Feulgen Reaction-Bismarck Brown; A Stain for Mast Cells in Mitosis

Dividing mast cells of the rat have been demonstrated previously by the Feulgen-methyl green staining method (Allen, A. M, Anat. Rec., 139, 13-21, 1961). In the present study, Bismarck brown was substituted for methyl green as a cytoplasmic stain because of its greater permanence in tissues previously subjected to the Feulgen reaction. Segments of mesentery of 30-day-old rats were spread on glass slides and fixed in 10% formalin for I hr. They were stained first by the Feulgen reaction, then by a solution of 0.5% Bismarck brown in 50% ethanol containing 0.2% acetic acid. The tissues were dehydrated, cleared, and mounted in synthetic resin (Permount). Nuclei and mitotic figures in mast cells were stained reddish violet; cytoplasmic granules, yellow-brown. The nuclei were clearly visible through the cytoplasm. Similar results were obtained with formalin-fixed, paraffin-embedded tissue.