Davidowitz J, Rubinson K, Jacoby J, Philips G
Department of Ophthalmology, New York University Medical Center 10016, USA.
Tissue Cell. 1996 Feb;28(1):63-76. doi: 10.1016/s0040-8166(96)80045-0.
It is generally assumed that a muscle fiber is structurally uniform along its length. That assumption is not consistent with the observed variation of myofibrillar profile size along the length of both singly innervated fibers (SIFs) and multiply innervated fibers (MIFs) in the orbital (outer) layer of extraocular muscle (EOM). Muscle fibers were reconstructed in serial sections along the orbital layer of rabbit and rat EOM. For both the SIFs and MIFs, myofibril profile size was smallest (narrowest) near the endplate. In the SIFs of rat, for example, the myofibril profiles were 28% wider at a distance of 1.5 mm from the endplate than at the endplate itself. 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 myofibrillar profile size data to a constant spacing of the myosin filament lattice. This morphometric approach was also used to quantify the further increase of profile size that occurs in the end portions of the orbital MIFs where the myobrillar organization is typically ill-defined.
一般认为，肌纤维在其长度上结构是均匀的。这一假设与在眼外肌（EOM）眶（外）层中观察到的单根神经支配纤维（SIFs）和多根神经支配纤维（MIFs）沿长度方向肌原纤维轮廓大小的变化不一致。沿着兔和大鼠EOM的眶层制作连续切片来重建肌纤维。对于SIFs和MIFs，肌原纤维轮廓大小在终板附近最小（最窄）。例如，在大鼠的SIFs中，距终板1.5毫米处的肌原纤维轮廓比终板处本身宽28%。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。通过将肌原纤维轮廓大小数据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。这种形态测量方法还用于量化在眶部MIFs末端部分发生的轮廓大小的进一步增加，在这些部位肌原纤维组织通常不明确。
