Schlaepfer W W, Zimmerman U P
Neurochem Res. 1981 Mar;6(3):243-55. doi: 10.1007/BF00964040.
Disruptive effects of calcium upon neurofilaments and glial filaments were studied in white matter of rat optic nerve and spinal cord and in rat peripheral nerve. Filament ultrastructure and tissue protein composition were compared following a calcium influx into excised tissues. A calcium influx was induced by freeze--thawing tissues in media containing calcium (5 mM) while control tissues were freeze--thawed in the presence of EGTA (5 mM). Experimental and control tissues were either fixed by immersion in glutaraldehyde and processed for electron microscopic examination or homogenized in a solubilizing buffer and analyzed for protein content by SDS-polyacrylamide gel electrophoresis. Morphological studies showed that calcium influxes led to the loss of neurofilaments and glial filaments and to their replacement by an amorphous granular material. These morphological changes were accompanied by the loss of neurofilament triplet proteins and glial fibrillary acidic (GFA) protein from whole-tissue homogenates. In addition, a calcium-sensitive 58,000-mol-wt protein was identified in rat optic and peripheral nerve. The findings indicate the widespread occurrence of neurofilament proteolysis following calcium influxes into CNS and PNS tissues. The parallel breakdown of glial filaments and loss of GFA protein subunits suggest the presence of additional calcium-activated proteases(s) in astroglial cells.
在大鼠视神经和脊髓的白质以及大鼠外周神经中，研究了钙对神经丝和胶质丝的破坏作用。在钙流入离体组织后，比较了细丝超微结构和组织蛋白质组成。通过在含钙（5 mM）的培养基中冻融组织来诱导钙流入，而对照组织在EGTA（5 mM）存在下进行冻融。将实验组织和对照组织要么浸入戊二醛中固定并进行电子显微镜检查，要么在增溶缓冲液中匀浆，并通过SDS-聚丙烯酰胺凝胶电泳分析蛋白质含量。形态学研究表明，钙流入导致神经丝和胶质丝丢失，并被无定形颗粒物质取代。这些形态学变化伴随着全组织匀浆中神经丝三联体蛋白和胶质纤维酸性（GFA）蛋白的丢失。此外，在大鼠视神经和外周神经中鉴定出一种对钙敏感的58,000道尔顿分子量的蛋白质。研究结果表明，钙流入中枢神经系统和外周神经系统组织后，神经丝蛋白水解广泛发生。胶质丝的平行分解和GFA蛋白亚基的丢失表明星形胶质细胞中存在其他钙激活蛋白酶。
