Riley D A, Ellis S, Slocum G R, Satyanarayana T, Bain J L, Sedlak F R
Muscle Nerve. 1987 Jul-Aug;10(6):560-8. doi: 10.1002/mus.880100612.
Prolonged exposure of humans to hypogravity causes weakening of their skeletal muscles. This problem was studied in rats exposed to hypogravity for 7 days aboard Spacelab 3. Hindlimb muscles were harvested 12-16 hours postflight for histochemical, biochemical, and ultrastructural analyses. The majority of the soleus and extensor digitorum longus fibers exhibited simple cell shrinkage. However, approximately 1% of the fibers in flight soleus muscles appeared necrotic. Flight muscle fibers showed increased glycogen, lower subsarcolemmal staining for mitochondrial enzymes, and fewer subsarcolemmal mitochondria. During atrophy, myofibrils were eroded by multiple focal losses of myofilaments; lysosomal autophagy was not evident. Tripeptidylaminopeptidase and calcium-activated protease activities of flight soleus fibers were significantly increased, implying a role in myofibril breakdown. Simple fiber atrophy appears to account for muscle weakening during spaceflight, but fiber necrosis is also a contributing factor.
人类长时间暴露在低重力环境中会导致骨骼肌衰弱。在搭载于太空实验室3号上暴露于低重力环境7天的大鼠身上研究了这个问题。飞行后12 - 16小时采集后肢肌肉进行组织化学、生物化学和超微结构分析。比目鱼肌和趾长伸肌的大多数纤维表现为单纯的细胞萎缩。然而，飞行后的比目鱼肌中约1%的纤维出现坏死。飞行肌肉纤维的糖原增加，线粒体酶的肌膜下染色减少，肌膜下线粒体数量减少。在萎缩过程中，肌原纤维因肌丝的多处局灶性丢失而受到侵蚀；溶酶体自噬不明显。飞行比目鱼肌纤维的三肽基氨基肽酶和钙激活蛋白酶活性显著增加，这意味着它们在肌原纤维分解中起作用。单纯的纤维萎缩似乎是太空飞行期间肌肉衰弱的原因，但纤维坏死也是一个促成因素。
