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The aggregation between lectins and lymphocyte surface receptors can be affected strongly by a low-level electric field induced in the cell suspension by a time-varying magnetic field. One of the possible mechanisms is the microelectrophoretic effect due to the electric field, which influences the distance (in the mean square sense) between charged ligands and receptors when they are about to separate. On a purely theoretical basis, it is shown that, at low frequencies, an externally induced periodic electric field always decreases the mean lifetime of ligand-receptor complexes. As a consequence, the mitogenic gain obtained by lectin addition to cell suspension is decreased. These results suggest that such a mechanism, if effective, reduces the lectin mitogenic capability and offers a way of handling similar phenomena which have been described for other biological systems.

This contribution introduces two algorithms for adaptive on-line planning of oceanographic missions to be performed in cooperation by a team of AUVs. The mission goal is defined in terms of accuracy in the reconstruction of the environmental field to be sampled. Adaptive cooperative behaviour is achieved by each vehicle in terms of locally evaluating the smoothness of the sampled field, and selecting the next sampling point in order to achieve the desired accuracy; smoothness evaluation and accuracy estimation have been proposed either in terms of analytical formulation related to field estimation with RBFs, or in terms of empirically derived fuzzy-like rules. Simulative results show that the vehicles team does behave as expected, increasing the spatial sampling rate as an increase in the environmental variability is detected. The number of samples required by both algorithms is sensibly inferior to those needed by sampling the area at equally spaced locations, as in the case of off-line, nonadaptive planners

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 = D213 All3, 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, ie., 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.Frog erythrocytes are nucleated cells that undergo morphologic changes when exposed to suitable electromagnetic (em) fields in a chemically potentiated microenvironment (I, 6, 12, 14).

We present some preliminary results of a study aimed to assess the actual effectiveness of fractal theory and to define its limitations in the area of medical image analysis for texture description, in particular, in radiological applications. A general analysis to select appropriate parameters (mask size, tolerance on fractal dimension estimation, etc.) has been performed on synthetically generated images of known fractal dimensions.Moreover, we analyzed some radiological images of human organs in which pathological areas can be observed.Input images were subdivided into blocks of 6x6 pixels; then, for each block, the fractal dimension was computed in order to create fractal images whose intensity was related to the D value, i.e., texture behaviour. Results revealed that the fractal images could point out the differences between normal and pathological tissues. By applying histogram -splitting segmentation to the fractal images, pathological areas were isolated.Two different techniques (i.e., the method developed by Pentland and the "blanket" method) were employed to obtain fractal dimension values, and the results were compared; in both cases, the appropriateness of the fractal description of the original images was verified.

The effects of Mg++ on the spatial organization of nuclei from rat hepatocytes are analyzed in the range 0-60 mM, in the presence of suitable concentrations of KCl to reproduce physiological conditions. It is shown that the scatter-signal distribution measured by means of a flow microfluorimeter is greatly affected by this range of Mg concentrations. By coupling this result to phase-contrast-automated image analysis, it is possible to identify a shrinking process induced by Mg++ in the range 0-2.5 mM, which reaches a plateau in the range 5-20 mM and is followed by a swelling process in the range 30-60 mM. The same Mg ranges are shown to affect the intercalation of the fluorochrome acridine orange into chromatin, suggesting that the shrinking-swelling phenomenon has also a molecular correspondence at the genome level. Possible implications in terms of the influence of Mg++ on the organization of chromatin inside intact cells are briefly discussed.

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