MICROELECTROPHORESIS OF DNA FROM INDIVIDUAL INTACT AND GAMMA-IRRADIATED THYMOCYTES

The in vitro gamma-irradiated mouse thymocytes were embedded in low melting agarose at 37-degrees-C. After getting at 4-degrees-C, the cells were lysed in neutral detergent solution containing proteinase K and ethidium bromide. Microscopic vizualization of single lysed and stained cells showed the presence of the central <<core>> (nuclear matrix) surrounded with <<halo>> (relaxed nuclear DNA). During electrophoresis (2-5 V/sm, 5 min) this <<halo>> migrated towards the anode forming a <<tail>>. The use of microdensito-metric system provided measuring the size of the tail (L) and quantity of migrated DNA (S) for individual cells as well as obtaining the distribution of these parameters among the cells. The latter may be characteristic of heterogeneity of the cell population. It was shown that L and S increased linearly with the dose irradiation at least between 0.2 and and 5.0 Gy. In irradiated thymocyte (3 Gy) the DNA repair occurred within 10-20 min, but residual DNA damage could be observed even after 60 min of incubation. These damages may initiate the degradation of DNA in irradiated thymocytes that was observed after the repair of DNA.