Pulmonary neoplasms in rats that inhaled cerium-144 dioxide.
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The lung neoplasms induced in rats by inhaled, internally deposited 144CeO2 were described and classified using histologic criteria. F344 rats were exposed once or repeatedly by inhalation to 144CeO2 and observed for their life span. There was significant life shortening only in those rats with the highest radiation doses. In these rats, there was a high percentage of squamous cell carcinomas of the lung, as well as much lower percentages of adenocarcinomas of the lung, hemangiosarcomas of the lung, and pleural mesotheliomas. At lower doses, adenocarcinomas were the most predominant tumor. These adenocarcinomas were subdivided based on their histologic pattern: alveolar, papillary, tubular, or undifferentiated. Neither the mode of exposure (single or repeated) nor the sex of the rat influenced the lung tumor incidence or tumor type. The lung neoplasms induced by this beta-emitting radionuclide are similar in nature to those induced by alpha-emitting radionuclides deposited in the lung in rats. However, the radiation-induced squamous cell carcinomas of the lung differ from those induced by heavy particle loads of nonradioactive compounds. The radiation-induced squamous cell carcinomas occur in higher incidence and have a more malignant behavior than those induced by heavy particle loads. (+info)
Using lanthanide ions to align troponin complexes in solution: order of lanthanide occupancy in cardiac troponin C.
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The potential for using paramagnetic lanthanide ions to partially align troponin C in solution as a tool for the structure determination of bound troponin I peptides has been investigated. A prerequisite for these studies is an understanding of the order of lanthanide ion occupancy in the metal binding sites of the protein. Two-dimensional [(1)H, (15)N] HSQC NMR spectroscopy has been used to examine the binding order of Ce(3+), Tb(3+), and Yb(3+) to both apo- and holo-forms of human cardiac troponin C (cTnC) and of Ce(3+) to holo-chicken skeletal troponin C (sTnC). The disappearance of cross-peak resonances in the HSQC spectrum was used to determine the order of occupation of the binding sites in both cTnC and sTnC by each lanthanide. For the lanthanides tested, the binding order follows that of the net charge of the binding site residues from most to least negative; the N-domain calcium binding sites are the first to be filled followed by the C-domain sites. Given this binding order for lanthanide ions, it was demonstrated that it is possible to create a cTnC species with one lanthanide in the N-domain site and two Ca(2+) ions in the C-domain binding sites. By using the species cTnC.Yb(3+).2 Ca(2+) it was possible to confer partial alignment on a bound human cardiac troponin I (cTnI) peptide. Residual dipolar couplings (RDCs) were measured for the resonances in the bound (15)N-labeled cTnI(129-148) by using two-dimensional [(1)H, (15)N] inphase antiphase (IPAP) NMR spectroscopy. (+info)
ppt level detection of samarium(III) with a coated graphite sensor based on an antibiotic.
(19/177)
N-[2-[4-[[[(Cyclohexylamino)carbonyl]amino]sulfonyl]phenyl]ethyl]-5-methyl pyrazine carboxamide (glipizid) was explored as an electro-active material for preparing a polymeric membrane-based sensor selective to samarium ions. The membrane incorporated 30% poly(vinyl chloride) (PVC), 53% benzyl acetate (BA), 11% glipizid and 6% sodium tetraphenyl borate. When coated on the surface of a graphite electrode, it exhibits Nernstian responses in the concentration range of 1.0 x 10(-5) to 1.0 x 10(-10) M, with a detection limit of 8.0 x 10(-11)M samarium. The electrode shows high selectivity towards samarium over several cations (alkali, alkaline earth, transition and heavy metal ions), and specially lanthanide ions. The proposed sensor has a very short response time (< 15 s), and can be used in a wide pH range for at least ten weeks. It was used as an indicator electrode in potentiometric titration of Sm(III) ions with an EDTA solution, and for determination of samarium in binary and ternary mixtures. (+info)
Site-selective and hydrolytic two-strand scission of double-stranded DNA using Ce(IV)/EDTA and pseudo-complementary PNA.
(20/177)
By combining Ce(IV)/EDTA with two pseudo-complementary peptide nucleic acids (pcPNAs), both strands in double-stranded DNA were site-selectively hydrolyzed at the target site. Either plasmid DNA (4361 bp) or its linearized form was used as the substrate. When two pcPNAs invaded into the double-stranded DNA, only the designated portion in each of the two strands was free from Watson-Crick base pairing with the counterpart DNA or the pcPNA. Upon the treatment of this invasion complex with Ce(IV)/EDTA at 37 degrees C and pH 7.0, both of these single-stranded portions were selectively hydrolyzed at the designated site, resulting in the site-selective two-strand scission of the double-stranded DNA. Furthermore, the hydrolytic scission products were successfully connected with foreign double-stranded DNA by using ligase. The potential of these artificial systems for manipulation of huge DNA has been indicated. (+info)
Induction of hepatic metallothionein by trivalent cerium: role of interleukin 6.
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Metallothionein (MT) is a small sulfydryl-rich protein that binds to and is inducible by heavy metals such as mercury, cadmium, zinc, and copper. However, little is known about the induction of MT by trivalent metals except for bismuth. In this study, we examined the induction of MT synthesis by cerium, a trivalent lanthanoid metal. Administration of cerium chloride (CeCl3) to mice resulted in accumulation of cerium and induction of MT in the liver in a dose-dependent manner. Distribution profiles of metals in the soluble fraction of the liver of CeCl3-treated mice analyzed by high performance liquid chromatography/inductively coupled argon plasma-mass spectrometry (HPLC/ICP-MS) demonstrated that the metal bound to MT-I and MT-II was zinc, but not cerium. Administration of CeCl3 caused increases in the activities of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and the levels of serum amyloid A (SAA), an acute phase protein. Among inflammatory cytokines examined, interleukin 6 (IL-6) exhibited a marked increase in the serum at 3 h after the CeCl3 administration. In order to evaluate the involvement of IL-6 in the induction of MT by cerium, we examined MT induction by CeCl3 in IL-6 null mice. Both the induction of hepatic MT and the increases in SAA levels were markedly suppressed in IL-6 null mice. These results suggest that IL-6 plays an important role in the induction of hepatic MT by cerium. (+info)
1H and 13C-NMR and molecular dynamics studies of cyclosporin a interacting with magnesium(II) or cerium(III) in acetonitrile. Conformational changes and cis-trans conversion of peptide bonds.
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Cyclosporin A (CsA) is an important drug used to prevent graft rejection in organ transplantations. Its immunosuppressive activity is related to the inhibition of T-cell activation through binding with the proteins Cyclophilin (Cyp) and, subsequently, Calcineurin (CN). In the complex with its target (Cyp), CsA adopts a conformation with all trans peptide bonds and this feature is very important for its pharmacological action. Unfortunately, CsA can cause several side effects, and it can favor the excretion of calcium and magnesium. To evaluate the possible role of conformational effects induced by these two metal ions in the action mechanism of CsA, its complexes with Mg(II) and Ce(III) (the latter as a paramagnetic probe for calcium) have been examined by two-dimensional NMR and relaxation rate analysis. The conformations of the two complexes and of the free form have been determined by restrained molecular dynamics calculations based on the experimentally obtained metal-proton and interproton distances. The findings here ratify the formation of 1:1 complexes of CsA with both Mg(II) and Ce(III), with metal coordination taking place on carbonyl oxygens and substantially altering the peptide structure with respect to the free form, although the residues involved and the resulting conformational changes, including cis-trans conversion of peptide bonds, are different for the two metals. (+info)
Redox titration of antioxidant mixtures with N-bromosuccinimide as titrant: analysis by non-linear least-squares with novel weighting function.
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Equations are presented by which potential-volume data from redox titrations can be analyzed. Mixtures of analytes as well as of titrants may be analyzed, yielding for each component its concentration, number of electrons, and reduction potential. A novel weighting function ensures endpoint accuracy in fitting. Standard deviation of each parameter is obtained. The equations can be readily implemented in Microsoft Excel. Agreement with true values and good precision of fit parameters is demonstrated for a number of test cases. Use of these exact equations enables analysis of analyte mixtures without prior separation using single titrant or titrant mixtures. The equations were used to demonstrate that N-bromosuccinimide, a useful oxidant for organic analytes, undergoes hydrolysis. (+info)
Indirect fluorometric determination of diclofenac sodium.
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A simple and easy method of analysis for diclofenac sodium is reported. A spectrofluorometric method for the microdetermination of diclofenac sodium has been developed through its reaction with cerium(IV) in an acidic solution and measurement of the fluorescence of the Ce(III) ions produced. Under the optimum experimental conditions for the oxidation reaction, 1.0 M H2SO4 with 90 min of heating time (100 degrees C), the range of application is 124.3-600 ng mL(-1) and the limit of detection is 72.7 ng mL(-1). The proposed method was applied to the determination of diclofenac sodium in pharmaceutical tablets. The results of the analysis show a good agreement with those obtained by the official USP 27 HPLC method. (+info)