Accumulation of molybdenum in major organs following repeated oral administration of bis-choline tetrathiomolybdate in the Sprague Dawley rat.

Molybdenum is an essential dietary trace element required for several critical enzyme systems. High intake is associated with toxicity in ruminants and animal studies. The proposed therapeutic use of molybdenum-based drugs poses a potential risk for accumulation through chronic administration of therapeutic doses of this element. The current experiment was designed to study the effect of daily dosing of a molybdenum compound, bis-choline tetrathiomolybdate (TTM), in Sprague Dawley rats using laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-ToF-MS) and two dosing levels of TTM for up to 3 months. To investigate if molybdenum accumulation was associated with tissue toxicity, histopathology, haematology and clinical biochemistry markers of toxicity were incorporated into the study design. There were no behavioural signs of toxicity to the rats, and no clinical or anatomic pathology was associated with treatment. The current data did show a progressive accumulation of molybdenum within the adrenal gland, kidneys, liver, spleen, brain and testes. Although this was not associated with tissue toxicity within the 3-month study design, greater exposure over a longer period of time has the potential for producing adverse pathophysiological cellular function. Tissue toxicity, as a result of local excessive accumulation of molybdenum over time, has clear implications for the therapeutic use of molybdenum in humans and demands sensitive monitoring of tissue molybdenum levels to avoid toxicity. The current study highlights the shortcomings of conventional biomonitoring approaches to detect molybdenum accumulation with the goal of avoiding molybdenum-associated toxicity.

Polymorphism of CaCO3 and the variability of elemental composition of the calcareous skeletons secreted by invertebrates along the salinity gradient of the Baltic Sea.

Biomineralization is of great importance in ecosystem functioning and for the use of carbonate skeleton as environmental proxies. Skeletal formation is controlled to different degrees by environmental parameters and biological mechanisms. While salinity is one of the most important factors affecting ecological processes and ocean physiochemistry, the goal of this investigation was to identify how salinity influences the mineral type and the concentrations of chemical elements in the whole skeleton of invertebrates from the Baltic Sea. In this model system, the surface salinity decreases from marine values (27.2) to almost fresh water (6.1). The selected organisms, mussels (Mytilus spp.), bryozoans (Einhornia crustulenta, Cribrilina cryptooecium, Cryptosula pallasiana, Electra pilosa, Escharella immersa), barnacles (Amphibalanus improvisus, Semibalanus balanoides), and polychaetes (Spirorbis tridentatus), precipitated skeleton composed of calcite and aragonite, most likely as a result of various interacting environmental and biological factors. The concentrations of all elements in bulk skeleton were highly variable between species from the same location, underlining the role of the biological mechanisms in skeletal formation. The concentration of Ca, Mg, Sr, and Na increased in the bulk skeleton of stenohaline organisms with increasing salinity, while in the bulk skeleton of euryhaline species, only the concentration of Na increased with increasing salinity. The concentrations of Mn, Ba, Cu, Pb, Y, V, Cd, and U in the skeleton of euryhaline species generally decreased at higher salinities, most likely reflecting the lower bioavailability of elements at higher salinity. However, the concentrations of elements in the skeleton of stenohaline organisms were highly variable with no clear salinity impact. This study suggests that, although the composition of skeleton of calcifying organisms along the salinity gradient of the Baltic Sea is to a large extent affected by biological mechanisms, it also reflects the responses to environmental conditions.

Wood Nutrient-Water-Density Linkages Are Influenced by Both Species and Environment.

Tropical trees store a large amount of nutrients in their woody tissues, thus triggering the question of what the functional association of these elements with other wood traits is. Given the osmotic activity of mineral elements such as potassium, sodium, and calcium, these elements should be strong candidates in mediating the water storing capacity in tropical trees. We investigated the role of wood nutrients in facilitating wood water storage in trees by using branch samples from 48 tropical tree species in South America and examined their associations with wood density (ρ). Wood density varied from 316 kg/m3 in Peru plots, where the soil nutrient status is relatively higher, to 908 kg/m3 in Brazil plots, where the nutrient availability is lower. Phosphorus content in wood varied significantly between plots with lowest values found in French Guiana (1.2 mol/m3) and plots with highest values found in Peru (43.6 mol/m3). Conversely, potassium in woody tissues showed a significant cross-species variation with Minquartia guianensis in Brazil showing the lowest values (8.8 mol/m3) and with Neea divaricata in Peru having the highest values (114 mol/m3). We found that lower wood density trees store more water in their woody tissues with cations, especially potassium, having a positive association with water storage. Specific relationships between wood cation concentrations and stem water storage potential nevertheless depend on both species' identity and growing location. Tropical trees with increased water storage capacity show lower wood density and have an increased reliance on cations to regulate this reservoir. Our study highlights that cations play a more important role in tropical tree water relations than has previously been thought, with potassium being particularly important.

Cadmium isotope fractionation reveals genetic variation in Cd uptake and translocation by Theobroma cacao and role of natural resistance-associated macrophage protein 5 and heavy metal ATPase-family transporters.

In response to new European Union regulations, studies are underway to mitigate accumulation of toxic cadmium (Cd) in cacao (Theobroma cacao, Tc). This study advances such research with Cd isotope analyses of 19 genetically diverse cacao clones and yeast transformed to express cacao natural resistance-associated macrophage protein (NRAMP5) and heavy metal ATPases (HMAs). The plants were enriched in light Cd isotopes relative to the hydroponic solution with Δ114/110Cdtot-sol = -0.22 ± 0.08‰. Leaves show a systematic enrichment of isotopically heavy Cd relative to total plants, in accord with closed-system isotope fractionation of Δ114/110Cdseq-mob = -0.13‰, by sequestering isotopically light Cd in roots/stems and mobilisation of remaining Cd to leaves. The findings demonstrate that (i) transfer of Cd between roots and leaves is primarily unidirectional; (ii) different clones utilise similar pathways for Cd sequestration, which differ from those of other studied plants; (iii) clones differ in their efficiency of Cd sequestration. Transgenic yeast that expresses TcNRAMP5 (T. cacao natural resistance-associated macrophage gene) had isotopically lighter Cd than did cacao. This suggests that NRAMP5 transporters constitute an important pathway for uptake of Cd by cacao. Cd isotope signatures of transgenic yeast expressing HMA-family proteins suggest that they may contribute to Cd sequestration. The data are the first to record isotope fractionation induced by transporter proteins in vivo.

Tropical Tree Branch-Leaf Nutrient Scaling Relationships Vary With Sampling Location.

Bivariate relationships between plant tissue nutrient concentration have largely been studied across broad environmental scales regardless of their covariation with soil and climate. Comparing leaf and branch wood concentrations of C, Ca, K, Mg, N, Na, and P for trees growing in tropical forests in Amazonia and Australia we found that the concentrations of most elements varied with sampling location, but with foliar and branch woody tissues varying from site to site in different ways. Using a Mixed Effect Model (MEM) approach it was further found that relationships between branch and leaf concentrations within individual plots differed in terms of both slope and/or significance to the ordinary least squares (OLS) estimates for most elements. Specifically, using MEM we found that within plots only K and Mg were correlated across organs, but with the K cross-organ intercept estimates varying significantly between sites. MEM analyses further showed that within-plot wood density variations were also negatively related to wood K and Na, suggesting a potentially important role for these cations in water transport and/or storage in woody tissues. The OLS method could not detect significant correlations in any of the above cases. By contrast, although Ca, N, and P leaf and wood tissue concentrations showed similar patterns when individual elements were compared across sites, MEM analyses suggested no consistent association within sites. Thus, for all these three elements, strong within-tree scaling relationships were inferred when data were analyzed across sites using OLS, even though there was no relationship within individual sites. Thus (as for Ca, N, and P) not only can a pooling of data across sites result in trait (co)variations attributable to the environment potentially being incorrectly attributed solely to the species and/or individual (the so-called "ecological fallacy"), but in some cases (as was found here for K and Na) the opposite can also sometimes occur with significant within-site covariations being obscured by large site-site variations. We refer to the latter phenomenon as "environmental obfuscation."

Determination of major and trace element variability in healthy human urine by ICP-QMS and specific gravity normalisation.

Sixty five urine samples obtained during one or two non-consecutive days from 10 healthy individuals were analysed for major (Na, Mg, K, Ca) and trace (Co, Cu, Zn, As, Rb, Sr, Mo and Pb) element concentrations. Following microwave digestion, the analyses were carried out using ICP-QMS (inductively coupled plasma quadrupole mass spectrometry) incorporating a collision/reaction cell. Repeat analyses of quality control samples show that the procedure produces unbiased results and is well suited for routine urinalysis of the investigated elements. Concentrations were normalised using specific gravity (SG) and the resultant decrease in variability supports previous conclusions that SG-normalisation appropriately corrects for differences in urine dilution. The elemental concentrations of the individual urine samples show large differences in dispersion. Most variable are As, Co and Zn, with CVs (coefficients of variation) of >75%. The major elements as well as Rb, Sr and Mo display intermediate variability, whilst Cu and Pb have the least elemental dispersion with CV values of about 30%. A detailed assessment shows that the overall elemental variability is governed both by differences between individuals and variations for a single individual over time. Spot urine samples exhibit elemental concentrations that, on average, resemble the daily mean values to within about 30% for all elements except K and Rb. Diet-related changes in urinary element concentration are most prominent for Mg, K, Co, Rb and Pb. The concentrations of Co, As and Rb appear to vary systematically with gender but this may primarily reflect co-variance with specific diets.

Size effect on the mineralogy and chemistry of Mytilus trossulus shells from the southern Baltic Sea: implications for environmental monitoring.

Mussels have the ability to control biomineral production and chemical composition, producing shells with a range of functions. In addition to biological control, the environment also seems to influence the process of biomineralization; thus, shells can be used as archives of ambient water parameters during the calcium carbonate deposition. Past and present environmental conditions are recorded in the shells in the form of various proxies including Mg/Ca or Sr/Ca ratios. For such proxies to be accurate and robust, the influence of biological effects including the size of studied organism must be examined and eliminated or minimized, so that the environmental signal can be efficiently extracted. This study considers mineralogy and elemental composition of shells representing four size classes of Mytilus trossulus from the Baltic Sea. Obtained results suggest that mineralogy and chemical composition change throughout the shell development due to most likely a combination of environmental and biological factors. The content of aragonite increases with increasing shell size, while the bulk concentrations of Na, Cd, Cu, U, V, Zn and Pb were found to decrease with increasing height of the shells. Therefore, using mussels for environmental monitoring requires analysis of individuals in the same size range.

Return of naturally sourced Pb to Atlantic surface waters.

Anthropogenic emissions completely overwhelmed natural marine lead (Pb) sources during the past century, predominantly due to leaded petrol usage. Here, based on Pb isotope measurements, we reassess the importance of natural and anthropogenic Pb sources to the tropical North Atlantic following the nearly complete global cessation of leaded petrol use. Significant proportions of up to 30-50% of natural Pb, derived from mineral dust, are observed in Atlantic surface waters, reflecting the success of the global effort to reduce anthropogenic Pb emissions. The observation of mineral dust derived Pb in surface waters is governed by the elevated atmospheric mineral dust concentration of the North African dust plume and the dominance of dry deposition for the atmospheric aerosol flux to surface waters. Given these specific regional conditions, emissions from anthropogenic activities will remain the dominant global marine Pb source, even in the absence of leaded petrol combustion.

Perovskites with the Framework-Forming Xenon.

The Group 18 elements (noble gases) were the last ones in the periodic system to have not been encountered in perovskite structures. We herein report the synthesis of a new group of double perovskites KM(XeNaO6) (M = Ca, Sr, Ba) containing framework-forming xenon. The structures of the new compounds, like other double perovskites, are built up of the alternating sequence of corner-sharing (XeO6) and (NaO6) octahedra arranged in a three-dimensional rocksalt order. The fact that xenon can be incorporated into the perovskite structure provides new insights into the problem of Xe depletion in the atmosphere. Since octahedrally coordinated Xe(VIII) and Si(IV) exhibit close values of ionic radii (0.48 and 0.40 Å, respectively), one could assume that Xe(VIII) can be incorporated into hyperbaric frameworks such as MgSiO3 perovskite. The ability of Xe to form stable inorganic frameworks can further extend the rich and still enigmatic chemistry of this noble gas.

Zinc isotopic compositions of breast cancer tissue.

An early diagnostic biomarker for breast cancer is essential to improve outcome. High precision isotopic analysis, originating in Earth sciences, can detect very small shifts in metal pathways. For the first time, the natural intrinsic Zn isotopic compositions of various tissues in breast cancer patients and controls were determined. Breast cancer tumours were found to have a significantly lighter Zn isotopic composition than the blood, serum and healthy breast tissue in both groups. The Zn isotopic lightness in tumours suggests that sulphur rich metallothionein dominates the isotopic selectivity of a breast tissue cell, rather than Zn-specific proteins. This reveals a possible mechanism of Zn delivery to Zn-sequestering vesicles by metallothionein, and is supported by a similar signature observed in the copper isotopic compositions of one breast cancer patient. This change in intrinsic isotopic compositions due to cancer has the potential to provide a novel early biomarker for breast cancer.

Stable isotope ratio measurements of Cu and Zn in mineral dust (bulk and size fractions) from the Taklimakan Desert and the Sahel and in aerosols from the eastern tropical North Atlantic Ocean.

Accurate characterization of the stable isotope composition of Cu and Zn in major global mineral dust sources and in aerosols is central to the application of these isotope systems to the studies of global geochemical processes and cycles. We test here for the first time Cu and Zn isotope ratios within a well-defined source-receptor setting on the continent-ocean interface and determine the isotope composition of (i) bulk surface soil dust samples from the Sahel region, (ii) individual size fractions of surface dust samples from the Taklimakan Desert, and (iii) aerosols collected in the equatorial eastern North Atlantic region. This is achieved reducing the blank contribution during the ion exchange step using small resin and acid volumes and using a second ion exchange passage to purify the Cu fraction. We find no significant correlation between size fractions and isotope ratios in the two samples analyzed from the Taklimakan Desert. Mass balance calculations suggest that isotope ratios of bulk samples are within the analytical precision of the <4 µm size fraction and can be used to characterize atmospheric long range transport of Cu and Zn in mineral dust from the Taklimakan Desert. The <1 µm size fractions of two aerosol samples collected over the equatorial eastern North Atlantic region have Cu and Zn isotope ratios that are different to Sahel surface soil dust suggesting important non-crustal sources, in line with calculated enrichment factors, and possibly of anthropogenic origin. Using previously reported δ(66)Zn values for anthropogenic emission from Europe, preliminary calculations suggest that up to 55% of Zn arriving at the sampling points in the equatorial eastern North Atlantic region could be of anthropogenic origin.

Bioaccumulation dynamics and modeling in an estuarine invertebrate following aqueous exposure to nanosized and dissolved silver.

Predicting the environmental impact of engineered nanomaterials (ENMs) is increasingly important owing to the prevalence of emerging nanotechnologies. We derived waterborne uptake and efflux rate constants for the estuarine snail, Peringia ulvae, exposed to dissolved Ag (AgNO(3)) and silver nanoparticles (Ag NPs), using biodynamic modeling. Uptake rates demonstrated that dissolved Ag is twice as bioavailable as Ag in nanoparticle form. Biphasic loss dynamics revealed the faster elimination of Ag from Ag NPs at the start of depuration, but similar slow efflux rate constants. The integration of biodynamic parameters into our model accurately predicted Ag tissue burdens during chronic exposure with 85% of predicted values within a factor of 2 of observed values. Zeta potentials for the Ag NPs were lower in estuarine waters than in waters of less salinity; and uptake rates in P. ulvae were slower than reported for the freshwater snail Lymnaea stagnalis in similar experiments. This suggests aggregation of Ag NPs occurs in estuarine waters and reduces, but does not eliminate, bioavailability of Ag from the Ag NPs. Biodynamic modeling provides an effective methodology to determine bioavailable metal concentrations (originating from metal and metal-oxide nanoparticles) in the environment and may aid future ENM risk assessment.

A single procedure for the accurate and precise quantification of the rare earth elements, Sc, Y, Th and Pb in dust and peat for provenance tracing in climate and environmental studies.

The geochemical provenancing of atmospheric dust deposited in terrestrial archives such as peat bogs using trace elements is central to the study of atmospheric deposition over the continents and at the heart of many climate and environmental studies. The use of a single digestion method on all sample types involved in such a study (dust archive and sources) minimizes the contribution of the total analytical error when comparing sample compositions and attributing a source to the deposited dust. To date, this factor is limiting progress in geographical areas where the compositional variations between the sources and within the archive are small. Here, seven microwave and hot plate digestion methods were tested on rock, soil and plant reference materials to establish a unique method optimizing precision and accuracy in all sample types. The best results were obtained with a hot plate closed-vessel digestion with 2 ml HF and 0.5 ml HNO(3) for 0.1g of sample, which allowed the precise, accurate and low blank quantification of the trace elements La-Yb, Sc, Y, Th and Pb by ICP-MS. This method was tested in a climate study in central Asia and temporal changes in the dominant dust source were for the first time successfully linked to changes in atmospheric circulation patterns above this region.

Elevated urinary excretion of aluminium and iron in multiple sclerosis.

Multiple sclerosis (MS) is a chronic, immune-mediated, demyelinating disease of the central nervous system of as yet unknown aetiology. A consensus of opinion has suggested that the disorder is the result of an interplay between environmental factors and susceptibility genes. We have used a battery of analytical techniques to determine if the urinary excretion of i) markers of oxidative damage; ii) iron and iii) the environmental toxin aluminium and its antagonist, silicon, are altered in relapsing-remitting (RRMS) and secondary progressive MS (SPMS). Urinary concentrations of oxidative biomarkers, MDA and TBARS, were not found to be useful indicators of inflammatory disease in MS. However, urinary concentrations of another potential marker for inflammation and oxidative stress, iron, were significantly increased in SPMS (P<0.01) and insignificantly increased in RRMS (P>0.05). Urinary concentrations of aluminium were also significantly increased in RRMS (P<0.001) and SPMS (P <0.05) such that the levels of aluminium excretion in the former were similar to those observed in individuals undergoing metal chelation therapy. The excretion of silicon was lower in MS and significantly so in SPMS (P<0.05). Increased excretion of iron in urine supported a role for iron dysmetabolism in MS. Levels of urinary aluminium excretion similar to those seen in aluminium intoxication suggested that aluminium may be a hitherto unrecognized environmental factor associated with the aetiology of MS. If aluminium is involved in MS then an increased dietary intake of its natural antagonist, silicon, might be a therapeutic option.

Non-invasive therapy to reduce the body burden of aluminium in Alzheimer's disease.

There are unexplained links between human exposure to aluminium and the incidence, progression and aetiology of Alzheimer's disease. The null hypothesis which underlies any link is that there would be no Alzheimer's disease in the effective absence of a body burden of aluminium. To test this the latter would have to be reduced to and retained at a level that was commensurate with an Alzheimer's disease-free population. In the absence of recent human interference in the biogeochemical cycle of aluminium the reaction of silicic acid with aluminium has acted as a geochemical control of the biological availability of aluminium. This same mechanism might now be applied to both the removal of aluminium from the body and the reduced entry of aluminium into the body while ensuring that essential metals, such as iron, are unaffected. Based upon the premise that urinary aluminium is the best non-invasive estimate of body burden of aluminium patients with Alzheimer's disease were asked to drink 1.5 L of a silicic acid-rich mineral water each day for five days and, by comparison of their urinary excretion of aluminium pre-and post this simple procedure, the influence upon their body burden of aluminium was determined. Drinking the mineral water increased significantly (P<0.001) their urinary excretion of silicic acid (34.3 +/- 15.2 to 55.7 +/- 14.2 micromol/mmol creatinine) and concomitantly reduced significantly P=0.037) their urinary excretion of aluminium (86.0 +/- 24.3 to 62.2 +/- 23.2 nmol/mmol creatinine). The latter was achieved without any significant (P>0.05) influence upon the urinary excretion of iron (20.7 +/- 9.5 to 21.7 +/- 13.8 nmol/mmol creatinine). The reduction in urinary aluminium supported the future longer-term use of silicic acid as non-invasive therapy for reducing the body burden of aluminium in Alzheimer's disease.