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PubMed1988

Antimicrobial and anticancer activity of tetrahedral, chelated, diphosphine silver(I) complexes: comparison with copper and gold.

Tetrahedral, bischelated Ag(I) diphosphine complexes [Ag(P-P)2]NO3, where P-P is Ph2P(CH2)2PPh2 (dppe), Et2P(CH2)2PPh2 (depe), and cis-Ph2P(CH = CH)PPh2 (dppey), are potently cytotoxic to B16 melanoma cells in vitro (IC50 4 microM) and exhibit good activity against ip P388 leukemia in mice. The complex [Ag(dppe)2]NO3 is active against M5076 reticulum cell sarcoma. The antibacterial and antifungal activities of Ag(I) diphosphine and related Cu(I) and Au(I) complexes were assessed. The complexes [Au(dppey)2]Cl, [Au(dppp)2]Cl and (CuCl)2(dppe)3 show modest activity against three of the 12 bacterial strains tested, but all complexes exhibit antifungal activity against three strains of C. albicans in a "defined" medium, [Ag(depe)2]NO3 and [Au(dppp)2]Cl having comparable activity to fungizone. Antifungal activity of the complexes is reduced in Sabouraud's broth medium, and lost altogether for the Ag(I) complexes. Reactions of some of the Ag(I) complexes with glutathione and blood plasma were studied by 31P NMR.

Animals↗
PubMed1993

Detection of dengue virus antigens in cultured cells by using protein A-gold-silver staining (pAgs) method.

A protein A-gold-silver (pAgs) staining was developed to detect dengue virus antigens in cultured cells. The method can be carried out in either newly-subcultured or monolayered cells. Dengue virus-inoculated C6/36 clone of Aedes albopictus cells and human endothelial cells appeared brown-yellowish color on the peripheral membrane of the infected cells. In many cases, the infected C6/36 cells appeared darker than that of the infected endothelial cells. The positive results from the inoculated C6/36 cells usually appeared as early as 2 days post-inoculation for types 1, 2, and 4 of dengue viruses and 3 days for the dengue 3 virus. The same batch of specimens detected by direct immunofluorescence antibody test (DFA) showed positive 4 days post-inoculation for the types 2, 3, and 4 of dengue viruses and 6 days for the dengue 1 virus. The result also showed that all pAgs-positive specimens were also DFA-positive, but not vice versa. It suggested that pAgs is not only sensitive but also specific for dengue virus detection from inoculated cultured cells.

Aedes↗
PubMed2005

Comparison of bond strength of a pressed ceramic fused to metal versus feldspathic porcelain fused to metal.

PURPOSE: To compare the debonding/crack initiation strength (D/CIS) of a low-fusing pressable leucite-based glass ceramic (PC) fused to metal to a feldspathic porcelain (FP) fused to metal. MATERIALS & METHODS: As per ISO 9693:1999, 40 rectangular metal specimens (25.0 mm x 0.5 mm x 3.0 mm) were prepared. Twenty of the specimens were cast in a base metal nickel-chromium alloy (BA), and 20 were cast in a noble metal palladium-silver alloy (NA). Ten randomly selected NA and BA alloy specimens had FP applied. The remaining 10 NA and BA alloy specimens had ash-free wax patterns applied, the metal-wax complexes invested, and were pressed with a PC. The dimensions of the ceramic specimens were 8.0 mm x 1.0 mm x 3.0 mm, creating a combined metal-ceramic complex thickness of 1.5 mm. All specimens were subject to a three-point bending test at a crosshead speed of 1.5 mm/min. Fracture loads were recorded in Newtons and D/CISs calculated by the formula tau(b)=k x F(fail). RESULTS: Mean D/CISs, measured in MPa (standard deviations): NA-FP 32.56 (4.62), NA-PC 30.23 (5.06), BA-FP 30.98 (4.41), and BA-PC 31.81 (3.48). A two-way ANOVA (p > 0.05) did not demonstrate significant difference between groups. CONCLUSION: The debonding/crack initiation strength of a low-fusing pressable leucite-based glass ceramic fused to metal was equivalent to that of a feldspathic porcelain fused to metal.

Aluminum Silicates↗
PubMed2005

Environmental factors determining the trace-level sorption of silver and thallium to soils.

Silver (Ag) and thallium (Tl) are nonessential elements that can be highly toxic to a number of biota even when present in the environment at trace levels. In spite of that, the literature on the chemistry and fate of Ag and Tl in soils is extremely scanty. In that context, the key objective of this research was to compare the sorption characteristics of trace amounts of Ag and Tl on a range of soils and minerals. A second objective was to determine the extent to which the composition and surface chemistry of the sorbents, as well as other environmental factors (simulated acid rain application and the presence of competing ions like K+ and NH4+) influence the sorption and lability of Ag and Tl. To this end, short-term and long-term sorption isotherms were generated under batch conditions for trace levels of Ag and Tl onto three illite-rich mineral soils from central New York (silt loam and fine sandy loam), a peaty-muck soil drained for agricultural use, and soil minerals (ferrihydrite and birnessite). Silver sorbed more strongly than thallium to all the soils. The peaty-muck soil sorbed Ag more strongly than the mineral soils, confirming that silver sorption to soils is dominated by soil organic matter either through exchange or complexation. The organic matter-rich soil's retention of Tl, however, was similar to that of the sandy soil. Amounts of Ag and Tl sorbed to the mineral soils increased after a 1-year incubation period. Whereas Ag sorption to the peaty-muck soil also increased with time, Tl sorption was unaffected. Short batch studies indicated that high amounts of Tl sorb to birnessite (30% by mass). However, subsequent X-ray diffraction (XRD) analysis of the solid did not detect the presence of any Tl3+ as Tl2O3 on the MnO4. In contrast, TlI was relatively poorly sorbed on noncrystalline ferrihydrite at pH 5.1 (1.5% by mass). Thus, Mn oxides may play a role in Tl retention by soils; whereas, contrary to previous reports, iron oxides do not effectively sorb Tl. Acid rain and addition of potassium (K+) and ammonium (NH4+) as competing ions had no long-term effect on Ag or Tl sorption. Thallium remaining in the all the batch sorption solutions, as determined by flame atomic absorption spectroscopy (FAAS) and differential pulse anodic stripping voltametry (DPASV), was completely labile, which may have important environmental consequences.

Adsorption↗
PubMedDate not supplied

Evidence that 4-allyl-o-quinones spontaneously rearrange to their more electrophilic quinone methides: potential bioactivation mechanism for the hepatocarcinogen safrole.

Several naturally occurring aromatic ethers, of which safrole [1-allyl-3,4-(methylenedioxy)-benzene] is one example, are hepatocarcinogens. One bioactivation pathway previously proposed for safrole involves hydroxylation of the benzyl carbon, conjugation with sulfate, and then alkylation of DNA with displacement of the sulfate group [Miller, J.A., and Miller, E.C. (1983) Br. J. Cancer 48, 1-15]. The fact that safrole is O-dealkylated to the corresponding catechol (hydroxychavicol, 1-allyl-3,4-dihydroxybenzene) indicates that quinoid formation is also possible and may contribute to the genotoxic and/or cytotoxic activity of this compound. In the present investigation we selectively oxidized hydroxychavicol to the corresponding o-quinone (HC-quinone, 4-allyl-3,5-cyclohexadiene-1,2-dione) or p-quinone methide (HC-QM, 2-hydroxy-4-allylidene-2,5-cyclohexadien-1-one) and trapped these reactive electrophiles with glutathione (GSH). The GSH adducts were fully characterized by UV, NMR, and mass spectrometry. Microsomal incubations with safrole or hydroxychavicol in the presence of glutathione produced only o-quinone glutathione conjugates. However, if the trapping agent (GSH) was added after an initial incubation of 10 min, both o-quinone and p-quinone methide GSH conjugates were observed. The first-order rate constant of isomerization was estimated from the decrease in HC-quinone GSH adducts to be 1.9 x 10(-3) s-1 (t1/2 = 9 min). Kinetic studies showed that while HC-QM reacts rapidly with water, the model o-quinone (4-tert-butyl-3,5-cyclohexadiene-1,2-dione), which cannot isomerize to a quinone methide, was remarkably resistant to hydrolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2004

Silver uptake by a marine diatom and its transfer to the coastal copepod Acartia spinicauda.

Silver (Ag) is an important metal contaminant in many coastal waters and often is accompanied by high nutrient concentrations in the effluent outfall. The biological uptake of Ag by the marine diatom Thalassiosira pseudonana at various levels of nitrate, ammonium, and phosphate was examined under different growth conditions of the cells. The biological uptake of Ag increased significantly with increasing concentrations of nitrate, ammonium, and phosphate, presumably because of the increase in algal growth rate or increasing sulfur-containing ligands available for Ag transport. The calculated Ag uptake rate constants increased by 3 to 16 times with increasing nitrate and ammonium concentration from 5.88 microM to 176 microM. The assimilation efficiency (AE) of Ag by the coastal copepod Acartia spinicauda was quantified under different ecological and chemical conditions of the diatom prey. The Ag AEs were in the range of 3 to 23%, and increased with decreasing diatom food concentrations or when the diatoms were grown at a lower nutrient level. Significant correlations were demonstrated between the AE and the distribution of Ag in the diatom's cytoplasm, the Ag concentration factor in the diatoms, Ag retention in the particles during the feeding period, and the Ag gut passage time in the copepods. Desorption within the copepod's gut appears to play a critical role in Ag assimilation and partially accounts for the variability of Ag AEs under different food and geochemical conditions. Our study highlights that several geochemical and physiological processes all significantly affect Ag trophic transfer in marine copepods. Given the dependence of Ag transfer on its concentration in ingested particles and food concentration, dietary uptake of Ag is probably variable in natural environments. The influence of eutrophication on Ag trophic transfer is dependent on the degree to which each kinetic parameter is affected by nutrient enrichments.

Animals↗
PubMed2004

The changes to apical silver membrane uptake, and basolateral membrane silver export in the gills of rainbow trout (Oncorhynchus mykiss) on exposure to sublethal silver concentrations.

Juvenile rainbow trout acclimated to softwater were exposed to 0 or 8.3 nM Ag (added as silver nitrate) for 21 days. On days 1, 7 and 21 gill, kidney and liver levels of silver; branchial Na+ influx, efflux and net flux rate; gill and kidney K+ -dependent p-nitrophenol phosphatase activity; and gill and liver accumulation of "new" Ag were measured. In addition, the concentration-dependent uptake of Ag by gill basolateral membrane vesicles (BLMV) was assessed in control fish and those exposed to 8.3 nM Ag for 7 days. Ag induced a significant increase in Na+ efflux following 1 day of exposure that resulted in an increase in net loss of Na+ and a reduction in Na+ influx. By day 21 this perturbation to Na+ balance had been corrected, but kidney K+ -dependent p-nitrophenol phosphatase activity was significantly reduced. Unexpectedly, the Ag concentrations in the liver of Ag exposed fish only significantly increased (two-fold) following 7 days of exposure and were not elevated when compared to controls on day 21. In contrast, the gill and kidney accumulated significant concentrations of Ag (20-fold increase) following 7 days of exposure, and the Ag concentration in these tissues remained similar on day 21. The gills of Ag exposed fish accumulated significantly less "new" Ag than the controls on days 7 and 21 following exposure, suggesting a down-regulation of branchial Ag uptake. The BLMV of Ag exposed fish showed a significant increase in V(max) [control fish BLMV V(max) = 2811.9+/-190.8 pmol (110 m)Ag/(mg protein x min) and Ag exposed fish BLMV V(max) = 3688.3+/-659.8 pmol (110 m)Ag/(mg protein x min) (P = 0.033)], suggesting that they are able to increase export of Ag from the gills on exposure to Ag. The results from this study demonstrate a complex array of physiological processes that control the bioreactive concentrations of Ag in the gills, including: cytoplasmic sequestration, a down-regulation of apical entry and potentially an increase in basolateral membrane extrusion.

Analysis of Variance↗
PubMed1995

Antimicrobial activity of silastic tympanostomy tubes impregnated with silver oxide. A double-blind randomized multicenter trial.

OBJECTIVE: To test the null hypothesis that impregnation of tympanostomy tubes with silver oxide did not alter the rate of postintubation otorrhea. DESIGN: Multicenter, double-blind, randomized clinical trial. OUTCOME MEASURE: Rates of postoperative otorrhea during a 1-year study in ears implanted with Silastic tubes compared with contralateral, identical tubes impregnated with silver oxide. SETTING AND PARTICIPANTS: Eight sites in the United States, 125 children aged 1.5 months to 12 years who had bilateral otitis media with effusion or bilateral recurrent acute otitis media. RESULTS: The overall incidence of postoperative otorrhea was 9.78% in the control ears and 5.08% in the ears with silver oxide-impregnated tubes (P = .01), but no effect was seen during the immediate postoperative period. Granulation tissue was seen adjacent to the tube during two visits in the ears with standard tubes (0.54%) and during two visits in the ears with experimental tubes (0.53%); cholesteatomas did not occur in either group. CONCLUSION: Silastic tubes impregnated with silver oxide seem to diminish the incidence of postoperative otorrhea in ears requiring long-term ventilation.

Anti-Infective Agents↗
PubMed1998

Combined characterization of composite tabular silver halide microcrystals by cryo-EFTEM/EELS and cryo-STEM/EDX techniques.

The combination of cryo-energy filtering transmission electron microscopy (EFTEM)/electron spectroscopic diffraction (ESD)/electron energy-loss spectroscopy (EELS) and cryo-energy-dispersive X-ray (EDX) analysis in the scanning transmission (STEM) and scanning (SEM) modes was applied for the characterization of composite tabular Ag(Br,I) microcrystals. A low-loss fine structure in EEL spectra between 4 and 26 eV was attributed to excitons and plasmons possibly superimposed with interband transitions and many-electron effects. The contrast tuning under the energy-filtering in the low-loss region was used to image the crystal morphology, defect structure (random dislocations and ¿111¿ stacking faults) and bend and edge contours as well as electron excitations in the microcrystals. Sharp extra reflections at commensurate positions in between the main Bragg reflections and diffuse honeycomb contours in ESD patterns of the microcrystals taken near the [111] zone were assigned to the number of defects in the shell region parallel to the grain edges and polyhedral clusters of interstitial silver cations, respectively. The imaginary part of the energy-loss function, Im (-1/epsilon), and the real and imaginary parts, epsilon1 and epsilon2, of the dielectric permittivity were determined by means of a Kramers-Kronig analysis. An assignment of exciton peaks based on calculations of electronic band structure of silver bromide is proposed. Inner-shell excitation bands of silver halide were detected in line with EDX-analyses. The energy-loss near-edge structure (ELNES) of the AgM4,5-edge governed by spin-orbital splitting between the 3d3/2- and 3d5/2-states has been evaluated. Combined silver and halide distributions were obtained by a three-window method (EFTEM) and by EDX/STEM including area mapping and line profiling of iodide.

Bromides↗
PubMed1998

Morphology and structure of photosensitive dye J-aggregates adsorbed on AgBr microcrystals grown in gelatin.

Though the cyanine dye J-aggregates carry the role to sense the exposing light in the silver halide photographic system, little research on the morphology of the aggregates in adsorption has been made with modern surface analytical methods. In this paper, we describe the size, epitaxy, multi-layered array formation, nucleation and preferential adsorption, and irregular distribution of population between particles and the segregation on a particle, of J-aggregates adsorbed on AgBr grown in gelatin. We employed cathodoluminescence microscopy, low energy high resolution scanning electron microscopy, and atomic force microscopy. Dye molecules aggregate together near the surface of AgBr and adsorb on the surface. The growth of adsorbed aggregates is controlled by the diffusion of dye molecules from the surrounding solution. The population of J-aggregates adsorbed on an AgBr particle varies from almost none to full coverage. Each aggregate is about (20-30) x (30-50) nm in size and is 2.1 nm thick for thiacarbocyanine with sodium ion, 1.04 nm for thiacarbocyanine with tosyl ion, and 0.5 nm for an oxacarbocyanine. The aggregates connect their longer edges to each other to form arrays, and the arrays build up multi-layered stacks. The arrays align parallel and segregate to form terraces. The longer edges of J-aggregates align along [210] on AgBr (100) or [632] on AgBr (111).

Bromides↗
PubMed1998

Investigation of growth of AgX tabular crystals.

The process of tabular crystal formation during physical ripening of fine AgX (X=Br,I) emulsions is investigated. The tabular crystal growth is realized simultaneously via two mechanisms: ionic and coalescent. The relative contribution of those mechanisms to the tabular crystal growth is determined by the conditions of the physical ripening. It is possible to control the size and shape uniformity of the final AgX tabular crystals by adjusting the relative contributions of these mechanisms.

Bromides↗
PubMed1998

Mass crystallization of silver chloride microcrystals.

In this work some problems on silver chloride isometric and flat crystals crystallization are considered. It is shown that the synthesis of monosize isometric microcrystals should proceed in the absence of a silver chloride solvent. The flat silver chloride microcrystals, in the absence of growth modifiers, are formed by a coalescent mechanism.

Crystallography↗
PubMed1998

Research of new AgX crystal forms by transmission electron microscopy.

The research of AgX (X=Cl, Br) crystals grown from ammonia solution as a function of X- supersaturation, gelatin concentration, temperature, and use of growth modificators, has been enhanced by data from transmission electron microscopy. The study resulted in preparing AgBr thin films with the most developed ¿100¿ side of rombododecahedron. The size of the crystals was 5 x 15 mm. The thickness was several microm. The new forms of AgBr and AgCl microcrystals were obtained from a high concentrated solution of the corresponding salts in NH4OH. These microcrystals were named "X," 'Y' crystals [AgBr] and stereostructures [AgCl] deriving from their external shapes. As a result of the variation of crystallization parameters, six various morphological types of stereostructures, distinguishable by the size of a central element in relation to external elements and a length of a binding element, were seen. Experiments on photolysis of the stereostructures at the substrate temperature 25-200 degrees C were carried out in vacuum. Exposure to mercury lamp light resulted in characteristic location of large particles of photolytic silver on the stereostructure surface, depending on substrate temperature.

Ammonia↗