MacKenzie M L, Ghabriel M N, Allt G
J Neurocytol. 1984 Dec;13(6):1043-55. doi: 10.1007/BF01148601.
The permeability of the tight junctional system of myelin, at the juxtanodal myelin terminal loops and Schmidt-Lanterman incisures, was investigated using the ionic tracer lanthanum (a) in vivo followed by fixation, (b) concurrently with fixation, (c) following fixation. Employing the same methods the juxtanodal membrane complex formed between myelin loops and axolemma was also tested. The results of this study demonstrate that the periaxonal space (between axon and Schwann cell) is apparently accessible to lanthanum via the myelin loop-axolemmal junction, irrespective of the mode of exposure of myelinated fibres to the tracer. Similarly, the tight junctions between adjacent myelin terminal loops apparently do not prevent lanthanum penetration either in living or in fixed nerves. By contrast the tracer obtained access to the extracellular space within incisures only in vivo. The results are interpreted in terms of the permeability of nodes and incisures in vivo to physiologically important ions and related to current concepts of the electrophysiology of the myelinated nerve fibre.
利用离子示踪剂镧，研究了髓鞘紧密连接系统在近结髓鞘终末环和施密特-兰特尔曼切迹处的通透性，具体方法如下：(a) 体内注射后固定；(b) 与固定同时进行；(c) 固定后进行。采用相同方法，还检测了髓鞘环与轴膜之间形成的近结膜复合体。本研究结果表明，无论有髓纤维接触示踪剂的方式如何，轴周间隙（轴突与施万细胞之间）显然可通过髓鞘环-轴膜连接被镧进入。同样，相邻髓鞘终末环之间的紧密连接在活神经或固定神经中显然都不能阻止镧的穿透。相比之下，示踪剂仅在体内进入切迹内的细胞外间隙。这些结果根据体内结和切迹对生理重要离子的通透性进行了解释，并与有髓神经纤维电生理学的当前概念相关。
