Biopolymers and cell. 1989. Volume 5. № 5. 87 - 93

S. V. Evsykov, L. M. Morozova, A. P. Solomko

ROLE OF THE NUCLEOCYTOPLASMIC RATIO IN THE REGULATION OF THE MAMMAL DEVELOPMENT. DEVELOPMENT OF ZYGOTBS WITH A DECREASED CYTOPLASM VOLUME

Summary

    Following 3 days after microsurgical removal' of '1/3 of the cytoplasm volume, more than 90 % of mouse zygotes developed in vitro into morulae and blastocysts. Development of such embryos was considerably delayed. The mean cell number of nascent blastocysts was significantly lower than in control, thus revealing that the start of cavitation somewhat depends upon the nucleocytoplasmic ratio. Comparison of preimplantation embryos developing under different conditions in vivo, in vitro from two-cell OT one-cell stages indicates that start cavitation depends on the absolute time passed from the beginning of the development. These results suggest that the «biological clock» works at the genomic level, while the nucleocytoplasmic .ratio can be considered as a feedback mechanism operating during the preimplantation development. The viability of morulae and blastocysts developed in vitro has been proved by their transplantations to pseudo-pregnant females.