The Journal of Cell Biology, Vol 67, 518-522, Copyright © 1975 by The Rockefeller University Press
Effect of cell population density on G2 arrest in Tetrahymena
IL Cameron and NC Bols
The ciliated protozoan, Tetrahymena pyriformis strain GL-C, has been used
to study the effect of cell population density during starvation on the
synchrony obtained after refeeding and on the number of cells arrested in
G2 phase of the cell cycle. At high cell densities two peaks of division
indices were observed after refeeding while only one was observed at low
cell densities. Cell division began earlier in cultures starved at high
cell densities. Most importantly, the proportion of cells in G2 was
considerably higher in populations starved at high cell densities. When
tritiated thymidine was present during the refeeding period,
radioautographs of cell samples at different times showed that the first
cells to exhibit division furrows contained unlabeled nuclei. The first
peak in the division index after refeeding was observed only at higher cell
densities and is attributed to the cells arrested in G2. These results
suggest that Tetrahymena is an excellent organism to study the concept of
resting stages in the cell cycle and their control.
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