Determination of total mercury in water, sediments and solids in suspension in aquatic systems by cold vapor atomic absorption spectrometry

The use of metallic mercury in the extraction and concentration of gold causes the discarding of tons of this metal in the environment, leading to a considerable increase in the natural levels of the same and the contamination of the surrounding areas. Thus it is extremely important to monitor the presence of this metal in various sectors of the environment with a view aiming to previnting human exposure to excessive concentrations which can result in serious episodes of mercury poisoning. It is also important to estimate the possibility of river sediments becoming potential sources of contamination of human beings. The determination of total mercury was undertaken by using cold vapor atomic absorption spectrometry. River waters, as well as sediments and suspended solids were used as samples for the standardization of the analytical procedure. Later on, this method was tested on samples originating in gold mining areas for the purpose of assessing its validity.O emprego de mercúrio metálico nos processos de extração do ouro libera toneladas de mercúrio ao meio ambiente, provocando um aumento considerável nas concentrações presentes. Com a finalidade de prevenir a exposição humana a concentrações excessivas, o que poderá resultar em graves episódios de intoxicação mercurial, bem como avaliar a possibilidade de sedimentos tornarem-se fontes potenciais de contaminação para os seres vivos, é de fundamental importância a monitorização do mercúrio em diversos compartimentos ambientais. Efetuou-se a padronização de uma metodologia analítica para determinação de mercúrio total em amostras de água, sólidos em suspensão e sedimentos de corpos aquáticos para monitorização ambiental do xenobiótico. Posteriormente, foram analisadas amostras oriundas de regiões garimpeiras, com vistas a avaliar o desempenho do método em amostras reais e efetuar levantamento preliminar sobre a contaminação mercurial na área de estudo

Adenosine and Immune Imbalance in Visceral Leishmaniasis: The Possible Role of Ectonucleotidases

Visceral leishmaniasis (VL) is the most severe form of leishmaniasis and is responsible for most Leishmania-associated deaths. VL represents a serious public health problem that affects many countries. The immune response in leishmaniasis is very complex and is poorly understood. The Th1 versus Th2 paradigm does not appear to be so clear in visceral leishmaniasis, suggesting that other immunosuppressive or immune-evasion mechanisms contribute to the pathogenesis of VL. It has been demonstrated that generation of adenosine, a potent endogenous immunosuppressant, by extracellular enzymes capable to hydrolyze adenosine tri-nucleotide (ATP) at the site of infection, can lead to immune impairment and contribute to leishmaniasis progression. In this regard, this paper discusses the unique features in VL immunopathogenesis, including a possible role for ectonucleotidases in leishmaniasis

Phosphatase activity characterization on the surface of intact bloodstream forms of Trypanosoma brucei

Procyclic forms of Trypanosoma brucei possess a phosphatase activity on their external cell surface. This activity, while it dephosphorylates [P-32]phosphocasein, is inhibited weakly by NaF and tartrate but strongly by vanadate. in this work, we describe the presence of an external phosphatase activity in intact bloodstream forms of T brucei. With p-nitrophenyl phosphate (pNPP) as substrate, these intact cells produced 3-5 nmol pNP min(-1) mg(-1), linearly for up to at least 30 min. the activity was not significantly increased by Mg2+, Mn2+, Ca2+ and Co2+, but was inhibited by vanadate, NaF, p-chloromercuribenzoate and Zn2+ and was insensitive to okadaic acid. Membrane-enriched fractions of parasites contained an acid phosphatase activity, with a pH optimum in the range of 4.5-5.5. This activity hydrolyzed phosphotyrosine (40 nmol phosphate min(-1) mg(-1)) better than phosphothreonine or phosphoserine. Partial purification of this phosphatase yielded a single activity band following gel electrophoresis, a K-m value of 0.29 mM with pNPP and was insensitive to the Fe2+/H2O2/ascorbate system. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.Universidade Federal de São Paulo, Dept Bioquim, BR-04023900 Sao Carlos, SP, BrazilUniv São Paulo, Fac Odontol, Dept Ciencias Biol, Bauru, SP, BrazilUniv Fed Rio de Janeiro, Inst Ciencias Biol, Dept Bioquim, Rio de Janeiro, RJ, BrazilUniv Estadual Campinas, Inst Biol, Dept Bioquim, BR-13083970 Campinas, SP, BrazilUniversidade Federal de São Paulo, Dept Bioquim, BR-04023900 Sao Carlos, SP, BrazilWeb of Scienc

Inorganic Phosphate as an Important Regulator of Phosphatases

Cellular metabolism depends on the appropriate concentration of intracellular inorganic phosphate (Pi). Pi starvation-responsive genes appear to be involved in multiple metabolic pathways, implying a complex Pi regulation system in microorganisms and plants. A group of enzymes is required for absorption and maintenance of adequate phosphate levels, which is released from phosphate esters and anhydrides. The phosphatase system is particularly suited for the study of regulatory mechanisms because phosphatase activity is easily measured using specific methods and the difference between the repressed and derepressed levels of phosphatase activity is easily detected. This paper analyzes the protein phosphatase system induced during phosphate starvation in different organisms

Leishmania amazonensis: Inhibition of 3′-nucleotidase activity by Cu2+ ions

AbstractFree Cu2+ is toxic due to the capacity of free copper ions to catalyze the production of reactive oxygen species (ROS) that can modify the structure and/or function of biomolecules. In addition, non-specific binding to enzymes, which modifies their catalytic activities, can occur. In this work, the mechanisms underlying the ability of copper to inhibit 3′-nucleotidase from Leishmania amazonensis (La3′-nucleotidase) were investigated. To that end, La3′-nucleotidase activity was assayed with CuCl2 in the presence of ascorbate or hydrogen peroxide to discriminate non-specific binding effects from pro-oxidant effects of copper. Copper inhibitory effects were greater at more acidic pH than at alkaline pH. The addition of enzyme substrate, adenosine 3′-monophosphate (3′AMP), prevented the inhibition of enzyme activity by copper. Thiol-containing compounds were able to protect the enzyme activity against inhibition due to copper. The specific copper chelating agent bathocuproine sulphonate (BCS) restored enzyme activity after pre-treatment of the enzyme with copper. La3′-nucleotidase activity was found to be resistant to ROS generated during oxidation reactions of ascorbate and hydrogen peroxide catalyzed by copper. Our results suggest that Cu2+ ions exert their inhibitory effects by binding to specific motifs of the 3′-nucleotidase protein and that the enzyme appears to be extremely resistant to ROS

O regresso dos Nacionalismos na Europa Central e Oriental

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Nota introdutória: Trinta anos do fim do comunismo: O regresso dos nacionalismos na Europa Central e Oriental

[Excerto] Trinta anos depois da queda do Muro de Berlim, em novembro de 1989, o famoso diagnóstico de Francis Fukuyama de que o fim do leninismo significava a vitória final do liberalismo parece definitivamente contestado. O regresso do nacionalismo, particularmente expressivo na Europa Central e Oriental, dá antes razão aos que, como Ken Jowitt, o anunciaram como resposta ao vazio ideológico deixado pelo leninismo. Já no início dos anos 1990 a alta fragmentação social que o comunismo e a transição impunham a estas sociedades e sistemas políticos faziam prever o apelo das políticas de identidade

Acute cerebellitis with tonsillar herniation: a case report

Acute cerebellitis is a rare inflammatory syndrome frequently characterized by fast onset of cerebellar dysfunction. The present case report describes imaging findings in a child with acute cerebellitis, tonsillar herniation and hypertensive hydrocephalus. The etiologic agent has not been determined. A conservative management was adopted, with corticoid and diuretic drugs. Imaging follow-up demonstrated resolution of the clinical condition with no sequela.A cerebelite aguda é uma síndrome inflamatória rara frequentemente caracterizada por rápida disfunção cerebelar. Neste estudo relatamos os achados de imagem do caso de uma criança com cerebelite aguda, herniação tonsilar e hidrocefalia hipertensiva. O agente etiológico não foi descoberto. O tratamento foi conservador, com manitol e corticoide. A análise evolutiva por imagem demonstrou resolução do quadro clínico sem sequelas.24424