Nuclear alterations induced in chick embryo fibroblasts by frog virus 3 (FV3) infection at permissive and non-permissive temperatures

Abstract

In chick embryo fibroblasts, FV3 infection induced early alterations of the shape of the nucleus and clumping of chromatin; later in infection, the nucleoli displayed a segregation between their fibrillar and granular components and a dilatation of their fibrillar centres; some dense spherical inclusions, microtubules and exceptionally microfilaments appeared in the nucleoplasm. Chromatin condensation, nucleolar segregation and dilatation of fibrillar centres could be explained by the inhibition of host cell DNA and RNA synthesis by FV3 infection. Such a correlation is more difficult to establish concerning the presence of dense spherules and microtubules in the nucleus. These nuclear alterations were observed both in permissive infections at 29°C and in non-permissive infections at 37°C, where FV3 exerts mainly a cytotoxic effect. Thus these nuclear impairments seem to be a consequence of FV3 toxicity and not of viral multiplication.