Effects of Alkylation on Potency of Benz[a]anthracene for AhR2 Transactivation in Nine Species of Freshwater Fish.

Polycyclic aromatic hydrocarbons (PAHs) are naturally occurring or anthropogenic organic chemicals that can activate the aryl hydrocarbon receptor 2 (AhR2) and induce toxicity in fishes. Alkyl PAHs are more abundant than nonalkylated PAHs in certain environmental matrices and there is growing evidence that alkylation can increase potency, dependent on the position of alkylation. However, it is unknown if the effect of alkylation on potency is conserved across species.

Alkylation of Benz[a]anthracene Affects Toxicity to Early-Life Stage Zebrafish and In Vitro Aryl Hydrocarbon Receptor 2 Transactivation in a Position-Dependent Manner.

Polycyclic aromatic hydrocarbons (PAHs) are structurally diverse organic chemicals that can have adverse effects on the health of fishes through activation of aryl hydrocarbon receptor 2 (AhR2). They are ubiquitous in the environment, but alkyl PAHs are more abundant in some environmental matrices. However, relatively little is known regarding the effects of alkylation on the toxicity of PAHs to fishes in vivo and how this relates to potency for activation of AhR2 in vitro.

Health status of fathead minnow (Pimephales promelas) populations in a municipal wastewater effluent-dominated stream in the Canadian prairies, Wascana Creek, Saskatchewan.

Their unique hydrological and climatic conditions render surface water systems in the southern Canadian Prairies at an elevated risk from exposure to contaminants released from municipal wastewater effluents (MWWEs). The aim of this study was to characterize the potential health effects and their underlying molecular mechanisms in populations of fathead minnow (Pimephales promelas; FHM) in Wascana Creek, an effluent dominated stream in Southern Saskatchewan, Canada. Studies were conducted during the spawning season in 2014 and 2015 to assess responses in terms of overall health, reproductive functions, plasma sex steroid hormone levels, and expression of selected genes along the hypothalamus-pituitary-gonadal axis.

Dicamba elevates concentrations of S-adenosyl methionine but does not induce oxidative stress or alter DNA methylation in rainbow trout (Oncorhynchus mykiss) hepatocytes.

Dicamba is a benzoic acid herbicide used to target woody and broadleaf weeds in industrial, domestic, and municipal spheres. Because of its widespread use, dicamba is frequently detected in surface waters near sites of application. However, little is known regarding the effects of dicamba on freshwater fishes.

Biological effects and toxicity of diluted bitumen and its constituents in freshwater systems.

Approximately 50 billion cubic meters of bitumen resides within the oil sands region of Alberta, Canada. To facilitate the transport of bitumen from where it is extracted to where it is processed, the bitumen is diluted with natural gas condensate ('dilbit'), synthetic crude from hydrocracking bitumen ('synbit'), or a mixture of both ('dilsynbit'). A primary consideration for the effects of diluted bitumen products on freshwater organisms and ecosystems is whether it will float on the water surface or sink and interact with the stream or lake sediments.

Impact of glyphosate and glyphosate-based herbicides on the freshwater environment.

Glyphosate [N-(phosphonomethyl) glycine] is a broad spectrum, post emergent herbicide and is among the most widely used agricultural chemicals globally. Initially developed to control the growth of weed species in agriculture, this herbicide also plays an important role in both modern silviculture and domestic weed control. The creation of glyphosate tolerant crop species has significantly increased the demand and use of this herbicide and has also increased the risk of exposure to non-target species.

Selenium bioaccumulation in stocked fish as an indicator of fishery potential in pit lakes on reclaimed coal mines in Alberta, Canada.

Pit lakes are a common reclamation strategy for open pit mines; however, there is a concern about their water quality and suitability as fish habitat because they are often contaminated by metals or metalloids. This study assessed the exposure of fish and invertebrates to selenium (Se) and other metals and metalloids in pit lakes formed by open pit coal mining in Tertiary (thermal coal) and in Cretaceous (metallurgical coal) bedrock. Juvenile hatchery rainbow trout, Oncorhynchus mykiss, and brook trout, Salvelinus fontinalis, were stocked into two thermal coal pit lakes (water Se < 2 μg/L, low water Se) and two metallurgical coal pit lakes (water Se > 15 μg/L, high water Se).

Parasite-induced oxidative stress in liver tissue of fathead minnows exposed to trematode cercariae.

Although results from field surveys have linked parasites to oxidative stress in their fish hosts, direct evidence involving experimentally infected hosts is lacking. We evaluated the effects of experimental infections with larval trematodes on induction of oxidative stress in fathead minnows, Pimephales promelas. Juvenile fish were exposed in the laboratory to the larvae (cercariae) of 2 species of trematode: Ornithodiplostomum sp.

Empirical relationships between body tissue composition and bioelectrical impedance of brook trout Salvelinus fontinalis from a Rocky Mountain Stream.

Bioelectrical impedance analysis (BIA) analysis was carried out in the field on anaesthetized Salvelinus fontinalis electrofished from a mountain stream in Alberta, Canada; the fish were then sacrificed for subsequent analysis of tissue composition. Water content was assessed by comparing wet and dry mass, and total body lipid content was measured by Soxhlet extraction with petroleum ether. A multivariate analysis of body composition and size metric against impedance measurements was carried out, and the main findings were (1) body size and related metrics were strongly related to volumetric impedance measures, as shown in several previous studies, (2) lipid content (%) and water content (%) were both well predicted by regression models whose main predictor was reactance and (3) reactance and resistance measures that were series-based produced excellent predictions of tissue composition, whereas the corresponding parallel-based models were crude.

Behavioural and physiological responses of brook trout Salvelinus fontinalis to midwinter flow reduction in a small ice-free mountain stream.

This study presents an experimental analysis of the effects of midwinter flow reduction (50-75%, reduction in discharge in 4 h daily pulses) on the physical habitat and on behaviour and physiology of overwintering brook trout Salvelinus fontinalis in a small mountain stream. Flow reduction did not result in significant lowering of temperature or formation of surface or subsurface ice. The main findings were (1) daily movement by S.

Species-specific sensitivity to selenium-induced impairment of cortisol secretion in adrenocortical cells of rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis).

Species differences in physiological and biochemical attributes exist even among closely related species and may underlie species-specific sensitivity to toxicants. Rainbow trout (RT) are more sensitive than brook trout (BT) to the teratogenic effects of selenium (Se), but it is not known whether all tissues exhibit this pattern of vulnerability. In this study, primary cultures of RT and BT adrenocortical cells were exposed to selenite (Na(2)SO(3)) and selenomethionine (Se-Met) to compare cell viability and ACTH-stimulated cortisol secretion in the two fish species.

Triclosan: environmental exposure, toxicity and mechanisms of action.

Triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol; TCS] is a broad spectrum antibacterial agent used in personal care, veterinary, industrial and household products. TCS is commonly detected in aquatic ecosystems, as it is only partially removed during the wastewater treatment process. Sorption, biodegradation and photolytic degradation mitigate the availability of TCS to aquatic biota; however the by-products such as methyltriclosan and other chlorinated phenols may be more resistant to degradation and have higher toxicity than the parent compound.

The physiological stress response and oxidative stress biomarkers in rainbow trout and brook trout from selenium-impacted streams in a coal mining region.

Selenium (Se) is an essential element that can be toxic at concentrations slightly greater than those required for homeostasis. The main chronic toxic effects of Se in fish are teratogenic deformities, but Se can also activate the physiological stress response and redox cycle with reduced glutathione causing oxidative damage. Rainbow trout, Oncorhynchus mykiss, appear to be more sensitive to Se than brook trout, Salvelinus fontinalis.

Physiological stress response in white suckers from agricultural drain waters containing pesticides and selenium.

To assess the effect of agriculture drain water, a complex mixture containing pesticides and selenium (Se), on the physiological stress response, white suckers were collected from irrigation return flows in the summer and the fall and subjected to a stress challenge. Water (0.40-26.

Purification and isolation of corticosteroidogenic cells from head kidney of rainbow trout (Oncorhynchus mykiss) for testing cell-specific effects of a pesticide.

The teleost head kidneys contain corticosteroidogenic cells, chromaffin cells, lymphoid cells, and melanomacrophages. We have developed and validated a method using a Percoll density gradient and differential staining for 3beta-hydroxysteroid dehydrogenase (3beta-HSD) to prepare fractions enriched with specific head kidney cell types. The proportion of steroidogenic cells to other cells in the head kidney was 1:8000 in rainbow trout, Oncorhynchus mykiss.

Effects of acute and subchronic exposures to waterborne selenite on the physiological stress response and oxidative stress indicators in juvenile rainbow trout.

Selenium (Se) is an essential element that may bioaccumulate to toxic levels. In fish, the major toxicity symptom is larval teratogenic deformities, but little is known about the effect of Se on other systems such as the physiological stress response and oxidative stress. To test the hypothesis that Se is a chemical stressor that causes toxicity through oxidative stress, juvenile rainbow trout were exposed to waterborne sodium selenite, and physiological stress response and stress-related parameters (plasma cortisol, glucose, T3 and T4, gill Na+/K+-ATPase, the ability of the head kidney to secrete cortisol, and condition factor) and hepatic oxidative stress indicators (reduced glutathione, glutathione peroxidase, and lipid peroxidation) were measured after 96 h (acute exposure to 0-2.

Reciprocal inhibition of Cd and Ca uptake in isolated head kidney cells of rainbow trout (Oncorhynchus mykiss).

Some environmental pollutants, including cadmium (Cd) and zinc (Zn), can act as endocrine disruptors in fish, either in vivo or through a direct action on steroidogenic cells, as has been demonstrated in vitro. We have previously characterized Cd uptake in head kidney (homologue of mammalian adrenal) cells of rainbow trout (Oncorhynchus mykiss) and have provided evidence for a Cd/Ca interaction. Here, we pursued our investigation of metal competition for uptake.

Role of calcium channels in cadmium-induced disruption of cortisol synthesis in rainbow trout (Oncorhynchus mykiss).

The mechanisms of toxicity of cadmium (Cd(2+)) in adrenal steroidogenesis were investigated in vitro in adrenocortical cells of rainbow trout (Oncorhynchus mykiss). Toxicity of Cd(2+) was increased in absence of extracellular Ca(2+), but was prevented in Ca(2+)-supplemented medium. Pretreatment of cells with BAY K8644 (BAY), an agonist of voltage-dependent calcium channels, increased the Cd(2+)-mediated inhibition of ACTH-stimulated secretion but not pregnenolone (PREG)-stimulated secretion.

Effects of Cu on plasma cortisol and cortisol secretion by adrenocortical cells of rainbow trout (Oncorhynchus mykiss).

Fish are exposed to multiple stressors, often acting concurrently, in their environment. To evaluate the potential of Cu to act as a chemical stressor, rainbow trout (Oncorhynchus mykiss) were exposed to Cu (30 or 80 microg/l) for 30 days in the laboratory and they were subjected to a physical stressor (1 min air exposure) before sampling. Physiological stress indicators in the whole fish as well as cortisol secretion by adrenocortical cells in vitro were measured.

Contamination and biomarkers in the great blue heron, an indicator of the state of the st. Lawrence river.

In 1996-1997, nine breeding colonies of the great blue heron on the St. Lawrence River and its estuary (Québec, Canada) were investigated in the framework of a biomonitoring program. Fledglings from colonies in freshwater were more contaminated with mercury, PCBs and many organic contaminants than those from estuarine colonies.

Oxidative stress and endocrine endpoints in white sucker (Catostomus commersoni) from a river impacted by agricultural chemicals.

The effects of agricultural chemicals on cortisol secretion, antioxidants, and lipid peroxidation were investigated in hepatic and adrenal tissue of white sucker (Catostomus commersoni) from a river (Yamaska) that drains an agricultural region in Québec (Canada). Plasma cholinesterase (ChE) activity, used as a biomarker of exposure to pesticides, was elevated in fish from the reference site compared to fish from the contaminated sites. Plasma concentrations of cortisol and thyroid hormones (T3 and T4) were higher in fish from the reference site compared to contaminated sites; reduced glutathione (GSH) levels, catalase (CAT), and glutathione peroxidase (GPx) activities were higher and lipid peroxidation (LPO) was lower.

Cadmium uptake in isolated adrenocortical cells of rainbow trout and yellow perch.

Cadmium uptake was studied in isolated adrenocortical cells of rainbow trout (Oncorhynchus mykiss) and yellow perch (Perca flavescens) to test the hypothesis that the greater sensitivity of trout cells to Cd-induced disruption of cortisol secretion observed in previous studies is correlated to higher level of metal accumulation. There was no evidence for interspecies differences in accumulation level, and a specific transport mechanism of similar affinity has been characterized in both fish species. However, inhibition of Cd uptake by calcium was observed in rainbow trout exclusively.

A comparative assessment of the adrenotoxic effects of cadmium in two teleost species, rainbow trout, Oncorhynchus mykiss, and yellow perch, Perca flavescens.

Rainbow trout (Oncorhynchus mykiss) and yellow perch (Perca flavescens) have a different sensitivity to cadmium (Cd) in vivo (trout < LC50 < perch). Metals and particularly Cd impair cortisol secretion by adrenocortical cells in both species. The purpose of the present study was to assess in vitro the effect of Cd on cortisol secretion by adrenocortical cells of trout and perch, to compare the sensitivity of adrenal steroidogenesis in these two teleosts.

Role of glutathione redox cycle and catalase in defense against oxidative stress induced by endosulfan in adrenocortical cells of rainbow trout (Oncorhynchus mykiss).

The role of antioxidants in maintaining the functional integrity of adrenocortical cells during in vitro exposure to endosulfan, an organochlorine pesticide, was investigated in rainbow trout (Oncorhynchus mykiss). Aminotriazole (ATA), an inhibitor of catalase (CAT), L-buthionine sulfoximine (L-BSO), an inhibitor of glutathione (GSH) synthesis, and N-acetyl cysteine (NAC), a glutathione precursor, were used to investigate the role of CAT and GSH redox cycle in protection against the adrenal toxicity of endosulfan, a pesticide that impairs cell viability (LC50 366 microM) and cortisol secretion (EC50 19 microM) in a concentration-related manner. Pretreatment with ATA and L-BSO enhanced the toxicity of endosulfan (LC50 and EC50, respectively, 302 and 2.