RESUMEN
The main objective of this study was to determine if the competitive adsorption of tryptophan (Trp) and aflatoxin B1 (AFB1) could potentially affect the ability of a sodium bentonite (NaB) to prevent aflatoxicosis in monogastric animals. The adsorption of Trp and AFB1 on this adsorbent is fast and could be operating on the same time-scale making competition feasible. In vitro competitive adsorption experiments under simulated gastrointestinal conditions were performed. A high affinity of the clay for Trp and NaB was observed. The effect of an excess of KCl to mimic the ionic strength of the physiological conditions were also investigated. A six-times decrease in the Trp surface excess at saturation was observed. A similar behaviour was previously found for AFB1 adsorption. Taking into account the amount of Trp adsorbed by the clay and the usual adsorbent supplementation level in diets, a decrease in Trp bioavailability is not expected to occur. Tryptophan adsorption isotherms on NaB were 'S'-shaped and were adjusted by the Frumkin-Fowler-Guggenheim model. The reversibility of the adsorption processes was investigated in order to check a potential decrease in the ability of NaB to protect birds against chronic aflatoxicoses. Adsorption processes were completely reversible for Trp, while almost irreversible for AFB1. In spite of the high affinity of the NaB for Trp, probably due to the reversible character of Trp adsorption, no changes in the AFB1 adsorption isotherm were observed when an excess of the amino acid was added to the adsorption medium. As a consequence of the preferential and irreversible AFB1 adsorption and the reversible weak binding of Trp to the NaB, no changes in the aflatoxin sorption ability of the clay are expected to occur in the gastrointestinal tract of birds.
Asunto(s)
Aflatoxina B1/química , Bentonita/química , Carcinógenos Ambientales/química , Quelantes/química , Modelos Químicos , Triptófano/química , Adsorción , Aflatoxina B1/antagonistas & inhibidores , Aflatoxina B1/metabolismo , Alimentación Animal , Animales , Argentina , Bentonita/metabolismo , Unión Competitiva , Carcinógenos Ambientales/metabolismo , Quelantes/metabolismo , Estudios de Factibilidad , Aditivos Alimentarios/química , Aditivos Alimentarios/metabolismo , Contaminación de Alimentos/prevención & control , Contenido Digestivo , Cinética , Concentración Osmolar , Aves de Corral , Triptófano/metabolismoRESUMEN
Methylmercury (MeHg) is an ubiquitous environmental pollutant which is transported into the mammalian cells when present as the methylmercury-cysteine conjugate (MeHg-Cys). With special emphasis on hepatic cells, due to their particular propensity to accumulate an appreciable amount of Hg after exposure to MeHg, this study was performed to evaluate the effects of methionine (Met) on Hg uptake, reactive species (RS) formation, oxygen consumption and mitochondrial function/cellular viability in both liver slices and mitochondria isolated from these slices, after exposure to MeHg or the MeHg-Cys complex. The liver slices were pre-treated with Met (250 µM) 15 min before being exposed to MeHg (25 µM) or MeHg-Cys (25 µM each) for 30 min at 37 °C. The treatment with MeHg caused a significant increase in the Hg concentration in both liver slices and mitochondria isolated from liver slices. Moreover, the Hg uptake was higher in the group exposed to the MeHg-Cys complex. In the DCF (dichlorofluorescein) assay, the exposure to MeHg and MeHg-Cys produced a significant increase in DFC reactive species (DFC-RS) formation only in the mitochondria isolated from liver slices. As observed with Hg uptake, DFC-RS levels were significantly higher in the mitochondria treated with the MeHg-Cys complex compared to MeHg alone. MeHg exposure also caused a marked decrease in the oxygen consumption of liver slices when compared to the control group, and this effect was more pronounced in the liver slices treated with the MeHg-Cys complex. Similarly, the loss of mitochondrial activity/cell viability was greater in liver slices exposed to the MeHg-Cys complex when compared to slices treated only with MeHg. In all studied parameters, Met pre-treatment was effective in preventing the MeHg- and/or MeHg-Cys-induced toxicity in both liver slices and mitochondria. Part of the protection afforded by Met against MeHg may be related to a direct interaction with MeHg or to the competition of Met with the complex formed between MeHg and endogenous cysteine. In summary, our results show that Met pre-treatment produces pronounced protection against the toxic effects induced by MeHg and/or the MeHg-Cys complex on mitochondrial function and cell viability. Consequently, this amino acid offers considerable promise as a potential agent for treating acute MeHg exposure.
Asunto(s)
Metionina/fisiología , Compuestos de Metilmercurio/antagonistas & inhibidores , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias Hepáticas/fisiología , Imitación Molecular/fisiología , Animales , Transporte Biológico/efectos de los fármacos , Transporte Biológico/fisiología , Carcinógenos Ambientales/química , Carcinógenos Ambientales/metabolismo , Carcinógenos Ambientales/toxicidad , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/fisiología , Interacciones Farmacológicas/fisiología , Hígado/química , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Metionina/química , Compuestos de Metilmercurio/química , Compuestos de Metilmercurio/toxicidad , Técnicas de Cultivo de Órganos , Consumo de Oxígeno/efectos de los fármacos , Consumo de Oxígeno/fisiología , Ratas , Ratas WistarRESUMEN
O câncer de pulmão é multicausal. Fatores hereditários, genéticos e ambientais interagem na sua gênese. O principal fator de risco é o tabagismo. Entretanto, o ambiente de trabalho é um local de possível exposição a agentes cancerígenos. Atualmente, a International Agency for Research on Cancer lista 19 substâncias/situações de trabalho/ocupações comprovadamente associadas ao câncer de pulmão (grupo 1). A abordagem da ocupação em pacientes portadores de câncer de pulmão é fraca, impactando negativamente na busca da causalidade e, consequentemente, no desvelamento de casos de câncer ocupacional. Os objetivos desta revisão foram elencar os agentes reconhecidamente indutores de câncer de pulmão, discutir a contribuição da ocupação no desenvolvimento da doença, citar as publicações nacionais sobre o tema e sugerir uma lista de procedimentos que são essenciais para uma adequada investigação da relação de causalidade entre câncer de pulmão e ocupação.
Lung cancer is a multifactorial disease. Hereditary, genetic, and environmental factors interact in its genesis. The principal risk factor for lung cancer is smoking. However, the workplace provides an environment in which there is a risk of exposure to carcinogens. The International Agency for Research on Cancer currently lists 19 substances/work situations/occupations that have been proven to be associated with lung cancer (group 1). Thorough occupational history taking is not widely practiced in patients with lung cancer, which has a negative impact on the investigation of causality and, consequently, on the identification of cases of occupational cancer. The objectives of this review were to list the agents that are recognized as causes of lung cancer, to discuss the contribution of occupation to the development of the disease, to cite national studies on the subject, and to propose a list of procedures that are essential to the appropriate investigation of causality between lung cancer and occupation.
Asunto(s)
Humanos , Carcinógenos Ambientales/toxicidad , Neoplasias Pulmonares/etiología , Enfermedades Profesionales/etiología , Exposición Profesional/efectos adversos , Carcinógenos Ambientales/química , Exposición Profesional/clasificaciónRESUMEN
Lung cancer is a multifactorial disease. Hereditary, genetic, and environmental factors interact in its genesis. The principal risk factor for lung cancer is smoking. However, the workplace provides an environment in which there is a risk of exposure to carcinogens. The International Agency for Research on Cancer currently lists 19 substances/work situations/occupations that have been proven to be associated with lung cancer (group 1). Thorough occupational history taking is not widely practiced in patients with lung cancer, which has a negative impact on the investigation of causality and, consequently, on the identification of cases of occupational cancer. The objectives of this review were to list the agents that are recognized as causes of lung cancer, to discuss the contribution of occupation to the development of the disease, to cite national studies on the subject, and to propose a list of procedures that are essential to the appropriate investigation of causality between lung cancer and occupation.
Asunto(s)
Carcinógenos Ambientales/toxicidad , Neoplasias Pulmonares/etiología , Enfermedades Profesionales/etiología , Exposición Profesional/efectos adversos , Carcinógenos Ambientales/química , Humanos , Exposición Profesional/clasificaciónRESUMEN
The economy of the state of Tabasco is based on oil extraction. However, this imposes major effects to the environment and communities. Examples are the Polycyclic Aromatic Hydrocarbons (PAHs) that may be found in the soil, water and sediment of the region. Their volatility makes them available to living beings and results in genotoxic activity. The purpose of this study was to quantify the levels of PAHs in the air at several points in the state, and to analyze their relationship with possible damage to DNA on local inhabitants. Single Cell Gel Electrophoresis Assay (Comet Assay) was applied to peripheral blood lymphocytes of five groups of children between six and 15 years of age. PAH samples were analyzed following US/EPA TO-13-A method. Results indicated the presence in the air of most of the 16 PAHs considered as high priority by EPA, some of which have been reported with carcinogenic activity. Differences (p<0.05) were found between PAHs concentration in the gaseous component and in the particulate component of air samples, with the greatest values for the gaseous component. Greatest PAH concentrations were detected in areas with high oil extraction activities. Children groups from high oil activity areas presented genotoxic damage labeled from moderate to high according to DNA migration from nuclei (Tail Length: 14.2 - 42.14 microm and Tail/Head: 0.97 - 2.83 microm) compared with control group (12.25 and 0.63 microm, respectively). The group with greatest cell damage was located in the area with the greatest oil activity. We conclude that the presence of PAHs in the air may represent a health risk to populations that are chronically exposed to them at high oil activity regions.
Asunto(s)
Contaminantes Atmosféricos/toxicidad , Carcinógenos Ambientales/toxicidad , Hidrocarburos Policíclicos Aromáticos/toxicidad , Adolescente , Contaminantes Atmosféricos/química , Carcinógenos Ambientales/química , Niño , Humanos , México , Pruebas de Mutagenicidad , Mutágenos/toxicidadRESUMEN
O modelo tecnológico empregado, na fruticultura irrigada do Vale do São Francisco utiliza grande quantidade e variedade de agrotóxicos, o que leva a efeitos na saúde humana. Entre esses efeitos está a problemática das neoplasias malignas. Porém a correlação de agrotóxicos e câncer é complexa principalmente pelas dificuldades dos modelos de estudo que são em sua maioria de tipo experimental, clínico e epidemiológico. Aqui reside a relevância desta investigação que objetivou estudar o potencial carcinogênico dos agrotóxicos utilizados na fruticultura do Vale do São Francisco mediante um modelo preditivo de utilidade para a Vigilância da Saúde. Para tanto, foi utilizado o modelo de carcinogenicidade químicoquântica computacional que parte da premissa que os carcinógenos interagem com o DNA através de um processo de transferência de elétrons. Para a correta interpretação dos indicadores que objetivavam a prevenção de situações de risco, foi feita a contextualização do problema através, de um estudo descritivo da avaliação do processo produtivo, ocupacional e ambiental da região, bem como um estudo com dados secundários da mortalidade por câncer. Os resultados apontam que a exposição é dependente de várias situações de risco, seja pelas práticas no manuseio de agrotóxicos e ou pelo contexto de contaminação ambiental. Foi observado que os agricultores fazem uso indiscriminado de agrotóxicos, muitas vezes sem assistência técnica e em condições inseguras e insalubres de trabalho, como também a falta de ações de promoção e proteção da saúde no nível individual e coletivo. A morbidade referida foi congruente com a esperada em situações de intoxicação por agrotóxicos e o perfil da mortalidade por câncer é semelhante ao encontrado em outras regiões agrícolas. Os agrotóxicos são em sua maioria inseticidas, do grupo organofosforados, dos quais 44% são classificados como muito perigosos para o ambiente e 18% extremamente tóxicos para a população...
Asunto(s)
Carcinógenos Ambientales/química , Vulnerabilidad ante Desastres , Neoplasias/mortalidad , Plaguicidas/toxicidad , Salud Ambiental , Promoción de la Salud , Salud Rural , Zona SemiáridaRESUMEN
Protonation of the epoxides, diol epoxides, and dihydrodiols of benzo[h]quinoline (BhQ), benzo[f]quinoline (BfQ), phenanthrene (Phe), benzo[c]phenanthridine (BcPhen), and chrysene (Chry) were studied by DFT at the B3LYP/6-31G* level, and selected cases were calculated with the 6-31+G* diffuse-function augmented basis set for comparison purposes. Bay-region carbocations were formed from O-protonated epoxides via a barrierless processes. Relative carbocation stabilities were determined in the gas phase and with water as solvent (PCM method). The presence of a heteroatom changes the regioselectivity of epoxide ring opening, in some cases favoring non-bay-region carbocations. The epoxide ring opening mode is also greatly influenced by N-protonation. The dications resulting from initial N-protonation followed by epoxide protonation were also studied by DFT. Charge delocalization modes in the resulting mono- and dications were derived by GIAO-NMR (based on Delta delta13C values) and via the NPA-derived changes in charges. Relative aromaticity in different rings in the arenium ions was gauged by NICS. In representative cases, the covalent adducts (syn and anti) formed by reaction of the benzylic carbocations derived from diol epoxides and dihydrodiols with methoxide and methanethiolate anions were studied. Relative energies (in the gas phase and with water as solvent) and geometries of the adducts formed by quenching of the carbocations derived from BhQ and Phe-epoxides with guanine via the exocyclic amino group and via the N-7 were also investigated computationally. Although aqueous phase calculations change the energy for the addition reactions because of greater stabilization of the reactants, relative reactivity trends remain the same. The data are discussed, taking into account the available experimental results concerning the biological activity of these compounds.
Asunto(s)
Compuestos Aza/química , Carcinógenos Ambientales/química , Hidrocarburos Policíclicos Aromáticos/química , Compuestos Aza/metabolismo , Carcinógenos Ambientales/metabolismo , Compuestos Epoxi/química , Modelos Químicos , Modelos Moleculares , Oxidación-Reducción , Hidrocarburos Policíclicos Aromáticos/metabolismo , TermodinámicaRESUMEN
Cr(VI) photocatalytic reduction experiments over TiO2 particles under near UV irradiation in the presence of excess oxalate were performed at acid pH (2 and 3) and under air and N2 bubbling. Initial photonic efficiencies for Cr(VI) reduction are nearly the same under aerobic and anaerobic conditions, but show a significant increase at the lowest pH. At pH 2, the addition of oxalate facilitates Cr(VI) reduction, hindering the electron-shuttle mechanism taking place in pure water. The oxalate synergistic effect at pH 2 is lower than that previously found for EDTA and negligible at pH 3. Chromium(V) oxalate concentration profiles were obtained by EPR spectroscopy in the presence of excess oxalate at pH 1.5. Coordinated Cr(V) complexes [Cr(V)(O)(Ox)2]-, [Cr(V)(OH2)(Ox)2]-, and [Cr(V)(O)(OH)2(Ox)]- were identified, on the basis of the comparison of their corresponding g values with recent literature data. The kinetic analysis of the temporal evolution of the paramagnetic Cr(V) species indicates also an effective photocatalytic degradation of chromium(V) oxalate complexes. This new evidence reinforces previous findings regarding sequential one-electron-transfer processes in Cr(VI) photocatalytic reduction, suggesting that this route may represent a general behavior for the Cr(VI) reduction over UV-irradiated TiO2 particles.
Asunto(s)
Carcinógenos Ambientales/química , Cromo/química , Colorantes/química , Titanio/química , Catálisis , Concentración de Iones de Hidrógeno , Oxidación-Reducción , FotoquímicaRESUMEN
The oxidation of D-lactobionic acid by Cr(VI) yields the 2-ketoaldobionic acid and Cr(3+) as final products when a 20-times or higher excess of the aldobionic acid over Cr(VI) is used. The redox reaction takes place through a complex multistep mechanism, which involves the formation of intermediate Cr(IV) and Cr(V) species. Cr(IV) reacts with lactobionic acid much faster than Cr(V) and Cr(VI) do, and cannot be directly detected. However, the formation of CrO(2)(2+), observed by the first time for an acid saccharide/Cr(VI) system, provides indirect evidence for the intermediacy of Cr(IV) in the reaction path. Cr(VI) and the intermediate Cr(V) react with lactobionic acid at comparable rates, being the complete rate laws for the Cr(VI) and Cr(V) consumption expressed by: -d[Cr(VI)]/dt=[k(I)+k(II)[H(+)]][lactobionicacid][Cr(VI)], where k(I)=(4.1+/-0.1) x 10(-3) M(-1) s(-1) and k(II)=(2.1+/-0.1) x 10(-2) M(-2) s(-1); and -d[Cr(V)]/dt=[k(III)[H(+)]+(k(IV)+k(V)[H(+)])[lactobionicacid]] [Cr(V)], where k(III)=(1.8+/-0.1) x 10(-3) M(-1) s(-1), k(IV)=(1.1+/-0.1) x 10(-2) M(-1) s(-1) and k(V)=(1.0+/-0.1) x 10(-2) M(-2) s(-1), at 33 degrees C. The Electron Paramagnetic Resonance (EPR) spectra show that five-co-ordinate oxo-Cr(V) bischelates are formed at pH 1-5 with the aldobionic acid bound to Cr(V) through the alpha-hydroxyacid group.