Georg Raber

Roxarsone, inorganic arsenic, and other arsenic species in chicken: a U.S.-based market basket sample.

Background: Inorganic arsenic (iAs) causes cancer and possibly other adverse health outcomes. Arsenic-based drugs are permitted in poultry production; however, the contribution of chicken consumption to iAs intake is unknown. Objectives: We sought to characterize the arsenic species profile in chicken meat and estimate bladder and lung cancer risk associated with consuming chicken produced with arsenic-based drugs. Methods: Conventional, antibiotic-free, and organic chicken samples were collected from grocery stores in 10 U.S. metropolitan areas from December 2010 through June 2011. We tested 116 raw and 142 cooked chicken samples for total arsenic, and we determined arsenic species in 65 raw and 78 cooked samples that contained total arsenic at ≥ 10 µg/kg dry weight. Results: The geometric mean (GM) of total arsenic in cooked chicken meat samples was 3.0 µg/kg (95% CI: 2.5, 3.6). Among the 78 cooked samples that were speciated, iAs concentrations were higher in conventional samples (GM = 1.8 µg/kg; 95% CI: 1.4, 2.3) than in antibiotic-free (GM = 0.7 µg/kg; 95% CI: 0.5, 1.0) or organic (GM = 0.6 µg/kg; 95% CI: 0.5, 0.8) samples. Roxarsone was detected in 20 of 40 conventional samples, 1 of 13 antibiotic-free samples, and none of the 25 organic samples. iAs concentrations in roxarsone-positive samples (GM = 2.3 µg/kg; 95% CI: 1.7, 3.1) were significantly higher than those in roxarsone-negative samples (GM = 0.8 µg/kg; 95% CI: 0.7, 1.0). Cooking increased iAs and decreased roxarsone concentrations. We estimated that consumers of conventional chicken would ingest an additional 0.11 µg/day iAs (in an 82-g serving) compared with consumers of organic chicken. Assuming lifetime exposure and a proposed cancer slope factor of 25.7 per milligram per kilogram of body weight per day, this increase in arsenic exposure could result in 3.7 additional lifetime bladder and lung cancer cases per 100,000 exposed persons. Conclusions: Conventional chicken meat had higher iAs concentrations than did conventional antibiotic-free and organic chicken meat samples. Cessation of arsenical drug use could reduce exposure and the burden of arsenic-related disease in chicken consumers.

Arsenic-Containing Long-Chain Fatty Acids in Cod-Liver Oil: A Result of Biosynthetic Infidelity?†

tioned between hexane and aqueous methanol, and the polar phase subjected to preparative chromatography with sizeexclusion and anion-exchange media to yield a fraction enriched in polar arsenolipids. Analysis of this fraction by HPLC–inductively coupled plasma mass spectrometry (ICPMS) revealed the presence of at least 15 arsenolipids (Figure 2). Further investigation of the fraction with HPLC– electrospray ionization MS (ESI-MS), under conditions that provided simultaneous detection of elemental arsenic and molecular masses, [3] showed that six of the major arsenicals (A–F in Figure 2) had the following molecular masses: A 334, B 362, C 390, D 418, E 388, and F 436. The mass spectral data for four of these compounds (A–D) were consistent with the presence of a homologous series of arsenic-containing saturated fatty acids of the type (CH3)2As(O)-(CH2)nCOOH (n = 12, 14, 16, and 18) with a dimethylarsinoyl group,

Arsenic concentrations and speciation in the tissues and blood of sea mullet (Mugil cephalus) from Lake Macquarie NSW, Australia

Total arsenic concentrations and species were measured in the tissues and blood of the mullet Mugil cephalus. Arsenic concentrations ranged from 0.54 μg/g dry mass in the gill tissue to 19.2 μg/g dry mass in liver tissue. The concentrations of arsenic in liver tissues were found to be significantly greater (P>0.01) than in other tissues. Significant correlations exist between arsenic concentrations in all tissues. There was no significant difference (P>0.05) in arsenic concentrations between male and female fish. Age was found not to influence arsenic concentration. Significant regressions of arsenic concentration against mass were found for stomach (r2=0.23, P<0.01), gill (r2=0.143, P<0.05), intestine (r2=0.138, P<0.05) and gonad tissues (r2=0.13, P<0.05). Most tissues and blood contained large percentages of arsenobetaine (35%–100%) and with the exception of muscle and gonad tissues, dimethylarsinic acid (7%–62%). Smaller percentages of trimethylarsine oxide (TMAO) (4%–14%) were found in stomach, intestine and kidney tissues; arsenate (1%–6%) in stomach, intestine, liver, gonad tissues and blood and arsenocholine (2%–3%) in all tissues except muscle. Traces of arsenic sugars were found in stomach, intestine, kidney and gonad tissues. The species of arsenic found in tissues and blood can be explained by the ingestion and degradation of organic arsenic compounds found in fauna and flora consumed by mullet. The conversion of inorganic arsenic obtained through ingestion of sediment to organic arsenic compounds by microbial processes in the digestive system and enzymes in the liver may also be occurring.

Arsenosugar phospholipids and arsenic hydrocarbons in two species of brown macroalgae

Environmental context Although organoarsenic compounds occur in marine organisms at high concentrations, the origin and role of these compounds is unknown. Arsenic-containing lipids (arsenolipids) are newly discovered compounds in fish. We identify a range of arsenolipids in algae and propose that algae are the origin of these unusual arsenic compounds in marine ecosystems. Abstract Fourteen arsenolipids, including 11 new compounds, were identified and quantified in two species of brown algae, Wakame (Undaria pinnatifida) and Hijiki (Hizikia fusiformis), by high resolution mass spectrometry, high performance liquid chromatography–mass spectrometry and gas chromatography–mass spectrometry. Both algal species contained arsenosugar-phospholipids as the major type of arsenolipid, and arsenic-hydrocarbons were also significant components, particularly in Hijiki. The origin of the various arsenolipids, and the possible significance of their relative quantities, is briefly discussed.

Arsenic-Containing Lipids Are Natural Constituents of Sashimi Tuna

Arsenic occurs naturally in many types of seafood as water- and fat-soluble organoarsenic compounds. Although water-soluble compounds have been well characterized, the fat-soluble compounds, so-called arsenolipids, have until recently remained unknown. We report that sashimi-grade tuna fish, with a total arsenic content of 5.9 microg of As/g dry mass, contains approximately equal quantities of water- and fat-soluble arsenic. The water-soluble arsenic comprised predominantly arsenobetaine (>95%) with a trace of dimethylarsinate. Two fat-soluble compounds, which together accounted for about 40% of the lipid-arsenic, were isolated and characterized. The first was identified as 1-dimethylarsinoylpentadecane [(CH(3))(2)As(O)(CH(2))(14)CH(3)] by comparison of HPLC/mass spectrometric data and accurate mass data with those of an authenticated synthesized standard. The second arsenolipid was postulated as 1-dimethylarsinoyl all-cis-4,7,10,13,16,19-docosahexane from mass spectrometric data and analogy with non-arsenic-containing lipids found in fish. The remaining fat-soluble arsenic consisted of less polar arsenolipids of currently unknown structure. This is the first identification of arsenolipids in commonly consumed seafood.

Characterization of recombinant human endothelial nitric-oxide synthase purified from the yeast Pichia pastoris.

Human endothelial nitric-oxide synthase (eNOS) was expressed in the methylotrophic yeast Pichia pastoris, making use of the highly inducible alcohol oxidase promoter. The recombinant protein constituted approximately 3% of total protein and was largely soluble (>75%). About 1 mg of purified eNOS was obtained from 100-ml yeast cell cultures by affinity chromatography of crude cell supernatants. The purified enzyme had aV max of 192 ± 18 nmol ofl-citrulline × mg−1 × min−1, had a K m forl-arginine of 3.9 ± 0.2 μm, and showed an absolute requirement for tetrahydrobiopterin (H4biopterin). NADPH oxidase activity was 136 ± 9 and 342 ± 24 nmol × mg−1 × min−1 in the absence and presence of 0.1 mm l-arginine, respectively, and not affected by H4biopterin. The protein contained 0.56 ± 0.06 equivalents of FAD and 0.79 ± 0.08 equivalents of FMN. On-line gel filtration/inductively coupled plasma mass spectrometry analysis confirmed that both iron (0.80 ± 0.09 mol/subunit) and zinc (0.43 ± 0.03 mol/subunit) were bound to the enzyme. Graphite furnace-atomic absorption spectroscopy yielded a value for bound iron of 0.84 ± 0.04 mol/subunit. The absorbance of the enzyme at 398 nm implied a heme content of 0.85 ± 0.09 mol/subunit, and the high pressure liquid chromatography heme assay gave an estimate of 0.71 ± 0.02 mol heme/subunit. Gel permeation chromatography yielded one single peak with a Stokes radius of 6.62 ± 0.7 nm, indicating that the native protein is dimeric. Upon low temperature gel electrophoresis the untreated protein appeared mainly as a monomer (88 ± 3%), but pretreatment with H4biopterin andl-arginine led to a pronounced shift toward dimers (77 ± 4%). Thus, in contrast to bovine eNOS (List, B. M., Klösch, B., Völker, C., Gorren, A. C. F., Sessa, W. C., Werner, E. R., Kukovetz, W. R., Schmidt, K., and Mayer, B. (1997) Biochem. J. 323, 159–165; Rodriguez-Crespo, I., Gerber, N. C., and Ortiz de Montellano, P. R. (1996) J. Biol. Chem. 271, 11462–11467), the human eNOS appears to be markedly stabilized by H4biopterin.

Anodic stripping voltammetric determination of titanium(IV) using a carbon paste electrode modified with cetyltrimethylammonium bromide.

A method is described for the voltammetric determination of titanium(IV) using a carbon paste electrode modified in situ with cetyltrimethylammonium bromide. The cationic micellar surfactant adsorbs onto the electrode particularly at negative potentials, simultaneously preconcentrating titanium(IV) as the oxalate complex with reduction to titanium(III). Anodic stripping voltammetry exploiting reoxidation can be used for the determination of trace levels of titanium(IV). Linearity between current and concentration exists between 5 and 160 mug l(-1) Ti(IV) (preconcentration time 2 min). The limit of detection (calculated as 3sigma) is 0.1 mug l(-1), with a preconcentration time of 10 min.

Individual variability in the human metabolism of an arsenic-containing carbohydrate, 2′,3′-dihydroxypropyl 5-deoxy-5-dimethylarsinoyl-β-D-riboside, a naturally occurring arsenical in seafood.

We report studies on the variability in human metabolism of an oxo-arsenosugar involving the ingestion of a chemically synthesized arsenosugar and quantitative determination of the arsenic metabolites in urine and serum by HPLC coupled with arsenic-selective mass spectrometric detection (ICPMS, inductively coupled plasma mass spectrometry). The total, four-day, urinary excretion of arsenic for six volunteers ranged widely from ca. 4-95%. The arsenic metabolites present in the urine also showed great variability: high arsenic excretion was accompanied by almost complete biotransformation of the ingested oxo-arsenosugar into a multitude of metabolites (>10), whereas the subjects that excreted low amounts of arsenic produced low quantities of metabolites relative to unchanged oxo-arsenosugar and its thio-analogue. Major arsenic urinary metabolites were dimethylarsinate (DMA) and possible intermediates in the degradation of arsenosugar to DMA, namely, dimethylarsinoylethanol (DMAE) and dimethylarsinoylacetate (DMAA) present both as their oxo- and thio-analogues. Thio-DMAE and thio-DMAA were also found in blood serum indicating that these species were formed in the liver rather than on storage of the urine in the bladder. The large variability in the way individuals metabolize arsenosugars has implications for risk assessment of arsenic intake from seafood.

Identification of arsenolipids with GC/MS

Arsenic-containing hydrocarbons have recently been reported as natural constituents of fish oil. We report a simple method for determining these compounds by GC/MS. Application of the methodology will delineate the distribution of these novel arsenic compounds in foods, and facilitate an assessment of the toxicological implications.

Flow-injection amperometric determination of glucose using a biosensor based on immobilization of glucose oxidase onto Au seeds decorated on core Fe3O4 nanoparticles

An amperometric biosensor based on chemisorption of glucose oxidase (GOx) on Au seeds decorated on magnetic core Fe3O4 nanoparticles (Fe3O4@Au) and their immobilization on screen-printed carbon electrode bulk-modified with manganese oxide (SPCE{MnO2}) was designed for the determination of glucose. The Fe3O4@Au/GOx modified SPCE{MnO2} was used in a flow-injection analysis (FIA) arrangement. The experimental conditions were investigated in amperometric mode with the following optimized parameters: flow rate 1.7 mL min(-1), applied potential +0.38 V, phosphate buffer solution (PBS; 0.1 mol L(-1), pH 7.0) as carrier and 3.89 unit mm(-2) enzyme glucose oxidase loading on the active surface of the SPCE. The designed biosensor in FIA arrangement yielded a linear dynamic range for glucose from 0.2 to 9.0 mmol L(-1) with a sensitivity of 2.52 µA mM(-1) cm(-2), a detection limit of 0.1 mmol L(-1) and a quantification limit of 0.3 mmol L(-1). Moreover, a good repeatability of 2.8% (number of measurements n=10) and a sufficient reproducibility of 4.0% (number of sensors n=3) were achieved. It was found that the studied system Fe3O4@Au facilitated not only a simpler enzyme immobilization but also provided wider linear range. The practical application of the proposed biosensor for FIA quantification of glucose was tested in glucose sirup samples, honeys and energy drinks with the results in good accordance with those obtained by an optical glucose meter and with the contents declared by the producers.