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At least 217 records · Page 12Linked to original sources
PubMed1986

The radiation exposure of black-headed gulls (Larus ridibundus) in the Ravenglass Estuary, Cumbria, U.K.: a preliminary assessment.

A variety of fission-product and transuranic radionuclides originating from the marine discharges from the fuel reprocessing plant at Sellafield, Cumbria are detectable in the bodies of black-headed gulls and their environment in the Ravenglass Estuary approximately 10 km to the south-west of the plant. The maximum concentrations of 95Nb, 137Cs and 239/240Pu detected in body tissues lie in the range 2 X 10(-3) to 1.5 X 10(-2) Bqg-1 wet weight. Many more radionuclides are detected in the regurgitated pellets and faeces produced by the gulls and have higher concentrations in the range 7 X 10(-3) to 1.7 Bqg-1 wet weight. The radionuclide contamination of the sediment produces a source of enhanced external gamma-ray exposure which can be measured directly. The available data on distributions and concentrations of radionuclides have been combined with simple dosimetry models to provide estimates of the radiation exposure of the birds. The total whole body dose rate to the adult birds from the contaminant radionuclides is approximately ten times that from the natural radiation background, while that to the developing eggs is approximately four times the natural background. The potential radiation exposure of the cells lining the alimentary tract could be much higher when contaminated food is in transit, but the long-term average exposure in this case is subject to uncertainty. The limited data on the effects of radiation exposure on birds do not indicate any response at dose rates below one hundred times that from the natural radiation background.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Apoptosis induced by low-dose and low-dose-rate radiation.

BACKGROUND: It has been claimed that external radiation, as a treatment modality for malignant diseases, partly induces apoptosis. It is not known, however, whether therapeutic low-dose and low-dose-rate radiation are able to induce apoptosis. METHODS: The effect of low-dose radiation on apoptosis induction in HeLa Hep2 cells was studied, and quantitation of the apoptotic cells was performed by immunocytochemistry using TdT-mediated dUtp-x Nick End Labeling (TUNEL) technology and the M30 CytoDEATH antibody method. RESULTS: When TUNEL staining was used to quantify apoptosis in untreated HeLa Hep2 cells kept in culture, approximately 5 plus minus 3% of the cells showed positive staining without any treatment. In the first experiment, the HeLa Hep2 cells were exposed to gamma radiation (i.e., 0.5, 1, 2, 5, 10, and 15 grays [Gy]) from a cobalt-60 radiation source delivering a dose rate of 0.80 Gy/min. The radiated cells were cultivated for 5, 10, 24, 48, 72 and 168 hours after irradiation. Radiation doses below 2 Gy did not cause any significant apoptosis, but between 5 and 15 Gy significant apoptosis was observed, with peak values at 5 Gy (P < 0.001). Up to 60% of the investigated cells were shown to display apoptosis. Time to this peak value was 168 hours after irradiation. The HeLa Hep2 cells were exposed to doses of 2, 5, and 10 Gy at a 10-fold lower dose rate (0.072 Gy/min). The cells that achieved a dose below 2 Gy did not present increased apoptosis. At doses above 2 Gy, however, the cells again demonstrated significant apoptosis. Up to 24 hours following irradiation, no apoptosis could be documented, whereas beyond 24 and up to 168 hours a highly significant apoptosis induction was observed. Significant cytotoxicity was confirmed by chromium-51 release from the cells at 5 Gy. CONCLUSIONS: Low-dose and low-dose-rate radiation are able to induce significant apoptosis, and apoptosis may be one of the mechanisms by which low-dose radiation causes growth inhibition.

Apoptosis↗
PubMed1994

Concerns with low-level ionizing radiation.

OBJECTIVE: To clarify the effects of ionizing radiation and to dispel fear associated with the use of radioactivity in medical diagnosis and therapy. DESIGN: Studies of populations in geographic areas of increased cosmic radiation and high natural background radiation, radiation-exposed workers, patients with medical exposure to radioactivity, and accidental exposure are reviewed. RESULTS: No reproducible evidence shows harmful effects associated with increases in background radiation of 3 to 10 times the usual levels. American military personnel who participated in nuclear testing had no increase in leukemia or other cancers. Among 22,000 patients with hyperthyroidism treated with 131I (mean dose, 10 rem), no increased incidence of leukemia was found in comparison with 14,000 similar patients who received other treatment. A 20-year follow-up of 35,000 patients who underwent 131I uptake tests for evaluation of thyroid function revealed that those studied for other than a suspected tumor had only 60% of the thyroid cancers expected in a control group. Although early studies showed that high exposures to miners to radon and its daughters resulted in a substantial increase in lung cancer, no evidence exists for an increase in lung cancer among nonsmokers exposed to increased radon levels in the home. CONCLUSION: Perhaps the association of radiation with the atomic bomb has created a climate of fear about the possible dangers of radiation at any level; however, no evidence indicates that current radiation exposures associated with medical usage are harmful.

Accidents, Occupational↗
PubMedDate not supplied

[The potability of the water in a region with a high level of natural radiation].

BACKGROUND: The recent Spanish legislation on drinkable waters for public use includes a paragraph establishing the requirements to be fulfilled by waters in relation with their radioactivity and the methods to be used to measure it. As water radioactivity depends on the radioactive content of the grounds and rocks where it flows, it is possible to expect high levels in those zones whose characteristic is their high level of natural radiation. METHODS: For this reason, we have organized two measurement campaigns with the objective of characterizing the drinkable waters in an Spanish area, where the radioactive elements concentration in the ground is high. The methodology used is as described in legislation, using a low-bottomed proportional counter. RESULTS: The results we have obtained indicate that the zone, where measurements have been made, shows lower radioactivity levels than the legally established limits, nevertheless, at same time, there appear several points, where the radioactivity levels are high, showing values exceeding in great measure the legal limit for drinkable waters. CONCLUSIONS: With the results, we have obtained, its seems necessary that a greater attention is paid to drinkable waters in those points, where the radioactivity levels are high including corrective measures.

Alpha Particles↗
PubMed1999

Analysis of electret ion chamber radon detector response to 222Rn and interference from background gamma radiation.

Environmental radon (222Rn) monitors that incorporate electret detectors are confounded by background gamma radiation, which may cause the electret to discharge by as much as 7.5 volts per mR. Although background gamma corrections were formerly made by multiplying the known background gamma exposure rate with a constant conversion factor, this research demonstrates that doing so introduces an error ranging up to about 20%, especially in high gamma background areas. A new, more accurate method of background gamma correction has been developed that uses an average, voltage-dependent discharge factor, Dgamma (V Kg C(-1)). This factor and its coefficients were experimentally determined by separately exposing groups of electret radon detectors to photons from 60Co and 137Cs. Statistical analysis shows that Dgamma is independent of the orientation of the electret during irradiation but that some dependency on dose rate or energy of the irradiating photons may be expected. The discharge of the electret due only to gamma irradiation, Vgamma is determined by multiplying the total integrated gamma exposure by Dgamma. The discharge of the electret during a radon measurement can then be corrected for background gamma radiation by subtracting Vgamma from the total discharge of the electret resulting in a net discharge due solely to radon. A new equation has also been developed in this study for the radon discharge factor, D(Rn)(V m3 Bq(-1) s(-1)), that is entirely consistent with the gamma discharge factor and was thoroughly evaluated by exposing the electret radon detectors to known concentrations of radon.

Air Pollution, Radioactive↗
PubMed1995

Radionuclides in the Great Lakes basin.

The Great Lakes basin is of radiologic interest due to the large population within its boundaries that may be exposed to various sources of ionizing radiation. Specific radionuclides of interest in the basin arising from natural and artificial sources include 3H, 14C, 90Sr, 129I, 131I, 137Cs, 222Rn, 226Ra, 235U, 238U, 239Pu, and 241Am. The greatest contribution to total radiation exposure is the natural background radiation that provides an average dose of about 2.6 mSv/year to all basin residents. Global fallout from atmospheric nuclear weapons tests conducted before 1963 has resulted in the largest input of anthropogenic radioactivity into the lakes. Of increasing importance is the radionuclide input from the various components of the nuclear fuel cycle. Although the dose from these activities is currently very low, it is expected to increase if there is continued growth of the nuclear industry. In spite of strict regulations on design and operation of nuclear power facilities, the potential exists for a serious accident as a result of the large inventories of radionuclides contained in the reactor cores; however, these risks are several orders of magnitude less than the risks from other natural and man-made hazards. An area of major priority over the next few decades will be the management of the substantial amounts of radioactive waste generated by nuclear fuel cycle activities. Based on derived risk coefficients, the theoretical incidence of fatal and weighted nonfatal cancers and hereditary defects in the basin's population, attributable to 50 years of exposure to natural background radiation, is conservatively estimated to be of the order of 3.4 x 10(5) cases. The total number of attributable health effects to the year 2050 from fallout radionuclides in the Great Lakes basin is of the order of 5.0 x 10(3). In contrast, estimates of attributable health effects from 50 years of exposure to current nuclear fuel cycle effluent in the basin are of the order of 2 x 10(2). Although these are hypothetical risks, they show that the radiologic impact of man-made sources is very small compared to the effects of normal background radiation.

Environmental Exposure↗
PubMed1998

Dose-response function for lens forward light scattering after in vivo exposure to ultraviolet radiation.

BACKGROUND: It is known that different types of radiation, as well as aging and metabolic disorders, can cause cataract. Several epidemiological investigations show a correlation between cataract development and the dose of ultraviolet radiation (UVR) received. It is well established experimentally that exposure of animal eyes to UVR induces cataract. The purpose of the present study was to determine the dose-response function for UVR-induced opacities in the rat lens after in vivo exposure. METHODS: Sprague-Dawley rats received 0.1, 0.4, 1.3, 3, 5, 8 or 14 kJ/m2 UVR (lambda MAX = 300 nm, lambda 0.5 = 10 nm) unilaterally for 15 min. At 1 week after exposure both lenses were removed, photographs were taken and the intensity of forward-scattered light was measured. RESULTS: One week after UVR exposure, opacities occurred on the lens surface, as observed with a microscope. With increased UVR dose the opacities became more intense and occurred also in the equatorial area of the lens, but not in the nucleus. The intensity of forward light scattering increased with increased UVR dose between 3 and 14 kJ/m2. No significant change in intensity of forward light scattering was observed for lower UVR doses. CONCLUSION: The intensity of forward light scattering in the rat lens increase exponentially with increased UVR dose between 0.1 and 14 kJ/m2.

Animals↗
PubMed1990

Background gamma radiation and childhood cancers within ten miles of a US nuclear plant.

In light of some recent reports concerning childhood leukaemia near nuclear installations, we examined rates of cancer in children in relation to background gamma ray exposure. Data from a national monitoring programme around nuclear facilities were used to map the distribution of background gamma radiation for 69 small geographical subunits (average population 2300) within ten miles of one US nuclear plant. An association was found for incidence of childhood cancers as a whole (odds ratio (OR) = 2.4; 95% confidence limits (CL) 1.2, 4.6). For leukaemias specifically, the odds ratio was also elevated but confidence limits were very wide (OR = 2.4; 95% CL 0.5, 12.9). Analyses adjusting for sociodemographic characteristics of study tracts (population density and income) gave similar results; data on other risk factors were unavailable. Conventional risk models would not predict a detectable increase in childhood cancer from background gamma radiation, particularly not an increase of this magnitude. The large effect for solid tumours as well as leukaemias is also somewhat counter to expectation. Since a priori the association we observed was unlikely, it is important to know if similar trends in childhood cancer with background radiation are seen in other areas before rejecting chance or bias as an explanation for the result.

Accidents↗
PubMed2004

Soybean (Glycine max) pollen germination characteristics, flower and pollen morphology in response to enhanced ultraviolet-B radiation.

BACKGROUND AND AIMS: Ultraviolet-B (UV-B) radiation effect on reproductive parts of the plants has received little attention. We studied the influence of UV-B radiation on flower and pollen morphology, pollen production and in vitro pollen germination and tube growth of six genotypes of soybean (Glycine max). METHODS: Soybean genotypes were investigated by growing them under four levels of biologically effective UV-B radiation of 0 (control), 5, 10 and 15 kJ m(-2) d(-1) in sunlit controlled-environment chambers. KEY RESULTS: Reductions in lengths of flower, standard petal, and staminal column along with reduced pollen production, germination and tube growth were observed in all genotypes with increasing UV-B radiation. Combined response index (CRI), the sum of percentage relative responses in flower size, pollen production, pollen germination and tube growth due to UV-B radiation varied with UV-B dosage: -67 to -152 with 5 kJ m(-2) d(-1), -90 to -212 with 10 kJ m(-2) d(-1), and -118 to -248 with 15 kJ m(-2) d(-1) of UV-B compared to controls. Genotypes were classified based on the UV-B sensitivity index (USI) calculated as CRI per unit UV-B, where D 90-9216, DG 5630RR and D 88-5320 were classified as tolerant (USI > -7.43), and DP 4933RR, Stalwart III and PI 471938 were sensitive (USI < -7.43) in their response to UV-B radiation. Pollen grains produced in plants grown at 15 kJ m(-2) d(-1) UV-B radiation were shrivelled and lacked apertures compared to control and other UV-B treatments in both sensitive and tolerant genotypes, and the differences were more conspicuous in the sensitive genotype (PI 471938) than in the tolerant genotype (D 90-9216). The number of columellae heads of the exine was reduced with increasing UV-B radiation. CONCLUSIONS: Soybean genotypes varied in their reproductive response to UV-B radiation. The identified UV-B tolerant genotypes could be used in future breeding programmes.

Dose-Response Relationship, Radiation↗
PubMed1996

[The dominant lethal mutation test in the study of genetic risks of continuous exposure to low-dose ionizing radiation].

BACKGROUND: Dissension in data on the effectivity of ionizing radiation at a low-dose rate do not enable to judge the extent of the genetic risk of such exposition. This estimation, however, is especially important in cases of irradiation of female germ cells in which the lesions can cumulate and persist for a long period. OBJECTIVES: The aim of this study is to judge the mutagenic effectivity of continuous irradiation on the basis of a model experiment founded on the test of dominantly lethal mutations. METHODS: Sexually mature female ICR mice were continuously irradiated by gama rays at daily dose rates 0.01 and 0.05 Gy to a total accumulated dose of 1 Gy. The frequency of genetic lesions induced by irradiation in dictyotene oocytes was evaluated by means of the test of dominantly lethal mutations within the periods of 1-2 and 21-22 weeks after the ultimation of irradiation. RESULTS: Continuous irradiation significantly increased the frequency of dominantly lethal mutations in germ cells of female mice. Induced lesions manifest themselves mostly in form of increased values of preimplantation lethality. The level of dominantly lethal mutations persists on a significantly increased level also in the period of 21-22 weeks after the ultimation of irradiation. CONCLUSION: Continuous irradiation of female mice represents a significant risk factor which induces a long-term increase in frequency of genetic lesions in germ cells. The negative selection of lesions in the preimplantation period can be subsequently the cause of decreased reproductive abilities of irradiated animals. (Tab. 1, Fig. 2, Ref. 13.).

Animals↗
PubMed1997

What a surgeon needs to know about radiation.

BACKGROUND: A better understanding of the physical and biologic principles of radiation oncology, along with improvements in the technical and clinical aspects of this field, have been gained in recent years. Some of these aspects are presented, with an emphasis on their relevance to the oncologic surgeon. RESULTS: Recent innovations have improved our ability to deliver high radiation doses safely and to increase the therapeutic ratio of radiation. They include the concurrent administration of radiation sensitizers and chemotherapy, altered fractionation schemes, and the conformal delivery of radiation using sophisticated imaging and planning tools. CONCLUSIONS: The increasing efficacy of radiation, resulting from innovations described in this review and others, enhances the role of radiotherapy in the struggle against cancer.

Antineoplastic Agents↗
PubMed2005

Differential expression of melanoma-associated growth factors in keratinocytes and fibroblasts by ultraviolet A and ultraviolet B radiation.

BACKGROUND: Besides the direct DNA-damaging effects of ultraviolet (UV) radiation on cells, indirect effects on the microenvironment of the skin may facilitate melanoma development. A stimulation of growth factor production by cells in the immediate environment of melanocytes may lead to a paracrine activation and proliferation of melanocytes that in turn become more susceptible to transformation. OBJECTIVES: We investigated whether the expression of growth factors for melanocytes can be modulated in keratinocytes and fibroblasts by UVA or UVB. METHODS: After irradiation with different doses of UVA or UVB, protein expression of basic fibroblast growth factor (bFGF), endothelin (ET)-1, transforming growth factor (TGF)-beta1, platelet-derived growth factor (PDGF)-AA, stem cell factor (SCF) and hepatocyte growth factor (HGF) was analysed by quantitative enzyme-linked immunosorbent assay. The mRNA expression of bFGF and ET-1 was analysed by quantitative real-time reverse transcriptase-polymerase chain reaction. RESULTS: In keratinocytes, UVB and UVA increased bFGF protein levels up to 2.6-fold. This increase was paralleled by elevated mRNA levels. UVB also induced ET-1 protein up to 1.8-fold, while UVA led to an 80% decrease. Secreted TGF-beta1 and PDGF-AA were downregulated by UVA by less than 50%, while there was no significant alteration by UVB. Secreted SCF was not changed significantly by UVA or UVB. In fibroblasts, bFGF protein levels were increased 11-64-fold by UVA and 34-61-fold by UVB. This was paralleled by elevated mRNA levels for bFGF up to 2.7-fold. HGF protein was stimulated by UVA up to 2.8-fold and by UVB up to 6.7-fold, while TGF-beta1 protein was increased up to 2.7-fold by UVB and 1.7-fold by UVA. CONCLUSIONS: UVA and UVB can stimulate and inhibit the production of growth factors for melanocytes in keratinocytes and fibroblasts dependent on the cell type and wavelength. We show for the first time that UVA and UVB can activate bFGF, HGF and TGF-beta1 in fibroblasts, while bFGF was the most inducible factor both in fibroblasts and in keratinocytes. The induction of bFGF and HGF in fibroblasts by UVA suggests that stroma cells in the dermis may be involved in the UV activation of melanocytes via paracrine ways and thus promote melanoma development.

Cells, Cultured↗
PubMed2002

Subgingival calculus detection with fluorescence induced by 655 nm InGaAsP diode laser radiation.

BACKGROUND: It has been suggested that the 655 nm InGaAsP diode laser radiation can induce considerably higher amounts of fluorescence in subgingival calculus than in cementum. This in vitro study evaluated the use of fluorescence induced by the diode laser radiation for the detection of subgingival calculus. METHODS: The study sample consisted of 30 extracted molars, premolars, canines, and incisors. The root surface of each sample was partially covered with subgingival calculus. The source of laser radiation was an InGaAsP diode laser emitting visible radiation at a wavelength of 655 nm. The fluorescent radiation reflected from the cementum and calculus was detected by a photoelectric cell integrated within the diagnostic system. The samples were randomly assigned to 3 experimental groups of 10 teeth each for detection of calculus in various media. Specifically, the fluorescence was determined in air (group A), in electrolytic salt solution (group B), and in blood (group C). For each sample, the intensity of the fluorescent light was evaluated separately for cementum and calculus in triplicate measurements. The statistical analysis was performed using a t test at a level of significance of 5% (P<0.05). RESULTS: The intensities of fluorescence radiation emitted by cementum were 0.4 (+/-0.51) in air, 0.4 (+/-0.51) in electrolytic solution, and 2.13 (+/-0.59) in blood. For calculus, the relative intensities of fluorescence radiation were 54.1 (+/-29.09) in air, 60.77 (+/-28.35) in electrolytic salt solution, and 39.63 (+/-29.79) in blood. The differences in fluorescence between cementum and calculus within each experimental unit were significant (group A: P= 0.0002, group B: P= 0.0001, group C: P= 0.031). The intensity of fluorescence in calculus was also significantly different between the 3 experimental groups. CONCLUSION: The present study indicates that subgingival calculus can be reliably detected on extracted teeth using laser fluorescence induced by the 655 nm diode-laser radiation. In vivo studies are necessary to evaluate the clinical utility of this procedure.

Dental Calculus↗
PubMed1995

[Experience in dealing with artificial pacemaker patients during therapy with ionizing radiation].

BACKGROUND: During radiotherapy the pacemaker-patient is exceptionally endangered by ionising radiation, because a damaging impact on the pacemaker's circuit is possible. PATIENTS AND METHODS: Guided by experiences of long standing dealing with pacemaker-patients during radiotherapy in our medical centre, we demonstrate possibilities to accompany these patients with well coordinated interdisciplinary co-operation. So the possible risks by ionising radiation can be identified and restricted. Our investigations on explanted pacemakers will explain the influence on programmable pacemaker systems. Standard values for the dose of 9-MV-photons will be recommended. RESULTS: The radiation dose, the pacemaker system is exposed during radiotherapy, should be kept as small as possible by suitable methods (e. g. shielding, selection of radiation quality, shifting of the pacemaker system to a region of less doses), to ensure that the functions and the duration of life is not effected. Because of the different manufacturing technologies and the scattering of the product parameters within a homogeneous set of pacemakers we are not able to specify a guaranteed value for the radiation resistance. CONCLUSIONS: The doses of pacemaker should be as minimal as possible. The patient's pacemaker system has to be controlled in adequate periods, in particular during radiotherapy. If the accumulate dose on the pacemaker system exceeds 5 Gy despite of all efforts, the pacemaker should be exchanged after the radiotherapy.

Female↗
PubMed2000

Late total occlusion after intracoronary brachytherapy for patients with in-stent restenosis.

OBJECTIVES: The study sought to determine the incidence and predictors of late total occlusion (LTO, >30 days) in-patients with in-stent restenosis who were treated with intracoronary radiation. BACKGROUND: Intracoronary radiation both with beta and gamma emitters has been shown to reduce recurrent in-stent restenosis. METHODS: We reviewed the records of 473 patients who presented with in-stent restenosis and who were enrolled in various radiation protocols, whether randomized to placebo versus radiation or entered into registries. There were 165 placebo and 308 radiated patients, including both gamma and beta emitters. Maximum dose to the vessel wall was 30 to 55 Gy. Following radiation, all patients received antiplatelet therapy with aspirin and either ticlopidine or clopidogrel for one month. All patients completed at least six months of angiographic follow-up. RESULTS: The LTO was documented in 28 patients (9.1%) from the irradiated group versus 2 placebo patients (1.2%), p < 0.0001. The LTO rates were similar across studies and emitters. In the irradiated group, LTO presented as acute myocardial infarction in 12 patients (43%), unstable angina in 14 (50%), and asymptotic in 2 (7%). Mean time to LTO was 5.4 +/- 3.2 months in the irradiated group versus 4.5 +/- 2.1 in placebo patients (p = NS). The overall rate of restenting for the entire study group at the time of radiation was 48.6%. Importantly, new stents were placed in 82% of the irradiated and in 100% of the placebo patients who presented with LTO. Multivariate analysis determined that new stenting was the main predictor of LTO. CONCLUSIONS: Intracoronary radiation for patients with in-stent restenosis is associated with a high rate of LTO. Restenting may contribute late thrombosis. Prolonged antiplatelet therapy (up to six months) should be considered for these patients.

Angioplasty, Balloon, Coronary↗
PubMedDate not supplied

[Embryonic mortality of the root vole as an index of the effect of small doses of natural radioactivity on genetic processes in populations].

A study was made of the pre- and post-implantation death of (F2--F4) Microtus oeconomus progeny whose parents lived in territories where natural radiation background was increased (an exposition dose-rate of 3.6-144.0 pC/kg X s). The spontaneous rate of pre- and post-implantation death of progeny of irradiated (experimental) animals was higher than that of intact ones (control). The animals kept in conditions of chronic irradiation (46.2 pC/kg X s) exhibited a more pronounced discrepancy in embryonal death rate. It is suggested that genetic differences in the populations were responsible for different rate of embryonal death of the control and experimental animals.

Animals↗
PubMedDate not supplied

[Possible effect of natural radioactivity on the induction of glucokinase synthesis in the liver of developing rats].

A decrease in the induced synthesis of glucokinase in the liver, at the time of spontaneous appearance of the enzyme, was observed in suckling rats kept for 10 days in a chamber with a decreased (by 10 times) natural radiation background. No changes were noted in the glucokinase synthesis induction after restoration of natural radioactivity by introducing of uranium salts.

Animals↗
PubMed1993

[The radiobiological problems of low doses of radiation].

Radioactive contamination of biosphere has acquired a global character with strong tendency towards further enhancement of radionuclide concentration. The article deals with the modern views concerning biological threat of the enhanced technogenic radiative background.

Background Radiation↗