[Selection in vivo in cell populations of rat RA-23 rhabdomyosarcoma at the trait "frequency of cells with bridges"].

Selection in vivo of cell clones of rat transplantable organospecific rhabdomyosarcoma RA-23 for increased and decreased frequencies of cells with chromosomal bridges (FCB) was performed. The initial average FCB in clones was 0.8% at a range of variation of from 0 to 3.0%. Selection for an increase, as well as for a decrease, in the FCB in RA-23 clones was effective. After one step of selection for an increase in the FCB, the average FCB increased to 3.0%. Thereafter, selection for an increase in the FCB was impracticable due to loss of transplantability in cell populations in which the FCB exceeded 5.0%. Over five steps of selection for a decrease in the FCB, the average FCB significantly decreased to 0.3% (P < 0.001). The heritability coefficient h2 of the trait FCB upon selection ranged from 0.25 to 0.30. The high and low FCBs attained by selection correlated with the index "frequency of cells with micronuclei." The population of RA-23 cells after selection for a decrease in the FCB differed from the population of cells of the original RA-23 strain by significantly lower karyotypic heterogeneity. The values of h2 obtained upon selection for the FCB and the effectiveness of selection for an increase, as well as for a decrease, in the FCB show that, with selection at the trait "frequency of cells with bridges," which characterizes the stability of the karyotype, existing cell strains can be subjected to karyotypic stabilization or destabilization.