Specific absorption rate (SAR) in models of the human head exposed to hand-held UHF portable radios

Specific absorption rate (SAR) was measured in models of the human head exposed to hand-held portable radios ("transceivers") transmitting at frequencies in the 800-MHz band. An isotropic implantable electric-field probe was used to measure internal fields induced in the head models, and SARs were determined by calculation. As well as determining representative values and distributions for SARs under various conditions, it was shown that antenna type and orientation with respect to the head are important factors affecting energy absorption.     

Estimation of the SAR in the human head and body due to radiofrequency radiation exposure from handheld mobile phones with hands-free accessories

It was reported by others that hands-free accessories increase the absorption of RF energy in a human head compared to a handset alone. The results of this study show that the opposite is observed when proper dosimetric methods are employed. It is pointed out that for correct estimation of the exposure level it is necessary to use appropriate physical and experimental models and measurement instrumentation, following internationally recommended standards. The human phantoms used for measurements involving the hands-free accessories should include the torso; i.e., measurements should not be performed on the head phantom alone. This has a significant impact on the results because the RF energy coupled into the leads of hands-free accessories is strongly attenuated by the body. Numerical simulations using the Finite-Difference Time-Domain (FDTD) method and experimental measurements with a miniature electric-field probe are in good agreement and show a decrease, not an increase, in RF energy exposure in the human head from hands-free accessories.     

Non-thermal exposure to radiofrequency energy from digital wireless phones does not affect ornithine decarboxylase activity in L929 cells

L929 murine fibroblast cells were exposed to radiofrequency (RF) radiation from a time division multiple access wireless phone operating at 835 MHz frequency to determine the effect of RF-radiation energy emitted by wireless phones on ornithine decarboxylase (ODC) activity in cultured cells. Exposure was for 8 h to an average specific absorption rate (SAR) from <1 W/kg up to 15 W/kg. After exposure, cells were harvested and ODC activity was measured. No statistically significant difference in ODC activity was found between RF-radiation-exposed and sham-exposed cells at non-thermal specific absorption rates. At SARs which resulted in measurable heating of the medium, a dose-dependent decrease in enzymatic activity was observed and was shown to be consistent with a comparable decrease caused by non-RF-radiation heating. Thus we observed only the well-known enzyme inhibition due to heating, rather than the previously reported enhancement attributed to RF-radiation exposure.     

Cold exposure and associated metabolic changes in adult tropical beetles exposed to fluctuating thermal regimes

Environmental stress deleteriously affects every aspect of an ectotherm's biological function. Frequent exposure of terrestrial insects to temperature variation has thus led to the evolution of protective biochemical and physiological mechanisms. However, the physiological mechanisms underlying the positive impact of fluctuating thermal regimes (FTRs) on the fitness and survival of cold-exposed insects have not been studied. We have thus investigated the metabolic changes in adults of the beetle Alphitobius diaperinus in order to determine whether FTRs trigger the initiation of a metabolic response involving synthesis of protective compounds, such as free amino acids (FAAs) and polyols. The metabolic profile was analyzed during constant fluctuating thermal regimes (the beetles had daily pulses at higher temperatures that enabled them to recover) and compared with constant cold exposure and untreated controls. The increase of several essential amino acids (Lys, Iso, Leu, Phe and Trp) in cold-exposed beetles supports the conclusion that it results from the breakdown of proteins. Some FAAs have been shown to have cryoprotective properties in insects, but the relationship between FAAs, cold tolerance and survival has not yet been well defined. Instead of considering FAAs only as a part of the osmo- and cryoprotective arsenal, they should also be regarded as main factors involved in the multiple regulatory pathways activated during cold acclimation. Under FTRs, polyol accumulation probably contributes to the increased duration of survival in A. diaperinus.     

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.     

No evidence for genotoxic effects from 24 h exposure of human leukocytes to 1.9 GHz radiofrequency fields

The current study extends our previous investigations of 2-h radiofrequency (RF)-field exposures on genotoxicity in human blood cell cultures by examining the effect of 24-h continuous-wave (CW) and pulsed-wave (PW) 1.9 GHz RF-field exposures on both primary DNA damage and micronucleus induction in human leukocyte cultures. Mean specific absorption rates (SARs) ranged from 0 to 10 W/kg, and the temperature within the cultures was maintained at 37.0 +/- 1.0 degrees C for the duration of the 24-h exposure period. No significant differences in primary DNA damage were observed between the sham-treated controls and any of the CW or PW 1.9 GHz RF-field-exposed cultures when processed immediately after the exposure period by the alkaline comet assay. Similarly, no significant differences were observed in the incidence of micronuclei, incidence of micronucleated binucleated cells, frequency of binucleated cells, or proliferation index between the sham-treated controls and any of the CW or PW 1.9 GHz RF-field-exposed cultures. In conclusion, the current study found no evidence of 1.9 GHz RF-field-induced genotoxicity in human blood cell cultures after a 24-h exposure period.     

An estimation of Canadian population exposure to cosmic rays from air travel

Based on air travel statistics in 1984, it was estimated that less than 4 % of the population dose from cosmic ray exposure would result from air travel. In the present study, cosmic ray doses were calculated for more than 3,000 flights departing from more than 200 Canadian airports using actual flight profiles. Based on currently available air travel statistics, the annual per capita effective dose from air transportation is estimated to be 32 μSv for Canadians, about 10 % of the average cosmic ray dose received at ground level (310 μSv per year).     

Viability and phagocytosis of neutrophils exposed in vitro to 100-MHz radiofrequency radiation

Rabbit polymorphonuclear leucocytes (PMN, neutrophils) obtained from peritoneal exudate were exposed in vitro for one-half or one hour to continuous wave or amplitude-modulated (20-Hz) 100-MHz RF radiation in a temperature-controlled coaxial exposure chamber at field strengths from 2.5 to 4.1 V/cm (SARs of 120 to 341 W/kg). RF exposure at 37 +/- 0.2 degrees C had no detectable effect on PMN viability or phagocytosis compared to sham-exposed cells simultaneously subjected to the same time-temperature regime. Temperature control studies indicated that at 37 degrees C no effect on PMN viability would be expected but phagocytosis would be reduced by approximately 6%/degrees C temperature increase. The absence of an effect of RF exposure suggests that there was minimal undetected intrasample heating and that phagocytosis was not affected by 100-MHz RF radiation under the conditions of this study.     

Direct transfer of adult hookworms (Ancylostoma duodenale) from dog to child for therapeutic purposes

To induce chronic and continuous intestinal blood loss as therapy for congenital polycythemia in a 3 year old child, adult Ancylostoma duodenale were transferred directly from a dog to the patient via a nasoduodenal tube. By transferring adult worms, larval migration via the skin, blood and lungs--with possible attendant undesired side effects--was avoided. Furthermore, by eliminating larval migration with associated intimate tissue contact, immunogenicity was presumably reduced, and a known number of adult worms could be delivered directly to the final predilection site, the small intestine. An eosinophilic reaction of up to 23,000 cells/mm3 was observed, which may have adversely affected attempted superinfection. The relatively small numbers of parasites given on three separate occasions did not result in blood loss to a degree sufficient to eliminate the need for other forms of therapy.     

Application of potential energy calculations to the determination of muscle structure from X-ray data with special reference to the configuration of myosin heads

A method that relates molecular structure to the forces that maintain it and to its X-ray diffraction pattern is described and applied to muscle. In a computer model, the potential energy of the moveable components (here the myosin heads) is minimized by letting them move down the steepest gradient in three dimensions from a variety of starting positions. Initial values are assumed for the parameters that determine the forces, and for those that define the structure and arrangement of the fixed components. The X-ray pattern expected from the resulting structures can be calculated in a straightforward manner and compared with relevant observed data. Discrepancies can then be minimized by varying the values initially assumed for the parameters, as in the conventional “trial and error” method.This first application of the present method is concerned with the effects of the hexagonal lattice on the myosin head configuration in thick filaments of the type found in vertebrate skeletal muscle. For that purpose, a very simple model was used with the following main features: smooth cylinders for the thin filaments and for the thick filament backbones, two spherical heads attached by Hookean springs to each point of a $\text{9}\text{3}$ helix on the surface of the backbone, and repulsive forces of the electrostatic double-layer type acting between each head and all other surfaces.The myosin head configuration was calculated for an isolated thick filament and a study was made of the effects of packing such filaments into a hexagonal lattice of various side spacings in the presence or absence of thin filaments. For the isolated filament, it was found that the $\text{9}\text{3}$ helical symmetry is maintained in the myosin head configuration and that the two heads of each molecule are splayed azimuthally. When such filaments are packed into the hexagonal lattice with thin filaments present, the $\text{9}\text{3}$ helical symmetry of the myosin head configuration is lost. As the lattice side spacing is reduced, the myosin heads become increasingly displaced not only in the radial and azimuthal directions but also in the axial direction, although they interact primarily with smooth cylinders. The axial separation of the two heads in each molecule becomes different in one level from that in the other two in the 43 nm axial repeat, thus increasing the repeat in projection onto the axis from 14.3 to 43 nm. This effect may contribute to the “forbidden meridionals” described by Huxley & Brown (1967). In the absence of thin filaments, the displacements of the myosin heads are much smaller, even when the lattice side spacing is reduced to that present in muscles stretched to non-overlap.Applying the method based on potential energy minimization to the evaluation of X-ray data from muscles in hypertonic Ringer reveals that, even in the case of patterns apparently free of lattice sampling (and thus normally considered to represent diffraction from single filaments), the interpretation must include the nearest myosin heads from neighbouring filaments, and that this may be necessary also for unsampled patterns obtained from muscles in normal Ringer. Furthermore, the method helps to explain several other major features of X-ray results obtained from muscles in the hypertonic state and from muscles stretched in normal Ringer to long sarcomere lengths including non-overlap. It is concluded that the method provides a powerful tool for the interpretation of muscle X-ray patterns.     

Proteomic profiling of a parasitic wasp exposed to constant and fluctuating cold exposure

When insects are exposed to fluctuating thermal regimes (FTRs) (i.e., cold exposure alternating with periodic short pulses to high temperature), in contrast to constant low temperature (CLT), mortality due to accumulation of chill injuries is markedly reduced. To investigate the physiological processes behind the positive impact of FTR, based on a holistic approach, two-dimensional electrophoresis (2-DE) analysis were performed with the parasitic wasp Aphidius colemani. Parasitoid proteomes revealed 369 well-distinguishable protein spots, where the overall response to cold exposure was clearly specific to treatments (CLT versus FTR). The reduced mortality under FTR was associated with up-regulation of several proteins playing key roles in energy metabolism (glycolysis, TCA cycle, synthesis and conversion of ATP), protein chaperoning (Hsp70/Hsp90), and protein degradation (proteasome). Our results also support the idea that cytoskeleton components, particularly actin arrangement, could play a role in the higher survival rates of insects under FTR.     

Binding of octopamine to membranes from the white-eyed and wild-type housefly heads

In attempting to develop an octopamine (OA) receptor preparation with ready access to large amounts of tissue, we examined the binding of OA to membranes from the heads of white and red houseflies (Musca domestica L.). Binding was dependent on the presence of L-ascorbic acid in the medium. However, equilibrium was reached only over 24–36 h at 4°C and reversal of binding was also slow and incomplete. Scatchard analysis revealed at least two binding sites in the white-eyed housefly. A high-affinity site (K_d = 13.9 nM and B_max = 3.9 pmol/mg protein) was present, but the majority of the binding had low affinity (K_d = 1130 nM and B_max = 165 pmol/mg protein). Scatchard analysis revealed a low affinity in the red-eyed housefly (K_d = 240 nM and B_max = 12 pmol/mg protein). Catecholamines were the best competitors for OA binding followed by phenolamines such as OA and synephrine. 5-Hydroxytryptamine was less effective. Phentolamine and mianserin, which are good antagonists of the ability of OA to stimulate adenylate cyclase in housefly head membranes, and formamidine and imidazolines, which are potent partial agonists of this adenylate cyclase, were poor competitors of OA binding. The slow kinetics, low affinity, large amount, and unconventional pharmacological profile of this binding is not congruent with it being a neuroreceptor. When the brain was dissected free from the head, less than 10% of the total specific binding of OA was found in the brain membrane fraction. This suggests that most of the binding of OA may be to cuticular sites that possibly are associated with the metabolism of catecholamines in cuticular synthesis. Thus, binding studies made with labeled catecholamines and phenolamines on insect tissues containing significant cuticular elements should be interpreted with caution.     

Dosimetry of electromagnetic field exposure of an active armlet and its electromagnetic interference to the cardiac pacemakers using adult,child and infant models

ABSTRACT

Wearable devices have been popularly used with people from different age groups. As a consequence, the concerns of their electromagnetic field (EMF) exposure to the human body and their electromagnetic interference (EMI) to the implanted medical devices have attracted many studies. The aim of this study was to evaluate the human exposure to the EMF of an active radiofrequency identification (RFID) armlet as well as its EMI to the cardiac pacemaker (CP). Different human models from various age groups were applied to assess the result variability. The scalar potential finite element method was utilized in the simulation. Local EMF exposure and the exposure to the central nerve system tissues were evaluated using different metrics. EMI to the CP was assessed in terms of the conducted voltage to the CP. The results from all the models revealed that the studied RFID armlet would not produce the EMF exposure exceeding the safety limits. The calculated interference voltage was highly dependent on the distance between the RFID armlet and the CP (i.e. the physical dimension of the individual model). The results proposed to evaluate the appropriateness of the current EMI measurement protocol for this kind of devices used by the infants.     

Efficacy of chlorfenapyr against adult Tribolium castaneum exposed on concrete: effects of exposure interval, concentration and the presence of a food source after exposure

Chlorfenapyr, an insecticidal pyrrole, was applied to concrete arenas at concentrations of 1.1, 0.825, 0.55, and 0.275 g of active ingredient [AI]/m². Adult Tribolium castaneum (Herbst), the red flour beetle, were exposed for 2, 4, or 8 h at each concentration, then removed and held either with or without food (wheat flour) for 7 days. Survival was assessed when the beetles were removed from the exposure arenas and daily during the post-exposure period. In the presence of food, survival was high regardless of concentration and the day on which post-treatment survival was assessed, but survival did decrease as the exposure period increased from 4 to 8 h. When the beetles were not given food after exposure, survival at each concentration and exposure period declined during the 1-week post-exposure assessments. This pattern of decrease could be described by linear and non-linear equations. Results show the presence of food material greatly compromised effectiveness of the insecticide, and emphasize the importance of cleaning and sanitation in conjunction with insecticide treatments.     

On the relationship between distance information derived from cross-linking and from resonance energy transfer, with specific reference to sites located on myosin heads.

The techniques of fluorescence resonance energy transfer (FRET) and cross-linking can provide complementary information concerning the relative separation of a pair of sites. Cross-linking experiments provide an assessment of the distance of closest approach between a pair of sites. FRET measurements, by contrast, yield information about the average distance between the pair of sites. We have taken advantage of hybrid myosins to understand the relationship between distances obtained for a pair of equivalent sites, one on each myosin head, using both FRET (steady-state and time-decay) and cross-linking techniques. The rigid cross-linker, 4-4'-dimaleimidyl-stilbene-2-2'-disulfonic acid (DMSDS), can efficiently cross-link the two myosin regulatory light-chains, each at residue Cys50 of the Mercenaria regulatory light chain (Chantler, P.D., and S. M. Bower. 1988. J. Biol. Chem. 263:938-944), indicating that these sites can come within 18 +/- 2 A of each other. In a complementary set of experiments, steady-state and time-decay measurements using fluorescence donor/acceptor pairs located at these same sites indicate transfer efficiencies of somewhat less than 20%, suggesting an average separation of greater than 50 A between sites (Chantler, P. D., and T. Tao. 1986. J. Mol. Biol. 192:87-99). Here, we present theoretical calculations which show that efficient cross-linking can be achieved readily in dynamic systems such as the heads of myosin, even though the necessary subpopulation of proximate molecules at any instant may be below the detection limits of time-decay-FRET.(ABSTRACT TRUNCATED AT 250 WORDS)     

Potential biomarkers of exposure and effect among glass craftsmen and braziers exposed to nitrogen oxides

The purpose of this research was to determine occupational exposure of glass craftsmen and braziers to inhaled nitrogen oxides nitrogen dioxide and nitric oxide and to relate this to urinary nitrate, hydroxyproline and thioethers and to breath pentane. The glass craftsmen were exposed to nitrogen oxides at levels exceeding the occupational exposure standard and higher than braziers or controls. Urinary nitrate excretion was elevated. In these exposed workers hydroxyproline, thioethers and breath pentane were all elevated compared with controls and higher than in braziers who were less exposed. There was, however, only a correlation between individual levels of exposure nitrogen oxides in the breathing zone and breath pentane and there were no individual correlations between markers of effect and excretion of nitrate in the urine at the sample time.     

The estimation of molecular and cytogenetic effects in mice exposed to chronic low dose gamma-radiation

Molecular and cytogenetic parameters were estimated in male CBA/lac mice exposed to chronic low dose-rate gamma-radiation (62 cGy/year) for 40, 80, 120, 210, and 365 days. After 40 days of exposure (6.7 cGy), spleen lymphocyte susceptibility to hydrogen peroxide was shown to increase. However, beginning from the day 120 of the treatment (20.4 cGy), the opposite effect was observed. An increase in number of the DNA-protein crosslinks was recorded in spleen lymphocytes only on day 40 of the experiment. The number of DNA breaks increased significantly beginning from day 120 of the experiment, as shown by the DNA-comet method. On the day 210 of irradiation, the frequency of abnormal sperm heads in the mice significantly increased. The number of normochromatic micronucleated erythrocytes of the peripheral blood remained unchanged.