Change of chromatin morphology during the cell cycle detected by means of automated image analysis

Mouse embryo fibroblasts growing asynchronously in vitro stained with Feulgen method and their nuclear chromatin was analysed by means of the image analysing computer Quantimet 720D. Cells with 2C, 3C and 4C content of DNA were considered as being in G1, middle S and G2 phase of cell cycle, respectively. It was found that the projected area of nuclei increases during the cell cycle and that the mean optical density of chromatin increases from G1 through S to G2 phase. The curves showing the areas of chromatin at different optical density thresholds are different for cells in G1, S and G2 phase. The results demonstrate cyclic changes in chromatin morphology in the interphase nuclei during the cell cycle.