Activated endogenous viruses of tumor induced by human adenovirus: an electron microscope study.

Virus particles were examined electron microscopically in human adenovirus 12-induced cells of $\text{C3H}\text{BifB}$ mice. Specimens examined included conventional thin-sections, freeze-fracture-etched preparations and scanning electron microscope preparations. Both C type virus particles and intracisternal A particles were quite numerous in primary and transplanted tumors. Intracisternal A particles were usually found in the endoplasmic reticulum in the center of tumor cells and sometimes in the perinuclear cistern. C type particle were massed in the intercellular spaces. The C particle budding processes protruded from many portions of the tumor cell surface. Immature particles often had a tail and the core configuration suggested an icosahedral symmetry.