2.11. DNA repair capacity
The challenge assay used in this study was carried out according to methods that have been previously described (Auet al., 1991; Au, 1993). At 24 h after blood culture, the cells were irradiated with 100 cGy using a 137Cs-source at a dose rate of 5 Gy/min. Fifty hours after culture initiation, cells were blocked with Colcemid (final concentration of 0.1 g/ml) for 1.5 h and harvested using the standard procedure. Cytological preparations were made, coded and stained with a 10% Giemsa solution for 15 min. Fifty metaphase cells were analyzed from each of the duplicated slides under the microscope. The presence of dicentric chromosomes and chromosome deletions per metaphase cell were determined.