Prakash Y S, Smithson K G, Sieck G C
Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
J Neurocytol. 1995 Mar;24(3):225-35. doi: 10.1007/BF01181536.
Using a double-labelling technique, and dual-channel confocal microscopy, we examined the three-dimensional and two-dimensional morphologies of motor endplates on type I and II muscle fibres of 21-day-old and adult rat diaphragms. Motor endplates were visualized with fluorescein-conjugated alpha-bungarotoxin, and muscle fibre type was immunocytochemically determined using an anti-fast (type II) myosin antibody with a Cy5-conjugated label. Surface (three-dimensional) and planar (two-dimensional) areas were obtained from three-dimensional reconstructions of confocal optical sections of labelled endplates. Muscle fibre diameters were also measured. Total branch lengths were measured from projection images of the three dimensional reconstructions. The surface and planar areas of endplates on type I fibres at day 21 were larger than those on type II fibres, and this difference increased with maturation. In adults, the surface area of endplates was positively correlated to muscle fibre size, but such a correlation was not found at day 21. When normalized for fibre diameter, the surface areas of endplates on type I fibres were still significantly larger than those on type II fibres in both age groups. The normalized endplate surface area for type II fibres remained constant with maturation, whereas for type I fibres, the increase in endplate surface area was disproportionate to fibre growth.
我们采用双标记技术和双通道共聚焦显微镜，研究了21日龄和成年大鼠膈肌I型和II型肌纤维运动终板的三维和二维形态。用荧光素偶联的α-银环蛇毒素使运动终板可视化，并用Cy5偶联标记的抗快肌（II型）肌球蛋白抗体免疫细胞化学法测定肌纤维类型。从标记终板的共聚焦光学切片的三维重建中获得表面（三维）和平坦（二维）面积。还测量了肌纤维直径。从三维重建的投影图像中测量总分支长度。21日龄时I型纤维上终板的表面和平面面积大于II型纤维上的终板，且这种差异随成熟而增加。在成年大鼠中，终板的表面积与肌纤维大小呈正相关，但在21日龄时未发现这种相关性。当按纤维直径进行归一化时，两个年龄组中I型纤维上终板的表面积仍显著大于II型纤维上终板的表面积。II型纤维的归一化终板表面积随成熟保持恒定，而对于I型纤维，终板表面积的增加与纤维生长不成比例。
