RESUMO
The response of Chlorella vulgaris when challenged by As(III), As(V) and dimethylarsinic acid (DMA) was assessed through experiments on adsorption, efflux and speciation of arsenic (reduction, oxidation, methylation and chelation with glutathione/phytochelatin [GSH/PC]). Our study indicates that at high concentrations of phosphate (1.62mM of HPO4(2-)), upon exposure to As(V), cells are able to shift towards methylation of As(V) rather than PC formation. Treatment with As(V) caused a moderate decrease in intracellular pH and a strong increase in the concentration of free thiols (GSH). Passive surface adsorption was found to be negligible for living cells exposed to DMA and As(V). However, adsorption of As(III) was observed to be an active process in C. vulgaris, because it did not show saturation at any of the exposure periods. Chelation of As(III) with GS/PC and to a lesser extent hGS/hPC is a major detoxification mechanism employed by C. vulgaris cells when exposed to As(III). The increase of bound As-GS/PC complexes was found to be strongly related to an increase in concentration of As(III) in media. C. vulgaris cells did not produce any As-GS/PC complex when exposed to As(V). This may indicate that a reduction step is needed for As(V) complexation with GSH/PC. C. vulgaris cells formed DMAS(V)-GS upon exposure to DMA independent of the exposure period. As(III) triggers the formation of arsenic complexes with PC and homophytochelatins (hPC) and their compartmentalisation to vacuoles. A conceptual model was devised to explain the mechanisms involving ABCC1/2 transport. The potential of C. vulgaris to bio-remediate arsenic from water appeared to be highly selective and effective without the potential hazard of reducing As(V) to As(III), which is more toxic to humans.
Assuntos
Arsênio/toxicidade , Ácido Cacodílico/toxicidade , Poluentes Químicos da Água/toxicidade , Análise de Variância , Arsênio/química , Arsênio/metabolismo , Biodegradação Ambiental , Transporte Biológico/efeitos dos fármacos , Biotransformação/fisiologia , Ácido Cacodílico/metabolismo , Chlorella vulgaris/efeitos dos fármacos , Chlorella vulgaris/crescimento & desenvolvimento , Chlorella vulgaris/metabolismo , Citometria de Fluxo , Glutationa/metabolismo , Metaloproteínas/metabolismo , Oxirredução/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Fitoquelatinas/metabolismo , Poluentes Químicos da Água/metabolismoRESUMO
Iron hydroxide supported onto porous diatomite (D-Fe) is a low-cost material with potential to remove arsenic from contaminated water due to its affinity for the arsenate ion. This affinity was tested under varying conditions of pH, contact time, iron content in D-Fe and the presence of competitive ions, silicate and phosphate. Batch and column experiments were conducted to derive adsorption isotherms and breakthrough behaviours (50 µg L(-1)) for an initial concentration of 1,000 µg L(-1). Maximum capacity at pH 4 and 17% iron was 18.12-40.82 mg of arsenic/g of D-Fe and at pH 4 and 10% iron was 18.48-29.07 mg of arsenic/g of D-Fe. Adsorption decreased in the presence of phosphate and silicate ions. The difference in column adsorption behaviour between 10% and 17% iron was very pronounced, outweighing the impact of all other measured parameters. There was insufficient evidence of a correlation between iron content and arsenic content in isotherm experiments, suggesting that ion exchange is a negligible process occurring in arsenate adsorption using D-Fe nor is there co-precipitation of arsenate by rising iron content of the solute above saturation.
Assuntos
Arseniatos/química , Terra de Diatomáceas/química , Ferro/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Arseniatos/análise , Hidróxidos/química , Fosfatos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análiseRESUMO
The discovery and introduction of antimicrobial agents to clinical medicine was one of the greatest medical triumphs of the 20th century that revolutionized the treatment of bacterial infections. However, the gradual emergence of populations of antimicrobial-resistant pathogenic bacteria resulting from use, misuse, and abuse of antimicrobials has today become a major global health concern. Antimicrobial resistance (AMR) genes have been suggested to originate from environmental bacteria, as clinically relevant resistance genes have been detected on the chromosome of environmental bacteria. As only a few new antimicrobials have been developed in the last decade, the further evolution of resistance poses a serious threat to public health. Urgent measures are required not only to minimize the use of antimicrobials for prophylactic and therapeutic purposes but also to look for alternative strategies for the control of bacterial infections. This review examines the global picture of antimicrobial resistance, factors that favor its spread, strategies, and limitations for its control and the need for continuous training of all stake-holders i.e., medical, veterinary, public health, and other relevant professionals as well as human consumers, in the appropriate use of antimicrobial drugs.
RESUMO
An empirical mathematical model, comprising 17 compartments, has been produced to describe the biokinetics of ingested inorganic arsenic (As) in man - required to interpret bioassay data and to predict As tissue concentrations resulting from acute and chronic intakes of inorganic As. The rate constants used to describe the bi-directional transfer of As between compartments were chosen to result in model outcomes that match published data on the distribution of As in tissues and on the retention and excretion of radioisotopes of As administered to human subjects. The model was deployed in acute and chronic intake modes to produce predictions of tissue concentrations and excretion levels. Under conditions of chronic daily intake (1 µg d(-1)) for 50 years predicted final tissue concentrations vary by a factor of â¼ 2. Highest concentrations are predicted to occur in skin and bone (â¼ 230 ng kg(-1)). Tissue concentrations in all tissues other than bone are predicted to reach equilibrium after â¼ 100 days, and at this time, the amount of As excreted in urine has also reached approximate equilibrium at 79% of the daily dietary intake. This level then remains relatively constant unless intake ceases when tissue levels of As fall rapidly. Data on organic and inorganic As concentrations in urine were used to predict inorganic As intake and average tissue content for the USA population. Predicted tissue concentrations ranged from 2.3 µg kg( -1) in skin to 1.1 µg kg(-1) in muscle for an average inorganic As intake of 9.3 µg d(-1).
Assuntos
Arseniatos/farmacocinética , Arsenitos/farmacocinética , Exposição Ambiental , Modelos Biológicos , Poluentes Químicos da Água/farmacocinética , Arseniatos/urina , Arsenitos/urina , Exposição Ambiental/análise , Humanos , Inativação Metabólica , Distribuição Tecidual , Poluentes Químicos da Água/urinaRESUMO
Two outdoor subsurface flow beds (control and experimental, 10 m x 1 m) were filled with a substrate of pea gravel (3-6 mm) to a depth of 60 cm. The experimental bed or small-scale constructed wetland was originally planted with Typha seedlings at a density of 7.5 plants/m2. Both beds (experimental and control) were treated with the same aqueous concentrations of diesel oil under identical dosing conditions. The average overall hydrocarbon removal efficiencies at the three monitored depths (top, middle and bottom) in the subsurface systems were 80.1 +/- 9.8%, 78.0 +/- 9.1% and 71.6 +/- 10.0% in the experimental bed and 72.3 +/- 11.9%, 69.1 +/- 10.3% and 63.4 +/- 9.4% in the control bed. The differences in the hydrocarbon removal efficiencies between corresponding months in 1999 and 2000 were statistically analysed and are generally not significant. The individual hydrocarbon removal efficiencies exceeded 60% in the top sections of both beds except for C-11 and C-25 with C-23 and C-26 also reduced in the control bed. Overall differences in the removal efficiencies of the planted and the unplanted beds as well as at different depths in both systems, indicate that Typha related removal processes complementing adsorption onto the gravel substrate are occurring.
Assuntos
Ecossistema , Hidrocarbonetos/isolamento & purificação , Typhaceae , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Biodegradação Ambiental , Sedimentos Geológicos , Tamanho da Partícula , Movimentos da ÁguaRESUMO
This study compared the performance of a commercial chromogenic medium, CHROMagarECC (CECC), and CECC supplemented with sodium pyruvate (CECCP) with the membrane filtration lauryl sulfate-based medium (mLSA) for enumeration of Escherichia coli and non-E. coli thermotolerant coliforms (KEC). To establish that we could recover the maximum KEC and E. coli population, we compared two incubation temperature regimens, 41 and 44.5 degrees C. Statistical analysis by the Fisher test of data did not demonstrate any statistically significant differences (P = 0.05) in the enumeration of E. coli for the different media (CECC and CECCP) and incubation temperatures. Variance analysis of data performed on KEC counts showed significant differences (P = 0.01) between KEC counts at 41 and 44.5 degrees C on both CECC and CECCP. Analysis of variance demonstrated statistically significant differences (P = 0.05) in the enumeration of total thermotolerant coliforms (TTCs) on CECC and CECCP compared with mLSA. Target colonies were confirmed to be E. coli at a rate of 91.5% and KEC of likely fecal origin at a rate of 77.4% when using CECCP incubated at 41 degrees C. The results of this study showed that CECCP agar incubated at 41 degrees C is efficient for the simultaneous enumeration of E. coli and KEC from river and marine waters.
Assuntos
Enterobacteriaceae/isolamento & purificação , Escherichia coli/isolamento & purificação , Microbiologia da Água , Técnicas Bacteriológicas , Compostos Cromogênicos , Meios de Cultura , Estudos de Avaliação como Assunto , Fezes/microbiologia , Água Doce/microbiologia , Humanos , Água do Mar/microbiologia , TemperaturaRESUMO
A hepatitis A vaccine was prepared by formaldehyde inactivation of purified hepatitis A virus (HAV) LSH/S strain grown on human diploid MRC-5 cells. The vaccine was devoid of residual infectivity in vitro and failed to induce in marmoset monkeys any pathological features or variations of haematological and clinical chemistry values. Infectious HAV particles were not detected in faeces and sera of the vaccinated primates by ELISA or after passages in MRC-5 cells. The immunogenicity of the vaccine was evaluated by injecting guinea-pigs with 0.8, 0.2 or 0.05 micrograms of HAV antigen adsorbed onto 0.5 and 1 mg of Al (OH)3 or 0.3 mg of AlPO4. The antibody response, measured by a competitive radioimmunoassay, was dose- and adjuvant-dependent. One injection of 0.2 micrograms of AlPO4-adsorbed HAV antigen induced seroconversion in 100% of animals and high levels of specific and neutralizing serum antibodies. A further increase of antibody titres was observed after the second and third inoculations. These results show that this vaccine formulation is safe and immunogenic in animal models, and suggest that it should be evaluated further by human clinical studies.
Assuntos
Compostos de Alumínio , Vacinas contra Hepatite Viral/isolamento & purificação , Adjuvantes Imunológicos/administração & dosagem , Alumínio/administração & dosagem , Hidróxido de Alumínio/administração & dosagem , Animais , Callithrix , Linhagem Celular , Cobaias , Anticorpos Anti-Hepatite A , Vacinas contra Hepatite A , Anticorpos Anti-Hepatite/sangue , Hepatovirus/crescimento & desenvolvimento , Hepatovirus/imunologia , Humanos , Fosfatos/administração & dosagem , Vacinas de Produtos Inativados/isolamento & purificação , Vacinas de Produtos Inativados/farmacologia , Vacinas de Produtos Inativados/toxicidade , Vacinas contra Hepatite Viral/farmacologia , Vacinas contra Hepatite Viral/toxicidadeRESUMO
A novel isolate of hepatitis A virus, obtained from a clinical sample, has been adapted to grow on cultured human diploid cells. Growth and purification parameters have been optimized to obtain conditions suitable for the development of an inactivated vaccine. The entire viral genome was molecularly cloned, and the gene encoding the VP3 capsid protein was expressed in Escherichia coli. The resulting recombinant VP3 was used to obtain rabbit antisera which recognize the denatured protein in purified virion preparations. Nucleotide sequencing data are presented and compared to known sequences of different strains.
Assuntos
Antígenos Virais/genética , Capsídeo/genética , Hepatovirus/genética , Vacinas Sintéticas , Vacinas Virais , Sequência de Aminoácidos , Antígenos Virais/imunologia , Sequência de Bases , Capsídeo/análise , Capsídeo/imunologia , Proteínas do Capsídeo , Linhagem Celular , Clonagem Molecular , Genoma Viral , Antígenos da Hepatite A , Vacinas contra Hepatite A , Hepatovirus/imunologia , Humanos , Immunoblotting , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Mapeamento por Restrição , Homologia de Sequência do Ácido Nucleico , Vacinas contra Hepatite ViralRESUMO
A peroxidase-labelled, specific mouse monoclonal antibody to hepatitis A virus (HAV) and an in situ hybridization technique (streptavidin-biotin-horseradish peroxidase reaction) with an HAV-specific cDNA probe (recombinant plasmid pAWHA comprising 1.8 kb of the HAV-specific cDNA, located toward the 3' end of the genome) were used to detect HAV in liver tissues in two patients with fulminant viral hepatitis type A treated by liver transplantation after a protracted (day 40: case 1) and relapsing (day 60: case 2) clinical course. HAV antigens and HAV-specific genomic sequences were detected in the hepatectomy tissues and in serial biopsies of the liver grafts through to final follow-up at 2 months (case 2) or death at 7 months after re-grafting for chronic rejection (case 1). In the fulminant liver parenchyma, numerous degenerating and some surviving hepatocytes were positive and randomly scattered. The immunoperoxidase staining was predominantly cytoplasmic and often granular. The localization of the cDNA probe was predominantly nuclear/perinuclear but was occasionally cytoplasmic. High-titre IgM-anti-HAV antibodies persisted until death (case 1) or resolution (5 months) of an acute hepatitis (case 2), which occurred at 2 months, accompanied by HAV antigen (ELISA), in stool. Intact replicating virus particles must have been present in one or more sites in each case, including extrahepatic locations, with a viraemia as the most likely explanation for subsequent reinfection of the grafts.
Assuntos
Portador Sadio , DNA Viral/análise , Hepatite A/imunologia , Anticorpos Anti-Hepatite/análise , Hepatovirus/imunologia , Transplante de Fígado , Adulto , Portador Sadio/imunologia , Criança , Fezes/microbiologia , Feminino , Hepatite A/complicações , Hepatite A/cirurgia , Hepatovirus/análise , Humanos , Fígado/microbiologia , Hepatopatias/etiologia , Hepatopatias/imunologia , Hepatopatias/cirurgia , MasculinoRESUMO
A new species of Fusobacterium, F. ulcerans, was isolated from 46 tropical ulcers. All the isolates had shown identical soluble cell protein patterns on polyacrylamide gel electrophoresis although there were two morphological types with slightly different biochemical properties. A representative strain of each of the two groups was selected for in- vitro cytotoxicity testing on a range of tissue-culture cell lines. Both strains of F. ulcerans induced a marked cytotoxic effect on Vero and Int-407 cells. This effect may contribute to the pathogenesis of tropical ulcers.
Assuntos
Infecções por Fusobacterium/microbiologia , Fusobacterium/patogenicidade , Úlcera Cutânea/microbiologia , Animais , Linhagem Celular , Humanos , Clima Tropical , Células VeroRESUMO
The serological response to measles vaccine was tested in Bangladesh in groups of infants aged 4-6 months who received equal doses of Edmonston-Zagreb or Schwarz vaccine by subcutaneous injection or by aerosol. Seroconversion (as measured by the haemagglutination test) occurred in 62% of infants receiving Edmonston-Zagreb strain by injection compared with only 37% of those receiving Schwarz strain. Seroconversion occurred in 35% of those given Edmonston-Zagreb and 34% of those given Schwarz vaccine by aerosol. Edmonston-Zagreb strain appears more effective than Schwarz vaccine in this population and further studies are indicated in other populations where early measles immunisation is desirable.