THE STUDY ON INDUCTION FROM PRESUMPTIVE PIGMENT EPITHELIUM INTO RETINA / 解剖学报

ABSTRACT

It is well-known that the presumptive significance of every part of the optic vesicle has already been decided. The centrifugal part (i. e. the far end wall) of the optic vesicle is called presumptive retina and its centripetal part, (i. e. the near end wall) the presumptive pigment epithelium. In the present study, we caused the latter to come into contact with different tissues and organs by transplanting and excising for the purpose of observing whether it would be able to alter normal course and form retina. The experimental material was the embryos of frogs (Rana nigromaculara, R. japonica and Bufo bufo gargarizans). The experiment was divided into two groups (1) brought presumptive pigment epithelium into contact with presumptive lens ectoderm, head ectoderm and abdomen ectoderm; (2) brought it into contact with other organs and tissues, including otic vesicle, pericardial membrane, nephridial tubule, pharyngeal wall, muscle, coelomic membrane, hepar, and cartilage.The results indicate that the contact with three kinds of ectoderm can alter normal course of development of presumptive pigment epithelium, transform it into retina and further produce secondary eye cup. As regard to its frequency of transformation into retina, the highest is in the case contacted with presumptive lens ectoderm; in the case contacted with head ectoderm come next and the lowest in the case contacted with abdomen ectoderm. The results also show that the above-mentioned organs and tissues can cause similar reactions, but the frequency of transformation is lower than that caused by abdomen ectoderm, and there are very few secondary eye cups which appear only under the conditions of contacting with otic vesicle, coelomic membrane and cartilage. This suggests that the action of the contact which brings presumptive pigment epithelium to transform into secondary retina might be an induction and material of induction widely distributed in the embryonic body.Two other reactions, moreover, were also found, i. e. the presumptive pigment epithelium was transformed into brain tissue and merged after the former came into contact with the latter, and the transplanted eye and the host eye fused in part or fully merged into a large eye when they came into contact.Above-mentioned phenomena further prove that the optic vesicle has a certain plasticity.