Cell-Cycle Time of Endosteal Cells in Estrogen-Treated Male Japanese Quails

Abstract

The cell cycle time of endosteal cells in the femur of male Japanese quails given estrogen was determined by the radioautographic technique using tritiated thymidine as a specific DNA precursor. In order to determine the proportion of cells engaged in DNA synthesis at the time of ³H-thymidine injection, the percentage of endosteal cells containing labeled nuclei was recorded at 1 hour after injection. It was approximately 21.58per cent. On the other hand, the percentage of labeled mitoses on the endosteum was recorded at different times after ³H-thymidine. The number of labeled mitoses rised to 50per cent at 4 hours after labeling, reached its maximum at 6 hours and decreased to 50per cent at about 10 hours. According to the method of YOUNG, the cell cycle time of endosteal cells was determined from the above results. The total cell cycle time was found to be 28 hours in which phases S, G₁, and G₂+M were 6 hours, 16 hours and 6 hours, respectively.