Analysis of micronuclei induced under hyperthermic conditions in human lymphocyte culture by fluorescence in situ hybridization (FISH) and spectral karyotyping (SKY) methods

The spectral karyotyping (SKY) method is a novel molecular cytogenetic tech nique which simultaneously discerns entire chromosomes. In order to elucida te the origins of micronuclei induced under hyperthermic conditions in huma n lymphocyte culture, peripheral blood cells were cultured at 40 degrees C or 42 degrees C for 3-24h, using the cytokinesis-block method with cytochal asin B. The induced micronuclei were identified by the fluorescence in situ hybridization (FISH) and SKY methods. At 42 degrees C for more than 6 h, t he frequency of occurrence of micronuclei in binucleated cells rose with in creasing incubation time. By the FISH method, 83.3% of micronuclei induced in 24 h culture at 42 degrees C were shown to be positive for the human cen tromeric probes. By the SKY method, each micronucleus induced under the hyp erthermic conditions was identified unequivocally and shown to contain a sp ecific chromosome. These results suggest that the micronuclei induced under the hyperthermic conditions in human lymphocyte culture contain chromosome s which do not migrate to the poles at the anaphase of the cell cycle becau se of the breakdown of the spindle apparatus.