Hahn A F, Whitaker J N, Kachar B, Webster H D
J Comp Neurol. 1987 Jun 22;260(4):501-12. doi: 10.1002/cne.902600404.
Myelination and the expression of myelin proteins P2, P1, and P0 were studied quantitatively in the rat sixth cranial nerve during development. The postnatal development and growth of all myelin sheaths in this nerve have been studied morphometrically in a companion paper. Epon-embedded blocks with closely matched topography in the transverse plane were selected from rats perfused at ages 1-4, 8, 15, and 20 days. From each block, serial semithin sections were cut, etched, and immunostained according to the peroxidase-antiperoxidase method with well-characterized polyclonal antisera that reacted specifically with P0 glycoprotein and the basic proteins P1 and P2. The immunoreactivities of individual myelin sheaths were measured by densitometry. Numbers of compact myelin lamellae, myelin spiral lengths, and axon diameters were determined on electronmicrographs of adjacent thin sections. At birth anti-P0 immunoreactivity was found on sheaths with two and more compact lamellae; neither P1 nor P2 immunoreactivity was observed. On day 2, myelin sheaths with five and eight lamellae were stained respectively by anti-P1 and anti-P2. On day 3 the percentages of myelin sheaths stained were substantially higher: P0 95%, P1 78%, P2 15%. By day 4, anti-P0 and anti-P1 immunoreactivity was present in 95% of myelin sheaths; 35% were stained by anti-P2. For P2, staining intensity and percentage of myelin sheaths stained continued to increase and by day 20, 85% were anti-P2-positive. The density of immunoreactivity was not uniform in all myelin sheaths. At young ages staining varied with all three proteins. The variability decreased as myelin sheaths thickened; it persisted longest for anti-P2. We conclude that the density and distribution of immunoreactivities of P0, P1, and P2 reflect their relative concentrations during myelin sheath development and growth. We attribute lack of detectable anti-P2 immunoreactivity in some small sheaths at 20 days to their early stage of myelination and also to limitations of the method. We infer from our observations that all myelin-forming Schwann cells express P2 basic protein.
在发育过程中，对大鼠第六脑神经的髓鞘形成以及髓鞘蛋白P2、P1和P0的表达进行了定量研究。在一篇配套论文中，已从形态计量学角度研究了该神经中所有髓鞘的出生后发育和生长情况。从1日龄、4日龄、8日龄、15日龄和20日龄灌注的大鼠中选取在横切面上具有紧密匹配地形的环氧树脂包埋块。从每个包埋块中切取连续的半薄切片，蚀刻后，根据过氧化物酶-抗过氧化物酶方法，用与P0糖蛋白以及碱性蛋白P1和P2特异性反应的特征明确的多克隆抗血清进行免疫染色。通过光密度测定法测量各个髓鞘的免疫反应性。在相邻薄切片的电子显微照片上确定紧密髓鞘板层数量、髓鞘螺旋长度和轴突直径。出生时，在具有两层及更多紧密板层的髓鞘上发现抗P0免疫反应性；未观察到P1和P2免疫反应性。在第2天，具有五层和八层板层的髓鞘分别被抗P1和抗P2染色。在第3天，被染色的髓鞘百分比显著更高：P0为95%，P1为78%，P2为15%。到第4天，95%的髓鞘存在抗P0和抗P1免疫反应性；35%被抗P2染色。对于P2，染色强度和被染色的髓鞘百分比持续增加，到第20天，85%为抗P2阳性。免疫反应性密度在所有髓鞘中并不均匀。在幼年时，三种蛋白的染色情况各不相同。随着髓鞘增厚，变异性降低；抗P2的变异性持续时间最长。我们得出结论，P0、P1和P2免疫反应性的密度和分布反映了它们在髓鞘发育和生长过程中的相对浓度。我们将20日龄时一些小髓鞘中未检测到抗P2免疫反应性归因于它们髓鞘形成的早期阶段以及该方法的局限性。从我们的观察中推断，所有形成髓鞘的施万细胞都表达P2碱性蛋白。
