2-hydroxystilbamidine isethionate: a new fluorochrome for use in general pathology. I. The selective staining of DNA, mucosubstances and elastic fibres.

2 mg of 2-Hydroxystilbamidine isethionate when dissolved in 50 ml 0.1 M citric acid produced nuclear fluorescence in paraffin sections. Pre-hydrolysis in 5N HCl at room temperature increased selectivity of nuclear fluorescence. The addition of 100-200 mg sodium metabisulphite to the fluorochrome solution and preoxidation in periodic acid produced selective fluorescence of mucosubstances. Pre-oxidation with potassium permanganate induced selective fluorescence of elastic fibres. Yellow nuclear fluorescence contrasted clearly with blue/white fluorescence of mucosubstances and elastic fibres when excited with UV light. Unwanted nuclear fluorescence was quenched with 5% iron alum solution. Mast cells selectively fluoresced in acid alcoholic solutions of the fluorochrome. The procedures described were simple and rapid and produced permanent fluorescent preparations. The metachromatic fluorescence of nuclei in contrast to that of mucosubstances and elastic fibres eliminated the need for counterstaining.