Increasing Exposure Concentration Research Articles

The antibiotic ciprofloxacin alters the growth, biochemical composition, and antioxidant response of toxin-producing and non-toxin-producing strains of Microcystis

The increased production, consumption, and release of antibiotics account for their frequent contamination of aquatic ecosystems and detection in different biological matrices. Several antibiotics affect non-target organisms such as algae, cyanobacteria, zooplankton, and fish, making investigations on them very crucial for the health and maintenance of biodiversity. The impact of broad-spectrum antibiotics like ciprofloxacin (CPX) on toxin-producing and non-toxin-producing cyanobacteria has been poorly investigated. Therefore, the present study investigated the physiological and toxicological effects of CPX on Microcystis aeruginosa EAWAG 198, Microcystis aeruginosa LE3, and Microcystis flos-aquae UTEX-LB 2677. CPX caused a significant (p < 0.05) decrease in the cell densities and chlorophyll-a of the three strains. The antibiotic caused oxidative stress in all the strains, as demonstrated by a significant rise in the levels of intracellular hydrogen peroxide (H2O2) of the treated cultures at 96 h post-exposure. Lipid peroxidation and the activity of the antioxidant enzyme—peroxidase (POD) and glutathione-S-transferase (GST)—of the cultures were significantly (p < 0.05) altered. Exposure to CPX generally stimulated the production of biomolecules such as total proteins, lipids, and total carbohydrates as a function of increasing exposure concentration. The exception to the general trend was M. aeruginosa EAWAG 198, a non-toxin-producing strain, which suffered a significant decline in carbohydrate content during exposure to CPX. This study revealed that environmentally relevant levels of CPX could alter the population dynamics, photosynthesis, biochemical composition, and the general physiology of Microcystis species/strains in aquatic ecosystems.

From air to heart: Particle pollution (PM2.5) and induced injury on cardioblast cells

This study evaluated toxicological effects owing to fine particulate matter (PM2.5) exposure in cardioblast cells (H9c2 lineage). The cells were treated with different particulate matter extract solutions for 24 h, F100% (1g of filter containing PM2.5 per 100 mL culture medium, used as stock), F50% (1/2 F100) and F10% (10% of stock). Cell viability, the production of reactive oxygen species (ROS), antioxidant capacity, lipid damage, necrosis, and apoptosis parameters were measured to assess cell damage. The results showed that cell injuries are related to increasing exposure concentrations. Effects exposure to PM2.5 in F10% was no harmful for H9c2 lineage. The lactate dehydrogenase activity and damage lipid membrane were increased in cells exposed to F50% and F100%. The ROS production was higher and total antioxidant capacity lower in F50% and F100% concentrations. Catalase activity decreased only in the F100% group. Apoptosis and necrosis percentages were higher for F50% and F100% groups. In the PM2.5 extracts some metals were detected (Co, Cd, Li, Mn, Ni, Sr, Ba, Rb, Cu, Pb, As, Zn, Al, Ti, Fe, Si, K, V), which could contribute for toxicological effects in H9c2 lineage. In conclusion, higher concentrations of PM2.5 in solutions were able to elicit cell injury and death cardiac cells in H9c2 through elevation ROS levels, imbalance redox, lysis membrane cell, necrosis and apoptosis.

Inhibition of swim bladder inflation in Japanese medaka (Oryzias latipes) embryos following exposure to select pharmaceuticals alone and in combination

This study leveraged the Japanese medaka fish embryo model for the assessment of effects of select contaminants on early development in fish. Fish embryos were exposed to various pharmaceutical contaminants including synthetic hormones and non-steroidal anti-inflammatory drugs and their effects on development were observed. Initial screening determined that swim bladder inflation failure was the most common endpoint detected. Swim bladder inflation failure was first explored in a study demonstrating that medaka require access to the air-water interphase to inflate their swim bladders in a time-dependent manner, and swim bladder inflation failure was correlated with mortality. Fish embryos were exposed 24-hours post fertilization until hatch to concentration ranges of various pharmaceutical contaminants including: 17β-estradiol, 17α-ethinylestradiol, and levonorgestrel (1 to 1000 µg/L), or diclofenac (0.32 to 100 mg/L). The main effect observed across all four compounds was a significant increase in failure of swim bladder inflation with increasing exposure concentration (24 to 72-hours post-hatch). Following single compound experiments combinatorial exposures using no-observed-effect concentrations were conducted. The main effect observed was a significant decrease in inflation success 24-hours post-hatch following a binary mixture of levonorgestrel and 17α-ethinylestradiol, as well as a significant decrease in swim bladder inflation success at all times following exposure to a quaternary mixture of all four compounds. This study demonstrated that embryonic exposure to pharmaceutical compounds, both alone and in combination, resulted in failure of swim bladder inflation in larval Japanese medaka.

Exposure to a common urban pollutant affects the survival and swimming behaviour of creek chub (Semotilus atromaculatus).

Anthropogenic effects on the aquatic environment are ever present and ever increasing and while a plethora of aquatic contaminants are known to affect fishes, one ubiquitous and increasingly prevalent world‐wide urban runoff pollutant is frequently disregarded, and that is pet waste. While dog waste has been identified as a significant factor contributing to bacteria and nutrient loading within receiving waters and the associated water quality changes are known to affect fishes, the impact of uncollected dog faeces on urban fish populations has never been directly investigated. In this study we exposed creek chub (Semotilus atromaculatus), a widespread tolerant stream minnow, to various realistic concentrations of dog waste as simulated urban park runoff testing both fresh and dried dog faeces in both stagnant and aerated water for 96 h to investigate the impact on fish survival and behaviour. Creek chub percentage mortality increased significantly relative to controls and across an exposure gradient and was likely caused by anoxic conditions. Survivors were initially smaller while those that died were initially larger and presented with abnormal abdominal subdermal lesions post‐exposure. Additional indicators of physiological stress included significantly increased rates of aquatic surface respiration and changes in flume test derived swimming motivation metrics with increased exposure concentrations. Both mortality and behavioural responses were alleviated by aeration. Furthermore, trials with fresh and dried faeces differed only in time‐to‐death and swimming metrics where results from dried trials were similar to those from aerated experiments. Results demonstrated the impact that the global dog waste management problem can have on aquatic communities with effects on creek chub likely to be more severe for less pollution‐tolerant species and also likely to be exacerbated under future scenarios that consider climate change and increased urbanization.

Concentration-dependent enantioselective accumulation of chiral polychlorinated biphenyls in Nelumbo nucifera Gaertn. root from contaminative sediment.

Nelumbo nucifera Gaertn. (lotus) roots were collected from contaminated sediments which were artificially adding different concentrations of chiral polychlorinated biphenyls (PCBs) to investigate the effect of concentration on the accumulation characteristics and chiral signatures of PCBs in lotus root during its growth period of 150 days. Under high PCB exposure concentration, the biota-sediment accumulation factors (BSAFs) of PCBs 91, 95, and 136 in the lotus root were up to 0.25-0.46 and 8.10-10.5 times higher than those under low-exposure concentration (0.024-0.052). The BSAFs of PCBs 149, 176, and 183 under high-exposure concentration were up to 0.24-0.44, while they were undetected at low concentration. The significant difference observed in the BSAFs based on different concentrations indicates that the lotus root accumulation efficiency toward chiral PCBs increases with the contaminate concentration. Although the (-)-enantiomers of PCBs 91, 95, and 136 wereall preferentially accumulated in lotus root under two exposure concentrations, the extent of the preferential accumulation of (-)-PCB 95 decreased with increasing exposure concentration throughout the whole growth period (30-150 days). In addition, the (-)-enantiomers of PCBs 91 and 136 also showed the same tendency during most of the growth period. Conclusively, the exposure concentrations are an important influence factor on the enantioselective accumulation of chiral PCBs in lotus root.

The study of the protection function of the sphingosine kinase 1 in the nerve cell damage caused by acrylamide

Objective: To study the protective effect and effect of SphK1 overexpression on the injury of nerve cells induced by acrylamide. Methods: ACR with 99% purity was prepared into 1.25 mmol/L and 2.5 mmol/L solutions. SH-SY5Y cells were divided into control group (NC group) , experimental group and SphK1 activator group. The experimental group was given ACR solution with final concentration of 1.25 mmol/L and 2.5 mmol/L respectively for 24 h. In the SphK1 activator group, on the basis of the exposure concentration of the experimental group, the SphK1 specific activator (12-) phorbol tetradecanoate (-13-) acetate (PMA) solution[prepared by dimethyl sulfoxide (DMSO) , the final concentration was 100 nmol/l], and other treatments were the same as the experimental group. Control group (NC group) added PMA solution into normal cells. Western blot was used to detect the expression of SphK1 protein; CCK-8 was used to detect the proliferation of SH-SY5Y cells; hoechst33342 method was used to observe the morphological changes of nerve cells; flow cytometry was used to analyze the apoptosis of cells. Results: Compared with NC group, the expression of SphK1 protein in the experimental group and the SphK1 activator group was significantly lower (P<0.05) . Compared with the experimental group, the expression of SphK1 protein in each concentration of SphK1 activator group was increased, and the difference was statistically significant (P<0.05) . In addition to 1.25 mmol/L SphK1 activator group, compared with NC group, the relative growth survival rate of experimental group and 2.5 mmol/L SphK1 activator group were lower, the difference was statistically significant (P<0.05) . Compared with the experimental group, the relative survival rate of cells in the SphK1 activator group was higher, and the difference was statistically significant (P<0.05) . With the increase of exposure concentration, the cells in the experimental group showed the morphological characteristics of early apoptosis at ACR 1.25 mmol/L and late apoptosis at ACR 2.5 mmol/L. Compared with NC group, the apoptosis rate of experimental group and SphK1 activator group at ACR 2.5 mmol/L was significantly different (P<0.05) ; compared with experimental group, the apoptosis rate of SphK1 activator group at ACR 2.5 mmol/L was lower, the difference was statistically significant (P<0.05) . Conclusion: The SphK1 excessive expression plays the protective function to the nerve cell damage caused by acrylamide.

Effects of fenvalerate concentrations and its chiral isomers on bacterial community structure in the sediment environment of aquaculture ponds.

To investigate the effect of chiral pesticide fenvalerate (FV) on the micro-ecological environment of aquaculture pond sediment, we used an indoor static experiment to observe the effects of FV added at different concentrations with different chiral isomers on the changes in the sediment bacterial community. The 16S rDNA high-throughput sequencing technique was used to conduct sequencing and analysis of the bacterial community structure as well as changes in aquaculture pond sediments after 4weeks of cultivation. The results showed that the microbial alpha diversity indices (Sobs and Shannon indices) of the treated groups were significantly lower than those of the control group after 4weeks (P < 0.05), and the values in the high-concentration group were significantly lower than those of the low-concentration group (P < 0.05). In terms of bacterial group composition, the proportion of abundance of Proteobacteria and Acidobacteria in the treated groups were greater than in the control group after 4weeks, while the proportion of abundance of Bacteroidetes and Verrucomicrobia were lower. In the high-concentration FV treatment group, the proportion of abundance of Bacteroidetes, Acidobacteria, Chloroflexi, Nitrospinae, unclassified_k_norank, Ignavibacteriae, and Nitrospirae were significantly different from those of the other groups (P < 0.05). Principal coordinate analysis (PCoA) and ANONISIM/Adonis analysis showed that the cis-enantiomer had a stronger effect on the bacterial community as the concentration of FV increased. In addition, the linear discriminant analysis effect size (LEfSe) and linear discriminant analysis (LDA) results revealed differences in the level of enrichment of bacterial groups caused by FV at different concentrations and isomer levels. Collectively, this study showed that FV residue has a pronounced effect on bacterial communities in sediment, which becomes more significant with increasing exposure concentration. The effects of the cis- and trans-enantiomers of FV on the sediment environment are different; the cis-enantiomer has a stronger effect on the bacterial community.

Medium-term effects of Ag supplied directly or via sewage sludge to an agricultural soil on Eisenia fetida earthworm and soil microbial communities

The widespread use of silver nanoparticles (AgNPs) in consumer products that release Ag throughout their life cycle has raised potential environmental concerns. AgNPs primarily accumulate in soil through the spreading of sewage sludge (SS). In this study, the effects of direct exposure to AgNPs or indirect exposure via SS contaminated with AgNPs on the earthworm Eisenia fetida and soil microbial communities were compared, through 3 scenarios offering increasing exposure concentrations. The effects of Ag speciation were analyzed by spiking SS with AgNPs or AgNO3 before application to soil. SS treatment strongly impacted Ag speciation due to the formation of Ag2S species that remained sulfided after mixing in the soil. The life traits and expression of lysenin, superoxide dismutase, cd-metallothionein genes in earthworms were not impacted by Ag after 5 weeks of exposure, but direct exposure to Ag without SS led to bioaccumulation of Ag, suggesting transfer in the food chain. Ag exposure led to a decrease in potential carbon respiration only when directly added to the soil. The addition of SS had a greater effect on soil microbial diversity than the form of Ag, and the formation of Ag sulfides in SS reduced the impact of AgNPs on E. fetida and soil microorganisms compared with direct addition.

Genomic investigations of acute munitions exposures on the health and skin microbiome composition of leopard frog (Rana pipiens) tadpoles

Natural communities of microbes inhabiting amphibian skin, the skin microbiome, are critical to supporting amphibian health and disease resistance. To enable the pro-active health assessment and management of amphibians on Army installations and beyond, we investigated the effects of acute (96h) munitions exposures to Rana pipiens (leopard frog) tadpoles and the associated skin microbiome, integrated with RNAseq-based transcriptomic responses in the tadpole host. Tadpoles were exposed to the legacy munition 2,4,6-trinitrotoluene (TNT), the new insensitive munition (IM) formulation, IMX-101, and the IM constituents nitroguinidine (NQ) and 1-methyl-3-nitroguanidine (MeNQ). The 96h LC50 values and 95% confidence intervals were 2.6 (2.4, 2.8) for ΣTNT and 68.2 (62.9, 73.9) for IMX-101, respectively. The NQ and MeNQ exposures caused no significant impacts on survival in 96h exposures even at maximum exposure levels of 3560 and 5285 mg/L, respectively. However, NQ and MeNQ, as well as TNT and IMX-101 exposures, all elicited changes in the tadpole skin microbiome profile, as evidenced by significantly increased relative proportions of the Proteobacteria with increasing exposure concentrations, and significantly decreased alpha-diversity in the NQ exposure. The potential for direct effects of munitions exposure on the skin microbiome were observed including increased abundance of munitions-tolerant phylogenetic groups, in addition to possible indirect effects on microbial flora where transcriptional responses suggestive of changes in skin mucus-layer properties, antimicrobial peptide production, and innate immune factors were observed in the tadpole host. Additional insights into the tadpole host's transcriptional response to munitions exposures indicated that TNT and IMX-101 exposures significantly enriched transcriptional expression within type-I and type-II xenobiotic metabolism pathways, where dose-responsive increases in expression were observed. Significant enrichment and increased transcriptional expression of heme and iron binding functions in the TNT exposures served as likely indicators of known mechanisms of TNT toxicity including hemolytic anemia and methemoglobinemia. The significant enrichment and dose-responsive decrease in transcriptional expression of cell cycle pathways in the IMX-101 exposures was consistent with previous observations in fish, while significant enrichment of immune-related function in response to NQ exposure were consistent with potential immune suppression at the highest NQ exposure concentration. Finally, the MeNQ exposures elicited significantly decreased transcriptional expression of keratin 16, type I, a gene likely involved in keratinization processes in amphibian skin. Overall, munitions showed the potential to alter tadpole skin microbiome composition and affect transcriptional profiles in the amphibian host, some suggestive of potential impacts on host health and immune status relevant to disease susceptibility.

Studying the mixture effects of brominated flame retardants and metal ions by comet assay

This study was designed to evaluate the sensitivities of diverse cell lines on DNA damage effects and genotoxic effects of three brominated flame retardants (BFRs) and three metal ions (Cu2+, Cd2+, Hg2+) by comet assay. First, THP-1 was identified as the most sensitive cell line in terms of DNA damage among 11 kinds of cells screened. Accordingly, the THP-1 cell line was used as a model in subsequent single/combined genotoxicity tests. Single exposure tests to BFRs or metal ions revealed that the DNA damage effects increased with increasing exposure concentration. In combined exposure tests, BFRs (at concentrations of 1/2 EC50) were deployed in combination with different concentrations of Cu2+, Cd2+, or Hg2+. The results showed that the % tail DNA values were significantly increased by most mixtures. Our findings on combined toxic effects by comet assay provide valuable information for setting valid environmental safety evaluation standards.

Cd exposure-induced growth retardation involves in energy metabolism disorder of midgut tissues in the gypsy moth larvae

Cadmium, a common environmental contaminant in both terrestrial and aquatic ecosystems, presented a serious hazard to growth and development of phytophagous insects. For better understanding the toxicology of Cd exposure on phytophagous insects, the physiological and molecular mechanisms underlying the energy metabolism disorder in midgut tissue of gypsy moth larvae fed on Cd-amended artificial diets (3.248 or 44.473 mg Cd/kg fresh food) were investigated. Our results showed that compared with control, Cd exposure at both two levels triggered detriment effects on growth indexes, and with the increase of exposure concentrations, the adverse effects were significantly exacerbated. Larval growth and nutritional indexes (except approximate digestibility) showed a strong positive correlation, indicating that growth retardation in the gypsy moth larvae under Cd stress was tightly related to the food utilization. The key genes at mRNA level in glycolysis/gluconeogenesis, citrate cycle pathway and starch/sucrose metabolism pathway also presented a significant and positive correlation with growth indexes, once again demonstrating that energy metabolism was the key factor that controls the growth and development of the gypsy moth larvae under Cd stress. Antioxidant system collapse and oxidative damage, a chief cause of histopathological alterations in midgut tissue, consist of the physiological basis of energy metabolism disorder in Cd-treated gypsy moth larvae. Together, these results suggest that histopathological alterations or oxidative damage of tissue structure significant disturbed physiological functions of midgut tissue in gypsy moth larvae exposed to Cd stress, as reflected via food utilization or energy metabolism disorder, and eventually resulted in larval growth retardation.

Analysis of the relationship between the changes of lung function and serum proinflammatory cytokines in workers occupationally exposed to toluene diisocyanate

Objective: To analyze the correlation between the changes of lung function and serum proinflammatory cytokines in workers occupationally exposed to toluene diisocyanate (TDI), and to explore the evaluation index of respiratory toxicity of TDI. Methods: In October 2014, 61 male workers engaged in TDI synthesis process, purification process, packaging process and the above production process in a TDI factory in western China were selected as TDI exposure group; 62 male enterprise managers who were not exposed to TDI and other known allergenic chemicals were selected as control group, which were matched at the age of workers in exposure group. The questionnaire survey obtained information such as gender, length of service, age, occupational history, exposed length of service and so on. The lung function indexes [forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), FEV1/FVC] and serum levels of interleukin (IL)-1 β, IL-6, IL-8, tumor necrosis factor (TNF)-α, macrophage inflammatory factor-1 β, monocyte chemoattractant factor-1 and vascular endothelial growth factor were measured. The urine was collected after the weekend shift, and the concentration of (TDA), the metabolite of TDI, was determined as the index of internal exposure. Spearman rank correlation was used to analyze the correlation between cytokines and lung function indexes, and multivariate linear regression was used to analyze the changes of lung function indexes and cytokines with TDI exposure concentration and time. Results: The median age (P5-P95) of the exposed group and the control group was 36.5 (24.0-51.0) and 38.0 (24.0-50.0) years, respectively. In the exposed group, the median length of service (P5-P95) was 6.94 (0.97-26.33) years, and the median concentration of TDA in urine was 15.56 (2.28-112.16) ng/ml. The three indexes of lung function, FVC, FEV1, FEV1/FVC and the levels of serum IL-8 and TNF-α were significantly lower than those in the control group (P<0.01). With the increase of exposure concentration and exposure time, the level of serum TNF-α, FVC and FEV1 decreased, and showed a good dose-effect and time-effect relationship (all Ptrend values< 0.05). Serum IL-8 and TNF-α were positively correlated with FVC, FEV1 and FEV1/FVC (all P values<0.01). Conclusion: The levels of serum inflammatory factors IL-8 and TNF-α in worker exposed to TDI are related to lung function indexes, which can be used as early evaluation indexes of respiratory toxicity induced by TDI.

Relationship among the acute toxicity, critical body residue, and bioconcentration of ortho-dinitrobenzene in zebrafish (Danio rerio) based on toxicokinetics.

The internal critical concentration represented by the critical body residue (CBR) is an ideal indicator for reflecting the toxicity of a chemical. Although some authors have realized that the CBR50 can be calculated from the LC50 via the bioconcentration factor (BCF), the effects of exposure time and exposure concentration on the relationship between the LC50 and CBR50 have not been investigated to date. In this paper, the LC50 and CBR50 of ortho-dinitrobenzene in zebrafish were experimentally determined and their relationship was investigated. The results showed that ortho-dinitrobenzene exhibited excess toxicity and cannot completely be identified as a reactive compound based on toxic ratio. Comparison of the measured CBR50 and the CBR50 calculated from the LC50 via the BCF showed that there was a 0.46 log unit difference. Investigation of the relationship between the concentration in fish calculated by the toxicokinetic model and exposure time showed that the bio-uptake of fish was fast and reached a steady state in the toxicity test, indicating that the difference in CBR50 values could not be attributed to the different exposure times used in toxicity and BCF assays. On the other hand, investigation of the measured bioconcentration ratio (BCR) showed that the BCR (or BCFapp) decreased with increasing exposure concentration. Compared with the CBR50 calculated from the LC50 via the BCF, the CBR50 calculated from the LC50 via the BCFapp is close to the measured CBR50, suggesting that the difference in CBR50 values is attributed to the different exposure concentrations used in the BCF and toxicity assays.

Toxicity mechanism of tetrabromobisphenol A to human respiratory system cells 16HBE and Beas2B

Tetrabromobisphenol A (TBBPA) is a high-production chemical widely used in printed circuit boards and other polymeric materials for inflaming. As an environmental pollutant, it is widely found in various abiotic and biological media. Usually, the TBBPA could enter the body through skin contact, respiratory exposure and the dietary intake, among which respiratory exposure may be a most important exposure route. Previous studies reported that TBBPA possesses the endocrine, liver and kidney toxicity. However, few studies focused on the effects of TBBPA on respiratory toxicity. Therefore, it is urgent to study the toxic effects of TBBPA on respiratory system. In this study, human bronchial cells Beas2B and pulmonary epithelial cells 16HBE were used as subjects to study the exposure toxicity of TBBPA. Firstly, the viability and permeability of cells were assayed during the TBBPA exposure process. When TBBPA was in low concentration range (0−0.4 μmol/L), 24 h of exposure cannot significantly affect cell viability. When concentration of TBBPA was greater than 10 μmol/L, the inhibitory effect on cell activity was obviously observed. When concentration of TBBPA was up to 50 μmol/L, the cell viabilities of 16HBE and Beas2B cells decreased to 80.9% and 86.2%. It is worth noting that, as compared with bronchial epithelial cell 16HBE, lung epithelial cell Beas2B has a higher tolerance to TBBPA, which may be due to the different cell structures. In addition, the oxidation stress of cells was also determined by assaying the cell intracellular reactive oxygen species (ROSs), antioxidant enzymatic activity of superoxide dismutase (SOD) and catalase (CAT) during the whole expose duration. The results showed that the levels of intracellular ROSs obviously increased in both cells, indicating that peroxidation occurred in the cells during TBBPA exposure. Correspondingly, the enzymatic activities of SOD and CAT also increased, indicating that oxidative stress happened in cells. After that, flow cytometry was applied to analyze cell apoptosis. The results showed that partial apoptosis occurred after 24 h of TBBPA exposure, indicating that TBBPA could induce cell apoptosis. Besides, with the increase of exposure concentration, the apoptosis rate of the two kinds of cells also increased. Furthermore, the q-PCR was used to determine the apoptosis-related gene expression. The results revealed that the expression levels of apoptosis-related genes p53, Survivin , bax , bcl-2 , caspase-3 , caspase-9 were all up-regulated to different degrees, further confirming that cells were apoptotic caused by TBBPA. Further, compared with the 12-h exposure data, 24-h exposure would stimulate more intense expression up-regulation. In all, this research mainly investigated the toxicity of typical generation bromide flame retardants TBBPA on human bronchial epithelial cells 16 HBE and lung epithelial cells Beas2B. Results showed that the exposure of TBBPA could cause damage to cell viability and elicit oxidative stress in cells, which could further induce cell apoptosis. The results of cytotoxicity related to human respiratory system in this work can provide a scientific basis for revealing the health risk of toxic organic pollutants to human respiratory system.

The immunotoxicity and neurobehavioral toxicity of zebrafish induced by famoxadone-cymoxanil

As a new protective and therapeutic fungicide, studies on famoxadone-cymoxanil are rare, and its toxicity to aquatic organisms has not been reported. In the present study, zabrafish embryos were exposed to several concentrations of famoxadone-cymoxanil at 10 hpf. Then, the changes of their shape, heart rate, development and function of innate and adaptive immune cells, oxidative stress, apoptosis, the expression of apoptosis-related genes and immune-related genes, the locomotor behavior were observed and detected in acute toxicity of famoxadone-cymoxanil. Our studies showed that, after exposure to famoxadone-cymoxanil, zebrafish embryos had decreased heart rate, shortened body length, swollen yolk sac. Secondly, the number of innate and adaptive immune cells was significantly reduced; and neutrophil migration and retention at the injury area were inhibited, indicating the developmental toxicity and immunotoxicity of famoxadone-cymoxanil on the zebrafish. We also found that the oxidative stress related indicators of embryos were changed significantly, and apoptosis were substantially increased. Further investigation of changes of some key genes in TLR signaling including TLR4, MYD88 and NF-κB p65 revealed that the mRNA expression of these genes was up-regulated. Meanwhile, the mRNA expression of some proinflammatory cytokines such as TNF-α, IFN-γ, IL6 and IL-1β was also up-regulated. In addition, the activity, the total distance, time and average speed were decreased along with the increase of exposure concentration. The absolute turn angle, sinuosity and the enzymatic activity of acetylcholinesterase (AChE) were also increased. These results suggested that famoxadone-cymoxanil can induce developmental toxicity, immunotoxicity and neurobehavioral toxicity in zebrafish larvae.

Locomotor response of diamondback moth (Plutella xylostella) populations to a neurotoxic insecticide under laboratory conditions

ABSTRACT: The present study aimed to evaluate changes in the locomotor activity of diamondback moth (Plutella xylostella) populations exposed to surfaces treated with the insecticide chlorantraniliprole under laboratory conditions. Diamondback moth populations from municipalities incorrectly using the insecticide [Camocim de São Félix, PE (CSF); Sairé, PE (SR); and Lajedo, PE (LJ)] and two laboratory populations from Recife, PE (RCF), and Viçosa, MG (VÇS) were exposed to dry insecticide residues in increasing concentrations. The following behavioral parameters of the populations were analyzed: walking time (WT), mean walking speed (MWS), and rest time (RT). Regarding RT, the SR and CSF populations demonstrated a behavior of irritability and increased WT with increased exposure concentration. The RCF population presented a contrasting response. The MWS values in the SR and CSF populations showed a decreasing trend with increased exposure concentration. The LJ and RCF populations showed no changes in terms of MWS. The RT values in the SR population decreased with increased insecticide concentration. In general, the SR and CSF populations presented a behavioral pattern different from that of laboratory populations. The changes in locomotor activity observed may result in lower control efficacy of the insecticide due to repellency or escape of insects. Regarding the effect of insecticide concentrations used in the populations, a defined pattern was not observed, and the effect alternated between an increase, a decrease, and an undefined pattern for the variables studied.

Microplastic (1 and 5 μm) exposure disturbs lifespan and intestine function in the nematode Caenorhabditis elegans

As an emerging environmental pollutant, microplastics (MPs) are increasingly viewed as a serious health concern to terrestrial and aquatic ecosystems. However, previous toxicological studies examining MPs on freshwater and terrestrial organisms provide contradictory results, possibly due to few investigations at environmentally relevant concentrations. Here, the nematode Caenorhabditis elegans (C. elegans), a model organisms with both aquatic and terrestrial free-living forms, was employed to investigate the effects of 1 and 5 μm MPs (107–1010 particles/m2) on the intake, lifespan, defecation rhythm, defecation-related neurons and transcriptional expression of related genes (skn-1, mkk-4, pmk-1, cpr-1 and itr-1). We demonstrated that the percentage of MP-contaminated nematodes increased with increasing exposure concentrations and duration. The lifespan of nematodes in the lower concentration exposure groups (2.4 × 107 and 2.4 × 108 particles/m2) decreased more prominently than that of higher concentration groups (2.4 × 109 and 2.4 × 1010 particles/m2) after a 72-h exposure period. Concomitantly, expression of the skn-1 gene, involved in detoxification and lifespan regulation, was significantly altered at lower MP concentrations. Physiologically, the defecation rhythm after a 72-h exposure period was most strongly affected by 1 μm MPs at 2.4 × 108 particles/m2. The significant up-regulation of related genes by 1 μm MPs appears responsible for the shortened defecation interval. Results of this study identified a potential toxicity threat to C. elegans from exposure to MPs at environmentally relevant concentrations and provide novel evidence for MP risks to freshwater and terrestrial organisms.Capsule.After exposure to 1 and 5 μm MPs (107–1010 particles/m2), the lifespan of C. elegans decreased more rapidly at lower concentrations.

New Perspective on the Nanoplastics Disrupting the Reproduction of an Endangered Fern in Artificial Freshwater.

The potential risks of micro/nanoplastics on the ecological environment, particularly aquatic fauna, have been realized in recent years. However, information about its potential effects on aquatic plants is scarce. In this study, a four-week exposure experiment was conducted to investigate the effects of varying polystyrene nanoplastics concentration (PS-NPs, 0-100 μg/mL) on the early development of an endangered aquatic plant, Ceratopteris pteridoides. Fluorescent observations demonstrated that PS-NPs were adsorbed and accumulated on the spore surface of C. pteridoides rapidly and massively with increasing exposure concentration and time. The adsorption and accumulation of PS-NPs on the spore surface posed a negative effect on spore imbibition, causing 2.3-22.4% reduction in final spore size. Spore germination and gametophyte sex differentiation were both negatively affected by PS-NP exposure, resulting in 10.4-88.0% inhibition in germination ratio and 2.9-53.4% reduction in hermaphroditic gametophyte ratio. Additionally, PS-NPs were observed to penetrate into the roots of gametophytes. Higher concentration of PS-NPs (100 μg/mL) can even induce pathological changes on gametophytes, although with a low incidence (4.9%). The results above indicated that exposure to PS-NPs caused a series of disruptions from the spore imbibition to germination and gametophyte stages, and are likely to pose an eco-physiological risk on the reproductive success of endangered ferns.

The enrichment and purification of hexabromocyclododecanes and its effects on thyroid in zebrafish

Hexabromocyclododecanes (HBCDs) are the third most highly produced brominated flame retardants (BFRs) all over the world. Based on the current research status of HBCDs, zebrafish were exposed to three dietary concentrations of HBCDs (0, 10, 100, 400 ng/g) for 56 days, and followed by clean food for 28 days. In order to investigate the enrichment and purification of HBCDs in zebrafish, HBCD enantiomers in zebrafish were determined using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). To investigate the effects of long-term exposure of HBCDs on thyroid dysfunction and oxidative stress in zebrafish, the concentrations of thyroid hormone (T3, T4, FT3 and FT4) and the activities of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) were measured. RT-PCR was used to reveal the molecular mechanism of HBCDs' influence on thyroid hormone in zebrafish. The result of UPLC-MS/MS showed that there were three main reasons for the existence of α-HBCD as the major isomer in the organism. HBCDs had significant inhibitory effect on T3 and T4 in liver of adult zebrafish after 56 days’ exposure. Compared with the control group, the ratio of T3 and T4was significantly higher in the medium and high concentration group. The content of FT3 and FT4 in the liver tissue of zebrafish increased first and then decreased with the increase of exposure concentration. With the increase of exposure concentration, the content of MDA in zebrafish liver decreased firstly and then increased. The activity of SOD and CAT in zebrafish liver showed the opposite trend with MDA. And the concentration of GSH in liver decreased gradually, which showed a significant dose-effect relationship. HBCDs exposure has an inhibitory effect on thyroid hormone receptor gene (TRβ) and adrenocorticotropin-releasing hormone gene (Crh) in zebrafish.

Compositional alterations in soil bacterial communities exposed to TiO2 nanoparticles are not reflected in functional impacts

Titanium dioxide nanoparticles (TiO2NP) are increasingly released in soil ecosystems, while there is limited understanding of the impacts of TiO2NP on soil bacterial communities. Here we investigated the effects of TiO2NP on the taxonomic composition and functional profile of a soil bacterial community over a 60-day exposure period. In short-term exposure (1-day), contradictory effects on the taxonomic composition of soil bacterial communities were found after exposure to a low realistic environmental concentration of TiO2NP at 1 mg/kg as compared to the effects induced by medium and high concentrations of TiO2NP at 500 and 2000 mg/kg. After long-term exposure (60-day), the negative effects of TiO2NP at the low concentration disappeared, and the inhibition by TiO2NP of the abundance of core taxa was enhanced along with increasing exposure concentrations. However, although significant alterations were observed in the taxonomic composition over time and exposure concentrations, no significant change was observed in the community functional profile as well as enzyme activity after 60-day exposure, indicating that functional redundancy likely contributed to the bacterial community tolerance after the exposure to TiO2NP. Our study highlighted the importance of assessing bacterial community compositional and functional responses in assessing the environmental risk of nanoparticles on soil ecosystems.