Structural and metabolic characteristics of human skeletal muscle following 30 days of simulated microgravity.
Structural and metabolic characteristics of human skeletal muscle following 30 days of simulated microgravity.
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发表时间：
1989-07
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通讯作者：
R. S. Hikida;P. D. Gollnick;G. Dudley;V. Convertino;P. Buchanan
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作者：
R. S. Hikida;P. D. Gollnick;G. Dudley;V. Convertino;P. Buchanan
在6 °头低位卧床30 d前后，从股外侧肌和比目鱼肌获得经皮穿刺活检样品，以确定该模拟微重力模型对人体骨骼肌的影响。纤维萎缩是明显的，在这两个肌肉的快肌和慢肌纤维横截面积减少。慢缩纤维的优势萎缩不明显。卧床前比目鱼肌慢缩纤维的比例比股外侧肌大。无论是肌肉纤维类型的百分比与卧床休息的变化。磷酸果糖激酶和乳酸脱氢酶活性在比目鱼肌和股外侧肌卧床休息前后相似。然而，β-羟酰辅酶A脱氢酶和柠檬酸合酶的活性在卧床期间降低，这些反应在比目鱼肌中略大。虽然大多数的比目鱼肌和股外侧肌的纤维的超微结构出现正常卧床休息后，重塑的证据存在于两个肌肉。核心/靶样病变，蜂窝网络，再生卫星细胞，坏死灶和肌原纤维解体后卧床的增殖表明，力的发展是一个重要的因素，在确定肌肉的精细结构的组织。结果表明，短时间暴露于模拟微重力会降低人体骨骼肌的纤维尺寸和有氧供能能力。此外，发生收缩机制的解体。因此，看来卧床休息改变了“正常”的负荷时间限制施加在骨骼肌足以改变其固有的结构和代谢特征。
Percutaneous needle biopsy samples were obtained from the vastus lateralis and soleus muscles before and after 30 d of 6 degree head-down bedrest to determine the influence of this model of simulated microgravity on human skeletal muscle. Fiber atrophy was evident in both muscles with both fast-twitch and slow-twitch fiber cross-sectional areas decreasing. Predominant atrophy of slow-twitch fibers was not evident. The soleus had a greater proportion of slow-twitch fibers than the vastus lateralis before bedrest. Neither muscle showed a change in fiber type percentage with bedrest. Phosphofructokinase and lactate dehydrogenase activities in the soleus and vastus lateralis muscles were similar before and after bedrest. The activities of beta-hydroxyacyl-CoA dehydrogenase and citrate synthase, however, were reduced during bedrest with these responses being somewhat greater in the soleus. While the ultrastructure of most of the fibers of the soleus and vastus lateralis appeared normal after bedrest, evidence of remodeling was present in both muscles. The proliferation of core/targetoid lesions, honeycomb networks, regenerating satellite cells, necrotic foci and myofibrillar disorganization after bedrest indicates that force development is an important factor in determining the organization of the fine structure of muscle. The results indicate that short-duration exposure to simulated microgravity decreases fiber size and the capacity for aerobic energy supply of human skeletal muscle. Moreover, disorganization of the contractile machinery occurs. Thus, it appears that bedrest alters the "normal" load-time constraints imposed on skeletal muscle sufficiently to change its inherent structural and metabolic characteristics.