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At least 1,603 records · Page 89Linked to original sources
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↗
PubMed2003

Anion dependent structures of luminescent silver(i) complexes.

The reaction of AgX, where X = trifluoroacetate (CF(3)CO(2)(-), tfa), nitrate (NO(3)(-)), trifluoromethanesulfonate (triflate, CF(3)SO(3)(-), OTf), hexafluorophosphate (PF(6)(-)), or perchlorate (ClO(4)(-)), with 2,2',3' '-tripyridylamine (tpa) yields five novel silver(I) complexes, which have been structurally characterized. The five complexes have the same 1:1 stoichiometry of Ag/tpa but exhibit different modes of coordination, depending upon the counterion present in the compound. Compound 1, [Ag(tpa)(tfa)](n)(), forms a 1D coordination polymer of [Ag(tpa)(tfa)](2) dimer units linked through bridging tfa counterions. Compound 2, [Ag(tpa)(CH(3)CN)(NO(3))](n), forms a zigzag chain 1D coordination polymer exclusively through Ag-N bonds. In compounds 1 and 2, each tpa ligand is bound to two Ag(I) ions via a 2-py and a 3-py group. Compound 3, [Ag(tpa)(OTf)](n), forms a ribbonlike 1D coordination polymer, in which each tpa ligand binds to three different silver centers via all three pyridyl groups, and the counterion remains coordinated to the Ag(I) center. Compounds 4, [Ag(tpa)(CH(3)CN)](n)(PF(6))(n), and 5, [Ag(tpa)(CH(3)CN)](n)() (ClO(4))(n), display ribbonlike structures resembling that of 3, except that the counterions are not coordinated. All complexes are luminescent in acetonitrile solution, with emission maxima in the near-UV region (lambda(max) = 366, 368, 367, 367, and 368 nm for 1-5, respectively). At 77 K, the emission maxima are red-shifted to lambda(max) = 452, 453, 450, 450, and 454 nm for 1-5, respectively.

Journal Article↗
PubMed2005

DNA-network-templated self-assembly of silver nanoparticles and their application in surface-enhanced Raman scattering.

A large-scale lambda-DNA network on a mica surface was successfully fabricated with a simple method. Silver nanoparticles capped with the cationic surfactant cetyltrimethylammonium bromide (CTAB) were self-assembled onto a two-dimensional DNA network template by electrostatic interaction and formed nanoporous silver films, which can be used as active surface-enhanced raman scattering (SERS) substrates. Two probe molecules, Rhodamine 6G (R6G) and 4-aminothiophenol (4-ATP), were studied on these substrates with very low concentrations, and great enhancement factors for R6G (0.21 x 10(10)-4.09 x 10(11)) and 4-ATP (approximately 1.70 x 10(5)) were observed. It was found that the enhancement ability was affected by the DNA concentration and the electrostatic absorption time of the CTAB-stabilized silver nanoparticles on the DNA strands. These SERS substrates formed by the self-assembly of silver nanoparticles on DNA network also show good stability and reproducibility in our experiments.

Aniline Compounds↗
PubMed1986

Glutathione: a protective agent in Salmonella typhimurium and Escherichia coli as measured by mutagenicity and by growth delay assays.

Cultures of some aerobically grown strains of Salmonella typhimurium and Escherichia coli contain up to 24 microM extracellular glutathione (GSH) [Owens RO, Hartman PE (1985): Environ Mutagen 7(Suppl 3): 47] in addition to having intracellular GSH concentrations in the millimolar range. The addition of 26 microM GSH to cultures of Salmonella typhimurium strain TA1534 partially protected the bacteria from the toxic effects causing growth delay by 54 microM N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). When MNNG was preincubated with equimolar GSH, the mutagenicity of the MNNG was neutralized. The addition of micromolar GSH to cultures of an Escherichia coli GSH- strain protected the cells from growth inhibition by micromolar concentrations of mercuric chloride, methyl mercuric chloride, silver nitrate, cisplatin, cadmium chloride, cadmium sulfate, and iodoacetamide. In the cases of mercuric chloride, cisplatin, MNNG, silver nitrate, and iodoacetamide, reaction products with GSH were detected by paper chromatography. In contrast to reduced GSH, micromolar concentrations of oxidized glutathione (GSSG) provided little or no protection and formed no detectable reaction products. Export of GSH by enteric bacteria may provide an important defense mechanism against exogenous toxic agents otherwise active in the micromolar range.

Cadmium↗
PubMed1989

Heavy metal resistance in clinical isolates of Pseudomonas aeruginosa.

One hundred clinical isolates of Pseudomonas aeruginosa were checked for their sensitivity towards silver nitrate. Majority of the isolates were resistant at 20 mg/L and the resistance decreased with increasing concentration of silver nitrate, only 5% of the organisms showed resistance above 70 mg/L. These silver-resistant isolates were further checked for their resistance towards mercury and cadmium at 20 mg/L of concentration and the level of resistance was found to be 33 and 40%, respectively. A correlation between silver ion resistance and concurrent mercury and cadmium ion resistance was observed, suggesting a possible linkage between resistance towards various metal ions.

Anti-Bacterial Agents↗
PubMed1990

The pattern of axonal degeneration in the peripheral nervous system varies with different types of lesion.

Degeneration of axons in the mouse sciatic nerve was examined using conventional silver staining and by noting the presence or absence of a compound action potential on stimulating the nerve distal to the point of crush or cut. The presence of myeloperoxidase-positive cells was also examined in frozen sections of the nerve. In all experiments the distal, disconnected segment was studied. Degeneration after crushing with fine watchmakers forceps always began in the most distal part of the nerve and proceeded in a distoproximal direction, from the nerve entry point into a muscle back to the crush site. Myeloperoxidase-positive cells were also recruited into the nerve starting at the distal rather than proximal (the originally injured) end. This result favours the view that degeneration is triggered by lack of trophic support from the cell body rather than entry of deleterious substances at the site of the injury, for the terminals furthest from both the source of supply and the injury are affected first. Degeneration following nerve section was always more rapid than after crushing. The rate of axonal sealing at the injury was, however, no slower than after crushing, so it does not seem likely that greater entry of possible degeneration-triggering material at the injury site is the explanation for this. Crush lesions in which the perineurium was also cut open and the blood supply at the site was damaged, degenerated at the slower rate characteristic of simple crushes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Simultaneous high-performance liquid chromatographic determination of a glucuronyl prodrug of doxorubicin, doxorubicin and its metabolites in human lung tissue.

A rapid and sensitive method was developed for the simultaneous determination of the new doxorubicin glucuronide prodrug HMR 1826, the parent drug doxorubicin and its metabolites in human lung tissue samples. Homogenization of frozen tissue samples with the micro-dismembrator was followed by a silver nitrate precipitation step. By removing the exceeding silver ions with sodium chloride further purification steps could be omitted. Compounds were separated by isocratic high-performance liquid chromatography on a LiChrospher 100 RP18 column and a mobile phase consisting of citric acid buffer-acetonitrile-methanol-tetrahydrofuran within 30 min and quantified with fluorescence detection. The method showed good recoveries for all compounds (86-99%) and a linear calibration range of 20 ng/g-80 microg/g for doxorubicin and 1-600 microg/g for HMR 1826.

Animals↗
PubMed2000

New linear tricobalt complex of di(2-pyridyl)amide (dpa), [Co3(dpa)4(CH3CN)2][PF6]2.

Reaction of the linear tricobalt compound Co3(dpa)4Cl2 (1) (dpa = di(2-pyridyl)amide) with silver hexafluorophosphate in acetonitrile yields [Co3(dpa)4(CH3CN)2][PF6]2 (2). Two crystalline forms are obtained from the same solution, namely, a monoclinic (P2(1)) form 2xCH3CNx2Et2O and a triclinic (P1) form, 2x3CH3CN. The tricobalt units in both crystals are essentially symmetrical, though this is not required by crystal symmetry, with Co-Co distances in the range 2298-2304 A. Each of the two terminal Co atoms is coordinated to an acetonitrile molecule with Co-N distances in the range 2068-2111 A at 213 K. The spiral arrangement of ligands gives an overall idealized D4 point group symmetry for the cation [Co3(dpa)4(CH3CN)2]2+ . Chiral crystals of both delta and lambda configurations in the P2(1) form have been isolated. The absolute configurations were determined by X-ray crystallography and their mirror-image circular dichroism spectra measured. The D4 symmetry of the cation appears to be preserved in solution as judged by the presence of only five proton resonance signals in the 1H NMR spectrum. Magnetic susceptibility measurements in the solid state indicates that 2 has a doublet ground state and exhibits an increase of the effective moment at high temperature (approximately 160 K) due to a spin crossover process.

Journal Article↗
PubMed2004

Formation and utility of oxasilacyclopentenes derived from functionalized alkynes.

Oxasilacyclopentenes were shown to be synthetically useful masked allylic alcohols constructed in high yields and regioselectivities from terminal and internal alkynes. Several functional groups were shown to be tolerated utilizing silver-catalyzed silacyclopropenation of alkynes. In situ insertion of various carbonyl compounds into silacyclopropenes afforded regioselective formation of oxasilacyclopentenes. Elaboration of the oxasilacyclopentenes displayed the synthetic utility of these substrates. Both diastereoselective hydrogenation and Diels-Alder reactions utilizing the vinylsilane functionality demonstrated the reactivity and synthetic utility of oxasilacyclopentenes.

Aldehydes↗
PubMed2003

Synthesis and complement inhibitory activity of B/C/D-ring analogues of the fungal metabolite 6,7-diformyl-3',4',4a',5',6',7',8',8a'-octahydro-4,6',7'-trihydroxy- 2',5',5',8a'-tetramethylspiro[1'(2'H)-naphthalene-2(3H)-benzofuran].

This paper reports the synthesis and the bioassay of 4-methoxy- and 4-hydroxyspiro[benzofuran-2(3H)-cyclohexane] partial analogues (5) of the complement inhibitory sesquiterpene fungal metabolite 6,7-diformyl-3',4',4a',5',6',7',8',8a'-octahydro-4,6',7'-trihydroxy-2',5',5',8a'-tetramethylspiro[1'(2'H)-naphthalene-2(3H)-benzofuran] (1a, K-76) and its silver oxide oxidized product (1b, K-76COOH). The described target compounds represent spirobenzofuran B/C/D-ring analogues lacking the A-ring component of the prototype structure. The target compounds were evaluated by the inhibition of total hemolytic complement activity in human serum. It was observed that the structurally simplified analogue 4-methoxyspiro[benzofuran-2(3H)-cyclohexane]-6-carboxylic acid (5a) exhibited an IC(50) = 0.53 mM similar to the IC(50) = 0.57 mM that was observed for the natural product derivative 1b. Exhibiting an IC(50) = 0.16 mM, the three-ringed partial structure 6-carboxy-7-formyl-4-methoxyspiro[benzofuran-2(3H)-cyclohexane] (5k)was found to be the most potent target compound. Like the natural product, 5k appears to inhibit primarily at the C5 activation step and inhibits both the classical and alternative human complement pathways. Several other analogues inhibited complement activation in vitro at concentrations similar to those required for inhibition by the natural product 1b.

Animals↗
PubMed1975

Ozone injury in soybeans: isoflavonoid accumulation is related to necrosis.

Fumigation of soybean leaves (Glycine max [L.] Merr. with ozone caused stippling and silvering at the same time that large accumulations of the isoflavonoid compounds daidzein, coumestrol, and sojagol occurred. Nitrogen dioxide and sulfur dioxide caused lesser accumulation of the isoflavonoids, and peroxyacetyl nitrate did not result in significant accumulation. Visible toxicity and chemical changes in ozone-fumigated leaves were similar to the hypersensitive disease defense reaction of soybean leaves to the pathogen Pseudomonas glycinea, except that the phytoalexin hydroxyphaseollin was not produced in the ozone-treated leaves.

Journal Article↗
PubMed2001

Polysulfonylamines. CXLV. N-diethylcarbamoyl-o-benzenedisulfonimide, a urea with non-planar geometry at nitrogen and an amide single bond.

The prominent features in the molecular structure of the title compound (alternative name: 2-diethylcarbamoyl-1,1,3,3-tetraoxo-1,3,2-benzodithiazole), C(11)H(14)N(2)O(5)S(2), arise in the urea moiety S(2)N-C(O)-N'C(2): the sum of the angles at N is 332.3 (1) degrees, the N-C(O)-N'C(2) unit is planar, and distances N-C(O) = 1.494 (3) A, N'-C(O) = 1.325 (2) A and C-O = 1.215 (2) A. The molecules are associated via five C-H...O hydrogen bonds to form layers parallel to the yz plane. This compound and its dimethyl homologue, which were synthesized by treating the silver salt of o-benzenedisulfonimide with carbamoyl chlorides, are prone to rapid hydrolysis at the weak N-C(O) bond. For both molecules, the rotational barrier about the partial N'-C(O) double bond is ca 50 kJ mol(-1) at 250 K (from dynamic (1)H NMR experiments).

Journal Article↗
PubMed1989

Comparison of the biological responses induced by lipopolysaccharide and endotoxin of Treponema hyodysenteriae and Treponema innocens.

The chemical composition and classical biologic activities of lipopolysaccharide (LPS; phenol-water) and endotoxin (butanol-water) preparations from virulent Treponema hyodysenteriae and avirulent Treponema innocens were examined. The LPS and endotoxin preparations from T. hyodysenteriae B204 contained approximately 80.9 and 35.2% hexose, 0.12 and 0.45% thiobarbituric acid-reactive compound, and less than 1 and 11.3% protein, respectively. The LPS and endotoxin preparations of T. innocens B1555a contained approximately 56.3 and 37.8% hexose, 0.45 and 0.4% thiobarbituric acid-reactive compound, and less than 1 and 26% protein, respectively. A silver-stained 7.5 to 15% sodium dodecyl sulfate-polyacrylamide gel showed four bands for the T. hyodysenteriae preparations, while the T. innocens preparations failed to resolve into discrete bands on electrophoresis. We determined by the Limulus amebocyte lysate assay that the treponemal preparations had comparable amounts of endotoxin activity when Escherichia coli LPS was used as a standard. The 50% lethal doses of LPS and endotoxin from T. hyodysenteriae for BALB/cByJ mice were 380 and 80 micrograms, respectively. The treponemal preparations were poor adjuvants, failed to induce a dermal Shwartzman reaction, and were not pyrogenic. The treponemal LPS preparations, unlike the endotoxin preparations, were not mitogenic for murine spleen cells. Differences in virulence between the two treponemal species could not be associated with the biologic activities of the respective LPS or endotoxin moieties, but the endotoxin preparations were consistently more active than the purified LPS preparations.

Adjuvants, Immunologic↗
PubMed2002

The effect of AH 26 and AH Plus on MCF-7 breast cancer cell proliferation in vitro.

AIM: The purpose of this study was to determine whether AH 26 and AH Plus have in vitro oestrogenic effects. METHODOLOGY: MCF-7 breast cancer cells were trypsinized and plated in 24-well plates at initial concentrations of 10,000 cells per well in 5% FBS in DME. Cells were allowed to attach for 24 h; then the seeding medium was replaced with 10% CDHuS-supplemented phenol red-free DME. Different concentrations of the test compound were added to sample wells (AH 26 and AH Plus at 1/100 to 1/1,000,000 dilutions), 10 pM estradiol-17beta to positive controL and no sub-stance to negative control (hormone-free control cells). The assay was stopped after 144 h. RESULTS: AH 26-powder induced MCF-7 cell proliferation in a dose-dependent manner. The cell yield obtained with AH 26-powder at 1/100 dilution sample was 2.5-fold greater than in control cultures. The sam-ple prepared with mixed AH 26 paste/powder 1:1 also induced MCF-7 cell proliferation, but showed less potency than AH 26-powder alone. The cell yield obtained with AH 26 paste/powder at 1/100 dilution sample was 1.9-fold greater than in control cultures. AH Plus did not show in vitro oestrogenic effect. CONCLUSIONS: AH 26 showed in vitro oestrogenic effect, but not AH Plus. The endodontist must consider the possible oestrogenic effect of AH 26, as well as the cytotoxic effects of root filling materials, and avoid the leakage of sealer through the apex during root canal treatment.

Benzhydryl Compounds↗
PubMed1983

Topical therapy and the development of silver sulfadiazine.

Topical therapy is a selective approach to the prevention and treatment of infection in burns and other surgical wounds. Effective compounds possess certain chemical and physical properties. Prerequisites include low solubility, slow absorption, nonreactivity with wound exudates, proteins and ions and ability to achieve prolonged antimicrobial activity in the wound. These compounds yield much higher levels in the zone of infection than can be achieved by diffusion into the wound after systemic administration. The wide spectrum of antibacterial activity, the low toxicity, minimal tissue reaction, ease of application suggest that topical silver sulfadiazine therapy can safely be extended to other wound infections, wound covers and certain transplant materials.

Administration, Topical↗