Synthesis of Endogenous Type-A Virus Particles in Parthenogenetically Stimulated Mouse Eggs2

Abstract

Parthenogenetic stimulation of normal mouse eggs induced production of type-A virus particles. Ultrastructural observations showed these virus particles in 3- to 4-celled embryos and in subsequent stages of development of these embryos in culture. Dense, granular structures in nucleoplasm and within the duplicated inner leaflet of nuclear membrane could eventually represent precursors of these type-A virus particles. Budding type-A virus particles were found in the large protrusions into the cytoplasm of the outer leaflet of nuclear membrane. Mature virus particles were in the cisternae of endoplasmic reticulum. Adjacent to the budding virus particles at the nuclear membrane were aggregates resembling the granular part of nucleoli. The production of type-A virus particles may depend on cellular RNA synthesis.