Nile blue inducible fluorescence of tumour cells.

An oxazine dye, Nile Blue sulfate, induces a fluorescent reaction in cytoplasmic granules (NBIFG) of living or fixed tumour cells in the same manner as reported before for Thiazine dyes. The NBIFG correspond to phase contrast positive granules when cells are viewed by phase contrast microscopy. Fluorescence disappears from NBIFG in a matter of 2—4 days and the bodies turn deep blue. These granules have a succinate dehydrogenase (SDG) activity and are negative for acid phosphatase, peroxidasic activity and porphyrin. The cytological findings support the assumption that Nile Blue sulfate forms a salt linkage with unsaturated fatty acids of NBIFG which also show an oxi-reductive activity. The molecular nature of the fluorophore (s) is (are) unknown.