The recently commercialized multiplex fluorescence in situ hybridization (FISH) technique, which allows human chromosomes to be painted in 24 different colors, was used to analyze chromosome aberrations in diploid human fibroblast cells after in vitro radiation exposure. Confluent flasks of a normal primary fibroblast cell line were irradiated at high dose rates with either g rays or 200 MeV/nucleon Fe ions (LET = 440 keV/mm), incubated at 37 0C for 24 hours after exposure, and subsequently subcultured. A chemically-induced premature chromosome condensation technique was used to collect chromosome samples 32 hours after subculture. Results showed that the fraction of exchanges which were identified as complex, i.e. involving three or more chromosomes, were higher in the Fe-irradiated samples compared with the g-irradiated samples, as has been shown previously using FISH with one or two painted chromosomes. The ratios of complex/simple type exchanges were similar for samples irradiated with 0.7 Gy and 3 Gy of Fe ions, although exchanges involving five or more breaks were found only in 3 Gy irradiated samples. The fraction of incomplete exchanges was also higher in Fe- than g-irradiated samples. Data on the distribution of individual chromosome involvement in exchanges will be presented.The 2nd International Workshop on Space Radiation Researc
