Hartman B K, Agrawal H C, Agrawal D, Kalmbach S
Proc Natl Acad Sci U S A. 1982 Jul;79(13):4217-20. doi: 10.1073/pnas.79.13.4217.
The immunohistochemical localization of two myelin specific proteins-basic protein (BP) and proteolipid protein (PLP)-was compared during the process of myelination. Although both proteins were present in oligodendrocytes, (i) neither protein was observed in oligodendrocytes not already closely associated with nerve fibers exhibiting a fluorescent coating; (ii) in any discrete anatomical area oligodendrocytes were positive for BP before PLP was visible; and (iii) as myelination progressed, immunoreactivity for BP in oligodendrocytes appeared to decrease and simultaneously PLP immunofluorescence became visible in this cell type. During the period of active myelination, fibers exhibited a distinct varicose appearance. As myelination progressed, the myelin sheath increased in thickness and these varicosities became less prominent, eventually completely disappearing. Therefore, the nature and the appearance of varicosities can be used as an index of the relative stage of maturation of myelin in an individual fiber. In general, PLP appeared in fibers at a later stage of maturation than did BP based on the above criteria. However, in a relatively small number of fine fibers PLP was observed at a very early stage. In fully mature myelin, very large fibers were frequently more intensely fluorescent for BP than PLP, whereas fine myelinated fibers were more intensely stained for PLP. These observations are consistent with the following interpretations. (i) Substantial differentiation of oligodendrocytes occurs prior to appearance of either of these proteins by immunofluorescence. (ii) BP is added to the myelin sheath prior to PLP and there appears to be a shift in priority of synthesis from BP to PLP in individual oligodendrocytes during the process of myelination. (iii) Very small fibers often contain low concentrations of BP relative to PLP, and conversely, very large fibers may contain a high concentration of BP relative to PLP. Thus, the relative concentration of these proteins in myelin appears not to be constant but may vary as a function of the size of the myelinated fiber.
在髓鞘形成过程中，对两种髓鞘特异性蛋白——碱性蛋白（BP）和蛋白脂蛋白（PLP）进行了免疫组织化学定位比较。虽然这两种蛋白都存在于少突胶质细胞中，但：（i）在尚未与呈现荧光包被的神经纤维紧密相关的少突胶质细胞中，均未观察到这两种蛋白；（ii）在任何离散的解剖区域，少突胶质细胞在PLP可见之前对BP呈阳性；（iii）随着髓鞘形成的进展，少突胶质细胞中BP的免疫反应性似乎降低，同时该细胞类型中PLP免疫荧光变得可见。在活跃的髓鞘形成期，纤维呈现出明显的曲张外观。随着髓鞘形成的进展，髓鞘厚度增加，这些曲张变得不那么明显，最终完全消失。因此，曲张的性质和外观可作为单个纤维中髓鞘成熟相对阶段的指标。一般来说，根据上述标准，PLP在纤维成熟的后期出现，而BP较早出现。然而，在相对少数的细纤维中，PLP在非常早期就被观察到。在完全成熟的髓鞘中，非常大的纤维对BP的荧光通常比PLP更强，而细的有髓纤维对PLP的染色更强。这些观察结果与以下解释一致。（i）在通过免疫荧光检测到这两种蛋白中的任何一种之前，少突胶质细胞就已经发生了实质性分化。（ii）BP在PLP之前添加到髓鞘中，并且在髓鞘形成过程中，单个少突胶质细胞的合成优先级似乎从BP转移到了PLP。（iii）非常小的纤维相对于PLP通常含有低浓度的BP，相反地，非常大的纤维相对于PLP可能含有高浓度的BP。因此，这些蛋白在髓鞘中的相对浓度似乎不是恒定的，而是可能随有髓纤维的大小而变化。
