251 research outputs found
Comparative metal oxide nanoparticle toxicity using embryonic zebrafish
AbstractEngineered metal oxide nanoparticles (MO NPs) are finding increasing utility in the medical field as anticancer agents. Before validation of in vivo anticancer efficacy can occur, a better understanding of whole-animal toxicity is required. We compared the toxicity of seven widely used semiconductor MO NPs made from zinc oxide (ZnO), titanium dioxide, cerium dioxide and tin dioxide prepared in pure water and in synthetic seawater using a five-day embryonic zebrafish assay. We hypothesized that the toxicity of these engineered MO NPs would depend on physicochemical properties. Significant agglomeration of MO NPs in aqueous solutions is common making it challenging to associate NP characteristics such as size and charge with toxicity. However, data from our agglomerated MO NPs suggests that the elemental composition and dissolution potential are major drivers of toxicity. Only ZnO caused significant adverse effects of all MO particles tested, and only when prepared in pure water (point estimate median lethal concentration=3.5–9.1mg/L). This toxicity was life stage dependent. The 24h toxicity increased greatly (∼22.7 fold) when zebrafish exposures started at the larval life stage compared to the 24h toxicity following embryonic exposure. Investigation into whether dissolution could account for ZnO toxicity revealed high levels of zinc ion (40–89% of total sample) were generated. Exposure to zinc ion equivalents revealed dissolved Zn2+ may be a major contributor to ZnO toxicity
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Toxicity of chlorine to zebrafish embryos
Surface disinfection of fertilized fish eggs is widely used in aquaculture to reduce
extraovum pathogens that may be released from brood fish during spawning, and this is routinely
used in zebrafish (Danio rerio) research laboratories. Most laboratories use approximately 25-50 ppm unbuffered chlorine solution for 5-10 min. Treatment of embryos with chlorine has significant germicidal effects for many Gram-negative bacteria, viruses, and trophozoite stages
of protozoa, it has reduced efficacy against cyst or spore stages of protozoa and certain
Mycobacterium spp. Therefore, we evaluated the toxicity of unbufferred and buffered chlorine
solution to embryos exposed at 6 or 24 hours post-fertilization (hpf) to determine if higher
concentrations can be used for treating zebrafish embryos. Most of our experiments entailed
using an outbred line (5D), with both mortality and malformations as endpoints. We found that 6
hpf embryos consistently were more resistant than 24 hpf embryos to the toxic effects of
chlorine. Chlorine is more toxic and germicidal at lower pHs, and chlorine causes elevated pH.
Consistent with this, we found that unbufferred chlorine solutions (pH ca 8-9) were less toxic at
corresponding concentrations than solutions buffered to pH 7. Based on our findings here, we
recommend treating 6 hpf embryos for 10 min and 24 hpf for 5 min with unbuffered chlorine
solution at 100 ppm. One trial indicated that AB fish, a popular outbred line, are more
susceptible to toxicity than 5Ds. This suggests that variability between zebrafish lines occurs, and researchers should evaluate each line or strain under their particular laboratory conditions for selection of the optimum chlorine treatment procedure.Keywords: Zebrafish, Danio rerio, Chlorine, Mortality, Malformation
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Case studies : Using the zebrafish to evaluate neurobehavioral phenotypes
The use of zebrafish in behavioral neuroscience is rapidly growing. Zebrafish can be assessed for alterations in multiple behavioral endpoints, creating opportunities to use this powerful model to identify chemicals that alter behavioral phenotypes. To evaluate the utility of zebrafish for neurotoxicity research, we designed custom instrumentation to evaluate numerous embryonic and adult zebrafish behaviors. PRAT or Photomotor Response Analysis Tool was used to analyze the embryonic photomotor response (EPR) behavior in embryonic zebrafish (24 hours post fertilization). Shuttleboxes were used to evaluate learning and active avoidance conditioning and a zebrafish Visual Imaging System (zVIS) was used to measure fear responses. Social behavior was observed using Viewpoint tracking software. Startle responses were also analyzed using taps and Noldus Ethiovision XT tracking software. EPR results showed differential movement activities throughout development of larval zebrafish. Highest movement peaks were seen in 35-37 hours post fertilization fish. Using these custom analysis tools, we also evaluated the impact of Vitamin E deficiency and developmental Benzo[a]pyrene exposure on complex adult behaviors. Generational effects of BaP exposure were also tested. Zebrafish were fed defined-diets that either had sufficient or deficient levels of Vitamin E. The vitamin E deficient zebrafish had a ~30% decrease in learning rate relative to the fish with sufficient levels of Vitamin E. Startle response data showed that vitamin E deficient fish do not get desensitized to tap stimulus. Three exposure groups and generations were reared and spawned for the BaP study (0.1% DMSO controls, 1.25 ppm BaP, 2.5 ppm BaP). The zVIS system consists of an array of 8 tanks with only single side views of video projections on LCD monitors. This allows individual fish to visualize either a group of swimming zebrafish or single predator fish. For the socialization assay zebrafish were tracked using Viewpoint tracking software. Distances apart from each other were measured and analyzed in BaP exposed fish. For the predator test, zebrafish were expected to move away from the screen. The proximity of the zebrafish is tracked relative to the LCD screen projections. The preliminary results from BaP exposed zebrafish and 0.1% DMSO controls showed the percent of time spent away from the screen during the predator test or fear response assay was in the high 70% range for all fish. The 2.5 ppm BaP fish had on average the highest percentage (65% vs 50%) time spent away from the screen. Although it is uncertain as of now if there are any generational effects because further analysis is needed. Preliminary shoaling data shows that shoaling speed may be affected by DMSO exposure. The use of DMSO controls may not be optimal for this study. Disassociation is seen in both 1.25 ppm BaP and 2.5 ppm BaP exposure groups in the F2 generation. Collectively, these data demonstrate that custom behavioral systems are able to measure complex behavioral phenotypes and suggests that there are enormous opportunities for translation neurotoxicity research using zebrafish
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Bisphenol A Exposure During Early Development Induces Sex-Specific Changes in Adult Zebrafish Social Interactions
Developmental bisphenol A (BPA) exposure is associated with adverse behavioral
effects, although underlying modes of action remain unclear. Because BPA is a
suspected xenoestrogen, the objective was to identify sex-based changes in adult
zebrafish social behavior developmentally exposed to BPA (0.0, 0.1 or 1 μM) or one of
two control compounds (0.1 μM 17β-estradiol [E2], and 0.1 μM GSK4716, a synthetic
estrogen-related receptor γ ligand). A test chamber was divided lengthwise so each
arena held one fish unable to detect the presence of the other fish. A mirror was
inserted at one end of each arena; baseline activity levels were determined without mirror. Arenas were divided into 3, computer-generated zones to represent different
distances from mirror image. Circadian rhythm patterns were evaluated at 1-3 (= AM)
and 5-8 (= PM) hr postprandial. Adult zebrafish were placed into arenas and monitored
by digital camera for 5 min. Total distance traveled, % time spent at mirror image, and
number of attacks on mirror image were quantified. E2, GSK4716, and all BPA
treatments dampened male activity and altered male circadian activity patterns; there
was no marked effect on female activity. BPA induced non-monotonic effects (response
curve changes direction within range of concentrations examined) on male % time at
mirror only in AM. All treatments produced increased % time at the mirror during PM.
Male attacks on the mirror were reduced by BPA exposure only during AM. There were
sex-specific effects of developmental BPA on social interactions and time-of-day of
observation affected results.Keywords: social behavior, bisphenol A, agonistic behavior, developmental exposure, zebrafish, circadian rhythms, sex-specific behavio
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Triclosan Exposure Is Associated with Rapid Restructuring of the Microbiome in Adult Zebrafish
Growing evidence indicates that disrupting the microbial community that comprises the intestinal tract, known as the gut microbiome, can contribute to the development or severity of disease. As a result, it is important to discern the agents responsible for microbiome disruption. While animals are frequently exposed to a diverse array of environmental chemicals, little is known about their effects on gut microbiome stability and structure. Here, we demonstrate how zebrafish can be used to glean insight into the effects of environmental chemical exposure on the structure and ecological dynamics of the gut microbiome. Specifically, we exposed forty-five adult zebrafish to triclosan-laden food for four or seven days or a control diet, and analyzed their microbial communities using 16S rRNA amplicon sequencing. Triclosan exposure was associated with rapid shifts in microbiome structure and diversity. We find evidence that several operational taxonomic units (OTUs) associated with the family Enterobacteriaceae appear to be susceptible to triclosan exposure, while OTUs associated with the genus Pseudomonas appeared to be more resilient and resistant to exposure. We also found that triclosan exposure is associated with topological alterations to microbial interaction networks and results in an overall increase in the number of negative interactions per microbe in these networks. Together these data indicate that triclosan exposure results in altered composition and ecological dynamics of microbial communities in the gut. Our work demonstrates that because zebrafish afford rapid and inexpensive interrogation of a large number of individuals, it is a useful experimental system for the discovery of the gut microbiome’s interaction with environmental chemicals.Data Availability Statement: All sequencing data files are available from the SRA database (accession number PRJNA313944)
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Aerobic Bioremediation of PAH Contaminated Soil Results in Increased Genotoxicity and Developmental Toxicity
This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Chemical Society and can be found at: https://doi.org/10.1021/acs.est.5b00499The formation of more polar and toxic polycyclic aromatic hydrocarbon (PAH)
transformation products is one of the concerns associated with the bioremediation of PAH-contaminated soils. Soil contaminated with coal tar (pre-bioremediation) from a former
manufactured gas plant (MGP) site was treated in a laboratory scale bioreactor (post-bioremediation) and extracted using pressurized liquid extraction. The soil extracts were
fractionated, based on polarity, and analyzed for 88 PAHs (unsubstituted, oxygenated, nitrated,
and heterocyclic PAHs). The PAH concentrations in the soil tested, post-bioremediation, were
lower than their regulatory maximum allowable concentrations (MACs), with the exception of
the higher molecular weight PAHs (BaA, BkF, BbF, BaP, and IcdP), most of which did not
undergo significant biodegradation. The soil extract fractions were tested for genotoxicity using the DT40 chicken lymphocyte bioassay and developmental toxicity using the embryonic
zebrafish (Danio rerio) bioassay. A statistically significant increase in genotoxicity was
measured in the unfractionated soil extract, as well as in four polar soil extract fractions, post-bioremediation (p < 0.05). In addition, a statistically significant increase in developmental
toxicity was measured in one polar soil extract fraction, post-bioremediation (p < 0.05). A series
of morphological abnormalities, including peculiar caudal fin malformations and
hyperpigmentation in the tail, were measured in several soil extract fractions in embryonic
zebrafish, both pre- and post-bioremediation. The increased toxicity measured post-bioremediation is not likely due to the 88 PAHs measured in this study (including quinones), because most were not present in the toxic polar fractions and/or because their concentrations did not increase post-bioremediation. However, the increased toxicity measured post-bioremediation is likely due to hydroxylated and carboxylated transformation products of the 3- and 4-ring PAHs (PHE, 1MPHE, 2MPHE, PRY, BaA, and FLA) that were most degraded
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Trade-offs in ecosystem impacts from nanomaterial versus organic chemical ultraviolet filters in sunscreens
Both nanoparticulate (nZnO and nTiO(2)) and organic chemical ultraviolet (UV) filters are active ingredients in sunscreen and protect against skin cancer, but limited research exists on the environmental effects of sunscreen release into aquatic systems. To examine the trade-offs of incorporating nano particles (NPs) into sunscreens over the past two decades, we targeted endpoints sensitive to the potential risks of different UV filters: solar reactive oxygen production in water and disruption of zebrafish embryo development. First, we developed methodology to extract nanoparticles from sunscreens with organic solvents. Zebrafish embryos exposed to parts-per-million NPs used in sunscreens displayed limited toxicological effects; nZnO particles appeared to be slightly more toxic than nTiO(2) at the highest concentrations. In contrast, seven organic UV filters did not affect zebrafish embryogenesis at or near aqueous solubility. Second, to simulate potent photo-initiated reactions upon release into water, we examined methylene blue (MB) degradation under UV light. nTiO(2) from sunscreen caused 10 times faster MB loss than nZnO and approached the photocatalytic degradation rate of a commercial nTiO(2) photo catalysts (P25). Organic UV filters did not cause measurable MB degradation. Finally, we estimated that between 1 and 10 ppm of sunscreen NPs in surface waters could produce similar steady state hydroxyl radical concentrations as naturally occurring fluvic acids under sunlight irradiation. Incorporation of NPs into sunscreen may increase environmental concentrations of reactive oxygen, albeit to a limited extent, which can influence transformation of dissolved substances and potentially affect ecosystem processes. (C) 2018 Elsevier Ltd. All rights reserved
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Chronic exposure of killifish to a highly polluted environment desensitizes estrogen–responsive reproductive and biomarker genes
Reproductive and endocrine disruption is commonly reported in aquatic species exposed to complex contaminant mixtures. We previously reported that Atlantic killifish (Fundulus heteroclitus) from the chronically contaminated Newark Bay, NJ, exhibit multiple endocrine disrupting effects, including inhibition of vitellogenesis (yolk protein synthesis) in females and false negative vitellogenin biomarker responses in males. Here, we characterized the effects on estrogen signaling and the transcriptional regulation of estrogen–responsive genes in this model population. First, a dose–response study tested the hypothesis that reproductive biomarkers (vtg1, vtg2, chg H, chg Hm, chg L) in Newark Bay killifish are relatively less sensitive to 17β–estradiol at the transcriptional level, relative to a reference (Tuckerton, NJ) population. The second study assessed expression for various metabolism (cyp1a, cyp3a30, mdr) and estrogen receptor (ER α, ER βa, ER βb) genes under basal and estrogen treatment conditions in both populations. Hepatic metabolism of 17β–estradiol was also evaluated in vitro as an integrated endpoint for adverse effects on metabolism. In the third study, gene methylation was evaluated for promoters of vtg1 (8 CpGs) and vtg2 (10 CpGs) in both populations, and vtg1 promoter sequences were examined for single nucleotide polymorphism (SNPs). Overall, these studies show that multi–chemical exposures at Newark Bay have desensitized all reproductive biomarkers tested to estrogen. For example, at 10 ng/g 17β–estradiol, inhibition of gene induction ranged from 62% to 97% for all genes tested in the Newark Bay population, relative to induction levels in the reference population. The basis for this recalcitrant phenotype could not be explained by a change in 17β–estradiol metabolism, nuclear estrogen receptor expression, promoter methylation (gene silencing) or SNPs, all of which were unaltered and normal in the Newark Bay population. The decreased transcriptional sensitivity of estrogen–responsive genes is suggestive of a broad effect on estrogen receptor pathway signaling, and provides insight into the mechanisms of the endocrine disrupting effects in the Newark Bay population.Keywords: Killifish, Vitellogenin, Choriogenin, Estrogen, Biomarkers, Endocrine disruptionKeywords: Killifish, Vitellogenin, Choriogenin, Estrogen, Biomarkers, Endocrine disruptio
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