Improved light sources for induction of sister chromatid differentiation.

Various light sources, including ultraviolet light, mercury, germicidal, fluorescent, and incandescent lamps, were studied for their ability to induce sister chromatid differentiation (SCD) in rat bone marrow cells. The light sources were used along with Hoechst 33258 and Giemsa stains for SCD induction. When those lamps which emit significant amounts of heat were used, 60 degrees C incubation in 2X SSC was found to be unnecessary for SCD induction. A high wattage lamp, a high ambient temperature, a short distance between the lamp and the slides, or a light with 360 nm wavelength, minimized the required exposure time to the light. The pH value of the mounting buffer was also a significant factor. Fluorescent black light and incandescent lamps were found to be ideal light sources for SCD induction.