[Electron microscopy studies on the proliferation of foot-and-mouth disease virus in cell cultures. II. Changes in nucleic acid metabolism of the cell nucleus].

BHK cells were infected with FMD virus and treated with tritium-labelled thymidine and uridine for examination by autoradiography under the electron microscope. Labelling of the DNA, examined by autoradiography under the optical microscope, showed inhibition of 3H-thymidine incorporation. For demonstrating RNA labelling of nuclei, some cells were treated with actinomycin D and others were left untreated. Under the lectron microscope there was no evidence of increased 3H-uridine incorporation in the untreated cells after virus infection, but actinomycin treatment increased RNA labelling in extranucleolar parts of the nucleus, evidently RNA synthesis independent of DNA. There was evidence of some synthesis of virus-specific RNA in the nuclei. The extent of virus-specific RNA synthesis in the cytoplasm was less extensive than in the nucleus.