Nuclear and nucleolar changes in preimplantation mouse embryos expressing numerous virus-like particles.

Preimplantation mouse embryos spontaneously arrested in development at the two-cell and three-cell stages were obtained from a pregnant Slc: ICR mouse. Numerous intracisternal A-type virus-like particles were expressed in the cytoplasm of these abnormal mouse embryos. Several nuclear and nucleolar changes observed in these embryos, probably related to the hyperactive synthesis of virus-like particles, were reported.