BIVARIATE FLOW KARYOTYPING WITH AIR-COOLED LASERS

An experimental flow cytometer was constructed using a quartz flow cel l optically coupled to a 1.22 NA lens. A pair of crossed cylindrical q uartz lenses allowed multilaser excitation. Two helium-cadmium (HeCd) lasers, emitting 16 mW at 442 nm and 35 mW at 325 nm, were used to exc ite chromomycin A3 and Hoechst 33258 fluorescence, respectively. Bivar iate flow karyotypes from normal human male chromosomes and from the D audi cell line were obtained and were compared to those from a standar d instrument using dual water-cooled lasers. The new experimental inst rument exhibited comparable resolution to that from the standard instr ument. In further experiments with Daudi chromosomes, the 35 mW HeCd l aser was replaced with a 10 mW HeCd laser, and the system still gave g ood, though slightly decreased, resolution. (C) 1994 Wiley-Liss, Inc.