Tidball J G, Quan D M
Department of Physiological Science, University of California, Los Angeles 90024-1527.
J Appl Physiol (1985). 1992 Jul;73(1):59-64. doi: 10.1152/jappl.1992.73.1.59.
The surface area of myotendinous junctions (MTJs), expressed relative to the cross-sectional area of myofibrils attached to them, was determined using established morphometric techniques in which the digitlike processes of the cell at MTJs are modeled as circular paraboloids. The relative area, called the folding factor, was measured for six rats after a 4-day spaceflight and six control rats maintained in a vivarium under otherwise identical conditions. Spaceflight resulted in a significant reduction in relative MTJ surface area, from 19.7 +/- 2.3 (SD) in control animals to 13.3 +/- 2.5 for animals after spaceflight. Furthermore, space animals displayed increased numbers of fibroblasts enriched in rough endoplasmic reticulum near the MTJ, a greater number of ribosomes and mitochondria within muscle at the MTJ, and increased occurrence of lesions in the connective tissue near the MTJ. The results indicate that spaceflight, possibly through the removal of gravity-associated loading from muscle, causes a modification in MTJ structure and may result in injuries at MTJs after return to normal loading.
利用既定的形态测量技术测定肌-腱连接点（MTJ）的表面积，该技术将MTJ处细胞的指状突起建模为圆形抛物面，并将其表面积与附着的肌原纤维横截面积相关联。在4天太空飞行后，对6只大鼠以及在相同条件下饲养在动物饲养室的6只对照大鼠测量了相对面积，即折叠因子。太空飞行导致MTJ相对表面积显著减少，对照动物为19.7±2.3（标准差），太空飞行后的动物为13.3±2.5。此外，太空飞行的动物在MTJ附近显示出富含粗面内质网的成纤维细胞数量增加，MTJ处肌肉内的核糖体和线粒体数量更多，MTJ附近结缔组织中的损伤发生率增加。结果表明，太空飞行可能通过消除肌肉与重力相关的负荷，导致MTJ结构发生改变，并可能在恢复正常负荷后导致MTJ损伤。
