A Class Act? Regulating Organohalogen Flame Retardants in Groups versus Singly.

Regulating chemicals by class based on chemical similarities may help reduce risk of regrettable substitutions while enhancing health protection. A new Commentary summarizes OFR toxicity and exposure research to inform this effort.

Immunotoxicity of Xenobiotics in Fish: A Role for the Aryl Hydrocarbon Receptor (AhR)?

The impact of anthropogenic contaminants on the immune system of fishes is an issue of growing concern. An important xenobiotic receptor that mediates effects of chemicals, such as halogenated aromatic hydrocarbons (HAHs) and polyaromatic hydrocarbons (PAHs), is the aryl hydrocarbon receptor (AhR). Fish toxicological research has focused on the role of this receptor in xenobiotic biotransformation as well as in causing developmental, cardiac, and reproductive toxicity. However, biomedical research has unraveled an important physiological role of the AhR in the immune system, what suggests that this receptor could be involved in immunotoxic effects of environmental contaminants. The aims of the present review are to critically discuss the available knowledge on (i) the expression and possible function of the AhR in the immune systems of teleost fishes; and (ii) the impact of AhR-activating xenobiotics on the immune systems of fish at the levels of immune gene expression, immune cell proliferation and immune cell function, immune pathology, and resistance to infectious disease. The existing information indicates that the AhR is expressed in the fish immune system, but currently, we have little understanding of its physiological role. Exposure to AhR-activating contaminants results in the modulation of numerous immune structural and functional parameters of fish. Despite the diversity of fish species studied and the experimental conditions investigated, the published findings rather uniformly point to immunosuppressive actions of xenobiotic AhR ligands in fish. These effects are often associated with increased disease susceptibility. The fact that fish populations from HAH- and PAH-contaminated environments suffer immune disturbances and elevated disease susceptibility highlights that the immunotoxic effects of AhR-activating xenobiotics bear environmental relevance.

Thyroid homeostasis in B6C3F1 mice upon sub-chronic exposure to trifluoroiodomethane (CF3I).

Trifluoroiodomethane (CF3I) is a fire suppressant gas with potential for use in low global-warming refrigerant blends. Data from studies in rats suggest that the most sensitive health effect of CF3I is thyroid hormone perturbation, but the rat is a particularly sensitive species for disruption of thyroid homeostasis. Mice appear to be less sensitive than rats but still a conservative model with respect to humans. The purpose of this study was to test tolerance and thyroid response to CF3I in B6C3F1 male mice. Male mice were exposed to CF3I for 6 h per day, for 28 days, via whole body exposure at concentrations of 2500, 5000 and 10,000 ppm. A 16-day recovery period was included to evaluate reversibility. No adverse clinical signs were observed throughout the study, and body weights were unaffected by exposure. CF3I exposure had no effect on thyroid histology. An increase in relative thyroid weight was observed at 10,000 ppm on day 28 but not in a separate group of animals evaluated on day 29, and thyroid weight was not different from controls at 44 days. Slight and sporadic changes in serum triiodothyronine, thyroxine, and thyroid-stimulating hormone were observed but did not follow a consistent pattern with respect to timing, dose, or direction. Overall, exposure at up to 10,000 ppm (1.0%) of CF3I gas for 28 days produced no overt general toxicity and only transient, recoverable effects on thyroid weight and hormones at certain concentrations. On the basis of the effect of CF3I exposure on the thyroid, including evaluation of thyroid histopathology, the no observed adverse effect level for this study is 10,000 ppm. Considering the apparently greater toxicity reported in prior studies in male rats, our data suggest a species difference between rats and mice in terms of susceptibility to CF3I-induced thyroid hormone perturbation.

Employment of cytology for in vitro skin irritation test using a reconstructed human epidermis model, Keraskin™.

Skin irritation tests using reconstructed human epidermis (RhE) employ viability as an endpoint, but color interference or borderline results are often problematic. We examined whether the cytology of cells from treated RhE could determine skin irritancy. Six chemicals (three irritants; DnP, 1-B, PH, three non-irritants; DP, APA, HS) were evaluated in a RhE, Keraskin™. DP, HS, and PH were clearly classified with viability, but DnP, 1-B, and APA were often falsely determined, due to borderline values falling near the cutoff, 50%. In histology, the tissues treated with DnP, 1-B, and PH showed erosion of the stratum corneum, vacuolization, and necrosis in the basal layer. DP- and HS-treated tissues showed relatively normal morphology but APA induced necrosis similar to irritants. Cytology revealed that DnP, 1-B or PH depleted cells and induced irregular and abnormal cell shapes. In contrast, relatively regular and normal shapes and clear distinction between the nucleus and cytoplasm was observed for DP, APA and HS. To further confirm it, additional 10 substances, including false positives from OECD TG 439, were tested. Overall (16 substances in total), cytology: total area predicted the skin irritancy of test chemicals with the highest accuracy (87.5%) followed by cytology: cell count (81.3%), histology (75%) and viability (68.8%), confirming the utility of cytology as an alternative endpoint in the skin irritation test using RhE.

Trifluoroiodomethane (CF3I) (2019).

Trifluoroiodomethane (CF3I) is a colorless and odorless gas used primarily as a fire suppressant. CF3I has low acute inhalation toxicity. The no-observed adverse effect level (NOAEL) of CF3I for cardiac sensitization in dogs was 2000 ppm. The potential effects of 4-week inhalation exposure in both rats and mice have been examined. In rats, the NOAEL was 10,000 ppm, and in mice, the NOAEL was 10,000 ppm. In a subchronic inhalation study in rats, the lowest observed adverse effect level (LOAEL) was 20,000 ppm for thyroid-related effects; the study NOAEL (for non-thyroid-related effects) was 20,000 ppm. In a reproductive/developmental inhalation toxicity study in rats, 20,000 ppm CF3I produced minimal general toxicity and no indication of reproductive or developmental toxicity. The LOAEL for parental toxicity (based on thyroid hormone effects) was 2000 ppm; excluding thyroid effects, the parental NOAEL was 7000 ppm CF3I. The observed effects on the thyroid in rats were considered of less relevance to human risk assessment than the other observed systemic effects because of known species-specific differences in sensitivity to thyroid hormone perturbations. There are no chronic toxicity or carcinogenicity studies available. CF3I had mixed results in various in vitro and in vivo genotoxicity assays. The NOAEL of 7000 ppm from the reproductive/developmental inhalation study was used as the point of departure (POD) for workplace environmental exposure level (WEEL) value development. This POD was adjusted to account for interindividual variability, duration of exposure, and database limitations. The resulting 8-h time-weighted average WEEL value of 500 ppm is expected to provide a significant margin of safety against any potential adverse health effects in workers exposed to CF3I. A 15-min short-term exposure limit of 1500 ppm was also established to protect workers from potential cardiac effects produced by acute, high-dose inhalation of CF3I.

Initial hazard assessment of 1,4-dichlorobutane: Genotoxicity tests, 28-day repeated-dose toxicity test, and reproductive/developmental toxicity screening test in rats.

1,4-Dichlorobutane (1,4-DCB) is used as raw materials for drugs, pesticides, fragrances, and chemical fibers, and being used as a solvent. Its toxicity data was insufficient for screening assessment under the Japanese Chemical Substances Control Law. We conducted toxicity tests and hazard classification for screening assessment 1,4-DCB showed negative in the Ames test, positive in the in vitro chromosomal aberrations test with metabolic activation, and negative in the in vivo mouse bone-marrow micronucleus test. The 28-day repeated-dose toxicity study, where male and female rats were administered 1,4-DCB by gavage at 0, 12, 60, and 300 mg/kg/day, showed significant effects on the liver and pancreas from 12 mg/kg/day and kidney at 300 mg/kg/day. Based on periportal hepatocellular hypertrophy and decreased zymogen granules in pancreas, the lowest observed adverse effect level (LOAEL) of 12 mg/kg/day was obtained. The reproductive/developmental toxicity screening study, in which male and female rats were administered 1,4-DCB by gavage at dose of 0, 2.4, 12, and 60 mg/kg/day for 42-46 days, showed that the delivery index was decreased at 60 mg/kg/day without maternal toxicity. Based on the general toxicity, we classified this chemical as hazard class 2, with a D-value (Derived No Effect Level) of 0.002 mg/kg/day.

Fluorinated diiodine alkanes exert developmental toxicity on embryo-larval stages of zebrafish strain AB via regulating the expression of the specific endocrine-related genes.

Fluorinated diiodine alkanes (FDIAs) are environmental pollutants, including octafluoro-1,4-diiodobutane (PFBDI), hexadecafluoro-1,8-diiodooctane (PFODI) and dodecafluoro-1,6-diiodohexane (PFHxDI). They showed an estrogenic effect in in vitro studies. However, little information is currently available regarding the toxicity of FDIAs in in vivo studies. Zebrafish (Danio rerio) is a vertebrate animal model that is increasingly used for toxicity and efficacy screening as well as for assessing the toxicity and safety of novel compounds, pollutants and pharmaceuticals. In the present study, we investigated the developmental toxicity of FDIAs (PFBDI, PFHxDI and PFODI) and the specific endocrine-related gene expression in zebrafish embryos. The results revealed that all three FDIAs showed developmental toxicity on zebrafish embryos. The half-maximal effective concentration values for PFBDI, PFHxDI and PFODI were 0.89 ± 0.07, 0.53 ± 0.04 and 0.04 ± 0.007 mm, respectively. PFHxDI exhibited the highest developmental toxicity compared with the other FDIAs. In addition, all three FDIAs significantly upregulated the expression of estrogen receptor (esr)1 and cytochrome P450 (CYP) 19b (CYP19b), but did not significantly affect the expression of esr2b, CYP17 and CYP19a in zebrafish. The upregulation effect of PFHxDI was greater than the effect of PFBDI and PFODI. This study furthers our knowledge on the effects of FDIAs on the developmental toxicity and the specific endocrine-related gene expression in the embryo-larval stages of zebrafish. Our results provided a preliminary insight into the toxicity of FDIAs in zebrafish, which will be of great relevance regarding future studies on FDIAs in the environment.

A Human Relevant Defined Mixture of Persistent Organic Pollutants (POPs) Affects In Vitro Secretion of Glucagon-Like Peptide 1 (GLP-1), but Does Not Affect Translocation of Its Receptor.

Environmental exposure to persistent organic pollutants (POPs) has been suggested as a contributing factor for the increased rate of type 2 diabetes and obesity. A complex mixture of 29 POPs (Total mixture), based on human blood concentrations, was used to expose a glucagon-like peptide 1 (GLP-1) secreting enteroendocrine cell line (pGIP/neo: STC-1) in vitro for 3 and 24 h. Significant increases of GLP-1 occurred when cells were exposed to the Total mixture at ×500 blood levels. Six sub-mixtures representing chlorinated (Cl), brominated (Br), and perfluorinated chemicals (PFAA), and their combinations (Cl + Br, Cl + PFAA, Br + PFAA) were also tested at ×500. Secretion levels seen for these remained lower than the Total mixture, and the Br mixture had no effect. After 24 h, increased secretion was seen with all mixtures at ×1 blood levels. Cytotoxicity was present for ×100 and ×500 blood levels. When tested in a GLP-1 receptor translocation assay (U2OS-GLP1R-EGFP), neither agonistic nor antagonist effects on receptor internalization were seen for any of the mixtures. We conclude individual classes of POPs, alone or in combination, can affect GLP-1 secretion and may contribute as a molecular mechanism linking environmental toxicants and diabetes.

Typical halogenated flame retardants affect human neural stem cell gene expression during proliferation and differentiation via glycogen synthase kinase 3 beta and T3 signaling.

2',2',4,4'-tetrabromo diphenyl ether (BDE-47), one of the most abundant congeners of commercial pentaBDE utilized as flame retardants, has been phased out of production due to its potential neural toxicity and endocrine disrupting activities, and yet still present in the environment. Several alternatives to BDE-47, including tetrabromobisphenol A (TBBPA), tetrabromobisphenol S (TBBPS), tetrachlorobisphenol A (TCBPA) and decabromodiphenyl ether (BDE-209), are presently employed without restrictions and their potential toxic effects on human neural development are still unclear. In this study, we utilized a human neural stem cell (hNSC)-based system to evaluate the potential developmental neurotoxic effects of the above-mentioned five chemicals, at environment and human exposure relevant concentrations. We found that those compounds slightly altered the expression of hNSC identity markers (SOX2, SOX3 and NES), without impairing cell viability or proliferation, in part by either modulating glycogen synthase kinase 3 beta (GSK3ß) signaling (TBBPS, TCBPA and BDE-47), and slightly disturbing the NOTCH pathway (TBBPA, TBBPS and TCBPA). Moreover, the five chemicals seemed to alter hNSC differentiation by perturbing triiodothyronine (T3) cellular signaling. Thus, our findings suggest that the five compounds, especially TBBPS, TCBPA, and BDE-47, may affect hNSC self-renewal and differentiation abilities and potentially elicit neural developmental toxicity.

Sex-specific endocrine-disrupting effects of three halogenated chemicals in Japanese medaka.

Several halogenated chemicals are found in an array of products that can cause endocrine disruption. Human studies have shown that endocrine responses are sex specific, with females more likely to develop hypothyroidism and males more likely to have reproductive impairment. The objective of this study was to assess sex differences on thyroid and estrogenic effects after exposure of Japanese medaka (Oryzias latipes, SK2MC) to halogenated compounds. This strain is an excellent model for these studies as sex can be determined non-destructively a few hours postfertilization. Medaka embryos were exposed to sublethal concentrations of Tris(1,3-dichloro-2-propyl) phosphate (TDCPP, 0.019 mg/L), perfluorooctanoic acid (PFOA, 4.7 mg/L) and its next generation alternative, perfluorobutyric acid (PFBA, 137 mg/L). Methimazole (inhibits thyroid hormone synthesis) and the thyroid hormone triiodothyronine served as reference controls. Fish were exposed throughout embryo development until 10 days postfertilization. Females displayed significantly larger swim bladders (which are under thyroid hormone control) after exposure to all chemicals with the exception of triiodothyronine, which caused the opposite effect. Females exposed to TDCPP and PFOA had increased expression of vitellogenin and exposure to PFOA upregulated expression of multiple thyroid-related genes. Upregulation of estrogenic-regulated genes after exposure to TDCPP, PFOA and methimazole was only observed in males. Overall, our results suggest that females and males show an estrogenic response when exposed to these halogenated chemicals and that females appear more susceptible to thyroid-induced swim bladder dysfunction compared with males. These results further confirm the importance of considering sex effects when assessing the toxicity of endocrine-disrupting compounds.

Persistent Halogenated Organic Pollutants in Surface Water in a Megacity: Distribution Characteristics and Ecological Risks in Wuhan, China.

Surface water pollution in megacities is strongly linked to human and environmental health, and surface water quality has deteriorated sharply recently because of increasing persistent halogenated organic pollutant (HOP) concentrations. In the present study, we collected 112 water samples from 14 lakes and 11 drinking water sources in Wuhan, China, and analyzed them for two typical groups of HOPs: polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). The mean values of the ΣPCB concentrations were 4.34 and 10.05 ng L-1 in winter and summer, respectively. For ΣPBDE concentrations, the mean values were 0.88 and 1.53 ng L-1 in winter and summer, respectively. The PCB and PBDE concentrations at most sites in summer were significantly higher than those in winter, probably because of heavy stormwater runoff in summer. The degree of urbanization predicted from the population density was positively correlated with ΣPCB concentrations in the drinking water sources in summer. PBDE and PCB composition analysis suggested the major sources were penta-BDE and Aroclor mixtures. Risk assessments showed the PBDEs in water from the Zhuankou site exceeded the threshold set by the European Union, which could result in adverse effects on aquatic organisms. Negligible noncarcinogenic risks were found for PCBs and PBDEs in the surface water with regard to drinking and bathing. However, the carcinogenic risks of PCBs for bathing in surface water were higher than the safe level of 1.00 × 10-6, implying that the surface water in Wuhan is not safe for bathing.

Drivers of maternal accumulation of organohalogen pollutants in Arctic areas (Chukotka, Russia) and 4,4'-DDT effects on the newborns.

BACKGROUND: One of the most worrying consequence of the production and use of persistent organohalogen pollutants (POPs) is the high accumulation in Arctic populations because of long-range transport. Study of the effects in these populations may illustrate human impacts that are difficult to assess in other locations with lower exposure to these compounds and more diverse pollutant influences. OBJECTIVE: We aimed to identify the main maternal characteristics influencing on the accumulation of these compounds and the effects on the newborns in a highly exposed Arctic population (Chukotka, Russia). METHODS: Organochlorine and organobromine compounds were analysed in maternal venous serum (n = 250). The study included data on residence, educational level, age, parity and body mass index (BMI) from self-reported questionnaires and measured anthropometric characteristics of newborns. RESULTS: Concentrations of ß-hexachlorocyclohexanes, hexachlorobenzene, 4,4'-DDT and polychlorobiphenyls were high when compared with those generally found in adult populations later than year 2000. The polybromodiphenyl ethers were negligible. These POP concentrations were higher than in Alaska and Arctic Norway and similar to those in Canada. The Chukotka mothers living in inland areas showed significant lower concentrations than those living in the coast (p < 0.001) except for 4,4'-DDT. The population from the Chukotsky District, a specific coastal area, showed the highest concentrations. Residence was therefore a main concentration determinant (p < 0.001) followed by maternal age, and in some cases parity and BMI (p < 0.05). 4,4'-DDT showed an association with the anthropometric characteristics of the newborns (p < 0.05). Mothers with higher 4,4'-DDT concentrations had longer gestational ages and gave birth to infants with higher weight and length. CONCLUSIONS: The maternal accumulation patterns of POPs were mainly related with residence. Most of these compounds were found in higher concentration in women living at coastal areas except 4,4'-DDE and 4,4'-DDT which were of inland origin. This last pesticide was the pollutant showing positive associations with gestational age and newborn's weight and length. To the best of our knowledge, this is the first study reporting statistically significant associations between maternal 4,4'-DDT exposure and anthropometric characteristics of the newborns.

A rapid method of preparing complex organohalogen extracts from avian eggs: Applications to in vitro toxicogenomics screening.

Double-crested cormorants are piscivorous birds that breed in variably contaminated colonies across the Laurentian Great Lakes of North America. Collection and preparation of environmentally relevant extracts from eggs that contain variable concentrations of organohalogen contaminants represents a minimally invasive approach to characterize potential effects of exposure using in vitro bioassays. In the present study, a rapid, efficient lipid freeze-filtration extraction method was used to prepare extracts from double-crested cormorant eggs collected from 5 breeding colonies that had variable organohalogen contaminant burdens. Extracts, solubilized in dimethyl sulfoxide, were administered to chicken embryonic hepatocytes (CEHs) to determine effects on cell viability, 7-ethoxyresorufin-O-deethylase (EROD) activity, and messenger RNA expression using a chicken ToxChip polymerase chain reaction (PCR) array. The EROD median effect concentration (EC50) values were lower for extracts with greater organohalogen contaminant burdens and thus permitted an initial ranking of colonies based on the efficacy of eliciting an aryl hydrocarbon receptor-mediated response. The ToxChip PCR array data provided a more exhaustive, pathway-based evaluation of extract effects; variability in the transcriptomic profiles was associated with organohalogen contaminant burdens. For example, extracts from Mud Island (Detroit River, MI, USA) had among the highest organohalogen contaminant burdens and elicited a greater biochemical (EROD EC50 = 0.005) and transcriptomic response (22/43 genes altered on the array) in CEHs compared with the least contaminated site, which was Mandarte Island (BC, Canada; EROD EC50 = 0.172; 8/43 genes altered). Avian eggs represent a useful biomonitoring tool for determining complex mixture effects, and the combination of a rapid extraction method, an in vitro bioassay, and targeted endpoint evaluation (biochemical and transcriptomic) shows great promise as an environmental effects monitoring approach. Environ Toxicol Chem 2019;38:811-819. © 2019 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.

Single or mixture halogenated chemicals? Risk assessment and developmental toxicity prediction on zebrafish embryos based on weighted descriptors approach.

Halogenated chemicals including perfluoroalkyl substances (PFASs) represent an emerging class of endocrine-disrupting pollutants for human populations across the globe. Distress related to their environmental fate and toxicity has initiated several research projects, but the amount of experimental data available for these pollutants is limited. The objective of this study is to assess the toxicity of potentially "safer" alternatives, in relation to their existing counterparts. Developmental toxicity data on zebrafish (Danio rerio) embryos of single and tertiary halogenated mixtures were modeled employing quantitative structure-toxicity relationship (QSTR) tool. The computed models are then employed for toxicity prediction of theoretically generated binary and tertiary mixtures (which have no experimental data) to check their possible threshold and mode of toxicity for future risk assessment. Further, for toxicity screening, we have prepared a huge external dataset consists of single (24), binary (276) and tertiary (2024) mixtures of PFASs. It was accomplished by combination method and predicted through developed models for interpretation of toxicity threats for individuals and mixtures along with identification of diverse range and combination of toxicity thresholds. We found that chemicals in mixtures displayed concentration addition of individual chemical suggesting a similar mode of toxic action and non-interaction of chemicals. Not only that, mixtures of halogenated compounds including PFASs showed less toxicity than their single counterparts and the obtained toxicity trend is: Single chemical > Binary mixture > Tertiary mixture.

Contributions of caspase-8 and -9 to liver injury from CYP2E1-produced metabolites of halogenated hydrocarbons.

1. Drug-induced liver injury is difficult to predict at the pre-clinical stage. This study aimed to clarify the roles of caspase-8 and -9 in CYP2E1 metabolite-induced liver injury in both rats and cell cultures in vitro treated with carbon tetrachloride (CCl4), halothane or sevoflurane. The human hepatocarcinoma functional liver cell line was maintained in 3-dimensional culture alone or in co-culture with human acute monocytic leukemia cells. 2. In vivo, laboratory indices of liver dysfunction and histology were normal after administration of sevoflurane. CCl4 treatment increased blood AST/ALT levels, liver caspase-3 and -9 activities and liver malondialdehyde, accompanied by centrilobular hepatocyte necrosis. Halothane increased AST/ALT levels, caspase-3 and -8 activities (but not malondialdehyde) concomitant with widespread hepatotoxicity. In vitro, CCl4 treatment increased caspase-9 activity and decreased both mitochondrial membrane potential (MMP) and cell viability. In co-culture, halothane increased caspase-8 activity and decreased MMP and cellular viability. There were no toxic responses in CYP2E1 knockdown in monoculture and co-culture. 3. CYP2E1-inducing compounds play a pivotal role in halogenated hydrocarbon toxicity. 4. Changes in hepatocyte caspase-8 and -9 activities could be novel biomarkers of metabolites causing DILI, and in pre-clinical development of new pharmaceuticals can predict nascent DILI in the clinical stage.

DNA damage in Arctic seabirds: Baseline, sensitivity to a genotoxic stressor, and association with organohalogen contaminants.

Environmental contaminants are found throughout Arctic marine ecosystems, and their presence in seabirds has been associated with toxicological responses. However, there are few studies of genotoxicity in Arctic avian wildlife. The purpose of the present study was to quantify deoxyribonucleic acid (DNA) damage in lymphocytes of selected seabird species and to examine whether accumulation of organohalogen contaminants (ΣOHCs) affects DNA damage. Blood was sampled from common eider (Somateria mollissima), black guillemot (Cepphus grylle), black-legged kittiwake (Rissa tridactyla), glaucous gull (Larus hyperboreus), arctic skua (Stercorarius parasiticus), and great skua (Stercorarius skua) in Kongsfjorden, Svalbard (Norway). Contaminant concentrations found in the 6 species differed, presumably because of foraging ecology and biomagnification. Despite large differences in contaminant concentrations, ranging from ΣOHCs 3.3 ng/g wet weight in the common eider to ΣOHCs 895 ng/g wet weight in the great skua, there was no strong difference among the species in baseline DNA damage or sensitivity to a genotoxic stressor (hydrogen peroxide). Baseline levels of DNA damage were low, with median values ranging from 1.7% in the common eider to 8.6% in the great skua. There were no associations between DNA damage and contaminants in the investigated species, suggesting that contaminant concentrations in Kongsfjorden are too low to evoke genotoxic effects, or possibly that lymphocytes are resistant to strand breakage. Clearly, genotoxicity is a topic for future studies of Arctic seabirds. Environ Toxicol Chem 2018;37:1084-1091. © 2017 SETAC.

The distribution and species of Ca2+ and subcellular localization of Ca2+ and Ca2+-ATPase in grape leaves of plants treated with fluoroglycofen.

Fluoroglycofen, a post-emergence herbicide used in vineyards to eradicate weeds, has previously been shown to turn grape leaves dark green following its use. Therefore, this study evaluates the relationship of dark green leaves with calcium form and subcellular distribution. To do this, we focused on the Ca2+ distribution and Ca2+-ATPase activity in leaf cells of one-year-old self-rooted Chardonnay grapevines treated with fluoroglycofen. Plants were separated into different treatments when they had seven or eight leaves, and different concentrations of fluoroglycofen were sprayed on the sand. The results showed that all of the soluble calcium content in the grape leaves that were treated with the highest concentration of fluoroglycofen (187.5gaiha-1) increased significantly. Specifically, the water-soluble organic acid calcium, pectate calcium, and calcium oxalate increased by 18.43%, 17.14%, and 31.05%, respectively, in the upper leaves than in the control. The subcellular distribution of Ca2+ in the dark green leaves increased significantly, especially in the cell wall and chloroplast, which increased by 25.54% and 24.10%, respectively. Through the ultrastructure localization of Ca2+ and Ca2+-ATPase contrasted with the control, the extracellular space and chloroplasts in the mesophyll cells of dark green leaves had large calcium pyroantimonate (Ca-PA) deposits. The extracellular space had fewer Ca2+-ATPase precipitation particles, whereas the chloroplasts had more. At the same time, a high concentration of fluoroglycofen decreased Ca2+-ATPase activity in grape leaves, which potentially might be due to disrupted regulation of calcium homeostatic mechanisms inside and outside of cells, resulting in a large number of Ca2+ accumulation in cells. The Ca2+ accumulation not only hindered the various cellular physiological reactions, but also caused leaves to become dark green in color.

Predictive QSAR Models for the Toxicity of Disinfection Byproducts.

Several hundred disinfection byproducts (DBPs) in drinking water have been identified, and are known to have potentially adverse health effects. There are toxicological data gaps for most DBPs, and the predictive method may provide an effective way to address this. The development of an in-silico model of toxicology endpoints of DBPs is rarely studied. The main aim of the present study is to develop predictive quantitative structure-activity relationship (QSAR) models for the reactive toxicities of 50 DBPs in the five bioassays of X-Microtox, GSH+, GSH-, DNA+ and DNA-. All-subset regression was used to select the optimal descriptors, and multiple linear-regression models were built. The developed QSAR models for five endpoints satisfied the internal and external validation criteria: coefficient of determination (R²) > 0.7, explained variance in leave-one-out prediction (Q²LOO) and in leave-many-out prediction (Q²LMO) > 0.6, variance explained in external prediction (Q²F1, Q²F2, and Q²F3) > 0.7, and concordance correlation coefficient (CCC) > 0.85. The application domains and the meaning of the selective descriptors for the QSAR models were discussed. The obtained QSAR models can be used in predicting the toxicities of the 50 DBPs.

Dissimilar effects of organohalogenated compounds on thyroid hormones in glaucous gulls.

The glaucous gull (Larus hyperboreus) is an arctic top predator and scavenger exposed to high levels of mixtures of organohalogenated contaminants (OHCs) of which many interfere with the thyroid hormone (TH) system. In the present study, we applied statistical modeling to investigate the potential combined influence of the mixture of chlorinated, brominated and perfluorinated organic compounds in plasma of glaucous gulls on their plasma TH concentrations. In females, there were significant negative associations between several organochlorinated compounds (OCs) and free thyroxin (FT4) and triiodothyronine (FT3), indicating additive negative effects on FT4 and FT3. However, in these females there was also a significant positive association between perfluorooctane sulfonate (PFOS) and FT3. The inverse associations between several OCs and FT3 and the contrasting positive association between PFOS and FT3, indicate that these two groups of OHCs may have dissimilar and antagonistic effects on FT3 in female glaucous gulls. In males, there were no associations between any of the OHCs and the THs. That OHCs affect THs in a complex manner involving both additive and antagonistic effects add to the challenge of interpreting the overall functional effect of thyroid disruptive chemicals in wildlife. However, experimental studies are needed to confirm or disprove such effects.