Intranuclear differences in the response of Purkinje cell DNA of the rat cerebellum to bleomycin. A microphotometric and autoradiographic study

The protein effect on determination of DNA with Hoechst 33258

The present study was designed to afford a critical review of the effect of proteins on the Hoechst 33258 method for determination of DNA of crude homogenates. A considerable effect of proteins on the fluorescence was observed when the concentration exceeded 100 micrograms BSA equivalent protein. Below that value, practically no effect of proteins was noted. We used proteinase K to remove the proteins, but dilution of homogenates could be used as well. Moreover, we found that the concentration of the fluorochrome should be between 1 microgram and 2 micrograms when microgram levels DNA are to be determined.

Simultaneous quantification of DNA and RNA in tissue sections. A comparative analysis of the methyl green-pyronin technique with the gallocyanin chromalum and Feulgen procedures using image cytometry

For simultaneous cytophotometric measurement of DNA and RNA, the standardized Methyl Green-Pyronin Y technique is an obvious choice. It is, however, first necessary to correlate the uptake of Pyronin Y to the staining intensity of RNA. The material consisted of paraffin sections of formalin- or Carnoy-fixed rat liver. The sections were pretreated with water, buffer, deoxyribonuclease, ribonuclease, or both enzymes in sequence, and stained with the standardized Methyl Green-Pyronin Y procedure, Gallocyanin chromalum, or the Feulgen reaction. Sections stained directly without pretreatment served as controls. Staining intensities were measured with an image analyser for cell nuclei, nucleoli and cytoplasm. After deoxyribonuclease treatment, nuclear staining intensity with Methyl Green, Gallocyanin chromalum, and Schiff's reagent dropped nearly to zero. The same was seen for both nucleoli and cytoplasm with Pyronin Y and Gallocyanin chromalum after ribonuclease treatment. Staining intensity of Pyronin Y correlated directly with that of Gallocyanin chromalum for nucleoli and cytoplasm. After ribonuclease treatment, a direct correlation was found between the nuclear staining intensity of Methyl Green and nuclear absorption of Gallocyanin chromalum. We conclude that the standardized Methyl Green-Pyronin Y stain is reliable for the simultaneous quantitative assessment of both RNA and DNA. The simplicity of this technique makes it a valuable tool even for daily routine.