Davidowitz J, Rubinson K, Jacoby J, Onejeme A
Department of Ophthalmology, New York University Medical Center 10016, USA.
Tissue Cell. 1996 Feb;28(1):77-87. doi: 10.1016/s0040-8166(96)80046-2.
Systematic variation of myofibril profile size was observed along the length of both singly innervated fibers (SIFs) and multiply innervated fibers (MIFs) of the global (inner) layer of extraocular muscle (EOM). These findings contrast with the assumption that global layer fibers of EOM are structurally uniform along their length. Muscle fibers were reconstructed in serial sections along the global layer of rabbit and rat EOM. Long fibers of the 'Pale' SIF (fast twitch glycolytic) and the MIF (tonic) populations were sampled by EM in both proximal and distal portions of the muscle. In rabbit, myofibril size of the Pale SIFs showed a proximal-to-distal increase of 28% whereas the MIFs showed a proximal-to-distal decrease of 10%. In rat, these two fiber populations showed analogous smaller changes. Measures of profile size included the mean intercept length and the mean shortest path from test points within the profile to the profile boundary. The possible effect of sarcomere length variation was controlled by normalizing the measures to a constant spacing of the myosin filament lattice.
在眼外肌（EOM）全局（内层）的单根神经支配纤维（SIFs）和多根神经支配纤维（MIFs）的长度上，均观察到肌原纤维轮廓大小的系统性变化。这些发现与眼外肌全局层纤维在其长度上结构均匀的假设形成对比。沿着兔和大鼠眼外肌全局层的连续切片重建肌肉纤维。通过电子显微镜在肌肉的近端和远端部分对“浅色”SIF（快缩糖酵解型）和MIF（紧张型）群体的长纤维进行采样。在兔中，浅色SIFs的肌原纤维大小显示近端到远端增加了28%，而MIFs显示近端到远端减少了10%。在大鼠中，这两个纤维群体显示出类似的较小变化。轮廓大小的测量包括平均截距长度以及从轮廓内测试点到轮廓边界的平均最短路径。通过将测量值归一化为肌球蛋白丝晶格的恒定间距，控制了肌节长度变化的可能影响。
