Axonal and nueronal degeneration in relation to balance changes in synthesis, transport and degradation of cytoskeletal proteins.

利用大鼠背根神经节细胞和腹角运动神经元系统，对轴突细胞骨架蛋白的动态组织和运输进行了研究，得到了以下结果。轴突细胞骨架的三个亚群根据它们在1%冷Triton X-100含有缓冲液中的溶解特性被区分为稳定聚合、动态和解聚形式。最后一张表格被认为是运输表格2。慢轴突运输的两个亚组分：慢组分a和b(分别为SCA和SCB)。前者主要为稳定聚合态，后者为动态聚合态。轴突运输缓慢的平均速率随年龄增长而减慢。在标记后几周的年轻成年大鼠，例如7周或更大的大鼠中，可以看到SCA和SCB的分离，但在年轻的大鼠，例如4周龄的大鼠中，则没有分离。然而，在年龄超过30周的大鼠中，稳定聚合形式的大峰出现在初始…处轴突的L部分较多，向远端迁移较少。从稳定聚合态的累积峰值开始，在接下来的几周内出现了一个动态聚合态的群体，而不是像幼鼠那样重组成稳定聚合的细胞质。这导致远端轴突的功能性失神经，可能导致轴突和神经元的变性。上述结果表明，轴突细胞三个亚群之间的相互转换速度随年龄增长而减慢，尤其是在老年大鼠，从动态聚合型到稳定聚合型的重组受到严重影响。不能重建稳定聚合形式的动态形式可能会被降解。当轴突损伤时，它迅速重新定位，沿其全长增加动态亚群，以修复损伤。同时，缓慢的轴突转运速度增加，神经元胞体内微管蛋白和肌动蛋白的合成也增加。轴突细胞骨架并不像人们所认为的那样是一种刚性结构，而是一种对环境条件做出迅速反应的动态结构。较少

Dynamic organization and transport of axonal cytoskeletal proteins were investigated using rat dorsal root ganglion cell and ventral horn motoneuron systems, and the following results were obtained.1. Three subpopulations of axonal cytoskeleton were distinguished by their solubility properties in 1% cold Triton X-100 containing buffer ; stably polymerized, dynamic and depolymerized froms. The last form was thought to be transported form.2. Two subcomponents of slow axonal transport were distinguished by their ratc and composition ; slow component a and b (Sca and Scb respectively). The formerconsisted mainly of stably polymerized form and the latter of dynamic form. The average rate of slow axonal transport slowed down with age.3. Separation into Sca and Scb was seen in young adult rat, e. g. 7weeks of age or older, a few weeks after labelling, but not in young rat, e. g. 4 weeks of age. In older rat than 30 weeks, however, a large peak of stably polymerized form appeared at the initia … More l portion of axon, which scarecely migrated distally. From the accumulated peak of stably polymerized form, a population of dynamic form came out during a next few weeks, which was not reorganized into stably polymerized cytoskletons as in the case of young rat. This resulted in functional denervation of distal axon, probably causing axonal and neuronal degeneration.4. From the results above mentioned, it is suggested that the rate of interconversion among three subpopulations of axonal cytosksleton slows down with age, and especially in the older rat, reorganization from dynamic to stably polymerized forms is severely affected. The dynamic form which fails to reconstitute stably polymerized form may be degraded.5. When axon was injured, it quickly respoded to increase dynamic subpopulation along its whole length for repairing the injury. At the same time the rate of slow axonal transport increased, and the synthesis of tubulin and actin in the neuronal cell body also increased after a while.6. The axonal cytoskeleton is not a rigid structure as ever thought, but rather a dynamic one responding promptly to its environmental conditions. Less