Price R L, Lasek R J, Katz M J
Bio-architectonics Center, CWRU School of Medicine, Cleveland, OH 44106.
Brain Res. 1991 Feb 1;540(1-2):209-16. doi: 10.1016/0006-8993(91)90509-t.
Ultrastructural morphometry was used to document the non-random spatial distributions of organelles within the compact myelinated region of avian oculomotor axons. These regions contain large numbers of loosely packed neurofilaments (NFs) (241/microns 2) and only a relatively small number of microtubules (MTs) (4/microns 2), mitochondria (0.6/microns 2), and smooth endoplasmic reticulum (SER) (1.6/microns 2). Random co-occurrences between the relatively sparsely distributed MTs, mitochondria, and SER are probably infrequent in these axons. The actual co-occurrences of MTs, mitochondria, and SER with MTs were counted and compared to the co-occurrences expected in a random Poisson distribution. At long distances (200 nm), the co-occurrences were random. At shorter distances (40 nm and less), MTs were still randomly associated with other MTs. However, at these shorter distances, the spatial associations of mitochondria with MTs and of SER with MTs were not random; such preferential stable associations may be produced by specific MT associated cross-bridging proteins. In axons, MTs tend to be clustered together, giving the appearance of MT bundles. We propose that the MT-MT bundling is an indirect result of MT concentration along the continuous intra-axonal SER network, to which the MTs are apparently tied directly by dynamic molecular cross-bridges.
利用超微结构形态测量法记录了禽类动眼神经轴突紧密髓鞘区域内细胞器的非随机空间分布。这些区域含有大量松散排列的神经丝（NFs）（241/平方微米），而微管（MTs）（4/平方微米）、线粒体（0.6/平方微米）和平滑内质网（SER）（1.6/平方微米）的数量相对较少。在这些轴突中，相对稀疏分布的微管、线粒体和滑面内质网之间的随机共现可能很少见。对微管、线粒体和滑面内质网与微管的实际共现情况进行了计数，并与随机泊松分布中预期的共现情况进行了比较。在长距离（200纳米）时，共现是随机的。在较短距离（40纳米及以下）时，微管与其他微管仍随机关联。然而，在这些较短距离时，线粒体与微管以及滑面内质网与微管的空间关联并非随机；这种优先的稳定关联可能是由特定的微管相关交联蛋白产生的。在轴突中，微管往往聚集在一起，形成微管束的外观。我们提出，微管-微管成束是微管沿着连续的轴突内滑面内质网网络集中的间接结果，微管显然通过动态分子交联直接与该网络相连。
