Effects of low-frequency magnetic fields on bacteria Escherichia coli.

The effects of low-frequency magnetic fields (Bm=2.7-10 mT, f=50 Hz, time of exposure t=0-12 min, laboratory temperature) on the viability and oxidoreductive activity of gram-negative bacteria Escherichia coli were investigated. The growth of these bacteria was negatively affected by such fields. We compared two experimental systems--solenoid [Sb. Lek. 99 (1998) 455] and a cylindrical spool--to find differences between nonhomogeneous and "more homogeneous" magnetic fields. We observed analogous effects in both experimental conditions. The growth curve of the exposed bacteria was lower than the control one. The ability of bacteria to form colonies decreased with increasing magnetic field intensity and with increasing time of exposure. The oxidoreductive activity was measured using reduction of a tetrazolium salt. The decrease in oxidoreductive activity with increasing time of exposure was observed, but the effect was due to a lower amount of bacteria surviving the exposure to the magnetic fields. The decrease in oxidoreductive activity and ability to form colonies were compared with the assumption that the effect of magnetic field is probably bactericidal.     

Acute effects of whole-body exposure to static magnetic fields and 50-Hz electromagnetic fields on muscle microcirculation in anesthetized mice

Acute microhemodynamic effects of static and alternating magnetic fields at a threshold level were investigated on modulating the muscle capillary mirocirculation in pentobarbital-anesthetized mice. The skin in a tibialis anterior was circularly removed with 1.5 mm diameter for intravital-microscopic recording of the capillary blood velocity in the tibialis anterior muscle. Fluorescein isothiocyanate (FITC)-labeled dextran (MW 150 kDa) was used for an in vivo fluorescent plasma marker of the muscle capillaries. Following a bolus injection of FITC-dextran solution into the caudal vein, the peak blood velocity in the muscle capillaries was measured prior to, during, and following exposure to static magnetic fields (SMF) or 50-Hz electromagnetic fields (EMF) using a fluorescence epi-illumination system. The whole body of experimental animals, placed on the observing stage of a fluorescence microscope, was exposed to SMF (0.3, 1 and 10 mT) or 50-Hz EMF (0.3 and 1 mT) for 10 min using a specially devised electromagnet. For sham exposure, the electromagnet was not energized. During exposure and post-exposure to SMF of 10 mT, the peak blood velocity significantly increased as compared to sham exposure. After the withdrawal of SMF and 50-Hz EMF of 1 mT, significant similar effects on the blood velocity were present or enhanced. These findings suggest that field intensity of 1 mT might be considered as a threshold level for enhancing muscle microcirculation under pentobarbital-induced hypnosis.     

Effects of low-frequency magnetic fields on the viability of yeast Saccharomyces cerevisiae

A 50 Hz magnetic field effect on the growth of yeasts Saccharomyces cerevisae was studied. The cylindrical coil induced magnetic fields with inductions up to 10 mT. Duration of exposure varied up to 24 min. Exposure took place at laboratory temperature (24-26 degrees C) and the air ventilator maintained the temperature at the place of the sample. We measured the growth curves of yeasts in broth and we calculated the number of CFU (colony forming units) on solid soil. We found that magnetic field decreases the number of yeasts, and slowed down their growth. The result is similar to the experiments with bacteria E. coli, S. aureus and L. adecarboxylata. It seems that the magnetic fields kill a part of yeasts and the bigger part of them survives and continues in their growth.     

Effects of sinusoidal magnetic field on adherence inhibition of leucocytes: preliminary results.

The leucocyte surface properties manifest the cell-mediated immunity. The response of the cell-mediated immunity to external magnetic field was examined by observing leucocyte adherence to solid state surfaces. In the presence of antigen, leucocytes taken from cancer patients exhibit decreased adherence in contrast with adherence of leucocytes from healthy humans. After 1 h exposure to a sinusoidal magnetic field of 50 Hz and of 1 mT or 10 mT, adherence of leucocytes taken from cancer patients is strongly increased. The 1 mT magnetic field has stronger effect than the 10 mT field.     

Effects of ELF Magnetic Field in Combination with Iron(III) Chloride (FeCl3) on Cellular Growth and Surface Morphology of Escherichia coli (E. coli)

This study investigated the effects of extremely low frequency (ELF) magnetic field with/without iron(III) chloride (FeCl₃) on bacterial growth and morphology. The ELF exposures were carried out using a pair of Helmholtz coil-based ELF exposure system which was designed to generate 50 Hz sinusoidal magnetic field. The field was approximately uniform throughout the axis of the coil pair. The samples which were treated or non-treated with different concentrations FeCl₃ were exposed to 50 Hz, 2 millitesla (mT) magnetic field for 24 h. ELF effect on viability was assessed in terms of viable colony counts (in colony-forming unit per milliliter) with the standard plate count technique. Scanning electron microscopy was used to investigate the magnetic field effect on surface morphology of Escherichia coli. No significant results were seen in terms of cell viability between ELF and sham-exposed bacterial strains. Similarly, FeCl₃ treatment did not change cell viability of E. coli samples. However, we observed some morphological changes on E. coli cell surfaces. Pore formations and membrane destruction were seen on the surface of 24 h ELF field-exposed cells. We concluded that ELF magnetic field exposure at 2 mT does not affect cell viability; however, it may affect bacterial surface morphology.     

Electrostimulation of proliferation of the denitrifying bacterium Pseudomonas stutzeri

The electrostimulation of proliferation of the denitrification strain Pseudomonas stutzeri occurs in an anaerobic culture by a magnetic flux around 1 mT inducing a low current in the electric field fermenter wrapped by Helmholtz coils. After 10 h of treatment the biomass was higher than in the control fermenter by 10–30% depending on magnetic flux intensity.     

Comparison of the low-frequency magnetic field effects on bacteria Escherichia coli, Leclercia adecarboxylata and Staphylococcus aureus

This work studies biological effects of low-frequency electromagnetic fields. We have exposed three different bacterial strains-Escherichia coli, Leclercia adecarboxylata and Staphylococcus aureus to the magnetic field (t<30 min, B(m)=10 mT, f=50 Hz) in order to compare their viability (number of colony-forming units (CFU)). We have measured the dependence of CFU on time of exposure and on the value of the magnetic field induction B(m). Viability decreases with longer exposure time and/or higher induction B(m) for all strains, but the quantity of the effect is strain-dependent. The highest decrease of the viability and the biggest magnetic field effect was observed with E. coli. The smallest magnetic field effect appears for S. aureus. From the measurement of the growth dynamics we have concluded that the decrease of the CFU starts immediately after the magnetic field was switched on.     

Synthesis of DnaK and GroEL in Escherichia coli cells exposed to different magnetic field signals

The effects of extremely low frequency magnetic field (ELF-MF)(1 mT, 50 Hz) on the heat shock protein (HSP) synthesis in Escherichia coli were investigated. Two magnetic field signals were studied: sinusoidal (SMF) and pulsed square wave (PMF). It was found that bacteria exposed to SMF showed a significantly higher level of DnaK and GroEL proteins as compared to sham-exposed bacteria as revealed by Western blot, whereas a lower level was observed after PMF exposure. Similar results were obtained when bacterial cells were exposed to heat shock (HS) after ELF-MF exposure: again SMF and PMF resulted in an increase and in a reduction of HSP amount in comparison with sham control, respectively. In conclusion, the MF influences the synthesis of HSPs in E. coli in a way that critically depends on the signal characteristics.     

Effect of 7 mT static magnetic field and iron ions on rat lymphocytes: apoptosis,necrosis and free radical processes

Simultaneous exposure of rat lymphocytes to 7 mT static magnetic field (SMF) and iron ions caused an increase in the number of cells with DNA damage. The mechanism by which MF induces DNA damage and the possible cytotoxic consequences are not known. However, we suppose that free radicals are involved. Potentially, the deterioration of DNA molecules by simultaneous exposure to 7 mT SMF and iron ions may lead to cell death: apoptosis or necrosis. The possible prooxidative properties of these two agents may result in an induction of the lipid peroxidation process as a marker of free radical mechanism in the cells. Experiments were performed on rat blood lymphocytes incubated for 3 h in Helmholtz coils at SMF of flux density 7 mT. During SMF exposure, some samples were treated with ferrous chloride (10 microg/ml), the rest serving as controls. We used the dye exclusion method with the DNA-fluorochromes: ethidium bromide and acridine orange. No significant differences were observed between unexposed lymphocytes incubated with medium alone and lymphocytes exposed to 7 mT SMF. Three-hour incubation with FeCl(2) (10 microg/ml) did not affect cell viability. However, when lymphocytes were exposed to 7 mT SMF and simultaneously treated with FeCl(2), there was a significant increase in the percentage of apoptotic and necrotic cells accompanied by significant alterations in cell viability. As compared to lipid peroxidation, there is a significant increase in the amount of lipid peroxidation end products MDA+4 HNE in rat lymphocytes after simultaneous exposure to 7 mT SMF and FeCl(2) (vs. to the control samples and those exposed to SMF alone). This suggests that 7 mT static magnetic field in the presence of Fe(2+) ions can increase the concentration of oxygen free radicals and thus may lead to cell death.     

Comparison of two innovatives approaches for bacterial detection: paramagnetic nanoparticles and self-assembled multilayer processes

Transfusion medicine is a field that has developed in the second half of the last century. Very rapidly, however, it became clear that this approach also carried its problems, such as the incompatibility of red blood cells and plasma between donors and recipients, and the possibility of transmitting viral and bacterial infections. An immunomagnetic biosensor for the label-free detection of a bacterial model, Escherichia coli, is described and compared to a self assembled multilayer system reported previously. The paramagnetic nanoparticles layer attracted to, and formed on, the gold electrode surface via a magnetic field up to 300 mT is not totally blocking for the redox probe comparing to the thiol self assembled monolayer (a biotin thiol and a spacer thioalcohol). Moreover, the modeling of the Nyquist spectra obtained by electrochemical impedance spectroscopy for increasing concentrations of E. coli shows for both system a sigmoid variation of the polarization resistance with increasing logarithmic concentration of bacteria. A sensitivity slope of 10.675 was obtained for the immunomagnetic sensor compared to 6.832 for the self assembled multilayer process, this indicating the higher sensitivity of the paramagnetic nanoparticles biosensor.     

Magnetic field effect on electrochemical oscillations during iron dissolution

A fairly low magnetic field of ca. 30 mT was found to affect the period and the amplitude of the self-sustained current oscillation of an iron electrode. This was observed much distinctively when the direction of the applied field was normal to the electrode surface, i.e., non-magnetohydrodynamic (MHD) configuration. The Flade potential of the iron electrode was not affected by the magnetic field intensity of up to 4 T. The observed magnetic field effect was attributed to the depression of the natural convection in the vicinity of the electrode surface which was caused by the two local paramagnetic body forces, the magnetic field gradient force and/or the concentration gradient force.     

Magnetic Field Treatments Improves Sunflower Yield by Inducing Physiological and Biochemical Modulations in Seeds

Magnetic seed enhancement has been practicing as a promising tool to improve germination and seedling growth of low vigor seeds stored under suboptimal conditions, but there is still ambiguity regarding the prospects for magnetism in oilseeds. Present study elucidates the potential of magnetic seed stimulation to improve sunflower germination, growth and yield. Germination and emergence tests were performed to optimize the strength of the magnetic field to sunflower seed enhancement. The seeds were directly exposed to magnetic field strengths of 50, 100 and 150 millitesla (mT) for 5, 10 and 15 min (min) and then standard germination tests were performed. Secondly, the emergence potential of untreated seeds was compared with seed exposed to hydropriming, priming with 3% moringa leaf extract (MLE), priming with magnetically treated water (MTW) for 10 min and priming with 3% MLE solution prepared in magnetically treated water (MTW + MLE). Germination, emergence, seedling growth and seed biochemical properties were used to select the best treatment for field evaluation. The results of the study revealed that magnetic seed treatment with 100 mT for 10 min and seed priming with 3% MLE solution in magnetically treated water (MTW + MLE) significantly improved emergence, crop growth rate and sunflower yield.     

Catecholamine release from cultured bovine adrenal medullary chromaffin cells in the presence of 60-Hz magnetic fields

Effects of powerline frequency (50/60 Hz) electric and magnetic fields on the central nervous system may involve altered neurotransmitter release. This possibility was addressed by determining whether 60-Hz linearly polarized sinusoidal magnetic fields (MFs) alter the release of catecholamines from cultured bovine adrenal chromaffin cells, a well-characterized model of neural-type cells. Dishes of cells were placed in the center of each of two four-coil Merritt exposure systems that were enclosed within mu-metal chambers in matched incubators for simultaneous sham and MF exposure. Following 15-min MF exposure of the cells to flux densities of 0.01, 0.1, 1.0 or 2 mT, norepinephrine and epinephrine release were quantified by high-performance liquid chromatography (HPLC) coupled with electrochemical detection. No significant differences in the release of either norepinephrine or epinephrine were detected between sham-exposed cells and cells exposed to MFs in either the absence or presence of Bay K-8644 (2 microM) or dimethylphenylpiperazinium (DMPP, 10 microM). Consistent with these null findings is the lack of effect of MF exposure on calcium influx. We conclude that catecholamine release from chromaffin cells is not sensitive to 60-Hz MFs at magnetic flux densities in the 0.01-2 mT range.     

Dynamics of magnetic-field-induced clustering in ionic ferrofluids from Raman scattering

Using Raman spectroscopy, the authors have investigated the aggregation/disgregation of magnetic nanoparticles in dense ionic ferrofluids (IFF) into clusters due to the action of an inhomogeneous external magnetic field. Evidence for changes in particle density and/or effective cluster size were obtained from the variation of the Raman intensity in a time window from 10 s to 10 min for magnetic fields up to 350 mT and at a temperature of 28 degrees C. Clustering sets in already at very low fields (>15 mT) and the IFF samples exhibit a clear hysteresis in the Raman spectra after releasing the magnetic field, which lasts for many hours at room temperature. The authors determined the characteristic times of the two competing processes, that of field-induced cluster formation and, at room temperature, that of thermal-activated dissociation, to range from 100 to 150 s.     

A weak pulsed magnetic field affects adenine nucleotide oscillations, and related parameters in aggregating Dictyostelium discoideum amoebae

A model eukaryotic cell system was used to explore the effect of a weak pulsed magnetic field (PMF) on time-varying physiological parameters. Dictyostelium discoideum cells (V12 strain) were exposed to a pulsed magnetic field (PMF) of flux density 0.4 mT, generated via air-cored coils in trains of 2 ms pulses gated at 20 ms. This signal is similar to those used to treat non-uniting fractures. Samples were taken over periods of 20 min from harvested suspensions of amoebae during early aggregation phase, extracted and derivatised for HPLC fluorescent assay of adenine nucleotides. Analysis of variance showed a significant athermal damping effect (P < 0.002, n = 22) of the PMF on natural adenine nucleotide oscillations and some consistent changes in phase relationships. The technique of nonlinear dielectric spectroscopy (NLDS) revealed a distinctive effect of PMF, caffeine and EGTA in modulating the cellular harmonic response to an applied weak signal. Light scattering studies also showed altered frequency response of cells to PMF, EGTA and caffeine. PMF caused a significant reduction of caffeine induced cell contraction (P < 0.0006, n = 19 by paired t-test) as shown by Malvern particle size analyser, suggesting that intracellular calcium may be involved in mediating the effect of the PMF.     

Biotinylated polypyrrole films: an easy electrochemical approach for the reagentless immobilization of bacteria on electrode surfaces

Biotinylated bacteria were immobilized onto biotin/avidin modified electrode surfaces. Firstly, an electrospotting deposition method, followed by fluorescence microscopy, showed that bacteria were specifically grafted onto a gold surface. Fluorescence intensity versus the quantity of bacteria deposited on the surface was correlated, allowing determination of the microbial saturation point. Secondly, biotinylated bacteria were immobilized onto a glassy carbon macro-electrode in order to assess immobilized bacterial denitrification activity. During a 7-day trial, the modified electrode completely denitrified 5 mM nitrate, with a rate of 1.66 mM/day over the first 3 days. When the same electrode was placed in fresh nitrate solution, the denitrification rate dropped to 0.80 mM/day. Crucially, the immobilized bacteria did not become detached from the electrode during the study.     

Alleviation of adverse effects of drought stress on growth and some potential physiological attributes in maize (Zea mays L.) by seed electromagnetic treatment

Effects of varying preseed magnetic treatments on growth, chlorophyll pigments, photosynthesis, water relation attributes, fluorescence and levels of osmoprotectants in maize plants were tested under normal and drought stress conditions. Seeds of two maize cultivars were treated with different (T0 [0 mT], T1 [100 mT for 5 min], T2 [100 mT for 10 min], T3 [150 mT for 5 min] and T4 [150 mT for 10 min]) electromagnetic treatments. Drought stress considerably suppressed growth, chlorophyll a and b pigments, leaf water potential, photosynthetic rate (A), stomatal conductance (g(s)) and substomatal CO(2) concentration (C(i)), while it increased leaf glycinebetaine and proline accumulation in both maize cultivars. However, pretreated seeds with different magnetic treatments significantly alleviated the drought-induced adverse effects on growth by improving chlorophyll a, A, E, g(s), C(i) and photochemical quenching and nonphotochemical quenching, while it had no significant effect on other attributes. However, different magnetic treatments negatively affected the g(s) and C(i) particularly in cv. Agaiti-2002 under drought stress conditions. Of all magnetic treatments, 100 and 150 mT for 10 min were most effective in alleviating the drought-induced adverse effects. Overall, preseed electromagnetic treatments could be used to minimize the drought-induced adverse effects on different crop plants.     

Electromagnetic field-induced protection of chick embryos against hypoxia exhibits characteristics of temporal sensing

We previously studied the response of mammalian cultured cells to weak, 60 Hz-electromagnetic (EM) fields. Two time constants, similar to those observed in chemotaxis, were found to govern the cellular response to the field. We concluded that a system of temporal sensing, similar to that employed in chemotaxis by motile bacteria, was operative. We termed the shorter time (approximately 0.1 s) the "sensing" time, and the longer time (approximately 10 s) the "memory" time. To investigate the possibility that temporal sensing was a general property of EM field-cell interaction, the temporal properties of another EM field-induced effect was studied. The EM field-induced protection against the effects of extreme hypoxia was examined in chick embryos. Embryos were exposed to 60 Hz-magnetic fields, the amplitudes of which were regularly altered throughout the 20-min exposure. Alteration was accomplished either by turning the field off and on at regular intervals (1-50 s), or by introducing brief (10 or 100 ms), zero amplitude gaps, once each second, throughout exposure. When the field was turned on and off at 0.1 s intervals, the protective effect conferred by a constant field was lost. At progressively longer on/off intervals, protection was progressively restored, maximizing at intervals of 10-30 s. Gapping the magnetic field for 10 ms, each second of exposure conferred the same protection as that observed for an uninterrupted field, but gapping the field at 100 ms each second produced a significant reduction in protection. These data exhibit remarkable consistency with those obtained in similar temporal studies of the magnetic field-induced enhancement of ornithine decarboxylase activity in L929 fibroblasts. It appears that temporal sensing is a general feature of the EM field-cell interaction.     

Power frequency magnetic field exposure and gap junctional communication in Clone 9 cells

Exposure to a power-frequency magnetic field has been reported to produce a statistically significant inhibition of gap junctional communication (GJC) in Clone 9 cells that have been pre-stressed by treatment with low concentrations of chloral hydrate (CH) [C.F. Blackman, J.P. Blanchard, S.G. Benane, D.E. House, J.A. Elder, Double blind test of magnetic field effects on neurite outgrowth, Bioelectromagnetics, 19 (1998) 204-209]. This observation might provide mechanistic insight into the possible role of electromagnetic fields (EMFs) in the carcinogenic process, since cancer cells frequently show decreased or absent GJC, and tumor promoting chemicals have been observed to inhibit GJC. Magnetic field exposure conditions were 45 Hz, 23.8 microT rms + parallel DC 36.6 microT, for 30 min of exposure. The responses of Clone 9 cells to the GJC-inhibiting effects of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate and the chemical CH were evaluated and compared to reported results [S.G. Benane, C.F. Blackman, D.E. House, Effects of perchloroethylene and its metabolites on intercellular communication in Clone 9 rat liver cells, J. Toxicol. Environ. Health, 48 (1996) 427-437]. Before magnetic field exposure, cells were exposed for 24 h to either 3 (nine experiments) or 5 mM (11 experiments) CH to produce GJC of 67% or 50%, respectively, relative to unexposed controls. GJC was assessed microscopically using the scrape-loading technique and a blinded protocol. No statistically significant effect was observed due to magnetic field exposure with either CH concentration.     

Interplay between crystal and magnetic structure of the anion-radical salt (N-Me-2,6-di-Me–Py)(TCNQ)2 (Py is pyridine)

Genuine organic anion-radical salt (N-Me-2,6-di-Me–Py)(TCNQ)₂ with pyridine-based cation was synthesized and its crystal structure was resolved. The DC magnetic susceptibility was measured in temperature range from 2 K to 300 K in magnetic fields 10 mT, 100 mT and 1 T. Zero field cooling (ZFC) and field cooling (FC) modes were used. The results were studied in terms of one-dimensional magnetic models and we have found that the most suitable of them is an antiferromagnetic linear Heisenberg S = 1/2 system with small amount of free spins. An additional peak observed at low temperatures can be explained by an interchain coupling between free chain-end spins.