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Arsenic (Inorganic)

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The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Proteomic analysis of arsenite - Mediated multiple antibiotic resistance in Yersinia enterocolitica biovar 1A

Authors: Mallik, S; Virdi, JS; Johri, AK (In Press) Journal of Basic Microbiology. HERO ID: 1003606

[Less] Arsenic is one of the most important global environmental pollutants. In the present study, fifty one . . . [More] Arsenic is one of the most important global environmental pollutants. In the present study, fifty one clinical strains of Yersinia enterocolitica biovar 1A showed high resistance to arsenite and arsenate. The minimum inhibitory concentration (MIC) of arsenite (0.625-20 mM) was lower than arsenate (10-80 mM). Growth of Y. enterocolitica in 2 mM arsenite led to 2-8 fold increase in MICs of the five antibiotics (amikacin, ciprofloxacin, gentamycin, kanamycin and tetracycline), suggesting expression of arsenite-induced multiple antibiotic resistance among the strains. Proteomic analysis of Y. enterocolitica revealed differential expression of certain proteins following arsenite exposure, which included a putative outer membrane porin (OmpA) and a putative amino acid transporter protein. In conclusion, modulation of membrane permeability may be involved in the induction of arsenite-mediated expression of multiple antibiotic resistance in Y. enterocolitica. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

A periplasmic arsenite-binding protein involved in regulating arsenite oxidation

Authors: Liu, G; Liu, M; Kim, E-H; Matty, WS; Bothner, B; Lei, B; Rensing, C; Wang, G; McDermott, TR (In Press) Environmental Microbiology. HERO ID: 1003591

[Less] Arsenic (As) is the most common toxic element in the environment, ranking first on the Superfund List . . . [More] Arsenic (As) is the most common toxic element in the environment, ranking first on the Superfund List of Hazardous Substances. Microbial redox transformations are the principal drivers of As chemical speciation, which in turn dictates As mobility and toxicity. Consequently, in order to manage or remediate environmental As, land managers need to understand how and why microorganisms react to As. Studies have demonstrated a two-component signal transduction system comprised of AioS (sensor kinase) and AioR (response regulator) is involved in regulating microbial AsIII oxidation, with the AsIII oxidase structural genes aioB and aioA being upregulated by AsIII. However, it is not known whether AsIII is first detected directly by AioS or by an intermediate. Herein we demonstrate the essential role of a periplasmic AsIII-binding protein encoded by aioX, which is upregulated by AsIII. An ΔaioX mutant is defective for upregulation of the aioBA genes and consequently AsIII oxidation. Purified AioX expressed without its TAT-type signal peptide behaves as a monomer (MW 32 kDa), and Western blots show AioX to be exclusively associated with the cytoplasmic membrane. AioX binds AsIII with a K(D) of 2.4 µM AsIII; however, mutating a conserved Cys108 to either alanine or serine resulted in lack of AsIII binding, lack of aioBA induction, and correlated with a negative AsIII oxidation phenotype. The discovery and characterization of AioX illustrates a novel AsIII sensing mechanism that appears to be used in a range of bacteria and also provides one of the first examples of a bacterial signal anchor protein.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

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

Authors: Zargar, K; Conrad, A; Bernick, DL; Lowe, TM; Stolc, V; Hoeft, S; Oremland, RS; Stolz, J; Saltikov, CW (In Press) Environmental Microbiology. HERO ID: 1015673

[Less] Arsenotrophy, growth coupled to autotrophic arsenite oxidation or arsenate respiratory reduction, occurs . . . [More] 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.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Members of rice plasma membrane intrinsic proteins subfamily are involved in arsenite permeability and tolerance in plants

Authors: Mosa, KA; Kumar, K; Chhikara, S; Mcdermott, J; Liu, Z; Musante, C; White, JC; Dhankher, OP (In Press) Transgenic Research. HERO ID: 1015734

[Less] Rice accumulates high level of arsenic (As) in its edible parts and thus plays an important role in . . . [More] Rice accumulates high level of arsenic (As) in its edible parts and thus plays an important role in the transfer of As into the food chain. However, the mechanisms of As uptake and its detoxification in rice are not well understood. Recently, members of the Nodulin 26-like intrinsic protein (NIP) subfamily of plant aquaporins were shown to transport arsenite in rice and Arabidopsis. Here we report that members of the rice plasma membrane intrinsic protein (PIP) subfamily are also involved in As tolerance and transport. Based on the homology search with the mammalian AQP9 and yeast Fps1 arsenite transporters, we identified and cloned five rice PIP gene subfamily members. qRT-PCR analysis of PIPs in rice root and shoot tissues revealed a significant down regulation of transcripts encoding OsPIP1;2, OsPIP1;3, OsPIP2;4, OsPIP2;6, and OsPIP2;7 in response to arsenite treatment. Heterologous expression of OsPIP2;4, OsPIP2;6, and OsPIP2;7 in Xenopus laevis oocytes significantly increased the uptake of arsenite. Overexpression of OsPIP2;4, OsPIP2;6, and OsPIP2;7 in Arabidopsis yielded enhanced arsenite tolerance and higher biomass accumulation. Further, these transgenic plants showed no significant accumulation of As in shoot and root tissues in long term uptake assays. Whereas, short duration exposure to arsenite caused both active influx and efflux of As in the roots. The data suggests a bidirectional arsenite permeability of rice PIPs in plants. These rice PIPs genes will be highly useful for engineering important food and biofuel crops for enhanced crop productivity on contaminated soils without increasing the accumulation of toxic As in the biomass or edible tissues.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Arsenate toxicity and stress responses in the freshwater ciliate Tetrahymena pyriformis

Authors: Zhang, Y-Y; Yang, J; Yin, X-X; Yang, S-P; Zhu, Y-G (In Press) European Journal of Protistology. HERO ID: 1015745

[Less] The arsenic metabolism in different biological organisms has been studied extensively. However, little . . . [More] The arsenic metabolism in different biological organisms has been studied extensively. However, little is known about protozoa. Herein, we investigated the cell stress responses of the freshwater ciliate Tetrahymena pyriformis to arsenate toxicity. An acute toxicity assay revealed an 18-h EC(50) arsenate concentration of ca. 40μM, which caused significant changes in the cell shape, growth and organism mobility. Whereas, under exposure to 30μM arsenate, T. pyriformis could grow reasonably well, indicating a certain resistance of this organism. Arsenic speciation analysis revealed that 94-98% of the total arsenate in cells of T. pyriformis could be transformed to monomethylarsonic acid, dimethylarsinic acid and a small proportion of arsenite after 18h of arsenate exposure, thus indicating the major detoxification pathway by arsenic oxidation/reduction and biomethylation. Finally, comparative proteomic analysis unveiled significant changes in the expression of multiple proteins involved in anti-oxidation, sugar and energy metabolism, proteolysis, and signal transduction. Our results revealed multiple pathways of arsenate detoxification in T. pyriformis, and indicated that protozoa may play important roles in the biogeochemical cycles of arsenic.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Arsenic, organic foods, and brown rice syrup

Authors: Jackson, BP; Taylor, VF; Karagas, MR; Punshon, T; Cottingham, KL (In Press) Environmental Health Perspectives. HERO ID: 1015755

[Less] BACKGROUND: Rice can be a major source of inorganic arsenic (Asi) for many sub-populations. Rice products . . . [More] BACKGROUND: Rice can be a major source of inorganic arsenic (Asi) for many sub-populations. Rice products are also used as ingredients in prepared foods, some of which may not be obviously rice-based. Organic brown rice syrup (OBRS) is used as a sweetener in organic food products as an alternative to high fructose corn syrup. We hypothesized that OBRS introduces arsenic into these products. OBJECTIVE: We determined the concentration and speciation of arsenic (As) in commercially available brown rice syrups, and in products containing OBRS including toddler formula, cereal/energy bars, and high energy foods used by endurance athletes. METHODS: We used ICP-MS and IC-ICP-MS to determine total As (Astotal) concentrations and As speciation in products purchased via the internet or in stores in the Hanover, NH area. DISCUSSION: We found that OBRS can contain high concentrations of Asi and dimethylarsenate (DMA). An 'organic' toddler milk formula containing OBRS as the primary ingredient had Astotal concentrations up to six times the EPA safe drinking water limit. Cereal bars and high energy foods containing OBRS also had higher As concentrations than equivalent products that did not contain OBRS. Inorganic As was the main As species in the majority of food products tested in this study. CONCLUSIONS: There are currently no US regulations applicable to As in food, but our findings suggest that the OBRS products we evaluated may introduce significant concentrations of Asi to an individual's diet. Thus, we conclude that there is an urgent need for regulatory limits on As in food.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Classification accuracy and cut point selection

Author: Liu, X (In Press) Statistics in Medicine. HERO ID: 1015791

[Less] In biomedical research and practice, quantitative tests or biomarkers are often used for diagnostic . . . [More] In biomedical research and practice, quantitative tests or biomarkers are often used for diagnostic or screening purposes, with a cut point established on the quantitative measurement to aid binary classification. This paper introduces an alternative to the traditional methods based on the Youden index and the closest-to-(0, 1) criterion for threshold selection. A concordance probability evaluating the classification accuracy of a dichotomized measure is defined as an objective function of the possible cut point. A nonparametric approach is used to search for the optimal cut point maximizing the objective function. The procedure is shown to perform well in a simulation study. Using data from a real-world study of arsenic-induced skin lesions, we apply the method to a measure of blood arsenic levels, selecting a cut point to be used as a warning threshold. Copyright © 2012 John Wiley & Sons, Ltd.

Journal Article
Journal Article

Silibinin potentially protects arsenic-induced oxidative hepatic dysfunction in rats

Authors: Muthumani, M; Prabu, SM (In Press) Toxicology Mechanisms and Methods. HERO ID: 1015878

[Less] Arsenic (As) compounds are reported as environmental toxicants and human carcinogens. Exposure to arsenic . . . [More] Arsenic (As) compounds are reported as environmental toxicants and human carcinogens. Exposure to arsenic imposes a big health issue worldwide. Silibinin (SB) is a major flavonolignan compound of silimarin and is found in milk thistle of Silybum marianum. It has been reported that silibinin has antioxidant efficacy as metal chelators due to the orientation of its functional groups. However, it has not yet been explored in experimental animals. In view of this fact, the purpose of this study was to delineate the ameliorative role of silibinin against arsenic-induced hepatotoxicity in rats. Rats were orally treated with arsenic alone (5 mg/kg body weight (bw)/day) plus silibinin (75 mg/kg bw/day) for 4weeks. Hepatotoxicity was evaluated by the increased activities of serum hepatospecific enzymes namely aspartate transaminase, alanine transaminase, alkaline phosphatase, gamma glutamyl transferase, lactate dehydrogenase and total bilirubin along with increased elevation of lipid peroxidative markers, thiobarbituric acid reactive substances, lipid hydroperoxides, protein carbonyl content and conjugated dienes. The toxic effect of arsenic was also indicated by significantly decreased activities of membrane bound ATPases, enzymatic antioxidants like superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, glutathione reductase and glucose-6-phosphate dehydrogenase along with nonenzymatic antioxidants like reduced glutathione, total sulfhydryl groups, vitamins C and E. Administration of silibinin exhibited a significant reversal of arsenic-induced toxicity in hepatic tissue. All these changes were supported by reduction of DNA damage in hepatocytes and histopathological observations of the liver. These results suggest that silibinin has a potential protective effect over arsenic-induced hepatotoxicity in rat.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

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

Authors: Mishra, S; Srivastava, S; Dwivedi, S; Tripathi, RD (In Press) Environmental Toxicology. HERO ID: 1017520

[Less] Widespread contamination of arsenic (As) is recognized as a global problem due to its well-known accumulation . . . [More] 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. © 2011 Wiley Periodicals, Inc. Environ Toxicol, 2011.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Oxidation of arsenite by two β-proteobacteria isolated from soil

Authors: Bachate, SP; Khapare, RM; Kodam, KM (In Press) Applied Microbiology and Biotechnology. HERO ID: 1003602

[Less] Two heterotrophic As(III)-oxidizing bacteria, SPB-24 and SPB-31 were isolated from garden soil. Based . . . [More] Two heterotrophic As(III)-oxidizing bacteria, SPB-24 and SPB-31 were isolated from garden soil. Based on 16S rRNA gene sequence analysis, strain SPB-24 was closely related to genus Bordetella, and strain SPB-31 was most closely related to genus Achromobacter. Both strains exhibited high As(III) (15 mM for SPB-24 and 40 mM for SPB-31) and As(V) (>300 mM for both strains) resistance. Both strains oxidized 5 mM As(III) in minimal medium with oxidation rate of 554 and 558 μM h(-1) for SPB-24 and SPB-31, respectively. Washed cells of both strains oxidized As(III) over broad pH and temperature range with optimum pH 6 and temperature 42°C for both strains. The As(III) oxidation kinetic by washed cells showed K (m) and V (max) values of 41.7 μM and 1,166 μM h(-1) for SPB-24, 52 μM and 1,186 μM h(-1) for SPB-31. In the presence of minimal amount of carbon source, the strains showed high As(III) oxidation rate and high specific arsenite oxidase activity. The ability of strains to resist high concentration of arsenic and oxidize As(III) with highest rates reported so far makes them potential candidates for bioremediation of arsenic-contaminated environment.