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At least 127 records · Page 7Linked to original sources
PubMed2005

Effects of extremely low-frequency electromagnetic fields on morphine-induced conditioned place preferences in rats.

In the present study, we examined the effects of extremely low-frequency (ELF) electromagnetic fields on morphine-induced conditioned place preferences in rats. During the conditioning phase (12 days), three groups of rats were placed in a sensory cue-defined environment paired with morphine (10mg/kg, i.p.) following exposure to either 20 Hz (1.80 mT) or 50 Hz (2.20 mT) or sham electromagnetic fields for 60 min/day, respectively, and were placed in another sensory cue-defined environment paired with physiological saline (1 ml/kg, i.p.) without exposure to electromagnetic fields. After finishing 12 days of conditioning, preference tests for the morphine-paired place were performed during a 10-day withdrawal period. The exposure to electromagnetic fields substantially potentiated morphine-induced place preferences in rodents, suggesting that ELF electromagnetic fields can increase the propensity for morphine-induced conditioned behaviors.

Analgesics, Opioid↗
PubMed1988

Pulsing electromagnetic field stimulation of the in vitro growth plate.

Specific pulsing electromagnetic fields (PEMFs) have been used to stimulate growth and repair of osteogenic tissues; however, the basis for this specificity is unknown. Previously, we determined the relevant electromagnetic field parameters of the clinically used PEMF and independently verified the beneficial effects of PEMFs on the rabbit fibula fracture healing model. The goal of the present study was to develop an in vitro model that would permit the effectiveness of various electric and magnetic field components of the PEMF to be determined. The costochondral junction (CCJ) of the 21-day-old rat was exposed in vitro to PEMFs with various electric and magnetic field component amplitudes. Response of this model to PEMFs was determined by nondestructive macrophotographic measurement of CCJ growth. Preliminary data indicated that temperature effects were present in this in vitro system. Subsequent experiments designed to separate the effects of temperature and PEMFs on the growth of CCJs in tissue culture were performed. Results indicate that accurate and frequent temperature measurements must be made for in vitro models being used to study effects of PEMFs. Small temperature differences induced by the coils used to produce PEMFs in the CCJ experimental system can have significant stimulatory effects, and the combined effects of temperature and PEMFs are not linearly additive in this model. Furthermore, our results suggest that thermal and PEMF stimuli could affect macrophotographically measured growth of the CCJ by separate mechanisms or could have a synergistic effect. Therefore, PEMF stimulation experiments should be performed under strictly "athermal" conditions.

Animals↗
PubMed2006

Growth of etiolated barley plants in weak static and 50 Hz electromagnetic fields tuned to calcium ion cyclotron resonance.

BACKGROUND: The effects of weak magnetic and electromagnetic fields in biology have been intensively studied on animals, microorganisms and humans, but comparably less on plants. Perception mechanisms were attributed originally to ferrimagnetism, but later discoveries required additional explanations like the "radical pair mechanism" and the "Ion cyclotron resonance" (ICR), primarily considered by Liboff. The latter predicts effects by small ions involved in biological processes, that occur in definite frequency- and intensity ranges ("windows") of simultaneously impacting magnetic and electromagnetic fields related by a linear equation, which meanwhile is proven by a number of in vivo and in vitro experiments. METHODS: Barley seedlings (Hordeum vulgare, L. var. Steffi) were grown in the dark for 5 and 6 days under static magnetic and 50 Hz electromagnetic fields matching the ICR conditions of Ca2+. Control cultures were grown under normal geomagnetic conditions, not matching this ICR. Morphology, pigmentation and long-term development of the adult plants were subsequently investigated. RESULTS: The shoots of plants exposed to Ca2+-ICR exposed grew 15-20% shorter compared to the controls, the plant weight was 10-12% lower, and they had longer coleoptiles that were adhering stronger to the primary leaf tissue. The total pigment contents of protochlorophyllide (PChlide) and carotenoids were significantly decreased. The rate of PChlide regeneration after light irradiation was reduced for the Ca2+-ICR exposed plants, also the Shibata shift was slightly delayed. Even a longer subsequent natural growing phase without any additional fields could only partially eliminate these effects: the plants initially exposed to Ca2+-ICR were still significantly shorter and had a lower chlorophyll (a+b) content compared to the controls. A continued cultivation and observation of the adult plants under natural conditions without any artificial electromagnetic fields showed a retardation of the originally Ca2+-ICR exposed plants compared to control cultures lasting several weeks, with an increased tendency for dehydration. CONCLUSION: A direct influence of the applied MF and EMF is discussed affecting Ca2+ levels via the ICR mechanism. It influences the available Ca2+ and thereby regulatory processes. Theoretical considerations on molecular level focus on ionic interactions with water related to models using quantum electrodynamics.

Journal Article↗
PubMed1996

[Evaluation of selected parameters of circulatory system function in various occupational groups of workers exposed to high frequency electromagnetic fields].

In various branches of the national economy there is a continuous increase in the use of devices producing electromagnetic fields (EMFs). Therefore, the number of persons exposed more or less to EMFs is still growing. Moreover, devices producing electromagnetic fields such as microwave ovens, cellular phones, microwave alarms etc. are now in common use. Both theoretical deliberations and laboratory studies indicate that electromagnetic fields affect the human body inducing a number of physical phenomena manifested by biological changes or even disorders in organic functions. Because of their electric character, the circulatory and nervous systems are particularly vulnerable to the EMF effect. Studies aimed at evaluating the circulatory system in persons exposed, in different degress, to EMF were initiated at the Nofer Institute of Occupational Medicine in 1993. To date, the studies have covered a group of workers employed at AM broadcast stations, radio link stations and radioservice. As were have obtained a quite an extensive material, it is our intention to present it in a series of publications. This one deals with the evaluation of exposure in the study group of workers. Evaluation methods and results of exposure to high frequency electromagnetic fields at workplaces under are study presented. No exposure to EMFs was found in workers at radio link stations. Therefore, they can serve as a control group in the studies of the EMF effect on the circulatory system. Exposure of radioservice and AM broadcast stations workers falls within allowable levels according to binding regulations, however, exposure of the latter was by several times higher than that of radioservice workers.

Blood Circulation↗
PubMed2001

Invited commentary: electromagnetic fields and cancer in railway workers.

The ideal study of occupational exposure to electromagnetic fields and cancer risk would have a clear exposure source, historically stable exposures, and comparable groups of exposed and unexposed workers. Cohorts of railway workers have marked exposure contrasts and limited job changes and provide marginally adequate study sizes, but there have been important changes in their exposures over time, and the field frequency involved is unusual. The results of Minder and Pfluger's study (Am J Epidemiol 2001;153:825--35) add modest support for an association between electromagnetic field exposure and leukemia. However, given the large size and high quality of a number of previous studies of occupational electromagnetic field exposure and cancer, additional studies similar to past ones are unlikely to yield important new insights.

Causality↗
PubMedDate not supplied

Exposure to electromagnetic fields and the risk of leukemia.

Evidence from animal experiments and human studies suggests that electromagnetic fields may be human leukemogens. Epidemiological studies of leukemia in occupational groups and in the general populations are reviewed. The results are inconsistent. In the few studies showing an association between exposure to electromagnetic fields and the risk of leukemia, the temporal relationship between exposure and effect was not established, the observed associations were weak, the dose-response relationships were based on qualitative levels of exposure without regard to the duration of exposure or secondary sources of exposure, and the risk ratios were probably biased due to the population selection procedures used and misclassification of exposure. The proportionate mortality or cancer incidence ratios are unreliable estimates of relative risk. Further epidemiological research is needed to establish an association between exposure to electromagnetic fields and the risk of leukemia.

Adolescent↗
PubMed1988

Exposure of salivary gland cells to low-frequency electromagnetic fields alters polypeptide synthesis.

This study demonstrates that exposure of cells to extremely low-frequency electromagnetic fields can cause measurable changes in protein synthesis. Sciara coprophila salivary gland cells were exposed to five low-frequency (1.5-72 Hz) electromagnetic signals: three signals (1.5, 15, and 72 Hz) produced pulsed asymmetric electromagnetic fields and two signals (60 and 72 Hz) were sinusoidal. Subsequent analyses of two-dimensional gels showed that cell exposure to either type of low-frequency electromagnetic field resulted in both qualitative and quantitative changes in patterns of protein synthesis. Thus, signals producing diverse waveform characteristics induced previously undetectable polypeptides, some of which were signal specific and augmented or suppressed other polypeptides as compared with nonexposed cells. The pattern of polypeptide synthesis differed from that seen with heat shock: only five polypeptides in cells exposed to electromagnetic signals overlap those polypeptides exposed to heat shock, and the suppression of protein synthesis characteristic of heat shock does not occur.

Animals↗
PubMed1985

[Somaticoautonomic functions of rabbits exposed to an ultrahigh-frequency electromagnetic field at acupuncture points].

The action of electromagnetic field of ultrahigh frequency with power from 1 to 1000 mwt and acupuncture on the functional state of rabbits under the tooth pulp irritation conditions has been investigated. The action on the points has been established to be accompanied by decrease of the rythm breathing irregularity and motion of animals jaws. The most effectiveness during the action of the field has been registered with power 1-20 mwt that corresponds to the effectiveness of acupuncture. However during the action of the field the frequency of breathing does not change while during acupuncture it increases. This fact points out the differences of the mechanism of normalized effect of these species influence on acupuncture points. The point of view concerning the invariable information action of fields upon the points and the system of points as constantly acting communication channel between an organism and the environment is under discussion.

Acupuncture Therapy↗
PubMed1988

[Subcellular mechanisms of the action of weak extra-low frequency electromagnetic fields on the cerebral cortex].

Electron microscopic examinations of the cerebral cortex in rabbits and rats after exposure to weak extra-low electromagnetic fields has detected ultrastructural changes whose degree in different nerve tissue elements was dependent on the duration of irradiation. Single exposure to weak extra-low electromagnetic field resulted only in the glial response of the neocortex, while multiple exposure resulted alternately in the response of glial cells or neuronal bodies. Three days after a single exposure and within 15 days after multiple exposure to electromagnetic field a complete repair of the nervous tissue was observed. No destructive or pathological alterations have been found which suggests the functional character of the reactions induced. Neuro-morphological alterations are of a similar character when induced by weak extra-low electromagnetic fields or other biophysical effects which points to common subcellular mechanisms of nonspecific adaptive reactions.

Animals↗
PubMedDate not supplied

[Use of pulsating high-frequency electromagnetic fields in patients with diabetic neuropathies and angiopathies].

High-frequency pulsating electromagnetic field therapy was carried out in 22 patients with diabetic polyneuropathy and angiopathy manifested on lower extremities (18 men, 4 women, aged 48.2 +/- 6.3 years; 10 insulin-dependent persons, and 12 on oral antidiabetic treatment). The aim of the study was to verify the effect of this therapy on symptoms, neurophysiological findings and peripheral circulation. The diagnose of diabetic polyneuropathy was based on the electromyographic examination of foot and calf muscles, measurement of motor nerve conduction velocity of peroneal and tibial nerve, and sensory nerve conduction velocity of sural nerve. Diagnosis of diabetic polyneuropathy was based on electromyographic examination of the foot and calf muscles, measurement of the motor nerve conduction velocity of peroneal and tibial nerves, and the sensory nerve conduction velocity of the sural nerve. Diagnosis of diabetic angiopathy was established by oscillometric examination, measurement of skin temperature and claudication distance. The same methods were used for the evaluation of the therapeutical effect of electromagnetic field. Significant improvement of symptoms, and of all registered parameters of peripheral circulation was established after the therapy, but there were no significant changes of neurophysiological parameters. Therefore, high-frequency pulsating electromagnetic field is recommended for the treatment of diabetic angiopathy. In patients with neuropathic changes it can be used as an introduction procedure, or as an additional procedure to physical agents which are commonly used in the treatment of peripheral nerve lesion.

Diabetic Angiopathies↗
PubMedDate not supplied

[Primary mechanisms of the biological effect of electromagnetic fields].

Based on the model of a bulk knitted structure, a possible mechanism of action of an external electromagnetic field on biological systems was proposed. The electromagnetic field affects biological processes through changes in the rates of biochemical reactions in response to changes in the conformational properties of water in the electromagnetic field.

Animals↗
PubMed1978

[Coagulation properties of the blood and tissues of the cardiovascular system exposed to an electromagnetic field].

The effect of low-frequency electromagnetic field on the coagulant and fibrinolytic properties of blood and tissues of the cardiovascular system was studied. Phase character of changes in the coagulative properties of blood as well as in those of the heart and aorta was established. Irradiation of rats for 8 days is attended by an increase in the coagulating and fibrinolytic activity of blood and simultaneous inhibition of the thromboplastic compounds of the heart and vascular wall. Increase of exposure to 20 days leads to inactivation of tissue and plasma blood coagulation factors. The possible mechanism of these changes is discussed.

Animals↗
PubMed1989

Prevention of osteoporosis by pulsed electromagnetic fields.

Using an animal model, we examined the use of pulsed electromagnetic fields, induced at a physiological frequency and intensity, to prevent the osteoporosis that is concomitant with disuse. By protecting the left ulnae of turkeys from functional loading, we noted a loss of bone of 13.0 per cent compared with the intact contralateral control ulnae over an eight-week experimental period. Using a treatment regimen of one hour per day of pulsed electromagnetic fields, we observed an osteogenic dose-response to induced electrical power, with a maximum osteogenic effect between 0.01 and 0.04 tesla per second. Pulse power levels of more or less than these levels were less effective. The maximum osteogenic response was obtained by a decrease in the level of intracortical remodeling, inhibition of endosteal resorption, and stimulation of both periosteal and endosteal new-bone formation. These data suggest that short daily periods of exposure to appropriate electromagnetic fields can beneficially influence the behavior of the cell populations that are responsible for bone-remodeling, and that there is an effective window of induced electrical power in which bone mass can be controlled in the absence of mechanical loading.

Animals↗
PubMed2006

[National system of protection against electromagnetic fields 0 Hz-300 GHz in the light of current legal regulations].

Exposure to electromagnetic fields (EMF) occurs when man is exposed to the effect of electric, magnetic and electromagnetic fields and contact currents different from those resulting from physiological processes in the organism or other natural phenomena. In Poland, the system of protection against EMF has been functioning for over 35 years. In 2001, when the Minister of Labor and Social Policy issued the regulation introducing the maximum admissible intensities (MAI) for electromagnetic fields and radiation within the range of 0 Hz-300 GHz, the system was directed mainly towards evaluation of exposure to EMF occurring in the occupational environment. The system is linked via MAI values with human protection in the natural environment. In this paper, the background, principles and the range of the national system of protection against EMF and its monitoring are presented. The project of implementation of EU directives, following Poland's accession to the European Union is also discussed.

Electromagnetic Fields↗
PubMed2001

[Exposure to electromagnetic fields and risk of central nervous system diseases among employees at Danish electric companies].

INTRODUCTION: Occupational exposure to electromagnetic fields has been associated with neurological diseases, such as amyotrophic lateral sclerosis, senile dementia, Parkinson's disease and Alzheimer's disease. MATERIAL AND METHOD: I studied the incidence of disease in the central nervous system in 30,631 persons employed at Danish electric companies between 1900 and 1993. I linked the cohort to the nationwide, population-based Danish National Register of Patients and compared the number of cases of these diseases found between 1978 and 1993 with the corresponding rates in the general population. In addition, I fit the data on utility workers to a multiplicative Poisson regression model in relation to estimated levels of exposure to 50 Hz electromagnetic fields. RESULTS: Overall, there was an increase in the risk of senile dementia and motor neuron diseases combined. The incidences of Parkinson's disease, Alzheimer's disease and other diseases of the central nervous system were essentially unrelated to exposure to electromagnetic fields. A decreased risk of epilepsy compared with the general population probably reflects a healthy worker effect; I observed an increased risk of epilepsy based on internal comparisons. DISCUSSION: The increased risk of senile dementia and motor neuron diseases may be associated with above average levels of exposure to electromagnetic fields.

Alzheimer Disease↗
PubMed1997

Influence of electromagnetic fields on bone mass and growth in developing rats: a morphometric, densitometric, and histomorphometric study.

The effect of electromagnetic fields on bone is debated. In an experimental study of this effect, we compared two lots of growing female rates (both lots n = 15, age 3 weeks, average weight 23.2 +/- 3.3 g), one of which was exposed to a 3-mT, 100-Hz, Helmholtz-type electromagnetic field for 24 hours a day for 30 days, and the other of which served as the control. Bone development and bone mass were evaluated by morphometry, densitometry, and histomorphometry. The rats were killed at 30 days and weighed. The right femurs were dissected, measured, and weighed; bone densitometry was used to determine femoral bone mineral content (BMC) and density (BMD), and histomorphometry of the nondecalcified bone was used to determine trabecular bone volume (Cn-BV-TV%), number (Tb-N mm) and thickness (Tb-Th microm), intertrabecular space (Tb-Sp microm) and growth cartilage thickness (Gc-Th microm). In the rats exposed to the electromagnetic field, BMC and BMD (P = 0.019 and P = 0.002, respectively) and Cn-BV-TV, Tb-N, Tb-Th (P = 0.005, P = 0.036, and P = 0.027, respectively) all were decreased, whereas Tb-Sp was increased (P = 0.002). There were no significant differences in initial and final body weight, or in final femur weight, femur length, and GC-Th. These findings indicate that electromagnetic fields of the type used here reduced bone formation and increased bone resorption without affecting bone development in rats.

Absorptiometry, Photon↗