钠和钙在郎飞结处施万细胞旁结环的定位以及钙在致密髓鞘中的定位。

The localization of sodium and calcium to schwann cell paranodal loops at nodes of Ranvier and of calcium to compact myelin.

作者信息

Ellisman M H, Friedman P L, Hamilton W J

出版信息

J Neurocytol. 1980 Apr;9(2):185-205. doi: 10.1007/BF01205157.

DOI:10.1007/BF01205157

Abstract

High-voltage electron microscopy (HVEM) has been used to determine the distribution of cationic precipitates in myelinated axons resulting from the application of two cytochemical techniques: a direct osmium pyroantimonate treatment for precipitating Na+, Ca2+ and Mg2+; and a 5 mM Ca2+ inclusion procedure (Oschman & Wall) for imparting electron density to Ca2+ binding sites. Electron probe wavelength spectroscopy was then used on semi-thick tissue sections to identify the species of ions present in the following regions: Schwann cell paranodal loops, axoplasm at the node, compact myelin and extracellular matrix. With these combined procedures we were able to localize elevated concentrations of both Na+ and Ca2+ to cytoplasmic compartments of the Schwann cell paranodal loops, as well as to detect the presence of Ca2+ at elevated levels in compact myelin. The involvement of the Schwann cell paranodal loops in providing a source and/or sink for Na+ involved in impulse conduction is suggested by these results, and the significance of such a role is discussed. A role for Ca2+ in the formation and stabilization of myelin lamellae is also suggested.

摘要

高压电子显微镜（HVEM）已被用于确定在有髓轴突中阳离子沉淀物的分布，这是通过应用两种细胞化学技术实现的：一种是直接用焦锑酸锇处理以沉淀Na⁺、Ca²⁺和Mg²⁺；另一种是5 mM Ca²⁺包埋程序（Oschman和Wall法），用于使Ca²⁺结合位点具有电子密度。然后，利用电子探针波长光谱法对半厚组织切片进行分析，以确定在以下区域中存在的离子种类：施万细胞节旁环、结处的轴浆、致密髓鞘和细胞外基质。通过这些联合程序，我们能够将Na⁺和Ca²⁺的高浓度定位到施万细胞节旁环的细胞质区室，同时也能检测到致密髓鞘中Ca²⁺的高浓度存在。这些结果表明施万细胞节旁环参与为冲动传导过程中涉及的Na⁺提供来源和/或汇，并讨论了这一作用的意义。还提出了Ca²⁺在髓鞘板层形成和稳定中的作用。