[Rate of spontaneous chromosome aberration occurrence in cultured Chinese hamster cells].

The spontaneous chromosome mutation rate was studied in cultured aneuploid Chinese hamster cells (clone 237(1)) using the method of slowing down the rate of cell division in a limiting medium containing 0.1% of serum. It was shown that during one cell generation (which lasted 14 days in limiting medium) the accumulation of chromosome aberrations with time took place.

[Development of spontaneous mutations in somatic mamalian cells and DNA replication. II. Expression of gene mutations in cultured cells].

The dependence of spontaneous rate and phenotypic expression of 6-mercaptopurine resistance mutations of DNA replication synthesis was studied in cultured Chinese hamster cells. Spontaneous mutations arising with a constant rate per cell per time unit independently on DNA replication rate were shown to be expressed only in the course of subsequent cell divisions. The frequency of N-nitrosomethylurea induced mutations in cells with reduced and normal DNA replication rate is approximately the same.

[DNA replication and the development of spontaneous mutations in the somatic cells of mammals. I. The relationship between the outcome of gene mutations and the duration of cell life].

The reduction of serum concentration in culture medium to 0,1% was proposed as a method of slowing division and DNA replication in Chinese hamster cells in vitro. Under these conditions the rate of DNA replication was reduced by more than one order of magnitude, while cell viability remained high enough (about 10%) for a long period up to 30 days. The spontaneous mutation rate to 6-mercaptopurine resistance, as calculated per day in cells with reduced DNA replication rate, was comparable to that in normally dividing cells [(1,2 +/- 0,3) X 10(-5) and (3,1 +/- 0,5) X 10(-5) per cell per day respectively].

[A further study of the mutation process in Chinese hamster cells in vitro].

Spontaneous mutagenesis and mutagenesis induced by chemical mutagens in culture Chinese hamster cells were investigated. Appearance of mutations controlling the resistance to 6-mercaptopurine (6M) and reverse mutations to sensitivity was studied. The rate of spontaneous mutations of 6M resistance in cells studied was found to be sufficiently stable: it was independent on the repeated freezing of these cells and the duration of their cultivation.