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PubMedDate not supplied

Industrial solution contaminated by polyacrylates: their elimination by electrochemical combustion.

The electrochemical combustion of polyacrylates was studied through both direct and indirect oxidation. The obtained results indicate the non elimination of the polyacrylates with the direct oxidation, while the indirect oxidation with NaCl completely eliminates these organic compounds. In the last case the effects of different initial concentrations of NaCl, anode materials and current densities was studied.

Acrylic Resins↗
PubMed2005

Synthesis of PtRu5(CO)14(PBu(t)3)(mu-H)2(mu6-C) and its reactions with Pt(PBut3)2, HGePh3, and HSnPh3.

Reaction of PtRu5(CO)15(PBut3)(C), 3, with hydrogen at 97 degrees C yielded the new dihydride-containing cluster compound PtRu5(CO)14(PBut3)(mu-H)2(mu6-C), 5. Compound 5 was characterized crystallographically and was shown to contain an octahedral cluster consisting of one platinum and five ruthenium atoms with a carbido ligand in the center. Two hydrido ligands bridge two oppositely positioned PtRu bonds. Compound 5 reacts with Pt(PBut3)2 to yield Pt2Ru5(CO)14(PBut3)2(mu-H)2(mu6-C), 6, a Pt(PBut3) adduct of 5, by adding a Pt(PBut3) group as a bridge across one of the Ru-Ru bonds in the square base of the Ru5 portion of the cluster. Compound 6 is dynamically active on the NMR time scale by a mechanism that appears to involve a shifting of the Pt(PBut3) group from one Ru-Ru bond to another. Two new complexes, PtRu5(CO)13(PBut3)(mu-H)3(GePh3)(mu5-C), 7, and PtRu5(CO)13(PBut3)(mu-H)2(mu-GePh2)(mu6-C), 8, were obtained from the reaction of 5 with HGePh3. The cluster of 7 has an open structure in which the Pt(PBut3) group bridges an edge of the square base of the square pyramidal Ru5 cluster. Compound 7 also has three bridging hydrido ligands and one terminal GePh3 ligand. When heated to 97 degrees C, 7 is slowly converted to 8 by cleavage of a phenyl group from the GePh3 ligand and elimination of benzene by its combination with one of the hydrido ligands. The PtRu5 metal cluster of 8 has a closed octahedral shape with a GePh2 ligand bridging one of the Ru-Ru bonds. Two tin-containing compounds, PtRu5(CO)13(PBut3)(mu-H)3(SnPh3)(mu5-C), 9, and PtRu5(CO)13(PBut3)(mu-H)2(mu-SnPh2)(mu6-C), 10, which are analogous to 7 and 8 were obtained from the reaction of 5 with HSnPh3.

Journal Article↗
PubMed1988

Dentine hypersensitivity. I. Effects produced by the uptake in vitro of metal ions, fluoride and formaldehyde onto dentine.

Dentine has been shown to possess affinity for a large number of varied compounds, many of which have been shown effective in clinical trials, for the treatment of dentine hypersensitivity. The mode of action of these compounds is unclear. The aim of this study was to investigate the uptake of metal ions, fluoride and formaldehyde in solution onto dentine in vitro and determine whether therapeutic effects could be mediated through occlusion of dentinal tubules. Etched dentine sections were exposed for 1 h to 1000 ppm solutions of fluoride and metal salts. Levels of fluoride and respective metals could be extracted and measured from the specimens. Saliva pretreatment had a variable but small effect on uptake of each ion, but post treatment washings reduced all levels of retained fluoride and metals. X-ray microanalysis indicated surface or immediate subsurface deposits of metals. However, surface changes were only consistently produced by zinc and more particularly tin salts. Both zinc and tin salts produced covering or obturation of tubules. The surface effects of zinc could largely be reversed by washing, but not those of tin. Formaldehyde alone or in the presence of saliva produced no effects. A 4-week study involving twice daily exposure of specimens to saliva and fluoride, metals or formaldehyde yielded essentially the same results. It is unlikely that, except for tin, the compounds tested achieve their apparent clinical effects mediated by direct occlusion of dentinal tubules.

Calcium↗
PubMed2005

The radiopharmaceutical chemistry of 99mTc-tin fluoride colloid-labeled-leukocytes.

Tc-99m-tin fluoride colloid is a radiotracer used to label patient white cells, for the diagnosis of infection and inflammation. The scintigraphic technique has been employed in routine clinical practice for approximately 20 years in Australia, yet the chemistry of the radiolabeling agent, and the physiological distribution of (99m)Tc-leukocytes, are not entirely understood. In this review, the physico-chemical characteristics of (99m)Tc-tin fluoride colloid are discussed, as well as the in vitro and in vivo distribution of (99m)Tc-tin fluoride-labeled-leukocytes. Furthermore, important animal and human studies are summarized, that emphasize the clinical usefulness of this radiopharmaceutical tracer in nuclear medicine today.

Animals↗
PubMed2005

Stereoselective syntheses of dihydroxerulin and xerulinic acid, anti-hypocholesterolemic dyes from the fungus Xerula melanotricha.

The title compounds 2 and 3, which are inhibitors of the biosynthesis of cholesterol, were synthesized in a convergent and perfectly stereoselective manner. In the key step, bromobutenolide 6 (obtained from levulinic acid in two steps) was coupled with either of the novel bis(stannanes) trans,cis,trans-35 or trans,trans,trans-35 [each accessible from 3-(tributylstannyl)allyl alcohol (17) in four steps], giving gamma-alkylidenebutenolide trans,trans,trans-32. This compound was coupled with iododiyne 42 or the bromoenediynoate 44 leading to dihydroxerulin (2) and to the (trimethylsilylethyl)ester 45 of xerulinic acid, respectively. Deprotection of the latter provided totally synthetic xerulinic acid (3) for the first time.

Agaricales↗
PubMed1985

Synthesis and biological activities of 2-pyrimidinone nucleosides. 2. 5-Halo-2-pyrimidinone 2'-deoxyribonucleosides.

1-(2-Deoxy-beta-D-ribofuranosyl)-5-bromo-2-pyrimidinone (BrPdR) and 1-(2-deoxy-beta-D-ribofuranosyl)-5-iodo-2-pyrimidinone (IPdR) have been synthesized by condensation of the appropriate silylated bases 2a and 2b, respectively, with 3,5-bis-O-(p-chlorobenzoyl)-2-deoxy-alpha-D-ribofuranosyl chloride (8) in 1,2-dichloroethane, in the presence of SnCl4, followed by separation of the anomeric blocked nucleosides via column chromatography and subsequent deprotection with methanolic ammonia. Both BrPdR and IPdR exhibited significant antiherpes activities against various strains of HSV-1 and HSV-2, the latter compound (IPdR) showing the higher activity as well as the stronger binding to the virus-specific thymidine kinase.

Animals↗
PubMed1989

[Induced remineralization of carious dentin. Electronic microprobe analysis].

Our electron microprobe studies show the preferential incorporation in vitro of tin and fluorure into carious dentin. These ions do penetrate only into carious dentin through the body of the lesion. These ions do not progress through the sclerotic dentin barrier, when it exists which tend to demonstrate their affinity for demineralized tissues. Results of microprobe analysis may suggest the hypothesis of a crystalline arrangement as the product of reaction between residual apatite in carious dentin with stannous fluoride. A new crystalline phase could occur within the carious zone, up to the sclerotic barrier. This method does not permit to indicate its identity or its structure. However, it has been recognized in previous studies as a tin phosphate compound. Further analytic studies, using crystallographic technics of the treated zones could provide additional data of the observations from the electron microprobe and confirm the hypothesis of the ability of carious dentin to be remineralized by the use of stannous fluoride containing solutions or materials.

Dental Caries↗
PubMed2000

Preparation of (188Re) Re-AEDP and its biodistribution studies.

The synthesis of the Re (V) complex and preparation of 188Re-AEDP are described using 188Re which was obtained from the alumina-based 188W/188Re generator. Dependence of the radiolabeling yields of 188Re-AEDP on reducing agent concentration, AEDP concentration, pH and addition of carrier was examined. In the case of optimum conditions, the radiolabeling yields of 188Re-AEDP were 92-93% for carrier-free 188Re and 95-98% for carrier-added 188Re. The stability of 188Re-AEDP at pH approximately 6 was studied and it is found that the carrier has a significant effect on the stability of 188Re-AEDP. The biodistribution of carrier-free and carrier-added 188Re-labelled compounds in rats was also measured. The results show that 188Re (carrier-added)-AEDP is a potential bone palliation radiopharmaceutical due to its high skeletal uptake, rapid blood clearance and relatively low soft tissue absorption.

Animals↗
PubMed1998

Differential xenobiotic induction of CYP2A5 in mouse liver, kidney, lung, and olfactory mucosa.

The effects of pyrazole, which is known to induce hepatic cytochrome P4502A5 (CYP2A5) through posttranscriptional mechanisms, on the level of CYP2A5 in liver and extrahepatic tissues were examined in this study. Intraperitoneal administration of pyrazole at 200 mg/kg for 3 days induced CYP2A4/5 mRNAs and proteins and microsomal coumarin 7-hydroxylation activity in liver and kidney of C57BL/6 mice. A marginal increase (30%) in CYP2A4/5 mRNAs was also observed in the olfactory mucosa but not in the lung, and no increase in CYP2A4/5 proteins or microsomal coumarin 7-hydroxylation activity was observed in either the olfactory mucosa or lung. CYP2A4/5 proteins were not detected on immunoblots in other tissues examined, including breast, bone marrow, testis, prostate, ovary, and uterus from control or pyrazole-treated mice. On the other hand, pyrazole treatment induced CYP2E1 in the olfactory mucosa as well as in liver and kidney, indicating that the olfactory mucosa was exposed to pyrazole. The lack of CYP2A inducibility in the olfactory mucosa was also observed for several other known inducers of hepatic CYP2A5, including cobaltous chloride, stannous chloride, griseofulvin, thioacetamide, and aminotriazole. These results suggest that the mechanisms involved in the induction of hepatic and renal CYP2A5 by pyrazole and other xenobiotic compounds may be tissue-specific.

Amitrole↗
PubMed2001

Effect of the Cymbopogon citratus, Maytenus ilicifolia and Baccharis genistelloides extracts against the stannous chloride oxidative damage in Escherichia coli.

Stannous ion has been used in different sectors of human interest, such as in food industry and in health sciences. Much is known about stannous chloride (SnCl(2)) toxicity, although, there is no general agreement regarding its genotoxicity. Cymbopogon citratus, Maytenus ilicifolia and Baccharis genistelloides extracts have been used in popular medicine. We evaluated the influence of these crude extracts on the survival of the Escherichia coli wild type (AB 1157) strain submitted to SnCl(2) treatment. Reactive oxygen species (ROS) can be generated by a Fenton like reaction induced by SnCl(2). E. coli culture was treated simultaneously with SnCl(2) and a specific extract. Our results showed a reduction of the SnCl(2) effect on the survival of the cultures in presence of the crude extracts. The extract of M. ilicifolia showed the highest level of protection action against the SnCl(2) effect in comparison with the other extracts. This protector effect could due to the redox properties of these crude extracts. The compounds in the crude extracts could (i) chelate stannous ions, protecting them against the oxidation and avoiding the generation of ROS, (ii) be a scavenger of the ROS generated by the SnCl(2) oxidation and/or (iii) have oxidant compounds that could oxidise the stannous ions, abolishing or reducing the SnCl(2) effect.

Antimutagenic Agents↗
PubMed1986

Effect of triethyltin on enzyme activity in human adult and cord red cells.

Since organotin compounds represent an environmental health hazard, we determined the effect of triethyltin bromide (TTB) on red blood cell (RBC) enzyme activity. TTB produced a concentration-dependent inhibition of hexokinase and pyrimidine 5'-nucleotidase for both adult and cord RBC. D-Glucose, but not ATP or MgCl2, prevented the hexokinase inhibition by TTB. Glucose-6-phosphate dehydrogenase, adenylate kinase, and hypoxanthine-guanine phosphoribosyltransferase were also inhibited by TTB. Cord RBC enzymes were more resistant to the effects of TTB than were adult RBC enzymes. Although TTB is a potent inhibitor of hexokinase, physiologic concentrations of glucose appear to protect the RBC during clinical tin intoxication.

5'-Nucleotidase↗
PubMed1988

Environmental methylation of tin: an assessment.

The chemical and biological methylation of tin under environmental conditions is reviewed. The question of whether methyltin species form in situ in the environment is also considered. Analytical approaches using hydridization techniques give quite sensitive results. Incubation studies of environmental microorganisms and sediment have demonstrated the formation of methyltin species, and similar conversions have been observed with chemical methylating agents such as methyl cobalamin and methyl iodide.

Environmental Pollution↗
PubMed2004

Cross-section analysis of organic light-emitting diodes.

The 'lift-out' technique using a focused ion beam microscope was applied to prepare cross-sectional specimens of organic light-emitting diodes for use in transmission electron microscopy. The focused ion beam equally thins the organic/inorganic hybrid devices despite the difference in material hardness of the compounds. This allowed to overcome preparation difficulties of conventional techniques such as ion thinning or ultra-microtomy. Two different samples were prepared and studied by both conventional transmission electron microscopy and analytical electron microscopy to display some of the investigation possibilities which become available with this sample preparation method.

Aluminum↗
PubMed2004

Convergent syntheses of polycyclic ethers. Illustrations of the utility of acetal-linked intermediates.

One of the most characteristic and spectacular class of compounds isolated from marine sources is the polycyclic ethers. Following the initial report of the structural determination of brevetoxin B, a variety of novel polycyclic ethers have begun to surface. These natural products include ciguatoxins, gambierol, gambieric acids, yessotoxins and gymnocins, each of which exhibit distinct biological properties such as cytotoxicity and neurotoxicity, as well as antiviral and antifungal activities. Because of these intriguing biological activities and their complex molecular architecture, the total synthesis of these compounds has been pursued by many laboratories over two decades. In particular, the development of novel convergent strategies to assemble the structural fragments is crucial for the successful construction of these nano-scale molecules. This Perspective will focus on a recent convergent methodology using an acetal-linkage as a key motif. Application of this methodology culminated in the total syntheses of gambierol and ciguatoxin CTX3C.

Acetals↗
PubMedDate not supplied

Electrochemical oxidation of para-chlorophenol on Ti/SnO2-PbO2 electrodes: introduction of a parameter for the estimation of their efficiency.

To oxidate otherwise non-biodegradable organic pollutants as chlorophenol has recently been proposed the promising electro-combustion technique. We considered two different types of electrodic material: boron doped diamond (BDD) and lead dioxide electro-deposited on a Ti/SnO2 substrate and we investigated differences between them in terms of organics oxidation efficiency. In the batch system we utilised for the combustion, the experimental parameters we investigated, initial concentration of the organic compound, temperature and current density furnished to the system--showed us that a parameter like the Instantaneous Current Efficiency (ICE) is affected by mass-transfer limitation at the end of the tests. In this paper we therefore introduce a new parameter not influenced by these problems that can be very effective for the description of electrode efficiency during the conduction of experiences.

Chlorophenols↗
PubMed2006

An efficient process for synthesis of 2'-O-methyl and 3'-O-methyl guanosine from 2-aminoadenosine using diazomethane and the catalyst stannous chloride.

An improved strategy for the selective synthesis of 2'-O-methyl and 3'-O-methyl guanosine from 2-aminoadenosine is reported by using the catalyst stannous chloride. The regioselectivity of the 2' and 3'-O-alkylation was achieved by optimizing the addition, timing, and concentration of the catalysts and diazomethane during the methylation reaction. An efficient and selective alkylation at 2'-OH of 2-aminoadenosine was achieved by mixing a stoichiometric amount of stannous chloride at room temperature in DME The reaction mixture was stirred at 50 degrees C for 1 min and immediately followed by addition of diazomethane. The resulting 2'-O-methyl 2-aminoadenosine was treated with the enzyme adenosine deaminase, which resulted in an efficient conversion to the desired 2'-O-methylguanosine (98% yield). The product was isolated by crystallization. In contrast, the methylation at 3'-OH of 2-aminoadenosine was achieved by mixing a stoichiometric amount of stannous chloride in DMF and stirring at 50 degrees C for 15 min, followed by addition of diazomethane. The resulting mixture containing 3'-O-methyl-2-aminoadenosine in 90% yield and 2'-O-methyl-2-aminoadenosine in 10% yield was treated with the enzyme adenosine deaminase, which preferentially deaminated only 3'-O-methyl-2-aminoadenosine, resulting in the production of 3'-O-methylguanosine in 88% yield. Due to the extremely low solubility 3'-O-methylguanosine, the compound precipitated and was isolated by centrifugation. This synthetic route obviates the chromatographic purification. Selective monomethylation is achieved by using the unprotected ribonucleoside. As a result, the method described herein represents a significant improvement over the current synthetic approach by providing superior product yield and economy, a much more facile purification of 2',3'-O-methylated isomers, and eliminating the need for protected ribonucleosides reagents.

Adenosine↗
PubMed1980

Thiol groups and reduced acidogenicity of dental plaque in the presence of metal ions in vivo.

Metal ions are known to influence the cariogenicity of dental plaque. Inhibition of acid metabolism in plaque may be of importance in this respect. Metal ions inhibit the acidogenicity of dental plaque to a different extent and it has been suggested that an enzyme inhibition based on oxidation of thiol groups may explain this observation. The aim of the present study was to evaluate the significance of oxidation of thiol groups in the inhibition of acid production in plaque by silver, tin and zinc salts. Nine subjects with 3-d sucrose induced plaque received topical applications of the metal ions. Cysteine or glutathione, which are known to reverse thiol oxidations, were then applied in one side of the mouth. Plaque pH measurements, in the presence of sucrose, were performed prior to and up to 2 h after treatment. The results showed that the acid production inhibited by the metal ions was reactivated by cysteine or glutathione. Iodoacetamide and p-chloromercuribenzoate were also shown to inhibit acid formation in dental plaque. The high affinity silver, tin and zinc have for SH groups, the observed inhibitory effect of these metals, the reactivation of the metabolism by monothiols and the fact that organic sulfhydryl reagents inhibit acid formation in plaque indicate that oxidation of thiol groups may be the mechanism by which these metals exert their effect.

Adult↗
PubMed2000

Evaluation of (99m)Tc-labeled photosan-3, a hematoporphyrin derivative, as a potential radiopharmaceutical for tumor scintigraphy.

A quick and reproducible method for radiolabeling of Photosan-3(R), a photosensitizer used worldwide for photodynamic therapy (PDT) of cancer, with radioisotope of technetium ((99m)Tc) was developed. The radiotracer was evaluated for radiochemical purity, stability, and finally tissue distribution in a murine tumor model. The (99m)Tc-Photosan-3 prepared by using (99m)Tc-pertechnetate in place of reduced (99m)Tc demonstrated better labeling efficiency (>90%) and reproducibility. The procedure also minimized the radiation exposure to the radiochemist as handling time was considerably reduced. Due to the commercial availability of Photosan-3, the risk of batch-to-batch variation in the in situ synthesis of hematoporphyrin derivative, which is a complex mixture of at least five compounds, was also significantly reduced. The biodistribution studies and tumor scintigraphy confirmed that (99m)Tc-labeled Photosan-3 was preferentially taken up by the neoplastic tissue in a manner similar to the parent compound. In addition to applications in tumor imaging, (99m)Tc-Photosan-3 could also be used for estimating tumor uptake of Photosan-3 as may be required for individualization of clinical protocols of PDT.

Animals↗