532—Re-evaluation of Feulgen stain for image cytometry

Automated cytometry has been proposed by us as an extremely sensitive probe of the electrochemical reactivation of quiescent cells, provided that quantitative and specific staining techniques are available for absorption or fluorescence measurements. A complete re-evaluation is given of cell staining by means of the Feulgen reaction for absorption image cytometry, in order to obtain quantitative specificity for DNA amount and chromatin conformation. The possibility of computing from image cytometry the number of chromatin sites accessible to intercalation of small molecules, which should be related to template activity, was previously anticipated by us on an experimental basis, and is now assessed on a theoretical basis, linking together fluorescence flow cytometry and absorption image cytometry. The Feulgen staining technique has been applied to measure the amount of DNA during reactivation of frog erythrocytes and human lymphocytes induced by exposure to electromagnetic (e.m.) fields and by chemical changes of cell environment. Static automated absorption image analysis of Feulgen stained nuclei allows us to evaluate the onset of DNA synthesis and the effectiveness of the electrochemical stimulus on chromatin conformation.