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J R Jauchem

Publications and source records attributed to J R Jauchem.

At least 19 recordsLinked to original sources
PubMed2004

Effects of histamine receptor blockade on cardiovascular changes induced by 35 GHz radio frequency radiation heating.

1. The role of histamine in heat-induced cardiovascular changes is uncertain. The purpose of this study was to examine effects of histamine H-1- and H-2-antagonism on heart rate, mean arterial blood pressure (MAP), localized body temperature changes, survival times, and lethal body temperatures that occur during the exposure of anaesthetized rats to 35 GHz radio frequency radiation (RFR). 2. Forty-eight ketamine-anaesthetized Sprague-Dawley rats were exposed, in several different treatment groups (n = 8 in each), to 35 GHz RFR at a level that resulted in significant body heating and subsequent death. During irradiation, a continuous increase in heart rate and a biphasic response in blood pressure (initial increase followed by a decrease) were observed in all groups of animals. 3. An H-1-antagonist, diphenhydramine (1 mg kg(-1) body wt) and an H-2-antagonist, cimetidine (5 mg kg(-1)), administered after sustained RFR exposure, failed to reverse the RFR-induced hypotension. High doses of the drugs (5 and 10 mg kg(-1), respectively) also did not alter the response. Post-RFR survival time was significantly decreased in the high-dose drug-treated group, compared with vehicle-treated (0.9% NaCl, 50% ethanol and 50% D5W) controls. 4. In experiments in which the two drugs were administered prior to RFR exposure, MAP in animals receiving high-dose antihistamines was significantly depressed compared with that of vehicle-treated animals during the first 35 min of RFR exposure. Antihistamine pretreatment, however, did not alter the total RFR exposure time required for death to occur. 5. In summary, pharmacological blockade of H-1 and H-2 receptors is not beneficial in anaesthetized rats made hypotensive by RFR exposure. This indicates that activation of H-1 and H-2 receptors by histamine does not occur to any significant extent and does not mediate the hypotensive response developed in this model of hyperthermia.

Animals↗
PubMed2002

Platelet-activating factor does not mediate circulatory failure induced by 35-GHz microwave heating.

Sustained whole-body exposure of anesthetized rats to 35-GHz radiofrequency radiation produces localized hyperthermia and hypotension, leading to circulatory failure and death. The physiological mechanism underlying the induction of circulatory failure by 35-GHz microwave (MW) heating is currently unknown. The purpose of this study was to determine whether platelet-activating factor (PAF) contributes to the hypotensive state induced by MW heating. Ketamine-anesthetized rats were instrumented for the measurement of arterial blood pressure, ECG and temperature at five sites. Administration of the PAF-receptor antagonist WEB 2086 (0.5 or 5 mg/kg) following the induction of circulatory failure (defined as a decrease in mean arterial blood pressure to 75 mmHg) failed to reverse the hypotension induced by MW heating and consequently did not alter the subsequent survival time. Furthermore, pretreatment with WEB 2086 at either dose did not alter subsequent mean arterial blood pressure, temperature responses to MW heating or survival time. Finally, MW heating did not alter either blood PAF levels or serum or lung PAF acetylhydrolase levels. Taken together, these results demonstrate that PAF does not mediate the hypotension induced by 35-GHz MW heating.

Animals↗
PubMed2001

Lack of effect of 94 GHz radio frequency radiation exposure in an animal model of skin carcinogenesis.

Although there is no evidence that electromagnetic energy in the radio frequency radiation (RFR) band is mutagenic, there have been suggestions that RFR energy might serve as either a promoter or co-promoter in some animal models of carcinogenesis. Recent developments in electromagnetic technology have resulted in the manufacture of RFR sources capable of generating frequencies in the millimeter wavelength (MMW) range (30-300 GHz). Because absorption of MMW energy occurs in the skin, it is to be expected that long-term detrimental health effects, if any, would most likely be manifest in the skin. In this study we investigated whether a single (1.0 W/cm(2) for 10 s) or repeated (2 exposures/week for 12 weeks, 333 mW/cm(2) for 10 s) exposure to 94 GHz RFR serves as a promoter or co-promoter in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced SENCAR mouse model of skin carcinogenesis. Neither paradigm of MMW exposure significantly affected papilloma development, as evidenced by a lack of effect on tumor incidence and multiplicity. There was also no evidence that MMW exposure served as a co-promoter in DMBA-induced animals repeatedly treated with 12-O-tetradecanoylphorbol 13-acetate. Therefore, we conclude that exposure to 94 GHz RFR under these conditions does not promote or co-promote papilloma development in this animal model of skin carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

Nitric oxide does not contribute to the hypotension of heatstroke.

The purpose of this study was to determine whether nitric oxide (NO) contributes to the hypotensive state induced by prolonged environmental heat (EH) stress. Ketamine-anesthetized rats were instrumented for the measurement of arterial blood pressure, electrocardiogram, and temperature at four sites. Rats were exposed to EH (ambient temperature, 40 +/- 1 degrees C) until mean arterial blood pressure (MAP) decreased to 75 mmHg, which was arbitrarily defined as the induction of heatstroke. In addition to cardiovascular and temperature measurements, the time required to reach this MAP end point and the subsequent survival time were measured. In three separate experimental series, the competitive NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) was administered (0, 10, or 100 mg/kg) either before, during (30 min after initiation of EH), or immediately after EH. L-NAME administered at any of these times transiently increased MAP. L-NAME infusion either before or during EH did not alter the EH time required to decrease MAP to 75 mmHg, but L-NAME pretreatment did decrease the colonic temperature at which this MAP end point was reached. L-NAME infusion before or after EH did not affect subsequent survival time, but L-NAME administered during EH significantly decreased survival time. The administration of L-NAME at any time point, therefore, did not prove beneficial in either preventing or reversing heatstroke. Taken together, these data suggest that NO does not mediate the hypotension associated with heatstroke.

Animals↗
PubMed2001

Repeated exposure of C3H/HeJ mice to ultra-wideband electromagnetic pulses: lack of effects on mammary tumors.

It has been suggested that chronic, low-level exposure to radiofrequency (RF) radiation may promote the formation of tumors. Previous studies, however, showed that low-level, long-term exposure of mammary tumor-prone mice to 435 MHz or 2450 MHz RF radiation did not affect the incidence of mammary tumors. In this study, we investigated the effects of exposure to a unique type of electromagnetic energy: pulses composed of an ultra-wideband (UWB) of frequencies, including those in the RF range. One hundred C3H/HeJ mice were exposed to UWB pulses (rise time 176 ps, fall time 3.5 ns, pulse width 1.9 ns, peak E-field 40 kV/m, repetition rate 1 kHz). Each animal was exposed for 2 min once a week for 12 weeks. One hundred mice were used as sham controls. There were no significant differences between groups with respect to incidence of palpated mammary tumors, latency to tumor onset, rate of tumor growth, or animal survival. Histopathological evaluations revealed no significant differences between the two groups in numbers of neoplasms in all tissues studied (lymphoreticular tissue, thymus, respiratory, digestive and urinary tracts, reproductive, mammary and endocrine systems, and skin). Our major finding was the lack of effects of UWB-pulse exposure on promotion of mammary tumors in a well-established animal model of mammary cancer.

Animals↗
PubMed2000

Cardiovascular and thermal effects of microwave irradiation at 1 and/or 10 GHz in anesthetized rats.

Relatively large thermal gradients may exist during exposure of an animal to microwaves (MWs), particularly at high frequencies. Differences in thermal gradients within the body may lead to noticeable differences in the magnitude of cardiovascular changes resulting from MW exposure. This study compares the thermal distribution and cardiovascular effects of exposure to a single MW frequency with effects of simultaneous exposure to two frequencies. Ketamine-anesthetized male Sprague-Dawley rats (n = 58) were exposed individually to one of three conditions: 1-GHz, 10-GHz, or combined 1- and 10-GHz MWs at an equivalent whole-body specific absorption rate of 12 W/kg. The continuous-wave irradiation was conducted under far-field conditions with animals in E orientation (left lateral exposure, long axis parallel to the electric field) or in H orientation (left lateral exposure, long axis perpendicular to the electric field). Irradiation was started when colonic temperature was 37.5 degrees C and was continued until lethal temperatures were attained. Colonic, tympanic, left and right subcutaneous, and tail temperatures, and arterial blood pressure, heart rate, and respiratory rate were continuously recorded. In both E and H orientations, survival time (i.e., time from colonic temperature of 37.5 degrees C until death) was lowest in animals exposed at 1-GHz, intermediate in those exposed at 1- and 10-GHz combined, and greatest in the 10-GHz group (most differences statistically significant). At all sites (with the exception of right subcutaneous), temperature values in the 1- and 10-GHz combined group were between those of the single-frequency exposure groups in both E and H orientations. During irradiation, arterial blood pressure initially increased and then decreased until death. Heart rate increased throughout the exposure period. The general, overall patterns of these changes were similar in all groups. The results indicate that no unusual physiological responses occur during multi-frequency MW exposure, when compared with results of single-frequency exposure. Bioelectromagnetics 21:159-166, 2000. Published 2000 Wiley-Liss, Inc.

Analysis of Variance↗
PubMed2000

Neural and behavioral teratological evaluation of rats exposed to ultra-wideband electromagnetic fields.

Several investigators have reported teratologic effects of electromagnetic field exposure. The majority of these studies have been performed at levels of exposure that could produce substantial heating of the animals. New and unique sources of ultra-wideband (UWB) electromagnetic fields are currently being developed and tested that are capable of generating nonthermalizing, high-peak-power, microwave (MW) pulses with nanosecond (ns) pulse widths, picosecond (ps) rise times, and an UWB of frequencies. Our study was performed to determine if teratological changes occur in rat pups as a result of (i) daily UWB exposures during gestation days 3-18, or (ii) as a result of both prenatal and postnatal (10 days) exposures. Dams were exposed either to (i) UWB irradiation from a Kentech system that emitted a 55 kV/m-peak E field, 300 ps rise time, and a 1.8 ns pulse width, average whole-body specific absorption rate 45 mW/kg; (ii) sham irradiation; or (iii) a positive control, lead (Pb) acetate solution (2000 microg/ml) continuously available in the drinking water. Offspring were examined for ontogeny (litter size, sex-ratios, weights, coat appearance, tooth-eruption, eye-opening, air-righting, and ultrasonic stress vocalizations). Male pups were tested on various performance measures (locomotor, water-maze learning, and fertilization capabilities). The pups postnatally exposed were examined for hippocampal morphology and operant behavior. Behavioral, functional, and morphological effects of UWB exposure were unremarkable with these exceptions: (i) The UWB-exposed pups emitted significantly more stress vocalizations than the sham-exposed pups; (ii) the medial-to-lateral length of the hippocampus was significantly longer in the UWB-exposed pups than in the sham-exposed animals; (iii) male offspring exposed in utero to UWB mated significantly less frequently than sham-exposed males, but when they did mate there was no difference in fertilization and offspring numbers from the sham group. There does not appear to be a unifying physiological or behavioral relationship among the significant differences observed, and our findings could be due to the expected spurious results derived when a large number of statistical comparisons are made. Significant effects found between our positive-controls and other groups on numerous measures indicates that the techniques used were sensitive enough to detect teratological effects. Bioelectromagnetics 21:524-537, 2000. Published 2000 Wiley-Liss, Inc.

Animals↗
PubMed2000

Radio frequency radiation of millimeter wave length: potential occupational safety issues relating to surface heating.

Currently, technology is being developed that makes use of the millimeter wave (MMW) range (30-300 GHz) of the radio frequency region of the electromagnetic spectrum. As more and more systems come on line and are used in everyday applications, the possibility of inadvertent exposure of personnel to MMWs increases. To date, there has been no published discussion regarding the health effects of MMWs; this review attempts to fill that void. Because of the shallow depth of penetration, the energy and, therefore, heat associated with MMWs will be deposited within the first 1-2 mm of human skin. MMWs have been used in states of the former Soviet Union to provide therapeutic benefit in a number of diverse disease states, including skin disorders, gastric ulcers, heart disease and cancer. Conversely, the possibility exists that hazards might be associated with accidental overexposure to MMWs. This review attempts to critically analyze the likelihood of such acute effects as burn and eye damage, as well as potential long-term effects, including cancer.

Accidents, Occupational↗
PubMed1999

Lack of effects on heart rate and blood pressure in ketamine-anesthetized rats briefly exposed to ultra-wideband electromagnetic pulses.

Fourteen Sprague-Dawley rats were exposed to pulses produced by a Bournlea ultra-wideband (UWB) pulse generator (rise time, 318-337 ps; maximum E field, 19-21 kV/m). Exposures at a repetition frequency of 1 kHz for 0.5 s or to repetitive pulse trains (2-s exposure periods alternating with 2 s of no exposure, for a total of 2 min) resulted in no significant changes in heart rate or mean arterial blood pressure. These results suggest that acute whole-body exposure to UWB pulses does not have a detrimental effect on the cardiovascular system.

Anesthetics, Dissociative↗
PubMed1999

Cardiovascular and thermal responses in rats during 94 GHz irradiation.

We investigated the thermal distribution and cardiovascular effects produced by sustained exposure of rats to 94 GHz radio-frequency electromagnetic radiation (RFR). Sixteen ketamine-anesthetized Sprague-Dawley rats were exposed individually at a power density of 75 mW/cm2 under far-field conditions in E orientation. Irradiation began when colonic temperature was 37 degrees C and continued until death. Large, immediate increases in subcutaneous temperature on the irradiated side were accompanied by more moderate, delayed increases in colonic temperature. These body-temperature responses were similar to previous results obtained during 35 GHz RFR exposure. During irradiation, arterial blood pressure initially increased and then precipitously decreased until death. The heart rate increased throughout the exposure period. When comparing the results of these 94 GHz exposures with those in previous studies of lower RFR frequencies, it appears that the patterns of heart-rate and blood-pressure changes that occur before death are similar. We conclude that exposure to 94 GHz RFR produces extreme peripheral heating without similar levels of core heating and that this pattern of heat deposition is sufficient to produce circulatory failure and subsequent death.

Animals↗
PubMed1998

Ultra-wideband electromagnetic pulses: lack of effects on heart rate and blood pressure during two-minute exposures of rats.

Exposure to fast-rise-time ultra-wideband (UWB) electromagnetic pulses has been postulated to result in effects on biological tissue (including the cardiovascular system). In the current study, 10 anesthetized Sprague-Dawley rats were exposed to pulses produced by a Sandia UWB pulse generator (average values of exposures over three different pulse repetition rates: rise time, 174-218 ps; peak E field, 87-104 kV/m; pulse duration, 0.97-0.99 ns). Exposures to 50, 500 and 1000 pulses/s resulted in no significant changes in heart rate or mean arterial blood pressure measured every 30 s during 2 min of exposure and for 2 min after the exposure. The results suggest that acute UWB whole-body exposure under these conditions does not have an immediate detrimental effect on these cardiovascular system variables in anesthetized rats.

Animals↗
PubMed1998

Health effects of microwave exposures: a review of the recent (1995-1998) literature.

Occupational or residential exposures to radio frequency radiation, including microwaves, have been alleged to result in health problems, including leukemia, other cancers, and reproductive mishaps. This review covers the recent literature (from 1995 to 1998) dealing with possible health effects, including original studies, reviews, commentaries, and editorials. A number of these articles have presented misconceptions, errors in citation, and inaccuracies regarding the alleged effects. Epidemiological reviews and studies dealing with exposures to radio frequency radiation from television transmitters, cellular telephones and towers, magnetic resonance imaging, phased array radar systems, and other occupational exposures are analyzed. On the basis of studies reported in the past several years, one can conclude that the evidence for any proven health effects of low-level microwave exposure is minimal to non-existent.

Electromagnetic Phenomena↗
PubMed1998

Chronic exposure of cancer-prone mice to low-level 2450 MHz radiofrequency radiation.

The purpose of this study was to determine whether chronic, low-level exposure of mammary-tumor-prone mice to 2450 MHz radiofrequency radiation (RFR) promotes an earlier onset (decreased latency), a greater total incidence, or a faster growth rate of mammary tumors. One hundred C3H/ HeJ mice were exposed in circularly polarized waveguides (CWG) for 18 months (20 h/day, 7 days/wk) to continuous-wave, 2450 MHz RFR at a whole body average specific absorption rate (SAR) of 0.3 W/kg; 100 mice were sham exposed. Before exposure, SARs were determined calorimetrically; during experimentation, SARs were monitored by differential power measurement. All animals were visually inspected twice daily and were removed from the CWG cages for a weekly inspection, palpation, and weighing. From the time of detection, tumor size was measured weekly. Animals that died spontaneously, became moribund, or were killed after 18 months of exposure were completely necropsied; tissues were fixed and subjected to histopathological evaluations. Results showed no significant difference in weight profiles between sham-irradiated and irradiated mice. Concerning mammary carcinomas, there was no significant difference between groups with respect to palpated tumor incidence (sham = 52%; irradiated = 44%), latency to tumor onset (sham = 62.3 +/- 1.2 wk; irradiated = 64.0 +/- 1.6 wk), and rate of tumor growth. In general, histopathological examination revealed no significant differences in numbers of malignant, metastatic, or benign neoplasms between the two groups; a significantly greater incidence of alveolar-bronchiolar adenoma in the sham-irradiated mice was the only exception. In addition, survival analysis showed no significant difference in cumulative percent survival between sham and irradiated animals. Thus, results indicate that under the conditions of this study, long-term, low-level exposure of mammary-tumor-prone mice to 2450 MHz RFR did not affect mammary tumor incidence, latency to tumor onset, tumor growth rate, or animal longevity when compared with sham-irradiated controls.

Animals↗
PubMed1998

Chronic, low-level (1.0 W/kg) exposure of mice prone to mammary cancer to 2450 MHz microwaves.

In a previous study (Frei et al., Bioelectromagnetics 19, 20-31, 1998), we showed that low-level (0.3 W/kg), long-term exposure of mice prone to mammary tumors to 2450 MHz radiofrequency (RF) radiation did not affect the incidence of mammary tumors, latency to tumor onset, tumor growth rate or animal survival when compared to sham-irradiated animals. In the current study, the specific absorption rate (SAR) was increased from 0.3 W/kg to 1.0 W/kg. The same biological end points were used. One hundred C3H/HeJ mice were exposed in circularly polarized waveguides for 78 weeks (20 h/day, 7 days/week) to continuous-wave, 2450 MHz RF radiation; 100 mice were sham-exposed. There was no significant difference between exposed and sham-exposed groups with respect to the incidence of palpated mammary tumors (sham-exposed = 30%; irradiated = 38%), latency to tumor onset (sham-exposed = 62.0 +/- 2.3 weeks; irradiated = 62.5 +/- 2.2 weeks) and rate of tumor growth. Histopathological evaluations revealed no significant difference in numbers of malignant, metastatic or benign neoplasms between the two groups. Thus long-term exposures of mice prone to mammary tumors to 2450 MHz RF radiation at SARs of 0.3 and 1.0 W/kg had no significant effects when compared to sham-irradiated animals.

Animals↗
PubMed1997

Body heating induced by sub-resonant (350 MHz) microwave irradiation: cardiovascular and respiratory responses in anesthetized rats.

These experiments were designed to investigate the effects of sub-resonant microwave (MW) exposure (350 MHz, E orientation, average power density 38 mW/cm2, average whole-body specific absorption rate 13.2 W/kg) on selected physiological parameters. The increase in peripheral body temperature during 350 MHz exposure was greater than that in earlier experiments performed at 700 MHz (resonance). Heart rate and mean arterial blood pressure were significantly elevated during a 1 degree C increase in colonic temperature due to 350 MHz exposure; respiratory rate showed no significant change. The results are consistent with other investigators' reports comparing sub-resonance exposures with those at resonance and above.

Anesthesia↗
PubMed1997

Exposure to extremely-low-frequency electromagnetic fields and radiofrequency radiation: cardiovascular effects in humans.

Cardiovascular changes in humans exposed to nonionizing radiation [including extremely-low-frequency electromagnetic fields (ELF EMFs) and radiofrequency radiation (RFR)] are reviewed. Both acute and long-term effects have been investigated. In general, if heating does not occur during exposure, current flow appears to be necessary for major cardiovascular effects to ensue, such as those due to electric shock. Whereas most studies have revealed no acute effect of static or time-varying ELF EMFs on the blood pressure, heart rate, or electrocardiogram waveform, others have reported subtle effects on the heart rate. The possible health consequences of these results are unknown. Regarding long-term effects of ELF EMFs, reports from the former Soviet Union in the early 1960s indicated arrhythmias and tachycardia in high-voltage-switchyard workers. Subsequent studies in Western countries, however, did not confirm these findings. These studies are limited by uncertainties regarding exposure durations and appropriate control groups. Investigations of acute cardiovascular changes in humans purposely exposed to RFR have been limited to studies of magnetic resonance imaging (which, in addition to RFR, involves static and time-varying magnetic fields). It has been concluded that such exposures, as presently performed, are not likely to cause adverse cardiovascular effects. Reports of hypertension in workers potentially exposed to high levels of RFR during accidents are considered to be incidental (due to anxiety and posttraumatic stress). Soviet investigators have also indicated that long-term RFR exposure may result in hypotension and bradycardia or tachycardia. Other researchers, however, have been incapable of replicating these results, and some scientists have attributed the effects to chance variations and mishandling of data. In summary, studies have not yielded any obvious cardiovascular-related hazards of acute or long-term exposures to ELF EMFs or RFR at levels below current exposure standards.

Animals↗
PubMed1997

Effects of esmolol on 35 GHz microwave-induced lethal heat stress.

1. The purpose of this study was to examine effects of the beta(1)-adrenoreceptor antagonist esmolol (infused at 2 or 4 mg kg-1 body wt min-1) on heart rate, blood pressure, respiratory rate, localized body temperature changes, survival times, and lethal body temperatures that occur during the exposure of anaesthetized rats to 35 GHz microwaves. 2. Forty Sprague-Dawley rats, anaesthetized with ketamine, were exposed to 35 GHz microwaves at a level that resulted in heating and death. During irradiation, a continuous increase in heart rate and a biphasic response in blood pressure (initial increase followed by a decrease) were observed in all groups of animals. 3. Esmolol caused a significant dose-dependent decrease in blood pressure, relative to saline-treated animals, but only a small attenuation of the heat-induced rise in heart rate. In experiments in which esmolol was infused and microwave exposure was continued until death, drug-treated animals survived for significantly shorter periods and died at significantly lower body temperatures. The change in survival may have been related to the lower blood pressure due to esmolol treatment.

Adrenergic beta-1 Receptor Antagonists↗