. After exercise, the participants were subjected to either a passive recovery or an active recovery protocol that consisted of pedalling for 45 min at 40% [OV0312]O(2peak). During active recovery, blood lactate and pH returned more rapidly toward preexercise levels than during passive recovery. In contrast, average muscle glycogen content remained at stable levels during active recovery (209 +/- 32 and 202 +/- 30 mmol.kg-1 at 0 and 45 min of recovery, respectively) but increased significantly in response to passive recovery (from 185 +/- 27 to 283 +/- 42 mmol.kg-1). The pattern of change in periodic acid-Schiff staining intensity across muscle fibers suggests that the impact of active recovery on average muscle glycogen content is different from that observed at the levels of the individual muscle fibers, with active recovery having no effect on glycogen resynthesis in Type II muscle fibers but causing glycogen breakdown in Type I muscle fibers. Although active recovery was also associated with higher plasma catecholamines and lower insulin levels, such an unfavorable hormonal environment had no effect on glycogen resynthesis in Type II muscle fibers. Active recovery in comparison to passive recovery does not affect glycogen resynthesis in Type II muscle fibers despite being associated with an unfavorable hormonal environment but results in a marked glycogen mobilization in Type I muscle fibers.

  14. Graded Activation in Frog Muscle Fibers

    PubMed Central

    Costantin, L. L.; Taylor, S. R.

    1973-01-01

    The membrane potential of frog single muscle fibers in solutions containing tetrodotoxin was controlled with a two-electrode voltage clamp. Local contractions elicited by 100-ms square steps of depolarization were observed microscopically and recorded on cinefilm. The absence of myofibrillar folding with shortening to striation spacings below 1.95 µm served as a criterion for activation of the entire fiber cross section. With depolarizing steps of increasing magnitude, shortening occurred first in the most superficial myofibrils and spread inward to involve axial myofibrils as the depolarization was increased. In contractions in which the entire fiber cross section shortened actively, both the extent of shortening and the velocity of shortening at a given striation spacing could be graded by varying the magnitude of the depolarization step. The results provide evidence that the degree of activation of individual myofibrils can be graded with membrane depolarization. PMID:4540418

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

    PubMed Central

    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

  16. Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training.

    PubMed

    McCall, G E; Byrnes, W C; Dickinson, A; Pattany, P M; Fleck, S J

    1996-11-01

    Twelve male subjects with recreational resistance training backgrounds completed 12 wk of intensified resistance training (3 sessions/wk; 8 exercises/session; 3 sets/exercise; 10 repetitions maximum/set). All major muscle groups were trained, with four exercises emphasizing the forearm flexors. After training, strength (1-repetition maximum preacher curl) increased by 25% (P < 0.05). Magnetic resonance imaging scans revealed an increase in the biceps brachii muscle cross-sectional area (CSA) (from 11.8 +/- 2.7 to 13.3 +/- 2.6 cm2; n = 8; P < 0.05). Muscle biopsies of the biceps brachii revealed increases (P < 0.05) in fiber areas for type I (from 4,196 +/- 859 to 4,617 +/- 1,116 microns2; n = 11) and II fibers (from 6,378 +/- 1,552 to 7,474 +/- 2,017 microns2; n = 11). Fiber number estimated from the above measurements did not change after training (293.2 +/- 61.5 x 10(3) pretraining; 297.5 +/- 69.5 x 10(3) posttraining; n = 8). However, the magnitude of muscle fiber hypertrophy may influence this response because those subjects with less relative muscle fiber hypertrophy, but similar increases in muscle CSA, showed evidence of an increase in fiber number. Capillaries per fiber increased significantly (P < 0.05) for both type I (from 4.9 +/- 0.6 to 5.5 +/- 0.7; n = 10) and II fibers (from 5.1 +/- 0.8 to 6.2 +/- 0.7; n = 10). No changes occurred in capillaries per fiber area or muscle area. In conclusion, resistance training resulted in hypertrophy of the total muscle CSA and fiber areas with no change in estimated fiber number, whereas capillary changes were proportional to muscle fiber growth.

  17. Regional heterogeneity in muscle fiber strain: the role of fiber architecture

    PubMed Central

    Azizi, E.; Deslauriers, Amber R.

    2014-01-01

    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. PMID:25161626

  18. Inactivity, age, and exercise: single-muscle fiber power generation.

    PubMed

    Kim, Jong-Hee; Thompson, Ladora V

    2013-01-01

    We examined the effects of mild therapeutic exercise during a period of inactivity on size and contractile functions of myosin heavy chain (MHC) type I (n = 204) and type II (n = 419) single fibers from the medial gastrocnemius in three age groups. Young adult (5-12 mo), middle-aged (24-31 mo), and old (32-37 mo) F344BNF1 rats were assigned to one of three groups: weight-bearing control, non-weight bearing (NWB), and NWB plus exercise (NWBX). Fourteen days of hindlimb suspension were applied in NWB rats. The NWBX rats exercised on the treadmill for 15 min, four times a day, during the period of NWB. The NWBX did not improve peak power, but increased normalized power of MHC type I fibers in young adult rats. In MHC type II fibers, NWBX did not change peak power, isometric maximal force, V(max), and fiber size from young adult and middle-aged rats. NWBX did not improve peak power and isometric maximal force and showed a dramatic decline in V(max) and normalized power in the old rats. Collectively, mild treadmill exercise during a period of inactivity does not improve peak power of MHC type I or type II fiber from the gastrocnemius in young, middle-aged, and old rats. However, NWBX is beneficial in enhancing normalized power of MHC type I fibers in young adult rats, most likely due to the stimulus intensity and the ability of the individual fibers to adapt to the stimulus. In contrast, several factors, such as impaired adaptation potential, inappropriate exercise intensity, or increased susceptibility to muscle damage, may contribute to the lack of improvement in the older rats.

  19. Contraction-induced injury to single permeabilized muscle fibers from normal and congenitally-clefted goat palates

    USDA-ARS?s Scientific Manuscript database

    A goat model in which cleft palate is induced by the plant alkaloid, anabasine was used to determine muscle fiber integrity of the levator veli palatine (LVP) muscle. It was determined that muscle fiber type, size, and sensitivity to contraction-induced injury was different between cleft palate ind...

  20. Changes in fiber composition of soleus muscle during rat hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Templeton, G. H.; Sweeney, H. L.; Timson, B. F.; Padalino, M.; Dudenhoeffer, G. A.

    1988-01-01

    A technique in which the gravitational load in the rear limbs of rats was chronically reduced is used to study soleus muscle atrophy in near-zero-gravity conditions. The results show a decline in the number of fibers in groups that contained the slow isoenzyme of myosin and which were classified as type I. The total number of fibers did not change, and fibers containing the intermediate isoenzyme and those classified as type IIa increased. The results are consistent with either a change in the composition within existing fibers or a simultaneous loss of slow fibers accompanied by de novo synthesis of intermediate and fast fibers.

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

    PubMed

    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.

  2. Comparison of Characteristics of Myosin Heavy Chain-based Fiber and Meat Quality among Four Bovine Skeletal Muscles

    PubMed Central

    Kim, Gap-Don; Yang, Han-Sul; Jeong, Jin-Yeon

    2016-01-01

    Muscle fiber characteristics account for meat quality and muscle fibers are mainly classified into three or more types according to their contractile and metabolic properties. However, the majority of previous studies on bovine skeletal muscle are based on myosin ATPase activity. In the present study, the differences in the characteristics of muscle fibers classified by the expression of myosin heavy chain (MHC) among four bovine skeletal muscles such as longissimus thoracis (LT), psoas major (PM), semimembranosus (SM) and semitendinosus (ST) and their relationships to beef quality were investigated. MHCs 2x, 2a and slow were identified by LC-MS/MS and IIX, IIA and I fiber types were classified. PM, which had the smallest size and highest density of fibers regardless of type, showed the highest myoglobin content, CIE L*, a*, b* and sarcomere length (p<0.05), whereas ST with the highest composition of IIX, showed high shear force and low sarcomere length (p<0.05). The correlation coefficients between muscle fiber characteristics and meat quality showed that type IIX is closely related to poor beef quality and that a high density of small-sized fibers is related to redness and tenderness. Therefore, the differences in meat quality between muscles can be explained by the differences in muscle fiber characteristics, and especially, the muscles with good quality are composed of more small-sized fibers regardless of fiber type. PMID:28115894

  3. Diffusion-Tensor MRI Based Skeletal Muscle Fiber Tracking.

    PubMed

    Damon, Bruce M; Buck, Amanda K W; Ding, Zhaohua

    2011-11-01

    A skeletal muscle's function is strongly influenced by the internal organization and geometric properties of its fibers, a property known as muscle architecture. Diffusion-tensor magnetic resonance imaging-based fiber tracking provides a powerful tool for non-invasive muscle architecture studies, has three-dimensional sensitivity, and uses a fixed frame of reference. Significant advances have been made in muscle fiber tracking technology, including defining seed points for fiber tracking, quantitatively characterizing muscle architecture, implementing denoising procedures, and testing validity and repeatability. Some examples exist of how these data can be integrated with those from other advanced MRI and computational methods to provide novel insights into muscle function. Perspectives are offered regarding future directions in muscle diffusion-tensor imaging, including needs to develop an improved understanding for the microstructural basis for reduced and anisotropic diffusion, establish the best practices for data acquisition and analysis, and integrate fiber tracking with other physiological data.

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

    PubMed

    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.

  5. Diffusion-Tensor MRI Based Skeletal Muscle Fiber Tracking

    PubMed Central

    Damon, Bruce M.; Buck, Amanda K. W.; Ding, Zhaohua

    2014-01-01

    A skeletal muscle's function is strongly influenced by the internal organization and geometric properties of its fibers, a property known as muscle architecture. Diffusion-tensor magnetic resonance imaging-based fiber tracking provides a powerful tool for non-invasive muscle architecture studies, has three-dimensional sensitivity, and uses a fixed frame of reference. Significant advances have been made in muscle fiber tracking technology, including defining seed points for fiber tracking, quantitatively characterizing muscle architecture, implementing denoising procedures, and testing validity and repeatability. Some examples exist of how these data can be integrated with those from other advanced MRI and computational methods to provide novel insights into muscle function. Perspectives are offered regarding future directions in muscle diffusion-tensor imaging, including needs to develop an improved understanding for the microstructural basis for reduced and anisotropic diffusion, establish the best practices for data acquisition and analysis, and integrate fiber tracking with other physiological data. PMID:25429308

  6. Skeletal muscle fiber, nerve, and blood vessel breakdown in space-flown rats

    NASA Technical Reports Server (NTRS)

    Riley, D. A.; Ilyina-Kakueva, E. I.; Ellis, S.; Bain, J. L.; Slocum, G. R.; Sedlak, F. R.

    1990-01-01

    Histochemical and ultrastructural analyses were performed postflight on hind limb skeletal muscles of rats orbited for 12.5 days aboard the unmanned Cosmos 1887 biosatellite and returned to Earth 2 days before sacrifice. The antigravity adductor longus (AL), soleus, and plantaris muscles atrophied more than the non-weight-bearing extensor digitorum longus, and slow muscle fibers were more atrophic than fast fibers. Muscle fiber segmental necrosis occurred selectively in the AL and soleus muscles; primarily, macrophages and neutrophils infiltrated and phagocytosed cellular debris. Granule-rich mast cells were diminished in flight AL muscles compared with controls, indicating the mast cell secretion contributed to interstitial tissue edema. Increased ubiquitination of disrupted myofibrils implicated ubiquitin in myofilament degradation. Mitochondrial content and succinic dehydrogenase activity were normal, except for subsarcolemmal decreases. Myofibrillar ATPase activity of flight AL muscle fibers shifted toward the fast type. Absence of capillaries and extravasation of red blood cells indicated failed microcirculation. Muscle fiber regeneration from activated satellite cells was detected. About 17% of the flight AL end plates exhibited total or partial denervation. Thus, skeletal muscle weakness associated with spaceflight can result from muscle fiber atrophy and segmental necrosis, partial motor denervation, and disruption of the microcirculation.

  7. Skeletal muscle fiber, nerve, and blood vessel breakdown in space-flown rats

    NASA Technical Reports Server (NTRS)

    Riley, D. A.; Ilyina-Kakueva, E. I.; Ellis, S.; Bain, J. L.; Slocum, G. R.; Sedlak, F. R.

    1990-01-01

    Histochemical and ultrastructural analyses were performed postflight on hind limb skeletal muscles of rats orbited for 12.5 days aboard the unmanned Cosmos 1887 biosatellite and returned to Earth 2 days before sacrifice. The antigravity adductor longus (AL), soleus, and plantaris muscles atrophied more than the non-weight-bearing extensor digitorum longus, and slow muscle fibers were more atrophic than fast fibers. Muscle fiber segmental necrosis occurred selectively in the AL and soleus muscles; primarily, macrophages and neutrophils infiltrated and phagocytosed cellular debris. Granule-rich mast cells were diminished in flight AL muscles compared with controls, indicating the mast cell secretion contributed to interstitial tissue edema. Increased ubiquitination of disrupted myofibrils implicated ubiquitin in myofilament degradation. Mitochondrial content and succinic dehydrogenase activity were normal, except for subsarcolemmal decreases. Myofibrillar ATPase activity of flight AL muscle fibers shifted toward the fast type. Absence of capillaries and extravasation of red blood cells indicated failed microcirculation. Muscle fiber regeneration from activated satellite cells was detected. About 17% of the flight AL end plates exhibited total or partial denervation. Thus, skeletal muscle weakness associated with spaceflight can result from muscle fiber atrophy and segmental necrosis, partial motor denervation, and disruption of the microcirculation.

  8. Fiber Composition of the Grasscutter (Thryonomys swinderianus, Temminck 1827) Thigh Muscle: An Enzyme-histochemical Study

    PubMed Central

    Bakou, Serge Niangoran; Nteme Ella, Gualbert Simon; Aoussi, Serge; Guiguand, Lydie; Cherel, Yannick; Fantodji, Agathe

    2015-01-01

    The aim of this study was to describe de fiber composition in the thigh muscles of grass cutter (Thryonomys swinderianus, Temminck 1827). Ten 4 to 6-month-old (3 to 4 kg) male grasscutter were used in this study. Eleven skeletal muscles of the thigh [M. biceps femoris (BF), M. rectus femoris (RF), M. vastus lateralis (VL), M. vastus medialis (VM), M. tensor fasciae latae (TFL), M. semitendinosus (ST), M. semimembranosus (SM), M. semimembranosus accessorius (SMA), M. Sartorius (SRT), M. pectineus (PCT), M. adductor magnus (AM)] were collected after animals euthanasia and examined by light microscopy. Three muscle fiber types (I, IIB and IIA) were found in these muscles using enzyme histochemical techniques [myosine adenosine triphosphatase (ATPase) and nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR)]. Ten of these eleven muscles are composed by 89% to 100% of fast contracting fibers (types IIA and IIB), while the SMA was almost exclusively formed by slow contracting fibers. PMID:26167391

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

    PubMed

    Andersen, Lars L; Tufekovic, Goran; Zebis, Mette K; Crameri, Regina M; Verlaan, George; Kjaer, Michael; Suetta, Charlotte; Magnusson, Peter; Aagaard, Per

    2005-02-01

    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 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. Muscle biopsy specimens were obtained from the vastus lateralis muscle and analyzed for muscle fiber cross-sectional area. Squat jump and countermovement jump were performed on a force platform to determine vertical jump height. Peak torque during slow (30 degrees s-1) and fast (240 degrees s-1) 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 < .01) and type II (26% +/- 5%; P < .01) muscle fibers, whereas no change above baseline occurred in the carbohydrate group. Squat jump height increased only in the protein group, whereas countermovement jump height and peak torque during slow isokinetic muscle contraction increased similarly in both groups. In conclusion, a minor advantage of protein supplementation over carbohydrate supplementation during resistance training on mechanical muscle function was found. However, the present results may have relevance for individuals who are particularly interested in gaining muscle size.

  10. Supplementing healthy rats with a high-niacin dose has no effect on muscle fiber distribution and muscle metabolic phenotype.

    PubMed

    Scholz, Kristen; Kynast, Anna Marie; Couturier, Aline; Mooren, Frank-Christoph; Krüger, Karsten; Most, Erika; Eder, Klaus; Ringseis, Robert

    2014-08-01

    It was recently shown that niacin prevents the obesity-induced type I to type II fiber switching in skeletal muscle of obese rats and favors the development of a more oxidative metabolic phenotype and thereby increases whole body utilization of fatty acids. Whether niacin also causes type II to type I fiber switching in skeletal muscle of healthy rats has not been investigated yet. Thus, the present study aimed to investigate whether niacin supplementation influences fiber distribution and metabolic phenotype of different skeletal muscles with a distinct type I-to-type II fiber ratio in healthy rats. Twenty-four male, 10-week-old Sprague-Dawley rats were randomly assigned into two groups of 12 rats each and fed either a control diet with 30 mg supplemented niacin/kg diet (control group) or a high-niacin diet with 780 mg supplemented niacin/kg diet (high-niacin group). After 27 days of treatment, the percentage number of type I fibers in rectus femoris, gastrocnemius, and tibialis anterior muscles was 5-10% greater in the niacin group than in the control group, but did not differ between groups in soleus and vastus intermedius muscles. Transcript levels of genes encoding transcription factors regulating fiber switching, fiber-specific myosin heavy chain isoforms, and proteins involved in fatty acid utilization, oxidative phosphorylation, and angiogenesis did not differ between groups. The results show that niacin has only negligible effects on fiber distribution and its regulation as well as the metabolic phenotype of skeletal muscle in healthy rats.

  11. Quantitative force comparison of polyacrylonitrile fibers with skeletal muscle

    NASA Astrophysics Data System (ADS)

    Gonzalez, Roger V.; Lee, Christopher Y.

    1998-07-01

    The possibility of using certain polymer gels as artificial skeletal muscle was investigated due to its ability to shorten or contract when saturated in acidic or basic solutions, respectively. Polyacrylonitrile (PAN) fiber is such an example of a polymer gel. Mechanical performance characteristics of PAN fibers were studied and compared to voluntary muscle mechanical properties. The experimental methods used to determine the mechanical properties of the PAN fibers were modeled after A. V. Hill's classic experiments of the force-length and force-velocity properties of voluntary muscle. In addition, the force-molarity, length-molarity, and force-time characteristics were measured for the PAN fibers. These characteristics were quantitatively and qualitatively compared to voluntary muscle properties when relevant and used to determine the feasibility of implementing PAN fibers as artificial skeletal muscle in modeling movement across the human elbow joint. The results indicated qualitative similarities with the mechanical characteristics of voluntary muscle, especially force-velocity property. The force capabilities of the PAN fibers were at the lower end of voluntary muscle force generation. (i.e. 20 - 200 N/cm2) Activation- contraction time was also substantially larger than skeletal muscle. Based on these data, it was concluded that using PAN fibers as artificial muscles in modeling the human elbow joint is feasible only under certain conditions. Additional characterization studies are needed to determine if individual PAN fibers can generate higher forces using a different experimental protocol or a different architectural arrangement of the fibers.

  12. Contraction-Induced Injury to Single Permeabilized Muscle Fibers From Normal and Congenitally-Clefted Goat Palates

    PubMed Central

    Rader, Erik P.; Cederna, Paul S.; Weinzweig, Jeffrey; Panter, Kip E.; Yu, Deborah; Buchman, Steven R.; Larkin, Lisa M.; Faulkner, John A.

    2009-01-01

    Objective Levator veli palatini muscles from normal palates of adult humans and goats are predominantly slow oxidative (type 1) fibers. However, 85% of levator veli palatini fibers from cleft palates of adult goats are physiologically fast (type 2). This fiber composition difference between cleft and normal palates may have implications in palatal function. For limb muscles, type 2 muscle fibers are more susceptible to lengthening contraction-induced injury than are type 1 fibers. We tested the hypothesis that, compared with single permeabilized levator veli palatini muscle fibers from normal palates of adult goats, those from cleft palates are more susceptible to lengthening contraction-induced injury. Interventions Congenital cleft palates were the result of chemically-induced decreased movement of the fetal head and tongue causing obstruction of palatal closure. Each muscle fiber was maximally activated and lengthened. Outcome Measures Fiber type was determined by contractile properties and gel electrophoresis. Susceptibility to injury was assessed by measuring the decrease in maximum force following the lengthening contraction, expressed as a percentage of the initial force. Results Compared with fibers from normal palates that were all type 1 and had force deficits of 23 ± 1%, fibers from cleft palates were all type 2 and sustained twofold greater deficits, 40 ± 1% (p = .001). Conclusion Levator veli palatini muscles from cleft palates of goats contain predominantly type 2 fibers that are highly susceptible to lengthening contraction-induced injury. This finding may have implications regarding palatal function and the incidence of velopharyngeal incompetence. PMID:17328650

  13. Cycle Training Increased GLUT4 and Activation of mTOR in Fast Twitch Muscle Fibers

    PubMed Central

    Stuart, Charles A.; Howell, Mary E.A.; Baker, Jonathan D.; Dykes, Rhesa J.; Duffourc, Michelle M.; Ramsey, Michael W.; Stone, Michael H.

    2009-01-01

    Purpose To determine if cycle training of sedentary subjects would increase the expression of the principle muscle glucose transporters, six volunteers completed six weeks of progressively increasing intensity stationary cycle cycling. Methods In vastus lateralis muscle biopsies, changes in expression of GLUT1, GLUT4, GLUT5, and GLUT12 were compared using quantitative immunoblots with specific protein standards. Regulatory pathway components were evaluated by immunoblots of muscle homogenates and immunohistochemistry of microscopic sections. Results GLUT1 was unchanged, GLUT4 increased 66%, GLUT12 increased 104%, and GLUT5 decreased 72%. A mitochondrial marker (cytochrome c) and regulators of mitochondrial biogenesis (PGC-1α and phospho-AMPK) were unchanged, but the muscle hypertrophy pathway component, phospho-mTOR increased 83% after the exercise program. In baseline biopsies, GLUT4 by immunohistochemical techniques was 37% greater in Type I (slow twitch, red) muscle fibers, but the exercise training increased GLUT4 expression in Type II (fast twitch, white) fibers by 50%, achieving parity with the Type I fibers. Baseline phospho-mTOR expression was 50% higher in Type II fibers and increased more in Type II fibers (62%) with training, but also increased in Type I fibers (34%). Conclusion Progressive intensity stationary cycle training of previously sedentary subjects increased muscle insulin-responsive glucose transporters (GLUT4 and GLUT12) and decreased the fructose transporter (GLUT5). The increase in GLUT4 occurred primarily in Type II muscle fibers and this coincided with activation of the mTOR muscle hypertrophy pathway. There was little impact on Type I fiber GLUT4 expression and no evidence of change in mitochondrial biogenesis. PMID:20010125

  14. ULTRASTRUCTURE OF BARNACLE GIANT MUSCLE FIBERS

    PubMed Central

    Hoyle, Graham; McNeill, Patricia A.; Selverston, Allen I.

    1973-01-01

    Increasing use of barnacle giant muscle fibers for physiological research has prompted this investigation of their fine structure. The fibers are invaginated by a multibranched system of clefts connecting to the exterior and filled with material similar to that of the basement material of the sarcolemmal complex. Tubules originate from the surface plasma membrane at irregular sites, and also from the clefts They run transversely, spirally, and longitudinally, making many diadic and some triadic contacts with cisternal sacs of the longitudinal sarcoplasmic reticulum. The contacts are not confined to any particular region of the sarcomere. The tubules are wider and their walls are thicker at points of contact with Z material. Some linking of the Z regions occurs across spaces within the fiber which contain large numbers of glycogen particles. A-band lengths are extremely variable, in the range 2.2 µm–20.3 µm (average 5.2 µm) Individual thick filaments have thin (110 Å) hollow regions alternating with thick (340 Å) solid ones. Bridges between thick filaments occur at random points and are not concentrated into an M band The thin:thick filament ratio is variable in different parts of a fiber, from 3:1 to 6:1. Z bands are basically perforated, but the number of perforations may increase during contraction. PMID:4264604

  15. The significance of type 1 fiber atrophy (hypotrophy) in childhood neuromuscular disorders.

    PubMed

    Imoto, C; Nonaka, I

    2001-08-01

    To determine the incidence of selective type 1 fiber atrophy (hypotrophy) and its possible significance in various muscle diseases of childhood, we reviewed 2212 muscle biopsies from children which we had examined in the past 20 years histochemically with ATPase staining. Type 1 fiber atrophy was seen in a variety of neuromuscular disorders, but predominantly in congenital myopathies, including all patients with congenital fiber type disproportion myopathy (20 patients), central core disease (12 patients) and multicore disease (four patients). Although type 1 fiber atrophy was not a constant feature in nemaline myopathy and myotubular myopathy, all patients with these diseases had abnormal fiber type distribution which included type 1 fiber predominance both with and without type 2B fiber deficiency. Together with abnormal fiber type distribution, type 1 fiber atrophy was a common finding in childhood neuromuscular disorders, especially congenital myopathies.

  16. Effect of altering starting length and activation timing of muscle on fiber strain and muscle damage.

    PubMed

    Butterfield, Timothy A; Herzog, Walter

    2006-05-01

    Muscle strain injuries are some of the most frequent injuries in sports and command a great deal of attention in an effort to understand their etiology. These injuries may be the culmination of a series of subcellular events accumulated through repetitive lengthening (eccentric) contractions during exercise, and they may be influenced by a variety of variables including fiber strain magnitude, peak joint torque, and starting muscle length. To assess the influence of these variables on muscle injury magnitude in vivo, we measured fiber dynamics and joint torque production during repeated stretch-shortening cycles in the rabbit tibialis anterior muscle, at short and long muscle lengths, while varying the timing of activation before muscle stretch. We found that a muscle subjected to repeated stretch-shortening cycles of constant muscle-tendon unit excursion exhibits significantly different joint torque and fiber strains when the timing of activation or starting muscle length is changed. In particular, measures of fiber strain and muscle injury were significantly increased by altering activation timing and increasing the starting length of the muscle. However, we observed differential effects on peak joint torque during the cyclic stretch-shortening exercise, as increasing the starting length of the muscle did not increase torque production. We conclude that altering activation timing and muscle length before stretch may influence muscle injury by significantly increasing fiber strain magnitude and that fiber dynamics is a more important variable than muscle-tendon unit dynamics and torque production in influencing the magnitude of muscle injury.

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

    PubMed Central

    Eiber, Nane; Simeone, Luca; Hashemolhosseini, Said

    2017-01-01

    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. PMID:28106831

  18. Myosin content of individual human muscle fibers isolated by laser capture microdissection

    PubMed Central

    Stone, William L.; Howell, Mary E. A.; Brannon, Marianne F.; Hall, H. Kenton; Gibson, Andrew L.; Stone, Michael H.

    2015-01-01

    Muscle fiber composition correlates with insulin resistance, and exercise training can increase slow-twitch (type I) fibers and, thereby, mitigate diabetes risk. Human skeletal muscle is made up of three distinct fiber types, but muscle contains many more isoforms of myosin heavy and light chains, which are coded by 15 and 11 different genes, respectively. Laser capture microdissection techniques allow assessment of mRNA and protein content in individual fibers. We found that specific human fiber types contain different mixtures of myosin heavy and light chains. Fast-twitch (type IIx) fibers consistently contained myosin heavy chains 1, 2, and 4 and myosin light chain 1. Type I fibers always contained myosin heavy chains 6 and 7 (MYH6 and MYH7) and myosin light chain 3 (MYL3), whereas MYH6, MYH7, and MYL3 were nearly absent from type IIx fibers. In contrast to cardiomyocytes, where MYH6 (also known as α-myosin heavy chain) is seen solely in fast-twitch cells, only slow-twitch fibers of skeletal muscle contained MYH6. Classical fast myosin heavy chains (MHC1, MHC2, and MHC4) were present in variable proportions in all fiber types, but significant MYH6 and MYH7 expression indicated slow-twitch phenotype, and the absence of these two isoforms determined a fast-twitch phenotype. The mixed myosin heavy and light chain content of type IIa fibers was consistent with its role as a transition between fast and slow phenotypes. These new observations suggest that the presence or absence of MYH6 and MYH7 proteins dictates the slow- or fast-twitch phenotype in skeletal muscle. PMID:26676053

  19. Myosin content of individual human muscle fibers isolated by laser capture microdissection.

    PubMed

    Stuart, Charles A; Stone, William L; Howell, Mary E A; Brannon, Marianne F; Hall, H Kenton; Gibson, Andrew L; Stone, Michael H

    2016-03-01

    Muscle fiber composition correlates with insulin resistance, and exercise training can increase slow-twitch (type I) fibers and, thereby, mitigate diabetes risk. Human skeletal muscle is made up of three distinct fiber types, but muscle contains many more isoforms of myosin heavy and light chains, which are coded by 15 and 11 different genes, respectively. Laser capture microdissection techniques allow assessment of mRNA and protein content in individual fibers. We found that specific human fiber types contain different mixtures of myosin heavy and light chains. Fast-twitch (type IIx) fibers consistently contained myosin heavy chains 1, 2, and 4 and myosin light chain 1. Type I fibers always contained myosin heavy chains 6 and 7 (MYH6 and MYH7) and myosin light chain 3 (MYL3), whereas MYH6, MYH7, and MYL3 were nearly absent from type IIx fibers. In contrast to cardiomyocytes, where MYH6 (also known as α-myosin heavy chain) is seen solely in fast-twitch cells, only slow-twitch fibers of skeletal muscle contained MYH6. Classical fast myosin heavy chains (MHC1, MHC2, and MHC4) were present in variable proportions in all fiber types, but significant MYH6 and MYH7 expression indicated slow-twitch phenotype, and the absence of these two isoforms determined a fast-twitch phenotype. The mixed myosin heavy and light chain content of type IIa fibers was consistent with its role as a transition between fast and slow phenotypes. These new observations suggest that the presence or absence of MYH6 and MYH7 proteins dictates the slow- or fast-twitch phenotype in skeletal muscle. Copyright © 2016 the American Physiological Society.

  20. Muscle fiber hypotrophy with intact neuromuscular junctions. A study of a patient with congenital neuromuscular disease and ophthalmoplegia.

    PubMed

    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.

  1. Electrical activation of artificial muscles containing polyacrylonitrile gel fibers.

    PubMed

    Schreyer, H B; Gebhart, N; Kim, K J; Shahinpoor, M

    2000-01-01

    Gel fibers made from polyacrylonitrile (PAN) are known to elongate and contract when immersed in caustic and acidic solutions, respectively. The amount of contraction for these pH-activated fibers is 50% or greater, and the strength of these fibers is shown to be comparable to that of human muscle. Despite these attributes, the need of strong acids and bases for actuation has limited the use of PAN gel fibers as linear actuators or artificial muscles. Increasing the conductivity by depositing platinum on the fibers or combining the fibers with graphite fibers has allowed for electrical activation of artificial muscles containing gel fibers when placed in an electrochemical cell. The electrolysis of water in such a cell produces hydrogen ions at an artificial muscle anode, thus locally decreasing the pH and causing the muscle to contract. Reversing the electric field allows the PAN muscle to elongate. A greater than 40% contraction in artificial muscle length in less than 10 min is observed when it is placed as an electrode in a 10 mM NaCl electrolyte solution and connected to a 10 V power supply. These results indicate potential in developing electrically activated PAN muscles and linear actuators, which would be much more applicable than chemically activated muscles.

  2. [Pathophysiology of muscular atrophy due to disuse--with special reference to a single muscle fiber and its ultrastructure].

    PubMed

    Sukegawa, T

    1983-08-01

    Immobilization muscule atrophy was experimentally induced by fixing one ankle joint with a K-wire in an extended position in rats. The animals were sacrificed at designated intervals to obtain the soleus muscle from the fixed (or disused) side and the free side; the muscles were weighed wet, evaluated (musculo) physiologically using a single-skinned muscle fiber method, and further examined histochemically and electron-microscopically. The wet weight of the disused soleus muscle was reduced to 54% of that of the healthy (used) muscle. According to classification by types of muscle fibers stained for ATPase, conversion of muscle fiber type, i.e., conversions of type 1 (red muscle) into type 2 (white muscle) was noted on the disused side, and similar findings were also observed by examination using a single skinned muscle fiber method. The maximal tension developed by the disused single muscle fiber was lower. This may be attributable to structural changes in the myofilament arrangement observed under an electron microscope. No abnormalities were found in calcium ion uptake by the sarcoplasmic reticulum. Under the present experimental conditions, it was clarified that the disuse atrophy of skeletal muscle induces not only reduction of muscle fibers in diameter but also their dedifferentiation and redifferentiation.

  3. Regeneration of reinnervated rat soleus muscle is accompanied by fiber transition toward a faster phenotype.

    PubMed

    Mendler, Luca; Pintér, Sándor; Kiricsi, Mónika; Baka, Zsuzsanna; Dux, László

    2008-02-01

    The functional recovery of skeletal muscles after peripheral nerve transection and microsurgical repair is generally incomplete. Several reinnervation abnormalities have been described even after nerve reconstruction surgery. Less is known, however, about the regenerative capacity of reinnervated muscles. Previously, we detected remarkable morphological and motor endplate alterations after inducing muscle necrosis and subsequent regeneration in the reinnervated rat soleus muscle. In the present study, we comparatively analyzed the morphometric properties of different fiber populations, as well as the expression pattern of myosin heavy chain isoforms at both immunohistochemical and mRNA levels in reinnervated versus reinnervated-regenerated muscles. A dramatic slow-to-fast fiber type transition was found in reinnervated soleus, and a further change toward the fast phenotype was observed in reinnervated-regenerated muscles. These findings suggest that the (fast) pattern of reinnervation plays a dominant role in the specification of fiber phenotype during regeneration, which can contribute to the long-lasting functional impairment of the reinnervated muscle. Moreover, because the fast II fibers (and selectively, a certain population of the fast IIB fibers) showed better recovery than did the slow type I fibers, the faster phenotype of the reinnervated-regenerated muscle seems to be actively maintained by selective yet undefined cues.

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

    PubMed Central

    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

    2012-01-01

    Summary 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, 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. PMID:22696414

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

    PubMed

    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.

  6. Expression profiling reveals heightened apoptosis and supports fiber size economy in the murine muscles of mastication.

    PubMed

    Evans, Marianna; Morine, Kevin; Kulkarni, Cyelee; Barton, Elisabeth R

    2008-09-17

    Distinctions between craniofacial and axial muscles exist from the onset of development and throughout adulthood. The masticatory muscles are a specialized group of craniofacial muscles that retain embryonic fiber properties in the adult, suggesting that the developmental origin of these muscles may govern a pattern of expression that differs from limb muscles. To determine the extent of these differences, expression profiling of total RNA isolated from the masseter and tibialis anterior (TA) muscles of adult female mice was performed, which identified transcriptional changes in unanticipated functional classes of genes in addition to those attributable to fiber type. In particular, the masseters displayed a reduction of transcripts associated with contractile and cytoskeletal load-sensing and anabolic processes, and heightened expression of genes associated with stress. Associated with these observations was a significantly smaller fiber cross-sectional area in masseters, significantly elevated load-sensing signaling (phosphorylated focal adhesion kinase), and increased apoptotic index in masseters compared with TA muscles. Based on these results, we hypothesize that masticatory muscles may have a fundamentally different strategy for muscle design, compared with axial muscles. Specifically there are small diameter fibers that have an attenuated ability to hypertrophy, but an increased propensity to undergo apoptosis. These results may provide insight into the molecular basis for specific muscle-related pathologies associated with masticatory muscles.

  7. Calcium Efflux from Barnacle Muscle Fibers

    PubMed Central

    Russell, J. M.; Blaustein, M. P.

    1974-01-01

    Calcium-45 was injected into single giant barnacle muscle fibers, and the rate of efflux was measured under a variety of conditions. The rate constant (k) for 45Ca efflux into standard seawater averaged 17 x 10–4 min–1 which corresponds to an efflux of about 1–2 pmol/cm2·s. Removal of external Ca (Cao) reduced the efflux by 50%. In most fibers about 40% of the 45Ca efflux into Ca-free seawater was dependent on external Na (Nao); treatment with 3.5 mM caffeine increased the magnitude of the Nao-dependent efflux. In a few fibers removal of Nao, in the absence of Cao, either had no effect or increased k; caffeine (2–3.5 mM) unmasked an Nao-dependent efflux in these fibers. The Nao-dependent Ca efflux had a Q10 of about 3.7. The data are consistent with the idea that a large fraction of the Ca efflux may be carrier-mediated, and may involve both Ca-Ca and Na-Ca counterflow. The relation between the Nao-dependent Ca efflux and the external Na concentration is sigmoid, and suggests that two, or more likely three, external Na+ ions may activate the efflux of one Ca+2. With a three-for-one Na-Ca exchange, the Na electrochemical gradient may be able to supply sufficient energy to maintain the Ca gradient in these fibers. Other, more complex models are not excluded, however, and may be required to explain some puzzling features of the Ca efflux such as the variable Nao-dependence. PMID:4812633

  8. Automated recognition of the iliac muscle and modeling of muscle fiber direction in torso CT images

    NASA Astrophysics Data System (ADS)

    Kamiya, N.; Zhou, X.; Azuma, K.; Muramatsu, C.; Hara, T.; Fujita, H.

    2016-03-01

    The iliac muscle is an important skeletal muscle related to ambulatory function. The muscles related to ambulatory function are the psoas major and iliac muscles, collectively defined as the iliopsoas muscle. We have proposed an automated recognition method of the iliac muscle. Muscle fibers of the iliac muscle have a characteristic running pattern. Therefore, we used 20 cases from a training database to model the movement of the muscle fibers of the iliac muscle. In the recognition process, the existing position of the iliac muscle was estimated by applying the muscle fiber model. To generate an approximation mask by using a muscle fiber model, a candidate region of the iliac muscle was obtained. Finally, the muscle region was identified by using values from the gray value and boundary information. The experiments were performed by using the 20 cases without abnormalities in the skeletal muscle for modeling. The recognition result in five cases obtained a 76.9% average concordance rate. In the visual evaluation, overextraction of other organs was not observed in 85% of the cases. Therefore, the proposed method is considered to be effective in the recognition of the initial region of the iliac muscle. In the future, we will integrate the recognition method of the psoas major muscle in developing an analytical technique for the iliopsoas area. Furthermore, development of a sophisticated muscle function analysis method is necessary.

  9. Ca fluxes in single twitch muscle fibers.

    PubMed

    Curtis, B A

    1966-11-01

    Ca influx and efflux in single twitch muscle fibers were determined by the movement of 45Ca. The isotope was assayed by counting the center 1 cm of a fiber while it was in nonradioactive Rnger's solution. The average resting influx in 1.0 mM Ca Ringer's was 0.26 pM Ca/cm2. sec for 5 to 20 min influx periods. The average additional influx upon stimulation in 1.0 mM Ca was 0.73 pM Ca/cm2. twitch. The efflux after both resting and stimulated 45Ca influx can be described by a single exponential curve with an average time constant of 125 min. This relationship is an indication of Ca exchange with a single intracellular compartment. This compartment contains an estimated 47% of the total muscle Ca at 1.0 mM Ca. When the Ca in the Ringer was reduced to 0.5 mM Ca, both the resting and stimulated Ca fluxes decreased. When Ca was raised to 1.8 mM, the stimulated influxes increased but the resting influx did not.

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

    NASA Technical Reports Server (NTRS)

    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.

  11. Influence of exercise and Dianabol on the degradation rate of myofibrillar proteins of the heart and three fiber types of skeletal muscle of female guinea pigs.

    PubMed

    Morano, I

    1984-12-01

    The influence of methandrostenolone (= Dianabol = 17-beta-hydroxy-17-methylandrosta-1,4-dien-3-one) and of a running training program on the degradation rate of myofibrillar proteins of the heart, soleus, red portion of the vastus lateralis, and white portion of the vastus lateralis of female guinea pigs was studied by measuring the time-dependent decrease of radioactive-labeled proteins. The following results were obtained: No alteration of absolute muscle or body weight An increased heart-to-body weight relation in the trained and in the trained group receiving Dianabol A significantly higher myofibrillar protein concentration in the skeletal muscle types than in the heart An increased concentration of myofibrillar proteins in all muscle types in the trained group receiving Dianabol and in the heart of the untrained group receiving Dianabol The degradation rate of the myofibrillar proteins decreased in all muscle types in the trained group receiving Dianabol and in the heart of the untrained group receiving Dianabol and in the trained group.

  12. Effects of high-intensity resistance training on untrained older men. II. Muscle fiber characteristics and nucleo-cytoplasmic relationships.

    PubMed

    Hikida, R S; Staron, R S; Hagerman, F C; Walsh, S; Kaiser, E; Shell, S; Hervey, S

    2000-07-01

    During growth and repair of skeletal muscle fibers, satellite cells become activated, undergo mitosis, and a daughter nucleus becomes incorporated into the muscle fiber to increase myonuclear numbers. An increase in myonuclei appears to be required for this postnatal growth. This study examined whether muscle fibers of elderly men can hypertrophy with strength training and, if so, whether they have the capacity to incorporate nuclei into the fibers. The sarcoplasmic area associated with each myonucleus was calculated in nine elderly men before and after 16 weeks of strength training, and compared to nine elderly control men. Muscle fiber type changes and myosin heavy chain composition were also compared. All major fiber types (I, IIA, IIB) became significantly larger after training, and a transition of type IIB fibers to IIA occurred with training. The area occupied by each fiber type correlated with myosin heavy chain percentage, and both of these changed similarly with strength training. The cytoplasm-to-myonucleus ratio increased, but not significantly (p = .07), with muscle fiber hypertrophy. Number of myonuclei per fiber and myonuclei per unit length of muscle fiber increased, but not significantly. Cross-sectional areas of the muscle fibers in untrained elderly men were much smaller than in untrained young men (when compared with our earlier studies). Training increased the sizes of the elderly muscle fibers to that of the untrained young men. This hypertrophy of muscle fibers by 30% with training resulted in no change in the cytoplasm-to-myonucleus ratio. This suggests that the myonuclear population continues to adapt to growth stimuli in the elderly muscles.

  13. Comparison of hemp and cotton fiber implants in muscle rat tissue. Study of the inflammatory response.

    PubMed

    Dorfman, S; Dorfman, D; Leonardi, R; Maroso, J; Cardozo, J; Durán, A

    1994-03-01

    Hemp fiber is obtained from the plant Musa textilis. The cost of preparation of its raw fibers is low. The purpose of this paper was to compare the inflammatory response in the rat muscle tissue originated by both hemp and cotton fibers. Both types of fibers, were implanted in gluteal muscles of Sprague Dawley rats. The rats were sacrificed at 15, 30 and 60 postoperative days. Muscle tissue sections were stained with hematoxilyneosin. The inflammatory response was measured by subtracting the suture surface area from the total granulomatous area. At 15 days, the inflammatory response was more conspicuous for hemp than for cotton fiber (P < 0.05). At 30 and 60 days, responses were similar (P > 0.05). We cannot conclude that the hemp fiber is superior to cotton, nevertheless, they behave the same. Therefore, hemp constitutes an alternative as suture material.

  14. Slow to fast alterations in skeletal muscle fibers caused by clenbuterol, a beta(2)-receptor agonist

    NASA Technical Reports Server (NTRS)

    Zeman, Richard J.; Ludemann, Robert; Easton, Thomas G.; Etlinger, Joseph D.

    1988-01-01

    The effects of a beta(2)-receptor agonist, clenbuterol, and a beta(2) antagonist, butoxamine, on the skeletal muscle fibers of rats were investigated. It was found that chronic treatment of rats with clenbuterol caused hypertrophy of histochemically identified fast-twitch, but not slow-twitch, fibers within the soleus, while in the extensor digitorum longus the mean areas of both fiber types were increased; in both muscles, the ratio of the number of fast-twitch to slow-twitch fibers was increased. In contrast, a treatment with butoxamine caused a reduction of the fast-twitch fiber size in both muscles, and the ratio of the fast-twitch to slow-twitch fibers was decreased.

  15. Slow to fast alterations in skeletal muscle fibers caused by clenbuterol, a beta(2)-receptor agonist

    NASA Technical Reports Server (NTRS)

    Zeman, Richard J.; Ludemann, Robert; Easton, Thomas G.; Etlinger, Joseph D.

    1988-01-01

    The effects of a beta(2)-receptor agonist, clenbuterol, and a beta(2) antagonist, butoxamine, on the skeletal muscle fibers of rats were investigated. It was found that chronic treatment of rats with clenbuterol caused hypertrophy of histochemically identified fast-twitch, but not slow-twitch, fibers within the soleus, while in the extensor digitorum longus the mean areas of both fiber types were increased; in both muscles, the ratio of the number of fast-twitch to slow-twitch fibers was increased. In contrast, a treatment with butoxamine caused a reduction of the fast-twitch fiber size in both muscles, and the ratio of the fast-twitch to slow-twitch fibers was decreased.

  16. Fiber-type distribution of the perivertebral musculature in Ambystoma.

    PubMed

    Schilling, Nadja; Deban, Stephen M

    2010-02-01

    Many salamanders locomote in aquatic and terrestrial environments. During swimming, body propulsion is solely produced by the axial musculature generating lateral undulations of the trunk and tail. During terrestrial locomotion, the trunk is oscillated laterally in a standing wave, and body propulsion is achieved by concerted trunk and limb muscle action. The goal of this study was to increase our knowledge of the functional morphology of the tetrapod trunk. We investigated the muscle-fiber-type distribution and the anatomical cross-sectional area of all perivertebral muscles in Ambystoma tigrinum and A. maculatum. Muscle-fiber-type composition was determined in serial cross-sections based on m-ATPase activity. Five different body segments were investigated to test for cranio-caudal changes along the trunk. The overall fiber-type distribution was very similar between the species, but A. tigrinum had relatively larger muscles than A. maculatum, which may be related to its digging behavior. None of the perivertebral muscles possessed a homogeneous fiber-type composition. The M. interspinalis showed a distinct layered organization and may function to ensure the integrity of the spine (local stabilization). The M. dorsalis trunci exhibited the plesiomorphic pattern for notochordates in having a distinct superficial layer of red and intermediate fibers, which covered the central white fibers; therefore, it is suggested to function as a mobilizer and a stabilizer of the trunk, but, may also be involved in modulating body stiffness. Similarly, the M. subvertebralis showed clear regionalizations, implying functional subunits that can stabilize and mobilize the trunk as well as modulate of body stiffness. Cranio-caudally, neither the fiber-type composition nor the a-csa changed dramatically, possibly reflecting the need to perform well in both aquatic and terrestrial habitats.

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

    NASA Technical Reports Server (NTRS)

    McCormick, K. M.; Schultz, E.

    1992-01-01

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

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

    NASA Technical Reports Server (NTRS)

    McCormick, K. M.; Schultz, E.

    1992-01-01

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

  19. Velocity, force, power, and Ca2+ sensitivity of fast and slow monkey skeletal muscle fibers

    NASA Technical Reports Server (NTRS)

    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.

  20. Further study of the electrical and machanical responses of slow fibers in cat extraocular muscles.

    PubMed

    Pilar, G

    1967-10-01

    Electrical and mechanical responses have been obtained in situ and in vitro from the superior oblique muscle stimulated by single and repetitive electrical pulses, applied to the trochlear nerve. Two different types of muscle fibers are described, the twitch and the slow. The slow type is characterized electrically by the presence of junctional potentials, which have reversal potentials between -10 and -20 mv, and do not show propagated responses or spikes, during nerve stimulation. When the slow muscle fibers are repetitively stimulated in situ, a prolonged contraction is maintained during stimulation. At the time, the recorded electrical activity is produced locally, at the level of the neuromuscular junctions of the slow fibers. These results indicate that the contractile mechanism of the slow muscle fibers is activated locally and segmentally.

  1. Muscle Fiber Orientation Angle Dependence of the Tensile Fracture Behavior of Frozen Fish Muscle

    NASA Astrophysics Data System (ADS)

    Hagura, Yoshio; Okamoto, Kiyoshi; Suzuki, Kanichi; Kubota, Kiyoshi

    We have proposed a new cutting method for frozen fish named "cryo-cutting". This method applied tensile fracture force or bending fracture force to the frozen fish at appropriate low temperatures. In this paper, to clarify cryo-cutting mechanism, we analyzed tensile fracture behavior of the frozen fish muscle. In the analysis, the frozen fish muscle was considered unidirectionally fiber-reinforced composite material which consisted of fiber (muscle fiber) and matrix (connective tissue). Fracture criteria (maximum stress criterion, Tsai-Hill criterion) for the unidirectionally fiber-reinforced composite material were used. The following results were obtained: (1) By using Tsai-Hill criterion, muscle fiber orientation angle dependence of the tensile fracture stress could be calculated. (2) By using the maximum stress theory jointly with Tsai-Hill criterion, muscle fiber orientation angle dependence of the fracture mode of the frozen fish muscle could be estimated.

  2. Effects of chronic centrifugation on skeletal muscle fibers in young developing rats

    NASA Technical Reports Server (NTRS)

    Martin, W. D.

    1980-01-01

    Three groups of 30-d old male and female rats were centrifuged for 2, 4, 8, and 16 weeks, after which their soleus and plantaris muscles were analysed for changes in proportions of muscle fiber types. The groups were: earth control, maintained at earth gravity without rotation; rotation control, subjected to a gravitational force of 1.05 G and 28 rpm; and rotation experimental, subjected to a gravitational force of 2 G and 28 rpm. Muscle fibers were classified into four fiber types on the basis of actomyosin ATPase activity as slow oxidative, fast oxidative glycolytic and either fast glycolytic (plantaris) or intermediate (soleus). Hypergravity resulted in an increase in slow oxidative fibers in soleus relative to the earth control, but not of females treated similarly. The relationship of body weight to the changes in proportion of slow oxidative fibers is discussed.

  3. Effects of chronic centrifugation on skeletal muscle fibers in young developing rats

    NASA Technical Reports Server (NTRS)

    Martin, W. D.

    1980-01-01

    Three groups of 30-d old male and female rats were centrifuged for 2, 4, 8, and 16 weeks, after which their soleus and plantaris muscles were analysed for changes in proportions of muscle fiber types. The groups were: earth control, maintained at earth gravity without rotation; rotation control, subjected to a gravitational force of 1.05 G and 28 rpm; and rotation experimental, subjected to a gravitational force of 2 G and 28 rpm. Muscle fibers were classified into four fiber types on the basis of actomyosin ATPase activity as slow oxidative, fast oxidative glycolytic and either fast glycolytic (plantaris) or intermediate (soleus). Hypergravity resulted in an increase in slow oxidative fibers in soleus relative to the earth control, but not of females treated similarly. The relationship of body weight to the changes in proportion of slow oxidative fibers is discussed.

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

    PubMed Central

    Buck, Amanda K. W.; Ding, Zhaohua; Elder, Christopher P.; Towse, Theodore F.; Damon, Bruce M.

    2015-01-01

    Purpose 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). Materials and Methods 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. Results 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. Conclusion Modest anisotropic smoothing (10%) improved fiber-tracking results, while preserving structural features. PMID:26010830

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  8. Metabolic and morphologic properties of single muscle fibers in the rat after spaceflight, Cosmos 1887

    NASA Technical Reports Server (NTRS)

    Miu, B.; Martin, T. P.; Roy, R. R.; Oganov, V.; Ilyina-Kakueva, E.; Marini, J. F.; Leger, J. J.; Bodine-Fowler, S. C.; Edgerton, V. R.

    1990-01-01

    The adaptation of a slow (soleus, Sol) and a fast (medial gastrocnemius, MG) skeletal muscle to spaceflight was studied in five young male rats. The flight period was 12.5 days and the rats were killed approximately 48 h after returning to 1 g. Five other rats that were housed in cages similar to those used by the flight rats were maintained at 1 g for the same period of time to serve as ground-based controls. Fibers were classified as dark or light staining for myosin adenosine triphosphatase (ATPase). On the average, the fibers in the Sol of the flight rats atrophied twice as much as those in the MG. Further, the fibers located in the deep (close to the bone and having the highest percentage of light ATPase and high oxidative fibers in the muscle cross section) region of the MG atrophied more than the fibers located in the superficial (away from the bone and having the lowest percentage of light ATPase and high oxidative fibers in the muscle cross-section) region of the muscle. Based on quantitative histochemical assays of single muscle fibers, succinate dehydrogenase (SDH) activity per unit volume was unchanged in fibers of the Sol and MG. However, in the Sol, but not the MG, the total amount of SDH activity in a 10-microns-thick section of a fiber decreased significantly in response to spaceflight. Based on population distributions, it appears that the alpha-glycerophosphate dehydrogenase (GPD) activities were elevated in the dark ATPase fibers in the Sol, whereas the light fibers in the Sol and both fiber types in the MG did not appear to change. The ratio of GPD to SDH activities increased in the dark (but not light) fibers of the Sol and was unaffected in the MG. Immunohistochemical analyses indicate that approximately 40% of the fibers in the Sol of flight rats expressed a fast myosin heavy chain compared with 22% in control rats. Further, 31% of the fibers in the Sol of flight rats expressed both fast and slow myosin heavy chains compared with 8% in

  9. Metabolic and morphologic properties of single muscle fibers in the rat after spaceflight, Cosmos 1887

    NASA Technical Reports Server (NTRS)

    Miu, B.; Martin, T. P.; Roy, R. R.; Oganov, V.; Ilyina-Kakueva, E.; Marini, J. F.; Leger, J. J.; Bodine-Fowler, S. C.; Edgerton, V. R.

    1990-01-01

    The adaptation of a slow (soleus, Sol) and a fast (medial gastrocnemius, MG) skeletal muscle to spaceflight was studied in five young male rats. The flight period was 12.5 days and the rats were killed approximately 48 h after returning to 1 g. Five other rats that were housed in cages similar to those used by the flight rats were maintained at 1 g for the same period of time to serve as ground-based controls. Fibers were classified as dark or light staining for myosin adenosine triphosphatase (ATPase). On the average, the fibers in the Sol of the flight rats atrophied twice as much as those in the MG. Further, the fibers located in the deep (close to the bone and having the highest percentage of light ATPase and high oxidative fibers in the muscle cross section) region of the MG atrophied more than the fibers located in the superficial (away from the bone and having the lowest percentage of light ATPase and high oxidative fibers in the muscle cross-section) region of the muscle. Based on quantitative histochemical assays of single muscle fibers, succinate dehydrogenase (SDH) activity per unit volume was unchanged in fibers of the Sol and MG. However, in the Sol, but not the MG, the total amount of SDH activity in a 10-microns-thick section of a fiber decreased significantly in response to spaceflight. Based on population distributions, it appears that the alpha-glycerophosphate dehydrogenase (GPD) activities were elevated in the dark ATPase fibers in the Sol, whereas the light fibers in the Sol and both fiber types in the MG did not appear to change. The ratio of GPD to SDH activities increased in the dark (but not light) fibers of the Sol and was unaffected in the MG. Immunohistochemical analyses indicate that approximately 40% of the fibers in the Sol of flight rats expressed a fast myosin heavy chain compared with 22% in control rats. Further, 31% of the fibers in the Sol of flight rats expressed both fast and slow myosin heavy chains compared with 8% in

  10. Slow fiber cluster pattern in pig longissimus thoracis muscle: implications for myogenesis.

    PubMed

    Fonseca, S; Wilsons, I J; Horgan, G W; Maltin, C A

    2003-04-01

    Recent evidence implicates fiber type proportions as playing a role in meat eating quality, and in pigs it has been suggested that the slow oxidative fibers contribute to both juiciness and tenderness. The fiber distribution in pigs is different from that found in most other species, in which the various types of skeletal muscle fiber are distributed in a "checkerboard" pattern, because in pigs the slow oxidative fibers have a clustered distribution. The initial processes leading to fiber clustering are likely to occur during myogenesis, but the precise mechanistic aetiology of this patterning and whether the slow oxidative fiber clusters occur in a random or ordered fashion is unknown. In the present study longissimus thoracis muscle from Large White crossbred pigs was sampled at the 10th rib, 48 h postmortem. Transverse cryo-sections were cut and histochemically stained to allow the identification of the main muscle fiber types: slow oxidative, fast glycolytic, and fast oxidative glycolytic. Images of the sections were captured and analyzed using point processes and Voronoi Tesselations to examine the randomness and spatial distribution of the clusters of slow oxidative fibers found in pig longissimus thoracis muscle. The results showed that an assumption of complete spatial randomness can be rejected and that a mathematical model incorporating a minimum distance of 1.7 to 2.0 microm between cluster centers produced fiber patterns similar to those observed in the original transverse sections of the muscle. In addition, if it assumed that the central fiber in each cluster is derived from primary myoblast progenitors, these results suggest that there may be some degree of repulsion between the primary fibers during the initial stages of cluster formation. The mechanistic basis of such repulsion is not clear, but it is speculated that secreted factors, such as sonic hedgehog or myostatin may play a role.

  11. Experiment K-308: Automatic analysis of muscle fibers from rats subjected to spaceflight

    NASA Technical Reports Server (NTRS)

    Castleman, K. R.; Chui, L. A.; Vandermeullen, J. P.

    1981-01-01

    The morphology of histochemically prepared muscle sections from the gastrocnemius and plantaris muscles of flight and vivarium control rats was studied quantitatively. Both fast-twitch and slow-twitch fibers were significantly smaller in flight groups than in control groups. Fibers in group 4F were somewhat larger than in 1F, presumably due to growth after recovery. Fibers in 4V were slightly larger than in 1V, presumably due to age. The slow fibers showed more spaceflight induced size loss than fast fibers, suggesting they suffered more from hypogravity. The proportion of slow fibers was also lower in the flight groups, suggesting spaceflight induced fiber type conversion from slow to fast.

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

    PubMed

    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.

  13. Contributions of dynamic phosphorus-31 magnetic resonance spectroscopy to the analysis of muscle fiber distribution.

    PubMed

    Schunk, K; Losch, O; Kreitner, K F; Kersjes, W; Schadmand-Fischer, S; Thelen, M

    1999-05-01

    In high-performance athletes, conclusions regarding the muscle fiber distribution were to be drawn from dynamic 31phosphorus magnetic resonance spectroscopy (31P MRS). Eleven volleyball players (V), eight bodybuilders (B), and 22 nonathletic volunteers (N) were examined by dynamic 31P MRS. During rest, exhaustive exercise, and recovery, respectively, up to 60 consecutive phosphorus spectra of the quadriceps muscle were acquired by "time series" in 36 s each. Two main spectroscopic approaches to the spectroscopic analysis of muscle fiber distribution were applied: evaluation of the ratio Pi/PCr at rest and the computer-assisted analysis of the Pi-peak at its exercise-induced line width maximum. At rest, the bodybuilders showed a significant lower Pi/PCr (0.07 +/- 0.03), in comparison with the volleyball players (0.11 +/- 0.03) and the nonathletic volunteers (0.11 +/- 0.02). The computer-assisted analysis of the Pi-peak at its line width maximum revealed a significantly lower pH of both of the subpeaks in the bodybuilders [6.30 versus 6.37 (V) and 6.38 (N); 6.89 versus 6.92 (V, N)], whereas the volleyball players provided the largest proportion of oxidative muscle fibers (68%), compared to bodybuilders (64%) and nonathletic volunteers (59%). A correlation between the ratio Pi/PCr and the area of the subpeak with the high pH (representing oxidative fibers) could not be demonstrated. Spectroscopic results during rest and exercise may be influenced by the muscle fiber distribution of the respective volunteer. The applied spectroscopic approaches to the analysis of muscle fiber composition are not compatible with each other; depending on the applied method, the classification of a muscle fiber as type I or type II fiber may change. The influence of physiologic factors like muscle fiber distribution on spectroscopic results has to be considered in the interpretation of pathological conditions.

  14. Size and myonuclear domains in Rhesus soleus muscle fibers: short-term spaceflight

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Talmadge, R. J.; Bodine, S. C.; Fanton, J. W.; Koslovskaya, I.; Edgerton, V. R.

    2001-01-01

    The cross-sectional area (CSA), myonuclear number per mm of fiber length, and myonuclear domain (cytoplasmic volume/myonucleus) of mechanically isolated single fibers from biopsies of the soleus muscle of 5 vivarium control, 3 flight simulation and 2 flight (BION 11) Rhesus monkeys (Macaca [correction of Macacca] mulatta) were determined using confocal microscopy before and after a 14-day experimental period. Simulation monkeys were confined in chairs placed in capsules identical to those used during the flight. Fibers were classified as type I, type II or hybrid (containing both types I and II) based on myosin heavy chain (MHC) gel electrophoresis. A majority of the fibers sampled contained only type I MHC, i.e. 89, 62 and 68% for the control, simulation and flight groups, respectively. Most of the remaining fibers were hybrids, i.e. 8, 36 and 32% for the same groups. There were no significant pre-post differences in the fiber type composition for any of the experimental groups. There also were no significant pre-post differences in fiber CSA, myonuclear number or myonuclear domain. There was, however, a tendency for the fibers in the post-flight biopsies to have a smaller mean CSA and myonuclear domain (approximately 10%, p=0.07) than the fibers in the pre-flight biopsy. The combined mean cytoplasmic volume/myonucleus for all muscle fiber phenotypes in the Rhesus soleus muscle was approximately 25,000 micrometers3 and there were no differences in pre-post samples for the control and simulated groups. The cytoplasmic domains tended to be lower (p=0.08) after than before flight. No phenotype differences in cytoplasmic domains were observed. These data suggest that after a relatively short period of actual spaceflight, modest fiber atrophy occurs in the soleus muscle fibers without a concomitant change in myonuclear number.

  15. Size and myonuclear domains in Rhesus soleus muscle fibers: short-term spaceflight

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Talmadge, R. J.; Bodine, S. C.; Fanton, J. W.; Koslovskaya, I.; Edgerton, V. R.

    2001-01-01

    The cross-sectional area (CSA), myonuclear number per mm of fiber length, and myonuclear domain (cytoplasmic volume/myonucleus) of mechanically isolated single fibers from biopsies of the soleus muscle of 5 vivarium control, 3 flight simulation and 2 flight (BION 11) Rhesus monkeys (Macaca [correction of Macacca] mulatta) were determined using confocal microscopy before and after a 14-day experimental period. Simulation monkeys were confined in chairs placed in capsules identical to those used during the flight. Fibers were classified as type I, type II or hybrid (containing both types I and II) based on myosin heavy chain (MHC) gel electrophoresis. A majority of the fibers sampled contained only type I MHC, i.e. 89, 62 and 68% for the control, simulation and flight groups, respectively. Most of the remaining fibers were hybrids, i.e. 8, 36 and 32% for the same groups. There were no significant pre-post differences in the fiber type composition for any of the experimental groups. There also were no significant pre-post diff