Hero I
Department of Morbid Anatomy, London Hospital, Whitechapel, England.
Invest Ophthalmol Vis Sci. 1990 Jan;31(1):197-216.
The purpose of this study was to determine the ultrastructural features of optic fissure closure. Serial coronal sections of fetal eyes from the eleventh to the thirteenth gestational day were examined by light and electron microscopy. Fusion was associated with inversion of the retinal pigment epithelium at the optic fissure and it occurred first between undifferentiated cells at the junction of the retina and retinal pigment epithelium. It later extended to involve the entire thickness of the pigment epithelium and neuroretina, with the inner aspect of the latter being the last area to fuse. There was some evidence that closure does not always start at the center of the fissure as generally described, but may sometimes start near the developing papilla. At an ultrastructural level, there was multifocal disintegration of the basement membrane associated with the formation of cytoplasmic processes at these sites. Simple appositional contacts between processes on either side of the fissure comprised the first stages of fusion. Later intermediate-type junctions were formed between adjacent outer retinal cells (presumptive photoreceptors) and junctional complexes were formed at the apices of pigment epithelial cells at the site of fusion. This suggests an increase in mechanical adherence between cells. While basement membrane disintegrated at the center of the fusion site, there was a continuous layer of basement membrane at the internal and external limits of fusion. Cell death together with two morphological types of phagocytic cells were a constant feature at the fissure margins before, during and after fusion. The possible origins and roles of these cells in the fusion process is discussed.
本研究的目的是确定视裂闭合的超微结构特征。对妊娠第11至13天胎儿眼睛的系列冠状切片进行了光镜和电镜检查。融合与视裂处视网膜色素上皮的反转有关，它首先发生在视网膜与视网膜色素上皮交界处的未分化细胞之间。随后扩展至色素上皮和神经视网膜的全层，其中神经视网膜的内侧是最后融合的区域。有证据表明，视裂闭合并不总是如通常所描述的那样从视裂中心开始，有时可能从发育中的视乳头附近开始。在超微结构水平上，基底膜出现多灶性崩解，同时在这些部位形成细胞质突起。视裂两侧突起之间简单的并列接触构成了融合的初始阶段。随后，相邻的视网膜外层细胞（推测为光感受器）之间形成中间型连接，融合部位色素上皮细胞顶端形成连接复合体。这表明细胞间的机械黏附增加。虽然融合部位中心的基底膜发生崩解，但在融合的内部和外部界限处仍有一层连续的基底膜。在融合前、融合期间和融合后，细胞死亡以及两种形态类型的吞噬细胞一直存在于视裂边缘。本文讨论了这些细胞在融合过程中的可能来源和作用。
