Connolly J L, Seeley P J, Greene L A
J Neurosci Res. 1985;13(1-2):183-98. doi: 10.1002/jnr.490130113.
The object of this study was to document and analyze local regulation by nerve growth factor (NGF) of neuronal growth cone properties and to explore the possible diversity of this effect in various NGF-responsive preparations. In particular, scanning electron microscopy was used to characterize the morphology of neuronal growth cones in cultures of dissociated chick embryo dorsal root ganglia (DRG) under conditions of continuous NGF exposure, withdrawal of NGF for 5-6 hr, and restoration of NGF for various times. Comparison was made with similarly manipulated cultures of dissociated newborn rat sympathetic ganglia and neurite-bearing PC12 pheochromocytoma cells. The growth cones of most of the continuously NGF-treated DRG neurons (cultured on poly-L-lysine or collagen-coated glass coverslips) had relatively compact central flattened areas and numerous prominent filopodia. Withdrawal of NGF resulted in a marked spreading of the central growth cone area so that the average maximum width of this structure increased by about threefold as compared to nondeprived cultures. The mean number and lengths of filopodia were unaffected. Restoration of NGF brought about, over a time course of tens of minutes, a return of the original type of growth cone morphology. Rather different responses were observed for the sympathetic neuron and PC12 cultures. Here, surface ruffles, only rarely seen in the chick cultures, were a major feature of the growth cones, whereas filopodia, though present, were less prominent. Removal of NGF led to loss of ruffles and to rounding up of the growth cones; NGF readdition elicited a rapid (less than 30 sec) reinitiation of ruffling and a more gradual (over tens of minutes) respreading of growth cones. These findings illustrate not only that NGF can regulate growth cone properties, but also that there is a diversity as to how this is manifested. Possible mechanisms and biological roles for this regulation are discussed.
本研究的目的是记录和分析神经生长因子（NGF）对神经元生长锥特性的局部调节作用，并探讨这种效应在各种对NGF有反应的制剂中的可能差异。特别是，利用扫描电子显微镜对解离的鸡胚背根神经节（DRG）培养物中神经元生长锥的形态进行表征，这些培养物处于持续暴露于NGF、NGF撤除5 - 6小时以及NGF恢复不同时间的条件下。将其与同样经过处理的新生大鼠交感神经节和带有神经突的PC12嗜铬细胞瘤细胞培养物进行比较。大多数持续接受NGF处理的DRG神经元（培养在聚-L-赖氨酸或胶原包被的玻璃盖玻片上）的生长锥具有相对紧凑的中央扁平区域和许多突出的丝状伪足。撤除NGF导致中央生长锥区域明显扩展，与未撤除的培养物相比，该结构的平均最大宽度增加了约三倍。丝状伪足的平均数量和长度未受影响。恢复NGF后，在几十分钟的时间进程中，生长锥形态恢复到原来的类型。交感神经元和PC12培养物观察到的反应则大不相同。在这里，表面褶皱是生长锥的主要特征，在鸡胚培养物中很少见到，而丝状伪足虽然存在，但不太突出。去除NGF导致褶皱消失，生长锥变圆；重新添加NGF引发褶皱迅速重新出现（不到30秒），生长锥更逐渐地（在几十分钟内）重新展开。这些发现不仅表明NGF可以调节生长锥特性，而且还表明这种调节的表现方式存在差异。讨论了这种调节的可能机制和生物学作用。
