Panchangam Appaji, Claflin Dennis R, Palmer Mark L, Faulkner John A
Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
Biophys J. 2008 Aug;95(4):1890-901. doi: 10.1529/biophysj.107.118109. Epub 2008 May 9.
A laser-diffraction technique was developed that rapidly reports the lengths of sarcomeres (L(s)) in serially connected sectors of permeabilized single fibers. The apparatus translates a laser beam along the entire length of a fiber segment within 2 ms, with brief stops at each of 20 contiguous sectors. We tested the hypothesis that during lengthening contractions, when maximally activated fibers are stretched, sectors that contain the longer sarcomeres undergo greater increases in L(s) than those containing shorter sarcomeres. Fibers (n = 16) were obtained from the soleus muscles of adult male rats and the middle portions (length = 1.05 +/- 0.11 mm; mean +/- SD) were investigated. Single stretches of strain 27% and a strain rate of 54% s(-1) were initiated at maximum isometric stress and resulted in a 19 +/- 9% loss in isometric stress. The data on L(s) revealed that 1), the stretch was not distributed uniformly among the sectors, and 2), during the stretch, sectors at long L(s) before the stretch elongated more than those at short lengths. The findings support the hypothesis that during stretches of maximally activated skeletal muscles, sarcomeres at longer lengths are more susceptible to damage by excessive strain.
一种激光衍射技术被开发出来，它能快速报告通透化单根纤维串联连接部分的肌节长度（L(s)）。该仪器在2毫秒内沿纤维段的整个长度平移激光束，在20个连续部分的每一个处短暂停留。我们测试了这样一个假设：在拉长收缩期间，当最大激活的纤维被拉伸时，包含较长肌节的部分L(s)的增加幅度大于包含较短肌节的部分。从成年雄性大鼠的比目鱼肌中获取纤维（n = 16），并对中间部分（长度 = 1.05 +/- 0.11毫米；平均值 +/- 标准差）进行研究。在最大等长张力下开始单次施加27%的应变和54% s(-1)的应变率，导致等长张力损失19 +/- 9%。关于L(s)的数据表明，1）拉伸在各部分之间分布不均匀，2）在拉伸过程中，拉伸前L(s)较长的部分比短长度部分伸长更多。这些发现支持了这样一个假设：在最大激活的骨骼肌拉伸期间，较长长度的肌节更容易因过度应变而受损。
