Application of bromodeoxyuridine incorporation measurements to the determination of cell distribution within the S phase of the cell cycle

Flow cytofluorimetric measurement of incorporated bromodeoxyuridine, using a double‐stained cell population, allows the determination of the distribution of cells along the cell cycle (1). We have developed a simple computer program for the direct treatment of 64 × 64 channel histograms. This analysis appears to provide interesting data about the distribution of cells in the various phases of the cell cycle, namely the S phase. Two examples have been chosen to illustrate possible fields for the application of such a program. Comparison of two cell lines such as friend murine erythroleukemia cells (MELC) and fibroblasts FR3T3 cells has shown that this analysis can be used for cell‐cycle characterization of a given cell line. The program also allows the differential analysis of cell distribution along the cell cycle as a function of a given parameter. This possibility has been applied to study the variation of cell‐cycle parameters as a function of the time of induced differentiation of MELC and reveals changes in the distribution of the cells along the various phases of the cell cycle, namely in the S phase.