Studies On Retinal Morphogenesis And The Effection Of Retinal Physiological Activity On The Corneal Induction Of Bufo Raddei Strauch

The toad, Bufo Raddei Strauch is the Model animal employed in the experiment about eye developmental biology in our laboratory. The retina was studied by Using conventional histological techniques, Immunohistochemistrial techniques and transmission electron microscopy (TEM), scanning electron microscopy(SEM), and research detail included in this dissertation carried out as follows:(1) the fine structure of retina and the retina morphogenesis in postembryonic stage; (2) the relationship between the retinal physiological activity and cornea induction; (3) the persistence of proliferative neural cells in various years of age toad.The retina fine structure of the adult toad was investigated employing the light microscopy(LM), electron microscopy (EM),and the observation result indicated that:The retina of the toad was composed of 10 layers, from the outside (nearest the blood vessel enriched choroid) to the inside (nearest the gelatinous vitreous humor).The observation of the retina ultrastructure shown that there was a giant phagosome in the cytoplasm of pigment epithelium (EP) cell, and in the inner segment of photoreceptors, the Ellipsoid and Myoid bodies were distinguished, but there were no oil droplet seen in the cone visual cell. In the cross-section of photoreceptor the accessory outer segment and calycal processes arranged around the photoreceptor outer segments. There were synaptic ribbon positioned between inner somata base of the visual cell and the dendrites of second-order neurons. The SEM investigation to the toad retina found that, the processes of the EP were arranged in a "tessellated" form, this array profile was revealed by tearing the EP from the photoreceptor layer. On the broken surface of across the whole retinas there were more rod cells than cone cells. On the surface of inner and outer segment of rod cells, the interlobular furrows were seen.The retina immunohistochemic staining result with GFAP antibody displayed the features of Muller cells, which was the only kind of glial cell in the toad retina, the cells arranged in monolayer, and its major stems radially arranged along the radius of eye ball,the terminals of major stems formed the endfeet in the inner limting layer of retina.The structure development of toad tadpole retina in the postembryo stages (stage 26-39) were characterised by employing semi-section technique and SEM technique, in this developmental phases, the differentiation of stratification continued and extended from retina central part to marginal region. In the sections of retina of tadpoles at stages 26,27,28 and 35, a pore through across the edge retina were found, referred to as retina pore. Besides the conventional structure development, for example, the accumulation of melanin granules, the form of inner and outer segment of photoreceptor cell, and so on, the oil droplet with lipid pigment were seen, and the lipid marterials of these inclusion bodies varied greatly.After the transplant skin epidermis replaced the tadpole normal cornea, the transplant skin could transfrom into corena under the influence of induction factors,this process is defined as cornea induction.In the cornea induction the physiologic activity of tadpole optic nerve was inhibited by intraocular injection of tetrodotoxin(TTX),and changes of the melansome aera in the graft skin scraps were investigated.The analysis of the datum from experiment result indicated that the difference between the test group and control group was significantly (p<0.05), the physiologic activity of retina was one of the important influence factors on cornea induction.To explore the relationship between the years of age of toad and the persistence of proliferative neural cells in retina, the years of age and life histories of toad B. Raddei were studied using the skeletochronology method, the result of this study showed the longevity of this amphibian was 6 years of age. The persistence of proliferative cells in retina study was carried out by marking DNA synthesis with BrdU of the retina cells of tadpoles at stages 30,35,39,postmetamorphosis juvenile, and adult toad at 1,2,3 years of age, respectively, the result revealed that the proliferative cells elapsed with the increasing of toads years of age, and there was almost no proliferative cells found in the 2 years old individuals. The amphibians anura maybe are the transitional status animals in the persistence of proliferative neural cells in retina.