Liposits Z, Kalló I, Hrabovszky E, Gallyas F
Department of Anatomy, Albert Szent-Györgyi Medical University, Szeged, Hungary.
Acta Biol Hung. 1997;48(2):173-87.
Adrenalectomy-evoked delayed degeneration and death of granule cells in the hippocampal dentate gyrus (DG) of the rat brain were studied by means of electron microscopy and a recently elaborated silver method that selectively stains the "dark", collapsed neurons in a Golgi-like manner. At the light microscopic level, the silver technique revealed degenerating granule cells located exclusively in the dentate gyrus; other glucocorticoid receptor-containing regions of the brain were not affected. The silver-stained cell bodies were shrunken, most of the dendrites had a beaded appearance, and the stained axons could be traced along their route to the CA3 pyramidal neurons of the hippocampus. The analysis of 2.5 microns thick Epon-embedded sections stained with toluidine blue revealed hyperchromatic, dark granule neurons and their remains and a heavy glial activity in the vicinity of collapsing neuronal profiles. At the ultrastructural level, early and late stages of neuronal degeneration were observed. The early phase was characterized by markedly increased electron density, a massive shrinkage of the whole somato-dendritic domain, vacuolization of mitochondria, swelling of the nucleolus and condensation of the nuclear chromatin. In the late stage, subcellular organelles were hardly recognizable due to the extremely high electron density and dramatic shrinkage of the cytoplasm. These profiles exhibited disintegration of the cellular organelles and loss of their afferents. Concomitantly, disintegration of granule cell dendrites (clasmatodendrosis) and lifting of "dark" mossy fibers from cell bodies and dendrites of CA3 pyramidal neurons were observed. In the latter cells, this partial denervation caused no apparent signs of ultrastructural alterations. Proliferation of astrocytes and microglial cells was also obvious as they engulfed and eliminated the degenerating neuronal elements. Degenerating neurons frequently occurred adjacent neurons with normal morphology. These morphological features indicate that the delayed degeneration of hippocampal granule cells following adrenalectomy might proceed through a cytoskeletal collapse terminating in cell death.
采用电子显微镜和一种最近改进的银染法，对大鼠脑内海马齿状回（DG）中肾上腺切除诱发的颗粒细胞延迟性退变和死亡进行了研究。这种银染法能以类似高尔基染色的方式选择性地标记“暗”的、皱缩的神经元。在光学显微镜水平，银染技术显示退变的颗粒细胞仅位于齿状回；脑内其他含有糖皮质激素受体的区域未受影响。银染的细胞体皱缩，大多数树突呈念珠状，染色的轴突可沿其路径追踪至海马的CA3锥体神经元。对用甲苯胺蓝染色的2.5微米厚的环氧树脂包埋切片进行分析，发现颗粒神经元及其残骸颜色加深、呈暗黑色，且在皱缩的神经元轮廓附近有大量的胶质细胞活动。在超微结构水平，观察到神经元退变的早期和晚期阶段。早期阶段的特征是电子密度显著增加、整个胞体 - 树突区域大量收缩、线粒体空泡化、核仁肿胀以及核染色质凝聚。在晚期，由于极高的电子密度和细胞质的剧烈收缩，亚细胞细胞器几乎无法辨认。这些轮廓显示细胞器解体且传入纤维丧失。同时，观察到颗粒细胞树突的解体（树突破碎）以及“暗”苔藓纤维从CA3锥体神经元的细胞体和树突上脱离。在后者的细胞中，这种部分去神经支配未引起明显的超微结构改变迹象。星形胶质细胞和小胶质细胞的增殖也很明显，因为它们吞噬并清除退变的神经元成分。退变的神经元经常出现在形态正常的相邻神经元附近。这些形态学特征表明，肾上腺切除后海马颗粒细胞的延迟性退变可能通过细胞骨架崩溃导致细胞死亡。
