Cell shape and plasma membrane alterations after static magnetic fields exposure

Magnetotactic bacteria (MTB) can use their unique intracellular magnetosome organelles to swim along the Earth's magnetic field. They play important roles in the biogeochemical cycles of iron and sulfur. Previous studies have shown that the applied magnetic fields could affect the magnetosome formation and antioxidant defense systems in MTB. However, the molecular mechanisms by which magnetic fields affect MTB cells remain unclear. We aim to better understand the dark at 28°C-29°C for 20 h, as shownthe interactions between magnetic fields and cells, and the mechanism of MTB adaptation to magnetic field at molecular levels. We performed microbiological, transcriptomic, and genetic experiments to analyze the effects of a weak static magnetic field (SMF) exposure on the cell growth and magnetosome formation in the MTB strain Magnetospirillum magneticum AMB-1. The results showed that a 1.5 mT SMF significantly promoted the cell growth but reduced magnetosome formation in AMB-1, compared to the geomagnetic field. Transcriptomic analysis revealed decreased expression of genes primarily involved in the sulfate reduction pathway. Consistently, knockout mutant lacking adenylyl-sulfate kinase CysC did no more react to the SMF and the differences in growth and Cmag disappeared. Together with experimental findings of increased reactive oxidative species in the SMF-treated wild-type strain, we proposed that cysC, as a key gene, can participate in the cell growth and mineralization in AMB-1 by SMF regulation. This study suggests that the magnetic field exposure can trigger a bacterial oxidative stress response involved in AMB-1 growth and magnetosome mineralization by regulating the sulfur metabolism pathway. CysC may serve as a pivotal enzyme in mediating sulfur metabolism to synchronize the impact of SMF on both growth and magnetization of AMB-1.

This study was designed to directly quantify the effect of localized static magnetic field (SMF) exposure on the diameter of microvessels in adult rat skeletal muscle in vivo. Microvascular networks in the exteriorized rat spinotrapezius microvasculature were exposed to a localized, uniform 70 mT SMF for 15 min. Arteriolar vessel diameters were measured; and the extent of vessel contraction, microvascular tone, was calculated before exposure, immediately after exposure, and 15 and 30 min after removal of the field. A calculated value of high tone corresponds to vessels that are vasoconstricted and a calculated value of low tone refers to vessels that are vasodilated. Vessels with initial tone <15% showed an increasing trend in tone and, conversely, vessels with initial tone >15% showed a significant (P < 0.05) decrease in tone 15 and 30 min following application, respectively. Further classification of the data with regards to the initial vessel diameter demonstrated that vessels with initial diameters <30 microm and initial tone <15%, smaller diameter vessels that are initially vasodilated, showed significant (P < 0.05) increase in tone immediately, 15 and 30 min following SMF exposure. Additionally, <30 microm vessels with >15% initial tone, smaller diameter vessels that are initially vasoconstricted, demonstrated a significant (P < 0.05) decrease in tone 30 min after SMF exposure. Vessels with initial diameters >30 microm had no significant response to the SMF. These results imply that SMF exposure influences arteriolar diameters, and therefore microvascular tone, in a restorative fashion acting to normalize the tone to the median tone value of 15% following exposure. Because this response occurs primarily in the resistance arterioles, which significantly influence tissue perfusion, SMF application could be efficacious for the treatment of both ischemic and edematous tissue disorders involving compromised microvascular function.

Magnetic fields are abiotic environmental factors that can cause a wide range of biological effects at both the cellular and whole-organism levels. In this study, we investigated the effects of a static magnetic field (SMF, 110 mT) on life history traits and antioxidant defence mechanisms during the preadult development of Lymantria dispar. SMF exposure did not affect the mass of younger larvae, whereas older larvae and pupae showed significantly reduced mass compared to controls. Estimated larval mortality was higher in the SMF group, while developmental duration was significantly prolonged in the fifth larval instar and in both male and female pupae. SMF induced stage-dependent modifications in antioxidant defence. Superoxide dismutase activity and catalase activities were significantly increased, predominantly in later developmental stages, while glutathione reductase and glutathione S-transferase showed instar-dependent responses. In addition, the content of total and oxidised glutathione was significantly higher in the fifth and sixth instars of SMF-exposed larvae compared to controls. The study shows that static magnetic field exposure can interfere with normal developmental processes and redox homeostasis in insects, implying potential adaptive mechanisms under stressful conditions.

Aim: To study the effects of static magnetic fields (SMF) on the electrophysiological properties of voltage-gated sodium and calcium channels on trigeminal ganglion (TRG) neurons. Methods: Acutely dissociated TRG neurons of neonatal SD rats were exposed to 125-mT and 12.5-mT SMF in exposure devices and whole-cell patch-clamp recordings were carried out to observe the changes of voltage-gated sodium channels (VGSC) and calcium channels (VGCC) currents, while laser scanning confocal microscopy was used to detect intracellular free Ca2+ concentration in TRG neurons, respectively. Results: (1) No obvious change of current–voltage (I–V) relationship and the peak current densities of VGSC and VGCC currents were found when TRG neurons were exposed to 125-mT and 12.5-mT SMF. However, the activation threshold, inactivation threshold and velocity of the channel currents above were significantly altered by 125-mT and 12.5-mT SMF. (2) The fluctuation of intracellular free Ca2+ concentration within TRG neurons were slowed by 125-mT and 12.5-mT SMF. When SMF was removed, the Ca2+ concentration level showed partial recovery in the TRG neurons previously exposed by 125-mT SMF, while there was a full recovery found in 12.5-mT-SMF-exposed neurons. Conclusions: Moderate-intensity SMF could affect the electrophysiological characteristics of VGCS and VGCC by altering their activation and inactivation threshold and velocity. The fluctuations of intracellular free Ca2+ caused by SMF exposure were not permanent in TRG neurons.

Introduction: The current understanding of the biological impacts of a static magnetic field (SMF) is restricted to the direct interactions of the magnetic field with biological membranes. The electrokinetic (zeta) potential is an electrochemical property of erythrocyte surfaces which was negatively charged in physiological media after SMF exposure (0.1‒2.0 T).Methods: The novel data about electrokinetic parameters of the erythrocytes is determined by microelectrophoresis after SMF-exposure in norm and heterozygous β-thalassemia. The methods of light scattering, lipid peroxidation, fluorescence microscopy are used.Results: The electrokinetic potential of erythrocytes in norm is increased after SMF intensities due to enhanced negatively exposed charges on the outer surface of the membrane accompanied by an increase in light scattering where changes in cell morphology are observed. Conversely, a decrease in the zeta potential of β-thalassemia erythrocytes upon SMF-treatment was determined because of the reduction in the surface electrical charge of the membranes, where a significant decrease in light scattering at 1.5 T and 2.0 T was recorded. Exposure to SMF (0.5–2.0 T) was associated with an increase in the malondialdehyde content in erythrocytes. Biophysical studies regarding the influence of SMF on the electrostatic free energy of cells shows an increase in negative values in healthy erythrocytes, which corresponds to the implementation of a spontaneous process. This is also the process in β-thalassemia cells after SMF exposure with lower negative values of free electrostatic energy than erythrocytes in norm.Discussion: The effect of static magnetic field (SMF 0.1–2.0 T) on the electrokinetic and morphological characteristics of erythrocytes in norm and β-thalassemia is determined and correlated with the increase/reduction in surface charge and shrinkage/swelling of the cells, respectively. Lipid peroxidation of healthy and β-thalassemia erythrocytes caused an enhancement of lipid peroxidation because of the higher concentrations of TBARS products in cellular suspension. SMF (0.1‒2.0 T) altered the spontaneous chemical processes with negative values of electrostatic free energy of erythrocytes in norm and β-thalassemia accompanied by a lower FITC-Concanavalin A binding affinity to membrane receptors (SMF 2.0 T). The electrokinetic properties of human erythrocytes in norm and β-thalassemia upon SMF treatment and their interrelationship with the structural-functional state of the membrane were reported. The presented work would have future fundamental applications in biomedicine.

The biphasic effects of locally applied static magnetic fields (SMF) on the cutaneous microcirculation within a rabbit ear chamber (REC) were evaluated under conscious conditions. The microcirculatory vasomotion within a REC was measured continuously and analyzed multilaterally by microphotoelectric plethysmography, a real-time image analyzer and an image shearing monitor. SMF intensities at the REC were controlled at 1 mT and the duration of exposure was 10 min. Seventy-eight experimental trials were carried out on 22 healthy adult rabbits weighing 2.6-3.5 kg. Five experimental groups were chosen at random: 1) no pharmacological treatment or SMF exposure, 2) increased vascular tone induced by noradrenaline infusion without SMF exposure, 3) increased vascular tone induced by noradrenaline infusion with SMF exposure, 4) decreased vascular tone induced by acetylcholine infusion without SMF exposure, 5) decreased vascular tone induced by acetylcholine infusion with SMF exposure. The results demonstrated that SMF significantly enhanced vasodilatation, with increased vasomotion under noradrenaline-induced high vascular tone as well as vasoconstriction with reduced vasomotion under acetylcholine-induced low vascular tone. This suggests, therefore, that SMF can modulate vascular tone due to biphasic modification of vasomotion in the cutaneous tissue.

Static magnetic fields (SMFs) and time-varying electromagnetic fields exposure is necessary to obtain the diagnostic information regarding the structure of patient's tissues, by the use of magnetic resonance imaging (MRI) scanners. A diagnostic procedure may also include the administration of pharmaceuticals called contrast, which are to be applied to a patient during the examination. The nurses involved in administering contrast into a patient during the pause in examination are approaching permanently active magnets of MRI scanners and are exposed to SMF. There were performed measurements of spatial distribution of SMF in the vicinity of MRI magnets and parameters of personal exposure of nurses (i.e. individual exposimetric profiles of variability in time of SMF affecting the nurse who is performing tasks in the vicinity of magnet, characterized by statistical parameters of recorded magnetic flux density affecting the nurse). The SMF exposure in the vicinity of various MRI magnets depends on both magnetic flux density of the main field B 0 (applicable to a patient) and the construction of the scanner, but the most important factor determining the workers' exposure is the work practice. In the course of a patient's routine examination in scanners of B 0 = 1.5 T, the nurses are present over ∼0.4–2.9 min in SMF exceeding 0.03% of B 0 (i.e. 0.5 mT), but only sometimes they are present in SMF exceeding 5% of B 0 (i.e. 75 mT). When patients need more attention because of their health status/condition, the nurses' exposure may be significantly longer – it may even exceed 10 min and 30% of B 0 (i.e. 500 mT). We have found that the level of exposure of nurses to SMF may vary from < 5% of the main field (a median value: 0.5–1.5%; inter-quartile range: 0.04–8.8%; max value: 1.3–12% of B 0) when a patient is moved from the magnets bore before contrast administration, up to the main field level (B 0) when a patient stays in the magnets bore and nurse is crawling into the bore.

To investigate the effects of static magnetic fields (SMFs) with different exposure time on the maturation of rat osteoblasts in vitro and the expression of the estrogen receptor (ER) gene. The calvarial osteoblasts were isolated from newborn rats by enzyme digestion and randomly divided into 9 groups after one passage based on the exposure time of the SMFs[0 (control), 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, and 4.0 h]. The intensity was 3.9 mT in all SMFs. Those without SMFs exposure were used as the controls. The oeteoblasts were observed under the contrast phase microscope on a daily basis. After 48 h, cell proliferation was assayed by MTT method. The osteocalcin contents were measured after exposure to SMFs for 3 d, 6 d, 9 d, and 12 d. ERΑ and ERΒ mRNA expressions were measured by real-time PCR after SMFs treatment for 0 h, 24 h, 48 h, and 72 h. Compared with the controls, the cell proliferation was significantly enhanced in the 2.0-h, 2.5-h, and 3.0-h groups (P<0.05). After SMFs treatment for 6 d, 9 d and 12 d, the 2.5-h group had significantly higher osteocalcin content than the control group did (P<0.05). After SMFs treatment for 0 h and 72 h, elevated ERΑ mRNA expression and reduced ERΒ mRNA expression were observed. Exposure to SMFs, regardless of exposure time, is associated with enhanced cell proliferation, increased osteocalcin contents, and altered ERΑ and ERΒ mRNA expressions in opposite directions.

There is considerable interest in the development of marine and hydrokinetic energy projects in rivers, estuaries, and coastal ocean waters of the United States. Hydrokinetic (HK) technologies convert the energy of moving water in river or tidal currents into electricity, without the impacts of dams and impoundments associated with conventional hydropower or the extraction and combustion of fossil fuels. The Federal Energy Regulatory Commission (FERC) maintains a database that displays the geographical distribution of proposed HK projects in inland and tidal waters (FERC 2012). As of March 2012, 77 preliminary permits had been issued to private developers to study HK projects in inland waters, the development of which would total over 8,000 MW. Most of these projects are proposed for the lower Mississippi River. In addition, the issuance of another 27 preliminary permits for HK projects in inland waters, and 3 preliminary permits for HK tidal projects (totaling over 3,100 MW) were under consideration by FERC. Although numerous HK designs are under development (see DOE 2009 for a description of the technologies and their potential environmental effects), the most commonly proposed projects entail arrays of rotating devices, much like submerged wind turbines, that are positioned in the high-velocity (high energy) river channels. The many diverse HK designs imply a diversity of environmental impacts, but a potential impact common to most is the effect on aquatic organisms of electromagnetic fields (EMF) created by the projects. The submerged electrical generator will emit an EMF into the surrounding water, as will underwater cables used to transmit electricity from the generator to the shore, between individual units in an array (inter-turbine cables), and between the array and a submerged step-up transformer. The electric current moving through these cables will induce magnetic fields in the immediate vicinity, which may affect the behavior or viability of fish and benthic invertebrates (Gill et al. 2005, 2009). It is known that numerous marine and freshwater organisms are sensitive to electrical and magnetic fields, often depending on them for such diverse activities as prey location and navigation (DOE 2009; Normandeau et al. 2011). Despite the wide range of aquatic organisms that are sensitive to EMF and the increasing numbers of underwater electrical transmitting cables being installed in rivers and coastal waters, little information is available to assess whether animals will be attracted, repelled, or unaffected by these new sources of EMF. This knowledge gap is especially significant for freshwater systems, where electrosensitive organisms such as paddlefish and sturgeon may interact with electrical transmission cables. We carried out a series of laboratory experiments to test the sensitivity of freshwater fish and invertebrates to the levels of EMF that are expected to be produced by HK projects in rivers. In this context, EM fields are likely to be emitted primarily by generators in the water column and by transmission cables on or buried in the substrate. The HK units will be located in areas of high-velocity waters that are used as only temporary habitats for most riverine species, so long-term exposure of fish and benthic invertebrates to EMF is unlikely. Rather, most aquatic organisms will be briefly exposed to the fields as they drift downstream or migrate upstream. Because the exposure of most aquatic organisms to EMF in a river would be relatively brief and non-lethal, we focused our investigations on detecting behavioral effects. For example, attraction to the EM fields could result in prolonged exposures to the fields or the HK rotor. On the other hand, avoidance reactions might hinder upstream migrations of fish. The experiments reported here are a continuation of studies begun in FY 2010, which focused on the potential effects of static magnetic fields on snails, clams, and fathead minnows (Cada et al. 2011). Those experiments found little indication that the behaviors of these freshwater species were altered by the static magnetic fields that would be created by submerged, direct current (DC)-transmitting electrical cables expected to be used by the HK developers. Laboratory experiments in FY 2011 examined the responses of additional fish species (sunfish, striped bass, and channel catfish) to the static magnetic fields. In addition, the effects of variable magnetic fields (that would be created by the HK generators and AC-transmitting cables) on swimming behavior of two electrosensitive fish species (paddlefish and lake sturgeon) were studied.

To elucidate the biological effect of static magnetic fields (SMF), we measured lipid peroxidation in the liver, kidneys, heart, lungs and brain of mice exposed to SMF and also evaluated the combined effect of SMF exposure on the hepatotoxicity induced by treatment with carbon tetrachloride (CCl4). Lipid peroxidation in the liver was significantly increased by exposure to 4.7 T of SMF for 3, 6, 24, or 48 h, whereas that in the kidneys, heart, lungs and brain was not changed compared to the control. The combination of CCl4 injection and SMF exposure caused an increase in lipid peroxidation in the liver exceeding that caused by either treatment alone. Furthermore, the increase in activities of both GOT and GPT caused by CCl4 administration were also enhanced by SMF exposure. These results indicate that the exposure to strong SMF induces lipid peroxidation in the liver of mice and enhances the hepatotoxicity caused by CCl4 administration.

Objective To evaluate the effects of static magnetic fields (SMFs) of different intensity and exposure duration on the proliferation and apoptosis of human umbilical cord endothelial cells (HUVECs),and their release of nitric oxide (NO),6-keto-prostacyclin 1α (6-keto-PGF1α) and endothelin (ET-1).Methods Cultured HUVECs were exposed to a SMF at 5,22,86 or 135 mT for 8,12 or 24 hours.Their proliferation and apoptosis were monitored by flow cytometry (FCM).The medium was collected to test its NO content by optical density.ET-1 and 6-keto-PGF1α were measured by radioimmunization.Results ( 1 ) The proliferation of HUVECs increased when the cells were exposed to a SMF at 5 mT for 8 h,but a SMF at 135 mT for 12 h or 24 h inhibited the proliferation of HUVECs.(2)An SMF had no effect on apoptosis of HUVECs.(3)An SMF at 5 mT for 8 h increased the release of NO and 6-keto-PGF1 a,but the release of NO and 6-keto-PGF1 a decreased when the SMF intensity was 135 mT or the cells were exposed to an SMF for 12 h or 24 h.(4) An SMF at 5 mT or 22 mT for 8 h did not effect the release of ET-1.An SMF at 86 mT or 135 mT increased the release of ET-1.Compared with a control group,an SMF at 5 mT for 12 or 24 h did not affect the release of ET1,but at 22,80 or 135 mT,the release of ET-1 decreased significantly.Conclusions Exposure to a low intensity SMF for a short duration could improve the proliferation of HUVECs and increase the release of vasoactive factors,but if HUVECs are exposed to a strong SMF or exposed for a long duration,the proliferation and the release of vasoactive factors is decreased. Key words: Static magnetic fields; Endothelial cells; Nitric oxide; Endothelin-1; 6-keto-prostacyclin 1 α

Static magnetic field (SMF) interacts with mammal skeletal muscle; however, SMF effects on skeletal muscle cells are poorly investigated. The myogenic cell line L6, an in vitro model of muscle development, was used to investigate the effect of a 80 +/- mT SMF generated by a custom-made magnet. SMF promoted myogenic cell differentiation and hypertrophy, i.e., increased accumulation of actin and myosin and formation of large multinucleated myotubes. The elevated number of nuclei per myotube was derived from increased cell fusion efficiency, with no changes in cell proliferation upon SMF exposure. No alterations in myogenin expression, a modulator of myogenesis, occurred upon SMF exposure. SMF induced cells to align in parallel bundles, an orientation conserved throughout differentiation. SMF stimulated formation of actin stress-fiber like structures. SMF rescued muscle differentiation in the presence of TNF, a muscle differentiation inhibitor. We believe this is the first report showing that SMF promotes myogenic differentiation and cell alignment, in the absence of any invasive manipulation. SMF-enhanced parallel orientation of myotubes is relevant to tissue engineering of a highly organized tissue such as skeletal muscle. SMF rescue of muscle differentiation in the presence of TNF may have important therapeutic implications.

The present work was a comparative study of the bio-effects induced by exposure to 6 mT static magnetic field (MF) on several primary cultures and cell lines. Particular attention was dedicated to apoptosis. Cell viability, proliferation, intracellular Ca(2+) concentration and morphology were also examined. Primary cultures of human lymphocytes, mice thymocytes and cultures of 3DO, U937, HeLa, HepG2 and FRTL-5 cells were grown in the presence of 6 mT static MF and different apoptosis-inducing agents (cycloheximide, H(2)O(2), puromycin, heat shock, etoposide). Biological effects of static MF exposure were found in all the different cells examined. They were cell type-dependent but apoptotic inducer-independent. A common effect of the exposure to static MF was the promotion of apoptosis and mitosis, but not of necrosis or modifications of the cell shape. Increase of the intracellular levels of Ca(2+) ions were also observed. When pro-apoptotic drugs were combined with static MF, the majority of cell types rescued from apoptosis. To the contrary, apoptosis of 3DO cells was significantly increased under simultaneous exposure to static MF and incubation with pro-apoptotic drugs. From these data we conclude that 6 mT static MF exposure interfered with apoptosis in a cell type- and exposure time-dependent manner, while the effects of static MF exposure on the apoptotic program were independent of the drugs used.

Spreading evidence suggests that geomagnetic field (GMF) modulates artificial magnetic fields biological effect and associated with increased cardiovascular morbidity. To explore the underlying physiological mechanism we studied 350 mT static magnetic field (SMF) effect on arterial baroreflex-mediated skin microcirculatory response in conjunction with actual geomagnetic activity, reflected by K and K ( p ) indices. Fourteen experiments were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h). Mean femoral artery blood pressure, heart rate, and the ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after 40 min of NdFeB magnets local exposure to sinocarotid baroreceptors. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. We found a significant positive correlation between SMF-induced increase in BRS and increment in microvascular blood flow (DeltaBRS with DeltaMPPG, r=0.7, p<0.009) indicated the participation of the arterial baroreflex in the regulation of the microcirculation and its enhancement after SMF exposure. Geomagnetic disturbance, as opposed to SMF, decreased both microcirculation and BRS, and counteracted SMF-induced increment in microcirculatory blood flow (K-index with DeltaMPPG; r (s)=-0.55, p<0.041). GMF probably affected central baroreflex pathways, diminishing SMF direct stimulatory effect on sinocarotid baroreceptors and on baroreflex-mediated vasodilatatory response. The results herein may thus point to arterial baroreflex as a possible physiological mechanism for magnetic-field cardiovascular effect. It seems that geomagnetic disturbance modifies artificial magnetic fields biological effect and should be taken into consideration in the assessment of the final effect.

Magnetic resonance imaging with high static magnetic fields (SMFs) has become widely used for medical imaging purposes because SMFs cause fewer genotoxic side effects than ionizing radiation (IR). However, the effect of exposure to high SMFs on global transcription is little understood. We demonstrate that genes involved in motor activity, actin binding, cell adhesion, and cuticles are transiently and specifically induced following exposure to 3 or 5 T SMF in the experimental model metazoan Caenorhabditis elegans. In addition, transient induction of hsp12 family genes was observed after SMF exposure. The small-heat shock protein gene hsp16 was also induced but to a much lesser extent, and the LacZ-stained population of hsp-16.1::lacZ transgenic worms did not significantly increase after exposure to SMFs with or without a second stressor, mild heat shock. Several genes encoding apoptotic cell-death activators and secreted surface proteins were upregulated after IR, but were not induced by SMFs. Real-time quantitative RT-PCR analyses for 12 of these genes confirmed these expression differences between worms exposed to SMFs and IR. In contrast to IR, exposure to high SMFs did not induce DNA double-strand breaks or germline cell apoptosis during meiosis. These results suggest that the response of C. elegans to high SMFs is unique and capable of adjustment during long exposure, and that this treatment may be less hazardous than other therapeutic tools.