The analysis of antigens, enzyme histochemical markers, and DNA has become an important part of the classification of some leukemias, lymphomas, and other neoplastic diseases. Many of the relevant antigens and most of the relevant enzyme histochemical activities are destroyed and others are less than optimally preserved in tissues embedded in hot paraffin. Most enzymatic activities and antigens are well preserved in tissues embedded at 4 degrees C in glycol methacrylate (GMA). The measurement of DNA content in neoplastic cells with the most commonly employed techniques depended on the availability of fresh suspensions of cells until the development by Hedley of methods that permit the recovery of nuclei from paraffin blocks for this purpose. In order to facilitate the analysis of antigens, enzymatic markers, and DNA from the same sample of tissue, we have developed a means of recovery of nuclei from GMA-embedded tissues. Twenty-microns-thick sections of GMA- embedded tonsil were either pretreated with an organic solvent (absolute ethanol or 2-ethoxyethanol) followed by rehydration in phosphate buffered saline (PBS) or directly rehydrated in PBS. The suspensions were formed mechanically by gentle sonication. The type of fixative and length of PBS rehydration were varied. Tissue fixed in 100% acetone, embedded in GMA, and rehydrated directly in PBS for six days gave the highest average yield of nuclei, 3.7 x 10(7) nuclei per gram tissue. In order to assess DNA binding of fluorescent dyes, 2- microns-thick GMA sections were stained with chromomycin, Hoechst 33342 (Sigma Chemical, St Louis, MO), and propidium iodide. Hoechst 33342 bound specifically to the nuclei with low background staining.

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