Hypogravity‐induced atrophy of rat soleus and extensor digitorum longus muscles

Riley, Denise; Ellis, Stanley; Slocum, Glenn R.; Satyanarayana, T.; Bain, James L. W.; Sedlak, F. R.

doi:10.1002/mus.880100612

Cited by 81 publications

(54 citation statements)

References 18 publications

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“…Elevated Ca 2ϩ activates calcium-activated proteases, calpains, which partially degrade myofibrillar proteins and ryanodine receptors, leading to breakdown of myofibrils and enhanced calcium efflux (11,27,31). Calcium-activated protease activity increases in atrophying soleus muscles during HSU (12,33) and spaceflight (28) and directly parallels the development of CCLs in tenotomy (5). Immobilized soleus muscles show significant increases in total calcium concentration (7).…”

Section: Discussionmentioning

confidence: 99%

Passive stretch inhibits central corelike lesion formation in the soleus muscles of hindlimb-suspended unloaded rats

Baewer

Hoffman²,

Romatowski³

et al. 2004

Journal of Applied Physiology

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. Passive stretch inhibits central corelike lesion formation in the soleus muscles of hindlimb-suspended unloaded rats. J Appl Physiol 97: 930 -934, 2004. First published May 7, 2004 10.1152/japplphysiol.00103.2004.-Hindlimb suspension unloading (HSU) is a ground-based model simulating the effects of microgravity unloading on the musculoskeletal system. In this model, gravity causes the hind foot of the rat to drop, opening the front of the ankle to 90 -105°plantar flexion at rest. As HSU proceeds, the normal weight-bearing angle of 30°dorsiflexion is achieved progressively less, and the contraction range of soleus is abbreviated. Our laboratory reported that 12 days of HSU caused central corelike lesions (CCLs) of myofibril breakdown (Riley DA, Slocum GR, Bain JL, Sedlak FR, Sowa TE, and Mellender JW. J Appl Physiol. 69: 58 -66, 1990). The present study investigated whether daily stretch of the calf muscles prevents CCL formation. The soleus muscles of HSU SpragueDawley male rats (ϳ287 g) were lengthened by unilateral ankle splinting at 30°. Compared with the nonsplinted side, splinting for 10 or 20 min per day in awake rats significantly decreased CCLs in soleus by 88 and 91%, respectively (P Ͻ 0.01). Compared with control muscle wet weight, 20-min splinting reduced atrophy by 33%, whereas 10-min splinting ameliorated atrophy by 17% (P Ͻ 0.01). Bilateral soleus electromyograph recording revealed higher levels of contractile activity on the splinted side during splinting. To isolate the effects of stretch from isometric contractile activity, contractions were eliminated by whole animal anesthesia with isoflurane during 10-min daily splinting. The percentage of fibers with CCLs was reduced by 57%, and the average lesion size was 29% smaller in the stretched muscle (P Ͻ 0.05). Soleus muscle wet weight and fiber area were unaltered by stretch alone. Loaded contractions during splinting are necessary to prevent muscle fiber atrophy. Passive muscle stretch acts to maintain myofibril structural integrity. length; countermeasure; splint; atrophy; calcium HINDLIMB SUSPENSION UNLOADING (HSU) of rats is a well-established experimental model for simulating the effects of microgravity unloading on weight-bearing muscles (25). Preventing rats from touching the ground with their hindlimbs causes the antigravity soleus muscles to atrophy due to decreased use, unloading, and shortened working range (29). Central corelike lesions (CCLs), which are areas of focal myofibril dissolution, appear within soleus fibers by day 12 of HSU. For rat solei, the CCLs were postulated to result from the ϳ20% shortened contraction range, which is a consequence of suspensioninduced foot drop posture (plantar flexion) (22,29). Foot drop posture of humans floating in microgravity was first documented in their neutral body position during Skylab missions (26). CCLs also occur in suspension-unloaded rabbits in which soleus shortening is ϳ35% because the large hind feet are weighed down by gravity (2). A shortened length is required for CCL generati...

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Section: Discussionmentioning

confidence: 99%

Passive stretch inhibits central corelike lesion formation in the soleus muscles of hindlimb-suspended unloaded rats

Baewer

Hoffman²,

Romatowski³

et al. 2004

Journal of Applied Physiology

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“…One of the most affected is the neuromuscular system. Weightlessness induces atrophy of skeletal muscle (Riley et al, 1987;Widrick et al, 1999) and cardiovascular deconditioning (Philpott et al, 1990;Antonutto and Prampero, 2003). Weightlessness also reduces functional capacity in limb skeletal muscle of animals including humans (Ilyina-Kakueva et al, 1976;Widrick et al, 1999;Fitts et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…Weightlessness also reduces functional capacity in limb skeletal muscle of animals including humans (Ilyina-Kakueva et al, 1976;Widrick et al, 1999;Fitts et al, 2000). In vertebrate skeletal muscle, the greatest changes are observed in the limb antigravity muscles, such as soleus (Riley et al, 1987;Widrick et al, 1999;Harrison et al, 2003). Major changes in these muscles alter the expression of muscle protein isoforms, mainly myosin heavy chains (MHCs).…”

Section: Introductionmentioning

confidence: 99%

Spaceflight results in increase of thick filament but not thin filament proteins in the paramyosin mutant of Caenorhabditis elegans

Adachi

Takaya

Kuriyama

et al. 2008

Advances in Space Research

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We have investigated the effect of microgravity during spaceflight on body-wall muscle fiber size and muscle proteins in the paramyosin mutant of Caenorhabditis elegans.Both mutant and wild-type strains were subjected to 10 days of microgravity during spaceflight and compared to ground control groups. No significant change in muscle fiber size or quantity of the protein was observed in wild-type worms; where as atrophy of body-wall muscle and an increase in thick filament proteins were observed in the paramyosin mutant unc-15(e73) animals after spaceflight. We conclude that the mutant with abnormal muscle responded to microgravity by increasing the total amount of muscle protein in order to compensate for the loss of muscle function.

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“…Some observations on fibers of young adult rats following 14 d of spaceflight suggest that subsarcolemmal mitochondria may be preferentially altered [47,69,70]. Bell et al [69] have shown that the relative loss of SDH activity in the subsarcolemmal vs. intermyofibril region following spaceflight is fiber-type dependent.…”

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confidence: 99%

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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Hypogravity‐induced atrophy of rat soleus and extensor digitorum longus muscles

Cited by 81 publications

References 18 publications

Passive stretch inhibits central corelike lesion formation in the soleus muscles of hindlimb-suspended unloaded rats

Passive stretch inhibits central corelike lesion formation in the soleus muscles of hindlimb-suspended unloaded rats

Spaceflight results in increase of thick filament but not thin filament proteins in the paramyosin mutant of Caenorhabditis elegans

Neuromuscular Adaptation to Microgravity Environment.

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