Electron microscopic staining of cytoplasmic crystalloid inclusions in preimplantation mouse embryos with Ag-NOR and glutaraldehyde-bismuth methods.

Cytoplasmic crystalloid inclusions in mouse preimplantation embryos are stained with both Ag-NOR and glutaraldehyde-bismuth methods, suggesting that these inclusions may contain certain phosphorylated molecules. Since the inclusions are never found in the one-cell embryos, and their precursor-like cytoplasmic bodies appear in the two-cell embryos, they may be a product synthesized under the control of the embryonic genome.