Studies on mouse embryo cultures infected with polyoma virus
<p>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...
| Summary: | <p>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.</p>
<p>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.</p>
<p>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.</p> |
|---|