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This paper investigated polarization properties of water molecules in close proximity to an ionic charge in the presence of external electric fields by using an approach based on simulations at the atomic level. We chose sodium and chloride ions in water as examples of dilute ionic solutions and used molecular dynamics simulations to systematically investigate the influence of an external static electric field on structural, dipolar, and polarization properties of water near charged ions. Results showed that a threshold electric field higher than 10(8) V/m is needed to affect water polarization and increase mean dipole moment of water molecules close to the ion. A similar threshold holds for water permittivity profiles, although a field 10× higher is needed to ensure that water permittivity is almost constant independently of the position close to the ion. Electric fields of such intensities can greatly enhance polarizability of water in hydration shells around ions., (© 2015 Wiley Periodicals, Inc.)

Protein functions and characteristics can highly differ from physiological conditions in presence of chemical, mechanical or electromagnetic stimuli. In this work we provide a rigorous picture of electric field effects on proteins behavior investigating, at atomistic details, the possible ways in which an external signal can be transduced into biochemical effects. Results from molecular dynamics (MD) simulations of a single superoxidismutase (SOD) enzyme in presence of high exogenous alternate electric fields will be discussed.

A microdosimetric study of nanosecond pulsed electric fields, including dielectric dispersivity of cell compartments, is proposed in our paper. A quasi-static solution based on the Laplace equation was adapted to wideband signals and used to address the problem of electric field estimation at cellular level. The electric solution was coupled with an asymptotic electroporation model able to predict membrane pore density. An initial result of our paper is the relevance of the dielectric dispersivity, providing evidence that both the transmembrane potential and the pore density are strongly influenced by the choice of modeling used. We note the crucial role played by the dielectric properties of the membrane that can greatly impact on the poration of the cell. This can partly explain the selective action reported on cancerous cells in mixed populations, if one considers that tumor cells may present different dielectric responses. Moreover, these kinds of studies can be useful to determine the appropriate setting of nsPEF generators as well as for the design and optimization of new-generation devices., (© 2011 IEEE)

Alteration of membrane surface charges represents one of the most interesting effects of the electromagnetic exposure on biological structures. Some evidence exists in the case of extremely low frequency whereas the same effect in the radiofrequency range has not been detected. Changes in transmembrane voltages are probably responsible for the mobilization of intracellular calcium described in some previous studies but not confirmed in others. These controversial results may be due to the cell type under examination and/or to the permeability properties of the membranes. According to such a hypothesis, calcium oscillations would be a secondary effect due to the induced change in the membrane voltage and thus dependent on the characteristics of ionic channels present in a particular preparation. Calcium increases could suggest more than one mechanism to explain the biological effects of exposure due to the fact that all the cellular pathways using calcium ions as a second messenger could be, in theory, disturbed by the electromagnetic field exposure. In the present work, we investigate the early phase of the signal transmission in the peripheral nervous system. We present evidence that the firing rate of rat sensory neurons can be modified by 50/60 Hz magnetic field but not by low level 900 MHz fields. The action of the 50/60 Hz magnetic field is biphasic. At first, the number of action potentials increases in time. Following this early phase, the firing rate decreases more rapidly than in control conditions. The explanation can be found at the single-channel level. Dynamic action current recordings in dorsal root ganglion neurons acutely exposed to the electromagnetic field show increased functionality of calcium channels. In parallel, a calcium-activated potassium channel is able to increase its mean open time.

Noise has already been shown to play a constructive role in neuronal processing and reliability, according to stochastic resonance (SR). Here another issue is addressed, concerning noise role in the detectability of an exogenous signal, here representing an electromagnetic (EM) field. A Hodgkin-Huxley like neuronal model describing a myelinated nerve fiber is proposed and validated, excited with a suprathreshold stimulation. EM field is introduced as an additive voltage input and its detectability in neuronal response is evaluated in terms of the output signal-to-noise ratio. Noise intensities maximizing spiking activity coherence with the exogenous EM signal are clearly shown, indicating a stochastic resonant behavior, strictly connected to the model frequency sensitivity. In this study SR exhibits a window of occurrence in the values of field frequency and intensity, which is a kind of effect long reported in bioelectromagnetic experimental studies. The spatial distribution of the modeled structure also allows to investigate possible effects on action potentials saltatory propagation, which results to be reliable and robust over the presence of an exogenous EM field and biological noise. The proposed approach can be seen as assessing biophysical bases of medical applications funded on electric and magnetic stimulation where the role of noise as a cooperative factor has recently gained growing attention.

We recorded the resting electroencephalogram of 20 healthy subjects in order to investigate the effect of electromagnetic field (EMF) exposure on EEG waking activity and its temporal development. The subjects were randomly assigned to two groups and exposed, in double-blind conditions, to a typical mobile phone signal (902.40 MHz, modulated at 217 Hz, with an average power of 0.25 W) before or during the EEG recording session. The results show that, under real exposure as compared to baseline and sham conditions, EEG spectral power was influenced in some bins of the alpha band. This effect was greater when the EMF was on during the EEG recording session than before it. The present data lend further support to the idea that pulsed high-frequency electromagnetic fields can affect normal brain functioning, also if no conclusions can be drawn about the possible health effects.

The study aimed to investigate the time-course of electromagnetic field (EMF)-induced effects on human cognitive and behavioral performance and on tympanic temperature. Subjects were randomly assigned to two groups, exposed to a 902.40 MHz EMF before the testing session, or to the same signal during the data collecting session. Following a double-blind paradigm, subjects were tested on four performance tasks: an acoustic simple-reaction time task, a visual search task, an arithmetic descending subtraction task and an acoustic choice-reaction time task. Moreover, tympanic temperature was collected five times during each session. Results indicated an improvement of both simple- and choice-reaction times and an increase of local temperature on the exposed region under the active exposure. There was a clear time-course of the reaction time and temperature data, indicating that performance and physiological measures need a minimum of 25 min of EMF exposure to show appreciable changes.

Measurements in the real environment, i.e. with several different electromagnetic field (EMF) sources and scattering problems, require an accurate analysis of problems concerning narrowband measurements. The aim of the present work was the development of an automatic procedure for narrowband electric field measurements in open sites with multiple sources, in order to perform accurate and reproducible measurements. Results regarding measurements carried out in a suburban site are reported.

Observations recently reported by our group indicate that combined 7 Hz sinusoidal (B(acpeak) = 50 mu T) and parallel static (B(dc) = 50 mu T) magnetic fields can induce a significant increase in diffusion rate of substrate across carbonic anhydrase (CA)-loaded liposomes (DPPC:Chol:SA). A direct involvement of charges of stearylamine (SA) on the lipid membrane surface was also demonstrated. Kinetic studies showed that CA was mainly entrapped in liposomes at 5:3:2 molar ratio, although a small amount (17%) of enzyme was also located on the external surface of these cationic liposomes. In this paper we report steady state kinetic studies on this latter CA after ELF-EMFs exposure. No difference in the apparent K(m) between exposed and sham samples was observed. On the contrary the apparent V(max) was increased by approximately a factor of 2 after field exposure. In spite of the proteolytic digestion of this external CA, a significant increase of enzymatic activity, as a function of increase in the diffusion rate of substrate across the lipid bilayer, was observed in the exposed samples. Based on these results, a conformational change induced by the field on the CA located on the external surface of 5:3:2 liposomes is excluded as an explanation for our previous observations, supporting the primary role of bilayer SA in the interaction with ELF. A model of ELF interaction, based on the Larmor precession theory, explaining the physical phenomenon induced on the dipole of SA has been developed., (Copyright 2000 Wiley-Liss, Inc.)

The influence of low frequency (4-16 Hz), low amplitude (25-75 mu T) magnetic fields on the diffusion processes in enzyme-loaded unilamellar liposomes as bioreactors was studied. Cationic liposomes containing dipalmitoylphosphatidylcholine, cholesterol, and charged lipid stearylamine (SA) at different molar ratios (6:3:1 or 5:3:2) were used. Previous kinetic experiments showed a very low self-diffusion rate of the substrate p-nitrophenyl acetate (p-NPA) across intact liposome bilayer. After 60 min of exposure to 7 Hz sinusoidal (50 mu T peak) and parallel static (50 mu T) magnetic fields the enzyme activity, as a function of increased diffusion rate of p-NPA, rose from 17 +/- 3% to 80 +/- 9% (P < .0005, n = 15) in the 5:3:2 liposomes. This effect was dependent on the SA concentration in the liposomes. Only the presence of combined sinusoidal (AC) and static (DC) magnetic fields affected the p-NPA diffusion rates. No enzyme leakage was observed. Such studies suggest a plausible link between the action of extremely low frequency magnetic field on charged lipids and a change of membrane permeability., (Copyright 2000 Wiley-Liss, Inc.)

In recent years, several studies have been focused on the problem of nonthermal interaction between extremely low-frequency (ELF) electromagnetic fields and cell environment at membrane level. In the paper, to analyse the dynamic effects of weak static and harmonic fields on charged particles, some new considerations have been developed, based on the Lorentz model. The authors have reached a suitable formulation so that the data processing has led expressly to the evaluation of ionic-velocity components against magnetic-field amplitudes and frequencies, as well as a viscosity parameter. Even through a direct and rough comparison, the results of the authors' investigation have demonstrated an interesting agreement with some experimental data relative to ionic fluxes through cell membranes. Indeed, by means of an algorithm based on the techniques of the inversion theory, the author's have found definite values of the viscosity parameter for which the expected resonant behaviours (amplitude and frequency windows) fit existing experiments well. It seems worthy of interest that such viscosity values fall within a consistent, narrow range of low amplitude.