Résumé
The tension generated by the contractile apparatus is transmitted through the plasma membrane to the tendon collagen fibers at the myotendinous junction (MTJ). At this specialized region of skeletal muscle fibers, the muscle-tendon interface is increased by folding the muscle fiber plasma membrane. The interfacial surface amplification results in a reduced stress applied to the plasma membrane during contraction. A chronic modification of the muscle use and/or loading leads to a structural remodeling of MTJ. The purpose of the present study was to investigate the effects of a 14-day spaceflight (Bion 11 mission) on soleus MTJ ultrastructure in the rhesus monkey (Macaca mulatta). We examined the ultrastructural organization of the nonhuman primate MTJ because, to our knowledge, only a histological study had previously addressed the rhesus muscle-tendon interface. (Author)