Sims T J, Durgun M B, Gilmore S A
Department of Anatomy, University of Arkansas for Medical Sciences, Little Rock 72205, USA.
J Neuropathol Exp Neurol. 1998 Sep;57(9):866-73. doi: 10.1097/00005072-199809000-00008.
This study examines a radiation-induced invasion and spread of Schwann cells into ventral gray regions of the lumbar spinal cord. The prevalence of these cells within the gray matter and the time course of their appearance in the ventral spinal cord is quite different from the pattern of Schwann cell development in dorsal spinal cord reported previously. The focus is on 2 possible pathways, each involving astrocytic barriers, by which Schwann cells access the ventral gray matter. The first of these is the glia limitans covering the ventral surface of the spinal cord and the possibility that its integrity has been disrupted by the exposure to x-rays. Comparisons of the glia limitans, including its thickness, between irradiated and nonirradiated rats revealed that exposure to radiation did not result in any morphologically discernible alterations. The second barrier examined was the astrocytic covering of blood vessels. In irradiated animals the astrocyte processes that normally surround blood vessels were missing in some instances, and Schwann cells were observed at these sites. The difference between the dorsal and ventral occurrence of Schwann cells is that, whereas Schwann cells primarily follow axons, specifically dorsal root axons, to access the dorsal spinal cord, it appears that the presence of Schwann cells in the ventral portion of the spinal cord where their location is primarily in the gray matter is associated with the vasculature.
本研究考察了辐射诱导的施万细胞侵入并扩散至腰段脊髓腹侧灰质区域的情况。这些细胞在灰质中的发生率及其在脊髓腹侧出现的时间进程，与先前报道的脊髓背侧施万细胞的发育模式截然不同。研究重点在于施万细胞进入腹侧灰质的两条可能途径，每条途径都涉及星形胶质细胞屏障。其中第一条途径是覆盖脊髓腹侧表面的胶质界膜，以及其完整性因X射线照射而被破坏的可能性。对辐照大鼠和未辐照大鼠的胶质界膜，包括其厚度进行比较后发现，辐射暴露并未导致任何形态上可辨别的改变。所考察的第二个屏障是血管的星形胶质细胞覆盖物。在辐照动物中，正常情况下围绕血管的星形胶质细胞突起在某些情况下缺失，并且在这些部位观察到了施万细胞。施万细胞在背侧和腹侧出现情况的差异在于，施万细胞主要沿着轴突，特别是背根轴突进入脊髓背侧，而脊髓腹侧施万细胞的存在似乎与脉管系统有关，其主要位于灰质中。
