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PubMed2000

27Al NMR study in UNiAl.

The ternary compound UNiAl exhibiting an antiferromagnetic order below T(N) = 19.3 K has been studied in the paramagnetic state using the 27Al NMR technique and different magnetically oriented samples. The quadrupole coupling constant e2qQ/h = 1.56 MHz is temperature independent. The dominant, longitudinal component of the Knight shift with respect to the hexagonal c axis, Kparallel, is positive and increases upon lowering the temperature down to 50 K. Much smaller in magnitude, the transverse component, Kperpendicular, is also positive and only slightly temperature dependent. The plots of the Knight shift vs magnetic susceptibility Kparallel(chi parallel) and Kperpendicular (chi perpendicular) form the same line, which implies that the transferred hyperfine field of 9.2 kOe/microB for 27Al nuclei should be considered isotropic.

Aluminum↗
PubMed2005

Structural model of dioxouranium(VI) with hydrazono ligands.

Synthesis and characterization of several new coordination compounds of dioxouranium(VI) heterochelates with bidentate hydrazono compounds derived from 1-phenyl-3-methyl-5-pyrazolone are described. The ligands and uranayl complexes have been characterized by various physico-chemical techniques. The bond lengths and the force constant have been calculated from asymmetric stretching frequency of OUO groups. The infrared spectral studies showed a monobasic bidentate behaviour with the oxygen and hydrazo nitrogen donor system. The effect of Hammett's constant on the bond distances and the force constants were also discussed and drawn. Wilson's matrix method, Badger's formula, Jones and El-Sonbati equations were used to determine the stretching and interaction force constant from which the UO bond distances were calculated. The bond distances of these complexes were also investigated.

Hydrazones↗
PubMed2004

Effect of the militarily-relevant heavy metals, depleted uranium and heavy metal tungsten-alloy on gene expression in human liver carcinoma cells (HepG2).

Depleted uranium (DU) and heavy-metal tungsten alloys (HMTAs) are dense heavy-metals used primarily in military applications. Chemically similar to natural uranium, but depleted of the higher activity 235U and 234U isotopes, DU is a low specific activity, high-density heavy metal. In contrast, the non-radioactive HMTAs are composed of a mixture of tungsten (91-93%), nickel (3-5%), and cobalt (2-4%) particles. The use of DU and HMTAs in military munitions could result in their internalization in humans. Limited data exist however, regarding the long-term health effects of internalized DU and HMTAs in humans. Both DU and HMTAs possess a tumorigenic transforming potential and are genotoxic and mutagenic in vitro. Using insoluble DU-UO2 and a reconstituted mixture of tungsten, nickel, cobalt (rWNiCo), we tested their ability to induce stress genes in thirteen different recombinant cell lines generated from human liver carcinoma cells (HepG2). The commercially available CAT-Tox (L) cellular assay consists of a panel of cell lines stably transfected with reporter genes consisting of a coding sequence for chloramphenicol acetyl transferase (CAT) under transcriptional control by mammalian stress gene regulatory sequences. DU, (5-50 microg/ml) produced a complex profile of activity demonstrating significant dose-dependent induction of the hMTIIA FOS, p53RE, Gadd153, Gadd45, NFkappaBRE, CRE, HSP70, RARE, and GRP78 promoters. The rWNiCo mixture (5-50 microg/ml) showed dose-related induction of the GSTYA, hMTIIA, p53RE, FOS, NFkappaBRE, HSP70, and CRE promoters. An examination of the pure metals, tungsten (W), nickel (Ni), and cobalt (Co), comprising the rWNiCo mixture, demonstrated that each metal exhibited a similar pattern of gene induction, but at a significantly decreased magnitude than that of the rWNiCo mixture. These data showed a synergistic activation of gene expression by the metals in the rWNiCo mixture. Our data show for the first time that DU and rWNiCo can activate gene expression through several signal transduction pathways that may be involved in the toxicity and tumorigenicity of both DU and HMTAs.

Carcinoma, Hepatocellular↗
PubMed1999

Phosphate release and heavy metal accumulation by biofilm-immobilized and chemically-coupled cells of a Citrobacter sp. pre-grown in continuous culture.

A heavy metal-accumulating Citrobacter sp. was grown in carbon-limiting continuous culture in an air-lift fermentor containing raschig rings as support for biofilm development. Planktonic cells from the culture outflow were immobilized in parallel on raschig rings by chemical coupling (silanization), for quantitative comparison of phosphatase activity and uranyl uptake by both types of immobilized cell. The flow rate giving 50% conversion of substrate to product (phosphate) in flow-through reactors was higher, by 35-40%, for the biofilm-immobilized cells, possibly exploiting a pH-buffering effect of inorganic phosphate species within the extracellular polymeric material. Upon incorporation of uranyl ions (0.2 mM UO22+), both types of cell removed more than 90% of the input UO22+ at slow flow rates, but the chemically-coupled cells performed better at higher flow rates. The deposited material (HUO2PO4) subsequently removed Ni2+ from a second flow via intercalative ion exchange of Ni2+ into the crystalline HUO2PO4.4H2O lattice. This occurred irrespective of the method of coupling of the biomass to the support and suggested that uranyl phosphate accumulated by both types of cell has potential as a bio-inorganic ion exchanger-a potential use for the uranium recoved from primary waste treatment processes.

Animals↗
PubMedDate not supplied

Sequence/structure selective thermal and photochemical cleavage of yeast-tRNA(Phe) by UO(2)2+.

The uranyl(VI) ion, UO(2)2+, cleaves yeast tRNA(Phe) both thermally and photochemically. Photochemical cleavage takes place at all positions but exhibits maxima at G10, G18, G30, A38, C49 and A62. Furthermore, in the presence of stoichiometric concentrations of citrate, the cleavage is generally suppressed except that strong cleavage at positions G10 and C48-U50 persists, indicating the presence of a high-affinity metal-ion binding site. It is proposed that these photocleavage sites reflect the tertiary structure of the yeast tRNA(Phe) molecule in terms of D-loop/T-loop interaction and anticodon loop conformation and that uranyl-mediated photocleavage of RNA may be used as a probe of RNA tertiary structure, and in particular for identifying binding sites for divalent metal ions. Thus a high-affinity metal-ion binding site is inferred in the "central pocket" formed by the D-loop, and the acceptor stem.

Hot Temperature↗
PubMed2004

Collision-induced dissociation tandem mass spectrometry of desferrioxamine siderophore complexes from electrospray ionization of UO2(2+), Fe3+ and Ca2+ solutions.

Desferrioxamine (DEF) is a trihydroxamate siderophore typical of those produced by bacteria and fungi for the purpose of scavenging Fe(3+) from environments where the element is in short supply. Since this class of molecules has excellent chelating properties, reaction with metal contaminants such as actinide species can also occur. The complexes that are formed can be mobile in the environment. Because the natural environment is extremely diverse, strategies are needed for the identification of metal complexes in aqueous matrices having a high degree of chemical heterogeneity, and electrospray ionization mass spectrometry (ESI-MS) has been highly effective for the characterization of siderophore-metal complexes. In this study, ESI-MS of solutions containing DEF and either UO(2)(2+), Fe(3+) or Ca(2+) resulted in generation of abundant singly charged ions corresponding to [UO(2)(DEF - H)](+), [Fe(DEF - 2H)](+) and [Ca(DEF - H)](+). In addition, less abundant doubly charged ions were produced. Mass spectrometry/mass spectrometry (MS/MS) studies of collision-induced dissociation (CID) reactions of protonated DEF and metal-DEF complexes were contrasted and rationalized in terms of ligand structure. In all cases, the most abundant fragmentation reactions involved cleavage of the hydroxamate moieties, consistent with the idea that they are most actively involved with metal complexation. Singly charged complexes tended to be dominated by cleavage of a single hydroxamate, while competitive fragmentation between two hydroxamate moieties increased when the doubly charged complexes were considered. Rupture of amide bonds was also observed, but these were in general less significant than the hydroxamate fragmentations. Several lower abundance fragmentations were unique to the metal examined: abundant loss of H(2)O occurred only for the singly charged UO(2)(2+) complex. Further, NH(3) was eliminated only from the singly charged Fe(3+) complex; this and fragmentation of C-C and C-N bonds derived from neither the hydroxamate nor the amide groups suggested that Fe(3+) insertion reactions were competing with ligand complexation. In no experiments were coordinating solvent molecules observed, attached either to the intact complexes or to the fragment ions, which indicated that both intact DEF and its fragments were occupying all of the coordination sites around the metal centers. This conclusion was based on previous experiments that showed that undercoordinated UO(2)(2+) and Fe(3+) readily added H(2)O and methanol in the ESI quadrupole ion trap mass spectrometer that was used in this study.

Calcium↗
PubMed1990

Moment analysis of drug disposition in kidney. III: Transport of p-aminohippurate and tetraethylammonium in the perfused kidney isolated from uranyl nitrate-induced acute renal failure rats.

A different manner of insufficiency of renal epithelial cell transport between the organic anion and cation, p-aminohippurate and tetraethylammonium, respectively, was observed in the perfused kidney isolated from uranyl nitrate-induced acute renal failure (ARF) rats. The single-pass outflow pattern of the perfused kidney was analyzed by noncompartmental moment analysis. The active tubular secretion was impaired faster than the reduction of glomerular filtration, and the tetraethylammonium secretion decreased at an earlier stage of ARF than p-aminohippurate. The apparent uptake rate constant from blood to cells of p-aminohippurate was reduced with the progress of ARF and associated with the amount of this drug secreted, whereas the uptake rate constant of tetraethylammonium did not change until the late stage of ARF. The mean residence time in renal epithelial cells of tetraethylammonium was prolonged with reduction of the amount to be secreted, while that of p-aminohippurate remained unchanged. Therefore, the uptake of p-aminohippurate across the basolateral membranes decreased gradually, and the transport across the brush border membranes was still unchanged after uranyl nitrate treatment. On the other hand, the secretion of tetraethylammonium from cells to lumen was impaired at first, and then the uptake from blood to cells was impaired. These results suggest that impairment by uranyl nitrate-induced ARF appears at the carrier-mediated transport process of the epithelial cell membranes for both organic anions and cations.

Acute Kidney Injury↗
PubMed1994

Distribution and short-term effects of intratracheally instilled neutron-irradiated UO2 particles in the rat.

In the present study we investigated the radionuclide distribution and histopathological effects of neutron-irradiated UO2 particles in the rat after intratracheal instillation. The kinetics and short-term effects of uranium fission products (95Zr, 95Nb, 103Ru, and 141Ce) were examined during a 3-month follow-up period. A rapid clearance (about 21%) of particles occurred via the gastrointestinal tract within 24 hr after the instillation. Autoradiographic and histological examinations revealed that the retained particles were nonuniformly distributed in the lungs. Translocation of the fission products from the lung to various other tissues was slow; 3 months after the instillation, the activity of the total body burden was below 1% in the liver, kidney, and spleen, whereas in the lungs it was 83%. Clearance of particles appeared to be mainly due to tracheobronchial mucociliary mechanisms. Translocation of the fission products to the bone and liver was significantly less than that reported by the ICRP, indicating that the clearance of uranium-matrix-associated fission products is preferably dependent on the physical characteristics of the particulate material. The cumulative lung doses ranging from 170 to 550 mSv caused slight or moderate local inflammatory reactions in the lungs, but at smaller dose levels there were no histopathological changes observed.

Animals↗
PubMed1995

Effects of simulated nuclear fuel particles on the histopathology and CYP enzymes in the rat lung and liver.

We studied both short-term (3 and 30 days) and long-term (3-24 months) effects of simulated nuclear fuel particles (neutron-activated UO2) on the rat lung and liver histopathology and cytochrome P450 (CYP) activities. In the short-term study, after a single intratracheal instillation with neutron-activated particles (administered activity 36 kBq), the lung histology revealed inflammation and a decrease in several lung testosterone hydroxylation levels. Liver exhibited normal histology but hepatic testosterone 7alpha-hydroxylase (T7alphaOH) was decreased by 30% at 3 days treatment with neutron-activated particles (9.3 kBq). At 30 days after treatment, hepatic T7alphaOH and testosterone 15alpha-hydroxylase activities were enhanced by 70 and 40%, respectively. At the long-term follow-up, benign and malignant lung tumors were observed but in the livers only slightly increased inflammation was found. At the 1.5-year follow-up (cumulated lung dose 0.4-0.66 Gy, 131 and 182 kBq), decreases in lung testosterone 6beta-hydroxylase (60%) and testosterone 6alpha-hydroxylase (30%) activities were found. In contrast to lungs, hepatic testosterone 16alpha-hydroxylase activity decreased by 60-75% with both nonactivated and neutron-activated particles. These findings indicate that when lung is exposed to nonactivated UO2 or beta-emitting UO2 particles they have differential effects on CYP enzymes in both the primary target organ (lung) and secondary tissue (liver).

Animals↗
PubMed1994

Cation channel blocked by extracellular Ca2+ in the apical membrane of the chick embryonic ectoderm.

In the chick embryo (20 h incubation, gastrula stage), the apical membrane of the ectodermal cells shows a high density of a non-selective cation channel which is blocked by very low extracellular Ca2+ concentrations. Properties of this channel were studied at the single-channel level using the patch-clamp technique in the cell-attached mode. With 1 mmol/l Ca2+ in the pipette, only outward current was present and the channel conductance measured at +120 mV was 25.5 pS. In the absence of Ca2+, also inward current through the channel was observed. The conductances measured at -50 mV were 49.5 pS with Na+ as the charge carrier, 72.5 pS with K+, 49.1 pS with Cs+, and 18.5 pS with Li+. The conductance measured at +80 mV was around 23 pS in all four cases. The reversal potential was similar (around 25 mV) for all four ions, which indicates a poor selectivity of the channel. In the absence of Ca2+ and the presence of 1 mmol/l ethylenebis(oxonitrilo)tetraacetate (EGTA), the kinetics of the channel were characterized by bursts of the order of seconds. During a burst, the channel flickered between one open and one closed level. The open time was constant between -30 mV and -80 mV, while the closed time decreased with hyperpolarization. The open time varied according to the permeant ion (K+ < Na+ = Cs+ < Li+). Extracellular Ca2+ blocked the inward current in a voltage-dependent manner. The Kd values, 1 mumol/l at -30 mV and 3.2 mumol/l at -80 mV, indicate that Ca2+ ions exit the channel toward the intracellular side. A weak voltage dependency of the association rate constant suggests that the Ca(2+)-binding site is close to the outside mouth. Extracellular Ca2+ was much less efficient at blocking the outward current (Kd about 1 mmol/l at 80 mV). Tetracaine, but not uraniumdioxide, decreased the opening probability of the channel. The embryonic channel shows similarities with the Ca(2+)-blockable, poorly selective channel described in the epithelium of toad urinary bladder.

Animals↗
PubMed1989

Studies of alveolar cell morphometry and mass clearance in the rat lung following inhalation of an enriched uranium dioxide aerosol.

Seventy-three rats were exposed to an aerosol of enriched uranium dioxide (UO2), giving initial lung burdens of 26 to 447 micrograms at 6 days post-inhalation (PI). At 7 days PI 35 of these rats were further exposed to thermalised neutrons at a fluence of 1 x 10(12) neutrons cm-2. There was no significant difference between the two groups in the clearance rate of the UO2 particles from the lung, up to 590 days PI. The particles cleared relatively slowly over this period with a retention half-time in the lung of 160 to 176 days. Transmission electron microscope (TEM) studies of tissue from the alveolar region at 8 days PI showed that inhalation of UO2 particles significantly increased the sizes of macrophage and type II cells, and the number of macrophage and type I cells. There was also a significant increase in the size of lysosomal granules within the macrophages after exposure to the UO2 particles. The exposure to UO2, neutrons and 235U fission fragments had no significant effect on any of the cells above that observed in the animals exposed to UO2 alone. Additional rats were exposed to the same neutron fluence without prior UO2 inhalation. The alveolar cells of neutron-only exposed rats were, in size and number, typically no different from those in the completely unexposed control rats.

Administration, Inhalation↗
PubMed1990

Detection of DNA damage in spermiogenic stages of mice treated with enriched uranyl fluoride by alkaline elution.

DNA breakage in spermiogenic stages of mice treated with enriched uranyl fluoride (UO2F2) was studied using an alkaline elution technique. Mature spermatozoa were sampled from the animal's vas and eluted with a buffer (PH 12.2) at 3-day intervals over a 33-day period after i.p. injection of 2 mg UO2F2/kg and always at 36 days after thymidine labeling in the testes. Elution of sperm DNA from treated animals varied with spermiogenic stages. At 12 days after exposure the amount of the elution of sperm DNA was found highest and increased with the increasing UO2F2 dose up to 6 mg/kg.

Animals↗
PubMed2005

Soft X-ray scanning transmission X-ray microscopy (STXM) of actinide particles.

A descriptive account is given of our most recent research on the actinide dioxides with the Advanced Light Source Molecular Environmental Science (ALS-MES) Beamline 11.0.2 soft X-ray scanning transmission X-ray microscope (STXM) at the Lawrence Berkeley National Laboratory (LBNL). The ALS-MES STXM permits near-edge X-ray absorption fine structure (NEXAFS) and imaging with 30-nm spatial resolution. The first STXM spectromicroscopy NEXAFS spectra at the actinide 4d5/2 edges of the imaged transuranic particles, NpO2 and PuO2, have been obtained. Radiation damage induced by the STXM was observed in the investigation of a mixed oxidation state particle (Np(V,VI)) and was minimized during collection of the actual spectra at the 4d5/2 edge of the Np(V,VI) solid. A plutonium elemental map was obtained from an irregular PuO2 particle with the dimensions of 650 x 650 nm. The Pu 4d5/2 NEXAFS spectra were collected at several different locations from the PuO2 particle and were identical. A representative oxygen K-edge spectrum from UO2 was collected and resembles the oxygen K-edge from the bulk material. The unique and current performance of the ALS-MES STXM at extremely low energies (ca. 100 eV) that may permit the successful measurement of the actinide 5d edge is documented. Finally, the potential of STXM as a tool for actinide investigations is briefly discussed.

Actinoid Series Elements↗
PubMed2005

Selective transport of copper(II) ions across a liquid membrane mediated by Piroxicam.

Piroxicam was found to be a highly selective carrier for uphill transport of Cu2+ ions through a chloroform liquid membrane. The transport occurs via a counterflow of protons from the receiving phase to the source phase. The effects of several parameters on the transport of Cu2+ ions, such as the carrier concentration, pH of the source phase, composition of the receiving phase, and duration are described. A high transport efficiency (98+/-2%) was provided by the carrier for Cu2+ ions in a receiving phase of 0.01 mol l(-1) sulfuric acid after 4 h. Different metal ion transport experiments showed that Cu2+ ions were selectively transported over other ions, such as Co2+, Ni2+, Cd2+, Pb2+, Zn2+, UO2(2+) and ZrO2(2+) . In the presence of fluoride ions (used as a suitable masking agent in the source phase), the interfering effects of UO2(2+) and ZrO2(2+) ions were eliminated. The applicability of the method was tested on a real sample, and the results obtained show that it is potentially useful for solvent extraction of copper.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1980

Fusion of human erythrocytes induced by uranyl acetate and rare earth metals.

Incubation of human erythrocytes with either uranyl ions (UO22+) or rare earth metals (La3+, Nd3+, Sm3+, Eu3+, Tb3+, Dy3+ and Yb3+) at 37 degrees C for 30-45 min resulted in the fusion of erythrocytes. Redistribution of membrane-associated particles was observed using colloidal-iron charge labelling and freeze-fracture electron microscopy. The fusion of erythrocytes induced by these agents, unlike Ca2+, did not exhibit the absolute requirement for phosphate. Moreover, agglutination and fusion by these agents was observed in neuraminidase-treated erythrocytes in contrast to Ca2+- and phosphate-induced fusion. Inhibitors of intrinsic transglutaminase activity partially inhibited (35-45%) the fusion induced by UO22+ suggesting that cross-linking of membrane proteins results in protein-free areas of lipid where fusion may be initiated.

Calcium↗
PubMed1983

Interaction of lanthanide cations and uranyl ion with the calcium/proton antiport system in Mycobacterium phlei.

Uranyl ions (UO2+(2)) and lanthanide cations (La3+, Nd3+, Sm3+, Eu3+, Tb3+ and Dy3+) at 100-200 microM concentration inhibited active transport of Ca2+, mediated by respiratory linked substrates as well as by ATP hydrolysis, without affecting respiration and membrane-bound ATPase activity, in inside-out membrane vesicles of Mycobacterium phlei. The extent of inhibition in the uptake of Ca2+, mediated by ATP hydrolysis, increased with increase in ionic radii of these cations. Lanthanide cations did not dissipate the formation of a proton gradient, as measured by determining the effect either on the uptake of [14C]methylamine or energy-linked quenching of the fluorescence of 9-aminoacridine. However, uranyl ion (UO2+(2+)) caused reversal of the energy-linked quenching of 9-aminoacridine. UO2+(2)) concentration yielding 50% of Vmax (S0.5) was approx. 15 microM. Kinetic studies revealed that inhibition in the uptake of Ca2+ was competitive with UO2+(2) while non-competitive with rare-earth metals. It is proposed that inhibition in the uptake of Ca2+ by uranyl ion occurs as a result of UO2+(2) transport into the interior of vesicles in exchange for protons, while lanthanide cations are not being transported but affect the binding of Ca2+ to the membrane, presumably to the Ca2+/H+ antiporter.

Antiporters↗