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1.
Aquat Toxicol ; 100(2): 202-10, 2010 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-19854522

RESUMO

The increased production of nanotechnology materials is a potential source of nano-sized particles (NSPs) in aquatic ecosystems. Meanwhile, polycyclic aromatic hydrocarbons (PAHs), in the presence of ecologically relevant levels of ultraviolet radiation (UV), can be acutely toxic to aquatic species including fish and invertebrates. Considering that suspended carbon-based NSPs (e.g., C60 fullerenes) may act in similar ways as dissolved organic matter (DOM) by altering the bioavailability of PAHs, the objective of this research was to determine the effect of suspended C60 on the photo-induced toxicity of fluoranthene. Transmission electron microscopy indicated that the presence of C60 protected cellular components (e.g., mitochondria, microvilli, and basal infoldings) in organisms exposed to UV and fluoranthene phototoxicity in short-term exposures. However, we found that long-term exposure (21d) of low-level C60 caused significant cellular damage in the Daphnia magna alimentary canal. This paper highlights the importance of examining the interactions between existing stressors and nanoparticles in the aquatic environment.


Assuntos
Daphnia/efeitos dos fármacos , Fluorenos/toxicidade , Fulerenos/farmacologia , Substâncias Protetoras/farmacologia , Raios Ultravioleta , Animais , Daphnia/efeitos da radiação , Daphnia/ultraestrutura , Sistema Digestório/efeitos dos fármacos , Sistema Digestório/efeitos da radiação , Sistema Digestório/ultraestrutura , Fulerenos/toxicidade , Processos Fotoquímicos/efeitos dos fármacos , Substâncias Protetoras/toxicidade , Poluentes Químicos da Água/toxicidade
2.
Arch Environ Contam Toxicol ; 53(3): 365-70, 2007 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-17571202

RESUMO

The purpose of the current study was to evaluate the role of visible light during trophic transfer of the essential metalloid, selenium (Se) from sediments by way of the microalgae Phaeodactylum tricornutum to bivalves. Initial experiments compared uptake of Se with algal cell number after deposit-feeding (Tellina deltoidalis) and filter-feeding (Soletellina alba) bivalves were exposed for 12 days under 16:8 h light:dark and 24-hour dark regimes to sediments amended with Se (17 mg/kg dry weight). Comparisons of filter-feeding with deposit-feeding organisms indicated >2-fold higher body burdens in the deposit-feeding organisms after 12 days. Darkness failed to significantly and consistently diminish algal cell densities. However, general trends indicated a decrease of pelagic algal numbers in +Se/dark treatments during the 12-day exposure. To determine whether time-dependent patterns were present in the uptake of Se by the deposit-feeding species, a second experiment was conducted using Se-laden sediments under light and dark conditions. Algal cell counts were measured and Se concentrations determined in animals sampled at days 0, 3, 6, 9, and 12. Deposit-feeding animals maintained in the dark accumulated, Se more rapidly than animals on light to dark cycles until 12 days at which time no significant differences were observed between treatments. Concentrations of Se in tissues of deposit-feeding bivalves were not directly related to algal cell density in lighted or dark chambers. These results indicate that pelagic microalgae may only play a key role in Se uptake during early hours of exposure, and feeding behavior may be a more important factor in deposite-feeding bivalves.


Assuntos
Bivalves/metabolismo , Sedimentos Geológicos/química , Luz , Selênio/farmacocinética , Animais , Eucariotos/metabolismo , Comportamento Alimentar
3.
Mar Pollut Bull ; 52(11): 1527-32, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16854435

RESUMO

The 1989 Exxon Valdez oil spill (EVOS) resulted in the release of 258,000 barrels of crude oil into the waters of Prince William Sound (PWS), Alaska. The current study, conducted in 2004, sought to use juvenile Coho salmon (Oncorhynchus kisutch) caged in situ to determine whether biomarker induction differed at sites where the adjacent shoreline contained buried residues from the 1989 oil spill compared to sites that were never oiled. Juvenile Coho salmon were caged at five sites; three oiled during the 1989 EVOS and two that were not oiled. Tissue samples were collected from organisms caged at each site as well as a control group housed onboard the research vessel. Analysis of CYP1A, superoxide dismutase (SOD), and glutathione peroxidase (GPO) gene expression was conducted using real time reverse transcriptase polymerase chain reaction (rtRT-PCR). Statistically significant levels of CYP1A expression were observed at some sites indicating increased hydrocarbon exposure. No patterns were observed regarding sites that were originally oiled or not oiled by the 1989 EVOS, indicating that sources of PAHs other than EVOS oil occur in PWS.


Assuntos
Aquicultura , Monitoramento Ambiental/estatística & dados numéricos , Expressão Gênica , Oncorhynchus kisutch/metabolismo , Alaska , Animais , Citocromo P-450 CYP1A1/metabolismo , Primers do DNA , Glutationa Peroxidase/metabolismo , Oncorhynchus kisutch/genética , Oceano Pacífico , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Superóxido Dismutase/metabolismo
5.
Arch Environ Contam Toxicol ; 41(4): 450-7, 2001 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-11598782

RESUMO

Several toxic effects of lead (Pb) have been documented in amphibians, but few studies have measured tissue levels of exposed specimens or examined toxicokinetics, availability of dietary versus waterborne sources, or route of entry. We modeled the toxicokinetics and examined the availability of dietary and waterborne Pb in both fed and food-deprived bullfrog (Rana catesbeiana) larvae. Uptake rates of Pb (1,000 microg Pb/L nominal exposure) were similar between fed and unfed larvae, but unfed larvae eliminated Pb slowly. Consequently, food-deprived larvae accumulated significantly more Pb compared to fed larvae. The intestinal tract contained > 90% of total body Pb in both fed and unfed larvae. Total body concentrations of Pb in fed larvae did not increase over 7 days although levels in food did increase. We concluded that food consumption influenced Pb accumulation through changes in elimination rates rather than in uptake rates. Pb appeared to enter the body of larvae through ingestion of contaminated water rather than food.


Assuntos
Ingestão de Alimentos , Chumbo/farmacocinética , Chumbo/toxicidade , Rana catesbeiana/fisiologia , Poluentes Químicos da Água/farmacocinética , Poluentes Químicos da Água/toxicidade , Animais , Sistema Digestório/química , Privação de Alimentos , Larva , Distribuição Tecidual
6.
Aquat Toxicol ; 54(1-2): 15-28, 2001 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11451422

RESUMO

The survival functions (SF) during acute exposures to cadmium, zinc or low pH were examined for amphipods exhibiting variation at three loci. Significant differences were observed in eight of nine locus/toxicant combinations. Two general types of survival curve patterns were identified when genotype-related SF differences were observed. In the first pattern, the survival differences between genotypes were immediately apparent with two SF curves separated at the beginning of exposure with little or no overlap. For the second pattern, both genotypes had similar SF for a period of time, during which the two survival curves crossed or overlapped. After this period, the survival probability of one genotype dropped sharply relative to the other. While SF was related to genotype, it was not related to heterozygosity. Genetic distance analysis showed that exposure to cadmium, zinc or low pH each resulted in directional selection, suggesting the potential use of genetic distance as a bioindicator.


Assuntos
Cádmio/toxicidade , Crustáceos/efeitos dos fármacos , Zinco/toxicidade , Fosfatase Ácida/metabolismo , Animais , Crustáceos/enzimologia , Crustáceos/genética , Genótipo , Glucose-6-Fosfato Isomerase/metabolismo , Concentração de Íons de Hidrogênio , Fosfoglucomutase/metabolismo
7.
J Appl Toxicol ; 20(2): 121-5, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10715609

RESUMO

The use of endpoint estimates based on modeling inhibition of test organism response relative to a baseline response is an important tool in the testing and evaluation of aquatic hazards. In the presence of a hormetic hazard, the definition of the baseline response is not clear because non-zero levels of the hazard stimulate an enhanced response prior to inhibition. In the present study, the methodology and implications of how one defines a baseline response for inhibition concentration estimation in aquatic toxicity tests was evaluated. Three possible baselines were considered: the control response level; the pooling of responses, including controls and all concentration conditions with responses enhanced relative to controls; and, finally, the maximal response. The statistical methods associated with estimating inhibition relative to the first two baseline definitions were described and a method for estimating inhibition relative to the third baseline definition was derived. These methods were illustrated with data from a standard aquatic zooplankton reproductive toxicity test in which the number of young produced in three broods of a cladoceran exposed to effluent was modeled as a function of effluent concentration.


Assuntos
Adaptação Fisiológica/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Daphnia , Relação Dose-Resposta a Droga , Feminino , Modelos Biológicos , Reprodução/efeitos dos fármacos , Testes de Toxicidade
8.
Artigo em Inglês | MEDLINE | ID: mdl-10190046

RESUMO

Over the past two decades a number of antifungal imidazole derivatives have been approved for use in agricultural. The purpose of this study was to characterize the interaction of a model antifungal imidazole compound with a cytochrome P450 isozyme in a species of fish. Clotrimazole inhibited rainbow trout (Oncorhyncus mykiss) hepatic CYP1A-catalyzed ethoxyresorufin O-deethylase (EROD) activity in vivo and in vitro. Although clotrimazole inhibited EROD activity in vivo, it did not effect CYP1A mRNA levels. Addition of clotrimazole to microsomes produced a type II binding spectrum and clotrimazole was determined to be a noncompetitive mixed-type inhibitor of EROD activity with an IC50 of 190 nM. Since antifungal imidazole compounds may be co-applied with other pesticides, inhibition of cytochrome P450 activity by antifungal imidazole compounds may lead to unexpected toxicological interactions.


Assuntos
Clotrimazol/farmacologia , Inibidores das Enzimas do Citocromo P-450 , Inibidores Enzimáticos/farmacologia , Oncorhynchus mykiss/metabolismo , Animais , Citocromo P-450 CYP1A1/antagonistas & inibidores , Citocromo P-450 CYP1A1/metabolismo , Sistema Enzimático do Citocromo P-450/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Cinética , Fígado/enzimologia , RNA Mensageiro/metabolismo , Espectrofotometria
9.
Hum Exp Toxicol ; 17(5): 247-50, 1998 May.
Artigo em Inglês | MEDLINE | ID: mdl-9663930

RESUMO

The phenomenon of subtoxic stimulation of organism response is not uncommon in aquatic toxicology experiments. We describe the presence of hormesis in both growth and reproduction experiments in aquatic toxicology where these responses are observed in both animals and plants and at different trophic levels of an ecosystem. The implications of ignoring hormetic responses in the analysis of toxicity data are discussed. In particular, we note that specification of models that explicitly cannot accommodate or remove potential effects of hormesis may lead to biased potency estimates. Further, the presence of hormesis has implications for the design of toxicology experiments, with the spacing of concentration test conditions being critical.


Assuntos
Poluentes Ambientais/toxicidade , Crescimento Demográfico , Toxicologia/métodos , Animais , Biologia Marinha/métodos , Projetos de Pesquisa
10.
Neurosci Lett ; 222(1): 21-4, 1997 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-9121713

RESUMO

The perivascular axons associated with the intradural segment of the internal carotid artery undergo a sprouting response following intracerebroventricular infusion of nerve growth factor (NGF). The objective of the present study was to determine whether a relationship exists between the number of sprouted axons and the amount of NGF infused into the ventricular system. Using regression analysis, we observed a significant log-log relationship between the dose of NGF and number of axons. No significant relationship was observed for the control (VEH) group. A significant increase in axonal number was observed following infusion of 3.0 micrograms NGF and higher when compared with VEH treatment of similar concentration. Results of this analysis suggest that a maximal response to NGF is approximated at doses of 15 micrograms or higher. These findings suggest a dose-dependent relationship between the response of mature sympathetic cerebrovascular axons in vivo and the dose of exogenous NGF.


Assuntos
Axônios/efeitos dos fármacos , Circulação Cerebrovascular/efeitos dos fármacos , Fatores de Crescimento Neural/farmacologia , Animais , Relação Dose-Resposta a Droga , Ratos , Ratos Sprague-Dawley
11.
Artigo em Inglês | MEDLINE | ID: mdl-9467892

RESUMO

The purpose of this study was to examine the concentration and time-dependent response of hepatic CYP1A mRNA levels and ethoxyresorufin O-deethylase (EROD) activity in gizzard shad (Dorosoma cepedianum) after waterborne exposure to the polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP). Gizzard shad hepatic CYP1A mRNA levels and EROD activity were increased within 6 hr by waterborne concentrations of 1.01 microgram BaP/l and were highest after 72 hr of exposure. The median effective time to reach 50% of maximum induction (ET50) values for CYP1A mRNA and EROD activity was 12 +/- 9 and 34 +/- 3 hr, respectively. The rise of CYP1A mRNA levels ahead of the rise of EROD activity showed that the CYP1A gene has the general pattern of a gene that is under transcriptional control. Although CYP1A mRNA levels were maximally induced after 72 hr of exposure, they returned to basal levels between 72 and 120 hr of exposure. Despite a decrease in CYP1A mRNA levels between 72 and 120 hr of exposure, EROD activity did not significantly change between 72 and 120 hr of exposure. These results indicate that hepatic CYP1A mRNA levels in gizzard shad can only feasibly identify short-term exposures to BaP concentrations of approximately 1 microgram/l and that are not longer than 72 hr. Consequently, hepatic CYP1A catalytic activity (e.g., EROD) and CYP1A protein levels should be measured in addition to hepatic CYP1A mRNA levels when biomonitoring aquatic systems for certain types of chemical contamination.


Assuntos
Benzo(a)pireno/toxicidade , Citocromo P-450 CYP1A1/biossíntese , Peixes/metabolismo , Mutagênicos/toxicidade , RNA Mensageiro/biossíntese , Poluentes Químicos da Água/toxicidade , Animais , Hidrocarboneto de Aril Hidroxilases/metabolismo , Citocromo P-450 CYP1A1/genética , DNA Complementar/biossíntese , Monitoramento Ambiental , Indução Enzimática/efeitos dos fármacos , Vesícula Biliar/efeitos dos fármacos , Vesícula Biliar/metabolismo , Microssomos Hepáticos/efeitos dos fármacos , Microssomos Hepáticos/enzimologia
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