Evaluation of acute toxicity and teratogenic effects of disinfectants by Daphnia magna embryo assay

Phytochemical, In Vitro, In Vivo, and In Silico Research on the Extract of Ajuga chamaepitys (L.) Schreb

The present study focuses on the chemical characterization of a dry extract obtained from the species Ajuga chamaepitys (L.) Schreb, evaluating its antioxidant properties, toxicity, and in silico profile. Quantitative analysis of the dry extract revealed a notable amount of phytochemical compounds: 59.932 ± 21.167 mg rutin equivalents (mg REs)/g dry weight, 45.864 ± 4.434 mg chlorogenic acid equivalents (mg ChAEs)/g dry weight and, respectively, 83.307 ± 3.989 mg tannic acid equivalents (TAEs)/g dry weight. By UHPLC-HRMS/MS, the following were quantified as major compounds: caffeic acid (3253.8 μg/g extract) and kaempherol (3041.5 μg/g extract); more than 11 types of polyphenolic compounds were quantified (genistin 730.2 μg/g extract, naringenin 395 μg/g extract, apigenin 325.7 μg/g extract, galangin 283.3 μg/g extract, ferulic acid 254.3 μg/g extract, p-coumaric acid 198.2 μg/g extract, rutin 110.6 μg/g extract, chrysin 90.22 μg/g extract, syringic acid 84.2 μg/g extract, pinocembrin 32.7 μg/g extract, ellagic acid 18.2 μg/g extract). The antioxidant activity was in accordance with the amount of phytochemical compounds: IC50DPPH = 483.6 ± 41.4 µg/mL, IC50ABTS•+ = 127.4 ± 20.2 µg/mL, and EC50FRAP = 491.6 ± 2 µg/mL. On the larvae of Artemia sp., it was found that the extract has a low cytotoxic action. In silico studies have highlighted the possibility of inhibiting the activity of protein kinases CDK5 and GSK-3b for apigenin, galangin, and kaempferol, with possible utility for treating neurodegenerative pathologies and neuropathic pain. Further studies are warranted to confirm the predicted molecular mechanisms of action and to further investigate the therapeutic potential in animal models of neurological disorders.

Concentration-dependent effects of lithium on Daphnia magna: Life-history profiles and integrated biomarker response implementation

The growing use of lithium (Li) in industrial and energy applications and increasing demand worldwide has inevitably resulted in its wide dispersal, representing a significant threat to aquatic systems. Unfortunately, as a ubiquitous emerging contaminant, the comprehensive toxicological information regarding Li at multifarious levels is limited. To diminish this gap, this work was focused to explore Li-induced cascading effects on Daphnia magna as a key species in freshwater ecosystems. Specifically, the organisms were chronically exposed to gradient Li concentrations with emphasis on characterizing life-history traits from individual to population scale, primarily as observed by a markedly concentration-dependent decrease along exposure gradients. In parallel, a robust set of biomarkers relating to energy reserves, antioxidant and biotransformation enzymes, cellular damage, ionoregulation and neurotoxicity were assayed for further understanding potential underlying mechanisms. As a result, biomarker alterations were characterized by significant decreases in energy storage and enzymatic profiles of antioxidant and biotransformation systems, not only triggering an imbalance between reactive oxygen species (ROS) generation and elimination under Li exposure, but compromising the fecundity fitness of phenotypical costs. In contrast, malondialdehyde (MDA) levels were remarkably enhanced as a consequence of inefficient antioxidant and biotransformation capacity leading to lipid peroxidation (LPO). Additionally, Li exerted a dose-dependent biphasic effect on the activities of superoxide dismutase (SOD), Na+,K+-ATPase and acetylcholinesterase (AChE) by interfering with inherent balance. In terms of responsive patterns and dose-effect trends, the integrated biomarker response indices (IBRv2) and star plots were consistent with the differences in biomarker profiles, not only presenting comprehensively biological effects in a visualized form, but signaling the importance of progressive induced changes in an integrative way. Overall, these findings highlighted the need for elucidating Li-produced impacts from a comprehensive perspective, providing valuable insights into better understanding the toxicity of Li in relation to aquatic ecosystem functioning and ecological relevance.

Integrated histopathology and transcriptome metabolome profiling reveal the toxicity mechanism of phenazine-1-carboxylic acid in zebrafish

Phenazine-1-carboxylic acid (PCA) is a new type of agrochemical used to prevent plant diseases, but its effects on aquatic organisms are unclear. To comprehensively assess the impacts of PCA for aquatic organisms and its associated environmental risks, this study investigated, taking zebrafish as the research object, the toxicological mechanism of PCA by means of optical microscopy, hematoxylin and eosin (HE) staining, ultrastructural observation, physiological and biochemical testing, transcriptome sequencing, metabolome analysis, fluorescence quantitative PCR and molecular simulation. The results indicated that PCA was detrimental to zebrafish embryos, larvae and adults, with LC50 values at 96 h of 3.9093 mg/L, 8.5075 mg/L, and 13.6388 mg/L, respectively. PCA caused abnormal spontaneous movement, slowed the heart rate, delayed hatching, shortened the body length, slowed growth, and caused malformations. PCA mainly affected the brain, liver, heart, and ovaries. PCA distorted cell morphology, damaged mitochondrial membranes, disintegrated mitochondrial ridges, and dissociated nuclear membranes. PCA inhibited the enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX), decreased the malondialdehyde (MDA) content and disrupted antioxidant effects. The results of omics studies confirmed that PCA interfered with the transcriptional and metabolic network of zebrafish, downregulating most genes and metabolites. PCA mainly affected functions related to mitochondrial steroids, lipids, sterols, oxidoreductase activity and pathways involving cofactors, steroids, porphyrin, cytochromes, which specifically bound to targets such as panx3, agmat, and ace2. PCA was moderately toxic to zebrafish, and its usage should be strictly controlled to reduce toxic effects on aquatic organisms. The results of this study provide a new insights for ecotoxicology research.

Thermal stress-stimulated ZnO toxicity inhibits reproduction of freshwater crustacean Daphnia magna

Elevated temperatures due to climate change pose a variety of environmental risks to the freshwater ecosystem. At the same time, zinc oxide (ZnO) has become widely used and has entered the freshwater environment. As thermal stress may potentially impact the physicochemical properties of ZnO, its toxicity to freshwater organisms in the face of global warming is poorly understood. The potential effects on reproductive performances, including oogenesis, are of particular concern. In this study, we investigate the reproductive performances and related mRNA abundance of the zooplankton Daphnia magna under conditions of ZnO exposure and heat stress. The results revealed that ZnO and elevated temperature delayed maturity and juvenile production of D. magna. Histological observations indicated that oogenesis was inhibited, and the number and size of oocytes were reduced in the condition of ZnO exposure under heat stress. Eventual offspring in the same treatment exhibited decreased numbers, size, and quality. Congenital juvenile anomalies were increased, such as deformed eye, and impaired antenna and tail spine. Moreover, both ZnO and elevated temperature treatments inhibited expression levels of reproduction-related genes (vtg, EcR and VMO1) and induced the dmrt93b gene involved in the production of male offspring. Furthermore, we found that D. magna tried to cope with ZnO and thermal stress by upregulating hsp90, HIF-1α and HIF-1β. ZnO and heat stress inhibited the reproductive capacity of D. magna, produced deleterious effects on reproduction-associated physiological pathways, and damaged reproductive outcomes.

Daphnia magna as a Model Organism to Predict the Teratogenic Effect of Different Compounds

For aquatic ecosystem Daphnia magna is evolving as a model organism to check the teratogenicity of numerous compounds. D. magna can be easily cultured in the laboratory, and the teratogen effect of several compounds can be easily studied. The developmental stages are well studied in D. magna. All the developmental stages are transparent so the defect can be easily accessed. So, the postembryonic developmental changes can be easily studied after the exposure with teratogen. More importantly, D. magna also have a swimming behavioral phenotype. The behavioral defect can be easily accessed after teratogen exposure. The current chapter summarizes numerous protocols associated with embryo and adult staining and adult behavioral assays that can be used to access the teratogenicity of any unknown compound.

Impacts of the COVID-19 pandemic on Chinese assisted reproductive technology institutions and human sperm banks: reflections in the post-pandemic era

OBJECTIVE

The COVID-19 pandemic has been the most serious public health emergency encountered in modern assisted reproductive technology (ART) development. In order to identify lessons learned, this study reviews the effect of the pandemic on ART institutions and human sperm banks in China, and summarizes the experiences and reflections of Chinese scholars post-pandemic era.

METHODS

This review is based on multiple consensus statements on the COVID-19 pandemic issued by Chinese experts as well as current national regulations and principles in ART institutions and human sperm banks to document the current situation of ART services in China, describe the impact of the pandemic on these services, and offer Chinese reflections on worrying issues in the post-pandemic era.

RESULTS

China reached one million ART cycles in 2016, and there are currently 540 ART medical institutions and 27 human sperm banks, with 540 licensed for AIH, 91 for AID, 415 for conventional IVF and ICSI and 85 for PGT. Of these, only 4 institutions carry out 10,000 cycles or more annually, and the proportion of institutions with less than 1,000 cycles has reached 66%, which means that a considerable number of ART institutions are still not saturated. As a consequence of the COVID-19 pandemic, 63.6% of ART providers and 95.5% of human sperm banks suspended operations. By the end of May 2020, China, as an early country affected by the pandemic achieved a national resumption rate of ART medical services of 99.2% and that of human sperm banks of 100.0%. Reports from the first and largest human sperm bank in China showed that qualification, semen concentration and sperm viability rates measured at primary screening have significantly decreased post-pandemic. Much like in other countries, Chinese experts developed a consensus on prevention and control measures during the pandemic. In principle, all ART activities should be suspended during acute phases of infection spread. Chinese scholars highlight that attention should be paid to young patients with fertility requirements during and after COVID-19, and emphasize the importance of fertility evaluation and clinical intervention. In addition, couples should be reminded that during ART treatment, disinfectants should not be used excessively to minimize risks of damaging the reproductive system, gametes and zygotes. At the same time, timely and reasonable guidance for tackling negative emotions from stress response is needed to provide reassurance and to avoid irrational fear and excessive stress. Seminal parameters should be re-examined 2 months after SARS-CoV-2 vaccination, and ART treatments recommenced if no abnormalities are detected.

CONCLUSIONS

Given the growing frequency of outbreaks of global infectious diseases in recent years, ART institutions and human sperm banks should pay attention to improving their prevention and control capabilities. To a certain extent, decisions and measures adopted in China during COVID-19 pandemic are worthy of recognition and acceptance. Chinese scholars have discussed, proactively responded to and understand the key issues surrounding ART development during the pandemic with the aim of contributing to the substantial progress and healthy development of ART services in the world.

Novel peptide identified from viable-cell based phage display technique regulates growth cycle of Daphnia magna

Phage display is a widely used technique for selecting specific binding peptides, but presenting antigens in their natural form can be challenging, as protein coating may induce structural changes. In this study, we employed a whole cell-based phage display technique without a coating step to select peptides that bind specifically to Daphnia magna eggs. Boiled eggs were used as a control to ensure that antigens were presented in their natural forms. We identified a peptide, DEP1 (LYALPLSHLKSHGGG), with the highest binding affinity to D. magna eggs. DEP1 did not affect zebrafish eggs, but it inhibited normal hatching and reproductive ability in D. magna eggs, and hindered growth in neonates before their first ecdysis. Morphological analysis revealed that DEP1 caused intestinal damage and tissue abnormalities. Our findings demonstrate that the whole cell-based phage display technique is successful in presenting antigens in their natural form, and that the DEP1 peptide can be applied to regulate the growth cycle of D. magna. These results have implications for the use of phage display in environmental research and the potential use of DEP1 for hazardous organisms in aquatic systems.

Assessment of eco-toxic effects of commonly used water disinfectant on zebrafish (Danio rerio) swimming behaviour and recovery responses: an early-warning biomarker approach

Eco-toxicity profiles for commonly used disinfectants were lacking. Available traditional toxicity techniques have some limitations (assessments and ethical issues). Behaviour toxicology is a promising research area towards early warning and non-invasive approaches. We studied the potential eco-toxic effects of sodium hypochlorite (NaOCl) on the swimming behaviour of zebrafish. Zebrafish were exposed to different concentrations (Treatment I, Treatment II, Treatment III, and Treatment IV) of NaOCl for 360 h. Recovery study (144 h) was conducted for NaOCl treatment groups. The swimming behaviour of zebrafish was quantified efficiently using an online monitoring system (OMS). OMS dataset was processed for determination of behavioural differences by MATLAB and SPSS. Compared to the control group, the swimming strength of zebrafish under NaOCl treatments declined significantly (p < 0.001). Avoidance behaviour has occurred on zebrafish under NaOCl exposure periods. Furthermore, NaOCl toxicity also adjusted circadian rhythms on zebrafish. Zebrafish swimming strength was significantly (p < 0.001) improved under-recovery periods. Moreover, normal diurnal patterns have occurred. NaOCl could cause behavioural abnormalities in non-target organisms. Continuous exposure to common disinfectants could cause external and internal stress on non-target organisms, resulting in behavioural changes and circadian rhythm adjustments. Continuous changes in behavioural and circadian rhythms might reduce organisms' fitness and adaptation capacity. This study highlights (1) the importance of computer-based toxicity assessments, and (2) swimming behaviour is an early warning biomarker for eco-toxicity studies.

A multi-biomarker approach for the early assessment of the toxicity of hospital wastewater using the freshwater organism Daphnia magna

Hospital wastewater (HWW) contains different hazardous substances resulting from a combination of medical and non-medical activities of hospitals, including pharmaceutical residues. These substances may represent a threat to the aquatic environment if they do not follow specific treatment processes. Therefore, we aimed to investigate the effects of the untreated effluent collected from a general hospital in Mahdia City (Tunisia) on neonatal stages of the freshwater crustacean Daphnia magna. Test organisms were exposed to three proportions (3.12%, 6.25%, and 12.5% v/v) of HWW. After 48 h of exposure, a battery of biomarkers was measured, including the quantification of antioxidant enzymes [catalase (CAT) and total and selenium-dependent glutathione peroxidase (total GPx; Se-GPx)], phase II biotransformation isoenzymes glutathione-S-transferases (GSTs), cyclooxygenases (COX) involved in the regulation of the inflammatory process, and total cholinesterases (ChEs) activities. Lipid peroxidation (LPO) was measured to estimate oxidative damage. The here-obtained results showed significant decreases of CAT and GSTs activities and also on LPO content in daphnids, whereas Se-GPx activity was significantly increased in a dose-dependent manner. Impairment of cholinesterasic and COX activities were also observed, with a significant decrease of ChEs and an increase of COX enzymatic activities. Considering these findings, HWW was capable of inducing an imbalance of the antioxidant defense system, but without resulting in oxidative damage in test organisms, suggesting that peroxidases and alternative detoxifying pathways were able to prevent the oxidant potential of several drugs, which were found in the tested effluents. In general, this study demonstrated the toxicity of hospital effluents, measured in terms of the potential impairment of key pathways, namely neurotransmission, antioxidant defense, and inflammatory homeostasis of crustaceans.

Chemical removal of m-cresol: a critical review

m-Cresol containing wastewater has generally become a globally environmental issue due to its refractory and high toxicity towards plants, animals and human being. The development of m-cresol related industries increases the risk of excessive m-cresol discharge, making high efficiency methods to treat m-cresol an urgent topic in both economic and environmental aspects. This review focuses on the chemical treatment methods of m-cresol wastewater, including chemical adsorption, photocatalytic degradation, electrocatalytic degradation and catalytic wet oxidation. The efficiency, cost and process optimization of different methods are discussed in detail. Chemical adsorption is convenient but has relatively low efficiency. Photocatalytic degradation is an easily operated technology with high efficiency, but the selection of catalyst is too limited and the cost of light source is relatively high. Electrocatalytic degradation is time-saving but energy-intensive, and operational difficulty brings a barrier to industrialization. Catalytic wet oxidation (CWO) is highly effective and easily modified, but the performance and stability of catalysts are still very moderate. Following this, the selection and application of different methods regarding the requirement of actual environment are analyzed. Finally, a perspective on the opportunities and development for efficient m-cresol removal method is given.

In silico modelling of acute toxicity of 1, 2, 4-triazole antifungal agents towards zebrafish (Danio rerio) embryos: Application of the Small Dataset Modeller tool

Nowadays, there is a widespread use of triazole antifungal agents to kill broad classes of fungi in farming lands and to protect herbs, fruits and grains. These agents further deposit into the aquatic systems causing toxicity to the living aquatic creatures, which can then affect human beings. Considering this issue, risk assessment of these toxic chemicals is a very essential task. Due to the inadequate experimental data on acute toxicity of antifungal agents containing the 1, 2, 4-triazole ring, higher testing costs along with the regulatory restrictions and the international regulations to lessen animal testing emphasize on in silico techniques such as quantitative structure-activity relationship (QSAR) studies. The application of QSAR modelling has created an easier avenue to predict activity/property/toxicity of newly synthesized compounds. In the present study, we have used 23 antifungal agents containing the 1, 2, 4-triazole ring to develop 2D-QSAR models and explored their structural attributes crucial for acute toxicity towards embryonic phase of zebrafish (Danio rerio). Here, we have employed simple 2D descriptors to develop the QSAR models. The models were evolved by executing the Small Dataset Modeller tool (https://dtclab.webs.com/software-tools), and the validation of the models was achieved by employing different precise validation principles. The statistical validation metrics confirm that built models are robust, useful and well predictive to forecast the acute toxicity of new compounds.

Evaluation of silver nanowires (AgNWs) toxicity on reproductive success of Daphnia magna over two generations and their teratogenic effect on embryonic development

This study assessed the reproductive toxicity of silver nanowires (AgNWs) in Daphnia magna over two consecutive generations. An acute immobilization test was conducted according to the ΟECD 202 guidelines. To perform reproductive toxicity tests in both F0 and F1 generations, the animals were exposed to different concentrations of AgNWs (0, 0.4, 2, 10, and 50 µg L^-1) and pyriproxyfen (0.4 µg L^-1), as a positive control, based on the ΟECD 211 principles. Overall, AgNWs were acutely toxic to D. magna with EC₅₀ value of 0.063 mg L^-1. Compared to the control groups, AgNWs disrupted reproductive performances of D. magna through increasing the egg development time and time to production of first brood as well as decreasing the total offspring production and molting frequency in both F0 and F1 generations. After exposure to AgNWs, the number of male neonates and non-reproductive females increased in the F0 generation, whereas just male neonates raised in the F1 generation. Moreover, AgNWs caused several congenital anomalies including underdeveloped antennae, 2nd antennae, malpighian tube, rostrum, sensory bristles, tail spine, and malformed eyes. Together, AgNWs could disrupt reproductive health of D. magna, and these types of bioperturbations could dramatically change the good health state of aquatic ecosystems.

Potential risks of SARS-CoV-2 infection on reproductive health

The outbreak of 2019 novel coronavirus disease (COVID-19) has become a major pandemic threat worldwide. Such a public health emergency can greatly impact various aspects of people's health and lives. This paper focuses on its potential risks for reproductive health, including the reproductive system and its functioning, as well as gamete and embryo development, which could be affected by the virus itself, drug treatments, chemical disinfectants and psychological effects related to panic during the COVID-19 outbreak.

Survival and malformation rate in oocytes and larvae of Cyprinus carpio by exposure to an industrial effluent

Pharmaceuticals are used for the prevention or treatment of diseases, and due to their manufacturing process they are continuously released to water bodies. One of the pharmacological groups detected in aquatic environments is non-steroidal anti-inflammatory drugs (NSAIDs) at trace concentrations. This study evaluated the survival and malformation rate in oocytes and larvae of Cyprinus carpio (C. carpio) after exposure to different proportions of an industrial effluent. Initially, the industrial effluent was sampled from an NSAID manufacturing plant located in the city of Toluca, State of Mexico, subsequently the physicochemical characterization and determination of the concentration of chemical compounds present were carried out. On the other hand, the lethal concentration 50 (LC50) and the effective concentration 50 (EC50) were calculated to determine the teratogenic index (TI), as well as the alterations to the embryonic development and the teratogenic effects on oocytes and larvae of C. carpio at the following proportions of the industrial effluent: 0.1, 0.3, 0.5, 0.7, 0.9 and 1.1%, following the Test Guideline 236, which describes a Fish Embryo Acute Toxicity test, the exposure times were 12, 24, 48, 72 and 96 h post-fertilization. The contaminants detected were NaClO (2.6 mg L^-1) and NSAIDs such as diclofenac, ibuprofen, naproxen and paracetamol in the range of 1.09-2.68 mg L^-1. In this study the LC50 was 0.275%, the EC50 0.133% and the TI 2.068. Several malformations were observed in all proportions of the industrial effluent evaluated, however the most severe such as spina bifida and paravertebral hemorrhage were observed at the highest effluent proportion. The industrial effluent evaluated in this study represents a risk for organisms that are in contact with it, since it contains chemical compounds that induce embryotoxic and teratogenic effects as observed in oocytes and larvae of C. carpio.

The use of freshwater planarians in environmental toxicology studies: Advantages and potential

Regarding the humane use of animals in scientific research, invertebrates are often recommended in toxicological studies. "Freshwater planarians" refers to numerous free-living freshwater members of the Class "Turbellaria" of the phylum Platyhelminthes. This group of invertebrates has received extensive attention from biologists for many years because of their unique biological characteristics, such as the primitive form of the central nervous system and notable capability to regenerate tissues. Using freshwater planarians as test animals in chemical toxicity studies has grown in popularity since the 1960s. Results from various toxicological experiments have collectively suggested that freshwater planarians can serve as not only alternative models for chemical toxicity screenings in laboratories but also as potential bioindicators for the quality of freshwater environments. However, thus far, no standardized battery of tests for conducting toxicological studies that includes freshwater planarians has been proposed. This paper comprehensively reviews the toxicological information obtained from chemically exposed planarians and proposes practical factors for consideration in toxicity experiments with freshwater planarians as test organisms.

Horseradish peroxidase immobilization by copolymerization into cross-linked polyacrylamide gel and its dye degradation and detoxification potential

Owing to the ever-increasing environmental and health impacts associated with the discharge of dye-based effluents, effective remediation of industrial waste have become a top priority for the industrialists and environmental fraternity, around the world. Plant-based peroxidases represent a suitable bio-remediating agent for the effective treatment of original dyes or dye-based colored wastewater effluents. In the present study, horseradish peroxidase was immobilized by copolymerization into cross-linked polyacrylamide gel and investigated its potential for the degradation and detoxification of an azo dye, methyl orange. In the presence of N, N'-methylenebisacrylamide as a cross-linker, polyacrylamide gel at 10% concentration furnished >80% of immobilization yield. The surface morphology of the control (free enzyme) and immobilized enzyme, i.e., horseradish peroxidase cross-linked polyacrylamide gel was characterized using scanning electron microscopy. The high yielded horseradish peroxidase cross-linked polyacrylamide gel concentration, i.e., 10% was used to develop a packed bed reactor and exploited for dye degradation and detoxification purposes. A noteworthy level (>90%) of dye degradation was recorded after polyacrylamide gel cross-linked horseradish peroxidase-catalyzed reaction in a packed bed bioreactor. The biodegradation was further assessed by Fourier-transform infrared spectral analysis. The acute toxicity assays demonstrated that enzyme-based bio-degradation might be used effectively for large-scale environmental remediation of dyes and dyes containing wastewater effluents.

Effect of organic loading rate on the removal of DMF, MC and IPA by a pilot-scale AnMBR for treating chemical synthesis-based antibiotic solvent wastewater

This study focuses on the effects of organic loading rate (OLR) on the removal of N,N-Dimethylformamide(DMF), m-Cresol (MC) and isopropyl alcohol (IPA) by a pilot-scale anaerobic membrane bioreactor (AnMBR) for treating chemical synthesis-based antibiotic solvent wastewater at period of improved influent COD concentration with decreased HRT. The whole process was divided into five stages in terms of the variation of OLR ranging from 3.9 to 12.7 kg COD/(m³·d). During 249 days of operating time, the average DMF, MC, IPA removal efficiency were 96.9%,98.2% and 96.4%, respectively. Cake layer was accumulated on the membrane surface acted as a dynamic secondary biofilm which lead to the increase of physical removal rate. In addition, mathematical statistical models was built on the linear regression techniques for exploring the inner relationship between EPS and the performance of the AnMBR.

Neonicotinoid insecticides imidacloprid, guadipyr, and cycloxaprid induce acute oxidative stress in Daphnia magna

Cycloxaprid (CYC) and guadipyr (GUA) are two new and promising neonicotinoid insecticides whose effects on Daphnia magna are as yet unknown. In this study, the acute toxicities of CYC and GUA to D. magna, including immobilization and embryo-hatching inhibition, and their effects on antioxidant enzymes and related gene expression were determined after a 48-h exposure. Imidacloprid (IMI) was evaluated at the same time as a reference agent. The 48-h EC₅₀ values of IMI, GUA, and CYC for neonate immobilization were 13.0-16.5mg/L and for embryo hatching were 11.3-16.2mg/L. The specific activity of the enzymes superoxide dismutase (SOD) and catalase (CAT) were interfered by IMI, but not by GUA and CYC, while the activity of acetylcholinesterase (AChE) was significantly increased by IMI, but inhibited by GUA and CYC. The relative expressions of the Sod-Cu/Zn, Sod-Mn, Cat, and Ache genes were usually inhibited by IMI, GUA, and CYC, except for Cat by CYC, Ache by GUA, and Sods by IMI. For vitellogenin genes with a SOD-like domain (Vtg1/2-sod), relative expression was increased by IMI and inhibited by GUA and CYC, indicating that IMI, GUA, and CYC have potential toxicity toward reproduction. CYC and GUA are highly active against IMI-resistant pests, and considering the similar toxicity of IMI to D. magna, CYC and GUA are suitable for use in future integrated pest management systems.

Effects of three diamides (chlorantraniliprole, cyantraniliprole and flubendiamide) on life history, embryonic development and oxidative stress biomarkers of Daphnia magna

The diamides have become one of the most promising new classes of insecticides. In this study, we evaluated the toxicity of three diamides (chlorantraniliprole, cyantraniliprole and flubendiamide) to Daphnia magna. The acute toxicity test showed that the 48-h EC₅₀ of chlorantraniliprole, cyantraniliprole and flubendiamide were 8.5, 23.9 and 63.5 μg/L, respectively. Biochemical measurements revealed a significant increase in reactive oxygen species (ROS) in D. magna after acute exposure to the three diamides. A significant decrease in activities of antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) was observed, which was consistent with the down-regulated transcription of antioxidant genes sod and gpx. Catalase (CAT) activity exhibited a significant increase while the related gene cat showed no obvious change in daphnids acutely exposed to the three diamides. The chronic test revealed that the three diamides could cause lethal and sub-lethal effects on daphnids within constricted range of concentrations at μg/L level. The 21-d EC₅₀ of chlorantraniliprole, cyantraniliprole and flubendiamide for mobility were 5.0, 13.6 and 36.8 μg/L, respectively. The chronic LOEC of chlorantraniliprole, cyantraniliprole and flubendiamide based on survival, growth and reproduction of D. magna were 4.05, 10.24 and 19.36 μg/L, respectively. Moreover, these three diamides can induce severe developmental abnormalities in D. magna embryos including underdeveloped second antennae, curved tail spine and abnormal body region after acute exposure and the 48-h EC₅₀ were 6.2, 14.1 and 30.8 μg/L for chlorantraniliprole, cyantraniliprole and flubendiamide respectively. Our findings indicate that even low levels of diamides can pose ecological risks to aquatic ecosystems.

Toxicity of three strobilurins (kresoxim-methyl, pyraclostrobin, and trifloxystrobin) on Daphnia magna

Strobilurins constitute a new class of fungicides that is the most widely used in the world. The present study was conducted to investigate the aquatic toxicity of 3 common strobilurin fungicides (kresoxim-methyl, pyraclostrobin, and trifloxystrobin) to Daphnia magna. The neonate acute immobilization test showed that the 48-h 50% effective concentration (EC50) values of kresoxim-methyl, pyraclostrobin, and trifloxystrobin were 443.3 µg/L, 20.9 µg/L, and 23.0 µg/L, respectively. In addition, the 3 strobilurins significantly induced activity of the important detoxification enzyme glutathione S-transferase (GST) in D. magna, and there was a significant positive relationship between GST activity and immobility of D. magna after acute exposure. The 3 strobilurins showed higher toxicity to D. magna embryos, and the 48-h EC50 were 157.3 µg/L, 3.9 µg/L, and 1.7 µg/L for kresoxim-methyl, pyraclostrobin, and trifloxystrobin, respectively. The 21-d chronic test revealed that the strobilurins could also significantly affect the reproduction, development, and growth of D. magna at sublethal concentrations. The lowest-observed-effect concentrations of kresoxim-methyl, pyraclostrobin, and trifloxystrobin for reproduction were 20 µg/L, 0.15 µg/L, and 0.2 µg/L, respectively, which were close to environmental concentrations. The findings indicate that strobilurin fungicides are very toxic to D. magna and they are sufficient to cause harm to D. magna at environmentally relevant concentrations. Environ Toxicol Chem 2017;36:182-189. © 2016 SETAC.

Biological response of zebrafish embryos after short-term exposure to thifluzamide

Thifluzamide is a new amide fungicide, and its extensive application may have toxic effects on zebrafish. To better understand the underlying mechanism, we investigated in detail the potential toxic effects of thifluzamide on zebrafish embryos. In the present study, embryos were exposed to 0, 0.19, 1.90, and 2.85 mg/L thifluzamide for 4 days. Obvious pathological changes were found upon a histological exam, and negative changes in mitochondrial structure were observed under Transmission Electron Microscopy (TEM), which qualitatively noted the toxic effects of thifluzamide on embryos. Moreover, we quantitatively evaluated the enzyme activities [succinate dehydrogenase (SDH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), caspases], the contents of malonaldehyde (MDA) and interleukin-8 (IL-8) and the expression levels of the related genes. This study suggests that the negative changes in mitochondrial structure and SDH activity might be responsible for oxidative damage, cell apoptosis and inflammation, which would facilitate the action of these factors in cell death and might play a crucial role during toxic events. In addition to providing the first description of the mechanism of the toxic effects of thifluzamide on embryos, this study also represents a step towards using embryos to assess mitochondrial metabolism and disease.

Acute toxicity and chemical evaluation of coking wastewater under biological and advanced physicochemical treatment processes

This study investigated the changes of toxic compounds in coking wastewater with biological treatment (anaerobic reactor, anoxic reactor and aerobic-membrane bioreactor, A1/A2/O-MBR) and advanced physicochemical treatment (Fenton oxidation and activated carbon adsorption) stages. As the biological treatment stages preceding, the inhibition effect of coking wastewater on the luminescence of Vibrio qinghaiensis sp. Nov. Q67 decreased. Toxic units (TU) of coking wastewater were removed by A1/A2/O-MBR treatment process, however approximately 30 % TU remained in the biologically treated effluent. There is a tendency that fewer and fewer residual organic compounds could exert equal acute toxicity during the biological treatment stages. Activated carbon adsorption further removed toxic pollutants of biologically treated effluent but the Fenton effluent increased acute toxicity. The composition of coking wastewater during the treatment was evaluated using the three-dimensional fluorescence spectra, gas chromatography-mass spectrometry (GC-MS). The organic compounds with high polarity were the main cause of acute toxicity in the coking wastewater. Aromatic protein-like matters in the coking wastewater with low biodegradability and high toxicity contributed mostly to the remaining acute toxicity of the biologically treated effluents. Chlorine generated from the oxidation process was responsible for the acute toxicity increase after Fenton oxidation. Therefore, the incorporation of appropriate advanced physicochemical treatment process, e.g., activated carbon adsorption, should be implemented following biological treatment processes to meet the stricter discharge standards and be safer to the environment.

Acute toxicity and histopathological effects of naproxen in zebrafish (Danio rerio) early life stages

Zebrafish (Danio rerio) embryos and larvae were selected to investigate the potential risk and aquatic toxicity of a widely used pharmaceutical, naproxen. The acute toxicity of naproxen to embryos and larvae was measured, respectively. The histopathology was investigated in the liver of zebrafish larvae after 8-day embryo-larvae exposure to naproxen. The values of 96-h LC50 were 115.2 mg/L for embryos and 147.6 mg/L for larvae, indicating that zebrafish embryos were more sensitive than larvae to naproxen exposure. Large suites of symptoms were induced in zebrafish (D. rerio) early life stages by different dosages of naproxen, including hatching inhibition, lower heart rate, and morphological abnormalities. The most sensitive sub-lethal effect caused by naproxen was pericardial edema, the 72-h EC50 values of which for embryos and larvae were 98.3 and 149.0 mg/L, respectively. In addition, naproxen-treated zebrafish larvae exhibited histopathological liver damage, including swollen hepatocytes, vacuolar degeneration, and nuclei pycnosis. The results indicated that naproxen is a potential threat to aquatic organisms.

Integrated adsorptive technique for efficient recovery of m-cresol and m-toluidine from actual acidic and salty wastewater

An integrated adsorptive technique combining an m-cresol adsorption unit, an acid retardation unit and an m-toluidine adsorption unit in sequence was designed to recover m-cresol and m-toluidine from highly acidic and salty m-cresol manufacturing wastewater. In the first column packed with hypercrosslinked polymeric resin (NDA-99), most m-cresol was captured through π-π and hydrogen-bonding interactions as well as the salting-out effect, while m-toluidine was not absorbed due to protonation. To separate acid from salt, an acid retardation unit was introduced successively to adsorb sulfuric acid by strong base anion exchange resin (201×7). After the acid retardation unit and mild neutralization reaction, the last column filled with NDA-99 was applied to trap neutral m-toluidine from the salty effluent. Moreover, the eluent of the acid retardation unit was utilized as the regenerant to recover m-toluidine, and the recycled high-acidity and low-salinity solution of m-toluidine was directly used to produce m-cresol as the raw material. Therefore, the proposed method not only efficiently recycled m-cresol and m-toluidine, but also reduced the consumption of alkali dramatically (saving 0.1628t/t wastewater). These findings will inspire design of integrated adsorptive techniques for treating complex organic wastewater with high efficiency and low cost.

Multi-generational effects of propranolol on Daphnia magna at different environmental concentrations

To evaluate the effects of propranolol on Daphnia magna (D. magna), we employed a multi-generational exposure period for eight generations and an environmentally relevant low concentration with 1.5 ng/L, 0.2 μg/L and 26 μg/L to reflect a realistic exposure scenario. Physiological endpoints were checked, including growth, number of neonates, heart rate, frequency of abdominal appendage movement and malformation rate of neonates. In the results, growth and abdominal appendage movement were affected by environmental concentration during several generations, and the responses showed consistent tendencies of response increase with concentration increase. Heart rate was the only endpoint affected throughout all exposure generations. Inhibitory and acceleratory effects on heart rate, growth and abdominal appendage movement suggest that it is necessary to cover sub-lethal endpoints of non-targeted organisms in eco-toxicity study because the physiological responses were detected at much lower concentrations than the results of traditional toxicity tests, including environmental concentration.

Ectoine alleviates behavioural, physiological and biochemical changes in Daphnia magna subjected to formaldehyde

Ectoine (ECT) is produced by halophilic microorganisms in response to various stressful factors. Its protective properties in bacteria and some populations of isolated cells are known; however, no data are available on its protective influence on aquatic invertebrates subjected to a common pollutant, formaldehyde (FA). The purpose of this study was to determine the effects of FA alone (at 20 and 60 mg/L) and in the combination with various concentrations of ECT (5, 10 and 25 mg/L) at various times of exposure on behavioural, physiological and biochemical parameters of Daphnia magna. Specifically, mortality, heart rate, thoracic limb movement, reduced glutathione (GSH)/oxidised glutathione (GSSG) ratio, catalase (CAT) activity and nitric oxide (NOx) levels were determined. The results showed that both concentrations of FA when administered alone induced significant alterations of the determined parameters. On the other hand, animals treated with the combinations of FA + ECT showed decreased mortalities, attenuated inhibition of heart rates and thoracic limb activities, less decreased GSH/GSSG ratios, lower stimulation of CAT activities and NOx levels when compared to the crustaceans subjected to FA alone. The most distinct attenuation of toxic effects was observed in the combinations in which the highest concentrations of ECT were used. The results suggest that oxidative stress induced by FA in daphnids is likely to be alleviated by the antioxidative action of ECT.

Occurrence and origin of sensitivity toward difenoconazole in zebrafish (Danio reio) during different life stages

We report here an investigation of the mechanisms contributing to the divergent sensitivity toward the triazole fungicide difenoconazole of zebrafish (Danio reio) during different life stages. Adult and embryonic zebrafish were exposed to three different concentrations of difenoconazole (0.01, 0.5 and 1.0mg/L). The death rate, bioaccumulation of difenoconazole, oxidative stress parameters and transcription of related genes were tested at 4 and 8 days post-exposure (dpe). The death rate for adult zebrafish was much higher than that of the embryos at an exposure concentration of 1.0mg/L at both 4 and 8 dpe. The concentrations of difenoconazole in both the embryos and adult fish were similar, except for the group exposed to 0.01mg/L difenoconazole. A decrease in antioxidant enzyme activities was observed in both the embryos and the livers of adult fish after exposure to difenoconazole. Significant lipid peroxidation was found in the livers of adult fish in all exposure groups at 8 dpe, but was not observed in the treated embryos. The gene transcription response of the embryos toward difenoconazole was different from that in the livers of adult fish at 4 dpe. At 8 dpe, the modification in the transcription of the tested genes in the embryos and adult fish was similar, except for the genes related to the synthesis of sterols.

Comparative study of non-invasive methods for assessing Daphnia magna embryo toxicity

Embryos, unlike adults, are typically sessile, which allows for an increase in the available metrics that can be used to assess chemical toxicity. We investigate Daphnia magna development rate and oxygen consumption as toxicity metrics and compare them to arrested embryo development using four different techniques with potassium cyanide (KCN) as a common toxicant. The EC50 (95 % CI) for arrested development was 2,535 (1,747-3,677) μg/L KCN. Using pixel intensity changes, recorded with difference imaging, we semi-quantitatively assessed a decrease in development rate at 200 μg/L KCN, threefold lower than the arrested development lowest observed effect concentration (LOEC). Respirometry and self-referencing (SR) microsensors were two unique techniques used to assess oxygen consumption. Using respirometry, an increase in oxygen consumption was found in the 5 μg/L KCN treatment and a decrease for 148 μg/L, but no change was found for the 78 μg/L KCN treatment. Whereas, with SR microsensors, we were able to detect significant changes in oxygen consumption for all three treatments: 5, 78, and 148 μg/L KCN. While SR offered the highest sensitivity, the respirometry platform developed for this study was much easier to use to measure the same endpoint. Oxygen consumption may be subject to change during the development process, meaning consumption assessment techniques may only be useful only for short-term experiments. Development rate was a more sensitive endpoint though was only reliable four of the six embryonic developmental stages examined. Despite being the least sensitive endpoint, arrested embryo development was the only technique capable of assessing the embryos throughout all developmental stages. In conclusion, each metric has advantages and limitations, but because all are non-invasive, it is possible to use any combination of the three.

Teratogenic effects of organic extracts from the Pearl River sediments on Xenopus laevis embryos

Toxicity of organic extracts from the Pearl River sediments was investigated with Xenopus laevis embryos. The effects of sediment organic extracts on the mortality, body length and malformation of X. laevis embryos were tested by the Frog Embryo Teratogenesis Assay-Xenopus (FETAX). The 96-h LC₅₀ values for X. laevis embryos ranged from 62 to 137 g/L (g extracted sediment per L), and the toxicity effect on body length of larvae was not significant under 20 g/L. However, the teratogenic effects produced by sediment organic extracts were diverse, including edema, hypopigmentation, cardiac and ocular malformations, abdomen recurved and curved spine. The percentage of malformations increased with increasing sediment organic extracts, and even reached almost 100% at 10 and 20 g/L in Guangzhou district. A gradient of pollution in the Pearl River sediments was discerned from the teratogenic toxicity. Guangzhou district showed higher teratogenic toxicity compared with Panyu and Nansha districts as a possible consequence of high levels of PAHs, PCBs, OCPs and NP in the sediments. The teratogenic effects of organic extracts from the Pearl River sediments were successfully assessed which indicated the feasibility of teratogenic potential studies of sediments using X. laevis embryos.

Evaluation of acute and developmental effects of difenoconazole via multiple stage zebrafish assays

Zebrafish, during embryo, larvae and adult stages were selected to investigate the potential environmental risk and aquatic toxicity of a widely used fungicide, difenoconazole. In addition to mortality, embryo development endpoints, teratogenic effects and behavior abnormity were measured. Finally, the developmental parameters of the adult fish were assessed after 14 days' exposure. This study concluded that the acute toxicity of difenoconazole to the three phases of zebrafish were larvae (1.17 mg/L) > adult fish (1.45 mg/L) > embryo (2.34 mg/L). A large suite of symptoms was induced in embryonic development by different dosages of difenoconazole, including hatching inhibition, abnormal spontaneous movement, slow heart rate, growth regression and morphological deformities. 0.50 mg/L of difenoconazole could cause significant body color blackening and decrease in the heart rate of zebrafish larvae over 24 h. In addition, 0.25 mg/L of difenoconazole apparently inhibited the growth weight of adult zebrafish measured after 14 days' exposure.