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PubMed1985

Environmental aspects of polymer additives.

The environmental behavior of stabilizers is not known for all chemicals which serve this purpose and further investigations will have to be done for a better understanding. From the investigations carried out on a few representative compounds, which are known to reach the environment, it can be shown that at the low concentrations at which such products appear in the environment even chemically inert substances such as hindered phenols or tin alkyl compounds are rapidly degraded and completely decomposed under the combined action of light, water, and microorganisms.

Butylated Hydroxytoluene↗
PubMed2006

New benchmark for water photooxidation by nanostructured alpha-Fe2O3 films.

Thin films of silicon-doped Fe2O3 were deposited by APCVD (atmospheric pressure chemical vapor deposition) from Fe(CO)5 and TEOS (tetraethoxysilane) on SnO2-coated glass at 415 degrees C. HRSEM reveals a highly developed dendritic nanostructure of 500 nm thickness having a feature size of only 10-20 nm at the surface. Real surface area determination by dye adsorption yields a roughness factor of 21. XRD shows the films to be pure hematite with strong preferential orientation of the [110] axis vertical to the substrate, induced by silicon doping. Under illumination in 1 M NaOH, water is oxidized at the Fe2O3 electrode with higher efficiency (IPCE = 42% at 370 nm and 2.2 mA/cm2 in AM 1.5 G sunlight of 1000 W/m2 at 1.23 VRHE) than at the best reported single crystalline Fe2O3 electrodes. This unprecedented efficiency is in part attributed to the dendritic nanostructure which minimizes the distance photogenerated holes have to diffuse to reach the Fe2O3/electrolyte interface while still allowing efficient light absorption. Part of the gain in efficiency is obtained by depositing a thin insulating SiO2 interfacial layer between the SnO2 substrate and the Fe2O3 film and a catalytic cobalt monolayer on the Fe2O3 surface. A mechanistic model for water photooxidation is presented, involving stepwise accumulation of four holes by two vicinal iron or cobalt surface sites.

Adsorption↗
PubMed1986

Comparison of three RE agents-99mTc-phytate, 99mTc-sulfur colloid and 99mTc-Sb2S3 colloid in the rodent species.

99mTc-phytate, 99mTc-sulfur colloid and 99mTc-antimony sulfide colloid are recognised as RE agents in clinical nuclear medicine. Since these three agents exist in vitro in different forms of particulate aggregation it was of interest to compare their properties and to evaluate the merits and limitations of each of these agents. A comparison was carried out in rats and rabbits as a prelude to a systematic study in human subjects. Quality tested radiopharmaceuticals were prepared and their pharmacokinetics studied in rats. The blood clearance, tissue distribution and scinti-imaging patterns of the RE system were also compared in rabbits. All the agents have excellent localizing properties in the liver but differ in varying extents in their disposition in other tissues. 99mTc-sulfur colloid has some predisposition for the lungs while 99mTc-phytate has a little propensity for the kidney and gut at late time periods. 99mTc-Sb2S3 colloid shows a more pronounced concentration in the bone-marrow, and displays intermediate properties between 99mTc-phytate and 99mTc-sulfur colloid, besides being the most stable (in vitro) radiopharmaceutical in this series of RE agents.

Animals↗
PubMed1998

Metal chloride primers for bonding dentine with tri-n-butylborane-initiated luting agents.

OBJECTIVES: The bonding of resin to dentine is dependent largely on surface modifications. The purpose of the present study was to test the hypothesis that a role of the metal chlorides used as primers is to initiate polymerization of resin at the resin-dentine interface, thereby affecting bond strength. METHODS: Nine primers were evaluated, comprising aqueous 2-hydroxyethyl methacrylate (HEMA) solutions containing AICl3, CeCl3, CoCl2, CuCl2, FeCl3, NiCl2, MgCl2, SnCl2 or ZnCl2, respectively. One of the two luting agents (Super-Bond resin) consisted of methyl methacrylate (MMA), 4-methacryloyloxyethyl trimellitate anhydride (4-META) and tri-n-butylborane (TBB) initiator. The other luting agent (MMA-TBB resin) consisted of MMA and TBB without 4-META. Extracted bovine teeth were ground to expose the dentine, etched with an aqueous solution of 10% phosphoric acid, primed, and then bonded with stainless-steel rods; tensile bond strengths were determined after 1-day immersion in water. Data were analysed by ANOVA and Duncan's new multiple range test (P < 0.05). RESULTS: Four of the metal chlorides (CuCl2, FeCl3, MgCl2 and ZnCl2) enhanced the bond strengths of MMA-TBB resin to dentine. With Super-Bond resin, maximum bond strengths of 15.6 MPa and 19.0 MPa were recorded with primer containing 2.0 x 10(-5) mol g(-1) FeCl3 and 2.0 x 10(-6) mol g(-1) CuCl2, respectively. CONCLUSIONS: Bonding techniques, combining the use of either cupric primer or ferric primer with 10% phosphoric acid etchant may be suitable for application in seating resin-bonded prostheses with TBB-initiated luting materials.

Acid Etching, Dental↗
PubMed1984

Tin--a toxic heavy metal? A review of the literature.

A tolerable limit for tin concentration in canned food of 250 ppm (Fritsch et al., 1977) is generally accepted. However, biochemical effects attributable to tin have been observed even after oral administration of 1 and 3 mg Sn/kg body wt (Yamaguchi et al., 1980). These doses reflect 10 and 30 ppm tin in the diet. The experiments of de Groot (1973) showed that hemoglobin concentrations in the blood of rats decreased significantly feeding a diet containing 150 ppm tin. The absorption of iron was diminished after simultaneous administration of 0.8 mumol Sn(II) and iron, reflecting a tin dose of 95 ppm tin, by injection into jejunal loops of rats (Schäfer and Forth, 1983). In general, however, canned food usually plays a secondary role in daily nutrition. Fortunately, concentrations of about 2000 ppm tin as reported by Warburton et al. (1962) and Barker and Runte (1972) are not found in canned food, but values between 50 and 500 ppm are not unusual (Piscator, 1979). If a large amount of canned food is eaten daily over a long period, disturbances of gastric acid secretion and a reduction in iron absorption or heme metabolism cannot be excluded. The storage of food, especially acid foods, in opened cans should be avoided as this practice increases the amount of tin in the food when it is consumed.

Animals↗
PubMed1979

Complexing of reduced technetium and tin (II) by chelating phosphate compounds. I. Chemical state of technetium.

Complexing of reduced 99mTc, 99Tc and of 113Sn(II) by pyrophosphate was studied, using the in vivo distribution in the rat as an indicator for complex formation. 99mTc-pyrophosphate was only formed at very low technetium concentrations, otherwise colloid formation occurred. Reduced 99mTc in trace amounts and 113Sn(II) complexed equimolarly with pyrophosphate were concentrated in bone and excreted in urine in comparable amounts. The in vivo distribution of 32P-orthophosphate and -pyrophosphate was characterized by a considerable uptake in the liver and a poor urinary excretion. The distribution patterns of 32P-pyrophosphate, complexed equimolarly with tin(II), remained unchanged. Despite these findings it is concluded that real chelates are formed, since non-complexed reduced 99mTc was not concentrated in bone. Two variants of reduced technetium could be discerned: a 99mTc-kidney agent and a 99mTc protein-bound agent. Some evidence was found that reduced technetium may change its oxidation state, but it seems much more likely that both agents are technetium(IV) compounds. It is suggested that the kidney agent is hydrated technetium dioxide whereas the protein-bound agent is a charged technetium(IV) compound. Only hydrated technetium dioxide is obviously complexed by chelating phosphate compounds.

Animals↗
PubMed2001

Antiproliferative activity and interactions with cell-cycle related proteins of the organotin compound triethyltin(IV)lupinylsulfide hydrochloride.

Organotin compounds, particularly tri-organotin, have demonstrated cytotoxic properties against a number of tumor cell lines. On this basis, triethyltin(IV)lupinylsulfide hydrochloride (IST-FS 29), a quinolizidine derivative, was synthesized and developed as a potential antitumor agent. This tin-derived compound exhibited potent antiproliferative effects on three different human cancer cell lines: teratocarcinoma of the ovary (PA-1), colon carcinoma (HCT-8) and glioblastoma (A-172). Cytotoxic activity was assessed by MTT and cell count assays during time course experiments with cell recovery after compound withdrawal. Significant cell growth inhibition (up to 95% in HCT-8 after 72 h of exposure), which also persisted after drug-free medium change, was reported in all the cell lines by both assays. In addition, the cytocidal effects exerted by IST-FS 29 appeared more consistent with necrosis or delayed cell death, rather than apoptosis, as shown by morphologic observations under light microscope, DNA fragmentation analysis and flow cytometry. In the attempt to elucidate whether this compound might affect genes playing a role in G1/S phase transition, the expressions of p53, p21(WAF1), cyclin D1 and Rb, mainly involved in response to DNA-damaging stress, were analyzed by Western blot. Heterogeneous patterns of expression during exposure to IST-FS 29 were evidenced in the different cell lines suggesting that these cell-cycle-related genes are not likely the primary targets of this compound. Thus, the present data seem more indicative of a direct effect of IST-FS-29 on macromolecular synthesis and cellular homeostasis, as previously hypothesized for other organotin complexes.

Antineoplastic Agents↗
PubMed2005

Synthesis and DNA topoisomerase-II inhibitory activity of unnatural nucleosides.

The synthesis and biological activities of a number of unnatural nucleosides (23-43) is described. Nucleosides have been synthesized by SnCl4-catalyzed condensation of amino sugar acetates and silylated modified pyrimidines. Few of the 2'-O-acetyl derivatives of the nucleosides were hydrolyzed to the respective hydroxy derivatives by treatment with methanol saturated with ammonia. The compounds were screened against Filarial DNA-topoisomerase-II but only one of the compounds (29) inhibited this enzyme at 40 microg/mL of reaction mixture.

Acetates↗
PubMed1997

A direct electrode-driven P450 cycle for biocatalysis.

The large potential of redox enzymes to carry out formation of high value organic compounds motivates the search for innovative strategies to regenerate the cofactors needed by their biocatalytic cycles. Here, we describe a bioreactor where the reducing power to the cycle is supplied directly to purified cytochrome CYP101 (P450cam; EC 1.14.15.1) through its natural redox partner (putidaredoxin) using an antimony-doped tin oxide working electrode. Required oxygen was produced at a Pt counter electrode by water electrolysis. A continuous catalytic cycle was sustained for more than 5 h and 2,600 enzyme turnovers. The maximum product formation rate was 36 nmol of 5-exo-hydroxycamphor/nmol of CYP101 per min.

Bioreactors↗
PubMed2000

Influence of amphiphilic compounds on membranes.

On the basis of Gortel & Grendel (J. Exp. Med., 1925, 41, 439-494) discovery, the importance of the lipid bilayer as an integral and indispensible component of the cell membrane is discussed. In particular, attention focuses on the interaction between membranes and amphiphilic substances. The effect on membranes of quaternary ammonium salts, both in the form of pesticides and oxidants as well as organic compounds of tin and lead are discussed in greater detail.

Antioxidants↗
PubMed1992

Quantitative bioassay using laser-monitored bacteria to assess toxicology and metabolism of bioactive Group IV compounds.

A new approach has been developed for assessing the toxicity and the metabolism of Group IV compounds and for other toxic substances that may interact with them at the molecular level. The approach is based upon the selective responses of sensitive biodetectors whose molecular interactions with a wide variety of toxic substances have been previously described and reported. Detection and quantitation of carbon, silicon, and tin-containing compounds has been accomplished using a laser-monitored bacterial bioassay. This system uses isogenic Bacillus subtilis strains that are genetically engineered to respond differentially to specific toxicants. The response of these biodetectors is monitored by differential light scattering of a laser that is integrated with a computerized system which collects and analyzes this data. The assay can routinely generate fully analyzed data for fixed time intervals, i.e. 60 or 90 min, or kinetic data so that the mechanisms of interactions can be elucidated.

Animals↗
PubMed1991

Comparison of sulphur-mode and tin-mode flame photometric detectors for the gas chromatographic determination of organotin compounds.

A comparison of sulphur-mode (393 nm) and tin-mode (610 nm) flame photometric detectors for the gas chromatographic determination of butyl- and phenyltin compounds is described. The chromatographic peaks of the butyl- and phenyltin compounds were well separated, and high sensitivity was achieved in both modes; however, the tin-mode was more specific for tin compounds than the sulphur-mode. The absolute detection limits with the sulphur-mode and the tin-mode were 3.9-7.6 pg and 2.6-5.1 pg as tin, respectively. The application of the tin-mode gas chromatographic method to the determination of organotin compounds in fish is presented. For this application, organotins are extracted (as chloride) with hydrochloric acid and n-hexane-benzene (3:2, containing 0.05% tropolone) and the extracts are pentylated by a Grignard reagent prior to gas chromatography. The absolute recoveries of butyl- and phenyltin compounds added to fish samples ranged from 68.5 to 84.4% (the coefficients of variation were less than 6.6% for all substances, n = 8). Significant amounts of three organotin compounds (di- and tributyltin and triphenyltin) in fish samples were detected by this method. This technique may have application for other organotin compounds and the monitoring of butyl- and phenyltin compounds in the environment.

Animals↗
PubMed1992

ESCA study on dental alloy surfaces modified by Ga-Sn alloy.

A new, simple surface modification method for adherend metals has been developed. It gives high bond strength and superior water durability to dental precious-metal alloys bonded with 4-META/MMA-TBB resin. However, there was no effect on the bonding of Ag-In-Zn alloy and base-metal alloys. In the present study, the alloy surfaces modified by the new method were analyzed by ESCA and SEM for determination of details of the modification effect. A new alloying layer containing Ga and Sn was formed on the precious-metal alloys. The main factor for excellent adhesion to be achieved was the formation of a very thin layer of Ga2O3 and SnO2, less than 1-2nm thick, on the alloy surface. A thicker modified layer, as formed on the Ag-In-Zn and Ni-Cr alloys, led to low bonding ability.

Acrylic Resins↗
PubMed2004

Synthesis of quaternary amino acids bearing a (2'Z)-fluorovinyl alpha-branch: potential PLP enzyme inactivators.

Protected alpha-formyl amino acids, themselves available from the corresponding alpha-vinyl amino acids, are stereoselectively transformed into the (Z)-configured alpha-(2'-fluoro)vinyl amino acids via a three-step sequence. The route employs McCarthy's reagent, diethyl alpha-fluoro-alpha-(phenylsulfonyl)methyl phosphonate, and proceeds via the intermediate (E)-alpha-fluorovinyl sulfones and (E)-alpha-fluorovinylstannanes. The latter may either be exploited as novel cross-coupling partners for fluorovinyl branch extension or be globally deprotected, to provide the title compounds. [structure: see text]

Amino Acids↗
PubMed1983

Variation of elastin fluorescence with method of preparation: determination of the major fluorophore of fibrillar elastin.

The variation of fluorescence of two fibrillar elastins as a result of preparation methods was studied and the major common fluorophore was identified. Dilution of acid-hydrolyzed bovine ligament elastin 1:2500 (g:ml) overcame inner filter effects (IFE) to reveal fluorescence excitation and emission maxima of 330/408 nm. An IFE effect observed in elastase-solubilized elastin was unresponsive to dilution. Elastase-solubilized elastin had maximal fluorescence at 338/410 nm (pH 2.3) and 325/394 nm (pH 7.4), and the fluorescence intensity was 35-40% of that of the acid-hydrolyzed elastin. Changes in fluorescence that occurred when an acid hydrolysate was evaporated to dryness were prevented by evaporation to a volume not less than 15 ml. As a result, there was an almost two-fold increase in the yield of a fluorophore with spectral maxima near 340/400 nm. Chick aorta elastin purified by enzymatic methods also contained substantial amounts of this fluorophore. It is concluded that the compound with fluorescence of 340/400 nm is the major common fluorophore of postnatal fibrillar elastins.

Animals↗
PubMed2006

Evaluation of oxidative stress in D-serine induced nephrotoxicity.

It has been suggested that oxidative stress is involved in d-serine-induced nephrotoxicity. The purpose of this study was to assess if oxidative stress is involved in this experimental model using several approaches including (a) the determination of several markers of oxidative stress and the activity of some antioxidant enzymes in kidney and (b) the use of compounds with antioxidant or prooxidant effects. Rats were sacrificed at several periods of time (from 3 to 24h) after a single i.p. injection of d-serine (400mg/kg). Control rats were injected with l-serine (400mg/kg) and sacrificed 24h after. The following markers were used to assess the temporal aspects of renal damage: (a) urea nitrogen (BUN) and creatinine in blood serum, (b) kidney injury molecule (KIM-1) mRNA levels, and (c) tubular necrotic damage. In addition, creatinine clearance, proteinuria, and urinary excretion of N-acetyl-beta-d-glucosaminidase (NAG) were measured 24h after d-serine injection. Protein carbonyl content, malondialdehyde (MDA), 4-hydroxy-2-nonenal (4-HNE), fluorescent products of lipid peroxidation, reactive oxygen species (ROS), glutathione (GSH) content, and heme oxygenase-1 (HO-1) expression were measured as markers of oxidative stress in the kidney. Additional experiments were performed using the following compounds with antioxidant or pro-oxidant effects before d-serine injection: (a) alpha-phenyl-tert-butyl-nitrone (PBN), a spin trapping agent; (b) 5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrinato iron(III) (FeTPPS), a soluble complex able to metabolize peroxynitrite; (c) aminotriazole (ATZ), a catalase (CAT) inhibitor; (d) stannous chloride (SnCl(2)), an HO-1 inductor; (e) tin mesoporphyrin (SnMP), an HO inhibitor. In the time-course study, serum creatinine and BUN increased significantly on 15-24 and 20-24h, respectively, and KIM-1 mRNA levels increased significantly on 6-24h. Histological analyses revealed tubular necrosis at 12h. The activity of antioxidant enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase remained unchanged at all times studied. Protein carbonyl content, MDA, 4-HNE, and ROS remained unchanged at all time-points studied. GSH content decreased transiently on 9 and 12h. Interestingly, fluorescent products of lipid peroxidation decreased significantly on 3-24h. HO-1 expression was undetectable by Western blot and the immunohistochemistry studies revealed that the intensity of HO-1 staining was weak. The administration of PBN, FeTPPS, ATZ, SnCl(2), and SnMP did not prevent or enhance renal damage induced by d-serine. Our data taken as a whole suggest that oxidative stress is not involved in the early phase of the nephrotoxicity induced by d-serine.

Acetylglucosaminidase↗