Matsubara I, Umazume Y, Yagi N
Adv Exp Med Biol. 1984;170:711-20. doi: 10.1007/978-1-4684-4703-3_66.
A toe muscle was isolated from a hind limb of the mouse and treated with saponin to make the sarcolemma more permeable to the solutes of the bathing medium. The equatorial X-ray diffraction pattern was recorded to determine the 1,0 spacing of the hexagonal myofilament lattice. The spacing in relaxed muscle at a sarcomere length of 2.5 microns was 408 A. When the muscle was maximally activated at pCa 4.4, a steady isometric tension of 1.3 kg/cm2 was produced and the spacing decreased to 384 A. A decrease in spacing of the same magnitude was observed when a relaxed muscle went into rigor, although the rigor tension was only 0.1 kg/cm2, 8% of the maximum contractile tension. From the intensity ratio of the 1,0 and 1,1 reflections the number of myosin heads transferred radially to the vicinity of the thin filament was calculated. During the maximum activation at pCa 4.4 the amount of the radial transfer was 96% of that in rigor. When the muscle was activated at a lower calcium concentration, the lattice shrinkage was smaller and the radial transfer was also smaller. These findings suggest that the lateral force underlying the lattice shrinkage may be due to lateral elasticity of cross-bridges.
从小鼠后肢分离出一块趾肌，用皂角苷处理，使肌膜对浴液介质中的溶质更具通透性。记录赤道面X射线衍射图谱，以确定六边形肌丝晶格的1,0间距。在肌节长度为2.5微米的松弛肌肉中，间距为408埃。当肌肉在pCa 4.4时最大激活时，产生1.3千克/平方厘米的稳定等长张力，间距减小到384埃。当松弛肌肉进入强直状态时，观察到间距有相同幅度的减小，尽管强直张力仅为0.1千克/平方厘米，是最大收缩张力的8%。根据1,0和1,1反射的强度比，计算出径向转移到细肌丝附近的肌球蛋白头部数量。在pCa 4.4的最大激活过程中，径向转移量是强直状态下的96%。当肌肉在较低钙浓度下激活时，晶格收缩较小，径向转移也较小。这些发现表明，晶格收缩背后的横向力可能归因于横桥的横向弹性。
