Autoimmune processes after long-term low-level exposure to electromagnetic fields (experimental results) part 3. The effect of long-term nonthermal RF EMF exposure on complement-fixation antibodies against homologenous tissue

The effect of long-term nonthermal EMF exposure of 2450 MHz (500 μW/cm²) on the level of antibodies against brain and liver tissues is studied on rats by the complement-fixation test (CFT) in the cold. It is found that a statistically significant increase in the level of antibodies against aqueous extracts of brain and liver tissues in blood serum is detected only on the 14th day after exposure is ended.     

Autoimmune processes after long-term low-level exposure to electromagnetic fields (experimental results) part 2. General scheme and conditions of the experiment. Development of the RF exposure conditions complying with the experimental tasks. Status of animals during long-term exposure.

The paper describes the conditions for handling and exposure to radiation of the experimental animals (Wistar rats) and the methods of statistical processing of the obtained data, which were used to determine the effect of long-term exposure of the animals to radio-frequency electromagnetic fields (2450 MHz) of nonthermal intensity (500 μW/cm²) on autoimmune processes; the study was performed under the auspices of the World Health Organization.     

Autoimmune processes after long-term low-level exposure to electromagnetic fields (experimental results) part 5. Study of the influence of blood serum from rats exposed to low-level electromagnetic fields on pregnancy and fetal and offspring development

The work evaluates the possible adverse effects on pregnancy and fetal and offspring development arising from the injection of blood serum from rats exposed to microwaves at a power density of 500 μW/cm² into intact female rats. The study is performed on 59 pregnant Wistar rats. Intrauterine mortality, embryo and fetal body weights, and placenta weight are used for the evaluation of embryo and fetal development. Generally accepted integral and specific parameters are used for the evaluation of the postnatal development of offspring during the first 30 days of life. It is shown that injection of blood serum from rats subjected to long-term RF exposure at 500 μW/cm² into intact rats on the tenth day of pregnancy results in adverse effects on fetal and offspring development. Higher total in utero and postnatal mortality, as well as delayed offspring development, are recorded.     

Increase in radiation-induced HPRT gene mutation frequency after nonthermal exposure to nonionizing 60 Hz electromagnetic fields

It is widely accepted that moderate levels of nonionizing electric or magnetic fields, for example 50/60 Hz magnetic fields of about 1 mT, are not mutagenic. However, it is not known whether such fields can enhance the action of known mutagens. To explore this question, a stringent experimental protocol, which included blinding and systematic negative controls, was implemented, minimizing the possibility of observer bias or experimental artifacts. As a model system, we chose to measure mutation frequencies induced by 2 Gy gamma rays in the redox-sensitive hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene in Chinese hamster ovary cells. We tested whether a 12-h exposure to a 60 Hz sinusoidally oscillating magnetic-flux density (Brms = 0.7 mT) could affect the mutagenic effects of ionizing radiation on the HPRT gene locus. We determined that the magnetic-field exposure induced an approximate 1.8-fold increase in HPRT mutation frequency. Additional experiments at Brms = 0.23 and 0.47 mT revealed that the effect was reduced at lower flux densities. The field exposure did not enhance radiation-induced cytotoxicity or mutation frequencies in cells not exposed to ionizing radiation. These results suggest that moderate-strength, oscillating magnetic fields may act as an enhancer of mutagenesis in mammalian cells.     

Oxidative stress effects on the central nervous system of rats after acute exposure to ultra high frequency electromagnetic fields

Mobile telephones and their base stations are an important source of ultra high frequency electromagnetic fields (UHF-EMFs; 800-1800 MHz) and their utilization is increasing all over the world. Epidemiological studies have suggested that low energy UHF-EMFs may have biological effects, such as changes in oxidative metabolism after exposure. Therefore, we have investigated the effect of acute UHF-EMF exposure on non-enzymatic antioxidant defense and lipid and protein oxidative damage in the rat frontal cortex and hippocampus. We have used malondialdehyde (MDA) and carbonyl assays to assess lipid and protein oxidative damages, respectively. No changes in lipid and protein damage, and also in non-enzymatic defense were found in frontal cortex or hippocampus. These results suggest that acute UHF-EMF exposure is not able to produce detectable oxidative stress in rats from any age tested. However, more tests using a longer period of exposure and evaluating other tissues are necessary to ensure that there is no health risk associated with the use of mobile phones.     

Autoimmune process after long-term low-level exposure to electromagnetic field (experimental results). Part I. Mobile communications and changes in electromagnetic conditions for the population. Need for additional substantiation of existing hygienic standards

Mobile communications provides a new source of electromagnetic exposure for almost the whole population of Russia. For the first time in the history of civilization, the brain of mobile phone users is exposed to localized radiofrequency (RF) electromagnetic fields (EMF). Base stations are a factor in the exposure of the population. Existing standards for limiting exposure do not account for the role of base stations as a source of EMF and cannot guarantee the absence of adverse health effects. It has become necessary to obtain reliable information to expand databases for the development of new standards. As recommended by the World Health Organization, an additional experiment is performed under the supervision of foreign experts, which shows changes in autoimmune status in rats after long-term low-level RF EMF exposure with an incident power of 500 μW/cm².     

Changes of insulin binding in rat tissues after exposure to stress.

The effects of various stressors on insulin receptors in adipose, liver and skeletal muscle tissues were studied in rats exposed to acute or repeated stress. Adult male rats were exposed to immobilization (IMO) for 2.5 hours daily for 1, 7 and 42 days, or to hypokinesia (HK) for 1, 7 and 21 days. We determined the values of specific insulin binding (SIB) and insulin receptor binding capacity (IR) of plasma cell membranes from adipose, liver and muscle tissue (IMO groups), or insulin binding to isolated adipocytes and hepatocytes (HK groups). A significant decrease of SIB and IR was observed in rats exposed to acute stress (1x IMO) in muscle, adipose and liver tissues. However, in animals exposed to repeated stress (7x and 42x IMO), SIB and IR were diminished in the muscle tissue, whereas no significant changes were noted in the liver and adipose tissue. When tissue samples were collected 3-24 hours after exposure to IMO stress, no changes of SIB and IR were found in liver and adipose tissue, but insulin binding was lowered in skeletal muscles. In animals exposed to HK for one day, a decrease of SIB and IR was found in isolated adipocytes, but no changes in insulin binding were noted in the liver tissue. In rats exposed to HK for 7 and 21 days, values of IR were similar as in control group. Our results indicate a) the different changes of IR in the liver, fat and muscle tissues after exposure to stress situations, b) a long-term decrease of insulin binding in muscles of rats exposed to repeated IMO stress, and c) the return of reduced SIB and IR (induced by acute stress) to control values in the liver and adipose tissue after a short recovery period.     

Oxidative stress is induced in the rat brain following repeated inhalation exposure to manganese sulfate

Eight-week-old rats inhaled manganese (Mn) in the form of MnSO₄ at 0, 0.03, 0.3, or 3.0 mg Mn/m³ for 6 h/d for 7 d/wk (14 consecutive exposures). Brain manganese concentrations in these animals were reported by Dorman et al. in 2001, noting the following rank order: olfactory bulb>striatum>cerebellum. We assessed biochemical end points indicative of oxidative stress in these three brain regions, as well as the hypothalamus and hippocampus. Glutamine synthetase (GS) protein levels and total glutathione (GSH) levels were determined for all five regions. GS mRNA and metallothionein (MT) mRNA levels were also evaluated for the cerebellum, hypothalamus, and hippocampus. Statistically significant increases (p<0.05) in GS protein were observed in the olfactory bulb upon exposure to the medium and high manganese doses. In the hypothalamus, statistically significant (p<0.05) but more modest increases were also noted in the medium and high manganese dose. Total GSH levels significantly (p<0.05) decreased only in the hypothalamus (high manganese dose), and MT mRNA significantly increased in the hypothalamus (medium manganese dose). No significant changes were noted in any of the measured parameters in the striatum, although manganese concentrations in this region were also increased. These results demonstrate that the olfactory bulb and hypothalamus represent potentially sensitive areas to oxidative stress induced by exceedingly high levels of inhaled manganese sulfate and that other regions, and especially the striatum, are resistant to manganese-induced oxidative stress despite significant accumulation of this metal.     

Local exposure of the rat cortex to radiofrequency electromagnetic fields increases local cerebral blood flow along with temperature

Few studies have shown that local exposure to radiofrequency electromagnetic fields (RF) induces intensity-dependent physiological changes, especially in the brain. The aim of the present study was to detect reproducible responses to local RF exposure in the parietal cortex of anesthetized rats and to determine their dependence on RF intensity. The target cortex tissue was locally exposed to 2-GHz RF using a figure-eight loop antenna within a range of averaged specific absorption rates (10.5, 40.3, 130, and 263 W/kg averaged over 4.04 mg) in the target area. Local cerebral blood flow (CBF) and temperatures in three regions (target area, rectum, and calf hypodermis) were measured using optical fiber blood flow meters and thermometers during RF exposure. All parameters except for the calf hypodermis temperature increased significantly in exposed animals compared with sham-exposed ones during 18-min exposures. Dependence of parameter values on exposure intensity was analyzed using linear regression models. The elevation of local CBF was correlated with temperature rise in both target and rectum at the end of RF exposure. However, the local CBF elevation seemed to be elevated by the rise in target temperature, but not by that of the rectal temperature, in the early part of RF exposure or at low-intensity RF exposure. These findings suggest that local RF exposure of the rat cortex drives a regulation of CBF accompanied by a local temperature rise, and our findings may be helpful for discussing physiological changes in the local cortex region, which is locally exposed to RF.     

Overexpression of the glutamine synthetase gene modulates oxidative stress response in rice after exposure to cadmium stress

Key message

Overexpression of OsGS gene modulates oxidative stress response in rice after exposure to cadmium stress. Our results describe the features of transformants with enhanced tolerance to Cd and abiotic stresses.

Abstract

Glutamine synthetase (GS) (EC 6.3.1.2) is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine. Exposure of plants to cadmium (Cd) has been reported to decrease GS activity in maize, pea, bean, and rice. To better understand the function of the GS gene under Cd stress in rice, we constructed a recombinant pART vector carrying the GS gene under the control of the CaMV 35S promoter and OCS terminator and transformed using Agrobacterium tumefaciens. We then investigated GS overexpressing rice lines at the physiological and molecular levels under Cd toxicity and abiotic stress conditions. We observed a decrease in GS enzyme activity and mRNA expression among transgenic and wild-type plants subjected to Cd stress. The decrease, however, was significantly lower in the wild type than in the transgenic plants. This was further validated by the high GS mRNA expression and enzyme activity in most of the transgenic lines. Moreover, after 10 days of exposure to Cd stress, increase in the glutamine reductase activity and low or no malondialdehyde contents were observed. These results showed that overexpression of the GS gene in rice modulated the expression of enzymes responsible for membrane peroxidation that may result in plant death.     

Health and safety implications of exposure to electromagnetic fields in the frequency range 300 Hz to 10 MHz.

An international seminar on health effects of exposure to electromagnetic fields (EMF) in the frequency range from 300 Hz to 10 MHz (referred to as the Intermediate Frequency (IF) range) was held in Maastricht, Netherlands, on 7-8 June 1999. The seminar, organized under the International EMF Project, was sponsored jointly by the World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and the Government of the Netherlands. This report does not attempt to summarize all of the material presented at the conference, but focuses on sources of exposure, biophysical and dosimetric considerations pertinent to extrapolating biological data from other frequency ranges to IF and identifies potential health concerns and needs for developing exposure guidelines. This paper is based on presentations at the conference and reports of working groups consisting of the speakers and other experts. It concludes with recommendations for further research aimed at improving health risk assessments in this frequency range.     

Islet cell response in the neonatal rat after exposure to a high-fat diet during pregnancy

Although pancreatic beta-cells are capable of adapting their mass in response to insulin requirements, evidence has shown that a dietary insult could compromise this ability. Fetal malnutrition has been linked to low birth weight and the development of type 2 diabetes later in life, while reduced beta-cell mass has been reported in adult rats fed a high-fat diet (HFD). Reported here are the effects of exposure to a HFD, during different periods of gestation, on neonatal rat weight and beta- and alpha-cell development. The experimental groups were composed of neonatal offspring obtained from Wistar rats fed a high-fat (40% as energy) diet for either the first (HF1), second (HF2), or third (HF3) week, or all three (HF1-3) weeks of gestation. Neonatal weights and circulating glucose and insulin concentrations were measured on postnatal day 1, after which the pancreata were excised and processed for histological immunocytochemical examination and image analysis. HF1 and HF2 neonates were hypoglycemic, whereas HF1-3 neonates were hyperglycemic. Low birth weights were observed only in HF1 neonates. No significant differences were detected in the circulating insulin concentrations in the neonates, although beta-cell volume and numbers were reduced in HF1-3 neonates. beta-cell numbers also declined in HF1 and HF3 neonates. alpha-cell volume, number and size were, however, increased in HF1-3 neonates. alpha-cell size was also increased in HF1 and HF3 neonates. In neonates, exposure to a maternal HFD throughout gestation was found to have the most adverse effect on beta-cell development and resulted in hyperglycemia.     

Disturbed testicular descent in the rat after prenatal exposure to the antiandrogen flutamide.

Exposure of rats in utero to the anti-androgen flutamide resulted in feminization of the external genitalia that was noticeable at birth. This exposure also resulted in a high degree of cryptorchidism during adulthood. In most affected animals, testes were lying in 'ovary position' close to the caudal pole of the ipsilateral kidney. Cryptorchidism occurred despite normal prenatal development of the gubernacular cones and the transformation of these structures, postnatally, into muscular cremaster sacs. Inter- and intralitter variation in the response to prenatal exposure to flutamide was observed as well as intra-individual variation. Cryptorchidism frequently occurred unilaterally with right side cryptorchidism predominating. Cryptorchidism occurred in association with marked suppression of the growth of the ipsilateral epididymis and deferent duct. The possibility is considered that the poor development or absence of these structures contributes to cryptorchidism. Intra-individual variation supports the concept of the local nature of the influence of testis hormones in stabilization and further differentiation of the ipsilateral Wolffian duct derivatives. Cryptorchidism was enhanced when rats were treated postnatally with testosterone or oestradiol. The effect of testosterone was unexpected in view of the generally held hypothesis that androgens enhance testis descent. The effect of oestradiol was as expected: other animal models have been described in which induction of cryptorchidism by oestradiol occurs. Additional treatment with oestradiol caused further suppression of growth of the epididymis and deferent duct. The response to prenatal exposure to flutamide was not altered by further injections of flutamide postnatally. Such injections were without effect in males not exposed to flutamide prenatally except for minor, but statistically significant, testicular enlargement during adulthood. A model is thus presented that describes cryptorchidism as an endogenous developmental disorder.     

Activation of the systemic production of tumor necrosis factor after exposure to acute stress.

Tumor necrosis factor (TNF), which was originally identified as a tumoricidal factor, is now regarded as one of the main regulators of inflammation and various immune systems. Thus it has been considered to be mobilized in case of emergency. However, we assume that TNF and the cytokine network driven by the monokine also function under normal condition for homeostasis of the animal body which is exposed to various kinds of physiological stress. To test this possibility, we exposed C3H/He mice for up to 3 days to five types of acute stress: food deprivation, drinking water deprivation, sleep deprivation, swimming, and physical restraint. After release from the stress, the level of priming for systemic production of TNF was examined using OK-432 (a streptococcal preparation) as a trigger. Priming of TNF production was not observed immediately after 2-day exposure to most of the stressors. Sleep deprivation alone tended to induce a primed state especially when the stress period was lengthened to 3 days. On the other hand, by keeping mice in a normal condition for a 2-day restorative interval after 2-day exposure to the stressors, systemic production of TNF was consistently primed for all the stress examined. The time course of the priming effect was examined in detail for water-deprivation stress. The effect was detected as early as 3 hours after release from stress, was sustained for 2 days, and returned to the basal level by 4 days after the release. Based on these results, we discussed the role of the TNF-driven cytokine circuit in adaptation to stress.     

Increased vitamin E content in the lung after ozone exposure: a possible mobilization in response to oxidative stress

Vitamin E (vE) is a biological free radical scavenger capable of providing antioxidant protection depending upon its tissue content. In previous studies, we observed that vE increased significantly in rat lungs after oxidant exposure, and we postulated that vE may be mobilized to the lung from other body sites under oxidative stress. To test this hypothesis, we fed Long-Evans rats either a vE-supplemented or a vE-deficient diet, injected them intraperitoneally with 14C-labeled vE, and then exposed half of each group to 0.5 ppm ozone (O3) for 5 days. After exposure, we determined vE content and label retention in lungs, liver, kidney, heart, brain, plasma, and white adipose tissue. Tissue vE content of all tissues generally reflected the dietary level, but labeled vE retention in all tissues was inversely related to tissue content, possibly reflecting a saturation of existing vE receptor sites in supplemented rats. Following O3 exposure, lung vE content increased significantly in supplemented rats and decreased in deficient rats, but the decrease was not statistically significant, and vE content remained unchanged in all other tissues of both dietary groups. Retention of 14C-labeled vE increased in all tissues of O3-exposed rats of both dietary groups, except in vE-deficient adipose tissue and vE-supplemented brain, where it decreased, and plasma, where it did not change. The marked increases in lung vE content and labeled vE retention of O3-exposed vE-supplemented rats support our hypothesis that vE may be mobilized to the lung in response to oxidative stress, providing that the vitamin is sufficiently available in other body sites.     

Integrity of lysosomes in the isolated perfused rat liver before and after exposure to dimethylsulphoxide.

We have studied the integrity of lysosomes in isolated rat livers perfused for 3, 4, or 6 hr at 35 °C with BSA (40 g/l) in Krebs Ringer bicarbonate buffer. The latency and sedimentability of β-glucuronidase in homogenates of these livers was well maintained even after 6 hr. The latency and sedimentability of acid phosphatase remained at about control levels during the first 4 hr of perfusion but decreased between 4 and 6 hr. These decreases in latency and sedimentability correlated with a decrease in bile production and an increase in the rate of release of GOT into the perfusate and could indicate either intracellular disruption of lysosomes

Latencies, Sedimentabilities, and Specific Activities of Acid Phosphatase and β-Glucuronidase in Homogenates of Rat Liver Prepared before or at Various Times after Exposure to 1.4 m Me₂SO for 1 hr

     

Time (hr)	0	3	4	6
Acid phosphatase
Latency (%)	83.2 ± 0.8	64.7 ± 5.1	62.4 ± 7.9	68.9 ± 5.4
Sedimentability (%)	81.7 ± 0.6	77.6 ± 3.1	81.0 ± 3.4	79.4 ± 5.1
Specific activity (mIU/mg protein)	2.8 ± 0.4	2.8 ± 0.2	2.4 ± 0.4	1.6 ± 0.2
β-Glucuronidase
Latency (%)	06.8 ± 1.5	71.3 ± 4.3	74.2 ± 2.5	63.3 ± 4.5
Sedimentability (%)	69.5 ± 0.3	75.4 ± 3.2	75.0 ± 1.1	74.6 ± 2.0
Specific activity (mIU/mg protein)	1.8 ± 0.1	1.6 ± 0.1	1.6 ± 0.2	1.6 ± 0.2