Simultaneous quantitation of DNA and nucleolar organizer regions by image cytometry

This paper describes a DNA/nucleolar organizer region-associated protein (NOR) double staining technic and quantitation method. On smeared cell slides, the acidic proteins associated with nucleolar organizer regions were revealed by the silver colloid technic, and DNA was stained with the fluorescent dye Hoechst 33342. The simultaneous quantitation of silver stained proteins (AgNORs) and DNA was performed with image cytometry. Two applications of this method are presented: a study of AgNOR expression during the MCF-7 cell line cycle and the simultaneous quantitation of DNA and AgNORs in non-Hodgkin's lymphoma node imprints. This method offers the advantage of evaluating, on the same cell at the same time, the DNA content (ploidy) and AgNOR expression, which constitute a good approximation of the cell's proliferation state. Since ploidy and proliferation index are being used more and more in tumor assessment, it is useful to obtain them in minimum time and with a minimum of biologic material.