Fedorenko Grigory M, Uzdensky Anatoly B
Southern Federal University, Rostov-on-Don, Russia.
Cell Tissue Res. 2009 Sep;337(3):477-90. doi: 10.1007/s00441-009-0825-7. Epub 2009 Jul 8.
In order to explore neuroglial relationships in a simple nervous system, we have studied the ultrastructure of the crayfish stretch receptor, which consists of only two mechanoreceptor neurons enwrapped by glial cells. The glial envelope comprises 10-30 glial layers separated by collagen sheets. The intercellular space between the neuronal and glial membranes is generally less than 10-15 nm in width. This facilitates diffusion between neurons and glia but restricts neuron communication with the environment. Microtubule bundles passing from the dendrites to the axon through the neuron body limit vesicular transport between the perikaryon and the neuronal membrane. Numerous invaginations into the neuron cytoplasm strengthen glia binding to the neuron and shorten the diffusion pathway between them. Double-membrane vesicles containing fragments of glial, but not neuronal cytoplasm, represent the captured tips of invaginations. Specific triads, viz., "flat submembrane cisterns - vesicles - mitochondria", are presumably involved in the formation of the invaginations and double-membrane vesicles and in neuroglial exchange. The tubular lattice in the glial cytoplasm might transfer ions and metabolites between the glial layers. The integrity of the neuronal and glial membranes is impaired in some places. However, free neuroglial passage might be prevented or limited by the dense diffuse material accumulated in these regions. Thus, neuroglial exchange with cellular components might be mediated by transmembrane diffusion, especially in the invaginations and submembrane cisterns, by the formation of double-walled vesicles in which large glial masses are captured and by transfer through tubular lattices.
为了探究简单神经系统中的神经胶质关系，我们研究了小龙虾牵张感受器的超微结构，该感受器仅由两个被神经胶质细胞包裹的机械感受器神经元组成。神经胶质包膜由10 - 30层被胶原片分隔的神经胶质层组成。神经元膜和神经胶质膜之间的细胞间隙宽度通常小于10 - 15纳米。这有利于神经元和神经胶质之间的扩散，但限制了神经元与外界环境的交流。从树突穿过神经元体到达轴突的微管束限制了核周体与神经元膜之间的囊泡运输。大量向神经元细胞质内的内陷增强了神经胶质与神经元的结合，并缩短了它们之间的扩散途径。含有神经胶质而非神经元细胞质片段的双膜囊泡代表了内陷的捕获末端。特定的三联体，即“扁平的膜下池 - 囊泡 - 线粒体”，可能参与了内陷和双膜囊泡的形成以及神经胶质交换。神经胶质细胞质中的管状晶格可能在神经胶质层之间传递离子和代谢产物。在某些部位，神经元膜和神经胶质膜的完整性受到损害。然而，这些区域积累的致密弥散物质可能会阻止或限制神经胶质的自由通过。因此，神经胶质与细胞成分的交换可能通过跨膜扩散介导，特别是在内陷和膜下池中，通过形成捕获大量神经胶质团块的双壁囊泡以及通过管状晶格进行转运。
