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. Bioelectromagnetics 19:335–340, 1998. © 1998 Wiley-Liss, Inc.     

Growth and developmental stability of Drosophila melanogaster in low frequency magnetic fields

Magnetic fields (60 Hz) of 1.5 and 80 microT caused a significant reduction in the weight of Drosophila melanogaster. Moreover, fruit flies in an 80 microT field showed lower developmental stability than either those in a 0 or 1.5 microT field. Developmental instability was measured by fluctuating asymmetry and frequency of phenodeviants. More of the flies in the 80 microT field had fused abdominal segments, and they were more asymmetrical for wing vein R(4+5). The flies in the 1.5 microT field actually showed greater developmental stability than the control flies. Fewer of them had fused abdominal segments, and they were more symmetrical for wing vein R(4+5). Thus, at low field strengths, flies are more developmentally stable than control flies, even though they weigh less.     

External control of the Drosophila melanogaster lifespan by combination of 3D oscillating low-frequency electric and magnetic fields

We demonstrate that the lifespan of Drosophila melanogaster population is controllable by a combination of external three-dimensional oscillating low-frequency electric and magnetic fields (3D OLFEMFs). The lifespan was decreased or increased in dependence of the parameters of the external 3D OLFEMFs. We propose that metabolic processes in D. melanogaster’s body are either accelerated (in the case of reduced lifespan) or slowed down (in the case of increased lifespan) in function of 3D OLFEMFs that induce vibrational motions on sub-cellular and larger scales.     

No influence of magnetic fields on cell cycle progression using conditions relevant for patients during MRI

The purpose of this study was to examine whether exposure to magnetic fields (MFs) relevant for magnetic resonance imaging (MRI) in clinical routine influences cell cycle progression in two tumor cell lines in vitro. HL60 and EA2 cells were exposed to four types of MFs: (i) static MF of 1.5 and 7.05 T, (ii) extremely low frequency magnetic gradient fields (ELFMGFs) with +/- 10 mT/m and 100 Hz, as well as +/- 100 mT/m and 100 Hz, (iii) pulsed high frequency MF in the radiofrequency (RF) range (63.6 MHz, 5.8 microT), and (iv) a combination of (i-iii). Exposure periods ranged from 1 to 24 h. Cell cycle distribution (G(0)/G(1), S, and G(2)/M phases) was analyzed by flow cytometry. Cell cycle analysis did not reveal differences between the exposed and the control cells. As expected, positive controls with irradiated (8 Gy) HL60 and EA2 cells showed a strong G(2)/M arrest. Using conditions that are relevant for patients during MRI, no influence of MFs on cell cycle progression was observed in these cell lines. Care was taken to control secondary parameters of influence, such as vibration by the MR scanner or temperature to avoid false positive results.     

Effect of a permanent magnetic field on wing size parameters in Drosophila melanogaster.

The width and length variability of both D. melanogaster wings were measured in samples of flies after two and six generations under a permanent magnetic field of 35 mT. While in earlier generations under exposure sexes differ in the size response, later they both show a decrease in the wing size under the magnetic field exposure if compared to the control. The bilateral asymmetry in wings as a potential indicator of developmental instability does not increase significantly under exposure. The ecological and adaptive implications of the change of the magnetic intensity as an environmental factor generating stress in populations is discussed.     

Developmental changes in Drosophila melanogaster following exposure to alternating electromagnetic fields

This study investigated the biological effects of alternating electromagnetic fields (EMFs) on developmental stages of Drosophila melanogaster eggs and the first, second and third instar larvae stages. D. melanogaster eggs and larval stages were exposed to a 11 mT 50 Hz field produced by a pair of Helmholtz coils. Each stage was exposed to aEMFs for 2, 4, 6 and 8 h. Features of adult flies such as head, thorax, abdomen and other morphological changes were studied and compared. The frequency of abnormal flies was calculated using statistical methods at P <.05. The results obtained from exposing larvae in different stages of development showed a significant increase in the number of abnormal adult flies, whereas no significant increase was observed in the group arising from eggs exposed to aEMFs. Also, it appeared that duration of exposure correlates with the increase in the number of abnormal flies. There was no significant difference in mortality rate and sex distribution of the abnormal flies between field exposed and the control groups.     

Effects of static magnetic fields on nicotinic cholinergic receptor function

Ligand-gated ion channel kinetics were studied in mammalian transfected cells encoding adult mouse muscle acetylcholine (ACh) receptors. We measured macroscopic and single-channel currents using the outside-out and cell-attached patch-clamp configurations. Cultured cells were exposed to moderate intensity inhomogeneous static magnetic fields up to 180 mT and measurements were performed for temperatures ranging from 5 to 50 °C. We found no significant changes in ACh-elicited macroscopic or single-channel currents. We observed the expected dependence in current decay constants with temperature, but negligible magnetic field influence on the channel's kinetics.     

The effects of spontaneous mutation on competitive fitness in Drosophila melanogaster

Abstract We have analysed the effect of 288 generations of mutation accumulation (MA) on chromosome II competitive fitness in 21 full‐sib lines of Drosophila melanogaster and in a large control population, all derived from the same isogenic base. The rate of mean log‐fitness decline and that of increase of the between‐line variance were consistent with a low rate (λ ≈ 0.03 per gamete and generation), and moderate average fitness effect [E(s) ≈ 0.1] of deleterious mutation. Subsequently, crosses were made between pairs of MA lines, and these were maintained with effective size on the order of a few tens. In these crosses, MA recombinant chromosomes quickly recovered to about the average fitness level of control chromosomes. Thus, deleterious mutations responsible for the fitness decline were efficiently selected against in relatively small populations, confirming that their effects were larger than a few percent.     

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.     

ELF in vitro exposure systems for inducing uniform electric and magnetic fields in cell culture media.

Many in vitro experiments on the biological effects of extremely low frequency (ELF) electromagnetic fields utilize a uniform external magnetic flux density (B) to expose biological materials. A significant number of researchers do not measure or estimate the resulting electric field strength (E) or current density (J) in the sample medium. The magnitude and spatial distribution of the induced E field are highly dependent on the sample geometry and its relative orientation with respect to the magnetic field. We have studied the E fields induced in several of the most frequently used laboratory culture dishes and flasks under various exposure conditions. Measurements and calculations of the E field distributions in the aqueous sample volume in the containers were performed, and a set of simple, quantitative tables was developed. These tables allow a biological researcher to determine, in a straightforward fashion, the magnitudes and distributions of the electric fields that are induced in the aqueous sample when it is subjected to a uniform, sinusoidal magnetic field of known strength and frequency. In addition, we present a novel exposure technique based on a standard organ culture dish containing two circular, concentric annular rings. Exposure of the organ culture dish to a uniform magnetic field induces different average electric fields in the liquid medium in the inner and outer rings. Results of experiments with this system, which were reported in a separate paper, have shown the dominant role of the magnetically induced E field in producing specific biological effects on cells, in vitro. These results emphasize the need to report data about the induced E field in ELF in-vitro studies, involving magnetic field exposures. Our data tables on E and J in standard containers provide simple means to enable determination of these parameters.     

The influence of static magnetic fields on mechanosensitive ion channel activity in artificial liposomes

The influence of static magnetic fields (SMFs) on the activity of recombinant mechanosensitive ion channels (the bacterial mechanosensitive ion channel of large conductance—MscL) following reconstitution into artificial liposomes has been investigated. Preliminary findings suggest that exposure to 80-mT SMFs does not induce spontaneous MscL activation in the absence of mechanical stimulation. However, SMFs do appear to influence the open probability and single channel kinetics of MscL exposed to negative pipette pressure. Typical responses include an overall reduction in channel activity or an increased likelihood of channels becoming trapped open in sub-conducting states following exposure to SMFs. There is a delay in the onset of this effect and it is maintained throughout exposure. Generally, channel activity showed slow or limited recovery following removal of the magnetic field and responses to the magnetic were often reduced or abolished upon subsequent exposures. Pre-exposure of the liposomes to SMFs resulted in reduced sensitivity of MscL to negative pipette pressure, with higher pressures required to activate the channels. Although the mechanisms of this effect are not clear, our initial observations appear to support previous work showing that the effects of SMFs on ion channels may be mediated by changes in membrane properties due to anisotropic diamagnetism of lipid molecules.     

In vitro exposure parameters with linearly and circularly polarized ELF magnetic fields.

A comparison is made of induced current densities, electric fields, and rates of energy deposition during in vitro studies with linearly and circularly polarized, extremely low frequency magnetic fields for a cylindrical volume of culture medium.     

烟田中静电喷雾和电动喷雾下噻虫嗪的防效及对昆虫群落的影响

【目的】探明静电喷雾与电动喷雾对噻虫嗪防治害虫效果及烟田昆虫群落的影响,为静电喷雾在烟草上的推广应用提供理论依据。【方法】利用静电喷雾与电动喷雾法喷施0.66 g·L~(-1)25%噻虫嗪水分散粒剂,施药1、3、7 d后,测定2种方法对烟蚜与斜纹夜蛾的防治效果、在烟株与土壤中的沉积以及对昆虫群落的影响。【结果】喷施25%噻虫嗪水分散粒剂1、3、7 d后,静电喷雾对烟蚜和斜纹夜蛾的防治效果均显著高于电动喷雾的防治效果,且防治效果均随时间的推移而升高。噻虫嗪在静电喷雾处理区烟叶上的沉积量高于电动喷雾处理区烟叶上的沉积量,而在静电喷雾处理区土壤中的沉积量低于电动喷雾处理区土壤中的沉积量,且都随时间的推移而降低。静电喷雾与电动喷雾均引起烟田昆虫群落的变化,静电喷雾引起的害虫和中性昆虫的数量变化大于电动喷雾,但天敌昆虫的数量变化小于电动喷雾,且静电喷雾区烟田的物种丰富度明显高于电动喷雾区,可见静电喷雾施药对烟田昆虫群落的影响小于电动喷雾施药。静电喷雾的S_t/S_i与S_n/S_p比值明显高于电动喷雾,说明静电喷雾烟田中昆虫群落稳定性高于电动喷雾烟田中昆虫群落的稳定性。【结论】相比电动喷雾,静电喷雾能够提高噻虫嗪在烟叶上的沉积量,从而提高噻虫嗪对害虫的防治效果,同时减少噻虫嗪在土壤中的沉积量,提高噻虫嗪的生态安全性,因此,静电喷雾在烟草病虫害防治上具有较好的应用前景。     

Glycosidases are present on the surface of Drosophila melanogaster spermatozoa

We investigated the presence of enzymes on the surface of Drosophila melanogaster spermatozoa that might bind to the carbohydrate residues of the egg shell. Spectrophotometric and fluorimetric studies were used on whole spermatozoa to assay galactosyltransferase and glycosidase activities. No galactosyltransferase is present on the sperm surface, whereas two glycosidases, β-N-acetylglucosaminidase (GlcNAc′ase) and α-mannosidase (Man′ase), have been evidenced. They have an optimal pH of 6–6.5 and 4, respectively. The same glycosidases were detected as soluble forms probably secreted by the seminal vesicle epithelium. We suggest that these enzymes might be involved in the recognition of α-mannose and β-N-acetylglucosamine residues present on the egg shell at the site of sperm entry. Mol. Reprod. Dev. 48:276–281, 1997. © 1997 Wiley-Liss, Inc.     

The trajectories of particles suspended in electrolytes under the influence of crossed electric and magnetic fields

We observed that particles, suspended in an electrolyte and brought into crossed magnetic and electric fields of low intensities, will deviate in the central part of the electrophoresis chamber of a standard Zeiss Cytopherometer with a component vertical to both fields. The direction and magnitude, however, were sharply at variance with what would be expected by the action of the Lorentz force (EMF) on the surface of the particles. The magnitude of the deviation depends upon the magnetic and electric field strength, the ion concentration of the suspension medium and the geometry of the chamber. The movement of the particles is due to streaming of the electrolyte which is mainly caused by inhomogeneities of the electric field in the electrophoresis chamber. The magnitude of the effect is high enough to occur under physiological conditions. Magneto-electrophoretic streaming might eventually act as a transducer mechanism which could explain the ability of some animals to orientate themselves in the geomagnetic field.