Tetzlaff W
J Neurocytol. 1982 Oct;11(5):839-58. doi: 10.1007/BF01153522.
Tight and gap junctions are described on the basis of freeze-fractures in normal chicken sciatic nerves as well as during Wallerian degeneration and subsequent regeneration. 1. Small calibre nerve fibres display a fairly continuous tight junction contact zone in the membranes of the mesaxons, paranodal loops and Schmidt-Lanterman incisures. Large fibres with more than 40 lamellae have only focal tight junction contacts in the mesaxonal membranes. 2. With the onset of Wallerian degeneration (days 2-4 post-crush, distal stump) myelinic tight junctions become arranged as maculae composed of one circular or several polygonally oriented strands that are criss-crossed by other tight junctional strands. These maculae are subsequently found in the membranes of cytoplasmic vacuoles of the Schwann cells, indicating an endocytotic mode of uptake. Tight junctions are not found between the 5th and 6th day after crush. 3. During the proliferation phase of the Schwann cells and the arrangement of these cells into Büngner cell bands (2 to 8 days post-crush) gap junctions appear between the Schwann cells of the bands. These junctions then disappear with the onset of remyelination (8 days post-crush). 4. With the onset of remyelination (from the 8th day onwards) short focal tight junctions appear in the membranes of the outer mesaxons. Shortly thereafter, when the sheaths possess 4 to 8 lamellae, tight junctions also appear in the membranes of the inner mesaxons, the paranodal loops and the cytoplasmic inclusions. The characteristic differences of tight junction elaboration in small versus large nerve fibres are re-established after three months of regeneration. The elaborated tight junctions in small and early remyelinating fibres point to a specific function; in small fibres (versus large fibres) the tight junctions might effect a separation of the intramyelinic extracellular space as a single compartment. The tight junction contacts in early remyelinating fibres support the hypothesis that myelin growth occurs within the myelin spiral and not by a free rotation and elongation of the Schwann cell tongues. It is assumed that the gap junctions between the Schwann cells contribute to the co-ordination of the Schwann cell band formation, which is involved in the guidance of sprouting axons.
紧密连接和缝隙连接是根据正常鸡坐骨神经的冷冻断裂情况以及在华勒氏变性和随后的再生过程中进行描述的。1. 小口径神经纤维在中轴突、结旁环和施密特-兰特尔曼切迹的膜中显示出相当连续的紧密连接接触区。具有40多个板层的大纤维在中轴突膜中只有局部紧密连接接触。2. 随着华勒氏变性的开始（挤压后2 - 4天，远侧残端），髓鞘紧密连接排列成由一条圆形或几条多边形排列的链组成的斑，这些链与其他紧密连接链相互交叉。随后在施万细胞的细胞质空泡膜中发现这些斑，表明存在内吞摄取模式。挤压后第5天到第6天未发现紧密连接。3. 在施万细胞增殖阶段以及这些细胞排列成束状细胞带时（挤压后2至8天），束状细胞带的施万细胞之间出现缝隙连接。随着髓鞘再生的开始（挤压后8天），这些连接随后消失。4. 随着髓鞘再生的开始（从第8天起），在外中轴突膜中出现短的局部紧密连接。此后不久，当髓鞘具有4至8个板层时，内中轴突、结旁环和细胞质内含物的膜中也出现紧密连接。再生三个月后，小神经纤维和大神经纤维中紧密连接形成的特征差异重新建立。小纤维和早期髓鞘再生纤维中形成的紧密连接指向一种特定功能；在小纤维（与大纤维相比）中，紧密连接可能会将髓鞘内细胞外空间分隔为一个单一的区室。早期髓鞘再生纤维中的紧密连接接触支持了这样一种假设，即髓鞘生长发生在髓鞘螺旋内，而不是通过施万细胞舌的自由旋转和伸长。据推测，施万细胞之间的缝隙连接有助于束状细胞带形成的协调，这与发芽轴突导向有关。
