[Detection of the biological activity of SV40 virus DNA after injection into the nuclei of simian cells].

EV40 DNA closed superhelical form was introduced into cell nuclei by means of direct microinjection and expression of the viral genome followed. The expression of viral T-antigen was observed 40 hours after the injection, and SV40-specific effect developed on the fifth day. Using the method discussed, the infection dose of SV40 DNA in a permissive cell culture system was shown to be approximately one molecule per cell nucleus.