Methylmercury and Paraquat are environmental toxins that affect the central nervous system. Exposure to Paraquat and methylmercury causes movement impairments similar to the symptoms of Parkinson’s disease (PD). The degeneration of dopamine neurons due to mitochondrial dysfunction has been implicated in PD. This study investigates the mechanism of methylmercury and Paraquat induced mitochondrial dysfunction in dopamine neurons. Using in vitro assays, it was found that exposure to methylmercury (0.1-5µM) and Paraquat (300-500µM) inhibited complex I of the electron transport chain in mitochondria. This was associated with an increase in superoxide anion levels, decrease in superoxide dismutase activity, and loss of ATP. All of these factors led to the loss of mitochondrial membrane potential. Similar results were found in co-exposure treatment of 300µM of Paraquat with 0.1µM of methylmercury. These results indicate that methylmercury and Paraquat induce mitochondrial dysfunction causing the death of dopamine neurons.

Paraquat (PQ) is a cationic non-selective bipyridyl herbicide widely used in agriculture to control weeds and grasses. Epidemiologic studies indicate that exposure to pesticides can be a risk factor in the incidence of Parkinson`s disease (PD). A strong correlation has been reported between exposure to paraquat and PD incidence in Canada, Taiwan, and United States. This correlation is supported by animal studies showing that paraquat produces toxicity in dopaminergic neurons of the rat and mouse brain. However, it is unclear how paraquat triggers toxicity in dopaminergic neurons. Based on the previous reports, it was hypothesized that paraquat may induce oxidative stress and proteasomal dysfunction-mediated toxicity in dopaminergic neurons. To explore this possibility, dopaminergic SH-SY5Y human neuroblastoma cells were treated with paraquat, and several biomarkers of oxidative stress or proteasomal dysfunction were investigated. First, a specific dopamine transporter inhibitor GBR12909 significantly protected SY5Y cells against the toxicity of paraquat, indicating that paraquat exerts its toxicity by a mechanism involving the dopamine transporter (DAT). Second, paraquat increased the levels of reactive oxygen species (ROS) in SY5Y cells, but decreased the levels of glutathione. Third, paraquat inhibited glutathione peroxidase activity, but did not affect glutathione reductase activity. On the other hand, paraquat increased GST activity by 24 hr, after which GST activity returned to the control value at 48 hr. Fourth, paraquat decreased mitochondrial transmembrane potential (MTP). Fifth, paraquat produced the increases in malondialdehyde (MDA) and protein carbonyls, as well as DNA fragmentation, indicating oxidative damage to major cellular components. Sixth, paraquat decreased proteasomal activity, the activities of mitochondrial complex I and V, and intracellular ATP levels, but increased the activities of caspase 3 and 9, indicating that proteasomal inhibition is linked to mitochondrial dysfunction accompanied by the activation of apoptotic signaling pathway. Seventh, paraquat increased the protein levels of heme oxygenase-1 (HO-1), p53, Bax, α-synuclein and ubiquitinated proteins. Eighth, paraquat induced nuclear condensation. Taken together, these findings support the hypothesis that paraquat produces oxidative stress and proteasomal dysfunctionmediated toxicity in SY5Y cells. Thus, current findings suggest that paraquat may induce the pathogenesis of dopaminergic neurons through oxidative stress and proteasomal dysfunction.

This thesis sets out to examine the problems that have been associated with paraquat, both in relation to its occupational use as a herbicide and its misuse in cases of accidental or deliberate human poisoning. In order to provide a frame of reference for the later discussion, the general properties of paraquat are reviewed, together with its general toxic effects and possible mode of action in mammalian systems. The degree of risk associated with paraquat use in normal agricultural practice is examined. The available published literature is reviewed and the results of studies on both formulation workers and spraymen are discussed. It is concluded that the use of paraquat does not constitute a significant risk to health when sprayed at concentrations of up to 0.5% paraquat ion. Studies of situations in which low volume/high concentration application methods have been used would indicate that they are likely to produce an unacceptable level of risk and constitute dangerous agricultural practice. The problem of paraquat misuse is examined, both in regard to its extent and the effectiveness of treatment in cases of human poisoning. Treatment measures currently advocated are reviewed and their effectiveness discussed in relation to the series of 108 poisoning cases which is presented. On the basis of the data set out it is concluded that the treatment of paraquat poisoning is only likely to be effective in those cases who have, (a) ingested less than 5g of paraquat ion, (b) had treatment instituted within 2 hours of ingestion, and (c) show plasma paraquat levels in the order of 1-2mg/litre 2-4 hours after ingestion. It is also concluded that the only effective form of treatment is the vigorous and rapid removal of paraquat from the gut using Fuller's Earth and purgation or gut lavage. There is little clinical evidence to suggest that measures designed to remove paraquat from the circulation after absorption or block its action in the body have any effect on the clinical course of poisoning. Some general conclusions are drawn and a select bibliography is appended.

Thesis (Ph.D.) University of Adelaide, Dept. of Agronomy. 1989.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas. Programa de Pós-Graduação em Bioquímica, Florianópolis, 2016 / Made available in DSpace on 2016-09-20T04:11:31Z (GMT). No. of bitstreams: 1 339435.pdf: 3716963 bytes, checksum: 8e99ae2ff4c70f00fc25869e89a97b06 (MD5) Previous issue date: 2016 / O paraquat (PQ) é um herbicida amplamente utilizado no Brasil, apesar de ser descrito como indutor da doença de Parkinson (DP) em modelo animal e em estudos epidemiológicos. A flora brasileira apresenta grande diversidade de plantas medicinais e inúmeros extratos de plantas são utilizados na medicina popular, demonstrando a relevância de investigar o potencial terapêutico de compostos naturais. Neste contexto, já foram descritas atividades antioxidante, antiparkinsoniana, antiobesogênica e anticarcinogênica para a erva-mate (Ilex paraguariensis St. Hilaire). O presente estudo investigou as alterações bioquímicas induzidas pela exposição in vivo ao herbicida PQ em hipocampo de ratos de 27 dias de idade, assim como o efeito neuroprotetor da erva-mate. Os animais receberam 10 mg/Kg de peso de PQ via intraperitoneal por 5 dias consecutivos, o grupo controle recebeu solução salina durante o mesmo período. Para avaliar o efeito neuroprotetor do extrato butanólico (BuOH) de I. paraguarienses, os animais receberam 200 mg/kg de peso do extrato via gavagem, o grupo controle recebeu o mesmo volume de água, 1 dia antes e durante o tratamento com PQ. Foram determinados marcadores de dano oxidativo, da neurotransmissão glutamatérgica e do metabolismo energético em hipocampo dos animais. Os resultados obtidos mostraram: aumento do influxo de 45Ca2+; diminuição da captação de 14C-glutamato e da atividade da glutamina sintetase (GS); diminuição da captação de 14C-2-desoxi-D-glicose; aumento da atividade das enzimas alanina aminotransferase (ALT), aspartato aminotransferase (AST) e lactato desidrogenase (LDH). Em relação as defesas antioxidantes, houve diminuição da atividade da gama glutamil transferase (GGT), da glicose-6-P desidrogenase (G6PD), aumento da atividade da superóxido dismutase (SOD) e catalase (CAT) e aumento da peroxidação lipídica causados pela exposição ao PQ. O tratamento com I. paraguariensis preveniu o efeito do paraquat na captação de glicose, na atividade da LDH e da ALT e na captação de glutamato, além de exercer efeito neuroprotetor nos mecanismos de defesa antioxidante avaliados, como na atividade da G6PD, SOD, GGT e conteúdo de glutationa (GSH). Os resultados obtidos neste estudo poderão sugerir o potencial terapêutico da erva-mate como protetor dos danos induzidos pela exposição a pesticidas. <br> / Abstract: Paraquat (PQ) is widely used in Brazil, despite being described as a Parkinson's disease (PD) inductor in animal models and in epidemiological studies. Considering that Brazilian flora has a great diversity of medicinal plants and many plant extracts are used in folk medicine, the investigation of the therapeutic potential of a natural compound is an important challenge to researchers. Considering that, several properties have been described such as antioxidant, anti-Parkinson, anti-obesity and anticarcinogenic for yerba mate (I. paraguariensis St. Hilaire). The present study investigated the biochemical changes induced by in vivo exposure to the herbicide PQ on hippocampus of 27 days old rats, as well as the neuroprotective effect of yerba mate. Animals received PQ (10 mg/kg body weight, i.p.) for 5 consecutive days, the control group received saline for the same period. In order to evaluate the neuroprotective effect of the butanolic (BuOH) extract of I. paraguarienses, rats received 200 mg/kg body weight by gavage) and the control group received the same amount of water, 1 day before and during PQ treatment. Biomarkers of oxidative damage, glutamatergic neurotransmission and energy metabolism were determined on hippocampus. The present study showed increased 45Ca2+ influx associated with decreased glutamate uptake and glutamine synthetase (GS) activity. Moreover, glucose uptake was decreased while alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activities were increased. Regarding the antioxidant defenses, PQ leads to decreased gamma-glutamyl transferase (GGT) and glucose-6-P dehydrogenase (G6PD) activities, as well as increased superoxide dismutase (SOD) and catalase (CAT) activities, which were associated with increased lipid peroxidation all caused by PQ exposure. The co-treatment with I. paraguariensis prevented the effect of PQ on glucose uptake, LDH and ALT activities and glutamate uptake. Besides, I. paraguariensis exerted neuroprotective effect on antioxidant defense mechanisms evaluated in this study, such as G6PD, SOD, GGT and GSH levels. In conclusion, these findings suggested the therapeutic potential of yerba mate as damage protector induced by exposure to pesticides.

A study was conducted in Stoneville and Verona, MS, to evaluate control of failed stands of corn and soybean with different herbicide treatments and application timings, as well as control of failed stand of corn with soybean planted 1 and 7 DAT (days after treatment). Clethodim plus glyphosate proved most effective across all growth stages of corn with > 90% control 7, 14, and 21 DAT. Paraquat plus metribuzin provided the greatest control of a simulated failed corn stand 3 DAT compared with all other treatments. Pooled across all herbicide treatments, 49% control was achieved when replant occurred 7 DAT compared with 46% following replant 1 DAT. These studies demonstrated clethodim plus glyphosate was most effective in control of failed stands of corn as well as the benefits of not replanting immediately after herbicide treatment. Paraquat and paraquat plus metribuzin both provided > 90% control 3, 7, and 14 DAT.

Orientador: Caio Antonio Carbonari / Banca: Edivaldo Domingues Velini / Banca: Alfredo Junior Paiola Albrecht / Resumo: A resistência de plantas daninhas a herbicidas é um problema que tem se agravado nos últimos anos, principalmente devido a seleção de biótipos resistentes de buva (Conyza spp.) a importantes herbicidas no manejo destas plantas daninhas, como é o caso do paraquat. Este herbicida atua no aparato fotossintético das plantas, desviando elétrons no fotossistema I, o que leva a formação de espécies reativas de oxigênio (EROs), causando reações oxidativas e morte das plantas. Neste contexto, o objetivo deste trabalho foi caracterizar o comportamento das plantas de Conyza sumatrensis resistentes frente à biótipos suscetíveis ao paraquat, com relação a adaptabilidade ecológica e respostas à ação do herbicida. Ensaios para a caracterização da resistência dos biótipos foram conduzidos através de curvas dose-resposta, a fim de identificar o fator de resistência destas plantas ao paraquat, selecionando-se o biotipo mais resistente para estudos posteriores (FR: 184,71). Foram conduzidos experimentos de adaptabilidade ecológica da espécie, sem a aplicação do herbicida, avaliando-se variáveis morfológicas das plantas como acúmulo de biomassa seca, área foliar, altura das plantas, densidade e tamanho de estômatos além de parâmetros relacionados a fluorescência das plantas (ETR, Fv/Fm). Um terceiro experimento foi conduzido com os mesmos biótipos, trabalhando-se com duas doses de paraquat (0 e 800 g i.a ha-1), a fim de avaliar variáveis fisiológicas no período de 2, 4 e 24 horas após a aplicaçã... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The weeds resistance to herbicides is a problem that has worsened in recent years, mainly due to the selection of resistant fleabane biotypes (Conyza spp.) to important herbicides in the management of these weeds, as is the case of paraquat. This herbicide acts on the photosynthetic apparatus of plants, diverting electrons from photosystem I, which leads to the formation of reactive oxygen species (ROS), causing oxidative reactions and plant death. In this context, the objective of this study was to characterize the behavior of resistant Conyza sumatrensis plants in relation to the paraquat susceptible biotypes, in terms of ecological adaptability and responses to herbicide effect. Resistance characterization tests were carried out through dose-response curves (assay 1) to identify the resistance factor of these plants to paraquat, selecting the most resistant biotype for later studies (FR: 184,71). Ecological adaptability experiments were carried out without herbicide application (assay 2), evaluating plant morphological variables such as accumulation of dry biomass, leaf area, plant height, stomata density and size, as well as parameters related to plant fluorescence (ETR, Fv/Fm). A third experiment was carried out with the same biotypes, two doses of paraquat (0 and 800 g ha-1) were applied, in order to evaluate physiological variables at 2, 4 and 24 hours after application (HAA). Some plants were collected 4 HAA to perform biochemical analyzes of plant antioxidant enzymes such as SOD, CAT, APX, POX and MDA. The data were submitted to analysis of variance by the F test (p≤0.05) and the means were compared by the tukey test (p≤0.05), and the confidence interval was calculated. The biotypes resistant to paraquat when in the absence of the herbicide, naturally presented greater accumulation of dry biomass and leaf area, besides higher CO2 assimilation rate (A), carboxylation efficiency (EC) ... / Mestre

[pt] A partir do trabalho de campo feito na região agrícola de Nova Friburgo, RJ, determinou-se que o pesticida Paraquat é altamente usado. Investigou-se o processo de adsorção com carvão ativado e carvão vegetal deste pesticida em solução aquosa, como uma alternativa para o tratamento de águas residuarias da região. Foi utilizado um resíduo de carvão vegetal, denominado carvão A; e dois carvões ativados comerciais de procedências distintas, denominados respectivamente de carvão B (Brasil) e carvão C (EUA). Realizou-se uma oxidação química com HNO3 do carvão brasileiro, sendo o carvão assim tratado denominado carvão B1. Os estudos de adsorção foram precedidos de um estudo de caracterização dos carvões utilizados, através de microscopia eletrônica de varredura (MEV) e espectroscopia de dispersão de raios X (EDS), para a sua caracterização morfológica. Da isoterma de adsorção de nitrogênio a 77 K, obtiveram-se dados do volume de microporos, área superficial e distribuição de tamanhos dos poros. Espectros de FT-IR detectaram a presença de grupos funcionais nas superfícies e medições de potencial zeta permitiram a determinação do ponto isoelétrico para cada carvão estudado. No processo de adsorção em batelada foram avaliados os efeitos do pH e do tempo para se alcançar o equilíbrio. Foram levantadas experimentalmente isotermas de adsorção para os quatro tipos de carvão. Os carvões ativados B, B1 e C se ajustaram satisfatoriamente ao modelo de isoterma de Freundlich. Estas isotermas forneceram informação a respeito das capacidades de carregamento desses carvões. No estudo da cinética de adsorção, foram avaliadas as correlações dos modelos de pseudo-primeira ordem e pseudo-segunda ordem com os dados experimentais obtidos. Finalmente, os testes preliminares em coluna, em regime contínuo, permitiram a obtenção da curva de carregamento (curva de breakthrough) para o carvão ativado comercial de fabricação brasileira. / [en] According to the work performed in the agricultural region in Nova Friburgo, RJ; it was determined that the Paraquat Pesticide is highly used. There have investigated the adsorption process with activated carbon and vegetal charcoal for pesticide treatment in aqueous solution, this will an alternative for the wastewater treatment in this region. The experimental study was conducted for a vegetal charcoal and two kinds of porous carbonaceous materials. The first of those was a charcoal made of Eucalyptus spp. wood shavings (carbon A). The second was Brazilian activated carbon (carbon B) made of coconut shell. The third material was an American coconut shell activated carbon (carbon C). The Brazilian activated carbon was further submitted to chemical modification treatment procedure with HNO3 (carbon B1). The tests of adsorption were preceded by study of characterization of the used carbons, through techniques such as scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), for its morphologic characterization. The nitrogen adsorption isotherm at 77 K, obtained data of micropore volume, superficial area and poro size distribution. Besides, the FT-IR spectroscopy detected the surfaces functional groups and the Zeta Potential Zeta determinate of the isoelectric point for each carbon. The main parameters influencing adsorption treatment process, pH and equilibrium time have been examined. There have been experimentally made adsorption isotherms for the four types of carbons, which for the carbons (B, B1 and C) adjust to the Freundlich isotherm model. The uptakes capacities information of carbons was originated by these isotherms. The pseudo-first order model and pseudo-second order model was used for evaluated the kinetic data experimental in this process. Finally, the preliminary tests in column had given a vision about of the continue adsorption and the breakthrough curve formation.

No description available.

Bibliography: leaves 126-143. / x, 143 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Adelaide University, Dept. of Applied and Molecular Ecology, 2001