High-Accuracy Relative Biological Effectiveness Values Following Low-Dose Thermal Neutron Exposures Support Bimodal Quality Factor Response with Neutron Energy.

Theoretical evaluations indicate the radiation weighting factor for thermal neutrons differs from the current International Commission on Radiological Protection (ICRP) recommended value of 2.5, which has radiation protection implications for high-energy radiotherapy, inside spacecraft, on the lunar or Martian surface, and in nuclear reactor workplaces. We examined the relative biological effectiveness (RBE) of DNA damage generated by thermal neutrons compared to gamma radiation. Whole blood was irradiated by 64 meV thermal neutrons from the National Research Universal reactor. DNA damage and erroneous DNA double-strand break repair was evaluated by dicentric chromosome assay (DCA) and cytokinesis-block micronucleus (CBMN) assay with low doses ranging 6-85 mGy. Linear dose responses were observed. Significant DNA aberration clustering was found indicative of high ionizing density radiation. When the dose contribution of both the 14N(n,p)14C and 1H(n,γ)2H capture reactions were considered, the DCA and the CBMN assays generated similar maximum RBE values of 11.3 ± 1.6 and 9.0 ± 1.1, respectively. Consequently, thermal neutron RBE is approximately four times higher than the current ICRP radiation weighting factor value of 2.5. This lends support to bimodal peaks in the quality factor for RBE neutron energy response, underlining the importance of radiological protection against thermal neutron exposures.

Profound DNA methylomic differences between single- and multi-fraction alpha irradiations of lung fibroblasts.

BACKGROUND: Alpha (α)-radiation is a ubiquitous environmental agent with epigenotoxic effects. Human exposure to α-radiation at potentially harmful levels can occur repetitively over the long term via inhalation of naturally occurring radon gas that accumulates in enclosed spaces, or as a result of a single exposure from a nuclear accident. Alterations in epigenetic DNA methylation (DNAm) have been implicated in normal aging and cancer pathogenesis. Nevertheless, the effects of aberrations in the methylome of human lung cells following exposure to single or multiple α-irradiation events on these processes remain unexplored. RESULTS: We performed genome-wide DNAm profiling of human embryonic lung fibroblasts from control and irradiated cells using americium-241 α-sources. Cells were α-irradiated in quadruplicates to seven doses using two exposure regimens, a single-fraction (SF) where the total dose was given at once, and a multi-fraction (MF) method, where the total dose was equally distributed over 14 consecutive days. Our results revealed that SF irradiations were prone to a decrease in DNAm levels, while MF irradiations mostly increased DNAm. The analysis also showed that the gene body (i.e., exons and introns) was the region most altered by both the SF hypomethylation and the MF hypermethylation. Additionally, the MF irradiations induced the highest number of differentially methylated regions in genes associated with DNAm biomarkers of aging, carcinogenesis, and cardiovascular disease. The DNAm profile of the oncogenes and tumor suppressor genes suggests that the fibroblasts manifested a defensive response to the MF α-irradiation. Key DNAm events of ionizing radiation exposure, including changes in methylation levels in mitochondria dysfunction-related genes, were mainly identified in the MF groups. However, these alterations were under-represented, indicating that the mitochondria undergo adaptive mechanisms, aside from DNAm, in response to radiation-induced oxidative stress. CONCLUSIONS: We identified a contrasting methylomic profile in the lung fibroblasts α-irradiated to SF compared with MF exposures. These findings demonstrate that the methylome response of the lung cells to α-radiation is highly dependent on both the total dose and the exposure regimen. They also provide novel insights into potential biomarkers of α-radiation, which may contribute to the development of innovative approaches to detect, prevent, and treat α-particle-related diseases.

The evolution of radiobiology through the work of women scientists: the work of Christiane Ferradini.

PURPOSE: Pay tribute to Christiane Ferradini and highlight the importance of her work as a scientist. CONCLUSIONS: Christiane Ferradini was born in 1924 in the south of France. She graduated from the Paul Sabatier University in Toulouse, France. In 1947, she joined the Curie Laboratory of the Radium Institute (which was then under the leadership of Madame Irène Joliot-Curie) to pursue her doctoral research. After her defence in 1955, she commenced her journey dedicated to the advancement of science. She became an exceptional teacher. She led a research group that contributed, through many fruitful collaborations, to the opening of a new chapter in radiation biology and medicine. Together they shed light on free radical formation and their reactions with biomolecules. Christiane published a total of 190 scientific articles and 9 books. She died in 2002.

A pilot study of radiation-induced bystander effect in radio-adapting frogs at a radiologically contaminated site located on the chalk river laboratories property.

PURPOSE: To measure medium borne bystander effects, to study the influence of radioadaptive response (RAR) on bystander response, and to discover reliable radioresponsive biomarkers in radio-adapting frogs from Duke Swamp contaminated with an above-background radiation level and in naïve frogs from Twin Lake as the background control site. MATERIALS AND METHODS: Frogs were captured at Duke Swamp and Twin Lake and brought to the lab at the Canadian Nuclear Laboratories facility. Half of the frogs from each site were irradiated with 4 Gy while the other half of the frogs were left with no further radiation treatment. Frog bladders were removed and placed in sterile culture media. Upon arrival at McMaster University, the bladders were processed for tissue cultures. After 48 h, the culture media conditioned by the bladder explants were harvested for clonogenic reporter survival assay and calcium flux measurements for assessing bystander effects. HPV-G cells were used as bystander reporter cells in all radiation-induced bystander effect (RIBE) assays. The frog bladder cultures were incubated for another 10-12 days followed by immunochemical staining for bcl-2 and c-myc expressions to analyze cellular anti-apoptotic (pro-survival) and pro-apoptotic (pro-death) responses, respectively. RESULTS: Only culture media conditioned by bladders from 4-Gy-irradiated naïve frogs from Twin Lake induced bystander effects (reduction of HPV-G reporter cells' clonogenic survival and presence of strong calcium flux activities). The 4 Gy irradiation dose increased pro-apoptotic c-myc expression in naïve frogs' bladder explants. Culture media conditioned by bladders from radio-adapting frogs from Duke Swamp enhanced HPV-G's clonogenic survival and a 4 Gy irradiation challenge did not change the enhanced clonogenic survival nature nor induce calcium flux. In bladder explants from both control and 4-Gy-irradiated radio-adapting frogs, anti-apoptotic bcl-2 expression for pro-survival responses was ubiquitous while c-myc expression for pro-death responses was limited to a small fraction of cells. CONCLUSION: The clonogenic RIBE reporter assay using HPV-G and calcium flux measurements are useful diagnostic tools for RIBE assessment of field biological samples, specifically those from frogs. RAR induced by environmentally relevant low-dose radiation induces protective bystander response. Bcl-2 and c-myc are reliable biomarkers for evaluating low dose radiation responses in wild populations of amphibians. Overall, this pilot study emphasizes the importance of looking at non-targeted effects (NTEs) in natural populations of non-human biota that could be vulnerable to chronic low-dose radiation exposures.

Assessing effects of legacy nuclear waste on plants: Sensitive fern (Onoclea sensibilis) gametophyte viability at the Chalk River site.

We evaluated the effects of chronic exposure to environmental radiological contamination on the reproductive fitness of sensitive fern (Onoclea sensibilis) by quantifying viability in haploid gametophytes of spores collected from ferns from background and contaminated areas of the Chalk River site. Dose rates measured in situ at field sites ranged from 60 to 849 µGy h-1, with effects possible at the more contaminated sites (greater than 400 µGy h-1). Fern spores were also irradiated from 1 to 1000 Gy to develop dose-response curves. We found no effects on gametophyte viability at the most contaminated areas of the Chalk River site, where we estimated growing season doses of 0.3-3.7 Gy. Dose-response curves show evidence of hormesis, with an increase in gametophyte viability up to 10 Gy, followed by a rapid decline to no viable gametophytes at doses of 1000 Gy. The sensitive fern is not a radiosensitive plant species, but effects do occur within the normal range (10-1000 Gy) of most plant species, making it useful as a sentinel species from a community perspective. Sensitive fern spore germination is high and stable over field dose ranges, with effects primarily on gametophyte viability. This method shows promise as an effects monitoring tool for sites with radiological contamination.

Sr-90 soil to plant transfer factor reduction using calcium and polymer soil amendments.

Introducing calcium into soils can inhibit Sr-90 uptake by plants. To test the efficacy of calcium amendments on the inhibition of Sr-90 uptake by edible plants, a number of different calcium applications, including calcium nitrate, calcium thiosulfate and a mixture of both liquid solutions, were used in this study. Pea plants (Pisum sativum 'Sabre') grown in Sr-90 contaminated soil from seeds to maturity were watered with these calcium solutions. Two different polymers, one inert and one nutrient enriched, were incorporated into the contaminated soil where pea seeds were sowed to ascertain a continuous supply of calcium and essential nutrients. Results show that the heterogeneity of Sr-90 distribution in soil translated to disparate Sr-90 contents in plant tissues. However, on average, irrigation with calcium solutions in conjunction with the usage of polymers consistently yielded a reduction in Sr-90 uptake by the plants. The lowest soil-to-plant transfer factor (TF) values were measured in the edible pea part of the plant, followed by the flowers, roots, stems, pea shells and then leaves. TF values for pea shells were between 4.9 and 20.9, and between 0.3 and 2.8 for the peas. Results do not allow the identification of one particular chemical solution that would systematically be the best choice to minimize Sr-90 uptake.

Effects of in vivo exposure to tritium: a multi-biomarker approach using the fathead minnow, Pimephales promelas.

Tritium (3H) is a radioactive isotope of hydrogen. In the environment, the most common form of tritium is tritiated water (HTO). However, tritium can also be incorporated into organic molecules, forming organically bound tritium (OBT). The present study characterized the effects of tritium on the health of the fathead minnow, Pimephales promelas. Fish were exposed to a gradient of HTO (activity concentrations of 12,000, 25,000, and 180,000 Bq/L) and OBT using food spiked with tritiated amino acids (OBT only, with an activity concentration of 27,000 Bq/L). A combined exposure condition where fish were placed in 25,000 Bq/L water and received OBT through feed was also studied. Fish were exposed for 60 days, followed by a 60-day depuration period. A battery of health biomarkers were measured in fish tissues at seven time points throughout the 120 days required to complete the exposure and depuration phases. HTO and OBT were also measured in fish tissues at the same time points. Results showed effects of increasing tritium activity concentrations in water after 60 days of exposure. The internal dose rates of tritium, estimated from the tissue free-water tritium (TFWT) and OBT activity concentrations, reached a maximum of 0.65 µGy/h, which is relatively low considering background levels. No effects were observed on survival, fish condition, and metabolic indices (gonado-, hepato-, and spleno-somatic indexes (GSI, HSI, SSI), RNA/DNA and proteins/DNA ratios). Multivariate analyses showed that several biomarkers (DNA damages, micronucleus frequency, brain acetylcholinesterase, lysosomal membrane integrity, phagocytosis activity, and reactive oxygen species production) were exclusively correlated with fish tritium internal dose rate, showing that tritium induced genotoxicity, as well as neural and immune responses. The results were compared with another study on the same fish species where fish were exposed to tritium and other contaminants in natural environments. Together with the field study, the present work provides useful data to identify biomarkers for tritium exposure and better understand modes of action of tritium on the fathead minnow.

The establishment of a new culture of Hyalella azteca that would permit toxicity tests to be conducted on low-ionic strength waters.

The objective of the present study was to establish a culture of Hyalella azteca that could be used for laboratory toxicity testing in low-ionic strength waters with electrical conductivities of <200 µS/cm. A wild strain of H. azteca was collected from Twin Lake, a small seepage lake with an electrical conductivity of 81 ± 27 µS/cm located on the property of Chalk River Laboratories in Chalk River, Canada. To determine the minimum aqueous ion requirements for an optimal culturing medium for the Twin Lake strain, Twin Lake was monitored for water quality and ionic content over 4 yr. Water quality parameters were averaged and used to formulate a medium containing NaHCO3 , CaCl2 , MgSO4 , KCl, NaBr, NaF, and LiCl, with an electrical conductivity of 89 ± 3 µS/cm. By evaluating survival and reproduction, it was concluded that this artificial medium promoted survival and supported reproduction (10 ± 4 neonates/female/wk) of the Twin Lake amphipod. The Twin Lake strain of H. azteca can, therefore, be maintained in laboratory settings, and this allows for toxicity testing to be conducted on low-ionic strength waters. Environ Toxicol Chem 2019;38:585-590. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Cellular responses in rainbow trout (Oncorhynchus mykiss) reared in tritiated water and/or fed organically bound tritium.

For the evaluation of biological effects of low level chronic tritium exposure in fish, rainbow trout (Oncorhynchus mykiss) were exposed to tritiated water and/or fed a diet spiked with tritiated essential amino acids. Differences in fatty acid composition were noted following the tritium exposures. In addition, changes in response to a subsequent acute high dose of gamma radiation delivered in vitro were noted when evaluating DNA repair activity and fatty acid composition.

Effects of 90Sr on Tree Swallow Nestlings Near Groundwater Contaminant Plumes.

Discharge of groundwater contaminant plumes has created elevated concentrations of Sr in some aquatic sediments at Chalk River Laboratories. Tree swallows (Tachycenita bicolor) feed and supply their nestlings almost exclusively with airborne insects that developed as larvae in aquatic sediments. To monitor the uptake and test for potential detriment due to Sr in a terrestrial animal, we measured the gross beta concentrations in the bone of 12-d-old tree swallow nestlings in areas having sediments with elevated levels of gross beta (Sr and Y) and in several control areas where sediment gross beta was primarily due to naturally occurring K. Nesting behavior and reproductive success of the tree swallows were similar regardless of the gross beta concentrations in sediments near their nest boxes. Radiation can damage DNA and cause micronuclei to form in cells, so we examined the frequency of micronuclei in erythrocytes of nestlings. The formation of micronuclei in the erythrocytes of the nestlings was also similar wherever nestlings were analyzed. The results revealed no significant increases even near sediments with the highest gross beta levels. At Perch Lake, where Chalk River Laboratories has a large area of Sr-contaminated sediments, the bones of 12-d-old nestlings contained gross beta concentrations as high as 29 Bq g. This would produce a skeletal dose rate of 9 µGy h, which is one-fourth of the threshold dose rate of 40 µGy h, above which detriment could occur. Failing to find any indication of detriment in the field study, we irradiated wild eggs in the lab and returned them to their nest for natural incubation, hatching, and feeding by the parents. There was an increase in formation of micronuclei following a dose of 3.2 Gy, and the other results were consistent with existing literature.

Correlated responses for DNA damage, phagocytosis activity and lysosomal function revealed in a comparison between field and laboratory studies: Fathead minnow exposed to tritium.

Tritium entering the aquatic environment can confer a whole body internal radiological dose to aquatic organisms. Multiple stressors inherent in natural environments, however, confound estimates for observable radiation specific responses. To disentangle differences between field and laboratory outcomes to tritium exposures, a multivariate analysis comparing biomarkers for radiation exposure at the cellular level with changes in biological processes within tissues is described for fathead minnows (Pimephales promelas). Over tritium activity concentrations up to 180,000 Bq/L, DNA damage in the field were lower than DNA damage in the laboratory. This finding does not support an increase in morbidity of biota in field exposures. Energy deposited by tritium decay produces oxidised free radicals, yet the biological responses in brain, muscle and liver to oxidative stress differed between the studies and were not related to the tritium. For both studies, DNA damage in gonad and blood increased with increased tritium as did the fluorescence associated with lysosomal function in spleen. The studies differed in spleen phagocytosis activity were, in the laboratory but not the field, activity increased with increased tritium-and was correlatd with lysosomal function (Spearman coefficient of 0.98 (p = 0.001). The higher phagocytosis activity in the field reflects exposures to unmeasured factors that were not present within the laboratory. In the laboratory, DNA damage and lysosomal function were correlated: Spearman coefficients of 0.9 (Comet, p = 0.03) and 0.9 (micronuclei, p = 0.08). In the field, DNA damage by the Comet assay, but not by micronucleus frequency, correlated with lysosomal function: Spearman coefficients of 0.91 (Comet, p < 0.001) and 0.47 (micronuclei, p = 0.21). These observations highlight a need for better physiologic understanding of linkages between radiation-induced damage within cells and responses at higher levels of biological organization.

Is there a role for the adverse outcome pathway framework to support radiation protection?

PURPOSE: In 2012, the Organization for Economic Cooperation and Development (OECD) formally launched the Adverse Outcome Pathway (AOP) Programme. The AOP framework has the potential for predictive utility in identifying early biological endpoints linked to adverse effects. It uses the weight of correlative evidence to identify a minimal set of measurable key events that link molecular initiating events to an adverse outcome. AOPs have the capability to identify knowledge gaps and priority areas for future research based on relevance to an adverse outcome. In addition, AOPs can identify pathways that are common among multiple stressors, thereby allowing for the possibility of refined risk assessments based on co-exposure considerations. The AOP framework is increasingly being used in chemical and ecological risk assessment; however, its use in the development of radiation-specific pathways has yet to be fully explored. To bring awareness of the AOP framework to the Canadian radiation community, a workshop was held in Canada in June 2018 that brought together radiation experts from Health Canada, the Canadian Nuclear Laboratories, and the Canadian Nuclear Safety Commission. METHODS: The purpose of the workshop was to share knowledge on the AOP framework, specifically (1) to introduce the concept of the AOP framework and its possible utility to Canadian radiation experts; (2) to provide examples on how it has advanced risk assessment; (3) to discuss an illustrative example specific to ionizing radiation; and lastly (4) to identify the broad benefits and challenges of the AOP framework to the radiation community. RESULTS: The participants showed interest in the framework, case examples were described and areas of challenge were identified. Herein, we summarize the outcomes of the workshop. CONCLUSIONS: Overall, participants agreed that by building AOPs in the radiation field, a network of data-sharing initiatives will enhance our interpretation of existing knowledge where current scientific evidence is minimal. They would provide new avenues to understand effects at low-dose and dose-rates and help to quantify the combined effect of multiple stressors on shared mechanistic pathways.

Study of morphology, chemical, and amino acid composition of red deer meat.

AIM: The aim of this study was to evaluate red deer (maral) meat quality based on chemical composition, pH, water-binding capacity (WBC), and amino acid content. MATERIALS AND METHODS: Maral meat surface morphology measurements were obtained by scanning electron microscopy. Active acidity (pH) was determined by potentiometry. Samples were analyzed for WBC by exudation of moisture to a filter paper by the application of pressure. Chemical composition (moisture, protein, fat, and ash fractions) was obtained by drying at 150°C and by extraction, using ethylic ether, and ashing at 500-600°C. The amino acid composition was obtained by liquid chromatography. RESULTS: Maral meat, with a pH of 5.85 and an average moisture content of 76.82%, was found to be low in fat (2.26%). Its protein content was 18.71% while its ash content was 2.21%. The amino acid composition showed that lysine (9.85 g/100 g), threonine (5.38 g/100 g), and valine (5.84 g/100 g) predominated in maral meat, while phenylalanine (4.08 g/100 g), methionine (3.29 g/100 g), and tryptophan (0.94 g/100 g) were relatively low in maral meat compared to other meats. The average WBC was found to be 65.82% and WBC was found to inversely correlate with moisture content. CONCLUSION: Low-fat content, high mineral content, and balanced amino-acid composition qualify maral meat as a worthy dietary and functional food.

Spatial Autocorrelation, Source Water and the Distribution of Total and Viable Microbial Abundances within a Crystalline Formation to a Depth of 800 m.

Proposed radioactive waste repositories require long residence times within deep geological settings for which we have little knowledge of local or regional subsurface dynamics that could affect the transport of hazardous species over the period of radioactive decay. Given the role of microbial processes on element speciation and transport, knowledge and understanding of local microbial ecology within geological formations being considered as host formations can aid predictions for long term safety. In this relatively unexplored environment, sampling opportunities are few and opportunistic. We combined the data collected for geochemistry and microbial abundances from multiple sampling opportunities from within a proposed host formation and performed multivariate mixing and mass balance (M3) modeling, spatial analysis and generalized linear modeling to address whether recharge can explain how subsurface communities assemble within fracture water obtained from multiple saturated fractures accessed by boreholes drilled into the crystalline formation underlying the Chalk River Laboratories site (Deep River, ON, Canada). We found that three possible source waters, each of meteoric origin, explained 97% of the samples, these are: modern recharge, recharge from the period of the Laurentide ice sheet retreat (ca. ∼12000 years before present) and a putative saline source assigned as Champlain Sea (also ca. 12000 years before present). The distributed microbial abundances and geochemistry provide a conceptual model of two distinct regions within the subsurface associated with bicarbonate - used as a proxy for modern recharge - and manganese; these regions occur at depths relevant to a proposed repository within the formation. At the scale of sampling, the associated spatial autocorrelation means that abundances linked with geochemistry were not unambiguously discerned, although fine scale Moran's eigenvector map (MEM) coefficients were correlated with the abundance data and suggest the action of localized processes possibly associated with the manganese and sulfate content of the fracture water.

Cs-137 in milk, vegetation, soil, and water near the former Soviet Union's Semipalatinsk Nuclear Test Site.

The present study was carried out to evaluate Cs-137 activity concentration in soil, water, vegetation, and cow's milk at 10 locations within three regions (Abai, Ayaguz, and Urdzhar) to the southeast of the Semipalatinsk Nuclear Test Site (SNTS) in Kazakhstan. Cs-137 activity concentrations, determined using a pure Ge gamma-ray spectrometer, showed that, all samples collected did not exceed the National maximum allowable limits of 10,000 Bq/kg for soil, 100 Bq/kg for cow's milk, 74 Bq/kg for vegetation, and 11 Bq/kg for water. Cs-137 is, therefore, not considered a health hazard in these regions. The highest levels of contamination were found in the Abai region, where the highest activity concentration of Cs-137 was 18.0 ± 1.0 Bq/kg in soil, 7.60 ± 0.31 Bq/kg in cow's milk, 4.00 ± 0.14 Bq/kg in the vegetation, and 3.00 ± 0.24 Bq/kg in water. The lowest levels were measured within the Urdzhar region, where 4.00 ± 0.14 Bq/kg was found in the soil, 0.30 ± 0.02 Bq/kg in the cow's milk, 1.00 ± 0.03 Bq/kg in the vegetation, and 0.20 ± 0.02 Bq/kg in the water.

Interlaboratory evaluation of the assessment of arsenic bioaccumulation from field collected sediments using Hexagenia spp.

Standardized bioaccumulation testing of aquatic organisms is essential to understanding the impact of historical contamination on the quality of water and sediment. A standardized 28-d laboratory bioaccumulation method with a freshwater burrowing mayfly, Hexagenia spp., has been developed and internally validated by the Ontario Ministry of the Environment and Climate Change (MOECC). An interlaboratory comparison was conducted to assess the precision of this method. Field-collected sediment contaminated with arsenic was chosen for the present study. Control and test sediments were subsampled and sent to 6 laboratories to perform the bioaccumulation test. One laboratory failed to meet the control survival criterion of ≥80%. When results of this laboratory are removed from the arsenic accumulation assessment, the mean interlaboratory variability (expressed as coefficient of variation) of the arsenic whole-body concentration is reduced from 44% to 24% in the test sediment-exposed Hexagenia spp. There was no significant interlaboratory difference between the Hexagenia spp. arsenic accumulations. While improved culturing and organism holding guidance may increase laboratory success, the MOECC Hexagenia spp. bioaccumulation test method has tight biological method precision when the control survival criterion is met. Environ Toxicol Chem 2016;35:2448-2455. © 2016 SETAC.

Biological effects of tritium on fish cells in the concentration range of international drinking water standards.

PURPOSE: To evaluate whether the current Canadian tritium drinking water limit is protective of aquatic biota, an in vitro study was designed to assess the biological effects of low concentrations of tritium, similar to what would typically be found near a Canadian nuclear power station, and higher concentrations spanning the range of international tritium drinking water standards. MATERIALS AND METHODS: Channel catfish peripheral blood B-lymphoblast and fathead minnow testis cells were exposed to 10-100,000 Bq l(-1) of tritium, after which eight molecular and cellular endpoints were assessed. RESULTS: Increased numbers of DNA strand breaks were observed and ATP levels were increased. There were no increases in γH2AX-mediated DNA repair. No differences in cell growth were noted. Exposure to the lowest concentrations of tritium were associated with a modest increase in the viability of fathead minnow testicular cells. Using the micronucleus assay, an adaptive response was observed in catfish B-lymphoblasts. CONCLUSIONS: Using molecular endpoints, biological responses to tritium in the range of Canadian and international drinking water standards were observed. At the cellular level, no detrimental effects were noted on growth or cycling, and protective effects were observed as an increase in cell viability and an induced resistance to a large challenge dose.

Local and Regional Diversity Reveals Dispersal Limitation and Drift as Drivers for Groundwater Bacterial Communities from a Fractured Granite Formation.

Microorganisms found in terrestrial subsurface environments make up a large proportion of the Earth's biomass. Biogeochemical cycles catalyzed by subsurface microbes have the potential to influence the speciation and transport of radionuclides managed in geological repositories. To gain insight on factors that constrain microbial processes within a formation with restricted groundwater flow we performed a meta-community analysis on groundwater collected from multiple discrete fractures underlying the Chalk River Laboratories site (located in Ontario, Canada). Bacterial taxa were numerically dominant in the groundwater. Although these were mainly uncultured, the closest cultivated representatives were from the phenotypically diverse Betaproteobacteria, Deltaproteobacteria, Bacteroidetes, Actinobacteria, Nitrospirae, and Firmicutes. Hundreds of taxa were identified but only a few were found in abundance (>1%) across all assemblages. The remainder of the taxa were low abundance. Within an ecological framework of selection, dispersal and drift, the local and regional diversity revealed fewer taxa within each assemblage relative to the meta-community, but the taxa that were present were more related than predicted by chance. The combination of dispersion at one phylogenetic depth and clustering at another phylogenetic depth suggest both niche (dispersion) and filtering (clustering) as drivers of local assembly. Distance decay of similarity reveals apparent biogeography of 1.5 km. Beta diversity revealed greater influence of selection at shallow sampling locations while the influences of dispersal limitation and randomness were greater at deeper sampling locations. Although selection has shaped each assemblage, the spatial scale of groundwater sampling favored detection of neutral processes over selective processes. Dispersal limitation between assemblages combined with local selection means the meta-community is subject to drift, and therefore, likely reflects the differential historical events that have influenced the current bacterial composition. Categorizing the study site into smaller regions of interest of more closely spaced fractures, or of potentially hydraulically connected fractures, might improve the resolution of an analysis to reveal environmental influences that have shaped these bacterial communities.

Health, growth and reproductive success of mice exposed to environmentally relevant levels of Ra-226 via drinking water over multiple generations.

PURPOSE: To assess health, growth and reproductive success of mammals exposed for multiple generations to levels of radium-226 known to occur in environments surrounding uranium mines and mills in Canada. METHODS: The study consisted of a control group and four treatment groups each containing 40 mice (20 males and 20 females) of the CBA/CaJ strain that were continuously exposed to a range of radium-226 levels via drinking water. Breeding was at 8-10 weeks of age and the study was concluded after three breeding cycles. RESULTS: When compared to control mice, constant consumption of drinking water containing 0.012, 0.076, 0.78 and 8.0 Bq/l of radium-226 over four generations of mice did not demonstrably affect physical condition, weight, pregnancy rate, number of pups per litter, sex ratio and bodyweight gain of pups. Between generations, the observed differences in pregnancy rates that were noted in all groups, including controls, seemed to directly correlate with the weight and age of the females at breeding. CONCLUSIONS: Based on the endpoints measured on four generations of mice, there is no indication that the consumption of radium-226 via drinking water (at activity concentrations up to 8.0 Bq/l) affects health, growth and reproductive fitness.

Use of Neonatal Fostering To Remove Helicobacter spp. from Deer Mice (Peromyscus maniculatus).

Helicobacter species can be found in a wide variety of animals and remain common contaminants of laboratory rodents. Fostering of neonatal pups has been used to eliminate Helicobacter spp. from various laboratory rodents, including laboratory mice and gerbils. Deer mice (Peromyscus maniculatus) from a captive colony enzootic for at least one Helicobacter species were mated, and the pups produced were fostered on laboratory mice 24 h after birth. After 2 rounds of fostering, both foster dams and pups were free of Helicobacter spp. as determined by fecal PCR analysis. Removal of Helicobacter infection through neonatal fostering has not been described previously for Peromyscus maniculatus.