Download the Free Unbound MEDLINE PubMed App to your smartphone or tablet.
Available for iPhone, iPad, iPod touch, and Android.
- Experimental System for Real-Time Assessment of Potential Changes in Protein Conformation Induced by Electromagnetic Fields. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 May 2.
A novel experimental system to distinguish between potential thermal and non-thermal effects of electromagnetic fields (EMFs) on the conformational equilibrium and folding kinetics of proteins is presented. The system comprises an exposure chamber installed within the measurement compartment of a spectropolarimeter and allows real-time observation of the circular dichroism (CD) signal of the protein during EMF exposure. An optical temperature probe monitors the temperature of the protein solution at the site of irradiation. The electromagnetic, thermal, and fluid-dynamic behavior of the system is characterized by numerical and experimental means. The number of repeated EMF on/off cycles needed for achieving a certain detection limit is determined on the basis of the experimentally assessed precision of the CD measurements. The isolated thermosensor protein GrpE of the Hsp70 chaperone system of Eschericha coli serves as the test protein. Long-term experiments show high thermal reproducibility as well as thermal stability of the experimental setup. Bioelectromagnetics. 9999:XX-XX. © 2013 Wiley Periodicals, Inc.
- The Biological Impact of Concurrent Exposure to Metallic Nanoparticles and a Static Magnetic Field. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 May 2.
The rapid advancement of technology has led to an exponential increase of both nanomaterial and magnetic field utilization in applications spanning a variety of sectors. While extensive work has focused on the impact of these two variables on biological systems independently, the existence of any synergistic effects following concurrent exposure has yet to be investigated. This study sought to ascertain the induced alterations to the stress and proliferation responses of the human adult low calcium, high temperature keratinocyte (HaCaT) cell line by the application of a static magnetic field (approximately 0.5 or 30 mT) in conjunction with either gold or iron oxide nanoparticles for a duration of 24 h. By evaluating targets at a cellular, protein, and genetic level a complete assessment of the HaCaT response was generated. A magnetic field-dependent proliferative effect was found (∼15%), which correlated with a decrease in reactive oxygen species and a simultaneous increase in ki67 expression, all occurring independently of nanoparticle presence. Furthermore, the application of a static magnetic field was able to counteract the cellular stress response induced by nanoparticle exposure through a combination of decreased reactive oxygen species production and modification of gene regulation. Therefore, we conclude that while these variables each introduce the potential to uniquely influence physiological events, no negative synergistic reactions were identified. Bioelectromagnetics. 9999:XX-XX. © 2013 Wiley Periodicals, Inc.
- Effects of 940 MHz EMF on Luciferase Solution: Structure, Function, and Dielectric Studies. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 Apr 30.
We designed a rectangular waveguide exposure system to study the effects of mobile phone frequency (940 MHz) electromagnetic fields (EMF) on luciferase structure and activity. The luciferase activity of exposed samples was significantly higher than that of unexposed samples. Dynamic light scattering of the exposed samples showed smaller hydrodynamic radii compared to unexposed samples (20 nm vs. 47 nm ± 5%). The exposed samples also showed less tendency to form aggregates, monitored by turbidity measurements at λ = 360 nm. A microwave dielectric measurement was performed to study the hydration properties of luciferase solutions with a precision network analyzer over frequency ranges from 0.2 to 20 GHz before and after exposure. The change in the dielectric properties of the exposed luciferase solution was related to the disaggregation potency of the applied field. Together, our results suggested that direct interactions with luciferase molecules and its dipole moment were responsible for the reduced aggregation and enhanced luciferase activity upon exposure to the EMF. Bioelectromagnetics. 9999:XX-XX. © 2013 Wiley Periodicals, Inc.
- SAR Exposure From UHF RFID Reader in Adult, Child, Pregnant Woman, and Fetus Anatomical Models. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 Apr 23.
The spread of radio frequency identification (RFID) devices in ubiquitous applications without their simultaneous exposure assessment could give rise to public concerns about their potential adverse health effects. Among the various RFID system categories, the ultra high frequency (UHF) RFID systems have recently started to be widely used in many applications. This study addresses a computational exposure assessment of the electromagnetic radiation generated by a realistic UHF RFID reader, quantifying the exposure levels in different exposure scenarios and subjects (two adults, four children, and two anatomical models of women 7 and 9 months pregnant). The results of the computations are presented in terms of the whole-body and peak spatial specific absorption rate (SAR) averaged over 10 g of tissue to allow comparison with the basic restrictions of the exposure guidelines. The SAR levels in the adults and children were below 0.02 and 0.8 W/kg in whole-body SAR and maximum peak SAR levels, respectively, for all tested positions of the antenna. On the contrary, exposure of pregnant women and fetuses resulted in maximum peak SAR10 g values close to the values suggested by the guidelines (2 W/kg) in some of the exposure scenarios with the antenna positioned in front of the abdomen and with a 100% duty cycle and 1 W radiated power. Bioelectromagnetics. 9999:XX-XX. © 2013 Wiley Periodicals, Inc.
- Effect of 1 mT Sinusoidal Electromagnetic Fields on Proliferation and Osteogenic Differentiation of Rat Bone Marrow Mesenchymal Stromal Cells. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 Apr 15.
Electromagnetic field (EMF) stimulation is clinically beneficial for fracture nonunion and a wide range of bone disorders. However, no consensus has been reached on the optimal parameters of the EMF. The exact mechanism by which EMFs enhance osteogenesis has also not been defined. In the present study, a sinusoidal 1 mT EMF at frequencies of 10, 30, 50, and 70 Hz were administered to rat bone marrow mesenchymal stromal cells (rBMSCs) in the cyclic mode of 2 h exposures followed by 4 h of culture without exposure. The cell viability, proliferation, expression of some osteogenic genes, and mineralization of the extracellular matrix were investigated. It was found that the cell viability was decreased by EMF exposures of 50 and 70 Hz. The proliferation of rBMSCs was elevated significantly in the 10 Hz EMF-treated group during the culture periods. The expression of alkaline phosphatase (ALP) and osteocalcin (OC), two early-phase osteogenic differentiation markers, was up-regulated by the 1 mT, 10 Hz EMF after 1 week. However, the expression of genes that marked the later-phase osteogenic differentiation and maturation of osteoblasts was elevated by the stimulation of 50 Hz EMFs after 2 weeks. In addition, it was observed that the mineralization of the extracellular matrix was enhanced by 50 Hz EMF exposure. These results indicated that the 1 mT EMF at different frequencies had disparate effects on the viability, proliferation and osteogenic differentiation of rBMSCs, and may be beneficial for developing novel therapeutic approaches in bone regenerative medicine. Bioelectromagnetics. 9999:XX-XX. © 2013 Wiley Periodicals, Inc.
- Removal of the local geomagnetic field affects reproductive growth in Arabidopsis. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 Apr 8.
The influence of the geomagnetic field-removed environment on Arabidopsis growth was investigated by cultivation of the plants in a near-null magnetic field and local geomagnetic field (45 µT) for the whole growth period under laboratory conditions. The biomass accumulation of plants in the near-null magnetic field was significantly suppressed at the time when plants were switching from vegetative growth to reproductive growth compared with that of plants grown in the local geomagnetic field, which was caused by a delay in the flowering of plants in the near-null magnetic field. At the early or later growth stage, no significant difference was shown in the biomass accumulation between the plants in the near-null magnetic field and local geomagnetic field. The average number of siliques and the production of seeds per plant in the near-null magnetic field was significantly lower by about 22% and 19%, respectively, than those of control plants. These resulted in a significant reduction of about 20% in the harvest index of plants in the near-null magnetic field compared with that of the controls. These results suggest that the removal of the local geomagnetic field negatively affects the reproductive growth of Arabidopsis, which thus affects the yield and harvest index. Bioelectromagnetics. © 2013 Wiley Periodicals, Inc.
- Analysis of mobile phone design features affecting radiofrequency power absorbed in a human head phantom. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 Mar 26.
The US FCC mandates the testing of all mobile phones to demonstrate compliance with the rule requiring that the peak spatial SAR does not exceed the limit of 1.6 W/kg averaged over any 1 g of tissue. These test data, measured in phantoms with mobile phones operating at maximum antenna input power, permitted us to evaluate the variation in SARs across mobile phone design factors such as shape and antenna design, communication technology, and test date (over a 7-year period). Descriptive statistical summaries calculated for 850 MHz and 1900 MHz phones and ANOVA were used to evaluate the influence of the foregoing factors on SARs. Service technology accounted for the greatest variability in compliance test SARs that ranged from AMPS (highest) to CDMA, iDEN, TDMA, and GSM (lowest). However, the dominant factor for SARs during use is the time-averaged antenna input power, which may be much less than the maximum power used in testing. This factor is largely defined by the communication system; e.g., the GSM phone average output can be higher than CDMA by a factor of 100. Phone shape, antenna type, and orientation of a phone were found to be significant but only on the order of up to a factor of 2 (3 dB). The SAR in the tilt position was significantly smaller than for touch. The side of the head did not affect SAR levels significantly. Among the remaining factors, external antennae produced greater SARs than internal ones, and brick and clamshell phones produced greater SARs than slide phones. Assuming phone design and usage patterns do not change significantly over time, we have developed a normalization procedure and formula that permits reliable prediction of the relative SAR between various communication systems. This approach can be applied to improve exposure assessment in epidemiological research. Bioelectromagnetics. © 2013 Wiley Periodicals, Inc.
- Inhomogeneous background magnetic field in biological incubators is a potential confounder for experimental variability and reproducibility. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 Mar 1.
This report shows that the background magnetic field in biological incubators can vary by orders of magnitude within and between incubators. These variations can be observed within the same incubator in locations that are centimeters apart from each other as well as between incubators that are identical and located in the same laboratory. Additionally, the values measured were frequently outside the range of magnitudes found naturally on the Earth's surface or ordinary habitation spaces. Exposure to such altered magnetic field environments has been experimentally shown to be sufficient to cause numerous effects in cell cultures. Examples of the effects reported span from differential generation of free radicals and heat shock proteins to differences in cellular proliferation, differentiation, and death. Although the effects are not well established and the molecular mechanism of action is currently under debate, these observations alone support the notion that the inhomogeneity of the background magnetic field in incubators is a potential confounding source of the variability and reproducibility for studies performed on cell cultures. In this regard, it is recommended that special measures be adopted to control the background magnetic fields in incubators when investigating the biological effects of exposure to magnetic fields of comparable characteristics as the ones measured in this study, or when studying small biological effects in general. Bioelectromagnetics. © 2013 Wiley Periodicals, Inc.
- Induction of heat shock gene expression in RAT1 primary fibroblast cells by ELF electric fields. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 Mar 1.
Recent studies have demonstrated that the Ku70 gene fragment can be placed in the anti-sense orientation under the control of a heat-inducible heat shock protein 70 (HSP70) promoter and activated through heat shock exposure. This results in attenuation of the Ku70 protein expression, inhibiting cellular repair processes, and sensitizing the transfected cells to exposures such as the ionizing radiation exposures used clinically. However, achieving the tissue temperatures necessary to thermally induce the HSP70 response presents significant limitations to the clinical application of this strategy. Previous findings suggest an alternative approach to inducing a heat shock response, specifically through the use of extremely low frequency (ELF) electrical field stimulation. To further pursue this approach, we investigated HSP70 responses in transfected rat primary fibroblast (RAT1) cells exposed to 10 Hz electric fields at intensities of 20-500 V/m. We confirmed that low frequency electric fields can induce HSP70 heat shock expression, with peak responses obtained at 8 h following a 2 h field exposure. However, the approximate threefold increase in expression is substantially lower than that obtained using thermal stimulation, raising questions of the clinical utility of the response. Bioelectromagnetics. © 2013 Wiley Periodicals, Inc.
- Changes in the electrical properties at an early stage of mouse liver carcinogenesis. [JOURNAL ARTICLE]
- Bioelectromagnetics 2013 Feb 22.
The present investigation reports the changes in the electrical properties of hepatic tissue in the frequency range of 100 Hz to 5 MHz at an early stage of liver carcinogenesis using the four-pin electrode method. The hepatocarcinogenesis model was developed by intraperitoneal injection of N-nitrosodiethylamine (NDEA) to male Balb/c mice. Histopathological assessment revealed high-grade dysplasia in the liver of NDEA-treated animals. The ultrastructural investigations indicated the presence of large and clumped cells with inconspicuous cell boundaries. The treatment resulted in significant changes in the dielectric properties of the tissues. A decrease in tissue conductivity along with an increase in relative permittivity was observed. The biophysical changes correlated well with histoarchitectural and morphological changes. The alterations in architectural arrangement and membrane structure of cells may be responsible for the observed changes in the dielectric properties. Bioelectromagnetics. © 2013 Wiley Periodicals, Inc.