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.

Automated cytometry has been proposed by us as an extremely sensitive probe of cell electrochemical reactivation, provided that quantitative and specific staining techniques are available for fluorescence or absorption measurements.

Automated cytometry has been proposed by us as an extremely sensitive probe of cell electrochemical reactivation, provided that quantitative and specific staining techniques are available for fluorescence or absorption measurements. A complete re-evaluation is given of cell staining by means of acridine orange for flow fluorescence cytometry, in order to obtain quantitative specificity for any conformational state of the chromatin DNA and for the amount of RNA. A good agreement is found with experimental data concerning rat thymocytes. The above technique has been applied to measure the structural changes of frog erythrocyte chromatin induced by exposure to electromagnetic fields and by chemical changes of cell environment. Flow automated fluorometry of cell nuclei allows us to evaluate the chromatin changes and the effectiveness of the electrochemical stimulus.

Frog erythrocytes dedifferentiate in vitro when exposed to a suitable electromagnetic field in a chemically potentiated microenvironment. These electrochemical stimuli are able to induce a chromatin decondensation, as previously shown by measuring the chromatin accessible sites for acridine orange intercalation by means of flow cytometry (acridine orange green fluorescence). Automated absorption image cytometry of Feulgen stained smeared erythrocytes has been performed to further elucidate the above processes. After measuring or computing the area A of the nucleus, which is related to its volume, the nucleic integrated optical density D, which is related to the DNA content, the average optical density DA = D/A, which is related to chromatin conformation, and the accessible chromatin sites SA = D2/3 A1/3, the following results have been obtained: (a) electromagnetically exposed cells progress to stages which correspond to values of D equal to those of controls, in the potentiating solution, whereas A increases, so that DA is smaller in exposed erythrocytes than in control ones, confirming that chromatin decondensation is occurring as an early dedifferentiation step. (b) By using the electromagnetic signal that is most effective in promoting dedifferentiation, erythrocytes further progress toward more advanced stages, which correspond to larger values of both D and A than in controls, i.e., to larger DNA content. (c) In all cases, the histograms of SA are in agreement with those previously obtained by flow microfluorometry of chromatin conformation (acridine orange green fluorescence). Finally, flow microfluorometric measurements of acridine orange red fluorescence give an increase of RNA content for case (a), as compared with controls, and for case (b) as compared with (a). These results point out that frog erythrocytes can be electromagnetically reactivated, resuming both RNA and DNA syntheses after initial chromatin decondensation.

The first-order nonlinear analysis of IMPATT diodes is performed and a model is obtained in which the nonlinear effects due to avalanche are separated from the activity and transit-time effects. Such a mildly nonlinear model is suitable for CAD applications. The determination of the model parameters by means of small signal measurements is outlined, and the applicability of the proposed model is demonstrated on real devices.