Jacobs J R, Stevens J K
J Cell Biol. 1986 Sep;103(3):895-906. doi: 10.1083/jcb.103.3.895.
After exposure to nerve growth factor, PC12 cells differentiate within a period of only a few days into cholinergic sympathetic neurons. Using computer-assisted three-dimensional serial electron microscopic reconstruction, we describe the progressive cytoskeletal and structural changes of PC12 neurites at different stages in their differentiation. Developmental changes in these neurites can be characterized by two major transitions. First, microtubules (MTs), which define the longitudinal axis of the neurite, increase in number leading to a more cylindrical and uniform neurite shape. Second, there are major changes in the relative numbers of other organelle types, which reflect the functional specialization of the neurite. These changes do not in themselves seriously affect shape change of the neurite during development, however the presence of these organelles and their associated obligatory volumes (volumes surrounding organelle) account for well over 50% of the neurite's volume at all stages of development. The MT-MT distances and obligatory volumes associated with the organelles remain constant throughout development. Thus, we can conclude that many of the observed changes seen in developing PC12 neurites are due simply to the production of a greater number of MTs in the cell, and that many of the other important parameters that can be measured and contribute to neurite shape remain constant during development.
在暴露于神经生长因子后，PC12细胞在短短几天内就分化为胆碱能交感神经元。利用计算机辅助三维连续电子显微镜重建技术，我们描述了PC12神经突在分化不同阶段的渐进性细胞骨架和结构变化。这些神经突的发育变化可由两个主要转变来表征。首先，确定神经突纵轴的微管（MTs）数量增加，导致神经突形状更呈圆柱形且更均匀。其次，其他细胞器类型的相对数量有重大变化，这反映了神经突的功能特化。这些变化本身在发育过程中并不会严重影响神经突的形状变化，然而这些细胞器及其相关的必需体积（围绕细胞器的体积）在发育的所有阶段占神经突体积的比例超过50%。在整个发育过程中，微管间距离以及与细胞器相关的必需体积保持恒定。因此，我们可以得出结论，在发育中的PC12神经突中观察到的许多变化仅仅是由于细胞中产生了更多的微管，并且在发育过程中许多可测量的、对神经突形状有贡献的其他重要参数保持恒定。
