花背蟾蜍角膜早期发育中胶原合成、分泌和分布的研究

STUDIES ON COLLAGEN SYNTHESIS, SECRETION AND DISTRIBUTION DURING EARLY CORNEAL DEVELOPMENT IN BUFO RADDEI STRAUCH

本文以花背蟾蜍19—25期胚胎为材料,采用半薄切片荧光标记胶原酶术及超薄切片分别在光镜及电镜水平观察了胶原蛋白在角膜早期形态发生中合成及分布并探讨其作用。结果表明:角膜上皮与内角膜细胞均可合成、分泌胶原蛋白。角膜上皮基底细胞与内角膜细胞中细胞器数量与位置随发育过程而发生的变化与角膜上皮及内角膜细胞合成及分泌胶原蛋白有关。

The synthesis, secretion and distribution of collagen in the cornea of developing toad embryos (19-25 stage) were studied by transmission electron microscopy and the hemisections treated with FITC-labeled collagenase were st(?)died on light microscopic level. Results indicate: (1) At stage 19 the lens plate separated from the presumptive corneal epithelium and weak fluorescence appeared in its basal cells. From stage 20 to 23, intense fluorescence was seen in these basal cells and reached its highest degree at stage 21. During stage 24 to 25, fluorescence could hardly be seen in basal cells but increased gradually in subepithelial layer from stage 23 to 25. It demonstrated that the collagen produced Dy the basal cells was secreted into the subepithelial layer. During stage 20 to 25. a number of mesenchymal cells migrated between the corneal epithelium and later became the inner cornea. Owing to the appearance of fluorescence in these mesenchymal cells, it convinced us that collagen could be synthesized in them. (2) During stage 19 to 20, a few thin and short collagen fibrils were seen distributed irregularly in the subepi- thelial layer. From stage 21 to 25, the corneal epithelium secreted collagen into the subepithelial layer where collagen fibrils reorganized and assembled into thick and long fibers. At stage 25, many collagen fibres were present in the subepithelial layer which arranged orthogonally to each other and formed a network. Meanwhile, some quantitative and localized changes of or-ganelles were observed in the basal cells. During stage 19 to 20. the basal cells contained less rough endoplasmic reticula and Golgi bodies and more mitochendria; from stage 21 to 23, more mitochondria, Golgi bodies and secreting vesicles localized at the base or sides of the nucleus were present in the basal cells. During stage 24 to 25, the number of organelles decreased and distributed randomly. (3) During stage 19 to 20, few rough endoplasmic reticula, Golgi bodies, secreting vesicles and more mitochondria were present in the mesenchymal cells which formed the inner cornea. From stage 22 to 24, in mesenchymal cells the number of mitochondria decreased, meanwhile, rough endoplasmic reticula, Golgi bodies and secreting vesicles increased and collagen fibrils appeared among these mesenchymal cells. At stage 25, the organelles decreased gradually in these mesenchymal cells.Based on the above mentioned results, we consider that the corneal epithelium and inner cornea may synthesize collagen. Close relationship might be present between the variation of organelle number and their distribution with development and collagen synthesis by corneal epithelium. Collagen secreted from the corneal epithelium into the subepithelial layer may be transported by two routes: i.e. the intercellular space and the basal cell surface. This confirms the theory that the collagen synthesized and secreted by corneal epithelium and inner cornea may play an important role in Strom formation and in various aspects of corneal development.