The vacuolating virus of monkeys. II. Virus morphology and intranuclear distribution with some histochemical observations.

Cells infected with the vacuolating virus, SV(40), respond by swelling to several times their normal volume. Within enlarged nuclei, virus-containing inclusions appear which are acidophilic and Feulgen-positive. The formation of nuclear inclusions is followed by the appearance of cytoplasmic vacuoles and then shrinkage of the cell. Inclusions were found to exhibit unique double staining when a light-green counterstain was used in the Feulgen reaction. The virus is of low electron density, round, and 300 A in diameter. It occurs in large numbers, singly and in short chains, and it appears to multiply at the expense of chromatin.