[Detection of endogenous intracisternal type A particles in early mouse zygotes]

Electron microscopy was used to examine early zygotes from C57BL/6 mice aged 5-7 h after mating. A great number of intracisternal type A particles (IAP) in the cavity of smooth endoplasmic reticulum and in the large vesicles of the Golgi complex were demonstrated in ultrathin sections of any of the 70 embryos under examination. IAP were detected in different areas of zygote cytoplasm and near the vitelline membrane of the zygote. Expression of virus particles in so early zygotes provides evidence in favour of the hypothesis of IAP involvement in the processes of normal differentiation.