Metabolic Modulation of Muscle Fiber Properties Unrelated to Mechanical Stimuli

Ohira, Yoshinobu; Kawano, Fuminori; Roy, Roland R.; Edgerton, V. Reggie

doi:10.2170/jjphysiol.53.389

Cited by 20 publications

(19 citation statements)

References 42 publications

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“…In contrast, fast-twitch muscles are responsible for strength and power activities of a relatively high-intensity and short-duration. Adult rats generally spend ~78% of their time in a recumbent, resting position, keeping the ankle joints in a dorsifl exed position [7,17]. Continuous electromyography (EMG) of a single neuromuscular unit in rats under normal conditions indicates that ~500,000 impulses are generated per pattern and metabolic capacity, along with mechanical and neural activity levels, would be the factors regulating mRNA expression levels of HSPs.…”

Section: Discussionmentioning

confidence: 99%

Gene Expression Levels of Heat Shock Proteins in the Soleus and Plantaris Muscles of Rats after Hindlimb Suspension or Spaceflight

et al. 2008

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Gene expression levels of heat shock proteins (HSPs) in the slow-twitch soleus and fast-twitch plantaris muscles of rats were determined after hindlimb suspension or spaceflight. Male rats were hindlimb-suspended for 14 d or exposed to microgravity for 9 d. The mRNA expression levels of HSP27, HSP70, and HSP84 in the hindlimb-suspended and microgravity-exposed groups were compared with those in the controls. The mRNA expression levels of the 3 HSPs in the soleus muscle under normal conditions were higher compared with those in the plantaris muscle. The mRNA expression levels of the 3 HSPs in the soleus muscle were inhibited by hindlimb suspension and spaceflight. The mRNA expression levels of the 3 HSPs in the plantaris muscle did not change after hindlimb suspension. It is suggested that the mRNA expression levels of the 3 HSPs are regulated by the mechanical and neural activity levels, and therefore the decreased mRNA expression levels of HSPs in the slow-twitch muscle following hindlimb suspension and spaceflight are related to a reduction in the mechanical and neural activity levels.

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Section: Discussionmentioning

confidence: 99%

Gene Expression Levels of Heat Shock Proteins in the Soleus and Plantaris Muscles of Rats after Hindlimb Suspension or Spaceflight

et al. 2008

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“…8A), suggesting that the behavior patterns become similar to those of 1-G controls, once the rats accustom themselves to 2-G environment. The rats generally spend ∼78% of their time in a recumbent resting position on the floor (Ohira et al, 2003). Thus, it is suggested that rat tibia and fibula do not always support the weight against gravitational loading, if the rat maintain the prone body posture keeping the ankle joints at a dorsiflexed position.…”

Section: Discussionmentioning

confidence: 99%

Irreversible morphological changes in leg bone following chronic gravitational unloading of growing rats

et al. 2006

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“…at a leg position equivalent to that observed during HU with or without various treatments. Sedentary adult rats spend most of their time ( ϳ 78%) in a recumbent position [Ohira et al, 2003]. Therefore, both joints of cage control rats were fixed at ϳ 30°, i.e.…”

Section: Determination Of Sarcomere Lengthmentioning

confidence: 99%

The Role of Neural and Mechanical Influences in Maintaining Normal Fast and Slow Muscle Properties

Ohira

Yoshinaga

Ohara

et al. 2006

Cells Tissues Organs

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The relative importance of neural and mechanical influences in maintaining normal slow and fast muscle properties remains unclear. To address this issue, we studied the effects of 10 days of hindlimb unloading (HU) with or without tenotomy and/or denervation on the cross-sectional area (CSA), myosin heavy chain (MHC) expression (immunohistochemistry) and composition (gel electrophoresis), and myonuclear number in soleus and plantaris fibers in adult male Wistar rats. In general, the adaptations in fiber type and size were similar using either single fiber gel or immunohistochemical analyses. HU resulted in atrophy of type I and I+IIa/x MHC fibers in the soleus and in type I, I+IIa/x, IIa/x, IIa/x+IIb, and IIb MHC fibers in the plantaris. Addition of tenotomy and/or denervation in HU rats had minimal effects on fiber CSA in the soleus, but fiber CSA in the plantaris further decreased, particularly in fibers expressing only fast MHCs. HU resulted in a de novo appearance of type I+IIa/x+IIb and IIa/x+IIb MHC fibers in the soleus and of type I+IIa/x+IIb MHC fibers in the plantaris.Tenotomy and/or denervation in HU rats had no further effect on the fiber type composition of either muscle. Mean myonuclear number/mm of type I fibers was decreased in the soleus of HU rats, and increased in type I and I+IIa/x fibers in HU plus tenotomy (HU+Ten) rats. In the plantaris, mean myonuclear number/mm of type IIa/x, IIa/x+IIb, and IIb fibers was lower after HU with or without tenotomy and/or denervation. Mean cytoplasmic volume/myonucleus ratio of type I and I+IIa/x fibers in the soleus of the HU group tended to be smaller than in controls. The largest decrease was noted in the HU+Ten group. In the plantaris, this ratio was unaffected by HU alone, but was decreased by addition of tenotomy and/or denervation when all fiber types were combined. These data indicate that the major cause of fiber atrophy and adaptations in myonuclear domain size in the slow soleus of HU rats is the chronic reduction in force generation, whereas the elimination of neuromuscular contact via denervation results in additional fiber atrophy and adaptations in myonuclear domain size in the fast plantaris.

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Metabolic Modulation of Muscle Fiber Properties Unrelated to Mechanical Stimuli

Cited by 20 publications

References 42 publications

Gene Expression Levels of Heat Shock Proteins in the Soleus and Plantaris Muscles of Rats after Hindlimb Suspension or Spaceflight

Gene Expression Levels of Heat Shock Proteins in the Soleus and Plantaris Muscles of Rats after Hindlimb Suspension or Spaceflight

Irreversible morphological changes in leg bone following chronic gravitational unloading of growing rats

The Role of Neural and Mechanical Influences in Maintaining Normal Fast and Slow Muscle Properties

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