THE HISTOGENESIS OF RAT INTERCOSTAL MUSCLE
THE HISTOGENESIS OF RAT INTERCOSTAL MUSCLE
复制标题
大鼠肋间肌的组织发生
作者：
A. Kelly;S. Zacks
对胎鼠和新生大鼠的肋间肌进行了电子显微镜观察。在妊娠16天时，发育中的肌肉由初代肌管组成，其中许多肌管成群聚集在一起。在这些组中，相邻肌管的膜通过特殊的连接相互连接，包括紧密连接。形态上未分化的细胞围绕着肌群，经常沿着相邻肌管之间的间隙延伸伪足，并似乎将相邻肌管彼此分开。在妊娠18天和20天时，肌肉也由多组细胞组成，但这些组的结构与16天时观察到的组不同。单个分化良好的肌管含有大量的中枢糖原和外周肌原纤维，在每组中占主导地位。这些大细胞被解释为初级肌管。小的、分化较少的肌肉细胞和未分化的细胞聚集在它们的壁上。每一簇由一个基底板包裹。这些小细胞被解释为新一代肌肉细胞的原基，这些细胞通过沿大的初级肌管的壁上的对位生长而分化。所有世代的大鼠肋间肌细胞均在妊娠20天至出生时成熟为肌纤维。巧合的是，大小肌纤维相互分化，导致肌细胞群解体。分离时，未分化细胞常出现在相邻肌细胞之间的空隙中。作为这种非同步发育模式的结果，在肌肉组织发生的不同阶段出现的肌纤维以棋盘式的方式混合在一起。讨论了在该发育系统中相邻肌细胞之间融合的可能性。
Intercostal muscle from fetal and newborn rats was examined with the electron microscope. At 16 days' gestation, the developing muscle was composed of primary generations of myotubes, many of which were clustered together in groups. Within these groups, the membranes of neighboring myotubes were interconnected by specialized junctions, including tight junctions. Morphologically undifferentiated cells surrounded the muscle groups, frequently extended pseudopodia along the interspace between adjacent myotubes, and appeared to separate neighboring myotubes from one another. At 18 and 20 days' gestation, the muscle was also composed of groups of cells but the structure of the groups differed from that of the groups observed at 16 days. Single, well differentiated myotubes containing much central glycogen and peripheral myofibrils dominated each group. These large cells were interpreted as primary myotubes. Small, less differentiated muscle cells and undifferentiated cells clustered around their walls. Each cluster was ensheated by a basal lamina. The small cells were interpreted as primordia of new generations of muscle cells which differentiated by appositional growth along the walls of the large primary myotubes. All generations of rat intercostal muscle cells matured to myofibers between 20 days' gestation and birth. Coincidentally, large and small myofibers diverged from each other, leading to disintegration of the groups of muscle cells. Undifferentiated cells frequently occurred in the interspaces between neighboring muscle cells at the time of separation. Myofibers arising at different stages of muscle histogenesis intermingled in a checkerboard fashion as a result of this asynchronous mode of development. The possibility of fusion between neighboring muscle cells in this developing system is discussed.