Studies on protein and nucleic acid metabolism in virus-infected mammalian cells. 1. Encephalomyocarditis virus in Krebs II mouse-ascites-tumour cells

Publisher Website
Google Scholar
Abstract
Conditions are described for the propagation of Krebs II ascites-tumor cells and for measurement of the effects of infection by encephalomyocarditis virus on these cells in circumstances favourable for quantitiative biochemical investigation. The rate of penetration of orotic acid and of valine into Krebs cells was measured. Infection caused no alteration in the rate of penetration of orotic acid during the first 4 hr. During the later stages of the infectious cycle, orotic acid was taken up at a progressively increased rate, and cells lost their capacity to concentrate valine. During the period of rapid virus synthesis there was a marked increase in the rate of ribo-nucleic acid turnover and a decrease in the size of the intracellular nucleotide pool. Virus synthesis was accompanied by a small increase in the rate of protein turnover, but this effect was obscured by the loss of capacity to concentrate the radioactive tracer (valine) used to measure turnover rate. In all experiments the infected cells showed a small increase in the rate of protein turnover during the first 2 hours after infection and before any synthesis of new virus could be detected. This stimulation may be associated with the need for synthesis of new enzymes before virus reproduction can commence. There was no change in the total deoxyribonucleic acid, ribonucleic acid or protein in infected cells. A method of hemagglutinin assay was developed which gave results within 30 minutes. A method for the measurement of the radioactivity of nucleotides present in aqueous acid extracts of tissues is also described.