Rapid and simple determination of selenium and other trace elements in very small blood samples by XRF

Selenium and other trace elements (Cu, Zn, Br, and Rb) were determined in very small (0.75 μL) human serum and mice whole blood samples, by an XRF method. Accurate results of elemental concentration were obtained without the need of exact volume measurement, because of the backscatter correction used. The XRF method is highly sensitive (M.D.L.=0.06, 0.13, 0.09, 0.07, and 0.05 ppm for Se, Cu, Zn, Br, and Rb, respectively), rapid (counting time—100 s/sample), easy to perform and therefore suitable for routine trace element analyses. The results obtained are in good agreement with the values reported in the literature.     

Reduction of selenium oxyanions by unicellular,polymorphic and filamentous fungi: Cellular location of reduced selenium and implications for tolerance

Summary The ability of several filamentous, polymorphic and unicellular fungi to reduce selenite to elemental selenium on solid medium was examined.Fusarium sp. andTrichoderma reeii were the only filamentous fungi, of those tested, which reduced selenite to elemental selenium on Czapek-Dox agar resulting in a red colouration of colonies. Other organisms (Aspergillus niger, Coriolus versicolor, Mucor SK, andRhizopus arrhizus) were able to reduce selenite only on malt extract agar. Several fungi were able to grow in the presence of sodium selenite but were apparently unable to reduce selenite to elemental selenium, indicating that other mechanisms of selenite tolerance were employed, such as reduced uptake and/or biomethylation to less toxic, volatile derivatives. Sodium selenate was more toxic toFusarium sp. than selenite, and the toxicity of both oxyanions was increased in sulphur-free medium, with this effect being more marked for selenate. Scanning electron microscopy ofAspergillus funiculosus andFusarium sp. incubated with sodium selenite showed the presence of needle-like crystals of elemental selenium on the surfaces of hyphae and conidia, while transmission electron microscopy ofA. funiculosus revealed the deposition of electron-dense granules in vacuoles of selenite-treated fungi. Several yeasts were able to grow on MYGP agar containing sodium selenate or sodium selenite at millimolar concentrations. Sone, notablyRhodotorula rubra andCandida lipolytica, and the polymorphic fungusAureobasidium pullulans were also effective at reducing selenite to elemental selenium, resulting in red-coloured colonies.Schizosaccharomyces pombe was able to grow at selenite concentrations up to 5 mmol L^–1 without any evidence of reduction, again indicating the operation of other tolerance mechanisms.     

The uptake of cadmium,lead and selenium by barley and cabbage grown on soils amended with refuse incinerator fly ash

Summary Barley and cabbage plants grown in the greenhouse on soils amended with refuse incinerator fly ash contained significantly elevated levels of Cd, Pb and Se, with Cd uptake being greatest in both plant species. Cabbage grown on 20% ash amended soil contained 146 times more Cd than controls. Cadmium and Se appeared to be less available in a successive barley crop after overwintering the pots of soil outside, but elemental concentrations still remained elevated. Comparisons with data from other studies indicated that Cd availability was greater from refuse fly ash than from sewage sludge.     

A comparative study of serum selenium and vitamin E levels in a population of male risk drinkers and abstainers

Depressed selenium and Vitamin E levels may contribute to hepatic injury through lipid peroxidation. To study the effect of moderate alcohol drinking (32.4±23.6 g ethanol/d) on serum selenium and serum vitamin E concentrations, we conducted a matched-pair study of 73 healthy, well-nourished risk drinkers and healthy controls with little or no alcohol consumption. Among risk drinkers, serum selenium was significantly lowered (1.49 vs 1.67 μmol/L;p<0.001) compared with controls. Difference in α-tocopherol concentrations did not, however, reach statistical significance (22.8 vs 24.9 μmol/L;p=0.06). Nutritional and life-style factors differed very little between the two groups. We conclude that even moderate alcohol consumption lowers selenium status. Selenium may thus represent a link joining the hepatotoxic and nutritional backgrounds of alcoholic liver disease.     

Interaction of Co,Mn, Mg and Al with d(GCGTACGC): a spectroscopic study

Spectroscopic study on the interactions of trace elements Co, Mn, Mg and Al with d(GCGTACGC) indicated the following: Al and Mg did not alter T_m values. Mn enhanced T_m at lower concentration and decreased it at higher concentrations. Interestingly Co at higher concentration elevated the T_m. These studies also showed lower concentrations of Mn displaced EtBr, whereas Al could displace it at higher ionic strength. Mg and Co displaced EtBr fluorescence at moderate concentrations. The binding constant values and CD spectra clearly indicated strong binding of these elements to DNA.     

Accumulation of an organic anticancer selenium compound in a transgenic Solanaceous species shows wider applicability of the selenocysteine methyltransferase transgene from selenium hyperaccumulators

Tolerance to high selenium (Se) soils in Se-hyperaccumulating plant species is correlated with the ability to biosynthesise methylselenocysteine (MeSeCys), due to the activity of selenocysteine methyltransferase (SMT). In mammals, inclusion of MeSeCys in the diet reduces the incidence of certain cancers, so increasing the range of crop plants that can produce this compound is an attractive biotechnology target. However, in the non-Se accumulator Arabidopsis, overexpression of SMT does not result in biosynthesis of MeSeCys from selenate because the rate at which selenate is reduced to selenite by ATP sulfurylase (ATPS) is low. This limitation is less problematic in other species of the Brassicaceae that can produce MeSeCys naturally. We investigated the potential for biosynthesis of MeSeCys in other plant families using Nicotiana tabacum L., a member of the Solanaceae. When plants were watered with 200 μM selenate, overexpression of a SMT transgene caused a 2- to 4-fold increase in Se accumulation (resulting in increased numbers of leaf lesions and areas of necrosis), production of MeSeCys (up to 20% of total Se) and generation of volatile dimethyl diselenide derived directly from MeSeCys. Despite the greatly increased accumulation of total Se, this did not result in increased Se toxicity effects on growth. Overexpression of ATPS did not increase Se accumulation from selenate. Accordingly, lines overexpressing both ATPS and SMT did not show a further increase in total Se accumulation or in leaf toxicity symptoms relative to overexpression of SMT alone, but directed a greater proportion of Se into MeSeCys. This work demonstrates that the production of the cancer-preventing compound MeSeCys in plants outside the Brassicaceae is possible. We conclude that while the SMT gene from Se hyperaccumulators can probably be utilised universally to increase the metabolism of Se into MeSeCys, the effects of enhancing ATPS activity will vary depending on the species involved.     

Diversity of microbial eukaryotes in sediment at a deep-sea methane cold seep: surveys of ribosomal DNA libraries from raw sediment samples and two enrichment cultures

Recent culture-independent surveys of eukaryotic small-subunit ribosomal DNA (SSU rDNA) from many environments have unveiled unexpectedly high diversity of microbial eukaryotes (microeukaryotes) at various taxonomic levels. However, such surveys were most probably biased by various technical difficulties, resulting in underestimation of microeukaryotic diversity. In the present study on oxygen-depleted sediment from a deep-sea methane cold seep of Sagami Bay, Japan, we surveyed the diversity of eukaryotic rDNA in raw sediment samples and in two enrichment cultures. More than half of all clones recovered from the raw sediment samples were of the basidiomycetous fungus Cryptococcus curvatus. Among other clones, phylotypes of eukaryotic parasites, such as Apicomplexa, Ichthyosporea, and Phytomyxea, were identified. On the other hand, we observed a marked difference in phylotype composition in the enrichment samples. Several phylotypes belonging to heterotrophic stramenopiles were frequently found in one enrichment culture, while a phylotype of Excavata previously detected at a deep-sea hydrothermal vent dominated the other. We successfully established a clonal culture of this excavate flagellate. Since these phylotypes were not identified in the raw sediment samples, the approach incorporating a cultivation step successfully found at least a fraction of the “hidden” microeukaryotic diversity in the environment examined. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Maternal-fetal transport kinetics of copper,selenium, magnesium and iron in perfused human placental lobule: in vitro study

Transport characteristics of certain inorganic elements such as copper, magnesium, selenium and iron have been studied in maternal-fetal direction in normal pregnancies, using in vitro perfusion of isolated placental lobules. Copper, selenium, magnesium and iron salts corresponding to twice physiological concentrations were injected as a 100 l bolus, into the maternal arterial perfusate. Serial perfusate samples were collected from venous outflows for a study period of 5 min. Concentrations of various inorganic elements and their transport kinetics were determined. Transport fractions of copper, selenium, magnesium and iron averaged 0.14, 0.19, 0.06 and 0.23% of maternal load respectively. The pharmacokinetic parameters such as area under the curve, clearance, elimination constant, and time for maximum response showed some significant differences between the various elements. We speculate that copper and selenium share the same transport pathway along a concentration gradient in maternal-fetal direction, while for iron and magnesium, active transport plays a predominant role for element transfer across the human placental membrane.     

Metals,trace elements,and organochlorine compounds in bottom sediment of Tuttle Creek Lake,Kansas, U.S.A.

Bottom-sediment cores were used to investigate the occurrence of 44 metals and trace elements, and 15 organochlorine compounds in Tuttle Creek Lake, a reservoir with an agricultural basin in northeast Kansas, U.S.A. On the basis of U.S. Environmental Protection Agency sediment-quality guidelines, concentrations of Ag, As, Cr, Cu, Ni, and Zn frequently or typically exceeded the threshold-effects levels for toxic biological effects. Organochlorine compounds either were not detected or were detected at concentrations generally below the threshold-effects levels. Statistically significant positive depositional trends were determined for several elements. However, because the vertical profiles of element concentrations typically indicated a bimodal distribution and much of the variability could be attributable to analytical variance, the statistical trends may not represent actual trends. DDE concentrations reflected the history of DDT use. Substantial increases in grain corn and soybean production, irrigated land, and hog production in the basin have not had a discernible effect on sediment quality in the reservoir. Future research focused on small impoundments throughout the basin may enhance understanding of the effects of human activity on sediment quality within the Tuttle Creek Lake system and elsewhere.     

Long-term study of ovine pulmonary adenocarcinogenesis in sheep with marginal vs. sufficient nutritional selenium supply: Results from computed tomography,pathology, immunohistochemistry,JSRV-PCR and lung biochemistry

The impact of selenium (Se) in carcinogenesis is still debatable due to inconsistent results of observational studies, recent suspicion of diabetic side effects and e.g. dual roles of glutathione peroxidases (GPx). Previously, our group introduced long-term studies on lung carcinogenesis using the jaagtsiekte sheep retrovirus (JSRV) induced ovine pulmonary adenocarcinoma (OPA) as an innovative animal model. The present report describes the results of sufficient (0.2 mg Se/kg dry weight (dw)) vs. marginal (<0.05 mg Se/kg dw) nutritional Se supply on cancer progression over a two-year period in 16 animals. Computed tomography (CT) evaluation of lung cancer progression, final pathological examination, evidence of pro-viral JSRV-DNA in lung, lymph nodes and broncho-alveolar lavage cells as well as biochemical analysis of Se, GPx1 and thioredoxin reductase (TrxR) activity in lung tissue were recorded. Additionally, immunohistochemical determination of GPx1 expression in unaffected and neoplastic lung cells was implemented.The feeding regime caused significant differences in Se concentration and GPx1 activity in lung tissue between groups, whereas TrxR activity remained unaffected. JSRV was evident in broncho-alveolar lavage cells, lung tissue and lung lymph nodes. Quarterly executed CT could not demonstrate differences in lung cancer proliferation intensity. Necropsy and histopathology substantiated CT findings. Immunohistochemical analysis of GPx1 in lung tissue suggested a coherency of GPx1 immunolabelling intensity in dependence of tumour size.It was concluded that the model proved to be suitable for long-term studies of lung cancer proliferation including the impact of modifiable nutritional factors. Proliferation of OPA was unaffected by marginal vs. sufficient nutritional Se supply.     

Lithium as a normal metabolite: some implications for cyclotron resonance of ions in magnetic fields

Cyclotron resonance of ions has been proposed as a mechanism by which weak, extremely-low-frequency (ELF) electromagnetic fields can act on biological systems. Critics of a mechanism predicated on resonance of lithium have argued that this element is virtually absent from the internal milieu of mammals and otherwise plays no role in the normal physiological functioning of the organism. Sophisticated techniques of trace-element analysis have recently revealed that lithium is a normal constituent of tissues of assayed mammals, including those of rats and human beings. There is evidence, too, that lithium is an important, biologically-active element. Cyclotron resonance may or may not be a mechanism by which ELF- and static-magnetic fields at low strengths combine to affect the organism, but rejection of this mechanism on the grounds that lithium is absent or is physiologically inadequate is unwarranted. Lithium is normally present and is metabolically active in many tissues, especially those of the neuroendocrine system.     

A study of some serum mineral levels before and during pregnancy and during lactation period of sheep and cattle

The purpose of this study was to determine serum Cu, Zn, Mn, K, and Mg levels before and during pregnancy and during the lactation period of sheep and cattle and to determine the relationships between periods. For this purpose, blood samples of 14 healthy, pregnant Brown Swiss cows fed under normal condition and 36 Karakaş (İvesi × Akkaraman) sheep were used. Blood samples were analyzed using an atomic absorption spectrophotometer. There were significant differences between before pregnancy and during pregnancy, and during pregnancy and the lactation period for serum Zn concentration; also before pregnancy and during pregnancy, and before pregnancy and the lactation period for serum K concentration in cows (p<0.05). There were significant differences between before pregnancy and the lactation period for serum Cu concentration, and before pregnancy and during pregnancy for serum K concentration; also pregnancy and the lactation period for serum Mg concentration in sheep (p<0.05).     

Characteristics of selenazolidine prodrugs of selenocysteine: toxicity, selenium levels, and glutathione peroxidase induction in A/J mice

We have previously reported the synthesis and characterization of two new classes of selenazolidine-4(R)-carboxylic acids (2-oxo and 2-methyl-SCAs) (OSCA and MSCA, respectively), as well as the "parent" compound, selenazolidine-4(R)-carboxylic acid (SCA, selenaproline). These compounds were designed as prodrugs of L-selenocysteine with potential application in cancer chemoprevention or other clinical uses. We will be exploring the chemopreventive activity of the new compounds in the well-established A/J mouse model of tobacco-induced lung carcinogenesis. The objectives of the present study were to investigate several fundamental biochemical endpoints after selenazolidine administration compared with other selenium-containing agents. Groups of mice were fed either AIN-76A diet alone or the diet supplemented with the following selenium compounds (ppm Se): sodium selenite (5), L-selenomethionine (3.75), L-selenocystine (15), Se-methyl-L-selenocysteine (3), MSCA (5, 10, or 15), OSCA (5, 10, or 15), or SCA (5, 10, or 15). After 28 days of supplementation, toxicity of the selenazolidines was not evident, as measured by outward appearance and behavior, body and organ weight changes, and histological evaluation of liver and lung tissue. Select treatment groups showed significant increases in selenium levels in blood and tissues. Increased activity of selenium-dependent glutathione peroxidase (GPx) in blood and liver illustrated that the selenazolidines provided a source of biologically-available selenium.     

Seasonal variations and inherent variability of selenium in marine biota of a tropical wetland ecosystem: implications for bioindicator species

The present study was designed to study the seasonal variations of selenium in marine biota of different trophic levels collected from Sunderban deltaic complex, northeast India. The primary objective of this work is to provide baseline data for a future environmental quality programme. In general, the sequence of Se accumulation observed in biota is as follows: Bivalve>Zooplankton>Macroalgae>Pisces>Seagrass. An elevated level of Se was recorded during monsoon season. The Se level in zooplankton (4 μg/g) was three to four times higher than seagrass. The content of various soft tissues and shell in bivalves molluscs showed an organ-specific pattern in the following order: gill > visceral MASS = mantle > adductor muscle > podium > shell. Fish contain less Se in comparison with macroalgae, zooplankton and bivalves revealing poor or insignificant trophic transfer of Se in the marine food chain. Pelecyora trigona (Bivalve) seems to be reliable indicator of Se contamination because of its high accumulation capacity. An in-depth monitoring program is recommended in order to clarify the present trend and to establish the studied biota as indicator species.     

A biomechanical and spectroscopic study of bone from rats with selenium deficiency and toxicity

Selenium, being an essential mineral in the mammalian diet, is important in providing protection against oxidative damage. Numerous in vitro studies of selenium compounds reveal a very high correlation between catalytic activity of selenium compounds and toxicity. The present study was designed to investigate the effects of dietary selenium on the biomechanical properties of bone. New born rats of both sexes were fed with either a control, or a selenium- and vitamin E-deficient, or a selenium-excess and vitamin E-adequate diet. We obtained the stiffness (modulus of elasticity) of bones (femur and tibia) by tensile test for all groups considered. Both the deficient and the excess groups have decreased biomechanical strength with respect to the control group. To support our biomechanical results for both experimental groups, X-ray diffraction analysis and FTIR spectroscopic study were performed on the femurs and tibiae. The X-ray diffraction analysis showed that the intensities of the peak observed at around 2°=31.820, in the control femur and tibia are stronger than the intensities of the corresponding peak of two experimental groups. In FTIR spectroscopy, the disappearance and/or reduction of the intensities of some carbonate bands in the two experimental groups indicate that there is a decrease in crystallinity and mineral contents which, together with X-ray diffraction analysis, correlate very well with the biomechanical data.     

Investigations into the uptake of copper,iron and selenium by a highly sulphated bacterial exopolysaccharide isolated from microbial mats

A bacterium isolated from microbial mats located on a polynesian atoll produced a high molecular weight (3,000 kDa) and highly sulphated exopolysaccharide. Previous studies showed that the chemical structure of this EPS consisted of neutral sugars, uronic acids, and high proportions of acetate and sulphate groups. The copper- and iron-binding ability of the purified pre-treated native EPS was investigated. Results showed that this EPS had a very high affinity for both copper (9.84 mmol g⁻¹ EPS) and ferrous iron (6.9 mmol g⁻¹ EPS). Amazingly, this EPS did not show any affinity for either ferric ions or selenium salts. This finding is one of the first steps in assessing the biotechnological potential of this polysaccharide.     

Human erythrocyte hemolysis induced by selenium and tellurium compounds increased by GSH or glucose: a possible involvement of reactive oxygen species

Oxidative stress can induce complex alterations of membrane proteins in red blood cells (RBCs) eventually leading to hemolysis. RBCs represent a good model to investigate the damage induced by oxidizing agents. Literature data have reported that chalcogen compounds can present pro-oxidant properties with potent inhibitory effects on cell growth, causing tissue damage and inhibit a variety of enzymes. In this study, human erythrocytes were incubated in vitro with various chalcogen compounds at 37 °C: diphenyl ditelluride (1), dinaphthalen diteluride (2), diphenyl diselenide (3), (S)-tert-butyl 1-diselenide-3-methylbutan-2-ylcarbamate (4), (S)-tert-butyl 1-diselenide-3-phenylpropan-2-ylcarbamate (5), selenium dioxide (6) and sodium selenite (7) in order to investigate their potential in vitro toxicity. After 6 h of incubation, all the tested compounds increased the hemolysis rate, when compared to control and compound (2) had the most potent hemolytic effect. The addition of reduced glutathione (GSH) or glucose to the incubation medium enhanced hemolysis caused by chalcogen compounds. The thiol oxidase activity of these compounds was evaluated by measuring the rate of cysteine (CYS) and dithiotreitol (DTT) oxidation. DTT and cysteine oxidation was increased by all the compounds tested. The results suggest a relationship between the oxidation of intracellular GSH and subsequent generation of free radicals with the hemolysis by chalcogen compounds.