Somasekhar T, Pollack E D
Institute for the Study of Developmental Disabilities, University of Illinois, Chicago 60680.
J Comp Neurol. 1992 Dec 8;326(2):314-26. doi: 10.1002/cne.903260212.
Nerve fibers extend from spinal cord explants of larval frog in an enhanced and directed manner when cocultured with limb mesenchyme target tissue. In order to gain a better understanding of the events involved in target directed neurite extension, a detailed examination of the nerve growth cone was undertaken. The growth cones of spinal neurites that had elongated in the presence or absence of target tissue were examined by light and electron microscopy. Scanning electron microscopy revealed that growth cones of cord+limb cultures were elaborate in form with numerous and long filopodia, while those cultured in the absence of the target tissue appeared relatively simple with few, short filopodia. A morphological parallel existed between those growth cones that were cultured without the target and those in cord+limb cultures but which grew from the side of the cord explant away from the mesenchyme tissue. When examined with the transmission electron microscope, growth cones under target influence were organelle-rich in contrast to target-deprived growth cones, which lacked the extensive array of vesicles, endoplasmic reticulum, and filaments. When the attachment substratum of polylysine was substituted by collagen, the dramatic differences in growth cones were not realized, although enhanced, oriented growth still occurred in the presence of limb target tissue. It appears that growth cone morphology is a dynamic reflection of the growth effects elicited by a target tissue factor that in turn may be mediated by the nature of the extracellular environment.
当与肢体间充质靶组织共培养时，来自幼蛙脊髓外植体的神经纤维会以增强且定向的方式延伸。为了更好地理解参与靶标导向神经突延伸的相关事件，对神经生长锥进行了详细检查。通过光学显微镜和电子显微镜检查了在有或没有靶组织存在的情况下伸长的脊髓神经突的生长锥。扫描电子显微镜显示，脊髓+肢体共培养物的生长锥形态复杂，有许多长丝状伪足，而在没有靶组织的情况下培养的生长锥则相对简单，丝状伪足较少且短。在没有靶标的情况下培养的生长锥与脊髓+肢体共培养物中但从脊髓外植体远离间充质组织一侧生长的生长锥之间存在形态学上的相似之处。当用透射电子显微镜检查时，受靶标影响的生长锥富含细胞器，这与缺乏大量囊泡、内质网和细丝的缺乏靶标的生长锥形成对比。当聚赖氨酸附着基质被胶原蛋白替代时，生长锥的显著差异并未显现，尽管在肢体靶组织存在的情况下仍会出现增强的定向生长。看来生长锥形态是靶组织因子引发的生长效应的动态反映，而靶组织因子反过来可能由细胞外环境的性质介导。
