Difference of acridine orange fluorescence among living, injured and fixed cells.

Acridine orange (AO) is a fluorescent dye which has been widely used in a staining method of exfoliative cytology. This basic dye has a str ong affinity for nucleic acids not only in fixed cells but also in living ones. Ehrlich ascites tumor cells stained with AO immediately after drawing out from, mice show a green fluorescence in both nuclei and cytoplasms, and the green stained cells were successfully transplanted. Holding the cells in ascites in vitro, a red fluorescence gradually appears and when the whole cells show red flu orescence of the cytoplasms, they lose transplant ability. Treatment of fresh cells with ethanole, formalin or heat causes cytoplasms and nucleoli to emit red fluorescence and nuclei yellow fluor escence. Dried cells also show this metachromatic fluorescence (the same pattern as by von Bertal anffy's method with fixed cells).According to our investigation of portio va ginalis by fluorescence cervicoscopy under vital staining with AO, normal intact epithelium shows green fluorescence and injured epithelium (for instance due to trichomonas infection) shows red fluorescence. Fluoromicroscopic observations of fresh smears and non-fixed frozen sections obtained from the vitally stained portio vaginalis indicate that the green fluorescence is the orthochromatic green fluorescence of the epithelial cells and the red fluorescence is metachromatic red fluorescence of the cytoplasm. We believe that many kinds of cytotoxic agents can cause metachromasia with AO dye.