Multiple stressor effects of radiation and metals in salmon (Salmo salar)

These experiments were designed to look at the cellular effects in key organs in Atlantic salmon (Salmo salar) after exposure in vivo to radiation and subtoxic levels of aluminum (Al) and cadmium (Cd), alone or in combination. Salmon (25g) were exposed to a single 0.5Gy dose of gamma-irradiation in water containing Cd, Al or Cd+Al. Three fish per group were sacrificed after 1h and the liver, pronephros, fin and gill of each was dissected. Small explants of each tissue were set up. After 2 days, the culture medium was harvested and filtered then placed on a reporter cell line for determination of stress signal activity (bystander effects). Radiation in combination with Cd and/or Al, caused bystander effects in tissues harvested from in vivo exposed salmon. The effects vary between different organs and are not consistently additive or synergistic for a given treatment. Tissue type appears to be critical. Liver cultures produce a toxic factor which is lethal to reporter cells, and therefore no liver data could be obtained. It is hoped that this stress signal response will prove to be a useful indicator of environmental stress in species inhabiting aquatic ecosystems.     

Effects of gamma irradiation on Holcus lanatus (Yorkshire fog grass) and associated soil microorganisms

An investigation was conducted to determine the impact of acute doses of gamma radiation on the microbial community structure of a Holcus lanatus dominated grassland soil. Mesocosms containing soil and established grass were irradiated using a sealed (137)Cs source (7.0 Gy min(-1)). Doses ranged from 5 to 160 Gy, analyses were conducted on the day of irradiation, then 7 and 30 days later. Plant growth and arbuscular mycorrhizal fungal colonisation of roots were reduced by irradiation. Gram-negative bacteria, and microbial metabolic capacity were also negatively affected by treatment. Microbial biomass measured by phospholipid fatty acid (PLFA) analysis, showed an increase at doses above 20 Gy, 7 and 30 days after treatment. Proportions of Gram-positive bacterial and fungal PLFAs fluctuated inversely to each other, in response to both sampling time and radiation dose. We hypothesise that many of the observed soil microbial responses are indirect effects mediated by the influence of ionising radiation on the plants in this system.     

Cytogenetic dose-response and adaptive response in cells of ungulate species exposed to ionizing radiation

In the studies reported here, the micronucleus assay, a common cytogenetic technique, was used to examine the dose-responses in fibroblasts from three ungulate species (white-tailed deer, woodland caribou, and Indian muntjac) exposed to high doses of ionizing radiation (1-4 Gy of (60)Co gamma radiation). This assay was also used to examine the effects of exposure to low doses (1-100 mGy) typical of what these species experience in a year from natural and anthropogenic environmental sources. An adaptive response, defined as the induction of resistance to a stressor by a prior exposure to a small "adapting" stress, was observed after exposure to low doses. This work indicates that very small doses are protective for the endpoint examined. The same level of protection was seen at all adapting doses, including 1 radiation track per cell, the lowest possible cellular dose. These results are consistent with other studies in a wide variety of organisms that demonstrate a protective effect of low doses at both cellular and whole-organism levels. This implies that environmental regulations predicated on the idea that even the smallest dose of radiation carries a quantifiable risk of direct adverse consequences to the exposed organism require further examination. Cytogenetic assays provide affordable and feasible biological effects-based alternatives that are more biologically relevant than traditional contaminant concentration-based radioecological risk assessment.     

High background radiation areas of Ramsar in Iran: evaluation of DNA damage by alkaline single cell gel electrophoresis (SCGE)

The hot springs in special areas in Ramsar, a northern coastal town in Iran, contain (226)Ra and (222)Rn. The natural radiation effects, radiosensitivity or adaptive responses, on the inhabitants of high natural radiation in Ramsar were studied. The single cell gel electrophoresis was used to monitor DNA damages. Three groups of volunteers were selected, one from high natural background radiation areas as the case group and two from normal background radiation areas as controls (control 1 and control 2). The latter one had the similar living situation to case group while the other (control 2) had different living situation from the other groups. Peripheral blood mononuclear cells (PMNCs) were separated and irradiated by (60)Co source at five different gamma doses. It was found that the spontaneous level of DNA damage and the induced DNA damage in all challenging doses in case group was considerably higher than control groups (p < 0.05). On the other hand, the repair rate in those volunteers, who received less than 10.2 mSv/y was significantly more than the control groups. In the contrary, individuals who live in homes with more than 10.2 mSv/y had incomplete repair. Additionally the plasma and urinary levels of vitamin C were measured spectrophotometrically. Although the concentration of vitamin C of plasma was equal in case and control 1 groups, the urinary level of vitamin C was found to be lower in the case group.     

Effects of acute γ-irradiation on community structure of the aquatic microbial microcosm

To characterise indirect effects of ionising radiation on aquatic microbial communities, effects of acute γ-irradiation were investigated in a microcosm consisting of populations of green algae (Chlorella sp. and Scenedesmus sp.) and a blue-green alga (Tolypothrix sp.) as producer; a ciliate protozoan (Cyclidium glaucoma), rotifers (Lecane sp. and Philodina sp.) and an oligochaete (Aeolosoma hemprichi) as consumer; and more than four species of bacteria as decomposers. Population changes in the constituent organisms were observed over 160 days after irradiation. Prokaryotic community structure was also examined by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA. Principle response curve analysis revealed that the populations of the microcosm as a whole were not significantly affected at 100 Gy while they were adversely affected at 500-5000 Gy in a dose-dependent manner. However, some effects on each population, including each bacterial population detected by DGGE, did not depend on radiation doses, and some populations in the irradiated microcosm were larger than those of the control. These unexpected results are regarded as indirect effects through interspecies interactions, and possible mechanisms are proposed originating from population changes in other organisms co-existing in the microcosm. For example, some indirect effects on consumers and decomposers likely arose from interspecies competition within each trophic level. It is also likely that prey-predator relationships between producers and consumers caused some indirect effects on producers.     

Terrestrial isopods congregate under a low-level beta-emitter source

Ionizing radiation is ubiquitous, but very few experiments have investigated the biological effects of the natural background radiation at very low doses (>10 mGy/yr). We examined whether the background radiation, or radiation of a slightly higher level, has a role in evoking changes in behaviors of terrestrial isopods (woodlice). Upon exposure to a source giving 15 times the background level placed at one end of a box, a significant increase in the number of woodlice gathering under the beta-source was observed with time, as compared with the sham control. Terrestrial isopods have chemoreceptors (the olfactory system) on the terminal segment of their antennae. An additional experiment confirmed the involvement of these antennae in the radiation effect on behavior. After the excision of the antennae, no beta-taxis response was observed. The behavior of the group exposed to the source giving 30 times the background tended to decrease gradually in the area of the source, and the individuals aggregated in the area away from the source. Thus, the olfactory sensor in the antennae may be an important organ involved in the prompt response to radiation exposure, and the discrimination of the radiation field strengths of radioisotopes.     

Effects of acute γ-irradiation on the aquatic microbial microcosm in comparison with chemicals

Effects of acute γ-irradiation were investigated in the aquatic microcosm consisting of green algae (Chlorella sp. and Scenedesmus sp.) and a blue–green alga (Tolypothrix sp.) as producers; an oligochaete (Aeolosoma hemprichi), rotifers (Lecane sp. and Philodina sp.) and a ciliate protozoan (Cyclidium glaucoma) as consumers; and more than four species of bacteria as decomposers. At 100 Gy, populations were not affected in any taxa. At 500–5000 Gy, one or three taxa died out and populations of two or three taxa decreased over time, while that of Tolypothrix sp. increased. This Tolypothrix sp. increase was likely an indirect effect due to interspecies interactions. The principal response curve analysis revealed that the main trend of the effects was a dose-dependent population decrease. For a better understanding of radiation risks in aquatic microbial communities, effect doses of γ-rays compared with copper, herbicides and detergents were evaluated using the radiochemoecological conceptual model and the effect index for microcosm.     

Genomic instability in human osteoblast cells after exposure to depleted uranium: delayed lethality and micronuclei formation

It is known that radiation can induce a transmissible persistent destabilization of the genome. We have established an in vitro cellular model using HOS cells to investigate whether genomic instability plays a role in depleted uranium (DU)-induced effects. Transmissible genomic instability, manifested in the progeny of cells exposed to ionizing radiation, has been characterized by de novo chromosomal aberrations, gene mutations, and an enhanced death rate. Cell lethality and micronuclei formation were measured at various times after exposure to DU, Ni, or gamma radiation. Following a prompt, concentration-dependent acute response for both endpoints, there was de novo genomic instability in progeny cells. Delayed reproductive death was observed for many generations (36 days, 30 population doublings) following exposure to DU, Ni, or gamma radiation. While DU stimulated delayed production of micronuclei up to 36 days after exposure, levels in cells exposed to gamma-radiation or Ni returned to normal after 12 days. There was also a persistent increase in micronuclei in all clones isolated from cells that had been exposed to nontoxic concentrations of DU. While clones isolated from gamma-irradiated cells (at doses equitoxic to metal exposure) generally demonstrated an increase in micronuclei, most clonal progeny of Ni-exposed cells did not. These studies demonstrate that DU exposure in vitro results in genomic instability manifested as delayed reproductive death and micronuclei formation.     

Adaptive response in frogs chronically exposed to low doses of ionizing radiation in the environment

Using the micronucleus assay, decreased levels of DNA damage were found after high dose ionizing radiation exposure of liver cells taken from frogs inhabiting a natural environment with above-background levels of ionizing radiation, compared to cells taken from frogs inhabiting background areas. The data obtained from a small number of animals suggest that stress present in the above-background environment could induce an adaptive response to ionizing radiation. This study did not reveal harmful effects of exposure to low levels of radioactivity. On the contrary, stress present in the above-background area may serve to enhance cellular defense mechanisms.     

An estimation of radiation doses to benthic invertebrates from sediments collected near a Canadian uranium mine.

A new method is described for calculating radiation doses to benthic invertebrates from radionuclide concentrations in freshwater sediment. Both internal and external radiation doses were estimated for all 14 principal radionuclides of the uranium-238 decay series. Sediments were collected from three sites downstream of a uranium mining operation in northern Saskatchewan, Canada. Sediments from two sites, located approximately 1.6 and 4.4 km downstream from mining operations, yielded absorbed doses to both larval midges, Chironomus tentans, and adult amphipods, Hyalella azteca, of 59-60 and 19 mGy/year, respectively, compared to 3.2 mGy/year for a nearby control site. External beta radiation from protactinium-234 (234Pa) and alpha radiation from uranium (U) contributed most of the dose at the impacted sites, whereas polonium-210 (210Po) was most important at the control site. If a weighting factor of 20 was employed for the greater biological effect of alpha vs. beta and gamma radiation, then total equivalent doses rose to 540-560 mGy/year at the site closest to uranium operations. Such equivalent doses are above the 360-mGy/year no-observed-effect level for reproductive effects in vertebrates from gamma radiation exposure. Data are not available to determine the effect of such doses on benthic organisms, but they are high enough to warrant concern. Detrimental effects have been observed in H. azteca at similar uranium concentration in laboratory toxicity tests, but it remains unclear whether the radiotoxicity or the chemotoxicity of uranium is responsible for these effects.     

Impact of gamma irradiation on the transformation efficiency for extracellular plasmid DNA

Extracellular DNA is omnipresent in aquatic environments and is thought to be a genetic material for horizontal gene transformation between microorganisms. We studied the impact of gamma irradiation on the transformation efficiency (transformants number per ng of DNA per ml) of extracellular DNA. Plasmid pEGFP as a model extracellular DNA was irradiated by gamma rays. The transformation efficiency decreased with the increase in radiation dose. A total dose of 10Gy is normally not lethal for microorganisms but certainly affects the transformation efficiency of extracellular DNA. The decrease in the efficiency would be induced by strand breaks of extracellular DNA because the yield of both single-strand breaks (SSBs) and double-strand breaks (DSBs) increased with the increase in radiation dose. The relative transformation efficiency of SSBs and DSBs to that of covalently closed circles (CCCs) was 30.3% and 0.2%, respectively. This impact on natural transformation suggests an inability of microorganisms to acquire new characteristics which should be normally acquired.     

Chronic exposure to gamma radiation of wild populations of meadow voles (Microtus pennsylvanicus)

Free-ranging, wild meadow voles (Microtus pennsylvanicus) were exposed to gamma radiation from a (137)Cs irradiator in a series of experiments conducted on six 1-ha meadows within a mixed deciduous forest in Manitoba, Canada. Over a period of 1-1.5 years in each of three experiments, vole populations were monitored with capture-mark-release techniques at nominal exposure rates of 200x, 9000x and 40,000x background. No effects on population or individual characteristics were detected up to the highest exposure rate (81 mGy/d). At this level, third generation voles were monitored up to a lifetime dose of about 5.7 Gy, at a measured dose rate of 44 mGy/d. Smaller numbers of overwintered animals survived and reproduced normally at doses up to 10 Gy. These results are discussed in terms of low-LET, external chronic radiation effects on rodents in the laboratory and the field, relative to current views on appropriate benchmarks for the protection of biota.     

Organic compounds in tire particle induce reactive oxygen species and heat-shock proteins in the human alveolar cell line A549

Debris produced from the attrition of tires of motor vehicles constitutes 5-7% of the atmospheric particulate matter (PM10). Debris particles are indeed small enough to enter human lung and thus morphological and chemical characterization has been performed. We demonstrated that the organic fraction of tire debris induces a dose-dependent increase in cell mortality, DNA damage, as well as a significant modification of cell morphology at the dose of 60 microg/ml, which may correspond to the quantity present in the air humans inhale daily. The present research aims at investigating if reactive oxygen species (ROS) production and Hsp70 expression are involved in the cascade of toxic effects produced on the A549 cell line, as it has been suggested for the ultrafine atmospheric particles and diesel exhaust. To this end, cells were exposed at the doses of 10, 50, 60, 75 microg/ml of TD organic extract (TDOE) and analyzed at different exposure time. ROS were detected by the oxidation of 2'7'-dichlorodihydrofluorescein diacetate to dichlorofluorescein, and fluorescence was measured by flow cytometry. Hsp70 protein expression was determined by immunochemical analysis, and protein expression quantification performed by optical densitometry. ROS production was analysed after 2 h of treatment. A statistically significant increase in fluorescence was observed and the intensity of the stress response was parallel to the increasing concentrations used. An evident increase of Hsp70 expression at lower doses (10, 50 microg/ml) and at longer exposure times (72 h) was observed, during the time that our previous studies showed that cell viability, plasma membrane integrity, and DNA molecules were not affected. Thus it can be deduced that the increase in Hsp70 expression protected the cells from those damages, which became evident at the higher doses, and that this parameter might be used as a sensitive indicator of exposure. These data suggest that ROS production may be the first event caused by A549 exposure to TDOE and this result is in line with other evidences provided for the role of ROS generation in ultrafine PM toxicity. It can be suggested that this event induces an overexpression of Hsp70 only at the lower doses and longer exposure time, when cells still appear unaffected. Subsequently when ROS generation reaches high levels, a general inhibition of protein synthesis probably occurs, culminating in cell toxicity.     

Derivation of hazardous doses for amphibians acutely exposed to ionising radiation

Derivation of effect benchmark values for each taxonomic group, which has been difficult due to lack of experimental effects data, is required for more adequate protection of the environment from ionising radiation. Estimation of effects doses from nuclear DNA mass and subsequent species sensitivity distribution (SSD) analysis were proposed as a method for such a derivation in acute irradiation situations for assumed nuclear accident scenarios. As a case study, 5% hazardous doses (HD₅s), at which only 5% of species are acutely affected at 50% or higher lethality, were estimated on a global scale. After nuclear DNA mass data were obtained from a database, 50% lethal doses (LD₅₀s) for 4.8 and 36% of the global Anura and Caudata species, respectively, were estimated by correlative equations between nuclear DNA mass and LD₅₀s. Differences between estimated and experimental LD₅₀s were within a factor of three. The HD₅s obtained by the SSD analysis of these estimated LD₅₀s data were 5.0 and 3.1 Gy for Anura and Caudata, respectively. This approach was also applied to the derivation of regional HD₅s. The respective HD₅s were 6.5 and 3.2 Gy for Anura and Caudata inhabiting Japan. This HD₅ value for the Japanese Anura was significantly higher than the global value, while Caudata had no significant difference in global and Japanese HD₅s. These results suggest that this approach is also useful for derivation of regional benchmark values, some of which are likely different from the global values.     

淡水养殖水体溶解氧含量诊断分析及浮头泛塘气象预报

通过实时监测荆州农试站养殖塘各种水质要素，结合2011~2012年养殖塘发生的25个鱼泛塘实例，探讨了养殖水体溶解氧含量与气象要素之间的联系。分析表明:养殖水体溶解氧含量与6 h变温、总辐射量、气压值正相关，与水温、空气相对湿度值负相关。从平时的调查记录来看，鱼泛塘事件主要发生在5~10月间，湿度大、气温低、气压下降、日照强度弱等都会引起溶解氧含量低，严重的会诱发鱼泛塘。根据25个鱼泛塘实例，结合气象要素的特点，提出了急剧降温降压型、寡照型、高温高热型3种鱼泛塘发生条件的概念模型，分别以实例进行了验证，并初步总结出根据气象要素观测资料进行浮头泛塘预报的方法和流程     

In vitro screening for population variability in toxicity of pesticide-containing mixtures

Population-based human in vitro models offer exceptional opportunities for evaluating the potential hazard and mode of action of chemicals, as well as variability in responses to toxic insults among individuals. This study was designed to test the hypothesis that comparative population genomics with efficient in vitro experimental design can be used for evaluation of the potential for hazard, mode of action, and the extent of population variability in responses to chemical mixtures. We selected 146 lymphoblast cell lines from 4 ancestrally and geographically diverse human populations based on the availability of genome sequence and basal RNA-seq data. Cells were exposed to two pesticide mixtures – an environmental surface water sample comprised primarily of organochlorine pesticides and a laboratory-prepared mixture of 36 currently used pesticides – in concentration response and evaluated for cytotoxicity. On average, the two mixtures exhibited a similar range of in vitro cytotoxicity and showed considerable inter-individual variability across screened cell lines. However, when in vitro-to-in vivo extrapolation (IVIVE) coupled with reverse dosimetry was employed to convert the in vitro cytotoxic concentrations to oral equivalent doses and compared to the upper bound of predicted human exposure, we found that a nominally more cytotoxic chlorinated pesticide mixture is expected to have greater margin of safety (more than 5 orders of magnitude) as compared to the current use pesticide mixture (less than 2 orders of magnitude) due primarily to differences in exposure predictions. Multivariate genome-wide association mapping revealed an association between the toxicity of current use pesticide mixture and a polymorphism in rs1947825 in C17orf54. We conclude that a combination of in vitro human population-based cytotoxicity screening followed by dosimetric adjustment and comparative population genomics analyses enables quantitative evaluation of human health hazard from complex environmental mixtures. Additionally, such an approach yields testable hypotheses regarding potential toxicity mechanisms.     

Ecological effects of various toxic agents on the aquatic microcosm in comparison with acute ionizing radiation

The purpose of this study was an evaluation of the effect levels of various toxic agents compared with acute doses of ionizing radiation for the experimental model ecosystem, i.e., microcosm mimicking aquatic microbial communities. For this purpose, the authors used the microcosm consisting of populations of the flagellate alga Euglena gracilis as a producer, the ciliate protozoan Tetrahymena thermophila as a consumer and the bacterium Escherichia coli as a decomposer. Effects of aluminum and copper on the microcosm were investigated in this study, while effects of gamma-rays, ultraviolet radiation, acidification, manganese, nickel and gadolinium were reported in previous studies. The microcosm could detect not only the direct effects of these agents but also the community-level effects due to the interspecies interactions or the interactions between organisms and toxic agents. The authors evaluated doses or concentrations of each toxic agent which had the following effects on the microcosm: (1) no effects; (2) recognizable effects, i.e., decrease or increase in the cell densities of at least one species; (3) severe effects, i.e., extinction of one or two species; and (4) destructive effects, i.e., extinction of all species. The resulting effects data will contribute to an ecological risk assessment of the toxic agents compared with acute doses of ionizing radiation.     

Ecogenetic Characteristics of Dandelion (Taraxacum officinale s.l.) Populations from the Techa River Floodplain Ecosystems

This study looks into T. officinale cenopopulations growing in the Techa River floodplain under conditions of chronic low-dose irradiation. It has been shown that the left-bank and right-bank cenopopulations differ from one another, as well as from the control (background) population, in the allozyme structure, viability, and radioresistance of the seed progeny and the mechanisms of antioxidant protection. In nature, cenopopulations differing in their phenogenetic structure may have different strategies of adaptation to the chronic influence of low radiation doses against the background of changing environmental conditions. The consequences of irradiation for such cenopopulations, including the viability and radiosensitivity of their seed progenies, may also differ considerably.