Interrelationship between growth factor and adhesion molecule in the formation of neuromuscular junctions and muscle apindles

用普通电镜观察了大鼠和中国仓鼠生后神经肌肉接头和肌梭的形态分化，并用免疫电镜观察了碱性成纤维细胞生长因子（bFGF）和神经细胞粘附分子（N-CAM）在其形成和成熟过程中的相互关系。就像凹陷处有几个初期的连接褶皱。多神经元运动终末逐渐消失，直到出生后第15天，只有运动终末保留。突触沟变得复杂，包含增加的连接褶皱。另一方面，在出生时的肌梭中，梭内肌管彼此建立侧对侧接触，而没有基底层的插入。感觉末梢局限于肌束的外表面。此后，梭内肌管分离成独立的肌纤维，肌纤维受感觉末梢支配，并被减弱的内囊细胞包裹，免疫电镜观察到bFGF在运动和感觉末梢中均呈阳性染色，直至成年。此外，肌纤维和肌梭的外囊和内囊之间的成纤维细胞也呈bFGF阳性。另一方面，N-CAM在运动末梢-肌纤维接触处被检测到，但在感觉末梢-梭内肌纤维接触处不一定被观察到。

The morphodifferentiation of neuromuscular junctions and muscle spindles in the postnatal rats and Chinese hamsters was observed by ordinary electron microscopy and the interrelationship between basic fibroblast growth factor (bFGF) and neural cell adhesion molecule (N-CAM) during their formation and maturation was examined by immuno-electron microscopy.Motor endings at birth were polyneuronal and subneural apparatuses consisted of shallow cup-like depressions with a few incipient junctional folds. Poly-neuronal motor endings gradually eliminated until the 15th postnatal day and only a motor ending retained. Synaptic gutters became complex and contained increased junctional folds. On the other hand, in muscle spindles at birth, intrafusal myotubes established side-to-side contact with each other without the intercalation of a basal lamina. Sensory endings were confined to the outer surface of the muscle bundle. Thereafter, intrafusal myotubes separated into independent muscle fibers which were innervated by sensory endings and ensheathed in attenuated inner capsule cells.In the examination by immunoelectron microscopy, positive staining for bFGF was observed in both motor and sensory endings until adulthood. Moreover, fibroblasts among muscle fibers and outer and inner capsules of the muscle spindles were also bFGF-positive. On the other hand, N-CAM was detected at motor ending-muscle fiber contacts, but was not necessarily observed at sensory ending-intrafusal muscle fiber contacts.