bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of exposure to a circularly polarized 50‐Hz magnetic field on plasma and pineal melatonin levels in rats
Authors: Kato Masamichi , Honma Ken‐Ichi , Shigemitsu Tsukasa , Shiga Yoichi
Published: February 2006

We sought to determine whether a 6‐week exposure to a 50‐Hz rotating magnetic field influences melatonin synthesis by 11–18 week‐old Wistar‐King male rats. Rats were exposed continuously to a rotating magnetic field at 1, 5, 50, or 250 μT (spatial vector rms) for 6 weeks, except for twice‐weekly breaks of about 2 h for cleaning of cages and feeding. The rats were housed in exposure and sham‐exposure facilities, which were located in the same room, under a 12:12 light‐dark photoperiod (lights on at 06:00 h). The room was constantly illuminated by 4 small, dim red lights (< 0.07 lux in dark period). Levels of plasma and pineal gland melatonin were determined by radioimmunoassay. A significant decrease of melatonin was observed between the control group and groups exposed to a magnetic field at a flux density in excess of l μT during the night time, but no statistical differences were found among the exposed groups. These results indicate that subchronic exposure of albino rats to a 50‐Hz rotating magnetic field influences melatonin production and secretion by the pineal gland. © 1993 Wiley‐Liss, Inc.
50‐Hz magnetic field exposure system for small animals
Authors: Shigemitsu Tsukasa , Takeshita Kazuma , Shiga Yoichi , Kato Masamichi
Published: February 2006

The design, construction, and results of evaluation of an animal‐exposure system for the study of biological effects of extremely low frequency (ELF) magnetic fields are described. The system uses a square coil arrangement based on a modification of the Helmholtz coil. Due to the cubic configuration of this exposure system, horizontal and vertical magnetic fields as high as 0.3 mT can be generated. Circularly polarized magnetic fields can also be generated by changing the current and phase difference between two sets of coils. Tests were made for uniformity of the magnetic field, stray fields, sham‐exposure ratio of stray field, changes of temperature and humidity, light intensity and distribution inside the animal‐housing space, and noise due to air‐conditioning equipment. Variation of the magnetic field was less than 2% inside the animal housing. The stray‐field level inside the sham‐exposure system is less than 2% of experimental exposure levels. The system can be used for simultaneous exposure of 48 rats (2 to a cage) or 96 mice (4 to a cage). © 1993 Wiley‐Liss. Inc.
Repeatability of measurements of residential magnetic fields and wire codes
Authors: Dovan Thanh , Kaune William T. , Savitz David A.
Published: February 2006

Several epidemiological studies have been based on wire codes (i.e., categories of electrical wiring configurations near residences) or on in‐home spot measurements of magnetic flux density (MFD) as surrogates for short‐ and long‐term exposure of children and adults to residential magnetic fields. We used wire code and MFD measurements that were made in 81 Colorado homes in 1985 and again in 1990 to assess their repeatability over periods of 0–24 h and 5 years. These homes, a subset of those lived in by subjects from the case‐control study of Savitz et al. [Am J Epidemiol 128:21–38, 1988]. were divided into four approximately equally sized groups that were differentiated by wire code and by case‐control status. Eight homes were assigned wire codes in 1990 that differed from the 1985 coding of Savitz and colleagues [1988]; of these, seven were coded as highcurrent configuration (HCC) and one as low‐current configuration (LCC) in 1985. Overall, 37 homes were coded as HCC in 1990 compared with 38 homes in 1985. Coding differences were due to differing distance measurements (four homes), differing “thick” vs. “thin” categorization of primary‐distribution line‐conductor sizes (two homes), differing “first‐span” vs. “second‐span” categorization of secondary wires (one home), and physical changes in proximate electrical wiring (one home). Coefficients of correlation between MFD spot measurements that were separated in time by 0–24 h range between 0.70 and 0.90. The coefficient between spot measurements made in 1985 and then again in 1990 is 0.70. These coefficients are similar for HCC and LCC homes and do not depend on whether residential appliances were turned on or off. The data show (at least for the portion of Colorado studied) that residential wire code and, more surprisingly, spot MFD measurements, are fairly reliable over 0–24‐h and 5‐year periods. © 1993 Wiley‐Liss, Inc.
Use of a spreadsheet program to calculate the electric field/current density distributions induced in irregularly shaped, inhomogeneous biological structures by low‐frequency magnetic fields
Authors: Hart Francis X. , Evely Kimberly , Finch Carla D.
Published: February 2006

A commercially available spreadsheet program is used on a microcomputer to calculate the electric field/current density distributions induced in irregularly shaped, inhomogeneous objects by low‐frequency magnetic fields. A finite‐difference method is applied to an impedance grid that represents the object being modeled. This approach is validated by comparison with 1) the analytical results of an eccentric cylinder model and 2) measurements made on a square dish containing a saline solution and square, insulating inclusions. Application of the method is also made to a culture dish with a layer of sediment exposed to a horizontal magnetic field. © 1993 Wiley‐Liss, Inc.
Effects of pulsed magnetic fields on the developing mouse embryo
Authors: Frölen Hakon , Svedenstål Britt‐Marie , Paulsson Lars‐Erik
Published: February 2006

The influence of a pulsed magnetic field (PMF; sawtooth with 45‐μs linear rise time and 5‐μs decay time, peak strength of 15 μT, and frequency 20 pps) on the embryogenesis of CBA/S mice was investigated in five experiments based on a total of 707 exposed and 543 unexposed primigravidas. Sham and PMF exposures began on day 1 of gestation (experiments 1 and 2), on day 2 (experiment 3), on day 5 (experiment 4). and on day 7 (experiment 5): all exposures continued until day 19 post conception (p.c.) when they were terminated, at which time the following variables were measured: number of implants; number of placental resorptions; number of living fetuses; number of dead fetuses; number of malformations in living and dead fetuses; and length and body mass of living fetuses. Control dams were sham‐exposed concurrently with corresponding. PMF‐exposed dams. With the exception of experiment 5, in which exposure to PMF started on day 7 p.c., all groups of exposed mice had significantly more placental resorptions when compared with concurrent controls. The increased resorption rate was not reflected in a reduction in litter size or in the number of litters. A significant increase in malformed fetuses was not seen in any of the exposed groups, or when groups were pooled. Only in experiment 1 was the number of dead fetuses affected by exposure to PMF. The effect of PMF on the implantation rate was not significant. Body mass and length of exposed fetuses were significantly reduced only when the PMF treatment began on day 7 p.c. That PMF‐treated mice had significantly more placental resorptions when exposure began on day 5 p.c. or earlier (before implantation), but not when exposure began on day 7 (after implantation), may indicate a causative pre‐implantation effect. Because a PMF‐induced increase in the number of resorptions has not been observed in other strains of mice, the effect might be strain‐related. © 1993 Wiley‐Liss, Inc.
Effects of low‐frequency magnetic fields on fetal development in rats
Authors: Huuskonen Hannele , Juutilainen Jukka , Komulainen Hannu
Published: February 2006

We studied effects of alternating magnetic fields on the embryonic and fetal development of rats. Mated females of the Han:Wistar‐strain were sham exposed or exposed continuously to a 50‐Hz field or to a 20,000 pulse‐per‐second (pps) sawtooth magnetic field from day 0 to day 20 of pregnancy for 24 h/day until necropsied on day 20. The respective peak‐to‐peak intensities of the fields were 35.6 μT (sinewave) and 15.0 μT (sawtooth). Each treatment group contained 72 bred females. Control animals were kept under the same conditions without the magnetic field. No adverse effects were seen in the dams. The mean numbers of implantations and living fetuses per litter were statistically significantly increased in the 50‐Hz group. There were, however, three total resorptions of litters in dams of the control group, which contributed to the difference in the number of living fetuses. The corrected body‐mass gains (gains without uterine content) of dams were similar in all groups. Pregnancy rates, incidences of resorptions. late fetal deaths, and fetal body masses were similar in all groups. The incidence of fetuses with minor skeletal anomalies was statistically significantly increased in both exposed groups. Only one serious malformation (anophthalmia, sawtooth‐exposed group) and a few minor visceral malformations were found. In conclusion, the magnetic fields used in this study did not increase the incidence of major malformations or resorptions in Wistar rats. The increased number of skeletal anomalies and implantations we observed indicates, however, that some developmental effects in rats may attend exposure to time‐varying magnetic fields. © 1993 Wiley‐Liss. Inc.
Chicken embryo fibroblasts exposed to weak, time‐varying magnetic fields share cell proliferation, adenosine deaminase activity, and membrane characteristics of transformed cells
Authors: Parola Abraham H. , Porat Nurith , Kiesow Lutz A.
Published: February 2006

Chicken embryo fibroblasts (CEF) exposed to a sinusoidally varying magnetic field (SVMF) (100 Hz, 700 μT, for 24 h) showed a remarkable rise of segmental rotational relaxation rate of adenosine deaminase (ADA, EC 3.5.4.4) as determined by multifrequency phase fluorometry. Pyrene‐labeled, small subunit ADA was applied to cultured (normal) CEF, which have available and abundant ADA complexing protein (ADCP) on their plasma membranes. Sine‐wave‐modulated fluorometry of the pyrene yielded a profile of phase angle vs. modulation frequency. In SVMF‐treated cells and in Rous‐sarcoma‐virus (RSV) transformed cells the differential phase values at low modulation frequencies of the excitation are remarkably reduced. This effect is magnetic rather than thermal, because the temperature was carefully controlled and monitored; nevertheless to further check this matter we studied CEF, infected by the RSV‐Ts68 temperature‐sensitive mutant (36°C transformed, 41°C “revertant”). When grown at 36°C in the SVMF, cells did not show the slightest trend towards reversion, as would be expected had there been local heating. Concomitant with the increased segmental rotational relaxation rate of ADA, there was a decrease in fluorescence lifetime and a slight, yet significant, increase in membrane lipid “microfluidity.” These biophysical observations prompted us to examine the effect of SVMF on cell proliferation and ADA activity (a malignancy marker): higher rates of cell proliferation and reduced specific activity of ADA were observed. © 1993 Wiley‐Liss, Inc.
Early pregnancy loss and exposure to 50‐Hz magnetic fields
Authors: Juutilainen Jukka , Matilainen Pekka , Saarikoski Seppo , Läärä Esa , Suonio Sakari
Published: February 2006

The possibility of an association of early pregnancy loss (EPL) with residential exposure to ELF magnetic fields was investigated in a case‐control study. Eighty‐nine cases and 102 controls were obtained from the data of an earlier study aimed at investigating the occurrence of EPL in a group of women attempting to get pregnant. Magnetic‐field exposure was characterized by measurements in residences. Strong magnetic fields were measured more often in case than in control residences. In an analysis based on fields measured at the front door, a cutoff score of 0.5 A/m (0.63 μT) resulted in an odds ratio of 5.1 (95% confidence interval 1.0–25). The results should be interpreted cautiously due to the small number of highly exposed subjects and other limitations of the data. © 1993 Wiley‐Liss. Inc.
A 50‐Hz magnetic field induces structural and biophysical changes in membranes
Authors: Paradisi Silvia , Donelli Gianfranco , Santini Maria Teresa , Straface Elisabetta , Malorni Walter
Published: February 2006

The effects of a 50‐Hz extremely low frequency magnetic field on cultured K562 cells growing in suspension were studied by means of scanning electron microscopy and electron paramagnetic resonance spectroscopy. Exposure of K562 cells at 2.5 mT for periods to 96 hours induced significant changes in cell‐surface structure and physiology without modification of proliferative capability as indicated by quantitative analysis. Thus extremely low frequency fields seem able to induce injurious, sublethal cell alterations, and the plasma membrane seems to play an important role in this effect. © 1993 Wiley‐Liss, Inc.
Perturbations of plant leaflet rhythms caused by electromagnetic radio‐frequency radiation
Authors: Ellingsrud Svein , Johnsson Anders
Published: February 2006

The minute‐range up and down rhythms of the lateral leaflets of Desmodium gyrans has been studied when exposed to electromagnetic radiation in the radio‐frequency (RF) range. The RF radiation was applied as homogeneous 27.12 MHz fields in specially‐designed exposure cells(and in some cases as non‐homogeneous radiation of 27 MHz. amplitude modulated by 50 Hz, in front of commercial diathermy equipment). All fields were applied as pulses. We report effects in the leaflet rhythms such as temporary changes in the amplitude, period, and phase. The radiation could also cause temporary or complete cessations of the rhythms. The lowest dose (8 W/cm2) used was still effective. © 1993 Wiley‐Liss. Inc.
Behavioral effects of long‐term exposure to magnetic fields in rats
Authors: Trzeciak Henryk I. , Grzesik Jan , Bortel Maria , Kuśka Rafał , Duda Dorota , Michnik Jerzy , Małecki Andrzej
Published: February 2006

Male rats and pregnant and nonpregnant female rats of the Wistar strain were sham‐exposed or exposed to static (0.49 T) or to extremely low frequency (50 Hz) magnetic fields (0.018 T) 2 h per day for 20 consecutive days. Measures of irritability, exploratory activity, and locomotion were made in that order before and after the 4th, 10th, and 17th 2‐h exposures. A reliable decrease in the irritability of rats after repeated exposure to a static or undulating field was found. No significant effects of treatment conditions on open‐field behavior and locomotor activity were observed. Pregnancy had no influence on the behavioral end points. These results indicate that irritability of rats may be used as a simple behavioral indicant of mammalian sensitivity to magnetic fields. © 1993 Wiley‐Liss. Inc.
Experimental search for combined AC and DC magnetic field effects on ion channels
Authors: Galt Sheila , Sandblom John , Hamnerius Yngve , Höjevik Per , Saalman Elisabeth , Nordén Bengt
Published: February 2006

The hypothesis that specific combinations of DC and low frequency AC magnetic fields at so‐called cyclotron‐resonance conditions could affect the transport of ions through ion channels, or alter the kinetics of ion channels (opening and closing rates), has been tested. As a model system, the ion channels formed by gramicidin A incorporated in lipid bilayer membranes were studied. No significant changes in channel conductance, average lifetime, or formation rate as a function of applied fields could be detected over a wide range of frequencies and field strengths. Experiments were carried out to measure the time‐resolved single‐channel events and the average conductances of many‐channel events in the presence of K+ and H+ ions. The channel blocking effect of Ca++ was also studied. © 1993 Wiley‐Liss. Inc.
In vivo studies of the effect of magnetic field exposure on ontogeny of choline acetyltransferase in the rat brain
Authors: Sakamoto Shuichi , Hagino Nobuyoshi , Winters Wendell D.
Published: February 2006

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. As far as the development of cholinergic neural circuits was concerned, these test magnetic environments did not interfere in their development and it suggested that parental‐fetal intercommunication might provide relatively stable states for neural development, even under these test magnetic environments. © 1993 Wiley‐Liss. Inc.
Studies on the possible biological effects of 50 Hz electric and/or magnetic fields: Evaluation of some glycolytic enzymes, glycolytic flux, energy and oxido‐reductive potentials in human erythrocytes exposed in vitro to power frequency fields
Authors: Dachà M. , Accorsi A. , Pierotti C. , Vetrano F. , Mantovani R. , Guidi G. , Conti R. , Nicolini P.
Published: February 2006

An attempt has been made to understand whether 50 Hz electric and magnetic fields (EMFs) are involved in producing bioeffects by exposing human erythrocytes in vitro. The study evaluated some key glycolytic enzymes, glucose consumption, lactate production, energy charge, 2,3‐diphosphoglycerate, and reduced glutathione levels. all of which are biochemical parameters significant to erythrocyte function. Cells exposed to individual or superimposed EMFs have not shown any significant difference compared with the controls. © 1993 Wiley‐Liss. Inc.
The role of coherence time in the effect of microwaves on ornithine decarboxylase activity
Authors: Litovitz T. A. , Krause D. , Penafiel Miguel , Elson Edward C. , Mullins J. M.
Published: February 2006

Previously, we demonstrated the requirement for a minimum coherence time of an applied, small amplitude (10 μT) ELF magnetic field if the field were to produce an enhancement of ornithine decarboxylase activity in L929 fibroblasts. Further investigation has revealed a remarkably similar coherence time phenomenon for enhancement of ornithine decarboxylase activity by amplitude‐modulated 915 MHz microwaves of large amplitude (SAR 2.5 W/kg). Microwave fields modulated at 55, 60, or 65 Hz approximately doubled ornithine decarboxylase activity after 8 h. Switching modulation frequencies from 55 to 65 Hz at coherence times of 1.0 s or less abolished enhancement, while times of 10 s or longer provided full enhancement. Our results show that the microwave coherence effects are remarkably similar to those observed with ELF fields. © 1993 Wiley‐Liss. Inc.
Effects of time‐varying uniform magnetic fields on Natural Killer cell activity and antibody response in mice
Authors: de Seze R. , Bouthet C. , Tuffet S. , Deschaux P. , Caristan A. , Moreau J. M. , Veyret B.
Published: February 2006

Natural Killer cell activity and antibody response were studied in Balb/c mice which were exposed in vivo to uniform pulsed magnetic fields (square‐wave, 0.8 Hz, 120 mT maximum field strength, 0.1 s rise‐time) for 5 days, 10 h/day. No effects were found in antibody response to sheep red blood cell (SRBC) immunization as assayed by counting the plaque‐forming cells (PFC) in the spleens of animals on the sixth day. Following 5‐day exposures, the activity of Natural Killer (NK) cells was measured in vitro by challenge with YAC‐1 cells, in experiments in which mice were not immunized. An increase of NK cytotoxic activity due to exposure was found which depended on the age of the mice (effect observed above 12 weeks) and on the strength of the applied field (effect observed above 30 mT). © 1993 Wiley‐Liss. Inc.
A scheme for incorporating DC magnetic fields into epidemiological studies of EMF exposure
Authors: Blackman Carl F. , Most Bernard
Published: February 2006

Experimental data on calcium‐ion release in chicken brain tissue suggest that biological effects of electric and magnetic fields (EMFs) are concentrated near certain “active combinations” of DC magnetic field strength and “effective” AC magnetic field frequencies. We hypothesize that active AC/DC combinations may exist and suggest that epidemiologic data, coupled with DC magnetic field measurements, may be used to identify critical exposure conditions. An empirical model is used to calculate these multiple active combinations at any given DC magnetic field strength and to define a rating system that incorporates the proximity of AC magnetic field frequencies generated by electric power lines to the new, computed effective frequencies. Such an exposure score may be useful in investigating correlations of EMF exposure with disease incidence. For 60 Hz and 50 Hz, the highest EMF exposure scores occurred at DC field strengths of 506 mG and 422 mG, respectively. The exposure score contains a factor which may be adjusted to reflect the importance of harmonics of the AC magnetic field as well as of the fundamental frequency. Using this factor, we consider two important special cases consistent with chick brain data: 1) we consider active pairs associated with all detectable harmonics (up to 660 Hz) without regard to relative intensity of the harmonics, and 2) we use the relative intensities of the AC field frequencies to adjust their contribution to the exposure score. © 1993 Wiley‐Liss. Inc.
Calcium‐ion movement and contractility in atrial strips of frog heart are not affected by low‐frequency‐modulated, 1 GHz electromagnetic radiation
Authors: Schwartz Jean‐Louis , Mealing Geoffrey A. R.
Published: February 2006

Calcium efflux from electrically stimulated, 45Ca2+‐preloaded atrial strips of the frog heart was measured from samples of the rinsing perfusate collected at 2‐min intervals for 32 min in a continuous perfusion chamber. Contractile force was simultaneously monitored. The specimen chamber was located in a stripline apparatus in which the atrial strips were exposed for 32 min to constant (CW) or amplitude‐modulated (AM), 1 GHz electromagnetic (EM) fields at specific absorption rates (SAR) ranging from 3.2 μW/kg to 1.6 W/kg. Amplitude modulation was either at 0.5 Hz, in synchrony with the electrical stimulus applied to the preparation, or at 16 Hz. Neither unmodulated nor 0.5 Hz or 16 Hz modulated 1 GHz waves affected the movement of calcium ions or the contractile force in isolated atrial strips of the frog heart. © 1993 Wiley‐Liss, Inc.
Facility for chronic exposure of rats to ELF magnetic fields
Authors: Yasui Mitsuru , Otaka Yoshihisa
Published: February 2006

The facility consists of a 12 × 11.5 × 2.4 m high room containing six sets of exposure apparatus and the other equipment necessary to maintain a pathogen‐free system. The apparatus sets produced 5 mT (rms), 0.5 mT, or a sham exposure. The apparatus was arranged in the room to minimize the fringing field of the 5 mT set at the sham position. Each set was 3.85 × 1.80 × 0.66 m in outside dimension, containing 24 cages in the magnetically homogeneous region. The apparatus was designed using Harvey's figure‐eight‐configuration and generated a horizontal sinusoidal alternating field. In order to save electric power, the coil of the apparatus constituted a 50 Hz LC resonance circuit with a condensor bank to which electric power was supplied to compensate losses. Magnetic flux density was kept constant by controlling the coil current. Although mild steel was used in the skeleton of the building, the fringing flux at the sham was as low as 0.1 to 1 μT. Stainless steel was used for ventilating ducts, racks for the cages, cage covers, feeder baskets, and watering nozzles. The homogeneity of the field was measured to be ± 10% in the animal residence area, and food and water consumption was found to be unaffected by the field. At 5 mT, the coil current was 370 A, and the hollow coil was cooled by a stream of 20°C water to prevent both heat and dew on the coil surface. Vibration and acoustic noise was prevented by fiber reinforced plastic framework of the coil. High harmonic distortion was not observed at the output terminal of the coil driver. The facility has operated without trouble for 2 years. © 1993 Wiley‐Liss, Inc.
Exposure to 60 Hz magnetic fields in the electric utility work environment
Authors: Sahl Jack D. , Kelsh Michael A. , Smith Robert W. , Aseltine Deborah A.
Published: February 2006

Research that has attempted to examine the relationship between work exposures to magnetic fields and health effects has suffered from limited exposure information. Power‐frequency electric and magnetic (EM) field exposures vary substantially between industries, occupations, and individuals. In this study magnetic field data were collected for a variety of occupational categories within an electric utility. The sampling procedures emphasized craft occupations that were presumed to have higher exposures to magnetic fields. The objectives were to provide better exposure information for an ongoing cancer mortality study, examine the relationship between different summary measures of magnetic field exposure, and make available descriptive information useful for exposure reduction and worker education. Principal components analysis (PCA) and Varimax rotation were used to explore the relationships between the different summary measures among all utility workers and among the subset of electrical craft occupations. Discriminant analysis was used to assess summary measures of exposure that differentiated occupational groups. Measurements for 770 days generated a total of 42378 hours of magnetic field data. Eleven summary indices of exposure were calculated for specific occupational groups. These include arithmetic mean, geometric mean, median, 95th and 99th percentiles, and fraction of measurements exceeding .5, 1, 5, 10, and 100 μT. Electrical craft occupations had higher work exposures than non‐craft occupations. Electricians and substation operators had the highest exposures among craft occupations.

We identified subsets of summary measures that were intercorrelated. The first PCA axis included the geometric mean, median, and the fractions exceeding 0.5 and 1.0 μT. This set of measures also were best at discriminating occupational groups. The relevance of these findings may become more important if consistent associations are found between particular occupations and disease and particular occupations and magnetic field summary measures. Further research is needed to evaluate these exposure assessment findings. © 1994 Wiley‐Liss, Inc.
Development of a protocol for assessing time‐weighted‐average exposures of young children to power‐frequency magnetic fields
Authors: Kaune W. T. , Darby S. D. , Gardner S. N. , Hrubec Z. , Iriye R. N. , Linet M. S.
Published: February 2006

A study was carried out in 1990 to guide the development of a protocol for assessing residential exposures of children to time‐weighted‐average (TWA) power‐frequency magnetic fields. The principal goal of this dosimetry study was to determine whether area (i.e., spot and/or 24 h) measurements of power‐frequency magnetic fields in the residences and in the schools and daycare centers of 29 children (4 months through 8 years of age) could be used to predict their measured personal 24‐h exposures. TWA personal exposures, measured with AMEX‐3D meters worn by subjects, were approximately log‐normally distributed with both residential and nonresidential geometric means of 0.10 μT (1.0 mG). Between‐subjects variability in residential personal exposure levels (geometric standard deviation of 2.4) was substantially greater than that observed for nonresidential personal exposure levels (1.4). The correlation between log‐transformed residential and total personal exposure levels was 0.97. Time‐weighted averages of the magnetic fields measured in children's bedrooms, family rooms, living rooms, and kitchens were highly correlated with residential personal exposure levels (r = 0.90). In general, magnetic field levels measured in schools and daycare centers attended by subjects were smaller and less variable than measured residential fields and were only weakly correlated with measured nonresidential personal exposures. The final measurement protocol, which will be used in a large US study examining the relationship between childhood leukemia and exposure to magnetic fields, contains the following elements: normal‐ and low‐power spot magnetic field measurements in bedrooms occupied by subjects during the 5 years prior to the date of diagnosis for cases or the corresponding date for controls; spot measurements under normal and low power‐usage conditions at the centers of the kitchen and the family room; 24‐h magnetic‐field recordings near subjects' beds; and wire coding using the Wertheimer‐Leeper method. © 1994 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Magnetic fields after translation in Escherichia coli
Authors: Goodman Eugene M. , Greenebaum Ben , Marron Michael T.
Published: February 2006

Quantitative two‐dimensional gel electrophoresis of proteins in E. coli exposed for 60 min to weak, pulsed magnetic fields (1.5 mT peak) show that numerous proteins are both increased and decreased by a factor of 2 or more. An increase in the levels of two proteins, the a subunit of DNA‐dependent RNA polymerase and NusA, was confirmed by Western blot analysis. © 1994 Wiley‐Liss, Inc.
Enhanced mutagenic effect of a 60 Hz time‐varying magnetic field on numbers of azide‐induced TA100 revertant colonies
Authors: Tabrah Frank L. , Mower Howard F. , Batkin Stanley , Greenwood Peter Bryant
Published: February 2006

Forty‐eight hours exposure to a two Gauss (0.2 mT) rms 60 Hz time varying sinusoidal electromagnetic field increased the number of azide induced TA100 revertant colonies of Salmonella typhimurium 14% as compared with controls in the ambient < 2 milli‐Gauss 60 Hz field. In the absence of the electromagnetic field, the numbers of mutant colonies grown within and outside the non‐energized coil were nearly identical. Without azide, the number of “spontaneous” mutant colonies forming in the experimental field was not statistically significant from numbers of colonies not exposed to field effects. Experimental temperature variation of 2 °C had little effect on colony formation, and the enhanced production of revertant colonies in the presence of the magnetic field was maintained during continued culture for 5 additional days. © 1994 Wiley‐Liss, Inc.
Microwave irradiation affects radial‐arm maze performance in the rat
Authors: Lai Henry , Horita Akira , Guy Arthur W.
Published: February 2006

After 45 min of exposure to pulsed 2450 MHz microwaves (2 μsec pulses, 500 pps, 1 mW/cm2, average whole body SAR 0.6 W/kg), rats showed retarded learning while performing in the radial‐arm maze to obtain food rewards, indicating a deficit in spatial “working memory” function. This behavioral deficit was reversed by pretreatment before exposure with the cholinergic agonist physostigmine or the opiate antagonist naltrexone, whereas pretreatment with the peripheral opiate antagonist naloxone methiodide showed no reversal of effect. These data indicate that both cholinergic and endogenous opioid neurotransmitter systems in the brain are involved in the microwave‐induced spatial memory deficit. © 1994 Wiley‐Liss, Inc.
Magnetic fields alter electrical properties of solutions and their physiological effects
Authors: Ayrapetyan Sinerik N. , Grigorian Khachik V. , Avanesian Arpat S. , Stamboltsian Khachik V.
Published: February 2006

Calcium chloride and snail physiological salt solutions were exposed to static magnetic fields (2.3–350 mT), and the physical properties of the solutions as well as their biologic effects were studied. Our preliminary observations show that these fields alter physicochemical properties of CaCl2 solutions and the functional effects of physiological solutions. Experiments on CaCl2 solutions demonstrated field‐dependent changes of electrical conductivity, with the magnitude and the direction of conductivity change being a function of both concentration and field intensity. The changes in conductivity were maintained for periods in excess of 1 h after exposure. Conductivity changes were not found after exposure of physiological solutions to static magnetic fields, but changes of biological consequence did occur. Other experiments showed that there were several changes in cellular function observed in ganglia and isolated neurons of Helix pomatia when the perfusing medium was changed from the normal physiologic solution to the same solution after exposure to magnetic fields. These changes include membrane depolarization and increased action potential discharge, reduced uptake of Ca into cells, altered content of cyclic nucleotides in ganglia, and increased volume of isolated cell bodies. A change in hydration of calcium ions may be one of the consequences of magnetic‐field exposure, and in physiological solutions this change may have functional consequences. © 1994 Wiley‐Liss, Inc.
Influence of microwaves on different types of receptors and the role of peroxidation of lipids on receptor‐protein shedding
Authors: Philippova T. M. , Novoselov V. I. , Alekseev S. I.
Published: February 2006

The effects of a continuous wave or pulse‐modulated, 900 MHz microwave field were studied by in vitro assays of rat chemoreceptors. The pulsed field was modulated as rectangular waves at rates of 1, 6, 16, 32, 75, or 100 pps. The pulse‐period to pulse‐duration ratio was 5 in all cases, and specific absorption rates (SARs) ranged from 0.5 to 18 W/kg. Binding of ligands to cell membranes was differentially affected by exposure to microwaves. For example, binding of H3‐glutamic acid to hippocampal cells was not altered by a 15 min exposure to a continuous wave field at 1 W/kg, but binding of H3‐dihydroalprenolol to liver‐cell membranes of neonates underwent a fivefold decrease under the same field conditions. This effect was not dependent on modulation or on a change in the constant of stimulus‐receptor binding but depended on a shedding of the membrane's receptor elements into solution. The magnitude of inhibition correlated with the oxygen concentration in the exposed suspension. Antioxidants (dithiothreitol and ionol) inhibited the shedding of receptor elements. The microwave exposure did not cause an accumulation of products from the peroxidation of lipids (POL). Ascorbate‐dependent or non‐enzymatic POL was not responsible for the inhibition, and POL was not found in other model systems. However, enzymatic POL mechanisms in localized areas of receptor binding remain a possibility. © 1994 Wiley‐Liss, Inc.
Protection against focal cerebral ischemia following exposure to a pulsed electromagnetic field
Authors: Grant Gerald , Cadossi Ruggero , Steinberg Gary
Published: February 2006

There is evidence that electromagnetic stimulation may accelerate the healing of tissue damage following ischemia. We undertook this study to investigate the effects of low frequency pulsed electromagnetic field (PEMF) exposure on cerebral injury in a rabbit model of transient focal ischemia (2 h occlusion followed by 4 h of reperfusion). PEMF exposure (280 V, 75 Hz, IGEA Stimulator) was initiated 10 min after the onset of ischemia and continued throughout reperfusion (six exposed, six controls). Magnetic resonance imaging (MRI) and histology were used to measure the degree of ischemic injury. Exposure to pulsed electromagnetic field attenuated cortical ischemic edema on MRI at the most anterior coronal level by 65% (P < 0.001). On histologic examination, PEMF exposure reduced ischemic neuronal damage in this same cortical area by 69% (P < 0.01) and by 43% (P < 0.05) in the striatum. Preliminary data suggest that exposure to a PEMF of short duration may have implications for the treatment of acute stroke. © 1994 Wiley‐Liss, Inc.
Simplification of the Wertheimer‐Leeper wire code
Authors: Kaune William T. , Savitz David A.
Published: February 2006

Wire codes, introduced by Wertheimer and Leeper as a surrogate for residential magnetic fields, divide imputed exposure into several categories based on the configurations of electrical wiring within 40 m of homes. Using the data set gathered by Savitz et al. in the Denver, Colorado, area of the United States, we determined which of the wiring attributes that contribute to Wertheimer‐Leeper coding are actually associated with lowpower magnetic fields measured in bedrooms of subjects. The results led us to propose a considerably simplified three‐category form of the Wertheimer‐Leeper code that 1) drops the distinctions between thick and thin primary wires and between first‐span and other secondary lines, 2) adds a new distinction between open (i.e., conductors not in physical contact) and spun secondaries, and 3) explains as much of the between‐home variability in log‐transformed bedroom fields as does the five categories of the original Wertheimer‐Leeper code. The data necessary to classify residences using the modified code are considerably simpler to obtain and should lead to more reliable results. A separate reanalysis of the Denver data set of Savitz et al. shows that the modified code yields risk estimates that are both precise and markedly elevated for the highest exposure category, suggesting that this code may be useful in other studies. © 1994 Wiley‐Liss, Inc.
Development and evaluation of a location‐specific wire code
Authors: Borghesi J. L. , Delpizzo V.
Published: February 2006

The development of a wire code protocol based on a study of electrical installations in Melbourne, Australia, is described. Because of very significant differences between the Melbourne power distribution system and that used in Denver, Colorado, an approach different from that used by Wertheimer and Leeper was required. A combined practical and theoretical approach was used to determine a continuous exposure index, defined as a measure of the potential for exposure due to external electrical installations. The protocol was tested on a convenient sample of 41 homes in which the field was monitored over a 12 hour overnight period. A correlation of 0.85 (95% CI 0.74–0.92, P < .0001) was obtained between the measured time‐weighted average and the wire coding exposure index. To assess the efficacy of the wiring configuration index, a computer simulation of a case‐control study was then performed. It was concluded that, using the same basic reasoning of the Wertheimer and Leeper code, it is possible to develop a location‐specific code that provides a good correlation with the residential time‐weighted average and an acceptable degree of exposure misclassification. © 1994 Wiley‐Liss, Inc.
Effects of prenatal exposure to 50 Hz magnetic fields on development in mice: I. Implantation rate and fetal development
Authors: Kowalczuk Christine I. , Robbins Lucy , Thomas Julia M. , Butland Barbara K. , Saunders Richard D.
Published: February 2006

Pregnant CD1 mice were exposed or sham‐exposed from day 0 to day 17 of gestation to a 50 Hz sinusoidal magnetic field at 20 mT (rms). Preimplantation and postimplantation survival were assessed and fetuses examined for the presence of gross external, internal, and skeletal abnormalities. There were no statistically significant field‐dependent effects on preimplantation or postimplantation survival, sex ratio, or the incidence of fetuses with internal or skeletal abnormalities. Magnetic field exposure was, however, associated with longer and heavier fetuses at term, with fewer external abnormalities. The results lend no support to suggestions of increased rates of spontaneous abortion or congenital malformation following prenatal exposure to power frequency magnetic fields. © 1994 Wiley‐Liss, Inc.
Effects of prenatal exposure to 50 Hz magnetic fields on development in mice: II. Postnatal development and behavior
Authors: Sienkiewicz Zenon J. , Robbins Lucy , Haylock Richard G. E. , Saunders Richard D.
Published: February 2006

To investigate the potential of magnetic fields to act as a behavioral teratogen, pregnant CD1 mice were exposed or sham‐exposed for all of gestation to a 50 Hz/20 mT magnetic field. Maturation of offspring was assessed using a range of standard developmental indices (eye opening, pinna detachment, hair coat, tooth eruption, sexual maturity, and weight) and simple reflexive behaviors (air righting, surface righting, forepaw grasp, cliff avoidance, and negative geotaxis). Activity and coordination levels were explored in juvenile and adult mice using an open field arena, a head‐dip board, an accelerating Rotarod, and a residential activity wheel. All assessments were carried out without knowledge of exposure condition. Results from 168 sham‐exposed mice from 21 litters and from 184 exposed mice from 23 litters were compared using survival analysis techniques and multivariate regression methods. Three possible field‐dependent effects were found: Exposed animals performed the air righting reflex earlier (P< 0.01); exposed males (but not females) were significantly lighter in weight (P= 0.008) at 30 days of age; and exposed animals remained on a Rota‐rod for less time as juveniles (P= 0.03). Some of these results have not been reported in other studies and may reflect spurious statistical significance, although some effect of magnetic field exposure cannot be ruled out. Overall, these results suggest that prenatal exposure to a 50 Hz magnetic field does not engender any gross impairments in the postnatal development or behavior of mice. This does not preclude such exposure affecting more subtle aspects of behavior. Published 1994 by Wiley‐Liss, Inc.
Chick embryo development can be irreversibly altered by early exposure to weak extremely‐low‐frequency magnetic fields
Authors: Ubeda Alejandro , Trillo María A. , Chacón Lucía , Blanco María J. , Leal Jocelyne
Published: February 2006

Several reports have shown that weak, extremely‐low‐frequency (ELF), pulsed magnetic fields (PMFs) can adversely affect the early embryonic development of the chick. In this study, freshly fertilized chicken eggs were exposed during the first 48 h of postlaying incubation to PMFs with 100 Hz repetition rate, 1.0 μT peak‐to‐peak amplitude, and 500 μs pulse duration. Two different pulse waveforms were used, having rise and fall times of 85 μs (PMF‐A) or 2.1 μs (PMF‐B). It has been reported that, with 2 day exposure, these fields significantly increase the proportion of developmental abnormalities. In the present study, following exposure, the eggs were allowed to incubate for an additional 9 days in the absence of the PMFs. The embryos were taken out of the eggs and studied blind. Each of the two PMF‐exposed groups showed an excess in the percentage of developmental anomalies compared with the respective sham‐exposed samples. This excess of anomalies was not significant for the PMF‐A‐treated embryos (P = 0.173), whereas it was significant for the PMF‐B‐exposed group (P = 0.007), which showed a particularly high rate of early embryonic death. These results reveal that PMFs can induce irreversible developmental alterations and confirm that the pulse waveform can be a determinant factor in the embryonic response to ELF magnetic fields. The data also validate previous work based on the study of PMFs' effects at day 2 of embryonic development under field exposure. © 1994 Wiley‐Liss, Inc.
Temporally incoherent magnetic fields mitigate the response of biological systems to temporally coherent magnetic fields
Authors: Litovitz T. A. , Krause D. , Montrose C. J. , Mullins J. M.
Published: February 2006

We have previously demonstrated that a weak, extremely‐low‐frequency magnetic field must be coherent for some minimum length of time (≈︁ 10 s) in order to affect the specific activity of ornithine decarboxylase (ODC) in L929 mouse cells. In this study we explore whether or not the superposition of an incoherent (noise) magnetic field can block the bioeffect of a coherent 60 Hz magnetic field, since the sum of the two fields is incoherent. An experimental test of this idea was conducted using as a biological marker the twofold enhancement of ODC activity found in L929 murine cells after exposure to a 60 Hz, 10 μTrms magnetic field. We superimposed an incoherent magnetic noise field, containing frequencies from 30 to 90 Hz, whose rms amplitude was comparable to that of the 60 Hz field. Under these conditions the ODC activity observed after exposure was equal to control levels. It is concluded that the superposition of incoherent magnetic fields can block the enhancement of ODC activity by a coherent magnetic field if the strength of the incoherent field is equal to or greater than that of the coherent field. When the superimposed, incoherent noise field was reduced in strength, the enhancement of ODC activity by the coherent field increased. Full ODC enhancement was obtained when the rms value of the applied EM noise was less than one‐tenth that of the coherent field. These results are discussed in relation to the question of cellular detection of weak EM fields in the presence of endogenous thermal noise fields. © 1994 Wiley‐Liss, Inc.
Electric field exposure alters serum melatonin but not pineal melatonin synthesis in male rats
Authors: Grota L. J. , Reiter R. J. , Keng P. , Michaelson S.
Published: February 2006

Sprague‐Dawley male rats, maintained in a 14:10 h light:dark cycl were exposed for 30 days (starting at 56 days of age) to a 65 kV/m, 60 Hz electric field or to a sham field for 20 h/day beginning at dark onset. Pineal N‐acetyltransferase (NAT), hydroxy‐indole‐o‐methyl transferase (HIOMT), and melatonin as well as serum melatonin were assayed. Preliminary data on unexposed animals indicated that samples obtained 4 h into the dark period would reveal either a phase delay or depression in circadian melatonin synthesis and secretion. Exposure to electric fields for 30 days did not alter the expected nighttime increase in pineal NAT, HIOMT, or melatonin. Serum melatonin levels were also increased at night, but the electric field‐exposed animals had lower levels than the sham‐exposed animals. Concurrent exposure to red light and the electric field or exposure to the electric field at a different time of the day‐night period did not reduce melatonin synthesis. These data do not support the hypothesis that chronic electric field exposure reduces pineal melatonin synthesis in young adult male rats. However, serum melatonin levels were reduced by electric field exposure, suggesting the possibility that degradation or tissue uptake of melatonin is stimulated by exposure to electric fields. © 1994 Wiley‐Liss, Inc.