Temporal changes in sarcomere lesions of rat adductor longus muscles during hindlimb reloading.

摘要: Focal sarcomere disruptions were previously observed in adductor longus muscles of rats flown approximately two weeks aboard the Cosmos 1887 and 2044 biosatellite flights. These lesions, characterized by breakage loss myofilaments Z-line streaming, resembled damage induced unaccustomed exercise that includes eccentric contractions which lengthen as they develop tension. We hypothesized lesions atrophied space flow not produced microgravity muscle unloading but resulted from reloading upon re-exposure to terrestrial gravity. To test this hypothesis, we examined temporal changes integrity subjected 12.5 days hindlimb suspension subsequent return vivarium cages for 0, 6, 12, or 48 hours normal weightbearing. Our ultrastructural observations suggested (0 h reloading) myofibril misalignment associated with myofiber atrophy. Muscle 6 focal cross striations abnormally widened. Such electron lucent due extensive myofilament loss. Lesions reloaded showed rapid restructuring. By 12 reloading, moderately stained foci darkly pattern was indistinct at light microscopic levels. spanned Z-line-like dense filamentous material. findings suggest a new role streaming lesion restructuring: rather than an antecedent damage, type may be indicative rapid, early repair.