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1.
Aquat Toxicol ; 224: 105481, 2020 Jul.
Article in English | MEDLINE | ID: mdl-32380301

ABSTRACT

Modern nano-engineered pesticides have great promise for agriculture due to their extended, low dose release profiles that are intended to increase effectiveness but reduce environmental harm. Whether nanopesticides, including copper (Cu) formulations, cause reduced levels of toxicity to non-target aquatic organisms is unclear but important to assess. Predicting how aquatic species respond to incidental exposure to Cu-based nanopesticides is challenging because of the expected very low concentrations in the environment, and the two forms of exposure that may occur, namely to Cu ions and Cu nanoparticles. We conducted Cu speciation, tissue uptake, and 7-day toxicity laboratory experiments to test how a model estuarine organism, the amphipod Leptocheirus plumulosus, responded to two popular Cu-based nanopesticides, CuPRO and Kocide, and conventional CuCl2. Exposure concentrations ranged from 0 to 2.5 ppm, which were similar to those found in estuarine water located downstream of agricultural fields. Cu dissolution rates were much slower for the nanopesticides than the ionic formula, and Cu body burden in amphipods increased approximately linearly with the nominal exposure concentration. Amphipod survival declined in a normal dose-response manner with no difference among Cu formulations. Growth and movement rates after 7 days revealed no difference among exposure levels when analyzed with conventional statistical methods. By contrast, analysis of respiration rates, inferred from biomass measurements, with a bioenergetic toxicodynamic model indicated potential for population-level effects of exposure to very low-levels of the two nanopesticides, as well as the control contaminant CuCl2. Our results indicate that toxicity assessment of environmental trace pollutant concentrations may go undetected with traditional ecotoxicological tests. We present a process integrating toxicity test results and toxicodynamic modeling that can improve our capacity to detect and predict environmental impacts of very low levels of nanomaterials released into the environment.


Subject(s)
Amphipoda/drug effects , Copper/toxicity , Estuaries , Nanoparticles/toxicity , Pesticides/toxicity , Water Pollutants, Chemical/toxicity , Amphipoda/chemistry , Animals , Body Burden , Copper/analysis , Dose-Response Relationship, Drug , Nanoparticles/analysis , Pesticides/analysis , Seawater/chemistry , Water Pollutants, Chemical/analysis
2.
Environ Sci Technol ; 51(3): 1213-1223, 2017 02 07.
Article in English | MEDLINE | ID: mdl-27998057

ABSTRACT

Twentieth century municipal wastewater infrastructure greatly improved U.S. urban public health and water quality. However, sewer pipes deteriorate, and their accumulated structural defects may release untreated wastewater to the environment via acute breaks or insidious exfiltration. Exfiltrated wastewater constitutes a loss of potentially reusable water and delivers a complex and variable mix of contaminants to urban shallow groundwater. Yet, predicting where deteriorated sewers impinge on shallow groundwater has been challenging. Here we develop and test a spatially explicit model of exfiltration probability based on pipe attributes and groundwater elevation without prior knowledge of exfiltrating defect locations. We find that models of exfiltration probability can predict the probable occurrence in underlying shallow groundwater of established wastewater indicators including the artificial sweetener acesulfame, tryptophan-like fluorescent dissolved organic matter, nitrate, and a stable isotope of water (δ18O). The strength of the association between exfiltration probability and indicators of wastewater increased when multiple pipe attributes, distance weighting, and groundwater flow direction were considered in the model. The results prove that available sanitary sewer databases and groundwater digital elevation data can be analyzed to predict where pipes are likely leaking and contaminating groundwater. Such understanding could direct sewer infrastructure reinvestment toward water resource protection.


Subject(s)
Waste Disposal, Fluid , Wastewater/chemistry , Groundwater/chemistry , Models, Theoretical , Sweetening Agents , Water Pollutants, Chemical
3.
Water Res ; 85: 467-75, 2015 11 15.
Article in English | MEDLINE | ID: mdl-26379202

ABSTRACT

Wastewater compounds are frequently detected in urban shallow groundwater. Sources include sewage or reclaimed wastewater, but origins are often unknown. In a prior study, wastewater compounds were quantified in waters sampled from shallow groundwater wells in a small coastal California city. Here, we resampled those wells and expanded sample analyses to include sewage- or reclaimed water-specific indicators, i.e. pharmaceutical and personal care product chemicals or disinfection byproducts. Also, we developed a geographic information system (GIS)-based model of sanitary sewer exfiltration probability--combining a published pipe failure model accounting for sewer pipe size, age, materials of construction, with interpolated depths to groundwater--to determine if sewer system attributes relate to wastewater compounds in urban shallow groundwater. Across the wells, groundwater samples contained varying wastewater compounds, including acesulfame, sucralose, bisphenol A, 4-tert-octylphenol, estrone and perfluorobutanesulfonic acid (PFBS). Fecal indicator bacterial concentrations and toxicological bioactivities were less than known benchmarks. However, the reclaimed water in this study was positive for all bioactivity tested. Excluding one well intruded by seawater, the similarity of groundwater to sewage, based on multiple indicators, increased with increasing sanitary sewer exfiltration probability (modeled from infrastructure within ca. 300 m of each well). In the absence of direct exfiltration or defect measurements, sewer exfiltration probabilities modeled from the collection system's physical data can indicate potential locations where urban shallow groundwater is contaminated by sewage.


Subject(s)
Groundwater/analysis , Waste Disposal, Fluid , Wastewater/analysis , Water Pollutants, Chemical/analysis , California , Models, Theoretical , Sewage/analysis , Water Wells
4.
Toxicol Int ; 21(1): 57-64, 2014 Jan.
Article in English | MEDLINE | ID: mdl-24748736

ABSTRACT

BACKGROUND/OBJECTIVE: The modulation of the toxic effects of 2-aminoanthracene (2AA) on the liver by apoptosis was investigated. Fisher-344 (F344) rats were exposed to various concentrations of 2AA for 14 and 28 days. The arylamine 2AA is an aromatic hydrocarbon employed in manufacturing chemicals, dyes, inks, and it is also a curing agent in epoxy resins and polyurethanes. 2AA has been detected in tobacco smoke and cooked foods. METHODS: Analysis of total messenger ribonucleic acid (mRNA) extracts from liver for apoptosis-related gene expression changes in apoptosis enhancing nuclease (AEN), Bcl2-associated X protein (BAX), CASP3, Jun proto-oncogene (JUN), murine double minute-2 p53 binding protein homolog (MDM2), tumor protein p53 (p53), and GAPDH genes by quantitative real-time polymerase chain reaction (qRT-PCR) was coupled with terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and caspase-3 (Casp3) activity assays. RESULTS: Specific apoptosis staining result does not seem to show significant difference between control and treated animals. This may be due to freeze-thaw artifacts observed in the liver samples. However, there appears to be a greater level of apoptosis in medium- and high-dose (MD and HD) 2AA treated animals. Analyses of apoptosis-related genes seem to show AEN and BAX as the main targets in the induction of apoptosis in response to 2AA exposure, though p53, MDM2, and JUN may play supporting roles. CONCLUSION: Dose-dependent increases in mRNA expression were observed in all genes except Casp3. BAX was very highly expressed in the HD rats belonging to the 2-week exposure group. This trend was not observed in the animals treated for 4 weeks. Instead, AEN was rather very highly expressed in the liver of the MD animals that were treated with 2AA for 28 days.

5.
J Toxicol Sci ; 37(5): 1001-16, 2012.
Article in English | MEDLINE | ID: mdl-23038007

ABSTRACT

The goal of the present study was to examine hepatic differential gene expression patterns in Fisher-344 rats in response to dietary 2-aminoanthracene (2AA) ingestion for 14 and 28 days. Twenty four post-weaning 3-4 week old F-344 male rats were exposed to 0 mgkg(-1)-diet (control), 50 mgkg(-1)-diet (low dose), 75 mgkg(-1)-diet (medium dose) and 100 mgkg(-1)-diet (high dose) 2AA for 14 and 28 days. This was followed by analysis of the liver for global gene expression changes. In both time points, the numbers of genes affected seem to correlate with the dose of 2AA. Sixteen mRNAs were differentially expressed in all treatment groups for the short-term exposure group. Similarly, 51 genes were commonly expressed in all 28-day exposure group. Almost all the genes seem to have higher expression relative to the controls. In contrast, cytochrome P450 family 4, subfamily a, polypeptide 8 (Cyp4a8), and monocyte to macrophage differentiation-associated (Mmd2) were down-regulated relative to controls. Differentially expressed mRNAs were further analyzed for associations via DAVID. GO categories show the effect of 2AA to be linked with genes responsible for carbohydrate utilization and transport, lipid metabolic processes, stress responses such as inflammation and apoptosis processes, immune system response, DNA damage response, cancer processes and circadian rhythm. The data from the current study identified altered hepatic gene expression profiles that may be associated with carcinoma, autoimmune response, and/or type 2 diabetes. Possible biomarkers due to 2AA toxicity in the liver for future study include Abcb1a, Nhej1, Adam8, Cdkn1a, Mgmt, and Nrcam.


Subject(s)
Anthracenes/toxicity , Carcinogens/toxicity , Gene Expression Regulation/drug effects , Liver/drug effects , Mutagens/toxicity , Animals , Carcinoma, Hepatocellular , Diabetes Mellitus, Type 2 , Gene Expression Profiling , Liver/metabolism , Liver Neoplasms , Male , Rats , Rats, Inbred F344
6.
Int J Toxicol ; 29(5): 532-45, 2010.
Article in English | MEDLINE | ID: mdl-20884862

ABSTRACT

Polycyclic aromatic hydrocarbons (PAH) have been demonstrated to affect immune system modulation. The freshwater species of fish, Lepomis macrochirus (bluegill), was employed to investigate the effects of a 14-day dietary exposure to PAH including 2-aminoanthracene (2-AA), 2-methylnaphthalene (2-MN), and 9,10-dimethylanthracene (9,10-DMA) and a mixture of these 3 compounds at a total dose of 3.1 ± 0.01 mg on lymphocyte proliferation stimulated with 3 mitogens (concanavalin A [Con A], phorbol ester, and calcium ionophore). 2-Aminoanthracene was mitogenic itself and with added mitogens. 2-Methylnaphthalene induced some stimulatory and some inhibitory effects upon cell proliferation by Con A. 9,10-DMA and the mixture each suppressed cell proliferation. The mixture was highly suppressive to lymphocytes. Intracellular baseline calcium levels were reduced, possibly as a step prior to cell death. All PAH compounds tested were immunomodulatory to bluegill lymphocytes. Bluegill were demonstrated to have utility as a biomarker species for investigation of immunotoxicity.


Subject(s)
Carcinogens/toxicity , Immunologic Factors/toxicity , Lymphocytes/drug effects , Perciformes/physiology , Polycyclic Aromatic Hydrocarbons/toxicity , Animal Feed/analysis , Animals , Anthracenes/toxicity , Biomarkers/blood , Calcium/analysis , Carcinogens/analysis , Cell Proliferation/drug effects , Cells, Cultured , Immunologic Factors/analysis , Lymphocyte Activation/drug effects , Lymphocytes/chemistry , Lymphocytes/physiology , Mitogens/analysis , Mitogens/toxicity , Models, Animal , Naphthalenes/toxicity , Perciformes/blood , Polycyclic Aromatic Hydrocarbons/analysis , Random Allocation , Reproducibility of Results , Toxicity Tests/methods
7.
Environ Toxicol Chem ; 29(7): 1537-44, 2010 Jul.
Article in English | MEDLINE | ID: mdl-20821603

ABSTRACT

Formation of DNA adducts by reactive chemicals or their metabolites are often a precursor of mutagenesis and other adverse effects. Studies in juvenile channel catfish (Ictalurus punctatus) were conducted to determine the dose-response, kinetics of formation, and persistence of S-[2-(N7-guanyl)ethyl]glutathione hepatic-DNA adducts following a 4-h in vivo aqueous exposure to ethylene dichloride (EDC) at several dose levels. S-[2-(N7-guanyl)ethyl] glutathione adducts were detectable in liver tissue after 2 h of exposure and were still detectable three weeks after a single pulse exposure (detection limit=approximately 10 fmol, approximately 1 DNA adduct in 10(7) bases). Pretreatment of catfish with the glutathione-depleting agent diethylmaleate significantly reduced the level of tissue glutathione levels and, as a result, DNA adducts were not detected in pretreated fish. Catfish may serve as a useful sentinel species for detecting DNA-reactive chemicals in aquatic systems.


Subject(s)
Carcinogens/toxicity , DNA Adducts/pharmacokinetics , Glutathione/analogs & derivatives , Ictaluridae/metabolism , Liver/drug effects , Animals , Carcinogens/pharmacokinetics , Dose-Response Relationship, Drug , Gas Chromatography-Mass Spectrometry , Glutathione/pharmacokinetics , Glutathione/toxicity , Limit of Detection , Liver/metabolism
8.
Int J Toxicol ; 29(3): 247-58, 2010.
Article in English | MEDLINE | ID: mdl-20448257

ABSTRACT

Chronic exposure to arylamines through diet and/or smoking has been associated with genetic changes and tumorigenesis. Cellular proliferation, apoptosis, and histological changes in liver tissue were investigated in Gambusia affinis (G affinis) after chronic dietary exposure to 6.9 mM and 0.069 mM concentrations of benzidine (BZ), 2-aminofluorene (2AF), and their combination for 4, 8, and 12 weeks, respectively. The proliferation assay indicated non-dose-dependent increases in cellular proliferation over the controls for all treatment groups at 4 and 12 weeks but not at 8 weeks except for the low dose of 2AF. The apoptosis assay showed effects in the low-dose group of 2AF and BZ at 4 weeks only. Hematoxylin/eosin staining of liver tissue revealed an increase in oval/spindle cell proliferation and altered foci formation in the treated groups compared with controls. These results demonstrate a mammalian-like response to 2AF and BZ in G affinis liver.


Subject(s)
Benzidines/toxicity , Carcinogens/toxicity , Cell Death/drug effects , Cell Proliferation/drug effects , Cyprinodontiformes , Fluorenes/toxicity , Liver/pathology , Algorithms , Animals , Benzidines/administration & dosage , Carcinogenicity Tests/methods , Carcinogens/administration & dosage , Diet , Dose-Response Relationship, Drug , Fluorenes/administration & dosage , In Situ Nick-End Labeling , Liver/drug effects , Liver/metabolism , Male , Models, Animal , Proliferating Cell Nuclear Antigen/metabolism , Random Allocation , Statistics, Nonparametric , Time Factors
9.
Toxicol Sci ; 93(1): 50-61, 2006 Sep.
Article in English | MEDLINE | ID: mdl-16760417

ABSTRACT

Toxic chemicals ingested as the result of environmental exposures or other risk factors such as cigarette smoking may increase the risk of developing cancer and other diseases such as diabetes. 2-Aminoanthracene (2-AA) was investigated to determine toxic effects of chronic dietary exposure upon major organ systems including the pancreas. Fisher-344 rats were fed 2-AA (50-100 mg/kg of diet) and euthanized at 14, 30, 63, and 80 days. Growth, tissue histological, immunocytochemical, and clinical pathological end points were examined at each time point. Significantly elevated plasma glucose and glycated hemoglobins and reduced serum protein levels were recognized after 80 days of feeding (100 mg/kg of diet 2-AA group). Similar results were observed in rats exposed to 75 mg/kg of diet but appeared to be absent in the 50-mg/kg group. An unexpected pattern of responses suggestive of diabetic sequelae was observed in a glucose tolerance test conducted during the seventh week. After 63 and 80 days, large cytoplasmic vacuoles in islet cells were observed by light microscopy. In addition, the immunocytochemical study demonstrated beta cell insulin insufficiency at 63 and 80 days. No inflammatory infiltration of the islets was observed. These findings suggest that depletion of secretory granules occurred in the beta cells. Necrotic changes occurred in the acinar cells of the pancreas with increasing duration and dose of 2-AA. The cytological, immunocytochemical, and histological results demonstrate that chronic dietary exposure to 2-amino anthracene alters the endocrine and exocrine pancreas cellular morphology and induces diabetic-like symptoms in the Fisher-344 rat.


Subject(s)
Anthracenes/toxicity , Diet , Pancreas/drug effects , Animals , Genes, myc , Genes, ras , Glucose Tolerance Test , Immunohistochemistry , Pancreas/cytology , Pancreas/metabolism , Rats , Rats, Inbred F344 , Weight Gain/drug effects
10.
Environ Res ; 98(1): 64-72, 2005 May.
Article in English | MEDLINE | ID: mdl-15721885

ABSTRACT

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that contribute to worldwide health problems. Despite data associating PCBs with adverse health effects, decisions to clean up contaminated sites remain controversial. Cleanup decisions are typically based on risk assessment methods that are not sensitive enough to detect subtle changes in health. We have recently shown that gene expression signatures can serve as sensitive molecular biomarkers of exposure and related health effects. Our initial studies were carried out with developing Xenopus laevis tadpoles that were exposed to the PCB mixture Aroclor 1254 (A1254) for 2 days. A1254 was dissolved in dimethyl sulfoxide and added to the aquarium water for rapid loading of PCBs into the tadpole tissue. These studies showed that increases in the expression of specific genes occurred independent of adverse health effects, and decreases in specific genes correlated with the appearance of observable health effects, including decreased survival and gross morphological and behavioral abnormalities. In this report, we extend our previous work to test the use of gene expression signatures as biomarkers in frogs exposed to PCBs through the diet from early tadpole stages through metamorphosis. This work showed that chronic low-dose exposure to A1254 (24 ppm) in food produced tissue levels of 17 ppm and increased gene expression of nerve growth factor and proopiomelanocortin independent of adverse health effects. Exposure to higher doses of A1254 (200 ppm) produced tissue levels of 80 ppm and increased expression of p450 1A1, also, independent of adverse health effects. This work provides further evidence for the use of gene expression changes as biomarkers of exposure to PCBs.


Subject(s)
/toxicity , Gene Expression Regulation, Developmental/drug effects , Metamorphosis, Biological/drug effects , Xenopus laevis/growth & development , Xenopus laevis/metabolism , Actins/biosynthesis , Actins/genetics , Animals , Caspase 1/biosynthesis , Caspase 1/genetics , Cytochrome P-450 CYP1A1/biosynthesis , Cytochrome P-450 CYP1A1/genetics , Female , Glyceraldehyde 3-Phosphate Dehydrogenase (NADP+)/biosynthesis , Glyceraldehyde 3-Phosphate Dehydrogenase (NADP+)/genetics , Larva/drug effects , Larva/genetics , Larva/growth & development , Larva/metabolism , Male , Metamorphosis, Biological/genetics , Nerve Growth Factor/biosynthesis , Nerve Growth Factor/genetics , Pro-Opiomelanocortin/biosynthesis , Pro-Opiomelanocortin/genetics , Random Allocation , Receptors, Dopamine D2/biosynthesis , Receptors, Dopamine D2/genetics , Reverse Transcriptase Polymerase Chain Reaction , Xenopus laevis/genetics
11.
J Am Soc Mass Spectrom ; 14(9): 1057-66, 2003 Sep.
Article in English | MEDLINE | ID: mdl-12954174

ABSTRACT

Polycyclic aromatic amines (arylamines) are a class of chemical carcinogens that are prevalent in environmental and industrial settings. They are metabolically activated to covalently bond to DNA, forming mutagenic adducts. In order to study the mechanisms of their toxicity, sensitive and selective quantitative LC/MS/MS detection methods were developed to measure the N-(adenin-8-yl)-benzidine adduct and N-(adenin-8-yl)-2-aminofluorene in total DNA extract samples. A novel synthetic method using a palladium catalyst was previously developed to prepare authentic and deuterated arylamine-adenine adducts to serve as standards. These standards were then used to develop an HPLC electrospray ionization tandem mass spectrometry, isotope dilution method. Sample detection limits in DNA samples were 22 pg on-column and 51 pg on-column for the N-(adenin-8-yl)-benzidine- and N-(adenin-8-yl)-2-aminofluorene-adenine adducts, respectively. This method has applications for the study of DNA adduct formation as a biological marker of exposure to carcinogens and for environmental and workplace monitoring of these aromatic amines.


Subject(s)
Amines/chemistry , Carcinogens/chemistry , Chromatography, High Pressure Liquid/methods , DNA Adducts/analysis , Spectrometry, Mass, Electrospray Ionization/methods , Amines/toxicity , Carcinogens/toxicity , DNA Adducts/chemistry , Isotopes , Molecular Structure , Reference Standards , Solutions/chemistry
12.
Environ Mol Mutagen ; 42(1): 1-10, 2003.
Article in English | MEDLINE | ID: mdl-12874807

ABSTRACT

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that pose global ecological and human health problems. Although it is well established that PCBs are associated with a variety of adverse health effects in wildlife and in humans, it is often difficult to determine direct cause-and-effect relationships between exposure and specific health outcomes. In this study, gene expression signatures were used to relate exposure to PCBs with altered physiological responses and/or specific health effects. Real-time PCR was used to measure gene expression levels for 10 genes in Xenopus laevis tadpoles (18 days postfertilization, PF) after acute exposure (2 days) to the PCB mixture Aroclor 1254. Specific gene expression signatures correlated with exposure and were predictive of adverse health effects. Exposure to low levels of Aroclor 1254 (5-50 ppb) significantly increased expression of six genes, independent of any health effects; exposure to midlevel concentrations (300-400 ppb) significantly decreased expression levels of two genes, NGF and beta-actin, prior to the onset of observable health effects; exposure to higher doses (500-700 ppb) significantly decreased NGF and beta-actin expression concomitant with the appearance of gross morphological abnormalities, behavioral deficits, and a statistically significant decrease in survival. This study expands upon our previous work that demonstrated an age-dependent susceptibility to Aroclor 1254 in Xenopus laevis tadpoles and that defined specific gene expression signatures as useful bioindicators of exposure and as predictors of overt or impending health effects.


Subject(s)
/toxicity , Environmental Pollutants/toxicity , Gene Expression Regulation, Developmental/drug effects , Genetic Markers/genetics , Xenopus laevis/physiology , Animals , Behavior, Animal/drug effects , Dose-Response Relationship, Drug , Gas Chromatography-Mass Spectrometry , Larva/anatomy & histology , Larva/drug effects , Larva/metabolism , Longevity/drug effects , RNA, Messenger/metabolism , Reverse Transcriptase Polymerase Chain Reaction
13.
Environ Toxicol Chem ; 22(2): 321-8, 2003 Feb.
Article in English | MEDLINE | ID: mdl-12558163

ABSTRACT

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that have damaging effects on both ecosystem and human health. Numerous studies have shown that exposure to PCBs can alter growth and development of aquatic organisms, including frogs. In this report, developing Xenopus laevis tadpoles were exposed to the PCB mixture Aroclor 1254. Tadpoles were exposed from 5 through 9 d postfertilization to either 0, 1, 10, 50, or 100 ppm Aroclor 1254. Exposure to an acute, high concentration of Aroclor 1254 (10, 50, and 100 ppm) caused statistically significant reductions in survival and body size. In addition, tadpoles exposed to these higher concentrations showed histological abnormalities, including aberrant tail tip, myotomal, and melanocyte morphologies. Described adverse health effects associated with PCB exposure of developing frogs will serve as useful health endpoints in ongoing and future molecular-based studies that correlate health effects with changes in gene expression.


Subject(s)
/toxicity , Environmental Pollutants/toxicity , Melanocytes/drug effects , Muscle, Skeletal/pathology , Tail/pathology , Animals , Dose-Response Relationship, Drug , Environmental Pollutants/pharmacokinetics , Larva/drug effects , Larva/growth & development , Larva/metabolism , Tissue Distribution , Xenopus laevis
14.
Environ Mol Mutagen ; 40(1): 24-35, 2002.
Article in English | MEDLINE | ID: mdl-12211073

ABSTRACT

PCBs are persistent environmental contaminants that cause a variety of adverse health effects in wildlife and humans. This article describes the use of signature gene expression patterns that link increased PCB exposure with progressive, adverse biological effects. Developing Xenopus laevis tadpoles of two age classes were exposed to the PCB mixture Aroclor 1254 for 2 days. Real-time PCR was used to quantitate mRNA expression for 11 physiologically relevant, potential bioindicator genes. Younger tadpoles (5 days postfertilization) were resistant to Aroclor 1254 and showed few changes in gross morphology, swimming behavior, survival, or gene expression. Older tadpoles (11 days postfertilization) were more susceptible to Aroclor 1254. Exposure to 25 and 50 ppm Aroclor 1254 caused alterations in gross morphology and swimming behavior and statistically significant decreases in survival. These tadpoles showed statistically significant decreases in gene expression for 9 out of the 11 genes measured. Tadpoles exposed to 10 ppm showed incipient health changes but had gene expression profiles similar to the tadpoles treated with higher doses of Aroclor 1254. Tadpoles exposed to 1 ppm did not exhibit any observable adverse health effects, yet statistically significant decreases in gene expression occurred in these tadpoles (4 out of 11 genes). After prolonged exposure, tadpoles exposed to 1 and 10 ppm Aroclor 1254 exhibited health effects similar to those exposed to higher concentrations. Therefore, changes in expression of specific genes may serve not only as molecular bioindicators of Aroclor 1254 exposure but also as predictors of impending adverse health effects.


Subject(s)
/toxicity , Gene Expression Regulation, Developmental/drug effects , Larva/drug effects , Animals , Base Sequence , DNA Primers , Gas Chromatography-Mass Spectrometry , Larva/anatomy & histology , Larva/metabolism , Polymerase Chain Reaction , Sensitivity and Specificity , Survival Analysis , Xenopus laevis/anatomy & histology , Xenopus laevis/genetics , Xenopus laevis/growth & development
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