Slit-scan flow cytometry: analysis of Chinese hamster M3-1 chromosomes

We have applied slit-scan flow cytometry to the measurement of the distribution of fluorescence along isolated Chinese hamster M3-1 chromosomes stained with ethidium bromide. One hundred chromosome profiles were measured for each of the chromosome numbers 1, 2, 4 + t (X; 5) and 5. DNA based centromeric indices calculated for these chromosomes are 0.54 ± 0.02, 0.52 ± 0.02, 0.57 ± 0.03 and 0.57 ± 0.03, respectively. These values are in good agreement with DNA based centomeric indices calculated for the same chromosomes using chromosome profiles extracted from scanning cytophotometric images of Chinese hamster M3-1 metaphase spreads stained with gallocyanin chrome alum. The pulse shapes from the Chinese hamster chromosomes in flow were found to be approximately constant in height and to fall within a pulse width range encompassing the largest and smallest chromosomes. Pulse height and width discrimination substantially reduced the contribution of non chromosomal debris to the total fluorescence distribution (flow karyotype).