The specific amino acid, vitamin, and salt requirements of the HeLa cell have been described in previous papers (1-5). On the omission from themediurn of a single essential amino acid, salt or vitamin, or of glucose, the cells stopped multiplying and eventually died. Depending on the specific growth factor, from 1 to 14 days were required for the cytopathogenic effects of the specific deficiency to become fully evident. In contrast, the maximum evolution of poliomyelitis virus from HeLa cultures after a suitably large viral inoculum was usually observed in 24 to 48 hours. It thus became possible to determine which of the nutrilites known to be necessary for the survival and growth of the cell were essential also for the propagation of poliomyelitis virus.As will be here shown, the omission from the medium of vitamins, 12 of the 13 essential amino acids, and of protein had only a minor effect on the amount of the virus formed, even when the cells had been deprived of these factors for 12 hours prior to inoculation. Under the conditions of the present experiments, only 2 components of the medium other than salts were demonstrably essential for the optimal propagation of poliomyelitis virus: glucose and glutamine.
Three mutants of simian virus 40 were isolated on the basis of the type of plaques produced in primary cultures of African green monkey kidney cells and designated as L (large), S (small), and M (minute) strains. Significant differences in oncogenicity for hamsters were observed, with the 50% oncogenic dose being 104.5 for the L, 105.2 for the S, and 105for the M strains. All three strains were capable of transforming human diploid cells (WI38 strain). At temperatures up to 41 C, the S and M mutants were capable of multiplying to titers almost equivalent to those obtained at 37 C. In contrast, infectious virus was not produced when cells were infected with the L mutant and were incubated at temperatures above 39 C, although complement-fixing viral and tumor antigens were formed. The temperature-sensitive phase of replication of the L strain was shown to be a late stage in viral maturation or assembly.
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