Suzuki Toshimi, Maruyama Akio, Sugiura Takao, Machida Shuichi, Miyata Hirofumi
Department of Biological Sciences, Graduate School of Medicine, Yamaguchi University, Yoshida 1677-1, Yamaguchi, 753-8515, Japan.
J Physiol Sci. 2009 Jan;59(1):57-62. doi: 10.1007/s12576-008-0005-7. Epub 2008 Nov 30.
To examine the age-related morphological changes in the motor endplate of type-identified muscle fibers, 20 male Wister rats were divided into 2-month-, 10-month-, 24-month- and 30-month-old groups (n = 5 in each group). Three segments of mid-costal diaphragm muscle were removed, and then a fluorescent double-labeling technique was used to visualize the endplates on type-identified muscle fibers. Endplates were labeled with alpha-bungarotoxin-tetramethylrhodamine. Muscle segments were first incubated in antibodies to MHC isoforms (I and/or IIa) and then labeled by a second antibody with FITC. The endplates were imaged using 3D confocal microscopy with two lasers. In each age group, the planar area and volume of endplates on type-IIx/b muscle fibers were larger than those on type-I and -IIa muscle fibers, while the normalized planar areas of the endplate (endplate area/muscle fiber diameter) and the mean thickness of the endplate (volume/endplate area) were identical on all fiber types within the same age group. Decreased endplate density (endplate area/surrounding area) in the old diaphragm indicated fragmentation of the endplate, especially on type IIx/b fibers. These morphological changes may lead to functional deficiency and selective denervation of type-IIx/b muscle fiber with aging.
为了研究特定类型肌纤维运动终板的年龄相关形态变化，将20只雄性Wister大鼠分为2月龄、10月龄、24月龄和30月龄组（每组n = 5）。取三段肋中膈肌，然后采用荧光双标记技术观察特定类型肌纤维上的终板。用α-银环蛇毒素-四甲基罗丹明标记终板。首先将肌段与MHC同工型（I和/或IIa）抗体孵育，然后用异硫氰酸荧光素标记二抗。使用双激光三维共聚焦显微镜对终板成像。在每个年龄组中，IIx/b型肌纤维上终板的平面面积和体积大于I型和IIa型肌纤维上的终板，而同一年龄组内所有纤维类型的终板标准化平面面积（终板面积/肌纤维直径）和终板平均厚度（体积/终板面积）相同。老年膈肌终板密度降低（终板面积/周围面积）表明终板发生碎片化，尤其是在IIx/b型纤维上。这些形态变化可能导致衰老过程中IIx/b型肌纤维功能缺陷和选择性失神经支配。
