Egensperger R, Maslim J, Bisti S, Holländer H, Stone J
Department of Neuromorphology, Max-Planck-Institute for Psychiatry, Martinsried, Germany.
Brain Res Dev Brain Res. 1996 Nov 22;97(1):1-8. doi: 10.1016/s0165-3806(96)00119-8.
The tunel technique of labelling fragmenting dna was used to examine cell death in the developing retina of the rabbit, rat and cat. TUNEL-labelled structures included the still-intact nuclei of retinal cells and smaller, strongly labelled bodies interpreted as fragments of disintegrating nuclei (apoptotic or pyknotic bodies). With confocal microscopy, the cytoplasm around labelled nuclei was observed to be labelled, suggesting that DNA fragments spread into the cytoplasm of the dying cell. Also observed were cells whose nuclei were TUNEL-but whose cytoplasm was TUNEL+, so that their morphology could be discerned. Evidence is presented that these are phagocytes, their cytoplasmic labelling resulting from the ingestion of the fragmenting DNA of a dying neighbour. Results suggest that in developing retina fragmenting DNA is phagocytosed principally by microglia and Müller cells, with a few neurones and no astrocytes active as phagocytes. In the postnatal material studied, microglia are the predominant phagocytes for cells dying in the ganglion cell and inner nuclear layers. Müller cells appear able to phagocytose cells dying in any retinal layer and, since microglia do not normally enter the outer nuclear layer, may be important for the phagocytosis of dying photoreceptors.
采用DNA片段末端标记（TUNEL）技术检测兔、大鼠和猫发育中的视网膜细胞死亡情况。TUNEL标记的结构包括视网膜细胞仍然完整的细胞核以及较小的、标记强烈的小体，这些小体被认为是正在解体的细胞核的碎片（凋亡小体或固缩小体）。利用共聚焦显微镜观察到，标记细胞核周围的细胞质也被标记，这表明DNA片段扩散到了正在死亡的细胞的细胞质中。还观察到一些细胞核未被TUNEL标记但细胞质被TUNEL标记的细胞，这样就可以辨别它们的形态。有证据表明这些是吞噬细胞，它们细胞质中的标记是由于吞噬了临近死亡细胞的正在断裂的DNA所致。结果表明，在发育中的视网膜中，断裂的DNA主要被小胶质细胞和穆勒细胞吞噬，只有少数神经元参与吞噬，星形胶质细胞不参与。在所研究的出生后材料中，小胶质细胞是神经节细胞层和内核层中死亡细胞的主要吞噬细胞。穆勒细胞似乎能够吞噬视网膜任何一层中死亡的细胞，而且由于小胶质细胞通常不会进入外核层，因此穆勒细胞对于吞噬死亡的光感受器可能很重要。
