Multicolour FISH painting for the analysis of chromosomal aberrations induced by 220 kV X-rays and fission neutrons

Purpose: The quantification of radiation-induced chromosome aberrations ide ntified by multicoloured FISH painting and classified according to differen t nomenclature systems (PAINT, S&S and a conventional method). Material and methods: Blood samples were irradiated with five different dos es of 220 kV X-rays or fission neutrons respectively. Cell cycle-controlled , multicoloured FISH painting was performed with a cocktail of chromosomes 1, 4, 12 and a pancentromeric probe. Results: Ten aberration parameters or categories were selected according to the three nomenclature systems and dose-response curves were constructed f or the observed yields. Fitted coefficients of the linear-quadratic dose-re sponse function show the relative importance of the quadratic term for aber ration parameters of the low-LET radiation (X-rays) data set and of the lin ear term for those of the high-LET radiation (fission neutrons) data set. T he relative proportion of complex aberrations observed was larger for the d ensely ionizing fission neutrons than for sparsely ionizing X-rays. Conclusion: Compared with single-colour FISH painting, a multicolour approa ch provides extended information for a mechanistic and quantitative interpr etation of radiation-induced chromosome aberrations. The choice of a nomenc lature system and the selection of an appropriate aberration parameter or c ategory depend on these specific aspects. Practical application requires a rapid and reproducible description of the observed painting patterns and sh ould also throw light on the origin of aberrations.