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PubMedDate not supplied

[Dosimetric aspects in studying the biological action of nonionizing electromagnetic radiation].

In order to clarify mechanisms of biological reactions, it is very important to study the absorption and spatial distribution of the absorbed electromagnetic energy. The procedures and methods of calculating the electromagnetic energy absorption of biological specimens exposed to nonionizing electromagnetic irradiation in a wide frequency range (0-300 GHz) are described. Also presented are formulas and plots to be used in calculating the specific absorption of the dose rate by biological specimens, with the inclusion of resonance absorption, polarization of the incident electromagnetic wave, presence of reflecting surfaces and grounding. The extrapolation of the average energy absorption from one animal species to another and to man is discussed, assuming that spatial and energy distributions are equivalent. The notion of the irradiation quality coefficient is introduced. The magnitudes of the coefficients are given as related to the irradiation frequency and polarization type. A mathematical relation is offered to determine the safety of a complex spectrum of electromagnetic irradiation. The relation takes into consideration different dimensionality of the parameters of the electromagnetic field in the low- and high-frequency ranges.

Absorption↗
PubMed1982

[Ultracytochemical changes in the brain and liver in exposure to low-intensity nonionizing microwave radiation].

The morphological (including electron microscopy, histochemistry, morphometry) and biochemical methods were used in experiments on 478 white rats to determine the content of glycogen, tigroid substance, RNA, DNA and activity of the enzymes (SDH, MDH, LDH, G-6-PDH, phosphorylase) in intact animals after and during exposure to nonionizing microwave radiation (NMR), 30 and 60 days after the rehabilitation period, as well as after physiological exposures (hypoxia and NMR of higher intensity). It was disclosed that repeated exposure to little doses of NMR alters the structural and functional bases of the mechanisms that regulate cell metabolism, produces conformational changes in the chemical substances and thus exerts a damaging action on the delicate cell structures; redistributes the action on the pathways of energy formation at the expense of compensatory protein synthesis and the increase enzymatic systems; increases the resistance to hypoxia and action of NMR of higher intensities.

Animals↗
PubMed1998

Exposure to low dose of gamma radiation enhances the excision repair in Saccharomyces cerevisiae.

The effect of low doses of ionizing and nonionizing radiation on the radiation response of yeast Saccharomyces cerevisiae toward ionizing and nonionizing radiation was studied. The wild-type strain D273-10B on exposure to 54 Gy gamma radiation (resulting in about 10% cell killing) showed enhanced resistance to subsequent exposure to UV radiation. This induced UV resistance increased with the incubation time between the initial gamma radiation stress and the UV irradiation. Exposure to low doses of UV light on the other hand showed no change in gamma or UV radiation response of this strain. The strains carrying a mutation at rad52 behaved in a way similar to the wild type, but with slightly reduced induced response. In contrast to this, the rad3 mutants, defective in excision repair, showed no induced UV resistance. Removal of UV-induced pyrimidine dimers in wild-type yeast DNA after UV irradiation was examined by analyzing the sites recognized by UV endonuclease from Micrococcus luteus. The samples that were exposed to low doses of gamma radiation before UV irradiation were able to repair the pyrimidine dimers more efficiently than the samples in which low gamma irradiation was omitted. The nature of enhanced repair was studied by scoring the frequency of induced gene conversion and reverse mutation at trp and ilv loci respectively in strain D7, which showed similar enhanced UV resistance induced by low-dose gamma irradiation. The induced repair was found to be essentially error-free. These results suggest that irradiation of strain D273-10B with low doses of gamma radiation enhances its capability for excision repair of UV-induced pyrimidine dimers.

Journal Article↗
PubMed1988

Biological effects of non-ionizing radiations: cellular properties and interactions.

The Lauriston Taylor lectures honor the founder of the National Committee on Radiation Protection and Measurement, soon to be followed by the corresponding international organization. These standard setting bodies had a vast influence on proper recognition of radiation hazards. The 10th Taylor lecture is the first to deal with nonionizing radiations and may be, therefore, of particular interest to the bioengineer. During early history biophysics and bioengineering were primarily concerned with ionizing radiation bioeffects and electrophysiology. The nonionizing part of the radiation field and electrophysiology are closely related. Biomedical observation, biophysical and bioengineering efforts in the nonionizing radiation field are defined and complement each other. Topics concentrate on the relevant biophysical and bioengineering efforts of the author and his colleagues. They include: electrical properties of biological systems; established electrical field interactions (excitation, macromolecular responses and cellular responses); problems of dosimetry (macroscopic and microscopic considerations); conclusions about relative merits of various research approaches.

Animals↗
PubMed1996

Breast cancer and environmental risk factors: epidemiological and experimental findings.

Breast cancer has long been associated with reproductive hormone exposures. Recently, greater attention has been focused on environmental exposures that may be responsible for some proportion of breast cancer incidence. Several etiologic aspects are discussed. A number of chemicals induce breast cancer in rodents--including solvents, pesticides, and polycyclic aromatic hydrocarbons--and these might serve as leads for studies in humans. In women, strong links have been established between breast cancer risk and ionizing radiation. Evidence for nonionizing radiation (electromagnetic field) exposures and breast cancer is suggestive, albeit limited. Occupational exposures have not been identified as breast cancer risks, but several associations need further study, including solvents and pesticides. Time of life when exposures take place is important, and this claim is strongly supported by data on cigarette smoking and radiation. Also, basic research has demonstrated that mammary tissue is more susceptible to carcinogenesis at certain periods of breast development. Likewise, prenatal, neonatal, and adolescent exposures deserve continuing attention. Research on etiology of breast cancer should measure environmental exposures and take into account the time of life at which these occur. Complex interactions between exogenous and endogenous carcinogenic agents need further focus, as modulated by varying genetically determined individual susceptibilities.

Animals↗
PubMed1998

Risk of ionizing radiation exposure to children: a subject review. American Academy of Pediatrics. Committee on Environmental Health.

Exposure of children to ionizing radiation most commonly is from the environment, chiefly through cosmic rays and radon, or from medical technology. Medical radiation exposure occurs during diagnosis, therapy, and dental radiography. More is known about the biological effects of exposure to ionizing radiation than to nonionizing radiation from microwaves, radiowaves, and the electrical fields of other electrical appliances. This review applies only to sources of ionizing radiation and does not include the potential risks of indoor radon. The effects on children of ionizing radiation have been studied from war activities and environmental accidents. Protections are mode from that data to help pediatricians evaluate risk from radiation when ordering radiographs.

Adolescent↗
PubMed1991

Comparison of initial yields of DNA-to-protein crosslinks and single-strand breaks induced in cultured human cells by far- and near-ultraviolet light, blue light and X-rays.

The initial yields of DNA-to-protein crosslinks (dpc) caused by ionizing and nonionizing radiations were compared, with emphasis upon values within the biological dose ranges (D0). Induction of dpc in cold (0-0.5 degrees C) human P3 teratocarcinoma cells was measured by using alkaline elution techniques after exposure to monochromatic UVC (254 nm), UVB (313 nm), UVA (365 and 405 nm), and blue light (434 nm). UVC and UVB light induced detectable numbers (about 100 dpc per cell per D0). Monochromatic UVA radiations produced yields about 8 times higher than UVC or UVB (for 365 nm, about 1500 dpc per cell per D0) Similar results at low doses were obtained for measurements of single-strand breaks induced by the different radiations. The action spectra for dpc were closely similar. The biological significance of these relatively high numbers of DNA lesions caused by environmental nonionizing radiation that readily penetrates into human skin is not understood.

Cells, Cultured↗
PubMed1994

Photochemotherapy beyond psoriasis.

Photochemotherapy involves the therapeutic use of nonionizing radiation in combination with a photosensitizing chemical to trigger a photochemical reaction that mediates a beneficial effect. The successful introduction and widespread use of psoralen photochemotherapy (PUVA) in the management of psoriasis was the chief stimulus for recent interest in the therapeutic use of nonionizing radiation in various other dermatoses. This article discusses the expanding spectrum of diseases responding to PUVA therapy. More than 30 conditions such as atopic dermatitis, mycosis fungoides, vitiligo, the photodermatoses, chronic graft-versus-host disease, and granuloma annulare have been successfully treated with oral psoralen photochemotherapy. Various mechanisms of response to treatment are discussed including photoimmunologic effects, selective cytotoxicity, alterations of cell function, and stimulation of melanocytes. Finally, the limitations to the use of PUVA therapy are identified and its future use in other cutaneous and systemic diseases are discussed.

Humans↗
PubMed2004

The cancer epidemiology of radiation.

Ionizing radiation has been the subject of intense epidemiological investigation. Studies have demonstrated that exposure to moderate-to-high levels can cause most forms of cancer, leukaemia and cancers of the breast, lung and thyroid being particularly sensitive to induction by radiation, especially at young ages at exposure. Predominant among these studies is the Life Span Study of the cohort of survivors of the atomic bombings of Japan in 1945, but substantial evidence is derived from groups exposed for medical reasons, occupationally or environmentally. Notable among these other groups are underground hard rock miners who inhaled radioactive radon gas and its decay products, large numbers of patients irradiated therapeutically and workers who received high doses in the nuclear weapons programme of the former USSR. The degree of carcinogenic risk arising from low levels of exposure is more contentious, but the available evidence points to an increased risk that is approximately proportional to the dose received. Epidemiological investigations of nonionizing radiation have established ultraviolet radiation as a cause of skin cancer. However, the evidence for a carcinogenic effect of other forms of nonionizing radiation, such as those associated with mobile telephones or electricity transmission lines, is not convincing, although the possibility of a link between childhood leukaemia and extremely low-frequency electromagnetic fields cannot be dismissed entirely.

Child↗
PubMed2002

Study of the G2/M cell cycle checkpoint in irradiated mammary epithelial cells overexpressing Cul-4A gene.

PURPOSE: Members of the cullin gene family are known to be involved in cell cycle control. One of the cullin genes, Cul-4A, is amplified and overexpressed in breast cancer cells. This study investigates the effect of Cul-4A overexpression upon G2/M cell cycle checkpoint after DNA damage induced by either ionizing or nonionizing radiation. METHODS AND MATERIALS: The normal mammary epithelial cell line MCF10A was stably transfected with full-length Cul-4A cDNA. Independent clones of MCF10A cells that overexpress Cul-4A proteins were selected and treated with either 8 Gy of ionizing radiation or 7 J/M(2) of UV radiation. The profile of cell cycle progression and the accumulation of several cell cycle proteins were analyzed. RESULTS: We found that overexpression of Cul-4A in MCF10A cells abrogated the G2/M cell cycle checkpoint in response to DNA damage induced by ionizing irradiation, but not to DNA damage induced by nonionizing radiation. Analysis of cell cycle proteins showed that after ionizing irradiation, p53 accumulated in the mock-transfected MCF10A cells, but not in the Cul-4A transfectants. CONCLUSION: Our results suggest a role for Cul-4A in tumorigenesis and/or tumor progression, possibly through disruption of cell cycle control.

Breast Neoplasms↗
PubMed1984

Science and standards. RF-hazards and standards: an historical perspective.

The following topics are discussed: Standard of safety considerations. Early efforts in bioengineering and biophysics before and after World War II, Work after World War II (1950s), Early interest in hazards, Soviet work and The Tri-Service area and ANSI. The author concludes that the historical development of biophysics and bioengineering, both as a whole and in the specialty area of nonionizing radiation, proceeded in a fairly rational fashion. Formulation of exposure standards in the West was based on the biophysical approach, which prevails in the interdisciplinary sciences involving biomedical and engineering disciplines. No pressure by an "industrial-military establishment" was evident in the quest for standards, and the Soviet approach and work were under surveillance from the late 1950's. A continuous interest in athermal effects has persisted since the 1930's. Historical accounts are based on personal experience and study of the literature. They are therefore limited to the extent that such experience and study is incomplete. The author had the good fortune to participate over a professional lifetime in the development of biophysical and biomedical engineering sciences, including those that address nonionizing radiation and Western standards of safety.

Biomedical Engineering↗
PubMed1979

Study of nonionizing microwave radiation effects upon the central nervous system and behavior reactions.

The biologic effect of an electromagnetic field of a frequency of 2375 +/- 50 MHz was studied in rats and rabbits in specially constructed absorbant chambers. The results of the investigations have shown that microwave radiation of 10, 50, 500 mu W/cm2 for 30 days, 7 hr/day, causes a number of changes in bioelectric brain activity and also in behavioral immunological, and cytochemical reactions. It was found that levels of 10 and 50 mu W/cm2 stimulate the electric brain activity at the initial stage of irradiation, while a level of 500 mu W/cm2 causes its suppression, as seen from the increase of slow, high amplitude delta-waves. At 500 mu W/cm2 a decrease in capacity of work, in value of unconditioned feeding stimulus, in investigating activity, electronic irradiation threshold, and in inhibition of cellular and humoral immunity were also observed.

Animals↗
PubMedDate not supplied

[The phenomenon of adaptive immunity in exposure to nonionizing microwave radiation].

In experiments with albino rats exposed to microwaves (500 microW/cm2), a model of adaptive immunity was developed by transferring lymphoid cells of exposed animals. The effect of microwave radiation was shown to cause autoimmune disorders that were displayed against the background of the structural and functional disturbances of the hematoencephalic barrier.

Adaptation, Physiological↗
PubMed1977

Trends in nonionizing electomagnetic radiation bioeffects research and related occupational health aspects.

The international literature (circa 1970-1977) on biological and clinical phenomena associated with exposure to microwave or radiofrequency (RF) electromagnetic (EM) fields was selectively reviewed. It was concluded that the mechanisms by which EM fields exert their biological effects are becoming better understood as investigative technology and methodology improve. Concurrent with this trend, there is some recent eivdence in the West which supports traditional Soviet and some European claims that EM fields can affect nervous system function and morphology in small mammals, birds and invertebrates at power levels below those defined as thermogenic in the West. These experimental findings coupled with the pressure of public opition may eventually have a significant effect on the establishment of revised occupational exposure limits and on unique positions regarding maximum permissible exposure (MPE). At present, the exposure level established in the Soviet Union is 0.01 m W/cm2 for a work day, while the United States adheres to a level of 10 m W/cm2 averaged over 0.1 h. At the same time, however, findings from clinical studies conducted in the West do not corroborate findings from extensive clinical surveys of occupational workers collected in Russia and in some East European countries. The latter continue to report a plethora of psychophysiological dysfunctions and impairments of a reversible nature as a result of chronic exposure to EM fields of relatively low power density (e.g., less than 10 m W/cm2, and occasionally below the 1 m W/cm2 level). Neither is there any recent compelling evidence to support certain speculations that modulated EM fields can be used to remotely control human behavior. Interaction between the concerned research and development communities in the East and West has increased substantially in the 1970s. Such interaction promises to provide a medium in which differences in doctrine, experimental methodology and protocol, and the interpretation of biological and clinical phenomena may be resolved.

Autonomic Nervous System↗