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Sample records for respiratory arsenate reductase

  1. Respiratory arsenate reductase as a bidirectional enzyme

    USGS Publications Warehouse

    Richey, C.; Chovanec, P.; Hoeft, S.E.; Oremland, R.S.; Basu, P.; Stolz, J.F.

    2009-01-01

    The haloalkaliphilic bacterium Alkalilimnicola ehrlichii is capable of anaerobic chemolithoautotrophic growth by coupling the oxidation of arsenite (As(III)) to the reduction of nitrate and carbon dioxide. Analysis of its complete genome indicates that it lacks a conventional arsenite oxidase (Aox), but instead possesses two operons that each encode a putative respiratory arsenate reductase (Arr). Here we show that one homolog is expressed under chemolithoautotrophic conditions and exhibits both arsenite oxidase and arsenate reductase activity. We also demonstrate that Arr from two arsenate respiring bacteria, Alkaliphilus oremlandii and Shewanella sp. strain ANA-3, is also biochemically reversible. Thus Arr can function as a reductase or oxidase. Its physiological role in a specific organism, however, may depend on the electron potentials of the molybdenum center and [Fe–S] clusters, additional subunits, or constitution of the electron transfer chain. This versatility further underscores the ubiquity and antiquity of microbial arsenic metabolism.

  2. Respiratory arsenate reductase as a bidirectional enzyme

    SciTech Connect

    Richey, Christine; Chovanec, Peter; Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15282 ; Hoeft, Shelley E.; Oremland, Ronald S.; Basu, Partha; Stolz, John F.

    2009-05-01

    The haloalkaliphilic bacterium Alkalilimnicola ehrlichii is capable of anaerobic chemolithoautotrophic growth by coupling the oxidation of arsenite (As(III)) to the reduction of nitrate and carbon dioxide. Analysis of its complete genome indicates that it lacks a conventional arsenite oxidase (Aox), but instead possesses two operons that each encode a putative respiratory arsenate reductase (Arr). Here we show that one homolog is expressed under chemolithoautotrophic conditions and exhibits both arsenite oxidase and arsenate reductase activity. We also demonstrate that Arr from two arsenate respiring bacteria, Alkaliphilus oremlandii and Shewanella sp. strain ANA-3, is also biochemically reversible. Thus Arr can function as a reductase or oxidase. Its physiological role in a specific organism, however, may depend on the electron potentials of the molybdenum center and [Fe-S] clusters, additional subunits, or constitution of the electron transfer chain. This versatility further underscores the ubiquity and antiquity of microbial arsenic metabolism.

  3. Diversity of Arsenate Respiratory Reductase Genes Along Gradients of Arsenate and Arsenite Within Hypersaline, Alkaline Sediments

    NASA Astrophysics Data System (ADS)

    Saltikov, C. W.; Nilsen, J.; Oremland, R. S.; Kulp, T. R.; Hoeft, S. E.; Miller, L. G.; Switzer Blum, J.; Baesman, S.; Han, S.; Lanoil, B.

    2005-12-01

    There are several soda lakes in western United States that contain high arsenic concentrations (up to 4 mM total As). Interestingly, these lakes have high rates of anaerobic arsenate reduction, which is catalyzed by arsenate respiring prokaryotes. Several cultured arsenate respiring prokaryotes have been shown to respire and reduce arsenate via a membrane-associated enzyme, ArrA. This enzyme is present in many diverse arsenate respiring prokaryotes. To investigate arsenate respiring microbial communities within these extreme environments, we used functional gene analysis to detect the presence, abundance, and diversity of the arrA gene in core samples collected from two arsenic enriched, hypersaline, alkaline lakes, Mono Lake and Searles Lake. Each sample exhibited concentration gradients for dissolved arsenic species and oxygen. Porewater arsenite concentration increased with depth and was correlated with oxygen depletion. To investigate the depth dependency of the arrA gene in these core samples we utilized the Malasarn et al. (2004) polymerase chain reaction (PCR) primers to detect a partial arrA gene fragment in nucleic acids extracted from sediment samples. The arrA gene fragment was detected only in the top 1-2 cm of the Mono Lake core and no detection was observed in the Searles Lake homogenized core. After the primers were redesigned to include the nucleotide codon bias for haloalkaliphilic archaea ( Halobacterium), the arrA gene fragments could be detected at each depth interval throughout the Mono Lake core and in the homogenized core of Searles Lake. Work is currently focused on characterizing the diversity and abundance of the arrA gene fragments obtained in each core sample and at different depths. Although no haloalkaliphilic arsenate respiring archaea have been isolated to date, these results suggest that the arrA gene fragments detected in these soda lakes may be of archaeal origins.

  4. Natural variation in arsenate tolerance identifies an arsenate reductase in Arabidopsis thaliana.

    PubMed

    Sánchez-Bermejo, Eduardo; Castrillo, Gabriel; del Llano, Bárbara; Navarro, Cristina; Zarco-Fernández, Sonia; Martinez-Herrera, Dannys Jorge; Leo-del Puerto, Yolanda; Muñoz, Riansares; Cámara, Carmen; Paz-Ares, Javier; Alonso-Blanco, Carlos; Leyva, Antonio

    2014-01-01

    The enormous amount of environmental arsenic was a major factor in determining the biochemistry of incipient life forms early in the Earth's history. The most abundant chemical form in the reducing atmosphere was arsenite, which forced organisms to evolve strategies to manage this chemical species. Following the great oxygenation event, arsenite oxidized to arsenate and the action of arsenate reductases became a central survival requirement. The identity of a biologically relevant arsenate reductase in plants nonetheless continues to be debated. Here we identify a quantitative trait locus that encodes a novel arsenate reductase critical for arsenic tolerance in plants. Functional analyses indicate that several non-additive polymorphisms affect protein structure and account for the natural variation in arsenate reductase activity in Arabidopsis thaliana accessions. This study shows that arsenate reductases are an essential component for natural plant variation in As(V) tolerance. PMID:25099865

  5. Dissimilatory arsenate reductase activity and arsenate-respiring bacteria in bovine rumen fluid, hamster feces, and the termite hindgut

    USGS Publications Warehouse

    Herbel, M.J.; Switzer, Blum J.; Hoeft, S.E.; Cohen, S.M.; Arnold, L.L.; Lisak, J.; Stolz, J.F.; Oremland, R.S.

    2002-01-01

    Bovine rumen fluid and slurried hamster feces completely reduced millimolar levels of arsenate to arsenite upon incubation under anoxic conditions. This activity was strongly inhibited by autoclaving or aerobic conditions, and partially inhibited by tungstate or chloramphenicol. The rate of arsenate reduction was faster in feces from a population of arsenate-watered (100 ppm) hamsters compared to a control group watered without arsenate. Using radioisotope methods, arsenate reductase activity in hamster feces was also detected at very low concentrations of added arsenate (???10 ??M). Bacterial cultures were isolated from these materials, as well as from the termite hindgut, that grew using H2 as their electron donor, acetate as their carbon source, and arsenate as their respiratory electron acceptor. The three cultures aligned phylogenetically either with well-established enteric bacteria, or with an organism associated with feedlot fecal wastes. Because arsenite is transported across the gut epithelium more readily than arsenate, microbial dissimilatory reduction of arsenate in the gut may promote the body's absorption of arsenic and hence potentiate its toxicity. ?? 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

  6. The arsenic hyperaccumulating Pteris vittata expresses two arsenate reductases

    NASA Astrophysics Data System (ADS)

    Cesaro, Patrizia; Cattaneo, Chiara; Bona, Elisa; Berta, Graziella; Cavaletto, Maria

    2015-09-01

    Enzymatic reduction of arsenate to arsenite is the first known step in arsenate metabolism in all organisms. Although the presence of one mRNA arsenate reductase (PvACR2) has been characterized in gametophytes of P. vittata, no arsenate reductase protein has been directly observed in this arsenic hyperaccumulating fern, yet. In order to assess the possible presence of arsenate reductase in P. vittata, two recombinant proteins, ACR2-His6 and Trx-His6-S-Pv2.5-8 were prepared in Escherichia coli, purified and used to produce polyclonal antibodies. The presence of these two enzymes was evaluated by qRT-PCR, immunoblotting and direct MS analysis. Enzymatic activity was detected in crude extracts. For the first time we detected and identified two arsenate reductase proteins (PvACR2 and Pv2.5-8) in sporophytes and gametophytes of P. vittata. Despite an increase of the mRNA levels for both proteins in roots, no difference was observed at the protein level after arsenic treatment. Overall, our data demonstrate the constitutive protein expression of PvACR2 and Pv2.5-8 in P. vittata tissues and propose their specific role in the complex metabolic network of arsenic reduction.

  7. The arsenic hyperaccumulating Pteris vittata expresses two arsenate reductases

    PubMed Central

    Cesaro, Patrizia; Cattaneo, Chiara; Bona, Elisa; Berta, Graziella; Cavaletto, Maria

    2015-01-01

    Enzymatic reduction of arsenate to arsenite is the first known step in arsenate metabolism in all organisms. Although the presence of one mRNA arsenate reductase (PvACR2) has been characterized in gametophytes of P. vittata, no arsenate reductase protein has been directly observed in this arsenic hyperaccumulating fern, yet. In order to assess the possible presence of arsenate reductase in P. vittata, two recombinant proteins, ACR2-His6 and Trx-His6-S-Pv2.5–8 were prepared in Escherichia coli, purified and used to produce polyclonal antibodies. The presence of these two enzymes was evaluated by qRT-PCR, immunoblotting and direct MS analysis. Enzymatic activity was detected in crude extracts. For the first time we detected and identified two arsenate reductase proteins (PvACR2 and Pv2.5–8) in sporophytes and gametophytes of P. vittata. Despite an increase of the mRNA levels for both proteins in roots, no difference was observed at the protein level after arsenic treatment. Overall, our data demonstrate the constitutive protein expression of PvACR2 and Pv2.5–8 in P. vittata tissues and propose their specific role in the complex metabolic network of arsenic reduction. PMID:26412036

  8. Response to Arsenate Treatment in Schizosaccharomyces pombe and the Role of Its Arsenate Reductase Activity

    PubMed Central

    Matia-González, Ana M.; Sotelo, Jael; Zarco-Fernández, Sonia; Muñoz-Olivas, Riansares; Cámara, Carmen; Rodríguez-Gabriel, Miguel A.

    2012-01-01

    Arsenic toxicity has been studied for a long time due to its effects in humans. Although epidemiological studies have demonstrated multiple effects in human physiology, there are many open questions about the cellular targets and the mechanisms of response to arsenic. Using the fission yeast Schizosaccharomyces pombe as model system, we have been able to demonstrate a strong activation of the MAPK Spc1/Sty1 in response to arsenate. This activation is dependent on Wis1 activation and Pyp2 phosphatase inactivation. Using arsenic speciation analysis we have also demonstrated the previously unknown capacity of S. pombe cells to reduce As (V) to As (III). Genetic analysis of several fission yeast mutants point towards the cell cycle phosphatase Cdc25 as a possible candidate to carry out this arsenate reductase activity. We propose that arsenate reduction and intracellular accumulation of arsenite are the key mechanisms of arsenate tolerance in fission yeast. PMID:22912829

  9. Purine nucleoside phosphorylase as a cytosolic arsenate reductase.

    PubMed

    Gregus, Zoltán; Németi, Balázs

    2002-11-01

    The findings of the accompanying paper (Németi and Gregus, Toxicol: Sci. 70, 4-12) indicate that the arsenate (AsV) reductase activity of rat liver cytosol is due to an SH enzyme that uses phosphate (or its analogue, arsenate, AsV) and a purine nucleoside (guanosine or inosine) as substrates. Purine nucleoside phosphorylase (PNP) is such an enzyme. It catalyzes the phosphorolytic cleavage of 6-oxopurine nucleosides according to the following scheme: guanosine (or inosine) + phosphate <--> guanine (or hypoxanthine) + ribose-1-phosphate. Therefore, we have tested the hypothesis that PNP is responsible for the thiol- and purine nucleoside-dependent reduction of AsV to AsIII by rat liver cytosol. AsIII formed from AsV was quantified by HPLC-hydride generation-atomic fluorescence spectrometry analysis of the deproteinized incubates. The following findings support the conclusion that PNP reduces AsV to AsIII, using AsV instead of phosphate in the reaction above: (1) Specific PNP inhibitors (CI-1000, BCX-1777) at a concentration of 1 microM completely inhibited cytosolic AsV reductase activity. (2) During anion-exchange chromatography of cytosolic proteins, PNP activity perfectly coeluted with the AsV reductase activity, suggesting that both activities belong to the same protein. (3) PNP purified from calf spleen catalyzed reduction of AsV to AsIII in the presence of dithiothreitol (DTT) and a 6-oxopurine nucleoside (guanosine or inosine). (4) AsV reductase activity of purified PNP, like the cytosolic AsV reductase activity, was inhibited by phosphate (a substrate of PNP alternative to AsV), guanine and hypoxanthine (products of PNP favoring the reverse reaction), mercurial thiol reagents (nonspecific inhibitors of PNP), as well as CI-1000 and BCX-1777 (specific PNP inhibitors). Thus, PNP appears to be responsible for the AsV reductase activity of rat liver cytosol in the presence of DTT. Further research should clarify the mechanism and the in vivo significance of PNP

  10. A novel arsenate reductase from the bacterium Thermus thermophilus HB27: its role in arsenic detoxification.

    PubMed

    Del Giudice, Immacolata; Limauro, Danila; Pedone, Emilia; Bartolucci, Simonetta; Fiorentino, Gabriella

    2013-10-01

    Microorganisms living in arsenic-rich geothermal environments act on arsenic with different biochemical strategies, but the molecular mechanisms responsible for the resistance to the harmful effects of the metalloid have only partially been examined. In this study, we investigated the mechanisms of arsenic resistance in the thermophilic bacterium Thermus thermophilus HB27. This strain, originally isolated from a Japanese hot spring, exhibited tolerance to concentrations of arsenate and arsenite up to 20mM and 15mM, respectively; it owns in its genome a putative chromosomal arsenate reductase (TtarsC) gene encoding a protein homologous to the one well characterized from the plasmid pI258 of the Gram+bacterium Staphylococcus aureus. Differently from the majority of microorganisms, TtarsC is part of an operon including genes not related to arsenic resistance; qRT-PCR showed that its expression was four-fold increased when arsenate was added to the growth medium. The gene cloning and expression in Escherichia coli, followed by purification of the recombinant protein, proved that TtArsC was indeed a thioredoxin-coupled arsenate reductase with a kcat/KM value of 1.2×10(4)M(-1)s(-1). It also exhibited weak phosphatase activity with a kcat/KM value of 2.7×10(-4)M(-1)s(-1). The catalytic role of the first cysteine (Cys7) was ascertained by site-directed mutagenesis. These results identify TtArsC as an important component in the arsenic resistance in T. thermophilus giving the first structural-functional characterization of a thermophilic arsenate reductase. PMID:23800470

  11. Adventitious Arsenate Reductase Activity of the Catalytic Domain of the Human Cdc25B and Cdc25C Phosphatases†

    PubMed Central

    Bhattacharjee, Hiranmoy; Sheng, Ju; Ajees, A. Abdul; Mukhopadhyay, Rita; Rosen, Barry P.

    2013-01-01

    A number of eukaryotic enzymes that function as arsenate reductases are homologues of the catalytic domain of the human Cdc25 phosphatase. For example, the Leishmania major enzyme LmACR2 is both a phosphatase and an arsenate reductase, and its structure bears similarity to the structure of the catalytic domain of human Cdc25 phosphatase. These reductases contain an active site C-X5-R signature motif, where C is the catalytic cysteine, the five X residues form a phosphate binding loop, and R is a highly conserved arginine, which is also present in human Cdc25 phosphatases. We therefore investigated the possibility that the three human Cdc25 isoforms might have adventitious arsenate reductase activity. The sequences for the catalytic domains of Cdc25A, -B, and -C were cloned individually into a prokaryotic expression vector, and their gene products were purified from a bacterial host using nickel affinity chromatography. While each of the three Cdc25 catalytic domains exhibited phosphatase activity, arsenate reductase activity was observed only with Cdc25B and -C. These two enzymes reduced inorganic arsenate but not methylated pentavalent arsenicals. Alteration of either the cysteine and arginine residues of the Cys-X5-Arg motif led to the loss of both reductase and phosphatase activities. Our observations suggest that Cdc25B and -C may adventitiously reduce arsenate to the more toxic arsenite and may also provide a framework for identifying other human protein tyrosine phosphatases containing the active site Cys-X5-Arg loop that might moonlight as arsenate reductases. PMID:20025242

  12. All intermediates of the arsenate reductase mechanism, including an intramolecular dynamic disulfide cascade

    PubMed Central

    Messens, Joris; Martins, José C.; Van Belle, Karolien; Brosens, Elke; Desmyter, Aline; De Gieter, Marjan; Wieruszeski, Jean-Michel; Willem, Rudolph; Wyns, Lode; Zegers, Ingrid

    2002-01-01

    The mechanism of pI258 arsenate reductase (ArsC) catalyzed arsenate reduction, involving its P-loop structural motif and three redox active cysteines, has been unraveled. All essential intermediates are visualized with x-ray crystallography, and NMR is used to map dynamic regions in a key disulfide intermediate. Steady-state kinetics of ArsC mutants gives a view of the crucial residues for catalysis. ArsC combines a phosphatase-like nucleophilic displacement reaction with a unique intramolecular disulfide bond cascade. Within this cascade, the formation of a disulfide bond triggers a reversible “conformational switch” that transfers the oxidative equivalents to the surface of the protein, while releasing the reduced substrate. PMID:12072565

  13. Genome-wide Association Mapping Identifies a New Arsenate Reductase Enzyme Critical for Limiting Arsenic Accumulation in Plants

    PubMed Central

    Chao, Dai-Yin; Chen, Yi; Chen, Jiugeng; Shi, Shulin; Chen, Ziru; Wang, Chengcheng; Danku, John M.; Zhao, Fang-Jie; Salt, David E.

    2014-01-01

    Inorganic arsenic is a carcinogen, and its ingestion through foods such as rice presents a significant risk to human health. Plants chemically reduce arsenate to arsenite. Using genome-wide association (GWA) mapping of loci controlling natural variation in arsenic accumulation in Arabidopsis thaliana allowed us to identify the arsenate reductase required for this reduction, which we named High Arsenic Content 1 (HAC1). Complementation verified the identity of HAC1, and expression in Escherichia coli lacking a functional arsenate reductase confirmed the arsenate reductase activity of HAC1. The HAC1 protein accumulates in the epidermis, the outer cell layer of the root, and also in the pericycle cells surrounding the central vascular tissue. Plants lacking HAC1 lose their ability to efflux arsenite from roots, leading to both increased transport of arsenic into the central vascular tissue and on into the shoot. HAC1 therefore functions to reduce arsenate to arsenite in the outer cell layer of the root, facilitating efflux of arsenic as arsenite back into the soil to limit both its accumulation in the root and transport to the shoot. Arsenate reduction by HAC1 in the pericycle may play a role in limiting arsenic loading into the xylem. Loss of HAC1-encoded arsenic reduction leads to a significant increase in arsenic accumulation in shoots, causing an increased sensitivity to arsenate toxicity. We also confirmed the previous observation that the ACR2 arsenate reductase in A. thaliana plays no detectable role in arsenic metabolism. Furthermore, ACR2 does not interact epistatically with HAC1, since arsenic metabolism in the acr2 hac1 double mutant is disrupted in an identical manner to that described for the hac1 single mutant. Our identification of HAC1 and its associated natural variation provides an important new resource for the development of low arsenic-containing food such as rice. PMID:25464340

  14. Specific potassium binding stabilizes pI258 arsenate reductase from Staphylococcus aureus.

    PubMed

    Lah, Nina; Lah, Jurij; Zegers, Ingrid; Wyns, Lode; Messens, Joris

    2003-07-01

    Arsenate reductase (ArsC) from Staphylococcus aureus plasmid pI258 catalyzes the reduction of arsenate to arsenite and plays a role in bacterial heavy metal resistance. The high resolution x-ray structure of ArsC reveals the atomic details of the K+ binding site situated next to the catalytic P-loop structural motif of this redox enzyme. A full thermodynamic study of the binding characteristics of a series of monovalent cations (Li+, Na+, K+, Rb+, and Cs+) and their influence on the thermal stability of ArsC was performed with isothermal titration calorimetry, circular dichroism spectroscopy, and differential scanning calorimetry. Potassium has the largest affinity with a Ka of 3.8 x 10(3) m(-1), and the effectiveness of stabilization of ArsC by monovalent cations follows the binding affinity order: K+ > Rb+ > Cs+ > Na+ > Li+. A mutagenesis study on the K+ binding side chains showed that Asn-13 and Asp-65 are essential for potassium binding, but the impact on the stability of ArsC was the most extreme when mutating Ser-36. Additionally, the thermal stabilization by K+ is significantly reduced in the case of the ArsC E21A mutant, showing the importance of a Glu-21-coordinated water molecule in its contact with K+. Although potassium is not essential for catalysis, in its presence the kcat/KM increases with a factor of 5. Altogether, the interaction of K+ with specific residues in ArsC is an enthalpydriven process that stabilizes ArsC and increases the specific activity of this redox enzyme. PMID:12682056

  15. The cytochrome bd respiratory oxygen reductases

    PubMed Central

    Borisov, Vitaliy B.; Gennis, Robert B.; Hemp, James; Verkhovsky, Michael I.

    2011-01-01

    Summary Cytochrome bd is a respiratory quinol:O2 oxidoreductase found in many prokaryotes, including a number of pathogens. The main bioenergetic function of the enzyme is the production of a proton motive force by the vectorial charge transfer of protons. The sequences of cytochromes bd are not homologous to those of the other respiratory oxygen reductases, i.e., the heme-copper oxygen reductases or alternative oxidases (AOX). Generally, cytochromes bd are noteworthy for their high affinity for O2 and resistance to inhibition by cyanide. In E. coli, for example, cytochrome bd (specifically, cytochrome bd-I) is expressed under O2-limited conditions. Among the members of the bd-family are the so-called cyanide-insensitive quinol oxidases (CIO) which often have a low content of the eponymous heme d but, instead, have heme b in place of heme d in at least a majority of the enzyme population. However, at this point, no sequence motif has been identified to distinguish cytochrome bd (with a stoichiometric complement of heme d) from an enzyme designated as CIO. Members of the bd-family can be subdivided into those which contain either a long or a short hydrophilic connection between transmembrane helices 6 and 7 in subunit I, designated as the Q-loop. However, it is not clear whether there is a functional consequence of this difference. This review summarizes current knowledge on the physiological functions, genetics, structural and catalytic properties of cytochromes bd. Included in this review are descriptions of the intermediates of the catalytic cycle, the proposed site for the reduction of O2, evidence for a proton channel connecting this active site to the bacterial cytoplasm, and the molecular mechanism by which a membrane potential is generated. PMID:21756872

  16. Development of a Molecular System for Studying Microbial Arsenate Respiration

    NASA Astrophysics Data System (ADS)

    Saltikov, C. W.; Newman, D. K.

    2002-12-01

    The toxic element arsenic is a major contaminant of many groundwaters and surface waters throughout the world. Arsenic enrichment is primarily of geological origin resulting from weathering processes and geothermal activity. Not surprisingly, microorganisms inhabiting anoxic arsenic-contaminated environments have evolved to exploit arsenate during respiration. Numerous bacteria have been isolated that use arsenate as a terminal electron acceptor for respiratory growth. The diversity of this metabolism appears to be widespread throughout the microbial tree of life, suggesting respiratory arsenate reduction is ancient in origin. Yet little is known about the molecular mechanisms for how these organisms respire arsenate. We have developed a model system in Shewanella trabarsenatis, strain ANA-3, a facultative anaerobe that respires arsenate and tolerates high concentrations of arsenite (10 mM). Through loss-of-function studies, we have identified genes involved in both arsenic resistance and arsenate respiration. The genes that confer resistance to arsenic are homologous to the well-characterized ars operon of E. coli. However, the respiratory arsenate reductase is predicted to encode a novel protein that shares homologous regions (~ 40 % similarity) to molybdopterin anaerobic reductases specific for DMSO, thiosulfate, nitrate, and polysulfide. I will discuss our emerging model for how strain ANA-3 respires arsenate and the relationship between arsenite resistance and arsenate respiration. I will also highlight the relevance of this type of analysis for biogeochemical studies.

  17. A SAM-dependent methyltransferase cotranscribed with arsenate reductase alters resistance to peptidyl transferase center-binding antibiotics in Azospirillum brasilense Sp7.

    PubMed

    Singh, Sudhir; Singh, Chhaya; Tripathi, Anil Kumar

    2014-05-01

    The genome of Azospirillum brasilense harbors a gene encoding S-adenosylmethionine-dependent methyltransferase, which is located downstream of an arsenate reductase gene. Both genes are cotranscribed and translationally coupled. When they were cloned and expressed individually in an arsenate-sensitive strain of Escherichia coli, arsenate reductase conferred tolerance to arsenate; however, methyltransferase failed to do so. Sequence analysis revealed that methyltransferase was more closely related to a PrmB-type N5-glutamine methyltransferase than to the arsenate detoxifying methyltransferase ArsM. Insertional inactivation of prmB gene in A. brasilense resulted in an increased sensitivity to chloramphenicol and resistance to tiamulin and clindamycin, which are known to bind at the peptidyl transferase center (PTC) in the ribosome. These observations suggested that the inability of prmB:km mutant to methylate L3 protein might alter hydrophobicity in the antibiotic-binding pocket of the PTC, which might affect the binding of chloramphenicol, clindamycin, and tiamulin differentially. This is the first report showing the role of PrmB-type N5-glutamine methyltransferases in conferring resistance to tiamulin and clindamycin in any bacterium. PMID:24573606

  18. Draft Genome Sequence of Anaeromyxobacter sp. Strain PSR-1, an Arsenate-Respiring Bacterium Isolated from Arsenic-Contaminated Soil.

    PubMed

    Tonomura, Mimori; Ehara, Ayaka; Suzuki, Haruo; Amachi, Seigo

    2015-01-01

    Here, we report a draft genome sequence of Anaeromyxobacter sp. strain PSR-1, an arsenate-respiring bacterium isolated from arsenic-contaminated soil. It contained three distinct arsenic resistance gene clusters (ars operons), while no respiratory arsenate reductase gene (arr) was identified. PMID:25977440

  19. Draft Genome Sequence of Anaeromyxobacter sp. Strain PSR-1, an Arsenate-Respiring Bacterium Isolated from Arsenic-Contaminated Soil

    PubMed Central

    Tonomura, Mimori; Ehara, Ayaka; Suzuki, Haruo

    2015-01-01

    Here, we report a draft genome sequence of Anaeromyxobacter sp. strain PSR-1, an arsenate-respiring bacterium isolated from arsenic-contaminated soil. It contained three distinct arsenic resistance gene clusters (ars operons), while no respiratory arsenate reductase gene (arr) was identified. PMID:25977440

  20. The activation of electrophile, nucleophile and leaving group during the reaction catalysed by pI258 arsenate reductase.

    PubMed

    Roos, Goedele; Loverix, Stefan; Brosens, Elke; Van Belle, Karolien; Wyns, Lode; Geerlings, Paul; Messens, Joris

    2006-06-01

    The reduction of arsenate to arsenite by pI258 arsenate reductase (ArsC) combines a nucleophilic displacement reaction with a unique intramolecular disulfide cascade. Within this reaction mechanism, the oxidative equivalents are translocated from the active site to the surface of ArsC. The first reaction step in the reduction of arsenate by pI258 ArsC consists of a nucleophilic displacement reaction carried out by Cys10 on dianionic arsenate. The second step involves the nucleophilic attack of Cys82 on the Cys10-arseno intermediate formed during the first reaction step. The onset of the second step is studied here by using quantum chemical calculations in a density functional theory context. The optimised geometry of the Cys10-arseno adduct in the ArsC catalytic site (sequence motif: Cys10-Thr11-Gly12-Asn13-Ser14-Cys15-Arg16-Ser17) forms the starting point for all subsequent calculations. Thermodynamic data and a hard and soft acids and bases (HSAB) reactivity analysis show a preferential nucleophilic attack on a monoanionic Cys10-arseno adduct, which is stabilised by Ser17. The P-loop active site of pI258 ArsC activates first a hydroxy group and subsequently arsenite as the leaving group, as is clear from an increase in the calculated nucleofugality of these groups upon going from the gas phase to the solvent phase to the enzymatic environment. Furthermore, the enzymatic environment stabilises the thiolate form of the nucleophile Cys82 by 3.3 pH units through the presence of the eight-residue alpha helix flanked by Cys82 and Cys89 (redox helix) and through a hydrogen bond with Thr11. The importance of Thr11 in the pKa regulation of Cys82 was confirmed by the observed decrease in the kcat value of the Thr11Ala mutant as compared to that of wild-type ArsC. During the final reaction step, Cys89 is activated as a nucleophile by structural alterations of the redox helix that functions as a pKa control switch for Cys89; this final step is necessary to expose a Cys82-Cys

  1. Draft Genome Sequence of Geobacter sp. Strain OR-1, an Arsenate-Respiring Bacterium Isolated from Japanese Paddy Soil

    PubMed Central

    Ehara, Ayaka; Suzuki, Haruo

    2015-01-01

    Here, we report a draft genome sequence of Geobacter sp. strain OR-1, an arsenate-respiring bacterium isolated from Japanese paddy soil. It contained two distinct arsenic islands, one including genes for a respiratory arsenate reductase (Arr) as well as for arsenic resistance (arsD-arsA-acr3-arsR-arrA-arrB) and the second containing only genes for arsenic resistance. PMID:25635012

  2. Draft Genome Sequence of Geobacter sp. Strain OR-1, an Arsenate-Respiring Bacterium Isolated from Japanese Paddy Soil.

    PubMed

    Ehara, Ayaka; Suzuki, Haruo; Amachi, Seigo

    2015-01-01

    Here, we report a draft genome sequence of Geobacter sp. strain OR-1, an arsenate-respiring bacterium isolated from Japanese paddy soil. It contained two distinct arsenic islands, one including genes for a respiratory arsenate reductase (Arr) as well as for arsenic resistance (arsD-arsA-acr3-arsR-arrA-arrB) and the second containing only genes for arsenic resistance. PMID:25635012

  3. Functional analysis of ars gene cluster of Pannonibacter indicus strain HT23(T) (DSM 23407(T)) and identification of a proline residue essential for arsenate reductase activity.

    PubMed

    Bandyopadhyay, Saumya; Das, Subrata K

    2016-04-01

    Arsenic is a naturally occurring ubiquitous highly toxic metalloid. In this study, we have identified ars gene cluster in Pannonibacter indicus strain HT23(T) (DSM 23407(T)), responsible for reduction of toxic pentavalent arsenate. The ars gene cluster is comprised of four non-overlapping open reading frames (ORFs) encoding a transcriptional regulator (ArsR), a low molecular weight protein tyrosine phosphatases (LMW-PTPase) with hypothetical function, an arsenite efflux pump (Acr3), and an arsenate reductase (ArsC). Heterologous expression of arsenic inducible ars gene cluster conferred arsenic resistance to Escherichia coli ∆ars mutant strain AW3110. The recombinant ArsC was purified and assayed. Site-directed mutagenesis was employed to ascertain the role of specific amino acids in ArsC catalysis. Pro94X (X = Ala, Arg, Cys, and His) amino acid substitutions led to enzyme inactivation. Circular dichroism spectra analysis suggested Pro94 as an essential amino acid for enzyme catalytic activity as it is indispensable for optimum protein folding in P. indicus Grx-coupled ArsC. PMID:26915994

  4. Glutathione-S-transferase-omega [MMA(V) reductase] knockout mice: Enzyme and arsenic species concentrations in tissues after arsenate administration

    SciTech Connect

    Chowdhury, Uttam K.; Zakharyan, Robert A.; Hernandez, Alba; Avram, Mihaela D.; Kopplin, Michael J.; Aposhian, H. Vasken . E-mail: aposhian@u.arizona.edu

    2006-11-01

    Inorganic arsenic is a human carcinogen to which millions of people are exposed via their naturally contaminated drinking water. Its molecular mechanisms of carcinogenicity have remained an enigma, perhaps because arsenate is biochemically transformed to at least five other arsenic-containing metabolites. In the biotransformation of inorganic arsenic, GSTO1 catalyzes the reduction of arsenate, MMA(V), and DMA(V) to the more toxic + 3 arsenic species. MMA(V) reductase and human (hGSTO1-1) are identical proteins. The hypothesis that GST-Omega knockout mice biotransformed inorganic arsenic differently than wild-type mice has been tested. The livers of male knockout (KO) mice, in which 222 bp of Exon 3 of the GSTO1 gene were eliminated, were analyzed by PCR for mRNA. The level of transcripts of the GSTO1 gene in KO mice was 3.3-fold less than in DBA/1lacJ wild-type (WT) mice. The GSTO2 transcripts were about two-fold less in the KO mouse. When KO and WT mice were injected intramuscularly with Na arsenate (4.16 mg As/kg body weight); tissues removed at 0.5, 1, 2, 4, 8, and 12 h after arsenate injection; and the arsenic species measured by HPLC-ICP-MS, the results indicated that the highest concentration of the recently discovered and very toxic MMA(III), a key biotransformant, was in the kidneys of both KO and WT mice. The highest concentration of DMA(III) was in the urinary bladder tissue for both the KO and WT mice. The MMA(V) reducing activity of the liver cytosol of KO mice was only 20% of that found in wild-type mice. There appears to be another enzyme(s) other than GST-O able to reduce arsenic(V) species but to a lesser extent. This and other studies suggest that each step of the biotransformation of inorganic arsenic has an alternative enzyme to biotransform the arsenic substrate.

  5. Crystallization and preliminary crystallographic characterization of LmACR2, an arsenate/antimonate reductase from Leishmania major

    SciTech Connect

    Bisacchi, Davide; Zhou, Yao; Rosen, Barry P.; Mukhopadhyay, Rita; Bordo, Domenico

    2006-10-01

    LmACR2 from L. major is the first rhodanese-like enzyme directly involved in the reduction of arsenate and antimonate to be crystallized. Diffraction data have been collected to 1.99 Å resolution using synchrotron X-rays. Arsenic is present in the biosphere owing either to the presence of pesticides and herbicides used in agricultural and industrial activities or to leaching from geological formations. The health effects of prolonged exposure to arsenic can be devastating and may lead to various forms of cancer. Antimony(V), which is chemically very similar to arsenic, is used instead in the treatment of leishmaniasis, an infection caused by the protozoan parasite Leishmania sp.; the reduction of pentavalent antimony contained in the drug Pentostam to the active trivalent form arises from the presence in the Leishmania genome of a gene, LmACR2, coding for the protein LmACR2 (14.5 kDa, 127 amino acids) that displays weak but significant sequence similarity to the catalytic domain of Cdc25 phosphatase and to rhodanese enzymes. For structural characterization, LmACR2 was overexpressed, purified to homogeneity and crystallized in a trigonal space group (P321 or P3{sub 1}21/P3{sub 2}21). The protein crystallized in two distinct trigonal crystal forms, with unit-cell parameters a = b = 111.0, c = 86.1 Å and a = b = 111.0, c = 175.6 Å, respectively. At a synchrotron beamline, the diffraction pattern extended to a resolution limit of 1.99 Å.

  6. Reductive activation of E. coli respiratory nitrate reductase.

    PubMed

    Ceccaldi, Pierre; Rendon, Julia; Léger, Christophe; Toci, René; Guigliarelli, Bruno; Magalon, Axel; Grimaldi, Stéphane; Fourmond, Vincent

    2015-10-01

    Over the past decades, a number of authors have reported the presence of inactive species in as-prepared samples of members of the Mo/W-bisPGD enzyme family. This greatly complicated the spectroscopic studies of these enzymes, since it is impossible to discriminate between active and inactive species on the basis of the spectroscopic signatures alone. Escherichia coli nitrate reductase A (NarGHI) is a member of the Mo/W-bisPGD family that allows anaerobic respiration using nitrate as terminal electron acceptor. Here, using protein film voltammetry on NarGH films, we show that the enzyme is purified in a functionally heterogeneous form that contains between 20 and 40% of inactive species that activate the first time they are reduced. This activation proceeds in two steps: a non-redox reversible reaction followed by an irreversible reduction. By carefully correlating electrochemical and EPR spectroscopic data, we show that neither the two major Mo(V) signals nor those of the two FeS clusters that are the closest to the Mo center are associated with the two inactive species. We also conclusively exclude the possibility that the major "low-pH" and "high-pH" Mo(V) EPR signatures correspond to species in acid-base equilibrium. PMID:26073890

  7. Molecular Cloning and Characterization of the srdBCA Operon, Encoding the Respiratory Selenate Reductase Complex, from the Selenate-Reducing Bacterium Bacillus selenatarsenatis SF-1▿†

    PubMed Central

    Kuroda, Masashi; Yamashita, Mitsuo; Miwa, Emiko; Imao, Kanako; Fujimoto, Noriyuki; Ono, Hisayo; Nagano, Kouta; Sei, Kazunari; Ike, Michihiko

    2011-01-01

    Previously, we isolated a selenate- and arsenate-reducing bacterium, designated strain SF-1, from selenium-contaminated sediment and identified it as a novel species, Bacillus selenatarsenatis. B. selenatarsenatis strain SF-1 independently reduces selenate to selenite, arsenate to arsenite, and nitrate to nitrite by anaerobic respiration. To identify the genes involved in selenate reduction, 17 selenate reduction-defective mutant strains were isolated from a mutant library generated by random insertion of transposon Tn916. Tn916 was inserted into the same genome position in eight mutants, and the representative strain SF-1AM4 did not reduce selenate but did reduce nitrate and arsenate to the same extent as the wild-type strain. The disrupted gene was located in an operon composed of three genes designated srdBCA, which were predicted to encode a putative oxidoreductase complex by the BLASTX program. The plasmid vector pGEMsrdBCA, containing the srdBCA operon with its own promoter, conferred the phenotype of selenate reduction in Escherichia coli DH5α, although E. coli strains containing plasmids lacking any one or two of the open reading frames from srdBCA did not exhibit the selenate-reducing phenotype. Domain structure analysis of the deduced amino acid sequence revealed that SrdBCA had typical features of membrane-bound and molybdopterin-containing oxidoreductases. It was therefore proposed that the srdBCA operon encoded a respiratory selenate reductase complex. This is the first report of genes encoding selenate reductase in Gram-positive bacteria. PMID:21357486

  8. Role of Campylobacter jejuni Respiratory Oxidases and Reductases in Host Colonization▿

    PubMed Central

    Weingarten, Rebecca A.; Grimes, Jesse L.; Olson, Jonathan W.

    2008-01-01

    Campylobacter jejuni is the leading cause of human food-borne bacterial gastroenteritis. The C. jejuni genome sequence predicts a branched electron transport chain capable of utilizing multiple electron acceptors. Mutants were constructed by disrupting the coding regions of the respiratory enzymes nitrate reductase (napA::Cm), nitrite reductase (nrfA::Cm), dimethyl sulfoxide, and trimethylamine N-oxide reductase (termed Cj0264::Cm) and the two terminal oxidases, a cyanide-insensitive oxidase (cydA::Cm) and cbb3-type oxidase (ccoN::Cm). Each strain was characterized for the loss of the associated enzymatic function in vitro. The strains were then inoculated into 1-week-old chicks, and the cecal contents were assayed for the presence of C. jejuni 2 weeks postinoculation. cydA::Cm and Cj0264c::Cm strains colonized as well as the wild type; napA::Cm and nrfA::Cm strains colonized at levels significantly lower than the wild type. The ccoN::Cm strain was unable to colonize the chicken; no colonies were recovered at the end of the experiment. While there appears to be a role for anaerobic respiration in host colonization, oxygen is the most important respiratory acceptor for C. jejuni in the chicken cecum. PMID:18192421

  9. Arsenic dissolution from Japanese paddy soil by a dissimilatory arsenate-reducing bacterium Geobacter sp. OR-1.

    PubMed

    Ohtsuka, Toshihiko; Yamaguchi, Noriko; Makino, Tomoyuki; Sakurai, Kazuhiro; Kimura, Kenta; Kudo, Keitaro; Homma, Eri; Dong, Dian Tao; Amachi, Seigo

    2013-06-18

    Dissimilatory As(V) (arsenate)-reducing bacteria may play an important role in arsenic release from anoxic sediments in the form of As(III) (arsenite). Although respiratory arsenate reductase genes (arrA) closely related to Geobacter species have been frequently detected in arsenic-rich sediments, it is still unclear whether they directly participate in arsenic release, mainly due to lack of pure cultures capable of arsenate reduction. In this study, we isolated a novel dissimilatory arsenate-reducing bacterium, strain OR-1, from Japanese paddy soil, and found that it was phylogenetically closely related to Geobacter pelophilus. OR-1 also utilized soluble Fe(III), ferrihydrite, nitrate, and fumarate as electron acceptors. OR-1 catalyzed dissolution of arsenic from arsenate-adsorbed ferrihydrite, while Geobacter metallireducens GS-15 did not. Furthermore, inoculation of washed cells of OR-1 into sterilized paddy soil successfully restored arsenic release. Arsenic K-edge X-ray absorption near-edge structure analysis revealed that strain OR-1 reduced arsenate directly on the soil solid phase. Analysis of putative ArrA sequences from paddy soils suggested that Geobacter-related bacteria, including those closely related to OR-1, play an important role in arsenic release from paddy soils. Our results provide direct evidence for arsenic dissolution by Geobacter species and support the hypothesis that Geobacter species play a significant role in reduction and mobilization of arsenic in flooded soils and anoxic sediments. PMID:23668621

  10. The evolution of respiratory O2/NO reductases: an out-of-the-phylogenetic-box perspective

    PubMed Central

    Ducluzeau, Anne-Lise; Schoepp-Cothenet, Barbara; van Lis, Robert; Baymann, Frauke; Russell, Michael J.; Nitschke, Wolfgang

    2014-01-01

    Complex life on our planet crucially depends on strong redox disequilibria afforded by the almost ubiquitous presence of highly oxidizing molecular oxygen. However, the history of O2-levels in the atmosphere is complex and prior to the Great Oxidation Event some 2.3 billion years ago, the amount of O2 in the biosphere is considered to have been extremely low as compared with present-day values. Therefore the evolutionary histories of life and of O2-levels are likely intricately intertwined. The obvious biological proxy for inferring the impact of changing O2-levels on life is the evolutionary history of the enzyme allowing organisms to tap into the redox power of molecular oxygen, i.e. the bioenergetic O2 reductases, alias the cytochrome and quinol oxidases. Consequently, molecular phylogenies reconstructed for this enzyme superfamily have been exploited over the last two decades in attempts to elucidate the interlocking between O2 levels in the environment and the evolution of respiratory bioenergetic processes. Although based on strictly identical datasets, these phylogenetic approaches have led to diametrically opposite scenarios with respect to the history of both the enzyme superfamily and molecular oxygen on the Earth. In an effort to overcome the deadlock of molecular phylogeny, we here review presently available structural, functional, palaeogeochemical and thermodynamic information pertinent to the evolution of the superfamily (which notably also encompasses the subfamily of nitric oxide reductases). The scenario which, in our eyes, most closely fits the ensemble of these non-phylogenetic data, sees the low O2-affinity SoxM- (or A-) type enzymes as the most recent evolutionary innovation and the high-affinity O2 reductases (SoxB or B and cbb3 or C) as arising independently from NO-reducing precursor enzymes. PMID:24968694

  11. IN VITRO INHIBITION OF GLUTATHIONE REDUCTASE BY ARSENOTRI-GLUTATHIONE

    EPA Science Inventory

    Arsenotriglutathione, a product of the reduction of arsenate and the complexation of arsenite by glutathione, is a mixed type inhibitor of the reduction of glutathione disulfide by purified yeast glutathione reductase or the glutathione reductase activity in rabbit erythrocyte ly...

  12. Novel channel enzyme fusion proteins confer arsenate resistance.

    PubMed

    Wu, Binghua; Song, Jie; Beitz, Eric

    2010-12-17

    Steady exposure to environmental arsenic has led to the evolution of vital cellular detoxification mechanisms. Under aerobic conditions, a two-step process appears most common among microorganisms involving reduction of predominant, oxidized arsenate (H(2)As(V)O(4)(-)/HAs(V)O(4)(2-)) to arsenite (As(III)(OH)(3)) by a cytosolic enzyme (ArsC; Escherichia coli type arsenate reductase) and subsequent extrusion via ArsB (E. coli type arsenite transporter)/ACR3 (yeast type arsenite transporter). Here, we describe novel fusion proteins consisting of an aquaglyceroporin-derived arsenite channel with a C-terminal arsenate reductase domain of phosphotyrosine-phosphatase origin, providing transposable, single gene-encoded arsenate resistance. The fusion occurred in actinobacteria from soil, Frankia alni, and marine environments, Salinispora tropica; Mycobacterium tuberculosis encodes an analogous ACR3-ArsC fusion. Mutations rendered the aquaglyceroporin channel more polar resulting in lower glycerol permeability and enhanced arsenite selectivity. The arsenate reductase domain couples to thioredoxin and can complement arsenate-sensitive yeast strains. A second isoform with a nonfunctional channel may use the mycothiol/mycoredoxin cofactor pool. These channel enzymes constitute prototypes of a novel concept in metabolism in which a substrate is generated and compartmentalized by the same molecule. Immediate diffusion maintains the dynamic equilibrium and prevents toxic accumulation of metabolites in an energy-saving fashion. PMID:20947511

  13. Novel Channel Enzyme Fusion Proteins Confer Arsenate Resistance*

    PubMed Central

    Wu, Binghua; Song, Jie; Beitz, Eric

    2010-01-01

    Steady exposure to environmental arsenic has led to the evolution of vital cellular detoxification mechanisms. Under aerobic conditions, a two-step process appears most common among microorganisms involving reduction of predominant, oxidized arsenate (H2AsVO4−/HAsVO42−) to arsenite (AsIII(OH)3) by a cytosolic enzyme (ArsC; Escherichia coli type arsenate reductase) and subsequent extrusion via ArsB (E. coli type arsenite transporter)/ACR3 (yeast type arsenite transporter). Here, we describe novel fusion proteins consisting of an aquaglyceroporin-derived arsenite channel with a C-terminal arsenate reductase domain of phosphotyrosine-phosphatase origin, providing transposable, single gene-encoded arsenate resistance. The fusion occurred in actinobacteria from soil, Frankia alni, and marine environments, Salinispora tropica; Mycobacterium tuberculosis encodes an analogous ACR3-ArsC fusion. Mutations rendered the aquaglyceroporin channel more polar resulting in lower glycerol permeability and enhanced arsenite selectivity. The arsenate reductase domain couples to thioredoxin and can complement arsenate-sensitive yeast strains. A second isoform with a nonfunctional channel may use the mycothiol/mycoredoxin cofactor pool. These channel enzymes constitute prototypes of a novel concept in metabolism in which a substrate is generated and compartmentalized by the same molecule. Immediate diffusion maintains the dynamic equilibrium and prevents toxic accumulation of metabolites in an energy-saving fashion. PMID:20947511

  14. Urocanate reductase: identification of a novel anaerobic respiratory pathway in Shewanella oneidensis MR-1.

    PubMed

    Bogachev, Alexander V; Bertsova, Yulia V; Bloch, Dmitry A; Verkhovsky, Michael I

    2012-12-01

    Interpretation of the constantly expanding body of genomic information requires that the function of each gene be established. Here we report the genomic analysis and structural modelling of a previously uncharacterized redox-metabolism protein UrdA (SO_4620) of Shewanella oneidensis MR-1, which led to a discovery of the novel enzymatic activity, urocanate reductase. Further cloning and expression of urdA, as well as purification and biochemical study of the gene's product UrdA and redox titration of its prosthetic groups confirmed that the latter is indeed a flavin-containing enzyme catalysing the unidirectional reaction of two-electron reduction of urocanic acid to deamino-histidine, an activity not reported earlier. UrdA exhibits both high substrate affinity and high turnover rate (K(m)  < 10 μM, k(cat)  = 360 s(-1) ) and strong specificity in favour of urocanic acid. UrdA homologues are present in various bacterial genera, such as Shewanella, Fusobacterium and Clostridium, the latter including the human pathogen Clostridium tetani. The UrdA activity in S. oneidensis is induced by its substrate under anaerobic conditions and it enables anaerobic growth with urocanic acid as a sole terminal electron acceptor. The latter capability can provide the cells of UrdA-containing bacteria with a niche where no other bacteria can compete and survive. PMID:23078170

  15. RNA-seq analyses reveal insights into the function of respiratory nitrate reductase of the diazotroph Herbaspirillum seropedicae.

    PubMed

    Bonato, Paloma; Batista, Marcelo B; Camilios-Neto, Doumit; Pankievicz, Vânia C S; Tadra-Sfeir, Michelle Z; Monteiro, Rose Adele; Pedrosa, Fabio O; Souza, Emanuel M; Chubatsu, Leda S; Wassem, Roseli; Rigo, Liu Un

    2016-09-01

    Herbaspirillum seropedicae is a nitrogen-fixing β-proteobacterium that associates with roots of gramineous plants. In silico analyses revealed that H. seropedicae genome has genes encoding a putative respiratory (NAR) and an assimilatory nitrate reductase (NAS). To date, little is known about nitrate metabolism in H. seropedicae, and, as this bacterium cannot respire nitrate, the function of NAR remains unknown. This study aimed to investigate the function of NAR in H. seropedicae and how it metabolizes nitrate in a low aerated-condition. RNA-seq transcriptional profiling in the presence of nitrate allowed us to pinpoint genes important for nitrate metabolism in H. seropedicae, including nitrate transporters and regulatory proteins. Additionally, both RNA-seq data and physiological characterization of a mutant in the catalytic subunit of NAR (narG mutant) showed that NAR is not required for nitrate assimilation but is required for: (i) production of high levels of nitrite, (ii) production of NO and (iii) dissipation of redox power, which in turn lead to an increase in carbon consumption. In addition, wheat plants showed an increase in shoot dry weight only when inoculated with H. seropedicae wild type, but not with the narG mutant, suggesting that NAR is important to H. seropedicae-wheat interaction. PMID:27322548

  16. Substrate-dependent modulation of the enzymatic catalytic activity: reduction of nitrate, chlorate and perchlorate by respiratory nitrate reductase from Marinobacter hydrocarbonoclasticus 617.

    PubMed

    Marangon, Jacopo; Paes de Sousa, Patrícia M; Moura, Isabel; Brondino, Carlos D; Moura, José J G; González, Pablo J

    2012-07-01

    The respiratory nitrate reductase complex (NarGHI) from Marinobacter hydrocarbonoclasticus 617 (Mh, formerly Pseudomonas nautica 617) catalyzes the reduction of nitrate to nitrite. This reaction is the first step of the denitrification pathway and is coupled to the quinone pool oxidation and proton translocation to the periplasm, which generates the proton motive force needed for ATP synthesis. The Mh NarGH water-soluble heterodimer has been purified and the kinetic and redox properties have been studied through in-solution enzyme kinetics, protein film voltammetry and spectropotentiometric redox titration. The kinetic parameters of Mh NarGH toward substrates and inhibitors are consistent with those reported for other respiratory nitrate reductases. Protein film voltammetry showed that at least two catalytically distinct forms of the enzyme, which depend on the applied potential, are responsible for substrate reduction. These two forms are affected differentially by the oxidizing substrate, as well as by pH and inhibitors. A new model for the potential dependence of the catalytic efficiency of Nars is proposed. PMID:22561116

  17. ArxA, a new clade of arsenite oxidase within the DMSO reductase family of molybdenum oxidoreductases

    USGS Publications Warehouse

    Zargar, Kamrun; Conrad, Alison; Bernick, David L.; Lowe, Todd M.; Stolc, Viktor; Hoeft, Shelley; Oremland, Ronald S.; Stolz, John; Saltikov, Chad W.

    2012-01-01

    Arsenotrophy, growth coupled to autotrophic arsenite oxidation or arsenate respiratory reduction, occurs only in the prokaryotic domain of life. The enzymes responsible for arsenotrophy belong to distinct clades within the DMSO reductase family of molybdenum-containing oxidoreductases: specifically arsenate respiratory reductase, ArrA, and arsenite oxidase, AioA (formerly referred to as AroA and AoxB). A new arsenite oxidase clade, ArxA, represented by the haloalkaliphilic bacterium Alkalilimnicola ehrlichii strain MLHE-1 was also identified in the photosynthetic purple sulfur bacterium Ectothiorhodospira sp. strain PHS-1. A draft genome sequence of PHS-1 was completed and an arx operon similar to MLHE-1 was identified. Gene expression studies showed that arxA was strongly induced with arsenite. Microbial ecology investigation led to the identification of additional arxA-like sequences in Mono Lake and Hot Creek sediments, both arsenic-rich environments in California. Phylogenetic analyses placed these sequences as distinct members of the ArxA clade of arsenite oxidases. ArxA-like sequences were also identified in metagenome sequences of several alkaline microbial mat environments of Yellowstone National Park hot springs. These results suggest that ArxA-type arsenite oxidases appear to be widely distributed in the environment presenting an opportunity for further investigations of the contribution of Arx-dependent arsenotrophy to the arsenic biogeochemical cycle.

  18. Structures of reduced and ligand-bound nitric oxide reductase provide insights into functional differences in respiratory enzymes.

    PubMed

    Sato, Nozomi; Ishii, Shoko; Sugimoto, Hiroshi; Hino, Tomoya; Fukumori, Yoshihiro; Sako, Yoshihiko; Shiro, Yoshitsugu; Tosha, Takehiko

    2014-07-01

    Nitric oxide reductase (NOR) catalyzes the generation of nitrous oxide (N2O) via the reductive coupling of two nitric oxide (NO) molecules at a heme/non-heme Fe center. We report herein on the structures of the reduced and ligand-bound forms of cytochrome c-dependent NOR (cNOR) from Pseudomonas aeruginosa at a resolution of 2.3-2.7 Å, to elucidate structure-function relationships in NOR, and compare them to those of cytochrome c oxidase (CCO) that is evolutionarily related to NOR. Comprehensive crystallographic refinement of the CO-bound form of cNOR suggested that a total of four atoms can be accommodated at the binuclear center. Consistent with this, binding of bulky acetaldoxime (CH3-CH=N-OH) to the binuclear center of cNOR was confirmed by the structural analysis. Active site reduction and ligand binding in cNOR induced only ∼0.5 Å increase in the heme/non-heme Fe distance, but no significant structural change in the protein. The highly localized structural change is consistent with the lack of proton-pumping activity in cNOR, because redox-coupled conformational changes are thought to be crucial for proton pumping in CCO. It also permits the rapid decomposition of cytotoxic NO in denitrification. In addition, the shorter heme/non-heme Fe distance even in the bulky ligand-bound form of cNOR (∼4.5 Å) than the heme/Cu distance in CCO (∼5 Å) suggests the ability of NOR to maintain two NO molecules within a short distance in the confined space of the active site, thereby facilitating N-N coupling to produce a hyponitrite intermediate for the generation of N2O. PMID:24338896

  19. Bacillus macyae sp. nov., an arsenate-respiring bacterium isolated from an Australian gold mine.

    PubMed

    Santini, Joanne M; Streimann, Illo C A; vanden Hoven, Rachel N

    2004-11-01

    A strictly anaerobic arsenate-respiring bacterium isolated from a gold mine in Bendigo, Victoria, Australia, belonging to the genus Bacillus is described. Cells are Gram-positive, motile rods capable of respiring with arsenate and nitrate as terminal electron acceptors using a variety of substrates, including acetate as the electron donor. Reduction of arsenate to arsenite is catalysed by a membrane-bound arsenate reductase that displays activity over a broad pH range. Synthesis of the enzyme is regulated; maximal activity is obtained when the organism is grown with arsenate as the terminal electron acceptor and no activity is detectable when it is grown with nitrate. Mass of the catalytic subunit was determined to be approximately 87 kDa based on ingel activity stains. The closest phylogenetic relative, based on 16S rRNA gene sequence analysis, is Bacillus arseniciselenatis, but DNA-DNA hybridization experiments clearly show that strain JMM-4(T) represents a novel Bacillus species, for which the name Bacillus macyae sp. nov. is proposed. The type strain is JMM-4(T) (=DSM 16346(T)=JCM 12340(T)). PMID:15545465

  20. Release of Arsenic from Soil by a Novel Dissimilatory Arsenate-Reducing Bacterium, Anaeromyxobacter sp. Strain PSR-1

    PubMed Central

    Kudo, Keitaro; Yamaguchi, Noriko; Makino, Tomoyuki; Ohtsuka, Toshihiko; Kimura, Kenta; Dong, Dian Tao

    2013-01-01

    A novel arsenate-reducing bacterium, designated strain PSR-1, was isolated from arsenic-contaminated soil. Strain PSR-1 was phylogenetically closely related to Anaeromyxobacter dehalogenans 2CP-1T with 16S rRNA gene similarity of 99.7% and coupled the oxidation of acetate with the reduction of arsenate. Arsenate reduction was inhibited almost completely by respiratory inhibitors such as dicumarol and 2-heptyl-4-hydroxyquinoline N-oxide. Strain PSR-1 also utilized soluble Fe(III), ferrihydrite, nitrate, oxygen, and fumarate as electron acceptors. Strain PSR-1 catalyzed the release of arsenic from arsenate-adsorbed ferrihydrite. In addition, inoculation of washed cells of strain PSR-1 into sterilized soil successfully reproduced arsenic release. Arsenic K-edge X-ray absorption near-edge structure (XANES) analysis revealed that the proportion of arsenite in the soil solid phase actually increased from 20% to 50% during incubation with washed cells of strain PSR-1. These results suggest that strain PSR-1 is capable of reducing not only dissolved arsenate but also arsenate adsorbed on the soil mineral phase. Arsenate reduction by strain PSR-1 expands the metabolic versatility of Anaeromyxobacter dehalogenans. Considering its distribution throughout diverse soils and anoxic sediments, Anaeromyxobacter dehalogenans may play a role in arsenic release from these environments. PMID:23709511

  1. Arsenate adsorption by unsaturated alluvial sediments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arsenate adsorption as a function of solution arsenic concentration and solution pH was investigated on five alluvial sediments from the Antelope Valley, Western Mojave Desert, California. Arsenate adsorption increased with increasing solution pH, exhibited a maximum around pH 4 to 5, and then decr...

  2. Phytochelatins are involved in differential arsenate tolerance in Holcus lanatus.

    PubMed

    Hartley-Whitaker, J; Ainsworth, G; Vooijs, R; Ten Bookum, W; Schat, H; Meharg, A A

    2001-05-01

    Arsenate tolerance is conferred by suppression of the high-affinity phosphate/arsenate uptake system, which greatly reduces arsenate influx in a number of higher plant species. Despite this suppressed uptake, arsenate-tolerant plants can still accumulate high levels of As over their lifetime, suggesting that constitutive detoxification mechanisms may be required. Phytochelatins are thiol-rich peptides, whose production is induced by a range of metals and metalloids including arsenate. This study provides evidence for the role of phytochelatins in the detoxification of arsenate in arsenate-tolerant Holcus lanatus. Elevated levels of phytochelatin were measured in plants with a range of tolerance to arsenate at equivalent levels of arsenate stress, measured as inhibition of root growth. The results suggest that arsenate tolerance in H. lanatus requires both adaptive suppression of the high-affinity phosphate uptake system and constitutive phytochelatin production. PMID:11351093

  3. Nitrate and periplasmic nitrate reductases

    PubMed Central

    Sparacino-Watkins, Courtney; Stolz, John F.; Basu, Partha

    2014-01-01

    The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types – periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed. PMID:24141308

  4. A novel pathway of arsenate detoxification.

    PubMed

    Zhao, Fang-Jie

    2016-06-01

    Microorganisms have evolved various mechanisms to detoxify arsenic, an ubiquitous environmental toxin. Known mechanisms include arsenite efflux, arsenate reduction followed by arsenite efflux and arsenite methylation. In this issue, Chen et al. describe a novel mechanism for arsenate detoxification via synergistic interaction of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a major facilitator superfamily protein (ArsJ). They propose that GAPDH catalyzes the formation of 1-arseno-3-phosphoglycerate, which is then extruded out of the cell by ArsJ. The significance of this pathway and questions for further research are discussed. PMID:27072877

  5. Dissolution of Arsenic Minerals Mediated by Dissimilatory Arsenate Reducing Bacteria: Estimation of the Physiological Potential for Arsenic Mobilization

    PubMed Central

    Lukasz, Drewniak; Liwia, Rajpert; Aleksandra, Mantur; Aleksandra, Sklodowska

    2014-01-01

    The aim of this study was characterization of the isolated dissimilatory arsenate reducing bacteria in the context of their potential for arsenic removal from primary arsenic minerals through reductive dissolution. Four strains, Shewanella sp. OM1, Pseudomonas sp. OM2, Aeromonas sp. OM4, and Serratia sp. OM17, capable of anaerobic growth with As (V) reduction, were isolated from microbial mats from an ancient gold mine. All of the isolated strains: (i) produced siderophores that promote dissolution of minerals, (ii) were resistant to dissolved arsenic compounds, (iii) were able to use the dissolved arsenates as the terminal electron acceptor, and (iii) were able to use copper minerals containing arsenic minerals (e.g., enargite) as a respiratory substrate. Based on the results obtained in this study, we postulate that arsenic can be released from some As-bearing polymetallic minerals (such as copper ore concentrates or middlings) under reductive conditions by dissimilatory arsenate reducers in indirect processes. PMID:24724102

  6. Dissolution of arsenic minerals mediated by dissimilatory arsenate reducing bacteria: estimation of the physiological potential for arsenic mobilization.

    PubMed

    Lukasz, Drewniak; Liwia, Rajpert; Aleksandra, Mantur; Aleksandra, Sklodowska

    2014-01-01

    The aim of this study was characterization of the isolated dissimilatory arsenate reducing bacteria in the context of their potential for arsenic removal from primary arsenic minerals through reductive dissolution. Four strains, Shewanella sp. OM1, Pseudomonas sp. OM2, Aeromonas sp. OM4, and Serratia sp. OM17, capable of anaerobic growth with As (V) reduction, were isolated from microbial mats from an ancient gold mine. All of the isolated strains: (i) produced siderophores that promote dissolution of minerals, (ii) were resistant to dissolved arsenic compounds, (iii) were able to use the dissolved arsenates as the terminal electron acceptor, and (iii) were able to use copper minerals containing arsenic minerals (e.g., enargite) as a respiratory substrate. Based on the results obtained in this study, we postulate that arsenic can be released from some As-bearing polymetallic minerals (such as copper ore concentrates or middlings) under reductive conditions by dissimilatory arsenate reducers in indirect processes. PMID:24724102

  7. Arsenate Resistance in the Unicellular Marine Diazotroph Crocosphaera watsonii

    PubMed Central

    Dyhrman, Sonya T.; Haley, Sheean T.

    2011-01-01

    The toxic arsenate ion can behave as a phosphate analog, and this can result in arsenate toxicity especially in areas with elevated arsenate to phosphate ratios like the surface waters of the ocean gyres. In these systems, cellular arsenate resistance strategies would allow phytoplankton to ameliorate the effects of arsenate transport into the cell. Despite the potential coupling between arsenate and phosphate cycling in oligotrophic marine waters, relatively little is known about arsenate resistance in the nitrogen-fixing marine cyanobacteria that are key components of the microbial community in low nutrient systems. The unicellular diazotroph, Crocosphaera watsonii WH8501, was able to grow at reduced rates with arsenate additions up to 30 nM, and estimated arsenate to phosphate ratios of 6:1. The genome of strain WH8501 contains homologs for arsA, arsH, arsB, and arsC, allowing for the reduction of arsenate to arsenite and the pumping of arsenite out of the cell. The short-term addition of arsenate to the growth medium had no effect on nitrogen fixation. However, arsenate addition did result in the up-regulation of the arsB gene with increasing arsenate concentrations, indicating the induction of the arsenate detoxification response. The arsB gene was also up-regulated by phosphorus stress in concert with a gene encoding the high-affinity phosphate binding protein pstS. Both genes were down-regulated when phosphate was re-fed to phosphorus-stressed cells. A field survey of surface water from the low phosphate western North Atlantic detected expression of C. watsonii arsB, suggestive of the potential importance of arsenate resistance strategies in this and perhaps other systems. PMID:22046174

  8. Interactions of arsenate and phenols in aqueous media

    SciTech Connect

    Huyck, K.A.; Daniel, S.R.; Macalady, D.L. )

    1989-01-01

    Arsenate is used in a number of environmental applications, including as an herbicide and in wood treatment. Phenols such as pentachlorophenol are also used in certain pesticide and herbicide applications and as wood preservatives. Although phenols in general are only slightly soluble in water at natural pH, arsenates are very soluble. They have investigated the interaction between arsenate and phenols with particular attention to adducts or complexes which may be significant under environmental conditions. Arsenate has been reported to form esters analogous to phosphate esters with sugars. Arsenate-phenol interactions were studied using UV spectrophotometry, potentiometry and liquid chromatography.

  9. Arsenolysis and Thiol-Dependent Arsenate Reduction

    EPA Science Inventory

    Conversion of arsenate to arsenite is a critical event in the pathway that leads from inorganic arsenic to a variety of methylated metabolites. The formation of methylated metabolites influences distribution and retention of arsenic and affects the reactivity and toxicity of thes...

  10. Sorption and desorption of arsenate and arsenite on calcite

    NASA Astrophysics Data System (ADS)

    Sø, Helle U.; Postma, Dieke; Jakobsen, Rasmus; Larsen, Flemming

    2008-12-01

    The adsorption and desorption of arsenate (As(V)) and arsenite (As(III)) on calcite was investigated in a series of batch experiments in calcite-equilibrated solutions. The solutions covered a broad range of pH, alkalinity, calcium concentration and ionic strength. The initial arsenic concentrations were kept low (<33 μM) to avoid surface precipitation. The results show that little or no arsenite sorbs on calcite within 24 h at an initial As concentration of 0.67 μM. In contrast, arsenate sorbs readily and quickly on calcite. Likewise, desorption of arsenate from calcite is fast and complete within hours, indicating that arsenate is not readily incorporated into the calcite crystal lattice. The degree of arsenate sorption depends on the solution chemistry. Sorption increases with decreasing alkalinity, indicating a competition for sorption sites between arsenate and (bi)carbonate. pH also affects the sorption behavior, likely in response to changes in arsenate speciation or protonation/deprotonation of the adsorbing arsenate ion. Finally, sorption is influenced by the ionic strength, possibly due to electrostatic effects. The sorption of arsenate on calcite was modeled successfully using a surface complexation model comprising strong and weak sites. In the model, the adsorbing arsenate species were HAsO4- and CaHAsO40. The model was able to correctly predict the adsorption of arsenate in the wide range of calcite-equilibrated solutions used in the batch experiments and to describe the non-linear shape of the sorption isotherms. Extrapolation of the experimental results to calcite bearing aquifers suggests a large variability in the mobility of arsenic. Under reduced conditions, arsenite, which does not sorb on calcite, will dominate and, hence, As will be highly mobile. In contrast, when conditions are oxidizing, arsenate is the predominant species and, because arsenate adsorbs strongly on calcite, As mobility will be significantly retarded. The estimated

  11. Understanding Arsenate Reaction Kinetics with Ferric Hydroxides

    PubMed Central

    Farrell, James; Chaudhary, Binod K.

    2015-01-01

    Understanding arsenic reactions with ferric hydroxides is important in understanding arsenic transport in the environment and in designing systems for removing arsenic from potable water. Many experimental studies have shown that the kinetics of arsenic adsorption on ferric hydroxides is biphasic, where a fraction of the arsenic adsorption occurs on a time scale of seconds while full equilibrium may require weeks to attain. This research employed density functional theory modeling in order to understand the mechanisms contributing to biphasic arsenic adsorption kinetics. The reaction energies and activation barriers for three modes of arsenate adsorption to ferric hydroxides were calculated. Gibbs free energies of reaction depended on the net charge of the complexes, which is a function of the system pH value. Physical adsorption of arsenate to ferric hydroxide proceeded with no activation barrier, with Gibbs free energies of reaction ranging from −21 to −58 kJ/mol. The highest Gibbs free energies of reaction for physical adsorption resulted from negative charge assisted hydrogen bonding between H atoms on the ferric hydroxide and O atoms in arsenate. The conversion of physically adsorbed arsenate into monodentate surface complexes had Gibbs free energies of activation ranging from 62 to 73 kJ/mol, and Gibbs free energies of reaction ranging from −23 to −38 kJ/mol. The conversion of monodentate surface complexes to bidentate, binuclear complexes had Gibbs free energies of activation ranging from 79 to 112 kJ/mol, and Gibbs free energies of reaction ranging from −11 to −55 kJ/mol. For release of arsenate from uncharged bidentate complexes, energies of activation as high as 167 kJ/mol were encountered. Increasingly negative charges on the complexes lowered the activation barriers for desorption of arsenate, and in complexes with −2 charges, the highest activation barrier was 65 kJ/mol. This study shows that the slow kinetics associated with arsenic

  12. Thioredoxin reductase.

    PubMed

    Mustacich, D; Powis, G

    2000-02-15

    The mammalian thioredoxin reductases (TrxRs) are a family of selenium-containing pyridine nucleotide-disulphide oxidoreductases with mechanistic and sequence identity, including a conserved -Cys-Val-Asn-Val-Gly-Cys- redox catalytic site, to glutathione reductases. TrxRs catalyse the NADPH-dependent reduction of the redox protein thioredoxin (Trx), as well as of other endogenous and exogenous compounds. The broad substrate specificity of mammalian TrxRs is due to a second redox-active site, a C-terminal -Cys-SeCys- (where SeCys is selenocysteine), that is not found in glutathione reductase or Escherichia coli TrxR. There are currently two confirmed forms of mammalian TrxRs, TrxR1 and TrxR2, and it is possible that other forms will be identified. The availability of Se is a key factor determining TrxR activity both in cell culture and in vivo, and the mechanism(s) for the incorporation of Se into TrxRs, as well as the regulation of TrxR activity, have only recently begun to be investigated. The importance of Trx to many aspects of cell function make it likely that TrxRs also play a role in protection against oxidant injury, cell growth and transformation, and the recycling of ascorbate from its oxidized form. Since TrxRs are able to reduce a number of substrates other than Trx, it is likely that additional biological effects will be discovered for TrxR. Furthermore, inhibiting TrxR with drugs may lead to new treatments for human diseases such as cancer, AIDS and autoimmune diseases. PMID:10657232

  13. Dissimilatory arsenate and sulfate reduction in sediments of two hypersaline, arsenic-rich soda lakes: Mono and Searles Lakes, California

    USGS Publications Warehouse

    Kulp, T.R.; Hoeft, S.E.; Miller, L.G.; Saltikov, C.; Murphy, J.N.; Han, S.; Lanoil, B.; Oremland, R.S.

    2006-01-01

    A radioisotope method was devised to study bacterial respiratory reduction of arsenate in sediments. The following two arsenic-rich soda lakes in California were chosen for comparison on the basis of their different salinities: Mono Lake (???90 g/liter) and Searles Lake (???340 g/liter). Profiles of arsenate reduction and sulfate reduction were constructed for both lakes. Reduction of [73As] arsenate occurred at all depth intervals in the cores from Mono Lake (rate constant [k] = 0.103 to 0.04 h-1) and Searles Lake (k = 0.012 to 0.002 h-1), and the highest activities occurred in the top sections of each core. In contrast, [35S] sulfate reduction was measurable in Mono Lake (k = 7.6 ?? 104 to 3.2 ?? 10-6 h-1) but not in Searles Lake. Sediment DNA was extracted, PCR amplified, and separated by denaturing gradient gel electrophoresis (DGGE) to obtain phylogenetic markers (i.e., 16S rRNA genes) and a partial functional gene for dissimilatory arsenate reduction (arrA). The amplified arrA gene product showed a similar trend in both lakes; the signal was strongest in surface sediments and decreased to undetectable levels deeper in the sediments. More arrA gene signal was observed in Mono Lake and was detectable at a greater depth, despite the higher arsenate reduction activity observed in Searles Lake. A partial sequence (about 900 bp) was obtained for a clone (SLAS-3) that matched the dominant DGGE band found in deeper parts of the Searles Lake sample (below 3 cm), and this clone was found to be closely related to SLAS-1, a novel extremophilic arsenate respirer previously cultivated from Searles Lake. Copyright ?? 2006, American Society for Microbiology. All Rights Reserved.

  14. Life cycle exposure of the frog Silurana tropicalis to arsenate: Steroid- and thyroid hormone-related genes are differently altered throughout development.

    PubMed

    Gibson, Laura A; Koch, Iris; Reimer, Kenneth J; Cullen, William R; Langlois, Valerie S

    2016-08-01

    Arsenic contaminates water surface and groundwater worldwide. Several studies have suggested that arsenic acts as an endocrine disruptor in mammalian and non-mammalian species, although its chronic effect during development remains largely unknown. To address this question, life cycle exposures to 0, 0.3 and 0.8ppm of arsenate (pentavalent arsenic; As(V)) were performed in the Western clawed frog (Silurana tropicalis) from the gastrulae stage (developmental stage Nieuwkoop-Faber; NF12) until metamorphosis (NF66). Tissue samples were collected at the beginning of feeding (NF46; whole body), sexual development (NF56; liver), and at metamorphosis completion (NF66; liver and gonadal mesonephros complex). Real-time RT-PCR analysis quantified decreases in mRNA levels of genes related to estrogen- (estrogen receptor alpha and aromatase), androgen- (androgen receptor and steroid 5-alpha-reductase type 2), and cholesterol metabolism- (steroidogenic acute regulatory protein) at stage NF46. Similarly, arsenate decreased steroid 5-alpha-reductase type 2 expression in stage NF56 livers, but transcript increases were observed for both estrogen receptor alpha and steroidogenic acute regulatory protein at this stage. Given the changes observed in the expression of genes essential for proper sexual development, gonadal histological analysis was carried out in stage NF66 animals. Arsenate treatments did not alter sex ratio or produce testicular oocytes. On the other hand, arsenate interfered with thyroid hormone-related transcripts at NF66. Specifically, thyroid hormone receptor beta and deiodinase type 2 mRNA levels were significantly reduced after arsenate treatment in the gonadal mesonephros complex. This reduction in thyroid hormone-related gene expression, however, was not accompanied by any morphological changes measured. In summary, environmentally relevant concentrations of As(V) altered steroidogenesis-, sex steroid signaling- and thyroid hormone-related gene expression

  15. Applicability of poorly crystalline aluminum oxide for adsorption of arsenate.

    PubMed

    Park, Youn-Jong; Yang, Jae-Kyu; Lee, Seung-Mok; Choi, Sang-Il

    2011-01-01

    This study examined the characteristics of arsenate adsorption on poorly crystalline oxide (PCAO) which was obtained from recycling of dry sanding powders (DSP) produced during sanding and sawing process in a decorative interior company. After calcinating DSP at 550°C, poorly crystalline oxide (PCAO) was obtained as an adsorbent. From the batch adsorption experiments, arsenate was completely removed up to the concentration of 10 mg/L by PCAO. The stability of PCAO as an adsorbent was evaluated at pH 7 and found that the arsenate adsorbed on PCAO was stable for 24 h. The predominant interaction between arsenate and PCAO was thought to be a strong chemical bond by spectroscopic analysis. The arsenate adsorption behavior onto PCAO was satisfactorily simulated with MINEQL+, suggesting that arsenate formed inner-sphere complexes with the surface of PCAO by chemisorption. Meanwhile, the presence of competitive anions such as PO(4) (3-), SO(4) (2-) and CO(3) (2-) decreased somewhat the removal efficiency of arsenate and the effects of competing anions on the adsorption of arsenate were in the order of PO(4) (3-) > SO(4) (2-) > CO(3) (2-) under pH 6. The application of PCAO to the real mine drainage was also carried out. Although the adsorption of arsenic on the PCAO was slightly decreased rather than that removed from synthetic wastewater due to competitive sorption by multiple ions, it was possible to meet the national discharge standard limit with increasing adsorbent concentration. PMID:21942390

  16. Mobilization of arsenite by dissimilatory reduction of adsorbed arsenate

    USGS Publications Warehouse

    Zobrist, J.; Dowdle, P.R.; Davis, J.A.; Oremland, R.S.

    2000-01-01

    Sulfurospirillum barnesii is capable of anaerobic growth using ferric iron or arsenate as electron acceptors. Cell suspensions of S. barnesii were able to reduce arsenate to arsenite when the former oxyanion was dissolved in solution, or when it was adsorbed onto the surface of ferrihydrite, a common soil mineral, by a variety of mechanisms (e.g., coprecipitation, presorption). Reduction of Fe(III) in ferrihydrite to soluble Fe(II) also occurred, but dissolution of ferrihydrite was not required in order for adsorbed arsenate reduction to be achieved. This was illustrated by bacterial reduction of arsenate coprecipitated with aluminum hydroxide, a mineral that does not undergo reductive dissolution. The rate of arsenate reduction was influenced by the method in which arsenate became associated with the mineral phases and may have been strongly coupled with arsenate desorption rates. The extent of release of arsenite into solution was governed by adsorption of arsenite onto the ferrihydrite or alumina phases. The results of these experiments have interpretive significance to the mobilization of arsenic in large alluvial aquifers, such as those of the Ganges in India and Bangladesh, and in the hyporheic zones of contaminated streams.Sulfurospirillum barnesii is capable of anaerobic growth using ferric iron or arsenate as electron acceptors. Cell suspensions of S. barnesii were able to reduce arsenate to arsenite when the former oxyanion was dissolved in solution, or when it was adsorbed onto the surface of ferrihydrite a common soil mineral, by a variety of mechanisms (e.g., coprecipitation, presorption). Reduction of Fe(III) in ferrihydrite to soluble Fe(II) also occurred, but dissolution of ferrihydrite was not required in order for adsorbed arsenate reduction to be achieved. This was illustrated by bacterial reduction of arsenate coprecipitated with aluminum hydroxide, a mineral that does not undergo reductive dissolution. The rate of arsenate reduction was

  17. Investigation of biochemical responses of Bacopa monnieri L. upon exposure to arsenate.

    PubMed

    Mishra, Seema; Srivastava, Sudhakar; Dwivedi, Sanjay; Tripathi, Rudra Deo

    2013-08-01

    Widespread contamination of arsenic (As) is recognized as a global problem due to its well-known accumulation by edible and medicinal plants and associated health risks for the humans. In this study, phytotoxicity imposed upon exposure to arsenate [As(V); 0-250 μM for 1-7 days] and ensuing biochemical responses were investigated in a medicinal herb Bacopa monnieri L. vis-à-vis As accumulation. Plants accumulated substantial amount of As (total 768 μg g(-1) dw at 250 μM As(V) after 7 days) with the maximum As retention being in roots (60%) followed by stem (23%) and leaves (17%). The level of cysteine and total nonprotein thiols (NP-SH) increased significantly at all exposure concentrations and durations. Besides, the level of metalloid binding ligands viz., glutathione (GSH) and phytochelatins (PCs) increased significantly at the studied concentrations [50 and 250 μM As(V)] in both roots and leaves. The activities of various enzymes viz., arsenate reductase (AR), glutathione reductase (GR), superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), and catalase (CAT) showed differential but coordinated stimulation in leaves and roots to help plants combat As toxicity up to moderate exposure concentrations (50 μM). However, beyond 50 μM, biomass production was found to decrease along with photosynthetic pigments and total soluble proteins, whereas lipid peroxidation increased. In conclusion, As accumulation potential of Bacopa may warrant its use as a phytoremediator but if Bacopa growing in contaminated areas is consumed by humans, it may prove to be toxic for health. PMID:21656644

  18. Phytochelatins Are Involved in Differential Arsenate Tolerance in Holcus lanatus1

    PubMed Central

    Hartley-Whitaker, Jeanette; Ainsworth, Gillian; Vooijs, Riet; Bookum, Wilma Ten; Schat, Henk; Meharg, Andrew A.

    2001-01-01

    Arsenate tolerance is conferred by suppression of the high-affinity phosphate/arsenate uptake system, which greatly reduces arsenate influx in a number of higher plant species. Despite this suppressed uptake, arsenate-tolerant plants can still accumulate high levels of As over their lifetime, suggesting that constitutive detoxification mechanisms may be required. Phytochelatins are thiol-rich peptides, whose production is induced by a range of metals and metalloids including arsenate. This study provides evidence for the role of phytochelatins in the detoxification of arsenate in arsenate-tolerant Holcus lanatus. Elevated levels of phytochelatin were measured in plants with a range of tolerance to arsenate at equivalent levels of arsenate stress, measured as inhibition of root growth. The results suggest that arsenate tolerance in H. lanatus requires both adaptive suppression of the high-affinity phosphate uptake system and constitutive phytochelatin production. PMID:11351093

  19. WRKY6 Transcription Factor Restricts Arsenate Uptake and Transposon Activation in Arabidopsis[W

    PubMed Central

    Castrillo, Gabriel; Sánchez-Bermejo, Eduardo; de Lorenzo, Laura; Crevillén, Pedro; Fraile-Escanciano, Ana; TC, Mohan; Mouriz, Alfonso; Catarecha, Pablo; Sobrino-Plata, Juan; Olsson, Sanna; Leo del Puerto, Yolanda; Mateos, Isabel; Rojo, Enrique; Hernández, Luis E.; Jarillo, Jose A.; Piñeiro, Manuel; Paz-Ares, Javier; Leyva, Antonio

    2013-01-01

    Stress constantly challenges plant adaptation to the environment. Of all stress types, arsenic was a major threat during the early evolution of plants. The most prevalent chemical form of arsenic is arsenate, whose similarity to phosphate renders it easily incorporated into cells via the phosphate transporters. Here, we found that arsenate stress provokes a notable transposon burst in plants, in coordination with arsenate/phosphate transporter repression, which immediately restricts arsenate uptake. This repression was accompanied by delocalization of the phosphate transporter from the plasma membrane. When arsenate was removed, the system rapidly restored transcriptional expression and membrane localization of the transporter. We identify WRKY6 as an arsenate-responsive transcription factor that mediates arsenate/phosphate transporter gene expression and restricts arsenate-induced transposon activation. Plants therefore have a dual WRKY-dependent signaling mechanism that modulates arsenate uptake and transposon expression, providing a coordinated strategy for arsenate tolerance and transposon gene silencing. PMID:23922208

  20. Phosphate transport and arsenate resistance in the cyanobacterium Anabaena variabilis

    SciTech Connect

    Thiel, T.

    1988-03-01

    Cells of the cyanobacterium Anabaena variabilis starved for phosphate for 3 days took up phosphate at about 100 times the rate of unstarved cells.Kinetic data suggested that a new transport system had been induced by starvation for phosphate. The inducible phosphate transport system was quickly repressed by addition of P/sub i/. Phosphate-starved cells were more sensitive to the toxic effects of arsenate than were unstarved cells, but phosphate could alleviate some of the toxicity. Arsenate was a noncompetitive inhibitor of phosphate transport; however, the apparent K/sub i/ values were high, particularly for phosphate-replete cells. Preincubation of phosphate-starved cells with arsenate caused subsequent inhibition of phosphate transport, suggesting that intracellular arsenate inhibited phosphate transport. This effect was not seen in phosphate-replete cells.

  1. Arsenic-lipid complex formatinon during the active transport of arsenate in yeast.

    PubMed

    Cerbón, J

    1969-02-01

    In studying formation of an arsenic-lipid complex during the active transport of (74)As-arsenate in yeast, it was found that adaptation of yeast to arsenate resulted in cell populations which showed a deficient inflow of arsenate as compared to the nonadapted yeast. Experiments with both types of cells showed a direct correlation between the arsenate taken up and the amount of As-lipid complex formed. (74)As-arsenate was bound exclusively to the phosphoinositide fraction of the cellular lipids. When arsenate transport was inhibited by dinitrophenol and sodium azide, the formation of the As-lipid complex was also inhibited. Phosphate did not interfere with the arsenate transport at a non-inhibitory concentration of external arsenate (10(-9)m). The As-adapted cells but not the unadapted cells were able to take up phosphate when growing in the presence of 10(-2)m arsenate. PMID:5773018

  2. Arsenic-Lipid Complex Formation During the Active Transport of Arsenate in Yeast

    PubMed Central

    Cerbón, Jorge

    1969-01-01

    In studying formation of an arsenic-lipid complex during the active transport of 74As-arsenate in yeast, it was found that adaptation of yeast to arsenate resulted in cell populations which showed a deficient inflow of arsenate as compared to the nonadapted yeast. Experiments with both types of cells showed a direct correlation between the arsenate taken up and the amount of As-lipid complex formed. 74As-arsenate was bound exclusively to the phosphoinositide fraction of the cellular lipids. When arsenate transport was inhibited by dinitrophenol and sodium azide, the formation of the As-lipid complex was also inhibited. Phosphate did not interfere with the arsenate transport at a non-inhibitory concentration of external arsenate (10−9m). The As-adapted cells but not the unadapted cells were able to take up phosphate when growing in the presence of 10−2m arsenate. PMID:5773018

  3. Expression profiling of Crambe abyssinica under arsenate stress identifies genes and gene networks involved in arsenic metabolism and detoxification

    PubMed Central

    2010-01-01

    Background Arsenic contamination is widespread throughout the world and this toxic metalloid is known to cause cancers of organs such as liver, kidney, skin, and lung in human. In spite of a recent surge in arsenic related studies, we are still far from a comprehensive understanding of arsenic uptake, detoxification, and sequestration in plants. Crambe abyssinica, commonly known as 'abyssinian mustard', is a non-food, high biomass oil seed crop that is naturally tolerant to heavy metals. Moreover, it accumulates significantly higher levels of arsenic as compared to other species of the Brassicaceae family. Thus, C. abyssinica has great potential to be utilized as an ideal inedible crop for phytoremediation of heavy metals and metalloids. However, the mechanism of arsenic metabolism in higher plants, including C. abyssinica, remains elusive. Results To identify the differentially expressed transcripts and the pathways involved in arsenic metabolism and detoxification, C. abyssinica plants were subjected to arsenate stress and a PCR-Select Suppression Subtraction Hybridization (SSH) approach was employed. A total of 105 differentially expressed subtracted cDNAs were sequenced which were found to represent 38 genes. Those genes encode proteins functioning as antioxidants, metal transporters, reductases, enzymes involved in the protein degradation pathway, and several novel uncharacterized proteins. The transcripts corresponding to the subtracted cDNAs showed strong upregulation by arsenate stress as confirmed by the semi-quantitative RT-PCR. Conclusions Our study revealed novel insights into the plant defense mechanisms and the regulation of genes and gene networks in response to arsenate toxicity. The differential expression of transcripts encoding glutathione-S-transferases, antioxidants, sulfur metabolism, heat-shock proteins, metal transporters, and enzymes in the ubiquitination pathway of protein degradation as well as several unknown novel proteins serve as

  4. RATES OF HYDROUS FERRIC OXIDE CRYSTALLIZATION AND THE INFLUENCE ON COPRECIPITATED ARSENATE: JOURNAL ARTICLE

    EPA Science Inventory

    NRMRL-ADA-02101 Ford*, R. Rates of Hydrous Ferric Oxide Crystallization and the Influence on Coprecipitated Arsenate. Environmental Science & Technology 36 (11):2459-2463 (2002). EPA/600/J-02/240. Arsenate coprecipitated with hydrous fer...

  5. ARSENATE CARRIER PRECIPITATION METHOD OF SEPARATING PLUTONIUM FROM NEUTRON IRRADIATED URANIUM AND RADIOACTIVE FISSION PRODUCTS

    DOEpatents

    Thompson, S.G.; Miller, D.R.; James, R.A.

    1961-06-20

    A process is described for precipitating Pu from an aqueous solution as the arsenate, either per se or on a bismuth arsenate carrier, whereby a separation from uranium and fission products, if present in solution, is accomplished.

  6. Shewanella sp. O23S as a Driving Agent of a System Utilizing Dissimilatory Arsenate-Reducing Bacteria Responsible for Self-Cleaning of Water Contaminated with Arsenic

    PubMed Central

    Drewniak, Lukasz; Stasiuk, Robert; Uhrynowski, Witold; Sklodowska, Aleksandra

    2015-01-01

    The purpose of this study was a detailed characterization of Shewanella sp. O23S, a strain involved in arsenic transformation in ancient gold mine waters contaminated with arsenic and other heavy metals. Physiological analysis of Shewanella sp. O23S showed that it is a facultative anaerobe, capable of growth using arsenate, thiosulfate, nitrate, iron or manganite as a terminal electron acceptor, and lactate or citrate as an electron donor. The strain can grow under anaerobic conditions and utilize arsenate in the respiratory process in a broad range of temperatures (10–37 °C), pH (4–8), salinity (0%–2%), and the presence of heavy metals (Cd, Co, Cr, Cu, Mn, Mo, Se, V and Zn). Under reductive conditions this strain can simultaneously use arsenate and thiosulfate as electron acceptors and produce yellow arsenic (III) sulfide (As2S3) precipitate. Simulation of As-removal from water containing arsenate (2.5 mM) and thiosulfate (5 mM) showed 82.5% efficiency after 21 days of incubation at room temperature. Based on the obtained results, we have proposed a model of a microbially mediated system for self-cleaning of mine waters contaminated with arsenic, in which Shewanella sp. O23S is the main driving agent. PMID:26121297

  7. Arsenate precipitation using ferric iron in acidic conditions

    SciTech Connect

    Cadena, F.; Kirk, T.L.

    1995-12-31

    Arsenates (i.e., As(V)) can be removed from aqueous solution by precipitation with ferric iron (i.e., Fe(III)). The chemistry of arsenic acid describes the main properties of arsenates. This triprotic acid resembles the phosphoric acid system. For example, free arsenate ions (i.e., AsO{sub 4}{sup 3-}), like free phosphates, are present in significant concentration at pH values above pK{sub a,3}. On the other hand, the concentration of free ferric iron in solution, Fe{sup 3+}, is limited by ferric hydroxide precipitation and hydroxy complexation under neutral or basic conditions. Fe{sup 3+} is the predominant iron form only under very acidic conditions. Therefore, the absence of either ferric ions or arsenate ligands prevents ferric arsenate (FeAsO{sub 4}) precipitation in extreme pH conditions. Precipitation studies using ferric chloride show that the formation of ferric arsenate in water containing 0.667 mM/L (50 mg/L as As) is favored in the pH range between 3 and 4. Ferric iron dose required to remove arsenic from solution increases with pH in the range of 3 to 10. Sludge production also increases with increasing pH conditions. Optimum ferric iron doses at pH 3 and 4 are 4.8 and 10.0 mM/L, respectively, where the arsenate is removed from solution by 98.72 and 99.68 percent. Corresponding iron requirement to arsenate ratios at these two pH conditions are 7.2 and 15.0. Adverse effects on arsenic removal are observed at pH = 3, where the concentration of applied ferric iron exceeds the optimal dose. This effect is probably due to charge reversal on the surface of the precipitates. Overdosing above the optimal iron concentration at pH = 4 does not reduce treatment efficiency significantly. Presence of sodium chloride in solution at a concentration of 171 mM/L (10,000 mg/L as NaCl) does not impair system performance. However, sodium sulfate at a concentration of 104 mM/L (10,000 mg/L) affects adversely treatment performance.

  8. Dissimilatory arsenate reduction with sulfide as electron donor: Experiments with Mono Lake water and isolation of strain MLMS-1, a chemoautotrophic arsenate respirer

    USGS Publications Warehouse

    Hoeft, S.E.; Kulp, T.R.; Stolz, J.F.; Hollibaugh, J.T.; Oremland, R.S.

    2004-01-01

    Anoxic bottom water from Mono Lake, California, can biologically reduce added arsenate without any addition of electron donors. Of the possible in situ inorganic electron donors present, only sulfide was sufficiently abundant to drive this reaction. We tested the ability of sulfide to serve as an electron donor for arsenate reduction in experiments with lake water. Reduction of arsenate to arsenite occurred simultaneously with the removal of sulfide. No loss of sulfide occurred in controls without arsenate or in sterilized samples containing both arsenate and sulfide. The rate of arsenate reduction in lake water was dependent on the amount of available arsenate. We enriched for a bacterium that could achieve growth with sulfide and arsenate in a defined, mineral medium and purified it by serial dilution. The isolate, strain MLMS-1, is a gram-negative, motile curved rod that grows by oxidizing sulfide to sulfate while reducing arsenate to arsenite. Chemoautotrophy was confirmed by the incorporation of H14CO3- into dark-incubated cells, but preliminary gene probing tests with primers for ribulose-1,5-biphosphate carboxylase/oxygenase did not yield PCR-amplified products. Alignment of 16S rRNA sequences indicated that strain MLMS-1 was in the ??-Proteobacteria, located near sulfate reducers like Desulfobulbus sp. (88 to 90% similarity) but more closely related (97%) to unidentified sequences amplified previously from Mono Lake. However, strain MLMS-1 does not grow with sulfate as its electron acceptor.

  9. Lowered dietary phosphate increases oral bioavailability of arsenate in mice

    EPA Science Inventory

    Arsenate (iAsv), an inorganic oxyanionic species, has physicochemical properties similar to inorganic phosphate (iP). There is evidence that iAsv competes with iP for transmembrane carriers that mediate iP uptake. Thus, it is possible that altered dietary intake of iP could modif...

  10. Epitactic ion-exchange reactions into vanadyl(IV) arsenate

    SciTech Connect

    Martinez-Lara, M.; Bruque, S.; Moreno, L.; Aranda, M.A.G. )

    1991-03-01

    The synthesis, structural characterization, thermal stability, and spectroscopic (IR, UV-vis-diffuse reflectance) properties of three vanadyl arsenates are described. Vanadyl(IV) bis(dihydrogenarsenate), (VO(H{sub 2}AsO{sub 4}){sub 2}) (1), lithium vanadyl arsenate, (Li{sub 4}VO(AsO{sub 4}){sub 2}{center dot}0.5H{sub 2}O) (2), and nickel(II) and lithium vanadyl arsenate, ((Li{sub 2.4}Ni){sub 0.8}VO(AsO{sub 4}){sub 2}{center dot}4H{sub 2}O) (3), have been prepared. (1) Tetragonal ({alpha} = 9.128 {angstrom}; c = 8.128 {angstrom}) is prepared by reduction with isobutanol or ethanol from vanadyl(V) arsenate. (2) Cubic (a = 9.024 {angstrom}) is obtained from (1) by lithium ion-exchange, and (3) tetragonal (a = 9.106 {angstrom}; c = 8.454 {angstrom}) is made from (2) by Ni{sup 2+} ion-exchange. These exchange reactions are epitactic and the overall result is a topotactic transformation.

  11. Arsenate Adsorption On Ruthenium Oxides: A Spectroscopic And Kinetic Investigation

    EPA Science Inventory

    Arsenate adsorption on amorphous (RuO2•1.1H2O) and crystalline (RuO2) ruthenium oxides was evaluated using spectroscopic and kinetic methods to elucidate the adsorption mechanism. Extended X-ray absorption fine structure spectroscopy (EXAFS) was ...

  12. Dielectric and structural properties of ferroelectric betaine arsenate films

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Zaitseva, N. V.; Yurko, E. I.; Svinarev, F. B.

    2014-12-01

    Ferroelectric films of betaine arsenate and partially deuterated betaine arsenate have been grown by evaporation on LiNbO3, α-Al2O3, and NdGaO3 substrates with a preliminarily deposited structure of interdigitated electrodes, as well as on the Al/glass substrate. This paper presents the results of the examination of the block structure of the films in a polarizing microscope, the X-ray diffraction analysis of their crystal structure, and the investigation of the dielectric properties in a measuring field oriented both parallel and perpendicular to the plane of the film. The transition of the films to the ferroelectric state at T = T c is accompanied by anomalies of the capacitance of the structure, an increase in the dielectric loss, and the appearance of dielectric hysteresis loops. The growth of the films from a solution of betaine arsenate in a heavy water leads to an increase in the ferroelectric transition temperature from T c = 119 K in the films without deuterium to T c = 149 K, which corresponds to the degree of deuteration of approximately 60-70%. The dielectric and structural properties of the films are compared with those of the betaine arsenate single crystals and the previously studied films of betaine phosphite and glycine phosphite.

  13. Quinone Reductase 2 Is a Catechol Quinone Reductase

    SciTech Connect

    Fu, Yue; Buryanovskyy, Leonid; Zhang, Zhongtao

    2008-09-05

    The functions of quinone reductase 2 have eluded researchers for decades even though a genetic polymorphism is associated with various neurological disorders. Employing enzymatic studies using adrenochrome as a substrate, we show that quinone reductase 2 is specific for the reduction of adrenochrome, whereas quinone reductase 1 shows no activity. We also solved the crystal structure of quinone reductase 2 in complexes with dopamine and adrenochrome, two compounds that are structurally related to catecholamine quinones. Detailed structural analyses delineate the mechanism of quinone reductase 2 specificity toward catechol quinones in comparison with quinone reductase 1; a side-chain rotational difference between quinone reductase 1 and quinone reductase 2 of a single residue, phenylalanine 106, determines the specificity of enzymatic activities. These results infer functional differences between two homologous enzymes and indicate that quinone reductase 2 could play important roles in the regulation of catecholamine oxidation processes that may be involved in the etiology of Parkinson disease.

  14. Exploring membrane respiratory chains.

    PubMed

    Marreiros, Bruno C; Calisto, Filipa; Castro, Paulo J; Duarte, Afonso M; Sena, Filipa V; Silva, Andreia F; Sousa, Filipe M; Teixeira, Miguel; Refojo, Patrícia N; Pereira, Manuela M

    2016-08-01

    Acquisition of energy is central to life. In addition to the synthesis of ATP, organisms need energy for the establishment and maintenance of a transmembrane difference in electrochemical potential, in order to import and export metabolites or to their motility. The membrane potential is established by a variety of membrane bound respiratory complexes. In this work we explored the diversity of membrane respiratory chains and the presence of the different enzyme complexes in the several phyla of life. We performed taxonomic profiles of the several membrane bound respiratory proteins and complexes evaluating the presence of their respective coding genes in all species deposited in KEGG database. We evaluated 26 quinone reductases, 5 quinol:electron carriers oxidoreductases and 18 terminal electron acceptor reductases. We further included in the analyses enzymes performing redox or decarboxylation driven ion translocation, ATP synthase and transhydrogenase and we also investigated the electron carriers that perform functional connection between the membrane complexes, quinones or soluble proteins. Our results bring a novel, broad and integrated perspective of membrane bound respiratory complexes and thus of the several energetic metabolisms of living systems. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi. PMID:27044012

  15. Respiratory acidosis

    MedlinePlus

    Ventilatory failure; Respiratory failure; Acidosis - respiratory ... Causes of respiratory acidosis include: Diseases of the airways (such as asthma and chronic obstructive lung disease ) Diseases of the chest ( ...

  16. Use of drinking water treatment solids for arsenate removal from desalination concentrate.

    PubMed

    Xu, Xuesong; Lin, Lu; Papelis, Charalambos; Myint, Maung; Cath, Tzahi Y; Xu, Pei

    2015-05-01

    Desalination of impaired water can be hindered by the limited options for concentrate disposal. Selective removal of specific contaminants using inexpensive adsorbents is an attractive option to address the challenges of concentrate management. In this study, two types of ferric-based drinking water treatment solids (DWTS) were examined for arsenate removal from reverse osmosis concentrate during continuous-flow once-through column experiments. Arsenate sorption was investigated under different operating conditions including pH, arsenate concentration, hydraulic retention time, loading rate, temperature, and moisture content of the DWTS. Arsenate removal by the DWTS was affected primarily by surface complexation, electrostatic interactions, and arsenate speciation. Results indicated that arsenate sorption was highly dependent on initial pH and initial arsenate concentration. Acidic conditions enhanced arsenate sorption as a result of weaker electrostatic repulsion between predominantly monovalent H2AsO4(-) and negatively charged particles in the DWTS. High initial arsenate concentration increased the driving force for arsenate sorption to the DWTS surface. Tests revealed that the potential risks associated with the use of DWTS include the leaching of organic contaminants and ammonia, which can be alleviated by using wet DWTS or discarding the initially treated effluent that contains high organic concentration. PMID:25622050

  17. Molecular Recognition and Scavenging of Arsenate from Aqueous Solution Using Dimetallic Receptors

    PubMed Central

    Moffat, Chris D; Weiss, Dominik J; Shivalingam, Arun; White, Andrew J P; Salaün, Pascal; Vilar, Ramon

    2014-01-01

    A series of copper(II), nickel(II) and zinc(II) dimetallic complexes were prepared and their affinities towards arsenate investigated. Indicator displacement assays (IDAs) were carried out to establish the complexes with best affinities towards arsenate. A di-zinc complex (3) was selected and its arsenate-binding abilities investigated by isothermal titration calorimetry (ITC). The X-ray crystal structure of this metallo-receptor bound to arsenate is also reported, which allowed us to establish the binding mode between 3 and this oxyanion. Immobilising 3 onto HypoGel resin yielded a novel adsorbent (Zn–HypoGel) with high affinity for arsenate. Adsorption of arsenate from competitive solutions and natural groundwater was greater than that of the commercially used iron oxide Bayoxide E33. Zn–HypoGel could be efficiently and simply regenerated by washing with sodium acetate solution. PMID:25338508

  18. Microbial Reduction of Ferrous Arsenate: Biogeochemical Implications for Arsenic Mobilization

    SciTech Connect

    Babechuk, M.; Weisener, C.G.; Fryer, B.; Paktunc, D.; Maunders, C.

    2010-11-12

    In reduced aqueous environments, the presence of As in solution is a function of both biotic and abiotic mechanisms. Recent studies have demonstrated a significant release of As(III) through the microbial reduction of dissolved and mineral-bound As(V), which raises health concerns when the greater comparative mobility and toxicity of As(III) is considered. These release mechanisms do not operate in isolation but occur in concert with a number of removal processes, including secondary mineralization and sorption to other natural substrates. Thermodynamic and applied experimental studies have shown that ferrous arsenates, such as symplesite [Fe(II){sub 3}(As(V)O{sub 4}){sub 2} {center_dot} 8H{sub 2}O], may provide a significant sink for Fe(II) and As(V). In this study, the stability of a representative ferrous arsenate phase in the presence of the arsenate-reducing bacterium Shewanella sp. strain ANA-3 is examined. The reduction of ferrous arsenate by ANA-3 results in the release of aqueous As(III) and, subsequently, the progressive nucleation of a biogenic ferrous arsenite phase proximal to the microbial cells. The valence states of secondary solid-phase products were verified using X-ray absorption spectroscopy (XAS). Electron microscopy reveals that nucleation occurs on cellular exudates which may imply a role of extracellular reduction through c-type cytochromes as investigated in recent literature. These observations provide new insights into the reduction mechanisms of ANA-3 and the biogeochemical cycling of As(III) in natural systems.

  19. Arsenate transport by sodium/phosphate cotransporter type IIb

    SciTech Connect

    Villa-Bellosta, Ricardo; Sorribas, Victor

    2010-08-15

    Arsenic is a metalloid that causes the dysfunction of critical enzymes, oxidative stress, and malignancies. In recent years several transporters of As{sup III} have been identified, including aquaglyceroporins (AQP) and multidrug resistance proteins (MRP). As{sup V} transport, however, has not been sufficiently studied because it has been assumed that arsenate is taken up by mammalian cells through inorganic phosphate (Pi) transporters. In this paper we have analyzed the role of Pi transporters in the uptake of arsenate by directly using {sup 73}As{sup V} as a radiotracer in phosphate transporter-expressing Xenopus laevis oocytes. The affinities of Pi transporters for H{sub 3}AsO{sub 4} were lower than the affinities for Pi. NaPiIIa, NaPiIIc, Pit1, and Pit2 showed a K{sub m} for arsenate that was > 1 mM (i.e., at least ten times lower than the affinities for Pi). The NaPiIIb isoform showed the highest affinity for As{sup V} in mouse (57 {mu}M), rat (51 {mu}M), and human (9.7 {mu}M), which are very similar to the affinities for Pi. Therefore, NaPiIIb can have a prominent role in the toxicokinetics of arsenic following oral exposure to freshwater or food contaminated with As{sup V}.

  20. Characterization of glutathione reductase and catalase in the fronds of two Pteris ferns upon arsenic exposure.

    PubMed

    Kertulis-Tartar, Gina M; Rathinasabapathi, Bala; Ma, Lena Q

    2009-10-01

    To better understand the mechanisms of plant tolerance to high concentration of arsenic, we characterized two antioxidant enzymes, glutathione reductase (GR) and catalase (CAT), in the fronds of Pteris vittata, an arsenic-hyperaccumulating fern, and Pteris ensiformis, an arsenic-sensitive fern. The induction, activation and apparent kinetics of GR and CAT in the plants upon arsenic exposure were investigated. Under arsenic exposure (sodium arsenate), CAT activity in P. vittata was increased by 1.5-fold, but GR activity was unchanged. Further, GR was not inhibited or activated by the arsenic in assays. No significant differences in K(m) and V(max) values of GR or CAT were observed between the two ferns. However, CAT activity in P. vittata was activated by 200 microM arsenate up to 300% compared to the control. Similar but much smaller increases were observed for P. ensiformis and purified bovine liver catalase (133% and 120%, respectively). This research reports, for the first time, the activation of CAT by arsenic in P. vittata. The increased CAT activities may allow P. vittata to more efficiently mediate arsenic-induced stress by preparing the fern for the impeding production of reactive oxygen species resulting from arsenate reduction to arsenite in the fronds. PMID:19574057

  1. Possible roles of plant sulfurtransferases in detoxification of cyanide, reactive oxygen species, selected heavy metals and arsenate.

    PubMed

    Most, Parvin; Papenbrock, Jutta

    2015-01-01

    Plants and animals have evolved various potential mechanisms to surmount the adverse effects of heavy metal toxicity. Plants possess low molecular weight compounds containing sulfhydryl groups (-SH) that actively react with toxic metals. For instance, glutathione (γ-Glu-Cys-Gly) is a sulfur-containing tripeptide thiol and a substrate of cysteine-rich phytochelatins (γ-Glu-Cys)2-11-Gly (PCs). Phytochelatins react with heavy metal ions by glutathione S-transferase in the cytosol and afterwards they are sequestered into the vacuole for degradation. Furthermore, heavy metals induce reactive oxygen species (ROS), which directly or indirectly influence metabolic processes. Reduced glutathione (GSH) attributes as an antioxidant and participates to control ROS during stress. Maintenance of the GSH/GSSG ratio is important for cellular redox balance, which is crucial for the survival of the plants. In this context, sulfurtransferases (Str), also called rhodaneses, comprise a group of enzymes widely distributed in all phyla, paving the way for the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors, at least in vitro. The best characterized in vitro reaction is the transfer of a sulfane sulfur atom from thiosulfate to cyanide, leading to the formation of sulfite and thiocyanate. Plants as well as other organisms have multi-protein families (MPF) of Str. Despite the presence of Str activities in many living organisms, their physiological role has not been clarified unambiguously. In mammals, these proteins are involved in the elimination of cyanide released from cyanogenic compounds. However, their ubiquity suggests additional physiological functions. Furthermore, it is speculated that a member of the Str family acts as arsenate reductase (AR) and is involved in arsenate detoxification. In summary, the role of Str in detoxification processes is still not well understood but seems to be a major function in the organism. PMID:25594348

  2. Arsenate-induced maternal glucose intolerance and neural tube defects in a mouse model

    SciTech Connect

    Hill, Denise S.; Wlodarczyk, Bogdan J.; Mitchell, Laura E.; Finnell, Richard H.

    2009-08-15

    Background: Epidemiological studies have linked environmental arsenic (As) exposure to increased type 2 diabetes risk. Periconceptional hyperglycemia is a significant risk factor for neural tube defects (NTDs), the second most common structural birth defect. A suspected teratogen, arsenic (As) induces NTDs in laboratory animals. Objectives: We investigated whether maternal glucose homeostasis disruption was responsible for arsenate-induced NTDs in a well-established dosing regimen used in studies of arsenic's teratogenicity in early neurodevelopment. Methods: We evaluated maternal intraperitoneal (IP) exposure to As 9.6 mg/kg (as sodium arsenate) in LM/Bc/Fnn mice for teratogenicity and disruption of maternal plasma glucose and insulin levels. Selected compounds (insulin pellet, sodium selenate (SS), N-acetyl cysteine (NAC), L-methionine (L-Met), N-tert-Butyl-{alpha}-phenylnitrone (PBN)) were investigated for their potential to mitigate arsenate's effects. Results: Arsenate caused significant glucose elevation during an IP glucose tolerance test (IPGTT). Insulin levels were not different between arsenate and control dams before (arsenate, 0.55 ng/dl; control, 0.48 ng/dl) or after glucose challenge (arsenate, 1.09 ng/dl; control, 0.81 ng/dl). HOMA-IR index was higher for arsenate (3.9) vs control (2.5) dams (p = 0.0260). Arsenate caused NTDs (100%, p < 0.0001). Insulin pellet and NAC were the most successful rescue agents, reducing NTD rates to 45% and 35%. Conclusions: IPGTT, insulin assay, and HOMA-IR results suggest a modest failure of glucose stimulated insulin secretion and insulin resistance characteristic of glucose intolerance. Insulin's success in preventing arsenate-induced NTDs provides evidence that these arsenate-induced NTDs are secondary to elevated maternal glucose. The NAC rescue, which did not restore maternal glucose or insulin levels, suggests oxidative disruption plays a role.

  3. Respiratory alkalosis

    MedlinePlus

    Alkalosis - respiratory ... leads to shortness of breath can also cause respiratory alkalosis (such as pulmonary embolism and asthma). ... Treatment is aimed at the condition that causes respiratory alkalosis. Breathing into a paper bag -- or using ...

  4. RATES OF HYDROUS FERRIC OXIDE CRYSTALLIZATION AND THE INFLUENCE ON COPRECIPITATED ARSENATE

    EPA Science Inventory

    Arsenate coprecipitated with hydrous ferric oxide (HFO) was stabilized against dissolution during transformation of HFO to more crystalline iron (hydr)oxides. The rate of arsenate stabilization approximately coincided with the rate of HFO transformation at pH 6 and 40 ?C. Compa...

  5. SORPTION OF ARSENITE AND ARSENATE ON A HIGH AFFINITY OXIDE: MACROSCOPIC AND MICROSCOPIC STUDIES

    EPA Science Inventory

    Sorption of arsenate and arsenite was examined on a Ru compound using macroscopic and microscopic techniques. Isotherms were constructed from batch studies at pH 4 through 8. Solution As was measured by ICAP. Samples of the Ru compound were equilibrated with arsenite and arsenate...

  6. Arsenic Recovery by Stinging Nettle From Lead-Arsenate Contaminated Orchard Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil contamination with arsenic (As) is common in orchards with a history of lead-arsenate pesticide application. This problem is prevalent in the U.S. Northeast where lead-arsenate foliar sprays were used to control codling moth (Cydia pomonella) in apple orchards. Arsenic is not easily biodegrad...

  7. Effect of arsenate As (V) on the biomarkers of Myriophyllum alterniflorum in oligotrophic and eutrophic conditions.

    PubMed

    Krayem, M; Deluchat, V; Rabiet, M; Cleries, K; Lenain, J F; Saad, Z; Kazpard, V; Labrousse, P

    2016-03-01

    Alternate watermilfoil, Myriophyllum alterniflorum is an aquatic macrophyte found in the Limousin rivers (France) whose potential for biomonitoring of metal pollution has been demonstrated. The objective of the present study carried out in vitro was to identify biomarkers for an early detection of the pollution by a metalloid As (V) in eutrophic and oligotrophic conditions. A synthetic medium of similar composition to the waters of the River Vienne was prepared. The morphological development of watermilfoil was monitored for 30 days, with or without contamination by 100 μg L(-1) As (V). In addition, the mineralization of plants and the analysis of biomarkers (chlorophylls, photosynthetic and respiratory intensities …) were investigated after 21 days. Our results indicated that eutrophic medium, induced a decrease in chlorophyll pigments, in growth and an increase in H2O2 compared to the oligotrophic medium. While, the presence of As (V), led to a decrease in the osmotic potential, pigment content, photosynthesis and respiration rates and an inhibition of shoot branching of plants in both conditions. However, a significant increase in H2O2 content was noted in the eutrophic medium. Finally, As (V) was found to be more accumulated in roots than shoots in both conditions but was more accumulated in oligotrophic one. Therefore, we can conclude that the water trophic level modifies the response of M. alterniflorum in presence of arsenate. Thus, M. alterniflorum shows a great promise in water-quality biomonitoring. PMID:26766024

  8. Arsenate adsorption mechanisms at the allophane - Water interface

    USGS Publications Warehouse

    Arai, Y.; Sparks, D.L.; Davis, J.A.

    2005-01-01

    We investigated arsenate (As(V)) reactivity and surface speciation on amorphous aluminosilicate mineral (synthetic allophane) surfaces using batch adsorption experiments, powder X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). The adsorption isotherm experiments indicated that As(V) uptake increased with increasing [As(V)]0 from 50 to 1000 ??M (i.e., Langmuir type adsorption isotherm) and that the total As adsorption slightly decreased with increasing NaCl concentrations from 0.01 to 0.1 M. Arsenate adsorption was initially (0-10 h) rapid followed by a slow continuum uptake, and the adsorption processes reached the steady state after 720 h. X-ray absorption spectroscopic analyses suggest that As(V) predominantly forms bidentate binuclear surface species on aluminum octahedral structures, and these species are stable up to 11 months. Solubility calculations and powder XRD analyses indicate no evidence of crystalline AI-As(V) precipitates in the experimental systems. Overall, macroscopic and spectroscopic evidence suggest that the As(V) adsorption mechanisms at the allophane-water interface are attributable to ligand exchange reactions between As(V) and surface-coordinated water molecules and hydroxyl and silicate ions. The research findings imply that dissolved tetrahedral oxyanions (e.g., H2PO42- and H2AsO42-) are readily retained on amorphous aluminosilicate minerals in aquifer and soils at near neutral pH. The innersphere adsorption mechanisms might be important in controlling dissolved arsenate and phosphate in amorphous aluminosilicate-rich low-temperature geochemical environments. ?? 2005 American Chemical Society.

  9. Raman Investigations of Rare Earth Arsenate Single Crystals

    SciTech Connect

    Barros, G; Santos, C. C.; Ayala, A. P.; Guedes, I.; Boatner, Lynn A; Loong, C. K.

    2010-01-01

    Polarized Raman Spectroscopy was used to investigate the room-temperature phonon characteristics of a series of rare-earth arsenate (REAsO4, RE = Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu) single crystals. The Raman data were interpreted in a systematic manner based on the known tetragonal zircon structure of these compounds, and assignments and correlations were made for the observed bands. We found that the wavenumber of the internal modes of the AsO4 tetrahedron increased with increasing atomic number, and for three out of four lattice wavenumbers observed, this tendency was not nearly so marked as in the case of the internal mode wavenumber.

  10. Leaching of chromated copper arsenate wood preservatives: a review.

    PubMed

    Hingston, J A; Collins, C D; Murphy, R J; Lester, J N

    2001-01-01

    Recent studies have generated conflicting data regarding the bioaccumulation and toxicity of leachates from preservative-treated wood. Due to the scale of the wood preserving industry, timber treated with the most common preservative, chromated copper arsenate (CCA), may form a significant source of metals in the aquatic environment. The existing literature on leaching of CCA is reviewed, and the numerous factors affecting leaching rates, including pH, salinity, treatment and leaching test protocols are discussed. It is concluded from the literature that insufficient data exists regarding these effects to allow accurate quantification of leaching rates, and also highlights the need for standardised leaching protocols. PMID:11202715

  11. Amino-functionalized MCM-41 and MCM-48 for the removal of chromate and arsenate.

    PubMed

    Benhamou, A; Basly, J P; Baudu, M; Derriche, Z; Hamacha, R

    2013-08-15

    The aim of the present work was to investigate the efficiency of three amino-functionalized (hexadecylamine, dodecylamine, and dimethyldodecylamine) mesoporous silicas (MCM-41 and MCM-48) toward the adsorption of arsenate and chromate. Hexadecylamine-functionalized materials were characterized; BET surface areas, pore volumes, and sizes decreased with the functionalization, whereas XRD patterns show that the hexagonal structure of MCM-41 and the cubic structure of MCM-48 were not modified. The zeta potential decreases with pH and the highest arsenate and chromate removal was observed at the lowest pHs. Adsorption of chromium and arsenate was significantly enhanced after functionalization and amino-functionalized MCM-41 adsorb larger amounts of arsenate when compared to expanded MCM-48 materials. Chromate sorption capacities increased with the chain length and the larger capacities were obtained with hexadecylamine-functionalized mesoporous silicas. Mesoporous silicas modified by dimethyldodecylamine exhibited the higher arsenate sorption capacities. PMID:23684231

  12. Arsenate arrests flagellar rotation in cytoplasm-free envelopes of bacteria.

    PubMed Central

    Margolin, Y; Barak, R; Eisenbach, M

    1994-01-01

    The effect of arsenate on flagellar rotation in cytoplasm-free flagellated envelopes of Escherichia coli and Salmonella typhimurium was investigated. Flagellar rotation ceased as soon as the envelopes were exposed to arsenate. Inclusion of phosphate intracellularly (but not extracellular) prevented the inhibition by arsenate. In a parallel experiment, the rotation was not affected by inclusion of an ATP trap (hexokinase and glucose) within the envelopes. It is concluded that arsenate affects the motor in a way other than reversible deenergization. This may be an irreversible damage to the cell or direct inhibition of the motor by arsenate. The latter possibility suggests that a process of phosphorylation or phosphate binding is involved in the motor function. PMID:8071237

  13. Photoinduced Oxidation of Arsenite to Arsenate on Ferrihydrite

    SciTech Connect

    N Bhandari; R Reeder; D Strongin

    2011-12-31

    The photochemistry of an aqueous suspension of the iron oxyhydroxide, ferrihydrite, in the presence of arsenite has been investigated using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray absorption near edge structure (XANES), and solution phase analysis. Both ATR-FTIR and XANES show that the exposure of ferrihydrite to arsenite in the dark leads to no change in the As oxidation state, but the exposure of this arsenite-bearing surface, which is in contact with pH 5 water, to light leads to the conversion of the majority of the adsorbed arsenite to the As(V) bearing species, arsenate. Analysis of the solution phase shows that ferrous iron is released into solution during the oxidation of arsenite. The photochemical reaction, however, shows the characteristics of a self-terminating reaction in that there is a significant suppression of this redox chemistry before 10% of the total iron making up the ferrihydrite partitions into solution as ferrous iron. The self-terminating behavior exhibited by this photochemical arsenite/ferrihydrite system is likely due to the passivation of the ferrihydrite surface by the strongly bound arsenate product.

  14. Fast removal of high quantities of toxic arsenate via cationic p(APTMACl) microgels.

    PubMed

    Rehman, Saif Ur; Siddiq, Mohammed; Al-Lohedan, Hamad; Aktas, Nahit; Sahiner, Mehtap; Demirci, Sahin; Sahiner, Nurettin

    2016-01-15

    Hydrogels are resourceful materials and can be prepared in different morphology, size, surface charge and porosity adopting different polymerization techniques and reaction conditions. The cationic poly(3-acrylamidopropyl)trimethylammonium chloride (p(APTMACl)) microgels were synthesized by photo-initiated inverse suspension polymerization technique. These microgels were utilized as absorbents for the removal of toxic arsenate (As) from different aqueous environments. The experimental parameters affecting absorption efficiency were investigated, and it was demonstrated that these types of microgels are highly efficient in removing arsenate anions from different aqueous environments compared to the previously reported bulk hydrogel, and cryogel of the same material. A removal efficiency of approximately 97.25% was obtained by immersing 0.5 g microgel in 250 ppm 100 mL solution of arsenate anions for 60 min. Both Langmuir and Freundlich adsorption isotherms were applied to adsorption of arsenate anions by p(APTMACl) microgels, and the Langmuir isotherm was a better representation of the adsorption of arsenate with a high value of R(2) (0.9982). Furthermore, mag-p(APTMACl) microgels were synthesized for the adsorption of arsenate anions to provide easy removal of the microgel composite by using an externally applied magnetic field. Furthermore, re-usability of the p(APTMACl) microgels was also investigated for the adsorption of arsenate anions. PMID:26513320

  15. Respiratory papillomas

    PubMed Central

    Alagusundaramoorthy, Sayee Sundar; Agrawal, Abhinav

    2016-01-01

    Papillomas are known to occur in the lower respiratory tract. They are however, rare compared to their occurrence in the upper respiratory tract. These are generally exophytic tumors in the more proximal upper airways however cases with more distal location with an inverted growth pattern have also been described in the literature. These can be solitary or multiple and multifocality associated with multiple papillomas in the upper respiratory/aerodigestive tract. The four major types of respiratory papillomas are (1) Recurrent respiratory papillomas, (2) solitary squamous papillomas, (3) solitary glandular papillomas, (4) mixed papillomas. We review the incidence, etiopathology, diagnosis, and possible treatment modalities and algorithms for these respiratory papillomas. PMID:27625447

  16. Human brain aldehyde reductases: relationship to succinic semialdehyde reductase and aldose reductase.

    PubMed

    Hoffman, P L; Wermuth, B; von Wartburg, J P

    1980-08-01

    Human brain contains multiple forms of aldehyde-reducing enzymes. One major form (AR3), as previously shown, has properties that indicate its identity with NADPH-dependent aldehyde reductase isolated from brain and other organs of various species; i.e., low molecular weight, use of NADPH as the preferred cofactor, and sensitivity to inhibition by barbiturates. A second form of aldehyde reductase ("SSA reductase") specifically reduces succinic semialdehyde (SSA) to produce gamma-hydroxybutyrate. This enzyme form has a higher molecular weight than AR3, and uses NADH as well as NADPH as cofactor. SSA reductase was not inhibited by pyrazole, oxalate, or barbiturates, and the only effective inhibitor found was the flavonoid quercetine. Although AR3 can also reduce SSA, the relative specificity of SSA reductase may enhance its in vivo role. A third form of human brain aldehyde reductase, AR2, appears to be comparable to aldose reductases characterized in several species, on the basis of its activity pattern with various sugar aldehydes and its response to characteristic inhibitors and activators, as well as kinetic parameters. This enzyme is also the most active in reducing the aldehyde derivatives of biogenic amines. These studies suggest that the various forms of human brain aldehyde reductases may have specific physiological functions. PMID:6778961

  17. Respiratory Failure

    MedlinePlus

    Respiratory failure happens when not enough oxygen passes from your lungs into your blood. Your body's organs, such ... brain, need oxygen-rich blood to work well. Respiratory failure also can happen if your lungs can't ...

  18. Respiratory system

    NASA Technical Reports Server (NTRS)

    Bartlett, R. G., Jr.

    1973-01-01

    The general anatomy and function of the human respiratory system is summarized. Breathing movements, control of breathing, lung volumes and capacities, mechanical relations, and factors relevant to respiratory support and equipment design are discussed.

  19. The role of Al-goethites on arsenate mobility.

    PubMed

    Silva, Juscimar; Mello, Jaime W V; Gasparon, Massimo; Abrahão, Walter A P; Ciminelli, Virgínia S T; Jong, Tony

    2010-11-01

    The geochemical fates of Fe and As are so closely correlated that methods of As removal from contaminated water are in general based on the high affinity of this metalloid for Fe (hydr)oxides. Dissimilatory Fe reducing bacteria, however, play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments. The potential of Al-goethites in adsorbing As(V) compared with hematite, goethite, ferrihydrite, and gibbsite, and the stability of As retained by the Fe compounds under anoxic conditions were investigated in this study. The (hydr)oxides were synthesised, and adsorption isotherms and As(V) adsorption maxima at different pH were measured. Arsenic loaded samples were anaerobically incubated in the presence of Shewanella putrefaciens, and periodically sampled to evaluate the contents of soluble As and Fe. The As(V) adsorption maxima decreased in the following order: Fh > AlGt(13) > AlGt(20) > AlGt(23) > Gb > Hm > Gt. In terms of surface area, Gb, Gt, and Hm showed higher As(V) loading capacity than Fh, suggesting available reactive sites not fully occupied by arsenate on Fh. The same hypothesis can be considered for Al-goethites, as they showed even lower arsenate loading capacity per surface area. The presence of structural Al in the goethites enhanced considerably the As uptake capacity and stability under reducing conditions. Therefore, the Al-goethites showed good potential as adsorbents to remove As from water. S. putrefaciens cells were able to utilise both noncrystalline and crystalline Fe (hydr)oxides as electron acceptors, releasing As into solution. Al-goethites showed a decrease in Fe and As mobilisation as structural Al increased. PMID:20638700

  20. Mechanism of arsenate activation of mammalian phosphoglycerate mutase

    SciTech Connect

    Rea, D.W.; McWilliams, A.D.; Hass, L.F.

    1987-05-01

    Towne demonstrated that arsenate (As/sub i/) can replace D-glycerate-2,3-P/sub 2/ (2,3-DPG) as an activator for cofactor-dependent phosphoglycerate mutase (PGM). Arsenate activation was found to be accompanied by a lag phase which, over a period of several minutes, gradually evolved into a region of steady-state kinetics. The authors have verified and expanded Towne's findings through isotope exchange studies and kinetic analysis. In the absence of 2,3-DPG, reciprocal plots of PGM-catalyzed steady-state velocities versus As/sub i/ concentrations at different D-glycerate-3-P (3-PGA) levels yield a family of curves which suggest a ping-pong mechanism accompanied by double competitive substrate inhibition. Other experiments show that incubation of doubly-labelled 0.25 mM (U-/sup 14/C, /sup 32/P)-3-PGA with 20 mM As/sub i/ and PGM for several hrs. promotes the release of P/sub i/ with the concomitant formation of D-glycerate. Addition of 0.2 mM glycolate-2-P to the reaction medium accelerates the process. P/sub i/, but not vanadate, also promotes hydrolysis of 3-PGA, but to a much lesser extent than As/sub i/, even in the presence of glycolate-2-P. The pH optimum for 3-PGA phosphatase activity is 6.0-6.2. These and other findings suggest that As/sub i/ accelerates PGM catalysis by first forming 2-As-3-PGA which in turn forms phosphoenzyme (EP). Previous studies have shown that EP is the active form of PGM.

  1. Complete Genome Sequences of Evolved Arsenate-Resistant Metallosphaera sedula Strains

    PubMed Central

    Ai, Chenbing; McCarthy, Samuel; Schackwitz, Wendy; Martin, Joel; Lipzen, Anna

    2015-01-01

    Metallosphaera sedula is a thermoacidophilic crenarchaeote with a 2.19-Mb genome. Here, we report the genome sequences of several evolved derivatives of M. sedula generated through adaptive laboratory evolution for enhanced arsenate resistance. PMID:26430052

  2. ASSESSING CHILDREN'S EXPOSURES TO THE WOOD PRESERVATIVE CCA (CHROMATED COPPER ARSENATE) ON TREATED PLAYSETS AND DECKS

    EPA Science Inventory

    Concerns have been raised regarding the safety of young children contacting arsenic and chromium residues while playing on and around Chromated Copper Arsenate (CCA) treated wood playground structures and decks. Although CCA registrants voluntarily canceled treated wood for re...

  3. Adsorption of arsenate from aqueous solution by rice husk-based adsorbent

    NASA Astrophysics Data System (ADS)

    Khan, Taimur; Chaudhuri, Malay

    2013-06-01

    Rice husk-based adsorbent (RHBA) was prepared by burning rice husk in a muffle furnace at 400°C for 4 h and adsorption of arsenate by the RHBA from aqueous solution was examined. Batch adsorption test showed that extent of arsenate adsorption depended on contact time and pH. Equilibrium adsorption was attained in 60 min, with maximum adsorption occurring at pH 7. Equilibrium adsorption data were well described by the Freundlich isotherm model. Freundlich constants Kf and 1/n were 3.62 and 2, respectively. The RHBA is effective in the adsorption of arsenate from water and is a potentially suitable filter medium for removing arsenate from groundwater at wells or in households.

  4. HISTOPATHOLOGY AND BIOACCUMULATION IN OYSTERS CRASSOSTREA VIRGINICA LIVING ON WOOD PRESERVED WITH CHROMATED COPPER ARSENATE

    EPA Science Inventory

    Oysters (Crassostrea virginica) growing on wood treated with chromated cooper arsenate (CCA) have elevated levels of metals, especially copper. oysters living inside a residential canal lined with CCA wood bulkheads were often green and had high copper concentrations. hese oyster...

  5. Complete Genome Sequences of Evolved Arsenate-Resistant Metallosphaera sedula Strains.

    PubMed

    Ai, Chenbing; McCarthy, Samuel; Schackwitz, Wendy; Martin, Joel; Lipzen, Anna; Blum, Paul

    2015-01-01

    Metallosphaera sedula is a thermoacidophilic crenarchaeote with a 2.19-Mb genome. Here, we report the genome sequences of several evolved derivatives of M. sedula generated through adaptive laboratory evolution for enhanced arsenate resistance. PMID:26430052

  6. DOSE DEPENDENT DISPOSITION OF SODIUM ARSENATE IN MICE FOLLOWING ACUTE ORAL EXPOSURE

    EPA Science Inventory

    The effect of dose on arsenate disposition was studied in adult female B6C3F, mice, dosed po with 0.5 to 5000 ug/kg [73As]-arsenate in water. rine was collected at 1, 2, 4, 8, 12, 24 and 48 hr and feces at 24 and 48 hr postexposure. he mice were sacrificed at 48 hr and tissues we...

  7. Concentration and chemical status of arsenic in the early placentas of arsenate-dosed hamsters

    SciTech Connect

    Hanlon, D.P.; Ferm, V.H.

    1987-04-01

    The authors determined the concentration and chemical status of arsenic in the placentas of hamsters following continuous exposure via the osmotic minipump to minimally and frankly teratogenic doses of arsenate. Close to 70% of the placental arsenic is bound to macromolecules, two-thirds of which is dialyzable. The remaining 30% of arsenic consists of low molecular weight species, predominantly inorganic arsenic. This mix is the same for minimally teratogenic and frankly teratogenic doses of arsenate.

  8. Raman spectroscopy of some complex arsenate minerals-implications for soil remediation.

    PubMed

    Frost, Ray L; Kloprogge, J Theo

    2003-10-01

    The application of spectroscopy to the study of contaminants in soils is important. Among the many contaminants is arsenic, which is highly labile and may leach to non-contaminated areas. Minerals of arsenate may form depending upon the availability of specific cations for example calcium and iron. Such minerals include carminite, pharmacosiderite and talmessite. Each of these arsenate minerals can be identified by its characteristic Raman spectrum enabling identification. PMID:14499841

  9. Characterization of microbial arsenate reduction in the anoxic bottom waters of Mono Lake, California

    USGS Publications Warehouse

    Hoeft, S.E.; Lucas, F.; Hollibaugh, J.T.; Oremland, R.S.

    2002-01-01

    Dissimilatory reduction of arsenate (DAsR) occurs in the arsenic-rich, anoxic water column of Mono Lake, California, yet the microorganisms responsible for this observed in situ activity have not been identified. To gain insight as to which microorganisms mediate this phenomenon, as well as to some of the biogeochemical constraints on this activity, we conducted incubations of arsenate-enriched bottom water coupled with inhibition/amendment studies and Denaturing Gradient Gel Electrophoresis (DGGE) characterization techniques. DAsR was totally inhibited by filter-sterilization and by nitrate, partially inhibited (~50%) by selenate, but only slightly (~25%) inhibited by oxyanions that block sulfate-reduction (molybdate and tungstate). The apparent inhibition by nitrate, however, was not due to action as a preferred electron acceptor to arsenate. Rather, nitrate addition caused a rapid, microbial re-oxidation of arsenite to arsenate, which gave the overall appearance of no arsenate loss. A similar microbial oxidation of As(III) was also found with Fe(III), a fact that has implications for the recycling of As(V) in Mono Lake's anoxic bottom waters. DAsR could be slightly (10%) stimulated by substrate amendments of lactate, succinate, malate, or glucose, but not by acetate, suggesting that the DAsR microflora is not electron donor limited. DGGE analysis of amplified 16S rDNA gene fragments from incubated arsenate-enriched bottom waters revealed the presence of two bands that were not present in controls without added arsenate. The resolved sequences of these excised bands indicated the presence of members of the epsilon (Sulfurospirillum) and delta (Desulfovibrio) subgroups of the Proteobacteria, both of which have representative species that are capable of anaerobic growth using arsenate as their electron acceptor.

  10. Arsenate adsorption and desorption kinetics on a Fe(III)-modified montmorillonite.

    PubMed

    Luengo, Carina; Puccia, Virginia; Avena, Marcelo

    2011-02-28

    The adsorption-desorption kinetics of arsenate on a Fe(III)-modified montmorillonite (Fe-M) was studied at different arsenate concentrations, pH and stirring rates. The synthesized solid was a porous sample with Fe(III) present as a mix of monomeric and polymeric Fe(III) species in the interlayer and on the external surface. Adsorption took place in a two-step mechanism, with an initial fast binding of arsenate to Fe(III) species at the external surface (half-lives of 1 min or shorter) followed by a slower binding to less accessible Fe(III) species in pores and the interlayer (half-lives of around 1 h). Desorption kinetics also reflected the presence of externally and internally adsorbed arsenate. At pH 6 the maximum adsorbed arsenate was 52 μmol/g, a value that is low as compared to adsorption on ferrihydrite (700 μmol/g) and goethite (192-220 μmol/g). However, since the Fe(III) content of Fe-M is much lower than that of ferrihydrite and goethite, Fe(III) species in Fe-M are more efficient in binding arsenate than in ferrihydrite or goethite (one As atom is attached every 8.95 iron atoms). This high binding efficiency indicates that Fe(III) species are well spread on montmorillonite, forming small oligomeric species or surface clusters containing just a few iron atoms. PMID:21242027

  11. A mechanistic study of arsenate removal from artificially contaminated clay soils by electrokinetic remediation.

    PubMed

    Suzuki, Tasuma; Moribe, Mai; Okabe, Yohhei; Niinae, Masakazu

    2013-06-15

    Batch desorption experiments and bench-scale electrokinetic experiments were performed to elucidate the electrokinetic remediation mechanisms of arsenate from artificially contaminated kaolinite. The electrokinetic experiments in which a constant voltage was applied demonstrated that high soil pH favored arsenate remediation with respect to both the remediation time and electricity consumption. It was also demonstrated that applying a pulse voltage (1 h ON, 1 h OFF) significantly improved the electricity consumption efficiency when the soil pH was maintained at the initial value during the experiments; this trend was not observed when the soil pH was gradually increased from the cathode side. These electrokinetic experimental results, with the support of arsenate desorption data obtained from batch experiments, indicate that the remediation rate-limiting step varied with soil pH. When the soil pH was maintained at the initial value of 7.2 during the experiments, arsenate desorption was the remediation rate-limiting step rather than the migration of dissolved arsenate toward the anode. Conversely, when the cathode pH was not controlled and the soil pH was correspondingly increased gradually from the cathode side, the migration of hydroxyl and desorbed arsenate ions toward the anode played a more important role in the control of the overall remediation efficiency. PMID:23643955

  12. Evidence for the aquatic binding of arsenate by natural organic matter-suspended Fe(III)

    USGS Publications Warehouse

    Ritter, K.; Aiken, G.R.; Ranville, J.F.; Bauer, M. E.; Macalady, D.L.

    2006-01-01

    Dialysis experiments with arsenate and three different NOM samples amended with Fe(III) showed evidence confirming the formation of aquatic arsenate-Fe(III)-NOM associations. A linear relationship was observed between the amount of complexed arsenate and the Fe(III) content of the NOM. The dialysis results were consistent with complex formation through ferric iron cations acting as bridges between the negatively charged arsenate and NOM functional groups and/or a more colloidal association, in which the arsenate is bound by suspended Fe(III)-NOM colloids. Sequential filtration experiments confirmed that a significant proportion of the iron present at all Fe/C ratios used in the dialysis experiments was colloidal in nature. These colloids may include larger NOM species that are coagulated by the presence of chelated Fe(III) and/or NOM-stabilized ferric (oxy)hydroxide colloids, and thus, the solution-phase arsenate-Fe(III)-NOM associations are at least partially colloidal in nature. ?? 2006 American Chemical Society.

  13. Comparison of arsenate and cadmium toxicity in a freshwater amphipod (Gammarus pulex).

    PubMed

    Vellinger, Céline; Parant, Marc; Rousselle, Philippe; Immel, Françoise; Wagner, Philippe; Usseglio-Polatera, Philippe

    2012-01-01

    Cadmium is largely documented on freshwater organisms while arsenic, especially arsenate, is rarely studied. The kinetic of the LC50s values for both metals was realized on Gammarus pulex. Physiological [i.e. metal concentration in body tissues, bioconcentration factor (BCF)] effects and behavioural responses (via pleopods beats) were investigated after 240-h exposure. Arsenate LC50 value was 100 fold higher than Cd-LC50 value after 240-h exposure, while concentrations in gammarids were similar for both metals at their respective LC50s. BCF decreased with increasing cadmium concentration while BCF remained stable with increasing arsenate concentration. Moreover, BCF was between 148 and 344 times lower for arsenate than cadmium. A significant hypoventilation was observed for cadmium concentrations exceeding or close to the 240h-LC50(Cd), while gammarids hyperventilated for the lowest arsenate concentrations and hypoventilated for the highest arsenate concentrations. We discussed the relationships between potential action mechanisms of these two metals and observed results. PMID:22035927

  14. Crystallization and preliminary crystallographic characterization of LmACR2, an arsenate/antimonate reductase from Leishmania major.

    PubMed

    Bisacchi, Davide; Zhou, Yao; Rosen, Barry P; Mukhopadhyay, Rita; Bordo, Domenico

    2006-10-01

    Arsenic is present in the biosphere owing either to the presence of pesticides and herbicides used in agricultural and industrial activities or to leaching from geological formations. The health effects of prolonged exposure to arsenic can be devastating and may lead to various forms of cancer. Antimony(V), which is chemically very similar to arsenic, is used instead in the treatment of leishmaniasis, an infection caused by the protozoan parasite Leishmania sp.; the reduction of pentavalent antimony contained in the drug Pentostam to the active trivalent form arises from the presence in the Leishmania genome of a gene, LmACR2, coding for the protein LmACR2 (14.5 kDa, 127 amino acids) that displays weak but significant sequence similarity to the catalytic domain of Cdc25 phosphatase and to rhodanese enzymes. For structural characterization, LmACR2 was overexpressed, purified to homogeneity and crystallized in a trigonal space group (P321 or P3(1)21/P3(2)21). The protein crystallized in two distinct trigonal crystal forms, with unit-cell parameters a = b = 111.0, c = 86.1 A and a = b = 111.0, c = 175.6 A, respectively. At a synchrotron beamline, the diffraction pattern extended to a resolution limit of 1.99 A. PMID:17012788

  15. [Respiratory behavior].

    PubMed

    Gallego, J; Gaultier, C

    2000-02-01

    The notion of respiratory behaviour is grounded, among other approaches, on studies of neuronal mechanisms of voluntary breathing, clinical data, conditioning experiments and respiratory sensations. The interactions between cortical centres of voluntary breathing and respiratory neurones in the brain stem are poorly understood: voluntary control operates through the direct action of corticomotor centres on respiratory motoneurones; however these cortical structures may directly act on bulbopontine centres, and therefore indirectly on respiratory motoneurones. Recordings in animals of brain stem neuronal activity, brain imaging in humans, and transcortical stimulation of the diaphragm in humans and in animal models support either one or the other hypothesis. The mutual independence of the automatic and the voluntary controls of breathing appears in patients with impaired bulbopontine automatism and operational voluntary control (Central Congenital Hypoventilation Syndrome), and in patients with the reverse impairment (locked-in syndrome). Finally, recent studies in humans and animals show that classical conditioning affects respiratory control and sensations. PMID:10756555

  16. The Pho4 transcription factor mediates the response to arsenate and arsenite in Candida albicans

    PubMed Central

    Urrialde, Verónica; Prieto, Daniel; Pla, Jesús; Alonso-Monge, Rebeca

    2015-01-01

    Arsenate (As (V)) is the dominant form of the toxic metalloid arsenic (As). Microorganisms have consequently developed mechanisms to detoxify and tolerate this kind of compounds. In the present work, we have explored the arsenate sensing and signaling mechanisms in the pathogenic fungus Candida albicans. Although mutants impaired in the Hog1 or Mkc1-mediated pathways did not show significant sensitivity to this compound, both Hog1 and Mkc1 became phosphorylated upon addition of sodium arsenate to growing cells. Hog1 phosphorylation upon arsenate challenge was shown to be Ssk1-dependent. A screening designed for the identification of transcription factors involved in the arsenate response identified Pho4, a transcription factor of the myc-family, as pho4 mutants were susceptible to As (V). The expression of PHO4 was shortly induced in the presence of sodium arsenate in a Hog1-independent manner. Pho4 level affects Hog1 phosphorylation upon As (V) challenge, suggesting an indirect relationship between Pho4 activity and signaling in C. albicans. Pho4 also mediates the response to arsenite as revealed by the fact that pho4 defective mutants are sensitive to arsenite and Pho4 becomes phosphorylated upon sodium arsenite addition. Arsenite also triggers Hog1 phosphorylation by a process that is, in this case, independent of the Ssk1 kinase. These results indicate that the HOG pathway mediates the response to arsenate and arsenite in C. albicans and that the Pho4 transcription factor can differentiate among As (III), As (V) and Pi, triggering presumably specific responses. PMID:25717325

  17. Effects of arsenate on growth and physiology in mallard ducklings

    USGS Publications Warehouse

    Camardese, M.B.; Hoffman, D.J.; LeCaptain, L.J.; Pendleton, G.W.

    1990-01-01

    Arsenic (As) has been found at elevated concentrations in irrigation drainwater and in aquatic plants utilized by waterfowl. Mallard (Anas platyrhynchos) duckings received an untreated diet (controls) or diets containing 30, 100 or 300 ppm As added as sodium arsenate. After 10 weeks blood and tissue samples were collected for biochemical and histological examination. Arsenic accumulated significantly in brain and liver of ducklings fed 100 or 300 ppm but did not result in histopathological lesions. The 300-ppm dietary As concentration decreased overall growth (weight gain) in males, whereas all concentrations of As decreased overall growth and rate of growth in females. Food consumption was less during the first three weeks in all 300-ppm group and during the second week for the 100-ppm compared to controls. Plasma sorbitol dehydrogenase activity and plasma glucose concentration were higher in the 300-ppm group compared to controls. Plasma triglyceride concentration increased in all As-treated groups. Brain ATP was lower in the 300-ppm group and sodium/potassium-dependent ATPase activity was higher in the 30- and 100-ppm groups. Hepatic glutathione peroxidase activity was lower in the 300-ppm group and malondialdehyde lower in all treatment groups. All treatment levels caused elevation in hepatic glutathione and ATP concentrations. These findings, in combination with altered duckling behavior (increased resting time) suggesting that concentrations of As that have been found in aquatic plants (up to 430 ppm dry weight) could adversely affect normal duckling development.

  18. Isolated menthone reductase and nucleic acid molecules encoding same

    DOEpatents

    Croteau, Rodney B; Davis, Edward M; Ringer, Kerry L

    2013-04-23

    The present invention provides isolated menthone reductase proteins, isolated nucleic acid molecules encoding menthone reductase proteins, methods for expressing and isolating menthone reductase proteins, and transgenic plants expressing elevated levels of menthone reductase protein.

  19. Zeatin reductase in Phaseolus embryos

    SciTech Connect

    Martin, R.C.; Mok, David, W.S.; Mok, M.C. )

    1989-04-01

    Zeatin was converted to O-xylosylzeatin in embryos of Phaseolus vulgaris . O-xylosyldihydrozeatin was also identified as a zeatin metabolite. Incubation of embryo extracts with {sup 14}C-zeatin and {sup 14}C-O-xylosylzeatin revealed that reduction preceeds the O-xylosylation of zeatin. An enzyme responsible for reducing the N{sup 6}-side chain was isolated and partially purified using ammonium sulfate fractionation and affinity, gel filtration and anion exchange chromatography. The NADPH dependent reductase was zeatin specific and did not recognize cis-zeatin, ribosylzeatin, i{sup 6}Ade or i{sup 6}Ado. Two forms of the reductase could be separated by either gel filtration or anion exchange HPLC. The HMW isozyme (Mr. 55,000) eluted from the anion exchange column later than the LMW isozyme (Mr. 25,000). Interspecific differences in zeatin reductase activity were also detected.

  20. Edaphic factors affecting the toxicity and accumulation of arsenate in the earthworm Lumbricus terrestris

    SciTech Connect

    Meharg, A.A.; Shore, R.F.; Broadgate, K.

    1998-06-01

    The toxicity and accumulation of arsenate was determined in the earthworm Lumbricus terrestris in soil from different layers of a forest profile. Toxicity increased fourfold between 2 and 10 d. Edaphic factors (pH, soil organic matter, and depth in soil profile) also affected toxicity with a three fold decrease in the concentration that causes 50% mortality with increasing depth in soil. In a 4-d exposure study, there was no evidence of arsenic bioconcentration in earthworm tissue, although bioaccumulation was occurring. There was a considerable difference in tissue residues between living and dead earthworms, with dead worms having higher concentrations. This difference was dependent on both soil arsenate concentration and on soil type. Over a wide range of soil arsenate concentrations, earthworm arsenic residues are homeostatically maintained in living worms, but this homeostasis breaks down during death. Alternatively, equilibration with soil residues may occur via accumulation after death. In long-term accumulation studies in soils dosed with a sublethal arsenate concentration, bioconcentration of arsenate did not occur until day 12, after which earthworm concentrations rose steadily above the soil concentration, with residues in worms three fold higher than soil concentrations by the termination of the study. This bioconcentration only occurred in depurated worms over the time period of the study. Initially, depurated worms had lower arsenic concentrations than undepurated until tissue concentrations were equivalent to the soil concentration. Once tissue concentration was greater than soil concentration, depurated worms had higher arsenic residues than undepurated.

  1. Constant rate exposure of pregnant hamsters to arsenate during early gestation

    SciTech Connect

    Ferm, V.H.; Hanlon, D.P.

    1985-08-01

    The teratogenic and embryotoxic effects of constant-rate exposure of pregnant hamsters to arsenate have been examined by means of subcutaneous implants of osmotic minipumps. Different total exposure regimes were established by varying the duration of minipump implants and by varying the concentration of arsenate in the minipumps. Dams were killed on Day 13 pregnancy, 5 days after the critical stage of organogenesis. Numbers of resorptions, dead fetuses, and living fetuses were obtained. Fetal weights, crown-rump lengths, and the incidence of malformations were recorded. Control animals were treated identically with minipumps containing demineralized water. The percentage of malformations per litter, a direct measure of teratogenesis, was dependent only upon the concentration of arsenate in the minipumps. The minimum teratogenic response was achieved with a dose of 70 ..mu..mol/kg dam/24 hr during the critical stages of organogenesis. The embryotoxic (fetotoxic) indicators, fetal weight and crown-rump length, decreased with increases in exposure time and with increased concentrations of arsenate. The resorption rate also depended directly upon duration of exposure and concentration of arsenate in the mini-pump.

  2. Adsorption kinetics of phosphate and arsenate on goethite. A comparative study.

    PubMed

    Luengo, Carina; Brigante, Maximiliano; Avena, Marcelo

    2007-07-15

    The adsorption kinetics of phosphate and arsenate on goethite is studied and compared. Batch adsorption experiments were performed at different adsorbate concentrations, pH, temperatures and stirring rates. For both oxoanions the adsorption rate increases by increasing adsorbate concentration, decreasing pH and increasing temperature. It does not change by changing stirring rate. The adsorption takes place in two processes: a fast one that takes place in less than 5 min and a slow one that takes place in several hours or more. The rate of the slow process does not depend directly on the concentration of phosphate or arsenate in solution, but depends linearly on the amount of phosphate or arsenate that was adsorbed during the fast process. Apparent activation energies and absence of stirring rate effects suggest that the slow process is controlled by diffusion into pores, although the evidence is not conclusive. The similarities in the adsorption kinetics of phosphate and arsenate are quantitatively shown by using a three-parameters equation that takes into account both the fast and the slow processes. These similarities are in line with the similar reactivity that phosphate and arsenate have in general and may be important for theoretical and experimental studies of the fate of these oxoanions in the environment. PMID:17448491

  3. Fabrication and evolution of multilayer silver nanofilms for surface-enhanced Raman scattering sensing of arsenate

    PubMed Central

    2011-01-01

    Surface-enhanced Raman scattering (SERS) has recently been investigated extensively for chemical and biomolecular sensing. Multilayer silver (Ag) nanofilms deposited on glass slides by a simple electroless deposition process have been fabricated as active substrates (Ag/GL substrates) for arsenate SERS sensing. The nanostructures and layer characteristics of the multilayer Ag films could be tuned by varying the concentrations of reactants (AgNO3/BuNH2) and reaction time. A Ag nanoparticles (AgNPs) double-layer was formed by directly reducing Ag+ ions on the glass surfaces, while a top layer (3rd-layer) of Ag dendrites was deposited on the double-layer by self-assembling AgNPs or AgNPs aggregates which had already formed in the suspension. The SERS spectra of arsenate showed that characteristic SERS bands of arsenate appear at approximately 780 and 420 cm-1, and the former possesses higher SERS intensity. By comparing the peak heights of the approximately 780 cm-1 band of the SERS spectra, the optimal Ag/GL substrate has been obtained for the most sensitive SERS sensing of arsenate. Using this optimal substrate, the limit of detection (LOD) of arsenate was determined to be approximately 5 μg·l-1. PMID:21711772

  4. Arsenate removal with 3-mercaptopropanoic acid-coated superparamagnetic iron oxide nanoparticles.

    PubMed

    Morillo, D; Uheida, A; Pérez, G; Muhammed, M; Valiente, M

    2015-01-15

    In the present work, superparamagnetic iron oxide nanoparticles (SPION) surface-coated with 3-mercaptopropanoic acid (3-MPA) were prepared and their feasibility for the removal of arsenate from dilute aqueous solutions was demonstrated. The synthesized 3-MPA-coated SPION was characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infra-red spectrometry (FTIR). Separation efficiency of the coated nanoparticles and the equilibrium isotherm of arsenate adsorption were investigated. The obtained results reveal the arsenate adsorption to be highly pH-dependent, and the maximum adsorption was attained in less than 60 min. The resulting increase of 3-MPA-coated SPION adsorption capacity to twice the adsorption capacity of SPION alone under the same conditions is attributed to the increase of active adsorption sites. An adsorption reaction is proposed. On the other hand, efficient recovery of arsenate from the loaded nanoparticles was achieved using nitric acid (HNO3) solution, which also provides a concentration over the original arsenate solution. PMID:25454446

  5. Genetics Home Reference: 5-alpha reductase deficiency

    MedlinePlus

    ... gene provides instructions for making an enzyme called steroid 5-alpha reductase 2. This enzyme is involved ... external genitalia. Mutations in the SRD5A2 gene prevent steroid 5-alpha reductase 2 from effectively converting testosterone ...

  6. Impact of chromated copper arsenate (CCA) in wood mulch.

    PubMed

    Townsend, Timothy G; Solo-Gabriele, Helena; Tolaymat, Thabet; Stook, Kristin

    2003-06-20

    The production of landscape mulch is a major market for the recycling of yard trash and waste wood. When wood recovered from construction and demolition (C&D) debris is used as mulch, it sometimes contains chromated copper arsenate (CCA)-treated wood. The presence of CCA-treated wood may cause some potential environmental problems as a result of the chromium, copper, and arsenic present. Research was performed to examine the leachability of the three metals from a variety of processed wood mixtures in Florida. The mixtures tested included mixed wood from C&D debris recycling facilities and mulch purchased from retail outlets. The synthetic precipitation leaching procedure (SPLP) was performed to examine the leaching of chromium, copper and arsenic. Results were compared to Florida's groundwater cleanup target levels (GWCTLs). Eighteen of the 22 samples collected from C&D debris processing facilities leached arsenic at concentrations greater than Florida's GWCTL of 50 microg/l. The mean leachable arsenic concentration for the C&D debris samples was 153 microg/l with a maximum of 558 microg/l. One of the colored mulch samples purchased from a retail outlet leached arsenic above 50 microg/l, while purchased mulch samples derived from virgin materials did not leach detectable arsenic (<5 microg/l). A mass balance approach was used to compute the potential metal concentrations (mg/kg) that would result from CCA-treated wood being present in wood mulch. Less than 0.1% CCA-treated wood would cause a mulch to exceed Florida's residential clean soil guideline for arsenic (0.8 mg/kg). PMID:12798102

  7. Effect of flooding lead-arsenate contaminated orchard soil on growth, arsenic and lead accumulation in rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lead-arsenate has been used as a pesticide in controlling codling moth (Cydia pomonella) in apple and plum orchards from 1900-1960. As a result, many old orchards contain high levels of arsenic. Flooding soils contaminated by lead-arsenate could increase plant arsenic and lead and become a human h...

  8. Combined Hydrous Ferric Oxide and Quaternary Ammonium Surfactant Tailoring of Granular Activated Carbon for Concurrent Arsenate and Perchlorate Removal

    SciTech Connect

    Jang, M.; Cannon, F; Parette, R; Yoon, S; Chen, W

    2009-01-01

    Activated carbon was tailored with both iron and quaternary ammonium surfactants so as to concurrently remove both arsenate and perchlorate from groundwater. The iron (hydr)oxide preferentially removed the arsenate oxyanion but not perchlorate; while the quaternary ammonium preferentially removed the perchlorate oxyanion, but not the arsenate. The co-sorption of two anionic oxyanions via distinct mechanisms has yielded intriguing phenomena. Rapid small-scale column tests (RSSCTs) with these dually prepared media employed synthetic waters that were concurrently spiked with arsenate and perchlorate; and these trial results showed that the quaternary ammonium surfactants enhanced arsenate removal bed life by 25-50% when compared to activated carbon media that had been preloaded merely with iron (hydr)oxide; and the surfactant also enhanced the diffusion rate of arsenate per the Donnan effect. The authors also employed natural groundwater from Rutland, MA which contained 60 microg/L As and traces of silica, and sulfate; and the authors spiked this with 40 microg/L perchlorate. When processing this water, activated carbon that had been tailored with iron and cationic surfactant could treat 12,500 bed volumes before 10 microg/L arsenic breakthrough, and 4500 bed volumes before 6 microg/L perchlorate breakthrough. Although the quaternary ammonium surfactants exhibited only a slight capacity for removing arsenate, these surfactants did facilitate a more favorably positively charged avenue for the arsenate to diffuse through the media to the iron sorption site (i.e. via the Donnan effect).

  9. Oxidation of NADH and ROS production by respiratory complex I.

    PubMed

    Vinogradov, Andrei D; Grivennikova, Vera G

    2016-07-01

    Kinetic characteristics of the proton-pumping NADH:quinone reductases (respiratory complexes I) are reviewed. Unsolved problems of the redox-linked proton translocation activities are outlined. The parameters of complex I-mediated superoxide/hydrogen peroxide generation are summarized, and the physiological significance of mitochondrial ROS production is discussed. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt. PMID:26571336

  10. Arsenate removal by layered double hydroxides embedded into spherical polymer beads: Batch and column studies.

    PubMed

    Nhat Ha, Ho Nguyen; Kim Phuong, Nguyen Thi; Boi An, Tran; Mai Tho, Nguyen Thi; Ngoc Thang, Tran; Quang Minh, Bui; Van Du, Cao

    2016-01-01

    In this study, the performance of poly(layered double hydroxides) [poly(LDHs)] beads as an adsorbent for arsenate removal from aqueous solution was investigated. The poly(LDHs) beads were prepared by immobilizing LDHs into spherical alginate/polyvinyl alcohol (PVA)-glutaraldehyde beads (spherical polymer beads). Batch adsorption studies were conducted to assess the effect of contact time, solution pH, initial arsenate concentrations and co-existing anions on arsenate removal performance. The potential reuse of these poly(LDHs) beads was also investigated. Approximately 79.1 to 91.2% of arsenic was removed from an arsenate solution (50 mg As L(-1)) by poly(LDHs). The adsorption data were well described by the pseudo-second-order kinetics model and the Langmuir isotherm model, and the adsorption capacities of these poly(LDHs) beads at pH 8 were from 1.64 to 1.73 mg As g(-1), as calculated from the Langmuir adsorption isotherm. The adsorption ability of the poly(LDHs) beads decreased by approximately 5-6% after 5 adsorption-desorption cycles. Phosphates markedly decreased arsenate removal. The effect of co-existing anions on the adsorption capacity declined in the following order: HPO4 (2-) > HCO3 (-) > SO4 (2-) > Cl(-). A fixed-bed column study was conducted with real-life arsenic-containing water. The breakthrough time was found to be from 7 to 10 h. Under optimized conditions, the poly(LDHs) removed more than 82% of total arsenic. The results obtained in this study will be useful for further extending the adsorbents to the field scale or for designing pilot plants in future studies. From the viewpoint of environmental friendliness, the poly(LDHs) beads are a potential cost-effective adsorbent for arsenate removal in water treatment. PMID:26818806

  11. Perchlorate Reductase Is Distinguished by Active Site Aromatic Gate Residues.

    PubMed

    Youngblut, Matthew D; Tsai, Chi-Lin; Clark, Iain C; Carlson, Hans K; Maglaqui, Adrian P; Gau-Pan, Phonchien S; Redford, Steven A; Wong, Alan; Tainer, John A; Coates, John D

    2016-04-22

    Perchlorate is an important ion on both Earth and Mars. Perchlorate reductase (PcrAB), a specialized member of the dimethylsulfoxide reductase superfamily, catalyzes the first step of microbial perchlorate respiration, but little is known about the biochemistry, specificity, structure, and mechanism of PcrAB. Here we characterize the biophysics and phylogeny of this enzyme and report the 1.86-Å resolution PcrAB complex crystal structure. Biochemical analysis revealed a relatively high perchlorate affinity (Km = 6 μm) and a characteristic substrate inhibition compared with the highly similar respiratory nitrate reductase NarGHI, which has a relatively much lower affinity for perchlorate (Km = 1.1 mm) and no substrate inhibition. Structural analysis of oxidized and reduced PcrAB with and without the substrate analog SeO3 (2-) bound to the active site identified key residues in the positively charged and funnel-shaped substrate access tunnel that gated substrate entrance and product release while trapping transiently produced chlorate. The structures suggest gating was associated with shifts of a Phe residue between open and closed conformations plus an Asp residue carboxylate shift between monodentate and bidentate coordination to the active site molybdenum atom. Taken together, structural and mutational analyses of gate residues suggest key roles of these gate residues for substrate entrance and product release. Our combined results provide the first detailed structural insight into the mechanism of biological perchlorate reduction, a critical component of the chlorine redox cycle on Earth. PMID:26940877

  12. Lead in tissue of cats fed pine voles from lead arsenate-treated orchards

    SciTech Connect

    Gilmartin, J.E.; Alo, D.K.; Richmond, M.E.; Bache, C.A.; Lisk, D.J.

    1985-02-01

    Lead arsenate has been used for many years for control of insects in apple orchards in the United States. In an earlier study, it was shown that such orchard soils may contain very high concentrations of lead and that orchards voles and mice inhibating such soils accumulate inordinately high levels of lead. It is of interest to learn the possible extent of deposition of lead in higher carnivores that may consume such orchard animals. In the work reported, cats were fed pine voles (Microtus pinetorum) captured in lead arsenate-treated orchards located in the vicinity of New Paltz, New York. Following sacrifice, the lead content of cat tissues was determined.

  13. Phosphate and arsenate removal efficiency by thermostable ferritin enzyme from Pyrococcus furiosus using radioisotopes.

    PubMed

    Sevcenco, Ana-Maria; Paravidino, Monica; Vrouwenvelder, Johannes S; Wolterbeek, Hubert Th; van Loosdrecht, Mark C M; Hagen, Wilfred R

    2015-06-01

    Oxo-anion binding properties of the thermostable enzyme ferritin from Pyrococcus furiosus were characterized with radiography. Radioisotopes (32)P and (76)As present as oxoanions were used to measure the extent and the rate of their absorption by the ferritin. Thermostable ferritin proved to be an excellent system for rapid phosphate and arsenate removal from aqueous solutions down to residual concentrations at the picomolar level. These very low concentrations make thermostable ferritin a potential tool to considerably mitigate industrial biofouling by phosphate limitation or to remove arsenate from drinking water. PMID:25817554

  14. Respiratory acidosis

    MedlinePlus

    ... when the lungs cannot remove all of the carbon dioxide the body produces. This causes body fluids, especially ... Acute respiratory acidosis is a condition in which carbon dioxide builds up very quickly, before the kidneys can ...

  15. The binding sites on human heme oxygenase-1 for cytochrome p450 reductase and biliverdin reductase.

    PubMed

    Wang, Jinling; de Montellano, Paul R Ortiz

    2003-05-30

    Human heme oxygenase-1 (hHO-1) catalyzes the NADPH-cytochrome P450 reductase-dependent oxidation of heme to biliverdin, CO, and free iron. The biliverdin is subsequently reduced to bilirubin by biliverdin reductase. Earlier kinetic studies suggested that biliverdin reductase facilitates the release of biliverdin from hHO-1 (Liu, Y., and Ortiz de Montellano, P. R. (2000) J. Biol. Chem. 275, 5297-5307). We have investigated the binding of P450 reductase and biliverdin reductase to truncated, soluble hHO-1 by fluorescence resonance energy transfer and site-specific mutagenesis. P450 reductase and biliverdin reductase bind to truncated hHO-1 with Kd = 0.4 +/- 0.1 and 0.2 +/- 0.1 microm, respectively. FRET experiments indicate that biliverdin reductase and P450 reductase compete for binding to truncated hHO-1. Mutation of surface ionic residues shows that hHO-1 residues Lys18, Lys22, Lys179, Arg183, Arg198, Glu19, Glu127, and Glu190 contribute to the binding of cytochrome P450 reductase. The mutagenesis results and a computational analysis of the protein surfaces partially define the binding site for P450 reductase. An overlapping binding site including Lys18, Lys22, Lys179, Arg183, and Arg185 is similarly defined for biliverdin reductase. These results confirm the binding of biliverdin reductase to hHO-1 and define binding sites of the two reductases. PMID:12626517

  16. Bioaccumulation and oxidative stress in Daphnia magna exposed to arsenite and arsenate.

    PubMed

    Fan, Wenhong; Ren, Jinqian; Li, Xiaomin; Wei, Chaoyang; Xue, Feng; Zhang, Nan

    2015-11-01

    Arsenic pollution and its toxicity to aquatic organisms have attracted worldwide attention. The bioavailability and toxicity of arsenic are highly related to its speciation. The present study investigated the differences in bioaccumulation and oxidative stress responses in an aquatic organism, Daphnia magna, induced by 2 inorganic arsenic species (As(III) and As(V)). The bioaccumulation of arsenic, Na(+) /K(+) -adenosine triphosphatase (ATPase) activity, reactive oxygen species (ROS) content, total superoxide dismutase (SOD) activity, total antioxidative capability, and malondialdehyde content in D. magna were determined after exposure to 500 µg/L of arsenite and arsenate for 48 h. The results showed that the oxidative stress and antioxidative process in D. magna exposed to arsenite and arsenate could be divided into 3 phases, which were antioxidative response, oxidation inhibition, and antioxidative recovery. In addition, differences in bioaccumulation, Na(+) /K(+) -ATPase activity, and total SOD activity were also found in D. magna exposed to As(III) and As(V). These differences might have been the result of the high affinity of As(III) with sulfhydryl groups in enzymes and the structural similarity of As(V) to phosphate. Therefore, arsenate could be taken up by organisms through phosphate transporters, could substitute for phosphate in biochemical reactions, and could lead to a change in the bioaccumulation of arsenic and activity of enzymes. These characteristics were the possible reasons for the different toxicity mechanisms in the oxidative stress process of arsenite and arsenate. PMID:26084717

  17. UPTAKE OF METALS FROM CHROMATED-COPPER-ARSENATE (CCA)-TREATED LUMBER BY EPIBIOTA IN ESTUARIES

    EPA Science Inventory

    Previous studies have shown that Cu, Cr, and As leach from chromated-copper-arsenate (CCA) in the aboratory. e nvestigated concentrations of these metals in tissues of estuarine organisms, including algae, barnacles, and oysters, collected from CCA pressure-treated wood in a resi...

  18. WASTE REDUCTION PRACTICES AT TWO CHROMATED COPPER ARSENATE WOOD-TREATING PLANTS

    EPA Science Inventory

    Two chromated copper arsenate (CCA) wood-treating plants were assessed for their waste reduction practices. he objectives of this study were to estimate the amount of hazardous wastes that a well-designed and well-maintained CCA treatment facility would generate and to identify w...

  19. WASTE REDUCTION PRACTICES AT TWO CHROMATED COPPER ARSENATE WOOD-TREATING PLANTS

    EPA Science Inventory

    Two chromated copper arsenate (CCA) wood-treating plants were assessed for their waste reduction practices. The objectives of this study were to estimate the amount of hazardous wastes that a well-designed and well-main- tained CCA treatment facility would generate and to iden- t...

  20. SORPTION OF ARSENATE AND ARSENITE ON RUO2.XH2O: A SPECTROSCOPIC AND MACROSCOPIC STUDY

    EPA Science Inventory

    The sorption of arsenate (As(V)) and arsenite (As(III)) on RuO2 xH2O was examined using macroscopic and microscopic techniques. Constant solid:solution ratio isotherms were constructed from batch sorption experiments to study the sorption of the inorganic arsenic species on RuO2...

  1. Accumulation of lead and arsenic by potato grown on lead-arsenate contaminated orchard soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Concerns have been raised about the potential food chain transfer of metals in crops grown on historic orchard soils where lead arsenate pesticide was used. The objective of this study was to evaluate the uptake of lead and arsenic (As) by four potato (Solanum tuberosum L.) cultivars (Atlantic, Dar...

  2. PATHOLOGICAL AND GENOTOXICOLOGICAL OBSERVATIONS IN OYSTERS (CRASSOSTREA VIRGINICA) LIVING ON CHROMATED COPPER ARSENATE (CCA) TREATED WOOD

    EPA Science Inventory

    Oysters living on chromated copper arsenate (CCA) treated wood in a residential canal were compared with oysters from a reference site 1.2 km distant. anal oysters were frequently green in color and had 15X more copper (app. 3 ug/g) than reference oysters. istological examination...

  3. COMPARATIVE METABOLISM OF ARSENIC IN MICE AFTER A SINGLE OR REPEATED ORAL ADMINISTRATION OF ARSENATE

    EPA Science Inventory

    COMPARATIVE METABOLISM OF ARSENIC IN MICE AFTER A SINGLE OR REPEATED ORAL ADMINISTRATION OF ARSENATE
    Michael F. Hughes*1, Elaina M. Kenyon1, Brenda C. Edwards1, Carol T. Mitchell1, Luz Maria Del Razo2 and David J. Thomas1
    1US EPA, ORD, NHEERL, ETD, PKB, Research Triangle Pa...

  4. ACCUMULATION AND METABOLISM OF ARSENIC IN MICE AFTER REPEATED ADMINISTRATION OF ARSENATE

    EPA Science Inventory

    Accumulation and metabolism of arsenic in mice after repeated oral administration of arsenate, Hughes, M. F., Kenyon, E. M., Edwards, B. C., Mitchell, C. T., Del Razo, L. M., and Thomas,
    D. J.

    The human carcinogen inorganic arsenic (iAs) is a pervasive environmental ...

  5. IN VITRO PERCUTANEOUS APPROACH OF SODIUM ARSENATE IN B6C3F1 MICE

    EPA Science Inventory

    Percutaneous absorption of sodium [73As] arsenate in female B6C3F1 mice was investigated in this study from various exposure conditions, including solid compound, aqueous solution (100 and 250 ul) and soil (= 23 mg/cm2). In vitro diffusion experiments were conducted for 24 hr usi...

  6. Accumulation of lead and arsenic by carrots grown on four lead-arsenate contaminated orchard soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Concerns have been raised about possible human food chain transfer of contaminants resulting from crops grown on orchard soils with histories of lead arsenate use. The objective of this study was to determine the uptake of arsenic and lead by three cultivars of carrots. Carrots were grown on four ...

  7. Differential Pair Distribution Function Study of the Structure of Arsenate Adsorbed on Nanocrystalline [gamma]-Alumina

    SciTech Connect

    Li, Wei; Harrington, Richard; Tang, Yuanzhi; Kubicki, James D.; Aryanpour, Masoud; Reeder, Richard J.; Parise, John B.; Phillips, Brian L.

    2012-03-15

    Structural information is important for understanding surface adsorption mechanisms of contaminants on metal (hydr)oxides. In this work, a novel technique was employed to study the interfacial structure of arsenate oxyanions adsorbed on {gamma}-alumina nanoparticles, namely, differential pair distribution function (d-PDF) analysis of synchrotron X-ray total scattering. The d-PDF is the difference of properly normalized PDFs obtained for samples with and without arsenate adsorbed, otherwise identically prepared. The real space pattern contains information on atomic pair correlations between adsorbed arsenate and the atoms on {gamma}-alumina surface (Al, O, etc.). PDF results on the arsenate adsorption sample on {gamma}-alumina prepared at 1 mM As concentration and pH 5 revealed two peaks at 1.66 {angstrom} and 3.09 {angstrom}, corresponding to As-O and As-Al atomic pair correlations. This observation is consistent with those measured by extended X-ray absorption fine structure (EXAFS) spectroscopy, which suggests a first shell of As-O at 1.69 {+-} 0.01 {angstrom} with a coordination number of 4 and a second shell of As-Al at 3.13 {+-} 0.04 {angstrom} with a coordination number of 2. These results are in agreement with a bidentate binuclear coordination environment to the octahedral Al of {gamma}-alumina as predicted by density functional theory (DFT) calculation.

  8. Accumulation of lead and arsenic by lettuce grown on lead-arsenate contaminated orchard soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lead-arsenate was one of the preferred insecticides used as foliar spray to control codling moth (Cydia pomonella) in apple (Malus sylvestris Mill) orchards from the 1900's to the 1960’s. Lead and arsenic are generally immobile and remain in the surface soil. Some of these contaminated lands are now...

  9. SORPTION OF ARSENATE AND ARSENITE ON A RUTHENIUM COMPOUND: A MACROSCOPIC AND MICROSCOPIC STUDY

    EPA Science Inventory

    Sorption of arsenate and arsenite was examined on a ruthenium compound using macroscopic and microscopic techniques. Batch sorption experiments at pH 4,5,6, 7 and 8 were employed to construct constant solid solution ratio isotherms (CSI). After equilibration at the appropriate pH...

  10. Genotoxic effects of sodium arsenite and sodium arsenate after chronic exposure of Drosophila melanogaster larvae

    SciTech Connect

    Ramos-Morales, P.; Ordaz, M.G.; Munoz, A.

    1995-11-01

    Two arsenic compounds, namely: NaAsO{sub 2} (Sodium Arsenite) and Na{sub 2}HAsO{sub 4} (Sodium Arsenate) were tested for its chronic effect in somatic cells of Drosophila melanogaster. In a previous study in Drosophila we found that both compounds induced SLRL mutations, but failed to induce sex chromosome loss. In the SMART, after acute exposure, only sodium arsenite was positive when cells of the wings were used; however, both were positives in cells of the eyes of Drosophila. The genotoxicity of both compounds localized mainly on somatic cells, in agreement with reports on the carcinogenicity potential of arsenical compounds. The Somatic mutation and recombination test (SMART) was run employing cells of the wing imaginal discs from flr{sup 3}/mwh larvae. First instar larvae (24 {plus_minus} 4 h) were treated during 96 hours with sodium arsenite [0.015-4.0 ppm], and sodium arsenate [0.2-10 ppm], negative control was treated with distilled water. The frequency of spots by wing induced by the two arsenic salts were compared with control according with Frei and Wuergler procedure. Data show that sodium arsenite tested negative at all concentrations, but sodium arsenate tested positive at 0.8, 2 and 10 ppm (P<0.05). This results were consistent with the co-mutagenic role of sodium arsenite, but show that sodium arsenate was mutagenic in Drosophila test system under chronic exposure.

  11. Competitive adsorption of arsenate and phosphate onto calcite; experimental results and modeling with CCM and CD-MUSIC

    NASA Astrophysics Data System (ADS)

    Sø, Helle Ugilt; Postma, Dieke; Jakobsen, Rasmus; Larsen, Flemming

    2012-09-01

    The competitive adsorption of arsenate and phosphate onto calcite was studied in batch experiments using calcite-equilibrated solutions. The solutions had circum-neutral pH (7-8.3) and covered a wide span in the activity of Ca2+ and CO32-. The results show that the adsorption of arsenate onto calcite is strongly reduced by the presence of phosphate, whereas phosphate adsorption is only slightly reduced by arsenate addition. Simultaneous and sequential addition (3 h apart) yields the same reduction in adsorption, underlining the high reversibility of the system. The reduction in adsorption of both arsenate and phosphate is most likely due to competition for the same sorption sites at the calcite surface, considering the similarity in sorption edges, pKa's and geometry of the two anions. The strong reduction in arsenate adsorption by competition with phosphate suggests that adsorption of arsenate onto calcite is of minor importance in most groundwater aquifers, as phosphate is often present at concentration levels sufficient to significantly reduce arsenate adsorption. The CD-MUSIC model for calcite was used successfully to model adsorption of arsenate and phosphate separately. By combining the models for single sorbate systems the competitive adsorption of phosphate and arsenate onto calcite in the binary system could be predicted. This is in contrast to the constant capacitance model (CCM) which under-predicted the competition when combining the models for single sorbate systems. This study clearly shows the importance of performing competitive adsorption studies for validation of multi-component models and for estimating the mobility of an ion in the environment.

  12. Effects of sodium arsenate exposure on liver fatty acid profiles and oxidative stress in rats.

    PubMed

    Kharroubi, Wafa; Dhibi, Madiha; Haouas, Zohra; Chreif, Imed; Neffati, Fadoua; Hammami, Mohamed; Sakly, Rachid

    2014-02-01

    The present study aimed to evaluate the effect of arsenic on liver fatty acids (FA) composition, hepatotoxicity and oxidative status markers in rats. Male rats were randomly devised to six groups (n=10 per group) and exposed to sodium arsenate at a dose of 1 and 10 mg/l for 45 and 90 days. Arsenate exposure is associated with significant changes in the FA composition in liver. A significant increase of saturated fatty acids (SFA) in all treated groups (p<0.01) and trans unsaturated fatty acids (trans UFA) in rats exposed both for short term for 10 mg/l (p<0.05) and long term for 1 and 10 mg/l (p<0.001) was observed. However, the cis UFA were significantly decreased in these groups (p<0.05). A markedly increase of indicator in cell membrane viscosity expressed as SFA/UFA was reported in the treated groups (p<0.001). A significant increase in the level of malondialdehyde by 38.3 % after 90 days of exposure at 10 mg/l was observed. Compared to control rats, significant liver damage was observed at 10 mg/l of arsenate by increasing plasma marker enzymes after 90 days. It is through the histological investigations in hepatic tissues of exposed rats that these damage effects of arsenate were confirmed. The antioxidant perturbations were observed to be more important at groups treated by the high dose (p<0.05). An increase in the level of protein carbonyls was observed in all treated groups (p<0.05). The present study provides evidence for a direct effect of arsenite on FA composition disturbance causing an increase of SFA and TFAs isomers, liver dysfunction and oxidative stress. Therefore, arsenate can lead to hepatic damage and propensity towards liver cancer. PMID:23949113

  13. Arabidopsis thaliana NIP7;1 is involved in tissue arsenic distribution and tolerance in response to arsenate.

    PubMed

    Lindsay, Emma R; Maathuis, Frans J M

    2016-03-01

    The Arabidopsis aquaglyceroporin NIP7;1 is involved in uptake and tolerance to the trivalent arsenic species arsenite. Here, we show that NIP7;1 is also involved in the response to pentavalent arsenate. Loss of function of NIP7;1 improved tolerance to arsenate and reduced arsenic levels in both the phloem and xylem, resulting in altered arsenic distribution between tissues. There was no clear correlation between growth and shoot arsenic concentration. This is the first report detailing the involvement of a NIP transporter in response to arsenate. The data suggest that these proteins are relevant targets for breeding and engineering arsenic tolerance in crops. PMID:26898223

  14. Fatty acyl-CoA reductase

    SciTech Connect

    Reiser, Steven E.; Somerville, Chris R.

    1998-12-01

    The present invention relates to bacterial enzymes, in particular to an acyl-CoA reductase and a gene encoding an acyl-CoA reductase, the amino acid and nucleic acid sequences corresponding to the reductase polypeptide and gene, respectively, and to methods of obtaining such enzymes, amino acid sequences and nucleic acid sequences. The invention also relates to the use of such sequences to provide transgenic host cells capable of producing fatty alcohols and fatty aldehydes.

  15. Respiratory Failure

    MedlinePlus

    ... from inhaling smoke or harmful fumes Treatment for respiratory failure depends on whether the condition is acute (short-term) or chronic (ongoing) and how severe it is. It also depends on the underlying cause. You may receive oxygen therapy and other treatment to help you breathe. NIH: ...

  16. Microbial arsenic metabolism: New twists on an old poison

    USGS Publications Warehouse

    Stolz, J.F.; Basu, P.; Oremland, R.S.

    2010-01-01

    Phylogenetically diverse microorganisms metabolize arsenic despite its toxicity and are part of its robust iogeochemical cycle. Respiratory arsenate reductase is a reversible enzyme, functioning in some microbes as an arsenate reductase but in others as an arsenite oxidase. As(III) can serve as an electron donor for anoxygenic photolithoautotrophy and chemolithoautotrophy. Organoarsenicals, such as the feed additive roxarsone, can be used as a source of energy, releasing inorganic arsenic.

  17. Respiratory Home Health Care

    MedlinePlus

    ... Healthy Living > Living With Lung Disease > Respiratory Home Health Care Font: Aerosol Delivery Oxygen Resources Immunizations Pollution Nutrition ... Disease Articles written by Respiratory Experts Respiratory Home Health Care Respiratory care at home can contribute to improved ...

  18. Effect of citrate on the local Fe coordination in ferrihydrite, arsenate binding, and ternary arsenate complex formation

    NASA Astrophysics Data System (ADS)

    Mikutta, Christian; Frommer, Jakob; Voegelin, Andreas; Kaegi, Ralf; Kretzschmar, Ruben

    2010-10-01

    In oxic environments contaminated with arsenate (As(V)), small polyhydroxycarboxylates such as citrate may impact the structure of precipitating ferrihydrite (Fh) and thus the surface speciation of As(V). In this study, '2-line' Fh was precipitated from ferric nitrate solutions that were neutralized to pH 6.5 in the presence of increasing citrate concentrations and in the absence or presence of As(V). The initial citrate/Fe and As/Fe ratios were 0-50 mol% and 5 mol%, respectively. The reaction products, enriched with up to 0.32 mol citrate per mole Fe, were characterized by X-ray diffraction, transmission electron microscopy, and Fe and As K-edge X-ray absorption spectroscopy. Citrate decreased the particle size of Fh by impairing the polymerization of Fe(O,OH) 6 octahedra via edge and corner linkages. In the presence of citrate and As(V), coordination numbers of Fe decreased by up to 28% relative to pure Fh. Citrate significantly reduced the static disorder of Fe-O bonds, implying a decreased octahedral distortion in Fh. Mean bond distances in Fh were not affected by citrate and remained constant within error at 1.98 Å for Fe-O, 3.03 Å for Fe-Fe1, and 3.45 Å for Fe-Fe2. Likewise, citrate had no effect on the As-Fe (3.31 Å) bond distance in As(V) coprecipitated with Fh. The As K-edge EXAFS data comply with the formation of (i) only monodentate binuclear ( 2C) As(V) surface complexes and (ii) combinations of 2C, monodentate mononuclear ( 1V), and outersphere As(V) surface complexes. Our results suggest that increasing citrate concentrations led to a decreasing 1V/ 2C ratio and/or that citrate increasingly impaired the formation of outersphere As(V) complexes. Moreover, citrate stabilized colloidal suspensions of Fh (pH 4.3-6.6, I ˜0.45 M) and reduced Fh formation at the expense of soluble Fe(III)-citrate complexes. At initial citrate/Fe ratios ⩾25 mol%, between 8% and 41% of total Fe was bound in Fe(III)-citrate complexes after Fh formation. Polynuclear Fe

  19. Mutational and gene expression analysis of mtrDEF, omcA and mtrCAB during arsenate and iron reduction in Shewanella sp. ANA-3

    PubMed Central

    Reyes, Carolina; Murphy, Julie N.; Saltikov, Chad W.

    2011-01-01

    Summary Arsenate respiration and Fe(III) reduction are important processes that influence the fate and transport of arsenic in the environment. The goal of this study was to investigate the impact of arsenate on Fe(III) reduction using arsenate and Fe(III) reduction deficient mutants of Shewanella sp. strain ANA-3. Ferrihydrite reduction in the absence of arsenate was similar for an arsenate reduction mutant (arrA and arsC deletion strain of ANA-3) compared with wild-type ANA-3. However, the presence of arsenate adsorbed onto ferrihydrite impeded Fe(III) reduction for the arsenate reduction mutant but not in the wild-type. In an Fe(III) reduction mutant (mtrDEF, omcA, mtrCAB null mutant of ANA-3), arsenate was reduced similarly to wild-type ANA-3 indicating the Fe(III) reduction pathway is not required for ferrihydrite-associated arsenate reduction. Expression analysis of the mtr/omc gene cluster of ANA-3 showed that omcA and mtrCAB were expressed under soluble Fe(III), ferrihydrite and arsenate growth conditions and not in aerobically grown cells. Expression of arrA was greater with ferrihydrite pre-adsorbed with arsenate relative to ferrihydrite only. Lastly, arrA and mtrA were simultaneously induced in cells shifted to anaerobic conditions and exposed to soluble Fe(III) and arsenate. These observations suggest that, unlike Fe(III), arsenate can co-induce operons (arr and mtr) implicated in arsenic mobilization. PMID:20236164

  20. Arsenic accumulation by the aquatic fern Azolla: comparison of arsenate uptake, speciation and efflux by A. caroliniana and A. filiculoides.

    PubMed

    Zhang, Xin; Lin, Ai-Jun; Zhao, Fang-Jie; Xu, Guo-Zhong; Duan, Gui-Lan; Zhu, Yong-Guan

    2008-12-01

    This study investigates As accumulation and tolerance of the aquatic fern Azolla. Fifty strains of Azolla showed a large variation in As accumulation. The highest- and lowest-accumulating ferns among the 50 strains were chosen for further investigations. Azolla caroliniana accumulated two times more As than Azolla filiculoides owing to a higher influx velocity for arsenate. A. filiculoides was more resistant to external arsenate due to a lower uptake. Both strains showed a similar degree of tolerance to internal As. Arsenate and arsenite were the dominant As species in both Azolla strains, with methylated As species accounting for <5% of the total As. A. filiculoides had a higher proportion of arsenite than A. caroliniana. Both strains effluxed more arsenate than arsenite, and the amount of As efflux was proportional to the amount of As accumulation. The potential of growing Azolla in paddy fields to reduce As transfer from soil and water to rice should be further evaluated. PMID:18457908

  1. Preabsorptive Metabolism of Sodium Arsenate by Anaerobic Microbiota of Mouse Cecum Forms a Variety of Methylated and Thiolated Arsenicals

    EPA Science Inventory

    The conventional scheme for arsenic methylation accounts for methylated oxyarsenical production but not for thioarsenical formation. Here, we report that in vitro anaerobic microbiota of mouse cecum converts arsenate into oxy- and thio- arsenicals. Besides methylarsonic acid (MMA...

  2. TROPHIC TRANSFER OF CONTAMINANTS FROM ORGANISMS LIVING BY CHROMATED-COPPER-ARSENATE (CCA)-TREATED WOOD TO THEIR PREDATORS

    EPA Science Inventory

    Oysters, Crassostrea virginica (Gmelin), collected from a residential canal lined with wood treated with chromated copper arsenate (CCA) had elevated levels of the metals in their tissues. arnivorous snail, Thais haemastoma floridana (Conrad), fed the oysters gradually ate less t...

  3. Respiratory Distress

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The University of Miami School of Medicine asked the Research Triangle Institute for assistance in improvising the negative pressure technique to relieve respiratory distress in infants. Marshall Space Flight Center and Johnson Space Center engineers adapted this idea to the lower-body negative-pressure system seals used during the Skylab missions. Some 20,000 babies succumb to respiratory distress in the U.S. each year, a condition in which lungs progressively lose their ability to oxygenate blood. Both positive and negative pressure techniques have been used - the first to force air into lungs, the second to keep infant's lungs expanded. Negative pressure around chest helps the baby expand his lungs and maintain proper volume of air. If doctors can keep the infant alive for four days, the missing substance in the lungs will usually form in sufficient quantity to permit normal breathing. The Skylab chamber and its leakproof seals were adapted for medical use.

  4. Coprecipitated arsenate inhibits thermal transformation of 2-line ferrihydrite: implications for long-term stability of ferrihydrite.

    PubMed

    Wang, Zhaohui; Xiao, Dongxue; Bush, Richard T; Liu, Jianshe

    2015-03-01

    2-line ferrihydrite, a ubiquitous iron oxy-hydroxide found in natural and engineered systems, is an efficient sink for the toxic metalloids such as arsenic. While much is known of the excellent capacity of ferrihydrite to coprecipitate arsenate, there is little information concerning the long-term stability of arsenate-accumulated ferrihydrite. By thermal treatment methodology, the expedited transformation of ferrihydrite in the presence of coprecipitated arsenate was studied at varying As/Fe ratios (0-0.5) and different heating temperature (40, 300, 450, 600°C). Pure and transformed minerals were characterized by thermogravimetry (TG), X-ray diffraction (XRD), Electron Spin Resonance (ESR), Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX) and Fourier Transform Infrared Spectroscopy (FTIR). Arsenate was found to retard the thermal transformation of ferrihydrite. The extents of ferrihydrite transformation to hematite decreased with increasing As/Fe ratios, but increased at a higher heating temperature. It is predicted that the coprecipitated arsenate can stabilize the amorphous iron oxides against the transformation to more crystalline solids. Arsenate concentration appears to play an important role in this predicted long-term stability. PMID:25433978

  5. Adsorption and transport of arsenate in carbonate-rich soils: coupled effects of nonlinear and rate-limited sorption.

    PubMed

    Yolcubal, Irfan; Akyol, Nihat Hakan

    2008-11-01

    The transport and fate of arsenate in carbonate-rich soil under alkaline conditions was investigated with multiple approaches combining batch, sequential extraction and column experiments as well as transport modeling studies. Batch experiments indicated that sorption isotherm was nonlinear over a wide range of concentration (0.1-200 mg L(-1)) examined. As(V) adsorption to the calcareous soil was initially fast but then continued at a slower rate, indicating the potential effect of rate-limited sorption on transport. Column experiments illustrated that transport of As(V) was significantly retarded compared to a non-reactive tracer. The degree of retardation decreased with increasing As(V) concentration. As(V) breakthrough curves exhibited nonideal transport behavior due to the coupled effects of nonlinear and rate-limited sorption on arsenate transport, which is consistent with the results of modeling studies. The contribution of nonlinear sorption to the arsenate retardation was negligible at low concentration but increased with increasing As(V) concentration. Sequential extraction results showed that nonspecifically sorbed (easily exchangeable, outer sphere complexes) fraction of arsenate is dominant with respect to the inner-sphere surface bound complexes of arsenate in the carbonate soil fraction, indicating high bioavailability and transport for arsenate in the carbonate-rich soils of which Fe and Al oxyhydroxide fractions are limited. PMID:18718636

  6. Uptake, Metabolic Effects and Toxicity of Arsenate and Arsenite in Astrocytes.

    PubMed

    Dringen, Ralf; Spiller, Sabrina; Neumann, Sarah; Koehler, Yvonne

    2016-03-01

    The inorganic arsenic species arsenate and arsenite are common environmental toxins which contaminate the drinking water in many countries. Chronic intoxication with arsenicals has been connected with various diseases, but causes also neurological complications and impairs cognitive development, learning and memory. In brain, astrocytes have a pivotal role as partners of neurons in homeostatic and metabolic processes. In addition, astrocytes are the first parenchymal brain cell type which encounters substances which cross the blood-brain barrier and are considered as first line of defence against the toxic potential of xenobiotics. Therefore, astrocytes are likely to play a prominent role in the metabolism and potential detoxification of arsenicals in brain. This article summarizes the current knowledge on the uptake and toxicity of arsenate and arsenite in astrocytes and discusses the modulation of the astrocytic glucose and glutathione metabolism by arsenicals. PMID:25862194

  7. Growth of strain SES-3 with arsenate and other diverse electron acceptors

    USGS Publications Warehouse

    Laverman, A.M.; Blum, J.S.; Schaefer, J.K.; Phillips, E.J.P.; Lovley, D.R.; Oremland, R.S.

    1995-01-01

    The selenate-respiring bacterial strain SES-3 was able to use a variety of inorganic electron acceptors to sustain growth. SES-3 grew with the reduction of arsenate to arsenite, Fe(III) to Fe(II), or thiosulfate to sulfide. It also grew in medium in which elemental sulfur, Mn(IV), nitrite, trimethylamine N-oxide, or fumarate was provided as an electron acceptor. Growth on oxygen was microaerophilic. There was no growth with arsenite or chromate. Washed suspensions of cells grown on selenate or nitrate had a constitutive ability to reduce arsenate but were unable to reduce arsenite. These results suggest that strain SES-3 may occupy a niche as an environmental opportunist by being able to take advantage of a diversity of electron acceptors.

  8. Goethite surface reactivity: III. Unifying arsenate adsorption behavior through a variable crystal face - Site density model

    NASA Astrophysics Data System (ADS)

    Salazar-Camacho, Carlos; Villalobos, Mario

    2010-04-01

    We developed a model that describes quantitatively the arsenate adsorption behavior for any goethite preparation as a function of pH and ionic strength, by using one basic surface arsenate stoichiometry, with two affinity constants. The model combines a face distribution-crystallographic site density model for goethite with tenets of the Triple Layer and CD-MUSIC surface complexation models, and is self-consistent with its adsorption behavior towards protons, electrolytes, and other ions investigated previously. Five different systems of published arsenate adsorption data were used to calibrate the model spanning a wide range of chemical conditions, which included adsorption isotherms at different pH values, and adsorption pH-edges at different As(V) loadings, both at different ionic strengths and background electrolytes. Four additional goethite-arsenate systems reported with limited characterization and adsorption data were accurately described by the model developed. The adsorption reaction proposed is: lbond2 FeOH +lbond2 SOH +AsO43-+H→lbond2 FeOAsO3[2-]…SOH+HO where lbond2 SOH is an adjacent surface site to lbond2 FeOH; with log K = 21.6 ± 0.7 when lbond2 SOH is another lbond2 FeOH, and log K = 18.75 ± 0.9, when lbond2 SOH is lbond2 Fe 2OH. An additional small contribution of a protonated complex was required to describe data at low pH and very high arsenate loadings. The model considered goethites above 80 m 2/g as ideally composed of 70% face (1 0 1) and 30% face (0 0 1), resulting in a site density for lbond2 FeOH and for lbond2 Fe 3OH of 3.125/nm 2 each. Below 80 m 2/g surface capacity increases progressively with decreasing area, which was modeled by considering a progressively increasing proportion of faces (0 1 0)/(1 0 1), because face (0 1 0) shows a much higher site density of lbond2 FeOH groups. Computation of the specific proportion of faces, and thus of the site densities for the three types of crystallographic surface groups present in

  9. Dihydropteridine reductase from Escherichia coli.

    PubMed Central

    Vasudevan, S G; Shaw, D C; Armarego, W L

    1988-01-01

    A dihydropteridine reductase from Escherichia coli was purified to apparent homogeneity. It is a dimeric enzyme with identical subunits (Mr 27000) and a free N-terminal group. It can use NADH (Vmax./Km 3.36 s-1) and NADPH (Vmax./Km 1.07 s-1) when 6-methyldihydro-(6H)-pterin is the second substrate, as well as quinonoid dihydro-(6H)-biopterin (Vmax./Km 0.69 s-1), dihydro-(6H)-neopterin (Vmax./Km 0.58 s-1), dihydro-(6H)-monapterin 0.66 s-1), 6-methyldihydro-(6H)-pterin and cis-6,7-dimethyldihydro-(6H)-pterin (Vmax./Km 0.66 s-1) when NADH is the second substrate. The pure reductase has a yellow colour and contains bound FAD. The enzyme also has pterin-independent NADH and NADPH oxidoreductase activities when potassium ferricyanide is the electron acceptor. Images Fig. 2. PMID:3060113

  10. Understanding Regeneration of Arsenate-Loaded Ferric Hydroxide-Based Adsorbents

    PubMed Central

    Chaudhary, Binod Kumar; Farrell, James

    2015-01-01

    Abstract Adsorbents comprising ferric hydroxide loaded on a variety of support materials are commonly used to remove arsenic from potable water. Although several studies have investigated the effects of support properties on arsenic adsorption, there have been no investigations of their effects on adsorbent regeneration. Furthermore, the effect of regenerant solution composition and the kinetics of regeneration have not been investigated. This research investigated the effects of adsorbent and regenerant solution properties on the kinetics and efficiency of regeneration of arsenate-loaded ferric hydroxide-based adsorbents. Solutions containing only 0.10–5.0 M NaOH or 0.10–1.0 M NaCl, as well as solutions containing both compounds, were used as regenerants. On all media, >99% of arsenate was adsorbed through complexation with ferric hydroxide. Arsenate recovery was controlled by both equilibrium and kinetic limitations. Adsorbents containing support material with weak base anion-exchange functionality or no anion-exchange functionality could be regenerated with NaOH solutions alone. Regeneration of media containing strong base anion (SBA)-exchange functionality was greatly enhanced by addition of 0.10 M NaCl to the NaOH regenerant solutions. Adsorbed silica had a significant effect on NaOH regeneration of media containing type I SBA-exchange functionality, but on other media, adsorbed silica had little impact on regeneration. On all media, 5–25% of arsenate was resistant to desorption in 1.0 M NaOH solutions. However, the use of 2.5–5.0 M NaOH solutions significantly reduced the desorption-resistant fraction. PMID:25873779

  11. Vanadium(V) oxide arsenate(V), VOAsO4

    PubMed Central

    Ezzine Yahmed, Safa; Zid, Mohamed Faouzi; Driss, Ahmed

    2011-01-01

    The vanadyl arsenate, VOAsO4, has been isolated by a solid-state reaction. The structure consists of distorted VO6 octa­hedra and AsO4 tetra­hedra sharing corners to build up VAsO7 layers parallel to ac linked by edge-sharing of VO6 octa­hedra, forming a three-dimensional framework. PMID:21522229

  12. Quantitative trace-level speciation of arsenite and arsenate in drinking water by ion chromatography.

    PubMed

    Johnson, Rebecca L; Aldstad, Joseph H

    2002-10-01

    We describe an improved method for the determination of inorganic arsenic in drinking water. The method is based on comprehensive optimization of the anion-exchange ion chromatographic (IC) separation of arsenite and arsenate with post-column generation and detection of the arsenate-molybdate heteropoly acid (AMHPA) complex ion. The arsenite capacity factor was improved from 0.081 to 0.13 by using a mobile phase (2.0 mL min(-1)) composed of 2.5 mM Na2CO3 and 0.91 mM NaHCO3 (pH 10.5). A post-column photo-oxidation reactor (2.5 m x 0.7 mm) was optimized (0.37 microM potassium persulfate at 0.50 mL min(-1)) such that arsenite was converted to arsenate with 99.8 +/- 4.2% efficiency. Multi-variate optimization of the complexation reaction conditions yielded the following levels: 1.3 mM ammonium molybdate, 7.7 mM ascorbic acid, 0.48 M nitric acid, 0.17 mM potassium antimony tartrate, and 1.0% (v/v) glycerol. A long-path length flow cell (Teflon AF, 100-cm) was used to measure the absorption of the AMHPA complex (818 +/- 2 nm). Figures of merit for arsenite/arsenate include: limit of detection (1.6/0.40 microg L(-1)): standard error in absorbance (5.1 x 10(-3)/3.5 x 10(-3)); and sensitivity (2.9 x 10(-3)/2.2 x 10(-3) absorbance units per ppb). Successful application of the method to fortified surface and ground waters (100 microL samples) is also described. PMID:12430600

  13. Enhanced Arsenate Removal Performance in Aqueous Solution by Yttrium-Based Adsorbents

    PubMed Central

    Lee, Sang-Ho; Kim, Kyoung-Woong; Lee, Byung-Tae; Bang, Sunbaek; Kim, Hyunseok; Kang, Hyorang; Jang, Am

    2015-01-01

    Arsenic contamination in drinking water has become an increasingly important issue due to its high toxicity to humans. The present study focuses on the development of the yttrium-based adsorbents, with basic yttrium carbonate (BYC), Ti-loaded basic yttrium carbonate (Ti-loaded BYC) and yttrium hydroxide prepared using a co-precipitation method. The Langmuir isotherm results confirmed the maximum adsorption capacity of Ti-loaded BYC (348.5 mg/g) was 25% higher than either BYC (289.6 mg/g) or yttrium hydroxide (206.5 mg/g) due to its increased specific surface area (82 m2/g) and surface charge (PZC: 8.4). Pseudo first- and second-order kinetic models further confirmed that the arsenate removal rate of Ti-loaded BYC was faster than for BYC and yttrium hydroxide. It was subsequently posited that the dominant removal mechanism of BYC and Ti-loaded BYC was the carbonate-arsenate ion exchange process, whereas yttrium hydroxide was regarded to be a co-precipitation process. The Ti-loaded BYC also displayed the highest adsorption affinity for a wide pH range (3–11) and in the presence of coexisting anionic species such as phosphate, silicate, and bicarbonate. Therefore, it is expected that Ti-loaded BYC can be used as an effective and practical adsorbent for arsenate remediation in drinking water. PMID:26516879

  14. Equilibrium and kinetics studies of arsenate adsorption by FePO(4).

    PubMed

    Hamayun, M; Mahmood, T; Naeem, A; Muska, M; Din, S U; Waseem, M

    2014-03-01

    The present work is focusing on removal of arsenate from aqueous solution using FePO4. The equilibrium study regarding the removal of arsenic by FePO4 was carried out at 298, 308, 318 and 328K. Langmuir parameters were found to increase with the increase in temperature indicating that the adsorption is favorable at high temperature. Kinetic study of arsenate adsorption on FePO4 was also carried out at different temperatures and at pH 6 and 8. Different kinetic models were used to the kinetic data amongst which pseudo second order model was best fitted. The mechanism of the adsorption kinetics was investigated by employing intraparticle diffusion and Richenberg models. The energy of activation (Ea) was found to be 30 and 35.52kJmol(-1) at pH 6 and pH 8, respectively, suggesting chemisorption nature of the adsorption process. The negative entropic values of activation signified the existence of entropy barrier while the positive ΔG(#) values indicated the existence of energy barrier to be crossed over for the occurrence of a chemical reaction. Both the spectroscopic studies and increase in equilibrium pH reveal the anion exchange removal of arsenate from aqueous solution to the solid surface. PMID:24280053

  15. Enhanced Arsenate Removal Performance in Aqueous Solution by Yttrium-Based Adsorbents.

    PubMed

    Lee, Sang-Ho; Kim, Kyoung-Woong; Lee, Byung-Tae; Bang, Sunbaek; Kim, Hyunseok; Kang, Hyorang; Jang, Am

    2015-10-01

    Arsenic contamination in drinking water has become an increasingly important issue due to its high toxicity to humans. The present study focuses on the development of the yttrium-based adsorbents, with basic yttrium carbonate (BYC), Ti-loaded basic yttrium carbonate (Ti-loaded BYC) and yttrium hydroxide prepared using a co-precipitation method. The Langmuir isotherm results confirmed the maximum adsorption capacity of Ti-loaded BYC (348.5 mg/g) was 25% higher than either BYC (289.6 mg/g) or yttrium hydroxide (206.5 mg/g) due to its increased specific surface area (82 m²/g) and surface charge (PZC: 8.4). Pseudo first- and second-order kinetic models further confirmed that the arsenate removal rate of Ti-loaded BYC was faster than for BYC and yttrium hydroxide. It was subsequently posited that the dominant removal mechanism of BYC and Ti-loaded BYC was the carbonate-arsenate ion exchange process, whereas yttrium hydroxide was regarded to be a co-precipitation process. The Ti-loaded BYC also displayed the highest adsorption affinity for a wide pH range (3-11) and in the presence of coexisting anionic species such as phosphate, silicate, and bicarbonate. Therefore, it is expected that Ti-loaded BYC can be used as an effective and practical adsorbent for arsenate remediation in drinking water. PMID:26516879

  16. Synergistic effect of calcium and bicarbonate in enhancing arsenate release from ferrihydrite

    NASA Astrophysics Data System (ADS)

    Saalfield, Samantha L.; Bostick, Benjamin C.

    2010-09-01

    Many groundwater systems contain anomalously high arsenic concentrations, associated with less than expected retention of As by adsorption to iron (hydr)oxides. Although carbonates are ubiquitous in aquifers, their relationship to arsenate mobilization is not well characterized. This research examines arsenate release from poorly crystalline iron hydroxides in abiotic systems containing calcium and magnesium with bicarbonate under conditions of static and dynamic flow (pH 7.5-8). Aqueous arsenic levels remained low when arsenate-bearing ferrihydrite was equilibrated with artificial groundwater solution containing Ca, Mg, and HCO 3-. In batch titrations in which a solution of Ca and HCO 3- was added repeatedly, the ferrihydrite surface became saturated with adsorbed Ca and HCO 3-, and aqueous As levels increased by 1-2 orders of magnitude. In columns containing Ca or Mg and HCO 3-, As solubility initially mimicked titrations, but then rapidly increased by an additional order of magnitude (reaching 12 μM As). Separately, calcium chloride and other simple salts did not induce As release, although sodium bicarbonate and lactate facilitated minor As release under flow. Results indicate that adsorption of calcium or magnesium with bicarbonate leads to As desorption from ferrihydrite, to a degree greater than expected from competitive effects alone, especially under dynamic flow. This desorption may be an important mechanism of As mobilization in As-impacted, circumneutral aquifers, especially those undergoing rapid mineralization of organic matter, which induces calcite dissolution and the production of dissolved calcium and bicarbonate.

  17. Antagonistic toxicity of arsenate and cadmium in a freshwater amphipod (Gammarus pulex).

    PubMed

    Vellinger, Céline; Parant, Marc; Rousselle, Philippe; Usseglio-Polatera, Philippe

    2012-10-01

    Because toxicants rarely occur alone in the environment, a major challenge in risk assessment is to address the combined effects of chemicals on aquatic organisms. This work is aimed at investigating the joint toxicity action of binary mixtures of cadmium and arsenate on Gammarus pulex. Individuals were exposed during 240 h to four single arsenate or cadmium concentrations and binary mixtures of these metals according to a complete factorial plane. Observed mortality in binary mixtures was compared to observed mortality in single arsenate or cadmium exposures. In addition, interactive effects (antagonistic, additive or synergistic) were evaluated using a predictive model for the theoretically expected interactive effect of chemicals. For all the tested concentration combinations, we observed an antagonist 'between-metals' interaction on G. pulex mortality. This antagonistic effect was more marked for the lowest than for the highest (i.e. 1502.0 μg(AsV) L(-1) and 28.5 μg(Cd) L(-1)) tested concentrations of individual metals in binary mixtures. Metal concentrations in body tissues were evaluated and were significantly lower in binary mixtures than in single metal exposures at similar concentration, especially for combinations corresponding to the highest concentrations of both metals (1502.0 μg(AsV) L(-1) and 28.5 μg(Cd) L(-1)). Results were discussed in terms of (1) mechanisms of uptake and bioconcentration and (2) relationships between metal concentration in gammarid body and observed toxicity. PMID:22535317

  18. [Occurrence Characteristics of Pyrene and Arsenate and Their Interaction in Pteris vittata L].

    PubMed

    Zhang, Yu-xiu; Ma, Xu; Liao, Xiao-yong; Yan, Xiu-lan; Ma, Dong; Gong, Xue-gang

    2015-12-01

    Pteris vittata L. can absorb and accumulate high arsenic levels in soil. To clarify the occurrence characteristics of pyrene (PYR) and arsenate (As) as well as their interaction in P. vittata L., the hosting and distribution rules of PYR were determined via two-photon laser scanning confocal microscopy (TPLSCM). The results showed that PYR addition resulted in obviously lower concentrations of total As in various parts of P. vittata, with a largest decrease of about 35% in the leaves and stem, and 20. 5% in the roots. PYR addition could also decrease the proportion of trivalent arsenic and increased that of pentavalent arsenate in different parts of P. vittata. The concentrations of trivalent and pentavalent arsenic in the leaves of P. vittata showed the largest decrement, which were 42.2% and 32.49%, respectively. Arsenate addition increased the accumulation of PYR in the root and stem of P. vittata by 9.8 µg and 139 ng per plant, respectively, while no obvious influence was found on the PYR in the leaves. Pyrene mainly attached to the cell membrane and other membrane structure such as nuclear membrane and organelle membrane, and there was less pyrene in the cytoplasm. There was little PYR in the phloem and cortex in the stem as well as palisade tissue and spongy tissue in leaves. PMID:27012002

  19. An SEM-EDX and Raman spectroscopic study of the fibrous arsenate mineral liskeardite and in comparison with other arsenates kaňkite, scorodite and yvonite.

    PubMed

    Frost, Ray L; Scholz, Ricardo; Jirásek, Jakub; Belotti, Fernanda Maria

    2015-12-01

    The mineral liskeardite, an arsenate mineral with major cations of iron and aluminium, has been studied by a combination of scanning electron microscopy with energy dispersive spectroscopy and Raman spectroscopy. The mineral shows a fibrous nature. Semi-quantitative chemical analysis shows an Al and Fe arsenate phase with minor amounts of K, Cu, S and Si. Scanning electron microscopy shows a fibrous material. Intense Raman bands at 893, 867 and 843 cm(-1) are assigned to the ν1 and ν3 AsO4(3)(-) and HOAsO3(2)(-) symmetric and antisymmetric stretching vibrations. Raman bands are observed at 514, 499, 485 and 477 cm(-1) and are assigned to the ν4 out of plane bending modes of the AsO4(3)(-) and HOAsO3(2)(-) units. The series of bands at 373, 356 and 343 cm(-1) are assigned to the ν2 symmetric bending modes. Two groups of OH stretching bands are observed and assigned to OH unit and water stretching vibrations. A comparison of the Raman spectrum of liskeardite with scorodite, kaňkite and yvonite is made. PMID:26162345

  20. A vibrational spectroscopic study of the arsenate mineral bayldonite (Cu,Zn)3Pb(AsO3OH)2(OH)2 - A comparison with other basic arsenates

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; de Oliveira Gonçalves, Guilherme; Scholz, Ricardo; Xi, Yunfei

    2014-01-01

    We have studied the vibrational spectra of the mineral bayldonite, a hydroxy arsenate of copper and lead of formula Cu3Pb(AsO3OH)2(OH)2 from the type locality, the Penberthy Croft Mine, St Hilary, Mount's Bay District, Cornwall, England and relate the spectra to the mineral structure. Raman bands at 896 and 838 cm-1 are assigned to the ( ν1 symmetric stretching mode and the second to the ( ν3 antisymmetric stretching mode. It is noted that the position of the symmetric stretching mode is at a higher position than the antisymmetric stretching mode. It is proposed that the Raman bands at 889 and 845 cm-1 are symmetric and antisymmetric stretching modes of the (HOAsO3)2- units. Raman bands of bayldonite at 490 and 500 cm-1 are assigned to the ( ν4 bending modes. Raman bands for bayldonite are noted at 396, 408 and 429 cm-1 and are assigned to the ( ν2 bending modes. A comparison is made with spectra of the other basic copper arsenate minerals, namely cornubite, olivenite, cornwallite.

  1. Glutathione-dependent reduction of arsenate in human erythrocytes--a process independent of purine nucleoside phosphorylase.

    PubMed

    Németi, Balázs; Gregus, Zoltán

    2004-12-01

    Reduction of arsenate (AsV) to the more toxic arsenite (AsIII) is toxicologically important, yet its mechanism is unknown. To clarify this, AsV reduction was investigated in human red blood cells (RBC), as they possess a simple metabolism. RBC were incubated with AsV in gluconate buffer, and the formed AsIII was quantified by high performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS). The observations are compatible with the following conclusions. (1) Human RBC reduce AsV intracellularly, because 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS, inhibitor of the chloride-bicarbonate exchanger, which also mediates phosphate and AsV uptake), as well as chloride and phosphate, countered AsIII formation. (2) Purine nucleoside phosphorylase (PNP), whose AsV reductase activity has been directly demonstrated, cannot be a physiologically relevant AsV reductase, because its inhibitor (BCX-1777) failed to decrease the basal erythrocytic AsV reduction, although it prevented the increase in AsIII formation caused by artificial activation of PNP with inosine and dithiothreitol. (3) The basal (PNP-independent) AsV reduction requires glutathione (GSH), because the GSH depletor diethylmaleate strongly diminished AsIII formation. (4) The erythrocytic AsV reduction apparently depends on NAD(P) supply, because oxidants of NAD(P)H (i.e., pyruvate, ferricyanide, methylene blue, nitrite, tert-butylhydroperoxide, dehydroascorbate, 4-dimethylaminophenol) enhanced AsIII formation from AsV. The oxidant-stimulated AsV reduction is PNP-independent, because BCX-1777 failed to affect it, but is GSH-dependent, because diethylmaleate impaired it. (5) Pyruvate-induced glucose depletion, which causes NAD enrichment in the erythrocytes at the expense of NADH, enhanced AsV reduction. This suggests that the erythrocytic AsV reduction requires both NAD supply and operation of the lower part of the glycolytic pathway starting from glyceraldehyde-3

  2. Periplasmic Nitrate Reductase (NapABC Enzyme) Supports Anaerobic Respiration by Escherichia coli K-12

    PubMed Central

    Stewart, Valley; Lu, Yiran; Darwin, Andrew J.

    2002-01-01

    Periplasmic nitrate reductase (NapABC enzyme) has been characterized from a variety of proteobacteria, especially Paracoccus pantotrophus. Whole-genome sequencing of Escherichia coli revealed the structural genes napFDAGHBC, which encode NapABC enzyme and associated electron transfer components. E. coli also expresses two membrane-bound proton-translocating nitrate reductases, encoded by the narGHJI and narZYWV operons. We measured reduced viologen-dependent nitrate reductase activity in a series of strains with combinations of nar and nap null alleles. The napF operon-encoded nitrate reductase activity was not sensitive to azide, as shown previously for the P. pantotrophus NapA enzyme. A strain carrying null alleles of narG and narZ grew exponentially on glycerol with nitrate as the respiratory oxidant (anaerobic respiration), whereas a strain also carrying a null allele of napA did not. By contrast, the presence of napA+ had no influence on the more rapid growth of narG+ strains. These results indicate that periplasmic nitrate reductase, like fumarate reductase, can function in anaerobic respiration but does not constitute a site for generating proton motive force. The time course of Φ(napF-lacZ) expression during growth in batch culture displayed a complex pattern in response to the dynamic nitrate/nitrite ratio. Our results are consistent with the observation that Φ(napF-lacZ) is expressed preferentially at relatively low nitrate concentrations in continuous cultures (H. Wang, C.-P. Tseng, and R. P. Gunsalus, J. Bacteriol. 181:5303-5308, 1999). This finding and other considerations support the hypothesis that NapABC enzyme may function in E. coli when low nitrate concentrations limit the bioenergetic efficiency of nitrate respiration via NarGHI enzyme. PMID:11844760

  3. Sodium arsenate induce changes in fatty acids profiles and oxidative damage in kidney of rats.

    PubMed

    Kharroubi, Wafa; Dhibi, Madiha; Mekni, Manel; Haouas, Zohra; Chreif, Imed; Neffati, Fadoua; Hammami, Mohamed; Sakly, Rachid

    2014-10-01

    Six groups of rats (n = 10 per group) were exposed to 1 and 10 mg/l of sodium arsenate for 45 and 90 days. Kidneys from treated groups exposed to arsenic showed higher levels of trans isomers of oleic and linoleic acids as trans C181n-9, trans C18:1n-11, and trans C18:2n-6 isomers. However, a significant decrease in eicosenoic (C20:1n-9) and arachidonic (C20:4n-6) acids were observed in treated rats. Moreover, the "Δ5 desaturase index" and the saturated/polyunsaturated fatty acids ratio were increased. There was a significant increase in the level of malondialdehyde at 10 mg/l of treatment and in the amount of conjugated dienes after 90 days (p < 0.05). Significant kidney damage was observed at 10 mg/l by increase of plasma marker enzymes. Histological studies on the ultrastructure changes of kidney supported the toxic effect of arsenate exposure. Arsenate intoxication activates significantly the superoxide dismutase at 10 mg/l for 90 days, whereas the catalase activity was markedly inhibited in all treated groups (p < 0.05). In addition, glutathione peroxidase activity was significantly increased at 45 days and dramatically declined after 90 days at 10 mg/l (p < 0.05). A significant increase in the level of glutathione was marked for the groups treated for 45 and 90 days at 1 mg/l followed by a significant decrease for rats exposed to 10 mg/l for 90 days. An increase in the level of protein carbonyl was observed in all treated groups (p < 0.05). In conclusion, the present study provides evidence for a direct effect of arsenate on fatty acid (FA) metabolism which concerns the synthesis pathway of n-6 polyunsaturated fatty acids and leads to an increase in the trans FAs isomers. Therefore, FA-induced arsenate kidney damage could contribute to trigger kidney cancer. PMID:24920263

  4. An electrogenic nitric oxide reductase.

    PubMed

    Al-Attar, Sinan; de Vries, Simon

    2015-07-22

    Nitric oxide reductases (Nors) are members of the heme-copper oxidase superfamily that reduce nitric oxide (NO) to nitrous oxide (N₂O). In contrast to the proton-pumping cytochrome oxidases, Nors studied so far have neither been implicated in proton pumping nor have they been experimentally established as electrogenic. The copper-A-dependent Nor from Bacillus azotoformans uses cytochrome c₅₅₁ as electron donor but lacks menaquinol activity, in contrast to our earlier report (Suharti et al., 2001). Employing reduced phenazine ethosulfate (PESH) as electron donor, the main NO reduction pathway catalyzed by Cu(A)Nor reconstituted in liposomes involves transmembrane cycling of the PES radical. We show that Cu(A)Nor reconstituted in liposomes generates a proton electrochemical gradient across the membrane similar in magnitude to cytochrome aa₃, highlighting that bacilli using Cu(A)Nor can exploit NO reduction for increased cellular ATP production compared to organisms using cNor. PMID:26149211

  5. Tetrathionate reductase of Salmonella thyphimurium: a molybdenum containing enzyme

    SciTech Connect

    Hinojosa-Leon, M.; Dubourdieu, M.; Sanchez-Crispin, J.A.; Chippaux, M.

    1986-04-29

    Use of radioactive molybdenum demonstrates that the tetrathionate reductase of Salmonella typhimurium is a molydenum containing enzyme. It is proposed that this enzyme shares with other molybdo-proteins, such as nitrate reductase, a common molybdenum containing cofactor the defect of which leads to the loss of the tetrathionate reductase and nitrate reductase activities.

  6. Dynamic subcellular localization of a respiratory complex controls bacterial respiration

    PubMed Central

    Alberge, François; Espinosa, Leon; Seduk, Farida; Sylvi, Léa; Toci, René; Walburger, Anne; Magalon, Axel

    2015-01-01

    Respiration, an essential process for most organisms, has to optimally respond to changes in the metabolic demand or the environmental conditions. The branched character of their respiratory chains allows bacteria to do so by providing a great metabolic and regulatory flexibility. Here, we show that the native localization of the nitrate reductase, a major respiratory complex under anaerobiosis in Escherichia coli, is submitted to tight spatiotemporal regulation in response to metabolic conditions via a mechanism using the transmembrane proton gradient as a cue for polar localization. These dynamics are critical for controlling the activity of nitrate reductase, as the formation of polar assemblies potentiates the electron flux through the complex. Thus, dynamic subcellular localization emerges as a critical factor in the control of respiration in bacteria. DOI: http://dx.doi.org/10.7554/eLife.05357.001 PMID:26077726

  7. Effect of silicic acid on arsenate and arsenite retention mechanisms on 6-L ferrihydrite: A spectroscopic and batch adsorption approach

    PubMed Central

    Gao, Xiaodong; Root, Robert A.; Farrell, James; Ela, Wendell; Chorover, Jon

    2014-01-01

    The competitive adsorption of arsenate and arsenite with silicic acid at the ferrihydrite-water interface was investigated over a wide pH range using batch sorption experiments, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) modeling. Batch sorption results indicate that the adsorption of arsenate and arsenite on the 6-L ferrihydrite surface exhibits a strong pH-dependence, and the effect of pH on arsenic sorption differs between arsenate and arsenite. Arsenate adsorption decreases consistently with increasing pH; whereas arsenite adsorption initially increases with pH to a sorption maximum at pH 7–9, where after sorption decreases with further increases in pH. Results indicate that competitive adsorption between silicic acid and arsenate is negligible under the experimental conditions; whereas strong competitive adsorption was observed between silicic acid and arsenite, particularly at low and high pH. In-situ, flow-through ATR-FTIR data reveal that in the absence of silicic acid, arsenate forms inner-sphere, binuclear bidentate, complexes at the ferrihydrite surface across the entire pH range. Silicic acid also forms inner-sphere complexes at ferrihydrite surfaces throughout the entire pH range probed by this study (pH 2.8 – 9.0). The ATR-FTIR data also reveal that silicic acid undergoes polymerization at the ferrihydrite surface under the environmentally-relevant concentrations studied (e.g., 1.0 mM). According to ATR-FTIR data, arsenate complexation mode was not affected by the presence of silicic acid. EXAFS analyses and DFT modeling confirmed that arsenate tetrahedra were bonded to Fe metal centers via binuclear bidentate complexation with average As(V)-Fe bond distance of 3.27 Å. The EXAFS data indicate that arsenite forms both mononuclear bidentate and binuclear bidentate complexes with 6-L ferrihydrite as indicated by

  8. Genetics Home Reference: sepiapterin reductase deficiency

    MedlinePlus

    ... reductase enzyme. This enzyme is involved in the production of a molecule called tetrahydrobiopterin (also known as ... is responsible for the last step in the production of tetrahydrobiopterin. Tetrahydrobiopterin helps process several building blocks ...

  9. A dissimilatory nitrite reductase in Paracoccus halodenitrificans

    NASA Technical Reports Server (NTRS)

    Grant, M. A.; Hochstein, L. I.

    1984-01-01

    Paracoccus halodenitrificans produced a membrane-associated nitrite reductase. Spectrophotometric analysis showed it to be associated with a cd-cytochrome and located on the inner side of the cytoplasmic membrane. When supplied with nitrite, membrane preparations produced nitrous oxide and nitric oxide in different ratios depending on the electron donor employed. The nitrite reductase was maximally active at relatively low concentrations of sodium chloride and remained attached to the membranes at 100 mM sodium chloride.

  10. Effect of inorganic and organic ligands on the sorption/desorption of arsenate on/from Al-Mg and Fe-Mg layered double hydroxides

    NASA Astrophysics Data System (ADS)

    Caporale, A. G.; Pigna, M.; Dynes, J. J.; Cozzolino, V.; Zhu, J.; Violante, A.

    2012-04-01

    In recent decades, a class of anionic clays known as layered double hydroxides (LDHs) has attracted substantial attention due to the potential use in many applications, such as photochemistry, electrochemistry, polymerization, magnetization and biomedical science. There has also been considerable interest in using LDHs as adsorbents to remove environmental contaminants due to their large surface area, high anion exchange capacity and good thermal stability. We studied the sorption of arsenate on Al-Mg and Fe-Mg layered double hydroxides (easily reproducible at low-cost) as affected by pH and varying concentrations of inorganic (nitrate, nitrite, phosphate, selenite and sulphate) and organic (oxalate and tartrate) ligands, ii) the effect of residence time on the arsenate desorption by these ligands, and iii) the kinetics of arsenate desorption by phosphate. The Fe-Mg-LDH sorbed nearly twice the amount of arsenate compared to the Al-Mg-LDH, due, in part, to its greater surface area and lower degree of crystallinity. Moreover, the Fe-Mg-LDH sorbed more arsenate than phosphate, in contrast to the Al-Mg-LDH, which adsorbed more phosphate than arsenate, probably because of the greater affinity of arsenate than phosphate for Fe sites and, vice versa, the greater affinity of phosphate than arsenate for Al sites. Arsenate sorption onto samples decreased by increasing pH, due, maybe, to the high affinity of hydroxyl ions for LDHs and/or to the value of zero point charge of two sorbents. The rate of decline in the amount of arsenate sorbed was, however, relatively constant, decreasing the fastest for the Fe-Mg-LDH compared to the Al-Mg-LDH. The capacity of ligands to inhibit the fixation of arsenate followed the sequence: nitrate < nitrite < sulphate < selenite < tartrate < oxalate << phosphate on Al-Mg-LDH and nitrate < sulphate ≈ nitrite < tartrate < oxalate < selenite << phosphate on Fe-Mg-LDH. The inhibition of arsenate sorption increased by increasing the initial

  11. Multiple aldehyde reductases of human brain.

    PubMed

    Hoffman, P L; Wermuth, B; von Wartburg, J P

    1980-01-01

    Human brain contains four forms of aldehyde reducing enzymes. One major activity, designated AR3, has properties indicating its identity with the NADPH-dependent aldehyde reductase, EC 1.1.1.2. The other major form of human brain enzyme, AR1, which is also NADPH-dependent, reduces both aldehyde and ketone-containing substrates, including vitamin K3 (menadione) and daunorubicin, a cancer chemotherapeutic agent. This enzyme is very sensitive to inhibition by the flavonoids quercitrin and quercetine, and may be analogous to a daunorubicin reductase previously described in liver of other species. One minor form of human brain aldehyde reductase, AR2, demonstrates substrate specificity and inhibitor sensitivity which suggest its similarity to aldose reductases found in lens and other tissues of many species. This enzyme, which can also use NADH as cofactor to some extent, is the most active in reducing the aldehyde derivatives of the biogenic amines. The fourth human brain enzyme ("SSA reductase") differs from the other forms in its ability to use NADH as well as or better than NADPH as cofactor, and in its molecular weight, which is nearly twice that of the other forms. It is quite specific for succinic semialdehyde (SSA) as substrate, and was found to be significantly inhibited only by quercetine and quercitrin. AR3 can also reduce SSA, and both enzymes may contribute to the production of gamma-hydroxybutyric acid in vivo. These results indicate that the human brain aldehyde reductases can play relatively specific physiologic roles. PMID:7424738

  12. Nitrogen and oxygen regulation of Bacillus subtilis nasDEF encoding NADH-dependent nitrite reductase by TnrA and ResDE.

    PubMed

    Nakano, M M; Hoffmann, T; Zhu, Y; Jahn, D

    1998-10-01

    The nitrate and nitrite reductases of Bacillus subtilis have two different physiological functions. Under conditions of nitrogen limitation, these enzymes catalyze the reduction of nitrate via nitrite to ammonia for the anabolic incorporation of nitrogen into biomolecules. They also function catabolically in anaerobic respiration, which involves the use of nitrate and nitrite as terminal electron acceptors. Two distinct nitrate reductases, encoded by narGHI and nasBC, function in anabolic and catabolic nitrogen metabolism, respectively. However, as reported herein, a single NADH-dependent, soluble nitrite reductase encoded by the nasDE genes is required for both catabolic and anabolic processes. The nasDE genes, together with nasBC (encoding assimilatory nitrate reductase) and nasF (required for nitrite reductase siroheme cofactor formation), constitute the nas operon. Data presented show that transcription of nasDEF is driven not only by the previously characterized nas operon promoter but also from an internal promoter residing between the nasC and nasD genes. Transcription from both promoters is activated by nitrogen limitation during aerobic growth by the nitrogen regulator, TnrA. However, under conditions of oxygen limitation, nasDEF expression and nitrite reductase activity were significantly induced. Anaerobic induction of nasDEF required the ResDE two-component regulatory system and the presence of nitrite, indicating partial coregulation of NasDEF with the respiratory nitrate reductase NarGHI during nitrate respiration. PMID:9765565

  13. Nitrogen and Oxygen Regulation of Bacillus subtilis nasDEF Encoding NADH-Dependent Nitrite Reductase by TnrA and ResDE

    PubMed Central

    Nakano, Michiko M.; Hoffmann, Tamara; Zhu, Yi; Jahn, Dieter

    1998-01-01

    The nitrate and nitrite reductases of Bacillus subtilis have two different physiological functions. Under conditions of nitrogen limitation, these enzymes catalyze the reduction of nitrate via nitrite to ammonia for the anabolic incorporation of nitrogen into biomolecules. They also function catabolically in anaerobic respiration, which involves the use of nitrate and nitrite as terminal electron acceptors. Two distinct nitrate reductases, encoded by narGHI and nasBC, function in anabolic and catabolic nitrogen metabolism, respectively. However, as reported herein, a single NADH-dependent, soluble nitrite reductase encoded by the nasDE genes is required for both catabolic and anabolic processes. The nasDE genes, together with nasBC (encoding assimilatory nitrate reductase) and nasF (required for nitrite reductase siroheme cofactor formation), constitute the nas operon. Data presented show that transcription of nasDEF is driven not only by the previously characterized nas operon promoter but also from an internal promoter residing between the nasC and nasD genes. Transcription from both promoters is activated by nitrogen limitation during aerobic growth by the nitrogen regulator, TnrA. However, under conditions of oxygen limitation, nasDEF expression and nitrite reductase activity were significantly induced. Anaerobic induction of nasDEF required the ResDE two-component regulatory system and the presence of nitrite, indicating partial coregulation of NasDEF with the respiratory nitrate reductase NarGHI during nitrate respiration. PMID:9765565

  14. Effect of inorganic and organic ligands on the sorption/desorption of arsenate on/from Al-Mg and Fe-Mg layered double hydroxides.

    PubMed

    Caporale, A G; Pigna, M; Dynes, J J; Cozzolino, V; Zhu, J; Violante, A

    2011-12-30

    This paper describes the sorption of arsenate on Al-Mg and Fe-Mg layered double hydroxides as affected by pH and varying concentrations of inorganic and organic ligands, and the effect of residence time on the desorption of arsenate by ligands. The capacity of ligands to inhibit the fixation of arsenate followed the sequence: nitratearsenate sorption increased by increasing the initial ligand concentration and was greater on Al-Mg-LDH than on Fe-Mg-LDH. The longer the arsenate residence time on the LDH surfaces the less effective the competing ligands were in desorbing arsenate from sorbents. A greater percentage of arsenate was removed by phosphate from Al-Mg-LDH than from Fe-Mg-LDH, due to the higher affinity of arsenate for iron than aluminum. PMID:22071258

  15. Speciation of arsenic in Greek travertines: Co-precipitation of arsenate with calcite

    NASA Astrophysics Data System (ADS)

    Winkel, Lenny H. E.; Casentini, Barbara; Bardelli, Fabrizio; Voegelin, Andreas; Nikolaidis, Nikolaos P.; Charlet, Laurent

    2013-04-01

    The western part of the Chalkidiki peninsula in Northern Greece is a geothermally active area that contains high levels of naturally derived arsenic in its alkaline groundwaters (up to 3760 μg/L). Near wells, equilibration of these groundwaters with atmospheric carbon dioxide leads to the precipitation of travertines that contain very high levels of arsenic (up to 913 mg/kg). To determine the mechanism of arsenic uptake in these travertines, we analyzed two different types of travertine from this region using both bulk and micro-focused X-ray absorption spectroscopy (XAS and μ-XAS) and micro-focused X-ray fluorescence spectroscopy (μ-XRF). Bulk XAS showed that in all of the studied samples arsenic is present in the pentavalent oxidation state (arsenate). μ-XRF analyses indicated that arsenic is closely associated with the calcite matrix and that it generally does not correlate well with iron. The arsenic K-edge XAS spectra of all samples closely matched each other and closely resembled a reference spectrum for arsenate coprecipitated with calcite (rather than adsorbed or pure calcium arsenate). Iron on the other hand was found to be mainly present as a constituent of clay minerals, of presumably detrital origin, suggesting that iron-(hydr)oxides were not sufficiently abundant to act as major scavengers for arsenic in the Chalkidiki travertines. We estimated that calcite in these travertines could sequester at least 25% of aqueous arsenic in the form of As(V) and thus immobilize a substantial part of arsenic present in the geothermal groundwaters. These results may also be relevant for other areas where geothermal groundwaters carry arsenic to the surface and possibly as well for arsenic geochemistry in other environments with CO2-enriched water.

  16. Influence of extreme conditions on the formation and structures of caesium uranium(VI) arsenates.

    PubMed

    Yu, Na; Kegler, Philip; Klepov, Vladislav V; Dellen, Jakob; Schlenz, Hartmut; Langer, Eike M; Bosbach, Dirk; Alekseev, Evgeny V

    2015-12-21

    Four new uranyl arsenates, Cs2[(UO2)(As2O7)] (1), α-Cs[(UO2)(HAs2O7)] (2), β-Cs[(UO2)(HAs2O7)] (3), Cs[(UO2)(HAs2O7)]·0.17H2O (4), were synthesized by high-temperature/high pressure (HT/HP) reactions at 900 °C and 3 GPa. These phases were subsequently characterised structurally as well as chemically. We demonstrated that compound 1 can also be obtained at ambient pressure. Compounds 1, 2, and 4 are based on two-dimensional (2D) anionic layers with two different topological types. The layers possess a similar composition, [(UO2)(As2O7)](2-) in 1 and [(UO2)(HAs2O7)](-) in 2 and 4. However, the presence of hydrogen in 2 and 4 leads to a change in coordination modes of the pyroarsenate groups. There are additional 0.17 H2O molecules per formula unit in 4, which cause slight distortions of the layers in 4. All these layers can be simplified to a common net, which is typical of autunite-like layered compounds. Compound 3 is a polymorph of compound 2, but the structural arrangements in these two are significantly different. The structure of 3 is based upon a three-dimensional (3D) framework, in which UO7 is coordinated by arsenate groups in order to form uranyl anion sheets, and UO6 is located within the interlayers. Bond valance analysis proved the presence of OH(-) groups in compounds 2, 3, and 4, respectively, and water molecules in 4. The Raman analyses enabled the study of the local environments of the arsenate and the uranyl groups within the investigated phases, respectively. It turned out that the applied HT/HP synthesis method strongly affects the crystal chemistry as well as the observed structural features of all obtained compounds. PMID:26567703

  17. Thioredoxin Reductase and its Inhibitors

    PubMed Central

    Saccoccia, Fulvio; Angelucci, Francesco; Boumis, Giovanna; Carotti, Daniela; Desiato, Gianni; Miele, Adriana E; Bellelli, Andrea

    2014-01-01

    Thioredoxin plays a crucial role in a wide number of physiological processes, which span from reduction of nucleotides to deoxyriboucleotides to the detoxification from xenobiotics, oxidants and radicals. The redox function of Thioredoxin is critically dependent on the enzyme Thioredoxin NADPH Reductase (TrxR). In view of its indirect involvement in the above mentioned physio/pathological processes, inhibition of TrxR is an important clinical goal. As a general rule, the affinities and mechanisms of binding of TrxR inhibitors to the target enzyme are known with scarce precision and conflicting results abound in the literature. A relevant analysis of published results as well as the experimental procedures is therefore needed, also in view of the critical interest of TrxR inhibitors. We review the inhibitors of TrxR and related flavoreductases and the classical treatment of reversible, competitive, non competitive and uncompetitive inhibition with respect to TrxR, and in some cases we are able to reconcile contradictory results generated by oversimplified data analysis. PMID:24875642

  18. Characterization of thyroidal glutathione reductase

    SciTech Connect

    Raasch, R.J.

    1989-01-01

    Glutathione levels were determined in bovine and rat thyroid tissue by enzymatic conjugation with 1-chloro-2,4-dinitrobenzene using glutathione S-transferase. Bovine thyroid tissue contained 1.31 {+-} 0.04 mM reduced glutathione (GSH) and 0.14 {+-} 0.02 mM oxidized glutathione (GSSG). In the rat, the concentration of GSH was 2.50 {+-} 0.05 mM while GSSG was 0.21 {+-} 0.03 mM. Glutathione reductase (GR) was purified from bovine thyroid to electrophoretic homogeneity by ion exchange, affinity and molecular exclusion chromatography. A molecular weight range of 102-109 kDa and subunit size of 55 kDa were determined for GR. Thyroidal GR was shown to be a favoprotein with one FAD per subunit. The Michaelis constants of bovine thyroidal GR were determined to be 21.8 {mu}M for NADPH and 58.8 {mu}M for GSSG. The effect of thyroid stimulating hormone (TSH) and thyroxine (T{sub 4}) on in vivo levels of GR and glucose 6-phosphate dehydrogenase were determined in rat thyroid homogenates. Both enzymes were stimulated by TSH treatment and markedly reduced following T{sub 4} treatment. Lysosomal hydrolysis of ({sup 125}I)-labeled and unlabeled thyroglobulin was examined using size exclusion HPLC.

  19. The cymA Gene, Encoding a Tetraheme c-Type Cytochrome, Is Required for Arsenate Respiration in Shewanella Species▿

    PubMed Central

    Murphy, Julie N.; Saltikov, Chad W.

    2007-01-01

    In Shewanella sp. strain ANA-3, utilization of arsenate as a terminal electron acceptor is conferred by a two-gene operon, arrAB, which lacks a gene encoding a membrane-anchoring subunit for the soluble ArrAB protein complex. Analysis of the genome sequence of Shewanella putrefaciens strain CN-32 showed that it also contained the same arrAB operon with 100% nucleotide identity. Here, we report that CN-32 respires arsenate and that this metabolism is dependent on arrA and an additional gene encoding a membrane-associated tetraheme c-type cytochrome, cymA. Deletion of cymA in ANA-3 also eliminated growth on and reduction of arsenate. The ΔcymA strains of CN-32 and ANA-3 negatively affected the reduction of Fe(III) and Mn(IV) but not growth on nitrate. Unlike the CN-32 ΔcymA strain, growth on fumarate was absent in the ΔcymA strain of ANA-3. Both homologous and heterologous complementation of cymA in trans restored growth on arsenate in ΔcymA strains of both CN-32 and ANA-3. Transcription patterns of cymA showed that it was induced under anaerobic conditions in the presence of fumarate and arsenate. Nitrate-grown cells exhibited the greatest level of cymA expression in both wild-type strains. Lastly, site-directed mutagenesis of the first Cys to Ser in each of the four CXXCH c-heme binding motifs of the CN-32 CymA nearly eliminated growth on and reduction of arsenate. Together, these results indicate that the biochemical mechanism of arsenate respiration and reduction requires the interactions of ArrAB with a membrane-associated tetraheme cytochrome, which in the non-arsenate-respiring Shewanella species Shewanella oneidensis strain MR-1, has pleiotropic effects on Fe(III), Mn(IV), dimethyl sulfoxide, nitrate, nitrite, and fumarate respiration. PMID:17209025

  20. Role of the Tat Transport System in Nitrous Oxide Reductase Translocation and Cytochrome cd1 Biosynthesis in Pseudomonas stutzeri

    PubMed Central

    Heikkilä, Mari P.; Honisch, Ulrike; Wunsch, Patrick; Zumft, Walter G.

    2001-01-01

    By transforming N2O to N2, the multicopper enzyme nitrous oxide reductase provides a periplasmic electron sink for a respiratory chain that is part of denitrification. The signal sequence of the enzyme carries the heptameric twin-arginine consensus motif characteristic of the Tat pathway. We have identified tat genes of Pseudomonas stutzeri and functionally analyzed the unlinked tatC and tatE loci. A tatC mutant retained N2O reductase in the cytoplasm in the unprocessed form and lacking the metal cofactors. This is contrary to viewing the Tat system as specific only for fully assembled proteins. A C618V exchange in the electron transfer center CuA rendered the enzyme largely incompetent for transport. The location of the mutation in the C-terminal domain of N2O reductase implies that the Tat system acts on a completely synthesized protein and is sensitive to a late structural variation in folding. By generating a tatE mutant and a reductase-overproducing strain, we show a function for TatE in N2O reductase translocation. Further, we have found that the Tat and Sec pathways have to cooperate to produce a functional nitrite reductase system. The cytochrome cd1 nitrite reductase was found in the periplasm of the tatC mutant, suggesting export by the Sec pathway; however, the enzyme lacked the heme D1 macrocycle. The NirD protein as part of a complex required for heme D1 synthesis or processing carries a putative Tat signal peptide. Since NO reduction was also inhibited in the tatC mutant, the Tat protein translocation system is necessary in multiple ways for establishing anaerobic nitrite denitrification. PMID:11160097

  1. Chemical Speciation and Bioaccessibility of Arsenic and Chromiumin Chromated Copper Arsenate-Treated Wood and Soils

    SciTech Connect

    Nico, Peter S.; Ruby, Michael V.; Lowney, Yvette W.; Holm,Stewart E.

    2005-10-12

    This research compares the As and Cr chemistry ofdislodgeable residues from Chromated Copper Arsenate (CCA)-treated woodcollected by two different techniques (directly from the board surfaceeither by rubbing with a soft bristle brush or from human hands aftercontact with CCA-treated wood), and demonstrates that these materials areequivalent in terms of the chemical form and bonding of As and Cr and interms of the As leaching behavior. This finding links the extensivechemical characterization and bioavailability testing that has been donepreviously on the brush-removed residue to a material that is derivedfrom human skin contact with CCA-treated wood. Additionally, thisresearch characterizes the arsenic present in biological fluids (sweatand simulated gastric fluid) following contact with these residues. Thedata demonstrate that in biological fluids, the arsenic is presentprimarily as free arsenate ions.Arsenic-containing soils were alsoextracted into human sweat to evaluate the potential for arsenicdissolution from soils at the skin surface. For soils from field sites,only a small fraction of the total arsenic is soluble in sweat. Based oncomparisons to reference materials that have been used in in vivo dermalabsorption studies, these findings suggest that the actual relativebioavailability via dermal absorption of As from CCA-residues and soilmay be well below the current default value of 3 percent used by U.S.EPA.

  2. Facile synthesis of highly active hydrated yttrium oxide towards arsenate adsorption.

    PubMed

    Yu, Yang; Yu, Ling; Sun, Min; Paul Chen, J

    2016-07-15

    A novel hydrated yttrium oxide adsorbent with high capacity towards the arsenate (As(V)) adsorption was fabricated by a one-step hydrothermal process. Structure analysis identified the hydrated yttrium oxide to be Y2O(OH)4·1.5H2O, which displayed as irregular rods in the range of tens to hundreds of nanometers. The adsorbent exhibited favorable As(V) adsorption efficiency in a wide pH range from 4.0 to 7.0, with the maximum adsorption capacity of 480.2mg-As/g obtained at pH 5.0. Both the kinetics and isotherm studies demonstrated that the adsorption of the As(V) was a monolayer chemical adsorption process, in which the ion exchange between the hydroxyl groups on the hydrated yttrium oxide and arsenate anions played a key role in the uptake of the As(V). During the adsorption, the As(V) anions were replaced the hydroxyl groups and bound to the hydrated yttrium oxide via the linkage of AsOY. The presence of fluoride and phosphate greatly hindered the As(V) uptake on the hydrated yttrium oxide, whereas the bicarbonate, sulfate and humic acid showed insignificant impacts on the removal. PMID:27135142

  3. Removing heavy metals in water: the interaction of cactus mucilage and arsenate (As (V)).

    PubMed

    Fox, Dawn I; Pichler, Thomas; Yeh, Daniel H; Alcantar, Norma A

    2012-04-17

    High concentrations of arsenic in groundwater continue to present health threats to millions of consumers worldwide. Particularly, affected communities in the developing world need accessible technologies for arsenic removal from drinking water. We explore the application of cactus mucilage, pectic polysaccharide extracts from Opuntia ficus-indica for arsenic removal. Synthetic arsenate (As (V)) solutions were treated with two extracts, a gelling extract (GE) and a nongelling extract (NE) in batch trials. The arsenic concentration at the air-water interface was measured after equilibration. The GE and NE treated solutions showed on average 14% and 9% increases in arsenic concentration at the air-water interface respectively indicating that the mucilage bonded and transported the arsenic to the air-water interface. FTIR studies showed that the -CO groups (carboxyl and carbonyl groups) and -OH (hydroxyl) functional groups of the mucilage were involved in the interaction with the arsenate. Mucilage activity was greater in weakly basic (pH 9) and weakly acidic (pH 5.5) pH. This interaction can be optimized and harnessed for the removal of arsenic from drinking water. This work breaks the ground for the application of natural pectic materials to the removal of anionic metallic species from water. PMID:22401577

  4. Bioaccumulation Dynamics of Arsenate at the Base of Aquatic Food Webs.

    PubMed

    Lopez, Adeline R; Hesterberg, Dean R; Funk, David H; Buchwalter, David B

    2016-06-21

    Periphyton is an important food source at the base of freshwater ecosystems that tends to bioconcentrate trace elements making them trophically available. The potential for arsenic-a trace element of particular concern due to its widespread occurrence, toxicity, and carcinogenicity-to bioconcentrate in periphyton and thus be available to benthic grazers is less well characterized. To better understand arsenate bioaccumulation dynamics in lotic food webs, we used a radiotracer approach to characterize accumulation in periphyton and subsequent trophic transfer to benthic grazers. Periphyton bioconcentrated As between 3,200-9,700-fold (dry weight) over 8 days without reaching steady state, suggesting that periphyton is a major sink for arsenate. However, As-enriched periphyton as a food source for the mayfly Neocloeon triangulifer resulted in negligible As accumulation in a full lifecycle exposure. Additional studies estimate dietary assimilation efficiency in several primary consumers ranging from 22% in the mayfly N. triangulifer to 75% in the mayfly Isonychia sp. X-ray fluorescence mapping revealed that As was predominantly associated with iron oxides in periphyton. We speculate that As adsorption to Fe in periphyton may play a role in reducing dietary bioavailability. Together, these results suggest that trophic movement of As in lotic food webs is relatively low, though species differences in bioaccumulation patterns are important. PMID:27223406

  5. Kinetics and thermodynamics of arsenate and arsenite biosorption by pretreated spent grains.

    PubMed

    Chai, Liyuan; Chen, Yunnen; Yang, Zhihui

    2009-01-01

    Using chemically modified spent grains as a new biosorbent to treat arsenate and arsenite ions was studied. The influences of pH, contact time, initial concentration and temperature were studied in batch experiments. The equilibrium process was described well by Langmuir isotherm model with maximum biosorption capacities of 13.39 and 4.86 mg/g of arsenate and arsenite on spent grains, respectively. The initial removal was rapid, and equilibrium was established in less than 180 min. Good correlation coefficients were obtained for the pseudo-second-order kinetic model. In the binary metal solutions, the finite sites on the surface of spent grains showed a greater preference for As(V) ions. The enthalpy of biosorption was exothermic and the increase in As(III) removal was larger than that of As(V) over the same rise in temperature. In this study, spent grains proved to be suitable for removal of As(V) and As(III) from the effluent of metallurgical industry. PMID:19860140

  6. Structural and mechanistic insights on nitrate reductases.

    PubMed

    Coelho, Catarina; Romão, Maria João

    2015-12-01

    Nitrate reductases (NR) belong to the DMSO reductase family of Mo-containing enzymes and perform key roles in the metabolism of the nitrogen cycle, reducing nitrate to nitrite. Due to variable cell location, structure and function, they have been divided into periplasmic (Nap), cytoplasmic, and membrane-bound (Nar) nitrate reductases. The first crystal structure obtained for a NR was that of the monomeric NapA from Desulfovibrio desulfuricans in 1999. Since then several new crystal structures were solved providing novel insights that led to the revision of the commonly accepted reaction mechanism for periplasmic nitrate reductases. The two crystal structures available for the NarGHI protein are from the same organism (Escherichia coli) and the combination with electrochemical and spectroscopic studies also lead to the proposal of a reaction mechanism for this group of enzymes. Here we present an overview on the current advances in structural and functional aspects of bacterial nitrate reductases, focusing on the mechanistic implications drawn from the crystallographic data. PMID:26362109

  7. Phylogenomics of Mycobacterium Nitrate Reductase Operon.

    PubMed

    Huang, Qinqin; Abdalla, Abualgasim Elgaili; Xie, Jianping

    2015-07-01

    NarGHJI operon encodes a nitrate reductase that can reduce nitrate to nitrite. This process enhances bacterial survival by nitrate respiration under anaerobic conditions. NarGHJI operon exists in many bacteria, especially saprophytic bacteria living in soil which play a key role in the nitrogen cycle. Most actinomycetes, including Mycobacterium tuberculosis, possess NarGHJI operons. M. tuberculosis is a facultative intracellular pathogen that expands in macrophages and has the ability to persist in a non-replicative form in granuloma lifelong. Nitrogen and nitrogen compounds play crucial roles in the struggle between M. tuberculosis and host. M. tuberculosis can use nitrate as a final electron acceptor under anaerobic conditions to enhance its survival. In this article, we reviewed the mechanisms regulating nitrate reductase expression and affecting its activity. Potential genes involved in regulating the nitrate reductase expression in M. tuberculosis were identified. The conserved NarG might be an alternative mycobacterium taxonomic marker. PMID:25980349

  8. Tissue Distribution and Urinary Excretion of Dimethylated Arsenic and Its Metabolites in Dimethylarsinic acid- or Arsenate-treated Rats - MCEARD

    EPA Science Inventory

    Adult female Fisher 344 rats received drinking water containing 0, 4, 40, 100, or 200 parts per million of dimethylarsinic acid or 100 parts per million of arsenate for 14 days. Urine was collected during the last 24 h of exposure. Tissues were then taken for analysis of dimethy...

  9. A green sorbent of esterified egg-shell membrane for highly selective uptake of arsenate and speciation of inorganic arsenic.

    PubMed

    Chen, Ming-Li; Gu, Cui-Bo; Yang, Ting; Sun, Yan; Wang, Jian-Hua

    2013-11-15

    Egg-shell membrane (ESM) is a promising adsorbent for heavy metal uptake. However, carboxylic groups on ESM surface barrier arsenic adsorption. Herein, ESM is modified by esterification and the methyl esterified egg-shell membrane (MESM) possesses positive charge within pH 1-9. As a novel green sorbent material, MESM exhibits 200-fold improvement on sorption capacity of arsenate with respect to bare ESM. It presents an ultra-high selectivity of 256:1 toward arsenate against arsenite. At pH 6, 100% sorption efficiency is achieved for 2 μg L(-1) As(V) by 10 mg MESM, while virtually no adsorption of As(III) is observed. This provides great potential for selective sorption of arsenate in the presence of arsenite. By loading 4.0 mL sample within 0.05-5.00 μg L(-1) As(V) followed by elution with 300 μL HCl (1.5 mol L(-1)), a detection limit of 15 ng L(-1) is obtained along with a RSD of 3.5% at 0.5 μg L(-1). Total inorganic arsenic is achieved by converting As(III) to As(V) and following the same sorption process. This procedure is applied for arsenate determination and inorganic arsenic speciation in Hijiki and water samples. The results are confirmed by graphite furnace atomic absorption spectrometry and spiking recovery. PMID:24148462

  10. Arsenate and Arsenite Sorption on Magnetite: Relations to Groundwater Arsenic Treatment Using Zerovalent Iron and Natural Attenuation

    EPA Science Inventory

    Magnetite (Fe3O4) is a zerovalent iron corrosion product; it is also formed in natural soil and sediment. Sorption of arsenate (As(V)) and arsenite (As(III)) on magnetite is an important process of arsenic removal from groundwater using zerovalent iron-based permeable reactive ba...

  11. Study of sorption processes and FT-IR analysis of arsenate sorbed onto red muds (a bauxite ore processing waste).

    PubMed

    Castaldi, Paola; Silvetti, Margherita; Enzo, Stefano; Melis, Pietro

    2010-03-15

    In this study we evaluated the arsenate adsorption capacity of red muds (RM), wastes tailing from the alumina production, at different pH values (4, 7, and 10). RM samples were artificially enriched in batch tests with solutions containing increasing concentrations of As(V). The pH of the solution significantly affected the adsorption, which increased with the decrease of pH. Moreover a sequential extraction procedure [H(2)O; (NH(4))(2)SO(4); NH(4)H(2)PO(4); NH(4)(+)-oxalate; NH(4)(+)-oxalate+ascorbic acid] was applied to RM samples exchanged with arsenate. Using this approach it was shown that low concentrations of arsenate sorbed in RM were present as water soluble and exchangeable fractions, while NH(4)(+)-oxalate and NH(4)(+)-oxalate+ascorbic acid extracted most of the adsorbed arsenate from RM at different pH values. Besides, FT-IR spectroscopy was used to better understand the nature of RM surface configuration after As(V) sorption. In the FT-IR spectra the presence of As(V) species was highlighted by a well resolved band at 865 cm(-1). The intensity and broadness of this band increased at the decreasing of pH. This band could be related to nu(As-O) vibration of an inner-sphere Al-O-As complex and/or due to As-O bonds of the adsorbed As(V) species on Fe oxides of RM samples. PMID:19853993

  12. Desulfohalophilus alkaliarsenatis gen. nov., sp. nov., an extremely halophilic sulfate- and arsenate-respiring bacterium from Searles Lake, California

    USGS Publications Warehouse

    Blum, Jodi Switzer; Kulp, Thomas R.; Han, Sukkyun; Lanoil, Brian; Saltikov, Chad W.; Stolz, John F.; Miller, Laurence G.; Oremland, Ronald S.

    2012-01-01

    A haloalkaliphilic sulfate-respiring bacterium, strain SLSR-1, was isolated from a lactate-fed stable enrichment culture originally obtained from the extreme environment of Searles Lake, California. The isolate proved capable of growth via sulfate-reduction over a broad range of salinities (125–330 g/L), although growth was slowest at salt-saturation. Strain SLSR-1 was also capable of growth via dissimilatory arsenate-reduction and displayed an even broader range of salinity tolerance (50–330 g/L) when grown under these conditions. Strain SLSR-1 could also grow via dissimilatory nitrate reduction to ammonia. Growth experiments in the presence of high borate concentrations indicated a greater sensitivity of sulfate-reduction than arsenate-respiration to this naturally abundant anion in Searles Lake. Strain SLSR-1 contained genes involved in both sulfate-reduction (dsrAB) and arsenate respiration (arrA). Amplicons of 16S rRNA gene sequences obtained from DNA extracted from Searles Lake sediment revealed the presence of close relatives of strain SLSR-1 as part of the flora of this ecosystem despite the fact that sulfate-reduction activity could not be detected in situ. We conclude that strain SLSR-1 can only achieve growth via arsenate-reduction under the current chemical conditions prevalent at Searles Lake. Strain SLSR-1 is a deltaproteobacterium in the family Desulfohalobiacea of anaerobic, haloalkaliphilic bacteria, for which we propose the name Desulfohalophilus alkaliarsenatis gen. nov., sp. nov.

  13. Facile synthesis of size-tunable gold nanoparticles by pomegranate (Punica granatum) leaf extract: Applications in arsenate sensing

    SciTech Connect

    Rao, Ashit; Mahajan, Ketakee; Bankar, Ashok; Srikanth, Rapole; Kumar, Ameeta Ravi; Gosavi, Suresh; Zinjarde, Smita

    2013-03-15

    Highlights: ► Pomegranate leaf extracts mediated rapid gold nanoparticle (AuNP) synthesis. ► The phyto-inspired AuNPs were size-tuned and characterized. ► The reducing and capping agents in the extract were identified. ► The nanoparticles reacted specifically with arsenate (V) ions. - Abstract: When pomegranate leaf extracts were incubated with chloroauric acid (HAuCl{sub 4}), gold nanoparticles (AuNPs) were synthesized. These were characterized by a variety of techniques. With an increasing content of the leaf extract, a gradual decrease in size and an increase in monodispersity were observed. Transmission electron microscope (TEM) images showed that the phyto-fabricated AuNPs were surrounded by an amorphous layer. Gallic acid in the extract mediated the reduction and a natural decapeptide capped the nanostructures. Blocking of thiol groups in the decapeptide cysteine residues caused the nanoparticles to aggregate. On interaction with arsenate (V) ions, the UV–vis spectra of the nanoparticles showed a decrease in intensity and a red-shift. Energy dispersive spectra confirmed the presence of arsenate associated with the AuNPs. Thus, by using these AuNPs, a method for sensing the toxic arsenate ions could be developed.

  14. Laccase Inhibition by Arsenite/Arsenate: Determination of Inhibition Mechanism and Preliminary Application to a Self-Powered Biosensor.

    PubMed

    Wang, Tao; Milton, Ross D; Abdellaoui, Sofiene; Hickey, David P; Minteer, Shelley D

    2016-03-15

    The reversible inhibition of laccase by arsenite (As(3+)) and arsenate (As(5+)) is reported for the first time. Oxygen-reducing laccase bioelectrodes were found to be inhibited by both arsenic species for direct electron-transfer bioelectrodes (using anthracene functionalities for enzymatic orientation) and for mediated electron-transfer bioelectrodes [using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as an electron mediator]. Both arsenic species were determined to behave via a mixed inhibition model (behaving closely to that of uncompetitive inhibitors) when evaluated spectrophotometrically using ABTS as the electron donor. Finally, laccase bioelectrodes were employed within an enzymatic fuel cell, yielding a self-powered biosensor for arsenite and arsenate. This conceptual self-powered arsenic biosensor demonstrated limits of detection (LODs) of 13 μM for arsenite and 132 μM for arsenate. Further, this device possessed sensitivities of 0.91 ± 0.07 mV/mM for arsenite and 0.98 ± 0.02 mV/mM for arsenate. PMID:26864988

  15. Expression and regulation of the antimonite, arsenite, and arsenate resistance operon of Staphylococcus xylosus plasmid pSX267.

    PubMed Central

    Rosenstein, R; Peschel, A; Wieland, B; Götz, F

    1992-01-01

    The arsenate, arsenite, and antimonite resistance region of the Staphylococcus xylosus plasmid pSX267 was subcloned in Staphylococcus carnosus. The sequenced DNA region revealed three consecutive open reading frames, named arsR, arsB, and arsC. Expression studies in Escherichia coli with the bacteriophage T7 RNA polymerase-promoter system yielded three polypeptides with apparent molecular weights of 8,000, 35,000, and 15,000, which very likely correspond to ArsR, ArsB, and ArsC, respectively. ArsB was distinguished by its overall hydrophobic character, suggesting a membrane association. The arsenate, arsenite, and antimonite resistance was shown to be inducible by all three heavy metal ions. Inactivation of the first gene, arsR, resulted in constitutive expression of resistance. Similar results were obtained with transcriptional fusions of various portions of the ars genes with a lipase reporter gene, indicating a function of ArsR as a negative regulator of a putative promoter in front of arsR. The inactivation of arsR also resulted in reduction of resistance to arsenite and antimonite, while arsenate resistance was unaffected. The three ars genes conferred arsenite resistance in E. coli and arsenite as well as arsenate resistance in Bacillus subtilis. Images PMID:1534327

  16. Lead and Arsenic Uptake by Carrots Grown on Five Orchard Soils With History of Lead Arsenate Used

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lead arsenate was used to control codling moth in apple and plum orchards from 1900 to 1960. Consequently, many orchard soils are contaminated with lead (Pb) and arsenic (As). Some of these lands are being used for urban development and vegetable crop production. Both soil Pb and As have become i...

  17. Genome wide analysis of DNA methylation and gene expression changes in the mouse lung following subchronic arsenate exposure

    EPA Science Inventory

    Alterations in DNA methylation have been proposed as a mechanism for the complex toxicological effects of arsenic. In this study, whole genome DNA methylation and gene expression changes were evaluated in lungs from female mice exposed for 90 days to 50 ppm arsenate (As) in drink...

  18. TISSUE DISTRIBUTION OF INORGANIC ARSENIC (AS) AND ITS METHYLATED METABOLITES IN MICE FOLLOWING ORAL ADMINISTRATION OF ARSENATE (ASV)

    EPA Science Inventory

    TISSUE DISTRIBUTION OF INORGANIC ARSENIC (iAs) AND ITS METHYLATED METABOLITES IN MICE FOLLOWING ORAL ADMINISTRATION OF ARSENATE (AsV). E M Kenyon1, L M Del Razo2, and M F Hughes1. 1NHEERL, ORD, US EPA, RTP, NC, USA; 2CINVESTAV-IPN, Mexico City, Mexico.

    The relationship o...

  19. Assessing Metal Contamination in Lead Arsenate Contaminated Orchard Soils Using Near and Mid-Infrared Diffuse Reflectance Spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Historic use of lead-arsenate as pesticide in apple orchards left many soils contaminated with arsenic (As) and lead (Pb). Notorious health effects and their severe soil contamination are of primary concerns for major regulatory agencies, and community at large. Wet chemistry methods for soil anal...

  20. Synergistic interaction of glyceraldehydes-3-phosphate dehydrogenase and ArsJ, a novel organoarsenical efflux permease, confers arsenate resistance.

    PubMed

    Chen, Jian; Yoshinaga, Masafumi; Garbinski, Luis D; Rosen, Barry P

    2016-06-01

    Microbial biotransformations are major contributors to the arsenic biogeocycle. In parallel with transformations of inorganic arsenic, organoarsenicals pathways have recently been recognized as important components of global cycling of arsenic. The well-characterized pathway of resistance to arsenate is reduction coupled to arsenite efflux. Here, we describe a new pathway of arsenate resistance involving biosynthesis and extrusion of an unusual pentavalent organoarsenical. A number of arsenic resistance (ars) operons have two genes of unknown function that are linked in these operons. One, gapdh, encodes the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase. The other, arsJ, encodes a major facilitator superfamily (MFS) protein. The two genes were cloned from the chromosome of Pseudomonas aeruginosa. When expressed together, but not alone, in Escherichia coli, gapdh and arsJ specifically conferred resistance to arsenate and decreased accumulation of As(V). Everted membrane vesicles from cells expressing arsJ accumulated As(V) in the presence of purified GAPDH, D-glceraldehylde 3-phosphate (G3P) and NAD(+) . GAPDH forms the unstable organoarsenical 1-arseno-3-phosphoglycerate (1As3PGA). We propose that ArsJ is an efflux permease that extrudes 1As3PGA from cells, where it rapidly dissociates into As(V) and 3-phosphoglycerate (3PGA), creating a novel pathway of arsenate resistance. PMID:26991003

  1. Evaluation of nitrate reductase activity in Rhizobium japonicum

    SciTech Connect

    Streeter, J.G.; DeVine, P.J.

    1983-08-01

    Nitrate reductase activity was evaluated by four approaches, using four strains of Rhizobium japonicum and 11 chlorate-resistant mutants of the four strains. It was concluded that in vitro assays with bacteria or bacteroids provide the most simple and reliable assessment of the presence or absence of nitrate reductase. Nitrite reductase activity with methyl viologen and dithionite was found, but the enzyme activity does not confound the assay of nitrate reductase. 18 references

  2. Tissue distribution and urinary excretion of dimethylated arsenic and its metabolites in dimethylarsinic acid- or arsenate-treated rats

    SciTech Connect

    Adair, Blakely M.; Moore, Tanya; Conklin, Sean D.; Creed, John T.; Wolf, Douglas C.; Thomas, David J. . E-mail: thomas.david@epa.gov

    2007-07-15

    Adult female Fisher 344 rats received drinking water containing 0, 4, 40, 100, or 200 parts per million of dimethylarsinic acid or 100 parts per million of arsenate for 14 days. Urine was collected during the last 24 h of exposure. Tissues were then taken for analysis of dimethylated and trimethylated arsenicals; urines were analyzed for these arsenicals and their thiolated derivatives. In dimethylarsinic acid-treated rats, highest concentrations of dimethylated arsenic were found in blood. In lung, liver, and kidney, concentrations of dimethylated arsenic exceeded those of trimethylated species; in urinary bladder and urine, trimethylated arsenic predominated. Dimethylthioarsinic acid and trimethylarsine sulfide were present in urine of dimethylarsinic acid-treated rats. Concentrations of dimethylated arsenicals were similar in most tissues of dimethylarsinic acid- and arsenate-treated rats, including urinary bladder which is the target for dimethylarsinic acid-induced carcinogenesis in the rat. Mean concentration of dimethylated arsenic was significantly higher (P < 0.05) in urine of dimethylarsinic acid-treated rats than in arsenate-treated rats, suggesting a difference between treatment groups in the flux of dimethylated arsenic through urinary bladder. Concentrations of trimethylated arsenic concentrations were consistently higher in dimethylarsinic acid-treated rats than in arsenate-treated rats; these differences were significant (P < 0.05) in liver, urinary bladder, and urine. Concentrations of dimethylthioarsinic acid and trimethylarsine sulfide were higher in urine from dimethylarsinic acid-treated rats than from arsenate-treated rats. Dimethylarsinic acid is extensively metabolized in the rat, yielding significant concentrations of trimethylated species and of thiolated derivatives. One or more of these metabolites could be the species causing alterations of cellular function that lead to tumors in the urinary bladder.

  3. Structures and syntheses of layered and framework amine-bearing uranyl phosphate and uranyl arsenates

    NASA Astrophysics Data System (ADS)

    Locock, Andrew J.; Burns, Peter C.

    2004-08-01

    Two hydrated uranyl arsenates and a uranyl phosphate were synthesized by hydrothermal methods in the presence of amine structure-directing agents and their structures determined: (N 2C 6H 14)[(UO 2)(AsO 4)] 2(H 2O) 3, DabcoUAs, {NH(C 2H 5) 3}[(UO 2) 2(AsO 4)(AsO 3OH)], TriethUAs, and (N 2C 4H 12)(UO 2)[(UO 2)(PO 4)] 4(H 2O) 2, PiperUP. Intensity data were collected at room temperature using Mo Kα X-radiation and a CCD-based area detector. The crystal structures were refined by full-matrix least-squares techniques on the basis of F2 to agreement indices ( DabcoUAs, TriethUAs, PiperUP) w R2=5.6%, 8.3%, 7.2% for all data, and R1=2.9%, 3.3%, 4.0%, calculated for 1777, 5822, 9119 unique observed reflections (| Fo|⩾4 σF), respectively. DabcoUAs is monoclinic, space group C2/ m, Z=2, a=18.581(1), b=7.1897(4), c=7.1909(4) Å, β=102.886(1)°, V=936.43(9) Å 3, Dcalc=3.50 g/cm 3. TriethUAs is monoclinic, space group P2 1/ n, Z=4, a=9.6359(4), b=18.4678(7), c=10.0708(4) Å, β=92.282(1)°, V=1790.7(1) Å 3, Dcalc=3.41 g/cm 3. PiperUP is monoclinic, space group Pn, Z=2, a=9.3278(4), b=15.5529(7), c=9.6474(5) Å, β=93.266(1)°, V=1397.3(1) Å 3, Dcalc=4.41 g/cm 3. The structure of DabcoUAs contains the autunite-type sheet formed by the sharing of vertices between uranyl square bipyramids and arsenate tetrahedra. The triethylenediammonium cations are located in the interlayer along with two H 2O groups and are disordered. Both TriethUAs and PiperUP contain sheets formed of uranyl pentagonal bipyramids and tetrahedra (arsenate and phosphate, respectively) with the uranophane sheet-anion topology. In TriethUAs, triethlyammonium cations are located in the interlayer. In PiperUP, the sheets are connected by a uranyl pentagonal bipyramid that shares corners with phosphate tetrahedra of adjacent sheets, resulting in a framework with piperazinium cations and H 2O groups in the cavities of the structure.

  4. Syntheses, crystal structures and characterizations of new vanadium arsenites and arsenates

    SciTech Connect

    Liu Junhui; He Zhangzhen; Kong Fang; Xu Xiang; Sun Chuanfu; Mao Jianggao

    2012-08-15

    Systematic explorations in vanadium arsenites and arsenates led to the isolation four new compounds, namely, {alpha}-(V{sup IV}O){sub 3}(As{sup III}O{sub 3}){sub 2} (1), {beta}-(V{sup IV}O){sub 3}(As{sup III}O{sub 3}){sub 2} (2), (V{sup IV}O)[V{sup IV}O(H{sub 2}O)]{sub 2}(As{sup V}O{sub 4}){sub 2} (3), V{sup III}V{sup IV}O{sub 2}(As{sup V}O{sub 4}) (4). Compounds 1, 2 and 4 were synthesized by standard solid-state reactions, and compound 3 is a vanadium arsenate dihydrate synthesized through hydrothermal reactions. Compounds 1 and 2 are isomers, and they represent the first examples of ternary inorganic vanadium(IV) arsenites. Single crystal X-ray diffraction analysis indicated that the four compounds display four different structural types. Magnetic property measurements for compound 1 indicated that it exhibits ferromagnetism with the Curie temperature T{sub c}=65 K. Thermal stability and optical properties for compounds 1 and 3 were also investigated. - Graphical abstract: Hydrothermal or solid state reactions of V{sub 2}O{sub 5} (or VO{sub 2}) and As{sub 2}O{sub 3} yielded four new ternary compounds with four different types of structures, namely, {alpha}-(VO){sub 3}(AsO{sub 3}){sub 2} (1), {beta}-(VO){sub 3}(AsO{sub 3}){sub 2} (2), (VO)[VO(H{sub 2}O)]{sub 2}(AsO{sub 4}){sub 2} (3), (VO){sub 2}(AsO{sub 4}) (4). {alpha}-(VO){sub 3}(AsO{sub 3}){sub 2} (1), {beta}-(VO){sub 3}(AsO{sub 3}){sub 2} (2) represent the first examples of ternary inorganic vanadium(IV) arsenites. Highlights: Black-Right-Pointing-Pointer Hydrothermal or solid state reactions of V{sub 2}O{sub 5} (or VO{sub 2}) and As{sub 2}O{sub 3} yielded two new arsenites. Black-Right-Pointing-Pointer They represent the first examples of ternary vanadium arsenites. Black-Right-Pointing-Pointer Two new ternary vanadium arsenates were also obtained. Black-Right-Pointing-Pointer They exhibit four different structural types.

  5. Arsenate Uptake by Calcite: Macroscopic and Spectroscopic Characterization of Adsorption and Incorporation Mechanisms

    SciTech Connect

    Alexandratos,V.; Elzinga, E.; Reeder, R.

    2007-01-01

    Batch uptake experiments and X-ray element mapping and spectroscopic techniques were used to investigate As(V) (arsenate) uptake mechanisms by calcite, including adsorption and coprecipitation. Batch sorption experiments in calcite-equilibrated suspensions (pH 8.3; PCO{sub 2} = 10{sup -3.5} atm) reveal rapid initial sorption to calcite, with sorption rate gradually decreasing with time as available sorption sites decrease. An As(V)-calcite sorption isotherm determined after 24 h equilibration exhibits Langmuir-like behavior up to As concentrations of 300 {mu}M. Maximum distribution coefficient values (K{sub d}), derived from a best fit to a Langmuir model, are {approx}190 L kg{sup -1}. Calcite single crystals grown in the presence of As(V) show well-developed rhombohedral morphology with characteristic growth hillocks on (10{bar 1}4) surfaces at low As(V) concentrations ({<=}5 {mu}M), but habit modification is evident at As(V) concentrations {>=}30 {mu}M in the form of macrostep development preferentially on the - vicinal surfaces of growth hillocks. Micro-X-ray fluorescence element mapping of (10{bar 1}4) surfaces shows preferential incorporation of As in the - vicinal faces relative to + vicinals. EXAFS fit results for both adsorption and coprecipitation samples confirm that As occurs in the 5+ oxidation state in tetrahedral coordination with oxygen, i.e., as arsenate. For adsorption samples, As(V) forms inner-sphere surface complexes via corner-sharing with Ca octahedra. As(V) coprecipitated with calcite substitutes in carbonate sites but with As off-centered, as indicated by two Ca shells, and with likely disruption of local structure. The results indicate that As(V) interacts strongly with the calcite surface, similar to often-cited analog phosphate, and uptake can occur via both adsorption and coprecipitation reactions. Therefore, calcite may be effective for partial removal of dissolved arsenate from aquatic and soil systems.

  6. Acute respiratory distress syndrome

    MedlinePlus

    ... chap 33. Lee WL, Slutsky AS. Acute hypoxemic respiratory failure and ARDS. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine . 6th ed. Philadelphia, PA: Elsevier Saunders; 2016: ...

  7. MSFC Respiratory Protection Services

    NASA Technical Reports Server (NTRS)

    CoVan, James P.

    1999-01-01

    An overview of the Marshall Space Flight Center Respiratory Protection program is provided in this poster display. Respiratory protection personnel, building, facilities, equipment, customers, maintenance and operational activities, and Dynatech fit testing details are described and illustrated.

  8. Neonatal respiratory distress syndrome

    MedlinePlus

    Hyaline membrane disease (HMD); Infant respiratory distress syndrome; Respiratory distress syndrome in infants; RDS - infants ... Neonatal RDS occurs in infants whose lungs have not yet fully ... disease is mainly caused by a lack of a slippery substance in ...

  9. Upper respiratory tract (image)

    MedlinePlus

    The major passages and structures of the upper respiratory tract include the nose or nostrils, nasal cavity, mouth, throat (pharynx), and voice box (larynx). The respiratory system is lined with a mucous membrane that ...

  10. Avian respiratory system disorders

    USGS Publications Warehouse

    Olsen, G.H.

    1989-01-01

    Diagnosing and treating respiratory diseases in avian species requires a basic knowledge about the anatomy and physiology of this system in birds. Differences between mammalian and avian respiratory system function, diagnosis, and treatment are highlighted.

  11. Neonatal respiratory distress syndrome

    MedlinePlus

    Hyaline membrane disease (HMD); Infant respiratory distress syndrome; Respiratory distress syndrome in infants; RDS - infants ... include: Bluish color of the skin and mucus membranes (cyanosis) Brief stop in breathing (apnea) Decreased urine ...

  12. Post-translational Regulation of Nitrate Reductase

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrate reductase (NR) catalyzes the reduction of nitrate to nitrite, which is the first step in the nitrate assimilation pathway, but can also reduce nitrite to nitric oxide (NO), an important signaling molecule that is thought to mediate a wide array of of developmental and physiological processes...

  13. Promiscuity and diversity in 3-ketosteroid reductases.

    PubMed

    Penning, Trevor M; Chen, Mo; Jin, Yi

    2015-07-01

    Many steroid hormones contain a Δ(4)-3-ketosteroid functionality that undergoes sequential reduction by 5α- or 5β- steroid reductases to produce 5α- or 5β-dihydrosteroids; and a subsequent 3-keto-reduction to produce a series of isomeric tetrahydrosteroids. Apart from steroid 5α-reductase all the remaining enzymes involved in the two step reduction process in humans belong to the aldo-keto reductase (AKR) superfamily. The enzymes involved in 3-ketosteroid reduction are AKR1C1-AKR1C4. These enzymes are promiscuous and also catalyze 20-keto- and 17-keto-steroid reduction. Interest in these reactions exist since they regulate steroid hormone metabolism in the liver, and in steroid target tissues, they may regulate steroid hormone receptor occupancy. In addition many of the dihydrosteroids are not biologically inert. The same enzymes are also involved in the metabolism of synthetic steroids e.g., hormone replacement therapeutics, contraceptive agents and inhaled glucocorticoids, and may regulate drug efficacy at their cognate receptors. This article reviews these reactions and the structural basis for substrate diversity in AKR1C1-AKR1C4, ketosteroid reductases. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'. PMID:25500069

  14. Promiscuity and diversity in 3-ketosteroid reductases

    PubMed Central

    Penning, Trevor M.; Chen, Mo; Jin, Yi

    2014-01-01

    Many steroid hormones contain a Δ4-3-ketosteroid functionality that undergoes sequential reduction by 5α- or 5β- steroid reductases to produce 5α- or 5β-dihydrosteroids; and a subsequent 3-keto-reduction to produce a series of isomeric tetrahydrosteroids. Apart from steroid 5α-reductase all the remaining enzymes involved in the two step reduction process in humans belong to the aldo-keto reductase (AKR) superfamily. The enzymes involved in 3-ketosteroid reduction are AKR1C1–AKR1C4. These enzymes are promiscuous and also catalyze 20-keto- and 17-keto-steroid reduction. Interest in these reactions exist since they regulate steroid hormone metabolism in the liver, and in steroid target tissues, they may regulate steroid hormone receptor occupancy. In addition many of the dihydrosteroids are not biologically inert. The same enzymes are also involved in the metabolism of synthetic steroids e.g., hormone replacement therapeutics, contraceptive agents and inhaled glucocorticoids, and may regulate drug efficacy at their cognate receptors. This article reviews these reactions and the structural basis for substrate diversity in AKR1C1–AKR1C4, ketosteroid reductases. This article is part of a Special Issue entitled ‘Steroid/Sterol signaling’. PMID:25500069

  15. Ferrisiderophore reductase activity in Agrobacterium tumefaciens.

    PubMed Central

    Lodge, J S; Gaines, C G; Arceneaux, J E; Byers, B R

    1982-01-01

    Reduction of the iron in ferriagrobactin by the cytoplasmic fraction of Agrobacterium tumefaciens strictly required NaDH as the reductant. Addition of flavin mononucleotide and anaerobic conditions were necessary for the reaction; when added with flavin mononucleotide, magnesium was stimulatory. This ferrisiderophore reductase activity may be a part of the iron assimilation process in A. tumefaciens. PMID:7056702

  16. Arsenite and arsenate removal from wastewater using cationic polymer-modified waste tyre rubber.

    PubMed

    Imyim, Apichat; Sirithaweesit, Thitayati; Ruangpornvisuti, Vithaya

    2016-01-15

    Waste tyre rubber (WTR) granulate was modified with a cationic polymer, poly(3-acrylamidopropyl)trimethylammonium chloride (p(APTMACl)). The resulting WTR/p(APTMACl) was utilized for the adsorption of arsenite, As(III) and arsenate, As(V) from aqueous medium in both batch and column methods. The level of adsorption increased gradually with increasing monomer concentration and contact time. The adsorption behavior obeyed the Freundlich model, and the rate of adsorption could be predicted by employing the pseudo-second order model. In the column method, As(V) could be adsorbed onto the sorbent more effectively than As(III). Remarkable desorption of As(III) and As(V) (99 and 92%, respectively) from the adsorbent was achieved using 0.10 M HCl as eluent. An approach of evaluation of adsorption capacity uncertainty is proposed. PMID:26607568

  17. A vibrational spectroscopic study of the arsenate minerals cobaltkoritnigite and koritnigite.

    PubMed

    Frost, Ray L; López, Andrés; Xi, Yunfei; Lana, Cristiano; Souza, Larissa; Scholz, Ricardo; Sejkora, Jiří; Čejka, Jiří

    2014-05-01

    Raman spectra of two well-defined types of cobaltkoritnigite and koritnigite crystals were recorded and interpreted. Significant differences in the Raman spectra of cobaltkoritnigite and koritnigite were observed. Observed Raman bands were attributed to the (AsO3OH)(2-) stretching and bending vibrations, stretching and bending vibrations of water molecules and hydroxyl ions. Both Raman and infrared spectra of cobaltkoritnigite identify bands which are attributable to phosphate and hydrogen phosphate anions proving some substitution of phosphate for arsenate in the structure of cobaltkoritnigite. The O-H⋯O hydrogen bond lengths in the crystal structure of koritnigite were inferred from the Raman spectra and compared with those derived from the X-ray single crystal refinement. The presence of (AsO3OH)(2-) units in the crystal structure of cobaltkoritnigite and koritnigite was proved from the Raman spectra which supports the conclusions of the X-ray structure analysis. PMID:24566109

  18. Dissolved Calcium and Magnesium Carbonates Promote Arsenate Release From Ferrihydrite in Flow Systems

    NASA Astrophysics Data System (ADS)

    Saalfield, S. L.; Bostick, B. C.

    2007-12-01

    Field data from water systems around the world have shown that arsenic can reach toxic concentrations in dynamic groundwater systems. This is generally in contrast to analogous static systems at circumneutral pH, where arsenic is strongly retained by sorption to iron (hydr)oxides. Our research examines the effect of calcium and magnesium carbonates on As(V) mobility. In both dynamic flow and static experiments, arsenate was pre- sorbed to poorly crystalline iron hydroxides (1-10% sorption capacity), with varying aqueous compositions including calcium, magnesium, carbonate, sulfate, lactate, and other common groundwater species (pH 7.5-8). Thus we investigated how the dissolution of common carbonate minerals, specifically CaCO3 and MgCO3, affect arsenic behavior in the context of groundwater solutions. Under static (batch) conditions, no measurable arsenic (<10 μg/L) is released into solutions containing alkaline earth metals (AEMs) and carbonates. When elevated concentrations of AEMs and carbonate are introduced by dynamic flow, however, arsenic is mobilized at up to 500 μg/L, releasing significant proportions the total arsenic present. This is only the case when both of these species are present; with other common ion pairs, little to no arsenic is released. These results indicate that arsenate adsorption is kinetically controlled under flow conditions, resulting in very different mobility relative to otherwise equivalent static systems. Furthermore, the combination of alkaline earth metals and carbonates promotes As(V) mobility in column-based systems. We propose that these phenomena indicate a combination of physical and chemical effects by which diffusion limitation becomes dominant in limiting arsenic sorption in flow systems. Many carbonate-buffered aquifers, as well as those undergoing rapid mineralization of organic matter, could be affected by these processes of AEM-carbonate-limited sorption and increased arsenic mobility.

  19. Bacterial dissimilatory reduction of arsenate and sulfate in meromictic Mono Lake, California

    USGS Publications Warehouse

    Oremland, R.S.; Dowdle, P.R.; Hoeft, S.; Sharp, J.O.; Schaefer, J.K.; Miller, L.G.; Switzer, Blum J.; Smith, R.L.; Bloom, N.S.; Wallschlaeger, D.

    2000-01-01

    The stratified (meromictic) water column of alkaline and hypersaline Mono Lake, California, contains high concentrations of dissolved inorganic arsenic (~200 ??mol/L). Arsenic speciation changes from arsenate [As (V)] to arsenite [As (III)] with the transition from oxic surface waters (misolimnion) to anoxic bottom waters (monimolimnion). A radioassay was devised to measure the reduction of 73As (V) to 73As (III) and tested using cell suspensions of the As (V)-respiring Bacillus selenitireducens, which completely reduced the 73As (V). In field experiments, no significant activity was noted in the aerobic mixolimnion waters, but reduction of 73As (V) to 73As (III) was observed in all the monimolimnion samples. Rate constants ranged from 0.02 to 0.3/day, with the highest values in the samples from the deepest depths (24 and 28 m). The highest activities occurred between 18 and 21 m, where As (V) abundant (rate, ~5.9 ??mol/L per day). In contrast, sulfate reduction occurred at depths below 21 m, with the highest rates attained at 28 m (rate, ~2.3 ??mol/L per day). These results indicate that As (V) ranks second in importance, after sulfate, as an electron acceptor for anaerobic bacterial respiration in the water column. Annual arsenate respiration may mineralize as much as 14.2% of the pelagic photosynthetic carbon fixed during meromixis. When combined with sulfate-reduction data, anaerobic respiration in the water column can mineralize 32-55% of this primary production. As lakes of this type approach salt saturation, As (V) can become the most important electron acceptor for the biogeochemical cycling of carbon. Copyright (C) 2000 Elsevier Science Ltd.

  20. Arsenic fractionation and bioaccessibility in two alkaline Texas soils incubated with sodium arsenate.

    PubMed

    Datta, Rupali; Makris, Konstantinos C; Sarkar, Dibyendu

    2007-05-01

    Elevated arsenic (As) concentrations in urban soils with prolonged arsenical pesticide application history have increased the risk associated with accidental hand-to-mouth soil ingestion by children. Earlier work by the authors suggested that the conservative statement of 100% As bioaccessibility in soils was not valid for a set of acidic soils incubated with sodium arsenate. In this study, two alkaline Texas soils incubated with a commonly used As pesticide (sodium arsenate) were evaluated for their potential in reducing soil As bioaccessibility. The objective of this study was to evaluate the effects of incubation time and As load on soil As fractionation and bioaccessibility. Soils were subjected to a sequential As fractionation scheme, and bioaccessible As was quantified using an in vitro stomach phase test. Results showed a reduction in the water-soluble As fraction with incubation time (after 4 months), which remained unchanged after 12 months. This reduction with time was accompanied by an increase in the NaOH- and H(2)SO(4)-extractable As fractions, suggesting As sorption by amorphous Fe/Al hydroxides and/or Ca/Mg compounds, respectively. Organic/sulfides-bound As increased with incubation time after 12 months but not after 4 months of incubation. The aging effect was also observed with the amount of bioaccessible As at all As loads, showing significant positive correlations with the water-extractable and exchangeable As fractions. Bioaccessible As concentrations even after 12 months of incubation were not significantly reduced, suggesting that natural attenuation might prove inadequate to control As bioaccessibility in these alkaline soils. PMID:17387422

  1. Functional studies of aldo-keto reductases in Saccharomyces cerevisiae*

    PubMed Central

    Chang, Qing; Griest, Terry A.; Harter, Theresa M.; Petrash, J. Mark

    2007-01-01

    SUMMARY We utilized the budding yeast Saccharomyces cerevisiae as a model to systematically explore physiological roles for yeast and mammalian aldo-keto reductases. Six open reading frames encoding putative aldo-keto reductases were identified when the yeast genome was queried against the sequence for human aldose reductase, the prototypical mammalian aldo-keto reductase. Recombinant proteins produced from five of these yeast open reading frames demonstrated NADPH-dependent reductase activity with a variety of aldehyde and ketone substrates. A triple aldo-keto reductase null mutant strain demonstrated a glucose-dependent heat shock phenotype which could be rescued by ectopic expression of human aldose reductase. Catalytically-inactive mutants of human or yeast aldo-keto reductases failed to effect a rescue of the heat shock phenotype, suggesting that the phenotype results from either an accumulation of one or more unmetabolized aldo-keto reductase substrates or a synthetic deficiency of aldo-keto reductase products generated in response to heat shock stress. These results suggest that multiple aldo-keto reductases fulfill functionally redundant roles in the stress response in yeast. PMID:17140678

  2. Inhibition of NADH-ubiquinone reductase activity by N,N'-dicyclohexylcarbodiimide and correlation of this inhibition with the occurrence of energy-coupling site 1 in various organisms

    SciTech Connect

    Yagi, T.

    1987-05-19

    The NADH-ubiquinone reductase activity of the respiratory chains of several organisms was inhibited by the carboxyl-modifying reagent N,N'-dicyclohexylcarbodiimide (DCCD). This inhibition correlated with the presence of an energy-transducing site in this segment of the respiratory chain. Where the NADH-quinone reductase segment involved an energy-coupling site (e.g., in bovine heart and rat liver mitochondria, and in Paracoccus denitrificans, Escherichia coli, and Thermus thermophilus HB-8 membranes), DCCD acted as an inhibitor of ubiquinone reduction by NADH. By contrast, where energy-coupling site 1 was absent (e.g., in Saccharomyces cerevisiae mitochondria and BacilLus subtilis membranes), there was no inhibition of NADH-ubiquinone reductase activity by DCCD. In the bovine and P. denitrificans systems, DCCD inhibition was pseudo first order with respect to incubation time, and reaction order with respect to inhibitor concentration was close to unity, indicating that inhibition resulted from the binding of one inhibitor molecule per active unit of NADH-ubiquinone reductase. In the bovine NADH-ubiquinone reductase complex (complex I), (/sup 14/C)DCCD was preferentially incorporated into two subunits of molecular weight 49,000 and 29,000. The time course of labeling of the 29,000 molecular weight subunit with (/sup 14/C)DCCD paralleled the time course of inhibition of NADH-ubiquinone reductase activity.

  3. The Distribution of Arsenate and Arsenite in Shoots and Roots of Holcus lanatus is Influenced by Arsenic Tolerance and Arsenate and Phosphate Supply

    PubMed Central

    Quaghebeur, Mieke; Rengel, Zdenko

    2003-01-01

    The recent discovery that phytochelatins are important for arsenic (As) detoxification in terrestrial plants results in the necessity to understand As speciation and metabolism in plant material. A hydroponic study was therefore conducted to examine the effects of different levels of phosphate and arsenate [As(V)] on As speciation and distribution in tolerant and non-tolerant clones of Holcus lanatus. Speciation of As in tissue (using high-performance liquid chromatography-inductively coupled plasma mass spectrometry) revealed that the predominant species present were the inorganic As species (As(V) and arsenite [As(III)]), although small levels (<1%) of organic As species (dimethylarsinic acid and monomethylarsonic acid) were detected in shoot material. In roots, the proportion of total As present as As(III) generally increased with increasing levels of As(V) in the nutrient solution, whereas in shoots, the proportion of total As present as As(III) generally decreased with increasing levels of As(V). H. lanatus plants growing in the high-phosphorus (P) (100 μm) solution contained a higher proportion of As(V) (with regard to total As) in both roots and shoots than plants supplied with low P (10 μm); in addition, tolerant clones generally contained a higher proportion of As(V) with regard to total As than non-tolerant clones. The study further revealed that As(V) can be reduced to As(III) in both roots and shoots. Although the reduction capacity was limited, the reduction was closely regulated by As influx for all treatments. The results therefore provide a new understanding about As metabolism in H. lanatus. PMID:12857839

  4. Continuous Culture of Rhodotorula rubra: Kinetics of Phosphate-Arsenate Uptake, Inhibition, and Phosphate-Limited Growth

    PubMed Central

    Button, D. K.; Dunker, Sally S.; Morse, M. L.

    1973-01-01

    The pink yeast Rhodotorula rubra of marine origin was found to be capable of extended growth at very low phosphate concentrations (K0.5 = 10.8 nm). Average intracellular phosphate concentrations, based on isotope exchange techniques, were 15 to 200 nm, giving concentration gradients across the cell envelope of about 106. Sensitivity to metabolic inhibitors occurred at micromolar concentrations. Inability of the phosphate transport system, Ks = 0.5 to 2.8 μm, Vmax = 55 μmoles per g of cells per min, to discriminate against arsenate transport led to arsenate toxicity at 1 to 10 nm, whereas environmental arsenate levels are reportedly much higher. Phosphate competitively prevented arsenate toxicity. The Ki for phosphate inhibition of arsenate uptake was 0.7 to 1.2 μm. Phosphate uptake experiments showed that maximal growth rates could be achieved with approximately 4% of the total phosphate-arsenate transport system. Organisms adapted to a range both of concentration of NaCl and of pH. Maximal affinity for phosphate occurred at pH 4 and at low concentrations of NaCl; however, Vmax for phosphate transport was little affected. Maximal specific growth rates on minimal medium were consistent in batch culture but gradually increased to the much higher rates found with yeast extract media when the population was subjected to long-term continuous culture with gradually increasing dilution rates. Phosphate initial uptake rates that were in agreement with the steady-state flux in continuous culture were obtained by using organisms and medium directly from continuous culture. This procedure resulted in rates about 500 times greater than one in which harvested batch-grown cells were used. Discrepancies between values found and those reported in the literature for other organisms were even larger. Growth could not be sustained below a threshold phosphate concentration of 3.4 nm. Such thresholds are explained in terms of a system where growth rate is set by intracellular

  5. Electron transport to periplasmic nitrate reductase (NapA) of Wolinella succinogenes is independent of a NapC protein.

    PubMed

    Simon, Jörg; Sänger, Monica; Schuster, Stephan C; Gross, Roland

    2003-07-01

    The rumen bacterium Wolinella succinogenes grows by respiratory nitrate ammonification with formate as electron donor. Whereas the enzymology and coupling mechanism of nitrite respiration is well known, nitrate reduction to nitrite has not yet been examined. We report here that intact cells and cell fractions catalyse nitrate and chlorate reduction by reduced viologen dyes with high specific activities. A gene cluster encoding components of a putative periplasmic nitrate reductase system (napA, G, H, B, F, L, D) was sequenced. The napA gene was inactivated by inserting a kanamycin resistance gene cassette. The resulting mutant did not grow by nitrate respiration and did not reduce nitrate during growth by fumarate respiration, in contrast to the wild type. An antigen was detected in wild-type cells using an antiserum raised against the periplasmic nitrate reductase (NapA) from Paracoccus pantotrophus. This antigen was absent in the W. succinogenes napA mutant. It is concluded that the periplasmic nitrate reductase NapA is the only respiratory nitrate reductase in W. succinogenes, although a second nitrate-reducing enzyme is apparently induced in the napA mutant. The nap cluster of W. succinogenes lacks a napC gene whose product is thought to function in quinol oxidation and electron transfer to NapA in other bacteria. The W. succinogenes genome encodes two members of the NapC/NirT family, NrfH and FccC. Characterization of corresponding deletion mutants indicates that neither of these two proteins is required for nitrate respiration. A mutant lacking the genes encoding respiratory nitrite reductase (nrfHA) had wild-type properties with respect to nitrate respiration. A model of the electron transport chain of nitrate respiration is proposed in which one or more of the napF, G, H and L gene products mediate electron transport from menaquinol to the periplasmic NapAB complex. Inspection of the W. succinogenes genome sequence suggests that ammonia formation from

  6. Salinity Effects on the Biogeochemical Cycles of Sulfate, Arsenate, Nitrate, and Methane in Anoxic Sediments of Mono Lake and Searles Lake, California.

    NASA Astrophysics Data System (ADS)

    Kulp, T. R.; Hoeft, S. E.; Miller, L. G.; Oremland, R. S.

    2005-12-01

    Mono Lake and Searles Lake are two members of a chain of hypersaline and alkaline soda lakes that occur in closed basins along the arid eastern escarpment of the Sierra Nevada in California. These lakes are alkaline (pH = 9.8), highly saline, and As-rich due to hydrothermal input and evaporative concentration. Mono Lake is characterized by a salinity of 90 g/L and contains 200μM dissolved As. Searles Lake, a partially-dry residual playa, exhibits salt concentrations >300 g/L (near saturation) and 3.9 mM dissolved As. We utilized 35SO4 and 73As(V) as radioactive tracers to compare sulfate and arsenate [As(V)] reductase activities at in-situ concentrations in sediment cores (25 cm depth) from Mono and Searles Lakes. Sulfate reduction activity was detected in sediments from Mono Lake, with the highest rates occurring in the upper 2 cm sediment depth. No sulfate reduction activity was observed in Searles Lake sediments, suggesting that this metabolic process may not provide sufficient energy to cope with the demands of osmoadaptation at saturated salt concentrations. Anaerobic pathways that utilize As(V) or nitrate as terminal electron acceptors are bioenergetically more favorable than sulfate reduction. Dissimilatory reduction of As(V) occurred in sediments from both lakes, with the fastest rates of As(V) reduction occurring at 3 cm sediment depth. We conducted additional experiments with As- or nitrate-amended slurries of Searles Lake sediment prepared in artificial media that mimicked lake water chemistry over a range of total salinities. Slurries were sampled periodically and analyzed to determine the rate of As(V) reduction or denitrification at each salinity. Methane production was also monitored in the headspace of As(V)-amended and non-amended slurries. As(V) and nitrate reduction rates, as well as methane production, demonstrated an inverse relationship with total salinity over the range of 50 - 346 g/L. These data suggest that halophilic bacteria capable of

  7. Structure of aldose reductase from Giardia lamblia

    PubMed Central

    Ferrell, M.; Abendroth, J.; Zhang, Y.; Sankaran, B.; Edwards, T. E.; Staker, B. L.; Van Voorhis, W. C.; Stewart, L. J.; Myler, P. J.

    2011-01-01

    Giardia lamblia is an anaerobic aerotolerant eukaryotic parasite of the intestines. It is believed to have diverged early from eukarya during evolution and is thus lacking in many of the typical eukaryotic organelles and biochemical pathways. Most conspicuously, mitochondria and the associated machinery of oxidative phosphorylation are absent; instead, energy is derived from substrate-level phosphorylation. Here, the 1.75 Å resolution crystal structure of G. lamblia aldose reductase heterologously expressed in Escherichia coli is reported. As in other oxidoreductases, G. lamblia aldose reductase adopts a TIM-barrel conformation with the NADP+-binding site located within the eight β-strands of the interior. PMID:21904059

  8. Methylenetetrahydrofolate reductase deficiency: importance of early diagnosis.

    PubMed

    Fattal-Valevski, A; Bassan, H; Korman, S H; Lerman-Sagie, T; Gutman, A; Harel, S

    2000-08-01

    Methylenetetrahydrofolate reductase deficiency is the most common inborn error of folate metabolism and should be suspected when homocystinuria is combined with hypomethioninemia. The main clinical findings are neurologic signs such as severe developmental delay, marked hypotonia, seizures, microcephaly, apnea, and coma. Most patients present in early life. The infantile form is severe, with rapid deterioration leading to death usually within 1 year. Treatment with betaine has been shown to be efficient in lowering homocysteine concentrations and returning methionine to normal, but the clinical response is variable. We report two brothers with methylenetetrahydrofolate reductase deficiency: the first was undiagnosed and died at 8 months of age from neurologic deterioration and apnea, while his brother, who was treated with betaine from the age of 4 months, is now 3 years old and has developmental delay. PMID:10961793

  9. Surface complexation studied via combined grazing-incidence EXAFS and surface diffraction: Arsenate on hematite (0001) and (10-12)

    USGS Publications Warehouse

    Waychunas, G.; Trainor, T.; Eng, P.; Catalano, J.; Brown, G.; Davis, J.; Rogers, J.; Bargar, J.

    2005-01-01

    X-ray diffraction [crystal-truncation-rod (CTR)] studies of the surface structure of moisture-equilibrated hematite reveal sites for complexation not present on the bulk oxygen-terminated surface, and impose constraints on the types of inner-sphere sorption topologies. We have used this improved model of the hematite surface to analyze grazing-incidence EXAFS results for arsenate sorption on the c(0001) and r(10-12) surfaces measured in two electric vector polarizations. This work shows that the reconfiguration of the surface under moist conditions is responsible for an increased adsorption density of arsenate complexes on the (0001) surface relative to predicted ideal termination, and an abundance of "edge-sharing" bidentate complexes on both studied surfaces. We consider possible limitations on combining the methods due to differing surface sensitivities, and discuss further analysis possibilities using both methods. ?? Springer-Verlag 2005.

  10. Investigation of surface structures by powder diffraction : a differential pair distribution function study on arsenate sorption on ferrihydrite.

    SciTech Connect

    Harrington, R.; Hausner, D. B.; Bhandari, N.; Strongin, D. R.; Chapman, K. W.; Chupas, P. J.; Middlemiss, D. S.; Grey, C. P.; Parise, J. B.; X-Ray Science Division; Stony Brook Univ.; Temple Univ.

    2010-01-01

    Differential pair distribution function (d-PDF) analysis of high energy powder X-ray diffraction data was carried out on 2-line ferrihydrite nanoparticles with arsenate oxyanions adsorbed on the surface to investigate the binding mechanism. In this analysis, a PDF of ferrihydrite is subtracted from a PDF of ferrihydrite with arsenate sorbed on the surface, leaving only correlations from within the surface layer and between the surface and the particle. As-O and As-Fe correlations were observed at 1.68 and 3.29 {angstrom}, respectively, in good agreement with previously published EXAFS data, confirming a bidentate binuclear binding mechanism. Further peaks are observed in the d-PDF which are not present in EXAFS, corresponding to correlations between As and O in the particle and As-2nd Fe.

  11. Different arsenate and phosphate incorporation effects on the nucleation and growth of iron(III) (Hydr)oxides on quartz.

    PubMed

    Neil, Chelsea W; Lee, Byeongdu; Jun, Young-Shin

    2014-10-21

    Iron(III) (hydr)oxides play an important role in the geochemical cycling of contaminants in natural and engineered aquatic systems. The ability of iron(III) (hydr)oxides to immobilize contaminants can be related to whether the precipitates form heterogeneously (e.g., at mineral surfaces) or homogeneously in solution. Utilizing grazing incidence small-angle X-ray scattering (GISAXS), we studied heterogeneous iron(III) (hydr)oxide nucleation and growth on quartz substrates for systems containing arsenate and phosphate anions. For the iron(III) only system, the radius of gyration (Rg) of heterogeneously formed precipitates grew from 1.5 to 2.5 (± 1.0) nm within 1 h. For the system containing 10(-5) M arsenate, Rg grew from 3.6 to 6.1 (± 0.5) nm, and for the system containing 10(-5) M phosphate, Rg grew from 2.0 to 4.0 (± 0.2) nm. While the systems containing these oxyanions had more growth, the system containing only iron(III) had the most nucleation events on substrates. Ex situ analyses of homogeneously and heterogeneously formed precipitates indicated that precipitates in the arsenate system had the highest water content and that oxyanions may bridge iron(III) hydroxide polymeric embryos to form a structure similar to ferric arsenate or ferric phosphate. These new findings are important because differences in nucleation and growth rates and particle sizes will impact the number of available reactive sites and the reactivity of newly formed particles toward aqueous contaminants. PMID:25232994

  12. Different Arsenate and Phosphate Incorporation Effects on the Nucleation and Growth of Iron(III) (Hydr)oxides on Quartz

    SciTech Connect

    Neil, Chelsea W.; Lee, Byeongdu; Jun, Young-Shin

    2014-10-21

    Iron(III) (hydr)oxides play an important role in the geochemical cycling of contaminants in natural and engineered aquatic systems. The ability of iron(III) (hydr)oxides to immobilize contaminants can be related to whether the precipitates form heterogeneously (e.g., at mineral surfaces) or homogeneously in solution. Utilizing grazing incidence small-angle X-ray scattering (GISAXS), we studied heterogeneous iron(III) (hydr)oxide nucleation and growth on quartz substrates for systems containing arsenate and phosphate anions. For the iron(III) only system, the radius of gyration ( R g ) of heterogeneously formed precipitates grew from 1.5 to 2.5 ( ± 1.0) nm within 1 h. For the system containing 10-5 M arsenate, R g grew from 3.6 to 6.1 ( ± 0.5) nm, and for the system containing 10-5 M phosphate, R g grew from 2.0 to 4.0 ( ± 0.2) nm. While the systems containing these oxyanions had more growth, the system containing only iron(III) had the most nucleation events on substrates. Ex situ analyses of homogeneously and heterogeneously formed precipitates indicated that precipitates in the arsenate system had the highest water content and that oxyanions may bridge iron(III) hydroxide polymeric embryos to form a structure similar to ferric arsenate or ferric phosphate. These new fi ndings are important because di ff erences in nucleation and growth rates and particle sizes will impact the number of available reactive sites and the reactivity of newly formed particles toward aqueous contaminants.

  13. Characterization of erythrose reductases from filamentous fungi.

    PubMed

    Jovanović, Birgit; Mach, Robert L; Mach-Aigner, Astrid R

    2013-01-01

    Proteins with putative erythrose reductase activity have been identified in the filamentous fungi Trichoderma reesei, Aspergillus niger, and Fusarium graminearum by in silico analysis. The proteins found in T. reesei and A. niger had earlier been characterized as glycerol dehydrogenase and aldehyde reductase, respectively. Corresponding genes from all three fungi were cloned, heterologously expressed in Escherichia coli, and purified. Subsequently, they were used to establish optimal enzyme assay conditions. All three enzymes strictly require NADPH as cofactor, whereas with NADH no activity could be observed. The enzymatic characterization of the three enzymes using ten substrates revealed high substrate specificity and activity with D-erythrose and D-threose. The enzymes from T. reesei and A. niger herein showed comparable activities, whereas the one from F. graminearum reached only about a tenth of it for all tested substrates. In order to proof in vivo the proposed enzyme function, we overexpressed the erythrose reductase-encoding gene in T. reesei. An increased production of erythritol by the recombinant strain compared to the parental strain could be detected. PMID:23924507

  14. Effects of Phosphate on Arsenate Uptake and Translocation in Nonmetallicolous and Metallicolous Populations of Pteris Vittata L. Under Solution Culture.

    PubMed

    Wu, Fuyong; Wu, Shengchun; Deng, Dan; Wong, Ming Hung

    2015-01-01

    An arsenic hyperaccumulator, Pteris vittata L., is common in nature and could occur either on As-contaminated soils or on uncontaminated soils. However, it is not clear whether phosphate transporter play similar roles in As uptake and translocation in nonmetallicolous and metallicolous populations of P. vittata. Five populations were used to investigate effects of phosphate on arsenate uptake and translocation in the plants growing in 1.2 L 20% modified Hoagland's nutrient solution containing either 100 μM phosphate or no phosphate and 10 μM arsenate for 1, 2, 6, 12, 24 h, respectively. The results showed that the nonmetallicolous populations accumulated apparently more As in their fronds and roots than the metallicolous populations at both P supply levels. Phosphate significantly (P < 0.01) decreased frond and root concentrations of As during short time solution culture. In addition, the effects of phosphate on As translocation in P. vittata varied among different time-points during time-course hydroponics (1-24 h). The present results indicated that the inhibitory effect of phosphate on arsenate uptake was larger in the three nonmetallicolous populations than those in the two metallicolous populations of P. vittata. PMID:26083716

  15. The removal of arsenate from water using iron-modified diatomite (D-Fe): isotherm and column experiments.

    PubMed

    Pantoja, M L; Jones, H; Garelick, H; Mohamedbakr, H G; Burkitbayev, M

    2014-01-01

    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. PMID:23807557

  16. Role of the Dinitrogenase Reductase Arginine 101 Residue in Dinitrogenase Reductase ADP-Ribosyltransferase Binding, NAD Binding, and Cleavage

    PubMed Central

    Ma, Yan; Ludden, Paul W.

    2001-01-01

    Dinitrogenase reductase is posttranslationally regulated by dinitrogenase reductase ADP-ribosyltransferase (DRAT) via ADP-ribosylation of the arginine 101 residue in some bacteria. Rhodospirillum rubrum strains in which the arginine 101 of dinitrogenase reductase was replaced by tyrosine, phenylalanine, or leucine were constructed by site-directed mutagenesis of the nifH gene. The strain containing the R101F form of dinitrogenase reductase retains 91%, the strain containing the R101Y form retains 72%, and the strain containing the R101L form retains only 28% of in vivo nitrogenase activity of the strain containing the dinitrogenase reductase with arginine at position 101. In vivo acetylene reduction assays, immunoblotting with anti-dinitrogenase reductase antibody, and [adenylate-32P]NAD labeling experiments showed that no switch-off of nitrogenase activity occurred in any of the three mutants and no ADP-ribosylation of altered dinitrogenase reductases occurred either in vivo or in vitro. Altered dinitrogenase reductases from strains UR629 (R101Y) and UR630 (R101F) were purified to homogeneity. The R101F and R101Y forms of dinitrogenase reductase were able to form a complex with DRAT that could be chemically cross-linked by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide. The R101F form of dinitrogenase reductase and DRAT together were not able to cleave NAD. This suggests that arginine 101 is not critical for the binding of DRAT to dinitrogenase reductase but that the availability of arginine 101 is important for NAD cleavage. Both DRAT and dinitrogenase reductase can be labeled by [carbonyl-14C]NAD individually upon UV irradiation, but most 14C label is incorporated into DRAT when both proteins are present. The ability of R101F dinitrogenase reductase to be labeled by [carbonyl-14C]NAD suggested that Arg 101 is not absolutely required for NAD binding. PMID:11114923

  17. The human respiratory gate

    PubMed Central

    Eckberg, Dwain L

    2003-01-01

    Respiratory activity phasically alters membrane potentials of preganglionic vagal and sympathetic motoneurones and continuously modulates their responsiveness to stimulatory inputs. The most obvious manifestation of this ‘respiratory gating’ is respiratory sinus arrhythmia, the rhythmic fluctuations of electrocardiographic R–R intervals observed in healthy resting humans. Phasic autonomic motoneurone firing, reflecting the throughput of the system, depends importantly on the intensity of stimulatory inputs, such that when levels of stimulation are low (as with high arterial pressure and sympathetic activity, or low arterial pressure and vagal activity), respiratory fluctuations of sympathetic or vagal firing are also low. The respiratory gate has a finite capacity, and high levels of stimulation override the ability of respiration to gate autonomic responsiveness. Autonomic throughput also depends importantly on other factors, including especially, the frequency of breathing, the rate at which the gate opens and closes. Respiratory sinus arrhythmia is small at rapid, and large at slow breathing rates. The strong correlation between systolic pressure and R–R intervals at respiratory frequencies reflects the influence of respiration on these two measures, rather than arterial baroreflex physiology. A wide range of evidence suggests that respiratory activity gates the timing of autonomic motoneurone firing, but does not influence its tonic level. I propose that the most enduring significance of respiratory gating is its use as a precisely controlled experimental tool to tease out and better understand otherwise inaccessible human autonomic neurophysiological mechanisms. PMID:12626671

  18. The respiratory system.

    PubMed

    Zifko, U; Chen, R

    1996-10-01

    Neurological disorders frequently contribute to respiratory failure in critically ill patients. They may be the primary reason for the initiation of mechanical ventilation, or may develop later as a secondary complication. Disorders of the central nervous system leading to respiratory failure include metabolic encephalopathies, acute stroke, lesions of the motor cortex and brain-stem respiratory centres, and their descending pathways. Guillan-Barré syndrome, critical illness polyneuropathy and acute quadriplegic myopathy are the more common neuromuscular causes of respiratory failure. Clinical observations and pulmonary function tests are important in monitoring respiratory function. Respiratory electrophysiological studies are useful in the investigation and monitoring of respiratory failure. Transcortical and cervical magnetic stimulation can assess the central respiratory drive, and may be useful in determining the prognosis in ventilated patients, with cervical cord dysfunction. It is also helpful in the assessment of failure to wean, which is often caused by a combination of central and peripheral nervous system disorders. Phrenic nerve conduction studies and needle electromyography of the diaphragm and chest wall muscles are useful to characterize neuropathies and myopathies affecting the diaphragm. Repetitive phrenic nerve stimulation can assess neuromuscular transmission defects. It is important to identify patients at risk of respiratory failure. They should be carefully monitored and mechanical ventilation should be initiated before the development of severe hypoxaemia. PMID:9117072

  19. The human respiratory gate

    NASA Technical Reports Server (NTRS)

    Eckberg, Dwain L.

    2003-01-01

    Respiratory activity phasically alters membrane potentials of preganglionic vagal and sympathetic motoneurones and continuously modulates their responsiveness to stimulatory inputs. The most obvious manifestation of this 'respiratory gating' is respiratory sinus arrhythmia, the rhythmic fluctuations of electrocardiographic R-R intervals observed in healthy resting humans. Phasic autonomic motoneurone firing, reflecting the throughput of the system, depends importantly on the intensity of stimulatory inputs, such that when levels of stimulation are low (as with high arterial pressure and sympathetic activity, or low arterial pressure and vagal activity), respiratory fluctuations of sympathetic or vagal firing are also low. The respiratory gate has a finite capacity, and high levels of stimulation override the ability of respiration to gate autonomic responsiveness. Autonomic throughput also depends importantly on other factors, including especially, the frequency of breathing, the rate at which the gate opens and closes. Respiratory sinus arrhythmia is small at rapid, and large at slow breathing rates. The strong correlation between systolic pressure and R-R intervals at respiratory frequencies reflects the influence of respiration on these two measures, rather than arterial baroreflex physiology. A wide range of evidence suggests that respiratory activity gates the timing of autonomic motoneurone firing, but does not influence its tonic level. I propose that the most enduring significance of respiratory gating is its use as a precisely controlled experimental tool to tease out and better understand otherwise inaccessible human autonomic neurophysiological mechanisms.

  20. Surface chemistry of ferrihydrite: Part 2. Kinetics of arsenate adsorption and coprecipitation

    USGS Publications Warehouse

    Fuller, C.C.; Dadis, J.A.; Waychunas, G.A.

    1993-01-01

    The kinetics of As(V) adsorption by ferrihydrite was investigated in coprecipitation and postsynthesis adsorption experiments conducted in the pH range 7.5-9.0. In coprecipitation experiments, As(V) was present in solution during the hydrolysis and precipitation of iron. In adsorption experiments, a period of rapid (<5 min) As(V) uptake from solution was followed by continued uptake for at least eight days, as As(V) diffused to adsorption sites on ferrihydrite surfaces within aggregates of colloidal particles. The time dependence of As(V) adsorption is well described by a general model for diffusion into a sphere if a subset of surface sites located near the exterior of aggregates is assumed to attain adsorptive equilibrium rapidly. The kinetics of As(V) desorption after an increase in pH were also consistent with diffusion as a rate-limiting process. Aging of pure ferrihydrite prior to As(V) adsorption caused a decrease in adsorption sites on the precipitate owing to crystallite growth. In coprecipitation experiments, the initial As(V) uptake was significantly greater than in post-synthesis adsorption experiments, and the rate of uptake was not diffusion limited because As(V) was coordinated by surface sites before crystallite growth and coagulation processes could proceed. After the initial adsorption, As(V) was slowly released from coprecipitates for at least one month, as crystallite growth caused desorption of As(V). Adsorption densities as high as 0.7 mole As(V) per mole of Fe were measured in coprecipitates, in comparison to 0.25 mole As(V) per mole of Fe in post-synthesis adsorption experiments. Despite the high Concentration of As(V) in the precipitates, EXAFS spectroscopy (Waychunas et al., 1993) showed that neither ferric arsenate nor any other As-bearing surface precipitate or solid solution was formed. The high adsorption densities are possible because the ferrihydrite particles are extremely small, approaching the size of small dioctahedral chains at

  1. In situ characterization of green rust in the presence of arsenate and phosphate in simulated oxidized and reduced environments.

    NASA Astrophysics Data System (ADS)

    Root, R. A.; O'Day, P. A.

    2008-12-01

    Nano- to micron-scale particles of mixed-valent iron hydroxide, specifically green rust (GR [FeII6- x(OH)y FeIIIx(OH)12-y]x+[Anionx- + H2O]x-), have been identified and studied as corrosion products of steel, and recently rediscovered in hydromorphic soils and sediments. Green rusts are intermediate phases produced by biotic and abiotic reductive dissolution of ferric oxyhydroxides, or by oxidation of dissolved ferrous iron. Adsorbed oxyanions can stabilize GR phases and inhibit the formation of thermodynamically favored iron phases such as magnetite or lepidocrocite in subsurface environments. This study used synchrotron XRD to characterize iron (hydr)oxide minerals precipitated from solution and subsequent aging products under different environmental conditions of pH and Eh. Here we show the in situ abiotic development of green rust and its stabilization by the addition of adsorbed oxyanions or alternatively, subsequent rapid transformation to magnetite or lepidocrocite in the absence of added anions. A closed batch reactor with an in-line capillary was used to expose the reaction products to continuous synchrotron radiation. Laue patterns were collected at time intervals of 3-5 minutes and used to detect the formation of crystalline iron (hydr)oxide minerals that precipitate as a function time and chemical perturbations to the system, i.e. changing the pH, redox potential, ratio of Fe2+ to OH- , and addition of an oxyanion, arsenate or phosphate. The reactions were monitored by observing the development of diagnostic green rust XRD d-spacing peak at 10.9 Å (300), the 3.29 Å (210) d- spacing for lepidocrocite, and the 2.53 Å (100) d-spacing for magnetite, with continuous in-line measurement of pH and ORP. We found that green rust was stabilized by the adsorption of arsenate and phosphate. In the presence of arsenate or phosphate at pH =7, green rust transformed to lepidocrocite after several hours when anoxic controls were removed. When pH and Eh were constant

  2. Fate of arsenate following arsenite oxidation in Agrobacterium tumefaciens GW4.

    PubMed

    Wang, Qian; Qin, Dong; Zhang, Shengzhe; Wang, Lu; Li, Jingxin; Rensing, Christopher; McDermott, Timothy R; Wang, Gejiao

    2015-06-01

    The fate of arsenate (As(V) ) generated by microbial arsenite (As(III) ) oxidation is poorly understood. Agrobacterium tumefaciens wild-type strain (GW4) was studied to determine how the cell copes with As(V) generated in batch culture. GW4 grown heterotrophically with mannitol used As(III) as a supplemental energy supply as reflected by enhanced growth and increased cellular levels of NADH and ATP. Under low phosphate (Pi) conditions and presence of As(III) oxidation, up to ∼ 50% of the resulting As(V) was taken up and found associated with the periplasm, membrane or cytoplasm fractions of the cells. Arsenic was found associated with proteins and polar lipids, but not in nucleic acids or sugars. Thin-layer chromatography and gas chromatography-mass spectrometry analysis suggested the presence of arsenolipids in membranes, presumably as part of the bilayer structure of the cell membrane and replacing Pi under Pi-limiting conditions. The potential role of a Pi-binding protein (PstS) for As(V) uptake was assessed with the His-tag purified protein. Intrinsic tryptophan fluorescence spectra analysis suggests that PstS can bind As(V) , but with lower affinity as compared with Pi. In early stationary phase cells, the As(V)  : Pi ratio was approximately 4.3 and accompanied by an altered cell ultrastructure. PMID:24673976

  3. Electrodialytic removal of Cu, Cr, and As from chromated copper arsenate-treated timber waste

    SciTech Connect

    Ribeiro, A.B.; Mateus, E.P.; Ottosen, L.M.; Bech-Nielsen, G.

    2000-03-01

    Waste of wood treated with chromated copper arsenate (CCA) is expected to increase in volume over the next decades. Alternative disposal options to landfilling are becoming more attractive to study, especially those that promote reuse. The authors have studied the electrodialytic removal of Cu, Cr, and As from CCA-treated timber wastes. The method uses a low-level direct current as the cleaning agent, combining the electrokinetic movement of ions in the matrix with the principle of electrodialysis. The technique was tested in four experiments using a laboratory cell on sawdust of an out-of-service CCA-treated Pinus pinaster Ait. pole. The duration of all the experiments was 30 days, and the current density was kept constant at 0.2 mA/cm{sup 2}. The experiments differ because in one the sawdust was saturated with water (experiment 1) and in the rest it was saturated with oxalic acid, 2.5, 5, and 7.5% (w/w), respectively, in experiments 2--4. The highest removal rates obtained were 93% of Cu, 95% of Cr, and 99% of As in experiment 2. Other experimental conditions might possibly optimize the removal rates.

  4. Growth, morphology, structure and characterization of L-histidinium dihydrogen arsenate orthoarsenic acid single crystal.

    PubMed

    Tyagi, Nidhi; Sinha, Nidhi; Yadav, Harsh; Kumar, Binay

    2016-08-01

    L-Histidinium dihydrogen arsenate orthoarsenic acid (LHAS) crystals were grown by the slow evaporation method. Single-crystal X-ray diffraction confirms monoclinic structure. The growth rates of various planes of LHAS crystals were estimated by morphological study. Hirshfeld surface and fingerprint plots were analyzed to investigate the intermolecular interactions at 0.002 a.u. present in the crystal structure. The functional groups and phase behavior of the compound are studied by FTIR spectroscopy and differential scanning calorimetry (DSC). A ferroelectric to paraelectric phase transition at 307 K was observed in dielectric studies. The piezoelectric charge coefficients of the grown crystal were found to be 2 pC/N. The values of coercive field (Ec), remnant polarization (Pr) and spontaneous polarization (Ps) in the hysteresis loop are found to be 5.236 kV cm(-1), 0.654 µC cm(-2) and 2.841 µC cm(-2), respectively. Piezoelectricity and ferroelectricity are reported for the first time in LHAS crystals. The mechanical strength was confirmed from microhardness study and void volume. Due to the low value of the dielectric constant, and good piezoelectric and ferroelectric properties, LHAS crystals can be used in microelectronics, sensors and advanced electronic devices. PMID:27484380

  5. Co-adsorption of Trichloroethylene and Arsenate by Iron-Impregnated Granular Activated Carbon.

    PubMed

    Deng, Baolin; Kim, Eun-Sik

    2016-05-01

    Co-adsorption of trichloroethylene (TCE) and arsenate [As(V)] was investigated using modified granular activated carbons (GAC): untreated, sodium hypochlorite-treated (NaClO-GAC), and NaClO with iron-treated GAC (NaClO/Fe-GAC). Batch experiments of single- [TCE or As(V)] and binary- [TCE and As(V)] components solutions are evaluated through Langmuir and Freundlich isotherm models and adsorption kinetic tests. In the single-component system, the adsorption capacity of As(V) was increased by the NaClO-GAC and the NaClO/Fe-GAC. The untreated GAC showed a low adsorption capacity for As(V). Adsorption of TCE by the NaClO/Fe-GAC was maximized, with an increased Freundlich constant. Removal of TCE in the binary-component system was decreased 15% by the untreated GAC, and NaClO- and NaClO/Fe-GAC showed similar efficiency to the single-component system because of the different chemical status of the GAC surfaces. Results of the adsorption isotherms of As(V) in the binary-component system were similar to adsorption isotherms of the single-component system. The adsorption affinities of single- and binary-component systems corresponded with electron transfer, competitive adsorption, and physicochemical properties. PMID:27131303

  6. Tolerance, arsenic uptake, and oxidative stress in Acacia farnesiana under arsenate-stress.

    PubMed

    Alcantara-Martinez, Nemi; Guizar, Sandra; Rivera-Cabrera, Fernando; Anicacio-Acevedo, Blanca E; Buendia-Gonzalez, Leticia; Volke-Sepulveda, Tania

    2016-07-01

    Acacia farnesiana is a shrub widely distributed in soils heavily polluted with arsenic in Mexico. However, the mechanisms by which this species tolerates the phytotoxic effects of arsenic are unknown. This study aimed to investigate the tolerance and bioaccumulation of As by A. farnesiana seedlings exposed to high doses of arsenate (AsV) and the role of peroxidases (POX) and glutathione S-transferases (GST) in alleviating As-stress. For that, long-period tests were performed in vitro under different AsV treatments. A. farnesiana showed a remarkable tolerance to AsV, achieving a half-inhibitory concentration (IC50) of about 2.8 mM. Bioaccumulation reached about 940 and 4380 mg As·kg(-1) of dry weight in shoots and roots, respectively, exposed for 60 days to 0.58 mM AsV. Seedlings exposed to such conditions registered a growth delay during the first 15 days, when the fastest As uptake rate (117 mg kg(-1) day(-1)) occurred, coinciding with both the highest rate of lipid peroxidation and the strongest up-regulation of enzyme activities. GST activity showed a strong correlation with the As bioaccumulated, suggesting its role in imparting AsV tolerance. This study demonstrated that besides tolerance to AsV, A. farnesiana bioaccumulates considerable amounts of As, suggesting that it may be useful for phytostabilization purposes. PMID:26618535

  7. Arsenic and Chromium Partitioning in a Podzolic Soil Contaminated by Chromated Copper Arsenate

    SciTech Connect

    Hopp, L.; Nico, P.S.; Marcus, M.A.; Peiffer, S.

    2008-10-14

    This research combined the use of selective extractions and X-ray spectroscopy to examine the fate of As and Cr in a podzolic soil contaminated by chromated copper arsenate (CCA). Iron was enriched in the upper 30 cm due to a previous one-time treatment of the soil with Fe(II). High oxalate-soluble Al concentrations in the Bs horizon of the soil and micro-XRD data indicated the presence of short-range ordered aluminosilicates (i.e., proto-imogolite allophane, PIA). In the surface layers, Cr, as Cr(III), was partitioned between a mixed Fe(III)/Cr(III) solid phase that formed upon the Fe(II) application (25--50%) and a recalcitrant phase (50--75%) likely consisting of organic material such as residual CCA-treated wood. Deeper in the profile Cr appeared to be largely in the form of extractable (hydr)oxides. Throughout the soil, As was present as As(V). In the surface layers a considerable fraction of As was also associated with a recalcitrant phase, probably CCA-treated woody debris, and the remainder was associated with (hydr)oxide-like solid phases. In the Bs horizon, however, XAS and XRF findings strongly pointed to the presence of PIA acting as an effective adsorbent for As. This research shows for the first time the relevance of PIA for the adsorption of As in natural soils.

  8. Interactive effects of arsenate, selenium, and dietary protein on survival, growth, and physiology in mallard ducklings

    USGS Publications Warehouse

    Hoffman, D.J.; Sanderson, C.J.; LeCaptain, L.J.; Cromartie, E.; Pendleton, G.W.

    1992-01-01

    High concentrations of arsenic (As) and selenium (Se) have been found in aquatic food chains associated with irrigation drainwater. Total biomass of invertebrates, a maJor source of protein for wild ducklings, may vary in environments that are contaminated with selenium. Dayold mallard (Anas platyrhynchos) ducklings received an untreated diet (controls) containing 22% protein or diets containing 15 ppm Se (as selenomethionine), 60 ppm Se, 200 ppm As (as sodium arsenate), 15 ppm Se with 200 ppm As, or 60 ppm Se with 200 ppm As. In a concurrent experiment, the same sequence was repeated with a proteinrestricted (7%) but isocaloric diet. After 4 weeks, blood and tissue samples were collected for biochemical and histological examination. With 22% protein and 60 ppm Se in the diet, duckling survival and growth was reduced and livers had histopathological lesions. Arsenic alone caused some reduction in growth. Antagonistic interactive effects occurred between As and Se, including complete to partial alleviation of the following Se effects: mortality, impaired growth, hepatic lesions and lipid peroxidation, and altered glutathione and thiol status. With 7% protein, survival and growth of controls was less than that with 22% protein, Se (60 ppm) caused 100% mortality, and As (200 ppm) caused mortality, decreased growth, and liver histopathology. These findings suggest the potential for antagonistic effects of Se and As on duckling survival, growth, and physiology with adequate dietary protein but more severe toxicological effects when dietary protein is diminished.

  9. Arsenic and chromium partitioning in a podzolic soil contaminated by chromated copper arsenate

    SciTech Connect

    Nico, Peter; Hopp, Luisa; Nico, Peter S.; Marcus, Matthew A.; Peiffer, Stefan

    2008-06-01

    This research combined the use of selective extractions and x-ray spectroscopy to examine the fate of As and Cr in a podzolic soil contaminated by chromated copper arsenate (CCA). Iron was enriched in the upper 30 cm due to a previous one-time treatment of the soil with Fe(II). High oxalate-soluble Al concentrations in the Bs horizon of the soil and micro-XRD data indicated the presence of short-range ordered aluminosilicates (i.e. proto-imogolite allophane, PIA). In the surface layers, Cr, as Cr(III), was partitioned between a mixed Fe(III)/Cr(III) solid phase that formed upon the Fe(II) application (25-50%) and a recalcitrant phase (50-75%) likely consisting of organic material such as residual CCA-treated wood. Deeper in the profile Cr appeared to be largely in the form of extractable (hydr)oxides. Throughout the soil, As was present as As(V). In the surface layers a considerable fraction of As was also associated with a recalcitrant phase, probably CCA-treated woody debris, and the remainder was associated with (hydr)oxide-like solid phases. In the Bs horizon, however, XAS and XRF findings strongly pointed to the presence of PIA acting as an effective adsorbent for As. This research shows for the first time the relevance of PIA for the adsorption of As in natural soils.

  10. Characterization of adsorption of aqueous arsenite and arsenate onto charred dolomite in microcolumn systems.

    PubMed

    Salameh, Yousef; Al-Muhtaseb, Ala'a H; Mousa, Hasan; Walker, Gavin M; Ahmad, Mohammad N M

    2014-01-01

    In this work, the removal of arsenite, As(III), and arsenate, As(V), from aqueous solutions onto thermally processed dolomite (charred dolomite) via microcolumn was evaluated. The effects of mass of adsorbent (0.5-2 g), initial arsenic concentration (50-2000 ppb) and particle size (<0.355-2 mm) on the adsorption capacity of charred dolomite in a microcolumn were investigated. It was found that the adsorption of As(V) and As(III) onto charred dolomite exhibited a characteristic 'S' shape. The adsorption capacity increased as the initial arsenic concentration increased. A slow decrease in the column adsorption capacity was noted as the particle size increased from>0.335 to 0.710-2.00 mm. For the binary system, the experimental data show that the adsorption of As(V) and As(III) was independent of both ions in solution. The experimental data obtained from the adsorption process were successfully correlated with the Thomas Model and Bed Depth Service Time Model. PMID:25244130

  11. Arsenate (As V) in water: quantitative sensitivity relationships among biomarker, ecotoxicity and genotoxicity endpoints.

    PubMed

    Silva, Valéria C; Almeida, Sônia M; Resgalla, Charrid; Masfaraud, Jean-François; Cotelle, Sylvie; Radetski, Claudemir M

    2013-06-01

    It is useful to test ecotoxicity and genotoxicity endpoints in the environmental impact assessment. Here, we compare and discuss ecotoxicity and genotoxicity effects in organisms in response to exposure to arsenate (As V) in solution. Eco(geno)toxicity responses in Aliivibrio fischeri, Lytechinus variegatus, Daphnia magna, Skeletonema costatum and Vicia faba were analyzed by assessing different endpoints: biomass growth, peroxidase activity, mitotic index, micronucleus frequency, and lethality in accordance with the international protocols. Quantitative sensitivity relationships (QSR) between these endpoints were established in order to rank endpoint sensitivity. The results for the QSR values based on the lowest observed effect concentration (LOEC) ratios varied from 2 (for ratio of root peroxidase activity to leaf peroxidase activity) to 2286 (for ratio of higher plant biomass growth to root peroxidase activity). The QSR values allowed the following sensitivity ranking to be established: higher plant enzymatic activity>daphnids≈echinoderms>bacteria≈algae>higher plant biomass growth. The LOEC values for the mitotic index and micronucleus frequency (LOEC=0.25mgAsL(-1)) were similar to the lowest LOEC values observed in aquatic organisms. This approach to the QSR of different endpoints could form the basis for monitoring and predicting early effects of pollutants before they give rise to significant changes in natural community structures. PMID:23597676

  12. No evidence for Evans' holes in the A, B, C vibrational structure of potassium dihydrogen arsenate

    NASA Astrophysics Data System (ADS)

    Tomkinson, John; Parker, Stewart F.; Lennon, David

    2010-07-01

    We have used inelastic neutron scattering (INS) spectroscopy to study the "A, B, C" region of the hydrogen bond in potassium dihydrogen arsenate. The broad spectral feature observed in infrared spectroscopy is shown to be associated with a ridge of constant intensity in the INS, which follows the recoil line for a unit-mass particle. The onset energy of the ridge is unclear but, we believe, is associated with the optical "C" feature at 1610 cm-1, and which we assign to ν(O-H). The "B" and "A" optical bands were both demonstrated to be two-quantum events and are, thus, not associated with the fundamental ν(O-H). They are readily assigned to the harmonic overtone δ(OH)(0-2) and the combination γ(OH)(0-1)+δ(OH)(0-1), which both sit astride the ridge and there is no evidence for Evans' holes. The other overtone, γ(OH)(0-2), has been assigned to a very weak feature, observed for the first time at 1900 cm-1. A simple model was used to describe the intensity distributions.

  13. A symbiotic bacterium differentially influences arsenate absorption and transformation in Dunaliella salina under different phosphate regimes.

    PubMed

    Wang, Ya; Zhang, Chun Hua; Lin, Man Man; Ge, Ying

    2016-11-15

    In this study, we investigated the effects of a symbiotic bacterium and phosphate (PO4(3-)) nutrition on the toxicity and metabolism of arsenate (As(V)) in Dunaliella salina. The bacterium was identified as Alteromonas macleodii based on analysis of its 16S rRNA gene sequence. When no As(V) was added, A. macleodii significantly enhanced the growth of D. salina, irrespective of PO4(3-) nutrition levels, but this effect was reversed after As(V)+PO4(3-) treatment (1.12mgL(-1)) for 3 days. Arsenic (As) absorption by the non-axenic D. salina was significantly higher than that by its axenic counterpart during incubation with 1.12mgL(-1) PO4(3-). However, when the culture was treated with 0.112mgL(-1) PO4(3-), As(V) reduction and its subsequent arsenite (As(III)) excretion by non-axenic D. salina were remarkably enhanced, which, in turn, contributed to lower As absorption in non-axenic algal cells from days 7 to 9. Moreover, dimethylarsinic acid was synthesized by D. salina alone, and the rates of its production and excretion were accelerated when the PO4(3-) concentration was 0.112mgL(-1). Our data demonstrate that A. macleodii strongly affected As toxicity, uptake, and speciation in D. salina, and these impacts were mediated by PO4(3-) in the cultures. PMID:27450336

  14. Arsenate (As) uptake by and distribution in two cultivars of winter wheat (Triticum aestivum L.).

    PubMed

    Geng, Chun-Nu; Zhu, Yong-Guan; Tong, Yi-Ping; Smith, Sally E; Smith, F A

    2006-01-01

    Two cultivars of winter wheat (Triticum aestivum L.) (Jing 411 and Lovrin 10) were used to investigate arsenate (As) uptake and distribution in plants grown in hydroponic culture and in the soil. Results showed that without As addition, Lovrin 10 had higher biomass than Jing 411 in the soil pot experiment; in the hydroponic experiment Lovrin 10 had similar root biomass to and lower shoot biomass than Jing 411. Increasing P supply from 32 to 161 microM resulted in lower tissue As concentrations, and increasing As supply from 0 to 2,000 microM resulted in lower tissue P concentrations. Increasing P supply tended to increase shoot-to-root ratios of As concentrations, and increasing As supply tended to decrease shoot-to-root ratios of As concentrations. Both cultivars invested more in root production under P deficient conditions than under P sufficient conditions. Lovrin 10 invested more biomass production to roots than Jing 411, which might be partly responsible for higher shoot P and As concentrations and higher shoot-to-root ratios of As concentrations. Moreover, Lovrin 10 allocated less As to roots than Jing 411 and the difference disappeared with decreasing P supply. PMID:16081139

  15. Kinetics and mechanism of arsenate removal by nanosized iron oxide-coated perlite.

    PubMed

    Mostafa, M G; Chen, Yen-Hua; Jean, Jiin-Shuh; Liu, Chia-Chuan; Lee, Yao-Chang

    2011-03-15

    This study discussed the adsorption kinetics of As(V) onto nanosized iron oxide-coated perlite. The effects of pH, initial concentration of As(V) and common anions on the adsorption efficiency were also investigated. It was observed that a 100% As(V) adsorption was achieved at pH value of 4-8 from the initial concentration containing 1.0 mg-As(V)L(-1) and the adsorption percentage depended on the initial concentration; the phosphate and silicate ions would not interfere with the adsorption efficiency. Furthermore, nanosized iron oxide-coated perlite (IOCP) has been shown to be an effective adsorbent for the removal of arsenate from water. The adsorption kinetics were studied using pseudo-first- and pseudo-second-order models, and the experimental data fitted well with the pseudo-second-order model. Moreover, it suggests that the Langmuir isotherm is more adequate than the Freundlich isotherm in simulating the adsorption isotherm of As(V). The adsorption rate constant is 44.84 L mg(-1) and the maximum adsorption capacity is 0.39 mg g(-1). These findings indicate that the adsorption property of IOCP gives the compound a great potential for applications in environmental remediation. PMID:21282000

  16. Nanoporous sorbent material as an oral phosphate binder and for aqueous phosphate, chromate, and arsenate removal

    PubMed Central

    Sangvanich, Thanapon; Ngamcherdtrakul, Worapol; Lee, Richard; Morry, Jingga; Castro, David; Fryxell, Glen E.; Yantasee, Wassana

    2014-01-01

    Phosphate removal is both biologically and environmentally important. Biologically, hyperphosphatemia is a critical condition in end-stage chronic kidney disease patients. Patients with hyperphosphatemia are treated long-term with oral phosphate binders to prevent phosphate absorption to the body by capturing phosphate in the gastrointestinal (GI) tract followed by fecal excretion. Environmentally, phosphate levels in natural water resources must be regulated according to limits set forth by the US Environmental Protection Agency. By utilizing nanotechnology and ligand design, we developed a new material to overcome limitations of traditional sorbent materials such as low phosphate binding capacity, slow binding kinetics, and negative interference by other anions. A phosphate binder based on iron-ethylenediamine on nanoporous silica (Fe-EDA-SAMMS) has been optimized for substrates and Fe(III) deposition methods. The Fe-EDA-SAMMS material had a 4-fold increase in phosphate binding capacity and a broader operating pH window compared to other reports. The material had a faster phosphate binding rate and was significantly less affected by other anions than Sevelamer HCl, the gold standard oral phosphate binder, and AG® 1-X8, a commercially available anion exchanger. It had less cytotoxicity to Caco-2 cells than lanthanum carbonate, another prescribed oral phosphate binder. The Fe-EDA-SAMMS also had high capacity for arsenate and chromate, two of the most toxic anions in natural water. PMID:25554735

  17. Hydrogen thresholds and steady-state concentrations associated with microbial arsenate respiration.

    PubMed

    Heimann, Axel C; Blodau, Christian; Postma, Dieke; Larsen, Flemming; Viet, Pham H; Nhan, Pham Q; Jessen, Søren; Duc, Mai T; Hue, Nguyen T M; Jakobsen, Rasmus

    2007-04-01

    H2 thresholds for microbial respiration of arsenate (As(V)) were investigated in a pure culture of Sulfurospirillum arsenophilum. H2 was consumed to threshold concentrations of 0.03-0.09 nmol/L with As(V) as terminal electron acceptor, allowing for a Gibbs free-energy yield of 36-41 kJ per mol of reaction. These thresholds are among the lowest measured for anaerobic respirers and fall into the range of denitrifiers or Fe(III)-reducers. In sediments from an arsenic-contaminated aquifer in the Red River flood plain, Vietnam, H2 levels decreased to 0.4-2 nmol/L when As(V) was added under anoxic conditions. When As-(V) was depleted, H2 concentrations rebounded by a factor of 10, a level similar to that observed in arsenic-free controls. The sediment-associated microbial population completely reduced millimolar levels of As(V) to arsenite (As-(III)) within a few days. The rate of As(V)-reduction was essentially the same in sediments amended with a pure culture of S. arsenophilum. These findings together with a review of observed H2 threshold and steady-state values suggest that microbial As(V)-respirers have a competitive advantage over several other anaerobic respirers through their ability to thrive at low H2 levels. PMID:17438780

  18. Effects of Sodium Arsenite and Arsenate in Testicular Histomorphometry and Antioxidants Enzymes Activities in Rats.

    PubMed

    Souza, Ana Cláudia Ferreira; Marchesi, Sarah Cozzer; Domingues de Almeida Lima, Graziela; Ferraz, Rafael Penha; Santos, Felipe Couto; da Matta, Sérgio Luis Pinto; Machado-Neves, Mariana

    2016-06-01

    The main source of environmental arsenic exposure in most countries of the world is drinking water in which inorganic forms of arsenic predominate. The present study was aimed to test the impact of two different compounds of inorganic arsenic in histomorphometric and enzymatic parameters in the testes by oral exposition. Adult Wistar male rats were exposed to sodium arsenite and arsenate in drinking water, testing for each chemical form the concentrations of 0.01 and 10 mg/L per 56 days. The animals intoxicated with arsenic, mainly sodium arsenite, showed reduction in the percentage of seminiferous epithelium and in proportion and volume of Leydig cells. Moreover, there was an increase in the percentage of tunica propria, lumen, lymphatic space, blood vessels, and macrophages. The activity of superoxide dismutase (SOD) did not change among the groups. However, the activity of catalase (CAT) decreased in animals exposed to both arsenic compounds. In addition, the higher concentration of arsenic, mainly as sodium arsenite, caused vacuolization in the seminiferous epithelium. The body and testes weight as well as testosterone concentration remained unchanged among the groups. In conclusion, exposition to arsenic, mainly as sodium arsenite, caused alteration in histomorphometric parameters and antioxidant defense system in the testes. PMID:26446860

  19. Respiratory Care Therapist.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document, which is designed for use in developing a tech prep competency profile for the occupation of respiratory care therapist, lists technical competencies and competency builders for 18 units pertinent to the health technologies cluster in general as well as those specific to the occupation of respiratory care therapist. The following…

  20. Respiratory Syncytial Virus

    MedlinePlus

    ... Palsy: Shannon's Story" 5 Things to Know About Zika & Pregnancy Respiratory Syncytial Virus KidsHealth > For Parents > Respiratory Syncytial Virus Print A ... often get it when older kids carry the virus home from school and pass it to ... often happen in epidemics that last from late fall through early spring. ...

  1. Structure and function of NADPH-cytochrome P450 reductase and nitric oxide synthase reductase domain

    SciTech Connect

    Iyanagi, Takashi . E-mail: iyanagi@spring8.or.jp

    2005-12-09

    NADPH-cytochrome P450 reductase (CPR) and the nitric oxide synthase (NOS) reductase domains are members of the FAD-FMN family of proteins. The FAD accepts two reducing equivalents from NADPH (dehydrogenase flavin) and FMN acts as a one-electron carrier (flavodoxin-type flavin) for the transfer from NADPH to the heme protein, in which the FMNH {sup {center_dot}}/FMNH{sub 2} couple donates electrons to cytochrome P450 at constant oxidation-reduction potential. Although the interflavin electron transfer between FAD and FMN is not strictly regulated in CPR, electron transfer is activated in neuronal NOS reductase domain upon binding calmodulin (CaM), in which the CaM-bound activated form can function by a similar mechanism to that of CPR. The oxygenated form and spin state of substrate-bound cytochrome P450 in perfused rat liver are also discussed in terms of stepwise one-electron transfer from CPR. This review provides a historical perspective of the microsomal mixed-function oxidases including CPR and P450. In addition, a new model for the redox-linked conformational changes during the catalytic cycle for both CPR and NOS reductase domain is also discussed.

  2. Reduction of tetrathionate by mammalian thioredoxin reductase

    PubMed Central

    Narayan, Vivek; Kudva, Avinash K.; Prabhu, K. Sandeep

    2016-01-01

    Tetrathionate, a polythionate oxidation product of microbial hydrogen sulfide and reactive oxygen species from immune cells in the gut, serves as a terminal electron acceptor to confer growth advantage for Salmonella and other enterobacteria. Here we show that the rat liver selenoen-zyme thioredoxin reductase (Txnrd1; TR1) efficiently reduces tetrathionate in vitro. Furthermore, lysates of selenium-supplemented murine macrophages also displayed activity towards tetrathionate, while cells lacking TR1 were unable to reduce tetrathionate. These studies suggest that upregulation of TR1 expression, via selenium supplementation, may modulate the gut microbiome, particularly during inflammation, by regulating the levels of tetrathionate. PMID:26252619

  3. Physical, Chemical, and Biological Methods for the Removal of Arsenic Compounds

    PubMed Central

    Lim, K. T.; Shukor, M. Y.; Wasoh, H.

    2014-01-01

    Arsenic is a toxic metalloid which is widely distributed in nature. It is normally present as arsenate under oxic conditions while arsenite is predominant under reducing condition. The major discharges of arsenic in the environment are mainly due to natural sources such as aquifers and anthropogenic sources. It is known that arsenite salts are more toxic than arsenate as it binds with vicinal thiols in pyruvate dehydrogenase while arsenate inhibits the oxidative phosphorylation process. The common mechanisms for arsenic detoxification are uptaken by phosphate transporters, aquaglyceroporins, and active extrusion system and reduced by arsenate reductases via dissimilatory reduction mechanism. Some species of autotrophic and heterotrophic microorganisms use arsenic oxyanions for their regeneration of energy. Certain species of microorganisms are able to use arsenate as their nutrient in respiratory process. Detoxification operons are a common form of arsenic resistance in microorganisms. Hence, the use of bioremediation could be an effective and economic way to reduce this pollutant from the environment. PMID:24696853

  4. Physical, chemical, and biological methods for the removal of arsenic compounds.

    PubMed

    Lim, K T; Shukor, M Y; Wasoh, H

    2014-01-01

    Arsenic is a toxic metalloid which is widely distributed in nature. It is normally present as arsenate under oxic conditions while arsenite is predominant under reducing condition. The major discharges of arsenic in the environment are mainly due to natural sources such as aquifers and anthropogenic sources. It is known that arsenite salts are more toxic than arsenate as it binds with vicinal thiols in pyruvate dehydrogenase while arsenate inhibits the oxidative phosphorylation process. The common mechanisms for arsenic detoxification are uptaken by phosphate transporters, aquaglyceroporins, and active extrusion system and reduced by arsenate reductases via dissimilatory reduction mechanism. Some species of autotrophic and heterotrophic microorganisms use arsenic oxyanions for their regeneration of energy. Certain species of microorganisms are able to use arsenate as their nutrient in respiratory process. Detoxification operons are a common form of arsenic resistance in microorganisms. Hence, the use of bioremediation could be an effective and economic way to reduce this pollutant from the environment. PMID:24696853

  5. Newborn Respiratory Distress.

    PubMed

    Hermansen, Christian L; Mahajan, Anand

    2015-12-01

    Newborn respiratory distress presents a diagnostic and management challenge. Newborns with respiratory distress commonly exhibit tachypnea with a respiratory rate of more than 60 respirations per minute. They may present with grunting, retractions, nasal flaring, and cyanosis. Common causes include transient tachypnea of the newborn, respiratory distress syndrome, meconium aspiration syndrome, pneumonia, sepsis, pneumothorax, persistent pulmonary hypertension of the newborn, and delayed transition. Congenital heart defects, airway malformations, and inborn errors of metabolism are less common etiologies. Clinicians should be familiar with updated neonatal resuscitation guidelines. Initial evaluation includes a detailed history and physical examination. The clinician should monitor vital signs and measure oxygen saturation with pulse oximetry, and blood gas measurement may be considered. Chest radiography is helpful in the diagnosis. Blood cultures, serial complete blood counts, and C-reactive protein measurement are useful for the evaluation of sepsis. Most neonates with respiratory distress can be treated with respiratory support and noninvasive methods. Oxygen can be provided via bag/mask, nasal cannula, oxygen hood, and nasal continuous positive airway pressure. Ventilator support may be used in more severe cases. Surfactant is increasingly used for respiratory distress syndrome. Using the INSURE technique, the newborn is intubated, given surfactant, and quickly extubated to nasal continuous positive airway pressure. Newborns should be screened for critical congenital heart defects via pulse oximetry after 24 hours but before hospital discharge. Neonatology consultation is recommended if the illness exceeds the clinician's expertise and comfort level or when the diagnosis is unclear in a critically ill newborn. PMID:26760414

  6. Biliverdin reductase: a target for cancer therapy?

    PubMed Central

    Gibbs, Peter E. M.; Miralem, Tihomir; Maines, Mahin D.

    2015-01-01

    Biliverdin reductase (BVR) is a multifunctional protein that is the primary source of the potent antioxidant, bilirubin. BVR regulates activities/functions in the insulin/IGF-1/IRK/PI3K/MAPK pathways. Activation of certain kinases in these pathways is/are hallmark(s) of cancerous cells. The protein is a scaffold/bridge and intracellular transporter of kinases that regulate growth and proliferation of cells, including PKCs, ERK and Akt, and their targets including NF-κB, Elk1, HO-1, and iNOS. The scaffold and transport functions enable activated BVR to relocate from the cytosol to the nucleus or to the plasma membrane, depending on the activating stimulus. This enables the reductase to function in diverse signaling pathways. And, its expression at the transcript and protein levels are increased in human tumors and the infiltrating T-cells, monocytes and circulating lymphocytes, as well as the circulating and infiltrating macrophages. These functions suggest that the cytoprotective role of BVR may be permissive for cancer/tumor growth. In this review, we summarize the recent developments that define the pro-growth activities of BVR, particularly with respect to its input into the MAPK signaling pathway and present evidence that BVR-based peptides inhibit activation of protein kinases, including MEK, PKCδ, and ERK as well as downstream targets including Elk1 and iNOS, and thus offers a credible novel approach to reduce cancer cell proliferation. PMID:26089799

  7. Flavodiiron Oxygen Reductase from Entamoeba histolytica

    PubMed Central

    Gonçalves, Vera L.; Vicente, João B.; Pinto, Liliana; Romão, Célia V.; Frazão, Carlos; Sarti, Paolo; Giuffrè, Alessandro; Teixeira, Miguel

    2014-01-01

    Flavodiiron proteins (FDPs) are a family of enzymes endowed with bona fide oxygen- and/or nitric-oxide reductase activity, although their substrate specificity determinants remain elusive. After a comprehensive comparison of available three-dimensional structures, particularly of FDPs with a clear preference toward either O2 or NO, two main differences were identified near the diiron active site, which led to the construction of site-directed mutants of Tyr271 and Lys53 in the oxygen reducing Entamoeba histolytica EhFdp1. The biochemical and biophysical properties of these mutants were studied by UV-visible and electron paramagnetic resonance (EPR) spectroscopies coupled to potentiometry. Their reactivity with O2 and NO was analyzed by stopped-flow absorption spectroscopy and amperometric methods. These mutations, whereas keeping the overall properties of the redox cofactors, resulted in increased NO reductase activity and faster inactivation of the enzyme in the reaction with O2, pointing to a role of the mutated residues in substrate selectivity. PMID:25151360

  8. Pediatric Respiratory Emergencies.

    PubMed

    Richards, Amber M

    2016-02-01

    Respiratory emergencies are 1 of the most common reasons parents seek evaluation for the their children in the emergency department (ED) each year, and respiratory failure is the most common cause of cardiopulmonary arrest in pediatric patients. Whereas many respiratory illnesses are mild and self-limiting, others are life threatening and require prompt diagnosis and management. Therefore, it is imperative that emergency clinicians be able to promptly recognize and manage these illnesses. This article reviews ED diagnosis and management of foreign body aspiration, asthma exacerbation, epiglottitis, bronchiolitis, community-acquired pneumonia, and pertussis. PMID:26614243

  9. Three classes of Escherichia coli mutants selected for aerobic expression of fumarate reductase.

    PubMed Central

    Iuchi, S; Kuritzkes, D R; Lin, E C

    1986-01-01

    Fumarate reductase (encoded by frd) and succinate dehydrogenase (encoded by sdh) of Escherichia coli are both known to catalyze the interconversion of fumarate and succinate. Fumarate reductase, however, is not inducible aerobically and therefore cannot participate in the dehydrogenation of succinate. Three classes of suppressor mutants, classified as frd oxygen-resistant [frd(Oxr)], constitutive [frd(Con)], and gene amplification [frd(Amp)] mutants, were selected from an sdh strain as pseudorevertants that regained the partial ability to grow aerobically on succinate. All contained increased aerobic levels of fumarate reductase activity. In frd(Oxr) mutants expression of the operon showed increased resistance to aerobic repression. Under anaerobic conditions expression of the operon became less dependent on the fnr+ gene product, a pleiotropic activator protein for genes encoding anaerobic respiratory enzymes. Exogenous fumarate, however, was still required for full induction, and repression by nitrate was undiminished. Thus, aerobic repression and anaerobic nitrate repression appear to involve separate mechanisms. In frd(Con) mutants expression of the operon became highly resistant to aerobic repression. Under anaerobic conditions expression of the operon no longer required the fnr+ gene product or exogenous fumarate and became immune to nitrate repression. In partial diploids bearing an frd(Oxr) or an frd(Con) allele and phi(frd+-lac) there was no mutual regulatory influence between the two genetic loci. Thus, the frd mutations act in cis and hence are probably in the promoter region. In frd(Amp) mutants the frd locus was amplified without significant alteration in the pattern of regulation. PMID:3536878

  10. High-temperature, high-pressure hydrothermal synthesis, characterization, and structural relationships of layered uranyl arsenates.

    PubMed

    Liu, Hsin-Kuan; Ramachandran, Eswaran; Chen, Yi-Hsin; Chang, Wen-Jung; Lii, Kwang-Hwa

    2014-09-01

    Five new uranyl arsenates, Na14[(UO2)5(AsO4)8]·2H2O (1), K6[(UO2)5O5(AsO4)2] (2a), K4[(UO2)3O2(AsO4)2] (2b), Rb4[(UO2)3O2(AsO4)2] (3), and Cs6[(UO2)5O2(AsO4)4] (4), were synthesized by high-temperature, high-pressure hydrothermal reactions at about 560 °C and 1440 bar and were characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and photoluminescence spectroscopy. Crystal data for compound 1: triclinic, P1, a = 7.0005(3) Å, b = 12.1324(4) Å, c = 13.7428(5) Å, α = 64.175(2)°, β = 89.092(2)°, γ = 85.548(2)°, V = 1047.26(7) Å(3), Z = 1, R1 = 0.0185; compound 2a: monoclinic, P2₁/c, a = 6.8615(3) Å, b = 24.702(1) Å, c = 7.1269(3) Å, β = 98.749(2)°, V = 1193.89(9) Å(3), Z = 2, R1 = 0.0225; compound 2b: monoclinic, P2₁/c, a = 6.7852(3) Å, b = 17.3640(8) Å, c = 7.1151(3) Å, β = 98.801(3)°, V = 828.42(6) Å(3), Z = 2, R1 = 0.0269; compound 3: monoclinic, P2₁/m, a = 6.9783(3) Å, b = 17.4513(8) Å, c = 7.0867(3) Å, β = 90.808(3)°, V = 862.94(7) Å(3), Z = 2, R1 = 0.0269; compound 4: triclinic, P1, a = 7.7628(3) Å, b = 9.3324(4) Å, c = 11.9336(4) Å, α = 75.611(2)°, β = 73.136(2)°, γ = 86.329(2)°, V = 801.37(5) Å(3), Z = 1, R1 = 0.0336. The five compounds have layer structures consisting of uranyl square, pentagonal, and hexagonal bipyramids as well as AsO4 tetrahedra. Compound 1 contains chains of discrete uranyl square and pentagonal bipyramids, 2a contains three-polyhedron-wide ribbons of edge- and corner-sharing uranyl square and pentagonal bipyramids, 2b and 3 contain dimers of edge-shairing pentagonal bipyramids that share edges with hexagonal bipyramids to form chains, and 4 contains one-polyhedron-wide zigzag chains of edge-sharing uranyl polyhedra. The double sheet structure of 1 is new, but the chain topology has been observed in an organically templated uranyl sulfate. Compound 2b is a new geometrical isomer of the phosphuranylite group. The sheet anion topologies of 2a and 4 can be obtained by

  11. Removal of arsenate with hydrous ferric oxide coprecipitation: effect of humic acid.

    PubMed

    Du, Jingjing; Jing, Chuanyong; Duan, Jinming; Zhang, Yongli; Hu, Shan

    2014-02-01

    Insights from the adverse effect of humic acid (HA) on arsenate removal with hydrous ferric oxide (HFO) coprecipitation can further our understanding of the fate of As(V) in water treatment process. The motivation of our study is to explore the competitive adsorption mechanisms of humic acid and As(V) on HFO on the molecular scale. Multiple complementary techniques were used including macroscopic adsorption experiments, surface enhanced Raman scattering (SERS), extended X-ray absorption fine structure (EXAFS) spectroscopy, flow-cell attenuated total reflectance Fourier transform infrared (ATR-FTIR) measurement, and charge distribution multisite complexation (CD-MUSIC) modeling. The As(V) removal efficiency was reduced from over 95% to about 10% with the increasing HA concentration to 25 times of As(V) mass concentration. The SERS analysis excluded the HA-As(V) complex formation. The EXAFS results indicate that As(V) formed bidentate binuclear surface complexes in the presence of HA as evidenced by an As-Fe distance of 3.26-3.31 angstroms. The in situ ATR-FTIR measurements show that As(V) replaces surface hydroxyl groups and forms innersphere complex. High concentrations of HA may physically block the surface sites and inhibit the As(V) access. The adsorption of As(V) and HA decreased the point of zero charge of HFO from 7.8 to 5.8 and 6.3, respectively. The CD-MUSIC model described the zeta potential curves and adsorption edges of As(V) and HA reasonably well. PMID:25076514

  12. Functionalized chitosan electrospun nanofiber for effective removal of trace arsenate from water.

    PubMed

    Min, Ling-Li; Zhong, Lu-Bin; Zheng, Yu-Ming; Liu, Qing; Yuan, Zhi-Huan; Yang, Li-Ming

    2016-01-01

    An environment-friendly iron functionalized chitosan elctrospun nanofiber (ICS-ENF) was synthesized for trace arsenate removal from water. The ICS-ENF was fabricated by electrospinning a mixture of chitosan, PEO and Fe(3+) followed by crosslinking with ammonia vapor. The physicochemical properties of ICS-ENF were characterized by FESEM, TEM-EDX and XRD. The ICS-ENF was found to be highly effective for As(V) adsorption at neutral pH. The As(V) adsorption occurred rapidly and achieved equilibrium within 100 min, which was well fitted by pseudo-second-order kinetics model. The As(V) adsorption decreased with increased ionic strength, suggesting an outer-sphere complexation of As(V) on ICS-ENF. Freundlich model well described the adsorption isotherm, and the maximum adsorption capacity was up to 11.2 mg/g at pH 7.2. Coexisting anions of chloride and sulfate showed negligible influence on As(V) removal, but phosphate and silicate significantly reduced As(V) adsorption by competing for adsorption sites. FTIR and XPS analysis demonstrated -NH, -OH and C-O were responsible for As(V) uptake. ICS-ENF was easily regenerated using 0.003 M NaOH, and the removal rate remained above 98% after ten successively adsorption-desorption recycles. This study extends the potential applicability of electrospun nanofibers for water purification and provides a promising approach for As(V) removal from water. PMID:27572634

  13. Glutathione-supported arsenate reduction coupled to arsenolysis catalyzed by ornithine carbamoyl transferase

    SciTech Connect

    Nemeti, Balazs; Gregus, Zoltan

    2009-09-01

    Three cytosolic phosphorolytic/arsenolytic enzymes, (purine nucleoside phosphorylase [PNP], glycogen phosphorylase, glyceraldehyde-3-phosphate dehydrogenase) have been shown to mediate reduction of arsenate (AsV) to the more toxic arsenite (AsIII) in a thiol-dependent manner. With unknown mechanism, hepatic mitochondria also reduce AsV. Mitochondria possess ornithine carbamoyl transferase (OCT), which catalyzes phosphorolytic or arsenolytic citrulline cleavage; therefore, we examined if mitochondrial OCT facilitated AsV reduction in presence of glutathione. Isolated rat liver mitochondria were incubated with AsV, and AsIII formed was quantified. Glutathione-supplemented permeabilized or solubilized mitochondria reduced AsV. Citrulline (substrate for OCT-catalyzed arsenolysis) increased AsV reduction. The citrulline-stimulated AsV reduction was abolished by ornithine (OCT substrate inhibiting citrulline cleavage), phosphate (OCT substrate competing with AsV), and the OCT inhibitor norvaline or PALO, indicating that AsV reduction is coupled to OCT-catalyzed arsenolysis of citrulline. Corroborating this conclusion, purified bacterial OCT mediated AsV reduction in presence of citrulline and glutathione with similar responsiveness to these agents. In contrast, AsIII formation by intact mitochondria was unaffected by PALO and slightly stimulated by citrulline, ornithine, and norvaline, suggesting minimal role for OCT in AsV reduction in intact mitochondria. In addition to OCT, mitochondrial PNP can also mediate AsIII formation; however, its role in AsV reduction appears severely limited by purine nucleoside supply. Collectively, mitochondrial and bacterial OCT promote glutathione-dependent AsV reduction with coupled arsenolysis of citrulline, supporting the hypothesis that AsV reduction is mediated by phosphorolytic/arsenolytic enzymes. Nevertheless, because citrulline cleavage is disfavored physiologically, OCT may have little role in AsV reduction in vivo.

  14. Biomineralization of arsenate to arsenic sulfides is greatly enhanced at mildly acidic conditions.

    PubMed

    Rodriguez-Freire, Lucia; Sierra-Alvarez, Reyes; Root, Robert; Chorover, Jon; Field, James A

    2014-12-01

    Arsenic (As) is an important water contaminant due to its high toxicity and widespread occurrence. Arsenic-sulfide minerals (ASM) are formed during microbial reduction of arsenate (As(V)) and sulfate (SO4(2-)). The objective of this research is to study the effect of the pH on the removal of As due to the formation of ASM in an iron-poor system. A series of batch experiments was used to study the reduction of SO4(2-) and As(V) by an anaerobic biofilm mixed culture in a range of pH conditions (6.1-7.2), using ethanol as the electron donor. Total soluble concentrations and speciation of S and As were monitored. Solid phase speciation of arsenic was characterized by x-ray adsorption spectroscopy (XAS). A marked decrease of the total aqueous concentrations of As and S was observed in the inoculated treatments amended with ethanol, but not in the non-inoculated controls, indicating that the As-removal was biologically mediated. The pH dramatically affected the extent and rate of As removal, as well as the stoichiometric composition of the precipitate. The amount of As removed was 2-fold higher and the rate of the As removal was up to 17-fold greater at pH 6.1 than at pH 7.2. Stoichiometric analysis and XAS results confirmed the precipitate was composed of a mixture of orpiment and realgar, and the proportion of orpiment in the sample increased with increasing pH. The results taken as a whole suggest that ASM formation is greatly enhanced at mildly acidic pH conditions. PMID:25222328

  15. Arsenic Retention in Foliage and Soil after Monosodium Methyl Arsenate (MSMA) Application to Turfgrass.

    PubMed

    Matteson, Audrey R; Gannon, Travis W; Jeffries, Matthew D; Haines, Stephanie; Lewis, Dustin F; Polizzotto, Matthew L

    2014-01-01

    Monosodium methyl arsenate (MSMA) is a commonly used herbicide for weed control in turfgrass systems. There is concern that arsenic from applied MSMA could leach to groundwater or run off into surface water, thereby threatening human and ecosystem health. The USEPA has proposed a phase-out of the herbicide but is seeking additional research about the toxicity and environmental impacts of MSMA before establishing a final ruling. Little research has systematically investigated MSMA in field-based settings; instead, risks have been inferred from isolated field measurements or model-system studies. Accordingly, the overall goal of this study was to quantify the fate of arsenic after MSMA application to a managed turfgrass system. After MSMA application to turfgrass-covered and bareground lysimeters, the majority of arsenic was retained in turfgrass foliage and soils throughout year-long experiments, with 50 to 101% of the applied arsenic recovered in turfgrass systems and 55 to 66% recovered in bareground systems. Dissolved arsenic concentrations from 76.2-cm-depth pore water in the MSMA-treated soils were consistently <2 μg L, indistinguishable from background concentrations. As measured by adsorption isotherm experiments, MSMA retention by the sandy soil from our field site was markedly less than retention by a washed sand and a clay loam. Collectively, these results suggest that under aerobic conditions, minimal arsenic leaching to groundwater would occur after a typical application of MSMA to turfgrass. However, repeated MSMA application may pose environmental risks. Additional work is needed to examine arsenic cycling near the soil surface and to define arsenic speciation changes under different soil conditions. PMID:25602572

  16. Functionalized chitosan electrospun nanofiber for effective removal of trace arsenate from water

    PubMed Central

    Min, Ling-Li; Zhong, Lu-Bin; Zheng, Yu-Ming; Liu, Qing; Yuan, Zhi-Huan; Yang, Li-Ming

    2016-01-01

    An environment-friendly iron functionalized chitosan elctrospun nanofiber (ICS-ENF) was synthesized for trace arsenate removal from water. The ICS-ENF was fabricated by electrospinning a mixture of chitosan, PEO and Fe3+ followed by crosslinking with ammonia vapor. The physicochemical properties of ICS-ENF were characterized by FESEM, TEM-EDX and XRD. The ICS-ENF was found to be highly effective for As(V) adsorption at neutral pH. The As(V) adsorption occurred rapidly and achieved equilibrium within 100 min, which was well fitted by pseudo-second-order kinetics model. The As(V) adsorption decreased with increased ionic strength, suggesting an outer-sphere complexation of As(V) on ICS-ENF. Freundlich model well described the adsorption isotherm, and the maximum adsorption capacity was up to 11.2 mg/g at pH 7.2. Coexisting anions of chloride and sulfate showed negligible influence on As(V) removal, but phosphate and silicate significantly reduced As(V) adsorption by competing for adsorption sites. FTIR and XPS analysis demonstrated –NH, –OH and C–O were responsible for As(V) uptake. ICS-ENF was easily regenerated using 0.003 M NaOH, and the removal rate remained above 98% after ten successively adsorption-desorption recycles. This study extends the potential applicability of electrospun nanofibers for water purification and provides a promising approach for As(V) removal from water. PMID:27572634

  17. Differential effect of biochar upon reduction-induced mobility and bioavailability of arsenate and chromate.

    PubMed

    Choppala, Girish; Bolan, Nanthi; Kunhikrishnan, Anitha; Bush, Richard

    2016-02-01

    Heavy metals such as chromium (Cr) and arsenic (As) occur in ionic form in soil, with chromate [Cr(VI)] and arsenate As(V) being the most pre-dominant forms. The application of biochar to Cr(VI) and As(V) spiked and field contaminated soils was evaluated on the reduction processes [(Cr(VI) to Cr(III)] and [As(V) to As(III))], and subsequent mobility and bioavailability of both As(V) and Cr(VI). The assays used in this study included leaching, soil microbial activity and XPS techniques. The reduction rate of As(V) was lower than that of Cr(VI) with and without biochar addition, however, supplementation with biochar enhanced the reduction process of As(V). Leaching experiments indicated Cr(VI) was more mobile than As(V). Addition of biochar reversed the effect by reducing the mobility of Cr and increasing that of As. The presence of Cr and As in both spiked and contaminated soils reduced microbial activity, but with the addition of biochar to these soils, the microbial activity increased in the Cr(VI) contaminated soils, while it was further decreased with As(V) contaminated soils. The addition of biochar was effective in mitigating Cr toxicity by reducing Cr(VI) to Cr(III). In contrast, the conversion process of As(V) to As(III) hastened by biochar was not favourable, as As(III) is more toxic in soils. Overall, the presence of functional groups on biochar promotes reduction by providing the electrons required for reduction processes to occur as determined by XPS data. PMID:26383264

  18. Biomineralization of Arsenate to Arsenic Sulfides is Greatly Enhanced at Mildly Acidic Conditions

    PubMed Central

    Rodriguez-Freire, Lucia; Sierra-Alvarez, Reyes; Root, Robert; Chorover, Jon; Field, James A.

    2014-01-01

    Arsenic (As) is an important water contaminant due to its high toxicity and widespread occurrence. Arsenic-sulfide minerals (ASM) are formed during microbial reduction of arsenate (AsV) and sulfate (SO42−). The objective of this research is to study the effect of the pH on the removal of As due to the formation of ASM in an iron-poor system. A series of batch experiments was used to study the reduction of SO42− and AsV by an anaerobic biofilm mixed culture in a range of pH conditions (6.1–7.2), using ethanol as the electron donor. Total soluble concentrations and speciation of S and As were monitored. Solid phase speciation of arsenic was characterized by x-ray adsorption spectroscopy (XAS). A marked decrease of the total aqueous concentrations of As and S was observed in the inoculated treatments amended with ethanol, but not in the non-inoculated controls, indicating that the As-removal was biologically mediated. The pH dramatically affected the extent and rate of As removal, as well as the stoichiometric composition of the precipitate. The amount of As removed was 2-fold higher and the rate of the As removal was up to 17-fold greater at pH 6.1 than at pH 7.2. Stoichiometric analysis and XAS results confirmed the precipitate was composed of a mixture of orpiment and realgar, and the proportion of orpiment in the sample increased with increasing pH. The results taken as a whole suggest that ASM formation is greatly enhanced at mildly acidic pH conditions. PMID:25222328

  19. Biosorption of arsenite (As(+3)) and arsenate (As(+5)) from aqueous solution by Arthrobacter sp. biomass.

    PubMed

    Prasad, Kumar Suranjit; Ramanathan, A L; Paul, Jaishree; Subramanian, Vaidyanathan; Prasad, Ram

    2013-01-01

    In this study we investigated the role of arsenic-resistant bacteria Arthrobacter sp. biomass for removal of arsenite as well as arsenate from aqueous solution. The biomass sorption characteristics were studied as a function of biomass dose, contact time and pH. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherm. The Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The biosorption capacity of the biomass for As(+3) and As(+5) was found to be 74.91 mg/g (pH 7.0) and 81.63 mg/g (pH 3.0), respectively using 1 g/L biomass with a contact time of 30 min at 28 degrees C. The mean sorption energy values calculated from the D-R model indicated that the biosorption of As(+3) and As(+5) onto Arthrobacter sp. biomass took place by chemical ion-exchange. The thermodynamic parameters showed that the biosorption of As(+3) and As(+5) ions onto Arthrobacter sp. biomass was feasible, spontaneous and exothermic in nature. Kinetic evaluation of experimental data showed that biosorption of As(+3) and As(+5) followed pseudo-second-order kinetics. Fourier transform infrared spectroscopy (FT-IR) analysis indicated the involvement of possible functional groups (-OH, -C=O and -NH) in the As(+3) and As(+5) biosorption process. Bacterial cell biomass can be used as a biosorbent for removal of arsenic from arsenic-contaminated water. PMID:24527632

  20. Evaluating respiratory patient disability.

    PubMed

    Ruiz Manzano, Juan; Alfageme Michavila, Inmaculada; Chiner Vives, Eusebi; Martínez González, Cristina

    2012-08-01

    The evaluation of the disabilities of patients with respiratory disease is regulated by the Spanish Ministry of Labor and Social Security, as are disabilities of any other type. We believe, however, that in respiratory pathologies this evaluation is especially complicated because, as they are chronic processes, they inter-relate with other systems. Furthermore, they tend to have occasional exacerbations; therefore, normal periods may alternate with other periods of important functional limitations. The present document arises from the desire of SEPAR to update this topic and to respond to the requests of respiratory disease patient associations who have asked us to do so. In this paper, we analyze the current situation of work disability legislation as well as the determination of degrees and percentages, including the current criteria for assigning disabilities due to respiratory tract deficiencies. Lastly, we propose work guidelines that would improve the existing scenario and outline this evaluation for specific pathologies. PMID:22341300

  1. Respiratory Syncytial Virus Infections

    MedlinePlus

    Respiratory syncytial virus (RSV) causes mild, cold-like symptoms in adults and older healthy children. It can cause serious problems in ... tests can tell if your child has the virus. There is no specific treatment. You should give ...

  2. Upper respiratory infections.

    PubMed

    Grief, Samuel N

    2013-09-01

    Upper respiratory infections (URIs) are infections of the mouth, nose, throat, larynx (voice box), and trachea (windpipe). This article outlines the epidemiology, etiology, diagnosis, and management of URIs, including nasopharyngitis (common cold), sinusitis, pharyngitis, laryngitis, and laryngotracheitis. PMID:23958368

  3. Respiratory chain supercomplexes.

    PubMed

    Schägger, H

    2001-01-01

    Respiratory chain supercomplexes have been isolated from mammalian and yeast mitochondria, and bacterial membranes. Functional roles of respiratory chain supercomplexes are catalytic enhancement, substrate channelling, and stabilization of complex I by complex III in mammalian cells. Bacterial supercomplexes are characterized by their relatively high detergent-stability compared to yeast or mammalian supercomplexes that are stable to sonication. The mobility of substrate cytochrome c increases in the order bacterial, yeast, and mammalian respiratory chain. In bacterial supercomplexes, the electron transfer between complexes III and IV involves movement of the mobile head of a tightly bound cytochrome c, whereas the yeast S. cerevisiae seems to use substrate channelling of a mobile cytochrome c, and mammalian respiratory chains have been described to use a cytochrome c pool. Dimeric ATP synthase seems to be specific for mitochondrial OXPHOS systems. Monomeric complex V was found in Acetobacterium woodii and Paracoccus denitrificans. PMID:11798023

  4. What Causes Respiratory Failure?

    MedlinePlus

    ... easily move oxygen into your blood and remove carbon dioxide from your blood (gas exchange). This can cause a low oxygen level or high carbon dioxide level, or both, in your blood. Respiratory failure ...

  5. A high-throughput assay format for determination of nitrate reductase and nitrite reductase enzyme activities

    SciTech Connect

    McNally, N.; Liu, Xiang Yang; Choudary, P.V.

    1997-01-01

    The authors describe a microplate-based high-throughput procedure for rapid assay of the enzyme activities of nitrate reductase and nitrite reductase, using extremely small volumes of reagents. The new procedure offers the advantages of rapidity, small sample size-nanoliter volumes, low cost, and a dramatic increase in the throughput sample number that can be analyzed simultaneously. Additional advantages can be accessed by using microplate reader application software packages that permit assigning a group type to the wells, recording of the data on exportable data files and exercising the option of using the kinetic or endpoint reading modes. The assay can also be used independently for detecting nitrite residues/contamination in environmental/food samples. 10 refs., 2 figs.

  6. Transcripts of anthocyanidin reductase and leucoanthocyanidin reductase and measurement of catechin and epicatechin in tartary buckwheat.

    PubMed

    Kim, Yeon Bok; Thwe, Aye Aye; Kim, Yeji; Li, Xiaohua; Cho, Jin Woong; Park, Phun Bum; Valan Arasu, Mariadhas; Abdullah Al-Dhabi, Naif; Kim, Sun-Ju; Suzuki, Tastsuro; Hyun Jho, Kwang; Park, Sang Un

    2014-01-01

    Anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR) play an important role in the monomeric units biosynthesis of proanthocyanidins (PAs) such as catechin and epicatechin in several plants. The aim of this study was to clone ANR and LAR genes involved in PAs biosynthesis and examine the expression of these two genes in different organs under different growth conditions in two tartary buckwheat cultivars, Hokkai T8 and T10. Gene expression was carried out by quantitative real-time RT-PCR, and catechin and epicatechin content was analyzed by high performance liquid chromatography. The expression pattern of ANR and LAR did not match the accumulation pattern of PAs in different organs of two cultivars. Epicatechin content was the highest in the flowers of both cultivars and it was affected by light in only Hokkai T8 sprouts. ANR and LAR levels in tartary buckwheat might be regulated by different mechanisms for catechin and epicatechin biosynthesis under light and dark conditions. PMID:24605062

  7. Transcripts of Anthocyanidin Reductase and Leucoanthocyanidin Reductase and Measurement of Catechin and Epicatechin in Tartary Buckwheat

    PubMed Central

    Kim, Yeon Bok; Thwe, Aye Aye; Kim, YeJi; Li, Xiaohua; Cho, Jin Woong; Park, Phun Bum; Valan Arasu, Mariadhas; Abdullah Al-Dhabi, Naif; Kim, Sun-Ju; Suzuki, Tastsuro; Hyun Jho, Kwang; Park, Sang Un

    2014-01-01

    Anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR) play an important role in the monomeric units biosynthesis of proanthocyanidins (PAs) such as catechin and epicatechin in several plants. The aim of this study was to clone ANR and LAR genes involved in PAs biosynthesis and examine the expression of these two genes in different organs under different growth conditions in two tartary buckwheat cultivars, Hokkai T8 and T10. Gene expression was carried out by quantitative real-time RT-PCR, and catechin and epicatechin content was analyzed by high performance liquid chromatography. The expression pattern of ANR and LAR did not match the accumulation pattern of PAs in different organs of two cultivars. Epicatechin content was the highest in the flowers of both cultivars and it was affected by light in only Hokkai T8 sprouts. ANR and LAR levels in tartary buckwheat might be regulated by different mechanisms for catechin and epicatechin biosynthesis under light and dark conditions. PMID:24605062

  8. Chaperone properties of Escherichia coli thioredoxin and thioredoxin reductase.

    PubMed Central

    Kern, Renée; Malki, Abderrahim; Holmgren, Arne; Richarme, Gilbert

    2003-01-01

    Thioredoxin, thioredoxin reductase and NADPH form the thioredoxin system and are the major cellular protein disulphide reductase. We report here that Escherichia coli thioredoxin and thioredoxin reductase interact with unfolded and denatured proteins, in a manner similar to that of molecular chaperones that are involved in protein folding and protein renaturation after stress. Thioredoxin and/or thioredoxin reductase promote the functional folding of citrate synthase and alpha-glucosidase after urea denaturation. They also promote the functional folding of the bacterial galactose receptor, a protein without any cysteines. Furthermore, redox cycling of thioredoxin/thioredoxin reductase in the presence of NADPH and cystine stimulates the renaturation of the galactose receptor, suggesting that the thioredoxin system functions like a redox-powered chaperone machine. Thioredoxin reductase prevents the aggregation of citrate synthase under heat-shock conditions. It forms complexes that are more stable than those formed by thioredoxin with several unfolded proteins such as reduced carboxymethyl alpha-lactalbumin and unfolded bovine pancreatic trypsin inhibitor. These results suggest that the thioredoxin system, in addition to its protein disulphide isomerase activity possesses chaperone-like properties, and that its thioredoxin reductase component plays a major role in this function. PMID:12549977

  9. Ribonucleotide reductase metallocofactor: assembly, maintenance and inhibition

    PubMed Central

    ZHANG, Caiguo; LIU, Guoqi; HUANG, Mingxia

    2014-01-01

    Ribonucleotide reductase (RNR) supplies cellular deoxyribonucleotide triphosphates (dNTP) pools by converting ribonucleotides to the corresponding deoxy forms using radical-based chemistry. Eukaryotic RNR comprises α and β subunits: α contains the catalytic and allosteric sites; β houses a diferric-tyrosyl radical cofactor (FeIII2-Y•) that is required to initiates nucleotide reduction in α. Cells have evolved multi-layered mechanisms to regulate RNR level and activity in order to maintain the adequate sizes and ratios of their dNTP pools to ensure high-fidelity DNA replication and repair. The central role of RNR in nucleotide metabolism also makes it a proven target of chemotherapeutics. In this review, we discuss recent progress in understanding the function and regulation of eukaryotic RNRs, with a focus on studies revealing the cellular machineries involved in RNR metallocofactor biosynthesis and its implication in RNR-targeting therapeutics. PMID:24899886

  10. Dynamics of trimethoprim bound to dihydrofolate reductase

    SciTech Connect

    Searle, M.S.; Forster, M.J.; Birdsall, B.; Roberts, G.C.K.; Feeney, J.; Cheung, H.T.A.; Kompis, I.; Geddes, A.J. )

    1988-06-01

    The conformation of a small molecule in its binding site on a protein is a major factor in the specificity of the interaction between them. In this paper, the authors report the use of {sup 1}H and {sup 13}C NMR spectroscopy to study the fluctuations in conformation of the anti-bacterial drug trimethoprim when it is bound to its target, dihydrofolate reductase. {sup 13}C relaxation measurements reveal dihedral angle changes of {plus minus}25{degree} to {plus minus}35{degree} on the subnanosecond time scale, while {sup 13}C line-shape analysis demonstrates dihedral angle changes of at least {plus minus}65{degree} on the millisecond time scale. {sup 1}H NMR shows that a specific hydrogen bond between the inhibitor and enzyme, which is believed to make an important contribution to binding, makes and breaks rapidly at room temperature.

  11. Nitrite Reductase Activity in Engineered Azurin Variants.

    PubMed

    Berry, Steven M; Strange, Jacob N; Bladholm, Erika L; Khatiwada, Balabhadra; Hedstrom, Christine G; Sauer, Alexandra M

    2016-05-01

    Nitrite reductase (NiR) activity was examined in a series of dicopper P.a. azurin variants in which a surface binding copper site was added through site-directed mutagenesis. Four variants were synthesized with copper binding motifs inspired by the catalytic type 2 copper binding sites found in the native noncoupled dinuclear copper enzymes nitrite reductase and peptidylglycine α-hydroxylating monooxygenase. The four azurin variants, denoted Az-NiR, Az-NiR3His, Az-PHM, and Az-PHM3His, maintained the azurin electron transfer copper center, with the second designed copper site located over 13 Å away and consisting of mutations Asn10His,Gln14Asp,Asn16His-azurin, Asn10His,Gln14His,Asn16His-azurin, Gln8Met,Gln14His,Asn16His-azurin, and Gln8His,Gln14His,Asn16His-azurin, respectively. UV-visible absorption spectroscopy, EPR spectroscopy, and electrochemistry of the sites demonstrate copper binding as well as interaction with small exogenous ligands. The nitrite reduction activity of the variants was determined, including the catalytic Michaelis-Menten parameters. The variants showed activity (0.34-0.59 min(-1)) that was slower than that of native NiRs but comparable to that of other model systems. There were small variations in activity of the four variants that correlated with the number of histidines in the added copper site. Catalysis was found to be reversible, with nitrite produced from NO. Reactions starting with reduced azurin variants demonstrated that electrons from both copper centers were used to reduce nitrite, although steady-state catalysis required the T2 copper center and did not require the T1 center. Finally, experiments separating rates of enzyme reduction from rates of reoxidation by nitrite demonstrated that the reaction with nitrite was rate limiting during catalysis. PMID:27055058

  12. Molecular evolution of nitrate reductase genes.

    PubMed

    Zhou, J; Kleinhofs, A

    1996-04-01

    To understand the evolutionary mechanisms and relationships of nitrate reductases (NRs), the nucleotide sequences encoding 19 nitrate reductase (NR) genes from 16 species of fungi, algae, and higher plants were analyzed. The NR genes examined show substantial sequence similarity, particularly within functional domains, and large variations in GC content at the third codon position and intron number. The intron positions were different between the fungi and plants, but conserved within these groups. The overall and nonsynonymous substitution rates among fungi, algae, and higher plants were estimated to be 4.33 x 10(-10) and 3.29 x 10(-10) substitutions per site per year. The three functional domains of NR genes evolved at about one-third of the rate of the N-terminal and the two hinge regions connecting the functional domains. Relative rate tests suggested that the nonsynonymous substitution rates were constant among different lineages, while the overall nucleotide substitution rates varied between some lineages. The phylogenetic trees based on NR genes correspond well with the phylogeny of the organisms determined from systematics and other molecular studies. Based on the nonsynonymous substitution rate, the divergence time of monocots and dicots was estimated to be about 340 Myr when the fungi-plant or algae-higher plant divergence times were used as reference points and 191 Myr when the rice-barley divergence time was used as a reference point. These two estimates are consistent with other estimates of divergence times based on these reference points. The lack of consistency between these two values appears to be due to the uncertainty of the reference times. PMID:8642612

  13. No laughing matter: the unmaking of the greenhouse gas dinitrogen monoxide by nitrous oxide reductase.

    PubMed

    Schneider, Lisa K; Wüst, Anja; Pomowski, Anja; Zhang, Lin; Einsle, Oliver

    2014-01-01

    The gas nitrous oxide (N₂O) is generated in a variety of abiotic, biotic, and anthropogenic processes and it has recently been under scrutiny for its role as a greenhouse gas. A single enzyme, nitrous oxide reductase, is known to reduce N₂O to uncritical N₂, in a two-electron reduction process that is catalyzed at two unusual metal centers containing copper. Nitrous oxide reductase is a bacterial metalloprotein from the metabolic pathway of denitrification, and it forms a 130 kDa homodimer in which the two metal sites CuA and CuZ from opposing monomers are brought into close contact to form the active site of the enzyme. CuA is a binuclear, valence-delocalized cluster that accepts and transfers a single electron. The CuA site of nitrous oxide reductase is highly similar to that of respiratory heme-copper oxidases, but in the denitrification enzyme the site additionally undergoes a conformational change on a ligand that is suggested to function as a gate for electron transfer from an external donor protein. CuZ, the tetranuclear active center of nitrous oxide reductase, is isolated under mild and anoxic conditions as a unique [4Cu:2S] cluster. It is easily desulfurylated to yield a [4Cu:S] state termed CuZ (*) that is functionally distinct. The CuZ form of the cluster is catalytically active, while CuZ (*) is inactive as isolated in the [3Cu(1+):1Cu(2+)] state. However, only CuZ (*) can be reduced to an all-cuprous state by sodium dithionite, yielding a form that shows higher activities than CuZ. As the possibility of a similar reductive activation in the periplasm is unconfirmed, the mechanism and the actual functional state of the enzyme remain under debate. Using enzyme from anoxic preparations with CuZ in the [4Cu:2S] state, N2O was shown to bind between the CuA and CuZ sites, suggesting direct electron transfer from CuA to the substrate after its activation by CuZ. PMID:25416395

  14. Simultaneous reduction of arsenic(V) and uranium(VI) by mackinawite: role of uranyl arsenate precipitate formation.

    PubMed

    Troyer, Lyndsay D; Tang, Yuanzhi; Borch, Thomas

    2014-12-16

    Uranium (U) and arsenic (As) often occur together naturally and, as a result, can be co-contaminants at sites of uranium mining and processing, yet few studies have examined the simultaneous redox dynamics of U and As. This study examines the influence of arsenate (As(V)) on the reduction of uranyl (U(VI)) by the redox-active mineral mackinawite (FeS). As(V) was added to systems containing 47 or 470 μM U(VI) at concentrations ranging from 0 to 640 μM. In the absence of As(V), U was completely removed from solution and fully reduced to nano-uraninite (nano-UO2). While the addition of As(V) did not reduce U uptake, at As(V) concentrations above 320 μM, the reduction of U(VI) was limited due to the formation of a trögerite-like uranyl arsenate precipitate. The presence of U also significantly inhibited As(V) reduction. While less U(VI) reduction to nano-UO2 may take place in systems with high As(V) concentrations, formation of trögerite-like mineral phases may be an acceptable reclamation end point due to their high stability under oxic conditions. PMID:25383895

  15. Thermodynamics of arsenates, selenites, and sulfates in the oxidation zone of sulfide ores: I. Thermodynamic constants at ambient conditions

    NASA Astrophysics Data System (ADS)

    Charykova, M. V.; Krivovichev, V. G.; Depmeir, W.

    2010-12-01

    Understanding and deciphering processes proceeding near the surface are among the urgent tasks of contemporary mineralogy and geochemistry, which are especially important for resolving ecological challenges and developing principles of rational environmental management. The paper presents systematized data published on thermodynamics of minerals (arsenates, sulfates, selenites, and selenates), which are formed in the weathering zone of sulfide ores, and determines approaches to quantitative physicochemical modeling of their formation conditions. Diagrams of phase and chemical equilibria (Eh-pH, diagrams of solubility) of the subsystems of the model system Fe-Cu-Zn-Pb-Co-Ni-As-Se-S-H2O (Fe2+, Fe3+, Cu2+, Zn2+, Pb2+, Ni2+, Co2+, H+//SeO{3/2-}, SeO{4/2-}, AsO{4/3-}, SO{4/2-}, OH--H2O) are used as a thermodynamic basis for modeling mineral-forming processes in the weathering zone of ore deposits. Seventy-two arsenates, about 70 sulfates, and 7 selenites and selenates have been identified in the framework of this system. The available published values of standard thermodynamic functions of the formation of minerals and chemical compounds are given, as well as the Pitzer equation parameters to describe the sulfate systems, which are substantially specific due to the high solubility of their components.

  16. Arsenate Accumulation, Distribution, and Toxicity Associated with Titanium Dioxide Nanoparticles in Daphnia magna.

    PubMed

    Li, Mengting; Luo, Zhuanxi; Yan, Yameng; Wang, Zhenhong; Chi, Qiaoqiao; Yan, Changzhou; Xing, Baoshan

    2016-09-01

    Titanium dioxide nanoparticles (nano-TiO2) are widely used in consumer products. Nano-TiO2 dispersion could, however, interact with metals and modify their behavior and bioavailability in aquatic environments. In this study, we characterized and examined arsenate (As(V)) accumulation, distribution, and toxicity in Daphnia magna in the presence of nano-TiO2. Nano-TiO2 acts as a positive carrier, significantly facilitating D. magna's ability to uptake As(V). As nano-TiO2 concentrations increased from 2 to 20 mg-Ti/L, total As increased by a factor of 2.3 to 9.8 compared to the uptake from the dissolved phase. This is also supported by significant correlations between arsenic (As) and titanium (Ti) signal intensities at concentrations of 2.0 mg-Ti/L nano-TiO2 (R = 0.676, P < 0.01) and 20.0 mg-Ti/L nano-TiO2 (R = 0.776, P < 0.01), as determined by LA-ICP-MS. Even though As accumulation increased with increasing nano-TiO2 concentrations in D. magna, As(V) toxicity associated with nano-TiO2 exhibited a dual effect. Compared to the control, the increased As was mainly distributed in BDM (biologically detoxified metal), but Ti was mainly distributed in MSF (metal-sensitive fractions) with increasing nano-TiO2 levels. Differences in subcellular distribution demonstrated that adsorbed As(V) carried by nano-TiO2 could dissociate itself and be transported separately, which results in increased toxicity at higher nano-TiO2 concentrations. Decreased As(V) toxicity associated with lower nano-TiO2 concentrations results from unaffected As levels in MSFs (when compared to the control), where several As components continued to be adsorbed by nano-TiO2. Therefore, more attention should be paid to the potential influence of nano-TiO2 on bioavailability and toxicity of cocontaminants. PMID:27485179

  17. Arsenate toxicity and metabolism in the halotolerant microalga Dunaliella salina under various phosphate regimes.

    PubMed

    Wang, Ya; Zheng, Yanheng; Liu, Cong; Xu, Pingping; Li, Hao; Lin, Qiaoyun; Zhang, Chunhua; Ge, Ying

    2016-06-15

    Microalgae play an important role in arsenic (As) biogeochemical cycles as they are capable of accumulating and metabolizing this metalloid efficiently. This study aimed to investigate the toxicity, accumulation and transformation of arsenate (As(v)) in Dunaliella salina, an exceptionally halotolerant microalga, under various phosphate (PO4(3-)) regimes. The results of the 72-h toxicity test showed that D. salina was tolerant to As(v). In addition, the toxicity of As(v) was mitigated by an increased PO4(3-) supply. D. salina resisted the adverse effects of As(v) through the suppression of As uptake, enhancement of As reduction, methylation in the cell and excretion from the cell. Our study revealed that D. salina reduced As(v) toxicity using different strategies, i.e., reduction of As uptake upon acute As stress (24 h) and increase of As efflux following chronic As exposure (9 day). Moreover, PO4(3-) strongly affected the adsorption, uptake and transformation of As(v) in D. salina. As(v) reduction, DMA production and As excretion were enhanced under P-limited conditions (0.112 mg L(-1)) or upon higher As(v) exposure (1120 μg L(-1)). Furthermore, PO4(3-) had a significant influence on the As removal ability of D. salina. A high As removal efficiency (>95.6%) was observed in the 5-day cultures at an initial As concentration of 11.2 μg L(-1) and PO4(3-) of 0.112 and 1.12 mg L(-1). However, only 10.9% of total As was removed under 11.2 mg L(-1) PO4(3-) after 9 days of incubation. The findings of this study illustrate the pivotal roles of extracellular PO4(3-) in As(v) toxicity and metabolism, and the results may be relevant for future research on the minimization of As contamination in algal products as well as on the enhancement of As removal from the environment. PMID:27243670

  18. Aerobic Reduction of Arsenate by a Bacterium Isolated From Activated Sludge

    NASA Astrophysics Data System (ADS)

    Kozai, N.; Ohnuki, T.; Hanada, S.; Nakamura, K.; Francis, A. J.

    2006-12-01

    Microlunatus phosphovorus strain NM-1 is a polyphosphate-accumulating bacterium isolated from activated sludge. This bacterium takes up a large amount of polyphosphate under aerobic conditions and release phosphate ions by hydrolysis of polyphosphate to orthophosphate under anaerobic conditions to derive energy for taking up substrates. To understand the nature of this strain, especially, influence of potential contaminants in sewage and wastewater on growth, we have been investigating behavior of this bacterium in media containing arsenic. The present paper mainly reports reduction of arsenate by this bacterium under aerobic conditions. The strain NM-1 (JCM 9379) was aerobically cultured at 30 °C in a nutrient medium containing 2.5 g/l peptone, 0.5 g/l glucose, 1.5 g/l yeast extract, and arsenic [Na2HAsO4 (As(V)) or Na3AsO3 (As(III))] at concentrations between 0 and 50 mM. The cells collected from arsenic-free media were dispersed in buffer solutions containing 2mM HEPES, 10mM NaCl, prescribed concentrations of As(V), and 0-0.2 percent glucose. Then, this cell suspension was kept at 20 °C under aerobic or anaerobic conditions. The speciation of arsenic was carried out by ion chromatography and ICP-MS. The growth of the strain under aerobic conditions was enhanced by the addition of As(V) at the concentration between 1 and 10 mM. The maximum optical density of the culture in the medium containing 5mM As(V) was 1.4 times greater than that of the control culture. Below the As(V) concentration of 10mM, most of the As(V) was reduced to As(III). The growth of the strain under anaerobic conditions has not been observed so far. The cells in the buffer solutions reduced As(V) under aerobic condition. The reduction was enhanced by the addition of glucose. However, the cell did not reduce As(V) under anaerobic conditions. The strain NM-1 showed high resistance to As(V) and As(III). The maximum optical density of the culture grown in a medium containing 50 mM As(V) was only

  19. Exogenous proline application ameliorates toxic effects of arsenate in Solanum melongena L. seedlings.

    PubMed

    Singh, Madhulika; Pratap Singh, Vijay; Dubey, Gunjan; Mohan Prasad, Sheo

    2015-07-01

    Hydroponic experiments were conducted to investigate an effect of exogenous application of proline (Pro; 25 µM) in alleviating arsenate (As(V); 5 and 25 µM) toxicity in Solanum melongena L. (eggplant) seedlings. Exposure of As(V) declined growth of eggplant, which was coincided with an enhanced accumulation of As. However, exogenous Pro application alleviated As(V) toxicity in eggplant seedlings by reducing the accumulation of As. The fluorescence characteristics (JIP-test): φP0, Ψ0, φE0, PIABS, ABS/RC, TR0/RC, ET0/RC, DI0/RC, NPQ and qP were also affected by As(V). However, the effects of As(V) were more prominent on PIABS DI0/RC and NPQ. In Pro treated seedlings, following parameters viz. φP0, Ψ0, φE0 and PIABS were stimulated, while, energy flux parameters (ABS/RC, TR0/RC, ET0/RC and DI0/RC) were inhibited. Toxic effects of As(V) on photochemistry of photosystem II (PS II) were ameliorated by an exogenous application of Pro. Oxidative stress markers: superoxide radical, hydrogen peroxide and malondialdehyde (lipid peroxidation) were enhanced by As(V) exposure, however, their levels were significantly diminished by an exogenous application of Pro. Treatment of As(V) stimulated the activities of superoxide dismutase, peroxidase and catalase except that of glutathione-S-transferase. Exogenous Pro application improved the activities of enzymatic antioxidants. The level of endogenous Pro was higher in As(V) treated as well as in Pro fed seedlings. The activity of a key enzyme of Pro biosynthesis: Δ(1)-pyrroline-5-carboxylate synthetase was higher in Pro fed seedlings. The activity of Pro dehydrogenase was inhibited under As(V) stress, and its activity was minimum in case of Pro+As(V) combination. These results indicate that Pro metabolism could play a key role in regulating the accumulation of As and levels of antioxidants, which concomitantly result into a better growth of eggplant seedlings when compared to the As(V) treatments alone. PMID:25881134

  20. New Functional Sulfide Oxidase-Oxygen Reductase Supercomplex in the Membrane of the Hyperthermophilic Bacterium Aquifex aeolicus*

    PubMed Central

    Prunetti, Laurence; Infossi, Pascale; Brugna, Myriam; Ebel, Christine; Giudici-Orticoni, Marie-Thérèse; Guiral, Marianne

    2010-01-01

    Aquifex aeolicus, a hyperthermophilic and microaerophilic bacterium, obtains energy for growth from inorganic compounds alone. It was previously proposed that one of the respiratory pathways in this organism consists of the electron transfer from hydrogen sulfide (H2S) to molecular oxygen. H2S is oxidized by the sulfide quinone reductase, a membrane-bound flavoenzyme, which reduces the quinone pool. We have purified and characterized a novel membrane-bound multienzyme supercomplex that brings together all the molecular components involved in this bioenergetic chain. Our results indicate that this purified structure consists of one dimeric bc1 complex (complex III), one cytochrome c oxidase (complex IV), and one or two sulfide quinone reductases as well as traces of the monoheme cytochrome c555 and quinone molecules. In addition, this work strongly suggests that the cytochrome c oxidase in the supercomplex is a ba3-type enzyme. The supercomplex has a molecular mass of about 350 kDa and is enzymatically functional, reducing O2 in the presence of the electron donor, H2S. This is the first demonstration of the existence of such a respirasome carrying a sulfide oxidase-oxygen reductase activity. Moreover, the kinetic properties of the sulfide quinone reductase change slightly when integrated in the supercomplex, compared with the free enzyme. We previously purified a complete respirasome involved in hydrogen oxidation and sulfur reduction from Aquifex aeolicus. Thus, two different bioenergetic pathways (sulfur reduction and sulfur oxidation) are organized in this bacterium as supramolecular structures in the membrane. A model for the energetic sulfur metabolism of Aquifex aeolicus is proposed. PMID:20971847

  1. Assembly of NADH: ubiquinone reductase (complex I) in Neurospora mitochondria. Independent pathways of nuclear-encoded and mitochondrially encoded subunits.

    PubMed

    Tuschen, G; Sackmann, U; Nehls, U; Haiker, H; Buse, G; Weiss, H

    1990-06-20

    NADH:ubiquinone reductase, the respiratory chain complex I of mitochondria, consists of some 25 nuclear-encoded and seven mitochondrially encoded subunits, and contains as redox groups one FMN, probably one internal ubiquinone and at least four iron-sulphur clusters. We are studying the assembly of the enzyme in Neurospora crassa. The flux of radioactivity in cells that were pulse-labelled with [35S]methionine was followed through immunoprecipitable assembly intermediates into the holoenzyme. Labelled polypeptides were observed to accumulate transiently in a Mr 350,000 intermediate complex. This complex contains all mitochondrially encoded subunits of the enzyme as well as subunits encoded in the nucleus that have no homologous counterparts in a small, merely nuclear-encoded form of the NADH:ubiquinone reductase made by Neurospora crassa cells poisoned with chloramphenicol. With regard to their subunit compositions, the assembly intermediate and small NADH:ubiquinone reductase complement each other almost perfectly to give the subunit composition of the large complex I. These results suggest that two pathways exist in the assembly of complex I that independently lead to the preassembly of two major parts, which subsequently join to form the complex. One preassembled part is related to the small form of NADH:ubiquinone reductase and contributes most of the nuclear-encoded subunits, FMN, three iron-sulphur clusters and the site for the internal ubiquinone. The other part is the assembly intermediate and contributes all mitochondrially encoded subunits, one iron-sulphur cluster and the catalytic site for the substrate ubiquinone. We discuss the results with regard to the evolution of the electron pathway through complex I. PMID:2141652

  2. Respiratory syncytial virus bronchiolitis.

    PubMed Central

    Leung, Alexander K. C.; Kellner, James D.; Davies, H. Dele

    2005-01-01

    Respiratory syncytial virus, the most common cause of bronchiolitis, is the leading cause of infant hospitalization in developed countries and accounts for substantial mortality and morbidity in developing countries. Children at increased risk of developing severe bronchiolitis are those <6 weeks of age, those born prematurely and those with an underlying cardiopulmonary disorder or immunodeficiency. Approximately 80% of cases occur in the first year of life. By two years of age, virtually all children have been infected by at least one strain of the virus. Classically, respiratory syncytial virus bronchiolitis manifests as cough, wheezing and respiratory distress. The mainstay of treatment is supportive care, consisting of adequate fluid intake, antipyretics to control fever and use of supplemental oxygen if necessary. Frequent and meticulous hand-washing is the best measure to prevent secondary spread. Treatment of respiratory syncytial virus bronchiolitis beyond supportive care should be individualized. Palivizumab has been shown to be effective in preventing severe respiratory syncytial virus bronchiolitis in high-risk children when given prophylactically. In the majority of cases, the disease is usually self-limited. The mortality rate is <1% and occurs predominantly in children at high risk for severe disease. PMID:16396064

  3. Carboxylation mechanism and stereochemistry of crotonyl-CoA carboxylase/reductase, a carboxylating enoyl-thioester reductase

    PubMed Central

    Erb, Tobias J.; Brecht, Volker; Fuchs, Georg; Müller, Michael; Alber, Birgit E.

    2009-01-01

    Chemo- and stereoselective reductions are important reactions in chemistry and biology, and reductases from biological sources are increasingly applied in organic synthesis. In contrast, carboxylases are used only sporadically. We recently described crotonyl-CoA carboxylase/reductase, which catalyzes the reduction of (E)-crotonyl-CoA to butyryl-CoA but also the reductive carboxylation of (E)-crotonyl-CoA to ethylmalonyl-CoA. In this study, the complete stereochemical course of both reactions was investigated in detail. The pro-(4R) hydrogen of NADPH is transferred in both reactions to the re face of the C3 position of crotonyl-CoA. In the course of the carboxylation reaction, carbon dioxide is incorporated in anti fashion at the C2 atom of crotonyl-CoA. For the reduction reaction that yields butyryl-CoA, a solvent proton is added in anti fashion instead of the CO2. Amino acid sequence analysis showed that crotonyl-CoA carboxylase/reductase is a member of the medium-chain dehydrogenase/reductase superfamily and shares the same phylogenetic origin. The stereospecificity of the hydride transfer from NAD(P)H within this superfamily is highly conserved, although the substrates and reduction reactions catalyzed by its individual representatives differ quite considerably. Our findings led to a reassessment of the stereospecificity of enoyl(-thioester) reductases and related enzymes with respect to their amino acid sequence, revealing a general pattern of stereospecificity that allows the prediction of the stereochemistry of the hydride transfer for enoyl reductases of unknown specificity. Further considerations on the reaction mechanism indicated that crotonyl-CoA carboxylase/reductase may have evolved from enoyl-CoA reductases. This may be useful for protein engineering of enoyl reductases and their application in biocatalysis. PMID:19458256

  4. Solubilization and Resolution of the Membrane-Bound Nitrite Reductase from Paracoccus Halodenitrificans into Nitrite and Nitric Oxide Reductases

    NASA Technical Reports Server (NTRS)

    Grant, Michael A.; Cronin, Sonja E.; Hochstein, Lawrence I.

    1984-01-01

    Membranes prepared from Paracoccus halodenitrificans reduced nitrite or nitric oxide to nitrous oxide. Extraction of these membranes with the detergent CHAPSO [3-(3-Chlolamidoporopyldimethylammonio)-1-(2- hydroxy-1-propanesulfonate)], followed by ammonium sulfate fractionation of the solubilized proteins, resulted in the separation of nitrite and nitric oxide reductase activities. The fraction containing nitrite reductase activity spectrally resembled a cd-type cytochrome. Several cytochromes were detected in the nitric oxide reductase fraction. Which, if any, of these cytochromes is associated with the reduction of nitric oxide is not clear at this time.

  5. Equine respiratory pharmacology.

    PubMed

    Foreman, J H

    1999-12-01

    Differentiation of diseases of the equine respiratory tract is based on history, clinical signs, auscultation, endoscopy, imaging, and sampling of airway exudate. Upper respiratory therapies include surgical correction of airway obstructions; flushing of localized abscesses (strangles), guttural pouch disease, or sinusitis; and oral or parenteral antibiotic and anti-inflammatory therapy if deemed necessary. Pneumonia usually is treated with antimicrobials, anti-inflammatories, and bronchodilators. Pleural drainage is indicated if significant pleural effusion is present. The most commonly used therapies for early inflammatory and chronic allergic obstructive conditions include bronchodilators and anti-inflammatories. Acute respiratory distress, particularly acute pulmonary edema, is treated with diuretics (usually furosemide), intranasal oxygen, bronchodilators, corticosteroids, and alleviation of the underlying cause. Furosemide also had been used in North America as a race-day preventative for exercise-induced pulmonary hemorrhage (EIPH), but recent data have shown that furosemide may be a performance-enhancing agent itself. PMID:10589473

  6. Respiratory Pathogens in Monkeys

    PubMed Central

    Good, Robert C.; May, Bessie D.

    1971-01-01

    Respiratory disease in a dynamic colony of nonhuman primates during a 4-year period was due primarily to infections caused by Klebsiella pneumoniae, Diplococcus pneumoniae, Bordetella bronchiseptica, Pasteurella multocida, and Haemophilus influenzae. The principal secondary invaders were Escherichia coli, Staphylococcus aureus, and streptococci. A high fatality rate was associated with infections caused by each of the primary pathogens, and females appeared to be more susceptible than males. Incidence of respiratory disease was greatest in the fall and early winter; however, at all times newly colonized monkeys had a higher infection rate than conditioned monkeys. Infections were occasionally confined only to the lungs and were sometimes present without grossly observable lung lesions. The information given on susceptibility of 10 species of nonhuman primates to respiratory infections provides a basis for developing disease models. PMID:16557951

  7. COMPARISON OF THE METHYL REDUCTASE GENES AND GENE PRODUCTS

    EPA Science Inventory

    The DNA sequences encoding component C of methyl coenzyme M reductase (mcr genes) in Methanothermus fervidus, Methanobacterium thermoautotrophicum, Methanococcus vannielii, and Methanosarcina barkeri have been published. omparisons of transcription initiation and termination site...

  8. Structural features of the ribonucleotide reductase of Aujeszky's disease virus.

    PubMed

    Kaliman, A V; Boldogköi, Z; Fodor, I

    1994-01-01

    A gene construct of the Aujeszky's disease virus (ADV) genome was prepared and the DNA fragment encoding the ribonucleotide reductase was structurally characterized. We determined the entire DNA sequence of two adjacent open reading frames of the ribonucleotide reductase genes with the intergenic sequence of nine base pairs. From the sequence analysis we predict that Aujeszky's disease virus encodes a ribonucleotide reductase which comprises two polypeptides--large and small subunits, with sizes of 835 and 303 amino acids, respectively. Nucleotide and amino acid sequences of the large and small subunits of the Aujeszky's disease virus ribonucleotide reductase have been compared with that of other herpesviruses, and structural features of both proteins have been characterized. PMID:7810419

  9. Management of Respiratory Failure.

    PubMed

    Singh Lamba, Tejpreet; Sharara, Rihab Saeed; Leap, Jennifer; Singh, Anil C

    2016-01-01

    The management of acute respiratory failure varies according to the etiology. A clear understanding of physiology of respiration and pathophysiological mechanisms of respiratory failure is mandatory for managing these patients. The extent of abnormality in arterial blood gas values is a result of the balance between the severity of disease and the degree of compensation by cardiopulmonary system. Normal blood gases do not mean that there is an absence of disease because the homeostatic system can compensate. However, an abnormal arterial blood gas value reflects uncompensated disease that might be life threatening. PMID:26919671

  10. INDUCTION OF CELL PROLIFERATION AND APOPTOSIS IN HL60 AND HACAT CELLS BY ARSENIC, ARSENATE, AND ARSENIC-CONTAMINATED DRINKING WATER

    EPA Science Inventory

    Induction of cell proliferation and apoptosis in HL-60 and HaCaT cells by arsenite, arsenate and arsenic-contaminated drinking water. T-C. Zhang, M. Schmitt, J. L. Mumford National Research Council, Washington DC and U.S. Environmental Protection Agency, NHEERL, Research Triangle...

  11. A PROBABILISTIC ARSENIC EXPOSURE ASSESSMENT FOR CHILDREN WHO CONTACT CHROMATED COPPER ARSENATE ( CAA )-TREATED PLAYSETS AND DECKS: PART 2 SENSITIVITY AND UNCERTAINTY ANALYSIS

    EPA Science Inventory

    A probabilistic model (SHEDS-Wood) was developed to examine children's exposure and dose to chromated copper arsenate (CCA)-treated wood, as described in Part 1 of this two part paper. This Part 2 paper discusses sensitivity and uncertainty analyses conducted to assess the key m...

  12. ARSENATE AND ARSENITE REMOVAL BY ZERO-VALENT IRON: EFFECTS OF PHOSPHATE, SILICATE, CARBONATE, BORATE, SULFATE, CHROMATE, MOLYBDATE, AND NITRATE, RELATIVE TO CHLORIDE

    EPA Science Inventory

    Batch tests were performed to evaluate the effects of inorganic anion competition on the kinetics of arsenate (As(V)) and arsenite (As(III)) removal by zerovalent iron (Peerless Fe0) in aqueous solution. The oxyanions underwent either sorption-dominated reactions (phosphate, sil...

  13. AN EVALUATION OF THE RELATIVE GENOTOXICITY OF ARSENITE, ARSENATE, AND FOUR METHYLATED METABOLITES IN VITRO USING THE ALKALINE SINGLE CELL GEL ASSAY

    EPA Science Inventory

    An Evaluation of the Relative Genotoxicity of Arsenite, Arsenate, and Four Methylated
    Metabolites In Vitro Using the Alkaline Single Cell Gel Assay (ASCG).

    Arsenic ( As) is a genotoxic and carcinogenic metal found in many drinking water systems throughout the world. ...

  14. COMPARATIVE TISSUE DISTRIBUTION AND URINARY EXCRETION OF INORGANIC ARSENIC (IAS) AND ITS METHYLATED METABOLITES IN MICE FOLLOWING ORAL ADMINISTRATION OF ARSENATE (ASV) AND ARSENITE (ASIII)

    EPA Science Inventory

    COMPARATIVE TISSUE DISTRIBUTION AND URINARY EXCRETION OF INORGANIC ARSENIC (iAs) AND ITS METHYLATED METABOLITES IN MICE FOLLOWING ORAL ADMINISTRATION OF ARSENATE (AsV) AND ARSENITE (AsIII). E M Kenyon, L M Del Razo and M F Hughes. U.S. EPA, ORD, NHEERL, ETD, PKB, RTP, NC, USA; ...

  15. Concentration-and time-dependent genomic changes in the mouse urinary bladder following exposure to arsenate in drinking water for up to twelve weeks

    EPA Science Inventory

    Inorganic arsenic (AsD is a known human bladder carcinogen. The objective of this study was to examine the concentration dependence of the genomic response to ASi in the urinary bladders of mice. C57BL/6J mice were exposed for 1 or 12 weeks to arsenate in drinking water at concen...

  16. Expression of bacterial mercuric ion reductase in Saccharomyces cerevisiae.

    PubMed Central

    Rensing, C; Kües, U; Stahl, U; Nies, D H; Friedrich, B

    1992-01-01

    The gene merA coding for bacterial mercuric ion reductase was cloned under the control of the yeast promoter for alcohol dehydrogenase I in the yeast-Escherichia coli shuttle plasmid pADH040-2 and transformed into Saccharomyces cerevisiae AH22. The resulting transformant harbored stable copies of the merA-containing hybrid plasmid, displayed a fivefold increase in the MIC of mercuric chloride, and synthesized mercuric ion reductase activity. Images PMID:1735719

  17. Comparative anatomy of the aldo-keto reductase superfamily.

    PubMed Central

    Jez, J M; Bennett, M J; Schlegel, B P; Lewis, M; Penning, T M

    1997-01-01

    The aldo-keto reductases metabolize a wide range of substrates and are potential drug targets. This protein superfamily includes aldose reductases, aldehyde reductases, hydroxysteroid dehydrogenases and dihydrodiol dehydrogenases. By combining multiple sequence alignments with known three-dimensional structures and the results of site-directed mutagenesis studies, we have developed a structure/function analysis of this superfamily. Our studies suggest that the (alpha/beta)8-barrel fold provides a common scaffold for an NAD(P)(H)-dependent catalytic activity, with substrate specificity determined by variation of loops on the C-terminal side of the barrel. All the aldo-keto reductases are dependent on nicotinamide cofactors for catalysis and retain a similar cofactor binding site, even among proteins with less than 30% amino acid sequence identity. Likewise, the aldo-keto reductase active site is highly conserved. However, our alignments indicate that variation ofa single residue in the active site may alter the reaction mechanism from carbonyl oxidoreduction to carbon-carbon double-bond reduction, as in the 3-oxo-5beta-steroid 4-dehydrogenases (Delta4-3-ketosteroid 5beta-reductases) of the superfamily. Comparison of the proposed substrate binding pocket suggests residues 54 and 118, near the active site, as possible discriminators between sugar and steroid substrates. In addition, sequence alignment and subsequent homology modelling of mouse liver 17beta-hydroxysteroid dehydrogenase and rat ovary 20alpha-hydroxysteroid dehydrogenase indicate that three loops on the C-terminal side of the barrel play potential roles in determining the positional and stereo-specificity of the hydroxysteroid dehydrogenases. Finally, we propose that the aldo-keto reductase superfamily may represent an example of divergent evolution from an ancestral multifunctional oxidoreductase and an example of convergent evolution to the same active-site constellation as the short

  18. Purification and characterization of assimilatory nitrite reductase from Candida utilis.

    PubMed Central

    Sengupta, S; Shaila, M S; Rao, G R

    1996-01-01

    Nitrate assimilation in many plants, algae, yeasts and bacteria is mediated by two enzymes, nitrate reductase (EC 1.6.6.2) and nitrite reductase (EC 1.7.7.1). They catalyse the stepwise reduction of nitrate to nitrite and nitrite to ammonia respectively. The nitrite reductase from an industrially important yeast, Candida utilis, has been purified to homogeneity. Purified nitrite reductase is a heterodimer and the molecular masses of the two subunits are 58 and 66 kDa. The native enzyme exhibits a molecular mass of 126 kDa as analysed by gel filtration. The identify of the two subunits of nitrite reductase was confirmed by immunoblotting using antibody for Cucurbita pepo leaf nitrite reductase. The presence of two different sized transcripts coding for the two subunits was confirmed by (a) in vitro translation of mRNA from nitrate-induced C. utilis followed by immunoprecipitation of the in vitro translated products with heterologous nitrite reductase antibody and (b) Northern-blot analysis. The 66 kDa subunit is acidic in nature which is probably due to its phosphorylated status. The enzyme is stable over a range of temperatures. Both subunits can catalyse nitrite reduction, and the reconstituted enzyme, at a higher protein concentration, shows an activity similar to that of the purified enzyme. Each of these subunits has been shown to contain a few unique peptides in addition to a large number of common peptides. Reduced Methyl Viologen has been found to be as effective an electron donor as NADPH in the catalytic process, a phenomenon not commonly seen for nitrite reductases from other systems. PMID:8694757

  19. Low apparent aldose reductase activity produced by monosaccharide autoxidation.

    PubMed Central

    Wolff, S P; Crabbe, M J

    1985-01-01

    Low apparent aldose reductase activity, as measured by NADPH oxidation, can be produced by the spontaneous autoxidation of monosaccharides. NADPH is oxidized to metabolically active NADP+ in a solution of autoxidizing DL-glyceraldehyde at rates of up to 15 X 10(-4) A340/min. The close parallelism between the effects of buffer salt type and concentration, monosaccharide structure and temperature activation on autoxidation and NADPH oxidation imply that autoxidation is a prerequisite for the NADPH oxidation, probably via the hydroperoxy radical. Nucleotide-binding proteins enhanced NADPH oxidation induced by DL-glyceraldehyde, up to 10.6-fold with glucose-6-phosphate dehydrogenase. Glutathione reductase-catalysed NADPH oxidation in the presence of autoxidizing monosaccharide showed many characteristics of the aldose reductase reaction. Aldose reductase inhibitors acted as antioxidants in inhibiting this NADPH oxidation. These results indicate that low apparent aldose reductase activities may be due to artifacts of monosaccharide autoxidation, and could provide an explanation for the non-linear steady-state kinetics observed with DL-glyceraldehyde and aldose reductase. PMID:2985042

  20. Reaction mechanism and regulation of mammalian thioredoxin/glutathione reductase.

    PubMed

    Sun, Qi-An; Su, Dan; Novoselov, Sergey V; Carlson, Bradley A; Hatfield, Dolph L; Gladyshev, Vadim N

    2005-11-01

    Thioredoxin/glutathione reductase (TGR) is a recently discovered member of the selenoprotein thioredoxin reductase family in mammals. In contrast to two other mammalian thioredoxin reductases, it contains an N-terminal glutaredoxin domain and exhibits a wide spectrum of enzyme activities. To elucidate the reaction mechanism and regulation of TGR, we prepared a recombinant mouse TGR in the selenoprotein form as well as various mutants and individual domains of this enzyme. Using these proteins, we showed that the glutaredoxin and thioredoxin reductase domains of TGR could independently catalyze reactions normally associated with each domain. The glutaredoxin domain is a monothiol glutaredoxin containing a CxxS motif at the active site, which could receive electrons from either the thioredoxin reductase domain of TGR or thioredoxin reductase 1. We also found that the C-terminal penultimate selenocysteine was required for transfer of reducing equivalents from the thiol/disulfide active site of TGR to the glutaredoxin domain. Thus, the physiologically relevant NADPH-dependent activities of TGR were dependent on this residue. In addition, we examined the effects of selenium levels in the diet and perturbations in selenocysteine tRNA function on TGR biosynthesis and found that expression of this protein was regulated by both selenium and tRNA status in liver, but was more resistant to this regulation in testes. PMID:16262253

  1. Effects of thioredoxin reductase-1 deletion on embryogenesis and transcriptome

    PubMed Central

    Bondareva, Alla A.; Capecchi, Mario R.; Iverson, Sonya V.; Li, Yan; Lopez, Nathan I.; Lucas, Olivier; Merrill, Gary F.; Prigge, Justin R.; Siders, Ashley M.; Wakamiya, Maki; Wallin, Stephanie L.; Schmidt, Edward E.

    2007-01-01

    Thioredoxin reductases (Txnrd)1 maintain intracellular redox homeostasis in most organisms. Metazoans Txnrds also participate in signal transduction. Mouse embryos homozygous for a targeted null mutation of the txnrd1 gene, encoding the cytosolic thioredoxin reductase, were viable at embryonic day 8.5 (E8.5) but not at E9.5. Histology revealed that txnrd1−/− cells were capable of proliferation and differentiation; however, mutant embryos were smaller than wild-type littermates and failed to gastrulate. In situ marker gene analyses indicated primitive streak mesoderm did not form. Microarray analyses on E7.5 txnrd−/− and txnrd+/+ littermates showed similar mRNA levels for peroxiredoxins, glutathione reductases, mitochondrial Txnrd2, and most markers of cell proliferation. Conversely, mRNAs encoding sulfiredoxin, IGF-binding protein 1, carbonyl reductase 3, glutamate cysteine ligase, glutathione S-transferases, and metallothioneins were more abundant in mutants. Many gene expression responses mirrored those in thioredoxin reductase 1-null yeast; however mice exhibited a novel response within the peroxiredoxin catalytic cycle. Thus, whereas yeast induce peroxiredoxin mRNAs in response to thioredoxin reductase disruption, mice induced sulfiredoxin mRNA. In summary, Txnrd1 was required for correct patterning of the early embryo and progression to later development. Conserved responses to Txnrd1 disruption likely allowed proliferation and limited differentiation of the mutant embryo cells. PMID:17697936

  2. An overview on 5alpha-reductase inhibitors.

    PubMed

    Aggarwal, Saurabh; Thareja, Suresh; Verma, Abhilasha; Bhardwaj, Tilak Raj; Kumar, Manoj

    2010-02-01

    Benign prostatic hyperplasia (BPH) is the noncancerous proliferation of the prostate gland associated with benign prostatic obstruction and lower urinary tract symptoms (LUTS) such as frequency, hesitancy, urgency, etc. Its prevalence increases with age affecting around 70% by the age of 70 years. High activity of 5alpha-reductase enzyme in humans results in excessive dihydrotestosterone levels in peripheral tissues and hence suppression of androgen action by 5alpha-reductase inhibitors is a logical treatment for BPH as they inhibit the conversion of testosterone to dihydrotestosterone. Finasteride (13) was the first steroidal 5alpha-reductase inhibitor approved by U.S. Food and Drug Administration (USFDA). In human it decreases the prostatic DHT level by 70-90% and reduces the prostatic size. Dutasteride (27) another related analogue has been approved in 2002. Unlike Finasteride, Dutasteride is a competitive inhibitor of both 5alpha-reductase type I and type II isozymes, reduced DHT levels >90% following 1 year of oral administration. A number of classes of non-steroidal inhibitors of 5alpha-reductase have also been synthesized generally by removing one or more rings from the azasteroidal structure or by an early non-steroidal lead (ONO-3805) (261). In this review all categories of inhibitors of 5alpha-reductase have been covered. PMID:19879888

  3. Regulation of the Neurospora crassa assimilatory nitrate reductase.

    PubMed Central

    Ketchum, P A; Zeeb, D D; Owens, M S

    1977-01-01

    Reduced nicotinamide adenine dinucleotide phosphate (NADPH)-nitrate reductase from Neurospora crassa was purified and found to be stimulated by certain amino acids, citrate, and ethylenediaminetetraacetic acid (EDTA). Stimulation by citrate and the amino acids was dependent upon the prior removal of EDTA from the enzyme preparations, since low quantities of EDTA resulted in maximal stimulation. Removal of EDTA from enzyme preparations by dialysis against Chelex-containing buffer resulted in a loss of nitrate reductase activity. Addition of alanine, arginine, glycine, glutamine, glutamate, histidine, tryptophan, and citrate restored and stimulated nitrate reductase activity from 29- to 46-fold. The amino acids tested altered the Km of NADPH-nitrate reductase for NADPH but did not significantly change that for nitrate. The Km of nitrate reductase for NADPH increased with increasing concentrations of histidine but decreased with increasing concentrations of glutamine. Amino acid modulation of NADPH-nitrate reductase activity is discussed in relation to the conservation of energy (NADPH) by Neurospora when nitrate is the nitrogen source. PMID:19423

  4. Respiratory Resistance In Family Therapy

    ERIC Educational Resources Information Center

    Beck, Michael J.

    1975-01-01

    Patients' respiratory problems may interfere with their talking in therapy sessions. Interventions by the therapist must be based on an understanding of the underlying dynamics which produced the respiratory problem. (Author)

  5. Respiratory failure in diabetic ketoacidosis

    PubMed Central

    Konstantinov, Nikifor K; Rohrscheib, Mark; Agaba, Emmanuel I; Dorin, Richard I; Murata, Glen H; Tzamaloukas, Antonios H

    2015-01-01

    Respiratory failure complicating the course of diabetic ketoacidosis (DKA) is a source of increased morbidity and mortality. Detection of respiratory failure in DKA requires focused clinical monitoring, careful interpretation of arterial blood gases, and investigation for conditions that can affect adversely the respiration. Conditions that compromise respiratory function caused by DKA can be detected at presentation but are usually more prevalent during treatment. These conditions include deficits of potassium, magnesium and phosphate and hydrostatic or non-hydrostatic pulmonary edema. Conditions not caused by DKA that can worsen respiratory function under the added stress of DKA include infections of the respiratory system, pre-existing respiratory or neuromuscular disease and miscellaneous other conditions. Prompt recognition and management of the conditions that can lead to respiratory failure in DKA may prevent respiratory failure and improve mortality from DKA. PMID:26240698

  6. Respiratory failure in diabetic ketoacidosis.

    PubMed

    Konstantinov, Nikifor K; Rohrscheib, Mark; Agaba, Emmanuel I; Dorin, Richard I; Murata, Glen H; Tzamaloukas, Antonios H

    2015-07-25

    Respiratory failure complicating the course of diabetic ketoacidosis (DKA) is a source of increased morbidity and mortality. Detection of respiratory failure in DKA requires focused clinical monitoring, careful interpretation of arterial blood gases, and investigation for conditions that can affect adversely the respiration. Conditions that compromise respiratory function caused by DKA can be detected at presentation but are usually more prevalent during treatment. These conditions include deficits of potassium, magnesium and phosphate and hydrostatic or non-hydrostatic pulmonary edema. Conditions not caused by DKA that can worsen respiratory function under the added stress of DKA include infections of the respiratory system, pre-existing respiratory or neuromuscular disease and miscellaneous other conditions. Prompt recognition and management of the conditions that can lead to respiratory failure in DKA may prevent respiratory failure and improve mortality from DKA. PMID:26240698

  7. Textbook of respiratory medicine

    SciTech Connect

    Murray, J.F.; Nadel, J.

    1987-01-01

    This book presents a clinical reference of respiratory medicine. It also details basic science aspects of pulmonary physiology and describes recently developed, sophisticated diagnostic tools and therapeutic methods. It also covers anatomy, physiology, pharmacology, and pathology; microbiologic, radiologic, nuclear medicine, and biopsy methods for diagnosis.

  8. Respiratory Diseases of Poultry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new Respiratory Diseases of Poultry CRIS will be established effective October 1, 2006. Initially, the disease agents to be studied will include Ornithobacterium rhinotracheale (ORT), Bordetella avium (BART) and Pasteurella multocida. The research will focus on development of more effective vacc...

  9. Middle East respiratory syndrome.

    PubMed

    Zumla, Alimuddin; Hui, David S; Perlman, Stanley

    2015-09-01

    Middle East respiratory syndrome (MERS) is a highly lethal respiratory disease caused by a novel single-stranded, positive-sense RNA betacoronavirus (MERS-CoV). Dromedary camels, hosts for MERS-CoV, are implicated in direct or indirect transmission to human beings, although the exact mode of transmission is unknown. The virus was first isolated from a patient who died from a severe respiratory illness in June, 2012, in Jeddah, Saudi Arabia. As of May 31, 2015, 1180 laboratory-confirmed cases (483 deaths; 40% mortality) have been reported to WHO. Both community-acquired and hospital-acquired cases have been reported with little human-to-human transmission reported in the community. Although most cases of MERS have occurred in Saudi Arabia and the United Arab Emirates, cases have been reported in Europe, the USA, and Asia in people who travelled from the Middle East or their contacts. Clinical features of MERS range from asymptomatic or mild disease to acute respiratory distress syndrome and multiorgan failure resulting in death, especially in individuals with underlying comorbidities. No specific drug treatment exists for MERS and infection prevention and control measures are crucial to prevent spread in health-care facilities. MERS-CoV continues to be an endemic, low-level public health threat. However, the virus could mutate to have increased interhuman transmissibility, increasing its pandemic potential. PMID:26049252

  10. Respiratory Muscle Plasticity

    PubMed Central

    Gransee, Heather M.; Mantilla, Carlos B.; Sieck, Gary C.

    2014-01-01

    Muscle plasticity is defined as the ability of a given muscle to alter its structural and functional properties in accordance with the environmental conditions imposed on it. As such, respiratory muscle is in a constant state of remodeling, and the basis of muscle’s plasticity is its ability to change protein expression and resultant protein balance in response to varying environmental conditions. Here, we will describe the changes of respiratory muscle imposed by extrinsic changes in mechanical load, activity, and innervation. Although there is a large body of literature on the structural and functional plasticity of respiratory muscles, we are only beginning to understand the molecular-scale protein changes that contribute to protein balance. We will give an overview of key mechanisms regulating protein synthesis and protein degradation, as well as the complex interactions between them. We suggest future application of a systems biology approach that would develop a mathematical model of protein balance and greatly improve treatments in a variety of clinical settings related to maintaining both muscle mass and optimal contractile function of respiratory muscles. PMID:23798306

  11. [Respiratory complications after transfusion].

    PubMed

    Bernasinski, M; Mertes, P-M; Carlier, M; Dupont, H; Girard, M; Gette, S; Just, B; Malinovsky, J-M

    2014-05-01

    Respiratory complications of blood transfusion have several possible causes. Transfusion-Associated Circulatory Overload (TACO) is often the first mentioned. Transfusion-Related Acute Lung Injury (TRALI), better defined since the consensus conference of Toronto in 2004, is rarely mentioned. French incidence is low. Non-hemolytic febrile reactions, allergies, infections and pulmonary embolism are also reported. The objective of this work was to determine the statistical importance of the different respiratory complications of blood transfusion. This work was conducted retrospectively on transfusion accidents in six health centers in Champagne-Ardenne, reported to Hemovigilance between 2000 and 2009 and having respiratory symptoms. The analysis of data was conducted by an expert committee. Eighty-three cases of respiratory complications are found (316,864 blood products). We have counted 26 TACO, 12 TRALI (only 6 cases were identified in the original investigation of Hemovigilance), 18 non-hemolytic febrile reactions, 16 cases of allergies, 5 transfusions transmitted bacterial infections and 2 pulmonary embolisms. Six new TRALI were diagnosed previously labeled TACO for 2 of them, allergy and infection in 2 other cases and diagnosis considered unknown for the last 2. Our study found an incidence of TRALI 2 times higher than that reported previously. Interpretation of the data by a multidisciplinary committee amended 20% of diagnoses. This study shows the imperfections of our system for reporting accidents of blood transfusion when a single observer analyses the medical records. PMID:24814817

  12. Role of directed van der Waals bonded interactions in the determination of the structures of molecular arsenate solids.

    PubMed

    Gibbs, G V; Wallace, A F; Cox, D F; Dove, P M; Downs, R T; Ross, N L; Rosso, K M

    2009-01-29

    Bond paths, local energy density properties, and Laplacian, L(r) = -wedge(2)rho(r), composite isosurfaces of the electron density distributions were calculated for the intramolecular and intermolecular bonded interactions for molecular solids of As(2)O(3) and AsO(2) composition, an As(2)O(5) crystal, a number of arsenate molecules, and the arsenic metalloid, arsenolamprite. The directed intermolecular van der Waals As-O, O-O, and As-As bonded interactions are believed to serve as mainstays between the individual molecules in each of the molecular solids. As-O bond paths between the bonded atoms connect Lewis base charge concentrations and Lewis acid charge depletion domains, whereas the O-O and As-As paths connect Lewis base pair and Lewis acid pair domains, respectively, giving rise to sets of intermolecular directed bond paths. The alignment of the directed bond paths results in the periodic structures adopted by the arsenates. The arrangements of the As atoms in the claudetite polymorphs of As(2)O(3) and the As atoms in arsenolamprite are similar. Like the As(2)O(3) polymorphs, arsenolamprite is a molecular solid connected by relatively weak As-As intermolecular directed van der Waals bond paths between the layers of stronger As-As intramolecular bonded interactions. The bond critical point and local energy density properties of the intermolecular As-As bonded interactions in arsenolamprite are comparable with the As-As interactions in claudetite I. As such, the structure of claudetite I can be viewed as a stuffed derivative of the arsenolamprite structure with O atoms between pairs of As atoms comprising the layers of the structure. The cubic structure adopted by the arsenolite polymorph can be understood in terms of sets of directed acid-base As-O and base-base O-O pair domains and bond paths that radiate from the tetrahedral faces of its constituent molecules, serving as face-to-face key-lock mainstays in forming a periodic tetrahedral array of molecules

  13. Structures and synthesis of framework Rb and Cs uranyl arsenates and their relationships with their phosphate analogues

    NASA Astrophysics Data System (ADS)

    Locock, Andrew J.; Burns, Peter C.

    2003-11-01

    Two hydrated uranyl arsenates, Cs 2(UO 2)[(UO 2)(AsO 4)] 4(H 2O) 2 ( CsUAs) and Rb 2(UO 2)[(UO 2)(AsO 4)] 4(H 2O) 4.5 ( RbUAs), were synthesized by hydrothermal methods. Intensity data were collected at room temperature using Mo Kα radiation and a CCD-based area detector. The crystal structure of RbUAs was solved by direct methods, whereas the structure model of the phosphate Cs 2(UO 2)[(UO 2)(PO 4)] 4(H 2O) 2 was used for CsUAs; both were refined by full-matrix least-squares techniques on the basis of F2 to agreement indices ( CsUAs, RbUAs) w R2=0.061,0.041, for all data, and R1=0.032,0.021, calculated for 5098, 4991 unique observed reflections (| Fo|>4 σF), respectively. The compound CsUAs is orthorhombic, space group Cmc2 1, Z=4, a=15.157(2), b=14.079(2), c=13.439(2) Å, V=2867.9(1) Å 3. RbUAs is monoclinic, space group C2/ m, Z=4, a=13.4619(4), b=15.8463(5), c=14.0068(4) Å, β=92.311(1)°, V=2985.52(2) Å 3. The structures consist of sheets of arsenate tetrahedra and uranyl pentagonal bipyramids, with composition [(UO 2)(AsO 4)] -, that are topologically identical to the uranyl silicate sheets in uranophane-beta. These sheets are connected by a uranyl pentagonal bipyramid in the interlayer that shares corners with two arsenate tetrahedra on each of two adjacent sheets and whose fifth equatorial vertex is an H 2O group, resulting in an open framework with alkali metal cations in the larger cavities of the structures. CsUAs is isostructural with its phosphate analogue, and has two Cs atoms and a H 2O group in its structural cavities. RbUAs is not isostructural with its phosphate analogue, although it has a homeotypic framework. Its structural cavities are occupied by three Rb atoms and four H 2O groups; one Rb position and three of the interstitial H 2O groups are half-occupied. The partial occupancies of these positions probably result from the accommodation of the larger As atoms (relative to P) in the framework and resultant larger cavities.

  14. Aldose reductase mediates retinal microglia activation.

    PubMed

    Chang, Kun-Che; Shieh, Biehuoy; Petrash, J Mark

    2016-04-29

    Retinal microglia (RMG) are one of the major immune cells in charge of surveillance of inflammatory responses in the eye. In the absence of an inflammatory stimulus, RMG reside predominately in the ganglion layer and inner or outer plexiform layers. However, under stress RMG become activated and migrate into the inner nuclear layer (INL) or outer nuclear layer (ONL). Activated RMG in cell culture secrete pro-inflammatory cytokines in a manner sensitive to downregulation by aldose reductase inhibitors. In this study, we utilized CX3CR1(GFP) mice carrying AR mutant alleles to evaluate the role of AR on RMG activation and migration in vivo. When tested on an AR(WT) background, IP injection of LPS induced RMG activation and migration into the INL and ONL. However, this phenomenon was largely prevented by AR inhibitors or in AR null mice, or was exacerbated in transgenic mice that over-express AR. LPS-induced increases in ocular levels of TNF-α and CX3CL-1 in WT mice were substantially lower in AR null mice or were reduced by AR inhibitor treatment. These studies demonstrate that AR expression in RMG may contribute to the proinflammatory phenotypes common to various eye diseases such as uveitis and diabetic retinopathy. PMID:27033597

  15. Aldose reductase, oxidative stress, and diabetic mellitus.

    PubMed

    Tang, Wai Ho; Martin, Kathleen A; Hwa, John

    2012-01-01

    Diabetes mellitus (DM) is a complex metabolic disorder arising from lack of insulin production or insulin resistance (Diagnosis and classification of diabetes mellitus, 2007). DM is a leading cause of morbidity and mortality in the developed world, particularly from vascular complications such as atherothrombosis in the coronary vessels. Aldose reductase (AR; ALR2; EC 1.1.1.21), a key enzyme in the polyol pathway, catalyzes nicotinamide adenosine dinucleotide phosphate-dependent reduction of glucose to sorbitol, leading to excessive accumulation of intracellular reactive oxygen species (ROS) in various tissues of DM including the heart, vasculature, neurons, eyes, and kidneys. As an example, hyperglycemia through such polyol pathway induced oxidative stress, may have dual heart actions, on coronary blood vessel (atherothrombosis) and myocardium (heart failure) leading to severe morbidity and mortality (reviewed in Heather and Clarke, 2011). In cells cultured under high glucose conditions, many studies have demonstrated similar AR-dependent increases in ROS production, confirming AR as an important factor for the pathogenesis of many diabetic complications. Moreover, recent studies have shown that AR inhibitors may be able to prevent or delay the onset of cardiovascular complications such as ischemia/reperfusion injury, atherosclerosis, and atherothrombosis. In this review, we will focus on describing pivotal roles of AR in the pathogenesis of cardiovascular diseases as well as other diabetic complications, and the potential use of AR inhibitors as an emerging therapeutic strategy in preventing DM complications. PMID:22582044

  16. Aldose reductase inhibitory compounds from Xanthium strumarium.

    PubMed

    Yoon, Ha Na; Lee, Min Young; Kim, Jin-Kyu; Suh, Hong-Won; Lim, Soon Sung

    2013-09-01

    As part of our ongoing search for natural sources of therapeutic and preventive agents for diabetic complications, we evaluated the inhibitory effects of components of the fruit of Xanthium strumarium (X. strumarium) on aldose reductase (AR) and galactitol formation in rat lenses with high levels of glucose. To identify the bioactive components of X. strumarium, 7 caffeoylquinic acids and 3 phenolic compounds were isolated and their chemical structures were elucidated on the basis of spectroscopic evidence and comparison with published data. The abilities of 10 X. strumarium-derived components to counteract diabetic complications were investigated by means of inhibitory assays with rat lens AR (rAR) and recombinant human AR (rhAR). From the 10 isolated compounds, methyl-3,5-di-O-caffeoylquinate showed the most potent inhibition, with IC₅₀ values of 0.30 and 0.67 μM for rAR and rhAR, respectively. In the kinetic analyses using Lineweaver-Burk plots of 1/velocity and 1/substrate, methyl-3,5-di-O-caffeoylquinate showed competitive inhibition of rhAR. Furthermore, methyl-3,5-di-O-caffeoylquinate inhibited galactitol formation in the rat lens and in erythrocytes incubated with a high concentration of glucose, indicating that this compound may be effective in preventing diabetic complications. PMID:23604720

  17. Microdistribution of chromated copper arsenate preservative in rubberwood (Hevea brasiliensis Muell. Arg.)

    NASA Astrophysics Data System (ADS)

    Jusoh, Ismail Bin

    2000-08-01

    Rubberwood is popular for making indoor furniture since rubberwood is relatively abundant and sustainable. Currently more than 60% of the total annual rubberwood produced by rubber plantation is used as fuelwood. Rubberwood has the potential for both indoor and outdoor application. For exterior applications, preservative treatment is needed to extend the service life of rubberwood. The objectives of this study are to (1) assess treatability of rubberwood with chromated copper arsenate (CCA) preservative, (2) evaluate the natural decay resistance and efficacy of CCA on rubberwood, and (3) study the microdistribution of CCA components in rubberwood cells. The treatability of rubberwood was determined by measuring the penetration and retention of CCA type C preservative after a full-cell treatment. Natural decay resistance and efficacy of CCA treatment on rubberwood was estimated using a laboratory soilblock test according to AWPA E 10-91. The microdistribution of chromium, copper and arsenic in CCA-treated rubberwood was studied using scanning electron microscope in conjunction with energy dispersive X-ray analyzer (SEM-EDXA). As expected, longitudinal permeability was found to be better than the radial and the tangential permeability. The penetration and retention in the radial direction was about 3 times better than in the tangential direction. Longer pressure period increased penetration and retention of CCA type C in rubberwood. Complete penetration was achieved after 4 hours of pressure (1240 kPa) treatment. A pre-treatment steaming improved the treatability of rubberwood regardless of the anatomical direction. The average weight loss by white rot and brown rot was about 1.5 times higher than that of soft rot. A linear relationship was found between the weight loss and the incubation period for all the six test fungi. A CCA retention of 4.1 kg/m3 reduced weight loss to about 10% and retention of 14.5 kg/m3 reduced the weight loss of all test fungi at less than 2

  18. Effects of Dissolved Carbonate on Arsenate Adsorption and Surface Speciation at the Hematite-Water Interface

    USGS Publications Warehouse

    Arai, Y.; Sparks, D.L.; Davis, J.A.

    2004-01-01

    Effects of dissolved carbonate on arsenate [As(V)] reactivity and surface speciation at the hematite-water interface were studied as a function of pH and two different partial pressures of carbon dioxide gas [PCO2 = 10 -3.5 atm and ???0; CO2-free argon (Ar)] using adsorption kinetics, pseudo-equilibrium adsorption/titration experiments, extended X-ray absorption fine structure spectroscopic (EXAFS) analyses, and surface complexation modeling. Different adsorbed carbonate concentrations, due to the two different atmospheric systems, resulted in an enhanced and/or suppressed extent of As(V) adsorption. As(V) adsorption kinetics [4 g L -1, [As(V)]0 = 1.5 mM and / = 0.01 M NaCl] showed carbonate-enhanced As(V) uptake in the air-equilibrated systems at pH 4 and 6 and at pH 8 after 3 h of reaction. Suppressed As(V) adsorption was observed in the air-equilibrated system in the early stages of the reaction at pH 8. In the pseudo-equilibrium adsorption experiments [1 g L-1, [As(V)] 0 = 0.5 mM and / = 0.01 M NaCl], in which each pH value was held constant by a pH-stat apparatus, effects of dissolved carbonate on As(V) uptake were almost negligible at equilibrium, but titrant (0.1 M HCl) consumption was greater in the air-equilibrated systems (PCO2 = 10-3.5 atm)than in the CO2-free argon system at pH 4-7.75. The EXAFS analyses indicated that As(V) tetrahedral molecules were coordinated on iron octahedral via bidentate mononuclear (???2.8 A??) and bidentate binuclear (???3.3 A??) bonding at pH 4.5-8 and loading levels of 0.46-3.10 ??M m-2. Using the results of the pseudoequilibrium adsorption data and the XAS analyses, the pH-dependent As(V) adsorption under the PCO2 = 10-3.5 atm and the CO2-free argon system was modeled using surface complexation modeling, and the results are consistent with the formation of nonprotonated bidentate surface species at the hematite surfaces. The results also suggest that the acid titrant consumption was strongly affected by changes to

  19. Climate change and respiratory disease: European Respiratory Society position statement.

    PubMed

    Ayres, J G; Forsberg, B; Annesi-Maesano, I; Dey, R; Ebi, K L; Helms, P J; Medina-Ramón, M; Windt, M; Forastiere, F

    2009-08-01

    Climate change will affect individuals with pre-existing respiratory disease, but the extent of the effect remains unclear. The present position statement was developed on behalf of the European Respiratory Society in order to identify areas of concern arising from climate change for individuals with respiratory disease, healthcare workers in the respiratory sector and policy makers. The statement was developed following a 2-day workshop held in Leuven (Belgium) in March 2008. Key areas of concern for the respiratory community arising from climate change are discussed and recommendations made to address gaps in knowledge. The most important recommendation was the development of more accurate predictive models for predicting the impact of climate change on respiratory health. Respiratory healthcare workers also have an advocatory role in persuading governments and the European Union to maintain awareness and appropriate actions with respect to climate change, and these areas are also discussed in the position statement. PMID:19251790

  20. Conjugative plasmid in Corynebacterium flaccumfaciens subsp. oortii that confers resistance to arsenite, arsenate, and antimony(III)

    SciTech Connect

    Hendrick, C.A.; Haskins, W.P.; Vidaver, A.K.

    1984-07-01

    Gene transfer systems for phytopathogenic corynebacteria have not been reported previously. In this paper a conjugative 46-megadalton plasmid (pDG101) found in Corynebacterium flaccumfaciens subsp. oorii CO101 is described that mediates resistance to arsenite, arsenate, and antimony(III). Transfer of the plasmid from CO101 to four other strains from the C. flaccumfaciens group occurred between cells immobilized on nitrocellulose filters or on agar surfaces. Transconjugant strains expressed the same levels of metal resistance as the donor strain and were able to act as donor strains in subsequent matings. The physical presence of the plasmid was detected by agarose gel electrophoresis. Arsenite-sensitive derivatives of the donor and transconjugant strains were obtained after heat treatment; these were cured of pDG101.

  1. Copper, zinc, and arsenic in soil surrounding Douglas-fir poles treated with ammoniacal copper zinc arsenate (ACZA).

    PubMed

    Morrell, J J; Keefe, Donn; Baileys, Randall T

    2003-01-01

    The levels of copper, zinc, and arsenic in soil surrounding Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] utility poles treated with ammoniacal copper zinc arsenate (ACZA) were investigated at sites in Florida, Virginia, and New York. Copper levels were elevated near the poles and declined with both horizontal distance away from the pole and depth beneath the soil surface. Zinc levels were also elevated next to the poles, but the levels declined more slowly than did those of copper. Arsenic levels were elevated in soil immediately next to the poles but declined to near background levels farther away. The results indicate that metals can leach from ACZA-treated poles, but do not migrate far in the soil, and thus the levels decline sharply with distance from the poles. PMID:14674531

  2. Effect of post-treatment processing on copper migration from Douglas-fir lumber treated with ammoniacal copper zinc arsenate.

    PubMed

    Ye, Min; Morrell, Jeffrey J

    2015-04-01

    Migration of heavy metals into aquatic environments has become a concern in some regions of the world. Many wood preservatives are copper based systems that have the potential to migrate from the wood and into the surrounding environment. Some wood treaters have developed "best management practices" (BMPs) that are designed to reduce the risk of migration, but there are few comparative studies assessing the efficacy of these processes. The potential for using various heating combinations to limit copper migration was assessed using ammoniacal coper zinc arsenate treated Douglas-fir lumber. Kiln drying and air drying both proved to be the most effective methods for limiting copper migration, while post-treatment steaming or hot water immersion produced more variable results. The results should provide guidance for improving the BMP processes. PMID:25659940

  3. Differential effects of arsenite and arsenate to Drosophila melanogaster in a combined adult/developmental toxicity assay

    SciTech Connect

    Goldstein, S.H.; Babich, H.

    1989-02-01

    Current concern of the environmental consequences of chemical wastes in soils has led to the development of microbial, plant, and, to a lesser extent, animal bioassays for terrestrial ecosystems. This paper evaluated a Drosophila assay that yields data both on acute toxicity to adults and on developmental toxicity to offspring and which is applicable for screening extracts from soils contaminated with chemical wastes. Acute toxicity assays with Drosophila have been used to evaluate the relative potencies of chemicals. The acute toxicity to adults and the developmental exposure bioassays were designed to be performed as separate tests. This paper combined these two tests into a single bioassay, using arsenic compounds as the test agents. Arsenite and arsenate were selected to evaluate the sensitivity of this combined assay in distinguishing between the toxicities of closely related chemicals.

  4. Isolation and Characterization of cDNAs Encoding Leucoanthocyanidin Reductase and Anthocyanidin Reductase from Populus trichocarpa

    PubMed Central

    Lu, Wanxiang; Yang, Li; Karim, Abdul; Luo, Keming

    2013-01-01

    Proanthocyanidins (PAs) contribute to poplar defense mechanisms against biotic and abiotic stresses. Transcripts of PA biosynthetic genes accumulated rapidly in response to infection by the fungus Marssonina brunnea f.sp. multigermtubi, treatments of salicylic acid (SA) and wounding, resulting in PA accumulation in poplar leaves. Anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR) are two key enzymes of the PA biosynthesis that produce the main subunits: (+)-catechin and (−)-epicatechin required for formation of PA polymers. In Populus, ANR and LAR are encoded by at least two and three highly related genes, respectively. In this study, we isolated and functionally characterized genes PtrANR1 and PtrLAR1 from P. trichocarpa. Phylogenetic analysis shows that Populus ANR1 and LAR1 occurr in two distinct phylogenetic lineages, but both genes have little difference in their tissue distribution, preferentially expressed in roots. Overexpression of PtrANR1 in poplar resulted in a significant increase in PA levels but no impact on catechin levels. Antisense down-regulation of PtrANR1 showed reduced PA accumulation in transgenic lines, but increased levels of anthocyanin content. Ectopic expression of PtrLAR1 in poplar positively regulated the biosynthesis of PAs, whereas the accumulation of anthocyanin and flavonol was significantly reduced (P<0.05) in all transgenic plants compared to the control plants. These results suggest that both PtrANR1 and PtrLAR1 contribute to PA biosynthesis in Populus. PMID:23741362

  5. Equine 5α-reductase activity and expression in epididymis.

    PubMed

    Corbin, C J; Legacki, E L; Ball, B A; Scoggin, K E; Stanley, S D; Conley, A J

    2016-10-01

    The 5α-reductase enzymes play an important role during male sexual differentiation, and in pregnant females, especially equine species where maintenance relies on 5α-reduced progesterone, 5α-dihydroprogesterone (DHP). Epididymis expresses 5α-reductases but was not studied elaborately in horses. Epididymis from younger and older postpubertal stallions was divided into caput, corpus and cauda and examined for 5α-reductase activity and expression of type 1 and 2 isoforms by quantitative real-time polymerase chain reaction (qPCR). Metabolism of progesterone and testosterone to DHP and dihydrotestosterone (DHT), respectively, by epididymal microsomal protein was examined by thin-layer chromatography and verified by liquid chromatography tandem mass spectrometry (LC-MS/MS). Relative inhibitory potencies of finasteride and dutasteride toward equine 5α-reductase activity were investigated. Pregnenolone was investigated as an additional potential substrate for 5α-reductase, suggested previously from in vivo studies in mares but never directly examined. No regional gradient of 5α-reductase expression was observed by either enzyme activity or transcript analysis. Results of PCR experiments suggested that type 1 isoform predominates in equine epididymis. Primers for the type 2 isoform were unable to amplify product from any samples examined. Progesterone and testosterone were readily reduced to DHP and DHT, and activity was effectively inhibited by both inhibitors. Using epididymis as an enzyme source, no experimental evidence was obtained supporting the notion that pregnenolone could be directly metabolized by equine 5α-reductases as has been suggested by previous investigators speculating on alternative metabolic pathways leading to DHP synthesis in placenta during equine pregnancies. PMID:27466384

  6. Ferrate(VI)-induced arsenite and arsenate removal by in situ structural incorporation into magnetic iron(III) oxide nanoparticles.

    PubMed

    Prucek, Robert; Tuček, Jiří; Kolařík, Jan; Filip, Jan; Marušák, Zdeněk; Sharma, Virender K; Zbořil, Radek

    2013-04-01

    We report the first example of arsenite and arsenate removal from water by incorporation of arsenic into the structure of nanocrystalline iron(III) oxide. Specifically, we show the capability to trap arsenic into the crystal structure of γ-Fe2O3 nanoparticles that are in situ formed during treatment of arsenic-bearing water with ferrate(VI). In water, decomposition of potassium ferrate(VI) yields nanoparticles having core-shell nanoarchitecture with a γ-Fe2O3 core and a γ-FeOOH shell. High-resolution X-ray photoelectron spectroscopy and in-field (57)Fe Mössbauer spectroscopy give unambiguous evidence that a significant portion of arsenic is embedded in the tetrahedral sites of the γ-Fe2O3 spinel structure. Microscopic observations also demonstrate the principal effect of As doping on crystal growth as reflected by considerably reduced average particle size and narrower size distribution of the "in-situ" sample with the embedded arsenic compared to the "ex-situ" sample with arsenic exclusively sorbed on the iron oxide nanoparticle surface. Generally, presented results highlight ferrate(VI) as one of the most promising candidates for advanced technologies of arsenic treatment mainly due to its environmentally friendly character, in situ applicability for treatment of both arsenites and arsenates, and contrary to all known competitive technologies, firmly bound part of arsenic preventing its leaching back to the environment. Moreover, As-containing γ-Fe2O3 nanoparticles are strongly magnetic allowing their separation from the environment by application of an external magnet. PMID:23451768

  7. [Respiratory failure in disseminated sclerosis].

    PubMed

    Popova, L M; Avdiunina, I A; Alferova, V P

    2000-01-01

    The development and patterns of respiratory failure (RF) are analyzed in 9 patients with disseminated sclerosis (DS). Forced ventilation of the lungs was carried out with consideration for main location of the process. Relationship between patterns of respiratory disorders and neuroanatomy of respiratory regulation is discussed. Involvement of the corticospinal routes is paralleled by dissociation during functional pulmonary tests: spontaneous volumes are less than controlled inspirations. The most severe symptom complexes were observed in RF of predominantly bulbar localization: respiratory anarchy, blocking of airways caused by impaired swallowing, impaired mechanism of coughing reflex, loss of spontaneous respiration, sometimes apnea during sleeping. Involvement of the respiratory nuclei of medullary respiratory center and airways and of the corticonuclear routes of caudal cranial nerves causes the development of a triad of symptoms: glossopharyngolaryngeal paralysis, dysfunction of respiratory nuclei of medulla oblongata, and decreased sensitivity of respiratory center to CO2. Aspiration complications caused by dysphagia are characteristic of bulbar DS. Respiratory function in 5 patients without clinical picture of RF are specially discussed. The authors emphasize unfavorable prognostic significance of signs of extracorporeal obstruction indicating the probability of RF long before its manifestation. Special attention is paid to early diagnosis of symptoms of coming RF when evaluating the status of patients with DS during treatment. Timely use of respiratory resuscitation methods reduces the mortality and ensures a good chance for remissions with recovery of respiratory function, which are characteristic of RF. PMID:11014001

  8. DNA damage induction of ribonucleotide reductase.

    PubMed Central

    Elledge, S J; Davis, R W

    1989-01-01

    RNR2 encodes the small subunit of ribonucleotide reductase, the enzyme that catalyzes the first step in the pathway for the production of deoxyribonucleotides needed for DNA synthesis. RNR2 is a member of a group of genes whose activities are cell cycle regulated and that are transcriptionally induced in response to the stress of DNA damage. An RNR2-lacZ fusion was used to further characterize the regulation of RNR2 and the pathway responsible for its response to DNA damage. beta-Galactosidase activity in yeast strains containing the RNR2-lacZ fusion was inducible in response to DNA-damaging agents (UV light, 4-nitroquinoline-1-oxide [4-NQO], and methyl methanesulfonate [MMS]) and agents that block DNA replication (hydroxyurea [HU] and methotrexate) but not heat shock. When MATa cells were arrested in G1 by alpha-factor, RNR2 mRNA was still inducible by DNA damage, indicating that the observed induction can occur outside of S phase. In addition, RNR2 induction was not blocked by the presence of cycloheximide and is therefore likely to be independent of protein synthesis. A mutation, rnr2-314, was found to confer hypersensitivity to HU and increased sensitivity to MMS. In rnr2-314 mutant strains, the DNA damage stress response was found to be partially constitutive as well as hypersensitive to induction by HU but not MMS. The induction properties of RNR2 were examined in a rad4-2 mutant background; in this genetic background, RNR2 was hypersensitive to induction by 4-NQO but not MMS. Induction of the RNR2-lacZ fusion in a RAD(+) strain in response to 4-NQO was not enhanced by the presence of an equal number of rad4-2 cells that lacked the fusion, implying that the DNA damage stress response in cell autonomous. Images PMID:2513480

  9. Respiratory assessment in centronuclear myopathies

    PubMed Central

    Smith, Barbara K; Goddard, Melissa; Childers, Martin K.

    2014-01-01

    The centronuclear myopathies (CNMs) are a group of inherited neuromuscular disorders classified as congenital myopathies. While several causative genes have been identified, some patients do not harbor any of the currently known mutations. These diverse disorders have common histological features, which include a high proportion of centrally-nucleated muscle fibers, and clinical attributes of muscle weakness and respiratory insufficiency. Respiratory problems in CNMs may manifest initially during sleep, but daytime symptoms, ineffective airway clearance, and hypoventilation predominate as more severe respiratory muscle dysfunction evolves. Respiratory muscle capacity can be evaluated using a variety of clinical tests selected with consideration for the age and baseline motor function of the patient. Similar clinical tests of respiratory function can also be incorporated into preclinical CNM canine models to offer insight for clinical trials. Since respiratory problems account for significant morbidity in patients, routine assessments of respiratory muscle function are discussed. PMID:24668768

  10. Ocular Tropism of Respiratory Viruses

    PubMed Central

    Rota, Paul A.; Tumpey, Terrence M.

    2013-01-01

    SUMMARY Respiratory viruses (including adenovirus, influenza virus, respiratory syncytial virus, coronavirus, and rhinovirus) cause a broad spectrum of disease in humans, ranging from mild influenza-like symptoms to acute respiratory failure. While species D adenoviruses and subtype H7 influenza viruses are known to possess an ocular tropism, documented human ocular disease has been reported following infection with all principal respiratory viruses. In this review, we describe the anatomical proximity and cellular receptor distribution between ocular and respiratory tissues. All major respiratory viruses and their association with human ocular disease are discussed. Research utilizing in vitro and in vivo models to study the ability of respiratory viruses to use the eye as a portal of entry as well as a primary site of virus replication is highlighted. Identification of shared receptor-binding preferences, host responses, and laboratory modeling protocols among these viruses provides a needed bridge between clinical and laboratory studies of virus tropism. PMID:23471620

  11. Respiratory viruses and children.

    PubMed

    Heikkinen, Terho

    2016-07-01

    Respiratory viruses place a great disease burden especially on the youngest children in terms of high rates of infection, bacterial complications and hospitalizations. In developing countries, some viral infections are even associated with substantial mortality in children. The interaction between viruses and bacteria is probably much more common and clinically significant than previously understood. Respiratory viruses frequently initiate the cascade of events that ultimately leads to bacterial infection. Effective antiviral agents can substantially shorten the duration of the viral illness and prevent the development of bacterial complications. Viral vaccines have the potential to not only prevent the viral infection but also decrease the incidence of bacterial complications. At present, antivirals and vaccines are only available against influenza viruses, but new vaccines and antivirals against other viruses, especially for RSV, are being developed. PMID:27177731

  12. Respiratory fluid mechanics

    NASA Astrophysics Data System (ADS)

    Grotberg, James B.

    2011-02-01

    This article covers several aspects of respiratory fluid mechanics that have been actively investigated by our group over the years. For the most part, the topics involve two-phase flows in the respiratory system with applications to normal and diseased lungs, as well as therapeutic interventions. Specifically, the topics include liquid plug flow in airways and at airway bifurcations as it relates to surfactant, drug, gene, or stem cell delivery into the lung; liquid plug rupture and its damaging effects on underlying airway epithelial cells as well as a source of crackling sounds in the lung; airway closure from "capillary-elastic instabilities," as well as nonlinear stabilization from oscillatory core flow which we call the "oscillating butter knife;" liquid film, and surfactant dynamics in an oscillating alveolus and the steady streaming, and surfactant spreading on thin viscous films including our discovery of the Grotberg-Borgas-Gaver shock.

  13. Electrode assemblies composed of redox cascades from microbial respiratory electron transfer chains

    SciTech Connect

    Gates, Andrew J.; Marritt, Sophie; Bradley, Justin; Shi, Liang; McMillan, Duncan G.; Jeuken, Lars J.; Richardson, David; Butt, Julea N.

    2013-10-01

    Respiratory and photosynthetic electron transfer chains are dependent on vectorial electron transfer through a series of redox proteins. Examples include electron transfer from NapC to NapAB nitrate reductase in Paracoccus denitrificans and from CymA to Fcc3 (flavocytochrome c3) fumarate reductase in Shewanella oneidensis MR-1. In the present article, we demonstrate that graphite electrodes can serve as surfaces for the stepwise adsorption of NapC and NapAB, and the stepwise adsorption of CymA and Fcc3. Aspects of the catalytic properties of these assemblies are different from those of NapAB and Fcc3 adsorbed in isolation. We propose that this is due to the formation of NapC-NapAB and of CymA-Fcc3 complexes that are capable of supporting vectorial electron transfer.

  14. Middle East Respiratory Syndrome

    PubMed Central

    Zumla, Alimuddin; Hui, David S; Perlman, Stanley

    2016-01-01

    SUMMARY The Middle East Respiratory Syndrome (MERS) is a newly recognized highly lethal respiratory disease caused by a novel single stranded, positive sense RNA betacoronavirus (MERS-CoV). Dromedary camels, host species for MERS-CoV are implicated in the direct or indirect transmission to humans, although the exact mode of transmission remains unknown. First isolated from a patient who died from a severe respiratory illness in June 2012 in Jeddah, Saudi Arabia, as of 16 February 2015, 983 laboratory-confirmed cases of MERS-CoV (360 deaths; 36.6% mortality) were reported to the WHO. Cases have been acquired in both the community and hospitals with limited human-to-human transmission reported in the community. Whilst the majority of MERS cases have occurred in Saudi Arabia and the United Arab Emirates, cases have been reported from Europe, USA and Asia in people who traveled from the Middle East or their contacts. Clinical features of MERS range from asymptomatic or mild disease to acute respiratory distress syndrome and multi-organ failure resulting in death, especially in individuals with underlying co-morbidities. There is no specific drug treatment for MERS and infection prevention and control measures are crucial to prevent spread of MERS-CoV in health care facilities. MERS-CoV continues to be an endemic,low level public health threat. However, the concern remains that the virus could mutate to exhibit increased interhuman transmissibility, increasing pandemic potential. Our seminar presents an overview of current knowledge and perspectives on the epidemiology, virology, mode of transmission, pathogen-host responses, clinical features, diagnosis and development of new drugs and vaccines. PMID:26049252

  15. Nanotechnology in respiratory medicine.

    PubMed

    Omlor, Albert Joachim; Nguyen, Juliane; Bals, Robert; Dinh, Quoc Thai

    2015-01-01

    Like two sides of the same coin, nanotechnology can be both boon and bane for respiratory medicine. Nanomaterials open new ways in diagnostics and treatment of lung diseases. Nanoparticle based drug delivery systems can help against diseases such as lung cancer, tuberculosis, and pulmonary fibrosis. Moreover, nanoparticles can be loaded with DNA and act as vectors for gene therapy in diseases like cystic fibrosis. Even lung diagnostics with computer tomography (CT) or magnetic resonance imaging (MRI) profits from new nanoparticle based contrast agents. However, the risks of nanotechnology also have to be taken into consideration as engineered nanomaterials resemble natural fine dusts and fibers, which are known to be harmful for the respiratory system in many cases. Recent studies have shown that nanoparticles in the respiratory tract can influence the immune system, can create oxidative stress and even cause genotoxicity. Another important aspect to assess the safety of nanotechnology based products is the absorption of nanoparticles. It was demonstrated that the amount of pulmonary nanoparticle uptake not only depends on physical and chemical nanoparticle characteristics but also on the health status of the organism. The huge diversity in nanotechnology could revolutionize medicine but makes safety assessment a challenging task. PMID:26021823

  16. Which preoperative respiratory evaluation?

    PubMed

    Zraier, S; Haouache, H; Dhonneur, G

    2014-01-01

    The preoperative respiratory evaluation aims at predicting the occurrence of postoperative respiratory complications (PORC), such as: atelectasis, pulmonary infection (bronchitis and pneumonia), acute ventilatory distress, pleural effusion, prolonged mechanical ventilation, exacerbation of chronic respiratory disease and bronchospasm. The incidence of (PORC) all surgeries combined is 6.8%. Individual surgical and anesthetic factors are impacting on the occurrence of PORC. Simple scores, including anamnestic data, clinical examination and some biological parameters were validated to assess the risk of PORC depending on the type of surgery. Data from standard pulmonary function tests (PFT) is of little use to estimate the individual risk of PORC. Most of the time, PFT abnormal parameters only confirm the clinical assessment of the severity of the illness. PFT may however be useful to confirm an improvement in the clinical condition of the patient related to the preoperative preparation. Specialized EFR, including standardized testing efforts are sometimes required in the case of lung reduction surgery. These specialized explorations can predict lung function and post-interventional pulmonary oxygenation and ensure that these are viable. PMID:25168302

  17. [Respiratory preparation before surgery in patients with chronic respiratory failure].

    PubMed

    Delay, Jean-Marc; Jaber, Samir

    2012-03-01

    Scheduled and/or thoracic, abdominal surgeries increase the risk of respiratory postoperative complications. In patients with chronic respiratory failure, preoperative evaluation should be performed to evaluate respiratory function in aim to optimize perioperative management. Preoperative gas exchange abnormalities (hypoxemia or hypercapnia) are associated with respiratory postoperative complications. Respiratory physiotherapy and prophylactic non-invasive ventilation should be integrated in a global rehabilitation management for cardiothoracic or abdominal surgery procedures, which are at high risk of postoperative respiratory dysfunction. Stopping tobacco consummation should be benefit, but decease risk of postoperative complications is relevant only after a period for 6 to 8 weeks of cessation. Bronchodilatator aerosol therapy (beta-agonists and atropinics) and inhaled corticotherapy allow a rapid preparation for 24 to 48 h. Systematic preoperative antibiotherapy should not be recommended. PMID:22004791

  18. Chemical-specific health consultation for chromated copper arsenate chemical mixture: port of Djibouti.

    PubMed

    Chou, Selene; Colman, Joan; Tylenda, Carolyn; De Rosa, Christopher

    2007-05-01

    The Agency for Toxic Substances and Disease Registry (ATSDR) prepared this health consultation to provide support for assessing the public health implications of hazardous chemical exposure, primarily through drinking water, related to releases of chromated copper arsenate (CCA) in the port of Djibouti. CCA from a shipment, apparently intended for treating electric poles, is leaking into the soil in the port area. CCA is a pesticide used to protect wood against decay-causing organisms. This mixture commonly contains chromium(VI) (hexavalent chromium) as chromic acid, arsenic(V) (pentavalent arsenic) as arsenic pentoxide and copper (II) (divalent copper) as cupric oxide, often in an aqueous solution or concentrate. Experimental studies of the fate of CCA in soil and monitoring studies of wood-preserving sites where CCA was spilled on the soil indicate that the chromium(VI), arsenic and copper components of CCA can leach from soil into groundwater and surface water. In addition, at CCA wood-preserving sites, substantial concentrations of chromium(VI), arsenic and copper remained in the soil and were leachable into water four years after the use of CCA was discontinued, suggesting prolonged persistence in soil, with continued potential for leaching. The degree of leaching depended on soil composition and the extent of soil contamination with CCA. In general, leaching was highest for chromium(VI), intermediate for arsenic and lowest for copper. Thus, the potential for contamination of sources of drinking water exists. Although arsenic that is leached from CCA-contaminated soil into surface water may accumulate in the tissues of fish and shellfish, most of the arsenic in these animals will be in a form (often called fish arsenic) that is less harmful. Copper, which leaches less readily than the other components, can accumulate in tissues of mussels and oysters. Chromium is not likely to accumulate in the tissues of fish and shellfish. Limited studies of air

  19. Sulfur Isotope Effects of Dissimilatory Sulfite Reductase

    PubMed Central

    Leavitt, William D.; Bradley, Alexander S.; Santos, André A.; Pereira, Inês A. C.; Johnston, David T.

    2015-01-01

    The precise interpretation of environmental sulfur isotope records requires a quantitative understanding of the biochemical controls on sulfur isotope fractionation by the principle isotope-fractionating process within the S cycle, microbial sulfate reduction (MSR). Here we provide the only direct observation of the major (34S/32S) and minor (33S/32S, 36S/32S) sulfur isotope fractionations imparted by a central enzyme in the energy metabolism of sulfate reducers, dissimilatory sulfite reductase (DsrAB). Results from in vitro sulfite reduction experiments allow us to calculate the in vitro DsrAB isotope effect in 34S/32S (hereafter, 34εDsrAB) to be 15.3 ± 2‰, 2σ. The accompanying minor isotope effect in 33S, described as 33λDsrAB, is calculated to be 0.5150 ± 0.0012, 2σ. These observations facilitate a rigorous evaluation of the isotopic fractionation associated with the dissimilatory MSR pathway, as well as of the environmental variables that govern the overall magnitude of fractionation by natural communities of sulfate reducers. The isotope effect induced by DsrAB upon sulfite reduction is a factor of 0.3–0.6 times prior indirect estimates, which have ranged from 25 to 53‰ in 34εDsrAB. The minor isotope fractionation observed from DsrAB is consistent with a kinetic or equilibrium effect. Our in vitro constraints on the magnitude of 34εDsrAB is similar to the median value of experimental observations compiled from all known published work, where 34εr−p = 16.1‰ (r–p indicates reactant vs. product, n = 648). This value closely matches those of MSR operating at high sulfate reduction rates in both laboratory chemostat experiments (34εSO4−H2S =  17.3 ± 1.5‰, 2σ) and in modern marine sediments (34εSO4−H2S =  17.3 ± 3.8‰). Targeting the direct isotopic consequences of a specific enzymatic processes is a fundamental step toward a biochemical foundation for reinterpreting the biogeochemical and geobiological sulfur isotope records in

  20. Sulfur Isotope Effects of Dissimilatory Sulfite Reductase.

    PubMed

    Leavitt, William D; Bradley, Alexander S; Santos, André A; Pereira, Inês A C; Johnston, David T

    2015-01-01

    The precise interpretation of environmental sulfur isotope records requires a quantitative understanding of the biochemical controls on sulfur isotope fractionation by the principle isotope-fractionating process within the S cycle, microbial sulfate reduction (MSR). Here we provide the only direct observation of the major ((34)S/(32)S) and minor ((33)S/(32)S, (36)S/(32)S) sulfur isotope fractionations imparted by a central enzyme in the energy metabolism of sulfate reducers, dissimilatory sulfite reductase (DsrAB). Results from in vitro sulfite reduction experiments allow us to calculate the in vitro DsrAB isotope effect in (34)S/(32)S (hereafter, [Formula: see text]) to be 15.3 ± 2‰, 2σ. The accompanying minor isotope effect in (33)S, described as [Formula: see text], is calculated to be 0.5150 ± 0.0012, 2σ. These observations facilitate a rigorous evaluation of the isotopic fractionation associated with the dissimilatory MSR pathway, as well as of the environmental variables that govern the overall magnitude of fractionation by natural communities of sulfate reducers. The isotope effect induced by DsrAB upon sulfite reduction is a factor of 0.3-0.6 times prior indirect estimates, which have ranged from 25 to 53‰ in (34)εDsrAB. The minor isotope fractionation observed from DsrAB is consistent with a kinetic or equilibrium effect. Our in vitro constraints on the magnitude of [Formula: see text] is similar to the median value of experimental observations compiled from all known published work, where (34)ε r-p = 16.1‰ (r-p indicates reactant vs. product, n = 648). This value closely matches those of MSR operating at high sulfate reduction rates in both laboratory chemostat experiments ([Formula: see text] 17.3 ± 1.5‰, 2σ) and in modern marine sediments ([Formula: see text] 17.3 ± 3.8‰). Targeting the direct isotopic consequences of a specific enzymatic processes is a fundamental step toward a biochemical foundation for reinterpreting the

  1. The inhibitory activity of aldose reductase in vitro by constituents of Garcinia mangostana Linn.

    PubMed

    Fatmawati, Sri; Ersam, Taslim; Shimizu, Kuniyoshi

    2015-01-15

    We investigated aldose reductase inhibition of Garcinia mangostana Linn. from Indonesia. Dichloromethane extract of the root bark of this tree was found to demonstrate an IC50 value of 11.98 µg/ml for human aldose reductase in vitro. From the dichloromethane fraction, prenylated xanthones were isolated as potent human aldose reductase inhibitors. We discovered 3-isomangostin to be most potent against aldose reductase, with an IC50 of 3.48 µM. PMID:25636870

  2. K[AsW2O9], the first member of the arsenate-tungsten bronze family: Synthesis, structure, spectroscopic and non-linear optical properties

    NASA Astrophysics Data System (ADS)

    Alekseev, Evgeny V.; Felbinger, Olivier; Wu, Shijun; Malcherek, Thomas; Depmeier, Wulf; Modolo, Giuseppe; Gesing, Thorsten M.; Krivovichev, Sergey V.; Suleimanov, Evgeny V.; Gavrilova, Tatiana A.; Pokrovsky, Lev D.; Pugachev, Alexey M.; Surovtsev, Nikolay V.; Atuchin, Victor V.

    2013-08-01

    K[AsW2O9], prepared by high-temperature solid-state reaction, is the first member of the arsenate-tungsten bronze family. The structure of K[AsW2O9] is based on a 3-dimensional (3D) oxotungstate-arsenate framework with the non-centrosymmetric P212121 space group, a=4.9747(3) Å, b=9.1780(8) Å, c=16.681(2) Å. The material was characterized using X-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Raman and infrared (IR) spectroscopic techniques. The results of DSC demonstrate that this phase is stable up to 1076 K. Second harmonic generation (SHG) measurements performed on a powder sample demonstrate noticeable (0.1 of LiIO3) non-linear optical (NLO) activity.

  3. Is the effect of silicon on rice uptake of arsenate (AsV) related to internal silicon concentrations, iron plaque and phosphate nutrition?

    PubMed

    Guo, W; Zhu, Y-G; Liu, W-J; Liang, Y-C; Geng, C-N; Wang, S-G

    2007-07-01

    Solution culture experiments were conducted to investigate the effects of silicon (Si) on arsenate (As(V)) uptake by rice. The addition of Si to the pretreatment or uptake solution significantly decreased shoot and root As concentrations (P<0.001 and P<0.05). The presence of Si in the pretreatment or uptake solution also significantly decreased shoot P concentrations (P<0.001). The data demonstrated that both internal and external Si inhibited the uptake of As and P. Results of As uptake kinetics showed that the mechanism of the effect of Si on arsenate uptake is not caused by direct competition for active sites of transporters with As. The effect of Si on As uptake was not entirely mediated through the effect of Si on P uptake. Although the addition of Si to pretreatment solutions still significantly decreased shoot and root As concentrations, the extent of reduction became smaller when rice roots were coated with iron plaque. PMID:17175078

  4. Stability of arsenate-bearing Fe(III)/Al(III) co-precipitates in the presence of sulfide as reducing agent under anoxic conditions.

    PubMed

    Doerfelt, Christoph; Feldmann, Thomas; Roy, Ranjan; Demopoulos, George P

    2016-05-01

    Currently, the co-precipitation of arsenate with ferric iron at molar ratios Fe(III)/As(V) ≥ 3 by lime neutralization produces tailings solids that are stable under oxic conditions. However not much is known about the stability of these hazardous co-precipitates under anoxic conditions. These can develop in tailings storage sites by the action of co-discharged reactive sulfides, organic reagent residuals or bacterial activity. The ferric matrix can then undergo reductive dissolution reactions, which could release arsenic into the pore water. Co-ions like aluminum could provide a redox-immune sink to scavenge any mobilized arsenic as a result of reduction of ferric. As such, in this work Fe(III)/As(V) = 4 and aluminum substituted Fe(III)/Al(III)/As(V) = 2/2/1 co-precipitates were produced in a mini continuous co-precipitation process circuit and subjected to excess sulfide addition under inert gas to evaluate their stability. It was found that the ferric-arsenate co-precipitate could retain up to 99% (30 mg/L in solution) of its arsenic content despite the high pH (10.5) and extremely reducing (Eh < -200 mV) environment. There was no significant reduction of arsenate and only 45% of ferric iron was reduced. Partial aluminum substitution was found to cut the amount of mobilized arsenic by 50% (down to 15 mg/L) hence mixed Fe(III)/Al(III)-arsenate co-precipitates may offer better resistance to reductive destabilization over the long term than all iron co-precipitates. PMID:26950022

  5. SORPTION OF ARSENATE AND ARSENITE ON RUO2 X H2O: ANALYSIS OF SORBED PHASE OXIDATION STATE BY XANES IN ADVANCED PHOTON SOURCE ACTIVITY REPORT 2002

    EPA Science Inventory

    The sorption reactions of arsenate (As(V)) and arsenite (As(III)) on RuO2 x H2O were examined by X-ray Absorption Near Edge Spectroscopy (XANES) to elucidate the solid state speciation of sorbed As. At all pH values studied (pH 4-8), RuO2 x H

  6. Prediction of the thermodynamic properties of metal-arsenate and metal-arsenite aqueous complexes to high temperatures and pressures and some geological consequences

    NASA Astrophysics Data System (ADS)

    Marini, Luigi; Accornero, Marina

    2007-07-01

    The standard thermodynamic properties at 25°C, 1 bar (Δ G {f/o}, Δ H {f/o}, S o, C {P/o}, V o, ω) and the coefficients of the revised Helgeson-Kirkham-Flowers equations of state were evaluated for several aqueous complexes formed by dissolved metals and either arsenate or arsenite ions. The guidelines of Shock and Helgeson (Geochim Cosmochim Acta 52:2009-2036, 1988) and Sverjensky et al. (Geochim Cosmochim Acta 61:1359-1412, 1997) were followed and corroborated with alternative approaches, whenever possible. The SUPCRT92 computer code was used to generate the log K of the destruction reactions of these metal-arsenate and metal-arsenite aqueous complexes at pressures and temperatures required by the EQ3/6 software package, version 7.2b. Apart from the AlAsO{4/o} and FeAsO{4/o} complexes, our log K at 25°C, 1 bar are in fair agreement with those of Whiting (MS Thesis, Colorado School of Mines, Golden, CO, 1992). Moreover, the equilibrium constants evaluated in this study are in good to fair agreement with those determined experimentally for the Ca-dihydroarsenate and Ca-hydroarsenate complexes at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) and for Fe(III)-hydroarsenate complex at 25°C (Raposo et al., J Sol Chem 35:79-94, 2006), whereas the disagreement with the log K measured for the Ca-arsenate complex at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) might be due to uncertainties in this measured value. The implications of aqueous complexing between dissolved metals and arsenate/arsenite ions were investigated for seawater, high-temperature geothermal liquids and acid mine drainage and aqueous solutions deriving from mixing of acid mine waters and surface waters.

  7. Respiratory System Disease.

    PubMed

    Goetz, Danielle M; Singh, Shipra

    2016-08-01

    Respiratory system involvement in cystic fibrosis is the leading cause of morbidity and mortality. Defects in the cystic fibrosis transmembrane regulator (CFTR) gene throughout the sinopulmonary tract result in recurrent infections with a variety of organisms including Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and nontuberculous mycobacteria. Lung disease occurs earlier in life than once thought and ideal methods of monitoring lung function, decline, or improvement with therapy are debated. Treatment of sinopulmonary disease may include physiotherapy, mucus-modifying and antiinflammatory agents, antimicrobials, and surgery. In the new era of personalized medicine, CFTR correctors and potentiators may change the course of disease. PMID:27469180

  8. Recurrent respiratory papillomatosis.

    PubMed

    Venkatesan, Naren N; Pine, Harold S; Underbrink, Michael P

    2012-06-01

    Recurrent respiratory papillomatosis (RRP) is a rare, benign disease with no known cure. RRP is caused by infection of the upper aerodigestive tract with the human papillomavirus (HPV). Passage through the birth canal is thought to be the initial transmission event, but infection may occur in utero. HPV vaccines have helped to provide protection from cervical cancer; however, their role in the prevention of RRP is undetermined. Clinical presentation of initial symptoms of RRP may be subtle. RRP course varies, and current management focuses on surgical debulking of papillomatous lesions with or without concurrent adjuvant therapy. PMID:22588043

  9. Compensatory periplasmic nitrate reductase activity supports anaerobic growth of Pseudomonas aeruginosa PAO1 in the absence of membrane nitrate reductase.

    PubMed

    Van Alst, Nadine E; Sherrill, Lani A; Iglewski, Barbara H; Haidaris, Constantine G

    2009-10-01

    Nitrate serves as a terminal electron acceptor under anaerobic conditions in Pseudomonas aeruginosa. Reduction of nitrate to nitrite generates a transmembrane proton motive force allowing ATP synthesis and anaerobic growth. The inner membrane-bound nitrate reductase NarGHI is encoded within the narK1K2GHJI operon, and the periplasmic nitrate reductase NapAB is encoded within the napEFDABC operon. The roles of the 2 dissimilatory nitrate reductases in anaerobic growth, and the regulation of their expressions, were examined by use of a set of deletion mutants in P. aeruginosa PAO1. NarGHI mutants were unable to grow anaerobically, but plate cultures remained viable up to 120 h. In contrast, the nitrate sensor-response regulator mutant DeltanarXL displayed growth arrest initially, but resumed growth after 72 h and reached the early stationary phase in liquid culture after 120 h. Genetic, transcriptional, and biochemical studies demonstrated that anaerobic growth recovery by the NarXL mutant was the result of NapAB periplasmic nitrate reductase expression. A novel transcriptional start site for napEFDABC expression was identified in the NarXL mutant grown anaerobically. Furthermore, mutagenesis of a consensus NarL-binding site monomer upstream of the novel transcriptional start site restored anaerobic growth recovery in the NarXL mutant. The data suggest that during anaerobic growth of wild-type P. aeruginosa PAO1, the nitrate response regulator NarL directly represses expression of periplasmic nitrate reductase, while inducing maximal expression of membrane nitrate reductase. PMID:19935885

  10. Acute Respiratory Infections in Children

    PubMed Central

    Laxdal, O. E.; Evans, G. E.; Braaten, V.; Robertson, H. E.

    1964-01-01

    A new polyvalent respiratory virus vaccine has been evaluated in a double-blind trial involving infants and children. Five hundred and sixteen healthy infants and children were given either nine-strain polyvalent respiratory virus vaccine or placebo. The vaccine contained four Influenza strains, three Adenovirus strains and two Parainfluenza strains. Serologic studies revealed that persistent protective antibody levels were achieved with only the Asian Influenza component. The children were followed up clinically for a one-year period and each respiratory illness was recorded. No protection appeared to have been conferred by the vaccine, and indeed a significantly greater number of respiratory illnesses occurred among the vaccinated group. PMID:14105010

  11. Management of Postoperative Respiratory Failure.

    PubMed

    Mulligan, Michael S; Berfield, Kathleen S; Abbaszadeh, Ryan V

    2015-11-01

    Despite best efforts, postoperative complications such as postoperative respiratory failure may occur and prompt recognition of the process and management is required. Postoperative respiratory failure, such as postoperative pneumonia, postpneumonectomy pulmonary edema, acute respiratory distress-like syndromes, and pulmonary embolism, are associated with high morbidity and mortality. The causes of these complications are multifactorial and depend on preoperative, intraoperative, and postoperative factors, some of which are modifiable. The article identifies some of the risk factors, causes, and treatment strategies for successful management of the patient with postoperative respiratory failure. PMID:26515943

  12. Role of Directed van der Waals Bonded Interactions in the Determination of the Structures of Molecular Arsenate Solids

    SciTech Connect

    Gibbs, Gerald V.; Wallace, Adam F.; Cox, David F.; Dove, Patricia M; Downs, R. T.; Ross, Nancy L.; Rosso, Kevin M.

    2009-01-05

    Bond paths, local energy density properties, and Laplacian, L(r) = -2ρ(r), composite isosurfaces of the electron density distributions were calculated for the intramolecular and intermolecular bonded interactions for molecular solids of As2O3 and AsO2 composition, an As2O5 crystal, a number of arsenate molecules, and the arsenic metalloid, arsenolamprite. The directed intermolecular van der Waals As-O, O-O, and As-As bonded interactions are believed to serve as mainstays between the individual molecules in each of the molecular solids. As-O bond paths between the bonded atoms connect Lewis base charge concentrations and Lewis acid charge depletion domains, whereas the O-O and As-As paths connect Lewis base pair and Lewis acid pair domains, respectively, giving rise to sets of intermolecular directed bond paths. The alignment of the directed bond paths results in the periodic structures adopted by the arsenates. The arrangements of the As atoms in the claudetite polymorphs of As2O3 and the As atoms in arsenolamprite are similar. Like the As2O3 polymorphs, arsenolamprite is a molecular solid connected by relatively weak As-As intermolecular directed van der Waals bond paths between the layers of stronger As-As intramolecular bonded interactions. The bond critical point and local energy density properties of the intermolecular As-As bonded interactions in arsenolamprite are comparable with the As-As interactions in claudetite I. As such, the structure of claudetite I can be viewed as a stuffed derivative of the arsenolamprite structure with O atoms between pairs of As atoms comprising the layers of the structure. The cubic structure adopted by the arsenolite polymorph can be understood in terms of sets of directed acid-base As-O and base-base O-O pair domains and bond paths that radiate from the tetrahedral faces of its constituent molecules, serving as face-to-face key

  13. The 2-Cys Peroxiredoxin Alkyl Hydroperoxide Reductase C Binds Heme and Participates in Its Intracellular Availability in Streptococcus agalactiae*

    PubMed Central

    Lechardeur, Delphine; Fernandez, Annabelle; Robert, Bruno; Gaudu, Philippe; Trieu-Cuot, Patrick; Lamberet, Gilles; Gruss, Alexandra

    2010-01-01

    Heme is a redox-reactive molecule with vital and complex roles in bacterial metabolism, survival, and virulence. However, few intracellular heme partners were identified to date and are not well conserved in bacteria. The opportunistic pathogen Streptococcus agalactiae (group B Streptococcus) is a heme auxotroph, which acquires exogenous heme to activate an aerobic respiratory chain. We identified the alkyl hydroperoxide reductase AhpC, a member of the highly conserved thiol-dependent 2-Cys peroxiredoxins, as a heme-binding protein. AhpC binds hemin with a Kd of 0.5 μm and a 1:1 stoichiometry. Mutagenesis of cysteines revealed that hemin binding is dissociable from catalytic activity and multimerization. AhpC reductase activity was unchanged upon interaction with heme in vitro and in vivo. A group B Streptococcus ahpC mutant displayed attenuation of two heme-dependent functions, respiration and activity of a heterologous catalase, suggesting a role for AhpC in heme intracellular fate. In support of this hypothesis, AhpC-bound hemin was protected from chemical degradation in vitro. Our results reveal for the first time a role for AhpC as a heme-binding protein. PMID:20332091

  14. Role of indigenous arsenate and iron(III) respiring microorganisms in controlling the mobilization of arsenic in a contaminated soil sample.

    PubMed

    Vaxevanidou, K; Christou, C; Kremmydas, G F; Georgakopoulos, D G; Papassiopi, N

    2015-03-01

    In this study two different treatment options were investigated for the release of arsenic from a contaminated soil sample. The first option was based on the "bioaugmentation" principle and involved addition of a pure Fe(III)-reducing culture, i.e. Desulfuromonas palmitatis. The second option consisted in the "biostimulation" of indigenous bacteria and involved simple addition of nutrients. Due to the strong association of As with soil ferric oxides, the reductive dissolution of soil oxides by D. palmitatis lead to 45 % arsenic release in solution (2.15 mM). When only nutrients were supplied to the soil, the same amounts of Fe and As were dissolved with slower rates and most aqueous As was found to be in the trivalent state, indicating the presence of arsenate reducing species. The arsenate reducing microorganisms were enriched with successive cultures, using Na2HAsO4 as electron acceptor. The phylogenetic analysis revealed that the enriched microbial consortium contained Desulfosporosinus species, which are known arsenate reducers. PMID:25588567

  15. Ultrasonic assisted arsenate adsorption on solvothermally synthesized calcite modified by goethite, α-MnO2 and goethite/α-MnO2.

    PubMed

    Markovski, Jasmina S; Đokić, Veljko; Milosavljević, Milutin; Mitrić, Miodrag; Perić-Grujić, Aleksandra A; Onjia, Antonije E; Marinković, Aleksandar D

    2014-03-01

    A highly porous calcium carbonate (calcite; sorbent 1) was used as a support for modification with α-FeOOH (calcite/goethite; sorbent 2), α-MnO2 (calcite/α-MnO2; sorbent 3) and α-FeOOH/α-MnO2 (calcite/goethite/α-MnO2; sorbent 4) in order to obtain a cheap hybrid materials for simple and effective arsenate removal from aqueous solutions. The adsorption ability of synthesized adsorbents was studied as a function of functionalization methods, pH, contact time, temperature and ultrasonic treatment. Comparison of the adsorptive effectiveness of synthesized adsorbents for arsenate removal, under ultrasound treatment and classical stirring method, has shown better performance of the former one reaching maximum adsorption capacities of 1.73, 21.00, 10.36 and 41.94 mg g(-1), for sorbents 1-4, respectively. Visual MINTEQ equilibrium speciation modeling was used for prediction of pH and interfering ion influences on arsenate adsorption. PMID:24210695

  16. [Asbestos and respiratory diseases].

    PubMed

    Scherpereel, Arnaud

    2016-01-01

    Previous occupational asbestos exposure (more rarely environmental or domestic exposure) may induce various pleural and/or pulmonary, benign or malignant diseases, sometimes with a very long latency for malignant mesothelioma (MM). Asbestos has been widely extracted and used in Western countries and in emerging or developing countries, resulting in a peak of MM incidence in France around 2020 and likely in a world pandemic of asbestos-induced diseases. These patients have mostly benign respiratory diseases (pleural plugs) but may also be diagnosed with lung cancer or malignant pleural mesothelioma, and have a global poor outcome. New therapeutic tools (targeted therapies, immunotherapy…) with first promising results are developed. However, it is crucial to obtain a full ban of asbestos use worldwide, and to do a regular follow-up of asbestos-exposed subjects, mostly if they are already diagnosed with benign respiratory diseases. Finally, new cancers (larynx and ovary) were recently added to the list of asbestos-induced tumors. PMID:26822071

  17. Total X-ray scattering, EXAFS, and Mössbauer spectroscopy analyses of amorphous ferric arsenate and amorphous ferric phosphate

    NASA Astrophysics Data System (ADS)

    Mikutta, Christian; Schröder, Christian; Marc Michel, F.

    2014-09-01

    Amorphous ferric arsenate (AFA, FeAsO4·xH2O) is an important As precipitate in a range of oxic As-rich environments, especially acidic sulfide-bearing mine wastes. Its structure has been proposed to consist of small polymers of single corner-sharing FeO6 octahedra (rFe-Fe ∼3.6 Å) to which arsenate is attached as a monodentate binuclear 2C complex (‘chain model’). Here, we analyzed the structure of AFA and analogously prepared amorphous ferric phosphates (AFP, FePO4·xH2O) by a combination of high-energy total X-ray scattering, Fe K-edge X-ray absorption spectroscopy, and 57Fe Mössbauer spectroscopy. Pair distribution function (PDF) analysis of total X-ray scattering data revealed that the coherently scattering domain size of AFA and AFP is about 8 Å. The PDFs of AFA lacked Fe-Fe pair correlations at r ∼3.6 Å indicative of single corner-sharing FeO6 octahedra, which strongly supports a local scorodite (FeAsO4·2H2O) structure. Likewise, the PDFs and Fe K-edge extended X-ray absorption fine structure data of AFP were consistent with a local strengite (FePO4·2H2O) structure of isolated FeO6 octahedra being corner-linked to PO4 tetrahedra (rFe-P = 3.25(1) Å). Mössbauer spectroscopy analyses of AFA and AFP indicated a strong superparamagnetism. While AFA only showed a weak onset of magnetic hyperfine splitting at 5 K, magnetic ordering of AFP was completely absent at this temperature. Mössbauer spectroscopy may thus offer a convenient way to identify and quantify AFA and AFP in mineral mixtures containing poorly crystalline Fe(III)-oxyhydroxides. In summary, our results imply a close structural relationship between AFA and AFP and suggest that these amorphous materials serve as templates for the formation of scorodite and strengite (phosphosiderite) in strongly acidic low-temperature environments.

  18. Respiratory Therapy and Respiratory Therapy Technician. Florida Vocational Program Guide.

    ERIC Educational Resources Information Center

    Florida State Univ., Tallahassee. Center for Instructional Development and Services.

    This program guide identifies primary considerations in the organization, operation, and evaluation of respiratory therapy and respiratory therapy technician programs. An occupational description and program content are presented. The curriculum framework specifies the exact course title, course number, levels of instruction, major course content,…

  19. Comparative Studies on the Induction and Inactivation of Nitrate Reductase in Corn Roots and Leaves 1

    PubMed Central

    Aslam, Muhammad; Oaks, Ann

    1976-01-01

    A comparison of induction and inactivation of nitrate reductase and two of its component activities, namely FMNH2-nitrate reductase and NO3−-induced NADH-cytochrome c reductase, was made in roots and leaves of corn (Zea mays L. var. W64A × 182E). The three activities were induced in parallel in both tissues when NO3− was supplied. WO4= suppressed the induction of NADH- and FMNH2-nitrate reductase activities in root tips and leaves. The NO3−-induced NADH-cytochrome c reductase activity showed a normal increase in roots treated with WO4=. In leaves, on the other hand, there was a marked superinduction of the NO3−-induced NADH-cytochrome c reductase in the presence of WO4=. The half-life values of NADH-nitrate reductase and FMNH2-nitrate reductase measured by removing NO3− and adding WO4= to the medium, were 4 hours in root tips and 6 hours in excised leaves. Addition of NO3− in the induction medium together with WO4= gave partial protection of NADH-nitrate reductase and FMNH2-nitrate reductase activities in both root tips and leaves with a t0.5 of 6 and 8 hours, respectively. NO3− also reduced the loss of nitrate reductase activity from mature root sections. In the presence of cycloheximide, both NADH-nitrate reductase and NO3−-induced NADH-cytochrome c reductase activities were lost at similar rates in root tips. NO3− protected the loss of NO3−-induced NADH-cytochrome c reductase to the same extent as that of NADH-nitrate reductase. PMID:16659529

  20. Thioredoxin and NADP-thioredoxin reductase from cultured carrot cells

    NASA Technical Reports Server (NTRS)

    Johnson, T. C.; Cao, R. Q.; Kung, J. E.; Buchanan, B. B.

    1987-01-01

    Dark-grown carrot (Daucus carota L.) tissue cultures were found to contain both protein components of the NADP/thioredoxin system--NADP-thioredoxin reductase and the thioredoxin characteristic of heterotrophic systems, thioredoxin h. Thioredoxin h was purified to apparent homogeneity and, like typical bacterial counterparts, was a 12-kdalton (kDa) acidic protein capable of activating chloroplast NADP-malate dehydrogenase (EC 1.1.1.82) more effectively than fructose-1,6-bisphosphatase (EC 3.1.3.11). NADP-thioredoxin reductase (EC 1.6.4.5) was partially purified and found to be an arsenite-sensitive enzyme composed of two 34-kDa subunits. Carrot NADP-thioredoxin reductase resembled more closely its counterpart from bacteria rather than animal cells in acceptor (thioredoxin) specificity. Upon greening of the cells, the content of NADP-thioredoxin-reductase activity, and, to a lesser extent, thioredoxin h decreased. The results confirm the presence of a heterotrophic-type thioredoxin system in plant cells and raise the question of its physiological function.

  1. The Kinetics and Inhibition of the Enzyme Methemoglobin Reductase

    ERIC Educational Resources Information Center

    Splittgerber, A. G.; And Others

    1975-01-01

    Describes an undergraduate biochemistry experiment which involves the preparation and kinetics of an oxidation-reduction enzyme system, methemoglobin reductase. A crude enzyme extract is prepared and assayed spectrophotometrically. The enzyme system obeys Michaelis-Menton kinetics with respect to both substrate and the NADH cofactor. (MLH)

  2. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7375...

  3. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7375...

  4. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7375...

  5. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7375...

  6. 21 CFR 864.7375 - Glutathione reductase assay.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Glutathione reductase assay. 864.7375 Section 864.7375 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7375...

  7. Domain Evolution and Functional Diversification of Sulfite Reductases

    NASA Astrophysics Data System (ADS)

    Dhillon, Ashita; Goswami, Sulip; Riley, Monica; Teske, Andreas; Sogin, Mitchell

    2005-02-01

    Sulfite reductases are key enzymes of assimilatory and dissimilatory sulfur metabolism, which occur in diverse bacterial and archaeal lineages. They share a highly conserved domain "C-X5-C-n-C-X3-C" for binding siroheme and iron-sulfur clusters that facilitate electron transfer to the substrate. For each sulfite reductase cluster, the siroheme-binding domain is positioned slightly differently at the N-terminus of dsrA and dsrB, while in the assimilatory proteins the siroheme domain is located at the C-terminus. Our sequence and phylogenetic analysis of the siroheme-binding domain shows that sulfite reductase sequences diverged from a common ancestor into four separate clusters (aSir, alSir, dsr, and asrC) that are biochemically distinct; each serves a different assimilatory or dissimilatory role in sulfur metabolism. The phylogenetic distribution and functional grouping in sulfite reductase clusters (dsrA and dsrB vs. aSiR, asrC, and alSir) suggest that their functional diversification during evolution may have preceded the bacterial/archaeal divergence.

  8. Activated and unactivated forms of human erythrocyte aldose reductase.

    PubMed Central

    Srivastava, S K; Hair, G A; Das, B

    1985-01-01

    Aldose reductase (alditol:NADP+ 1-oxidoreductase, EC 1.1.1.21) has been partially purified from human erythrocytes by DEAE-cellulose (DE-52) column chromatography. This enzyme is activated severalfold upon incubation with 10 microM each glucose 6-phosphate, NADPH, and glucose. The activation of the enzyme was confirmed by following the oxidation of NADPH as well as the formation of sorbitol with glucose as substrate. The activated form of aldose reductase exhibited monophasic kinetics with both glyceraldehyde and glucose (Km of glucose = 0.68 mM and Km of glyceraldehyde = 0.096 mM), whereas the native (unactivated) enzyme exhibited biphasic kinetics (Km of glucose = 9.0 and 0.9 mM and Km of glyceraldehyde = 1.1 and 0.14 mM). The unactivated enzyme was strongly inhibited by aldose reductase inhibitors such as sorbinil, alrestatin, and quercetrin, and by phosphorylated intermediates such as ADP, glycerate 3-phosphate, glycerate 1,3-bisphosphate, and glycerate 2,3-trisphosphate. The activated form of the enzyme was less susceptible to inhibition by aldose reductase inhibitors and phosphorylated intermediates. PMID:3933003

  9. Characterization of mitochondrial thioredoxin reductase from C. elegans

    SciTech Connect

    Lacey, Brian M.; Hondal, Robert J. . E-mail: Robert.Hondal@uvm.edu

    2006-08-04

    Thioredoxin reductase catalyzes the NADPH-dependent reduction of the catalytic disulfide bond of thioredoxin. In mammals and other higher eukaryotes, thioredoxin reductases contain the rare amino acid selenocysteine at the active site. The mitochondrial enzyme from Caenorhabditis elegans, however, contains a cysteine residue in place of selenocysteine. The mitochondrial C. elegans thioredoxin reductase was cloned from an expressed sequence tag and then produced in Escherichia coli as an intein-fusion protein. The purified recombinant enzyme has a k {sub cat} of 610 min{sup -1} and a K {sub m} of 610 {mu}M using E. coli thioredoxin as substrate. The reported k {sub cat} is 25% of the k {sub cat} of the mammalian enzyme and is 43-fold higher than a cysteine mutant of mammalian thioredoxin reductase. The enzyme would reduce selenocysteine, but not hydrogen peroxide or insulin. The flanking glycine residues of the GCCG motif were mutated to serine. The mutants improved substrate binding, but decreased the catalytic rate.

  10. 5. cap alpha. -reductase activity in rat adipose tissue

    SciTech Connect

    Zyirek, M.; Flood, C.; Longcope, C.

    1987-11-01

    We measured the 5 ..cap alpha..-reductase activity in isolated cell preparations of rat adipose tissue using the formation of (/sup 3/H) dihydrotestosterone from (/sup 3/H) testosterone as an endpoint. Stromal cells were prepared from the epididymal fat pad, perinephric fat, and subcutaneous fat of male rats and from perinephric fat of female rats. Adipocytes were prepared from the epididymal fat pad and perinephric fat of male rats. Stromal cells from the epididymal fat pad and perinephric fat contained greater 5..cap alpha..-reductase activity than did the adipocytes from these depots. Stromal cells from the epididymal fat pad contained greater activity than those from perinephric and subcutaneous depots. Perinephric stromal cells from female rats were slightly more active than those from male rats. Estradiol (10/sup -8/ M), when added to the medium, caused a 90% decrease in 5..cap alpha..-reductase activity. Aromatase activity was minimal, several orders of magnitude less than 5..cap alpha..-reductase activity in each tissue studied.

  11. Respiratory disease and cardiovascular morbidity

    PubMed Central

    Koskela, R; Mutanen, P; Sorsa, J; Klockars, M

    2005-01-01

    Background: Work related dust exposure is a risk factor for acute and chronic respiratory irritation and inflammation. Exposure to dust and cigarette smoke predisposes to exogenous viral and bacterial infections of the respiratory tract. Respiratory infection can also act as a risk factor in the development of atherosclerotic and coronary artery disease. Aims: To investigate the association of dust exposure and respiratory diseases with ischaemic heart disease (IHD) and other cardiovascular diseases (CVDs). Methods: The study comprised 6022 dust exposed (granite, foundry, cotton mill, iron foundry, metal product, and electrical) workers hired in 1940–76 and followed until the end of 1992. National mortality and morbidity registers and questionnaires were used. The statistical methods were person-year analysis and Cox regression. Results: Co-morbidity from cardiovascular and respiratory diseases ranged from 17% to 35%. In at least 60% of the co-morbidity cases a respiratory disease preceded a cardiovascular disease. Chronic bronchitis, pneumonia, and upper respiratory track infections predicted IHD in granite workers (rate ratio (RR) = 1.9; 95% CI 1.38 to 2.72), foundry workers (2.1; 1.48 to 2.93), and iron foundry workers (1.7; 1.16 to 2.35). Dust exposure was not a significant predictor of IHD or other CVD in any group. Dust exposure was related to respiratory morbidity. Thus, some respiratory diseases appeared to act as intermediate variables in the association of dust exposure with IHD. Conclusion: Dust exposure had only a small direct effect on IHD and other CVD. IHD morbidity was associated with preceding respiratory morbidity. A chronic infectious respiratory tract disease appeared to play an independent role in the development of IHD. PMID:16109822

  12. Implementing change in respiratory care.

    PubMed

    Stoller, James K

    2010-06-01

    Though people are generally averse to change, change and innovation are critically important in respiratory care to maintain scientific and clinical progress. This paper reviews the issue of change in respiratory care. I summarize several available models of organizational and personal change (ie, those of Kotter and of Silversin and Kornacki, and the Intentional Change Theory of Boyatzis), review the characteristics of change-avid respiratory therapy departments, offer an example of a change effort in respiratory care (implementation of respiratory care protocols) and then analyze this change effort as it took place at one institution, the Cleveland Clinic, using these models. Finally, I present the results of an analysis of change-avid respiratory therapy departments and offer some suggestions regarding change management for the profession and for individual respiratory care clinicians. Common features of theories of organizational change include developing a sense of urgency, overcoming resistance, developing a guiding coalition, and involving key stakeholders early. With the understanding that change efforts may seem unduly "clean" and orderly in retrospect, the models help explain the sustainable success of efforts to implement the Respiratory Therapy Consult Service at the Cleveland Clinic. By implication, these models offer value in planning change efforts prospectively. Further analysis of features of change-avid respiratory therapy departments indicates 11 highly desired features, of which four that especially characterize change-avid departments include: having an up-to-date leadership team; employee involvement in change; celebrating wins; and an overall sense of progressiveness in the department. This analysis suggests that understanding and embracing change is important. To anchor change in our profession, greater attention should be given to developing a pipeline of respiratory care clinicians who, by virtue of their advanced training, have the skills

  13. Modulation of the Respiratory Supercomplexes in Yeast

    PubMed Central

    Cui, Tie-Zhong; Conte, Annalea; Fox, Jennifer L.; Zara, Vincenzo; Winge, Dennis R.

    2014-01-01

    Yeast cells deficient in the Rieske iron-sulfur subunit (Rip1) of ubiquinol-cytochrome c reductase (bc1) accumulate a late core assembly intermediate, which weakly associates with cytochrome oxidase (CcO) in a respiratory supercomplex. Expression of the N-terminal half of Rip1, which lacks the C-terminal FeS-containing globular domain (designated N-Rip1), results in a marked stabilization of trimeric and tetrameric bc1-CcO supercomplexes. Another bc1 mutant (qcr9Δ) stalled at the same assembly intermediate is likewise converted to stable supercomplex species by the expression of N-Rip1, but not by expression of intact Rip1. The N-Rip1-induced stabilization of bc1-CcO supercomplexes is independent of the Bcs1 translocase, which mediates Rip1 translocation during bc1 biogenesis. N-Rip1 induces the stabilization of bc1-CcO supercomplexes through an enhanced formation of CcO. The association of N-Rip1 with the late core bc1 assembly intermediate appears to confer stabilization of a CcO assembly intermediate. This induced stabilization of CcO is dependent on the Rcf1 supercomplex stabilization factor and only partially dependent on the presence of cardiolipin. N-Rip1 exerts a related induction of CcO stabilization in WT yeast, resulting in enhanced respiration. Additionally, the impact of CcO stabilization on supercomplexes was observed by means other than expression of N-Rip1 (via overexpression of CcO subunits Cox4 and Cox5a), demonstrating that this is a general phenomenon. This study presents the first evidence showing that supercomplexes can be stabilized by the stimulated formation of CcO. PMID:24421313

  14. Differential molecular response of monodehydroascorbate reductase and glutathione reductase by nitration and S-nitrosylation.

    PubMed

    Begara-Morales, Juan C; Sánchez-Calvo, Beatriz; Chaki, Mounira; Mata-Pérez, Capilla; Valderrama, Raquel; Padilla, María N; López-Jaramillo, Javier; Luque, Francisco; Corpas, Francisco J; Barroso, Juan B

    2015-09-01

    The ascorbate-glutathione cycle is a metabolic pathway that detoxifies hydrogen peroxide and involves enzymatic and non-enzymatic antioxidants. Proteomic studies have shown that some enzymes in this cycle such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), and glutathione reductase (GR) are potential targets for post-translational modifications (PMTs) mediated by nitric oxide-derived molecules. Using purified recombinant pea peroxisomal MDAR and cytosolic and chloroplastic GR enzymes produced in Escherichia coli, the effects of peroxynitrite (ONOO(-)) and S-nitrosoglutathione (GSNO) which are known to mediate protein nitration and S-nitrosylation processes, respectively, were analysed. Although ONOO(-) and GSNO inhibit peroxisomal MDAR activity, chloroplastic and cytosolic GR were not affected by these molecules. Mass spectrometric analysis of the nitrated MDAR revealed that Tyr213, Try292, and Tyr345 were exclusively nitrated to 3-nitrotyrosine by ONOO(-). The location of these residues in the structure of pea peroxisomal MDAR reveals that Tyr345 is found at 3.3 Å of His313 which is involved in the NADP-binding site. Site-directed mutagenesis confirmed Tyr345 as the primary site of nitration responsible for the inhibition of MDAR activity by ONOO(-). These results provide new insights into the molecular regulation of MDAR which is deactivated by nitration and S-nitrosylation. However, GR was not affected by ONOO(-) or GSNO, suggesting the existence of a mechanism to conserve redox status by maintaining the level of reduced GSH. Under a nitro-oxidative stress induced by salinity (150mM NaCl), MDAR expression (mRNA, protein, and enzyme activity levels) was increased, probably to compensate the inhibitory effects of S-nitrosylation and nitration on the enzyme. The present data show the modulation of the antioxidative response of key enzymes in the ascorbate-glutathione cycle by nitric oxide (NO)-PTMs, thus indicating the close involvement of

  15. Differential molecular response of monodehydroascorbate reductase and glutathione reductase by nitration and S-nitrosylation

    PubMed Central

    Begara-Morales, Juan C.; Sánchez-Calvo, Beatriz; Chaki, Mounira; Mata-Pérez, Capilla; Valderrama, Raquel; Padilla, María N.; Luque, Francisco; Corpas, Francisco J.; Barroso, Juan B.

    2015-01-01

    The ascorbate–glutathione cycle is a metabolic pathway that detoxifies hydrogen peroxide and involves enzymatic and non-enzymatic antioxidants. Proteomic studies have shown that some enzymes in this cycle such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), and glutathione reductase (GR) are potential targets for post-translational modifications (PMTs) mediated by nitric oxide-derived molecules. Using purified recombinant pea peroxisomal MDAR and cytosolic and chloroplastic GR enzymes produced in Escherichia coli, the effects of peroxynitrite (ONOO–) and S-nitrosoglutathione (GSNO) which are known to mediate protein nitration and S-nitrosylation processes, respectively, were analysed. Although ONOO– and GSNO inhibit peroxisomal MDAR activity, chloroplastic and cytosolic GR were not affected by these molecules. Mass spectrometric analysis of the nitrated MDAR revealed that Tyr213, Try292, and Tyr345 were exclusively nitrated to 3-nitrotyrosine by ONOO–. The location of these residues in the structure of pea peroxisomal MDAR reveals that Tyr345 is found at 3.3 Å of His313 which is involved in the NADP-binding site. Site-directed mutagenesis confirmed Tyr345 as the primary site of nitration responsible for the inhibition of MDAR activity by ONOO–. These results provide new insights into the molecular regulation of MDAR which is deactivated by nitration and S-nitrosylation. However, GR was not affected by ONOO– or GSNO, suggesting the existence of a mechanism to conserve redox status by maintaining the level of reduced GSH. Under a nitro-oxidative stress induced by salinity (150mM NaCl), MDAR expression (mRNA, protein, and enzyme activity levels) was increased, probably to compensate the inhibitory effects of S-nitrosylation and nitration on the enzyme. The present data show the modulation of the antioxidative response of key enzymes in the ascorbate–glutathione cycle by nitric oxide (NO)-PTMs, thus indicating the close involvement

  16. Measurement of nitrous oxide reductase activity in aquatic sediments

    SciTech Connect

    Miller, L.G.; Oremland, R.S.; Paulsen, S.

    1986-01-01

    Denitrification in aquatic sediments was measured by an N/sub 2/O reductase assay. Sediments consumed small added quantities of N/sub 2/O over short periods (a few hours). In experiments with sediment slurries, N/sub 2/O reductase activity was inhibited by 0/sub 2/, C/sub 2/H/sub 2/, heat treatment, and by high levels of nitrate (1 mM) or sulfide (10 mM). However, ambient levels of nitrate (<100 ..mu..M) did not influence activity, and moderate levels (about 150 ..mu..M) induced only a short lag before reductase activity began. Moderate levels of sulfide (<1 mM) had no effect on N/sub 2/O reductase activity. Nitrous oxide reductase displayed Michaelis-Menten kinetics in sediments from freshwater, estuarine, and alkaline-saline environments. An in situ assay was devised in which a solution of N/sub 2/O was injected into sealed glass cores containing intact sediment. Two estimates of net rates of denitrification in San Francisco Bay under approximated in situ conditions were 0.009 and 0.041 mmol of N/sub 2/O per m/sup 2/ per h. Addition of chlorate to inhibit denitrification in these intact-core experiments (to estimate gross rates of N/sub 2/O consumption) resulted in approximately a 14% upward revision of estimates of net rates. These results were comparable to an in situ estimate of 0.022 mmol of N/sub 2/O per m/sup 2/ per h made with the acetylene block assay.

  17. Nickel site of methane catalysis in the methyl reductase enzyme

    SciTech Connect

    Shelnutt, J.A.; Shiemke, A.K.; Scott, R.A.

    1988-01-01

    Methyl reductase is the enzyme of methanogenic bacteria that catalyzed the two-electron reduction of the methyl group of 2-(methylthio)ethanesulfonic acid (methyl-S-CoM) to methane and HS-CoM. The methyl group of methyl-S-CoM ultimately comes from the six-electron reduction of CO/sub 2/ by hydrogen, which also provides the reducing equivalents needed by methyl reductase. The nature of the catalytic site of methyl reductase is of current interest from the point of view of developing biomimetic C/sub 1/, chemistries directed toward methane synthesis and activation. In particular, Sandia is using molecular graphics and energy optimization techniques to design macromolecular catalysts that mimic the structure of sites of proteins that carry out C/sub 1/ chemistry. The goal is to produce catalysts whose function is the oxidation of low molecular weight hydrocarbon gases to generate liquid fuels or, alternatively, the reduction of abundant inorganic resources such as CO/sub 2/ to generate gaseous fuels. Unfortunately, the catalytic sites of many of the enzymes of interest, e.g., methyl reductase and methane monooxygenase, have not been characterized by X-ray crystallography and other structural techniques. With the goal of learning more about the structure of one of these naturally occurring sites of C/sub 1/ chemistry, we have obtained the first resonance Raman spectra of the nickel-macrocycle, called F/sub 430/, at the site of catalysis in methyl reductase. To help us structurally interpret the Raman spectra of the enzyme we have also obtained Raman spectra of solutions of the major forms of F/sub 430/ (salt-extracted and cytosol-free) at room temperature and at 77/degree/K and also, under similar solution conditions, spectra of a nickel-corphinoid derivative that is related to F/sub 430/.

  18. Characterization of recombinant glutathione reductase from the psychrophilic Antarctic bacterium Colwellia psychrerythraea.

    PubMed

    Ji, Mikyoung; Barnwell, Callie V; Grunden, Amy M

    2015-07-01

    Glutathione reductases catalyze the reduction of oxidized glutathione (glutathione disulfide, GSSG) using NADPH as the substrate to produce reduced glutathione (GSH), which is an important antioxidant molecule that helps maintain the proper reducing environment of the cell. A recombinant form of glutathione reductase from Colwellia psychrerythraea, a marine psychrophilic bacterium, has been biochemically characterized to determine its molecular and enzymatic properties. C. psychrerythraea glutathione reductase was shown to be a homodimer with a molecular weight of 48.7 kDa using SDS-PAGE, MALDI-TOF mass spectrometry and gel filtration. The C. psychrerythraea glutathione reductase sequence shows significant homology to that of Escherichia coli glutathione reductase (66 % identity), and it possesses the FAD and NADPH binding motifs, as well as absorption spectrum features which are characteristic of flavoenzymes such as glutathione reductase. The psychrophilic C. psychrerythraea glutathione reductase exhibits higher k cat and k cat/K m at lower temperatures (4 °C) compared to mesophilic Baker's yeast glutathione reductase. However, C. psychrerythraea glutathione reductase was able to complement an E. coli glutathione reductase deletion strain in oxidative stress growth assays, demonstrating the functionality of C. psychrerythraea glutathione reductase over a broad temperature range, which suggests its potential utility as an antioxidant enzyme in heterologous systems. PMID:26101017

  19. Crystal structures of pinoresinol-lariciresinol and phenylcoumaran benzylic ether reductases and their relationship to isoflavone reductases.

    PubMed

    Min, Tongpil; Kasahara, Hiroyuki; Bedgar, Diana L; Youn, Buhyun; Lawrence, Paulraj K; Gang, David R; Halls, Steven C; Park, HaJeung; Hilsenbeck, Jacqueline L; Davin, Laurence B; Lewis, Norman G; Kang, ChulHee

    2003-12-12

    Despite the importance of plant lignans and isoflavonoids in human health protection (e.g. for both treatment and prevention of onset of various cancers) as well as in plant biology (e.g. in defense functions and in heartwood development), systematic studies on the enzymes involved in their biosynthesis have only recently begun. In this investigation, three NADPH-dependent aromatic alcohol reductases were comprehensively studied, namely pinoresinol-lariciresinol reductase (PLR), phenylcoumaran benzylic ether reductase (PCBER), and isoflavone reductase (IFR), which are involved in central steps to the various important bioactive lignans and isoflavonoids. Of particular interest was in determining how differing regio- and enantiospecificities are achieved with the different enzymes, despite each apparently going through similar enone intermediates. Initially, the three-dimensional x-ray crystal structures of both PLR_Tp1 and PCBER_Pt1 were solved and refined to 2.5 and 2.2 A resolutions, respectively. Not only do they share high gene sequence similarity, but their structures are similar, having a continuous alpha/beta NADPH-binding domain and a smaller substrate-binding domain. IFR (whose crystal structure is not yet obtained) was also compared (modeled) with PLR and PCBER and was deduced to have the same overall basic structure. The basis for the distinct enantio-specific and regio-specific reactions of PCBER, PLR, and IFR, as well as the reaction mechanism and participating residues involved (as identified by site-directed mutagenesis), are discussed. PMID:13129921

  20. Crystal structures of pinoresinol-lariciresinol and phenylcoumaran benzylic ether reductases and their relationship to isoflavone reductases

    NASA Technical Reports Server (NTRS)

    Min, Tongpil; Kasahara, Hiroyuki; Bedgar, Diana L.; Youn, Buhyun; Lawrence, Paulraj K.; Gang, David R.; Halls, Steven C.; Park, HaJeung; Hilsenbeck, Jacqueline L.; Davin, Laurence B.; Lewis, Norman G.; Kang, ChulHee

    2003-01-01

    Despite the importance of plant lignans and isoflavonoids in human health protection (e.g. for both treatment and prevention of onset of various cancers) as well as in plant biology (e.g. in defense functions and in heartwood development), systematic studies on the enzymes involved in their biosynthesis have only recently begun. In this investigation, three NADPH-dependent aromatic alcohol reductases were comprehensively studied, namely pinoresinol-lariciresinol reductase (PLR), phenylcoumaran benzylic ether reductase (PCBER), and isoflavone reductase (IFR), which are involved in central steps to the various important bioactive lignans and isoflavonoids. Of particular interest was in determining how differing regio- and enantiospecificities are achieved with the different enzymes, despite each apparently going through similar enone intermediates. Initially, the three-dimensional x-ray crystal structures of both PLR_Tp1 and PCBER_Pt1 were solved and refined to 2.5 and 2.2 A resolutions, respectively. Not only do they share high gene sequence similarity, but their structures are similar, having a continuous alpha/beta NADPH-binding domain and a smaller substrate-binding domain. IFR (whose crystal structure is not yet obtained) was also compared (modeled) with PLR and PCBER and was deduced to have the same overall basic structure. The basis for the distinct enantio-specific and regio-specific reactions of PCBER, PLR, and IFR, as well as the reaction mechanism and participating residues involved (as identified by site-directed mutagenesis), are discussed.

  1. Assembly of the mitochondrial membrane system. Cytoplasmic mutants of Saccharomyces cerevisiae with lesions in enzymes of the respiratory chain and in the mitochondrial ATPase.

    PubMed

    Tzagoloff, A; Akai, A; Needleman, R B; Zulch, G

    1975-10-25

    Mutants of Saccharomyces cervisiae with defects in enzymes of the electron transfer chain and in the rutamycin-sensitive ATPase have been isolated. Some of the mutants are specifically affected in either cytochrome oxidase, coenzyme QH2-cytochrome c reductase or ATPase. Other strains are deficient in both cytochrome oxidase and coenzyme QH2-cytochrome c reductase but still have rutamycin-sensitive ATPase. All the mutants reported in this study fail to be complemented by a rho0 tester derived from a respiratory competent strain. The meiotic spore progeny obtained by mating the mutants to a respiratory competent haploid yeast, when scored for growth on glycerol, show a non-Mendelian segregation of the phenotype. These two genetic tests indicate the mutations to be cytoplasmically inherited. PMID:171256

  2. Photosynthesis is induced in rice plants that associate with arbuscular mycorrhizal fungi and are grown under arsenate and arsenite stress.

    PubMed

    de Andrade, Sara Adrian Lopez; Domingues, Adilson Pereira; Mazzafera, Paulo

    2015-09-01

    The metalloid arsenic (As) increases in agricultural soils because of anthropogenic activities and may have phytotoxic effects depending on the available concentrations. Plant performance can be improved by arbuscular mycorrhiza (AM) association under challenging conditions, such as those caused by excessive soil As levels. In this study, the influence of AM on CO2 assimilation, chlorophyll a fluorescence, SPAD-chlorophyll contents and plant growth was investigated in rice plants exposed to arsenate (AsV) or arsenite (AsIII) and inoculated or not with Rhizophagus irregularis. Under AsV and AsIII exposure, AM rice plants had greater biomass accumulation and relative chlorophyll content, increased water-use efficiency, higher carbon assimilation rate and higher stomatal conductance and transpiration rates than non-AM rice plants did. Chlorophyll a fluorescence analysis revealed significant differences in the response of AM-associated and -non-associated plants to As. Mycorrhization increased the maximum and actual quantum yields of photosystem II and the electron transport rate, maintaining higher values even under As exposure. Apart from the negative effects of AsV and AsIII on the photosynthetic rates and PSII efficiency in rice leaves, taken together, these results indicate that AM is able to sustain higher rice photosynthesis efficiency even under elevated As concentrations, especially when As is present as AsV. PMID:25935603

  3. Chromated copper arsenate-treated fence posts in the agronomic landscape: soil properties controlling arsenic speciation and spatial distribution.

    PubMed

    Schwer Iii, Donald R; McNear, David H

    2011-01-01

    Soils adjacent to chromated copper arsenate (CCA)-treated fence posts along a fence line transecting different soil series, parent material, drainage classes, and slope were used to determine which soil properties had the most influence on As spatial distribution and speciation. Metal distribution was evaluated at macroscopic (total metal concentration contour maps) and microscopic scales (micro-synchrotron X-ray fluorescence maps), As speciation was determined using extended X-ray absorption fine structure spectroscopy, and redox status and a myriad of other basic soil properties were elucidated. All geochemical parameters measured point to a condition in which the mobilization of As becomes more favorable moving down the topographic gradient, likely resulting through competition (Meh-P, SOM), neutral or slightly basic pH, and redox conditions that are favorable for As mobilization (higher Fe(II) and total-Fe concentrations in water extracts). On the landscape scale, with hundreds of kilometers of fence, the arsenic loading into the soil can be substantial (∼8-12 kg km). Although a significant amount of the As is stable, extended use of CCA-treated wood has resulted in elevated As concentrations in the local environment, increasing the risk of exposure and ecosystem perturbation. Therefore, a move toward arsenic-free alternatives in agricultural applications for which it is currently permitted should be considered. PMID:21712587

  4. Arsenate Impact on the Metabolite Profile, Production, and Arsenic Loading of Xylem Sap in Cucumbers (Cucumis sativus L.)

    PubMed Central

    Uroic, M. Kalle; Salaün, Pascal; Raab, Andrea; Feldmann, Jörg

    2012-01-01

    Arsenic uptake and translocation studies on xylem sap focus generally on the concentration and speciation of arsenic in the xylem. Arsenic impact on the xylem sap metabolite profile and its production during short term exposure has not been reported in detail. To investigate this, cucumbers were grown hydroponically and arsenate (AsV) and DMA were used for plant treatment for 24 h. Total arsenic and arsenic speciation in xylem sap was analyzed including a metabolite profiling under AsV stress. Produced xylem sap was quantified and absolute arsenic transported was determined. AsV exposure had a significant impact on the metabolite profile of xylem sap. Four m/z values corresponding to four compounds were up-regulated, one compound down-regulated by AsV exposure. The compound down-regulated was identified to be isoleucine. Furthermore, AsV exposure had a significant influence on sap production, leading to a reduction of up to 96% sap production when plants were exposed to 1000 μg kg−1 AsV. No difference to control plants was observed when plants were exposed to 1000 μg kg−1 DMA. Absolute arsenic amount in xylem sap was the lowest at high AsV exposure. These results show that AsV has a significant impact on the production and metabolite profile of xylem sap. The physiological importance of isoleucine needs further attention. PMID:22536187

  5. Leaching of chromated copper arsenate (CCA)-treated wood in a simulated monofill and its potential impacts to landfill leachate.

    PubMed

    Jambeck, Jenna R; Townsend, Timothy; Solo-Gabriele, Helena

    2006-07-31

    The proper end-of-life management of chromated copper arsenate (CCA)-treated wood, which contains arsenic, copper, and chromium, is a concern to the solid waste management community. Landfills are often the final repository of this waste stream, and the impacts of CCA preservative metals on leachate quality are not well understood. Monofills are a type of landfill designed and operated to dispose a single waste type, such as ash, tires, mining waste, or wood. The feasibility of managing CCA-treated wood in monofills was examined using a simulated landfill (a leaching lysimeter) that contained a mix of new and weathered CCA-treated wood. The liquid to solid ratio (LS) reached in the experiment was 0.63:1. Arsenic, chromium, and copper leached from the lysimeter at average concentrations of 42 mg/L for arsenic, 9.4 mg/L for chromium, and 2.4 mg/L for copper. Complementary batch leaching studies using deionized water were performed on similar CCA-treated wood samples at LS of 5:1 and 10:1. When results from the lysimeter were compared to the batch test results, copper and chromium leachability appeared to be reduced in the lysimeter disposal environment. Of the three metals, arsenic leached to the greatest extent and was found to have the best correlation between the batch and the lysimeter experiments. PMID:16406290

  6. Raman spectroscopic identification of arsenate minerals in situ at outcrops with handheld (532 nm, 785 nm) instruments.

    PubMed

    Culka, Adam; Kindlová, Helena; Drahota, Petr; Jehlička, Jan

    2016-02-01

    Minerals are traditionally identified under field conditions by experienced mineralogists observing the basic physical properties of the samples. Under laboratory conditions, a plethora of techniques are commonly used for identification of the geological phases based on their structural and spectroscopic parameters. In this area, Raman spectrometry has become a useful tool to complement the more widely applied XRD. Today, however, there is an acute need for a technique for unambiguous in situ identification of minerals, within the geological as well as planetary/exobiology realms. With the potential for miniaturization, Raman spectroscopy can be viewed as a practical technique to achieve these goals. Here, for the first time, the successful application of handheld Raman spectrometers is demonstrated to detect and discriminate arsenic phases in the form of earthy aggregates. The Raman spectroscopic analyses of arsenate minerals were performed in situ using two handheld instruments, using 532 and 785 nm excitation. Bukovskýite, kaňkite, parascorodite, and scorodite were identified from Kaňk near Kutná Hora, CZE; kaňkite, scorodite, and zýkaite were identified at the Lehnschafter gallery in an old silver mine at Mikulov near Teplice, Bohemian Massif, CZE. PMID:26523686

  7. Pyrobaculum ferrireducens sp. nov., a hyperthermophilic Fe(III)-, selenate- and arsenate-reducing crenarchaeon isolated from a hot spring.

    PubMed

    Slobodkina, G B; Lebedinsky, A V; Chernyh, N A; Bonch-Osmolovskaya, E A; Slobodkin, A I

    2015-03-01

    A novel hyperthermophilic, anaerobic, archaeon was isolated from a terrestrial hot spring at Uzon Caldera, Kronotsky Nature Reserve, Kamchatka, Russia. The isolate, strain 1860(T), grew optimally at 90-95 °C and pH 6.0-7.0. The cells were non-motile straight rods, 1.5-5.0 µm in length, covered with surface-layer lattice. Strain 1860(T) utilized complex proteinaceous compounds as electron donors and ferrihydrite, Fe(III) citrate, nitrate, thiosulfate, selenite, selenate and arsenate as electron acceptors for growth. The sequence of the 16S rRNA gene of strain 1860(T) had 97.9-98.7 % similarity with those of members of the genus Pyrobaculum. On the basis of its physiological properties and phylogenetic analyses including in silico genome to genome hybridization, the isolate is considered to represent a novel species, for which the name Pyrobaculum ferrireducens sp. nov. is proposed. The type strain is 1860(T) ( = DSM 28942(T) = VKM B-2856(T)). PMID:25510975

  8. Natural variations in expression of regulatory and detoxification related genes under limiting phosphate and arsenate stress in Arabidopsis thaliana

    PubMed Central

    Shukla, Tapsi; Kumar, Smita; Khare, Ria; Tripathi, Rudra D.; Trivedi, Prabodh K.

    2015-01-01

    Abiotic stress including nutrient deficiency and heavy metal toxicity severely affects plant growth, development, and productivity. Genetic variations within and in between species are one of the important factors in establishing interactions and responses of plants with the environment. In the recent past, natural variations in Arabidopsis thaliana have been used to understand plant development and response toward different stresses at genetic level. Phosphorus deficiency negatively affects plant growth and metabolism and modulates expression of the genes involved in Pi homeostasis. Arsenate, As(V), a chemical analog of Pi, is taken up by the plants via phosphate transport system. Studies suggest that during Pi deficiency, enhanced As(V) uptake leads to increased toxicity in plants. Here, the natural variations in Arabidopsis have been utilized to study the As(V) stress response under limiting Pi condition. The primary root length was compared to identify differential response of three Arabidopsis accessions (Col-0, Sij-1, and Slavi-1) under limiting Pi and As(V) stress. To study the molecular mechanisms responsible for the differential response, comprehensive expression profiling of the genes involved in uptake, detoxification, and regulatory mechanisms was carried out. Analysis suggests genetic variation-dependent regulatory mechanisms may affect differential response of Arabidopsis natural variants toward As(V) stress under limiting Pi condition. Therefore, it is hypothesized that detailed analysis of the natural variations under multiple stress conditions might help in the better understanding of the biological processes involved in stress tolerance and adaptation. PMID:26557133

  9. Exergy analysis of the Chartherm process for energy valorization and material recuperation of chromated copper arsenate (CCA) treated wood waste

    SciTech Connect

    Bosmans, A.; Auweele, M. Vanden; Govaerts, J.; Helsen, L.

    2011-04-15

    The Chartherm process (Thermya, Bordeaux, France) is a thermochemical conversion process to treat chromated copper arsenate (CCA) impregnated wood waste. The process aims at maximum energy valorization and material recuperation by combining the principles of low-temperature slow pyrolysis and distillation in a smart way. The main objective of the exergy analysis presented in this paper is to find the critical points in the Chartherm process where it is necessary to apply some measures in order to reduce exergy consumption and to make energy use more economic and efficient. It is found that the process efficiency can be increased with 2.3-4.2% by using the heat lost by the reactor, implementing a combined heat and power (CHP) system, or recuperating the waste heat from the exhaust gases to preheat the product gas. Furthermore, a comparison between the exergetic performances of a 'chartherisation' reactor and an idealized gasification reactor shows that both reactors destroy about the same amount of exergy (i.e. 3500 kW kg{sub wood}{sup -1}) during thermochemical conversion of CCA-treated wood. However, the Chartherm process possesses additional capabilities with respect to arsenic and tar treatment, as well as the extra benefit of recuperating materials.

  10. Evaluating the potential for environmental pollution from chromated copper arsenate (CCA)-treated wood waste: a new mass balance approach.

    PubMed

    Mercer, T G; Frostick, L E

    2014-07-15

    The potential for pollution from arsenic, chromium and copper in chromated copper arsenate (CCA) treated wood waste was assessed using two lysimeter studies. The first utilised lysimeters containing soil and CCA wood waste mulch exposed to natural conditions over a five month period. The second study used the same lysimeter setup in a regulated greenhouse setting with a manual watering regime. Woodchip, soil and leachate samples were evaluated for arsenic, chromium and copper concentrations. Resultant concentration data were used to produce mass balances, an approach thus far unused in such studies. This novel analysis revealed new patterns of mobility and distribution of the elements in the system. The results suggest that CCA wood waste tends to leach on initial exposure to a leachant and during weathering of the wood. When in contact with soil, metal(loid) transport is reduced due to complexation reactions. With higher water application or where the adsorption capacity of the soil is exceeded, the metal(loid)s are transported through the soil column as leachate. Overall, there was an unexplained loss of metal(loid)s from the system that might be attributed to volatilisation of arsenic and plant uptake. This suggests a hitherto unidentified risk to both the environment and human health. PMID:24858049

  11. Exergy analysis of the Chartherm process for energy valorization and material recuperation of chromated copper arsenate (CCA) treated wood waste.

    PubMed

    Bosmans, A; Auweele, M Vanden; Govaerts, J; Helsen, L

    2011-04-01

    The Chartherm process (Thermya, Bordeaux, France) is a thermochemical conversion process to treat chromated copper arsenate (CCA) impregnated wood waste. The process aims at maximum energy valorization and material recuperation by combining the principles of low-temperature slow pyrolysis and distillation in a smart way. The main objective of the exergy analysis presented in this paper is to find the critical points in the Chartherm process where it is necessary to apply some measures in order to reduce exergy consumption and to make energy use more economic and efficient. It is found that the process efficiency can be increased with 2.3-4.2% by using the heat lost by the reactor, implementing a combined heat and power (CHP) system, or recuperating the waste heat from the exhaust gases to preheat the product gas. Furthermore, a comparison between the exergetic performances of a 'chartherisation' reactor and an idealized gasification reactor shows that both reactors destroy about the same amount of exergy (i.e. 3500kWkg(wood)(-1)) during thermochemical conversion of CCA-treated wood. However, the Chartherm process possesses additional capabilities with respect to arsenic and tar treatment, as well as the extra benefit of recuperating materials. PMID:21195596

  12. Arsenate adsorption onto Fe-TNTs prepared by a novel water-ethanol hydrothermal method: mechanism and synergistic effect.

    PubMed

    Wang, Yanqi; Liu, Wen; Wang, Ting; Ni, Jinren

    2015-02-15

    Arsenate adsorption onto Fe2O3 was highly restricted at acidic condition due to dramatic dissolution. To overcome this difficulty, iron oxide nanoparticle-grafted titanate nanotubes (Fe-TNTs) were synthesized by a facile one-step water-ethanol hydrothermal method and used to remove As(V) from aqueous solutions. This new adsorbent was acid-resistant, and showed a large As(V) adsorption capacity of 90.96 mg/g determined by two-site Langmuir model, which was almost 3 times of the original TNTs. Fe2O3 was proved to bonded to the surface of TNTs by TEM and XRD analysis and synergy of Fe2O3 and TNTs was of great help to excellent As(V) adsorption. Load of Fe2O3 greatly enhanced the point of zero charge. Moreover, tubular TNTs not only inhibited dissolution of Fe2O3 at low pH, but also maintained good sedimentation property. The hydroxyl groups on Fe-TNTs surface played the most important role in As(V) adsorption. Electrostatic interaction followed by complexation was confirmed to be the primary adsorption mechanism by means of XPS analysis. Desorption capability and reuse performance of Fe-TNTs were also investigated, and satisfactory As(V) adsorption was further found with NaOH desorbed even after three reuse cycles. PMID:25460713

  13. Transcriptomics profiling of Indian mustard (Brassica juncea) under arsenate stress identifies key candidate genes and regulatory pathways

    PubMed Central

    Srivastava, Sudhakar; Srivastava, Ashish K.; Sablok, Gaurav; Deshpande, Tejaswini U.; Suprasanna, Penna

    2015-01-01

    Arsenic (As) is a non-essential element, a groundwater pollutant, whose uptake by plants produces toxic effects. The use of As-contaminated groundwater for irrigation can affect the crop productivity. Realizing the importance of the Brassica juncea as a crop plant in terms of oil-yield, there is a need to unravel mechanistic details of response to As stress and identify key functional genes and pathways. In this research, we studied time-dependent (4–96 h) transcriptome changes in roots and shoots of B. juncea under arsenate [As(V)] stress using Agilent platform. Among the whole transcriptome profiled genes, a total of 1,285 genes showed significant change in expression pattern upon As(V) exposure. The differentially expressed genes were categorized to various signaling pathways including hormones (jasmonate, abscisic acid, auxin, and ethylene) and kinases. Significant effects were also noticed on genes related to sulfur, nitrogen, CHO, and lipid metabolisms along with photosynthesis. Biochemical assays were conducted using specific inhibitors of glutathione and jasmonate biosynthesis, and kinases. The inhibitor studies revealed interconnection among sulfur metabolism, jasmonate, and kinase signaling pathways. In addition, various transposons also constituted a part of the altered transcriptome. Lastly, we profiled a set of key functional up- and down-regulated genes using real-time RT-PCR, which could act as an early indicators of the As stress. PMID:26347763

  14. Raman spectroscopic identification of arsenate minerals in situ at outcrops with handheld (532 nm, 785 nm) instruments

    NASA Astrophysics Data System (ADS)

    Culka, Adam; Kindlová, Helena; Drahota, Petr; Jehlička, Jan

    2016-02-01

    Minerals are traditionally identified under field conditions by experienced mineralogists observing the basic physical properties of the samples. Under laboratory conditions, a plethora of techniques are commonly used for identification of the geological phases based on their structural and spectroscopic parameters. In this area, Raman spectrometry has become a useful tool to complement the more widely applied XRD. Today, however, there is an acute need for a technique for unambiguous in situ identification of minerals, within the geological as well as planetary/exobiology realms. With the potential for miniaturization, Raman spectroscopy can be viewed as a practical technique to achieve these goals. Here, for the first time, the successful application of handheld Raman spectrometers is demonstrated to detect and discriminate arsenic phases in the form of earthy aggregates. The Raman spectroscopic analyses of arsenate minerals were performed in situ using two handheld instruments, using 532 and 785 nm excitation. Bukovskýite, kaňkite, parascorodite, and scorodite were identified from Kaňk near Kutná Hora, CZE; kaňkite, scorodite, and zýkaite were identified at the Lehnschafter gallery in an old silver mine at Mikulov near Teplice, Bohemian Massif, CZE.

  15. Retention of arsenate using genetically modified coryneform bacteria and determination of arsenic in solid samples by ICP-MS.

    PubMed

    Villadangos, A F; Ordóñez, E; Muñoz, M I; Pastrana, I M; Fiuza, M; Gil, J A; Mateos, L M; Aller, A J

    2010-01-15

    A novel method for the retention of arsenate [As(V)] combining time-controlled solid-phase extraction with living bacterial biomass is presented. As(V) retention was carried out by exposing the extractant, consisting of a living double-mutant of Corynebacterium glutamicum strain ArsC1-C2, to the sample for a retention time of 1-7min, before the arsenic distribution equilibrium between the sample solution and the extractant was established. The amount of As(V) retained in the biomass was measured by inductively coupled plasma-mass spectrometry (ICP-MS) after the sample had been treated with nitric acid. A theoretical model of the retention process was developed to describe the experimental retention-time profiles obtained with the bacterial cells. This relationship provided a feasible quantification of the retention process before steady-state was reached, providing that the agitation conditions and the retention time had been controlled. An analytical procedure for the retention/quantification of As(V) was then developed; the detection limit was 0.1 ng As(V)mL(-1) and the relative standard deviation 2.4-3.0%. The maximum effective retention capacity for As(V) was about 12.5mgAs(g biomass)(-1). The developed procedure was applied to the determination of total arsenic in coal fly ash, using a sample that had undergone oxidative pre-treatment. PMID:20006108

  16. NATIONAL RESPIRATORY AND ENTERIC VIRUS SURVEILLANCE SYSTEM

    EPA Science Inventory

    The National Respiratory and Enteric Virus Surveillance System is a lab based system which monitors temporal and geographic patterns associated with the detection of respiratory syncytial virus (RSV), human parainfluenza viruses (HPIV), respiratory and enteric adenoviruses, and r...

  17. Response to a Respiratory Survey

    PubMed Central

    Anderson, Donald O.; Zickmantel, Rosalie; Ferris, Benjamin G.

    1963-01-01

    Respondents to a respiratory survey of Berlin, New Hampshire, residents in 1961 have been studied to assess the relationship between co-operation and respiratory disease prevalence. Two hundred and forty-three unco-operative subjects, interviewed at home, had significantly more morning phlegm and a lower vital capacity than carefully matched subjects who attended the central clinic. Fifty-one volunteers had the same prevalence of respiratory disease symptoms and physiological abnormalities as carefully matched subjects drawn from a probability sample of the city. It is concluded that respiratory disease prevalence will be underestimated if calculated from studies of co-operative subjects who attend a clinic. Case-finding by respiratory disease screening clinics will also miss many persons who suffer from chronic bronchitis. PMID:14012836

  18. Structure of the Membrane-intrinsic Nitric Oxide Reductase from Roseobacter denitrificans.

    PubMed

    Crow, Allister; Matsuda, Yuji; Arata, Hiroyuki; Oubrie, Arthur

    2016-06-14

    Membrane-intrinsic nitric oxide reductases (NORs) are key components of bacterial denitrification pathways with a close evolutionary relationship to the cytochrome oxidase (COX) complex found in aerobic respiratory chains. A key distinction between COX and NOR is the identity of the metal directly opposite heme b3 within the active site. In NOR, this metal is iron (FeB), whereas in COX, it is copper (CuB). The purified NOR of Roseobacter denitrificans contains copper and has modest oxidase activity, raising the possibility that a COX-like active site might have independently arisen within the context of a NOR-like protein scaffold. Here we present the crystal structure of the Roseobacter denitrificans NorBC complex and anomalous scattering experiments probing the identity of each metal center. Our results refute the hypothesis that copper occupies the active site and instead reveal a new metal center in the small subunit not seen in any other NOR or COX. PMID:27185533

  19. Recombinant pinoresinol/lariciresinol reductase, recombinant dirigent protein, and methods of use

    DOEpatents

    Lewis, Norman G.; Davin, Laurence B.; Dinkova-Kostova, Albena T.; Fujita, Masayuki; Gang, David R.; Sarkanen, Simo; Ford, Joshua D.

    2001-04-03

    Dirigent proteins and pinoresinol/lariciresinol reductases have been isolated, together with cDNAs encoding dirigent proteins and pinoresinol/lariciresinol reductases. Accordingly, isolated DNA sequences are provided which code for the expression of dirigent proteins and pinoresinol/lariciresinol reductases. In other aspects, replicable recombinant cloning vehicles are provided which code for dirigent proteins or pinoresinol/lariciresinol reductases or for a base sequence sufficiently complementary to at least a portion of dirigent protein or pinoresinol/lariciresinol reductase DNA or RNA to enable hybridization therewith. In yet other aspects, modified host cells are provided that have been transformed, transfected, infected and/or injected with a recombinant cloning vehicle and/or DNA sequence encoding dirigent protein or pinoresinol/lariciresinol reductase. Thus, systems and methods are provided for the recombinant expression of dirigent proteins and/or pinoresinol/lariciresinol reductases.

  20. Recominant Pinoresino-Lariciresinol Reductase, Recombinant Dirigent Protein And Methods Of Use

    DOEpatents

    Lewis, Norman G.; Davin, Laurence B.; Dinkova-Kostova, Albena T.; Fujita, Masayuki , Gang; David R. , Sarkanen; Simo , Ford; Joshua D.

    2003-10-21

    Dirigent proteins and pinoresinol/lariciresinol reductases have been isolated, together with cDNAs encoding dirigent proteins and pinoresinol/lariciresinol reductases. Accordingly, isolated DNA sequences are provided from source species Forsythia intermedia, Thuja plicata, Tsuga heterophylla, Eucommia ulmoides, Linum usitatissimum, and Schisandra chinensis, which code for the expression of dirigent proteins and pinoresinol/lariciresinol reductases. In other aspects, replicable recombinant cloning vehicles are provided which code for dirigent proteins or pinoresinol/lariciresinol reductases or for a base sequence sufficiently complementary to at least a portion of dirigent protein or pinoresinol/lariciresinol reductase DNA or RNA to enable hybridization therewith. In yet other aspects, modified host cells are provided that have been transformed, transfected, infected and/or injected with a recombinant cloning vehicle and/or DNA sequence encoding dirigent protein or pinoresinol/lariciresinol reductase. Thus, systems and methods are provided for the recombinant expression of dirigent proteins and/or pinoresinol/lariciresinol reductases.

  1. Tungstate, a Molybdate Analog Inactivating Nitrate Reductase, Deregulates the Expression of the Nitrate Reductase Structural Gene

    PubMed Central

    Deng, Mingde; Moureaux, Thérèse; Caboche, Michel

    1989-01-01

    Nitrate reductase (NR, EC 1.6.6.1) from higher plants is a homodimeric enzyme carrying a molybdenum cofactor at the catalytic site. Tungsten can be substituted for molybdenum in the cofactor structure, resulting in an inactive enzyme. When nitratefed Nicotiana tabacum plants were grown on a nutrient solution in which tungstate was substituted for molybdate, NR activity in the leaves decreased to a very low level within 24 hours while NR protein accumulated progressively to a level severalfold higher than the control after 6 days. NR mRNA level in molybdate-grown plants exhibited a considerable day-night fluctuation. However, when plants were treated with tungstate, NR mRNA level remained very high. NR activity and protein increased over a 24-hour period when nitrate was added back to N-starved molybdate-grown plants. NR mRNA level increased markedly during the first 2 hours and then decreased. In the presence of tungstate, however, the induction of NR activity by nitrate was totally abolished while high levels of NR protein and mRNA were both induced, and the high level of NR mRNA was maintained over a 10-hour period. These results suggest that the substitution of tungsten for molybdenum in NR complex leads to an overexpression of the NR structural gene. Possible mechanisms involved in this deregulation are discussed. Images Figure 2 Figure 3 Figure 5 PMID:16667015

  2. [Acute respiratory distress syndrome].

    PubMed

    Estenssoro, Elisa; Dubin, Arnaldo

    2016-01-01

    Acute respiratory distress syndrome (ARDS) is an acute respiratory failure produced by an inflammatory edema secondary to increased lung capillary permeability. This causes alveolar flooding and subsequently deep hypoxemia, with intrapulmonary shunt as its most important underlying mechanism. Characteristically, this alteration is unresponsive to high FIO2 and only reverses with end-expiratory positive pressure (PEEP). Pulmonary infiltrates on CXR and CT are the hallmark, together with decreased lung compliance. ARDS always occurs within a week of exposition to a precipitating factor; most frequently pneumonia, shock, aspiration of gastric contents, sepsis, and trauma. In CT scan, the disease is frequently inhomogeneous, with gravitational infiltrates coexisting with normal-density areas and also with hyperaerated parenchyma. Mortality is high (30-60%) especially in ARDS associated with septic shock and neurocritical diseases. The cornerstone of therapy lies in the treatment of the underlying cause and in the use mechanical ventilation which, if inappropriately administered, can lead to ventilator-induced lung injury. Tidal volume = 6 ml/kg of ideal body weight to maintain an end-inspiratory (plateau) pressure = 30 cm H2O ("protective ventilation") is the only variable consistently associated with decreased mortality. Moderate-to-high PEEP levels are frequently required to treat hypoxemia, yet no specific level or titration strategy has improved outcomes. Recently, the use of early prone positioning in patients with PaO2/FIO2 = 150 was associated with increased survival. In severely hypoxemic patients, it may be necessary to use adjuvants of mechanical ventilation as recruitment maneuvers, pressure-controlled modes, neuromuscular blocking agents, and extracorporeal-membrane oxygenation. Fluid restriction appears beneficial. PMID:27576283

  3. Lamin B receptor (LBR) regulates the growth and maturation of myeloid progenitors via its sterol reductase domain: Implications for cholesterol biosynthesis in regulating myelopoiesis

    PubMed Central

    Subramanian, Gayathri; Chaudhury, Pulkit; Malu, Krishnakumar; Fowler, Samantha; Manmode, Rahul; Gotur, Deepali; Zwerger, Monika; Ryan, David; Roberti, Rita; Gaines, Peter

    2011-01-01

    Lamin B receptor (LBR) is a bifunctional nuclear membrane protein with N-terminal lamin B and chromatin binding domains plus a C-terminal sterol Δ14 reductase domain. LBR expression increases during neutrophil differentiation and deficient expression disrupts neutrophil nuclear lobulation characteristic of Pelger-Huët anomaly. Thus LBR plays a critical role in regulating myeloid differentiation, but how the two functional domains of LBR support this role is currently unclear. We previously identified abnormal proliferation and deficient functional maturation of promyelocytes (EPRO cells) derived from EML-ic/ic cells, a myeloid model of ichthyosis (ic) bone marrow that lacks Lbr expression. Here we provide new evidence that cholesterol biosynthesis is important to myeloid cell growth and is supported by the sterol reductase domain of Lbr. Cholesterol biosynthesis inhibitors caused growth inhibition of EML cells that increased in EPRO cells, whereas cells lacking Lbr exhibited complete growth arrest at both stages. Lipid production increased during wild-type neutrophil maturation, but ic/ic cells exhibited deficient levels of lipid and cholesterol production. Ectopic expression of a full length Lbr in EML-ic/ic cells rescued both nuclear lobulation and growth arrest in cholesterol starvation conditions. Lipid production also was rescued, and a deficient respiratory burst was corrected. Expression of just the C-terminal sterol reductase domain of Lbr in ic/ic cells also improved each of these phenotypes. Our data support the conclusion that the sterol Δ14 reductase domain of LBR plays a critical role in cholesterol biosynthesis, and that this process is essential to both myeloid cell growth and functional maturation. PMID:22140257

  4. Dysrhythmias of the respiratory oscillator

    NASA Astrophysics Data System (ADS)

    Paydarfar, David; Buerkel, Daniel M.

    1995-03-01

    Breathing is regulated by a central neural oscillator that produces rhythmic output to the respiratory muscles. Pathological disturbances in rhythm (dysrhythmias) are observed in the breathing pattern of children and adults with neurological and cardiopulmonary diseases. The mechanisms responsible for genesis of respiratory dysrhythmias are poorly understood. The present studies take a novel approach to this problem. The basic postulate is that the rhythm of the respiratory oscillator can be altered by a variety of stimuli. When the oscillator recovers its rhythm after such perturbations, its phase may be reset relative to the original rhythm. The amount of phase resetting is dependent upon stimulus parameters and the level of respiratory drive. The long-range hypothesis is that respiratory dysrhythmias can be induced by stimuli that impinge upon or arise within the respiratory oscillator with certain combinations of strength and timing relative to the respiratory cycle. Animal studies were performed in anesthetized or decerebrate preparations. Neural respiratory rhythmicity is represented by phrenic nerve activity, allowing use of open-loop experimental conditions which avoid negative chemical feedback associated with changes in ventilation. In animal experiments, respiratory dysrhythmias can be induced by stimuli having specific combinations of strength and timing. Newborn animals readily exhibit spontaneous dysrhythmias which become more prominent at lower respiratory drives. In human subjects, swallowing was studied as a physiological perturbation of respiratory rhythm, causing a pattern of phase resetting that is characterized topologically as type 0. Computational studies of the Bonhoeffer-van der Pol (BvP) equations, whose qualitative behavior is representative of many excitable systems, supports a unified interpretation of these experimental findings. Rhythmicity is observed when the BvP model exhibits recurrent periods of excitation alternating with

  5. Differentiating causes of respiratory distress.

    PubMed

    Davis, Mark; Holliday, Jack

    2005-01-01

    Respiratory emergencies will continue to make up a large percentage of our EMS calls. Many of these conditions will be managed in the same fashion early on with a focus on oxygenation and adequate ventilation. Once the ABCs have been stabilized, use your assessment skills to create a differential diagnosis for respiratory distress. Once a field impression has been made, you can better direct a specific treatment. As always, follow your local treatment protocols established by your medical director. Practice your assessment skills and attend as much training as you can on airway and respiratory emergencies. PMID:15743124

  6. Multiplex detection of respiratory pathogens

    DOEpatents

    McBride, Mary; Slezak, Thomas; Birch, James M.

    2012-07-31

    Described are kits and methods useful for detection of respiratory pathogens (influenza A (including subtyping capability for H1, H3, H5 and H7 subtypes) influenza B, parainfluenza (type 2), respiratory syncytial virus, and adenovirus) in a sample. Genomic sequence information from the respiratory pathogens was analyzed to identify signature sequences, e.g., polynucleotide sequences useful for confirming the presence or absence of a pathogen in a sample. Primer and probe sets were designed and optimized for use in a PCR based, multiplexed Luminex assay to successfully identify the presence or absence of pathogens in a sample.

  7. Auscultation of the respiratory system

    PubMed Central

    Sarkar, Malay; Madabhavi, Irappa; Niranjan, Narasimhalu; Dogra, Megha

    2015-01-01

    Auscultation of the lung is an important part of the respiratory examination and is helpful in diagnosing various respiratory disorders. Auscultation assesses airflow through the trachea-bronchial tree. It is important to distinguish normal respiratory sounds from abnormal ones for example crackles, wheezes, and pleural rub in order to make correct diagnosis. It is necessary to understand the underlying pathophysiology of various lung sounds generation for better understanding of disease processes. Bedside teaching should be strengthened in order to avoid erosion in this age old procedure in the era of technological explosion. PMID:26229557

  8. Aldose and aldehyde reductases : structure-function studies on the coenzyme and inhibitor-binding sites.

    SciTech Connect

    El-Kabbani, O.; Old, S. E.; Ginell, S. L.; Carper, D. A.; Biosciences Division; Monash Univ.; NIH

    1999-09-03

    PURPOSE: To identify the structural features responsible for the differences in coenzyme and inhibitor specificities of aldose and aldehyde reductases. METHODS: The crystal structure of porcine aldehyde reductase in complex with NADPH and the aldose reductase inhibitor sorbinil was determined. The contribution of each amino acid lining the coenzyme-binding site to the binding of NADPH was calculated using the Discover package. In human aldose reductase, the role of the non-conserved Pro 216 (Ser in aldehyde reductase) in the binding of coenzyme was examined by site-directed mutagenesis. RESULTS: Sorbinil binds to the active site of aldehyde reductase and is hydrogen-bonded to Trp 22, Tyr 50, His 113, and the non-conserved Arg 312. Unlike tolrestat, the binding of sorbinil does not induce a change in the side chain conformation of Arg 312. Mutation of Pro 216 to Ser in aldose reductase makes the binding of coenzyme more similar to that of aldehyde reductase. CONCLUSIONS: The participation of non-conserved active site residues in the binding of inhibitors and the differences in the structural changes required for the binding to occur are responsible for the differences in the potency of inhibition of aldose and aldehyde reductases. We report that the non-conserved Pro 216 in aldose reductase contributes to the tight binding of NADPH.

  9. Infant respiratory infections and later respiratory hospitalisation in childhood.

    PubMed

    Moore, Hannah C; Hall, Graham L; de Klerk, Nicholas

    2015-11-01

    Acute respiratory infections (ARI) cause significant morbidity in infancy. We sought to quantify the relationship between ARI and development of respiratory morbidity in early childhood. Population-based longitudinal hospitalisation data were linked to perinatal, birth and death records for 145,580 Western Australian children from 1997 to 2002. We conducted Cox regression with sensitivity analyses to quantify the risk of recurrent ARI in infancy for respiratory hospitalisation after the age of 3 years. ARI in infancy was significantly related to respiratory hospitalisation before (hazard ratio (HR) 3.5, 95% CI 3.1-3.8) and after (HR 3.0, 95% CI 2.6-3.4) adjusting for known risk factors including maternal smoking during pregnancy, season of birth, delivery mode and gestational age. We noted a dose response with the number and length of infant ARI hospitalisations and increasing risk with no effect modification by gestational age. Results were similar when later respiratory hospitalisations were restricted to asthma hospitalisations only. Recurrent hospitalisations for ARI in infancy significantly increase the risk of respiratory morbidity and asthma requiring hospitalisation after the age of 3 years in a dose-response fashion. The increase in relative risk is not modified by gestational age. Efforts to reduce the occurrence of infant ARI are likely to have significant public health benefits. PMID:26293501

  10. Involvement of nitrate reductase in auxin-induced NO synthesis

    PubMed Central

    Erdei, L

    2008-01-01

    It is well known for a long time, that nitric oxide (NO) functions in variable physiological and developmental processes in plants, however the source of this signaling molecule in the diverse plant responses is very obscure.1 Although existance of nitric oxide sythase (NOS) in plants is still questionable, LNMMA (NG-monomethyl-L-arginine)-sensitive NO generation was observed in different plant species.2,3 In addition, nitrate reductase (NR) is confirmed to have a major role as source of NO.4,5 This multifaced molecule acts also in auxin-induced lateral root (LR) formation, since exogenous auxin enhanced NO levels in regions of Arabidopsis LR initiatives. Our results pointed out the involvement of nitrate reductase enzyme in auxin-induced NO formation. In this addendum, we speculate on auxin-induced NO production in lateral root primordial formation. PMID:19704423

  11. Involvement of nitrate reductase in auxin-induced NO synthesis.

    PubMed

    Kolbert, Zsuzsanna; Erdei, L

    2008-11-01

    It is well known for a long time, that nitric oxide (NO) functions in variable physiological and developmental processes in plants, however the source of this signaling molecule in the diverse plant responses is very obscure.1 Although existance of nitric oxide sythase (NOS) in plants is still questionable, LNMMA (N(G)-monomethyl-L-arginine)-sensitive NO generation was observed in different plant species.2,3 In addition, nitrate reductase (NR) is confirmed to have a major role as source of NO.4,5 This multifaced molecule acts also in auxin-induced lateral root (LR) formation, since exogenous auxin enhanced NO levels in regions of Arabidopsis LR initiatives. Our results pointed out the involvement of nitrate reductase enzyme in auxin-induced NO formation. In this addendum, we speculate on auxin-induced NO production in lateral root primordial formation. PMID:19704423

  12. Methyltetrahydrofolate reductase polymorphism influences onset of Huntington's disease.

    PubMed

    Brune, N; Andrich, J; Gencik, M; Saft, C; Müller, Th; Valentin, S; Przuntek, H; Epplen, J T

    2004-01-01

    Onset of Huntington's disease (HD) negatively correlates with CAG repeat length of the HD gene, which encodes the protein huntingtin. This protein interacts with the homocysteine metabolizing enzyme cystathionine betasynthase (CBS). Objective of this study was to analyze the impact of CAG repeats, polymorphisms of various homocysteine metabolizing enzymes, like CBS, Methyltetrahydrofolate Reductase (MTHTR), Methionine Synthase Reductase (MSR) and methionine synthase (MS) on HD onset in 171 patients. The significant impact of CAG repeats on HD onset (chi2= 25.54, FG = 4, p<0.0001) with a significant correlation between both (R= -0.521, p=0.01) was obvious. HD patients with the homozygous MTHFR-1298-CC significantly (p = 0.024) earlier experienced HD symptoms. There was no influence demonstrable of CBS, MSR and MS. Determination of MTHFR polymorphisms and CAG repeats enables screening for subjects with putative early HD onset in order to study neuroprotective compounds in their efficacy to delay HD symptoms. PMID:15354395

  13. Respiratory Conditions Update: Asthma.

    PubMed

    Zeller, Timothy A

    2016-09-01

    Asthma is a chronic respiratory disease characterized by chronic airway inflammation and variable expiratory airflow limitation. Related clinical features include wheezing, dyspnea, chest tightness, and cough that worsens at night or in the early morning, and that varies over time and in intensity. A finding of variable expiratory airflow limitation on spirometry confirms the diagnosis. A forced expiratory volume in 1 second to forced vital capacity ratio less than the level predicted for the patient's age is suggestive of airflow limitation. Variability also must be confirmed. Updated guidelines recommend control-based management administered in a stepwise manner, with goals of achieving symptom control and minimizing the risks of exacerbations, future fixed airway limitation, and adverse effects of therapy. There is good evidence for the effectiveness of asthma education and self-management plans. Short-acting bronchodilators should be used as needed for symptom relief, with the addition of an inhaled corticosteroid early as maintenance therapy if symptoms are not well controlled. If asthma remains uncontrolled despite therapy, patients should be referred for more specialized treatment. Biomarkers, biologic drugs, and endoscopic treatments are being studied in the management of severe asthma, and ongoing research may determine which patients might benefit most from these emerging therapies. PMID:27576231

  14. Achromobacter respiratory infections.

    PubMed

    Swenson, Colin E; Sadikot, Ruxana T

    2015-02-01

    Achromobacteria are ubiquitous environmental organisms that may also become opportunistic pathogens in certain conditions, such as cystic fibrosis, hematologic and solid organ malignancies, renal failure, and certain immune deficiencies. Some members of this genus, such as xylosoxidans, cause primarily nosocomially acquired infections affecting multiple organ systems, including the respiratory tract, urinary tract, and, less commonly, the cardiovascular and central nervous systems. Despite an increasing number of published case reports and literature reviews suggesting a global increase in achromobacterial disease, most clinicians remain uncertain of the organism's significance when clinically isolated. Moreover, effective treatment can be challenging due to the organism's inherent and acquired multidrug resistance patterns. We reviewed all published cases to date of non-cystic fibrosis achromobacterial lung infections to better understand the organism's pathogenic potential and drug susceptibilities. We found that the majority of these cases were community acquired, typically presenting as pneumonias (88%), and were most frequent in individuals with hematologic and solid organ malignancies. Our findings also suggest that achromobacterial lung infections are difficult to treat, but respond well to extended-spectrum penicillins and cephalosporins, such as ticarcillin, piperacillin, and cefoperazone. PMID:25706494

  15. Acute Respiratory Distress Syndrome.

    PubMed

    Yadam, Suman; Bihler, Eric; Balaan, Marvin

    2016-01-01

    Acute respiratory distress syndrome (ARDS) is a serious inflammatory disorder with high mortality. Its main pathologic mechanism seems to result from increased alveolar permeability. Its definition has also changed since first being described according to the Berlin definition, which now classifies ARDS on a severity scale based on PaO2 (partial pressure of oxygen, arterial)/FIO2 (fraction of inspired oxygen) ratio. The cornerstone of therapy was found to be a low tidal volume strategy featuring volumes of 6 to 8 mL per kg of ideal body weight that has been shown to have decreased mortality as proven by the ARDSnet trials. There are other areas of treatment right now that include extracorporeal membrane oxygenation, as well for severe refractory hypoxemia. Other methods that include prone positioning for ventilation have also shown improvements in oxygenation. Positive end-expiratory pressure with lung recruitment maneuvers has also been found to be helpful. Other therapies that include vasodilators and neuromuscular agents are still being explored and need further studies to define their role in ARDS. PMID:26919679

  16. [Major respiratory tract traumas].

    PubMed

    Petrov, D; Obretenov, E; Kalaĭdzhiev, G; Plochev, M; Kostadinov, D

    2002-01-01

    Between 1988 and 2000 a total of 33 patients with traumatic tracheobronchial lesions were diagnosed and treated. The trauma was penetrating in 7 (stab and gun-shot), blunt in 10 (car accidents, compression and falling from heights) and iatrogenic in 16 of them (postintubational--15, after foreign body extraction--1). The main clinical and radiological features were subcutaneous emphysema, hemoptysis, respiratory insufficiency, pneumomediastinum and pneumothorax. The diagnosis was confirmed in all patients by early fiberoptic bronchoscopy. "Watch and see" tactics with massive antibiotics therapy was followed in 4 (12%) patients. A surgical treatment was carried out in 29 (88%) patients as follows: simple repair--19 (58%), left pneumonectomy--2 (6%), tracheal resection and anastomosis "end to end"--2 (6%), tracheostomy--1 (3%), thoracocenthesis and drainage--3 (9%) and cervical mediastinotomy--2 (6%). The operative mortality was 9%. The cause of death in these 3 patients were associated brain and spinal cord injuries. In the rest of patients the early and long-term postoperative results were considered very good. PMID:12515032

  17. [Vaccinations in respiratory medicine].

    PubMed

    Lode, H M; Stahlmann, R

    2015-09-01

    Vaccinations are the most successful and cost-effective measures for prevention of infections. Important pathogens of respiratory tract infections (e.g. influenza viruses and pneumococci) can be effectively treated by vaccinations. The seasonal trivalent and recently now quadrivalent influenza vaccines include antigens from influenza A and B type viruses, which have to be modified annually oriented to the circulating strains. The effective protection by influenza vaccination varies considerably (too short protection time, mismatch); therefore, administration late in the year is the best approach (November/December). Two pneumococcal vaccines are recommended for adults: the over 30-year-old 23-valent polysaccharide vaccine (PPV23) and the 4-year-old 13-valent conjugate vaccine (PCV13). The immunological and clinical efficacy of PPV23 is controversially discussed; however, a moderate reduction of invasive pneumococcal infections is widely accepted. The PCV13 stimulates a T-cell response and has currently demonstrated its clinical efficacy in an impressive study (CAPiTA). The problem of PCV13 is the relatively limited coverage of only 47% of the currently circulating invasive pneumococcal serotypes. PMID:26330051

  18. Structural Basis for Substrate Specificity in Human Monomeric Carbonyl Reductases

    PubMed Central

    El-Hawari, Yasser; Dunford, James E.; Kochan, Grazyna; Wsol, Vladimir; Martin, Hans-Joerg; Maser, Edmund; Oppermann, Udo

    2009-01-01

    Carbonyl reduction constitutes a phase I reaction for many xenobiotics and is carried out in mammals mainly by members of two protein families, namely aldo-keto reductases and short-chain dehydrogenases/reductases. In addition to their capacity to reduce xenobiotics, several of the enzymes act on endogenous compounds such as steroids or eicosanoids. One of the major carbonyl reducing enzymes found in humans is carbonyl reductase 1 (CBR1) with a very broad substrate spectrum. A paralog, carbonyl reductase 3 (CBR3) has about 70% sequence identity and has not been sufficiently characterized to date. Screening of a focused xenobiotic compound library revealed that CBR3 has narrower substrate specificity and acts on several orthoquinones, as well as isatin or the anticancer drug oracin. To further investigate structure-activity relationships between these enzymes we crystallized CBR3, performed substrate docking, site-directed mutagenesis and compared its kinetic features to CBR1. Despite high sequence similarities, the active sites differ in shape and surface properties. The data reveal that the differences in substrate specificity are largely due to a short segment of a substrate binding loop comprising critical residues Trp229/Pro230, Ala235/Asp236 as well as part of the active site formed by Met141/Gln142 in CBR1 and CBR3, respectively. The data suggest a minor role in xenobiotic metabolism for CBR3. Enhanced version This article can also be viewed as an enhanced version in which the text of the article is integrated with interactive 3D representations and animated transitions. Please note that a web plugin is required to access this enhanced functionality. Instructions for the installation and use of the web plugin are available in Text S1. PMID:19841672

  19. Two fatty acyl reductases involved in moth pheromone biosynthesis.

    PubMed

    Antony, Binu; Ding, Bao-Jian; Moto, Ken'Ichi; Aldosari, Saleh A; Aldawood, Abdulrahman S

    2016-01-01

    Fatty acyl reductases (FARs) constitute an evolutionarily conserved gene family found in all kingdoms of life. Members of the FAR gene family play diverse roles, including seed oil synthesis, insect pheromone biosynthesis, and mammalian wax biosynthesis. In insects, FAR genes dedicated to sex pheromone biosynthesis (pheromone-gland-specific fatty acyl reductase, pgFAR) form a unique clade that exhibits substantial modifications in gene structure and possesses unique specificity and selectivity for fatty acyl substrates. Highly selective and semi-selective 'single pgFARs' produce single and multicomponent pheromone signals in bombycid, pyralid, yponomeutid and noctuid moths. An intriguing question is how a 'single reductase' can direct the synthesis of several fatty alcohols of various chain lengths and isomeric forms. Here, we report two active pgFARs in the pheromone gland of Spodoptera, namely a semi-selective, C14:acyl-specific pgFAR and a highly selective, C16:acyl-specific pgFAR, and demonstrate that these pgFARs play a pivotal role in the formation of species-specific signals, a finding that is strongly supported by functional gene expression data. The study envisages a new area of research for disclosing evolutionary changes associated with C14- and C16-specific FARs in moth pheromone biosynthesis. PMID:27427355

  20. Aldose reductase inhibitory activity of compounds from Zea mays L.

    PubMed

    Kim, Tae Hyeon; Kim, Jin Kyu; Kang, Young-Hee; Lee, Jae-Yong; Kang, Il Jun; Lim, Soon Sung

    2013-01-01

    Aldose reductase (AR) inhibitors have a considerable therapeutic potential against diabetes complications and do not increase the risk of hypoglycemia. Through bioassay-guided fractionation of an EtOH extract of the kernel from purple corn (Zea mays L.), 7 nonanthocyanin phenolic compounds (compound 1-7) and 5 anthocyanins (compound 8-12) were isolated. These compounds were investigated by rat lens aldose reductase (RLAR) inhibitory assays. Kinetic analyses of recombinant human aldose reductase (rhAR) were performed, and intracellular galactitol levels were measured. Hirsutrin, one of 12 isolated compounds, showed the most potent RLAR inhibitory activity (IC(50), 4.78 μ M). In the kinetic analyses using Lineweaver-Burk plots of 1/velocity and 1/substrate concentration, hirsutrin showed competitive inhibition against rhAR. Furthermore, hirsutrin inhibited galactitol formation in rat lens and erythrocytes sample incubated with a high concentration of galactose; this finding indicates that hirsutrin may effectively prevent osmotic stress in hyperglycemia. Therefore, hirsutrin derived from Zea mays L. may be a potential therapeutic agent against diabetes complications. PMID:23586057

  1. Aldo-Keto Reductases 1B in Adrenal Cortex Physiology

    PubMed Central

    Pastel, Emilie; Pointud, Jean-Christophe; Martinez, Antoine; Lefrançois-Martinez, A. Marie

    2016-01-01

    Aldose reductase (AKR1B) proteins are monomeric enzymes, belonging to the aldo-keto reductase (AKR) superfamily. They perform oxidoreduction of carbonyl groups from a wide variety of substrates, such as aliphatic and aromatic aldehydes or ketones. Due to the involvement of human aldose reductases in pathologies, such as diabetic complications and cancer, AKR1B subgroup enzymatic properties have been extensively characterized. However, the issue of AKR1B function in non-pathologic conditions remains poorly resolved. Adrenal activities generated large amount of harmful aldehydes from lipid peroxidation and steroidogenesis, including 4-hydroxynonenal (4-HNE) and isocaproaldehyde (4-methylpentanal), which can both be reduced by AKR1B proteins. More recently, some AKR1B isoforms have been shown to be endowed with prostaglandin F synthase (PGFS) activity, suggesting that, in addition to possible scavenger function, they could instigate paracrine signals. Interestingly, the adrenal gland is one of the major sites for human and murine AKR1B expression, suggesting that their detoxifying/signaling activity could be specifically required for the correct handling of adrenal function. Moreover, chronic effects of ACTH result in a coordinated regulation of genes encoding the steroidogenic enzymes and some AKR1B isoforms. This review presents the molecular mechanisms accounting for the adrenal-specific expression of some AKR1B genes. Using data from recent mouse genetic models, we will try to connect their enzymatic properties and regulation with adrenal functions. PMID:27499746

  2. Using chemical approaches to study selenoproteins - focus on thioredoxin reductases

    PubMed Central

    Hondal, Robert J.

    2009-01-01

    The study of selenocysteine-containing proteins is difficult due to the problems associated with the heterologous production of these proteins. These problems are due to the intricate recoding mechanism used by cells to translate the UGA codon as a sense codon for selenocysteine. The process is further complicated by the fact that eukaryotes and prokaryotes have different UGA recoding machineries. This review focuses on chemical approaches to produce selenoproteins and study the mechanism of selenoenzymes. The use of intein-mediated peptide ligation is discussed with respect to the production of the mammalian selenoenzymes thioredoxin reductase and selenoprotein R, also known as methionine sulfoxide reductase B1. New methods for removing protecting groups from selenocysteine post-synthesis and methods for selenosulfide/diselenide formation are also reviewed. Chemical approaches have also been used to study the enzymatic mechanism of thioredoxin reductase. The approach divides the enzyme into two modules, a large protein module lacking selenocysteine and a small, synthetic selenocysteine-containing peptide. Study of this semisynthetic enzyme has revealed three distinct enzymatic pathways that depend on the properties of the substrate. The enzyme utilizes a macromolecular mechanism for protein substrates, a second mechanism for small molecule substrates and a third pathway for selenium-containing substrates such as selenocystine. PMID:19406205

  3. CADMIUM AS A RESPIRATORY TOXICANT

    EPA Science Inventory

    Cadmium is a major respiratory toxicant as evidenced by numerous human and animal studies. Controlled animal inhalation studies provide supporting evidence to the associations observed in epidemiological studies that Cd has the potential to cause lung fibrosis, emphysema, cancer,...

  4. Respiratory Therapy Technology Program Standards.

    ERIC Educational Resources Information Center

    Georgia Univ., Athens. Dept. of Vocational Education.

    This publication contains statewide standards for the respiratory therapy technology program in Georgia. The standards are divided into 12 categories: Foundations (philosophy, purpose, goals, program objectives, availability, evaluation; Admissions (admission requirements, provisional admission requirements, recruitment, evaluation and planning);…

  5. Middle East Respiratory Syndrome (MERS)

    MedlinePlus

    Middle East Respiratory Syndrome Coronavirus; MERS-CoV; Novel coronavirus; nCoV ... Centers for Disease Control and Prevention. Middle East ... 2, 2015. www.cdc.gov/coronavirus/mers/faq.html . Accessed April ...

  6. How Is Respiratory Failure Treated?

    MedlinePlus

    ... Once your doctor figures out what's causing your respiratory failure, he or she will plan how to treat that disease or condition. Treatments may include medicines, procedures, and other therapies. Rate This Content: NEXT >> Updated: December 19, 2011 Twitter ...

  7. Acute respiratory failure in pregnancy.

    PubMed

    Lapinsky, Stephen E

    2015-09-01

    Respiratory failure affects up to 0.2% of pregnancies, more commonly in the postpartum period. Altered maternal respiratory physiology affects the assessment and management of these patients. Respiratory failure may result from pregnancy-specific conditions such as preeclampsia, amniotic fluid embolism or peripartum cardiomyopathy. Pregnancy may increase the risk or severity of other conditions, including thromboembolism, asthma, viral pneumonitis, and gastric acid aspiration. Management during pregnancy is similar to the nonpregnant patient. Endotracheal intubation in pregnancy carries an increased risk, due to airway edema and rapid oxygen desaturation following apnea. Few data are available to direct prolonged mechanical ventilation in pregnancy. Chest wall compliance is reduced, perhaps permitting slightly higher airway pressures. Optimizing oxygenation is important, but data on the use of permissive hypercapnia are limited. Delivery of the fetus does not always improve maternal respiratory function, but should be considered if benefit to the fetus is anticipated. PMID:27512467

  8. Human respiratory mechanics demonstration model.

    PubMed

    Anderson, Janelle; Goplen, Chris; Murray, Lynn; Seashore, Kristen; Soundarrajan, Malini; Lokuta, Andrew; Strang, Kevin; Chesler, Naomi

    2009-03-01

    Respiratory mechanics is a difficult topic for instructors and students alike. Existing respiratory mechanics models are limited in their abilities to demonstrate any effects of rib cage movement on alveolar and intrapleural pressures. We developed a model that can be used in both large and small classroom settings. This model contains digital pressure displays and computer integration for real-time demonstration of pressure changes that correspond to the different phases of breathing. Moving the simulated diaphragm and rib cage causes a volume change that results in pressure changes visible on the digital sensors and computer display. Device testing confirmed the model's ability to accurately demonstrate pressure changes in proportion to physiological values. Classroom testing in 427 surveyed students showed improved understanding of respiratory concepts (P < 0.05). We conclude that our respiratory mechanics model is a valuable instructional tool and provide detailed instructions for those who would like to create their own. PMID:19261761

  9. ARDS (Acute Respiratory Distress Syndrome)

    MedlinePlus

    ... Twitter. What Is ARDS? ARDS, or acute respiratory distress syndrome, is a lung condition that leads to low oxygen levels in the blood. ARDS can be life threatening because your body's organs need oxygen-rich ...

  10. In silico analysis of bacterial arsenic islands reveals remarkable synteny and functional relatedness between arsenate and phosphate

    PubMed Central

    Li, Hang; Li, Mingshun; Huang, Yinyan; Rensing, Christopher; Wang, Gejiao

    2013-01-01

    In order to construct a more universal model for understanding the genetic requirements for bacterial AsIII oxidation, an in silico examination of the available sequences in the GenBank was assessed and revealed 21 conserved 5–71 kb arsenic islands within phylogenetically diverse bacterial genomes. The arsenic islands included the AsIII oxidase structural genes aioBA, ars operons (e.g., arsRCB) which code for arsenic resistance, and pho, pst, and phn genes known to be part of the classical phosphate stress response and that encode functions associated with regulating and acquiring organic and inorganic phosphorus. The regulatory genes aioXSR were also an island component, but only in Proteobacteria and orientated differently depending on whether they were in α-Proteobacteria or β-/γ-Proteobacteria. Curiously though, while these regulatory genes have been shown to be essential to AsIII oxidation in the Proteobacteria, they are absent in most other organisms examined, inferring different regulatory mechanism(s) yet to be discovered. Phylogenetic analysis of the aio, ars, pst, and phn genes revealed evidence of both vertical inheritance and horizontal gene transfer (HGT). It is therefore likely the arsenic islands did not evolve as a whole unit but formed independently by acquisition of functionally related genes and operons in respective strains. Considering gene synteny and structural analogies between arsenate and phosphate, we presumed that these genes function together in helping these microbes to be able to use even low concentrations of phosphorus needed for vital functions under high concentrations of arsenic, and defined these sequences as the arsenic islands. PMID:24312089

  11. Adsorption and desorption of arsenate on sandy sediments from contaminated and uncontaminated saturated zones: Kinetic and equilibrium modeling.

    PubMed

    Hafeznezami, Saeedreza; Zimmer-Faust, Amity G; Dunne, Aislinn; Tran, Tiffany; Yang, Chao; Lam, Jacquelyn R; Reynolds, Matthew D; Davis, James A; Jay, Jennifer A

    2016-08-01

    Application of empirical models to adsorption of contaminants on natural heterogeneous sorbents is often challenging due to the uncertainty associated with fitting experimental data and determining adjustable parameters. Sediment samples from contaminated and uncontaminated portions of a study site in Maine, USA were collected and investigated for adsorption of arsenate [As(V)]. Two kinetic models were used to describe the results of single solute batch adsorption experiments. Piecewise linear regression of data linearized to fit pseudo-first order kinetic model resulted in two distinct rates and a cutoff time point of 14-19 h delineating the biphasic behavior of solute adsorption. During the initial rapid adsorption stage, an average of 60-80% of the total adsorption took place. Pseudo-second order kinetic models provided the best fit to the experimental data (R(2) > 0.99) and were capable of describing the adsorption over the entire range of experiments. Both Langmuir and Freundlich isotherms provided reasonable fits to the adsorption data at equilibrium. Langmuir-derived maximum adsorption capacity (St) of the studied sediments ranged between 29 and 97 mg/kg increasing from contaminated to uncontaminated sites. Solid phase As content of the sediments ranged from 3.8 to 10 mg/kg and the As/Fe ratios were highest in the amorphous phase. High-pH desorption experiments resulted in a greater percentage of solid phase As released into solution from experimentally-loaded sediments than from the unaltered samples suggesting that As(V) adsorption takes place on different reversible and irreversible surface sites. PMID:27218893

  12. Behavioural and Physiological Responses of Gammarus pulex Exposed to Cadmium and Arsenate at Three Temperatures: Individual and Combined Effects

    PubMed Central

    Vellinger, Céline; Felten, Vincent; Sornom, Pascal; Rousselle, Philippe; Beisel, Jean-Nicolas; Usseglio-Polatera, Philippe

    2012-01-01

    This study aimed at investigating both the individual and combined effects of cadmium (Cd) and arsenate (AsV) on the physiology and behaviour of the Crustacean Gammarus pulex at three temperatures (5, 10 and15°C). G. pulex was exposed during 96 h to (i) two [Cd] alone, (ii) two [AsV] alone, and (iii) four combinations of [Cd] and [AsV] to obtain a complete factorial plane. After exposure, survival, [AsV] or [Cd] in body tissues, behavioural (ventilatory and locomotor activities) and physiological responses (iono-regulation of [Na+] and [Cl−] in haemolymph) were examined. The interactive effects (antagonistic, additive or synergistic) of binary mixtures were evaluated for each tested temperature using a predictive model for the theoretically expected interactive effect of chemicals. In single metal exposure, both the internal metal concentration in body tissues and the mortality rate increased along metallic gradient concentration. Cd alone significantly impaired both [Na+] and [Cl−] while AsV alone had a weak impact only on [Cl−]. The behavioural responses of G. pulex declined with increasing metal concentration suggesting a reallocation of energy from behavioural responses to maintenance functions. The interaction between AsV and Cd was considered as ‘additive’ for all the tested binary mixtures and temperatures (except for the lowest combination at 10°C considered as “antagonistic”). In binary mixtures, the decrease in both ventilatory and locomotor activities and the decline in haemolymphatic [Cl−] were amplified when respectively compared to those observed with the same concentrations of AsV or Cd alone. However, the presence of AsV decreased the haemolymphatic [Na+] loss when G. pulex was exposed to the lowest Cd concentration. Finally, the observed physiological and behavioural effects (except ventilation) in G. pulex exposed to AsV and/or Cd were exacerbated under the highest temperature. The discussion encompasses both the toxicity

  13. Arsenic (+ 3 oxidation state) methyltransferase genotype affects steady-state distribution and clearance of arsenic in arsenate-treated mice

    SciTech Connect

    Hughes, Michael F.; Edwards, Brenda C.; Herbin-Davis, Karen M.; Saunders, Jesse; Styblo, Miroslav; Thomas, David J.

    2010-12-15

    Arsenic (+ 3 oxidation state) methyltransferase (As3mt) catalyzes formation of mono-, di-, and tri-methylated metabolites of inorganic arsenic. Distribution and retention of arsenic were compared in adult female As3mt knockout mice and wild-type C57BL/6 mice using a regimen in which mice received daily oral doses of 0.5 mg of arsenic as arsenate per kilogram of body weight. Regardless of genotype, arsenic body burdens attained steady state after 10 daily doses. At steady state, arsenic body burdens in As3mt knockout mice were 16 to 20 times greater than in wild-type mice. During the post dosing clearance period, arsenic body burdens declined in As3mt knockout mice to {approx} 35% and in wild-type mice to {approx} 10% of steady-state levels. Urinary concentration of arsenic was significantly lower in As3mt knockout mice than in wild-type mice. At steady state, As3mt knockout mice had significantly higher fractions of the body burden of arsenic in liver, kidney, and urinary bladder than did wild-type mice. These organs and lung had significantly higher arsenic concentrations than did corresponding organs from wild-type mice. Inorganic arsenic was the predominant species in tissues of As3mt knockout mice; tissues from wild-type mice contained mixtures of inorganic arsenic and its methylated metabolites. Diminished capacity for arsenic methylation in As3mt knockout mice prolongs retention of inorganic arsenic in tissues and affects whole body clearance of arsenic. Altered retention and tissue tropism of arsenic in As3mt knockout mice could affect the toxic or carcinogenic effects associated with exposure to this metalloid or its methylated metabolites.

  14. Investigating the Proton Donor in the NO Reductase from Paracoccus denitrificans.

    PubMed

    Ter Beek, Josy; Krause, Nils; Ädelroth, Pia

    2016-01-01

    Variant nomenclature: the variants were made in the NorB subunit if not indicated by the superscript c, which are variants in the NorC subunit (e.g. E122A = exchange of Glu-122 in NorB for an Ala, E71cD; exchange of Glu-71 in NorC for an Asp). Bacterial NO reductases (NORs) are integral membrane proteins from the heme-copper oxidase superfamily. Most heme-copper oxidases are proton-pumping enzymes that reduce O2 as the last step in the respiratory chain. With electrons from cytochrome c, NO reductase (cNOR) from Paracoccus (P.) denitrificans reduces NO to N2O via the following reaction: 2NO+2e-+2H+→N2O+H2O. Although this reaction is as exergonic as O2-reduction, cNOR does not contribute to the electrochemical gradient over the membrane. This means that cNOR does not pump protons and that the protons needed for the reaction are taken from the periplasmic side of the membrane (since the electrons are donated from this side). We previously showed that the P. denitrificans cNOR uses a single defined proton pathway with residues Glu-58 and Lys-54 from the NorC subunit at the entrance. Here we further strengthened the evidence in support of this pathway. Our further aim was to define the continuation of the pathway and the immediate proton donor for the active site. To this end, we investigated the region around the calcium-binding site and both propionates of heme b3 by site directed mutagenesis. Changing single amino acids in these areas often had severe effects on cNOR function, with many variants having a perturbed active site, making detailed analysis of proton transfer properties difficult. Our data does however indicate that the calcium ligation sphere and the region around the heme b3 propionates are important for proton transfer and presumably contain the proton donor. The possible evolutionary link between the area for the immediate donor in cNOR and the proton loading site (PLS) for pumped protons in oxygen-reducing heme-copper oxidases is discussed. PMID

  15. Investigating the Proton Donor in the NO Reductase from Paracoccus denitrificans

    PubMed Central

    ter Beek, Josy; Krause, Nils; Ädelroth, Pia

    2016-01-01

    Variant nomenclature: the variants were made in the NorB subunit if not indicated by the superscript c, which are variants in the NorC subunit (e.g. E122A = exchange of Glu-122 in NorB for an Ala, E71cD; exchange of Glu-71 in NorC for an Asp). Bacterial NO reductases (NORs) are integral membrane proteins from the heme-copper oxidase superfamily. Most heme-copper oxidases are proton-pumping enzymes that reduce O2 as the last step in the respiratory chain. With electrons from cytochrome c, NO reductase (cNOR) from Paracoccus (P.) denitrificans reduces NO to N2O via the following reaction: 2NO+2e-+2H+→N2O+H2O. Although this reaction is as exergonic as O2-reduction, cNOR does not contribute to the electrochemical gradient over the membrane. This means that cNOR does not pump protons and that the protons needed for the reaction are taken from the periplasmic side of the membrane (since the electrons are donated from this side). We previously showed that the P. denitrificans cNOR uses a single defined proton pathway with residues Glu-58 and Lys-54 from the NorC subunit at the entrance. Here we further strengthened the evidence in support of this pathway. Our further aim was to define the continuation of the pathway and the immediate proton donor for the active site. To this end, we investigated the region around the calcium-binding site and both propionates of heme b3 by site directed mutagenesis. Changing single amino acids in these areas often had severe effects on cNOR function, with many variants having a perturbed active site, making detailed analysis of proton transfer properties difficult. Our data does however indicate that the calcium ligation sphere and the region around the heme b3 propionates are important for proton transfer and presumably contain the proton donor. The possible evolutionary link between the area for the immediate donor in cNOR and the proton loading site (PLS) for pumped protons in oxygen-reducing heme-copper oxidases is discussed. PMID

  16. Climate Change and Respiratory Infections.

    PubMed

    Mirsaeidi, Mehdi; Motahari, Hooman; Taghizadeh Khamesi, Mojdeh; Sharifi, Arash; Campos, Michael; Schraufnagel, Dean E

    2016-08-01

    The rate of global warming has accelerated over the past 50 years. Increasing surface temperature is melting glaciers and raising the sea level. More flooding, droughts, hurricanes, and heat waves are being reported. Accelerated changes in climate are already affecting human health, in part by altering the epidemiology of climate-sensitive pathogens. In particular, climate change may alter the incidence and severity of respiratory infections by affecting vectors and host immune responses. Certain respiratory infections, such as avian influenza and coccidioidomycosis, are occurring in locations previously unaffected, apparently because of global warming. Young children and older adults appear to be particularly vulnerable to rapid fluctuations in ambient temperature. For example, an increase in the incidence in childhood pneumonia in Australia has been associated with sharp temperature drops from one day to the next. Extreme weather events, such as heat waves, floods, major storms, drought, and wildfires, are also believed to change the incidence of respiratory infections. An outbreak of aspergillosis among Japanese survivors of the 2011 tsunami is one such well-documented example. Changes in temperature, precipitation, relative humidity, and air pollution influence viral activity and transmission. For example, in early 2000, an outbreak of Hantavirus respiratory disease was linked to a local increase in the rodent population, which in turn was attributed to a two- to threefold increase in rainfall before the outbreak. Climate-sensitive respiratory pathogens present challenges to respiratory health that may be far greater in the foreseeable future. PMID:27300144

  17. Structural characterization of poorly-crystalline scorodite, iron(III)-arsenate co-precipitates and uranium mill neutralized raffinate solids using X-ray absorption fine structure spectroscopy

    SciTech Connect

    Chen, N; Jiang, D T; Cutler, J; Kotzer, T; Jia, Y F; Demopoulos, G P; Rowson, J W

    2009-12-01

    X-ray absorption fine structure (XAFS) is used to characterize the mineralogy of the iron(III)-arsenate(V) precipitates produced during the raffinate (aqueous effluent) neutralization process at the McClean Lake uranium mill in northern Saskatchewan, Canada. To facilitate the structural characterization of the precipitated solids derived from the neutralized raffinate, a set of reference compounds were synthesized and analyzed. The reference compounds include crystalline scorodite, poorly-crystalline scorodite, iron(III)-arsenate co-precipitates obtained under different pH conditions, and arsenate-adsorbed on goethite. The poorly-crystalline scorodite (prepared at pH 4 with Fe/As = 1) has similar As local structure as that of crystalline scorodite. Both As and Fe K-edge XAFS of poorly-crystalline scorodite yield consistent results on As-Fe (or Fe-As) shell. From As K-edge analysis the As-Fe shell has an inter-atomic distance of 3.33 ± 0.02 Å and coordination number of 3.2; while from Fe K-edge analysis the Fe-As distance and coordination number are 3.31 ± 0.02 Å and 3.8, respectively. These are in contrast with the typical arsenate adsorption on bidentate binuclear sites on goethite surfaces, where the As-Fe distance is 3.26 ± 0.03 Å and coordination number is close to 2. A similar local structure identified in the poorly-crystalline scorodite is also found in co-precipitation solids (Fe(III)/As(V) = 3) when precipitated at the same pH (pH = 4): As-Fe distance 3.30 ± 0.03 Å and coordination number 3.9; while at pH = 8 the co-precipitate has As-Fe distance of 3.27 ± 0.03 Å and coordination number about 2, resembling more closely the adsorption case. The As local structure in the two neutralized raffinate solid series (precipitated at pH values up to 7) closely resembles that in the poorly-crystalline scorodite. All of the raffinate solids have the same As-Fe inter-atomic distance as that in the poorly-crystalline scorodite, and a systematic decrease in the

  18. Draft Genome Sequence of Ochrobactrum pseudogrignonense Strain CDB2, a Highly Efficient Arsenate-Resistant Soil Bacterium from Arsenic-Contaminated Cattle Dip Sites

    PubMed Central

    Yang, Yiren; Yu, Xuefei

    2013-01-01

    We report the 4.97-Mb draft genome sequence of a highly efficient arsenate-resistant bacterium, Ochrobactrum sp. strain CDB2. It contains a novel arsenic resistance (ars) operon (arsR-arsC1-ACR3-arsC2-arsH-mfs) and two non-operon-associated ars genes, arsC3 and arsB. The genome information will aid in the understanding of the arsenic resistance mechanism of this and other bacterial species. PMID:23599296

  19. Biogeochemical reductive release of soil embedded arsenate around a crater area (Guandu) in northern Taiwan using X-ray absorption near-edge spectroscopy.

    PubMed

    Chiang, Kai-Ying; Chen, Tsan-Yao; Lee, Chih-Hao; Lin, Tsang-Lang; Wang, Ming-Kuang; Jang, Ling-Yun; Lee, Jyh-Fu

    2013-03-01

    This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan, using a combination of X-ray absorption near-edge structure (XANES) and atomic absorption spectrometry. Total arsenic (As) concentrations in the soil were more than 200 mg/kg. Over four months of laboratory experiments, less than 0.8% As was released into solution after reduction experiments. The 71% to 83% As was chemically reduced into arsenite (As(III)) and partially weathering into the soluble phase. The kinetic dissolution and re-precipitation of As, Fe, Pb and sulfate in this area of paddy soils merits further study. PMID:23923437

  20. Respiration and respiratory enzyme activity in aerobic and anaerobic cultures of the marine denitrifying bacterium, Pseudomonas perfectomarinus

    NASA Astrophysics Data System (ADS)

    Packard, T. T.; Garfield, P. C.; Martinez, R.

    1983-03-01

    Oxygen consumption, nitrate reduction, respiratory electron transport activity, and nitrate reductase activity were measured in aerobic and anaerobic cultures of the marine bacterium, Pseudomonas perfectomarinus. The respiratory electron transport activity was closely correlated with oxygen consumption ( r = 0.98) in aerobic cultures and nearly as well correlated with nitrate reductase activity ( r = 0.91) and nitrate reduction ( r = 0.85) in anaerobic cultures. It was also well correlated with biomass in both aerobic ( r = 0.99) and anaerobic ( r = 0.94) cultures supporting the use of tetrazolium reduction as an index of living biomass. Time courses of nitrate and nitrate in the anaerobic cultures demonstrated that at nitrate concentrations above 1 mM, denitrification proceeds stepwise. Time courses of pH in anaerobic cultures revealed a rise from 7 to 8.5 during nitrite reduction indicating net proton utilization. This proton utilization is predicted by the stoichiometry of denitrification. Although the experiments were not under 'simulated in situ' conditions, the results are relevant to studies of denitrification, to bacterial ATP production, and to the respiratory activity of marine plankton in the ocean.

  1. Selenite reduction by Shewanella oneidensis MR-1 is mediated by fumarate reductase in periplasm

    NASA Astrophysics Data System (ADS)

    Li, Dao-Bo; Cheng, Yuan-Yuan; Wu, Chao; Li, Wen-Wei; Li, Na; Yang, Zong-Chuang; Tong, Zhong-Hua; Yu, Han-Qing

    2014-01-01

    In situ reduction of selenite to elemental selenium (Se(0)), by microorganisms in sediments and soils is an important process and greatly affects the environmental distribution and the biological effects of selenium. However, the mechanism behind such a biological process remains unrevealed yet. Here we use Shewanella oneidensis MR-1, a widely-distributed dissimilatory metal-reducing bacterium with a powerful and diverse respiration capability, to evaluate the involvement of anaerobic respiration system in the microbial selenite reduction. With mutants analysis, we identify fumarate reductase FccA as the terminal reductase of selenite in periplasm. Moreover, we find that such a reduction is dependent on central respiration c-type cytochrome CymA. In contrast, nitrate reductase, nitrite reductase, and the Mtr electron transfer pathway do not work as selenite reductases. These findings reveal a previously unrecognized role of anaerobic respiration reductases of S. oneidensis MR-1 in selenite reduction and geochemical cycles of selenium in sediments and soils.

  2. Respiratory involvement in inherited primary muscle conditions

    PubMed Central

    Shahrizaila, N; Kinnear, W J M; Wills, A J

    2006-01-01

    Patients with inherited muscle disorders can develop respiratory muscle weakness leading to ventilatory failure. Predicting the extent of respiratory involvement in the different types of inherited muscle disorders is important, as it allows clinicians to impart prognostic information and offers an opportunity for early interventional management strategies. The approach to respiratory assessment in patients with muscle disorders, the current knowledge of respiratory impairment in different muscle disorders and advice on the management of respiratory complications are summarised. PMID:16980655

  3. Heliox reduces respiratory system resistance in respiratory syncytial virus induced respiratory failure

    PubMed Central

    Kneyber, Martin CJ; van Heerde, Marc; Twisk, Jos WR; Plötz, Frans B; Markhors, Dick G

    2009-01-01

    Introduction Respiratory syncytial virus (RSV) lower respiratory tract disease is characterised by narrowing of the airways resulting in increased airway resistance, air-trapping and respiratory acidosis. These problems might be overcome using helium-oxygen gas mixture. However, the effect of mechanical ventilation with heliox in these patients is unclear. The objective of this prospective cross-over study was to determine the effects of mechanical ventilation with heliox 60/40 versus conventional gas on respiratory system resistance, air-trapping and CO2 removal. Methods Mechanically ventilated, sedated and paralyzed infants with proven RSV were enrolled within 24 hours after paediatric intensive care unit (PICU)admission. At T = 0, respiratory system mechanics including respiratory system compliance and resistance, and peak expiratory flow rate were measured with the AVEA ventilator. The measurements were repeated at each interval (after 30 minutes of ventilation with heliox, after 30 minutes of ventilation with nitrox and again after 30 minutes of ventilation with heliox). Indices of gas exchange (ventilation and oxygenation index) were calculated at each interval. Air-trapping (defined by relative change in end-expiratory lung volume) was determined by electrical impedance tomography (EIT) at each interval. Results Thirteen infants were enrolled. In nine, EIT measurements were performed. Mechanical ventilation with heliox significantly decreased respiratory system resistance. This was not accompanied by an improved CO2 elimination, decreased peak expiratory flow rate or decreased end-expiratory lung volume. Importantly, oxygenation remained unaltered throughout the experimental protocol. Conclusions Respiratory system resistance is significantly decreased by mechanical ventilation with heliox (ISCRTN98152468). PMID:19450268

  4. Chloroplast NDH: A different enzyme with a structure similar to that of respiratory NADH dehydrogenase.

    PubMed

    Shikanai, Toshiharu

    2016-07-01

    Eleven genes encoding chloroplast NADH dehydrogenase-like (NDH) complex have been discovered in plastid genomes on the basis of their homology with genes encoding respiratory complex I. Despite this structural similarity, chloroplast NDH and its evolutionary origin NDH-1 in cyanobacteria accept electrons from ferredoxin (Fd), indicating that chloroplast NDH is an Fd-dependent plastoquinone (PQ) reductase rather than an NAD(P)H dehydrogenase. In Arabidopsis thaliana, chloroplast NDH interacts with photosystem I (PSI); this interaction is needed to stabilize NDH, especially under high light. On the basis of these distinct characters of chloroplast and cyanobacterial NDH, it can be distinguished as a photosynthetic NDH from respiratory complex I. In fact, chloroplast NDH forms part of the machinery of photosynthesis by mediating the minor pathway of PSI cyclic electron transport. Along with the antimycin A-sensitive main pathway of PSI cyclic electron transport, chloroplast NDH compensates the ATP/NADPH production ratio in the light reactions of photosynthesis. In this review, I revisit the original concept of chloroplast NDH on the basis of its similarity to respiratory complex I and thus introduce current progress in the field to researchers focusing on respiratory complex I. I summarize recent progress on the basis of structure and function. Finally, I introduce the results of our examination of the process of assembly of chloroplast NDH. Although the process requires many plant-specific non-subunit factors, the core processes of assembly are conserved between chloroplast NDH and respiratory complex I. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt. PMID:26519774

  5. A flavone from Manilkara indica as a specific inhibitor against aldose reductase in vitro.

    PubMed

    Haraguchi, Hiroyuki; Hayashi, Ryosuke; Ishizu, Takashi; Yagi, Akira

    2003-09-01

    Isoaffinetin (5,7,3',4',5'-pentahydroxyflavone-6-C-glucoside) was isolated from Manilkara indica as a potent inhibitor of lens aldose reductase by bioassay-directed fractionation. This C-glucosyl flavone showed specific inhibition against aldose reductases (rat lens, porcine lens and recombinant human) with no inhibition against aldehyde reductase and NADH oxidase. Kinetic analysis showed that isoaffinetin exhibited uncompetitive inhibition against both dl-glyceraldehyde and NADPH. A structure-activity relationship study revealed that the increasing number of hydroxy groups in the B-ring contributes to the increase in aldose reductase inhibition by C-glucosyl flavones. PMID:14598214

  6. Purification and partial characterization of an aldo-keto reductase from Saccharomyces cerevisiae.

    PubMed Central

    Kuhn, A; van Zyl, C; van Tonder, A; Prior, B A

    1995-01-01

    A cytosolic aldo-keto reductase was purified from Saccharomyces cerevisiae ATCC 26602 to homogeneity by affinity chromatography, chromatofocusing, and hydroxylapatite chromatography. The relative molecular weights of the aldo-keto reductase as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size exclusion chromatography were 36,800 and 35,000, respectively, indicating that the enzyme is monomeric. Amino acid composition and N-terminal sequence analysis revealed that the enzyme is closely related to the aldose reductases of xylose-fermenting yeasts and mammalian tissues. The enzyme was apparently immunologically unrelated to the aldose reductases of other xylose-fermenting yeasts. The aldo-keto reductase is NADPH specific and catalyzes the reduction of a variety of aldehydes. The best substrate for the enzyme is the aromatic aldehyde p-nitrobenzaldehyde (Km = 46 microM; kcat/Km = 52,100 s-1 M-1), whereas among the aldoses, DL-glyceraldehyde was the preferred substrate (Km = 1.44 mM; kcat/Km = 1,790 s-1 M-1). The enzyme failed to catalyze the reduction of menadione and p-benzoquinone, substrates for carbonyl reductase. The enzyme was inhibited only slightly by 2 mM sodium valproate and was activated by pyridoxal 5'-phosphate. The optimum pH of the enzyme is 5. These data indicate that the S. cerevisiae aldo-keto reductase is a monomeric NADPH-specific reductase with strong similarities to the aldose reductases. PMID:7747971

  7. Structure of the Molybdenum Site of EEcherichia Coli Trimethylamine N-Oxide Reductase

    SciTech Connect

    Zhang, L.; Nelson, K.Johnson; Rajagopalan, K.V.; George, G.N.

    2009-05-28

    We report a structural characterization of the molybdenum site of recombinant Escherichia coli trimethylamine N-oxide (TMAO) reductase using X-ray absorption spectroscopy. The enzyme active site shows considerable similarity to that of dimethyl sulfoxide (DMSO) reductase, in that, like DMSO reductase, the TMAO reductase active site can exist in multiple forms. Examination of the published crystal structure of TMAO oxidase from Shewanella massilia indicates that the postulated Mo coordination structure is chemically impossible. The presence of multiple active site structures provides a potential explanation for the anomalous features reported from the crystal structure.

  8. Probiotics in respiratory virus infections.

    PubMed

    Lehtoranta, L; Pitkäranta, A; Korpela, R

    2014-08-01

    Viral respiratory infections are the most common diseases in humans. A large range of etiologic agents challenge the development of efficient therapies. Research suggests that probiotics are able to decrease the risk or duration of respiratory infection symptoms. However, the antiviral mechanisms of probiotics are unclear. The purpose of this paper is to review the current knowledge on the effects of probiotics on respiratory virus infections and to provide insights on the possible antiviral mechanisms of probiotics. A PubMed and Scopus database search was performed up to January 2014 using appropriate search terms on probiotic and respiratory virus infections in cell models, in animal models, and in humans, and reviewed for their relevance. Altogether, thirty-three clinical trials were reviewed. The studies varied highly in study design, outcome measures, probiotics, dose, and matrices used. Twenty-eight trials reported that probiotics had beneficial effects in the outcome of respiratory tract infections (RTIs) and five showed no clear benefit. Only eight studies reported investigating viral etiology from the respiratory tract, and one of these reported a significant decrease in viral load. Based on experimental studies, probiotics may exert antiviral effects directly in probiotic-virus interaction or via stimulation of the immune system. Although probiotics seem to be beneficial in respiratory illnesses, the role of probiotics on specific viruses has not been investigated sufficiently. Due to the lack of confirmatory studies and varied data available, more randomized, double-blind, and placebo-controlled trials in different age populations investigating probiotic dose response, comparing probiotic strains/genera, and elucidating the antiviral effect mechanisms are necessary. PMID:24638909

  9. Respiratory infections unique to Asia.

    PubMed

    Tsang, Kenneth W; File, Thomas M

    2008-11-01

    Asia is a highly heterogeneous region with vastly different cultures, social constitutions and populations affected by a wide spectrum of respiratory diseases caused by tropical pathogens. Asian patients with community-acquired pneumonia differ from their Western counterparts in microbiological aetiology, in particular the prominence of Gram-negative organisms, Mycobacterium tuberculosis, Burkholderia pseudomallei and Staphylococcus aureus. In addition, the differences in socioeconomic and health-care infrastructures limit the usefulness of Western management guidelines for pneumonia in Asia. The importance of emerging infectious diseases such as severe acute respiratory syndrome and avian influenza infection remain as close concerns for practising respirologists in Asia. Specific infections such as melioidosis, dengue haemorrhagic fever, scrub typhus, leptospirosis, salmonellosis, penicilliosis marneffei, malaria, amoebiasis, paragonimiasis, strongyloidiasis, gnathostomiasis, trinchinellosis, schistosomiasis and echinococcosis occur commonly in Asia and manifest with a prominent respiratory component. Pulmonary eosinophilia, endemic in parts of Asia, could occur with a wide range of tropical infections. Tropical eosinophilia is believed to be a hyper-sensitivity reaction to degenerating microfilariae trapped in the lungs. This article attempts to address the key respiratory issues in these respiratory infections unique to Asia and highlight the important diagnostic and management issues faced by practising respirologists. PMID:18945321

  10. The respiratory health of swimmers.

    PubMed

    Bougault, Valérie; Turmel, Julie; Levesque, Benoît; Boulet, Louis-Philippe

    2009-01-01

    Regular physical activity is recognized as an effective health promotion measure. Among various activities, swimming is preferred by a large portion of the population. Although swimming is generally beneficial to a person's overall health, recent data suggest that it may also sometimes have detrimental effects on the respiratory system. Chemicals resulting from the interaction between chlorine and organic matter may be irritating to the respiratory tract and induce upper and lower respiratory symptoms, particularly in children, lifeguards and high-level swimmers. The prevalence of atopy, rhinitis, asthma and airway hyper-responsiveness is increased in elite swimmers compared with the general population. This may be related to the airway epithelial damage and increased nasal and lung permeability caused by the exposure to chlorine subproducts in indoor swimming pools, in association with airway inflammatory and remodelling processes. Currently, the recommended management of swimmers' respiratory disorders is similar to that of the general population, apart from the specific rules for the use of medications in elite athletes. Further studies are needed to better understand the mechanisms related to the development or worsening of respiratory disorders in recreational or competitive swimmers, to determine how we can optimize treatment and possibly help prevent the development of asthma. PMID:19317518

  11. A Raman spectroscopic study of the arsenate mineral chenevixite Cu2Fe2(3+)(AsO4)2(OH)4⋅H2O.

    PubMed

    Frost, Ray L; López, Andrés; Scholz, Ricardo; Lana, Cristiano; Xi, Yunfei

    2015-01-25

    We have studied the mineral chenevixite from Manto Cuba Mine, San Pedro de Cachiyuyo District, Inca de Oro, Chañaral Province, Atacama Region, Chile, using a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX) and vibrational spectroscopy. Qualitative chemical analysis shows a homogeneous composition, with predominance of As, Fe, Al, Cu, Fe and Cu. Minor amounts of Si were also observed. Raman spectroscopy complimented with infrared spectroscopy has been used to assess the molecular structure of the arsenate minerals chenevixite. Characteristic Raman and infrared bands of the (AsO4)(3-) stretching and bending vibrations are identified and described. The observation of multiple bands in the (AsO4)(3-) bending region offers support for the loss of symmetry of the arsenate anion in the structure of chenevixite. Raman bands attributable to the OH stretching vibrations of water and hydroxyl units were analysed. Estimates of the hydrogen bond distances were made based upon the OH stretching wavenumbers. PMID:25064502

  12. Pyrobaculum yellowstonensis Strain WP30 Respires on Elemental Sulfur and/or Arsenate in Circumneutral Sulfidic Geothermal Sediments of Yellowstone National Park.

    PubMed

    Jay, Z J; Beam, J P; Dohnalkova, A; Lohmayer, R; Bodle, B; Planer-Friedrich, B; Romine, M; Inskeep, W P

    2015-09-01

    Thermoproteales (phylum Crenarchaeota) populations are abundant in high-temperature (>70°C) environments of Yellowstone National Park (YNP) and are important in mediating the biogeochemical cycles of sulfur, arsenic, and carbon. The objectives of this study were to determine the specific physiological attributes of the isolate Pyrobaculum yellowstonensis strain WP30, which was obtained from an elemental sulfur sediment (Joseph's Coat Hot Spring [JCHS], 80°C, pH 6.1, 135 μM As) and relate this organism to geochemical processes occurring in situ. Strain WP30 is a chemoorganoheterotroph and requires elemental sulfur and/or arsenate as an electron acceptor. Growth in the presence of elemental sulfur and arsenate resulted in the formation of thioarsenates and polysulfides. The complete genome of this organism was sequenced (1.99 Mb, 58% G+C content), revealing numerous metabolic pathways for the degradation of carbohydrates, amino acids, and lipids. Multiple dimethyl sulfoxide-molybdopterin (DMSO-MPT) oxidoreductase genes, which are implicated in the reduction of sulfur and arsenic, were identified. Pathways for the de novo synthesis of nearly all required cofactors and metabolites were identified. The comparative genomics of P. yellowstonensis and the assembled metagenome sequence from JCHS showed that this organism is highly related (∼95% average nucleotide sequence identity) to in situ populations. The physiological attributes and metabolic capabilities of P. yellowstonensis provide an important foundation for developing an understanding of the distribution and function of these populations in YNP. PMID:26092468

  13. Pyrobaculum yellowstonensis Strain WP30 Respires on Elemental Sulfur and/or Arsenate in Circumneutral Sulfidic Geothermal Sediments of Yellowstone National Park

    PubMed Central

    Jay, Z. J.; Beam, J. P.; Dohnalkova, A.; Lohmayer, R.; Bodle, B.; Planer-Friedrich, B.; Romine, M.

    2015-01-01

    Thermoproteales (phylum Crenarchaeota) populations are abundant in high-temperature (>70°C) environments of Yellowstone National Park (YNP) and are important in mediating the biogeochemical cycles of sulfur, arsenic, and carbon. The objectives of this study were to determine the specific physiological attributes of the isolate Pyrobaculum yellowstonensis strain WP30, which was obtained from an elemental sulfur sediment (Joseph's Coat Hot Spring [JCHS], 80°C, pH 6.1, 135 μM As) and relate this organism to geochemical processes occurring in situ. Strain WP30 is a chemoorganoheterotroph and requires elemental sulfur and/or arsenate as an electron acceptor. Growth in the presence of elemental sulfur and arsenate resulted in the formation of thioarsenates and polysulfides. The complete genome of this organism was sequenced (1.99 Mb, 58% G+C content), revealing numerous metabolic pathways for the degradation of carbohydrates, amino acids, and lipids. Multiple dimethyl sulfoxide-molybdopterin (DMSO-MPT) oxidoreductase genes, which are implicated in the reduction of sulfur and arsenic, were identified. Pathways for the de novo synthesis of nearly all required cofactors and metabolites were identified. The comparative genomics of P. yellowstonensis and the assembled metagenome sequence from JCHS showed that this organism is highly related (∼95% average nucleotide sequence identity) to in situ populations. The physiological attributes and metabolic capabilities of P. yellowstonensis provide an important foundation for developing an understanding of the distribution and function of these populations in YNP. PMID:26092468

  14. A Raman spectroscopic study of the arsenate mineral chenevixite Cu2Fe23+(AsO4)2(OH)4ṡH2O

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Scholz, Ricardo; Lana, Cristiano; Xi, Yunfei

    2015-01-01

    We have studied the mineral chenevixite from Manto Cuba Mine, San Pedro de Cachiyuyo District, Inca de Oro, Chañaral Province, Atacama Region, Chile, using a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX) and vibrational spectroscopy. Qualitative chemical analysis shows a homogeneous composition, with predominance of As, Fe, Al, Cu, Fe and Cu. Minor amounts of Si were also observed. Raman spectroscopy complimented with infrared spectroscopy has been used to assess the molecular structure of the arsenate minerals chenevixite. Characteristic Raman and infrared bands of the (AsO4)3- stretching and bending vibrations are identified and described. The observation of multiple bands in the (AsO4)3- bending region offers support for the loss of symmetry of the arsenate anion in the structure of chenevixite. Raman bands attributable to the OH stretching vibrations of water and hydroxyl units were analysed. Estimates of the hydrogen bond distances were made based upon the OH stretching wavenumbers.

  15. Variation in arsenic accumulation and translocation among wheat cultivars: the relationship between arsenic accumulation, efflux by wheat roots and arsenate tolerance of wheat seedlings.

    PubMed

    Shi, Gao Ling; Zhu, Shun; Meng, Ji Rong; Qian, Meng; Yang, Na; Lou, Lai Qing; Cai, Qing Sheng

    2015-05-30

    Fifty-seven wheat cultivars were used to investigate the differences in arsenic (As) accumulation, efflux and translocation among wheat cultivars and their relationship with arsenate (As(V)) tolerance under hydroponic condition. The relationship between wheat root As accumulation, As(V) uptake, arsenite (As(III)) efflux and As(V) tolerance of 14 wheat cultivars were also investigated. The results showed there were significant (p<0.001) differences in As(V) tolerance, As accumulation and translocation among 57 wheat cultivars. Arsenate tolerance of wheat seedlings was positively correlated with As(V) uptake (p<0.05), root As concentration (p<0.001), but negatively correlated (p<0.05) with TFs and relative As(III) efflux. No significant correlation between As(III) efflux and As(V) tolerance was found (p=0.442). 56-83% of total As taken up by roots was extruded to nutrient solution. Root As concentration was positively correlated with As(V) uptake (not significant, p=0.100), negatively correlated (p<0.001) with relative As(III) efflux, whereas not significantly correlated (p=0.773) with As(III) efflux. The results indicated that As(V) tolerant wheat cultivars have much higher capacity of root As accumulation. Arsenic detoxification in root cells is important for wheat seedlings under As(V) exposure. PMID:25725341

  16. Nitrite Reductase from Pseudomonas aeruginosa Released by Antimicrobial Agents and Complement Induces Interleukin-8 Production in Bronchial Epithelial Cells

    PubMed Central

    Sar, Borann; Oishi, Kazunori; Wada, Akihiro; Hirayama, Toshiya; Matsushima, Kouji; Nagatake, Tsuyoshi

    1999-01-01

    We have recently reported that nitrite reductase, a bifunctional enzyme located in the periplasmic space of Pseudomonas aeruginosa, could induce interleukin-8 (IL-8) generation in a variety of respiratory cells, including bronchial epithelial cells (K. Oishi et al. Infect. Immun. 65:2648–2655, 1997). In this report, we examined the mode of nitrite reductase (PNR) release from a serum-sensitive strain of live P. aeruginosa cells during in vitro treatment with four different antimicrobial agents or human complement. Bacterial killing of P. aeruginosa by antimicrobial agents induced PNR release and mediated IL-8 production in human bronchial epithelial (BET-1A) cells. Among these agents, imipenem demonstrated rapid killing of P. aeruginosa as well as rapid release of PNR and resulted in the highest IL-8 production. Complement-mediated killing of P. aeruginosa was also associated with PNR release and enhanced IL-8 production. The immunoprecipitates of the aliquots of bacterial culture containing imipenem or complement with anti-PNR immunoglobulin G (IgG) induced a twofold-higher IL-8 production than did the immunoprecipitates of the aliquots of bacterial culture with a control IgG. These pieces of evidence confirmed that PNR released in the aliquots of bacterial culture was responsible for IL-8 production in the BET-1A cells. Furthermore, the culture supernatants of the BET-1A cells stimulated with aliquots of bacterial culture containing antimicrobial agents or complement similarly mediated neutrophil migration in vitro. These data support the possibility that a potent inducer of IL-8, PNR, could be released from P. aeruginosa after exposure to antimicrobial agents or complement and contributes to neutrophil migration in the airways during bronchopulmonary infections with P. aeruginosa. PMID:10103183

  17. Sensitivity of jarrah (Eucalyptus marginata) to phosphate, phosphite, and arsenate pulses as influenced by fungal symbiotic associations.

    PubMed

    Kariman, Khalil; Barker, Susan J; Jost, Ricarda; Finnegan, Patrick M; Tibbett, Mark

    2016-07-01

    Many plant species adapted to P-impoverished soils, including jarrah (Eucalyptus marginata), develop toxicity symptoms when exposed to high doses of phosphate (Pi) and its analogs such as phosphite (Phi) and arsenate (AsV). The present study was undertaken to investigate the effects of fungal symbionts Scutellospora calospora, Scleroderma sp., and Austroboletus occidentalis on the response of jarrah to highly toxic pulses (1.5 mmol kg(-1) soil) of Pi, Phi, and AsV. S. calospora formed an arbuscular mycorrhizal (AM) symbiosis while both Scleroderma sp. and A. occidentalis established a non-colonizing symbiosis with jarrah plants. All these interactions significantly improved jarrah growth and Pi uptake under P-limiting conditions. The AM fungal colonization naturally declines in AM-eucalypt symbioses after 2-3 months; however, in the present study, the high Pi pulse inhibited the decline of AM fungal colonization in jarrah. Four weeks after exposure to the Pi pulse, plants inoculated with S. calospora had significantly lower toxicity symptoms compared to non-mycorrhizal (NM) plants, and all fungal treatments induced tolerance against Phi toxicity in jarrah. However, no tolerance was observed for AsV-treated plants even though all inoculated plants had significantly lower shoot As concentrations than the NM plants. The transcript profile of five jarrah high-affinity phosphate transporter (PHT1 family) genes in roots was not altered in response to any of the fungal species tested. Interestingly, plants exposed to high Pi supplies for 1 day did not have reduced transcript levels for any of the five PHT1 genes in roots, and transcript abundance of four PHT1 genes actually increased. It is therefore suggested that jarrah, and perhaps other P-sensitive perennial species, respond positively to Pi available in the soil solution through increasing rather than decreasing the expression of selected PHT1 genes. Furthermore, Scleroderma sp. can be considered as a fungus with

  18. Wide angle X-ray scattering (WAXS) study of "two-line" ferrihydrite structure: Effect of arsenate sorption and counterion variation and comparison with EXAFS results

    USGS Publications Warehouse

    Waychunas, G.A.; Fuller, C.C.; Rea, B.A.; Davis, J.A.

    1996-01-01

    Wide angle X-ray scattering (WAXS) measurements have been made on a suite of "two-line" ferrihydrite (FHY2) samples containing varying amounts of coprecipitated arsenate. Samples prepared at pH 8 with counter ions chloride, nitrate, and a mixture of both also were examined. The raw WAXS scattering functions show that "two-line" ferrihydrite actually has a large number of non-Bragg (i.e., diffuse scattering) maxima up to our observation limit of 16 A??-1. The type of counter ion used during synthesis produces no significant change in this function. In unarsenated samples, Radial Distribution Functions (RDFs) produced from the scattering functions show a well-defined Fe-O peak at 2.02 A?? in excellent agreement with the mean distance of 2.01 A?? from extended X-ray absorption fine structure (EXAFS) analysis. The area under the Fe-O peak is consistent with only octahedral oxygen coordination about iron, and an iron coordination about oxygen of 2.2, in agreement with the EXAFS results, the sample composition, and XANES measurements. The second peak observed in the RDFs is clearly divided into two populations of correlations, at 3.07 and 3.52 A??, respectively. These distances are close to the EXAFS-derived Fe-Fe subshell distances of 3.02-3.05 and 3.43-3.46 A??, respectively, though this is misleading as the RDF peaks also include contributions from O-Fe and O-O correlations. Simulated RDFs of the FeOOH polymorphs indicate how the observed RDF structure relates to the EXAFS pair-correlation function, and allow comparisons with an ordered ferrihydrite structure. The effect of increasing arsenate content is dramatic, as the RDF peaks are progressively smeared out, indicating a wider range of interatomic distances even at moderate surface coverages, and a loss of longer range correlations. At an As/Fe ratio of 0.68, the surface saturation level of arsenate, the RDF shows little order beyond what would be expected from small pieces of dioctahedral Fe oxyhydroxyl chains or

  19. Differential Light Induction of Nitrate Reductases in Greening and Photobleached Soybean Seedlings 1

    PubMed Central

    Kakefuda, Genichi; Duke, Stanley H.; Duke, Stephen O.

    1983-01-01

    Soybean (Glycine max [L.] Merr.) seeds were imbibed and germinated with or without NO3−, tungstate, and norflurazon (San 9789). Norflurazon is a herbicide which causes photobleaching of chlorophyll by inhibiting carotenoid synthesis and which impairs normal chloroplast development. After 3 days in the dark, seedlings were placed in white light to induce extractable nitrate reductase activity. The induction of maximal nitrate reductase activity in greening cotyledons did not require NO3− and was not inhibited by tungstate. Induction of nitrate reductase activity in norflurazon-treated cotyledons had an absolute requirement for NO3− and was completely inhibited by tungstate. Nitrate was not detected in seeds or seedlings which had not been treated with NO3−. The optimum pH for cotyledon nitrate reductase activity from norflurazon-treated seedlings was at pH 7.5, and near that for root nitrate reductase activity, whereas the optimum pH for nitrate reductase activity from greening cotyledons was pH 6.5. Induction of root nitrate reductase activity was also inhibited by tungstate and was dependent on the presence of NO3−, further indicating that the isoform of nitrate reductase induced in norflurazon-treated cotyledons is the same or similar to that found in roots. Nitrate reductases with and without a NO3− requirement for light induction appear to be present in developing leaves. In vivo kinetics (light induction and dark decay rates) and in vitro kinetics (Arrhenius energies of activation and NADH:NADPH specificities) of nitrate reductases with and without a NO3− requirement for induction were quite different. Km values for NO3− were identical for both nitrate reductases. PMID:16663185

  20. The effect of copper and gallium compounds on ribonucleotide reductase

    SciTech Connect

    Narasimhan, J.

    1992-01-01

    The mode of action of copper complexes (CuL and CuKTS) and gallium compounds (gallium nitrate and citrate) in cytotoxicity was studied. The effects of these agents on the enzyme ribonucleotide reductase was investigated by monitoring the tyrosyl free radical present in the active site of the enzyme through electron spin resonance (ESR) spectroscopy. Ribonucleotide reductase, a key enzyme in cellular proliferation, consists of two subunits. M1, a dimer of molecular weight 170,000 contains the substrate and effector binding sites. M2, a dimer of molecular weight 88,000, contains non-heme iron and tyrosyl free radical essential for the activity of the enzyme. In studies using copper complexes, the cellular oxidative chemistry was examined by ESR studies on adduct formation with membranes, and oxidation of thiols. Membrane thiols were oxidized through the reduction of the ESR signal of the thiol adduct and the analysis of sulfhydryl content. Using the radiolabel [sup 59]Fe, the inhibitory action of copper thiosemicarbazones on cellular iron uptake was shown. The inhibitory action of CuL on ribonucleotide reductase was shown by the quenching of the tyrosyl free radical on the M2 subunit. The hypothesis that gallium directly interacts with the M2 subunit of the enzyme and displaces the iron from it was proven. The tyrosyl free radical signal from cell lysates was inhibited by the direct addition of gallium compounds. Gallium content in the cells was measured by a fluorimetric method, to ensure the presence of sufficient amounts of gallium to compete with the iron in the M2 subunit. The enzyme activity, measured by the conversion of [sup 14]C-CDP to the labeled deoxy CDP, was inhibited by the addition of gallium nitrate in a cell free assay system. The immunoprecipitation studies of the [sup 59]Fe labeled M2 protein using the monoclonal antibody directed against this subunit suggested that gallium releases iron from the M2 subunit.