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

Electromagnetic radiation: a new charming actor in hematopoiesis?

INTRODUCTION

Electromagnetic waves play indispensable roles in life. Many studies addressed the outcomes of Electromagnetic field (EMF) on various biological functions such as cell proliferation, gene expression, epigenetic alterations, genotoxic, and carcinogenic effects, and its therapeutic applications in medicine. The impact of EMF on bone marrow (BM) is of high importance; however, EMF effects on BM hematopoiesis are not well understood.

AREAS COVERED

Publications in English were searched in ISI Web of Knowledge and Google Scholar with no restriction on publication date. A literature review has been conducted on the consequences of EMF exposure on BM non-hematopoietic stem cells, mesenchymal stem cells, and the application of these waves in regenerative medicine. Human blood cells such as lymphocytes, red blood cells and their precursors are altered qualitatively and quantitatively following electromagnetic radiation. Therefore, studying the impact of EMF on related signaling pathways in hematopoiesis and hematopoietic stem cell (HSC) differentiation could give a better insight into its efficacy on hematopoiesis and its potential therapeutic usage.

EXPERT OPINION

In this review, authors evaluated the possible biologic consequences of EMF on the hematopoiesis process in addition to its probable application in the treatment of hematologic disorders.

Application of a static magnetic field as a complementary aid to healing in an in vitro wound model

OBJECTIVE

Static magnetic field (SMF) has long been used as a therapeutic means, though its effects on the activity of cells and the mechanism(s) involved remain unknown. The purpose of this study is to determine the effect of a moderate-intensity SMF on the activity, growth and migration of mouse embryonic fibroblast (NIH 3T3), aiming to mimic wound healing and to study it in real time.

METHOD

A cell-free area (a scratch with a 200-500µm width) was formed in NIH 3T3 cultured cells and used as a wound model. The effects of a SMF (10, 50, 80 and 100mT) on the survival rate (MTT assay), integrity of cell membranes (lactate dehydrogenase (LDH) assay), the morphology of the cell (circularity, number and length of filopodia), cell orientation, and migration (speed, direction, rate) were studied as a function of the incubation time in a time-lapse manner.

RESULTS

The exposure of cells to SMF at all intensities had no cytotoxic effect, as revealed by the MTT assay. The integrity of the membranes of the SMF-treated cells studied by the LDH assay test showed no effects. The structure of the membrane at the leading edge of the cells changed and showed several filopodia extended parallel to the field direction. The exposure to the SMF elongated the cells and decreased their circularity at SMF 10mT. The migration of the cells from one edge of the gap towards the other was affected by the applied SMF. The maximum and minimum effects were monitored at 80mT and 10mT, respectively. Analysis of cell migration revealed an average directness of 0.73, 0.66, 0.78, 0.78 and 0.69 under SMF 10, 50, 80, 100mT and control, respectively.

CONCLUSION

The morphological and functional changes of the cells in the presence of SMF revealed particular effects on the membrane and cytoskeleton. Cells were affected by physicochemical changes caused by the applied SMF, though the extent of the incurred effects was not a linear function of the field intensity. This low cost, non-invasive approach can be used as a magneto-manipulative means to tailor a practical, independent or complementary means of manipulating the activities of cells and tissues for clinical purposes.

Extremely Low-Frequency Pulsed Magnetic Fields and Multiple Sclerosis: Effects on Neurotransmission Alone or Also on Immunomodulation? Building a Working Hypothesis

This paper outlines the current state of knowledge on the pathology and treatment of multiple sclerosis (MS) and critically analyses the vast clinical experience of Sandyk in the use of pulsed magnetic fields of 5 Hz at 7.5 pT to treat many symptoms of MS. A complete regression of symptoms, or at least a major improvement, is sometimes so rapid as to suggest that ELF fields exert a greater effect on axonal and synaptic neurotransmission than on the processes leading to demyelination. Pulsed magnetic fields of 50–100 Hz and a few mT (whose flux intensity is 109 times greater than that of the fields used by Sandyk) have been seen to induce profound morphological changes (the Marinozzi effect) in the plasma membrane of several cell types, including Raji human lymphoblastoid cells. These observations underlie the author's hypothesis on the possible use of such fields in the treatment of MS. Indeed, these fields should induce the functional arrest of the cells (B- and T-lymphocytes, macrophages, microglia, dendritic cells) of the MS plaque, thereby providing an ‘electromagnetic immunomodulatory boost’ to the effects of drug therapy. To test this working hypothesis, it is suggested that preliminary experimental research be carried out to ascertain: 1) the Marinozzi effect in vivo; 2) the Marinozzi effect on microglia and dendritic cells; and 3) the duration of the membrane changes and their relaxation rate. ELF magnetic fields in the picotesla and millitesla ranges are aimed at improving neurotransmission and correcting local immune pathology, respectively. Both types of field might find application in the treatment of MS patients who no longer respond to or tolerate currently used drugs.

Shielding of the Geomagnetic Field Alters Actin Assembly and Inhibits Cell Motility in Human Neuroblastoma Cells

Accumulating evidence has shown that absence of the geomagnetic field (GMF), the so-called hypomagnetic field (HMF) environment, alters the biological functions in seemingly non-magnetosensitive cells and organisms, which indicates that the GMF could be sensed by non-iron-rich and non-photo-sensing cells. The underlying mechanisms of the HMF effects on those cells are closely related to their GMF sensation but remain poorly understood so far. Previously, we found that the HMF represses expressions of genes associated with cell migration and cytoskeleton assembly in human neuroblastoma cells (SH-SY5Y cell line). Here, we measured the HMF-induced changes on cell morphology, adhesion, motility and actin cytoskeleton in SH-SY5Y cells. The HMF inhibited cell adhesion and migration accompanied with a reduction in cellular F-actin amount. Moreover, following exposure to the HMF, the number of cell processes was reduced and cells were smaller in size and more round in shape. Furthermore, disordered kinetics of actin assembly in vitro were observed during exposure to the HMF, as evidenced by the presence of granule and meshed products. These results indicate that elimination of the GMF affects assembly of the motility-related actin cytoskeleton, and suggest that F-actin is a target of HMF exposure and probably a mediator of GMF sensation.

Weak power frequency magnetic field acting similarly to EGF stimulation, induces acute activations of the EGFR sensitive actin cytoskeleton motility in human amniotic cells

In this article, we have examined the motility-related effects of weak power frequency magnetic fields (MFs) on the epidermal growth factor receptor (EGFR)-sensitive motility mechanism, including the F-actin cytoskeleton, growth of invasive protrusions and the levels of signal molecules in human amniotic epithelial (FL) cells. Without extracellular EGF stimulation, the field stimulated a large growth of new protrusions, especially filopodia and lamellipodia, an increased population of vinculin-associated focal adhesions. And, an obvious reduction of stress fiber content in cell centers was found, corresponding to larger cell surface areas and decreased efficiency of actin assembly of FL cells in vitro, which was associated with a decrease in overall F-actin content and special distributions. These effects were also associated with changes in protein content or distribution patterns of the EGFR downstream motility-related signaling molecules. All of these effects are similar to those following epidermal growth factor (EGF) stimulation of the cells and are time dependent. These results suggest that power frequency MF exposure acutely affects the migration/motility-related actin cytoskeleton reorganization that is regulated by the EGFR-cytoskeleton signaling pathway. Therefore, upon the MF exposure, cells are likely altered to be ready to transfer into a state of migration in response to the stimuli.

ELF-MF transiently increases skeletal myoblast migration: possible role of calpain system

PURPOSE

Cell migration is crucial for myogenesis since it is required for the alignment and fusion of myoblast. Ca(2+) signals are involved in regulating myoblast migration and an extremely low frequency (ELF) magnetic field (MF) increases intracellular calcium levels in C2C12 myoblast. This study was aimed at investigating whether ELF-MF could affect myoblast migration. As calpains contribute to the regulation of myoblast motility, the effect of ELF-MF on μ- and m-calpain was also investigated.

MATERIALS AND METHODS

The effect of ELF-MF (1 mT; 50 Hz) on C2C12 cell motility was observed by wound-healing assay. Protein expression of calpains, calpastatin, myristoylated alanine-rich C-kinase substrate (MARCKS) and vinculin were examined by Western blot analysis. Casein zymography and immunofluorescence analysis were carried out to evaluate, respectively, activity levels of calpains and intracellular distribution of calpains, calpastatin and actin.

RESULTS

Exposure to ELF-MF resulted in a transient but significant increase of myoblast migration. This stimulatory effect was associated with a marked increase of μ- and m-calpain activity followed by the concomitant variation in their subcellular localization. No significant changes in intracellular distribution and protein levels of calpastatin were detected. Finally, a significant decrease of MARCKS expression and modifications of actin dynamics were reported.

CONCLUSIONS

This study clearly outlines an involvement of calpains in ELF-MF-mediated myoblast migration.

Effect of magnetic fields on antioxidative defense and fitness-related traits of Baculum extradentatum (insecta, phasmatodea)

This study aimed to determine the effect of magnetic fields on the antioxidative defense and fitness-related traits of Baculum extradentatum. Following exposure to magnetic fields, antioxidative defense (superoxide dismutase (SOD), catalase (CAT) activities, and total glutathione (GSH) content) and fitness-related traits (egg mortality, development dynamics, and mass of nymphs) were monitored in nymphs. The experimental groups were: control (kept out of influence of the magnets), a group exposed to a constant magnetic field (CMF) of 50 mT, and a group exposed to an alternating magnetic field (AMF) of 50 Hz, 6 mT. We found increased SOD and CAT activities in animals exposed to constant and AMFs, whereas GSH activity was not influenced by experimental magnetic fields. No differences were found in egg mortality between control and experimental groups. Significant differences in the time of development between the control and the CMF group were observed, as well as between the CMF and the AMF group. No differences were found in the mass of the nymphs between the three experimental groups. In conclusion, CMF and AMF have the possibility to modulate the antioxidative defense and some of the fitness-related traits in B. extradentatum.

Gene expression profile in cultured human umbilical vein endothelial cells exposed to a 300 mT static magnetic field

In a previous investigation we reported that exposure to a moderate (300 mT) static magnetic field (SMF) causes transient DNA damage and promotes mitochondrial biogenesis in human umbilical vein endothelial cells (HUVECs). To better understand the response of HUVECs to the 300 mT SMF, a high-quality subtracted cDNA library representative of genes induced in cells after 4 h of static magnetic exposure was constructed. The global gene expression profile showed that several genes were induced after the SMF exposure. The characterized clones are involved in cell metabolism, energy, cell growth/division, transcription, protein synthesis, destination and storage, membrane injury, DNA damage/repair, and oxidative stress response. Quantitative real-time polymerase chain reaction (qRT-PCR) experiments were performed at 4 and 24 h on four selected genes. Their expression profiles suggest that HUVEC's response to SMF exposure is transient. Furthermore, compared to control cells, an up-regulation of several genes involved in cell growth and division was observed. This up-regulation is likely to be the cause of the slight, but significant, increase in cell proliferation at 12 h post-treatment. These results provide additional support to the notion that SMFs may be harmless to human health, and could support the rationale for their possible use in medical treatments.

Phagocytosis of dying cells: influence of smoking and static magnetic fields

It is becoming evident that failure in the removal of dying cells causes and/or promotes the onset of chronic diseases. Impairment of phagocytosis of apoptotic cells can be due not only to genetic or molecular malfunctioning but also to external/environmental factors. Two of these environmental factors have been recently reported to down regulate the clearance of apoptotic cells: cigarette smoke and static magnetic fields. Cigarette smoke contains highly reactive carbonyls that modify proteins which directly/indirectly affects cellular function. Human macrophages interacting with carbonyl or cigarette smoke modified extracellular matrix (ECM) proteins dramatically down regulated their ability to phagocytose apoptotic neutrophils. It was postulated that changes in the ECM environment as a result of cigarette smoke affect the ability of macrophages to remove apoptotic cells. This decreased phagocytic activity was as a result of sequestration of receptors involved in the uptake of apoptotic cells towards that of recognition of carbonyl adducts on the modified ECM proteins leading to increased macrophage adhesion. Downregulation of the phagocytosis of apoptotic cells was also described when performed in presence of static magnetic fields (SMFs) of moderate intensity. SMFs have been reported to perturb distribution of membrane proteins and glycoproteins, receptors, cytoskeleton and trans-membrane fluxes of different ions, especially calcium [Ca(2+)]i, that in turn, interfere with many different physiological activities, including phagocytosis. The effects of cigarette smoke and SMF on the phagocytosis of dying cells will be here discussed.

Effects of the Electromagnetic field, 60 Hz, 3 µT, on the hormonal and metabolic regulation of undernourished pregnant rats

Epidemiological studies have implicated maternal protein-calorie deficiency as an important public health problem in developing countries. Over the last decades, a remarkable diffusion of electricity and an increased level of the electromagnetic field (EMF) in the environment have characterized modern societies. Therefore, researchers are concerned with the biological effects of 50-60 Hz, EMF. The aim of this paper is to show the effects of EMF of 60 Hz, 3 μT, exposure for two hours per day in the regulation of the hormonal and metabolic concentrations in pregnant rats, which were fed by Regional Basic Diet (RBD) during their pregnancy as compared with pregnant rats fed a standard diet. Pregnant rats exposed to EMF of 60 Hz, 3 μT, over the pregnancy and fed with RBD presented an increase in glucose release when compared with the Group subjected only to the RBD ration. Rats fed RBD presented a decrease in their insulin and cortisol serum levels when compared with the Group fed with casein. The T3 and T4 concentrations presented the greatest variation among the Groups. The relation T4:T3 was much exaggerated in the Group subjected to RDB and exposed to EMF when compared to the others. In conclusion, the group subjected to the association of EMF and undernutrition suffered a decrease in its serum concentration of T4 and T3 when compared to the well-nourished group and the relationship T4:T3 in the former group was almost eighteen-fold the later one.

Changes of leukocyte adherence ability under the influence of magnetic field in the course of a treatment of patients with laryngeal and pharyngeal carcinoma

The authors were monitoring adherence ability of T lymphocytes in vitro in patients with laryngeal and pharyngeal carcinoma at the presence of tumor-specific and viral LDH antigen. The results were assessed and expressed in percent of non adherent T lymphocytes (NAL). First, NAL in patients before initiating the treatment was compared with NAL control group (voluntary blood donors). The ability of the adherence in T lymphocytes in the control group is statistically significantly higher. Further on, NAL in the course of a successful oncological treatment was monitored at the interval of 6 months following the treatment, and further on at yearly intervals. NAL level drops statistically significantly within 6 months and then hold on at levels with no statistical difference unlike the control group, however, the ability of T lymphocyte in patients to adhere remains statistically significantly lower. Statistically significantly higher levels of NAL are at the presence of LDH viral antigen. Further on, the authors were following the influence of magnetic sinusoidal field of power frequency (50 Hz) of a low induction (0.5, 0.1, and 0.05 mT) on NAL. NAL values under the influence of an experimental magnetic field before initiating the treatment as well as in the course of a successful oncological treatment are statistically significantly lower. It means that magnetic filed increases the adherence ability of T lymphocytes in patients with laryngeal and pharyngeal cancer in vitro.

Effects of sinusoidal electromagnetic field on structure and function of different kinds of cell lines

This study investigated that whether a 2 mT, 60 Hz, sinusoidal electromagnetic field (EMF) alters the structure and function of cells. This research compared the effects of EMF on four kinds of cell lines: hFOB 1.19 (fetal osteoblast), T/G HA-VSMC (aortic vascular smooth muscle cell), RPMI 7666 (B lymphoblast), and HCN-2 (cortical neuronal cell). Over 14 days, cells were exposed to EMF for 1, 3, or 6 hours per day (hrs/d). The results pointed to a cell type-specific reaction to EMF exposure. In addition, the cellular responses were dependent on duration of EMF exposure. In the present study, cell proliferation was the trait most sensitive to EMF. EMF treatment promoted growth of hFOB 1.19 and HCN-2 compared with control cells at 7 and 14 days of incubation. When the exposure time was 3 hrs/d, EMF enhanced the proliferation of RPMI 7666 but inhibited that of T/G HA- VSMC. On the other hand, the effects of EMF on cell cycle distribution, cell differentiation, and actin distribution were unclear. Furthermore, we hardly found any correlation between EMF exposure and gap junctional intercellular communication in hFOB 1.19. This study revealed that EMF might serve as a potential tool for manipulating cell proliferation.

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.

Extremely low frequency electromagnetic field exposure promotes differentiation of pituitary corticotrope-derived AtT20 D16V cells

The pituitary corticotrope-derived AtT20 D16V cell line responds to nerve growth factor (NGF) by extending neurite-like processes and differentiating into neurosecretory-like cells. The aim of this work is the study of the effect of extremely low frequency electromagnetic fields (ELF-EMF) at a frequency of 50 Hz on these differentiation activities. To establish whether exposure to the field could influence the molecular biology of the cells, they were exposed to a magnetic flux density of 2 milli-Tesla (mT). Intracellular calcium ([Ca2+]i) and intracellular pH (pHi) were monitored in single exposed AtT20 D16V cells using fluorophores Indo-1 and SNARF for [Ca2+]i and pHi, respectively. Single-cell fluorescence microscopy showed a statistically significant increase in [Ca2+]i followed by a drop in pHi in exposed cells. Both scanning electron microscopy (SEM) and transmission microscopy of exposed AtT20 D16V cells show morphological changes in plasma membrane compared to non-exposed cells; this modification was accompanied by a rearrangement in actin filament distribution and the emergence of properties typical of peptidergic neuronal cells-the appearance of secretory-like granules in the cytosol and the increase of synaptophysin in synaptic vesicles, changes typical of neurosecretory-like cells. Using a monoclonal antibody toward the neurofilament protein NF-200 gave additional evidence that exposed cells were in an early stage of differentiation compared to control. Pre-treatment with 0.3 microM nifedipine, which specifically blocks L-type Ca2+ channels, prevented NF-200 expression in AtT20 D16V exposed cells. The above findings demonstrate that exposure to 50 Hz ELF-EMF is responsible for the premature differentiation in AtT20 D 16 V cells.

Effect of extremely low frequency electromagnetic fields (ELF-EMF) on Kaposi's sarcoma-associated herpes virus in BCBL-1 cells

Association between extremely low frequency electromagnetic fields (ELF-EMF) and human cancers is controversial, and few studies have been conducted on their influence on oncogenic viruses. We studied the effects of 1 mT, 50 Hz sine waves, applied for 24-72 h, on Kaposi's sarcoma (KS)-associated herpesvirus (KSHV or HHV-8) in BCBL-1, a latently infected primary effusion lymphoma (PEL) cell line. ELF-EMF exposure did not affect the growth and viability of BCBL-1 cells, either stimulated or not with TPA. The total amount of KSHV DNA detected in ELF-EMF exposed cultures not stimulated with TPA did not differ from that of the unexposed controls (P = ns). However, in the presence of TPA stimulation, total KSHV DNA content was found higher in ELF-EMF exposed than in control BCBL-1 cultures (P = .024) at 72 h exposure, but not earlier. Viral DNA increase significantly correlated with increased mean fluorescence intensity/cell for the lytic antigen gp K8.1A/B (P < .01), but not with percentage of gp K8.1A/B-positive cells or of cells containing virions. Viral progeny produced under ELF-EMF exposure consisted mainly of defective viral particles.

Time dependent modifications of Hep G2 cells during exposure to static magnetic fields

Morphological modifications, i.e., cell shape, cell surface sugar residues, cytoskeleton, and apoptosis of Hep G2 cells during 24 h exposure to 6 mT static magnetic field (static MF) were studied by means of light and electron microscopy and cytochemistry. Progressive modifications of cell shape and surface were observed during the entire period of exposure to static MF. Control cells were polyhedric with short microvilli covering the cell surface, while those exposed to static MF, were elongated with many irregular microvilli randomly distributed on the cell surface. At the end of the exposure period, the cells had a less flat shape due to partial detachment from the culture dishes. However, throughout the period of exposure under investigation, the morphology of the organelles remained unmodified and cell proliferation was only partially affected. In parallel with cell shape changes, the microfilaments and microtubules, as well as the quantity and distribution of surface ConA-FITC and Ricinus communnis-FITC labeling sites, were modified in a time dependent manner. Apoptosis, which was almost negligible at the beginning of experiment, increased to about 20% after 24 h of continuous exposure. The induction of apoptosis was likely due to the increment of [Ca2+]i during exposure. In conclusion, the data reported in the present work indicates that 6 mT static MF exposure exerts time dependent biological effects on Hep G2 cells.

Acute and chronic effects of exposure to a 1-mT magnetic field on the cytoskeleton, stress proteins, and proliferation of astroglial cells in culture

This paper reports the effects of exposure to static, sinusoidal (50 Hz), and combined static/sinusoidal magnetic fields on cultured astroglial cells. Confluent primary cultures of astroglial cells were exposed to a 1-mT sinusoidal, static, or combined magnetic field for 1h. In another experiment, cells were exposed to the combined magnetic field for 1, 2, and 4h. The hsp25, hsp60, hsp70, actin, and glial fibrillary acidic protein contents of the astroglial cells were determined by immunoblotting 24h after exposure. No significant differences were seen between control and exposed cells with respect to their contents of these proteins, neither were any changes in cell morphology observed. In a third experiment to determine the effect of a chronic (11-day) exposure to a combined 1-mT static/sinusoidal magnetic field on the proliferation of cultured astroglial cells, no significant differences were seen between control, sham-exposed, or exposed cells. These results suggest that exposure to 1-mT sinusoidal, static, or combined magnetic fields has no significant effects on the stress, cytoskeletal protein levels in, or proliferation of cultured astroglial cells.

Visualization of cytoskeletal elements by the atomic force microscope

We describe a novel application of atomic force microscopy (AFM) to directly visualize cytoskeletal fibers in human foreskin epithelial cells. The nonionic detergent Triton X-100 in a low concentration was used to remove the membrane, soluble proteins, and organelles from the cell. The remaining cytoskeleton can then be directly visualized in either liquid or air-dried ambient conditions. These two types of scanning provide complimentary information. Scanning in liquid visualizes the surface filaments of the cytoskeleton, whereas scanning in air shows both the surface filaments and the total "volume" of the cytoskeletal fibers. The smallest fibers observed were ca. 50 nm in diameter. The lateral resolution of this technique was ca.20 nm, which can be increased to a single nanometer level by choosing sharper AFM tips. Because the AFM is a true 3D technique, we are able to quantify the observed cytoskeleton by its density and volume. The types of fibers can be identified by their size, similar to electron microscopy.

Bioeffects of moderate-intensity static magnetic fields on cell cultures

The interaction of static magnetic fields (SMFs) with living organisms is a rapidly growing field of investigation. However, despite the increasing number of studies on the effects of the interaction of SMFs with living organisms, many gaps in our knowledge still remain. One reason why it is extremely important to deeply understand the true mode of action of MFs on living organisms, is the need to protect human health in consideration of the probable future introduction of new technologies such as magnetically levitated trains and the therapeutical use of MFs (e.g. magnetic resonance imaging, MRI, coupling of MF exposure with chemotherapy). The lack of knowledge of the morphological modifications brought about by exposure to moderate-intensity SMFs prompted us to investigate the bioeffects of 6mT SMFs on different cell types, by means of light and electron microscopy, confocal laser scanning microscopy and immuno- or cytochemistry. In the present article we report our own and other data from the literature on the morphological studies of the bioeffects of moderate-intensity SMFs. We focus on morphological modifications related to cell shape, cell surface, cytoskeleton, and plasma membrane expression of molecules and carbohydrate residues. The effects of exposure to moderate-intensity SMF for 24 or 48 h, on apoptosis, on apoptotic related gene products, on macrophagic differentiation and on phagocytosis of apoptotic cells in primary cell cultures (transformed or stabilized cell lines) will be also discussed. Moderate-intensity (6mT) SMFs induced modifications of cell shape, cell surface and cytoskeleton, progressively achieved during the entire period of exposure. In general, at the end of the exposure period, the cells had a less flat shape due to partial detachment from the culture dishes or a more round-elongated shape (in relation to adhesion growth or in suspension growth respectively) with many irregular lamellar microvilli, while the morphology of the organelles remained unmodified. In parallel with cell shape changes, the microfilaments and microtubules, as well as the quantity and distribution of surface ConA-FITC and Ricinus Comm.-FITC labelling sites, were modified in a time-dependent manner. Apoptosis was influenced in a cell type-dependent manner: for some cells spontaneous apoptosis decreased while, for others, it increased to about 20% after 24h of continuous exposure. The induction of apoptosis was likely due to the increment of [Ca(2+)]i during exposure. Cell proliferation was only slightly affected. Indeed, in addition to the cell type, the time of exposure was also an important factor in the intensity of the effects produced. Both apoptotic rate and cell and surface shape were influenced by exposure to SMFs when simultaneously administered with apoptogenic drugs. Apoptotic cells were cleared by an efficient and fast process of phagocytosis mediated by specific epitopes, externalized during the formation of the apoptotic cells, on the dead cells and by specific receptors on the phagocytes (both "professional" and "nonprofessional"). The recognition of apoptotic lymphocytes as well as of control cells exposed for at least 24h to 6mT SMF by liver sinusoidal cells was influenced by the cell surface modifications which both apoptotic or normal exposed cells underwent during the induction of apoptosis or SMF exposure. The degree of macrophagic differentiation of human pro-monocytic U937 cells induced by phorbol ester was decreased by exposure to 6mT SMFs, with a consequent fall in cell adhesion and increased polarization of pseudopodia and cytoplasmic protrusions. Differentiation alone, or in combination with exposure to SMFs, affects distribution and quantity of cell surface carbohydrate residues, surface expression of markers of macrophage differentiation, and phagocytic capability. The increasing amount of data reporting on the bioeffects of SMFs is leading researchers to an understanding of how important it is to fully understand the mode of action of MFs on living organisms. Indeed, even if the perturbations of biological systems by SMFs are sublethal at shorter times of exposure, these perturbations could, especially at longer times of exposure, evolve into a progressive accumulation of modifications, whose ultimate effects still need to be clarified.

Exposure to 50 Hz electromagnetic radiation promote early maturation and differentiation in newborn rat cerebellar granule neurons

The wish of this work is the study of the effect of electromagnetic (EMF) radiations at a frequency of 50 Hz on the development of cerebellar granule neurons (CGN). Granule neurons, prepared from newborn rat cerebellum (8 days after birth), were cultured after plate-seeding in the presence of EMF radiations, with the plan of characterizing their cellular and molecular biochemistry, after exposure to the electromagnetic stimulus. Five days challenge to EMF radiations showed, by the cytotoxic glutamate (Glu) pulse test, a 30% decrease of cells survival, while only 5% of mortality was reported for unexposed sample. Moreover, blocking the glutamate receptor (GluR) with the Glu competitor MK-801, no toxicity effect after CGN challenge to EMF radiations and Glu was detected. By patch-clamp recording technique, the Kainate-induced currents from 6 days old exposed CGN exhibited a significant increase with respect to control cells. Western blot and reverse transcription-polymerase chain reaction (RT-PCR) analyses show that EMF exposure of rats CGN, induces a change in both GluRs proteins and mRNAs expression with respect to control. In addition, the use of monoclonal antibody raised against neurofilament protein (NF-200) reveals an increase in NF-200 synthesis in the exposed CGN. All these results indicate that exposure to non-ionizing radiations contribute to a premature expression of GluRs reducing the life span of CGN, leading to a more rapid cell maturation.

The relations between neurite development and the subcellular structures of hippocampal neuron somata

The relations between neurite development and the subcellular structures of the hippocampal neuron somata have been studied with atomic force microscopy (AFM). The conformation of the neuron was achieved by the synapse-like structures found by AFM scanning along a neurite of the cell. Hippocampal neuron somata were divided into two or three subcellular parts by one or two horizontal grooves. The upper parts increased while the middle and the lower parts decreased with the number and the length of the neurites and the formation of the neurosynapse-like structures. When neurites sufficiently developed, the middle parts were lost and the lower parts became very small. Mitosis inhibitors could prevent the formation of such subcellular structures of hippocampal neuron somata, which was accompanied by the loss of ability to form synapse-like structures. These results suggest that the upper parts are responsible for neuritogenesis while the middle and the lower parts only have indirect effect on it.

Low electromagnetic field (50 Hz) induces differentiation on primary human oral keratinocytes (HOK)

This work concerns the effect of low frequency electromagnetic fields (ELF) on biochemical properties of human oral keratinocytes (HOK). Cells exposed to a 2 mT, 50 Hz, magnetic field, showed by scanning electron microscopy (SEM) modification in shape and morphology; these modifications were also associated with different actin distribution, revealed by phalloidin fluorescence analysis. Moreover, exposed cells had a smaller clonogenic capacity, and decreased cellular growth. Indirect immunofluorescence with fluorescent antibodies against involucrin and beta-catenin, both differentiation and adhesion markers, revealed an increase in involucrin and beta-catenin expression. The advance in differentiation was confirmed by a decrease of expression of epidermal growth factor (EGF) receptor in exposed cells, supporting the idea that exposure to electromagnetic field carries keratinocytes to higher differentiation level. These observations support the hypothesis that 50 Hz electromagnetic fields may modify cell morphology and interfere in differentiation and cellular adhesion of normal keratinocytes.

Evaluation of rat thyroid gland morphophysiological status after three months exposure to 50 Hz electromagnetic field

Objective of our study was to use morphophysiological criteria in order to determine the sensitivity of male rat thyroid gland to an extremely low frequency electromagnetic field (ELF-EMF) influence and the ability of the gland to repair after period of exposure. Animals were exposed to 50Hz, 50-500 microT ELF-EMF for 3 months when a part of them (group I) were sacrificed, while the rest of animals were subjected to recovery evaluation of the gland and sacrificed after 1 (group II), 2 (group III) and 3 (group IV) weeks. Histological and stereological analyses were performed on paraffin and semifine thyroid gland sections. Serum T3 and T4 were also determined. Histological and stereological analyses showed that the volume density of follicular epithelium and thyroid activation index decreased, while the volume density of colloid and capillary network increased in group I, II and III. The values of all these parameters in group IV were similar to corresponding controls. Serum T3 and T4 concentrations were significantly lower in all exposed animals, except in group I. Results of this study demonstrate that after significant morphophysiological changes caused by ELF-EMF exposure thyroid gland recovered morphologically, but not physiologically, during the investigated repair period.

Cellular target of weak magnetic fields: ionic conduction along actin filaments of microvilli

The interaction of weak electromagnetic fields (EMF) with living cells is a most important but still unresolved biophysical problem. For this interaction, thermal and other types of noise appear to cause severe restrictions in the action of weak signals on relevant components of the cell. A recently presented general concept of regulation of ion and substrate pathways through microvilli provides a possible theoretical basis for the comprehension of physiological effects of even extremely low magnetic fields. The actin-based core of microfilaments in microvilli is proposed to represent a cellular interaction site for magnetic fields. Both the central role of F-actin in Ca2+ signaling and its polyelectrolyte nature eliciting specific ion conduction properties render the microvillar actin filament bundle an ideal interaction site for magnetic and electric fields. Ion channels at the tip of microvilli are connected with the cytoplasm by a bundle of microfilaments forming a diffusion barrier system. Because of its polyelectrolyte nature, the microfilament core of microvilli allows Ca2+ entry into the cytoplasm via nonlinear cable-like cation conduction through arrays of condensed ion clouds. The interaction of ion clouds with periodically applied EMFs and field-induced cation pumping through the cascade of potential barriers on the F-actin polyelectrolyte follows well-known physical principles of ion-magnetic field (MF) interaction and signal discrimination as described by the stochastic resonance and Brownian motor hypotheses. The proposed interaction mechanism is in accord with our present knowledge about Ca2+ signaling as the biological main target of MFs and the postulated extreme sensitivity for coherent excitation by very low field energies within specific amplitude and frequency windows. Microvillar F-actin bundles shielded by a lipid membrane appear to function like electronic integration devices for signal-to-noise enhancement; the influence of coherent signals on cation transduction is amplified, whereas that of random noise is reduced.

ELF magnetic fields increase amino acid uptake into Vicia faba L. roots and alter ion movement across the plasma membrane

Vicia faba seedlings, subjected to a 10 microT 50 Hz square wave magnetic field for 40 min together with a radioactive pulse, showed a marked increase in amino acid uptake into intact roots. A more modest increase was observed with a 100 microT 50 Hz square wave. An increase in media conductivity at low field intensities from 10 microT 50 Hz square wave, 100 microT 50 Hz sine wave, and 100 microT 60 Hz square wave fields, indicated an alteration in the movement of ions across the plasma membrane, most likely due to an increase in net outflow of ions from the root cells. Similarly, marked elevation in media pH, indicating increased alkalinity, was observed at 10 and 100 microT for both square and sine waves at both 50 and 60 Hz. Our data would indicate that low magnetic field intensities of 10 and 100 microT at 50 or 60 Hz can alter membrane transport processes in root tips.

50 Hz magnetic fields of varying flux intensity affect cell shape changes in invertebrate immunocytes: the role of potassium ion channels

The effect induced by exposure to 50 Hz magnetic fields (MFs) in immunocytes from the mussel Mytilus galloprovincialis is evaluated. The whole animal was exposed for 15 and 30 min to MF intensities ranging from 200 to 1,000 microT. The changes in the cellular shape of immunocytes, expressed as shape factor (SF), were studied at different times after addition of the chemotacting substance N-formyl-Meth-Leu-Phe (fMLP). Results show that MFs provoke differing delays in fMLP-induced cellular shape changes: 200 microT are ineffective, while levels from 300 microT upwards cause a significant increase in immunocyte SF values compared to controls. Reactivation of the cells is possible up to an intensity of 600 microT. The use of PCO 400, an opener of ATP-sensitive K+ channels, shows that potassium channels are involved in the effect of MFs on M. galloprovincialis immunocytes.