Publications by authors named "Natacha Hogan"

41 Publications

Toxicokinetic Models for Bioconcentration of Organic Contaminants in Two Life Stages of White Sturgeon ().

Environ Sci Technol 2021 09 12;55(17):11590-11600. Epub 2021 Aug 12.

Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada.

The white sturgeon () is an endangered ancient fish species that is known to be particularly sensitive to certain environmental contaminants, partly because of the uptake and subsequent toxicity of lipophilic pollutants prone to bioconcentration as a result of their high lipid content. To better understand the bioconcentration of organic contaminants in this species, toxicokinetic (TK) models were developed for the embryo-larval and subadult life stages. The embryo-larval model was designed as a one-compartment model and validated using whole-body measurements of benzo[]pyrene (B[]P) metabolites from a waterborne exposure to B[]P. A physiologically based TK (PBTK) model was used for the subadult model. The predictive power of the subadult model was validated with an experimental data set of four chemicals. Results showed that the TK models could accurately predict the bioconcentration of organic contaminants for both life stages of white sturgeon within 1 order of magnitude of measured values. These models provide a tool to better understand the impact of environmental contaminants on the health and the survival of endangered white sturgeon populations.
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http://dx.doi.org/10.1021/acs.est.0c06867DOI Listing
September 2021

A Novel Multispecies Toxicokinetic Modeling Approach in Support of Chemical Risk Assessment.

Environ Sci Technol 2021 07 24;55(13):9109-9118. Epub 2021 Jun 24.

Toxicology Centre, University of Saskatchewan, Saskatoon S7N 5B3, Canada.

Standardized laboratory tests with a limited number of model species are a key component of chemical risk assessments. These surrogate species cannot represent the entire diversity of native species, but there are practical and ethical objections against testing chemicals in a large variety of species. In previous research, we have developed a multispecies toxicokinetic model to extrapolate chemical bioconcentration across species by combining single-species physiologically based toxicokinetic (PBTK) models. This "top-down" approach was limited, however, by the availability of fully parameterized single-species models. Here, we present a "bottom-up" multispecies PBTK model based on available data from 69 freshwater fishes found in Canada. Monte Carlo-like simulations were performed using statistical distributions of model parameters derived from these data to predict steady-state bioconcentration factors (BCFs) for a set of well-studied chemicals. The distributions of predicted BCFs for 1,4-dichlorobenzene and dichlorodiphenyltrichloroethane largely overlapped those of empirical data, although a tendency existed toward overestimation of measured values. When expressed as means, predicted BCFs for 26 of 34 chemicals (82%) deviated by less than 10-fold from measured data, indicating an accuracy similar to that of previously published single-species models. This new model potentially enables more environmentally relevant predictions of bioconcentration in support of chemical risk assessments.
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http://dx.doi.org/10.1021/acs.est.1c02055DOI Listing
July 2021

Effects of Agricultural Stressors on Growth and an Immune Status Indicator in Wood Frog (Lithobates sylvaticus) Tadpoles and Metamorphs.

Environ Toxicol Chem 2021 Aug 7;40(8):2269-2281. Epub 2021 Jul 7.

Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

Like many amphibians, wood frog (Lithobates sylvaticus) populations have likely declined or experienced local extirpations as a result of habitat alterations. Despite this, wood frogs are still present and breeding in altered landscapes, like the agricultural Prairie Pothole Region of central Canada, and are exposed to a variety of anthropogenic impacts. As tadpoles, water contamination can have negative effects on growth, development, and immune systems. To investigate the potential effects of agricultural land use on tadpole growth and immune system stress, we used boosted regression trees to model body mass, body condition, and neutrophil to lymphocyte ratios, a measure of immune stress, against 32 variables including water quality, wetland habitat, and landscape-level measures. Developmental stage strongly influenced all 3 endpoints, and body mass was negatively influenced by higher levels of total dissolved solids (>600-700 mg/L) and at the first sign of pesticide detection (>0.01 proportion pesticides detected of those screened). While correlative, these data suggest that tadpoles developing in agricultural environments may experience survival and reproductive disadvantages if they metamorphose at smaller body sizes. Given the potential impacts this can have on adult frogs and frog populations, these results provide an impetus for further field-based investigation into the effects that pesticides, and especially total dissolved solids, may have on tadpoles. Environ Toxicol Chem 2021;40:2269-2281. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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http://dx.doi.org/10.1002/etc.5107DOI Listing
August 2021

Development of a Comprehensive Toxicity Pathway Model for 17α-Ethinylestradiol in Early Life Stage Fathead Minnows ().

Environ Sci Technol 2021 04 23;55(8):5024-5036. Epub 2021 Mar 23.

Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada.

There is increasing pressure to develop alternative ecotoxicological risk assessment approaches that do not rely on expensive, time-consuming, and ethically questionable live animal testing. This study aimed to develop a comprehensive early life stage toxicity pathway model for the exposure of fish to estrogenic chemicals that is rooted in mechanistic toxicology. Embryo-larval fathead minnows (FHM; ) were exposed to graded concentrations of 17α-ethinylestradiol (water control, 0.01% DMSO, 4, 20, and 100 ng/L) for 32 days. Fish were assessed for transcriptomic and proteomic responses at 4 days post-hatch (dph), and for histological and apical end points at 28 dph. Molecular analyses revealed core responses that were indicative of observed apical outcomes, including biological processes resulting in overproduction of vitellogenin and impairment of visual development. Histological observations indicated accumulation of proteinaceous fluid in liver and kidney tissues, energy depletion, and delayed or suppressed gonad development. Additionally, fish in the 100 ng/L treatment group were smaller than controls. Integration of omics data improved the interpretation of perturbations in early life stage FHM, providing evidence of conservation of toxicity pathways across levels of biological organization. Overall, the mechanism-based embryo-larval FHM model showed promise as a replacement for standard adult live animal tests.
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http://dx.doi.org/10.1021/acs.est.0c05942DOI Listing
April 2021

Does habitat quality matter to soil invertebrates in metal-contaminated soils?

J Hazard Mater 2021 05 25;409:124969. Epub 2020 Dec 25.

Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada; Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A8, Canada. Electronic address:

This study investigated the influence of habitat quality (HQ) on the reproduction and bioenergetics (energy reserve and metabolic enzyme activities) of the oribatid mite, Oppia nitens, in response to cadmium (Cd). In the baseline toxicity test, Cd elevated the carbohydrate reserve of adult mites at intermediate Cd concentrations (88 and 175 mg Cd kg) but without a change in lipid and protein reserve across 0-700 mg Cd kg. The activities of glucose metabolism enzymes, glucose-6-phosphate dehydrogenase (G6PDH) and pyruvate kinase (PK) were inhibited in the mites at 700 mg Cd kg. Adult mites reared in high HQ soils had higher reproduction relative to mites from low HQ soils when exposed to Cd in OECD soil, but there was no difference in bioenergetics between mites from low and high HQ soils. Hence, HQ significantly (p = 0.024) influenced the reproduction of mites (i.e., juvenile production) irrespective of the Cd concentration in the OECD soil but did not significantly affect the bioenergetics of the mites. We suggest that habitat quality's effect could be more significant than metal concentration on the biological fitness (juvenile production) of O. nitens in metal-contaminated soils.
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http://dx.doi.org/10.1016/j.jhazmat.2020.124969DOI Listing
May 2021

Uptake, toxicity, and maternal transfer of cadmium in the oribatid soil mite, Oppia nitens: Implication in the risk assessment of cadmium to soil invertebrates.

Environ Pollut 2020 Apr 7;259:113912. Epub 2020 Jan 7.

Department of Soil Science, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; Toxicology Centre, University of Saskatchewan, Saskatoon, SK S7N 5B3, Canada. Electronic address:

Cadmium (Cd) is a heavy metal of concern in contaminated sites because of its high toxicity to soil biota and humans. Typically, Cd exposure is thought to be dominated by dissolved Cd in soil pore water and, thus, dermal uptake. In this study, we investigated the uptake, toxicity, and maternal transfer of Cd in a standard soil invertebrate, the oribatid mite (Oppia nitens), which is common to boreal and temperate ecozones. We found total soil Cd predicted Cd uptake in adult and juvenile O. nitens with no significant uptake from pore water by juvenile mites. Cadmium significantly inhibited juvenile production and recruitment as well as reduced adult fecundity. Adult O. nitens maternally transferred 39-52% of their Cd body burden to juveniles (tritonymphs) while the maternally-acquired Cd accounted for 41% of the juvenile internal Cd load. Our results suggest that dermal adsorption of metal ions is not important for O. nitens and that maternal transfer of Cd in soil invertebrates has ecological and toxicological implications for populations of soil invertebrates. Maternal transfer should be incorporated as a criterion in setting environmental soil quality guidelines (SQG) for cadmium and other non-essential heavy metals.
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http://dx.doi.org/10.1016/j.envpol.2020.113912DOI Listing
April 2020

Detecting Amphibians in Agricultural Landscapes Using Environmental DNA Reveals the Importance of Wetland Condition.

Environ Toxicol Chem 2019 12 16;38(12):2750-2763. Epub 2019 Nov 16.

School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

Amphibians are declining worldwide, in part because of large-scale degradation of habitat from agriculture and pervasive pathogens. Yet a common North American amphibian, the wood frog (Lithobates sylvaticus), ranges widely and persists in agricultural landscapes. Conventional survey techniques rely on visual encounters and dip-netting efforts, but detectability limits the ability to test for the effects of environmental variables on amphibian habitat suitability. We used environmental DNA to determine the presence of wood frogs and an amphibian pathogen (ranavirus) in Prairie Pothole wetlands and investigated the effects of 32 water quality, wetland habitat, and landscape-level variables on frog presence at sites representing different degrees of agricultural intensity. Several wetland variables influenced wood frog presence, the most influential being those associated with wetland productivity (i.e., nutrients), vegetation buffer width, and proportion of the surrounding landscape that is comprised of other water bodies. Wood frog presence was positively associated with higher dissolved phosphorus (>0.4 mg/L), moderate dissolved nitrogen (0.1-0.2 mg/L), lower chlorophyll a (≤15 µg/L), wider vegetation buffers (≥10 m), and more water on the landscape (≥0.25). These results highlight the effects of environmental factors at multiple scales on the presence of amphibians in this highly modified landscape-namely the importance of maintaining wetland water quality, vegetation buffers, and surrounding habitat heterogeneity. Environ Toxicol Chem 2019;38:2750-2763. © 2019 SETAC.
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http://dx.doi.org/10.1002/etc.4598DOI Listing
December 2019

Yellow Mealworm Larvae () Fed Mycotoxin-Contaminated Wheat-A Possible Safe, Sustainable Protein Source for Animal Feed?

Toxins (Basel) 2019 05 21;11(5). Epub 2019 May 21.

Department of Animal and Poultry Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada.

The aim of this study was to determine the potential for accumulation of deoxynivalenol (DON) in yellow mealworm larvae () reared on high DON -infected wheat and investigate the effects on production, survival and nutritional traits. Wheat containing 200 μg/kg DON was used as the control diet. A different source of wheat was sorted into six fractions and mixed to obtain low (2000 μg/kg), medium (10,000 μg/kg) and high (12,000 μg/kg) levels of DON. Each diet was replicated five times with 300 or 200 mealworms per replicate for the feeding and breeding trials, respectively. Trial termination occurred when the first two pupae were observed (32-34 days). There was no difference in the concentrations of DON detected in the larvae between diets that ranged from 122 ± 19.3 to 136 ± 40.5 μg/kg ( = 0.88). Excretion of DON was 131, 324, 230 and 742 μg/kg for control, low, medium and high, respectively. Nutritional analysis of larvae showed maximum crude protein of 52% and crude fat of 36%. Ash, fiber, chitin, fatty-acids and amino-acid content were consistent across diets. Survival was greater than 96% for all life stages and average daily gain ranged from 1.9 ± 0.1 to 2.1 ± 0.1 mg/day per mealworm. Larvae accumulated low levels of DON from -infected wheat diets suggesting contaminated wheat could be used to produce a sustainable, safe protein source.
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http://dx.doi.org/10.3390/toxins11050282DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6563207PMC
May 2019

Performance effects of feed-borne mycotoxins on broiler chickens: Influences of timing and duration of exposure.

Anim Nutr 2019 Mar 25;5(1):32-40. Epub 2018 Sep 25.

Department of Animal and Poultry Science, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, SK, S7N 5A8, Canada.

In commercial practice, broiler chickens may be exposed to mycotoxins either during specific growth stages or throughout the entire production cycle. A 34-day feeding trial was conducted to identify sensitive periods for mycotoxin effects during the growth cycle of broiler chickens. A total of 420 newly-hatched Ross 308 male broilers were randomly assigned to 60 cages with 7 birds/cage. Sources of clean wheat (<0.5 mg/kg deoxynivalenol [DON]) and -contaminated wheat (11.4 mg/kg DON) were used to formulate the starter diets (0.41 and 6.62 mg/kg DON) provided from 1 to 21 d of age and the grower diets (0.54 and 7.90 mg/kg DON) provided from 22 to 34 d. Control and DON diets were provided to broilers according to treatments (control, DON 1 to 14 d, DON 15 to 21 d, DON 22 to 34 d and DON 1 to 34 d). Birds were monitored daily for morbidity or mortality. Broiler growth performance (body weight, average daily gain, average daily feed intake and feed to gain ratio) was measured weekly. Segments of duodenum, jejunum and ileum were collected at 21 and 34 d and morphometric parameters (villus height, crypt depth, villus width, muscularis thickness and villi:crypt ratio) were measured. Birds fed the DON starter diet during the first 14 d did not exhibit any changes in growth performance; however, growth performance was suppressed in birds fed DON-contaminated diets during the grower period (22 to 34 d). At 34 d, birds that received the DON grower diet (DON 22 to 34 d and DON 1 to 34 d) were lighter (1,433 vs. 1,695 g) than birds fed the control diet. Feed to gain ratio was higher in birds fed the DON grower diet from 22 to 28 d (1.77 vs. 1.56) and 28 to 34 d (2.24 vs. 1.85) compared with corresponding controls. These results suggest that providing older broiler chicks (22 to 34 d) feed contaminated with mycotoxins (specifically DON) may result in production losses. Histopathological analysis of the ileum region revealed that birds provided the DON diets throughout the entire trial (1 to 34 d) had shorter villi (506 vs. 680 μm) and shallower crypt (85 vs. 115 μm) than control birds. Taken together, these results indicate that DON-induced growth suppression may be a result of adverse effects on intestinal morphology during later growth phases of broilers.
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http://dx.doi.org/10.1016/j.aninu.2018.08.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6407085PMC
March 2019

Advancing soil ecological risk assessments for petroleum hydrocarbon contaminated soils in Canada: Persistence, organic carbon normalization and relevance of species assemblages.

Sci Total Environ 2019 Jun 1;668:400-410. Epub 2019 Mar 1.

Toxicology Group, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

Sediment toxicity studies and ecological risk assessments on organic contaminants routinely apply organic carbon normalization to toxicity data; however, no studies examine its potential for use in soils with petroleum hydrocarbon (PHC) contamination. Limited studies in soil ecotoxicology assess the influence of species assemblages used in species sensitivity distribution construction on the resulting guideline designated to of soil dwelling organisms. Canadian regulations utilize more conservative approaches to deriving guidelines with soil ecotoxicology data compared to the rest of the world, so we investigated the impact of these on soil invertebrates in a variety of field soils. In addition to toxicity, the persistence of a medium PHC mixture was also assessed in the field soils to determine the duration of toxic effects. We found organic matter influenced PHC toxicity to soil invertebrates, but persistence was influenced more by soil cation exchange capacity. Incorporating organic carbon normalization into species sensitivity distribution curves provided a higher level of protection to soil dwelling receptors in low organic matter soils as well as reduce the variability of PHC soil toxicity data. Soil remediation guidelines derived for protection of soil dwelling organisms using a diverse species assemblage provided similar levels of protection as guidelines developed with test species specific for remote, forested land uses in Canada. We conclude that: (i) Canadian hazard concentration values for PHC contamination of soils should be revisited as they may not be protective and (ii) that soil PHC guidelines for protection of soil dwelling organisms should be expressed as carbon normalized values.
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http://dx.doi.org/10.1016/j.scitotenv.2019.02.459DOI Listing
June 2019

EcoToxChip: A next-generation toxicogenomics tool for chemical prioritization and environmental management.

Environ Toxicol Chem 2019 02;38(2):279-288

Toxicology Center, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

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http://dx.doi.org/10.1002/etc.4309DOI Listing
February 2019

Soil invertebrate avoidance behavior identifies petroleum hydrocarbon contaminated soils toxic to sensitive plant species.

J Hazard Mater 2019 01 29;361:338-347. Epub 2018 Aug 29.

Toxicology Group, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

In recent years, laboratory soil toxicity testing has advanced with the introduction of ecologically relevant boreal forest soil invertebrate and plant species, as well as increased adoption of avoidance toxicity tests. In this study, we investigated the toxicity of a binary petroleum hydrocarbon (PHC) mixture to six agronomic and boreal forest plant species (Elymus lanceolatus, Lactuca sativa, Medicago sativa, Raphanus sativus, Pinus banksiana and Picea glauca) and the avoidance response of five soil invertebrate species (Eisenia fetida, Enchytraeus crypticus, Folsomia candida, Oppia nitens and Hypoaspis aculeifer). We assessed concentration addition and independent action mixture toxicity reference models, with potential interactions, using observed responses from the mixture and individual component toxicity endpoints from literature. Our key finding was soil invertebrate avoidance of PHC-contaminated soil was in the similar range of growth measurements for plant species sensitive to PHC-contaminated soils. This study further supports the inclusion of avoidance tests in toxicity test batteries for assessing PHC toxicity as invertebrate avoidance response appears to be linked to plant growth and informative of plant habitat quality.
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http://dx.doi.org/10.1016/j.jhazmat.2018.08.086DOI Listing
January 2019

Petroleum hydrocarbon mixture toxicity and a trait-based approach to soil invertebrate species for site-specific risk assessments.

Environ Toxicol Chem 2018 08 19;37(8):2222-2234. Epub 2018 Jun 19.

Toxicology Group, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

Although petroleum hydrocarbons released to the environment typically occur as mixtures, petroleum hydrocarbon remediation guidelines often reflect individual substance toxicity. It is well documented that groups of aliphatic petroleum hydrocarbons act via the same mechanism of action (nonpolar narcosis) and, theoretically, concentration addition mixture toxicity principles apply. To assess this theory, 10 standardized acute and chronic soil invertebrate toxicity tests on a range of organisms (Eisenia fetida, Lumbricus terrestris, Enchytraeus crypticus, Folsomia candida, Oppia nitens, and Hypoaspis aculeifer) were conducted with a refined petroleum hydrocarbon binary mixture. Reference models for concentration addition and independent action were applied to the mixture toxicity data with consideration of synergism, antagonism, and dose level toxicity. Both concentration addition and independent action, without further interactions, provided the best fit with observed response to the mixture. Individual fraction effective concentration values were predicted from optimized, fitted reference models. Concentration addition provided a better estimate than independent action of individual fraction effective concentrations based on comparison with available literature and species trends observed in toxic responses to the mixture. Interspecies differences in standardized laboratory soil invertebrate species responses to petroleum hydrocarbon-contaminated soil was reflected in unique traits. Diets that included soil, large body size, permeable cuticle, low lipid content, lack of ability to molt, and no maternal transfer were traits linked to a sensitive survival response to petroleum hydrocarbon-contaminated soil in laboratory tests. Traits linked to sensitive reproduction response in organisms tested were long life span and small clutch size. By deriving single-fraction toxicity endpoints considerate of mixtures, we can reduce the resources and time required to conduct site-specific risk assessments for the protection of a soil organism's exposure pathway. Environ Toxicol Chem 2018;37:2222-2234. © 2018 SETAC.
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http://dx.doi.org/10.1002/etc.4164DOI Listing
August 2018

Developmental expression profiles and thyroidal regulation of cytokines during metamorphosis in the amphibian Xenopus laevis.

Gen Comp Endocrinol 2018 07 12;263:62-71. Epub 2018 Apr 12.

Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada; Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A8, Canada. Electronic address:

Early life-stages of amphibians rely on the innate immune system for defense against pathogens. While thyroid hormones (TH) are critical for metamorphosis and later development of the adaptive immune system, the role of TH in innate immune system development is less clear. An integral part of the innate immune response are pro-inflammatory cytokines - effector molecules that allow communication between components of the immune system. The objective of this study was to characterize the expression of key pro-inflammatory cytokines, tumor necrosis factor-α (TNFα), interleukin-1β (IL-1β) and interferon-γ (IFN-γ), throughout amphibian development and determine the impacts of thyroidal modulation on their expression. Xenopus laevis were sampled at various stages of development encompassing early embryogenesis to late prometamorphosis and cytokine expression was measured by real-time PCR. Expression of TNFα and IL-1β were transient over development, increasing with developmental stage, while IFN-γ remained relatively stable. Functionally athyroid, premetamorphic tadpoles were exposed to thyroxine (0.5 and 2 μg/L) or sodium perchlorate (125 and 500 μg/L) for seven days. Tadpoles demonstrated characteristic responses of advanced development with thyroxine exposure and delayed development (although to a lesser extent) and increased thyroid gland area and follicular cell height with sodium perchlorate exposure. Exposure to thyroxine for two days resulted in decreased expression of IL-1β in tadpole trunks. Sodium perchlorate had negligible effects on cytokine expression. Overall, these results demonstrate that cytokine transcript levels vary with stage of tadpole development but that their ontogenic regulation is not likely exclusively influenced by thyroid status. Understanding the direct and indirect effects of altered hormone status may provide insight into potential mechanisms of altered immune function during amphibian development.
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http://dx.doi.org/10.1016/j.ygcen.2018.04.008DOI Listing
July 2018

Opportunistic disease in yellow perch in response to decadal changes in the chemistry of oil sands-affected waters.

Environ Pollut 2018 Mar 21;234:769-778. Epub 2017 Dec 21.

Canadian Rivers Institute, University of Prince Edward Island, 550 University Ave, Charlottetown, Prince Edward Island, C1A 4P3, Canada.

Oil sands-affected water from mining must eventually be incorporated into the reclaimed landscape or treated and released. However, this material contains petrogenic organic compounds, such as naphthenic acids and traces of polycyclic aromatic hydrocarbons. This has raised concerns for impacts of oil sands process-affected waters on the heath of wildlife and humans downstream of receiving environments. The objective of this study was to evaluate the temporal association of disease states in fish with water chemistry of oil sands-affected waters over more than a decade and determine the pathogens associated with disease pathologies. Yellow perch (Perca flavescens) captured from nearby lakes were stocked into two experimental ponds during 1995-1997 and 2008-2010. South Bison Pond is a drainage basin that has received unextracted oil sands-contaminated material. Demonstration Pond is a constructed pond containing mature fine tailings capped with fresh water. Two disease pathologies, fin erosion for which a suspected bacterial pathogen (Acinetobacter Iwoffi) is identified, and lymphocystis (confirmed using a real-time PCR) were associated with oil sands-affected water exposure. From 1995 to 1997 pathologies were most prevalent in the South Bison Pond; however, from 2008 to 2009, disease was more frequently observed in the Demonstration Pond. CYP1A activity was 3-16 fold higher in fish from experimental ponds as compared to reference populations and this pattern was consistent across all sampling years. Bile fluorescence displayed a gradient of exposure with experimental ponds being elevated over local perch populations. Naphthenic acids decreased in the Bison Pond from approximately 12 mg/L to <4 mg/L while naphthenic acids increased in the Demonstration Pond from 6 mg/L to 12 mg/L due to tailings densification. Temporal changes in naphthenic acid levels, CYP1A activity and bile fluorescent metabolites correlate positively with incidence of disease pathologies whereas all inorganic water quality changes (major ions, pH, metals) were not associated with disease responses.
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http://dx.doi.org/10.1016/j.envpol.2017.11.091DOI Listing
March 2018

Transcriptional response in rainbow trout (Oncorhynchus mykiss) B cells and thrombocytes following in vivo exposure to benzo[a]pyrene.

Environ Toxicol Pharmacol 2017 Jul 19;53:212-218. Epub 2017 Jun 19.

Canadian Rivers Institute, Department of Biology, University of Prince Edward Island, Charlottetown, Canada. Electronic address:

Immune toxicity of polycyclic aromatic hydrocarbons (PAHs) in fishes has been frequently reported but the reasons for differential cell toxicity remains unclear. Rainbow trout were exposed in vivo with a single intraperitoneal injection of corn oil or 100mg/kg of the immunotoxic PAH benzo[a]pyrene (B[a]P) in corn oil. Leukocytes were harvested from head kidney, spleen and blood after 14days, the optimal time for B cell depletion found in a previous study. The mRNA expression of five cytochrome P450 (CYP) enzymes, the aryl hydrocarbon receptor (AhR), and an intrinsic pathway apoptosis checkpoint (p53) in B cells and thrombocytes were examined. Transcript levels were measured in immunomagnetically-isolated B cells and thrombocytes from those tissues as well as in liver as B cells had been previously shown to be responsive the BaP whereas thrombocytes were not. There was induction of CYP1A1 in liver, blood B cells, and blood and spleen thrombocytes; CYP1B1 in blood B cells, blood and spleen thrombocytes; CYP1A3 in liver, blood and spleen B cells, and blood thrombocytes; CYP1C1 in liver; and AhR in liver and spleen thrombocytes. There was no change in CYP1C2, or p53 mRNA levels across tissues or cell type. Induction in mRNA was observed 14 d after exposure, indicating a prolonged physiological effect of a single B[a]P injection. CYP1A1 and CYP1A3 were the most abundantly expressed CYP genes and CYP1B1 was generally least abundant. B[a]P-induced thrombocytes had a significantly different pattern of CYP expression than either liver or B cells. Given the importance of metabolites in the toxicity of PAHs, differences in CYP expression between tissues may explain differences in toxicity previously observed between B cells and thrombocytes.
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http://dx.doi.org/10.1016/j.etap.2017.06.002DOI Listing
July 2017

Population impacts in white sucker (Catostomus commersonii) exposed to oil sands-derived contaminants in the Athabasca River.

Environ Toxicol Chem 2017 08 13;36(8):2058-2067. Epub 2017 Feb 13.

Canadian Rivers Institute, Department of Biology, University of Prince Edward Island, Charlottetown, Canada.

Biological and chemical endpoints were measured in white sucker collected downstream of Athabasca oil sands developments (AB, Canada) and compared with those at Calling Lake (AB, Canada), a reference location upstream of the Athabasca oil sands deposit. Naphthenic acid concentrations were also measured at 14 sites in the Athabasca River watershed. Concentrations of naphthenic acids were elevated in tributaries adjacent to oil sands mining developments. Tributary naphthenic acid profiles were more similar to aged oil sands process water than samples from the Athabasca River, suggesting an influence of tailings in the tributaries. White sucker showed higher energy storage in the Athabasca River as indicated by significantly higher condition and liver size. White sucker were not investing that energy into reproductive effort as measured by gonad size and fecundity, which were significantly reduced relative to the reference location. White sucker showed increased exposure to polycyclic aromatic hydrocarbons as indicated by hepatic cytochrome P4501A (CYP1A) activity and fluorescent bile metabolites, as well as higher concentrations of naphthenic acids in bile. Cadmium, copper, nickel, and selenium were also elevated in white sucker liver tissue compared with the reference location. Based on the exposure profile and response pattern observed, effects on energy storage and utilization in white sucker from the Athabasca River most likely resulted from exposure to polycyclic aromatic hydrocarbons derived from petrogenic and pyrolytic sources. Environ Toxicol Chem 2017;36:2058-2067. © 2017 SETAC.
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http://dx.doi.org/10.1002/etc.3735DOI Listing
August 2017

Tissue-specific selenium accumulation and toxicity in adult female Xenopus laevis chronically exposed to elevated dietary selenomethionine.

Environ Toxicol Chem 2017 04 28;36(4):1047-1055. Epub 2016 Oct 28.

Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

Selenium (Se) is a developmental toxicant that is also capable of altering the bioenergetic and endocrine status of adult fish. To date, aquatic ecotoxicological research has predominantly focused on the toxic effects of Se in fish, and minimal information has been published related to amphibians. The objective of the present study was to investigate the potential toxicity associated with chronically elevated dietary Se consumption in adult female amphibians utilizing the model species Xenopus laevis. Adult X. laevis females were fed a diet augmented with L-selenomethionine at measured concentrations of 0.7 µg Se/g (control), 10.9 µg Se/g, 30.4 µg Se/g, or 94.2 µg Se/g dry mass for 68 d, after which they were bred with untreated males. Ovary, egg, liver, muscle, and blood samples were collected from female frogs after completion of the exposure period and subsequent breeding to ascertain Se tissue distribution, muscle and liver triglyceride and glycogen levels, and plasma cortisol concentrations. The concentrations of Se measured in female tissues excluding the liver were significantly increased in proportion with dietary intake. No significant differences were observed among treatment groups with respect to biometric indices, energy stores, or stress response of adult female X. laevis after Se exposure, which suggests that this amphibian species is capable of accumulating substantial quantities of this element in their tissues with no adverse effects on fitness. Environ Toxicol Chem 2017;36:1047-1055. © 2016 SETAC.
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http://dx.doi.org/10.1002/etc.3627DOI Listing
April 2017

Hematologic reference intervals for Rana sylvatica (Lithobates sylvaticus) and effect of infection with Frog Virus 3 (Ranavirus sp., Iridoviridae).

Vet Clin Pathol 2016 Sep 26;45(3):430-43. Epub 2016 Aug 26.

Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada.

Background: Although the Wood Frog, Rana sylvatica, is used in research on infectious diseases of amphibians, hematologic RIs or response to infection have not been established.

Objectives: The purpose of the study was to determine hematologic RIs for adult Wood Frogs and alterations associated with infection with Frog Virus 3 (FV3, Ranavirus sp.).

Methods: Blood was collected from 40 wild-caught adult Wood Frogs that had been in captivity for 6 months. Complete (Natt-Herrick solution hemocytometry) and differential (Wright-Giemsa-stained smears) WBC, RBC, and thrombocyte cell counts, PCV, and automated total cell counts (WBC+RBC+thrombocytes, Sysmex particle counting) were determined. Concordance correlation coefficients determined agreement between hemocytometric and automated total cell counts. Thirteen frogs were orally infected with a lethal dose of 10(4.43) plaque-forming units of FV3 and terminally sampled 4, 9, or 14 days postinfection (dpi). Pre- and postinfection variables for each frog were compared.

Results: Leukocyte morphology was similar to that of other amphibians and mammals. Lymphocytes were the most numerous WBC. PCV and RBC counts were similar to other frogs in the same family. Agreement was good between hemocytometry and automated total cell counts. Infection with FV3 caused neutrophilia, increase in undifferentiated blast-like cells, and reduction in the percentage of basophils. Lymphocytes decreased at 4 and 9 dpi but increased at 14 dpi. From 9 dpi onwards, nuclear deterioration and mild toxic change were present in neutrophils; viral cytoplasmic inclusion bodies were observed in lymphocytes, monocytes, neutrophils, and eosinophils.

Conclusion: We provide hematology RIs for Rana sylvatica, and report hematologic changes associated with a lethal FV3 infection.
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http://dx.doi.org/10.1111/vcp.12393DOI Listing
September 2016

Hematologic reference intervals for Xenopus tropicalis with partial use of automatic counting methods and reliability of long-term stored samples.

Vet Clin Pathol 2016 Jun 3;45(2):291-9. Epub 2016 May 3.

Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada.

Background: The African frog, Xenopus tropicalis, is widely used in biomedical and toxicologic research. Reference intervals (RI) for hematologic variables, valuable to research and health status assessment, have not been established.

Objectives: The purpose of the study was to determine hematologic RI of X tropicalis, and establish whether automated cell counting can facilitate routine hematologic assessment in frogs.

Methods: Blood from 41 adult healthy X tropicalis was collected via cardiac puncture, and diluted in Natt-Herrick solution. Complete WBC, RBC, and thrombocyte counts (hemocytometry), differential WBC counts (Wright-Giemsa-stained smears), PCV (centrifugation), total protein (refractometry), and automated total cell counts (WBC + RBC + thrombocytes, Sysmex particle counting) were determined. Concordance correlation coefficients calculated the agreement between total cell counts obtained by hemocytometry and automated particle counting, and between total cell counts at collection and after 2 years of storage.

Results: Leukocyte morphology was similar to other amphibians and mammals. PCV was similar to other frogs; RBC counts were higher, and MCV was lower than in other frog species. Neutrophils were the most numerous WBC. Agreement was good between hemocytometry and automated cell counts. Subtracting the hemocytometer WBC and thrombocyte counts from the automated total cell count reliably yielded the RBC count. Cellular integrity evaluated 2 years post collection was good, and automated counts were not clinically different from counts at collection.

Conclusion: We provide hematologic RI for X tropicalis, suggest how automated cell counts may facilitate hematologic assessments of frogs, and establish that blood in Natt-Herrick solution is stable 2 years post collection.
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http://dx.doi.org/10.1111/vcp.12362DOI Listing
June 2016

Biomarker responses to estrogen and androgen exposure in the brook stickleback (Culaea inconstans): A new bioindicator species for endocrine disrupting compounds.

Comp Biochem Physiol C Toxicol Pharmacol 2016 Feb 6;180:1-10. Epub 2015 Nov 6.

Toxicology Centre, University of Saskatchewan, Saskatoon, SK S7N 5B3, Canada; Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada. Electronic address:

Small-bodied freshwater fish are commonly used in regulatory testing for endocrine disrupting compounds (EDCs) but most lack a sensitive and quantifiable androgen-specific biomarker. Brook stickleback (Culaea inconstans) are a North American freshwater fish whose males produce an androgen-regulated glycoprotein in the kidney called spiggin. Although spiggin induction in females has been used as an androgen-specific biomarker of exposure in other stickleback species it has not been characterized in brook stickleback. Therefore, our objective was to develop a bioassay using brook stickleback to measure estrogenic and androgenic responses and establish the sensitivity of traditional and novel biomarkers of exposure. We first developed and optimized a qPCR assay to measure spiggin and vitellogenin transcript levels in kidney and liver tissue, respectively. Basal levels were differentially expressed in mature wild-caught male and female brook stickleback. To determine their sensitivity to EDCs, fish were exposed to nominal concentrations of 1, 10 and 100ng/L of 17α-methyltestosterone (MT) or 17α-ethinylestradiol (EE2) for 21days (sampled at 7 and 21days) under semi-static renewal conditions. MT and EE2 exposure induced spiggin and vitellogenin transcripts in female kidneys and male livers, respectively. Exposure to EE2 also increased hepatosomatic index in both sexes and decreased gonadosomatic index in females. Histopathological alterations were observed in the kidney of EE2-exposed fish and an increase in kidney epithelium cell height occurred in MT-exposed females. Given the sensitivity of these endpoints, the brook stickleback is a promising new freshwater fish model for EDC evaluation and a potential bioindicator for EDCs in North American freshwater environments.
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http://dx.doi.org/10.1016/j.cbpc.2015.10.013DOI Listing
February 2016

Using near infrared transmittance to generate sorted fractions of Fusarium-infected wheat and the impact on broiler performance.

Poult Sci 2015 Jul 25;94(7):1619-28. Epub 2015 May 25.

Department of Animal and Poultry Science, College of Agriculture, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5A8

The objective of this study was to investigate the effects of naturally contaminated Fusarium wheat containing deoxynivalenol (DON) on growth and performance of broiler chickens from 0 to 35 d. The BoMill TriQ individual kernel sorting technology uses near infrared transmittance (NIT) spectra to separate Fusarium-damaged kernels (FDK) from healthy kernels based on individual kernel CP. Three Fusarium-contaminated wheat sources were individually sorted into 3 test fractions: outlier (10% of the source), high mycotoxin (20% of the source), and low mycotoxin (70% of the source). These fractions were reconstituted into 4 ratios-M0, M20, M40, and M60-relating to the proportion of the high mycotoxin fraction in the reconstituted diets. These 12 reconstituted wheat sources with varying levels of DON were incorporated at ∼70% (starter) or ∼75% (grower/finisher) into diets. The fractions of wheat used had FDK ranging from 0.1 to 25.8% and DON from 0.0 to 14.3 ppm. A total of 480 newly hatched Ross 308 male broilers were randomly divided into 96 cages. Each test diet was assigned to 8 replicates with 5 birds per replicate cage. At 21 d, 180 birds were transferred to 36 cages, allowing 3 replicates of 5 birds per diet until 35 d. A factorial arrangement analysis compared the 3 wheat sources and 4 ratios produced from each sorted wheat. Growth and performance were evaluated as BW (g), feed intake (FI; g/bird/day), feed conversion ratio (FCR; g:g), AME (kcal ME/kg diet), nitrogen retention (NR; %), and mortality (%) for 0 to 21 d and 21 to 35 d. Results indicate no significant difference in BW, FI, and FCR (P > 0.05). Significant differences were seen in AME and NR (P < 0.01). This study demonstrates the potential of this novel sorting technology to produce naturally contaminated diets with a large range of mycotoxin concentrations from a single wheat source to enable future investigations of mycotoxin exposure in any species.
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http://dx.doi.org/10.3382/ps/pev135DOI Listing
July 2015

In vitro assessment of endocrine disrupting potential of naphthenic Acid fractions derived from oil sands-influenced water.

Environ Sci Technol 2015 May 22;49(9):5743-52. Epub 2015 Apr 22.

‡Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada.

Oil sands-influenced process waters have been observed to cause reproductive effects and to induced CYP1A activity in fishes; however, little progress has been made in determining causative agents. Naphthenic acids (NAs) are the predominant organic compounds in process-affected waters, but due to the complexity of the mixture, it has been difficult to examine causal linkages in fishes. The aim of this study was to use in vitro assays specific to reproductive and CYP1A mechanisms to determine if specific acid extractable fractions of NAs obtained from oil sands-influenced water are active toward reproductive processes or interact with the Ah receptor responsible for CYP1A activity. NAs were extracted from aged oil sands-influenced waters by use of acid precipitation, and the mixture was fractionated into three acidic and one neutral fraction. The four fractions were examined for Ah receptor-mediated potency by use of the H4IIE-luc bioassay, effects on production of steroid hormones by use of the H295R steroidogenesis assay, and sex steroid receptor binding activity using the yeast estrogen screen and yeast androgen screen. The mixtures were characterized by high resolution mass spectrometry, (1)H nuclear magnetic resonance, and attenuated total reflectance infrared spectroscopy. The neutral fraction elicited Ah-receptor mediated activity after 24 h but not after 48 or 72 h. None of the fractions contained measurable levels of estrogen or androgen receptor agonists nor did they cause reductions in steroidogenesis. A number of fractions showed antiestrogenic or antiandrogenicity potency, with the neutral and main acidic fractions being the most potent. Neutral aromatic compounds are likely responsible for the CYP1A activity observed. Direct estrogenic, androgenic, or steroidogenic mechanisms are unlikely for NAs based on these results, but NAs act as potent antiandrogen or antiestrogens.
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http://dx.doi.org/10.1021/acs.est.5b00077DOI Listing
May 2015

Sublethal effects of aged oil sands-affected water on white sucker (Catostomus commersonii).

Environ Toxicol Chem 2015 Mar 2;34(3):589-99. Epub 2015 Feb 2.

Canadian Rivers Institute, Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada.

To investigate impacts of proposed oil sands aquatic reclamation techniques on benthic fish, white sucker (Catostomus commersonii Lacépède, 1803) were stocked in 2 experimental ponds-Demonstration Pond, containing aged fine tailings capped with fresh water, consistent with proposed end-pit lake designs, and South Bison Pond, containing aged unextracted oil sands material-to examine the effects of unmodified hydrocarbons. White sucker were stocked from a nearby reservoir at both sites in May 2010 and sampled 4 mo later to measure indicators of energy storage and utilization. Comparisons were then made with the source population and 2 reference lakes in the region. After exposure to aged tailings, white sucker had smaller testes and ovaries and reduced growth compared with the source population. Fish introduced to aged unextracted oil sands material showed an increase in growth over the same period. Limited available energy, endocrine disruption, and chronic stress likely contributed to the effects observed, corresponding to elevated concentrations of naphthenic acids, aromatic compounds in bile, and increased CYP1A activity. Because of the chemical and biological complexity of these systems, direct cause-effect relationships could not be identified; however, effects were associated with naphthenic acids, polycyclic aromatic hydrocarbons, ammonia, and high pH. Impacts on growth have not been previously observed in pelagic fishes examined in these systems, and may be related to differences in sediment interaction.
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http://dx.doi.org/10.1002/etc.2845DOI Listing
March 2015

The effects of benzo[a]pyrene on leucocyte distribution and antibody response in rainbow trout (Oncorhynchus mykiss).

Aquat Toxicol 2014 Feb 24;147:121-8. Epub 2013 Dec 24.

Canadian Rivers Institute, Department of Biology, University of Prince Edward Island, Charlottetown, Canada.

Polycyclic aromatic hydrocarbons (PAHs) are a group of compounds with immunotoxic and carcinogenic potential that may pose a threat to fish populations. This study aims to utilize a newly developed fish immunotoxicology model to determine the immune tissue/cell population level effects of PAHs on rainbow trout, using benzo[a]pyrene (BaP) as a representative immunotoxic PAH. Intraperitoneal injection of 25 or 100mg/kg BaP resulted in sustained exposure as indicated by biliary fluorescence at BaP wavelengths for up to 42 days. A new flow cytometry method for absolute counts of differential leucocyte distributions in spleen, blood, and head kidney was developed by combining absolute quantitative counts of total leukocytes in the tissue (3,3'-dihexyloxacarbocyanine iodide (DiOC6) dye) with relative differential counts using monoclonal antibodies for B cells, T cells, myeloid cells, and thrombocytes. Experiments indicated dose- and time-dependent decreases in the absolute number of B cells, myeloid cells, or T cells in blood, spleen, or head kidney after 7, 14 or 21 d of exposure. There was no change in the absolute numbers of erythrocytes or thrombocytes in any tissue. When rainbow trout were exposed to inactivated Aeromonas salmonicida after a 21 d exposure to 100mg/kg BaP, circulating antibody concentrations were decreased by 56%. It was concluded that BaP has a cell lineage-specific toxic effect on some immune cells of rainbow trout, and causes a decrease in circulating antibody levels.
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http://dx.doi.org/10.1016/j.aquatox.2013.12.017DOI Listing
February 2014

Assessing accumulation and biliary excretion of naphthenic acids in yellow perch exposed to oil sands-affected waters.

Chemosphere 2014 Jan 30;95:619-27. Epub 2013 Oct 30.

Canadian Rivers Institute, Department of Biology, University of Prince Edward Island, Canada. Electronic address:

Naphthenic acids are known to be the most prevalent group of organic compounds in oil sands tailings-associated waters. Yellow perch (Perca flavescens) were exposed for four months to oil sands-influenced waters in two experimental systems located on an oil sands lease 30 km north of Fort McMurray Alberta: the Demonstration Pond, containing oil sands tailings capped with natural surface water, and the South Bison Pond, integrating lean oil sands. Yellow perch were also sampled from three lakes: Mildred Lake that receives water from the Athabasca River, Sucker Lake, at the edge of oil sands extraction activity, and Kimowin Lake, a distant reference site. Naphthenic acids were measured in perch muscle tissue using gas chromatography-mass spectrometry (GC-MS). Bile metabolites were measured by GC-MS techniques and by high performance liquid chromatography (HPLC) with fluorescence detection at phenanthrene wavelengths. A method was developed using liquid chromatography-high resolution mass spectrometry (LC-HRMS) to evaluate naphthenic acids in bile. Tissue analysis did not show a pattern of naphthenic acids accumulation in muscle tissue consistent with known concentrations in exposed waters. Bile fluorescence and LC-HRMS methods were capable of statistically distinguishing samples originating from oil sands-influenced waters versus reference lakes. Although the GC-MS and HPLC fluorescence methods were correlated, there were no significant correlations of these methods and the LC-HRMS method. In yellow perch, naphthenic acids from oil sands sources do not concentrate in tissue at a measurable amount and are excreted through a biliary route. LC-HRMS was shown to be a highly sensitive, selective and promising technique as an indicator of exposure of biota to oil sands-derived naphthenic acids.
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http://dx.doi.org/10.1016/j.chemosphere.2013.10.021DOI Listing
January 2014

The immunological effects of oil sands surface waters and naphthenic acids on rainbow trout (Oncorhynchus mykiss).

Aquat Toxicol 2013 Oct 28;142-143:185-94. Epub 2013 Aug 28.

Canadian Rivers Institute, Department of Biology, University of Prince Edward Island, Charlottetown, Canada. Electronic address:

There is concern surrounding the immunotoxic potential of naphthenic acids (NAs), a major organic constituent in waters influenced by oil sands contamination. To assess the immunological response to NAs, rainbow trout (Oncorhynchus mykiss) waterborne exposures were conducted with oil sands-influenced waters, NAs extracted and purified from oil sands tailings waters, and benzo[a]pyrene (BaP) as a positive control. After a 7d exposure, blood, spleen, head kidney, and gill samples were removed from a subset of fish in order to evaluate the distribution of thrombocytes, B-lymphocytes, myeloid cells, and T-lymphocytes using fluorescent antibodies specific for those cell types coupled with flow cytometry. The remaining trout in each experimental tank were injected with inactivated Aeromonas salmonicida and held in laboratory water for 21 d and subjected to similar lymphatic cell evaluation in addition to evaluation of antibody production. Fluorescent metabolites in bile as well as liver CYP1A induction were also determined after the 7 and 21 d exposure. Oil sands waters and extracted NAs exposures resulted in an increase in bile fluorescence at phenanthrene wavelengths, though liver CYP1A was not induced in those treatments as it was with the BaP positive control. Trout in the oil sands-influenced water exposure showed a decrease in B- and T-lymphocytes in blood as well as B-lymphocytes and myeloid cells in spleen and an increase in B-lymphocytes in head kidney. The extracted NAs exposure showed a decrease in thrombocytes in spleen at 8 mg/L and an increase in T-lymphocytes at 1mg/L in head kidney after 7d. There was a significant decrease in antibody production against A. salmonicida in both oil sands-influenced water exposures. Because oil sands-influenced waters affected multiple immune parameters, while extracted NAs impacts were limited, the NAs tested here are likely not the cause of immunotoxicity found in the oil sands-influenced water.
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http://dx.doi.org/10.1016/j.aquatox.2013.08.009DOI Listing
October 2013

Evaluating cumulative effects of anthropogenic inputs in Prince Edward Island estuaries using the mummichog (Fundulus heteroclitus).

Integr Environ Assess Manag 2013 Jul 28;9(3):496-507. Epub 2013 May 28.

Canadian Rivers Institute, Department of Biology, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada.

Estuarine eutrophication as a result of agricultural land use, including the use of chemical fertilizers, is increasing worldwide. Prince Edward Island (PEI), Canada has very high agricultural intensity by international standards with approximately 44% of the land area under production, and some watersheds in excess of 75% agricultural land-use. The type of agriculture is also intensive with primarily row crops that have high chemical fertilizer and pesticide usage. In light of these stressors, the hypothesis of this study was that mummichog (Fundulus heteroclitus) population parameters would change with point and nonpoint source pollution, and that multivariate statistics could be used to draw associations with specific stressors. Fish were sampled on a monthly basis from May through August at 7 estuaries spanning a range of land use, nutrient, and contaminant loadings. A suite of environmental variables were simplified into 3 principal components: PC1 representing agricultural land use, N loading, and plant habitat, PC2 being dominated by sediment sand and silt distribution, and PC3 largely reflecting P loading and sediment organic matter. There were significant differences in abundance of both adult and young-of-the-year mummichog, and these changes associated most strongly with PC1, the largely N-driven agricultural influences. In contrast, somatic variables such as liver and gonad size did not show strong association with the environmental quality principal component scores. The sand and silt PC2 appeared to have the opposite association with the biological data, with siltier environments correlating to older, larger, less dense populations of mummichog. Although pesticide residues were detected in estuarine sediment, there was no clear relationship between these and watershed agricultural intensity or biochemical indicators. There was, however, a strong relationship between agricultural environmental variables (PC1) and in vitro steroid production that is suggestive of a potential chemical effect. Eutrophication appeared to be a primary stressor affecting mummichog populations, as nutrient enrichment was associated with changes in habitat variables and these in turn were associated with high mummichog density. Thus, mummichog population demographics appear to have use as an indicator of adverse or worsening conditions in estuaries. We concluded that, based on the subset of environmental factors evaluated, the nonpoint-source inputs of sediments and nutrients exerted the greatest influence on mummichog populations in PEI estuaries.
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http://dx.doi.org/10.1002/ieam.1396DOI Listing
July 2013

Immunotoxic effects of oil sands-derived naphthenic acids to rainbow trout.

Aquat Toxicol 2013 Jan 27;126:95-103. Epub 2012 Oct 27.

Canadian Rivers Institute, Department of Biology, University of Prince Edward Island, Charlottetown, Canada.

Naphthenic acids are the major organic constituents in waters impacted by oil sands. To investigate their immunotoxicity, rainbow trout (Oncorhynchus mykiss) were injected with naphthenic acids extracted from aged oil sands tailings water. In two experiments, rainbow trout were injected intraperitoneally with 0, 10, or 100 mg/kg of naphthenic acids, and sampled after 5 or 21 d. Half of the fish from the 21 d exposure were co-exposed to inactivated Aeromonas salmonicida (A.s.) to induce an immune response. A positive control experiment was conducted using an intraperitoneal injection of 100 mg/kg of benzo[a]pyrene, a known immune suppressing compound. T-lymphocytes, B-lymphocytes, thrombocytes, and myeloid cells were counted in blood and lymphatic tissue using flow cytometry. In the 5d exposure, there was a reduction in blood leucocytes and spleen thrombocytes at the 100 mg/kg dose. However, at 21 d, leucocyte populations showed no effects of exposure with the exception that spleen thrombocyte populations increase at the 100 mg/kg dose. In the 21 d exposure, B- and T-lymphocytes in blood showed a significant Dose × A.s. interaction, indicating stimulated blood cell proliferation due to naphthenic acids alone as well as due to A.s. Naphthenic acid injections did not result in elevated bile fluorescent metabolites or elevated hepatic EROD activity. In contrast to naphthenic acids exposures, as similar dose of benzo[a]pyrene caused a significant decrease in B- and T-lymphocyte absolute counts in blood and relative B-lymphocyte counts in spleen. Results suggest that the naphthenic acids may act via a generally toxic mechanism rather than by specific toxic effects on immune cells.
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http://dx.doi.org/10.1016/j.aquatox.2012.10.009DOI Listing
January 2013

The effects of the urea-based herbicide linuron on reproductive endpoints in the fathead minnow (Pimephales promelas).

Comp Biochem Physiol C Toxicol Pharmacol 2013 Jan 13;157(1):24-32. Epub 2012 Sep 13.

Nautilus Environmental, Imperial Square Lake City, Burnaby, British Columbia, Canada.

Linuron is a widely used urea-based herbicide that has anti-androgenic activity in both fish and rodents. To further elucidate the potential mode of action (MOA) of linuron on the vertebrate endocrine system, adult male and female fathead minnows were exposed for 21 days to dechlorinated water, a solvent control, 17β-estradiol (E2; 0.1 μg/L), dihydrotestosterone (DHT; 100 μg/L), linuron (1, 10, 100 μg/L) and one co-treatment of DHT (100 μg/L) and linuron (100 μg/L). There were no effects of linuron on egg hatching, 7 day egg survival, nuptial tubercle formation or gonadal histopathology. Administration of DHT and 1 and 100 μg/L linuron reduced plasma vitellogenin in females, while male plasma vitellogenin were induced after E2 exposure and co-exposure of DHT and linuron. Ovarian mRNA levels were examined for several genes involved in steroidogenesis (e.g. p450scc, cyp19a, star, tspo, hsd17b and hsd11b) and estrogen-mediated responses (esr1, esr2b, esr2a). Only p450scc mRNA was significantly decreased with DHT+linuron co-treatment. Clustering of steroidogenic mRNA transcript expression patterns revealed that patterns for linuron were more similar to E2 compared to DHT. Collectively, this study supports the hypothesis that linuron may not be a pure anti-androgen and may have multiple MOAs that affect vertebrate reproduction.
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http://dx.doi.org/10.1016/j.cbpc.2012.09.001DOI Listing
January 2013
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