眼前房내에 이식한 생쥐배의 초기발생에 관한 연구

Studies on the Early Development of the Mouse Embryo Transplanted in the Anterior Chamber of the Eye

배아의 발생에 대한 연구는 in vivo 나 in vitro의 방법을 통해 근래 비?적 활발하게 진행되고 있다. 이들의 연구결과에 따르자면, 성분이나 함량 혹은 물리학적 성질이 혈청따위의 체액과는 다른 전방수가 들어차 있는 안전방의 환경은 배아의 발생에 극히 부적당한 곳이라 할 수 있다. 그럼에도 불구하고 본실험의 결과를 보면 초기배아의 발생은 극히 정상적으로 진행되고 있다. 이런 점에 비추어 우리는 두 가지 가능성을 추론할 수 있다. 첫째는, 배아의 어느 한정된 범위에서는 그의 환경에 쉽게 적응할 수 있는 능력을 가지고 있을 것이라는 생각이다. 배아세포가 미분화의 상태에 있다는 점과 대사의 정도가 분화된 다른 세포들에 비해 비교적 낮다는 점을 고려할 때 이들 배아는 안전방내의 환경과 같은 특수한 곳에서도 능히 생존할 수가 있는 것이다. 둘째는, 배아를 받아들인 후 전방수의 특성이 달라질 것이라는 점이다. 토끼에서는 일단 안전방내의 전방수가 유출되고 나면 혈청과 비슷한 체액이 약8시간 동안 안전방내에 형성되고 그뒤 차차로 본래의 전방수로 대치된다. 쥐에서도 이러한 체액이 안전방내에 형성된다면 배아를 받아들인 안전방내의 전방수의 성질이 혈청과 비슷해지므로 배아의 발생이 가능해질 수가 있다. 단지 그러한 체액이 전방수의 유출 후 120시간까지 그대로 남아있을 것인가에 대한 의문은 그대로 남아있지만 위의 두가지 가능성에 대하여는 배아의 생태나 행동과 관련시켜 앞으로 더 연구해야 할 것이다.

Two-Cell mouse embryos were incubated in the anterior chamber of the rat eye, which has been known as the best place among other animals' for the mouse ovum maturation, in order to observe the capability of their early development. Within 120 hours after incubation, 71.0% of two-cell embryos have developed to the blastocysts in the male rat eye, while only 38.5% in the eye of the same mouse as donated two-cell embryos. Thus, the rat eye chamber provides more favourable environment to the embryos than the mouse itself. The results are consistent with those of the previous studies comparing the maturation of the mouse follicular oocytes in the mouse and the rat eye chamber. Although the aqueous humor which is filled in the anterior chamber of the eye is characterized by its specific properties, being of higher osmolarity, higher concentrations of ascorbic acid, pyruvate and lactate, but lower of proteins and lower temperature than those in blood or lymph serum, The embryos are able to under-take their cleavage as normal as in vivo or in vitro. Concerning with a number of studies in vitro on the development of the mouse embryos which are requiring a very limited condition, the fact that they are able to manage their further development under very different enviroment from our knowledges would provide us a moment to understand their behavior during the early development. The difference of the proportion of the developed blastocysts between in the mouse eye chamber and in the rat can possibly be resulted from the species specific difference in the physicochemical properties between their eye chambers. This assumption is based upon the findings by many investigators who chmpared the nature of the eye chamber of various animals. As a consequence, the rat eye chamber might consist of better properties for the embryonal growth than the mouse eye chamber. The mouse embryos cleaved with a delayed period. In normal development they complete almost the cleavage within 94 hours after fertilization. However, in the present studies, 81.1% of two-cell embryos developed to the blastocysts and the morula in 120 hours in the eye chamber, assumed to be about 154 hours after fertilization. Such delay in development would be caused mainly by the low temperature of the eye chamber. At present we can make two assumptions to explain the capability of the emtryonal development in the eye chambers. One is that the embryos would possess an ability to adapt themselves to the environment which provides unfavourable conditions. The other is that the embryos might remain for a certain duration in the eye chamber, which is filled with a new body fluid produced immediately after the loss of the aqueous humor and the fluid of which becomes similar to blood serum in component. The first assumption is highly reliable since the embryonal cells are mostly at the undifferentiated state and so they probably engage a simple metabolism during their early period. The second assumption is induced by the fact that the rabbit eye chamber produces a plasmoid humor which has mostly similar components to blood serum after loss of aqueous humor through cornea by puncturing. However, the plasmoid humor is substituted by the initial aqueous humor in eight hours. Even though this finding, production of the new fluid, could be applied to the rat eye, it is hardly reliabel that the plasmoid humor remains for such a long period as 120 hours. Consequently, the development of the embryos is more likely due to their adaptability to the new environment during their early developmental stages.