Studies On Morphogenesis Of Optic Vesicle And Apoptosis During Development In Bufo Raddei

Optic vesicle of Bufo raddei was studied and the growing process of optic vesicle were observed and described in detail. Based on some typical events that happened in this process, we divided the growing process of optic vesicle into eight representative phases and two different phases (2 and 3) were choosed to determine apoptosis using in situ hybridization. Result:The process of optic vesicle development can be divided into 4 phases: 1 Phase of preparing for optic vesicle: optic vesicle can not be seen, but nuclei in future retinal pigmented epithelium (RPE) domains are gathering and realigning. 2 Phase of optic vesicle extruding: first, nuclei in the presumptive RPE domains are rearranging activity and almost form two layers; nuclei in the presumptive NR domains almost displays a single layer near the outside of wall, Optic vesicle cavity comes into being; Then the presumptive RPE holding out: he areas of the presumptive neural retina (NR) layer in contact with the surface ectoderm are more broad than before and optic vesicle cavity expands more. optic vesicle can be seen obviously; Last, nuclei that reached in future RPE domains early already have linaged, many nuclei of neuroepithelium nearly the presumptive RPE are gathering or rearraying actively, and then they come into being the presumptive RPE later. 3 Phase of optic vesicle cavity beginning to expand toward dorsal: At first, cavity of optic vesicle begins to expand toward dorsal along the dorsoventral axis;The length of presumptive RPE layer is further shorter than presumptive neural retina layer; The wall of optic vesicle is thinner than neuroepithelium. Then, the optic vesicle cavity expanding more toward dorsal and the dorsal portion of the optic vesical closes to neuroepithelium, subsequently, the length of presumptive RPE layer increases dramatically, close to half length of presumptive neural retina layer. 4 Phase of the presumptive NR layer was thickening: In transverse, the presumptive RPE layer thinning and shows itself in the shape of "S";The number of nuclei in the centre of NR domain are increasing.Apoptosis was determined by TUNEL labeling, apoptotic nuclei was virtually absent in the presumptive RPE domains and presumptive neural retina domains, These results indicate that the large number of cells are necessary to developmental optical vesicle. There may be two sources of increasing cells, the one is neuroepithelium, from which cells moves in presumptive RPE domains and then transfer to the presumptive NR domains during early optic vesicle development, the other is proliferation of the optic vesicle cells during late optic vesicle development.