Microwave effect on camphor binding to rat olfactory epithelium

Microwave radiation decreased specific camphor binding to a membrane fraction of rat epithelium but not to a Triton X-100 extract of this fraction. Inhibition of the ligand binding did not depend on the modulation frequency of the microwave field in the region 1-100 Hz and was not a linear function of specific absorption rate (SAR). The decreased ligand binding was due to a shedding or release of the specific camphor-binding protein from the membrane into solution. It is highly probable that several other membrane proteins may be shed into solution during microwave exposure.     

Microwaves affect <Emphasis Type="Italic">Myriophyllum aquaticum</Emphasis> plants differently depending on the wave polarization

Previous studies on microwave exposure on plants have revealed variations in sensitivity of plants to different microwave frequencies, exposure durations, and power intensities. However, the effects of different polarizations of microwaves on plants have not been studied. Therefore, we investigated the effect of horizontally and vertically polarized 2 GHz continuous microwaves on Myriophyllum aquaticum plants at 1.8 W m^-2 power density. The electric potential variation along the vascular tissues were investigated for 1.5 h and growth parameters, pigmentation, and H₂O₂ formation were studied during 48 h microwave exposure. Exposure to horizontally polarized microwaves, decreased standard deviation of electric potential variation and increased H₂O₂ content significantly. Vertically polarized microwaves increased the standard deviation of electric potential variation and photosynthetic pigments significantly. However, none of the polarizations altered growth parameters (shoot length, stem diameter, and internodal length). Thermographic images taken for 1 h continuous microwave exposure did not indicate alteration in the temperature of the plants for both vertical and horizontal polarities.     

β2-Adrenoceptor Agonist-Induced Down-Regulation After Short-Term Exposure

Abstract

We examined the effect of duration of β₂-adrenergic receptor (β₂AR) occupancy by isoproterenol on specific binding of ¹²⁵l-lodocyanopindolol (¹²⁵I-ICYP) in membranes from rat L6 myoblasts. Ten minute exposure caused a time- and concentration-dependent maximal decrease in ¹²⁵-?YP binding 24 hours after exposure equal to that following continuous exposure (p < 0.05). Low temperature, concanavalin A, H89 and ICI 118,551 blocked the decline in ¹²⁵I-ICYP binding during the first hour following exposure probably representing receptor sequestration to a compartment or change to a form incapable of ligand binding. Compared to controls, receptor binding 4 and 24 hours following exposure was reduced 56 ± 8.7% and 72 ± 8.8%, respectively (p < 0.05), and was blocked by ICI 118,551 but not CGP12177. Isoproterenol-induced, but not forskolinstimulated, cAMP accumulation was reduced 35% 24 hours following exposure (p < 0.05). ¹²⁵I-ICYP binding in intact L6 cells 4 and 24 hours after exposure were respectively 56 ± 8.9 and 61 ± 13% of controls (p < 0.05). Following agonist exposure, CHO cell membranes expressing human β₂ARs exhibited ¹²⁵I-ICYP binding 85 ± 2.0% and 6 ± 2.8% of control values 4 and 24 hours, respectively (p < 0.05). A model predicting that full occupation of the β₂AR activates receptor degradation explains our results that agonist-induced down-regulation of β₂AR does not require continuous presence of the agonist.     

Stress proteins are not induced in mammalian cells exposed to radiofrequency or microwave radiation

The induction of stress proteins in HeLa and CHO cells was investigated following a 2 h exposure to radiofrequency (RF) or microwave radiation. Cells were exposed or sham exposed in vitro under isothermal (37 ± 0.2 °C) conditions. HeLa cells were exposed to 27- or 2450 MHz continuous wave (CW) radiation at a specific absorption rate (SAR) of 25 W/kg. CHO cells were exposed to CW 27 MHz radiation at a SAR of 100 W/kg. Parallel positive control studies included 2 h exposure of HeLa or CHO cells to 40 °C or to 45 μM cadmium sulfate. Stress protein induction was assayed 24 h after treatment by electrophoresis of whole-cell extracted protein labeled with [³⁵S]-methionine. Both cell types exhibited well-characterized responses to the positive control stresses. Under these exposure conditions, neither microwave nor RF radiation had a detectable effect on stress protein induction as determined by either comparison of RF-exposed cells with sham-exposed cells or comparison with heat-stressed or Cd⁺⁺ positive control cells. Bioelectromagnetics 18:499–505, 1997. © 1997 Wiley-Liss, Inc.     

Fluorescence depolarization studies of red cell membrane fluidity. The effect of exposure to 1.0-GHz microwave radiation

The internal viscosity of human red blood cell membranes was investigated during exposure to continuous wave 1.0-GHz microwave radiation using fluorescence measurements of a lipid seeking molecular probe, diphenylhexatriene. Samples were exposed in a Crawford cell arranged so that fluorescence was measured during microwave exposure; specific absorption rates calculated from electrical measurements were approximately 0.6, 2 and 15 W/kg. Measurements were obtained at selected temperatures between 15 °C and 40 °C and as a function of the duration of exposure at 23 °C. Arrhenius-type plots of the temperature profile data were linear and showed no difference between exposed and control samples. The exposure duration data also showed no difference between exposed and control samples except for a small effect of elevated temperature at the highest exposure. The activation energy for motion of the fluorescent probe in its environment within the membrane lipid was not affected by the application of the microwave energy and no evidence for a lipid phase transition was found. These results indicate that the increased cation efflux from red cells, observed by others at certain transition temperatures during microwave exposure, was more likely to have been caused by alteration of the membrane bound protein than by changes in the lipid constituents of the red cell membrane.     

Absence of corneal endothelium injury in non‐human primates treated with and without ophthalmologic drugs and exposed to 2.8 GHz pulsed microwaves

Microwave‐induced corneal endothelial damage was reported to have a low threshold (2.6 W/kg), and vasoactive ophthalmologic medications lowered the threshold by a factor of 10–0.26 W/kg. In an attempt to confirm these observations, four adult male Rhesus monkeys (Macaca mulatta) under propofol anesthesia were exposed to pulsed microwaves in the far field of a 2.8 GHz signal (1.43 ± 0.06 µs pulse width, 34 Hz pulse repetition frequency, 13.0 mW/cm² spatial and temporal average, and 464 W/cm² spatial and temporal peak (291 W/cm² square wave equivalent) power densities). Corneal‐specific absorption rate was 5.07 W/kg (0.39 W/kg/mW/cm²). The exposure resulted in a 1.0–1.2 °C increase in eyelid temperature. In Experiment I, exposures were 4 h/day, 3 days/week for 3 weeks (nine exposures and 36 h total). In Experiment II, these subjects were pretreated with 0.5% Timolol maleate and 0.005% Xalatan® followed by 3 or 7 4‐h pulsed microwave exposures. Under ketamine–xylazine anesthesia, a non‐contact specular microscope was used to obtain corneal endothelium images, corneal endothelial cell density, and pachymetry at the center and four peripheral areas of the cornea. Ophthalmologic measurements were done before and 7, 30, 90, and 180 days after exposures. Pulsed microwave exposure did not cause alterations in corneal endothelial cell density and corneal thickness with or without ophthalmologic drugs. Therefore, previously reported changes in the cornea exposed to pulsed microwaves were not confirmed at exposure levels that are more than an order of magnitude higher. Bioelectromagnetics 31:324–333, 2010. Published 2010 Wiley‐Liss, Inc.     

Cytogenetic damage in human lymphocytes following GMSK phase modulated microwave exposure.

The present study investigated, using in vitro experiments on human lymphocytes, whether exposure to a microwave frequency used for mobile communication, either unmodulated or in presence of phase only modulation, can cause modification of cell proliferation kinetics and/or genotoxic effects, by evaluating the cytokinesis block proliferation index and the micronucleus frequency. In the GSM 1800 mobile communication systems the field is both phase (Gaussian minimum shift keying, GMSK) and amplitude (time domain multiple access, TDMA) modulated. The present study investigated only the effects of phase modulation, and no amplitude modulation was applied. Human peripheral blood cultures were exposed to 1.748 GHz, either continuous wave (CW) or phase only modulated wave (GMSK), for 15 min. The maximum specific absorption rate (approximately 5 W/kg) was higher than that occurring in the head of mobile phone users; however, no changes were found in cell proliferation kinetics after exposure to either CW or GMSK fields. As far as genotoxicity is concerned, the micronucleus frequency result was not affected by CW exposure; however, a statistically significant micronucleus effect was found following exposure to phase modulated field. These results would suggest a genotoxic power of the phase modulation per se.     

Beta 2-adrenoceptor agonist-induced down-regulation after short-term exposure.

We examined the effect of duration of beta 2-adrenergic receptor (beta 2AR) occupancy by isoproterenol on specific binding of 125I-lodocyanopindolol (125I-ICYP) in membranes from rat L6 myoblasts. Ten minute exposure caused a time-and concentration-dependent maximal decrease in 125I-ICYP binding 24 hours after exposure equal to that following continuous exposure (p < 0.05). Low temperature, concanavalin A, H89 and ICl 118,551 blocked the decline in 125I-ICYP binding during the first hour following exposure probably representing receptor sequestration to a compartment or change to a form incapable of ligand binding. Compared to controls, receptor binding 4 and 24 hours following exposure was reduced 56 +/- 8.7% and 72 +/- 8.8%, respectively (p < 0.05), and was blocked by ICl 118,551 but not CGP12177. Isoproterenol-induced, but not forskolin-stimulated, cAMP accumulation was reduced 35% 24 hours following exposure (p < 0.05). 125I-ICYP binding in intact L6 cells 4 and 24 hours after exposure were respectively 56 +/- 8.9 and 61 +/- 13% of controls (p < 0.05). Following agonist exposure, CHO cell membranes expressing human beta 2ARs exhibited 125I-ICYP binding 85 +/- 2.0% and 6 +/- 2.8% of control values 4 and 24 hours, respectively (p < 0.05). A model predicting that full occupation of the beta 2AR activates receptor degradation explains our results that agonist-induced down-regulation of beta 2AR does not require continuous presence of the agonist.     

Impact of 864 MHz or 935 MHz radiofrequency microwave radiation on the basic growth parameters of V79 cell line

The aim of this study was to evaluate and compare the influence of 864 MHz and 935 MHz radiofrequency/microwave (RF/MW) fields on the growth, colony-forming ability, and viability of V79 cells (continuous line). Cell samples with 1 x 10(4) V79 cells each, were exposed to continuous wave frequencies of 864 MHz and 935 MHz for 1, 2 and 3 hours. Exposed samples were matched with unexposed control samples. Specific absorption rate (SAR) was 0.08 W/kg for the 864 MHz or 0.12 W/kg for the 935 MHz field. Cell growth and viability were determined by counting cells every day for five days after exposure. Colony-forming ability was assessed by counting colonies seven days after exposure. The growth of the 864 MHz-irradiated cells was significant after two- and three-hour exposure 72 hours after irradiation (p < 0.05). The similar was observed 72 hours after exposure for cells exposed to 935 MHz microwaves for three hours (p <0.05). Colony-forming ability and cell viability in V79 cells exposed to 864 MHz or 935 MHz microwaves did not significantly differ from control cells. The two applied RF/MW fields showed similar effects on the growth, colony-forming ability and viability of V79 cells. Cell growth impact was time-dependent for both fields.     

The Effect of Microwave Radiation on Binding of Propyl-2,3-[3H]-Dehydroalprenololto β-Adrenergic Receptors of Rat Erythrocyte Membranes

The effect of microwave radiation (2450 MHz) on binding of the ligand propyl-2,3-[³H]-dehydroalprenolol to β-adrenergic receptors of rat erythrocyte membranes has been studied. It is shown that microwave exposure decreases specific binding of the ligand to receptors. The effect is dependent on time of exposure (66.2% on 10 min exposure and 37.3% on 30 min exposure). EDTA and heparin used as anticoagulants do not significantly alter the experimental results. However, the Ca²⁺ content in the incubation medium is essential for the effect. Exposure of erythrocytes isolated in the presence of EDTA and incubated in Hanks' solution without CA²⁺ has no effect on binding. The effect is manifest when Ca²⁺ is added to the specimen exposed. Possible mechanisms of action of microwaves on the studied parameter are discussed.     

Effects of X-band microwave exposure on rabbit erythrocytes

Rabbit erythrocytes were exposed in vitro to continuous wave (CW) and pulse-modulated X-band microwaves in wave guide exposure chambers. Erythrocytes were exposed as whole (hep-arinized) blood suspensions or as washed cells in 1:1 isotonic buffered K⁺-free saline suspensions. Statistically significant increases in K⁺ efflux relative to thermal controls were detected when red cells were exposed in whole blood suspensions to either CW or pulsed 8.42-GHz microwaves at SARs that resulted in equilibrium sample temperatures of approximately 24 °C. Under the same exposure conditions, no statistically significant K⁺ efflux occurred in the case of 1:1 red cell suspensions. Measured differences in sample heating rates and temperature gradients between microwave-exposed and heated control suspensions may account in part for the differential effect of microwave exposure but such effects do not appear to explain the results of this study fully.     

Properties of 3H-cimetidine binding in rat brain membrane fractions

In an attempt to characterize the brain histamine H₂ receptor, experiments were undertaken to study the binding properties of (N-methyl-³H) -cimetidine, an H₂ receptor antagonist, in rat brain membranes. Using a centrifugation assay, ³H-cimetidine binding having a K_d of 0.40μM and a Bmax of 3.9 pmoles/mg protein was detected. Of fourteen anions and cations tested, one, Cu⁺⁺, dramatically increased specific ³H-cimetidine binding, the increase being due mainly to a change in Bmax. Studies of substrate specificity for ³H-cimetidine binding revealed that Cu⁺⁺, while not significantly affecting the potency of H₂ receptor agonists and antagonists, dramatically decreases the potency of H₁ receptor substances on the ³H-cimetidine binding site. In addition, both the relative and absolute potencies of various H₂ receptor agonistsv and antagonists in displacing the ligand in the presence of Cu⁺⁺ parallels their potencies in biological systems. These findings suggest that, under these conditions, ³H-cimetidine may be labelling a biologically relevant H₂ binding site in brain and that Cu⁺⁺ may regulate the substrate specificity for this site. The brain regional distribution and kinetic analysis of the binding suggest that it is not localized solely to the synaptic receptor for histamine, but may also be associated with histamine receptors at other neuronal, glial or vascular sites.     

Ultraviolet radiation,thiol reagents,and solubilization enhance AMPA receptor binding affinity via a common mechanism

The binding properties of membrane-bound or solubilized AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid)-type glutamate receptors from rat brain were tested following exposure to ultraviolet (UV)_radiation or incubation with the thiol reagent p-chloromercuriphenyl-sulfonic acid (PCMBS). Brief exposure to UV radiation (254 nm) increased [³H]AMPA binding to brain membranes, while binding to soluble fractions decreased. The increase in brain membrane binding was caused by an apparent interconversion of low-affinity [³H]AMPA binding sites into a higher-affinity state. Incubation with PCMBS caused a significant increase in [³H]AMPA binding to brain membranes but had no significant effect on [³HAMPA binding to solubilized receptors. There was an interaction between the PCMBS and UV effects in the brain membranes such that prior exposure to one of the treatments reduced the relative magnitude of the other's effects. The present results suggest that ultraviolet radiation, PCMBS and solubilization all increase AMPA receptor binding affinity via a common mechanism.     

Temperature-specific inhibition of human red cell Na+/K+ ATPase by 2,450-MHz microwave radiation

The ATPase activity in human red blood cell membranes was investigated in vitro as a function of temperature and exposure to 2,450-MHz continuous wave microwave radiation to confirm and extend a report of Na+ transport inhibition under certain conditions of temperature and exposure. Assays were conducted spectrophotometrically during microwave exposure with a custom-made spectrophotometer-waveguide apparatus. Temperature profiles of total ATPase and Ca+2 ATPase (ouabain-inhibited) activity between 17 and 31 degrees C were graphed as an Arrhenius plot. Each data set was fitted to two straight lines which intersect between 23 and 24 degrees C. The difference between the total and Ca+2 ATPase activities, which represented the Na+/K+ ATPase activity, was also plotted and treated similarly to yield an intersection near 25 degrees C. Exposure of membrane suspensions to electromagnetic radiation, at a dose rate of 6 W/kg and at five temperatures between 23 and 27 degrees C, resulted in an activity change only for the Na+/K+ ATPase at 25 degrees C. The activity decreased by approximately 35% compared to sham-irradiated samples. A possible explanation for the unusual temperature/microwave interaction is proposed.     

Absence of Non-Thermal Microwave Effects on the Function of Giant Nerve Fibers

Functioning of the giant axon of the isolated earthworm ventral nerve cord was examined during exposure to 6.45 GHz microwaves. We used continuous wave and pulsed irradiation, either synchronized with stimuli or asynchronous, lasting for 10–50 min at specific absorption rate from 30 to 230 W/kg. Action potential (AP) conduction velocity and the capability of nerve fiber to answer long-lasting high-frequency stimulation served as indices of microwave effect. Under some experimental conditions the nerve appeared to have extreme sensitivity to subtle temperature changes, induced by irradiation, but no non-thermal microwave effects were detected.     

Effects of continuous and intermittent exposure to RF fields with a wide range of SARs on cell growth, survival, and cell cycle distribution

To examine the biological effects of radio frequency (RF) electromagnetic fields in vitro, we have examined the fundamental cellular responses, such as cell growth, survival, and cell cycle distribution, following exposure to a wide range of specific absorption rates (SAR). Furthermore, we compared the effects of continuous and intermittent exposure at high SARs. An RF electromagnetic field exposure unit operating at a frequency of 2.45 GHz was used to expose cells to SARs from 0.05 to 1500 W/kg. When cells were exposed to a continuous RF field at SARs from 0.05 to 100 W/kg for 2 h, cellular growth rate, survival, and cell cycle distribution were not affected. At 200 W/kg, the cell growth rate was suppressed and cell survival decreased. When the cells were exposed to an intermittent RF field at 300 W/kg(pk), 900 W/kg(pk) and 1500 W/kg(pk) (100 W/kg(mean)), no significant differences were observed between these conditions and intermittent wave exposure at 100 W/kg. When cells were exposed to a SAR of 50 W/kg for 2 h, the temperature of the medium around cells rose to 39.1 degrees C, 100 W/kg exposure increased the temperature to 41.0 degrees C, and 200 W/kg exposure increased the temperature to 44.1 degrees C. Exposure to RF radiation results in heating of the medium, and the thermal effect depends on the mean SAR. Hence, these results suggest that the proliferation disorder is caused by the thermal effect.     

Chronic exposure of rabbits to 0.5 and 5 mW/cm2 2450-MHz CW Microwave Radiation

Two groups of 16 male New Zealand rabbits were exposed to 2450-MHz continuous wave microwave fields in two experiments of 90 days each. The incident power densities of the first and second experiment were 0.5 and 5 mW/cm², respectively. During each study, 16 animals were adapted to a miniature anechoic chamber exposure system for at least 2 weeks, then 8 of them were exposed for 7 h daily, 5 days a week for 13 weeks, and the other 8 animals were sham exposed. The rabbits were placed in acrylic cages, and each was exposed from the top in an individual miniature anechoic chamber. Thermography showed a maximum specific absorption rate of 5.5 W/kg in the head and 7 W/kg in the back at 5-mW/cm² incident power density. After each 7-h exposure session, the animals were returned to their home cages. Food consumption in the exposure chamber and body mass were measured daily. Blood samples were taken before exposure and monthly thereafter for hematological, morphological, chemical, protein electrophoresis, and lymphocyte blast transformation studies. Eyes were examined for cataract formation. Finally, pathological examinations of 28 specimens of organs and tissues of each rabbit were performed. Statistically, there was a significant (P < .01) decrease only of food consumption during the 5-mW/cm² exposure; other variables were not significantly different between exposed and control groups.     

Effects of chaotropic anions on bicuculline inhibition of high affinity γ-aminobutyric acid binding in bovine retina and rat brain membranes

Chaotropic anions (ions that favour transfer of apolar groups to water) increased bicuculline inhibition of ³H-γ-aminobutyric acid binding to bovine retinal membranes as previously reported for rat forebrain membranes. The increased bicuculline inhibition was reversible when the chaotropic anion was removed thus ruling out the possibility that ‘endogenous regulators’ were being removed by the chaotropic anions. Another possible explanation for the enhanced bicuculline inhibition is an increase in the solubility of bicuculline, an organic compound that is sparingly soluble in water; however, when bicuculline-methiodide, a more water soluble form of bicuculline was used, no difference was noted in this enhancement.Although the chaotropic anions temporarily increase the bicuculline inhibition of γ-aminobutyric acid binding, they do not increase ³H-γ-aminobutyric acid receptor binding as previously suggested. Thiocyanate or perchlorate have no effect on ³H-γ-aminobutyric acid receptor binding to rat forebrain or cerebellar membranes. Although thiocyanate slightly inhibits γ-aminobutyric acid receptor binding to bovine retinal membranes, perchlorate has no effect. The previous observation that sodium perchlorate enhanced γ-aminobutyric acid binding in bovine retina was due to the enhancement of sodium-dependent binding to a nipecotic acid-sensitive binding site (perhaps an uptake site).The mechanism of action of chaotropic anions in vitro on γ-aminobutyric acid binding may be through an alteration in the interaction of the receptor with the antagonists, bicuculline or bicuculline-methiodide, but is not through the removal of a component that blocks the binding site or regulates the receptor's properties, as evidenced by the reversibility of the chaotropic anion effect and the lack of effect on agonist binding.     

Fusicoccin Binding to its Plasma Membrane Receptor and the Activation of the Plasma Membrane H+-ATPase. II. Stimulation of the H+-ATPase in a Plasma Membrane Fraction Purified by Phase-partitioning

The effect of fusicoccin (FC) on the activity of the PM H⁺-ATPase was investigated in a plasma membrane (PM) fraction from radish seedlings purified by the phase-partitioning procedure. FC stimulated the PM H⁺-ATPase activity by up to 100 %; the effect was essentially on V_max with only a slight decrease of the apparent K_M of the enzyme for ATP. FC-induced stimulation of the PM H⁺-ATPase was evident within the first minute and maximal within five minutes of membrane treatment with the toxin indicating that transmission of the signal from the activated receptor to the PM H⁺-ATPase is very rapid. Both FC-induced stimulation of the PM H⁺-ATPase and FC binding to its receptor decreased dramatically upon incubation of the membranes in ATPase assay medium at 33 °C in the absence of FC, due to the lability of the free FC receptor. FC-induced stimulation of the PM H⁺-ATPase was strongly pH dependent: absolute increase of activity was maximal at pH 7, while percent stimulation increased with the increase of pH up to pH 7.5; FC binding was scarcely influenced by pH in the pH range investigated. Taken as a whole, these results indicate that FC binding is a condition necessary, but not sufficient, for FC-induced stimulation of the PM H⁺-ATPase.     

Thermoregulatory consequences of long-term microwave exposure at controlled ambient temperatures

This study was designed to identify and measure changes in thermoregulatory responses, both behavioral and physiological, that may occur when squirrel monkeys are exposed to 2450-MHz continuous wave microwaves 40 hr/week for 15 weeks. Power densities of 1 or 5 mW/cm2 (specific absorption rate = 0.16 W/kg per mW/cm2) were presented at controlled environmental temperatures of 25, 30, or 35 degrees C. Standardized tests, conducted periodically, before, during, and after treatment, assessed changes in thermoregulatory responses. Dependent variables that were measured included body mass, certain blood properties, metabolic heat production, sweating, skin temperatures, deep body temperature, and behavioral responses by which the monkeys selected a preferred environmental temperature. Results showed no reliable alteration of metabolic rate, internal body temperature, blood indices, or thermoregulatory behavior by microwave exposure, although the ambient temperature prevailing during chronic exposure could exert an effect. An increase in sweating rate occurred in the 35 degrees C environment, but sweating was not reliably enhanced by microwave exposure. Skin temperature, reflecting vasomotor state, was reliably influenced by both ambient temperature and microwaves. The most robust consequence of microwave exposure was a reduction in body mass, which appeared to be a function of microwave power density.