Aqueous solutions of some basic dyes--their use in the cytochemical detection of DNA

The paper contains results of staining DNA-aldehyde molecules with aqueous solutions of brilliant cresyl blue, thionin or neutral red, following Feulgen procedure and also reports on the use of aqueous solutions of these dyes, with primary amino group(s) in their molecules, for staining animal tissue nuclei after extraction of RNA with cold phosphoric acid. The pH of the dye solutions most suitable for optimum staining is 6.0. The time necessary for optimum staining of DNA-aldehydes and DNA-phosphate groups are 10 and 2 min respectively for tissues fixed in formalin, paraformaldehyde or Craf. Tissue fixed in Buin-fluid stain slower. The absorption curves of nuclei stained for DNA-aldehyde molecules and DNA-phosphate groups, stained with each of the three dyes are different from each other. The in vitro absorption curves of aqueous solutions of the three dyes have also been presented. Some implications of the results obtained are discussed.