Browsing by Author "Brinkmann, Markus"
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Item Modelling Transport and Fate of Copper and Nickel across the South Saskatchewan River Using WASP—TOXI(MDPI, 2023) Prajapati, Saurabh; Sabokruhie, Pouya; Brinkmann, Markus; Lindenschmidt, Karl-ErichThe South Saskatchewan River (SSR) is one of the most important river systems in Saskatchewan and, arguably, in Canada. Most of the Saskatchewan residents, industries, and powerplants depend on the SSR for their water requirements. An established 1D modelling approach was chosen and coupled with the Hydrologic Engineering Center’s River Analysis System (HEC-RAS). The WASP (Water Quality Analysis Simulation Program) stream transport module, TOXI, is coupled with flow routing for free-flow streams, ponded segments, and backwater reaches and is capable of calculating the flow of water, sediment, and dissolved constituents across branched and ponded segments. Copper and nickel were chosen as two metals with predominantly anthropogenic (agriculture, mining, and municipal and industrial waste management) and geogenic (natural weathering and erosion) sources, respectively. Analysis was carried out at ten different sites along the South Saskatchewan River, both upstream and downstream of the City of Saskatoon, in the years 2020 and 2021. Model performance was evaluated by comparing model predictions with concentrations of copper and nickel measured in a previously published study. The model performed well in estimating the concentrations of copper and nickel in water samples and worked reasonably well for sediment samples. The model underestimated the concentration values at certain segments in both water and sediment samples. In order to calibrate the model more accurately, extra diffusive contaminant loads were added. While several default parameter values had to be used due to the unavailability of primary historical data, our study demonstrates the predictive power of combining WASP—TOXI and HEC-RAS models for the prediction of contaminant loading. Future studies, including those on the impacts of global climate change on water quality on the Canadian prairies, will benefit from this proof-of-concept study.Item Multiple lines of evidence to assess risk from dioxins and dioxin-like chemicals in sediment and fish from waterbodies along a large prairie river(2023) Brinkmann, Markus; Petersen, Stephanie; Pelletier, Alex; Bryshun, Leland; Schaefer, Nicole; Barnes, Michaella; Doig, Lorne; Strickert, Graham; Jardine, TimItem A rapid and sensitive fluorometric method for determination of aldehyde oxidase activity(Elsevier, 2018) Apenova, Nancy; Peng, Hui; Hecker, Markus; Brinkmann, MarkusPrevious research has characterized the important role of aldehyde oxidases (AOX) in biotransformation of N-heterocyclic therapeutic drugs and environmental contaminants in mammals. Research pertaining to AOX activity in non-mammalian vertebrates, however, is scarce, despite its biological role as a potentially important metabolic pathway for xenobiotics. One of the limiting factors of research on AOX is that available photometric methods are relatively insensitive, limited in throughput, and prone to cross-reactivity from other enzymes. Therefore, this study aimed to develop a novel and improved fluorometric AOX assay. This assay is based on the conversion of the exogenous aldehyde substrate 4-(dimethyl)amino cinnamaldehyde to its corresponding fluorescent acid by AOX, and was evaluated using partially purified hepatic cytosol from rat, human, and rainbow trout. Purification of native cytosol by heat treatment and ammonium sulfate precipitation resulted in increased specific activity of AOX. Michaelis-Menten kinetic parameters (Km and Vmax) were comparable to values previously generated by photometric methods. Furthermore, effects of the inhibitor hydralazine on AOX activity revealed half maximal inhibitory concentrations comparable to those generated using conventional methods. Product identity was confirmed by liquid chromatography and mass spectrometry. In summary, this study successfully developed a rapid and sensitive assay for determination of AOX activity in across different vertebrate species that is 4- to 10-fold more sensitive compared to conventional absorbance-based methods. It can be applied in environmental, toxicological, and pharmacological studies relating to identification of AOX substrates, as well as the induction of AOX expression through drugs and environmental contaminants.Item Unveiling the molecular effects of replacement and legacy PFASs: Transcriptomic analysis of zebrafish embryos reveals surprising similarities and potencies.(American Chemical Society, 2024-10-11) Mahoney, Hannah; Ankley, Phillip; Roberts, Catherine; Lamb, Alicia; Schultz, Matthew; Zhou, Yutong; Giesy, John; Brinkmann, MarkusThe prevalence of per- and poly fluoroalkyl substances (PFASs) in the environment has prompted restrictions on legacy PFASs due to their recognized toxic effects. Consequently, alternative “replacement” PFASs have been introduced and are prevalent in environmental matrices. Few studies have investigated the molecular effects of both legacy and replacement PFASs under short-term exposures. This study aimed to address this by utilizing transcriptomic sequencing to compare the molecular impacts of exposure to concentrations 0.001–5 mg/L of the legacy PFOS and two of its replacements, PFECHS and FBSA. Using zebrafish embryos, the research assessed apical effects (mortality, morphology, and growth), identified differentially expressed genes (DEGs) and enriched pathways, and determined transcriptomic points of departure (tPoDs) for each compound. Results indicated that PFOS exhibited the highest relative potency, followed by PFECHS and then FBSA. While similarities were observed among the ranked DEGs across all compounds, over-representation analysis revealed slight differences. Notably, PFOS demonstrated the lowest tPoD identified to date. These findings raise concerns regarding the safety of emerging replacement PFASs and challenge assumptions about PFAS toxicity solely resulting from their accumulative potential. As replacement PFASs proliferate in the environment, this study underscores the need for heightened scrutiny of their effects and questions current regulatory thresholds.