Direct Laser Writing (DLW) is an innovative tool that allows the photofabrication of high resolution 3D structures, which can be successfully exploited for the study of the physical interactions between cells and substrates. In this work, we focused our attention on the topographical effects of submicrometric patterned surfaces fabricated via DLW on neuronal cell behavior. In particular, we designed, prepared, and characterized substrates based on aligned ridges for the promotion of axonal outgrowth and guidance. We demonstrated that both rat PC12 neuron-like cells and human SH-SY5Y derived neurons differentiate on parallel 2.5 μm spaced submicrometric ridges, being characterized by strongly aligned and significantly longer neurites with respect to those differentiated on flat control substrates, or on more spaced (5 and 10 μm) ridges. Furthermore, we detected an increased molecular differentiation toward neurons of the SH-SY5Y cells when grown on the submicrometric patterned substrates. Finally, we observed that the axons can exert forces able of bending the ridges, and we indirectly estimated the order of magnitude of these forces thanks to scanning probe techniques. Collectively, we showed as submicrometric structures fabricated by DLW can be used as a useful tool for the study of the axon mechanobiology.

The results confirm that percutaneous interventional perforation is an effective first-stage procedure in patients with pulmonary atresia with intact ventricular septum. The right heart appeared to be adequate to maintain a long-term biventricular circulation in the large majority of cases.

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Single Ca2+-activated K+ channels of human erythrocytes were studied with the patch-clamp technique, to identify the mechanisms of their modulation by phosphorylation. In the cell-attached configuration, the openings of these channels were infrequent, as expected by the low cell Ca2+ content. After patch excision, the activity increased to levels determined by the Ca2+ concentration (0.5-10 microM) in the bath solution, then the channel activity ran down within a few minutes, to reach values of open probability lower than 0.10. The perfusion of the patch with MgATP increased the channel activity, with delayed and variable effects. Furthermore, the application of a mixture of cAMP (1 mM), MgATP (1 mM) and theophylline (1 mM) to the cytoplasmic side of excised patches led to dramatic enhancement of channel activity, which appeared within 20-120 s and decayed in tens of seconds after wash-out. The activation of the channel by the mixture was reversibly blocked by PKI5-24, a peptide inhibitor specific to cAMP-dependent protein kinase (PKA). The level of activation promoted by cAMP and ATP was dependent on the Ca2+ concentration in the bathing solution. These results provide direct evidence that an endogenous PKA modulates the calcium sensitivity of Ca2+-activated K+ channels of human erythrocytes.

The random sequence of openings and closings of single ion channels and the channel conductances have been the object of intense study over the past two decades with a view toward illuminating the underlying kinetics of the channel protein molecules. Channels that are sensitive to voltage, such as many K(+)-selective channels, have been particularly useful, because the kinetic rates can be manipulated by changing the membrane voltage. Most such studies have been performed under stationary conditions and usually at a single temperature. Here we report the results of experiments with sinusoidal modulation of the membrane potential performed at several temperatures. Dwell time and cycle histograms, objects not normally associated with ion channel experiments, are herein reported. From the last, the transition probability densities for channel opening and closing events are obtained. A new and unusual phase anticipation is observed in the cycle histograms, and its temperature dependence is measured.