Influence of UV rays on Feulgen-type staining with azure A-SO2 prepared with normal hydrochloric acid and sodium thiosulphate.

This communication presents a new method for the preparation of azure A-SO2 for use in Feulgen procedure. The salient feature of this method lies in the fact that azure A-SO2 can be decolourised with normal hydrochloric acid and sodium thiosulphate. The pH of this dye reagent is 2.3 and it is of water colour after filtration. The pH of this dye-reagent is raised to 4.0 with an aqueous solution of sodium hydroxide. Nuclear colouration with this newly developed dye-reagent on acid-hydrolysed DNA of tissue sections becomes fairly satisfactory under the usual laboratory conditions. Staining with this dye-reagent under exposure to UV ray is, however, vastly improved within 5 minutes as compared with the control. Stained sections do withstand treatment in SO2 water without exhibiting any leaching of the dye from the nuclei. Possible mode of action of UV rays in increasing the intensity of staining as well as the speed of reaction has been suggested.