Static magnetic fields affect cell size, shape, orientation, and membrane surface of human glioblastoma cells, as demonstrated by electron, optic, and atomic force microscopy.

BACKGROUND: It is common knowledge that static magnetic fields (SMF) do not interact with living cells; thus, fewer studies of SMF compared with variable magnetic fields are carried out. However, evidence demonstrated that SMF affect cellular structures. To investigate the effect of exposure to increasing doses of SMF on cell morphology, human glioblastoma cells were exposed to SMF ranging between 80 and 3,000 G (8 and 300 mT). METHODS: Cell morphology of human glioblastoma cells, derived from a primary culture, was studied by electron and optic microscopy. FITC-phalloidin staining of actin filaments was also investigated. Finally, cell surface structure changes were detected by atomic force microscopy. RESULTS: Scanning electron microscopy demonstrated a dose-dependent cell shape modification, progressive cell detachment, loss of the long villi, and appearance of membrane roughness and blebs. FITC-phalloidin staining confirmed the villi retention and cell dimension decrease. At 3,000 G, the appearance of apoptotic morphology was also observed by transmission electron microscopy. Cell exposed to SMF showed different orientation and alignment when compared with nonexposed cells. The atomic force microscopy of the exposed cells' membrane surfaces demonstrated the disappearance of the ordered surface ripples and furrows typical of the unexposed cells, and the occurrence of surface membrane corrugation at increasing dose exposure CONCLUSIONS: Our experimental procedures demonstrated that exposure to SMF affects not only cell size, shape, and orientation but also human glioblastoma cells' membrane surfaces.     

Three dimensional (3D) analysis of the morphological changes induced by 50 Hz magnetic field exposure on human lymphoblastoid cells (Raji)

Human Raji B lymphoid cells after exposure for 64 h to a 1 mT (rms) 50 Hz sinusoidal magnetic field showed a reorganization of membrane and cytoskeletal components. Atomic force microscopy in air revealed several modifications in 80% of the exposed cells, such as loss of microvilli-like structures followed by progressive appearance of membrane introflections. This change in plasma membrane morphology was also accompanied by a different actin distribution, as detected by phalloidin fluorescence. These observations support our previous hypothesis that electric and magnetic fields may modify the plasma membrane structure.     

Mechanobiology of MG63 osteoblast-like cells adaptation to static magnetic forces

The aim of this study was to explore the biophysical effects of static magnetic field on osteoblastic cells. MG63 cells were exposed to 0.25 and 0.4-T static magnetic fields (SMF). The cell cycle effects were tested by flow cytometry. The differentiation of the cells was assessed by detecting the changes in prostaglandin E2, osteocalcin, and extracellular matrix expression. Membrane fluidity was used to evaluate the alterations in the biophysical properties of cellular membranes after the SMF simulations. Our results show that SMF exposure increases prostaglandin E2 level and extracellular matrix express in MG63 cells. On the other hand, MG63 cells exposed to 0.4-T SMF exhibited a significant decrease in membrane fluidity at 8 h. Based on these findings, it appears reasonable to suggest that SMF affect osteoblastic maturation by increasing membrane rigidity and then inducing differentiation pathway.     

Effect of an aqueous salt solution exposed to weak magnetic fields on the sensitivity of bacterial plasma membrane to reactive oxygen species

It was shown by electroorientation spectroscopy that hydroxyl radicals OH* generated in a Cu(2+)-ascorbate system disturb the barrier properties of the plasma membrane in Escherichia coli K12 cells. It was also found that in water containing small additions of H+, Na+, and Cl-, preliminarily exposed to weak combined permanent (42 microT) and polyfrequency alternating (amplitude 0.06 microT and frequencies 1, 3.7, and 32.2 Hz) magnetic fields, the sensitivity of the plasma membrane to the radical attack considerably decreased, whereas dimethylsulfoxide did not protect active oxygen species in this system. It was assumed that treating the aqueous solution with magnetic fields affects the oxidation of ascorbate. Spectrophotometric measurements did reveal a decrease in the rate of oxidation of ascorbate by Cu2+ ions in a solution preliminarily treated with magnetic fields.     

A STUDY OF THE EFFECTS OF STATIC AND EXTREMELY LOW FREQUENCY MAGNETIC FIELDS ON LIPID PEROXIDATION PRODUCTS IN SUBCELLULAR FIBROBLAST FRACTIONS

Cultured fibroblasts isolated from murine livers by tissue trypsinization were exposed to a static magnetic field (0.490 T) and to extremely low frequency (ELF) magnetic field (50 Hz, 0.020 T). The cultures were exposed to magnetic fields on four consecutive days for exposure times of 2, 4, 8, 16, 32, and 64 min. After such exposures and obtaining of fibroblast subcellular fractions, lipid peroxidation product—malondialdehyde (MDA) was measured. Increased peroxidation of fibroblasts' membrane structures exposed to an ELF magnetic field was observed in subcellular fractions—microsomal, mitochondrial, and nuclear. No changes in peroxidation of membrane structures were found in fibroblasts exposed to a static magnetic field.     

Effects of extremely low frequency (50 Hz) magnetic field on morphological and biochemical properties of human keratinocytes

We investigated the effects on human keratinocytes (HaCaT) of exposure to a sinusoidal magnetic field of 2 mT (50 Hz). These cells are a good model for studying interaction of nonionising radiation, because they are not shielded from fields in vivo and also because they are resistant to both mechanical and thermal stimuli. We performed scanning microscopy which showed modification in shape and morphology in exposed cells. This modification is related to differential actin distribution as revealed by phalloidin fluorescence analysis. Moreover, the exposed cells show increased clonogenic capacity, as well as increased cellular growth as showed by clonogenicity assays and growth curves. Indirect immunofluorescence analysis using a fluorescent antibody against involucrin and beta4 integrin, which are respectively differentiation and adhesion markers, revealed an increase of involucrin expression and segregation of beta4 integrin in the cell membrane in cells exposed to 50 Hz; a higher percentage of the exposed cells shows a modified pattern of adhesion and differentiation markers. We also present evidence that exposure of HaCaT cells can interfere with protein kinase activity. Our observations confirm the hypothesis that electromagnetic fields at 50 Hz may modify cell membrane morphology and interfere with initiation of the signal cascade pathway and cellular adhesion.     

Effects of exposure to a time-varying 1.5 T magnetic field on the neurotransmitter-activated increase in intracellular Ca in relation to actin fiber and mitochondrial functions in bovine adrenal chromaffin cells

Background

It has been reported that exposure to electromagnetic fields influences intracellular signal transduction. We studied the effects of exposure to a time-varying 1.5 T magnetic field on membrane properties, membrane cation transport and intracellular Ca²⁺ mobilization in relation to signals. We also studied the mechanism of the effect of exposure to the magnetic field on intracellular Ca²⁺ release from Ca²⁺ stores in adrenal chromaffin cells.

Methods

We measured the physiological functions of ER, actin protein, and mitochondria with respect to a neurotransmitter-induced increase in Ca²⁺ in chromaffin cells exposed to the time-varying 1.5 T magnetic field for 2 h.

Results

Exposure to the magnetic field significantly reduced the increase in [Ca²⁺]i. The exposure depolarized the mitochondria membrane and lowered oxygen uptake, but did not reduce the intracellular ATP content. Magnetic field-exposure caused a morphological change in intracellular F-actin. F-actin in exposed cells seemed to be less dense than in control cells, but the decrease was smaller than that in cytochalasin D-treated cells. The increase in G-actin (i.e., the decrease in F-actin) due to exposure was recovered by jasplakinolide, but inhibition of Ca²⁺ release by the exposure was unaffected.

Conclusions and general significance

These results suggest that the magnetic field-exposure influenced both the ER and mitochondria, but the inhibition of Ca²⁺ release from ER was not due to mitochondria inhibition. The effect of eddy currents induced in the culture medium may indirectly influence intracellular actin and suppress the transient increase in [Ca²⁺]i.     

Decreased chemotaxis of human peripheral phagocytes exposed to a strong static magnetic field

The chemotaxis of human peripheral phagocytes, neutrophils and monocytes was examined in a strong static magnetic field (0.317+/-0.012 Tesla). The chemotaxis of the suspension of purified neutrophils and monocytes was tested in the Boyden chamber using C5a as a chemotactic signal. The chambers were placed into a temperature regulated (36.6 degrees C) equipment producing a strong static magnetic field (0.317 Tesla) for 60 minutes. The movement of cells proceeded into a nitrocellulose membrane toward the north-pole of the magnet, i.e. in the direction of the Earth's gravitational pull. The C5a induced chemotaxis of human neutrophils decreased significantly in the strong static magnetic field. Monocytes were not significantly effected. The strong static magnetic field decreased the chemotactic movement of neutrophils and this phenomenon may have implications when humans are exposed to magnetic resonance imaging for extended periods of time.     

外加磁场作用下磁性Fe3O4纳米粒子对肝癌细胞增殖和凋亡的影响

目的：观察磁性四氧化三铁（Fe3O4）纳米粒子对肝癌细胞的体外作用,并研究外加稳恒磁场（SMF）或交变磁场（EMF）对FeID4纳米粒子作用的影响。方法：光镜下观察CBRH-7919细胞对Fe3O4纳米粒子的吞噬作用;MTT法检测Fe304纳米粒子对大鼠肝癌细胞株CBRH-7919的毒性及外加磁场的影响;流式细胞术检测外加磁场作用下Fe3O4纳米粒子对细胞凋亡及线粒体膜电位的影响。结果：光镜下可见CBRH-7919细胞吞噬大量Fe3O4纳米粒子入胞浆,且交变磁场作用下细胞的吞噬量增加。30-100μg／mLFe3O4纳米粒子作用于CBRH-7919细胞未产生细胞毒性,稳恒磁场对其作用无影响,而交变磁场能增加Fe3O4纳米粒子的毒性,使细胞活性降低、凋亡率增加、线粒体膜电位降低。结论：交变磁场能增加CBRH-7919细胞对Fe3O4纳米粒子的吞噬并产生细胞毒性。     

Modulation of membrane composition of swine vascular smooth muscle cells by homologous lipoproteins in culture

Swine vascular smooth muscle cells were exposed to homologous low-density or high-density lipoprotein fractions for 24 h. Total cell membranes were isolated from the post-nuclear supernatant of the cell homogenates, fractionated by sucrose density gradient centrifugation and characterized by enzyme assays. The membrane fraction with the lowest density was enriched in plasma membrane marker enzymes. Cholesterol analysis showed that cells exposed to low-density lipoprotein had higher cholesterol-to-protein ratios in total cells, total cell membranes and individual membrane fractions than had the cells exposed to high-density lipoproteins. Cholesterol-to-phospholipid ratios of the plasma membrane-enriched fraction from cells exposed to low-density lipoprotein were higher than the same membrane fraction of cells exposed to high-density lipoprotein. Studies with iodinated lipoproteins showed that these compositional changes could not be due to lipoprotein contamination. Membrane microviscosity was determined by fluorescence depolarization with diphenylhexatriene and the microviscosity of the plasma membrane-enriched fraction was different in the cells exposed to the two different lipoprotein fractions. This difference in membrane microviscosity was significant only when the medium cholesterol content was 40 μg per ml or greater; cells exposed to low-density lipoprotein gave membranes with higher microviscosity.These results demonstrate that the properties of vascular smooth muscle cell membranes are influenced by exposure of the cells to homologous lipoprotein fractions.     

Effect of magnetic field exposure on calcium channel currents using patch clamp technique

Calcium influxes through the membrane of PC-12D cells were measured under exposure to DC biased AC magnetic fields in resonant conditions of the ion cyclotron and the ion parametric resonance hypotheses and compared with influxes in cells without exposure to the magnetic field. After cancellation of the geomagnetic field, the cells were exposed to the horizontal fields generated by a current sheet, a planar sheet of conductor which generated a satisfactorily homogeneous horizontal magnetic field on the stage of a microscope without hindering treatment of a cell under observation. At or near any resonant conditions, no change in calcium influx could be detected under standard patch clamp conditions.     

The use of nonlinear dielectric spectroscopy to monitor the bioelectromagnetic effects of a weak pulsed magnetic field in real time

Nonlinear dielectric spectroscopy (NLDS) was used to detect interaction of a pulsed magnetic field (PMF) with membrane protein dynamics in aggregating Dictyostelium discoideum amoebae. In the experiments reported here, a strong nonlinear dielectric response of Dictyostelium discoideum cells is shown, and a distinctive nonlinear dielectric response of cells previously exposed to PMF is shown. The method of NLDS is shown to be capable of monitoring and charting the dynamic frequency response of the cell to an electromagnetic field.     

The effects of pulsed magnetic field exposure on the permeability of leukemia cancer cells

Purpose: The newer methods of cancer treatment require new idea of drug delivery in cancer cells. Due to numerous researches electromagnetic field affect on cell function and cell membrane for possible therapeutic and drug delivery. In this article, we determined in vitro uptake of fluorescent dyes into the attached K562 cells due to time-varying magnetic field exposure. Method and material: The K562 cells were exposed to magnetic pulses via Magstim stimulator and double 70?mm coil. The strength and duration of pulses in all experiments were the same and three different frequencies of 0.25, 1 and 10?Hz pulses for 56, 112 and 28 numbers of pulses were applied (nine experimental groups) and uptake of Ly and PI was measured in each group. Result: Our results show that magnetic field can efficiently increase permeability. Among the treatment groups, the system gives the optimal permeabilization when cells are exposed to a train of 28 pulses with 1?Hz frequency.     

Vacuolar symplast formation is due to highly permeable gap junctions between the tonoplast and endoplasmic reticulum membrane

An NMR method with a pulsed magnetic field gradient was applied to study changes in water permeability of the vacuolar symplast in maize (Zea mays L.) seedling roots treated with various inhibitors of cell metabolism. The results were qualitatively analogous to literature data on conductivity changes of intercellular gap junctions in animal cells exposed to similar treatments. Electron microscopy examination of root cells provided evidence for the existence of membrane contacts between the endoplasmic reticulum and the tonoplast. It is supposed that vacuoles of neighboring plant cells are interconnected through highly dynamical gap junctions between the tonoplast and the endoplasmic reticulum membrane.     

Effects of static magnetic fields on growth of Paramecium caudatum

Little is known about the influence of magnetic fields on growth of primitive eukaryotes such as the ciliate Paramecium. The latter are known to exhibit interesting characteristics such as electrotaxis, gravitaxis, and membrane excitability not commonly encountered in higher organisms. This preliminary study reports the effects of static magnetic fields on growth of Paramecium caudatum. The microorganisms were either permanently or 24 h on-and-off exposed to North and South polarity magnetic fields of average field gradient 4.3 T/m, for a period of 96 h. The growth rate and lag phase of all exposed populations were not significantly different from control ones exposed to normal geomagnetic field (P > .05). However, a significant negative shift in t(max) (time taken for maximum growth) of 10.5%-12.2% and a significant decrease (P < .05) in population size of 10.2%-15.1% during the 96 h of experimental conditions were recorded for exposed populations compared to control. Our results suggest that magnetic fields, irrespective of polarity and exposure period reduce Paramecium growth by triggering early senescence of the population. The mechanisms underlying the small changes in population growth are unknown at this level, but various hypotheses have been suggested, including disorganization of swimming patterns resulting from (i) changes in cell membrane electric potential due to high speed movement through a gradient magnetic field and (ii) thermodynamic effect of anisotropic magnetic energies on cell membrane components affecting functioning of calcium channels. Altered swimming movements could in turn affect highly orchestrated processes such as conjugation, essential for survival of the organisms during development of adverse environmental conditions as thought to occur in the closed culture system used in this study.     

Effect of 50 Hz, 0.2 mT magnetic fields on RBC properties and heart functions of albino rats

In this work the effect of sinusoidal 50 Hz, 0.2 mT magnetic fields on the red blood cells (RBCs) and heart functions of Albino rats were investigated. Twenty-four male Albino rats were equally divided into four groups, A, B, C, and D. Animals from groups B were continuously exposed to the magnetic field for 15 days; and groups C and D, for 30 days. Group A was used as control. Animals from group D were kept after exposure to the magnetic field for a period of 45 days for delayed effect studies. The osmotic fragility and shape of RBCs' membrane and hemoglobin (Hb) structure tests were carried out for all groups. The dielectric relaxation of Hb molecules was measured in the frequency range of 0.1-10 MHz and the dielectric increment (Deltaepsilon), relaxation time (tau), molecular radius (r), and Cole-Cole parameter (alpha) were calculated for all groups. The ECG was measured for all animals before and after exposure to the magnetic field. The results indicated that exposure of the animals to 50 Hz, 0.2 mT magnetic fields resulted in the decrease of RBCs membrane elasticity and permeability and changes in the molecular structure of Hb. The ECG of the exposed animals was considerably altered. The data also indicated that there was no sign of repair in the newly generated RBCs structure and the ECG after removing the animals from the magnetic field, which indicates that the blood generating system was severely injured. The injuries in the heart of the animals were attributed to the loss of some physiological functions of the RBCs as a result of exposures of the rats to the magnetic field.     

The Effect of ELF Magnetic Field on Tumor Growth after Electrochemotherapy

From a fundamental point of view, chemotherapy is the most widely used treatment for cancers despite its side effects on normal cells and tissues. Electrochemotherapy (ECT) is a method for increasing the permeability of cancer cells to drugs and, hence, decreasing their dosage. It apparently creates electropores on the cell membrane using electric pulses. ECT can decrease tumor volume; but this effect is not permanent, and partial regrowth has been reported. The aim of this study was to investigate the potential of magnetic fields in preventing the regrowth of tumors after ECT. Tumoral Balb/c mice were exposed to a magnetic field (15 mT, 50 Hz) for 12 days after treating additionally with 70 V/cm electric pulses and bleomycin at the first day. The magnetic field caused a significant reduction in tumor volumes, while there was no significant difference between the ECT and the electroporation with ECT and magnetic field groups. The exploited magnetic field (15 mT, 50 Hz) could decrease the tumor growth rate significantly, without any effect on ECT efficiency.     

Rapid, high-yield purification of cell surface membrane using colloidal magnetite coated with polyvinylamine: sedimentation versus magnetic isolation

A new technique for the magnetic isolation of external plasma membrane from Dictyostelium discoideum is described and compared to a previously published procedure employing sedimentation of silica-coated plasma membrane. The magnetic isolation technique involves coating intact cells with a polyvinylamine-magnetite colloid and overcoating with polyacrylate to form a dense pellicle. The magnetite pellicle totally coated the cells and was not internalized. Coated cells were lysed and membrane fragments retrieved from the cell homogenate using a diverging field electromagnet. The membrane obtained in such a manner was analyzed for marker enzyme activity and cell surface label. The plasma membrane was obtained in high yield (42%) with an average purification of 8-fold. The polyvinylamine-magnetite pellicle shielded the external plasma membrane face to proteolysis by papain and pronase. It also acted as a barrier to alpha-methylmannoside in concanavalin A-carbohydrate competition studies.     

Enhancement of the hydrolysis activity of F0F1‐ATPases using 60 Hz magnetic fields

The effects of extremely low frequency (ELF) magnetic fields on membrane F₀F₁‐ATPase activity have been studied. When the F₀F₁‐ATPase was exposed to 60 Hz magnetic fields of different magnetic intensities, 0.3 and 0.5 mT magnetic fields enhanced the hydrolysis activity, whereas 0.1 mT exposure caused no significant changes. Even if the F₀F₁‐ATPase was inhibited by N,N‐dicyclohexylcarbodiimide, its hydrolysis activity was enhanced by a 0.5 mT 60 Hz magnetic field. Moreover, when the chromatophores which were labeled with F‐DHPE were exposed to a 0.5 mT, 60 Hz magnetic field, it was found that the pH of the outer membrane of the chromatophore was unchanged, which suggested that the magnetic fields used in this work did not affect the activity of F0. Taken together, our results show that the effects of magnetic fields on the hydrolysis activity of the membrane F₀F₁‐ATPases were dependent on magnetic intensity and the threshold intensity is between 0.1 and 0.3 mT, and suggested that the F1 part of F₀F₁‐ATPase may be an end‐point affected by magnetic fields. Bioelectromagnetics 30:663–668, 2009. © 2009 Wiley‐Liss, Inc.     

0.2 T magnetic field inhibits angiogenesis in chick embryo chorioallantoic membrane

Inhibition of angiogenesis is a major target in the fight against cancer and other diseases. Although the effects of static magnetic fields on cancer development and cell growth have been investigated, effects on angiogenesis have received no attention so far. In this study we report the effects on angiogenesis of exposure to 0.2 T static magnetic field. Angiogenesis was analyzed using the chick embryo chorioallantoic membrane assay. Exposure to 0.2 T static magnetic field was achieved by placing the eggs for 3 hr in the isocentre of the magnet of a sectorial magnetic resonance tomograph used in clinical practice. In sham exposed specimens treated with phosphate buffered saline (negative control), no significant vascular reaction was detectable; 3 hr exposure to 0.2 T static magnetic field did not affect the basal pattern of vascularization or chick embryo viability. Prostaglandin E1 and fetal calf serum elicited a strong angiogenic response in sham exposed eggs. This angiogenic response was significantly inhibited by 3 hr exposure to 0.2 T static magnetic field. These findings point to possible use of static magnetic field in inhibiting angiogenesis; this effect could be exploited for treatment of cancer and other diseases where excessive angiogenesis is involved.