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PubMed1991

Non-thermal vasodilatation by radio frequency burst-type electromagnetic field radiation in the frog.

1. When the web of the anaesthetized Xenopus laevis was perfused with Ringer solution maintained at 20 degrees C, radio frequency (RF) burst-type electromagnetic (EM) field radiation not only dilated arterioles of the web which had been preconstricted with noradrenaline, but also dilated arterioles under non-stimulated conditions. The EM field-induced vasodilatation increased slowly and reached a plateau 60 min after the onset of radiation. After the cessation of radiation, vasodilatation remained for 10-20 min, then slowly subsided. 2. When a 10 MHz, 1 V (peak to peak) generator voltage induced a 7.3 milliGauss, 2.19 V cm-1 EM field, the vasodilatory effect was optimum when bursts were applied 50% of the total time at 10 kHz burst rate. 3. The vasodilatory effect was not secondary to dielectric heat in the web, because the EM field was too weak to have produced enough heat to dilate the arterioles and heat would have been constantly conducted away by the perfusion solution. 4. During perfusion with Ringer solution warmed to 30 degrees C, no vasodilatation was found, but perfusion with Ringer solution warmed to 35 degrees C induced only 11% vasodilatation. Perfusion with Ringer solution warmed to 37 degrees C induced irreversible vasoconstriction. The pattern of vasodilatation induced by warm Ringer solution was different from the vasodilatory effect of weak EM field radiation. 5. The extent of the vasodilatory effect was influenced by Ca2+ concentration of the perfusion medium. Under normal Ca2+ conditions arterioles dilated to 126% of the control diameter, while under Ca(2+)-free conditions arterioles dilated to 131% of the control value and under high-Ca2+ conditions (twice the normal level) arterioles dilated to 111% of the control value. This suggests that the vasodilatory effect may be caused by facilitation of Ca2+ outflow, and the extent of this flow may settle down to the equilibrium level of countercurrent flux between Ca2+ influx and outflow. 6. The vasodilatory effect was not inhibited under perfusion with Na(+)-free Ringer solution, suggesting that Na(+)-Ca2+ exchange system may not be involved in the vasodilatory effect. The vasodilatory effect was inhibited by vanadate, an inhibitor of Ca(2+)-ATPase, and was abolished by Methylene Blue, an inhibitor of guanylate cyclase. The evidence suggests that the mechanism of the vasodilatory effect may depend on an increase in Ca2+ outflow through the plasma membrane of the smooth muscle and/or an increase in Ca2+ influx into the sarcoplasmic reticulum.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1981

[Protection of personnel exposed to very high frequency electromagnetic fields (author's transl)].

After a short review of biological effects of non-ionising electromagnetic radiations, their pathological effects are examined, insisting on methods usable to gain informations. Techniques used for field surveys are studied with definition of various irradiation classes. Then protection methods are dealt with, either individual or global, together with medical surveillance.

Electromagnetic Fields↗

PubMed1993

Electromagnetic fields and male breast cancer.

The aetiology of male breast cancer is still considered to be rather unclear. Epidemiological studies have recently shown an excess risk of male breast cancer in "electrical workers" with potential exposure to electromagnetic (EM) fields. Interest on the possible association between pineal function and breast cancer has come into focus. The pineal hormone melatonin has been shown to reduce the incidence of experimentally-induced breast cancer in rats, the hormone is oncostatic and cytotoxic to breast, ovarian, and bladder cancer cell lines in vitro. Treatment of cancer patients with orally administered melatonin has been tried. Pineal function in humans is suppressed by light-at-night (LAN). Animal studies have shown that exposure to 60-Hz electric fields may also suppress the nocturnal rise in pineal melatonin production in adult rats. Breast cancer is the leading cause of cancer death among women in industrialised world. No good explanation has so far been provided for the increased incidence of this site during the last decades, although changes in fertility factors have had some effect. If new epidemiological and experimental data give support to the hypothesis that exposure to LAN and EM fields may increase breast cancer risk, this may have regulatory and political consequences for future use of electric power.

Breast Neoplasms↗

PubMed2005

Influence of 400, 900, and 1900 MHz electromagnetic fields on Lemna minor growth and peroxidase activity.

Increased use of radio and microwave frequencies requires investigations of their effects on living organisms. Duckweed (Lemna minor L.) has been commonly used as a model plant for environmental monitoring. In the present study, duckweed growth and peroxidase activity was evaluated after exposure in a Gigahertz Transversal Electromagnetic (GTEM) cell to electric fields of frequencies 400, 900, and 1900 MHz. The growth of plants exposed for 2 h to the 23 V/m electric field of 900 MHz significantly decreased in comparison with the control, while an electric field of the same strength but at 400 MHz did not have such effect. A modulated field at 900 MHz strongly inhibited the growth, while at 400 MHz modulation did not influence the growth significantly. At both frequencies a longer exposure mostly decreased the growth and the highest electric field (390 V/m) strongly inhibited the growth. Exposure of plants to lower field strength (10 V/m) for 14 h caused significant decrease at 400 and 1900 MHz while 900 MHz did not influence the growth. Peroxidase activity in exposed plants varied, depending on the exposure characteristics. Observed changes were mostly small, except in plants exposed for 2 h to 41 V/m at 900 MHz where a significant increase (41%) was found. Our results suggest that investigated electromagnetic fields (EMFs) might influence plant growth and, to some extent, peroxidase activity. However, the effects of EMFs strongly depended on the characteristics of the field exposure.

Araceae↗

PubMed2003

[Proposed exposure levels of pulse-modulated electromagnetic fields].

Numerous investigations have confirmed the occurrence of various biological effects evoked in humans by pulse microwave radiation emitted from radars or cellular phones. In such exposures, the electromagnetic energy may reach very high values of power density in peak at relatively low time-averaged levels of power density. Up till now, no one has evidenced that the relationship between radiation dose and biological effects has the same correlation function for weak field as well as for a very strong field in peak. The proposed exposure levels of pulse-modulated electromagnetic fields (Smax pulse) for the general and occupational populations are described.

Cell Phone↗

PubMedDate not supplied

[New mechanisms of biological effects of electromagnetic fields].

The production of ATP in mitochondria depends on the magnesium nuclear spin and magnetic moment of a Mg2+ ion in creatine kinase and ATPase. This suggests that enzymatic synthesis of ATP is an ion-radical process and thus depends on the external magnetic field (magnetobiology originates from this fact) and microwave fields, which control the spin states of ion-radical pairs and affect the ATP synthesis. The chemical mechanism of ATP synthesis and the origin of biological effects of electromagnetic (microwave) fields are discussed.

Adenosine Triphosphate↗

PubMed2004

[Electromagnetic fields in melting divisions of nickel production].

The authors evaluated electromagnetic situation in melting divisions, on transformer substation. Studies covered alternating electric and magnetic fields of industrial frequencies and direct magnetic fields in fire mode of nickel production on workplaces during working shifts. Results proved that induction of the magnetic fields varies widely. Magnetic fields influence is accidental and remains additional factor affecting human body.

Accidents, Occupational↗

PubMed2006

Electromagnetic field computation in semiconductor laser resonators.

An electromagnetic method based on rigorous diffraction theory of gratings is applied to the analysis of fields in semiconductor laser cavities. The method is based on the Fourier modal method; it is fully rigorous for infinitely periodic resonators and highly accurate for single resonators when absorbing boundary conditions are applied. Fundamental-mode intracavity and near-field distributions are evaluated for some selected geometries, and resonance frequencies are predicted.

Journal Article↗

PubMed2005

3-D numerical study on the induced heating effects of embedded micro/nanoparticles on human body subject to external medical electromagnetic field.

Advancement of the recent micro/nanotechnology stimulates the renaissance of using magnetic micro/nanoparticles embedded in tissues for the target tumor hyperthermia. However, there is a strong lack of quantitative understanding of the temperature profiles thus induced by the applied external electromagnetic (EM) field, which may impede the successful operation of this therapy. In the current study, the three-dimensional quasi-steady-state EM field and transient tissue temperature behavior induced by two planar electrodes were numerically investigated. Detailed computations indicated that nanoparticles exhibit an extraordinary highly focused heating on target tumor tissue, which is much stronger than that in the surrounding areas. This heating effect depends heavily on the properties of the magnetic nanoparticles, which may vary appreciably for different samples depending on their particle sizes and microstructures. The effect of micro/nanoparticle concentration, heating area, and the frequency and strength of the external alternating EM field were also tested. Moreover, a criterion to determine the appropriate particle concentration thermally important for medical treatment was established. Given accurate thermal and EM parameters for cancerous tissue embedded with nanoparticles, the current model could possibly be applied in the hyperthermia treatment planning and help optimize the surgical procedures.

Computer Simulation↗

PubMed2006

Interaction of radio frequency electromagnetic fields and passive metallic implants--a brief review.

During the last decade, use of radio frequency (RF) applications like mobile phones and other wireless devices, has increased remarkably. This has triggered numerous studies related to possible health risks due to the exposure of RF electromagnetic (EM) fields. One safety aspect is the coupling of EM fields with active and passive implants in the human body. While interactions with active implants have been quite extensively researched, only a few studies have focused on passive implants. The present article reviews interaction mechanisms and studies of passive metallic, that is, conductive, implants in common external RF EM fields. It is found that implants have been mostly studied numerically, and experimental studies are rare. Furthermore, the studies cover mostly far-field conditions and only a few have studied implants in near fields. A summary of results indicates that a conductive object in tissues may cause notable local enhancement of the EM field and thus enhanced power absorption. The degree of enhancement depends, for example, on the orientation, the dimensions, the shape, and the location of the implant. However, in most of the cases, the field enhancement has not been strong enough to cause remarkable excess heating (more than 1 degrees C) of tissues.

Absorption↗

PubMed1990