Publications by authors named "Darren Van Essen"

2 Publications

  • Page 1 of 1

The brominated flame retardant, TBCO, impairs oocyte maturation in zebrafish (Danio rerio).

Aquat Toxicol 2021 Aug 3;238:105929. Epub 2021 Aug 3.

Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada; Intersectoral Centre for Endocrine Disruptor Analysis (ICEDA), Institut National de la Recherche Scientifique (INRS), Centre Eau Terre Environnement, Québec City, QC, G1K 9A9, Canada; Water Institute for Sustainable Environments, University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada. Electronic address:

The brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO), has been shown to decrease fecundity in Japanese medaka (Oryzias latipes) and there is indirect evidence from analysis of the transcriptome and proteome that this effect might be due to impaired oogenesis. An assay for disruption of oocyte maturation by chemical stressors has not been developed in Japanese medaka. Thus, using zebrafish (Danio rerio) as a model, objectives of the present study were to determine whether exposure to TBCO has effects on maturation of oocytes and to investigate potential mechanisms. Sexually mature female zebrafish were given a diet of 35.3 or 628.8 μg TBCO / g food for 14 days after which, stage IV oocytes were isolated to assess maturation in response to maturation inducing hormone. To explore potential molecular mechanisms, abundances of mRNAs of a suite of genes that regulate oocyte maturation were quantified by use of quantitative real-time PCR, and abundances of microRNAs were determined by use of miRNAseq. Ex vivo maturation of oocytes from fish exposed to TBCO was significantly less than maturation of oocytes from control fish. The percentage of oocytes which matured from control fish and those exposed to low and high TBCO were 89, 71, and 67%, respectively. Among the suite of genes known to regulate oocyte maturation, mRNA abundance of insulin like growth factor-3 was decreased by 1.64- and 3.44-fold in stage IV oocytes from females given the low and high concentrations of TBCO, respectively, compared to the control group. Abundances of microRNAs regulating the expression of proteins that regulate oocyte maturation, including processes related to insulin-like growth factor, were significantly different in stage IV oocytes from fish exposed to TBCO. Overall, results of this study indicated that impaired oocyte maturation might be a mechanism of reduced reproductive performance in TBCO-exposed fish. Results also suggested that effects of TBCO on oocyte maturation might be due to molecular perturbations on insulin-like growth factor signaling and expression of microRNAs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.aquatox.2021.105929DOI Listing
August 2021

Effects of the brominated flame retardant, TBCO, on development of zebrafish (Danio rerio) embryos.

Chemosphere 2021 Mar 4;266:129195. Epub 2020 Dec 4.

Department of Biological Sciences, University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada; Water Institute for Sustainable Environments (WISE), University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada. Electronic address:

Brominated flame retardants (BFRs) can enter aquatic environments where they can have adverse effects on organisms. The BFR, 1,2,5,6-Tetrabromocyclooctane (TBCO), has been introduced as a potential replacement for the major use BRF, Hexabromocyclododecane (HBCD). However, little is known about effects of TBCO on aquatic organisms. Using zebrafish (Danio rerio) as a model species, objectives of this study were to determine whether TBCO has adverse effects on early life-stages and to investigate the molecular and biochemical mechanisms of any effects on development. Exposure to TBCO caused a concentration dependant increase in mortality, decrease in heart rate, and increase in incidences of spinal curvature and uninflated swim bladders. Neither peroxidation of lipids or mRNA abundances of genes important for the response to oxidative stress were greater in embryos exposed to TBCO suggesting effects were not caused by oxidative stress. The mRNA abundance of cytochrome p4501a was not greater in embryos exposed to TBCO suggesting that effects were not caused by activation of the aryl hydrocarbon receptor. Finally, mRNA abundances of genes important for development and inflation of the swim bladder were not affected by TBCO. Overall, TBCO causes adverse effects on early life-stages of zebrafish, but mechanisms of effects require further investigation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2020.129195DOI Listing
March 2021
-->