Effect of static magnetic fields on the budding of yeast cells

The effect of static magnetic fields on the budding of single yeast cells was investigated using a magnetic circuit that was capable of generating a strong magnetic field (2.93 T) and gradient (6100 T² m^?1). Saccharomyces cerevisiae yeast cells were grown in an aqueous YPD agar in a silica capillary under either a homogeneous or inhomogeneous static magnetic field. Although the size of budding yeast cells was only slightly affected by the magnetic fields after 4 h, the budding angle was clearly affected by the direction of the homogeneous and inhomogeneous magnetic fields. In the homogeneous magnetic field, the budding direction of daughter yeast cells was mainly oriented in the direction of magnetic field B. However, when subjected to the inhomogeneous magnetic field, the daughter yeast cells tended to bud along the axis of capillary flow in regions where the magnetic gradient, estimated by B(dB/dx), were high. Based on the present experimental results, the possible mechanism for the magnetic effect on the budding direction of daughter yeast cells is theoretically discussed. Bioelectromagnetics 31:622–629, 2010. © 2010 Wiley‐Liss, Inc.     

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.     

Spatial gradient effects of 120 mT static magnetic field on endothelial tubular formation in vitro

This study investigated the spatial magnetic gradient effects of static magnetic fields (SMF) on endothelial tubular formation by applying the maximum spatial gradient to a target site of culture wells for cell growth. The respective maximum values of magnetic flux density (B(max)), magnetic flux gradient (G(max)) and the magnetic force product of the magnetic flux density and its gradient (a parameter of magnetic force) were 120 mT, 28 mT/mm and 1428 mT(2)/mm. The effects of gradient SMF on tubular formation were compared with those of uniform SMF that has no spatial gradients on the entire bottom area of culture wells. Five experimental groups of 25 samples each were examined: (1) sham exposure (control); (2) peak gradient exposure in the peripheral part; (3) peak gradient exposure in the central part; (4) uniform exposure to 20 mT; (5) uniform exposure to 120 mT. The SMF or sham exposure was carried out for 10 days. Photomicrographs of tubular cells, immunostained with an anti-platelet-endothelial cell adhesion molecule-1 (PECAM-1 [CD31]) antibody as a pan-endothelial marker, were analyzed after the 10-day culture. Gradient SMF in the peripheral or central part was found to significantly promote tubular formation in terms of the area density and length of tubules in each peak gradient/force part of the wells, compared with the sham exposure. In contrast, uniform SMF did not induce any significant change in the tubular formation. These findings suggest that tubule formation can be promoted by applying the peak gradient/force to a target site of culture wells.     

The Influence of a gradient static magnetic field on an unstirred Belousov-Zhabotinsky reaction

It is believed that static magnetic fields (SMF) cannot affect the pattern formation of the Belousov-Zhabotinsky (BZ) reaction, which has been frequently studied as a simplified experimental model of a nonequilibrium open system, because SMF produces no induced current and the magnetic force of SMF far below 1 T is too low to expect the effects on electrons in the BZ reaction. In the present study, we examined whether the velocity of chemical waves in the unstirred BZ reaction can be affected by a moderate-intensity SMF exposure depending on the spatial magnetic gradient. The SMF was generated by a parallel pair of attracting rectangular NdFeB magnets positioned opposite each other. The respective maximum values of magnetic flux density (B(max)), magnetic flux gradient (G(max)), and the magnetic force product of the magnetic flux density its gradient (a magnetic force parameter) were 206 mT, 37 mT/mm, and 3,000 mT(2)/mm. The ferroin-catalyzed BZ medium was exposed to the SMF for up to 16 min at 25 degrees C. The experiments demonstrated that the wave velocity was significantly accelerated primarily by the magnetic gradient. The propagation of the fastest wave front indicated a sigmoid increase along the peak magnetic gradient line, but not along the peak magnetic force product line. The underlying mechanisms of the SMF effects on the anomalous wave propagation could be attributed primarily to the increased concentration gradient of the paramagnetic iron ion complexes at the chemical wave fronts induced by the magnetic gradient.     

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.     

旋磁场对健康人和矽肺病人血清铜蓝蛋白活力的影响

目的 :为了解旋磁场对健康人、矽肺患者血清铜蓝蛋白 (Cp)活力的影响。方法 :Cp采用联大茴香胺法进行测定。结果 :在旋磁场中曝磁 30分钟后 ,健康曝磁组血清Cp( 1 0 1 .1 2± 39.35 )与健康对照组血清Cp( 73.0 9± 36.72 )相比活力显著增加 (p <0 .0 5 ) ;矽肺曝磁组血清Cp( 1 63.36± 32 .64)与矽肺对照组血清Cp( 1 2 3.80± 2 8.2 5 )相比活力显著增加 (p <0 .0 1 )。结论 :旋磁场影响健康人和矽肺患者血清铜蓝蛋白的活力。     

磁流体在交变磁场中的热效应

以大豆卵磷脂为表面活性剂制备Fe₃O₄平均粒径为20 nm的磁流体,在10 kW,100 kHz的磁场中研究该磁流体的热效应.用温度计测量不同Fe₃O₄含量的水、琼脂的温度变化值,探讨Fe₃O₄含量和介质对温度的影响,为磁流体用于肿瘤热疗提供实验依据.实验结果表明,脂质磁流体在交变磁场作用下使周围升温,升温速度及平稳时的温度和Fe₃O₄的含量、磁场强度及周围介质有关,含量高,场强大,平稳温度值高,介质流动性好,加快热传递,升温快.通过调节磁场强度和磁流体的量可达到所需温度值.     

The detection threshold for extremely low frequency magnetic fields may be below 1000 nT-Hz in mice

Previous experiments with mice have shown that a repeated 1 h daily exposure to an ambient magnetic field shielded environment induces analgesia (anti-nociception). This shielding reduces ambient static and extremely low frequency magnetic fields (ELF-MF) by approximately 100 times for frequencies below 120 Hz. To determine the threshold of ELF-MF amplitude that would attenuate or abolish this effect, 30 and 120 Hz magnetic fields were introduced into the shielded environment at peak amplitudes of 25, 50, 100 and 500 nT. At 30 Hz, peak amplitudes of 50, 100, and 500 nT attenuated this effect in proportion to the amplitude magnitude. At 120 Hz, significant attenuation was observed at all amplitudes. Exposures at 10, 60, 100, and 240 Hz with peak amplitudes of 500, 300, 500, and 300 nT, respectively, also attenuated the induced analgesia. No exposure abolished this effect except perhaps at 120 Hz, 500 nT. If the peak amplitude frequency product was kept constant at 6000 nT-Hz for frequencies of 12.5, 25, 50, and 100 Hz, the extent of attenuation was constant, indicating that the detection mechanism is dependent on the nT-Hz product. A plot of effect versus the induced current metric nT-Hz suggests a threshold of ELF-MF detection in mice at or below 1000 nT-Hz.     

Magnetic field characteristics of electric bed-heating devices

Measurements of the flux density and spectra of magnetic fields (MFs) generated by several types of electric bed heaters (EBH) were made in order to characterize the MFs to which the fetus may be exposed in utero from the mother's use of these devices. Data on MFs were gathered from more than 1,300 in-home and laboratory spot measurements. In-home measurements taken at seven different positions 10 cm from the EBHs determined that the mean flux density at the estimated position of the fetus relative to the device was 0.45 μT (4.5 mG) for electric blankets and 0.20 μT (2.0 mG) for electrically heated water beds. A rate-of-change (RC) metric applied to the nighttime segment of 24 h EMDEX-C personal-dosimeter measurements, which were taken next to the bed of volunteers, yielded an approximate fourfold to sixfold higher value for electric blanket users compared to water-bed heater users. These same data records yielded an approximate twofold difference for the same measurements when evaluated by the time-weighted-average (TWA) MF exposure metric. Performance of exposure meters was checked against standard fields generated in the laboratory, and studies of sources of variance in the in-home measurement protocols were carried out. Spectral measurements showed that the EBH's measured produced no appreciable high-frequency MFs. Data gathered during this work will be used in interpreting results from a component of the California Pregnancy Outcome Study, which evaluates the use of EBHs as a possible risk factor in miscarriage. © 1996 Wiley-Liss, Inc.     

Waveform magnetic field survey in Russian DC and Swiss AC powered trains: a basis for biologically relevant exposure assessment

Recent epidemiological studies suggest a link between transport magnetic fields (MF) and certain adverse health effects. We performed measurements in workplaces of engineers on Russian DC and Swiss AC powered (16.67 Hz) electric trains using a computer based waveform capture system with a 200 Hz sampling rate. MF in DC and AC trains show complex combinations of static and varying components. The most probable levels of quasistatic MF (0.001-0.03 Hz) were in the range 40 microT. Maximum levels of 120 microT were found in DC powered locomotives. These levels are much higher than the geomagnetic field at the site of measurements. MF encountered both in DC and AC powered rail systems showed irregular temporal variability in frequency composition and amplitude characteristics across the whole frequency range studied (0-50 Hz); however, more than 90% of the magnetic field power was concentrated in frequencies 相似文献   

The wonders of magnetism

In this acceptance address for the Bioelectromagnetics Society's 2001 d'Arsonval Award, Dr. Tenforde reviews the highlights of the nonionizing field aspects of his research and scientific service career. These are focused in four areas: (a). development and application of microelectrophoretic methods to probe the surface chemistry of normal and cancerous cells; (b). research on the biophysical mechanisms of interaction and the dosimetry of static and extremely low frequency magnetic fields; (c). application of extremely high intensity magnetic fields in several spectroscopic methods for probing the detailed structures of large biological macromolecules; and (d). development of national and international guidelines for the exposure of workers and members of the general public to electromagnetic fields with frequencies spanning the entire nonionizing electromagnetic spectrum.     

Reduction of the background magnetic field inhibits ability of Drosophila melanogaster to survive ionizing radiation

The effects of exposure to an environment where the background magnetic field (BMF) has been reduced were studied on wild‐type Drosophila melanogaster by measuring its ability to survive a single exposure to ionizing radiation (IR) during its larval stage. The experimental design presented shows a timeframe, IR dose, and BMF parameters that will cause a significant and reproducible reduction of survival on this insect model. These results suggest that BMFs may play a fundamental role in the recovery or harm of a biological system that is exposed to single doses of IR. Bioelectromagnetics 33:706–709, 2012. © 2012 Wiley Periodicals, Inc.     

Inhibition of pentylenetetrazole-induced seizure in mice by using a 4 Hz magnetic field: a comparative study with a 60 Hz magnetic field

We investigated the comparative effects of 4 and 60 Hz magnetic fields on pentylenetetrazole (PTZ)-induced seizure in mice. For this study, we measured the latent time to seizure, seizure duration, and lethality induced by PTZ in mice exposed to 4 and 60 Hz magnetic fields (MF) for 30 min. Compared to sham-exposed controls, the latent time to tail twitching and seizure in the 4 Hz MF group was significantly decreased while the latent time to seizure in the 60 Hz MF group was significantly increased. The seizure duration in the 4 Hz MF group was significantly decreased while that in the 60 Hz MF group was significantly increased. More importantly, while the mice exposed to a 60 Hz MF experienced significantly increased lethality after seizure convulsion, those exposed to a 4 Hz MF showed no lethality, with a shortening of the duration of seizure. This beneficial effect of a 4 Hz MF on seizure has the same implication as the anti-oxidative effects of a 4 Hz MF observed in our previous work. The results of our current and previous works indicate that a 4 Hz MF may be used as a therapeutic physical agent for the treatment of oxidative stress-induced diseases, including seizure, with or without chemical drugs.     

Magnetoreception in fish

Magnetoreception is the ability of organisms to perceive magnetic fields in the surrounding environment and changes in its properties such as field direction, intensity and gradient, where the effect on organisms can manifest as an array of reactions. As the magnetic sense is found in many taxa, both evolutionarily young and old, it can be assumed that magnetoreception came into existence as one of the first sensory systems. Many studies on the effect of magnetic fields on fishes have considered both fishes that migrate for long distances and those that are more or less sedentary. Research has focused on tracing the perception of the geomagnetic field by fishes and understanding magnetic fields that are smaller and larger than the ambient Earth's geomagnetic field. The question of the effect of magnetic fields of values higher than the Earth's is gaining importance with the increasing effect of anthropogenic magnetic and electromagnetic fields in aquatic ecosystems. This review draws together the results of studies on the effect and reception of natural and human-generated magnetic fields on fishes at various stages of ontogeny, chronologically arranged from gametes, through embryonic development, embryonic and larval motor function, directional reactions of embryos and larvae, orientation of fishes, to the mechanisms of magnetic field reception. The present state of knowledge indicates a common nature of effect on various ontogenetic stages of fishes. However, understanding of the mechanisms of magnetic sense in fishes and its relevance for ecological outcomes highlights that further progress requires more detailed research.     

Human exposure to magnetic fields: A comparative assessment of two dosimeters

Two types of dosimeters for measuring human exposure to 60 Hz magnetic fields were compared. Fifty adults wore the single-axis, wrist model AMEX (average magnetic field exposure system) and the triple axis, hip-pocket or pouch model AMEX-3D meters for 2 days. Ninety-six percent of the tests were accomplished without apparent dosimeter failure. The average root mean square magnetic flux density measurements with the AMEX3D (mean = 0.10 μT, S.D. = 0.07, range = 0.03 ? 0.31) were significantly higher than with the AMEX meter (mean = 0.07 μT, S.D. 0.05, range = 0.02 ? 0.27 μT) (t test, P < 0.01). There was substantial correlation between the AMEX and the AMEX-3D measurements (Pearson's correlation coefficient = 0.65, P < 0.01) but poor concordance (Intraclass correlation coefficient = ? 0.25). These results suggest that there is a wide variation in exposure to extremely low frequency magnetic fields in the population. Magnetic field measurements with the AMEX-3D are nearly always higher than with the AMEX dosimeters. Caution is advised when comparing magnetic field measurements made with different types of dosimeters. © 1994 Wiley-Liss, Inc.     

Contribution of a 300 kHz alternating magnetic field on magnetic hyperthermia treatment of HepG2 cells

We investigated the relative contributions of temperature and a 300 kHz alternating magnetic field (AMF) on magnetic hyperthermia treatment (MHT). Our system consisted of an induction coil, which generated AMF by electric current flow, and a newly developed, temperature‐controlled circulating water‐jacketed glass bottle placed inside the coil. The AMF generator operated at a frequency of 300 kHz with variable field strength ranging from 0 to 11 mT. Four treatment conditions were employed: (A) control (37 °C, 0 mT), (B) AMF exposure (37 °C, 11 mT), (C) hyperthermia (46 °C, 0 mT), and (D) hyperthermia plus AMF exposure (46 °C, 11 mT) for 30 min. Cell viability and apoptotic death rate were estimated. The relative contributions or interactions of hyperthermia (46 °C) and AMF (11 mT) on MHT were evaluated using 2 × 2 factorial experiment analysis. Group A was statistically different (P < 0.05) from each of the other treatments. The observed effects on both cell viability and apoptotic cell death were influenced by temperature (97.36% and 92.15%, respectively), AMF (1.78% and 4.99%, respectively), and the interactions between temperature and AMF (0.25% and 2.36%, respectively). Thus, the effect of hyperthermia was significant. Also, AMF exposure itself might play a role in MHT, although these observations were made in vitro. These findings suggest a possible presence of an AMF effect during clinical magnetic hyperthermia. Bioelectromagnetics 34:95–103, 2013. © 2012 Wiley Periodicals, Inc.     

Acute exposure to 50 Hz magnetic fields with harmonics and transient components: lack of effects on nighttime hormonal secretion in men

The purpose of this study was to examine whether low frequency magnetic field (MF) influences nighttime secretion of hormones, particularly melatonin. Ten healthy males stayed in the experimental room (2.7 m cube with 3 axis Merritt coils) on two separate nights. On one night, subjects were exposed to linearly polarized 50 Hz, 20 microT sinusoidal MF with the third (30%) and the fifth (10%) harmonics and repetitive transient waves (1 burst/s of 1 kHz waves, exponentially attenuated with a duration of 50 ms; initially 100 microT peak), and the other night was for blind control. During the nights (2000-0800 h, including sleeping time, 2300-0700 h), blood samples were collected from the subjects at 1 h intervals for determining the levels of plasma hormones (melatonin, growth hormone (GH), cortisol, prolactin) and at 10 min intervals from 2200 to 0200 h for observing the GH surge induced by sleep. Statistical analyses revealed no significant difference between the 2 nights in the profiles of the four hormones, and the result suggested that extremely low frequency (ELF) or intermediate frequency (IF) MF to which humans are exposed residentially has no acute effect on nighttime secretion of hormones, particularly melatonin.     

极低频磁场对大鼠急性和慢性关节炎影响的研究

目的：探讨极低频磁场对大鼠急性和慢性关节炎模型的影响。方法：大鼠足内皮下注射角叉菜胶建立急性关节炎模型,磁场分别暴露6h和8h,注射弗氏完全佐剂建立慢性关节炎模型,磁场暴露7d,每天6h,观察炎症肿胀和炎性细胞因子的改变情况。结果：急性和慢性关节炎大鼠经过不同时间的磁场暴露后,踝关节和足垫肿胀均有不同程度的减轻,急性模型暴露6h和慢性模型血清和关节液的细胞因子均无改变,急性模型暴露8h血清IL-6,关节浸液IL-6和TNF-α均比对照组降低,其余指标无变化,但是有下降的趋势。结论：极低频磁场对急性和慢性关节炎肿胀有抑制作用,每天暴露8h可以部分抑制细胞因子的产生,但其详细机制还有待于进一步研究。     

Magnetic field influence on electrical properties of human blood measured by impedance spectroscopy

The impedance spectroscopy technique (IST) was used for studying the effect of a 0.5 T magnetic field on the electrical properties of whole human blood. A Solartron SI 1260 spectrometer was used to measure the impedance spectra of magnetic field exposed blood samples compared to non-exposed samples. An equivalent electrical circuit model, consisting in a resistance Rs in series with a parallel circuit formed by a constant phase element (CPE) and another resistance Rp, is proposed to fit the data in both cases. The experiment used 3 ml human blood samples from 160 healthy donors. A Wilcoxon matched pairs statistical test was applied to the data. The data analysis seems to show a statistically significant increase of the values of resistance Rp (Z = 5.06, P < 0.001) and capacitance CT (Z = 3.32, P < 0.001) of the blood exposed to magnetic field, by approximately 10.4% and 1.9%, respectively.     

A dosimeter for assessment of exposures to ELF fields

There are currently no biological indicators of electromagnetic field exposure to aid investigation of the biological effects of ELF fields, but this hiatus is partly compensated for by the ease with which the external fields can be measured. The subject of this report is a small electronic instrument that can log electric-, magnetic-, and transient-field intensities of individual subjects for a duration of two weeks, thus allowing exposure to be assessed in considerable detail. A preliminary survey conducted with the instrument has shown clear differences in domestic and occupational exposures of specific groups. Simple analytical models can be fitted to the field-exposure data by adjusting a few parameters such as current, intensity, and distance. Such modeling may be increasingly useful as the data base on exposures expands.