Tsukasa Shigemitsu

Circularly polarized 50-Hz magnetic field exposure reduces pineal gland and blood melatonin concentrations of Long-Evans rats

In order to determine if pigmented rats also exhibit melatonin suppression like that described for albino rats exposed to circularly polarized, 50-Hz, 1-muT magnetic fields for 6 weeks, two experiments were conducted with Long-Evans rats. The field-exposed experimental group received circularly polarized, 50-Hz, 1-muT magnetic fields for 6 weeks, the concurrent sham-exposed control group was exposed to the stray field of 0.02 muT. In addition, prior to the exposure experiment, two cage-control groups were placed in the facility for 6 weeks without activation of the 50-Hz magnetic field generation apparatus. Rats were sacrificed at 12.00 and at 24.00 h for collection of plasma and pineal gland: melatonin was determined by radioimmunoassay. Significant reductions of plasma and pineal gland melatonin contents were observed at 0.02 muT as compared to the control values, and a further reduction was observed at 1 muT. As do albino rats, pigmented rats rats also exhibit melatonin suppression when exposed to time-varying magnetic fields.

Horizontal or vertical 50-Hz, 1-μT magnetic fields have no effect on pineal gland or plasma melatonin concentration of albino rats

Three experiments were carried out on male Wistar-King rats to determine if 6 weeks of exposure to horizontally- or vertically-oriented 1-microT, 50-Hz magnetic fields suppresses melatonin content in plasma and pineal gland, as does 6 weeks of exposure to circularly-polarized, 50-Hz, 1-microT magnetic fields. In each experiment, a concurrent sham-exposed control group was exposed to a stray field of 0.02 microT. In addition, a separate control experiment was completed between the horizontal and vertical field experiments in which cage-controls were housed in the exposure facility for 6 weeks without activation of the magnetic field coils. Subjects were sacrificed at 12:00 or at 24:00 h for collection of plasma and pineal gland; melatonin was determined by radioimmunoassay. In contrast to the results of experiments with rotating-vector magnetic fields, there were no significant differences among 1-microT, 0.02-microT and control groups in melatonin concentration of pineal gland or plasma.

Equivalent dipole moment method to characterize magnetic fields generated by electric appliances: extension to intermediate frequencies of up to 100 kHz

A previously proposed simple method to characterize magnetic fields near electric appliances was extended to intermediate frequencies of up to 100 kHz. The method consists of identification of the magnetic dipole moment that is equivalent to a magnetic field source of an electric appliance and simple estimation of the magnetic field distribution around the appliance. In addition, frequency characteristics of the magnetic field were taken into account by considering the harmonic components in the magnetic-field waveform for both power frequency and intermediate frequency ranges. For the application of the method, a wide-frequency range (from power frequency to 100 kHz) magnetic-field measuring instrument was developed and applied to appliances that generate intermediate frequency magnetic fields, i.e., an induction heating cooker, a TV set, and a metal detector. The results revealed that the method is adequate to quantify the magnetic field near the electric appliances at frequencies of up to 100 kHz.

Low stray ELF magnetic field exposure system for in vitro study.

An exposure facility for wide application to cell exposure to an ELF (extremely low frequency) magnetic field was developed. It is suitable for conducting experiments under a high-intensity, variable-frequency magnetic field, on the biological effects of the ELF magnetic field in an in vitro study. The exposure system consists of Merritts 4-square coil as a basic component to generate the required magnetic field intensity of 10 mT at 50 Hz with spatial field uniformity less than +/-3% in a 400 mm cube. Concentric compensation coils are adopted to eliminate the effects of stray fields on sham (control) samples in the vicinity of the exposure system. The uniformity of the magnetic field in the exposure coil, the increase in the power supply capacity due to the existence of compensation coils, and the stray field estimation were investigated carefully. After fabricating the system, performance tests were carried out and all the characteristics were found to be satisfactory. In addition, the ideal configuration for a concentric coil system was proposed.

Investigation of ELF magnetically induced current inside the human body: Development of estimation tools and effect of organ conductivity

Regarding the possible biological effects caused by exposure to ELF (extremely low frequency) magnetic fields, magnetically induced current inside the human boldy has been a focus of research. To clarify the induced current characteristics inside the human body, we develop estimation tools. One was a numerical calculation code and the other was a human model. The numerical calculation code was based on a surface charge method. The human model was composed of several organs and other parts of the human body, whose shapes were spheroids or cylinders. Organs taken into account were the brain, heart, lungs, liver, and intestines. The validity of the calculation code was shown by comparing it with an analytical solution using a homogeneous spheroid model. The discrepancy was within 6.5%. Applicability of the code to the human body was shown. In addition, by applying the calculation code to the human model, effects of organ conductivity differences vis-a-vis the induced current distribution were estimated. It was found that the organ conductivity value very much affected the induced current distribution inside the human body.

A newly designed and constructed 20 kHz magnetic field exposure facility for in vivo study.

Exposure to man-made electromagnetic fields has increased over the past century. As a result of exposure to these fields, concerns have been raised regarding the relationship between electromagnetic fields and human health. Interest in the biological and health effects of intermediate frequency (IF) magnetic fields has grown recently because of the increase in public concern. In order to investigate whether IF magnetic fields have biological effects, we have developed a 20 kHz (IF) magnetic field exposure system for in vivo studies. The exposure facility was designed to study the biological effects of IF magnetic field on laboratory animals. The facility consists of a 9 m x 9 m x 5 m high room containing seven separate rooms including a 5.3 m x 4.5 m x 3 m high specific-pathogen free exposure room. The dimensions of the exposure system are 1.6 m x 1.6 m x 1.616 m high located inside this exposure room. The system is designed to provide magnetic fields up to 200 microT at 20 kHz with the uniformity within +/-5% over the space occupied by animals. After constructing the facility, performance tests were carried out. As a result, it was confirmed that our facility met requirements for evaluation of the biological effects of IF magnetic field on small animal experiments. In this paper, the design, construction, and results of evaluation of an animal exposure facility for the in vivo biological effects of an IF magnetic field are described.

Effect of magnetic field on pineal gland volume and pinealocyte size in the rat.

Abstract: Light microscopic observations on the superficial pineal gland of Wistar‐King rats were made to examine whether or not pineal volume and pinealocyte size, expressed as nuclear density, at daytime or nighttime are affected by long‐term exposure to 50 Hz rotating magnetic field (MF) at 5.0 μT. Determinations of pineal volume and pinealocyte size were repeated twice (April and October) during the year. Size of pinealocytes in MF‐exposed and sham‐exposed rats exhibited, in addition to the difference between peripheral and central regions, regional differences in a proximodistal direction; pinealocytes in the distal and middle‐peripheral regions were usually larger than those in the proximal and middle‐central regions at daytime or nighttime. In October, distal and proximal pinealocytes showed significant day‐night changes in size in sham‐exposed rats, but not in MF‐exposed animals. The situations in the two groups were almost reversed in April. Significant day‐night differences were scarcely found in pinealocyte size in the middle region in the two groups. Throughout the study, pineal volume and pinealocyte size in each region were generally the same between MF‐exposed and sham‐exposed rats at daytime or nighttime. The results suggest that pinealocytes in the distal and proximal regions, but not those in the middle region, are affected by MF‐exposure; day‐night differences in sizes of distal and proximal pinealocytes appear in April and disappear in October under the influence of MF. MF may exert an effect on mechanisms controlling day‐night rhythms of pinealocyte size in the rat.

Biological and Health Effects of Electromagnetic Fields Related to the Operation of MRI/TMS

This paper reviews issues of biological effects and safety aspects of the electromagnetic fields related to both Magnetic Resonance Imaging (MRI) and Transcranial Magnetic Stimulation (TMS) as a diagnostic technique. The noninvasive character of these diagnostic techniques is based on the utilization of the electromagnetic fields such as the static magnetic field, time-varying magnetic field, and radiofrequency electromagnetic field. Following the short view of the history and the principle of these noninvasive techniques, we review the biological effects of the electromagnetic fields, the health effects and safety issues related to MRI/TMS environments. Through a discussion of biological and health effects, it shows briefly guidelines which provide a consideration in human risk for both patients and medical staff. Finally, safety issues related to MRI/TMS are discussed with the highlighting of the guideline such as the International Commission on NonIonizing Radiation Protection (ICNIRP) and EMF Directive (Directve2013/35/EU) of European Union.

50-Hz Magnetic Field Exposure and Melatonin in the Rat

In order to understand possible effects of magnetic fields exposure on biological system, it is important to carry out the experiments under well defined experimental conditions. Circularly polarized, elliptically polarized at various ratios of major versus minor axes, as well as linearly polarized fields can be found under AC three-phase transmission lines.1,2 Although circularly polarized field exists only very close to the transmission lines and not at the ground level, we have carried out exposure experiments of circularly polarized, elliptically polarized and linearly polarized fields for the later consideration of the possible mechanisms involved in the animal exposure.

Electromagnetic Fields, Biophysical Processes, and Proposed Biophysical Mechanisms

As described in previous section 1.3.3, there are many sources of ELF electromagnetic fields. Humans are exposed daily to these naturally and artificially originated fields. During the past three decades, questions have been raised about whether the exposure to human-made ELF electromagnetic fields might be linked to adverse health effects. Since the paper of Wertheimer and Leeper (1979), there have been many reports on the question of an association between seemingly small increased exposure to ELF magnetic fields in the environment and an approximately two-fold increase in the incidence of the rare disease state of leukemia in children. Although ELF magnetic field interactions with biological systems have been proposed, no biophysical mechanism that explains biological effects produced by lowlevel magnetic fields, those less than 0.1 mT, has been established. There are several hypotheses about interactions of ELF magnetic fields with living organisms. Proposed mechanism include (1) induced current, (2) direct effect, (3) force on biomagnetic materials, (4) effects on free radicals, (5) ion cyclotron resonance, (6) charge transfer processes, and (7) stochastic resonance, etc.