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At least 991 records · Page 55Linked to original sources
PubMed1991

[Interrelationships between methylmercury exposure and selenium supplementation in cockerels using selected laboratory diagnostic parameters and toxicological parameters of residues].

A feed loading experiment was applied in 2 phases to 45 young cocks over 12 weeks, using 1,2-N,N-bis(methylmercury)-p-toluolsulphamide-dressed wheat (50% of base ration). Investigations were conducted to study the effects of selenium supplementation (0,2 mg Se as sodium selenite/l drinking water) on biochemical and hematological parameters (calcium, phosphorus, total protein, albumin, creatinine, urea, activity of alkaline phosphatase, hematocrit, hemoglobin, leucocyte count) as well as on parameters relating to toxicological residues (selenium and mercury levels in liver, musculature and kidneys). Statistically secured differences were found to exist between the experimental groups with regard to selenium and mercury in the liver and mercury concentrations in kidneys. Possible interrelationships were discussed.

Animals↗
PubMed2006

Uncoated, broad fluorescent, and size-homogeneous CdSe quantum dots for bioanalyses.

In the present study, we describe the synthesis of highly luminescent uncoated water-soluble CdSe quantum dots (QDs) possessing the following characteristics: approximately 2 nm in diameter, with very good size distribution (in 95% homodispersed) accompanied by a broad-band photoluminescent spectrum. The synthetic procedure is simple, is conducted at room temperature, in the absence of the most popular coordinating ligands (as TOPO or HDA), and is highly reproducible. The obtained CdSe core QDs possessed a comparatively long fluorescence half-life (approximately 30-90 ns, depending on the emission wavelength) detected by time-resolved spectroscopy. These QDs were further conjugated with antibodies and applied in several biochemical analyses.

Antigen-Antibody Complex↗
PubMedDate not supplied

Cellular thioredoxin reductase activity is regulated by selenium.

Selenium (Se) is an essential trace element and has been reported to decrease the incidence of some human cancers. We have investigated the effects of Se on thioredoxin reductase, a selenocysteine containing flavoenzyme, in HT-29 human colon cancer cells grown in serum-free medium. Sodium selenite and other Se containing compounds produced a time and concentration dependent increase in intracellular thioredoxin reductase activity and protein levels. Selenite was the most active of the Se compounds examined: 1 microM selenite produced a 28-fold increase in thioredoxin reductase activity by 1 day and 10 microM selenite over a 60-fold increase by 5 days. The activity of a related non-selenocysteine containing flavoenzyme glutathione reductase was not increased by selenite. Selenite, but not the other Se containing compounds inhibited cell growth at concentrations above 2 microM. The results show that Se can produce large increases in cell thioredoxin reductase activity.

Blotting, Western↗
PubMed2006

Binding of muscimol-conjugated quantum dots to GABAC receptors.

Functionalization of highly fluorescent CdSe/ZnS core-shell nanocrystals (quantum dots, qdots) is an emerging technology for labeling cell surface proteins. We have synthesized a conjugate consisting of approximately 150-200 muscimols (a GABA receptor agonist) covalently joined to the qdot via a poly(ethylene glycol) (PEG) linker (approximately 78 ethylene glycol units) and investigated the binding of this muscimol-PEG-qdot conjugate to homomeric rho1 GABAC receptors expressed in Xenopus oocytes. GABAC receptors mediate inhibitory synaptic signaling at multiple locations in the central nervous system (CNS). Binding of the conjugate was analyzed quantitatively by determining the fluorescence intensity of the oocyte surface membrane in relation to that of the surrounding incubation medium. Upon 5- to 10-min incubation with muscimol-PEG-qdots (34 nM in qdot concentration), GABAC-expressing oocytes exhibited a fluorescent halo at the surface membrane that significantly exceeded the fluorescence of the incubation medium. This halo was absent following muscimol-PEG-qdot treatment of oocytes lacking GABAC receptors. Incubation of the oocyte with free muscimol (100 microM-5 mM), PEG-muscimol (500 microM), or GABA (100 microM - 5 mM) substantially reduced or eliminated the fluorescence halo produced by muscimol-PEG-qdots, and the removal of GABA or free muscimol led to a recovery of muscimol-PEG-qdot binding. Unconjugated qdots and PEG-qdots that lacked conjugated muscimol neither exhibited significant binding activity nor diminished the subsequent binding of muscimol-PEG-qdots. The results indicate that muscimol joined to qdots via a long-chain PEG linker exhibits specific binding activity at the ligand-binding pocket of expressed GABAC receptors, despite the presence of both the long PEG linker and the sterically bulky qdot.

Animals↗
PubMed2004

Semiconductor nanocrystal probes for human metaphase chromosomes.

To improve signal stability and quantitation, an optically stable, novel class of fluorophore for hybridization analysis of human metaphase chromosomes is demonstrated. Detection of hybridization sites in situ was based on fluorescence from streptavidin-linked inorganic crystals of cadmium selenide [(CdSe)ZnS]. Fluorescence of nanocrystal fluorophores was significantly brighter and more photostable than organic fluorophores Texas Red and fluorescein. Thus, semiconductor nanocrystal fluorophores offer a more stable and quantitative mode of fluorescence in situ hybridization (FISH) for research and clinical applications.

Biotinylation↗
PubMed2002

Solid-phase extraction for the simultaneous preconcentration of organic (selenocystine) and inorganic [Se(IV), Se(VI)] selenium in natural waters.

This paper describes the combined use of a new preconcentration method using the Amberlite IRA-743 resin and high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry to determine simultaneously inorganic and organic selenium species in aquatic systems. The developed enrichment procedure, whose accuracy has been checked by recovery tests, is suitable for selenium speciation at environmental levels of 10 ng (Se) l(-1). The method has been applied to mineral and freshwater samples.

Chromatography, High Pressure Liquid↗
PubMed2000

Organoselenium Chemistry in Stereoselective Reactions.

Selenium-based methods have developed rapidly over the past few years asnd organoselenium chemistry has become a very useful tool in the hands of synthetic chemists. The different reactivity of selenium-containing compounds in contrast to the sulfur analogues has led to versatile and new synthetic methods in organic chemistry. Various functionalities can be selectively introduced into complex molecules under very mild reaction conditions. In this review, the principles of organoselenium chemistry are traced back to their origins and are highlighted with respect to stereoselective synthesis. The unique properties of selenium allow the development of new and highly selective transformations, which can be employed subsequently in new routes for the synthesis of versatile chiral building blocks and for natural product synthesis.

Journal Article↗
PubMed2006

CdSe quantum dots induce apoptosis in human neuroblastoma cells via mitochondrial-dependent pathways and inhibition of survival signals.

Quantum dots (QDs) may be useful as novel luminescent markers, but their cytotoxicity has not been fully investigated. In this report, we demonstrate that CdSe-core QDs can induce apoptotic biochemical changes, including JNK activation, loss of mitochondrial membrane potential, mitochondrial release of cytochrome c and activation of caspase-9 and caspase-3 in the IMR-32 human neuroblastoma cell line. Importantly, treatment of IMR-32 cells with CdSe-core QD triggered an increase in reactive oxygen species (ROS) and inhibited survival-related signaling events, such as decreased Ras and Raf-1 protein expression and decreased ERK activation. These apoptotic biochemical changes were not detected in cells treated with ZnS-coated CdSe QDs. Collectively, these results demonstrate that CdSe-core QD treatment of IMR-32 cells induced JNK activation and mitochondrial-dependent apoptotic processes while inhibiting Ras-->ERK survival signaling and that a ZnS coating could effectively reduce QD cytotoxicity.

Apoptosis↗
PubMed1993

Synthesis of 2,4-disubstituted thiazoles and selenazoles as potential antifilarial and antitumor agents. 2. 2-Arylamido and 2-alkylamido derivatives of 2-amino-4-(isothiocyanatomethyl)thiazole and 2-amino-4-(isothiocyanatomethyl)selenazole.

The synthesis of a series of 2-arylamido and 2-alkylamido derivatives of 2-amino-4-(isothiocyanatomethyl)thiazole and 2-amino-4-(isothiocyanatomethyl)selenazole is described. In vitro antiproliferative evaluations were carried out using L1210 cells. The 2-(alkylamido)thiazole derivatives were moderately antiproliferative, with IC50's of 4-8 microM. A significant increase in activity was obtained for the arylamido derivatives, with IC50's of 0.2-1 microM. The results obtained for the selenazoles were similar to those for the thiazoles. 2-Benzamido-4-(isothiocyanatomethyl)-thiazole (19) was found to be a potent inhibitor of GMP synthetase. None of the compounds prepared in this study demonstrated antifilarial activity.

Animals↗
PubMed1978

Ecological aspects of mercury--selenium interactions in the marine environment.

In the marine environment, mercury is accompanied by selenium in all investigated species of mammals, birds, and fish--possibly due to a normal homeostatic regulation. It therefore seems likely that selenium will exert its protective action against mercury toxicity in the marine environment, decreasing its detrimental effects on reproduction, behavior, growth, etc. of the organisms and thus protect the population and ecosystem. On the other hand, the increased retention of mercury caused by selenium may lead to a higher level of biomagnification in the food chain and a higher burden in the individual. This might counteract the positive effect of decreased intoxication.

Animals↗
PubMed2001

Selenite or selenomethionine interaction with methylmercury on uptake and toxicity showing a weak selenite protection: studies on cultured K-562 cells.

Selenium and methylmercuric chloride (MMC) interactions regarding cellular uptake and selenium protection on MMC toxicity have been studied. Human K-562 cells were pretreated or simultaneously treated with either selenite (5 or 50 microM) or selenomethionine (10 or 50 microM) together with (3.5 or 5 microM) MMC. Cells simultaneously treated with selenite or selenomethionine and 3.5 microM MMC showed a decreased mercury concentration with increased selenium dose especially seen in the selenite combinations. The simultaneous selenite and MMC 3.5 microM combinations showed growth curves with an increasing number of viable cells with increased selenite dose. All combinations with 5 microM MMC were toxic to the cells. Interactions between selenite or selenomethionine and MMC regarding cellular uptake of mercury and selenium were observed and indications of selenite protection against MMC toxicity in human K-562 cells were noticed.

Cell Division↗
PubMed2004

Influence of the crystal field stabilization energy of metal(II) ions on the structural distortion of matrix-isolated SO4(2-) guest ions in selenate matrices.

Infrared spectra of metal(II) selenate hydrates (MeSeO4.nH2O and Na2Me(SeO4)2.2H2O; n=6, 5, 4, 1; Me=Mg, Mn, Co, Ni, Cu, Zn, Cd) containing matrix-isolated SO42- guest ions are reported and discussed with respect to the S-O stretching modes 3 and 1. An adequate measure for the SO42- guest ion distortion is the site group splitting deltanuas (deltanuab and deltanuac in the case of a doublet and a triplet for 3, respectively; a, being the highest wavenumbered component of nu3) and deltanumax (the difference between the highest and the lowest wave numbered S-O stretching modes). It has been shown that the SO42- guest ion distortion depends on both the number of the sulfate oxygen atoms involved in coordinative bonds with the metal(II) ions and the electronic configuration of the metal(II) ions, i.e. their crystal field stabilization energy (CFSE) additionally to the site symmetry and the local potential at the lattice site of the host lattice. The SO42- guest ions matrix-isolated in MeSeO4.H2O (Me=Mn, Co, Zn) and in Na2Me(SeO4)2.2H2O (Me=Mn, Cu, Cd) exhibit three bands corresponding to the nu3 modes as deduced from the site group analysis and deltanuab approximately equal to deltanubc. When SO42- guest ions are incorporated in the triclinic Na2Me(SeO4)2.2H2O host lattices (Me=Co, Ni, Zn) the nu3 stretching region resembles a higher local symmetry of the SO42- guest ions (an approximate (A1 + E) splitting) than the crystallographic one (i.e. deltanuab>deltanubc instead of deltanuab approximately equal to deltanubc) and, hence, the ratio deltanuab/deltanubc has to be taken into account (the higher value of the ratio deltanuab/deltanubc, the weaker is the distortion of the SO42- guest ions). The SO42- guest ions incorporated in MeSeO4.nH2O (n=6, 5, 4) exhibit a higher local symmetry of the guest ions than that deduced from the site group analysis (D2d for the SO42- guest ions in MeSeO4.5H2O, MeSeO4.4H2O and in the monoclinic MeSeO4.6H2O host lattices and close to Td in the tetragonal MeSeO4.6H2O host lattices). The analysis of the infrared spectra of selenate host lattices containing SO42- guest ions reveals that the guest ions are stronger distorted when the adjacent metal(II) ions have CFSE not equal to 0. These ions are more resistant to angular deformations of the MeO6-octahedra (i.e. changes in the O-Me-O bond angles), thus facilitating the SO42- guest ion distortion as compared to those having CFSE=0 which allow stronger angular deformations of the respective metal octahedra. Infrared spectra of kieserite-type compounds MeSeO4.H2O (Me=Mn, Co, Zn) containing matrix-isolated SO42- guest ions and Me'2+ guest ions different from those of the host ions (i.e. Me'SO4.H2O in MeSeO4.H2O) are also presented and discussed (double matrix-spectroscopy).

Selenic Acid↗
PubMedDate not supplied

Response to barium selenate supplementation in sheep kept at pasture in the Mediterranean area.

This work evaluated the efficacy of barium selenate supplements in the prevention of disorders related to Se deficiency in sheep maintained at pasture in the Mediterranean area. Ewes on five farms were divided into two equal groups of 1,750 animals: a) the treated group and b) the control group. The animals of the treated group were injected subcutaneously, in the first third of gestation, with a barium selenate compound at a dose of 1 mg Se/kg. The ewes in the control group did not receive any supplement of Se and/or vitamin E. The two groups were managed under the same feeding and husbandry practices throughout the experiment. After lambing, blood glutathione peroxidase (GSHPx) and serum aspartate aminotransferase (AST), creatine kinase (CK) and lactate dehydrogenase (LDH) activities were measured in the lambs born to both group. Blood GSHPx activity was higher in the treated animals, with statistically significant differences due to the response to injection of barium selenate. Mean global serum activities of AST and CK tended to be higher in the control group, as a consequence of the protection given to the treated group by the supplement, but the differences were not statistically significant. This was possibly due to the absence of clinical cases of nutritional myodystrophy (NMD) in the animals of the control group. Therefore it can be stated that barium selenate supplementation can prevent Se deficiency in sheep herds maintained at pasture in this area.

Animal Feed↗
PubMed1990

The presence of inorganic and organic mercury and selenium in Nephrops norvegicus from the Ligurian Sea.

Samples of Nephrops norvegicus from the Ligurian Sea were analysed for contents of organic mercury, total mercury and selenium. Results for 37 specimens are reported. Total mercury concentrations increase with size of the specimens. Percentage of organic mercury ranges from 31 to 88% with an average of 58%. Selenium does not correlate with size and the average content is 0.88 micrograms g-1 fresh weight (range 0.30-1.74 micrograms g-1 fresh weight).

Animals↗
PubMed2001

Two-, three-, and four-coordination at gold(I) supported by the bidentate selenium ligand [Ph2P(Se)NP(Se)Ph2](-).

Treatment of the gold(I) halide complexes LAuCl (L = PMe3, PPh3, CNC6H3Me2-2,6) with K[Ph2P(Se)NP(Se)Ph2] provides the gold-selenium coordination compounds [(N(Ph2PSe)2-Se,Se')AuL]. However, on standing for a number of days, the complex [(N(Ph2PSe)2-Se,Se')AuPMe3] gains a phosphine to provide the bis(phosphine) species [(N(Ph2PSe)2-Se,Se')Au(PMe3)2]. Treatment of the K[Ph2P(Se)NP(Se)Ph2] ligand with [(Ph3PAu)3O]BF4 allows the isolation of [(N(Ph2PSe)2-Se,Se')(AuPPh3)2]BF4. Reaction of the complex [(dppm)(AuCl)2] with AgSO3CF3 followed by addition of the ligand K[Ph2P(Se)NP(Se)Ph2] results in the formation of [(N(Ph2PSe)2-Se,Se')Au2(dppm)]OSO2CF3 and treatment of [(tht)AuCl] (tht = tetrahydrothiophene) with an equimolar quantity of K[Ph2P(Se)NP(Se)Ph2] affords the complex [(N(Ph2PSe)2-Se,Se')2Au2]. The compounds [(N(Ph2PSe)2-Se,Se')Au2(dppm)]OSO2CF3, [(N(Ph2PSe)2-Se,Se')AuPPh3] and [(N(Ph2PSe)2-Se,Se')Au(PMe3)2] have been investigated crystallographically. The results reveal that the metal centers are two-, three-, and four-coordinate, respectively. The cationic, eight-membered ring complex bearing the dppm ligand displays transannular aurophilic bonding and is further associated into dimers via intermolecular gold-selenium contacts. The six-membered rings in the other two structures have C2-symmetrical twist conformations, however, the Au(I) coordination sphere in [N(PPh2Se)2]AuPPh3 is not fully symmetrical. The Au-Se bond lengths increase dramatically as the coordination number of the metal atom becomes larger.

Journal Article↗
PubMed2003

Mortalin imaging in normal and cancer cells with quantum dot immuno-conjugates.

Quantum dots are the nanoparticles that are recently emerging as an alternative to organic fluorescence probes in cell biology and biomedicine, and have several predictive advantages. These include their i) broad absorption spectra allowing visualization with single light source, ii) exceptional photo-stability allowing long term studies and iii) narrow and symmetrical emission spectrum that is controlled by their size and material composition. These unique properties allow simultaneous excitation of different size of quantum dots with a single excitation light source, their simultaneous resolution and visualization as different colors. At present there are only a few studies that have tested quantum dots in cellular imaging. We describe here the use of quantum dots in mortalin imaging of normal and cancer cells. Mortalin staining pattern with quantum dots in both normal and cancer cells mimicked those obtained with organic florescence probes and were considerably stable.

Antibodies, Monoclonal↗