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Journal articles on the topic 'Skeletal Muscle Fibers'
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1
Larson, Lauren, Jessica Lioy, Jordan Johnson, and Scott Medler. "Transitional Hybrid Skeletal Muscle Fibers in Rat Soleus Development." Journal of Histochemistry & Cytochemistry 67, no. 12 (September 11, 2019): 891–900. http://dx.doi.org/10.1369/0022155419876421.
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Skeletal muscles comprise hundreds of individual muscle fibers, with each possessing specialized contractile properties. Skeletal muscles are recognized as being highly plastic, meaning that the physiological properties of single muscle fibers can change with appropriate use. During fiber type transitions, one myosin heavy chain isoform is exchanged for another and over time the fundamental nature of the fiber adapts to become a different fiber type. Within the rat triceps surae complex, the soleus muscle starts out as a muscle comprised of a mixture type IIA and type I fibers. As neonatal rats grow and mature, the soleus undergoes a near complete transition into a muscle with close to 100% type I fibers at maturity. We used immunohistochemistry and single fiber SDS-PAGE to track the transformation of type IIA into type I fibers. We found that transitioning fibers progressively incorporate new myofibrils containing type I myosin into existing type IIA fibers. During this exchange, distinct type I-containing myofibrils are segregated among IIA myofibrils. The individual myofibrils within existing muscle fibers thus appear to represent the functional unit that is exchanged during fiber type transitions that occur as part of normal muscle development:
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Mattson, John P., Todd A. Miller, David C. Poole, and Michael D. Delp. "Fiber Composition and Oxidative Capacity of Hamster Skeletal Muscle." Journal of Histochemistry & Cytochemistry 50, no. 12 (December 2002): 1685–92. http://dx.doi.org/10.1177/002215540205001214.
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The hamster is a valuable biological model for physiological investigation. Despite the obvious importance of the integration of cardiorespiratory and muscular system function, little information is available regarding hamster muscle fiber type and oxidative capacity, both of which are key determinants of muscle function. The purpose of this investigation was to measure immunohistochemically the relative composition and size of muscle fibers composed of types I, IIA, IIX, and IIB fibers in hamster skeletal muscle. The oxidative capacity of each muscle was also assessed by measuring citrate synthase activity. Twenty-eight hindlimb, respiratory, and facial muscles or muscle parts from adult (144–147 g bw) male Syrian golden hamsters ( n=3) were dissected bilaterally, weighed, and frozen for immunohistochemical and biochemical analysis. Combining data from all 28 muscles analyzed, type I fibers made up 5% of the muscle mass, type IIA fibers 16%, type IIX fibers 39%, and type IIB fibers 40%. Mean fiber cross-sectional area across muscles was 1665 ± 328 μm2 for type I fibers, 1900 ± 417 μm2 for type IIA fibers, 3230 ± 784 μm2 for type IIX fibers, and 4171 ± 864 μm2 for type IIB fibers. Citrate synthase activity was most closely related to the population of type IIA fibers ( r=0.68, p<0.0001) and was in the rank order of type IIA > I > IIX > IIB. These data demonstrate that hamster skeletal muscle is predominantly composed of type IIB and IIX fibers.
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Donovan, C. M., and J. A. Faulkner. "Plasticity of skeletal muscle: regenerating fibers adapt more rapidly than surviving fibers." Journal of Applied Physiology 62, no. 6 (June 1, 1987): 2507–11. http://dx.doi.org/10.1152/jappl.1987.62.6.2507.
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The properties of mammalian skeletal muscle demonstrate a high degree of structural and functional plasticity as evidenced by their adaptability to an atypical site after cross-transplantation and to atypical innervation after cross-innervation. We tested the hypothesis that, regardless of fiber type, skeletal muscles composed of regenerating fibers adapt more readily than muscles composed of surviving fibers when placed in an atypical site with atypical innervation. Fast muscles of rats were autografted into the site of slow muscles or vice versa with the donor muscle innervated by the motor nerve to the recipient site. Surviving fibers in donor muscles were obtained by grafting with vasculature intact (vascularized muscle graft), and regenerating fibers were obtained by grafting with vasculature severed (free muscle graft). Our hypothesis was supported because 60 days after grafting, transposed muscles with surviving fibers demonstrated only a slight change from the contractile properties and fiber typing of donor muscles, whereas transplanted muscles with regenerating fibers demonstrated almost complete change to those of the muscle formerly in the atypical site.
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Emerson, Geoffrey G., and Steven S. Segal. "Alignment of microvascular units along skeletal muscle fibers of hamster retractor." Journal of Applied Physiology 82, no. 1 (January 1, 1997): 42–48. http://dx.doi.org/10.1152/jappl.1997.82.1.42.
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Emerson, Geoffrey G., and Steven S. Segal. Alignment of microvascular units along skeletal muscle fibers of hamster retractor. J. Appl. Physiol. 82(1): 42–48, 1997.—When muscle fibers contract, blood flow requirements increase along their entire length. However, the organization of capillary perfusion along muscle fibers is unclear. The microvascular unit (MVU) is defined as a terminal arteriole and the group of capillaries it supplies. We investigated whether neighboring MVUs along the fiber axis perfused the same group of muscle fibers by using the parallel-fibered retractor muscle. Hamsters were anesthetized and perfused with Microfil to visualize MVUs relative to muscle fibers. Fields of study, which encompassed five to seven neighboring MVUs along a muscle fiber, were chosen from the interior of muscles and along muscle edges. On average, MVUs were 1 mm in length, 0.50 mm in width, and 0.1 mm deep; segments of ∼30 fibers were contained in this tissue volume of 0.05 mm3 (20 MVUs/mg muscle). The total distance across muscle fibers encompassed by a pair of MVUs is designated “union” (U); the fraction of this distance common to both MVUs is designated “intersection” (I). The ratio of I to U for the widths of neighboring MVUs provides an index of MVU alignment along muscle fibers (e.g., I/U = 1.0 indicates complete alignment, where the fibers perfused by one MVU are the same as those perfused by the neighboring MVU). We found that I/U along muscle edges (0.71 ± 0.02) was greater ( P < 0.05) than the ratio measured within muscles (0.66 ± 0.02). A model predicted a maximum I/U of 0.58 with random MVU alignment. Thus measured values were closer to random than to complete alignment. These findings indicate that an increase in blood flow along muscle fibers requires the perfusion of many MVUs and imply that vasodilation is coordinated among the parent arterioles from which corresponding MVUs arise.
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Brunner, Florian, Annina Schmid, Ali Sheikhzadeh, Margareta Nordin, Jangwhon Yoon, and Victor Frankel. "Effects of Aging on Type II Muscle Fibers: A Systematic Review of the Literature." Journal of Aging and Physical Activity 15, no. 3 (July 2007): 336–48. http://dx.doi.org/10.1123/japa.15.3.336.
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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.
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Caiozzo, Vincent J., Michael J. Baker, Karen Huang, Harvey Chou, Ya Zhen Wu, and Kenneth M. Baldwin. "Single-fiber myosin heavy chain polymorphism: how many patterns and what proportions?" American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 285, no. 3 (September 2003): R570—R580. http://dx.doi.org/10.1152/ajpregu.00646.2002.
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Previous studies have reported the existence of skeletal muscle fibers that coexpress multiple myosin heavy chain isoforms. These surveys have usually been limited to studying the polymorphic profiles of skeletal muscle fibers from a limited number of muscles (i.e., usually <4). Additionally, few studies have considered the functional implications of polymorphism. Hence, the primary objective of this study was to survey a relatively large number of rat skeletal muscle/muscle regions and muscle fibers ( n≈ 5,000) to test the hypothesis that polymorphic fibers represent a larger fraction of the total pool of fibers than do so-called monomorphic fibers, which express only one myosin heavy chain isoform. Additionally, we used Hill's statistical model of the force-velocity relationship to differentiate the functional consequences of single-fiber myosin heavy chain isoform distributions found in these muscles. The results demonstrate that most muscles and regions of rodent skeletal muscles contain large proportions of polymorphic fibers, with the exception of muscles such as the slow soleus muscle and white regions of fast muscles. Several muscles were also found to have polymorphic profiles that are not consistent with the I↔IIA↔IIX↔IIB scheme of muscle plasticity. For instance, it was found that the diaphragm muscle normally contains I/IIX fibers. Functionally, the high degree of polymorphism may 1) represent a strategy for producing a spectrum of contractile properties that far exceeds that simply defined by the presence of four myosin heavy chain isoforms and 2) result in relatively small differences in function as defined by the force-velocity relationship.
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Wei, Wei, Chengwan Zha, Aiwen Jiang, Zhe Chao, Liming Hou, Honglin Liu, Ruihua Huang, and Wangjun Wu. "A Combined Differential Proteome and Transcriptome Profiling of Fast- and Slow-Twitch Skeletal Muscle in Pigs." Foods 11, no. 18 (September 14, 2022): 2842. http://dx.doi.org/10.3390/foods11182842.
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Skeletal muscle fiber types can contribute in part to affecting pork quality parameters. Biceps femoris (Bf) (fast muscle or white muscle) and Soleus (Sol) (slow muscle or red muscle) are two typical skeletal muscles characterized by obvious muscle fiber type differences in pigs. However, the critical proteins and potential regulatory mechanisms regulating porcine skeletal muscle fibers have yet to be clearly defined. In this study, the isobaric Tag for Relative and Absolute Quantification (iTRAQ)-based proteome was used to identify the key proteins affecting the skeletal muscle fiber types with Bf and Sol, by integrating the previous transcriptome data, while function enrichment analysis and a protein–protein interaction (PPI) network were utilized to explore the potential regulatory mechanisms of skeletal muscle fibers. A total of 126 differentially abundant proteins (DAPs) between the Bf and Sol were identified, and 12 genes were found to be overlapping between differentially expressed genes (DEGs) and DAPs, which are the critical proteins regulating the formation of skeletal muscle fibers. Functional enrichment and PPI analysis showed that the DAPs were mainly involved in the skeletal-muscle-associated structural proteins, mitochondria and energy metabolism, tricarboxylic acid cycle, fatty acid metabolism, and kinase activity, suggesting that PPI networks including DAPs are the main regulatory network affecting muscle fiber formation. Overall, these data provide valuable information for understanding the molecular mechanism underlying the formation and conversion of muscle fiber types, and provide potential markers for the evaluation of meat quality.
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Paul, Angelika C., and Nadia Rosenthal. "Different modes of hypertrophy in skeletal muscle fibers." Journal of Cell Biology 156, no. 4 (February 11, 2002): 751–60. http://dx.doi.org/10.1083/jcb.200105147.
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Skeletal muscles display a remarkable diversity in their arrangement of fibers into fascicles and in their patterns of innervation, depending on functional requirements and species differences. Most human muscle fascicles, despite their great length, consist of fibers that extend continuously from one tendon to the other with a single nerve endplate band. Other mammalian muscles have multiple endplate bands and fibers that do not insert into both tendons but terminate intrafascicularly. We investigated whether these alternate structural features may dictate different modes of cell hypertrophy in two mouse gracilis muscles, in response to expression of a muscle-specific insulin-like growth factor (IGF)-1 transgene (mIGF-1) or to chronic exercise. Both hypertrophic stimuli independently activated GATA-2 expression and increased muscle cross-sectional area in both muscle types, with additive effects in exercising myosin light chain/mIGF transgenic mice, but without increasing fiber number. In singly innervated gracilis posterior muscle, hypertrophy was characterized by a greater average diameter of individual fibers, and centralized nuclei. In contrast, hypertrophic gracilis anterior muscle, which is multiply innervated, contained longer muscle fibers, with no increase in average diameter, or in centralized nuclei. Different modes of muscle hypertrophy in domestic and laboratory animals have important implications for building appropriate models of human neuromuscular disease.
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Braund, Kyle G., Karen A. Amling, Jagjivan R. Mehta, Janet E. Steiss, and Carole Scholz. "Histochemical and morphometric study of fiber types in ten skeletal muscles of healthy young adult cats." American Journal of Veterinary Research 56, no. 3 (March 1, 1995): 349–57. http://dx.doi.org/10.2460/ajvr.1995.56.03.349.
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SUMMARY A histochemical and morphometric study of fiber types in a variety of skeletal muscles of healthy young adult cats was undertaken to provide normative data not available previously. Using a standardized system of nomenclature, fiber types 1, 2A, 2B, and 2C were identified in most cat muscles on the basis of myosin ATPase staining at pH 4.45. Type-2M fibers were present in temporalis (tem) and masseter (mas) muscles. Type-1 fibers predominated in medial head of triceps (mht) and soleus muscles. Type-2B fibers were dominant in biceps femoris, lateral head of gastrocnemius, cranial tibial, long head of triceps, and superficial digital flexor muscles; type-2A fibers were dominant in buccinator muscle samples; and type-2M fibers were dominant in tem and mas muscles. Numbers of type-2C fibers did not exceed 2 to 3% of the myofiber population in any muscle. In CT and LHT muscles, a gradient of fiber type distribution was observed, with significant (P < 0.05) increase in numbers of type-1 and type-2A fibers in deeper regions of the muscles. The distribution of fiber types was compartmentalized in mht and mas specimens. Diameter of type-2B fibers was significantly (P < 0.05) larger than that of type-1 and type-2A fibers in biceps femoris, lateral head of gastrocnemius, cranial tibial, long head of triceps, and superficial mht muscles. Diameter of type-2M fibers was significantly (P < 0.05) larger than that of type-1 fibers in tem and mas muscles. The soleus type-1 muscle fibers were the largest fibers encountered in any muscle. In mht muscle, fiber diameter of type-1 and type-2B fibers varied significantly (P < 0.05) in oxidative and glycolytic compartments. Variability coefficients were less than 200 in all muscles. In every muscle specimen, the number of fibers with internal nuclei was less than or equal to 2%.
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Thabet, M., T. Miki, S. Seino, and J. M. Renaud. "Treadmill running causes significant fiber damage in skeletal muscle of KATP channel-deficient mice." Physiological Genomics 22, no. 2 (July 14, 2005): 204–12. http://dx.doi.org/10.1152/physiolgenomics.00064.2005.
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Although it has been suggested that the ATP-sensitive K+ (KATP) channel protects muscle against function impairment, most studies have so far given little evidence for significant perturbation in the integrity and function of skeletal muscle fibers from inactive mice that lack KATP channel activity in their cell membrane. The objective was, therefore, to test the hypothesis that KATP channel-deficient skeletal muscle fibers become damaged when mice are subjected to stress. Wild-type and KATP channel-deficient mice (Kir6.2−/− mice) were subjected to 4–5 wk of treadmill running at either 20 m/min with 0° inclination or at 24 m/min with 20° uphill inclination. Muscles of all wild-type mice and of nonexercised Kir6.2−/− mice had very few fibers with internal nuclei. After 4–5 wk of treadmill running, there was little evidence for connective tissues and mononucleated cells in Kir6.2−/− hindlimb muscles, whereas the number of fibers with internal nuclei, which appear when damaged fibers are regenerated by satellite cells, was significantly higher in Kir6.2−/− than wild-type mice. Between 5% and 25% of the total number of fibers in Kir6.2−/− extensor digitum longus, plantaris, and tibialis muscles had internal nuclei, and most of such fibers were type IIB fibers. Contrary to hindlimb muscles, diaphragms of Kir6.2−/− mice that had run at 24 m/min had few fibers with internal nuclei, but mild to severe fiber damage was observed. In conclusion, the study provides for the first time evidence 1) that the KATP channels of skeletal muscle are essential to prevent fiber damage, and thus muscle dysfunction; and 2) that the extent of fiber damage is greater and the capacity of fiber regeneration is less in Kir6.2−/− diaphragm muscles compared with hindlimb muscles.
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Braga, Sérgio De Almeida, Felipe Gomes Ferreira Padilha, and Ana Maria Reis Ferreira. "Needle muscle biopsy: technique validation and histological and histochemical methods for evaluating canine skeletal muscles." Semina: Ciências Agrárias 38, no. 2 (May 2, 2017): 765. http://dx.doi.org/10.5433/1679-0359.2017v38n2p765.
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This study evaluated the needle muscle biopsy technique using a 6G Bergström percutaneous needle combined with histological and histochemical methods to analyze the skeletal muscle of dogs. There are few studies about canine skeletal muscles and a lack of reports in the literature about tissue collection and analysis for canine species. Evaluation of 32 German Shepherd samples collected from the gluteus medius, at a depth of 3 cm, was performed. The choice of gluteus medius and the 3-cm depth provided good quantity fragments with sufficient sizes (3–5 mm), which permitted optimal visualization of muscle fibers. Myosin ATPase, at pH 9.4, 4.6, and 4.3, and SDH reactions revealed that all muscle samples analyzed had fibers in the classic mosaic arrangement, enabling counting and typification. The mean percentages of fibers were 29.95% for type I and 70.05% for type II. On the basis of these results, we concluded that the percutaneous needle biopsy technique for canine skeletal muscles is a safe and easy procedure that obtains fragments of proper sizes, thereby enabling the study of muscle fibers. Standardization of the muscle of choice and the depth of muscle sample collection significantly contributed to this success. This is an important method to evaluate muscle fiber types of dogs and diagnose important diseases affecting the skeletal muscles.
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Delp, Michael D., Changping Duan, John P. Mattson, and Timothy I. Musch. "Changes in skeletal muscle biochemistry and histology relative to fiber type in rats with heart failure." Journal of Applied Physiology 83, no. 4 (October 1, 1997): 1291–99. http://dx.doi.org/10.1152/jappl.1997.83.4.1291.
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Delp, Michael D., Changping Duan, John P. Mattson, and Timothy I. Musch. Changes in skeletal muscle biochemistry and histology relative to fiber type in rats with heart failure. J. Appl. Physiol. 83(4): 1291–1299, 1997.—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 β-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.
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Eggers, Britta, Karin Schork, Michael Turewicz, Katalin Barkovits, Martin Eisenacher, Rolf Schröder, Christoph S. Clemen, and Katrin Marcus. "Advanced Fiber Type-Specific Protein Profiles Derived from Adult Murine Skeletal Muscle." Proteomes 9, no. 2 (June 8, 2021): 28. http://dx.doi.org/10.3390/proteomes9020028.
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Skeletal muscle is a heterogeneous tissue consisting of blood vessels, connective tissue, and muscle fibers. The last are highly adaptive and can change their molecular composition depending on external and internal factors, such as exercise, age, and disease. Thus, examination of the skeletal muscles at the fiber type level is essential to detect potential alterations. Therefore, we established a protocol in which myosin heavy chain isoform immunolabeled muscle fibers were laser microdissected and separately investigated by mass spectrometry to develop advanced proteomic profiles of all murine skeletal muscle fiber types. All data are available via ProteomeXchange with the identifier PXD025359. Our in-depth mass spectrometric analysis revealed unique fiber type protein profiles, confirming fiber type-specific metabolic properties and revealing a more versatile function of type IIx fibers. Furthermore, we found that multiple myopathy-associated proteins were enriched in type I and IIa fibers. To further optimize the assignment of fiber types based on the protein profile, we developed a hypothesis-free machine-learning approach, identified a discriminative peptide panel, and confirmed our panel using a public data set.
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Giacomello, Emiliana, Emanuela Crea, Lucio Torelli, Alberta Bergamo, Carlo Reggiani, Gianni Sava, and Luana Toniolo. "Age Dependent Modification of the Metabolic Profile of the Tibialis Anterior Muscle Fibers in C57BL/6J Mice." International Journal of Molecular Sciences 21, no. 11 (May 30, 2020): 3923. http://dx.doi.org/10.3390/ijms21113923.
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Skeletal muscle aging is accompanied by mass reduction and functional decline, as a result of multiple factors, such as protein expression, morphology of organelles, metabolic equilibria, and neural communication. Skeletal muscles are formed by multiple fibers that express different Myosin Heavy Chains (MyHCs) and have different metabolic properties and different blood supply, with the purpose to adapt their contraction to the functional need. The fine interplay between the different fibers composing a muscle and its architectural organization determine its functional properties. Immunohistochemical and histochemical analyses of the skeletal muscle tissue, besides evidencing morphological characteristics, allow for the precise determination of protein expression and metabolic properties, providing essential information at the single-fiber level. Aiming to gain further knowledge on the influence of aging on skeletal muscles, we investigated the expression of the MyHCs, the Succinate Dehydrogenase (SDH) activity, and the presence of capillaries and Tubular Aggregates (TAs) in the tibialis anterior muscles of physiologically aging C57BL/6J mice aged 8 (adult), 18 (middle aged), and 24 months (old). We observed an increase of type-IIB fast-contracting fibers, an increase of the oxidative capacity of type-IIX and -IIA fibers, a general decrease of the capillarization, and the onset of TAs in type-IIB fibers. These data suggest that aging entails a selective modification of the muscle fiber profiles.
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Laszewski-Williams, B., R. L. Ruff, and A. M. Gordon. "Influence of fiber type and muscle source on Ca2+ sensitivity of rat fibers." American Journal of Physiology-Cell Physiology 256, no. 2 (February 1, 1989): C420—C427. http://dx.doi.org/10.1152/ajpcell.1989.256.2.c420.
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This study investigated the influence of muscle source and fiber type on the calcium sensitivity of skinned rat skeletal muscle fibers from predominantly slow muscles [soleus (SOL) and adductor longus (AL)], mixed muscle [posterior gracilis (PG)], and predominantly fast-twitch muscle [extensor digitorum longus (EDL)]. Fibers were characterized histochemically and by one-dimensional protein gel electrophoresis, and calcium-tension relationships were determined. Fiber type and muscle source had significant effects on the negative log of the calcium concentration associated with half-maximal tension (pCa1/2). Slow-twitch fibers had larger values of pCa1/2 than did fast-twitch fibers. Slow-twitch fibers from the predominantly slow muscles, SOL and AL, had similar values of pCa1/2 but slightly smaller values than from the mixed muscle, PG. Fast-glycolytic (FG) fibers from the predominantly fast muscle, EDL, had a higher pCa1/2 than fibers from the mixed fiber type muscle, PG. There were no differences between the pCa1/2 associated with FG and fast-oxidative-glycolytic fibers.
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Flucher, Bernhard E., Antonio Conti, Hiroshi Takeshima, and Vincenzo Sorrentino. "Type 3 and Type 1 Ryanodine Receptors Are Localized in Triads of the Same Mammalian Skeletal Muscle Fibers." Journal of Cell Biology 146, no. 3 (August 9, 1999): 621–30. http://dx.doi.org/10.1083/jcb.146.3.621.
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The type 3 ryanodine receptor (RyR3) is a ubiquitous calcium release channel that has recently been found in mammalian skeletal muscles. However, in contrast to the skeletal muscle isoform (RyR1), neither the subcellular distribution nor the physiological role of RyR3 are known. Here, we used isoform-specific antibodies to localize RyR3 in muscles of normal and RyR knockout mice. In normal hind limb and diaphragm muscles of young mice, RyR3 was expressed in all fibers where it was codistributed with RyR1 and with the skeletal muscle dihydropyridine receptor. This distribution pattern indicates that RyR3 is localized in the triadic junctions between the transverse tubules and the sarcoplasmic reticulum. During development, RyR3 expression declined rapidly in some fibers whereas other fibers maintained expression of RyR3 into adulthood. Comparing the distribution of RyR3-containing fibers with that of known fiber types did not show a direct correlation. Targeted deletion of the RyR1 or RyR3 gene resulted in the expected loss of the targeted isoform, but had no adverse effects on the expression and localization of the respective other RyR isoform. The localization of RyR3 in skeletal muscle triads, together with RyR1, is consistent with an accessory function of RyR3 in skeletal muscle excitation–contraction coupling.
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Reyes, Nicholas L., Glen B. Banks, Mark Tsang, Daciana Margineantu, Haiwei Gu, Danijel Djukovic, Jacky Chan, et al. "Fnip1 regulates skeletal muscle fiber type specification, fatigue resistance, and susceptibility to muscular dystrophy." Proceedings of the National Academy of Sciences 112, no. 2 (December 29, 2014): 424–29. http://dx.doi.org/10.1073/pnas.1413021112.
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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.
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Gaster, M., P. Poulsen, A. Handberg, H. D. Schrøder, and H. Beck-Nielsen. "Direct evidence of fiber type-dependent GLUT-4 expression in human skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 278, no. 5 (May 1, 2000): E910—E916. http://dx.doi.org/10.1152/ajpendo.2000.278.5.e910.
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GLUT-4 expression in individual fibers of human skeletal muscles in younger and older adults was studied. Furthermore, the dependency of insulin-stimulated glucose uptake on fiber type distribution was investigated. Fiber type distribution was determined in cryosections of muscle biopsies from 8 younger (29 yr) and 8 older (64 yr) healthy subjects, and estimates of GLUT-4 expression in individual fibers were obtained by combining immunohistochemistry and stereology. GLUT-4 was more abundantly expressed in slow compared with fast muscle fibers in both younger ( P < 0.007) and older ( P < 0.001) subjects. A 25% reduction of GLUT-4 density in fast fibers ( P < 0.001) and an unchanged GLUT-4 density in slow fibers were demonstrated in older compared with younger subjects. Insulin-stimulated glucose uptake rates measured by hyperinsulinemic, euglycemic clamp were not correlated with the fraction of slow fibers in the young ( r = −0.45, P > 0.25) or in the elderly ( r = 0.11, P > 0.75) subjects. In conclusion, in human skeletal muscle, GLUT-4 expression is fiber type dependent and decreases with age, particularly in fast muscle fibers.
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Eddinger, T. J., R. G. Cassens, and R. L. Moss. "Mechanical and histochemical characterization of skeletal muscles from senescent rats." American Journal of Physiology-Cell Physiology 251, no. 3 (September 1, 1986): C421—C430. http://dx.doi.org/10.1152/ajpcell.1986.251.3.c421.
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Maximal shortening velocity (Vmax) and isometric tension (Po) were measured in living fiber bundles and skinned fibers from extensor digitorum longus (EDL) and soleus (SOL) muscles of young adult (9 mo) and senescent (30 mo) Fisher 344 rats. The fiber type composition of each muscle preparation was determined using myosin (M)-ATPase histochemistry. Vmax, determined by the slack test method, was unchanged in the EDL but was increased in the SOL muscles of young adult vs. senescent rats. Velocities determined at intermediate loads using the load-stepping technique were slower for EDL bundles but were nearly identical for SOL bundles from senescent vs. young adult rats. Po was greater in SOL and was unchanged in EDL bundles and skinned fibers from senescent vs. young adult rats. M-ATPase histochemistry and Vmax were in agreement for fast and slow muscle bundles and fibers. The relationship between tension and pCa (i.e.,--log[Ca2+]) in skinned fibers from each muscle was similar in both age groups. Sodium dodecyl sulfate-polyacrylamide gels of the skinned fibers consistently showed fast light chains (LCs) in the EDL fibers and slow LCs in the SOL fibers, with no apparent age-related differences.
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Azab, Azab. "Skeletal Muscles: Insight into Embryonic Development, Satellite Cells, Histology, Ultrastructure, Innervation, Contraction and Relaxation, Causes, Pathophysiology, and Treatment of Volumetric Muscle I." Biotechnology and Bioprocessing 2, no. 4 (May 28, 2021): 01–17. http://dx.doi.org/10.31579/2766-2314/038.
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Background: Skeletal muscles are attached to bone and are responsible for the axial and appendicular movement of the skeleton and for maintenance of body position and posture. Objectives: The present review aimed to high light on embryonic development of skeletal muscles, histological and ultrastructure, innervation, contraction and relaxation, causes, pathophysiology, and treatment of volumetric muscle injury. The heterogeneity of the muscle fibers is the base of the flexibility which allows the same muscle to be used for various tasks from continuous low-intensity activity, to repeated submaximal contractions, and to fast and strong maximal contractions. The formation of skeletal muscle begins during the fourth week of embryonic development as specialized mesodermal cells, termed myoblasts. As growth of the muscle fibers continues, aggregation into bundles occurs, and by birth, myoblast activity has ceased. Satellite cells (SCs), have single nuclei and act as regenerative cells. Satellite cells are the resident stem cells of skeletal muscle; they are considered to be self-renewing and serve to generate a population of differentiation-competent myoblasts that will participate as needed in muscle growth, repair, and regeneration. Based on various structural and functional characteristics, skeletal muscle fibres are classified into three types: Type I fibres, Type II-B fibres, and type II-A fibres. Skeletal muscle fibres vary in colour depending on their content of myoglobin. Each myofibril exhibits a repeating pattern of cross-striations which is a product of the highly ordered arrangement of the contractile proteins within it. The parallel myofibrils are arranged with their cross-striations in the register, giving rise to the regular striations seen with light microscopy in longitudinal sections of skeletal muscle. Each skeletal muscle receives at least two types of nerve fibers: motor and sensory. Striated muscles and myotendinous junctions contain sensory receptors that are encapsulated proprioceptors. The process of contraction, usually triggered by neural impulses, obeys the all-or-none law. During muscle contraction, the thin filaments slide past the thick filaments, as proposed by Huxley's sliding filament theory. In response to a muscle injury, SCs are activated and start to proliferate; at this stage, they are often referred to as either myogenic precursor cells (MPC) or myoblasts. In vitro, evidence has been presented that satellite cells can be pushed towards the adipogenic and osteogenic lineages, but contamination of such cultures from non-myogenic cells is sometimes hard to dismiss as the underlying cause of this observed multipotency. There are, however, other populations of progenitors isolated from skeletal muscle, including endothelial cells and muscle-derived stem cells (MDSCs), blood-vessel-associated mesoangioblasts, muscle side-population cells, CD133+ve cells, myoendothelial cells, and pericytes. Volumetric muscle loss (VML) is defined as the traumatic or surgical loss of skeletal muscle with resultant functional impairment. It represents a challenging clinical problem for both military and civilian medicine. VML results in severe cosmetic deformities and debilitating functional loss. In response to damage, skeletal muscle goes through a well-defined series of events including; degeneration (1 to 3days), inflammation, and regeneration (3 to 4 weeks), fibrosis, and extracellular matrix remodeling (3 to 6 months).. Mammalian skeletal muscle has an impressive ability to regenerate itself in response to injury. During muscle tissue repair following damage, the degree of damage and the interactions between muscle and the infiltrating inflammatory cells appear to affect the successful outcome of the muscle repair process. The transplantation of stem cells into aberrant or injured tissue has long been a central goal of regenerative medicine and tissue engineering. Conclusion: It can be concluded that the formation of skeletal muscle begins during the fourth week of embryonic development as specialized mesodermal cells, termed myoblasts, by birth myoblast activity has ceased. Satellite cells are considered to be self-renewing, and serve to generate a population of differentiation-competent myoblasts. Skeletal muscle fibres are classified into three types. The process of contraction, usually triggered by neural impulses, obeys the all-or-none law. VML results in severe cosmetic deformities and debilitating functional loss. Mammalian skeletal muscle has an impressive ability to regenerate itself in response to injury. The transplantation of stem cells into aberrant or injured tissue has long been a central goal of regenerative medicine and tissue engineering.
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van der Poel, Chris, Joshua N. Edwards, William A. Macdonald, and D. George Stephenson. "Mitochondrial superoxide production in skeletal muscle fibers of the rat and decreased fiber excitability." American Journal of Physiology-Cell Physiology 292, no. 4 (April 2007): C1353—C1360. http://dx.doi.org/10.1152/ajpcell.00469.2006.
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Mammalian skeletal muscles generate marked amounts of superoxide (O2·−) at 37°C, but it is not well understood which is the main source of O2·− production in the muscle fibers and how this interferes with muscle function. To answer these questions, O2·− production and twitch force responses were measured at 37°C in mechanically skinned muscle fibers of rat extensor digitorum longus (EDL) muscle. In mechanically skinned fibers, the sarcolemma is removed avoiding potential sources of O2·− production that are not intrinsically part of the muscle fibers, such as nerve terminals, blood cells, capillaries and other blood vessels in the whole muscle. O2·− production was also measured in split single EDL muscle fibers, where part of the sarcolemma remained attached, and small bundles of intact isolated EDL muscle fibers at rest, in the presence and absence of modifiers of mitochondrial function. The results lead to the conclusion that mitochondrial production of O2·− accounts for most of the O2·− measured intracellularly or extracellularly in skeletal muscle fibers at rest and at 37°C. Muscle fiber excitability at 37°C was greatly improved in the presence of a membrane permeant O2·− dismutase mimetic (Tempol), demonstrating a direct link between O2·− production in the mitochondria and muscle fiber performance. This implicates mitochondrial O2·− production in the down-regulation of skeletal muscle function, thus providing a feedback pathway for communication between mitochondria and plasma membranes that is not directly related to the main function of mitochondria as the power plant of the mammalian muscle cell.
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Pette, Dirk, and Dejan Škorjanc. "Adaptive Potentials of Skeletal Muscle in Young and Aging Rats." International Journal of Sport Nutrition and Exercise Metabolism 11, s1 (December 2001): S3—S8. http://dx.doi.org/10.1123/ijsnem.11.s1.s3.
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We compared responses of the fast extensor digitorum longus (EDL) and tibialis anterior (TA) muscles in young (15-week) and aging (101-week) male Brown Norwegian rats to 50 days of chronic low-frequency stimulation (CLFS, 10 Hz, 10 hours/day). After 50 days of CLFS, the EDL muscles of the young (22-week) and aging (108-week) rats displayed similar increases in type IIA fibers, relative concentration of myosin heavy chain MHCIIa, elevations in mitochondrial citrate synthase and 3-hydroxyacyl-CoA dehydrogenase activities, and similar decreases in glycolytic enzyme activities (glyceraldehydephosphate dehydrogenase, lactate dehydrogenase). TA muscle in young rats contained a few cytochrome c oxidase negative (COX−) type I fibers. Their number was ~2-fold elevated by CLFS. Conversely, aging muscle, which contained a slightly higher amount of COX− fibers than young TA muscle, responded to CLFS with a significant decrease in COX− fibers. The appearance of small COX-positive type I fibers in stimulated aging muscle indicated that regenerating type I fibers “diluted” the COX-deficient fiber population.
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Martin, W. H., T. K. Tolley, and J. E. Saffitz. "Autoradiographic delineation of skeletal muscle alpha 1-adrenergic receptor distribution." American Journal of Physiology-Heart and Circulatory Physiology 259, no. 5 (November 1, 1990): H1402—H1408. http://dx.doi.org/10.1152/ajpheart.1990.259.5.h1402.
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We used light microscopic autoradiography to quantify the distribution of alpha 1-adrenergic receptors in vessels and muscle fibers of slow-twitch (type I), fast-twitch (types IIa and IIb), and mixed fiber muscles of the rat hindquarter. Frozen cross sections of soleus, vastus lateralis, and gastrocnemius muscles were incubated under equilibrium binding conditions with 10-200 pM [3H]prazosin with or without 10(-5) M phentolamine. Because of the low concentration of bound radioligand, specific binding could not be detected with scintillation spectrometry in whole tissue sections scraped from slides. However, quantitative autoradiographic analysis after extended intervals of emulsion exposure revealed a low but significant level of specific binding in muscle fibers. No difference in alpha 1-receptor density was observed among types I, IIa, and IIb fibers. Small blood vessels had a much greater alpha 1-receptor density than muscle fibers. Resistance arterioles (20-100 microns diam) and small arteries (100-500 microns diam) contained 5.8 +/- 0.9 and 31.6 +/- 7.6 (+/- SE) times more binding sites per unit section area, respectively, than did surrounding muscle fibers (both P less than 0.001). Ratios of specific grain densities in fibers and blood vessels did not vary with radioligand concentration, indicating that observed grain densities reflected differences in receptor concentration rather than radioligand affinity by fiber and vessel receptors. The densities of vascular alpha 1-receptors did not vary in slow- and fast-twitch muscles, but resistance arterioles were six and eight times more numerous in soleus than in gastrocnemius and vastus muscles, respectively (both P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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Prosser, Benjamin L., Erick O. Hernández-Ochoa, Richard M. Lovering, Zoita Andronache, Danna B. Zimmer, Werner Melzer, and Martin F. Schneider. "S100A1 promotes action potential-initiated calcium release flux and force production in skeletal muscle." American Journal of Physiology-Cell Physiology 299, no. 5 (November 2010): C891—C902. http://dx.doi.org/10.1152/ajpcell.00180.2010.
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The role of S100A1 in skeletal muscle is just beginning to be elucidated. We have previously shown that skeletal muscle fibers from S100A1 knockout (KO) mice exhibit decreased action potential (AP)-evoked Ca2+ transients, and that S100A1 binds competitively with calmodulin to a canonical S100 binding sequence within the calmodulin-binding domain of the skeletal muscle ryanodine receptor. Using voltage clamped fibers, we found that Ca2+ release was suppressed at all test membrane potentials in S100A1−/− fibers. Here we examine the role of S100A1 during physiological AP-induced muscle activity, using an integrative approach spanning AP propagation to muscle force production. With the voltage-sensitive indicator di-8-aminonaphthylethenylpyridinium, we first demonstrate that the AP waveform is not altered in flexor digitorum brevis muscle fibers isolated from S100A1 KO mice. We then use a model for myoplasmic Ca2+ binding and transport processes to calculate sarcoplasmic reticulum Ca2+ release flux initiated by APs and demonstrate decreased release flux and greater inactivation of flux in KO fibers. Using in vivo stimulation of tibialis anterior muscles in anesthetized mice, we show that the maximal isometric force response to twitch and tetanic stimulation is decreased in S100A1−/− muscles. KO muscles also fatigue more rapidly upon repetitive stimulation than those of wild-type counterparts. We additionally show that fiber diameter, type, and expression of key excitation-contraction coupling proteins are unchanged in S100A1 KO muscle. We conclude that the absence of S100A1 suppresses physiological AP-induced Ca2+ release flux, resulting in impaired contractile activation and force production in skeletal muscle.
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Rant, Witold, and Aurelia Radzik-Rant. "The effect of breed and body weight at slaughter on histochemical muscle fiber characteristics and meat quality of longissimus lumborum and semitendinosus lamb muscles." Archives Animal Breeding 66, no. 4 (December 13, 2023): 439–49. http://dx.doi.org/10.5194/aab-66-439-2023.
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Abstract. The skeletal muscles of mammals are composed of fibers of different morphological, metabolic and functional characteristics. The properties of muscle fibers may be determined genetically as well as by environmental factors such as the age of the animals, their physical activity, the level of nutrition, or the selection intensity. The present study was conducted to determine the influence of genotype (Polish Lowland vs. Polish Heath) and body weight at slaughter (23–25 kg vs. 35–40 kg) of lambs on histological characteristics of muscle fibers in musculus longissimus lumborum (LL) and musculus semitendinosus (ST) skeletal muscles and their impact on chosen meat quality features. Three types of muscle fibers were identified: slow-twitch oxidative (STO), fast-twitch oxidative (FTO) and fast-twitch glycolytic (FTG). Differences in the diameters of individual fiber types between the LL and ST muscles have been found in both investigated genotypes. The diameters of the analyzed types of fibers were usually larger in the ST muscle compared to the LL muscle. The lambs of the more primitive Polish Heath breed were characterized by a smaller diameter of all fiber types, especially in the LL muscle. The higher proportion of STO fibers and the lower proportion of FTO fibers have been found in the LL muscle of Polish Heath lambs in the group with lower body weight. The breed of lambs, muscle type and slaughter body weight had an impact on some meat quality characteristics, especially color, intramuscular fat content and expressed juice.
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Carson, J. A., M. Yamaguchi, and S. E. Alway. "Hypertrophy and proliferation of skeletal muscle fibers from aged quail." Journal of Applied Physiology 78, no. 1 (January 1, 1995): 293–99. http://dx.doi.org/10.1152/jappl.1995.78.1.293.
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The purpose of this study was to determined whether fibers in the anterior latissimus dorsi (ALD) muscle from aged Japanese quail have decreased hypertrophic or proliferative responses to 30 days of stretch overload compared with fibers from adult birds. Two groups of quail were studied, 12-wk-old quail (adult; n = 16) and 90-wk-old quail (aged; n = 16). The left wing of each bird was overloaded with a weight corresponding to 10% of the bird's body weight, and the right wing served as the intra-animal control. Quails were killed after 30 days of stretch overload. Total fiber number was quantified by counting all the fibers in a transverse section from the midbelly of the ALD muscle. ALD muscles in aged quails retained the capacity to increase their muscle mass (145%), total fiber number (49%), and fiber cross-sectional area (54%) in response to stretch overload. The ALD muscle in aged quail had a significantly lower increase in muscle mass (33%) and mass corrected for nonmuscle tissue (36%) compared with the ALD from young adult birds. Age had no effect on fiber type distribution shifts with stretch. These results suggest that although muscles in old birds have a substantial ability to adapt to enlarge, stretch-induced hypertrophy is attenuated in muscles from old quail.
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Toursel, Thierry, Laurence Stevens, Henk Granzier, and Yvonne Mounier. "Passive tension of rat skeletal soleus muscle fibers: effects of unloading conditions." Journal of Applied Physiology 92, no. 4 (April 1, 2002): 1465–72. http://dx.doi.org/10.1152/japplphysiol.00621.2001.
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In this work we studied changes in passive elastic properties of rat soleus muscle fibers subjected to 14 days of hindlimb unloading (HU). For this purpose, we investigated the titin isoform expression in soleus muscles, passive tension-fiber strain relationships of single fibers, and the effects of the thick filament depolymerization on passive tension development. The myosin heavy chain composition was also measured for all fibers studied. Despite a slow-to-fast transformation of the soleus muscles on the basis of their myosin heavy chain content, no modification in the titin isoform expression was detected after 14 days of HU. However, the passive tension-fiber strain relationships revealed that passive tension of both slow and fast HU soleus fibers increased less steeply with sarcomere length than that of control fibers. Gel analysis suggested that this result could be explained by a decrease in the amount of titin in soleus muscle after HU. Furthermore, the thick filament depolymerization was found to similarly decrease passive tension in control and HU soleus fibers. Taken together, these results suggested that HU did not change titin isoform expression in the soleus muscle, but rather modified muscle stiffness by decreasing the amount of titin.
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Mitchell, Emma A., Neil R. W. Martin, Stephen J. Bailey, and Richard A. Ferguson. "Critical power is positively related to skeletal muscle capillarity and type I muscle fibers in endurance-trained individuals." Journal of Applied Physiology 125, no. 3 (September 1, 2018): 737–45. http://dx.doi.org/10.1152/japplphysiol.01126.2017.
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The asymptote [critical power (CP)] and curvature constant ( W′) of the hyperbolic power-duration relationship can predict performance within the severe-intensity exercise domain. However, the extent to which these parameters relate to skeletal muscle morphology is less clear, particularly in endurance-trained individuals, who, relative to their lesser-trained counterparts, possess skeletal muscles that can support high levels of oxygen transport and oxidative capacity, i.e., elevated type I fiber proportion and cross-sectional area (CSA) and capillarity. Fourteen endurance-trained men performed a maximal incremental test to determine peak oxygen uptake (V̇o2peak; 63.2 ± 4.1 ml·min−1·kg−1, mean ± SD) and maximal aerobic power (406 ± 63 W) and three to five constant-load tests to task failure for the determination of CP (303 ± 52 W) and W′ (17.0 ± 3.0 kJ). Skeletal muscle biopsies were obtained from the vastus lateralis and analyzed for percent proportion of fiber types, CSA, and indexes of capillarity. CP was positively correlated with the percent proportion ( r = 0.79; P = 0.001) and CSA ( r = 0.73; P = 0.003) of type I fibers, capillary-to-fiber ratio ( r = 0.88; P < 0.001), and capillary contacts around type I fibers ( r = 0.94; P < 0.001) and type II fibers ( r = 0.68; P = 0.008). W′ was not correlated with any morphological variables. These data reveal a strong positive association between CP and skeletal muscle capillarity. Our findings support the assertion that CP is an important parameter of aerobic function and offer novel insights into the physiological bases of CP. NEW & NOTEWORTHY This investigation demonstrated very strong positive correlations between critical power and skeletal muscle capillarity, particularly around type I fibers, and type I fiber composition. These correlations were demonstrated in endurance-trained individuals expected to possess well-adapted skeletal muscles, such as high levels of oxygen transport structures and high oxidative capacities, supporting the view that critical power is an important parameter of aerobic function. In contrast, the curvature constant W′ was not associated with fiber type composition or capillarity.
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Mcguigan, Michael R. M., William J. Kraemer, Michael R. Deschenes, Scott E. Gordon, Takashi Kitaura, Timothy P. Scheett, Matthew J. Sharman, and Robert S. Staron. "Statistical Analysis of Fiber Area in Human Skeletal Muscle." Canadian Journal of Applied Physiology 27, no. 4 (August 1, 2002): 415–22. http://dx.doi.org/10.1139/h02-022.
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Previous research has indicated that 50 fiber measurements per individual for type I and II fibers would be sufficient to characterize the fiber areas. This study replicated the work of McCall et al. (1998) using the three major fiber types (I, IIA, and IIB) and sampling larger populations of fibers. Random blocks of fibers were also examined to investigate how well they correlated with the overall mean average fiber area. Using random blocks of 50 fibers provided an accurate reflection of the type IIB fibers (r = 0.96-0.98) but not for the type I (r = 0.85-0.94) or IIA fibers (r = 0.80-0.91). Type I fibers were consistently reflected by a random block of 150 fibers (r = 0.95-0.98) while type IIA fibers required random blocks of 200 fibers (r = 0.94-0.98), which appeared to provide an accurate reflection of the cross-sectional area. These results indicate that for a needle biopsy different numbers of fibers are needed depending on the fiber type to accurately characterize the mean fiber population. Key words: fiber type, sample size, cross-sectional area, biopsy
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Schiaffino, S., and C. Reggiani. "Myosin isoforms in mammalian skeletal muscle." Journal of Applied Physiology 77, no. 2 (August 1, 1994): 493–501. http://dx.doi.org/10.1152/jappl.1994.77.2.493.
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Skeletal muscles of different mammalian species contain four major myosin heavy-chain (MHC) isoforms: the “slow” or beta-MHC and the three “fast” IIa-, IIx-, and IIb-MHCs; and three major myosin light-chain (MLC) isoforms, the “slow” MLC1s and the two “fast” MLC1f and MLC3f. The differential distribution of the MHCs defines four major fiber types containing a single MHC isoform and a number of intermediate hybrid fiber populations containing both beta/slow- and IIa-MHC, IIa- and IIx-MHC, or IIx- and IIb-MHC. The IIa-, IIx-, and IIb-MHCs were first detected in neonatal muscles, and their expression in developing and adult muscle is regulated by neural, hormonal, and mechanical factors. The transcriptional mechanisms responsible for the fiber type-specific regulation of MHC and MLC gene expression are not known and are presently being explored by in vivo transfection experiments. The functional role of MHC isoforms has been in part clarified by correlated biochemical-physiological studies on single skinned fibers: these studies, in agreement with results from in vitro motility assays, indicate that both MHC and MLC isoforms determine the maximum velocity of shortening of skeletal muscle fibers.
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Grifone, Raphaelle, Christine Laclef, François Spitz, Soledad Lopez, Josiane Demignon, Jacques-Emmanuel Guidotti, Kiyoshi Kawakami, et al. "Six1 and Eya1 Expression Can Reprogram Adult Muscle from the Slow-Twitch Phenotype into the Fast-Twitch Phenotype." Molecular and Cellular Biology 24, no. 14 (July 15, 2004): 6253–67. http://dx.doi.org/10.1128/mcb.24.14.6253-6267.2004.
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ABSTRACT Muscle fibers show great differences in their contractile and metabolic properties. This diversity enables skeletal muscles to fulfill and adapt to different tasks. In this report, we show that the Six/Eya pathway is implicated in the establishment and maintenance of the fast-twitch skeletal muscle phenotype. We demonstrate that the MEF3/Six DNA binding element present in the aldolase A pM promoter mediates the high level of activation of this promoter in fast-twitch glycolytic (but not in slow-twitch) muscle fibers. We also show that among the Six and Eya gene products expressed in mouse skeletal muscle, Six1 and Eya1 proteins accumulate preferentially in the nuclei of fast-twitch muscles. The forced expression of Six1 and Eya1 together in the slow-twitch soleus muscle induced a fiber-type transition characterized by the replacement of myosin heavy chain I and IIA isoforms by the faster IIB and/or IIX isoforms, the activation of fast-twitch fiber-specific genes, and a switch toward glycolytic metabolism. Collectively, these data identify Six1 and Eya1 as the first transcriptional complex that is able to reprogram adult slow-twitch oxidative fibers toward a fast-twitch glycolytic phenotype.
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Pilegaard, Henriette, Gerasimos Terzis, Andrew Halestrap, and Carsten Juel. "Distribution of the lactate/H+ transporter isoforms MCT1 and MCT4 in human skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 276, no. 5 (May 1, 1999): E843—E848. http://dx.doi.org/10.1152/ajpendo.1999.276.5.e843.
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The profiles of the lactate/H+ transporter isoforms [monocarboxylate transporter isoforms (MCT)] MCT1 and MCT4 (formerly MCT3 of Price, N. T., V. N. Jackson, and A. P. Halestrap. Biochem. J. 329: 321–328, 1998) were studied in the soleus, triceps brachii, and vastus lateralis muscles of six male subjects. The fiber-type compositions of the muscles were evaluated from the occurrence of the myosin heavy chain isoforms, and the fibers were classified as type I, IIA, or IIX. The total content of MCT1 and MCT4 was determined in muscle homogenates by Western blotting, and MCT1 and MCT4 were visualized on cross-sectional muscle sections by immunofluorescence microscopy. The Western blotting revealed a positive, linear relationship between the MCT1 content and the occurrence of type I fibers in the muscle, but no significant relation was found between MCT4 content and fiber type. Moreover, the interindividual variation in MCT4 content was much larger than the interindividual variation in MCT1 content in homogenate samples. The immunofluorescence microscopy showed that within a given muscle section, the MCT4 isoform was clearly more abundant in type II fibers than in type I fibers, whereas only minor differences existed in the occurrence of the MCT1 isoform between type I and II fibers. Together the present results indicate that the content of MCT1 in a muscle varies between different muscles, whereas fiber-type differences in MCT1 content are minor within a given muscle section. In contrast, the content of MCT4 is clearly fiber-type specific but apparently quite similar in various muscles.
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Fraysse, Bodvaël, Thierry Rouaud, Marie Millour, Josiane Fontaine-Pérus, Marie-France Gardahaut, and Dmitri O. Levitsky. "Expression of the Na+/Ca2+exchanger in skeletal muscle." American Journal of Physiology-Cell Physiology 280, no. 1 (January 1, 2001): C146—C154. http://dx.doi.org/10.1152/ajpcell.2001.280.1.c146.
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The expression of the Na+/Ca2+ exchanger was studied in differentiating muscle fibers in rats. NCX1 and NCX3 isoform (Na+/Ca2+ exchanger isoform) expression was found to be developmentally regulated. NCX1 mRNA and protein levels peaked shortly after birth. Conversely, NCX3 isoform expression was very low in muscles of newborn rats but increased dramatically during the first 2 wk of postnatal life. Immunocytochemical analysis showed that NCX1 was uniformly distributed along the sarcolemmal membrane of undifferentiated rat muscle fibers but formed clusters in T-tubular membranes and sarcolemma of adult muscle. NCX3 appeared to be more uniformly distributed along the sarcolemma and inside myoplasm. In the adult, NCX1 was predominantly expressed in oxidative (type 1 and 2A) fibers of both slow- and fast-twitch muscles, whereas NCX3 was highly expressed in fast glycolytic (2B) fibers. NCX2 was expressed in rat brain but not in skeletal muscle. Developmental changes in NCX1 and NCX3 as well as the distribution of these isoforms at the cellular level and in different fiber types suggest that they may have different physiological roles.
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DeNardi, C., S. Ausoni, P. Moretti, L. Gorza, M. Velleca, M. Buckingham, and S. Schiaffino. "Type 2X-myosin heavy chain is coded by a muscle fiber type-specific and developmentally regulated gene." Journal of Cell Biology 123, no. 4 (November 15, 1993): 823–35. http://dx.doi.org/10.1083/jcb.123.4.823.
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We have previously reported the identification of a distinct myosin heavy chain (MyHC) isoform in a major subpopulation of rat skeletal muscle fibers, referred to as 2X fibers (Schiaffino, S., L. Gorza, S. Sartore, L. Saggin, M. Vianello, K. Gundersen, and T. Lømo. 1989. J. Muscle Res. Cell Motil. 10:197-205). However, it was not known whether 2X-MyHC is the product of posttranslational modification of other MyHCs or is coded by a distinct mRNA. We report here the isolation and characterization of cDNAs coding a MyHC isoform that is expressed in type 2X skeletal muscle fibers. 2X-MyHC transcripts differ from other MyHC transcripts in their restriction map and 3' end sequence and are thus derived from a distinct gene. In situ hybridization analyses show that 2X-MyHC transcripts are expressed at high levels in the diaphragm and fast hindlimb muscles and can be coexpressed either with 2B- or 2A-MyHC transcripts in a number of fibers. At the single fiber level the distribution of each MyHC mRNA closely matches that of the corresponding protein, determined by specific antibodies on serial sections. In hindlimb muscles 2X-, 2A-, and 2B-MyHC transcripts are first detected by postnatal day 2-5 and display from the earliest stages a distinct pattern of distribution in different muscles and different fibers. The emergence of type 2 MyHC isoforms thus defines a distinct neonatal phase of fiber type differentiation during muscle development. The functional significance of MyHC isoforms is discussed with particular reference to the velocity of shortening of skeletal muscle fibers.
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Tavernier, Benoit M., Elie Haddad, Pascal J. Adnet, Toussaint S. Etchrivi, Dominique Lacroix, and Hugo Reyford. "Isoform-dependent Effects of Halothane in Human Skinned Striated Fibers." Anesthesiology 84, no. 5 (May 1, 1996): 1138–47. http://dx.doi.org/10.1097/00000542-199605000-00016.
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Background Reports of the effects of halothane on isoform contractile proteins of striated muscles are conflicting. To determine whether halothane affects cardiac and skeletal contractile proteins differently, the authors examined the effects of two doses of halothane (0.44 and 1.26 mM, equivalent to 0.75 and 2.25 vol%, respectively) on the Ca++ sensitivity and maximal force in human skinned cardiac, type I (slow twitch), and type II (fast twitch) skeletal muscle fibers. Methods Left ventricular muscle strips and skeletal muscle biopsy specimens were obtained from eight and ten patients undergoing cardiac and orthopedic surgery, respectively. Sarcolemma and sarcoplasmic reticulum were destroyed with ethylene glycol bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid plus Brij 58. Ca++ sensitivity was studied by observing the isometric tension developed by skinned fibers challenged with increasing concentrations of Ca++. Muscle fiber type was determined in each skeletal fiber by the difference in strontium-induced tension measurements. Results Halothane shifted the Ca++ tension curves toward higher Ca++ concentrations and increased the Ca++ concentrations for half-maximal activation in both cardiac and type I skeletal muscle fibers (from 1.96 microM and 1.06 microM under control conditions to 2.92 microM and 1.71 microM in presence of 0.75 vol% halothane, respectively) without changing the slope of this relationship (Hill coefficient). In contrast, no significant effect was observed in type II fibers. Halothane also decreased the maximal activated tension in the three groups of fibers with a lesser effect in type II fibers. Conclusions Halothane decreases Ca++ sensitivity and maximal force in human skinned cardiac and type I fibers at 20 degrees C. It is concluded that the negative inotropic effects of halothane depend on contractile proteins isoforms.
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Trappe, Scott, Nicholas Luden, Kiril Minchev, Ulrika Raue, Bozena Jemiolo, and Todd A. Trappe. "Skeletal muscle signature of a champion sprint runner." Journal of Applied Physiology 118, no. 12 (June 15, 2015): 1460–66. http://dx.doi.org/10.1152/japplphysiol.00037.2015.
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We had the unique opportunity to study the skeletal muscle characteristics, at the single fiber level, of a world champion sprint runner who is the current indoor world record holder in the 60-m hurdles (7.30 s) and former world record holder in 110-m hurdles (12.91 s). Muscle biopsies were obtained from the vastus lateralis at rest and 4 h after a high-intensity exercise challenge (4 × 7 repetitions of resistance exercise). Single muscle fiber analyses were conducted for fiber type distribution (myosin heavy chain, MHC), fiber size, contractile function (strength, speed, and power) and mRNA expression (before and after the exercise bout). The world-class sprinter's leg muscle had a high abundance (24%) of the pure MHC IIx muscle fibers with a total fast-twitch fiber population of 71%. Power output of the MHC IIx fibers (35.1 ± 1.4 W/l) was 2-fold higher than MHC IIa fibers (17.1 ± 0.5 W/l) and 14-fold greater than MHC I fibers (2.5 ± 0.1 W/l). Additionally, the MHC IIx fibers were highly responsive to intense exercise at the transcriptional level for genes involved with muscle growth and remodeling ( Fn14 and myostatin). To our knowledge, the abundance of pure MHC IIx muscle fibers is the highest observed in an elite sprinter. Further, the power output of the MHC IIa and MHC IIx muscle fibers was greater than any human values reported to date. These data provide a myocellular basis for the high level of sprinting success achieved by this individual.
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Wood, Lauren K., Erdan Kayupov, Jonathan P. Gumucio, Christopher L. Mendias, Dennis R. Claflin, and Susan V. Brooks. "Intrinsic stiffness of extracellular matrix increases with age in skeletal muscles of mice." Journal of Applied Physiology 117, no. 4 (August 15, 2014): 363–69. http://dx.doi.org/10.1152/japplphysiol.00256.2014.
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Advanced age is associated with increases in muscle passive stiffness, but the contributors to the changes remain unclear. Our purpose was to determine the relative contributions of muscle fibers and extracellular matrix (ECM) to muscle passive stiffness in both adult and old animals. Passive mechanical properties were determined for isolated individual muscle fibers and bundles of muscle fibers that included their associated ECM, obtained from tibialis anterior muscles of adult (8–12 mo old) and old (28–30 mo old) mice. Maximum tangent moduli of individual muscle fibers from adult and old muscles were not different at any sarcomere length tested. In contrast, the moduli of bundles of fibers from old mice was more than twofold greater than that of fiber bundles from adult muscles at sarcomere lengths >2.5 μm. Because ECM mechanical behavior is determined by the composition and arrangement of its molecular constituents, we also examined the effect of aging on ECM collagen characteristics. With aging, muscle ECM hydroxyproline content increased twofold and advanced glycation end-product protein adducts increased threefold, whereas collagen fibril orientation and total ECM area were not different between muscles from adult and old mice. Taken together, these findings indicate that the ECM of tibialis anterior muscles from old mice has a higher modulus than the ECM of adult muscles, likely driven by an accumulation of densely packed extensively crosslinked collagen.
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Pette, Dirk. "The Adaptive Potential of Skeletal Muscle Fibers." Canadian Journal of Applied Physiology 27, no. 4 (August 1, 2002): 423–48. http://dx.doi.org/10.1139/h02-023.
Full textAbstract:
Mammalian skeletal muscle fibers display a great adaptive potential. This potential results from the ability of muscle fibers to adjust their molecular, functional, and metabolic properties in response to altered functional demands, such as changes in neuromuscular activity or mechanical loading. Adaptive changes in the expression of myofibrillar and other protein isoforms result in fiber type transitions. These transitions occur in a sequential order and encompass a spectrum of pure and hybrid fibers. Depending on the quality, intensity, and duration of the alterations in functional demand, muscle fibers may undergo functional transitions in the direction of slow or fast, as well as metabolic transitions in the direction of aerobic-oxidative or glycotytic. The maximum range of possible transitions in either direction depends on the fiber phenotype and is determined by its initial location in the fiber spectrum. Key words: Ca-sequestering proteins, energy metabolism, fiber type transition, myofibrillar protein isofonns, myosin, neuromuscular activity
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Zhou, Daixing, Jeanine A. Ursitti, and Robert J. Bloch. "Developmental Expression of Spectrins in Rat Skeletal Muscle." Molecular Biology of the Cell 9, no. 1 (January 1998): 47–61. http://dx.doi.org/10.1091/mbc.9.1.47.
Full textAbstract:
Skeletal muscle contains spectrin (or spectrin I) and fodrin (or spectrin II), members of the spectrin supergene family. We used isoform-specific antibodies and cDNA probes to investigate the molecular forms, developmental expression, and subcellular localization of the spectrins in skeletal muscle of the rat. We report that β-spectrin (βI) replaces β-fodrin (βII) at the sarcolemma as skeletal muscle fibers develop. As a result, adult muscle fibers contain only α-fodrin (αII) and the muscle isoform of β-spectrin (βIΣ2). By contrast, other types of cells present in skeletal muscle tissue, including blood vessels and nerves, contain only α- and β-fodrin. During late embryogenesis and early postnatal development, skeletal muscle fibers contain a previously unknown form of spectrin complex, consisting of α-fodrin, β-fodrin, and the muscle isoform of β-spectrin. These complexes associate with the sarcolemma to form linear membrane skeletal structures that otherwise resemble the structures found in the adult. Our results suggest that the spectrin-based membrane skeleton of muscle fibers can exist in three distinct states during development.
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Martin, W. H., A. R. Coggan, R. J. Spina, and J. E. Saffitz. "Effects of fiber type and training on beta-adrenoceptor density in human skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 257, no. 5 (November 1, 1989): E736—E742. http://dx.doi.org/10.1152/ajpendo.1989.257.5.e736.
Full textAbstract:
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.
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Toth, Michael J., Timothy W. Tourville, Thomas B. Voigt, Rebecca H. Choquette, Bradley M. Anair, Michael J. Falcone, Mathew J. Failla, et al. "Utility of Neuromuscular Electrical Stimulation to Preserve Quadriceps Muscle Fiber Size and Contractility After Anterior Cruciate Ligament Injuries and Reconstruction: A Randomized, Sham-Controlled, Blinded Trial." American Journal of Sports Medicine 48, no. 10 (July 6, 2020): 2429–37. http://dx.doi.org/10.1177/0363546520933622.
Full textAbstract:
Background: Anterior cruciate ligament (ACL) injuries and reconstruction (ACLR) promote quadriceps muscle atrophy and weakness that can persist for years, suggesting the need for more effective rehabilitation programs. Whether neuromuscular electrical stimulation (NMES) can be used to prevent maladaptations in skeletal muscle size and function is unclear. Purpose: To examine whether early NMES use, started soon after an injury and maintained through 3 weeks after surgery, can preserve quadriceps muscle size and contractile function at the cellular (ie, fiber) level in the injured versus noninjured leg of patients undergoing ACLR. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: Patients (n = 25; 12 men/13 women) with an acute, first-time ACL rupture were randomized to NMES (5 d/wk) or sham (simulated microcurrent electrical nerve stimulation; 5 d/wk) treatment to the quadriceps muscles of their injured leg. Bilateral biopsies of the vastus lateralis were performed 3 weeks after surgery to measure skeletal muscle fiber size and contractility. Quadriceps muscle size and strength were assessed 6 months after surgery. Results: A total of 21 patients (9 men/12 women) completed the trial. ACLR reduced single muscle fiber size and contractility across all fiber types ( P < .01 to P < .001) in the injured compared with noninjured leg 3 weeks after surgery. NMES reduced muscle fiber atrophy ( P < .01) through effects on fast-twitch myosin heavy chain (MHC) II fibers ( P < .01 to P < .001). NMES preserved contractility in slow-twitch MHC I fibers ( P < .01 to P < .001), increasing maximal contractile velocity ( P < .01) and preserving power output ( P < .01), but not in MHC II fibers. Differences in whole muscle strength between groups were not discerned 6 months after surgery. Conclusion: Early NMES use reduced skeletal muscle fiber atrophy in MHC II fibers and preserved contractility in MHC I fibers. These results provide seminal, cellular-level data demonstrating the utility of the early use of NMES to beneficially modify skeletal muscle maladaptations to ACLR. Clinical Relevance: Our results provide the first comprehensive, cellular-level evidence to show that the early use of NMES mitigates early skeletal muscle maladaptations to ACLR. Registration: NCT02945553 (ClinicalTrials.gov identifier)
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McEwen, S. A., and T. J. Hulland. "Histochemical and Morphometric Evaluation of Skeletal Muscle from Horses with Exertional Rhabdomyolysis (Tying-up)." Veterinary Pathology 23, no. 4 (July 1986): 400–410. http://dx.doi.org/10.1177/030098588602300409.
Full textAbstract:
Thirteen horses with histories of exertional rhabdomyolysis were exercised for 20 minutes to induce clinical signs of lameness, elevated serum creatine kinase (CK), and aspartate aminotransferase (AST) activities and skeletal muscle morphologic lesions. The clinical signs exhibited by affected horses included trembling, sweating, increased rate of respiration, and restricted limb movement. Serum CK reached maximal activity between 4 and 8 hours after the exercise period and serum AST activity peaked between 24 and 48 hours. Histologically, the skeletal muscle lesions in muscle biopsies 24 hours after the exercise period consisted of segmental muscle fiber degeneration. Damaged muscle fibers were repaired by myoblastic regeneration. Horses with moderate (>1,500 U/liter) to severe (>5,000 U/liter) elevations of serum CK activity accompanied by clinical signs of muscle soreness induced by exercise, had visible muscle fiber degeneration microscopically. Frozen sections of biopsies of the gluteus medius muscle from affected ( n = 13) and control ( n = 11) groups of horses were processed to demonstrate myofibrillar ATPase activity. These sections were then used to determine fiber types, area percentages, and mean cross sectional fiber sizes. The mean type I, type II, and intermediate fiber sizes were significantly larger in the affected group than in the control group. In the gluteus medius muscles of the affected group, there was a significantly greater percentage of intermediate fibers and a significantly greater percentage of area occupied by intermediate fibers than in the control group. In the muscle samples with acute lesions of exertional rhabdomyolysis, type II fibers were selectively but not exclusively affected. In one horse which was subsequently necropsied 24 hours after the exercise period, lesions were present in several postural muscles, the masseter muscle and the heart. We conclude that the gluteus medius muscle fibers of affected horses are larger in cross sectional area than those of control horses and that there is preferential degeneration of type II fibers in acute lesions of exertional rhabdomyolysis.
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Sharlo, Kristina A., Irina D. Lvova, Sergey A. Tyganov, Ksenia V. Sergeeva, Vitaly Y. Kalashnikov, Ekaterina P. Kalashnikova, Timur M. Mirzoev, Grigoriy R. Kalamkarov, Tatiana F. Shevchenko, and Boris S. Shenkman. "A Prochlorperazine-Induced Decrease in Autonomous Muscle Activity during Hindlimb Unloading Is Accompanied by Preserved Slow Myosin mRNA Expression." Current Issues in Molecular Biology 45, no. 7 (June 30, 2023): 5613–30. http://dx.doi.org/10.3390/cimb45070354.
Full textAbstract:
Skeletal muscle disuse leads to pathological muscle activity as well as to slow-to-fast fiber-type transformation. Fast-type fibers are more fatigable than slow-type, so this transformation leads to a decline in muscle function. Prochlorperazine injections previously were shown to attenuate autonomous rat soleus muscle electrical activity under unloading conditions. In this study, we found that prochlorperazine blocks slow-to-fast fiber-type transformation in disused skeletal muscles of rats, possibly through affecting calcium and ROS-related signaling.
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Robison, Patrick, Erick O. Hernández-Ochoa, and Martin F. Schneider. "Adherent Primary Cultures of Mouse Intercostal Muscle Fibers for Isolated Fiber Studies." Journal of Biomedicine and Biotechnology 2011 (2011): 1–11. http://dx.doi.org/10.1155/2011/393740.
Full textAbstract:
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.
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Kondratov, Gleb V., Viktor V. Stepanishin, and Stanislav G. Kumirov. "Comparative characteristics of the quadriceps femoral muscle in postnatal ontogenesis in Cobb-500 chickens and the Yurlovskaya golosistaya." Veterinariya, Zootekhniya i Biotekhnologiya 1, no. 98 (2022): 6–11. http://dx.doi.org/10.36871/vet.zoo.bio.202201001.
Full textAbstract:
Histological and morphological characteristics of skeletal muscles in chickens of the meat productivity direction Cobb-500 and egg productivity direction Yurlovskaya golosistaya on the 8-th and 20-th days of postembryonic development were studied. The skeletal striated muscle tissue of the studied bird obeys the general principles of myogenesis inherent in most animal species and is characterized by signs of a definitive structure. It is shown that on the 8-th and 20-th days of postembryonic ontogenesis, the quadriceps femoral muscle of the Yurlovskaya golosistaya breed is ahead of the Cobb-500 cross in terms of the thickness of muscle fibers, while the opposite pattern is established in terms of the thickness of muscle fiber bundles, as well as endomysium and perimysium in the connective tissue component. The area of muscle tissue and the number of muscle fibers in the field of vision in the studied periods of ontogenesis prevail in digital values in Cobb-500 compared to the Yurlovskaya golosistaya. Based on the obtained morphometric parameters of muscle fibers, the concept of histogenesis of skeletal muscles in poultry of egg and meat productivity directions is presented.
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Schafer, DA, and FE Stockdale. "Identification of sarcolemma-associated antigens with differential distributions on fast and slow skeletal muscle fibers." Journal of Cell Biology 104, no. 4 (April 1, 1987): 967–79. http://dx.doi.org/10.1083/jcb.104.4.967.
Full textAbstract:
We have identified three sarcolemma-associated antigens, including two antigens that are differentially distributed on skeletal muscle fibers of the fast, fast/slow, and slow types. Monoclonal antibodies were prepared using partially purified membranes of adult chicken skeletal muscles as immunogens and were used to characterize three antigens associated with the sarcolemma of muscle fibers. Immunofluorescence staining of cryosections of adult and embryonic chicken muscles showed that two of the three antigens differed in expression by fibers depending on developmental age and whether the fibers were of the fast, fast/slow, or slow type. Fiber type was assigned by determining the content of fast and slow myosin heavy chain. MSA-55 was expressed equally by fibers of all types. In contrast, MSA-slow and MSA-140 differed in their expression by muscle fibers depending on fiber type. MSA-slow was detected exclusively at the periphery of fast/slow and slow fibers, but was not detected on fast fibers. MSA-140 was detected on all fibers but fast/slow and slow fibers stained more intensely suggesting that these fiber types contain more MSA-140 than fast fibers. These sarcolemma-associated antigens were developmentally regulated in ovo and in vitro. MSA-55 and MSA-140 were detected on all primary muscle fibers by day 8 in ovo of embryonic development, whereas MSA-slow was first detected on muscle fibers just before hatching. Those antigens expressed by fast fibers (MSA-55 and MSA-140) were expressed only after myoblasts differentiated into myotubes, but were not expressed by fibroblasts in cell culture. Each antigen was also detected in one or more nonskeletal muscle cell types: MSA-55 and MSA-slow in cardiac myocytes and smooth muscle of gizzard (but not vascular structures) and MSA-140 in cardiac myocytes and smooth muscle of vascular structures. MSA-55 was identified as an Mr 55,000, nonglycosylated, detergent-soluble protein, and MSA-140 was an Mr 140,000, cell surface protein. The Mr of MSA-slow could not be determined by immunoblotting or immunoprecipitation techniques. These findings indicate that muscle fibers of different physiological function differ in the components associated with the sarcolemma. While the function of these sarcolemma-associated antigens is unknown, their regulated appearance during development in ovo and as myoblasts differentiate in culture suggests that they may be important in the formation, maturation, and function of fast, fast/slow, and slow muscle fibers.
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Kirkendall, Donald T., and William E. Garrett. "The Effects of Aging and Training on Skeletal Muscle." American Journal of Sports Medicine 26, no. 4 (July 1998): 598–602. http://dx.doi.org/10.1177/03635465980260042401.
Full textAbstract:
Aging results in a gradual loss of muscle function, and there are predictable age-related alterations in skeletal muscle function. The typical adult will lose muscle mass with age; the loss varies according to sex and the level of muscle activity. At the cellular level, muscles loose both cross-sectional area and fiber numbers, with type II muscle fibers being the most affected by aging. Some denervation of fibers may occur. The combination of these factors leads to an increased percentage of type I fibers in older adults. Metabolically, the glycolytic enzymes seem to be little affected by aging, but the aerobic enzymes appear to decline with age. Aged skeletal muscle produces less force and there is a general “slowing” of the mechanical characteristics of muscle. However, neither reduced muscle demand nor the subsequent loss of function is inevitable with aging. These losses can be minimized or even reversed with training. Endurance training can improve the aerobic capacity of muscle, and resistance training can improve central nervous system recruitment of muscle and increase muscle mass. Therefore, physical activity throughout life is encouraged to prevent much of the age-related impact on skeletal muscle.
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Murphy, Kate T., Andrew M. Allen, Annabel Chee, Timur Naim, and Gordon S. Lynch. "Disruption of muscle renin-angiotensin system in AT1a−/−mice enhances muscle function despite reducing muscle mass but compromises repair after injury." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 303, no. 3 (August 1, 2012): R321—R331. http://dx.doi.org/10.1152/ajpregu.00007.2012.
Full textAbstract:
The role of the renin-angiotensin system (RAS) in vasoregulation is well established, but a localized RAS exists in multiple tissues and exerts diverse functions including autonomic control and thermogenesis. The role of the RAS in the maintenance and function of skeletal muscle is not well understood, especially the role of angiotensin peptides, which appear to contribute to muscle atrophy. We tested the hypothesis that mice lacking the angiotensin type 1A receptor (AT1A−/−) would exhibit enhanced whole body and skeletal muscle function and improved regeneration after severe injury. Despite 18- to 20-wk-old AT1A−/−mice exhibiting reduced muscle mass compared with controls ( P < 0.05), the tibialis anterior (TA) muscles produced a 25% higher maximum specific (normalized) force ( P < 0.05). Average fiber cross-sectional area (CSA) and fiber oxidative capacity was not different between groups, but TA muscles from AT1A−/−mice had a reduced number of muscle fibers as well as a higher proportion of type IIx/b fibers and a lower proportion of type IIa fibers ( P < 0.05). Measures of whole body function (grip strength, rotarod performance, locomotor activity) were all improved in AT1A−/−mice ( P < 0.05). Surprisingly, the recovery of muscle mass and fiber CSA following myotoxic injury was impaired in AT1A−/−mice, in part by impaired myoblast fusion, prolonged collagen infiltration and inflammation, and delayed expression of myogenic regulatory factors. The findings support the therapeutic potential of RAS inhibition for enhancing whole body and skeletal muscle function, but they also reveal the importance of RAS signaling in the maintenance of muscle mass and for normal fiber repair after injury.
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Allen, D. L., S. R. Monke, R. J. Talmadge, R. R. Roy, and V. R. Edgerton. "Plasticity of myonuclear number in hypertrophied and atrophied mammalian skeletal muscle fibers." Journal of Applied Physiology 78, no. 5 (May 1, 1995): 1969–76. http://dx.doi.org/10.1152/jappl.1995.78.5.1969.
Full textAbstract:
Although a mammalian skeletal muscle fiber may contain thousands of myonuclei, the importance of this number or the potential to modulate it in adult muscle has not been clearly demonstrated. Using immunohistochemistry and confocal microscopy, we examined the plasticity of myonuclear number and fiber size in isolated fast and slow fiber segments from adult cat hindlimb muscles in response to chronic alterations in neuromuscular activity and loading. Compared with slow fibers in the soleus of control cats, myonuclear number in presumably transformed fast fibers was 32% lower and fiber size was decreased 73% after elimination of neuromuscular activation for 6 mo by spinal isolation. Slow fibers in the soleus of spinal-isolated cats had smaller cross-sectional areas, whereas myonuclear number was not significantly different than that in the control cats. Myonuclear number in fast plantaris fibers was more than threefold higher and fiber size was 2.8-fold higher after 3 mo of functional overload compared with the plantaris of control cats. Compared with control slow plantaris fibers, myonuclear number and fiber size also increased in overloaded slow plantaris fibers. These results demonstrate that changes in myonuclear number are associated with changes in myosin type and suggest that modulations in the amount of available DNA may be a factor in regulating cytoplasmic volume of muscle fibers in response to chronic changes in neuromuscular activity.
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Powers, Scott K. "Exercise: Teaching myocytes new tricks." Journal of Applied Physiology 123, no. 2 (August 1, 2017): 460–72. http://dx.doi.org/10.1152/japplphysiol.00418.2017.
Full textAbstract:
Endurance exercise training promotes numerous cellular adaptations in both cardiac myocytes and skeletal muscle fibers. For example, exercise training fosters changes in mitochondrial function due to increased mitochondrial protein expression and accelerated mitochondrial turnover. Additionally, endurance exercise training alters the abundance of numerous cytosolic and mitochondrial proteins in both cardiac and skeletal muscle myocytes, resulting in a protective phenotype in the active fibers; this exercise-induced protection of cardiac and skeletal muscle fibers is often referred to as “exercise preconditioning.” As few as 3–5 consecutive days of endurance exercise training result in a preconditioned cardiac phenotype that is sheltered against ischemia-reperfusion-induced injury. Similarly, endurance exercise training results in preconditioned skeletal muscle fibers that are resistant to a variety of stresses (e.g., heat stress, exercise-induced oxidative stress, and inactivity-induced atrophy). Many studies have probed the mechanisms responsible for exercise-induced preconditioning of cardiac and skeletal muscle fibers; these studies are important, because they provide an improved understanding of the biochemical mechanisms responsible for exercise-induced preconditioning, which has the potential to lead to innovative pharmacological therapies aimed at minimizing stress-induced injury to cardiac and skeletal muscle. This review summarizes the development of exercise-induced protection of cardiac myocytes and skeletal muscle fibers and highlights the putative mechanisms responsible for exercise-induced protection in the heart and skeletal muscles.