Dicentric chromosome frequency analysis using slit-scan flow cytometry

Slit-scan flow cytometry (SSFCM) was used to quantify the frequency of dicentric chromosomes in human lymphoblastoid cells following gamma irradiation. In this study, cultured human cells were irradiated with 0, 0.25, 0.5, 1.0, and 2.0 Gy of 0.66 MeV gamma-rays, cultured for an additional 11 h, and treated for 5 h with colcemid. Chromosomes were then isolated, stained with propidium iodide, and analyzed using SSFCM for total fluorescence and slit-scan profile. The frequency of chromosomes having DNA contents greater than once and less than twice the DNA content of the number 1 chromosome and producing trimodal profiles was determined at each dose. This frequency was used as an estimate of the relative dicentric chromosome frequency at that dose. The estimated dicentric chromosome frequency per cell, f(D), increased with dose, D, in a linear-quadratic manner according to the relation f(D) = 4.52 x 10(-5) + 5.72 x 10(-5) D + 1.19 x 10(-4) D2.