Chromosomal pattern in some mouse ascites tumours after deep freezing

Five different lines of Ehrlich's near tetraploid mouse ascites cancer with different chromosome patterns and chromosome morphology as well as one line of Landschütz diploid mouse ascites cancer were studied for any reaction to a long period of deep freezing. In none of the cancers was deep freezing found to have any effect on the mean number of chromosomes per cell or on the distribution of the cells according to chromosome number. Neither did the length of the chromosomes in the individual cells appear to undergo any change. Nor was any change observed in the frequency of “marker chromosomes” or in the frequency of cells with such chromosomes in 5 of the experiments. Only in experiment 1 had the frequency of cells with one long submetacentric chromosome appreciably increased, but such a chromosome had also been observed in some cells already before the tumour had been frozen, and it is probable that the increase in frequency of such cells had occurred during the 190 days between the last chromosome count and deep freezing. During the first passage of the tumours after deep freezing they usually showed a somewhat lower rate of growth, but during the subsequent passages the rate of growth was identical with that before freezing. No change was observed in the heterologous transplantability of the tumours.