Elemental hyper-accumulation in mushrooms with a focus on arsenic

Mushrooms play an important role in the biogeochemical cycling of trace elements. They do neither belong to plants nor to animals but form their own kingdom. Some mushrooms live in symbiosis with plants or as parasites on other living organisms. Mushrooms are abundant worldwide. Although omnipresent, they only become noticeable when fruiting bodies are produced. Mushrooms are becoming a more important part of our diet and are used in various aspects of our life. They are used for antibiotics production, in the food industry(wine, cheese...) but also as biological pesticides. New applications cover plastics degradation and use as a leather replacement. Some mushrooms can grow very fast and are able to (hyper)accumulate elements from the surrounding soil. This presentation will cover elemental accumulation by mushrooms with a focus on the unique arsenic speciation in mushrooms

The contents of risk elements, arsenic speciation, and possible interactions of elements and betalains in beetroot (Beta vulgaris, L.) growing in contaminated soil

The effect of enhanced soil risk element contents on the uptake of As, Cd, Pb, and Zn was determined in two pot experiments. Simultaneously, transformation of arsenic and its compounds in beetroot (Beta vulgaris L.) plants was investigated. The mobile fractions of elements were determined in 0.05 mol L−1 (NH4)2SO4 extracts and did not exceed 2% of total soil arsenic, 9% of total cadmium, 3% of total lead, and 8% of total zinc, respectively. Although the soils were extremely contaminated the mobile portions of the elements represented only a small fragment of the total element content. Arsenic contents in beet plants reached up to 25 mg As kg−1 in roots and 48 mg As kg−1 in leaves in the soil characterized by the highest mobile arsenic portion. Arsenic portions extractable with water and phosphate buffer from the beetroot samples did not show significant differences between the extraction agents but the extractability was affected by the arsenic concentration. Arsenic was almost quantitatively extractable from the samples with the lowest total arsenic concentration, whereas in the samples with the highest total arsenic concentration less than 25% was extractable. Arsenate was the dominant arsenic compound in the extracts (70% in phosphate buffer, 50% in water extracts). A small portion of dimethylarsinic acid, not exceeding 0.5%, was detected only in the sample growing in the soil with the highest arsenic concentration. The role of betalains (betanin, isobetanin, vulgaxanthin I and vulgaxanthin II) in transformation/detoxification of arsenic in plants was not confirmed in this experiment because the plants were able to grow in the contaminated soil without any symptoms of arsenic toxicity

METAL CONTENTS IN FISH AND CRUSTACEANS FROM BRACKISH, FRESHWATER AND MARINE SYSTEMS IN SOUTH-WESTERN NIGERIA

Prikazanom studijom istražene su koncentracije elemenata u tragovima u mišićima ili cijelim uzorcima 37 riba i rakova sakupljenim mrežama stajačicama u slatkovodnim (Olomore), morskim (Eti osa) i boćatim vodama nigerijskih država Ogun i Lagos, od lipnja do kolovoza 2013. Elementi u tragovima utvrđeni su pomoću ICP-MS nakon digestije u mikrovalnom autoklavnom sustavu. Razultati su otkrili kako je opći trend elemenata u tragovima u uzorkovanim ribama i rakovima morski > boćati > slatkovodni. Uzimajući u obzir sve uzorke, 16,2% i 13,5% prekoračilo je granice bakra i cinka (20 µg g-1 i 30 µg g-1), propisane od strane Europske Unije, dok je 71%, 50%, 79% morskih, slatkovodnih i boćatih uzoraka prekoračilo granicu od 48mg željeza na 60kg čovjeka, koju je postavila FAO/WHO. Uzorci su premašili prihvatljivu granicu postavljenu od strane FAO/WHO, čime je dokazano kako je potrebno uložiti trud u monitoring otpadnih voda koje se ispuštaju u otvorene vode Nigerije.Present study investigated trace element concentrations in either muscles or whole samples of 37 finfish and crustaceans harvested with gillnet from fresh (Olomore), marine (Eti osa) and brackish (Lekki Lagoon) waters of Ogun and Lagos states, Nigeria between June and August 2013. Trace elements were determined using ICP-MS after digestion with a microwave autoclave system. The results revealed that the general trend of trace elements in the sampled finfish and crustaceans was marine > brackish > freshwater. If all the samples are considered, 16.2% and 13.5% exceeded the 20 µg g-1 and 30 µg g-1 limits for Cu and Zn, respectively, as set by the European Union, while 71%, 50%, 79% of marine, fresh and brackish samples, respectively, exceeded the limit of 48 mg Fe per 60 kg person as set by FAO/WHO. In addition, samples exceeded the acceptable limit set by WHO/FAO, thus adequate efforts should be placed on the monitoring of effluents that are being discharged into open water bodies in Nigeria

METAL CONTENTS IN FISH AND CRUSTACEANS FROM BRACKISH, FRESHWATER AND MARINE SYSTEMS IN SOUTH-WESTERN NIGERIA

Prikazanom studijom istražene su koncentracije elemenata u tragovima u mišićima ili cijelim uzorcima 37 riba i rakova sakupljenim mrežama stajačicama u slatkovodnim (Olomore), morskim (Eti osa) i boćatim vodama nigerijskih država Ogun i Lagos, od lipnja do kolovoza 2013. Elementi u tragovima utvrđeni su pomoću ICP-MS nakon digestije u mikrovalnom autoklavnom sustavu. Razultati su otkrili kako je opći trend elemenata u tragovima u uzorkovanim ribama i rakovima morski > boćati > slatkovodni. Uzimajući u obzir sve uzorke, 16,2% i 13,5% prekoračilo je granice bakra i cinka (20 µg g-1 i 30 µg g-1), propisane od strane Europske Unije, dok je 71%, 50%, 79% morskih, slatkovodnih i boćatih uzoraka prekoračilo granicu od 48mg željeza na 60kg čovjeka, koju je postavila FAO/WHO. Uzorci su premašili prihvatljivu granicu postavljenu od strane FAO/WHO, čime je dokazano kako je potrebno uložiti trud u monitoring otpadnih voda koje se ispuštaju u otvorene vode Nigerije.Present study investigated trace element concentrations in either muscles or whole samples of 37 finfish and crustaceans harvested with gillnet from fresh (Olomore), marine (Eti osa) and brackish (Lekki Lagoon) waters of Ogun and Lagos states, Nigeria between June and August 2013. Trace elements were determined using ICP-MS after digestion with a microwave autoclave system. The results revealed that the general trend of trace elements in the sampled finfish and crustaceans was marine > brackish > freshwater. If all the samples are considered, 16.2% and 13.5% exceeded the 20 µg g-1 and 30 µg g-1 limits for Cu and Zn, respectively, as set by the European Union, while 71%, 50%, 79% of marine, fresh and brackish samples, respectively, exceeded the limit of 48 mg Fe per 60 kg person as set by FAO/WHO. In addition, samples exceeded the acceptable limit set by WHO/FAO, thus adequate efforts should be placed on the monitoring of effluents that are being discharged into open water bodies in Nigeria

Susceptibility induced gray–white matter MRI contrast in the human brain

AbstractMR phase images have shown significantly improved contrast between cortical gray and white matter regions compared to magnitude images obtained with gradient echo sequences. A variety of underlying biophysical mechanisms (including iron, blood, myelin content, macromolecular chemical exchange, and fiber orientation) have been suggested to account for this observation but assessing the individual contribution of these factors is limited in vivo.For a closer investigation of iron and myelin induced susceptibility changes, postmortem MRI of six human corpses (age range at death: 56–80years) was acquired in situ. Following autopsy, the iron concentrations in the frontal and occipital cortex as well as in white matter regions were chemically determined. The magnetization transfer ratio (MTR) was used as an indirect measure for myelin content. Susceptibility effects were assessed separately by determining R2* relaxation rates and quantitative phase shifts. Contributions of myelin and iron to local variations of the susceptibility were assessed by univariate and multivariate linear regression analysis.Mean iron concentration was lower in the frontal cortex than in frontal white matter (26±6 vs. 45±6mg/kg wet tissue) while an inverse relation was found in the occipital lobe (cortical gray matter: 41±10 vs. white matter: 34±10mg/kg wet tissue). Multiple regression analysis revealed iron and MTR as independent predictors of the effective transverse relaxation rate R2* but solely MTR was identified as source of MR phase contrast. R2* was correlated with iron concentrations in cortical gray matter only (r=0.42, p<0.05).In conclusion, MR phase contrast between cortical gray and white matter can be mainly attributed to variations in myelin content, but not to iron concentration. Both, myelin and iron impact the effective transverse relaxation rate R2* significantly. Magnitude contrast is limited because it only reflects the extent but not the direction of the susceptibility shift

Association of Cardiometabolic Genes with Arsenic Metabolism Biomarkers in American Indian Communities: The Strong Heart Family Study (SHFS)

Background: Metabolism of inorganic arsenic (iAs) is subject to inter-individual variability, which is explained partly by genetic determinants. Objectives: We investigated the association of genetic variants with arsenic species and principal components of arsenic species in the Strong Heart Family Study (SHFS). Methods: We examined variants previously associated with cardiometabolic traits (~ 200,000 from Illumina Cardio MetaboChip) or arsenic metabolism and toxicity (670) among 2,428 American Indian participants in the SHFS. Urine arsenic species were measured by high performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICP-MS), and percent arsenic species [iAs, monomethylarsonate (MMA), and dimethylarsinate (DMA), divided by their sum × 100] were logit transformed. We created two orthogonal principal components that summarized iAs, MMA, and DMA and were also phenotypes for genetic analyses. Linear regression was performed for each phenotype, dependent on allele dosage of the variant. Models accounted for familial relatedness and were adjusted for age, sex, total arsenic levels, and population stratification. Single nucleotide polymorphism (SNP) associations were stratified by study site and were meta-analyzed. Bonferroni correction was used to account for multiple testing. Results: Variants at 10q24 were statistically significant for all percent arsenic species and principal components of arsenic species. The index SNP for iAs%, MMA%, and DMA% (rs12768205) and for the principal components (rs3740394, rs3740393) were located near AS3MT, whose gene product catalyzes methylation of iAs to MMA and DMA. Among the candidate arsenic variant associations, functional SNPs in AS3MT and 10q24 were most significant (p \u3c 9.33 × 10–5). Conclusions: This hypothesis-driven association study supports the role of common variants in arsenic metabolism, particularly AS3MT and 10q24

Quantitative susceptibility mapping (QSM) as a means to measure brain iron? A post mortem validation study

AbstractQuantitative susceptibility mapping (QSM) is a novel technique which allows determining the bulk magnetic susceptibility distribution of tissue in vivo from gradient echo magnetic resonance phase images. It is commonly assumed that paramagnetic iron is the predominant source of susceptibility variations in gray matter as many studies have reported a reasonable correlation of magnetic susceptibility with brain iron concentrations in vivo. Instead of performing direct comparisons, however, all these studies used the putative iron concentrations reported in the hallmark study by Hallgren and Sourander (1958) for their analysis. Consequently, the extent to which QSM can serve to reliably assess brain iron levels is not yet fully clear. To provide such information we investigated the relation between bulk tissue magnetic susceptibility and brain iron concentration in unfixed (in situ) post mortem brains of 13 subjects using MRI and inductively coupled plasma mass spectrometry. A strong linear correlation between chemically determined iron concentration and bulk magnetic susceptibility was found in gray matter structures (r=0.84, p<0.001), whereas the correlation coefficient was much lower in white matter (r=0.27, p<0.001). The slope of the overall linear correlation was consistent with theoretical considerations of the magnetism of ferritin supporting that most of the iron in the brain is bound to ferritin proteins. In conclusion, iron is the dominant source of magnetic susceptibility in deep gray matter and can be assessed with QSM. In white matter regions the estimation of iron concentrations by QSM is less accurate and more complex because the counteracting contribution from diamagnetic myelinated neuronal fibers confounds the interpretation

Does plant growing condition affects biodistribution and biological effects of silver nanoparticles?

Among the many different types, silver nanoparticles (AgNPs) are the most commercialized and applied engineered nanoparticles in a wide range of areas, including agriculture. Despite numerous studies on their safety and toxicity of AgNPs, data on their effect and interactions with terrestrial plants are largely unknown. This study aimed to investigate the effect of growing conditions on the response of pepper plants (Capsicum annuum L.) to citrate-coated AgNPs. Growth parameters, biodistribution, and defence response were examined in peppers grown hydroponically or in soil substrate. In addition, the effects of nano and ionic form of silver were compared. The leaves and stems of peppers grown in substrate showed a higher bioaccumulation compared to hydroponically cultivated plants. The nano form of silver accumulated to a higher extent than ionic form in both leaves and stems. Both silver forms inhibited pepper growth to a very similar extent either through hydroponic or substrate growing settings. Unlike other studies, which investigated the effects of unrealistically high doses of AgNPs on different plant species, this study revealed that vascular plants are also susceptible to very low doses of AgNPs. Both silver forms affected all parameters used to evaluate oxidative stress response in pepper leaves ; plant pigment and total phenolics contents were decreased, while lipid peroxidation and hydrogen peroxide level were increased in treated plants. Similar biological effects of both nano and ionic Ag forms were observed for both substrate and hydroponic growing systems

Metal Concentrations in e-Cigarette Liquid and Aerosol Samples:The Contribution of Metallic Coils

Supplemental Material is available online (https://doi.org/10.1289/EHP2175)Electronic cigarettes (e-cigarettes) generate an aerosol by heating a solution (e-liquid) with a metallic coil. Whether metals are transferred from the coil to the aerosol is unknown. Objective: Our goal was to investigate the transfer of metals from the heating coil to the e-liquid in the e-cigarette tank and the generated aerosol. Methods: We sampled 56 e-cigarette devices from daily e-cigarette users and obtained samples from the refilling dispenser, aerosol, and remaining e-liquid in the tank. Aerosol liquid was collected via deposition of aerosol droplets in a series of conical pipette tips. Metals were reported as mass fractions (μg/kg) in liquids and converted to mass concentrations (mg/m3) for aerosols. Results: Median metal concentrations (μg/kg) were higher in samples from the aerosol and tank vs. the dispenser (all p<0.001): 16.3 and 31.2 vs. 10.9 for Al; 8.38 and 55.4 vs. <0.5 for Cr; 68.4 and 233 vs. 2.03 for Ni; 14.8 and 40.2 vs. 0.476 for Pb; and 515 and 426 vs. 13.1 for Zn. Mn, Fe, Cu, Sb, and Sn were detectable in most samples. Cd was detected in 0.0, 30.4, and 55.1% of the dispenser, aerosol, and tank samples respectively. Arsenic was detected in 10.7% of dispenser samples (median 26.7 μg/kg) and these concentrations were similar in aerosol and tank samples. Aerosol mass concentrations (mg/m3) for the detected metals spanned several orders of magnitude and exceeded current health-based limits in close to 50% or more of the samples for Cr, Mn, Ni, and Pb. Conclusions: Our findings indicate that e-cigarettes are a potential source of exposure to toxic metals (Cr, Ni, and Pb), and to metals that are toxic when inhaled (Mn and Zn). Markedly higher concentrations in the aerosol and tank samples versus the dispenser demonstrate that coil contact induced e-liquid contamination.This study is supported by the Cigarette Restitution Fund (State of Maryland; grant PHPA-G2034). P.O. was supported by the Alfonso Martín Escudero Foundation (postdoctoral fellowship 2014). A.A. was supported by the American Heart Association Tobacco Regulation and Addiction Center (grant 1P50HL120163). A.N.A., M.H., and P.O. are supported by the National Institute of Environmental Health Sciences/National Institutes of Health (grant 5P30ES009089)

Reaction Mechanism and Substrate Specificity of Iso-orotate Decarboxylase: A Combined Theoretical and Experimental Study

The C-C bond cleavage catalyzed by metal-dependent iso-orotate decarboxylase (IDCase) from the thymidine salvage pathway is of interest for the elucidation of a (hypothetical) DNA demethylation pathway. IDCase appears also as a promising candidate for the synthetic regioselective carboxylation of N-heteroaromatics. Herein, we report a joint experimental-theoretical study to gain insights into the metal identity, reaction mechanism, and substrate specificity of IDCase. In contrast to previous assumptions, the enzyme is demonstrated by ICPMS/MS measurements to contain a catalytically relevant Mn2+ rather than Zn2+. Quantum chemical calculations revealed that decarboxylation of the natural substrate (5-carboxyuracil) proceeds via a (reverse) electrophilic aromatic substitution with formation of CO2. The occurrence of previously proposed tetrahedral carboxylate intermediates with concomitant formation of HCO3- could be ruled out on the basis of prohibitively high energy barriers. In contrast to related o-benzoic acid decarboxylases, such as γ-resorcylate decarboxylase and 5-carboxyvanillate decarboxylase, which exhibit a relaxed substrate tolerance for phenolic acids, IDCase shows high substrate fidelity. Structural and energy comparisons suggest that this is caused by a unique hydrogen bonding of the heterocyclic natural substrate (5-carboxyuracil) to the surrounding residues. Analysis of calculated energies also shows that the reverse carboxylation of uracil is impeded by a strongly disfavored uphill reaction