Unique neuromuscular activation of the rectus femoris during concentric and eccentric cycling

This study investigated neuromuscular activations of thigh muscles during concentric cycling (CON_cycling) and eccentric cycling (ECC_cycling). Eleven untrained men completed 30 s of CON_cycling and ECC_cycling each at 5 power outputs of 100–300 W (every 50-W interval). During cycling, root mean square of surface electromyographic signals (RMS-EMG) were obtained from the proximal and distal regions of the rectus femoris (RFp and RFd), vastus lateralis (VL), and biceps femoris (BF). The rating of perceived exertion (RPE) was evaluated using the 6–20 Borg Scale. The RMS-EMG of VL and BF were 21.6%–67.6% higher (P < 0.05) during CON_cycling than ECC_cycling at all power outputs, while those of RFp and RFd at 100–200 W were 29.6%–40.4% lower during CON_cycling than ECC_cycling. The RPE was similar between CON_cycling at 150 W (10 ± 2) and ECC at 250 W (10 ± 2). There were no significant differences in the RMS-EMG for VL or BF between CON_cycling at 150 W and ECC_cycling at 250 W; however, the RF RMS-EMG was greater during ECC_cycling as compared with CON_cycling. There were no regional differences in RF activations. These results demonstrated the unique neuromuscular activation of RF as compared to those of other thigh muscles during CON_cycling and ECC_cycling.     

Investigation of Parallel Radiofrequency Transmission for the Reduction of Heating in Long Conductive Leads in 3 Tesla Magnetic Resonance Imaging

Deep Brain Stimulation (DBS) is increasingly used to treat a variety of brain diseases by sending electrical impulses to deep brain nuclei through long, electrically conductive leads. Magnetic resonance imaging (MRI) of patients pre- and post-implantation is desirable to target and position the implant, to evaluate possible side-effects and to examine DBS patients who have other health conditions. Although MRI is the preferred modality for pre-operative planning, MRI post-implantation is limited due to the risk of high local power deposition, and therefore tissue heating, at the tip of the lead. The localized power deposition arises from currents induced in the leads caused by coupling with the radiofrequency (RF) transmission field during imaging. In the present work, parallel RF transmission (pTx) is used to tailor the RF electric field to suppress coupling effects. Electromagnetic simulations were performed for three pTx coil configurations with 2, 4, and 8-elements, respectively. Optimal input voltages to minimize coupling, while maintaining RF magnetic field homogeneity, were determined for all configurations using a Nelder-Mead optimization algorithm. Resulting electric and magnetic fields were compared to that of a 16-rung birdcage coil. Experimental validation was performed with a custom-built 4-element pTx coil. In simulation, 95-99% reduction of the electric field at the tip of the lead was observed between the various pTx coil configurations and the birdcage coil. Maximal reduction in E-field was obtained with the 8-element pTx coil. Magnetic field homogeneity was comparable to the birdcage coil for the 4- and 8-element pTx configurations. In experiment, a temperature increase of 2±0.15°C was observed at the tip of the wire using the birdcage coil, whereas negligible increase (0.2±0.15°C) was observed with the optimized pTx system. Although further research is required, these initial results suggest that the concept of optimizing pTx to reduce DBS heating effects holds considerable promise.     

Biological and molecular comparison between localized and systemic acquired resistance induced in tobacco by a Phytophthora megasperma glycoprotein elicitin

We have compared localized (LAR) and systemic (SAR) acquired resistance induced in tobacco by a hypersensitive response (HR) inducing Phytophthora megasperma glycoprotein elicitin. Three different zones were taken into account: LAR, SAR_T and SAR_S. The LAR zone was 5–10 mm wide and surrounded the HR lesion. SAR_T was the tissue of the elicitor-treated leaf immediately beyond the LAR zone. The systemic leaf was called SAR_S. Glycoprotein-treated plants showed enhanced resistance to challenge infection by tobacco mosaic virus (TMV). Disease resistance was similar in SAR_T and SAR_S, and higher in LAR. The expression pattern, in glycoprotein-treated plants, of acidic and basic PR1, PR2, PR3 and PR5 proteins and of O-methyltransferases (OMT), enzymes of the phenylpropanoid pathway, was similar to that in TMV-infected plants. OMT was stimulated in LAR but not in SAR_T and SAR_S. The four classes of acidic and basic PR proteins accumulated strongly in LAR. Reduced amounts of acidic PR1, PR2, PR3 and only minute amounts of basic PR2 and PR3 accumulated in SAR_T and SAR_S. In glycoprotein-treated plants, expression of the acidic and basic PR proteins in LAR and SAR of transgenic NahG and ETR tobacco plants and in LAR of plants treated with inhibitors of salicylic acid accumulation and of ethylene biosynthesis indicated a salicylic acid-dependent signalling pathway for acidic isoform activation and an ethylene-dependent signalling pathway for basic isoform activation.     

Thymosin beta 4 improves dermal burn wound healing via downregulation of receptor of advanced glycation end products in db/db mice

BackgroundThe delay of dermal burn wound healing caused by vascular disorders is a critical problem for many diabetic patients. Thymosin β₄ (Tβ₄), identified by subtractive cloning of endothelial cells on plastic versus basement membrane substrates, has been found to promote angiogenesis and dermal wound repair in rats, aged mice, and db/db diabetic mice. However, previous studies involving the role of Tβ₄ in wound repair were limited to mechanical damage and dermal impairment. Thus, this study aimed to evaluate the improvement of healing of burn wounds by Tβ₄ in relation to advanced glycation end products (AGE), which are pathological factors in diabetes.MethodsWe adapted a dermal burn wound in vivo model in which the dorsal skin of db/db mice was exposed for 10 s to 100 °C heated water to produce a deep second-degree burn 10 mm in diameter. Five mg/kg of Tβ₄ was then injected intradermally near the burn wound twice a week for 2 weeks.ResultsAfter treatment, Tβ₄ improved wound healing markers such as wound closure, granulation, and vascularization. Interestingly, Tβ₄ reduced levels of receptor of AGE (RAGE) during the wound healing period.ConclusionsTβ₄ exerts effects to remedy burn wounds via downregulation of RAGE.General significanceOur results suggest the potential importance of Tβ₄ as a new therapy for impaired burn wound healing that is associated with diabetes.     

Ablation index-guided 50W radiofrequency ablation for left atrial posterior wall isolation in atrial fibrillation

BackgroundAblation index (AI)-guided ablation for posterior wall isolation (PWI) using high-power, short-duration remains untested. We sought to evaluate the acute outcomes of AI-guided 50 W ablation vs. conventional ablation, and investigate the differences in relationship between contact force (CF), time and AI in both groups.MethodsConsecutive patients undergoing first-time AI-guided ablation with PWI using either 50 W or 35–40 W ablation were enrolled. Acute procedural metrics and individual lesion level ablation data were compared between groups.Results40 patients (50 W: n = 20, 35–40 W: n = 20) with atrial fibrillation were included. Total procedure time was significantly reduced with 50 W (120 vs. 143 mins, p = 0.004) and there was a trend toward decreased ablation time (22 vs. 28 mins, p = 0.052). First pass and acute success of PWI were comparable between the 50 W and 35–40 W groups (10 vs. 8 patients, p = 0.525 and 20 vs. 19 patients, p = 1.000, respectively). Individual lesion analysis of all 959 RF applications (50 W: n = 458, 35–40 W: n = 501) demonstrated that 50 W ablation led to lower ablation time per lesion (10.4 vs. 13.0s, p < 0.001), and increased AI (471 vs. 461, p < 0.001) and impedance drop (7.4 vs. 6.9ohms, p = 0.007). Excessive ablations (AI>600 for roof line; AI>500 elsewhere) were more frequently observed in the 50 W group (9.0% vs. 4.6%, p = 0.007). CF had very good discriminative capability for excessive ablation in both groups. At 50 W, limiting the CF to <10 g reduced the number of excessive ablations on the floor line and within the posterior box to 12% and 4%,respectively. Recurrence of atrial arrhythmias at 12 months were comparable between the groups.ConclusionAI-guided 50 W RF ablation reduces the ablation time of individual lesions and total procedure time without compromising first pass and acute success rates of PWI or 12-month outcomes compared to conventional powers.     

Spatial autocorrelation and the selection of simultaneous autoregressive models

Aim Spatial autocorrelation is a frequent phenomenon in ecological data and can affect estimates of model coefficients and inference from statistical models. Here, we test the performance of three different simultaneous autoregressive (SAR) model types (spatial error = SAR_err, lagged = SAR_lag and mixed = SAR_mix) and common ordinary least squares (OLS) regression when accounting for spatial autocorrelation in species distribution data using four artificial data sets with known (but different) spatial autocorrelation structures. Methods We evaluate the performance of SAR models by examining spatial patterns in model residuals (with correlograms and residual maps), by comparing model parameter estimates with true values, and by assessing their type I error control with calibration curves. We calculate a total of 3240 SAR models and illustrate how the best models [in terms of minimum residual spatial autocorrelation (minRSA), maximum model fit (R²), or Akaike information criterion (AIC)] can be identified using model selection procedures. Results Our study shows that the performance of SAR models depends on model specification (i.e. model type, neighbourhood distance, coding styles of spatial weights matrices) and on the kind of spatial autocorrelation present. SAR model parameter estimates might not be more precise than those from OLS regressions in all cases. SAR_err models were the most reliable SAR models and performed well in all cases (independent of the kind of spatial autocorrelation induced and whether models were selected by minRSA, R² or AIC), whereas OLS, SAR_lag and SAR_mix models showed weak type I error control and/or unpredictable biases in parameter estimates. Main conclusions SAR_err models are recommended for use when dealing with spatially autocorrelated species distribution data. SAR_lag and SAR_mix might not always give better estimates of model coefficients than OLS, and can thus generate bias. Other spatial modelling techniques should be assessed comprehensively to test their predictive performance and accuracy for biogeographical and macroecological research.     

Detailing Radio Frequency Heating Induced by Coronary Stents: A 7.0 Tesla Magnetic Resonance Study

The sensitivity gain of ultrahigh field Magnetic Resonance (UHF-MR) holds the promise to enhance spatial and temporal resolution. Such improvements could be beneficial for cardiovascular MR. However, intracoronary stents used for treatment of coronary artery disease are currently considered to be contra-indications for UHF-MR. The antenna effect induced by a stent together with RF wavelength shortening could increase local radiofrequency (RF) power deposition at 7.0 T and bears the potential to induce local heating, which might cause tissue damage. Realizing these constraints, this work examines RF heating effects of stents using electro-magnetic field (EMF) simulations and phantoms with properties that mimic myocardium. For this purpose, RF power deposition that exceeds the clinical limits was induced by a dedicated birdcage coil. Fiber optic probes and MR thermometry were applied for temperature monitoring using agarose phantoms containing copper tubes or coronary stents. The results demonstrate an agreement between RF heating induced temperature changes derived from EMF simulations versus MR thermometry. The birdcage coil tailored for RF heating was capable of irradiating power exceeding the specific-absorption rate (SAR) limits defined by the IEC guidelines by a factor of three. This setup afforded RF induced temperature changes up to +27 K in a reference phantom. The maximum extra temperature increase, induced by a copper tube or a coronary stent was less than 3 K. The coronary stents examined showed an RF heating behavior similar to a copper tube. Our results suggest that, if IEC guidelines for local/global SAR are followed, the extra RF heating induced in myocardial tissue by stents may not be significant versus the baseline heating induced by the energy deposited by a tailored cardiac transmit RF coil at 7.0 T, and may be smaller if not insignificant than the extra RF heating observed under the circumstances used in this study.     

Human exposure at two radio frequencies (450 and 2450 MHz): Similarities and differences in physiological response

Thermoregulatory responses of heat production and heat loss were measured in two different groups of seven adult volunteers (males and females) during 45‐min dorsal exposures of the whole body to 450 or 2450 MHz continuous‐wave radio frequency (RF) fields. At each frequency, two power densities (PD) were tested at each of three ambient temperatures (T_a = 24, 28, and 31 °C) plus T_a controls (no RF). The normalized peak surface specific absorption rate (SAR), measured at the location of the subject's center back, was the same for comparable PD at both frequencies, i.e., peak surface SAR = 6.0 and 7.7 W/kg. No change in metabolic heat production occurred under any exposure conditions at either frequency. The magnitude of increase in those skin temperatures under direct irradiation was directly related to frequency, but local sweating rates on back and chest were related more to T_a and SAR. Both efficient sweating and increased local skin blood flow contributed to the regulation of the deep body (esophageal) temperature to within 0.1 °C of the baseline level. At both frequencies, normalized peak SARs in excess of ANSI/IEEE C95.1 guidelines were easily counteracted by normal thermophysiological mechanisms. The observed frequency‐related response differences agree with classical data concerning the control of heat loss mechanisms in human beings. However, more practical dosimetry than is currently available will be necessary to evaluate realistic human exposures to RF energy in the natural environment. Bioelectromagnetics 20:12–20, 1999. Published 1999 Wiley‐Liss, Inc.     

Birdcage volume coils and magnetic resonance imaging: a simple experiment for students

Background

This article explains some simple experiments that can be used in undergraduate or graduate physics or biomedical engineering laboratory classes to learn how birdcage volume radiofrequency (RF) coils and magnetic resonance imaging (MRI) work. For a clear picture, and to do any quantitative MRI analysis, acquiring images with a high signal-to-noise ratio (SNR) is required. With a given MRI system at a given field strength, the only means to change the SNR using hardware is to change the RF coil used to collect the image. RF coils can be designed in many different ways including birdcage volume RF coil designs. The choice of RF coil to give the best SNR for any MRI study is based on the sample being imaged.

Results

The data collected in the simple experiments show that the SNR varies as inverse diameter for the birdcage volume RF coils used in these experiments. The experiments were easily performed by a high school student, an undergraduate student, and a graduate student, in less than 3 h, the time typically allotted for a university laboratory course.

Conclusions

The article describes experiments that students in undergraduate or graduate laboratories can perform to observe how birdcage volume RF coils influence MRI measurements. It is designed for students interested in pursuing careers in the imaging field.

     

Dosimetry evaluation of a cylindrical waveguide chamber for unrestrained small rodents at 1.9 GHz

An exposure system, consisting of four identical cylindrical waveguide chambers, was developed for studying the effects of radiofrequency (RF) energy on laboratory mice at a frequency of 1.9 GHz. The chamber was characterized for RF dose rate as a function of animal body mass and dose rate variations due to animal movement in the cage. Dose rates were quantified in terms of whole‐body average (WBA) specific absorption rate (SAR), brain average (BA) SAR and peak spatial‐average (PSA) SAR using measurement and computational methods. Measurements were conducted on mouse cadavers in a multitude of possible postures and positions to evaluate the variations of WBA‐SAR and its upper and lower bounds, while computations utilizing the finite‐difference time‐domain method together with a heterogeneous mouse model were performed to determine variations in BA‐SAR and the ratio of PSA‐SAR to WBA‐SAR. Measured WBA‐SAR variations were found to be within the ranges of 9–23.5 W/kg and 5.2–13.8 W/kg per 1 W incident power for 20 and 40 g mice, respectively. Computed BA‐SAR variations were within the ranges of 3.2–10.1 W/kg and 3.3–9.2 W/kg per 1 W incident power for 25 and 30 g mouse models, respectively. Ratios of PSA‐SAR to WBA‐SAR, averaged over 0.5 mg and 5 mg tissue volumes, were observed to be within the ranges of 6–15 and 4–10, respectively. Bioelectromagnetics 33:575–584, 2012. © 2012 Wiley Periodicals, Inc.     

New fin-line devices for radiofrequency exposure of small biological samples in vitro allowing whole-cell patch clamp recordings

The development and analysis of three waveguides for the exposure of small biological in vitro samples to mobile communication signals at 900 MHz (GSM, Global System for Mobile Communications), 1.8 GHz (GSM), and 2 GHz (UMTS, Universal Mobile Telecommunications System) is presented. The waveguides were based on a fin‐line concept and the chamber containing the samples bathed in extracellular solution was placed onto two fins with a slot in between, where the exposure field concentrates. Measures were taken to allow for patch clamp recordings during radiofrequency (RF) exposure. The necessary power for the achievement of the maximum desired specific absorption rate (SAR) of 20 W/kg (average over the mass of the solution) was approximately P_in = 50 mW, P_in = 19 mW, and P_in = 18 mW for the 900 MHz, 1800 MHz, and 2 GHz devices, respectively. At 20 W/kg, a slight RF‐induced temperature elevation in the solution of no more than 0.3 °C was detected, while no thermal offsets due to the electromagnetic exposure could be detected at the lower SAR settings (2, 0.2, and 0.02 W/kg). A deviation of 10% from the intended solution volume yielded a calculated SAR deviation of 8% from the desired value. A maximum ±10% variation in the local SAR could occur when the position of the patch clamp electrode was altered within the area where the cells to be investigated were located. Bioelectromagnetics 32:102–112, 2011. © 2010 Wiley‐Liss, Inc.     

Safety and efficacy of cryoballoon versus radiofrequency ablation for atrial fibrillation in elderly patients: A real-world evidence

BackgroundThere are limited data describing the experience of radiofrequency (RF) vs. cryoballoon (CB) ablation for atrial fibrillation (AF) among elderly patients in the United States.MethodsWe conducted a retrospective analysis of patients ≥75 years of age undergoing index RF vs. CB ablation between January 2014 and May 2020 at our center. The choice of ablation technique was left to the operator's discretion. Major complications and efficacy, defined as freedom from any atrial tachyarrhythmia (ATA) lasting ≥30 s after one year of follow-up, were assessed in patients with index RF vs. CB ablation.ResultsIn our cohort of 186 patients, the median age was 78 (76–81) years, 54.8% were men, and 39.2% had persistent AF. The median CHA₂DS₂-VASc score was 4 (3–4), while the median duration of AF was 3 (1–7) years. The majority (n = 112, 60.2%) underwent RF ablation. The median procedure time was significantly lower in CB group (197 vs 226.5 min, p=<0.01). The incidence of complications was similar in the two sub-groups (RF: 1.8% vs. CB: 2.7%, p = 0.67). Similarly, arrhythmia-free survival rate on antiarrhythmic drugs at 1-year follow-up remained statistically comparable (63.4% vs. 68.9%, p = 0.33) between patients receiving RF vs. CB ablation.ConclusionThe safety and efficacy of RF vs. CB ablation for AF remained comparable in our cohort of patients older than 75 years. CB ablation was associated with a shorter procedure time.     

Body temperature in the mouse,hamster, and rat exposed to radiofrequency radiation: An interspecies comparison

• 1.1.|Colonic temperatures of BALB/c and CBA/J mice, golden hamsters, and Sprague-Dawley rats were taken immediately after exposure for 90 min to radiofrequency (RF) radiation.
• 2.2.|Exposures were made in 2450 MHz (mouse and hamster) or 600 MHz (rat) waveguide exposure systems while the dose rate, specific absorption rate (SAR), was continuously recorded. Experiments were performed on naive, unrestrained animals at ambient temperatures (T_a) of 20 and 30°C.
• 3.3.|Body mass and T_a) were found to be significant factors in influencing the threshold SAR for the elevation of colonic temperature. The threshold SARs at T_a's of 20 and 30°C were respectively: 27.5 and 12.1 W/kg for the BALB/c mouse; 40.7 and 8.5 W/kg for the CBA/J mouse; 8.7 and 0.61 W/kg for the golden hamster; and 1.58 and 0.4 W/kg for the Sprague-Dawley rat.
• 4.4.|The relationship between threshold SAR or SAR for a 1.0°C elevation in colonic temperature vs body mass were linearly and inversely related on a double logarithmic plot. The results of this study suggest that the thermoregulatory sensitivity to RF radiation in these rodent species is heavily dependent on body mass and T_a.

     

No effects of mobile phone use on cortical auditory change‐detection in children: An ERP study

We investigated the effect of mobile phone use on the auditory sensory memory in children. Auditory event‐related potentials (ERPs), P1, N2, mismatch negativity (MMN), and P3a, were recorded from 17 children, aged 11–12 years, in the recently developed multi‐feature paradigm. This paradigm allows one to determine the neural change‐detection profile consisting of several different types of acoustic changes. During the recording, an ordinary GSM (Global System for Mobile Communications) mobile phone emitting 902 MHz (pulsed at 217 Hz) electromagnetic field (EMF) was placed on the ear, over the left or right temporal area (SAR_1g = 1.14 W/kg, SAR_10g = 0.82 W/kg, peak value = 1.21 W/kg). The EMF was either on or off in a single‐blind manner. We found that a short exposure (two 6 min blocks for each side) to mobile phone EMF has no statistically significant effects on the neural change‐detection profile measured with the MMN. Furthermore, the multi‐feature paradigm was shown to be well suited for studies of perception accuracy and sensory memory in children. However, it should be noted that the present study only had sufficient statistical power to detect a large effect size. Bioelectromagnetics 31:191–199, 2010. © 2009 Wiley‐Liss, Inc.     

Effects of radiofrequency field exposure on proteotoxic-induced and heat-induced HSF1 response in live cells using the bioluminescence resonance energy transfer technique

As of today, only acute effects of RF fields have been confirmed to represent a potential health hazard and they are attributed to non-specific heating (≥ 1 °C) under high-level exposure. Yet, the possibility that environmental RF impact living matter in the absence of temperature elevation needs further investigation. Since HSF1 is both a thermosensor and the master regulator of heat-shock stress response in eukaryotes, it remains to assess HSF1 activation in live cells under exposure to low-level RF signals. We thus measured basal, temperature-induced, and chemically induced HSF1 trimerization, a mandatory step on the cascade of HSF1 activation, under RF exposure to continuous wave (CW), Global System for Mobile (GSM), and Wi-Fi-modulated 1800 MHz signals, using a bioluminescence resonance energy transfer technique (BRET) probe. Our results show that, as expected, HSF1 is heat-activated by acute exposure of transiently transfected HEK293T cells to a CW RF field at a specific absorption rate of 24 W/kg for 30 min. However, we found no evidence of HSF1 activation under the same RF exposure condition when the cell culture medium temperature was fixed. We also found no experimental evidence that, at a fixed temperature, chronic RF exposure for 24 h at a SAR of 1.5 and 6 W/kg altered the potency or the maximal capability of the proteasome inhibitor MG132 to activate HSF1, whatever signal used. We only found that RF exposure to CW signals (1.5 and 6 W/kg) and GSM signals (1.5 W/kg) for 24 h marginally decreased basal HSF1 activity.Electronic supplementary materialThe online version of this article (10.1007/s12192-020-01172-3) contains supplementary material, which is available to authorized users.     

Temperature regulation in the unrestrained rabbit during exposure to 600 MHz radiofrequency radiation

Six male New Zealand white rabbits were individually exposed to 600 MHz radiofrequency (RF) radiation for 90 min in a waveguide exposure system at an ambient temperature (Ta) of 20 or 30 degrees C. Immediately after exposure, the rabbit was removed from the exposure chamber and its colonic and ear skin temperatures were quickly measured. The whole-body specific absorption rate (SAR) required to increase colonic and ear skin temperature was determined. At a Ta of 20 degrees C the threshold SAR for elevating colonic and ear skin temperature was 0.64 and 0.26 W/kg, respectively. At a Ta of 30 degrees C the threshold SARs were slightly less than at 20 degrees C, with values of 0.26 W/kg for elevating colonic temperature and 0.19 W/kg for elevating ear skin temperature. The relationship between heat load and elevation in deep body temperature shown in this study at 600 MHz is similar to past studies which employed much higher frequencies of RF radiation (2450-2884 MHz). On the other hand, comparison of these data with studies on exercise-induced heat production and thermoregulation in the rabbit suggest that the relationship between heat gain and elevation in body temperature in exercise and from exposure to RF radiation may differ considerably. When combined with other studies, it was shown that the logarithm of the SAR required for a 1.0 degree C elevation in deep body temperature of the rabbit, rat, hamster, and mouse was inversely related to the logarithm of body mass. The results of this study are consistent with the conclusion that body mass strongly influences thermoregulatory sensitivity of the aforementioned laboratory mammals during exposure to RF radiation.     

Preattentive auditory information processing under exposure to the 902 MHz GSM mobile phone electromagnetic field: A mismatch negativity (MMN) study

Previous studies on the effects of the mobile phone electromagnetic field (EMF) on various event‐related potential (ERP) components have yielded inconsistent and even contradictory results, and often failed in replication. The mismatch negativity (MMN) is an auditory ERP component elicited by infrequent (deviant) stimuli differing in some physical features from the repetitive frequent (standard) stimuli in a sound sequence. The MMN provides a sensitive measure for cortical auditory stimulus feature discrimination, regardless of attention and other contaminating factors. In this study, MMN responses to duration, intensity, frequency, and gap changes were recorded in healthy young adults (n = 17), using a multifeature paradigm including several types of auditory change in the same stimulus sequence, while a GSM mobile phone was placed on either ear with the EMF (902 MHz pulsed at 217 Hz; SAR_1g = 1.14 W/kg, SAR_10g = 0.82 W/kg, peak value = 1.21 W/kg, measured with an SAM phantom) on or off. An MMN was elicited by all deviant types, while its amplitude and latency showed no significant differences due to EMF exposure for any deviant types. In the present study, we found no conclusive evidence that acute exposure to GSM mobile phone EMF affects cortical auditory change detection processing reflected by the MMN. Bioelectromagnetics 30:241–248, 2009. © 2009 Wiley‐Liss, Inc.     

Role of blood flow on RF exposure induced skin temperature elevations in rabbit ears

In this in vivo study, we measured local temperature changes in rabbit pinnae, which were evoked by radiofrequency (RF) exposure for 20 min at localized SAR levels of 0 (sham exposure), 2.3, 10.0, and 34.3 W/kg over 1.0 g rabbit ear tissue. The effects of RF exposures on skin temperature were measured under normal blood flow and without blood flow in the ear. The results showed: (1) physiological blood flow clearly modified RF induced thermal elevation in the pinna as blood flow significantly suppressed temperature increases even at 34.3 W/kg; (2) under normal blood flow conditions, exposures at 2.3 and 10.0 W/kg, approximating existing safety limits for the general public (2 W/kg) and occupational exposure (10 W/kg), did not induce significant temperature rises in the rabbit ear. However, 2.3 W/kg induced local skin temperature elevation under no blood flow conditions. Our results demonstrate that the physiological effects of blood flow should be considered when extrapolating modeling data to living animals, and particular caution is needed when interpreting the results of modeling studies that do not include blood flow.     

Effect of Exposure to a Radiofrequency Electromagnetic Field on Body Temperature in Anesthetized and Non-Anesthetized Rats

Exposure to a radiofrequency (RF) signal at a specific absorption rate (SAR) of 4 W/kg can increase the body temperature by more than 1 °C. In this study, we investigated the effect of anesthesia on the body temperature of rats after exposure to an RF electromagnetic field at 4 W/kg SAR. We also evaluated the influence of body mass on rats’ body temperature. Rats weighing 225 and 339 g were divided into sham- and RF-exposure groups. Each of the resulting four groups was subdivided into anesthetized and non-anesthetized groups. The free-moving rats in the four RF-exposure groups were subjected to a 915 MHz RF identification signal at 4 W/kg whole-body SAR for 8 h. The rectal temperature was measured at 1-h intervals during RF exposure using a small-animal temperature probe. The body temperatures of non-anesthetized, mobile 225 and 339 g rats were not significantly affected by exposure to an RF signal. However, the body temperatures of anesthetized 225 and 339 g rats increased by 1.9 °C and 3.3 °C from baseline at 5 and 6 h of RF exposure, respectively. Three of the five 339 g anesthetized and exposed rats died after 6 h of RF exposure. Thus, anesthesia and body mass influenced RF exposure-induced changes in the body temperature of rats. Bioelectromagnetics. 2020;41:104–112. © 2019 Bioelectromagnetics Society.     

DNA synthesis and cell proliferation in C6 glioma and primary glial cells exposed to a 836.55 MHz modulated radiofrequency field

We have tested the hypothesis that modulated radiofrequency (RF) fields may act as a tumor-promoting agent by altering DNA synthesis, leading to increased cell proliferation. In vitro tissue cultures of transformed and normal rat glial cells were exposed to an 836.55 MHz, packet-modulated RF field at three power densities: 0.09, 0.9, and 9 mW/cm², resulting in specific absorption rates (SARs) ranging from 0.15 to 59 μW/g. TEM-mode transmission-line cells were powered by a prototype time-domain multiple-access (TDMA) transmitter that conforms to the North American digital cellular telephone standard. One sham and one energized TEM cell were placed in standard incubators maintained at 37 °C and 5% CO₂. DNA synthesis experiments at 0.59–59 μW/g SAR were performed on log-phase and serum-starved semiquiescent cultures after 24 h exposure. Cell growth at 0.15–15 μW/g SAR was determined by cell counts of log-phase cultures on days 0, 1, 5, 7, 9, 12, and 14 of a 2 week protocol. Results from the DNA synthesis assays differed for the two cell types. Sham-exposed and RF-exposed cultures of primary rat glial cells showed no significant differences for either log-phase or serum-starved condition. C₆ glioma cells exposed to RF at 5.9 μW/g SAR (0.9 mW/cm²) exhibited small (20–40%) significant increases in 38% of [³H]thymidine incorporation experiments. Growth curves of sham and RF-exposed cultures showed no differences in either normal or transformed glial cells at any of the power densities tested. Cell doubling times of C₆ glioma cells [sham (21.9 ± 1.4 h) vs. field (22.7 ± 3.2 h)] also demonstrated no significant differences that could be attributed to altered DNA synthesis rates. Under these conditions, this modulated RF field did not increase cell proliferation of normal or transformed cultures of glial origin. Bioelectromagnetics 18:230–236, 1997. © 1997 Wiley-Liss, Inc.