[Calculation of the duration of mitosis for a population with an exponential growth of the cell number].

A formula was received for the mean mitotic duration of a cell population being at the phase of exponential growth of the cell number with the cell loss: tM = nM.tD.(1-phi)/ln 2, where nM is the mitotic index, tD is the doubling time of the cell number, and phi is the Steel cell loss factor. In the case when after irradiation of such a population a 100% radiation G2-block arises, the method of calculation of the tM according to the curve of the relative mitotic index decrease was shown to be independent on the value of parameter phi and to coincide with the same method to be used in the case when the cell population is at the steady state before irradiation. As the result of analysis of literary experimental data the following values were received: tM = 20 min and tM = 37-42 min for two cell subpopulations of the Ehrlich ascite tumour, resp., tM = 39 min for epithelial cells of the mouse cornea, and tM = 29 min for enterocytes of the mouse jejunum. It has been also shown that the values of the dose of cell irradiation and of the mean duration tG2" of the subphase G2" localized at the end of phase G2 and preceded by the G2-block satisfy the next formula: Ig D = -a . Ig tG2" + b.