Metachromatic differential fluorochroming of living and dead ascites tumor cells with acridine orange.

Acridine orange (AO) has been used to vitally stain somatic and germinal nuclei in vivo (1, 2) and to differentially fluorochrome living and dead bacteria, yeast, and onion root tip cells. The latter phenomenon was discovered by Strugger, whose book, Fluoreszenzmikroskopie und Mikrobiologie (7), details the technics required for adapting the metafluorochromatic staining as a test of cell viability. Recent papers (3, 6) have questioned the validity of Strugger's test, and the work pre