Effects of continuous-wave, pulsed, and sinusoidal-amplitude-modulated microwaves on brain energy metabolism

A comparison of the effects of continuous-wave, sinusoidal-amplitude-modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague-Dawley rats (175-225 g). Brain NADH fluorescence, adenosine triphosphate (ATP) concentration, and creatine phosphate (CP) concentration were determined as a function of modulation frequency. Brain temperatures of animals were maintained between -0.1 and -0.4 degrees C from the preexposure temperature when subjected to as much as 20 mW/cm2 (average power) CW, pulsed, or sinusoidal-amplitude modulated 591-MHz radiation for 5 min. Sinusoidal-amplitude-modulated exposures at 16-24 Hz showed a trend toward preferential modulation frequency response in inducing an increase in brain NADH fluorescence. The pulse-modulated and sinusoidal-amplitude-modulated (16 Hz) microwaves were not significantly different from CW exposures in inducing increased brain NADH fluorescence and decreased ATP and CP concentrations. When the pulse-modulation frequency was decreased from 500 to 250 pulses per second the average incident power density threshold for inducing an increase in brain NADH fluorescence increased by a factor of 4--ie, from about 0.45 to about 1.85 mW/cm2. Since brain temperature did not increase, the microwave-induced increase in brain NADH and decrease in ATP and CP concentrations was not due to hyperthermia. This suggests a direct interaction mechanism and is consistent with the hypothesis of microwave inhibition of mitochondrial electron transport chain function of ATP production.     

Biological effects of high-frequency electromagnetic fields on Salmonella typhimurium and Drosophila melanogaster

Salmonella typhimurium and Drosophila melanogaster were exposed to continuous wave (CW) 2.45-GHz electromagnetic radiation, pulsed 3.10-GHz electromagnetic radiation, CW 27.12-MHz magnetic fields, or CW 27.12-MHz electric fields (only Drosophila). The temperatures of the treated sample and the nonexposed control sample were kept constant. The temperature difference between exposed and control samples was less than +/- 0.3 degrees C. Ames' assays were made on bacteria that had been exposed to microwaves (SAR 60-130 W/kg) or RF fields (SAR up to 20 W/kg) when growing exponentially in nutrient broth. Survival and number of induced revertants to histidine prototrophy were determined by common plating techniques on rich and minimal agar plates. The Drosophila test consisted of a sensitive somatic system where the mutagenicity was measured by means of mutations in a gene-controlling eye pigmentation. In none of these test systems did microwave or radiofrequency fields induce an elevated mutation frequency. However, a significantly higher concentration of cells was found in the bacterial cultures exposed to the 27-MHz magnetic field or 2.45-GHz CW and 3.10-GHz pulsed microwave radiation.     

Acute effects of pulsed microwaves and 3-nitropropionic acid on neuronal ultrastructure in the rat caudate-putamen

Ultrastructure of the medium sized "spiny" neuron in rat dorsal-lateral caudate-putamen was assessed after administration of 3-nitropropionic acid (3-NP) and exposure to pulsed microwaves. Sprague-Dawley male rats were given two daily intraperitoneal doses of 0 or 10 mg/kg 3-NP and 1.5 h after each dose were exposed to microwave radiation at a whole body averaged specific absorption rate (SAR) of 0 (sham exposure), 0.6, or 6 W/kg for 30 min. Microwave exposure consisted of 1.25 GHz radiation delivered as 5.9 micros pulses with repetition frequency 10 Hz. Tissue samples taken 2-3 h after the second sham or microwave exposure showed no injury with light microscope methods. Blinded qualitative assessment of ultrastructure of randomly selected neurons from the same samples did reveal differences. Subsequent detailed, quantitative measurements showed that, when followed by sham exposure, administration of 3-NP significantly increased endoplasmic reticulum (ER) intracisternal width, ER area density, and nuclear envelope thickness. Microwave exposure at 6 W/kg alone also significantly increased these measures. Exposure of 3-NP treated animals at 6 W/kg significantly increased effects of 3-NP on ultrastructure. Although exposure at 0.6 W/kg alone did not affect ultrastructure measures, exposure of 3-NP treated animals at 0.6 W/kg reduced the effects of 3-NP. We concluded that 3-NP changed neuronal ultrastructure and that the microwave exposures used here changed neuronal ultrastructure in ways that depended on microwave SAR and neuron metabolic status. The apparent cancellation of 3-NP induced changes by exposure to pulsed microwaves at 0.6 W/kg indicated the possibility that such exposure can protect against the effects of mitochondrial toxins on the nervous system.     

Lack of behavioral effects in the rhesus monkey: high peak microwave pulses at 1.3 GHz

The current safety standards for radiofrequency and microwave exposure do not limit the peak power of microwave pulses for general or occupational exposures. While some biological effects, primarily the auditory effect, depend on pulsed microwaves, hazards associated with very high peak-power microwave pulses in the absence of whole-body heating are unknown. Five rhesus monkeys, Macaca mulatta, were exposed to peak-power densities of 131.8 W/cm2 (RMS) while performing a time-related behavioral task. The task was composed of a multiple schedule of reinforcement consisting of three distinct behavioral components: inter-response time, time discrimination, and fixed interval. Trained monkeys performed the multiple schedule during exposure to 1.3-GHz pulses at low pulse-repetition rates (2-32 Hz). No significant change was observed in any behavior during irradiation as compared to sham-irradiation sessions. Generalization of these findings to experimental results with higher peak-power densities, other pulse rates, different carrier frequencies, or other behaviors is limited.     

Ejaculatory pattern of llamas during copulation

The objective of this study was to use transrectal digital palpation of urethral pulses to define the ejaculatory pattern of llamas during copulation. Five male llamas were palpated during 5 to 6 copulations each with receptive female llamas (n = 28 copulations). The time from first exposure of a male to a female until mounting was 0.7 +/- 1.1 min (mean +/- SD), time to the first intromission was 1.7 +/- 1.4 min, and time from initial mount to final dismount (copulation duration) was 21.7 +/- 7.8 min. A total of 121.9 +/- 61.0 urethral pulses per copulation (5.6 +/- 1.7 pulses/min) was palpated. During the first 3.9 +/- 3.7 min of copulation, urethral pulses (11.0 +/- 10.1 urethral pulses at 3.5 +/- 2.5 pulses/min) occurred randomly and were not associated with whole-body strains. After the first 4 min of copulation, urethral pulses occurred in a pattern of clusters of frequent urethral pulses associated with whole-body strains, alternating with intercluster intervals of infrequent urethral pulses without whole-body strains. Individual clusters were characterized by 4.3 +/- 2.7 urethral pulses at 16.7 +/- 4.5 pulses/min during strains, and intercluster intervals were characterized by 1.7 +/- 2.3 urethral pulses at 2.2 +/- 1.8 pulses/min. Each cluster of urethral pulses during a strain was preceded by 2.3 +/- 1.8 repositions of the male's hindlegs and by 38.1 +/- 20.8 pelvic thrusts. There were 18.5 +/- 10.6 clusters of urethral pulses accompanied by strains per copulation at 0.9 +/- 0.3 clusters/min. The 18 to 19 clusters of urethral pulses appeared to be individual ejaculations. Therefore, we hypothesize that llamas ejaculated 18 to 19 times during their 22-min copulations.     

Immediate post-exposure effects of high-peak-power microwave pulses on operant behavior of Wistar rats.

Behavioral effects of high-peak-power microwave pulses on Wistar rats were studied by operant schedules. Each of twelve rats that had been trained to press a lever to receive food pellets was assigned randomly in groups of four to three different schedules of reinforcement: fixed-ratio (FR), variable-interval (VI), and differential-reinforcement-of-low-rates (DRL). After achieving a steady baseline performance, each animal was exposed for 10 min to 1.25-GHz microwave radiation at 1-MW peak-power (10-microseconds pulse width). Each pulse produced a peak whole-body SA and SAR of 2.1 J/kg and 0.21 MW/kg. Total doses (SAs) were set to 0.50, 1.5, 4.5, and 14 kJ/kg by adjusting the pulse-repetition rate. The corresponding time-averaged whole-body SARs were 0.84, 2.5, 7.6, and 23 W/kg. A microwave-transparent animal holder was used to keep the animal's body axis parallel to the E-field. Exposures at the highest dose caused an average colonic temperature rise of 2.5 degrees C and these animals failed to respond at all for about 13 minutes after the exposure. Their colonic temperatures had decreased to 1.1 degrees C, or less, above their pre-exposure (normal) temperature level when they began to respond. The FR and VI animals failed to reach their baseline levels of performance thereafter, while those on the DRL schedule displayed variable effects. No behavioral effects were found at the lower dose levels. It is concluded that the behavioral perturbations produced by pulsed microwave irradiation were thermal in nature.     

Endometrial thermal balloon ablation using a high temperature, pulsed system: a mathematical model

A new endometrial thermal balloon ablation treatment for menorrhagia is modeled mathematically to predict its efficacy and safety. A device preheats a fluid to 173 degrees C within a reservoir external to the uterus, and then pulses this fluid without further heating between the reservoir and the balloon for 2.1 min of treatment time. The model predicted this treatment to result in consistent immediate tissue death (coagulation) depths of 3.4 +/- 0.1 mm for uterine cavities of 7 to 26 mL, and that eventual necrosis (tissue death that would occur 1-5 days post burn) may occur to depths of 6.5 +/- 0.2 mm. Whereas, burn depths varied with uterine cavity volume when a low temperature treatment (constant 75 degrees C for 15 min) was modeled (2.3-2.9 mm and 6.8-8.2 mm, for immediate tissue death and eventual necrosis respectively). Similarly, the high temperature, pulsed treatment was less sensitive to blood perfusion rate than the low temperature treatment. Predicted eventual necrosis depth was 1.5 mm less for the high temperature, pulsed treatment than that predicted for a low temperature treatment (constant 87 degrees C for 7 min) for the same immediate tissue death depth (3.5 mm), indicating that the new high temperature treatment may result in less damage to non targeted tissues.     

Apoptosis in HeLa Hep2 cells is induced by low-dose,low-dose-rate radiation

Radioimmunotherapy with radiolabeled antibodies may cause inhibition of the growth of epithelial tumors, despite low total radiation doses and comparatively low radiosensitivity of epithelial tumor cells. The induction of apoptosis by low-dose radiation, such as delivered in radioimmunotherapy, was investigated in vitro in human HeLa Hep2 carcinoma cells. The cultured cells were exposed to defined radiation doses from a (60)Co radiation therapy source. The radiation source delivered 0.80 +/- 0.032 (mean +/- SD) Gy/min and the cells were given total doses of 1, 2, 5, 10 and 15 Gy. Using fluorescein-labeled Annexin V, followed by flow cytometry and DNA ladder analysis, apoptotic cells were detected and quantified. Radiation doses below 2 Gy did not cause any significant increase in apoptosis. Compared to control cells, apoptosis was pronounced after 5-10 Gy irradiation and was correlated to the radiation dose, with up to 42 +/- 3.5% of the cells examined displaying apoptosis. Clonogenic assays confirmed significantly decreased viability of the cells in the interval 2 to 10 Gy with low-dose-rate radiation, 60 +/- 2% compared to 2 +/- 2%. Lethal effects on the tumor cells were also evaluated by an assay of the cytotoxic effects of the release of (51)Cr. Significant cytotoxicity, with up to 64 +/- 6% dead cells, was observed at 5 Gy. Similar results were obtained when the dose rate was reduced to 0.072 +/- 0.003 Gy/min (mean +/- SD). In the case of the (137)Cs source, the dose rate could be reduced to 0.045 Gy/h, a level comparable to radioimmunotherapy, which induced significant apoptosis, and was most pronounced at 72-168 h postirradiation. It can be concluded that in vitro low-dose and low-dose-rate radiation induces apoptosis in epithelial HeLa Hep2 cells and thus may explain a mechanism by which pronounced inhibition of growth of HeLa Hep2 tumors at doses used in radioimmunotherapy has been obtained previously.     

Vanadate and dicyclohexylcarbodiimide insensitive proton extrusion from oxygen pulsed cells of the cyanobacterium Anacystis nidulans

Oxygen pulses applied to dark anaerobic suspensions of Anacystis nidulans provoked immediate acidification of the external medium. The reaction was inhibited only 75% by dicyclohexylcarbodiimide and 7-chloro-4-nitrobenz-2-oxa-1,3-diazole at concentrations which completely arrested all oxidative phosphorylation. Carbonyl cyanide m-chlorophenylhydrazone eliminated the acidification of oxygen pulsed cell suspensions while ortho-vanadate and diethylstilbestrol had no effect. No lag occurred between the onset of respiration and proton extrusion. H+/O ratios were 4.1 +/- 0.5 in the absence, and 1.9 +/- 0.4 in the presence, of dicyclohexylcarbodiimide. These results are consistent with a recently described proton-translocating aa3-type cytochrome c oxidase (H+/O = 1.6 +/- 0.4) in the cell membrane of A. nidulans (G.A. Peschek, J. Bacteriol. 153 (1983) 539-542).     

The effect of exposure of acetylcholinesterase to 2,450-MHz microwave radiation

The effect of 2,450-MHz pulsed microwave radiation on the enzyme activity of membrane-free acetylcholinesterase was studied while the enzyme was in the microwave field. We found no significant effect of microwave radiation on enzyme activity using a wide variety of power densities, pulse widths, repetition rates, and duty cycles. This suggests that simple, direct modification by microwave energy of acetylcholinesterase structure and enzymic activity is not related to microwave alteration of acetylcholinesterase central nervous system levels.     

Psychoactive-drug response is affected by acute low-level microwave irradiation

The effects of various psychoactive drugs were studied in rats exposed for 45 min in a circularly polarized, pulsed microwave field (2450 MHz; SAR 0.6 W/kg; 2-microseconds pulses, 500 pps). Apomorphine-induced hypothermia and stereotypy were enhanced by irradiation. Amphetamine-induced hyperthermia was attenuated while stereotypy was unaffected. Morphine-induced catalepsy and lethality were enhanced by irradiation at certain dosages of the drug. Since these drugs have different modes of action on central neural mechanisms and the effects of microwaves depend on the particular drug studied, these results show the complex nature of the effect of microwave irradiation on brain functions.     

Changes in pulsatile secretion patterns of LH, FSH, progesterone, androstenedione and oestradiol in cows after superovulation with PMSG

Six heifers were injected i.m. with 2500 i.u. PMSG followed by 15 mg prostaglandin 48 h later. Serial blood samples were collected through a catheter in the caudal vena cava every 10 min for 8 h on Day 10 (7 h after PMSG administration), during luteal regression (7 h after prostaglandin administration) and on the day thereafter. Four normally cyclic heifers served as a control group. Concentrations of progesterone, androstenedione, oestradiol, LH, FSH, and PMSG in the vena cava samples were measured and the frequency and amplitudes of episodic pulses of all hormones were estimated except for PMSG. Ovaries were collected by ovariectomy at 50 h after onset of luteal regression to determine the number of preovulatory follicles (non-atretic follicles greater than or equal to 10 mm). Stimulation of follicular growth by administration of PMSG resulted in the following effects on the secretion of steroids and endogenous gonadotrophins. (1) There were no alterations in progesterone concentration and the amplitude and frequency of episodic pulses. Mean (+/- s.e.m.) concentrations were 54.1 +/- 5.8, 19.1 +/- 3.1 and 3.4 +/- 0.9 nmol/l on Day 10 (L), during luteal regression (LR) and on the day thereafter (F) respectively. (2) There were no alterations in the episodic secretion patterns of androstenedione. Mean concentrations were 0.20 +/- 0.02, 0.15 +/- 0.02 and 0.11 +/- 0.02 nmol/l for the L, LR and F periods respectively. (3) There was an increase in oestradiol concentration from 17.1 +/- 3.0 pmol/l during the L period to 233.7 +/- 86.4 pmol/l during the F period. Pulse amplitude was enhanced compared to corresponding periods in control animals whereas pulse frequency remained the same. The oestradiol concentration was significantly correlated with the number of preovulatory follicles (r = 0.82, P less than 0.05). (4) There was a suppression of the frequency of episodic LH pulses (/8 h) during the LR (3.2 +/- 0.7) and F (4.3 +/- 0.4) periods compared to corresponding periods in control heifers (9.5 +/- 0.9 and 7.0 +/- 1.5 respectively). The preovulatory LH peak occurred earlier in 4 of 6 treated heifers. (5) There was a suppression of FSH concentrations, pulse amplitude and frequency during the LR and F (17.4 +/- 0.9 mg/l, 4.7 +/- 0.8 microgram/l and 7.5 +/- 0.4 pulses/8 h) periods compared to the corresponding F-period values (35.6 +/- 6.2 mg/l, 9.8 +/- 1.6 micrograms/l and 9.3 +/- 0.3 pulses/8 h) in control heifers.(ABSTRACT TRUNCATED AT 400 WORDS)     

Metabolic effects of microwave radiation and convection heating on human mononuclear leukocytes

The effects of microwave radiation (2450 MHz, continuous wave, mean specific absorption rate of 103.5 +/- 4.2 W/kg) and convection heating on the nonphosphorylating oxidative metabolism of human peripheral mononuclear leukocytes (96% lymphocytes, 4% monocytes) at 37 degrees C were investigated. Metabolic activity, determined by chemiluminescence (CL) of cells challenged with luminol (5-amino-2,3-dihydro-1,4-phthalazinedione) linked to bovine serum albumin, was detected with a brightness photometer. A significant stimulation after microwave exposure (p less than 0.005) over total CL of matched 37 degrees C incubator controls was observed. A similar degree of stimulation compared to incubator controls was also detected after sham treatment. There was no significant difference between changes in total CL or stimulation indices of the microwave and sham exposed groups. It appears that exposure to microwave radiation, under normothermic (37 +/- 0.03 degrees C) conditions, has no effect on the oxidative metabolic activity of human peripheral mononuclear leukocytes. However, the significant differences between microwave or sham exposed cells and their respective incubator controls occurred because the temperature of the incubator controls did not exceed 35.9 degrees C and this temperature required 39 minutes to reach from 22 degrees C. Slow heating of incubator controls must be accounted for in thermal and radiofrequency radiation studies in vitro.     

Cardiovascular, hematologic, and biochemical effects of acute ventral exposure of conscious rats to 2450-MHz (CW) microwave radiation

In this study the influence of acute (6 hr) exposure to 2450 MHz (CW) microwave radiation on certain cardiovascular, biochemical, and hematologic indices was examined in unanesthetized rats. Under methoxyflurane anesthesia, a catheter was inserted into the right femoral artery, which was used for monitoring blood pressure, heart rate, and blood sampling. Colonic temperature was monitored via a VITEK thermistor probe inserted rectally to a depth of 5 cm. The rat was subsequently placed into a ventilated restraining cage which was located inside an anechoic chamber. The temperature and humidity in the chamber were maintained at 22 +/- 0.5 degrees C and 60 +/- 5% (means +/- S.E.), respectively, during the experimental period. Rats (60) were exposed to either 0 (sham) or 10 mW/cm2 (exposed) for 6 hr. During exposure rats were oriented perpendicular to the E-field, and the measured specific absorption rate (SAR) was 3.7 mW/g. In the sham and exposed rats, the preexposure (time 0) mean +/- S.E. arterial blood pressure (MABP), heart rate, and colonic temperature were approximately 120 +/- 5 mmHg, 450 +/- 10 beats/min, and 37.0 +/- 0.2 degrees C, respectively. In the sham-exposed rats these values remained stable throughout the 6-hr exposure period. In the exposed rats, no effects were noted on MABP or colonic temperature; however after 1 hr of exposure, a significant reduction in heart rate was noted (450 versus 400 beats/min). This decrease in heart rate persisted throughout the remainder of the exposure period. None of the hematologic or biochemical parameters examined were affected by the microwave exposure. Although other mechanisms may be responsible, this decrease in heart rate may have been due to subtle cardiovascular adjustments because of microwave-induced heating with a resultant reduction in resting metabolic rate.     

DNA double-strand breaks in human lymphocytes after single irradiation by low doses of pulsed X-rays: non-linear dose-response relationship

Effects of ionizing radiation registered in cells after low dose irradiation are still poorly understood. A pulsed mode of irradiation is even more problematic in terms of predicting the radiation-induced response in cells. Thus, the aim of this paper was to study and analyze the effects of dose and frequency of pulsed X-rays on the frequency of radiation-induced DNA double-strand breaks and their repair kinetics in human peripheral blood lymphocytes in vitro. Analysis of radiation-induced gammaH2AX and 53BP1 repair foci was used to assess the DNA damage in these cells. The dose-response curve of radiation-induced foci of both proteins has shown deviations from linearity to a higher effect in the 12-32 mGy dose range and a lower effect at 72 mGy. The dose-response curve was linear at doses higher than 100 mGy. The number of radiation-induced gammaH2AX and 53BP1 foci depended on the frequency of X-ray pulses: the highest effect was registered at 13 pulses per second. Moreover, slower repair kinetics was observed for those foci induced by very low doses with a nonlinear dose-response relationship.     

Microwave-induced thermoelastic pressure wave propagation in the cat brain

This paper presents direct measurements of acoustic pressure wave propagation in cat brains irradiated with pulsed 2.45-GHz microwaves. Short rectangular microwave pulses (2 microseconds, 15 kW peak power) were applied singly through a direct-contact applicator located at the occipital pole of a cat's head. Acoustic pressure waves were detected by using a small hydrophone transducer, which was inserted stereotaxically into the brain of an anesthetized animal through a matrix of holes drilled on the skull. The measurements clearly indicate that pulsed microwaves induce acoustic pressure waves which propagate with an acoustic wave velocity of 1523 m/s.     

Rhesus monkey behavior during exposure to high-peak-power 5.62-GHz microwave pulses

Limits on the exposure to high-peak-power, short-duration microwave pulses have only recently been adopted. Additional data, however, are needed to understand the effects that may be produced by exposure to high-peak-power pulsed microwaves. Four male rhesus monkeys (Macaca mulatta) were trained on an operant task for food pellet reward to investigate the behavioral effects of very high-peak-power 5.62 GHz microwaves. The operant task required monkeys to pull one plastic lever on a variable interval schedule (VI-25 s) and then respond to color signals and pull a second lever to obtain food. The monkeys were conditioned to perform a color discrimination task using one of three colors displayed by a fiber-optic cable. A red signal was the discriminative stimulus for responding on the first lever. A response on the second lever when a green signal was presented (1 s duration) delivered a food pellet. If a response on the second lever was made in the presence of a white signal, a 30-s timeout occurred. While performing the behavioral task, the monkeys were exposed to microwave pulses produced by either a military radar (FPS-26A) operating at 5.62 GHz or the same radar coupled to a Stanford linear energy doubler (SLED) pulse-forming device (ITT-2972) that enhanced peak power by a factor of nine by adding a high power pulse to the radar pulse. The effects of both types of pulses were compared to sham exposure. Peak field power densities tested were 518, 1270, and 2520 W/cm² for SLED pulses and 56, 128, and 277 W/cm² for the radar pulses. The microwave pulses (radar or SLED) were delivered at 100 pps (2.8 μs radar pulse duration, ≈ 50 ns SLED pulse duration) for 20 min and produced averaged whole-body SARs of 2,4, or 6 W/kg. Compared to sham exposures, significant alterations of lever responding, reaction time, and earned food pellets occurred during microwave exposure at 4 and 6 W/kg but not 2 W/kg. There were no differences between radar or SLED pulses in producing behavioral effects. ©1994 Wiley-Liss, Inc.

1 This is a US Government work and, as such, is in the public domain in the United States of America.

     

Influence of gonadotropin-releasing hormone pulse amplitude, frequency, and treatment duration on the regulation of luteinizing hormone (LH) subunit messenger ribonucleic acids and LH secretion

The effects of GnRH pulse amplitude, frequency, and treatment duration on pituitary alpha and LH beta subunit mRNA concentrations were examined in castrate-testosterone replaced male rats. Experimental groups received iv GnRH pulses (5, 25, or 125 ng) at 7.5-, 30-, or 120-min intervals for 8, 24, or 48 h. Saline pulses were given to control rats. Acute LH secretion was measured in blood drawn before and 20 min after the last GnRH pulse. In saline controls, alpha and LH beta mRNAs (150 +/- 14, 23 +/- 2 pg cDNA bound/100 micrograms pituitary DNA) fell to 129 +/- 14 and 18 +/- 2, respectively, after 48 h. In animals receiving GnRH pulses (7.5-min intervals), the 125-ng dose stimulated a slight increase (P less than 0.01) in alpha mRNA levels after 8 and 24 h and both LH subunit mRNAs were increased by the 25- and 125-ng doses after 48 h. The 30-min pulse interval injections (25- and 125-ng doses) increased LH beta mRNA levels after 8 h, but alpha mRNAs were not elevated until after 24 h. Maximum (3-fold) increases in alpha and LH beta mRNAs were seen in rats receiving 25-ng pulses every 30 min for 48 h. Using 120-min pulses, LH subunit mRNAs were not increased by any GnRH dose through 48 h. Acute LH release was not seen in rats receiving 5 ng GnRH pulses at any pulse interval.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antibody responses of mice exposed to low-power microwaves under combined, pulse-and-amplitude modulation

Irradiation by pulsed microwaves (9.4 GHz, 1 microsecond pulses at 1,000/s), both with and without concurrent amplitude modulation (AM) by a sinusoid at discrete frequencies between 14 and 41 MHz, was assessed for effects on the immune system of Balb/C mice. The mice were immunized either by sheep red blood cells (SRBC) or by glutaric-anhydride conjugated bovine serum albumin (GA-BSA), then exposed to the microwaves at a low rms power density (30 microW/cm2; whole-body-averaged SAR approximately 0.015 W/kg). Sham exposure or microwave irradiation took place during each of five contiguous days, 10 h/day. The antibody response was evaluated by the plaque-forming cell assay (SRBC experiment) or by the titration of IgM and IgG antibodies (GA-BSA experiment). In the absence of AM, the pulsed field did not greatly alter immune responsiveness. In contrast, exposure to the field under the combined-modulation condition resulted in significant, AM-frequency-dependent augmentation or weakening of immune responses.