Abstract
Distributional changes in lysosomes in hamster eggs and embryos during the folliculogenesis and early development were observed using the acridine orange (AO) staining method. AO-stained lysosomes were densely observed all over the cytoplasm of eggs in secondary follicles and of eggs in antral follicles until 13 hrs before ovulation, but were sparsely observed in the cytoplasm of eggs in primordial follicles. The lyso-somes were distributed throughout the cytoplasm in about a half of eggs in antral follicles at 12 and 10 hrs before ovulation, while they gathered around nuclei in the remaining half of the eggs. The lysosomes were distributed all over the cytoplasmic region of all eggs from 8 to 3 hrs before ovulation and of unfertilized eggs 2 hrs after ovulation. Such a distributional pattern remained unchanged until uncompacted 8-cell embryos. In compacted 8-cell embryos and blastocysts, the lysosomes were densely observed all over the cytoplasm in round blastomeres or inner-cell-mass cells, whereas they were sparsely observed in flattened blastomeres or trophoblast cells, mainly around nuclei. From the results on 8-cell embryos and blastocysts, it was suggested that there is the close relation between distributional changes of lysosomes and differentiation of blastomeres.
