The selective fluorescence staining of two fungi, Candida albicans and Blastomyces
dermatitides, with
Uvitex 2B and
Calcofluor White M2R was studied in deparaffinized and frozen sections of mouse kidney and lung. Both
fluorochromes emitted maximally at about 430 nm, independent of the mounting media (Kaiser's
gelatin or
Entellan). In addition to fungi, both
fluorochromes also stained elastic fibres. The fluorescence intensity remained unchanged after storage of sections for more than 6 months in conventional slide boxes. The two
fluorochromes showed the following differences: Calcofluor faded 1.25 times faster than Uvitex when illuminated with ultraviolet light. Calcofluor showed a greater affinity for tissues in general, and red cells and renal tubular casts in particular. Counterstaining of deparaffinized sections with Hemalum and
Eosin reduced the fungi fluorescence and suppressed the general background fluorescence. However, it led to an intensification of
Eosin staining and the fluorescence of red cells in Calcofluor-stained sections but not in Uvitex-stained ones. Similarly, the background fluorescence in frozen sections was reduced by
Evans Blue, although elastic fibres still fluoresced after staining with Calcofluor. The degree of staining selectivity, and thus the contrast produced within a histological specimen, was greater with
Uvitex 2B than with
Calcofluor White M2R.