Myonuclear domain and myosin phenotype in human soleus  after bed rest with or without loading

Ohira, Yoshinobu; Yoshinaga, Tetsutaro; Ohara, Makoto; Nonaka, Ikuya; Yoshioka, Toshitada; Yamashita-Goto, Katsumasa; Шенкман, Борис; Kozlovskaya, I. B.; Roy, Roland R.; Edgerton, V. Reggie

doi:10.1152/jappl.1999.87.5.1776

Cited by 119 publications

(121 citation statements)

References 29 publications

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“…The ex-pression of IId MHC (most likely analogous to IIx) has also been observed in the rat soleus of 21-and 28-d suspended rats [67]. A similar tendency in fiber type transformation was also seen in the human vastus lateralis muscle after 11 d of spaceflight [77,78] and in the soleus after 4 months of bedrest associated with fiber atrophy [79,80].…”

Section: Fiber Phenotypementioning

confidence: 66%

Neuromuscular Adaptation to Microgravity Environment.

Ohira

2000

JJP

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The pattern of muscle activity influences the morphological, metabolic, and contractile properties of skeletal muscles. For example, the metabolic capacity of muscles is affected specifically by the type of exercise training [1][2][3]. Increased activity or over-loading by removing the synergists causes a compensatory hypertrophy [4][5][6][7][8][9][10][11]. Hypertrophy is also induced by the stretching of matured muscles in vivo [12,13] and cultured myotubes and fibroblasts [14][15][16][17]. Exercise-induced metabolic adaptation of muscles is lost when exercise training is stopped [18]. Further, muscle atrophy is induced by denervation [10,19], spinal cord transection [20], joint immobilization [21][22][23], tenotomy [24,25], spaceflight [26][27][28][29], and/or hindlimb suspension [29][30][31][32]. Most of these models are generally presumed to be models of reduced neuromuscular activity. But the level of use may not be the only factor involved in the atrophic process.There is a close association in the physiological, biochemical, and morphological properties between a motoneuron and the muscle fibers it innervates [1]. Studies to support this view are those in which chronic electrical stimulation at low frequency (1-10 Hz) changes the properties of fast-twitch muscles toward those of slow-twitch muscles [33][34][35][36][37][38].Some of the characteristics of muscle fibers are also altered following cross-innervation [39][40][41][42]. Buller et al. [40] suggested that the neural influence on muscle could be due to neurotrophic effect as well as via nerve impulses. Muscular Responses to Gravitational Unloading Morphological propertiesGravitational unloading by exposure to weightlessness [26][27][28][29][43][44][45][46][47] and/or its simulation model, hindlimb suspension [29][30][31][32][48][49][50][51][52][53][54][55][56], causes rapid atrophy in muscles, such as soleus and adductor longus, that are composed predominantly of slow fibers. The cross-sectional areas (CSAs) of both slow-and fasttwitch fibers of rats were less after 14 d of spaceflight and hindlimb suspension than those in the agematched controls [29]. But the degree of atrophy was greater in slow-than fast-twitch fibers [28,29]. Therefore, muscles composed of predominantly slow fibers are more susceptible to atrophy [26,28, 47]. The weights of fast-twitch ankle dorsi-flexors, such as the tibialis anterior (TA) and extensor digitorum longus (EDL), are also generally less after unloading than those of age-matched controls [31, 57]. But these were Japanese Journal of Physiology, 50, 303-314, 2000 Key words: atrophy, fiber-type transformation, contractile properties, neural responses, microgravity.Abstract: Morphological and/or functional characteristics of skeletal muscles have a greater adaptability in response to changes in environmental stimuli. For example, an atrophy associated with a shift of fiber characteristics toward fast-twitch type is a common adaptation of antigravity muscle to a microgravity environment. Neuromuscular responses and ...

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Section: Fiber Phenotypementioning

confidence: 66%

Neuromuscular Adaptation to Microgravity Environment.

Ohira

2000

JJP

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“…Furthermore, unilateral knee extension resistance exercise performed during unilateral lower limb unloading was capable not only of offsetting atrophy but promoting marked hypertrophy of chronically unloaded muscles (169). In another study, a 2-mo bed rest with 10 h per day wearing an antigravity, elastic device that provided a modest but continuous resistance at the leg muscles was shown to prevent decreases in muscle fiber size and myonuclear domain (170). In addition, leg resistance exercise carried out every other day throughout a 2-wk bed rest challenge could counteract the decrease in muscle protein synthesis observed during strict inactivity (171), probably through blunting total RNA and mRNA deficits and improving IGF-1 signaling (172).…”

Section: 1) Exercise Interventionmentioning

confidence: 97%

Determinants of Disuse-Induced Skeletal Muscle Atrophy: Exercise and Nutrition Countermeasures to Prevent Protein Loss

Bajotto

Shimomura

2006

J Nutr Sci Vitaminol

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Summary Muscle atrophy results from a variety of conditions such as disease states, neuromuscular injuries, disuse, and aging. Absence of gravitational loading during spaceflight or long-term bed rest predisposes humans to undergo substantial loss of muscle mass and, consequently, become unfit and/or unhealthy. Disuse-or inactivity-induced skeletal muscle protein loss takes place by differential modulation of proteolytic and synthetic systems. Transcriptional, translational, and posttranslational events are involved in the regulation of protein synthesis and degradation in myofibers, and these regulatory events are known to be responsive to contractile activity. However, regardless of the numerous studies which have been performed, the intracellular signals that mediate skeletal muscle wasting due to muscular disuse are not completely comprehended. Understanding the triggers of atrophy and the mechanisms that regulate protein loss in unloaded muscles may lead to the development of effective countermeasures such as exercise and dietary intervention. The objective of the present review is to provide a window into the molecular processes that underlie skeletal muscle remodeling and to examine what we know about exercise and nutrition countermeasures designed to minimize muscle atrophy. Key Words Skeletal muscle disuse atrophy, microgravity, hindlimb suspension, protein synthesis and degradation, exercise and nutrition countermeasures Because skeletal muscle is the most abundant tissue of the human body, we may hypothesize that decreases in its mass possibly will profoundly impact the wholebody metabolism and ultimately lead to the development of lifestyle-related diseases. In addition, muscle deconditioning (reduced strength, abnormal reflex patterns, increased fatigability) could limit the ability of astronauts to work in space and/or to rapidly egress the spacecraft in an emergency landing ( 1 ). Even though various functional and morphological alterations are noticeable in inactive muscles, decreased protein content has been regarded as the hallmark of skeletal muscle atrophy. Muscle protein can be either gained or lost by relative changes in protein synthesis and degradation rates, which are known to be modulated by contractile activity. Thus, understanding about the molecular regulators of protein turnover during different mechanical loading conditions and their response to specific treatments leads to the likelihood of developing effective countermeasures for preventing disuseinduced muscle wasting.This article provides a review of muscular adaptations to disuse, with emphasis on protein kinetics. We describe first the general aspects of muscle wasting with regard to exposure to actual or ground-based, simulated microgravity and some of the most significant findings that provide evidence for a close connection between skeletal muscle plasticity and protein metabolism. Next, we present a review of the literature in which results of measurements of protein synthesis/ degradation rates during unloading are avail...

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“…A relationship between the number of myonuclei and fibre size has been reported in trained young (Kadi et al, 1999) and old (Manta et al, 1987;Hikida et al, 2000) individuals, but not in untrained elderly subjects (Hikida et al, 1998), reflecting an aging-and ⁄ or atrophy-related deterioration of this relationship (Ohira et al, 1999). In humans, there are a few reports in the literature on the effects of aging on myonuclear density, describing a constant (Vassilopoulos et al, 1977) or decreased (Manta et al, 1987) cytoplasmic density in old age.…”

Section: Introductionmentioning

confidence: 99%

Effects of aging and gender on the spatial organization of nuclei in single human skeletal muscle cells

et al. 2010

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SummaryThe skeletal muscle fibre is a syncitium where each myonucleus regulates the gene products in a finite volume of the cytoplasm, i.e., the myonuclear domain (MND). We analysed aging-and gender-related effects on myonuclei organization and the MND size in single muscle fibres from six young (21-31 years) and nine old men (72-96 years), and from six young (24-32 years) and nine old women (65-96 years), using a novel image analysis algorithm applied to confocal images. Muscle fibres were classified according to myosin heavy chain (MyHC) isoform expression. Our image analysis algorithm was effective in determining the spatial organization of myonuclei and the distribution of individual MNDs along the single fibre segments. Significant linear relations were observed between MND size and fibre size, irrespective age, gender and MyHC isoform expression. The spatial organization of individual myonuclei, calculated as the distribution of nearest neighbour distances in 3D, and MND size were affected in old age, but changes were dependent on MyHC isoform expression. In type I muscle fibres, average NN-values were lower and showed an increased variability in old age, reflecting an aggregation of myonuclei in old age. Average MND size did not change in old age, but there was an increased MND size variability. In type IIa fibres, average NN-values and MND sizes were lower in old age, reflecting the smaller size of these muscle fibres in old age. It is suggested that these changes have a significant impact on protein synthesis and degradation during the aging process.

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Myonuclear domain and myosin phenotype in human soleus after bed rest with or without loading

Cited by 119 publications

References 29 publications

Neuromuscular Adaptation to Microgravity Environment.

Neuromuscular Adaptation to Microgravity Environment.

Determinants of Disuse-Induced Skeletal Muscle Atrophy: Exercise and Nutrition Countermeasures to Prevent Protein Loss

Effects of aging and gender on the spatial organization of nuclei in single human skeletal muscle cells

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