Effects of quillaja saponin (Quillaja saponaria) on early embryonic zebrafish (Danio rerio) development

Although much attention has focused on environmental contamination by heavy metals, pesticides, and polychlorinated biphenyls, potential deleterious effects of naturally occurring organic compounds have received much less consideration. Saponins, which are glycosides found in many plants, are important, environmentally ubiquitous organic compounds. Saponins have both beneficial and deleterious effects in adults, but little is known about how saponins effect early vertebrate embryonic development. The authors tested the toxicity of quillaja saponin using a zebrafish embryo assay. Quillaja saponin, extracted from bark of the tree, Quillaja saponaria, is a common foaming agent used in foods and beverages. At 6 h post fertilization, zebrafish embryos were exposed to five concentrations (0 [negative control], 1, 5, 10 or 20 micro g) of quillaja saponin per milliliter of medium. Zebrafish embryos exposed to 2% ethanol were positive controls (100% embryonic death). Embryos were assessed at 30, 54, and 72 h post fertilization for changes in embryonic development, mortality, time of hatching, and morphological deformities. Embryos exposed to 1 and 5 micro g saponin were healthy, showed no obvious deformities, but exhibited shrinkage of the chorion. Hatching time for zebrafish embryos exposed to 1 and 5 micro g/ml saponin decreased by 18 h compared to unexposed embryos. Zebrafish embryos treated with 5 micro g/ml saponin responded less to touch than embryos treated with 1 micro g/ml saponin or controls. Zebrafish embryos exposed to more than 5 micro g/ml saponin exhibited 100% embryonic mortality. These results indicate that exposure to 5 micro g/ml or less of quillaja saponin acts as a growth promoter, whereas concentrations of 10 micro g/ml or greater are lethal.     

Cadmium significantly changes major morphometrical points and cardiovascular functional parameters during early development of zebrafish

Living organisms are commonly exposed to cadmium and other toxic metals. A vast body of research has shown the significant effects of these toxic metals on developmental processes. In order to study the role of toxic metals on early developmental stages of eukaryotes, we explored the effect of cadmium (Cd²⁺) contaminant on zebrafish. Thus, zebrafish embryos were exposed to 3 mg/L (16.7 μM) Cd²⁺ for 96 h and imaged every 24 h from the exposure onwards. Hatching rates of the eggs were determined at 72 h, followed by analyses at 96 h for: survival rate, morphometrical factors, and functional parameters of the cardiovascular system. Interestingly enough, significant hatching delays along with smaller cephalic region and some morphological abnormalities were observed in the treatment group. Moreover, substantial changes were noticed in the length of notochord and embryo, absorption of yolk sac with shorter extension, area of swimming bladder, as well as pericardium sac after Cd²⁺ treatment. Cadmium also caused significant abnormalities in heart physiology which could be the leading cause of mentioned morphological deformities. Herein, our results shine light on systematic acute embryological effects of cadmium in the early development of zebrafish for the first time.     

Comparison of the toxicity of silver, gold and platinum nanoparticles in developing zebrafish embryos

Nanoparticles have diverse applications in electronics, medical devices, therapeutic agents and cosmetics. While the commercialization of nanoparticles is rapidly expanding, their health and environmental impact is not well understood. Toxicity assays of silver, gold, and platinum nanoparticles, using zebrafish embryos to study their developmental effects were carried out. Gold (Au-NP, 15-35 nm), silver (Ag-NP, 5-35 nm) and platinum nanoparticles (Pt-NP, 3-10 nm) were synthesized using polyvinyl alcohol (PVA) as a capping agent. Toxicity was recorded in terms of mortality, hatching delay, phenotypic defects and metal accumulation. The addition of Ag-NP resulted in a concentration-dependant increase in mortality rate. Both Ag-NP and Pt-NP induced hatching delays, as well as a concentration dependant drop in heart rate, touch response and axis curvatures. Ag-NP also induced other significant phenotypic changes including pericardial effusion, abnormal cardiac morphology, circulatory defects and absence or malformation of the eyes. In contrast, Au-NP did not show any indication of toxicity. Uptake and accumulation of nanoparticles in embryos was confirmed by inductively coupled plasma optical emission spectroscopy (ICP-OES), which revealed detectable levels in embryos within 72 hpf. Ag-NP and Au-NP were taken up by the embryos in relatively equal amounts whereas lower Pt concentrations were observed in embryos exposed to Pt-NP. This was probably due to the small size of the Pt nanoparticles compared to Ag-NP and Au-NP, thus resulting in fewer metal atoms being retained in the embryos. Among the nanoparticles studied, Ag-NPs were found to be the most toxic and Au-NPs the non-toxic. The toxic effects exhibited by the zebrafish embryos as a consequence of nanoparticle exposure, accompanied by the accumulation of metals inside the body calls for urgent further investigations in this field.     

Toxicity and cardiac effects of carbaryl in early developing zebrafish (Danio rerio) embryos

Carbaryl, an acetylcholinesterase inhibitor, is known to be moderately toxic to adult zebrafish and has been reported to cause heart malformations and irregular heartbeat in medaka. We performed experiments to study the toxicity of carbaryl, specifically its effects on the heart, in early developing zebrafish embryos. LC50 and EC50 values for carbaryl at 28 h post-fertilization were 44.66 microg/ml and 7.52 microg/ml, respectively, and 10 microg/ml carbaryl was used in subsequent experiments. After confirming acetylcholinesterase inhibition by carbaryl using an enzymatic method, we observed red blood cell accumulation, delayed hatching and pericardial edema, but not heart malformation as described in some previous reports. Our chronic exposure data also demonstrated carbaryl-induced bradycardia, which is a common effect of acetylcholinesterase inhibitors due to the accumulation of acetylcholine, in embryos from 1 day post-fertilization (dpf) to 5 dpf. The distance between the sinus venosus, the point where blood enters the atrium, and the bulbus arteriosus, the point where blood leaves the ventricle, indicated normal looping of the heart tube. Immunostaining of myosin heavy chains with the ventricle-specific antibody MF20 and the atrium-specific antibody S46 showed normal development of heart chambers. At the same time, acute exposure resulted in carbaryl-induced bradycardia. Heart rate dropped significantly after a 10-min exposure to 100 microg/ml carbaryl but recovered when carbaryl was removed. The novel observation of carbaryl-induced bradycardia in 1- and 2-dpf embryos suggested that carbaryl affected cardiac function possibly through an alternative mechanism other than acetylcholinesterase inhibition such as inhibition of calcium ion channels, since acetylcholine receptors in zebrafish are not functional until 3 dpf. However, the exact nature of this mechanism is currently unknown, and thus further studies are required.     

Aflatoxin B1 Toxicity in Zebrafish Larva (Danio rerio): Protective Role of Hericium erinaceus

Aflatoxin B1 (AFB1), a secondary metabolite produced by fungi of the genus Aspergillus, has been found among various foods as well as in fish feed. However, the effects of AFB1 on fish development and its associated toxic mechanism are still unclear. In the present study, we confirmed the morphological alterations in zebrafish embryos and larvae after exposure to different AFB1 doses as well as the oxidative stress pathway that is involved. Furthermore, we evaluated the potentially protective effect of Hericium erinaceus extract, one of the most characterized fungal extracts, with a focus on the nervous system. Treating the embryos 6 h post fertilization (hpf) with AFB1 at 50 and 100 ng/mL significantly increased oxidative stress and induced malformations in six-day post-fertilization (dpf) zebrafish larvae. The evaluation of lethal and developmental endpoints such as hatching, edema, malformations, abnormal heart rate, and survival rate were evaluated after 96 h of exposure. Hericium inhibited the morphological alterations of the larvae as well as the increase in oxidative stress and lipid peroxidation. In conclusion: our study suggests that a natural extract such as Hericium may play a partial role in promoting antioxidant defense systems and may contrast lipid peroxidation in fish development by counteracting the AFB1 toxicity mechanism.     

核酸染料Goodview、Gelred和Gelsafe对斑马鱼胚胎发育的毒性作用

目的研究核酸染料Goodview、Gelred和Gelsafe对斑马鱼胚胎发育的影响。方法将受精后时间（hpf）为3hpf的斑马鱼胚胎随机分组,分别加入0、0.01%、0.02%、0.04%、0.08%、0.16%和0.32%浓度的Goodview、Gelred和Gelsafe 3种核酸染料,观察3种核酸染料对斑马鱼胚胎发育的影响,记录胚胎48 hpf心率,计算72和96 hpf孵化率,96 hpf死亡率及畸形率;同时观察了4、24和48 hpf 3种染料穿透胚胎膜的情况。结果 Goodview、Gelred和Gelsafe 3种核酸染料半数致死浓度（LC50）分别为0.037%、0.092%和0.130%。3种核酸染料0.04%～0.32%浓度组的胚胎48 hpf心率、72和96 hpf孵化率、96hpf死亡率和畸形率与对照组相比都存在显著差异,3种核酸染料96 hpf死亡率、72和96 hpf孵化率还存在剂量-效应关系。Gelsafe 0.08%～0.32%浓度组部分幼鱼出现心囊水肿和脊柱弯曲,0.32%Gelred组染毒后还出现眼点发育不全,Goodview0.04～0.16%浓度组部分幼鱼除心囊水肿和脊柱弯曲外,还出现尾部发育不全等畸形表征。0.01%Goodview 4 hpf能穿透胚胎膜进入胚胎内,随着浓度和时间增加,胚胎内荧光增强。而Gelred和Gelsafe 0.32%浓度下4 hpf未发现明显荧光蓄积点,24hpf和48 hpf仍未发现。结论 3种核酸染料对斑马鱼胚胎发育有毒性,随着使用浓度的增加毒性增加。     

Effect of fluorescent whitening agent on the transcription of cell damage-related genes in zebrafish embryos

7‐Diethylamino‐4‐methylcoumarin (DEMC) is a fluorescent whitening agent (FWAs). There have been some studies on DEMC's protective effects against biological activity but there are few papers about the in vivo toxicity of DEMC. In this study, we used wild‐type zebrafish embryos 3 days post fertilization (dpf). Test solutions with DEMC concentrations were negative control (without vehicle), 0 (with vehicle, 0.01% v/v ethanol), 0.25, 0.5, 0.75, 1.0, 1.25, 1.5 and 2 ppm. Embryos and larvae were counted for survival rate and hatching rate. Heart rates were also counted at 2.5 and 3.0 dpf. At 3.0 dpf, quantitative RT‐PCR was performed with some samples (0, 0.25, 0.75 and 1.25 ppm) to determine the toxic effect to DEMC by detecting the expression levels of toxic‐responsive genes. We used 11 genes, which included oxidative stress‐related genes [sod(Mn), sod(Cu,Zn) and hsp70], mitochondrial metabolism‐related genes (coxI, pyc, cyt and cyclinG1) and apoptosis‐related genes (c‐jun, bcl2, bax and p53). High‐concentration DEMC‐treated groups showed significant different survival rate, hatching rate and heart rate compared with low‐concentration DEMC‐treated groups. The LC₅₀ of this chemical, 0.959 ppm, was calculated. We also confirmed that some genes in the DEMC exposure groups showed significantly up‐regulations in expression levels compared with control groups. We concluded that the fluorescence agent, DEMC, has possible developmental toxicities and alteration effect of gene expression, which are related to oxidative stress, mitochondrial metabolism and apoptosis in zebrafish embryos. Copyright © 2011 John Wiley & Sons, Ltd.     

The teratogenic effects of polychlorinated naphthalenes (PCNs) on early development of the zebrafish (Danio rerio)

The present study examines the effects of PCN congeners (PCN50 and PCN66) on zebrafish embryos. The embryos were exposed to different concentrations (20, 30 and 50μg/l) of the respective congeners by dissolving 0.08% acetone. The following endpoints were investigated (mortality, hatching rate, abnormalities and heart rate). No effect on survival was recorded for 20μg/l PCN congeners. On the other hand, embryos exposed to 30 and 50μg/l PCNs showed a significant reduction in survival rate. No developmental defects occurred with any of the congeners at the 20μg/l concentration. However, starting with 30μg/l, weak to very pronounced abnormalities (Lordosis, Kyphosis, disrupted axial body, tail defect, reduced heartbeat, and abnormal hatching) were observed depending on the congener and the concentration used. PCN66 has been shown to be more embryotoxic congener than PCN50. This demonstration of zebrafish responsiveness to PCNs early life stage toxicity coupled with the considerable information on developmental biology and genetics of zebrafish provides a foundation for future investigations into the mechanism of PCNs developmental toxicity.     

A representative retinoid X receptor antagonist UVI3003 induced teratogenesis in zebrafish embryos

Retinoid X receptor (RXR) interfering activity has been detected in different water resources. To study RXR disruptor‐induced toxicological effects on vertebrates, embryos of zebrafish (Danio rerio) were exposed to a representative RXR antagonist UVI3003. Results showed that the teratogenic index (LC₅₀/EC₅₀) of UVI3003 was as high as 5.4. UVI3003 induced multiple malformations of embryos, including deformed fins, reduced brains, small jaws, bent tails and edema in hearts, the degree of which became more severe with increasing exposure concentration. Although no significant difference was observed in the hatching rates between the exposure group and control, the whole body length was significantly reduced by 6.5% and 8.9% when exposed to 200 and 300 µg l^?1 of UVI3003, respectively. The heart rate also significantly decreased by 8.8–50.2% during exposure. Further experiments revealed that the pharyngula stage was the most sensitive development phase in terms of embryo response to UVI3003. The results demonstrated severe teratogenicity of RXR antagonist in zebrafish embryos and provided important data for ecotoxicological evaluation of RXR antagonists. Copyright © 2014 John Wiley & Sons, Ltd.     

TBBPA induces developmental toxicity,oxidative stress,and apoptosis in embryos and zebrafish larvae (Danio rerio)

Tetrabromobisphenol A (TBBPA) is currently one of the most frequently used brominated flame retardants and can be considered as a high production volume chemical. In this study, zebrafish embryos and larvae served as a biological model to evaluate TBBPA‐induced developmental toxicity, oxidative stress, oxidant‐associated gene expression, and cell apoptosis. Abnormalities, including hyperemia and pericardial edema, were induced in zebrafish larvae. The results showed that toxicity endpoints such as hatching rate, survival rate, malformation rate, and growth rate had a significant dose–response relationship with TBBPA. Further studies revealed that TBBPA did not alter the enzyme activities of Copper/Zinc Superoxide dismutase (Cu/Zn‐SOD), catalase (CAT), and glutathioneperoxidase (GPx) at 0.10 mg/L, but decreased activities following exposure to 0.40, 0.70, and 1.00 mg/L. Despite the significantly decreased gene expression of Cu/Zn‐SOD, CAT, and GPx1a in the 1.00 mg/L treatment group, other treatments (0.10, 0.40, 0.70 mg/L) did not alter gene expression. Moreover, Acridine orange staining results showed that apoptotic cells mainly accumulated in the brain, heart, and tail, indicating possible TBBPA‐induced brain, cardiac, and blood circulation system impairment in zebrafish embryos and larvae. Histological analysis also showed evidence of obvious heart impairment in TBBPA‐treated groups. This study provides new evidence on the developmental toxicity, oxidative stress, and apoptosis of embryos and zebrafish larvae, which is important for the evaluation of environmental toxicity and chemical risk. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1241–1249, 2016.     

The effect of methylmercury exposure on early central nervous system development in the zebrafish (Danio rerio) embryo

Much attention is focused on environmental contamination by heavy metals. The heavy metal mercury is found worldwide and is ranked number 3 on the Comprehensive Environmental Response, Compensation and Liability Act substance list. We examined the effect of low‐level methylmercury exposure on central nervous system development of wild‐type zebrafish embryos (ZFEs) of the AB strain because methylmercury is the most common form of mercury to which humans are exposed in the environment. ZFEs were exposed to nine different concentrations of methylmercury [0 (negative control), 5, 10, 50, 80, 100, 200, 500 and 1000 parts per billion (μg l^?1)] starting at 6 h post‐fertilization, which is the time the neural tube is first beginning to form. ZFEs were exposed to 2% ethanol as positive controls (100% embryonic death). ZFEs were assessed at 30, 54, 72 and 96 h post‐fertilization for changes in embryonic development, mortality, time of hatching and morphological deformities. No abnormalities were observed in ZFEs exposed to 5 μg l^?1 methylmercury. The time of hatching from the chorion was delayed in ZFEs exposed to methylmercury concentrations of 50 μg l^?1 or higher. Significantly more ZFEs exposed to 0, 5 or 10 μg l^?1 methylmercury successfully completed hatching compared with ZFEs exposed to 50 μg l^?1 or higher methylmercury. ZFEs exposed to more than 200 μg l^?1 methylmercury exhibited 100% embryonic mortality. The rate of cell proliferation within the neural tube was significantly decreased in embryos exposed to 10, 50 and 80 μg l^?1 methylmercury and there were no differences between these doses. Copyright © 2011 John Wiley & Sons, Ltd.     

Environmental concentration of carbamazepine accelerates fish embryonic development and disturbs larvae behavior

Environmental pollution caused by pharmaceuticals has been recognized as a major threat to the aquatic ecosystems. Carbamazepine, as the widely prescribed antiepileptic drug, has been frequently detected in the aquatic environment and has created concerns about its potential impacts in the aquatic organisms. The effects of carbamazepine on zebrafish embryos were studied by examining their phenotype, behavior and molecular responses. The results showed that carbamazepine disturbed the normal growth and development of exposed zebrafish embryos and larvae. Upon exposure to carbamazepine at 1 μg/L, the hatching rate, body length, swim bladder appearance and yolk sac absorption rate were significantly increased. Embryos in treatment groups were more sensitive to touch and light stimulation. At molecular level, exposure to an environmentally relevant concentration (1 μg/L) of carbamazepine disturbed the expression pattern of neural-related genes of zebrafish embryos and larvae. This study suggests that the exposure of fish embryo to antiepileptic drugs, at environmentally relevant concentrations, affects their early development and impairs their behavior. Such impacts may have future repercussions by affecting fish population structure.     

Toxicity evaluation of β‐diketone antibiotics on the development of embryo‐larval zebrafish (Danio rerio)

This study evaluated the effects of β‐diketone antibiotics (DKAs) on the development of embryo‐larval zebrafish (Danio rerio). When exposure to DKAs, developmental malformations, such as hatching delay, curved body axis, pericardial edema, uninflated swim bladder and yolk sac edema, were observed at 120 h postfertilization (hpf). The estimated 120 hpf nominal concentrations of no observed effect concentration and lowest observed effect concentration for DKAs were 18.75 and 37.50 mg/L, respectively, suggesting that DKAs have much lower toxicity than other persistent pollutants. Following DKA exposure, embryonic heart rates were significantly reduced as compared to the controls at 48 and 60 hpf. The peak bending motion frequency appeared 1 h earlier than in control embryos. The 2.34 and 9.38‐mg/L treatment groups had a higher basal swim rate than control groups at 120 hpf in both light and light‐to‐dark photoperiod experiments. The occurrence of high speed swim rates was enhanced approximately threefold to sevenfold in the 2.34 and 9.38 mg/L treatments compared to the control. Glutathione (GSH) concentrations in the 2.34 and 9.38‐mg/L treatments were significantly higher than the control at 72 hpf, suggesting that GSH production was induced at the end of the hatching period. When exposed to DKAs, zebrafish superoxide dismutase enzyme (SOD) activities were significantly inhibited in the early embryonic period, demonstrating that the clearing ability in zebrafish was lower than the generation rate of free radicals. In summary, the combined DKAs were developmentally toxic to zebrafish in their early life stages and had the ability to impair individual behaviors that are of great importance in the assessment of their ecological fitness. © 2013 Wiley Periodicals, Inc. Environ Toxicol 29: 1134–1146, 2014.     

Study on chemical constituents of Folium Artemisiae argyi Carbonisatum,toxicity evaluation on zebrafish and intestinal hemostasis

Folium Artemisiae argyi Carbonisatum (FAAC) is a traditional medicine widely used in clinic. It has the effect of hemostasis by warming meridians. In order to further explore the chemical composition and biological activity of FAAC, the methanol extract of FAAC was isolated and purified by open column and high- performance liquid chromatography. and the complete structure was characterized by nuclear magnetic resonance (NMR) and LREI-MS for the first time, namely rutin, quercetin and octacosanol respectively. Initially the toxic effect of methanol extract of FAAC on zebrafish was evaluated by observing the phenotypic characteristics, spontaneous twitch times, heart rate, hatching rate, the distance of SV-BA and cardiomyocyte apoptosis of zebrafish. The results showed that FAAC has embryonic development toxicity and cardiotoxicity when it was higher than 62.5 μg/mL. Meanwhile, the hemostatic effect of methanol extract of FAAC was compared with FAA (Folium Artemisia argyi) by zebrafish intestinal bleeding model originally. The results showed that the hemostatic effect of the medium and high concentration dose groups (3.0 and 30.0 μg/mL) was enhanced for both FAAC and FAA. This study provided an experimental basis for the clinical application of FAAC.     

Sex steroids in the female zebrafish (Danio rerio). Effects of cyproterone acetate and leachate-contaminated sediment extract

In Molnbyggen, a leachate-contaminated lake in Sweden, effects on the reproductive system of perch included a decreased frequency of sexually mature female perch, reduced gonadosomatic index and decreased plasma levels of androstenedione and testosterone, but the contaminants responsible for these effects have not yet been identified. A biomarker-directed fractionation approach could be used to narrow the search for the compound(s) responsible for the adverse effects in Molnbyggen female perch. Thus, it is important to develop and test a suitable biomarker, which can be used in this type of approach. We evaluated if decreased concentrations of sex steroids could work as an in vivo end-point in female zebrafish fed an organic extract of bottom sediments from Molnbyggen. The responsiveness of zebrafish to endocrine alteration was evaluated using a positive control substance, cyproterone acetate (CA), which is known to inhibit steroid biosynthesis. After the 21-day exposure period the concentrations of testosterone (T) and estradiol (E2) were successfully determined by HRGC/HRMS in whole-body homogenates of individual fish. Median T concentrations were 1.7pmol/g fish in controls and were decreased after exposure both to CA (0.55pmol/g fish) and Molnbyggen sediment extract (1.2-1.3pmol/g fish). Median E2 concentrations were 5.3pmol/g fish in controls and were decreased after CA exposure (2.3pmol/g fish) and after exposure to Molnbyggen sediment extract (4.0-4.5pmol/g fish). This suggests that sex steroid concentrations in zebrafish are responsive to endocrine alteration and indicates that compounds with endocrine altering potency are present in Molnbyggen sediments.     

Potential ecological risk of heavy metals and metalloid in the sediments of Wuyuer River basin,Heilongjiang Province,China

The spatial distribution, sources, and potential ecological risk of heavy metals and metalloid were evaluated in sediments of the Wuyuer River and its tributaries. Metal and metalloid concentrations and chemical speciation (Cr, Cu, Ni, Pb, Cd, As, Zn and Hg) in 187 surface sediment samples were measured using inductively coupled plasma mass spectrometry. Metals and metalloid in the sediments of the Wuyuer River were greater than the background values of the Songnen Plain, and mean heavy metal concentrations were greater in downstream segments of the river than in upstream segments. Speciation results indicated that Cd was chemically mobile and Cu, Pb, Zn, Cr, and Ni were potentially bioavailable. Mercury and As existed mainly in the residual fraction. Hakanson’s potential risk index indicated that the total potential ecological risk of these elements was moderate in the Wuyuer River. Among the selected metals and metalloid, Hg and Cd were the most potentially toxic and mainly distributed near the cities of Keshan, Yi’an and Fuyü. Because the speciation of Cd in the river sediments is highly bioavailable, the concentrations of Cd should be closely monitored. This research provides managers with information needed to better regulate the environment of the Wuyuer River.     

Xenoestrogenic effects of ethinylestradiol in zebrafish (Danio rerio)

To assess the estrogenic effects of ethinylestradiol on zebrafish, zebrafish at different developmental stages (embryos, juveniles, and adults) were exposed to the synthetic hormone ethinylestradiol (EE2) in concentrations of 1, 10, and 100 ng/L for up to 33 days. Survival, hatching, length, weight, growth, condition, hepatosomatic index, gonadosomatic index, and vitellogenin (VTG) production were examined. Exposure of zebrafish juveniles and embryos to 100 ng EE2/L for up to 33 days had significant effects on survival, growth, and hatching. Two VTG fragments with molecular weights of approximately 140 and 170 kDa were detected with protein electrophoresis and Western blotting in the blood of exposed males and exposed and unexposed females, as well as in whole-body homogenates of exposed and unexposed juveniles. Significantly higher VTG concentrations (compared to controls) were measured in adults exposed to 10 and 100 ng EE2/L for 14 days, but not in fish exposed to 1 ng EE2/L. This study demonstrated that (1) zebrafish juveniles, larvae, and embryos are sensitive to the toxic effects of the endocrine disrupter EE2; (2) the effects on VTG production in adults are detected after exposure to environmentally relevant concentrations of EE2; (3) unexposed juvenile zebrafish produce measurable concentrations of VTG.     

Characterization and toxicology evaluation of zirconium oxide nanoparticles on the embryonic development of zebrafish,Danio rerio

Zirconia oxide nanoparticles (ZrO₂NPs) are known to be one of the neutral bioceramic metal compounds that has been widely used for their beneficial applications in many biomedical areas, in dental implants, bone joint replacements, drug delivery vehicles, and in various industrial applications. To study the effects of ZrO₂NPs on zebrafish model, we used early life stages of the zebrafish (Danio rerio) to examine such effects on embryonic development in this species. ZrO₂NPs were synthesized by the sol-gel method, size about 15–20?nm and characterized by SEM, EDX, XRD, FTIR, UV-Vis Spectra. In this study, zebrafish embryos were treated with ZrO₂NPs 0.5, 1, 2, 3, 4, or 5?μg of nanoparticles/ml during 24–96?hour post fertilization (hpf). The results showed that ≥0.5–1?μg/ml of ZrO₂NPs instigated developmental acute toxicity in these embryos, causing mortality, hatching delay, and malformation. ZrO₂NPs exposure induced axis bent, tail bent, spinal cord curvature, yolk-sac, and pericardial edema. A typical phenotype was observed as an unhatched dead embryo at ≥1?μg/ml of ZrO₂NPs exposure. This study is one of the first reports on developmental toxicity of zebrafish embryos caused by zirconium oxide nanoparticles in aquatic environments. Our results show that exposure of zirconium oxide nanoparticles is more toxic to embryonic zebrafish at lower concentrations. The results will contribute to the current understanding of the potential biomedical toxicological effects of nanoparticles and support the safety evaluation and synthesis of Zirconia oxide nanoparticles.     

Distribution and pollution, toxicity and risk assessment of heavy metals in sediments from urban and rural rivers of the Pearl River delta in southern China

Sediments were collected from the upper, middle and lower reaches of both urban and rural rivers in a typical urbanization zone of the Pearl River delta. Six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) were analyzed in all sediment samples, and their spatial distribution, pollution levels, toxicity and ecological risk levels were evaluated to compare the characteristics of heavy metal pollution between the two rivers. Our results indicated that the total contents of the six metals in all samples exceeded the soil background value in Guangdong province. Based on the soil quality thresholds of the China SEPA, Cd levels at all sites exceeded class III criteria, and other metals exhibited pollution levels exceeding class II or III criteria at both river sites. According to the sediment quality guidelines of the US EPA, all samples were moderately to heavily polluted by Cr, Cu, Ni, Pb and Zn. Compared to rural river sites, urban river sites exhibited heavier pollution. Almost all sediment samples from both rivers exhibited moderate to serious toxicity to the environment, with higher contributions from Cr and Ni. A “hot area” of heavy metal pollution being observed in the upper and middle reaches of the urban river area, whereas a “hot spot” was identified at a specific site in the middle reach of the rural river. Contrary metal distribution patterns were also observed along typical sediment profiles from urban and rural rivers. However, the potential ecological risk indices of rural river sediments in this study were equal to those of urban river sediments, implying that the ecological health issues of the rivers in the undeveloped rural area should also be addressed. Sediment organic matter and grain size might be important factors influencing the distribution profiles of these heavy metals.     

Toxic effects of indoxacarb enantiomers on the embryonic development and induction of apoptosis in zebrafish larvae (Danio rerio)

Indoxacarb is a highly potent insecticide widely used to control Lepidoptera insects in vegetable, tea, cotton, and rice fields. It can run off into aquatic environments. It is consisted of two enantiomers. Environmental risks and aquatic toxicity of indoxacarb enantiomers have not been fully investigated. In this study, zebrafish (Danio rerio ) embryos were exposed to varying concentrations of (?)‐R‐indoxacarb and (+)‐S‐indoxacarb until 96‐h post‐fertilization (hpf) to assess the embryonic toxicity. (?)‐R‐indoxacarb was 1.3‐fold more toxic than (+)‐S‐isomer to zebrafish embryos at 96 hpf. (?)‐R‐indoxacarb exhibited reduction in body length and pericardial edema compared with (+)‐S‐indoxacarb. (?)‐R‐indoxacarb decreased the hatching rate sixfold greater than (+)‐S‐indoxacarb. The rate of pericardial edema induced by (?)‐R‐indoxacarb was 2.5 times greater than that by (+)‐S‐indoxacarb. The heart rate of the larvae exposed to (?)‐R‐indoxacarb was 30% lower than that to (+)‐S‐indoxacarb. In addition, exposure to the chiral isomers resulted in significant increases in apoptosis; interestingly (?)‐R‐indoxacarb induced apoptosis in the heart area, whereas (+)‐S‐indoxacarb induced apoptosis in the head area. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 7–16, 2017.