Gallamine blue staining of DNA in mammalian tissue sections: analyses of in situ absorption spectra

Abstract

This paper reports on the use of gallamine blue (GB), a dye of the oxazine group, as a specific stain for DNA in animal tissue nuclei. The dye can be used as 1% aqueous solution in boiling distilled water at ph 1.0 to 1.5. Not only this, GB dye-reagent can also be prepared after dispersing the dye with concentrated sulphuric acid and then dissolving the friable mass in 1% cobalt chloride and then used to stain nuclei at very low pH. Although the dye does not contain any primary amino group in its molecules, it can be used as aqueous solution or as dye-reagent to stain DNA-aldehyde molecules in tissue sections which are hydrolysed in 6N HCl at 28 degrees C or at 40 degrees C for 15 and 5 min, respectively. Following staining of the DNA-aldehyde molecules, the preparations cannot be treated with SO2 water, since this treatment brings about complete leaching of the dye from the nuclei. It has, therefore, been concluded that GB staining of DNA-aldehyde molecules is due to a modified Feulgen reaction in which tertiary amino group may be involved. Moreover, GB in an aqueous solution or as a dye-reagent can be used to stain DNA-phosphate groups in tissue sections from which RNA has been extracted selectively with cold concentrated phosphoric acid. Sections from which RNA has been extracted and then hydrolysed in 6N HCl at 28 degrees C or at 40 degrees C for 15 and 5 min, respectively, can also be stained with this dye. The absorption spectra of nuclei stained following the various procedures have been presented. The paper contains a discussion on the implications of all these findings.