Cell cycle characteristics of synchronized and asynchronous populations of human cells and effect of cooling of selected mitotic cells.

The method of synchronizing cells by means of mitotic selection has been adapted to the human line NHIK 3025. Increase in cell number as a function of time in asynchronous and synchronous populations was studied as well as mitotic index as a function of time after selection of synchronized populations. Phase durations of the cell cycle of synchronous populations were determined by 3H-thymidine incorporation and scintillation counting. The relative phase durations of exponentially growing asynchronous populations were determined by mathematical analysis of DNA-histograms recorded by flow cytofluorimetry. Both the generation time and the various phase durations of the cell cycle were found to be the same in asynchronous and synchronous populations. It was found that NHIK 3025 cells are damaged by cooling to 4 and 0 degrees C so that cooling of selected cells in order to increase the yield would reduce the quality of the synchronized populations.