Oviposition and development of Drosophila modified by magnetic fields

Biological Effects of Magnetic Storms and ELF Magnetic Fields

Magnetic fields are a constant and essential part of our environment. The main components of ambient magnetic fields are the constant part of the geomagnetic field, its fluctuations caused by magnetic storms, and man-made magnetic fields. These fields refer to extremely-low-frequency (<1 kHz) magnetic fields (ELF-MFs). Since the 1980s, a huge amount of data has been accumulated on the biological effects of magnetic fields, in particular ELF-MFs. However, a unified picture of the patterns of action of magnetic fields has not been formed. Even though a unified mechanism has not yet been generally accepted, several theories have been proposed. In this review, we attempted to take a new approach to analyzing the quantitative data on the effects of ELF-MFs to identify new potential areas for research. This review provides general descriptions of the main effects of magnetic storms and anthropogenic fields on living organisms (molecular-cellular level and whole organism) and a brief description of the main mechanisms of magnetic field effects on living organisms. This review may be of interest to specialists in the fields of biology, physics, medicine, and other interdisciplinary areas.

The Impact of Magnetic Field on Insecticide Toxicity Measured by Biological and Biochemical Parameters of Earias insulana (Boisd)

This study illustrates the effect of magnetic field (MF) on the toxicity of two insecticides, emamectin benzoate (Emazoate 2.15% EC) and spinosad (SpinTor 24% SC), and determines their adverse effects on the bollworm (Earias insulana) through various biological and biochemical assays. The investigation indicated that exposure to the insecticides in a MF of 180 mT resulted in stronger toxicity, with LC₅₀ values of 0.162, 1.211, and 1.770 ppm, respectively. In addition, the results showed that magnetized insecticides significantly increased in the duration of the total immature stages (larvae and/or pupae) 32.1 and 36.6 days, compared with 27.9 and 30.5 days, respectively, in the nonmagnetized insecticides, while untreated check was 21 days. Also, the magnetized insecticides reduced the percentage of adult emergence, and increased deformations in the larval and pupal stages. Furthermore, sex ratio was greatly affected by exposure to both insecticides in conjunction with the MF. Exposure of the larvae of E insulana to magnetized insecticides can bring about malfunction in some biochemical process and significantly decreased the invertase activity, and decreased the total protein and carbohydrates. In contrast, it can increase amylase compared with nonmagnetized insecticides and untreated controls. Results concluded that the two insecticides' MF affected growth, survival time, and biological and biochemical parameters of E. insulana. © 2022 Bioelectromagnetics Society.

Anti-Oxidative and Immune Regulatory Responses of THP-1 and PBMC to Pulsed EMF Are Field-Strength Dependent

Innate immune cells react to electromagnetic fields (EMF) by generating reactive oxygen species (ROS), crucial intracellular messengers. Discrepancies in applied parameters of EMF studies, e.g., flux densities, complicate direct comparison of downstream anti-oxidative responses and immune regulatory signaling. We therefore compared the impact of different EMF flux densities in human leukemic THP1 cells and peripheral blood mononuclear cells (PBMC) of healthy donors to additionally consider a potential disparate receptivity based on medical origin. ROS levels increased in THP1 cells stimulated with lipopolysaccharide (LPS) after one hour of EMF exposure. Moreover, weak EMF mitigated the depletion of the reducing agent NAD(P)H in THP1. Neither of these effects occurred in PBMC. Landscaping transcriptional responses to varied EMF revealed elevation of the anti-oxidative enzymes PRDX6 (2-fold) and DHCR24 (6-fold) in THP1, implying involvement in lipid metabolism. Furthermore, our study confirmed anti-inflammatory effects of EMF by 6-fold increased expression of IL10. Strikingly, THP1 responded to weak EMF, while PBMC were primarily affected by strong EMF, yet with severe cellular stress and enhanced rates of apoptosis, indicated by HSP70 and caspase 3 (CASP3). Taken together, our results emphasize an altered susceptibility of immune cells of different origin and associate EMF-related effects with anti-inflammatory signaling and lipid metabolism.

Effects of extremely low-frequency electromagnetic field on different developmental stages of Drosophila melanogaster

PURPOSE

The model biological organism Drosophila melanogaster has been utilized to assess the effect of extremely low-frequency electromagnetic field (ELF-EMF) on locomotion, longevity, developmental dynamics, cell viability and oxidative stress.

MATERIALS AND METHOD

Developmental stages of Drosophila melanogaster (Oregon R strain) individually exposed to ELF-EMF (75 Hz, 550 µT) for 6 h once for acute exposure. For chronic exposure, complete life cycle of fly, that is, egg to adult fly was exposed to ELF-EMF for 6 h daily. The effect of exposure on their crawling and climbing ability, longevity, development dynamics, cellular damage and oxidative stress (generation of reactive oxygen species (ROS)) was evaluated.

RESULTS

The crawling ability of larvae was significantly (p < .05) reduced on acute (third stage instar larvae) as well as chronic exposure (F0 and F1 larvae). When locomotion of flies was tested using climbing assay, no alteration was observed in their climbing ability under both acute and chronic exposure; however, when their speed of climbing was compared, a significant decrease in speed of F1 flies was observed (p = .0027) on chronic exposure. The survivability of flies was significantly affected under chronic and acute exposure (at third stage instar larvae). In case of acute exposure of the third stage instar larvae, although all the flies were eclosed by the 17th day, there was a significant decline in the number of flies (p = .007) in comparison to control. While in case of chronic exposure apart from low number of flies eclosed in comparison to control, there was delay in eclosion by one day (p = .0004). Using trypan blue assay, the internal gut damage of third stage instar larvae was observed. Under acute exposure condition at third stage instar larvae, 30% larvae has taken up trypan blue, while only 10% larvae from acute exposure at adult stage. On chronic exposure, 50% larvae of the F1 generation have taken up trypan blue. On evaluation of oxidative stress, there is a significant rise in ROS in case of acute exposure at third stage instar larvae (p = .0004), adult fly stage (p = .0004) and chronic exposure (p = .0001).

CONCLUSION

ELF-EMF has maximum effects on acute exposure of third stage instar larvae and chronic exposure (egg to adult fly stage). These results suggest that electromagnetic radiations, though, have become indispensible part of our lives but they plausibly affect our health.

Alterations of Immune Parameters on Trichoplusia ni (Lepidoptera: Noctuidae) Larvae Exposed to Extremely Low-Frequency Electromagnetic Fields

Worldwide mobile telephone and microwave use have resulted in an increasing presence of extremely low-frequency electromagnetic field radiations (ELF-EMFs) in ecosystems. ELF-EMFs have been associated with altered physiological processes that can adversely affect exposed organisms. In this study, Trichoplusia ni Hübner larvae were exposed for 24, 48, or 72 h to ELF-EMFs (60 Hz and 2.0 mT) to assess effects on immune response parameters and fertility. Trichoplusia ni life cycle and fertility were not affected by 24-h exposure. However, the number of apoptotic-like cells and cellular immune response significantly increased (P < 0.01) after 72-h exposure (2- and 1.1-fold, respectively), whereas hemolymph total protein and hemocyte cells were reduced (P < 0.01; 16 and 50%, respectively) after 48-h exposure. Hemocyte cell type analysis resulted in significantly (P < 0.01) higher granulocytes number in the unexposed (2-fold increase) and oenocytoids in the 72-h-exposed larvae (28.6-fold increase). Quantitative retrotranscription (RT-qPCR) showed that after 72-h ELF-EMF exposure, the antimicrobial peptides cecropin, lysozyme, gallerimycin, and pgrp were downregulated by 24,866.0, 2.69-, 119.1-, and 1.45-fold, respectively, whereas attacin and defensin were upregulated by 1.59- and 1.85-fold, respectively. The effect of ELF-EMFs on the T. ni larvae immune response and their potential impact on its physiology and susceptibility to pathogens are discussed. This information may provide new insight of ELF-EMFs on other pest species, as well as for the preservation of ecologically important species.

Different responses of Drosophila subobscura isofemale lines to extremely low frequency magnetic field (50 Hz, 0.5 mT): fitness components and locomotor activity

PURPOSE

Extremely low frequency (ELF) magnetic fields as essential ecological factors may induce specific responses in genetically different lines. The object of this study was to investigate the impact of the ELF magnetic field on fitness components and locomotor activity of five Drosophila subobscura isofemale (IF) lines.

MATERIALS AND METHODS

Each D. subobscura IF line, arbitrarily named: B16/1, B24/4, B39/1, B57/2 and B69/5, was maintained in five full-sib inbreeding generations. Their genetic structures were defined based on the mitochondrial DNA variability. Egg-first instar larvae and 1-day-old flies were exposed to an ELF magnetic field (50 Hz, 0.5 mT, 48 h) and thereafter, fitness components and locomotor activity of males and females in an open field test were observed for each selected IF line, respectively.

RESULTS

Exposure of egg-first instar larvae to an ELF magnetic field shortened developmental time, and did not affect the viability and sex ratio of D. subobscura IF lines. Exposure of 1-day-old males and females IF lines B16/1 and B24/4 to an ELF magnetic field significantly decreased their locomotor activity and this effect lasted longer in females than males.

CONCLUSIONS

These results indicate various responses of D. subobscura IF lines to the applied ELF magnetic field depending on their genetic background.

Exposure to extremely low frequency electromagnetic fields alters the behaviour, physiology and stress protein levels of desert locusts

Electromagnetic fields (EMFs) are present throughout the modern world and are derived from many man-made sources including overhead transmission lines. The risks of extremely-low frequency (ELF) electromagnetic fields are particularly poorly understood especially at high field strengths as they are rarely encountered at ground level. Flying insects, however, can approach close to high field strength transmission lines prompting the question as to how these high levels of exposure affect behaviour and physiology. Here we utilise the accessible nervous system of the locust to ask how exposure to high levels of ELF EMF impact at multiple levels. We show that exposure to ELF EMFs above 4 mT leads to reduced walking. Moreover, intracellular recordings from an identified motor neuron, the fast extensor tibiae motor neuron, show increased spike latency and a broadening of its spike in exposed animals. In addition, hind leg kick force, produced by stimulating the extensor tibiae muscle, was reduced following exposure, while stress-protein levels (Hsp70) increased. Together these results suggest that ELF EMF exposure has the capacity to cause dramatic effects from behaviour to physiology and protein expression, and this study lays the foundation to explore the ecological significance of these effects in other flying insects.

Diverse radiofrequency sensitivity and radiofrequency effects of mobile or cordless phone near fields exposure in Drosophila melanogaster

Introduction

The impact of electromagnetic fields on health is of increasing scientific interest. The aim of this study was to examine how the Drosophila melanogaster animal model is affected when exposed to portable or mobile phone fields.

Methods/Results

Two experiments have been designed and performed in the same laboratory conditions. Insect cultures were exposed to the near field of a 2G mobile phone (the GSM 2G networks support and complement in parallel the 3G wide band or in other words the transmission of information via voice signals is served by the 2G technology in both mobile phones generations) and a 1880 MHz cordless phone both digitally modulated by human voice. Comparison with advanced statistics of the egg laying of the second generation exposed and non-exposed cultures showed limited statistical significance for the cordless phone exposed culture and statistical significance for the 900 MHz exposed insects. We calculated by physics, simulated and illustrated in three dimensional figures the calculated near fields of radiation inside the experimenting vials and their difference. Comparison of the power of the two fields showed that the difference between them becomes null when the experimental cylinder radius and the height of the antenna increase.

Conclusions/Significance

Our results suggest a possible radiofrequency sensitivity difference in insects which may be due to the distance from the antenna or to unexplored intimate factors. Comparing the near fields of the two frequencies bands, we see similar not identical geometry in length and height from the antenna and that lower frequencies tend to drive to increased radiofrequency effects.

External control of the Drosophila melanogaster egg to imago development period by specific combinations of 3D low-frequency electric and magnetic fields

We report that the duration of the egg-to-imago development period of the Drosophila melanogaster, and the imago longevity, are both controllable by combinations of external 3-dimensional (3D) low-frequency electric and magnetic fields (LFEMFs). Both these periods may be reduced or increased by applying an appropriate configuration of external 3D LFEMFs. We report that the longevity of D. melanogaster imagoes correlates with the duration of the egg-to-imago development period of the respective eggs. We infer that metabolic processes in both eggs and imago are either accelerated (resulting in reduced time periods) or slowed down (resulting in increased time periods). We propose that external 3D LFEMFs induce electric currents in live systems as well as mechanical vibrations on sub-cell, whole-cell and cell-group levels. These external fields induce media polarization due to ionic motion and orientation of electric dipoles that could moderate the observed effects. We found that the longevity of D. melanogaster imagoes is affected by action of 3D LFEMFs on the respective eggs in the embryonic development period (EDP). We interpret this effect as resulting from changes in the regulation mechanism of metabolic processes in D. melanogaster eggs, inherited by the resulting imagoes. We also tested separate effects of either 3D electric or 3D magnetic fields, which were significantly weaker.

Bio-effects of near-zero magnetic fields on the growth, development and reproduction of small brown planthopper, Laodelphax striatellus and brown planthopper, Nilaparvata lugens

Magnetic fields markedly affect the growth and development of many species of organisms potentially due to cryptochrome and endogenous presence of magnetic materials. Sensitivity to magnetic fields can also be involved in geomagnetic orientation by some long-distance migratory insects. In this study, near-zero magnetic fields (NZMF) in relation to normal geomagnetic fields (GMF) were setup using the Hypomagnetic Field Space System (HMFs) to investigate the effects of magnetic fields on the growth, development and reproduction of two species of migratory planthopper, the small brown planthopper (abbr. SBPH), Laodelphax striatellus, and the brown planthopper (abbr. BPH), Nilaparvata lugens. Exposure of both L. striatellus and N. lugens to NZMF delayed egg and nymphal developmental durations and decreased adult weight and female fecundity. The 1st-5th instars of SBPH and BPH showed different responses to NZMF. The 4th instar was significantly affected by NZMF, especially for BPH males, in which NZMF exposure reduced the difference in development duration between females and males. Compared with GMF, the vitellogenin transcript levels of newly molted female adults and the number of eggs per female were significantly reduced in both planthopper species, indicating a negative effect on fertility under NZMF. Our findings provided experimental evidence that NZMF negatively affected the growth and development of SBPH and BPH, with particularly strong effects on reproduction.

Gravitational and magnetic field variations synergize to cause subtle variations in the global transcriptional state of Arabidopsis in vitro callus cultures

BACKGROUND

Biological systems respond to changes in both the Earth's magnetic and gravitational fields, but as experiments in space are expensive and infrequent, Earth-based simulation techniques are required. A high gradient magnetic field can be used to levitate biological material, thereby simulating microgravity and can also create environments with a reduced or an enhanced level of gravity (g), although special attention should be paid to the possible effects of the magnetic field (B) itself.

RESULTS

Using diamagnetic levitation, we exposed Arabidopsis thaliana in vitro callus cultures to five environments with different levels of effective gravity and magnetic field strengths. The environments included levitation, i.e. simulated μg* (close to 0 g* at B = 10.1 T), intermediate g* (0.1 g* at B = 14.7 T) and enhanced gravity levels (1.9 g* at B = 14.7 T and 2 g* at B = 10.1 T) plus an internal 1 g* control (B = 16.5 T). The asterisk denotes the presence of the background magnetic field, as opposed to the effective gravity environments in the absence of an applied magnetic field, created using a Random Position Machine (simulated μg) and a Large Diameter Centrifuge (2 g).Microarray analysis indicates that changes in the overall gene expression of cultured cells exposed to these unusual environments barely reach significance using an FDR algorithm. However, it was found that gravitational and magnetic fields produce synergistic variations in the steady state of the transcriptional profile of plants. Transcriptomic results confirm that high gradient magnetic fields (i.e. to create μg* and 2 g* conditions) have a significant effect, mainly on structural, abiotic stress genes and secondary metabolism genes, but these subtle gravitational effects are only observable using clustering methodologies.

CONCLUSIONS

A detailed microarray dataset analysis, based on clustering of similarly expressed genes (GEDI software), can detect underlying global-scale responses, which cannot be detected by means of individual gene expression techniques using raw or corrected p values (FDR). A subtle, but consistent, genome-scale response to hypogravity environments was found, which was opposite to the response in a hypergravity environment.

Microgravity simulation by diamagnetic levitation: effects of a strong gradient magnetic field on the transcriptional profile of Drosophila melanogaster

BACKGROUND

Many biological systems respond to the presence or absence of gravity. Since experiments performed in space are expensive and can only be undertaken infrequently, Earth-based simulation techniques are used to investigate the biological response to weightlessness. A high gradient magnetic field can be used to levitate a biological organism so that its net weight is zero.

RESULTS

We have used a superconducting magnet to assess the effect of diamagnetic levitation on the fruit fly D. melanogaster in levitation experiments that proceeded for up to 22 consecutive days. We have compared the results with those of similar experiments performed in another paradigm for microgravity simulation, the Random Positioning Machine (RPM). We observed a delay in the development of the fruit flies from embryo to adult. Microarray analysis indicated changes in overall gene expression of imagoes that developed from larvae under diamagnetic levitation, and also under simulated hypergravity conditions. Significant changes were observed in the expression of immune-, stress-, and temperature-response genes. For example, several heat shock proteins were affected. We also found that a strong magnetic field, of 16.5 Tesla, had a significant effect on the expression of these genes, independent of the effects associated with magnetically-induced levitation and hypergravity.

CONCLUSIONS

Diamagnetic levitation can be used to simulate an altered effective gravity environment in which gene expression is tuned differentially in diverse Drosophila melanogaster populations including those of different age and gender. Exposure to the magnetic field per se induced similar, but weaker, changes in gene expression.

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.

The effects of acute exposure to magnetic fields on morphometric characteristics of bombyxin-producing neurosecretory neurons in gypsy moth caterpillars

PURPOSE

To examine the effects of acute exposure to strong static magnetic fields and extremely low frequency magnetic fields, on neurosecretory neurons which synthesise insulin-like neurohormone.

MATERIALS AND METHODS

Immunocytochemical detection of bombyxin-like material in the protocerebral neurosecretory neurons of Lymantria dispar caterpillars was performed using a monoclonal antibody directed against a synthetic dekapeptide corresponding to the N-terminus of the bombyxin A-chain. Caterpillars were exposed to strong static magnetic fileds (235 mT) and extremely low frequency magnetic fields (2 mT) for three days after moulting into the 4th instar.

RESULTS

We report the presence of immunoreactive molecules in A2 type of medial neurosecretory neurons (nsn) in caterpillars' brain of L. dispar. The three-day exposure of caterpillars to stresogenic external magnetic fields changed the size of A2 type nsn, their nuclei and the intensity of protein band in the region of bombyxin molecular mass (4-6 kD) after exposure to extremely low frequency magnetic fields in comparison to control group and group treated by strong static magnetic fields.

CONCLUSION

These are the first data on the influence of external magnetic fields on the polyphagous phytophagous forest pest L. dispar L. (Lepidoptera: Lymantridae) indicating an intensive synthesis of insulin-like neurosecretory material.

The response of dorsomedial A1’ and dorsolateral L2’ neurosecretory neurons of Lymantria dispar L. caterpillars to the acute effects of magnetic fields

The morphometric changes (size of neurons and their nuclei) of protocerebral dorsomedial A1? and dorsolateral L2? neurosecretory neurons were analyzed in Lymantria dispar larvae after exposure to strong static (SMF, 235 mT) and extremely low frequency magnetic fields (ELF MF, 2 mT). Increase in the size of A1? neurons and their nuclei were observed after acute exposure to SMF. Decrease in the size of these neurons and their nuclei was observed after exposure to ELF MF. The size of L2? neurons and their nuclei tend to decrease after exposure to SMF and ELF MF. The quantification of protein bands within the Mr range corresponding to the large form of the prothoracicotropic neurohormone indicates that the amount of protein decreased after exposure to both types of magnetic fields.

Protocerebral Mediodorsal A2′ Neurosecretory Neurons in Late Pupae of Yellow Mealworm (Tenebrio molitor) after Exposure to a Static Magnetic Field

The activity of large dorsomedial protocerebral A2' neurosecretory neurons were investigated in late pupae of Tenebrio molitor L, which were exposed to a static magnetic field of 320 mT. Experimental groups were C: the control group which was kept at 5 meters from the magnet; CMF: pupae which were reared in control conditions and sacrificed on the eighth day of pupal stage (parents were kept in a magnetic field); and MF: pupae kept in a permanent magnetic field for eight days. Our results indicate the effects of a static magnetic field on the cytological characteristics and activity of large A2' neurosecretory neurons of Tenebrio molitor pupae.

Effects of 10-T static magnetic field on human peripheral blood immune cells

The exposure of peripheral blood mononuclear cells (PBMCs) was performed in a 10-T static magnetic field. Without lymphocyte stimulation, there were no significant differences in the viability of the exposed and unexposed CD4(+) T cells, CD8(+) T cells, B cells, and natural killer (NK) cells. The expression of Th1 type chemokine receptor, CXCR3, and Th2 type receptor, CCR3, was unaltered after magnetic-field exposure. No differences were observed in the naive T cells and memory T-cell subclasses in either CD4(+) or CD8(+) T cells. In contrast to the unstimulated condition, the magnetic-field exposure reduced the viability of phytohemagglutinin (PHA)-activated T cells in both the CD4(+) and CD8(+) subclasses. In particular, the number of PHA-treated naive CD8(+) T cells (CD45RA(+)CD4(-)CD8(+)) was markedly decreased after the magnetic-field exposure, while PHA-treated memory CD8(+) cells (CD45RA(-)CD4(-)CD8(+)) were resistant to the exposure. The number of PHA-treated naive CD4(+) T cells (CD45RA(+)CD4(+)CD8(-)) and memory cells (CD45RA(-)CD4(+)CD8(-)) was markedly decreased to a similar degree. Thus the susceptibility of lymphocytes to the magnetic-field exposure differed among activated T-cell subtypes. The magnetic-field exposure significantly increased the death of PHA-stimulated lymphocytes by apoptosis. These results suggest that a strong static magnetic field has acute effects on immune cells during cell division, while the field exposure has a minimal effect on immune cells in a nondividing phase.

Mechanism for action of electromagnetic fields on cells

A biophysical model for the action of oscillating electric fields on cells, presented by us before [Biochem. Biophys. Res. Commun. 272(3) (2000) 634-640], is extended now to include oscillating magnetic fields as well, extended to include the most active biological conditions, and also to explain why pulsed electromagnetic fields can be more active biologically than continuous ones. According to the present theory, the low frequency fields are the most bioactive ones. The basic mechanism is the forced-vibration of all the free ions on the surface of a cell's plasma membrane, caused by an external oscillating field. We have shown that this coherent vibration of electric charge is able to irregularly gate electrosensitive channels on the plasma membrane and thus cause disruption of the cell's electrochemical balance and function [Biochem. Biophys. Res. Commun. 272(3) (2000) 634-640]. It seems that this simple idea can be easily extended now and looks very likely to be able to give a realistic basis for the explanation of a wide range of electromagnetic field bioeffects.

Effects of a 4.7 T static magnetic field on fetal development in ICR mice

In order to determine the effects of a 4.7 T static magnetic field (SMF) on fetal development in mice, we evaluated fetal teratogenesis and endochondral ossification following exposure in utero. Pregnant ICR mice were exposed to a 4.7 T SMF from day 7.5 to 9.5 of gestation in a whole-body dose, and sacrificed on day 18.5 of gestation. We examined the incidence of prenatal death, external malformations and fetal skeletal malformations. There were no significant differences observed in the incidence of prenatal death and/or malformations between SMF-exposed mice and control mice. Further, we evaluated the immunoreactivity for the vascular endothelial growth factor (VEGF), which is implicated in angiogenesis and osteogenesis, in the sternum of fetal mice following magnetic exposure. Our studies also indicated that on day 16.5 of gestation following SMF exposure, the immunoreactivity for VEGF was increased compared to unexposed controls. However, it was decreased in the exposed group compared to the control group on day 18.5 of gestation. DNA and proteoglycan (PG) synthesis were also measured in rabbit costal growth plate chondrocytes in vitro. No significant differences were observed in DNA synthesis between the SMF exposed chondrocytes and the control chondrocytes; however, PG synthesis in SMF exposed chondrocytes increased compared to the controls. Based on these results, we suggest that while SMF exposure promoted the endochondral ossification of chondrocytes, it did not induce any harmful effects on fetal development in ICR mice.

Multigeneration exposure test of Drosophila melanogaster to ELF magnetic fields

Mutations, other than dominant lethals, were accumulated on wild type second chromosomes (+) of Drosophila melanogaster during exposure to 50 Hz sinusoidal alternating magnetic fields of 0.5 or 5 mT (rms) for 40 generations by the Curly/Plum(Cy/Pm) accumulation method. We maintained, for 40 generations under continuous exposure, each (+) chromosome as a heterozygote with (Cy) chromosome. Viability of the (+) chromosome was tested by sib-mating of (Cy/+) male and (Cy/+) female in a culture every 10th generation to obtain the homozygote. Viability indices, defined as twice the ratio of number of (+/+) flies to that of (Cy/+) flies plus 1 in the progeny of the test mating, also were calculated, which equaled 1.00 at the starting point. For the control and 0.5 and 5 mT exposed groups, percent frequencies of recessive lethal lines, defined as a line with (+/+) flies less than 0.3% in the test mating, were, respectively, 1.9, 0.9, and 2.9% (10th), 9.0, 4.9, and 9.5% (20th), 30.3, 22.9, and 30.4% (30th), and 39.9, 32.4, and 43.3% (40th generation). For the control and 0.5 and 5 mT groups, average viability indices, excluding lethals and markedly deleterious, were, respectively, 0.778, 0.796, and 0.752 (20th), 0.704, 0.698, and 0.694 (30th), and 0.669, 0.678, and 0.595 (40th generation). Their decreasing rates were 0.0054, 0.0059, and 0.0078 per generation. No significant difference was detected among the exposure levels in either the recessive lethal mutation frequency or the viability index.

Exposure of Drosophila melanogaster embryonic cell cultures to 60-Hz sinusoidal magnetic fields: assessment of potential teratogenic effects

There is considerable concern about potential detrimental health effects associated with exposure to environmentally relevant magnetic fields. One specific concern relates to potential effects of magnetic field (MF) exposure on reproduction and development. Consequently, an in vitro teratogenesis (developmental toxicity) assay employing embryonic Drosophila cells has been used to determine whether exposure to a 60-Hz MF of 100 microT for 16-18 hr is itself teratogenic and whether such an exposure could potentiate the teratogenic response induced by a chemical teratogen (developmental toxicant). The results demonstrated that (1) MF exposure alone did not induce a teratogenic response, whether the MF was oriented parallel or perpendicular to the plane of the culture dishes; and (2) MF exposure did not alter the teratogenic response induced by optimal or suboptimal concentrations of three chemical teratogens (retinoic acid, hydroxyurea, and cadmium). Furthermore, in additional studies, Drosophila embryos were exposed to 60-Hz MFs of 10 and 100 microT for 24 hr or for their entire development time (i.e., until adult ecolsion, about 10 days). Results demonstrated that MF exposure did not produce an increase in developmental abnormalities over those observed in unexposed controls.

Biological responses in Caenorhabditis elegans to high magnetic fields

Here we describe a device for testing possible influences of high magnetic fields on biological processes, by which alternating-current magnetic stimuli as high as 1.7 T can be administered. Experiments with a simple multicellular organism, the nematode Caenorhabditis elegans, revealed that intermittent exposure to the magnetic fields modestly inhibited the animal's reproduction as well as its post-embryonic development, and caused a marked but transient derangement in its locomotory behavior. Available evidence indicates that alternating high magnetic fields can elicit both chronic and acute biological effects, but that the effects may be well tolerated or compensated for by the living organism.

Applied AC and DC magnetic fields cause alterations in the mitotic cycle of early sea urchin embryos

This study demonstrates that exposure to 60 Hz magnetic fields (3.4-8.8 mT) and magnetic fields over the range DC-600 kHz (2.5-6.5 mT) can alter the early embryonic development of sea urchin embryos by inducing alterations in the timing of the cell cycle. Batches of fertilized eggs were exposed to the fields produced by a coil system. Samples of the continuous cultures were taken and scored for cell division. The times of both the first and second cell divisions were advanced by ELF AC fields and by static fields. The magnitude of the 60 Hz effect appears proportional to the field strength over the range tested. The relationship to field frequency was nonlinear and complex. For certain frequencies above the ELF range, the exposure resulted in a delay of the onset of mitosis. The advance of mitosis was also dependent on the duration of exposure and on the timing of exposure relative to fertilization.

Search for influence of 1.5 Tesla magnetic field on growth of yeast cells

We have used a clinical magnetic resonance imager to search for the possible effects of a 1.5 T magnetic fields on the growth of the yeast Saccharomyces cerevisiae. Yeast samples were grown in nutrient broth contained in constant-temperature boxes, both in and out of the magnetic field of the imager. Growth was measured by using a hemocytometer and light microscope to calculate cell densities. Over the time span corresponding to approximately seven cell divisions, we find no convincing statistical evidence for an effect of magnetic field on cell density.

Environmental magnetic fields: influences on early embryogenesis

A 10-mG, 50 to 60-Hz magnetic field is in the intensity and frequency range that people worldwide are often exposed to in homes and in the workplace. Studies about the effects of 50- to 100-Hz electromagnetic fields on various species of animal embryos (fish, chick, fly, sea urchin, rat, and mouse) indicate that early stages of embryonic development are responsive to fluctuating magnetic fields. Chick, sea urchin, and mouse embryos are responsive to magnetic field intensities of 10-100 mG. Results from studies on sea urchin embryos indicate that exposure to conditions of rotating 60-Hz magnetic fields, e.g., similar to those in our environment, interferes with cell proliferation at the morula stage in a manner dependent on field intensity. The cleavage stages, prior to the 64-cell stage, were not delayed by this rotating 60-Hz magnetic field suggesting that the ionic surges, DNA replication, and translational events essential for early cleavage stages were not significantly altered. Studies of histone synthesis in early sea urchin embryos indicated that the rotating 60-Hz magnetic field decreased zygotic expression of "early" histone genes at the morula stage and suggests that this decrease in early histone production was limiting to cell proliferation. Whether these comparative observations from animal development studies will be paralleled by results from studies of human embryogenesis, as suggested by some epidemiology studies, has yet to be established.

In vivo studies of the effect of magnetic field exposure on ontogeny of choline acetyltransferase in the rat brain

Developmental increases of the activity of choline acetyltransferase (ChAT) were examined in the brains of fetuses and offspring from parent rats continuously exposed to a 500 mG, 60 Hz circularly polarized (CP) magnetic field (MF) prior to pregnancy, and further, during pregnancy and lactation. In developing rats between 12 days and 20 days of embryogenesis that were housed in a control unit, i.e., nonexposed to MF, the specific activity of ChAT in whole brain specimens increased from 2.4% to 6.9% of adult activity, while specific activity of ChAT in rat brain specimens between 12 days of embryogenesis and 10 days of postpartum increased from 2.4% to 21.6% of adult activity. On the other hand, the specific activity of ChAT in whole brain specimens from rats under housed MF exposure conditions was found to increase from 2.6% to 6.7% of adult activity between 12 days and 20 days of embryogenesis and from 2.6% to 21.6% of adult activity between 12 days of embryogenesis and 10 days postpartum. Furthermore, the effect of the same test magnetic environment on the specific activity of ChAT in the brains of parental rats was examined in order to determine whether magnetic field exposure of parental rats might reflect onto the development of fetal brain. It was observed that continuous exposure of parental rats to a 500 mG, 60 Hz CP MF did not show any significant changes in the specific activity of ChAT in the septodiagonal band complex, dorsal and ventral hippocampus, striatum, and frontoparietal cerebral cortex, as compared with the same brain regions of control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Sex-linked recessive lethal test of Drosophila melanogaster after exposure to 50-Hz magnetic fields

To determine whether a 50-Hz magnetic field will induce mutations, a sex-linked recessive lethal test of Drosophila melanogaster was performed. Adult flies were exposed at an rms flux density of 500 mu T or 5 mT to the homogeneous field of a Helmholtz coil. The ambient field to which controls were exposed was less than 1 mu T. Exposures took place continuously for 13 to 14 days, which correspond to the life cycle of Drosophila at 25 degrees C. About 10,000 X-chromosomes were tested at each flux density. Recessive lethal mutation rates of 0.13, 0.21, and 0.18 percent were observed, respectively, for control, 500-mu T, and 5-mT conditions. By the Kastenbaum-Bowman significance test, the recessive lethal mutation rates in the 500-mu T and 5-mT conditions did not differ from the mutation rate of controls.

Inhibitory effects of powerline-frequency (60-Hz) magnetic fields on pentylenetetrazol-induced seizures and mortality in rats

The possibility that exposure to powerline frequency (60-Hz) magnetic fields might affect the form or intensity of epileptic seizures, induced by administration of pentylenetetrazol (PTZ) in rats, was examined. Male adult rats were exposed to either 60-Hz magnetic fields with intensities of up to 1.85 gauss (185 microT) or to a sham field condition, for 1 h prior to injections of PTZ (45-75 mg/kg). The subsequent seizures were monitored and recorded on videotape and any subsequent mortalities were noted. Exposure to 60-Hz magnetic fields prior to administration of PTZ was found to significantly (P less than 0.005) reduce the lethality of the drug-induced seizures. The LD50 for the sham-exposed group was 65.88 mg/kg, whereas for the 60-Hz magnetic field-exposed rats, the LD50 was 85.33 mg/kg. In some experiments exposure to the 1.0 and 1.5 gauss magnetic fields also produced significant (P less than 0.05) reductions in seizure durations. These findings suggest that acute exposure to low intensity 60-Hz magnetic fields has an inhibitory effect on the lethality and expression of PTZ-induced seizures in rats. Some possible mechanisms, which could account for these observed effects of magnetic field exposure on seizures, are discussed.

Day-night rhythms in the inhibitory effects of 60 Hz magnetic fields on opiate-mediated 'analgesic' behaviors of the land snail, Cepaea nemoralis

There is accumulating evidence that magnetic fields can affect a variety of opioid-mediated behavioral and physiological functions. The present experiments were designed to examine the effects of various durations of day- and night-time exposures to low intensity (1.0 gauss rms) 60 Hz magnetic fields on light (L) and dark (D) period opioid-mediated aversive thermal ('nociceptive') responses and morphine-induced 'analgesia' in the nocturnally-crepuscularly active land snail, Cepaea nemoralis. The snails displayed a LD rhythm in the latency of their aversive (40 degrees C) thermal (nociceptive) responses, showing a significantly greater response latency at night than during the day. Administration of morphine (10 mg/kg/2.0 microliters) elicited significant increases in the thermal response latencies indicative of the induction of analgesia. The snails displayed a significantly greater analgesic response at night than during the day. Exposure (0.50, 2, 12, 48 or 120 h in L or D) to the 60 Hz fields reduced morphine-induced analgesia in both the L and D periods, with the magnetic stimuli having significantly greater inhibitory effects in the D period. The magnetic fields also significantly attenuated the level of the dark period basal nociceptive response latencies, while not affecting the light period responses. In both the L and D periods the degree of attenuation of the analgesic and nociceptive response latencies was related to the duration of exposure to the 60 Hz magnetic fields.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of 60-Hz magnetic fields on sea urchin development

Continuous exposure of sea urchin (Strongylocentrotus purpuratus) embryos at 18 degrees C to a cyclic 60-Hz magnetic field at 0.1 mT rms beginning 4 min after insemination caused a significant developmental delay during the subsequent 23 hours. No delay in development was recorded for periods up to 18 hours after fertilization. At 18 h, most embryos were in the mesenchyme blastula stage. At 23 h, most control embryos were in mid-gastrula whereas most magnetic-field-exposed embryos were in the early gastrula stage. Thus an estimated 1-h delay occurred between these developmental stages. The results are discussed in terms of possible magnetic-field modification of transcription as well as interference with cell migration during gastrulation. The present study extends and supports the growing body of information about potential effects of exposures to extremely-low-frequency (ELF) magnetic fields on developing organisms.

Development of chicken embryos in a pulsed magnetic field

Six independent experiments of common design were performed in laboratories in Canada, Spain, Sweden, and the United States of America. Fertilized eggs of domestic chickens were incubated as controls or in a pulsed magnetic field (PMF); embryos were then examined for developmental anomalies. Identical equipment in each laboratory consisted of two incubators, each containing a Helmholtz coil and electronic devices to develop, control, and monitor the pulsed field and to monitor temperature, relative humidity, and vibrations. A unipolar, pulsed, magnetic field (500-microseconds pulse duration, 100 pulses per s, 1-microT peak density, and 2-microseconds rise and fall time) was applied to experimental eggs during 48 h of incubation. In each laboratory, ten eggs were simultaneously sham exposed in a control incubator (pulse generator not activated) while the PMF was applied to ten eggs in the other incubator. The procedure was repeated ten times in each laboratory, and incubators were alternately used as a control device or as an active source of the PMF. After a 48-h exposure, the eggs were evaluated for fertility. All embryos were then assayed in the blind for development, morphology, and stage of maturity. In five of six laboratories, more exposed embryos exhibited structural anomalies than did controls, although putatively significant differences were observed in only two laboratories (two-tailed Ps of .03 and less than .001), and the significance of the difference in a third laboratory was only marginal (two-tailed P = .08). When the data from all six laboratories are pooled, the difference in incidence of abnormalities in PMF-exposed embryos (approximately 25 percent) and that of controls (approximately 19 percent), although small, is highly significant, as is the interaction between incidence of abnormalities and laboratory site (both Ps less than .001). The factor or factors responsible for the marked variability of inter-laboratory differences are unknown.

Magnetic fields inhibit opioid-mediated 'analgesic' behaviours of the terrestrial snail, Cepaea nemoralis

1. The terrestrial snail, Cepaea nemoralis, when placed on a warmed surface (40 degrees C) displays a thermal avoidance behaviour that entails an elevation of the anterior portion of the fully extended foot. The latency of this nociceptive response was increased by the prototypical mu and specific kappa opiate agonists, morphine and U-50, 488H, respectively, in a manner indicative of anti-nociception and the induction of 'analgesia'. Pretreatment with the prototypical opiate antagonist, naloxone, blocked the morphine- and reduced the U-50, 488H-induced analgesia. Naloxone had no effects on the thermal response latencies of saline treated animals. 2. Exposure to either cold (7 degrees C) or warm (38 degrees C) temperature stress increased the nociceptive thresholds of Cepaea in a manner indicative of the induction of 'stress-induced analgesia'. The warm stress-induced analgesia was opioid mediated, being blocked by naloxone, whereas, the cold stress-induced analgesia was insensitive to naloxone. 3. Exposure for 15-30 min to 0.5 Hz weak rotating magnetic fields (1.5-8.0 G) significantly reduced the analgesic effects of the mu and kappa opiate agonists in a manner similar to that observed with naloxone. The magnetic stimuli also inhibited the endogenous opioid mediated warm stress-induced analgesia and significantly reduced the cold stress-induced analgesia. The magnetic stimuli had no evident effects on the nociceptive responses of saline-treated animals. The dihydropyridine (DHP) and non-DHP calcium channel antagonists diltiazem, verapamil. and nifedipine differentially and significantly reduced, while the DHP calcium channel agonist, BAY K8644, significantly enhanced the inhibitory effects of the magnetic fields on morphine-induced analgesia.

Morphine-induced analgesia and exposure to low-intensity 60-Hz magnetic fields: inhibition of nocturnal analgesia in mice is a function of magnetic field intensity

In 2 experiments male CF-1 mice were exposed for 60 min, during the mid-dark period of the day-night cycle, to low-intensity (0.5-1.5 gauss, rms) 60-Hz magnetic fields and then tested for levels of analgesia induced by morphine (10 mg/kg) injections. The magnetic field exposures inhibited the degree of morphine-induced analgesia in a field intensity-dependent manner in both experiments (P less than 0.01) with the largest inhibitory effect after exposure to the 1.5-gauss field. Analysis of the combined data from the two experiments revealed a significant (P less than 0.001) linear relationship between level of analgesia and magnetic field intensity. Thus, these data demonstrated a functional relationship between the behavioral effects of morphine in mice and the strength of the 60-Hz magnetic field. Possible mechanisms underlying these effects are discussed.