Studies on Mouse Embryo Cultures Infected with Polyoma Virus

Citation

Weisberg, Robert Avrum (1963) Studies on Mouse Embryo Cultures Infected with Polyoma Virus. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/D4P8-0E51. https://resolver.caltech.edu/CaltechTHESIS:10082012-162250806

Abstract

After exposure of mouse embryo cultures to high concentrations of Py, a variable fraction of the cell population is converted to virus producers, but a fraction also survives and proliferates. The surviving fraction can be 20% of the population at input virus:cell ratios of 500 pfu/cell. Resistance to the cytocidal action of the virus in mouse embryo cultures is due neither to interferon nor to genetically resistant cells; it appears to be due to a transient physiological state of the cells.

No transformed cells have been found among the cells surviving a brief exposure to high concentrations of virus. Cultures derived from these cells by growth in antiviral medium resemble uninfected cultures in cell morphology, growth pattern, and sensitivity to reinfection. Transformed cells arise only in cultures which are exposed to Py over a period of two to five weeks. It has been shown that clonal cultures respond in the same way to Py infection as do un- cloned mouse embryo cultures; thus, transformation does not result from the infection of rare "transformable variants" preexisting in the cell population.

Changes similar to the transformation which takes place in infected mouse embryo cultures also occur, and rapidly, in uninfected cultures. The occurrence of these changes complicates the analysis of Py induced transformation. It has been shown that "spontaneous" and virus induced transformation are two different phenomena, since transplantable cells arising in infected cultures differ antigenically from those arising in uninfected cultures. The relationship between alterations of cell lines observable in vitro and the ability of these lines produce tumors upon implantation have been studied; definite correlations have been demonstrated between these properties. These facts have been discussed in the light of various theories of Py induced transformations.

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