THE EFFECTS OF MESENCHYMAL CELLS ON PIGMENT EPITHELIUM OF FROG EMBRYO EYE BEFORE AND AFTER ITS DIFFERENTIATION / 解剖学报

The mesenchymal cells were carefully scraped off from the optic vesicles or eye cups at 15 to 24 stages in Rana limnocharis by a hair loop (those specimens from 21 to 24 stages were treated with trypsin in order to separate the mesenchymal cells easier) and then the optic vesicles or eye cups were transplanted into the coelom of tadpoles for 1 to 2 weeks. The transplantation of the eye cups Without scraping mesenchymal cells off at 21 to 24 stages were used as control. The results are as follows: 1.The pigment epithelium of eye, which was transplanted at 15 to 20 stages, (the pigment epithelium have not differentiated at those stages) can not fully develop or only a tiny piece of pigment epithelium layer occurs. 2.The pigment epithelium of eye, which was transplanted at 21 to 24 stages, (the pigment epithelium have differentiated at those stages) can develop, but separates itself from the normal position and hangs outside the eye or curls inside the cavity of eye in a vesicular form. 3.In the intact mesenchymal cells, the pigment epithelium of eye, which was transplanted at 21 to 24 stages, can develop well and remain in normal position. These results suggest that the mesenchymal cells might have an important effect on the development and morphology of eye pigment epithelium before and after its differentiation. Before differentiation of pigment epithelium, the existence of mesenchymal cells is a necessary condition for its normal differentiation; after its differentiation, the mesenchymal cells might play a mechanical role to keep the pigment epithelium layer in normal position.

EXPERIMENTAL STUDIES ON THE FORMATION OF SECONDARY OPTIC CUP FROM BRAIN WALL OF FROG EMBRYO UNDER THE INDUCTION OF THE PRESUMPTIVE LENS ECTODERM / 解剖学报

Three types of microscopic operations were used in this study: 1. excision of the optic vesicle alone; 2. after excising the optic vesicle, a piece of forebrain tissue taken from another donor was inserted in between presumptive lens ectoderm and forebrain wall; 3. cut down the optic vesicle and portion of forebrain tissue and replaced them back in situ by turning over 180?. The operations were carried out on Rana nigromaculata at 15 and 16 stages, in order to bring the presumptive lens ectoderm to come into contact directly with the forebrain tissue for the purpose to analyse the possibility of eye cup formation from the brain wall. The results indicate that the forebrain wall which came into contact with the presumptive lens ectoderm could be induced and differentiated into a secondary eye cup or retina. A total of 81 cases of secondary eye cups among 282 operations (28.8%) were observed. The mechanism for the induction and its significance were discussed.

SOME EXPERIMENT ON THE DEPENDENCE OF THE DEVELOPMENT OF LENSES AND THE ABILITY OF INDUCTION OF THE EYE CUPS / 解剖学报

This study was an attempt to excise or transplant optic vesicles, and excise or transplant presumptive lens ectoderms, by means of microscopic manipulations. Its purpose was to explore the dependence of the development of lens on the eye cup and the ability of induction of the eye cup to develop lens in liana nigromaculata, R. limnocharis, and Kaloula barealis, which are frequently used in experimental embryology in China. The results show that their lenses cannot develop without eye vesicles. This indicates that they belong to the pattern of dependent differentiation. The results also indicate that the situation of forming lenses from ectoderms under induction of eye cup is different in three kinds of frogs: the lenses can be frequently formed from ectoderm of both Lead and abdomen in Rana nigromaculata; but the frequency of lens formation from ectoderm of abdomen is rather low in R. limrocharis; and only the ectoderm of head is positive in Kaloula barealis. The interrelation in size between the eye cup and the lens was recorded. The formation of a secondary eye cup from brain wall under condition of the contact with the presumptive lens ectoderm was reported too. In addition, it was found that the temperature might have influence on eye differentiation.

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

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.