Matsunaga T, Kanzaki J, Hosoda Y
Department of Otolaryngology, School of Medicine, Keio University, Tokyo, Japan.
Hear Res. 1994 Jun 1;76(1-2):118-26. doi: 10.1016/0378-5955(94)90093-0.
The nerve root segment where the transition from central to peripheral nervous tissue occurs is referred to as the transitional region (TR). Part of the TR is a continuation of the subpial glial limiting membrane (SGLM) which covers the surface of the brain. To assess the physiological and pathophysiological roles of astrocytes in the TR of the human eighth cranial nerve, electron microscopy was performed on surgically resected specimens of the eight cranial nerve root obtained from patients with cerebellopontine angle tumors. The astrocytic glial dome was sharply bounded by a basement membrane and was mainly composed of the bodies and processes of fibrous astrocytes. Desmosomes and gap junctions were found between these astrocytic processes. Half-desmosomes were found on the edge of the astrocytic glial dome and at the luminal surface of the perivascular glial limiting membrane. These ultrastructural features indicate that the astrocytes of the TR might have some motility capacity that allows adjustment to changes in the pressure exerted by the vessels, the peripheral nervous tissue, and the cerebrospinal fluid. In addition, it is also suggested that lack of structures linking the central and peripheral portions of the nerve and the abrupt change of nerve composition at the TR might predispose this area to injury by tractional forces or pathologic conditions such as tumor or arterial compression.
中枢神经组织向周围神经组织过渡的神经根节段被称为过渡区（TR）。TR的一部分是覆盖在脑表面的软膜下神经胶质界膜（SGLM）的延续。为了评估星形胶质细胞在人类第八颅神经TR中的生理和病理生理作用，对从桥小脑角肿瘤患者手术切除的第八颅神经根标本进行了电子显微镜检查。星形胶质细胞胶质穹顶由基底膜清晰界定，主要由纤维性星形胶质细胞的胞体和突起组成。在这些星形胶质细胞突起之间发现了桥粒和缝隙连接。在星形胶质细胞胶质穹顶边缘和血管周围神经胶质界膜的管腔表面发现了半桥粒。这些超微结构特征表明，TR的星形胶质细胞可能具有一定的运动能力，能够适应血管、周围神经组织和脑脊液所施加压力的变化。此外，还表明神经中枢和外周部分之间缺乏连接结构以及TR处神经组成的突然变化可能使该区域易受牵拉力或肿瘤或动脉压迫等病理状况的损伤。
