PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “SILVER”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2004

Silver coordination chemistry of a new versatile "Janus"-type N(2),O(2)-bichelating donor, formation of an unprecedented supramolecular network of binuclear silver building blocks containing a five-coordinate beta-diketonate, and isolation of unexpected silver-tin-silver heterotrimetallic complexes from silver metathesis reactions.

Synthetic, spectroscopic, and single-crystal X-ray studies are reported for several complexes of silver(I) with the N(2),O(2)-bichelating Q(py) ligand (HQ(py) = 1-(2-pyridyl)-3-methyl-4-trifluoroacetylpyrazol-5-one). Direct interaction between HQ(py) and AgNO(3) in methanol, in the presence of NaOCH(3), affords derivative Ag(Q(py)), showing a polynuclear structure composed of dinuclear building blocks with two different Ag environments and two Q(py) donors differently connected. By adding neutral ligands such as PR(3) (R = Ph, Cy, C(6)H(4)-o-CH(3), C(6)H(4)-p-F, Bu(i)) to Ag(Q(py)), dinuclear Ag(Q(py))(PR(3)) derivatives have been isolated, containing bridging N(2),O-exotridentate Q(py) donors spanning a pair of AgPR(3) moieties. Reaction of Ag(Q(py))(PPh(3)) with excess PPh(3) produces the mononuclear Ag(Q(py))(PPh(3))(2) containing N(2)-chelate Q(py). Ag(Q(py)) interacts with 1,2-bis(diphenylphosphino)ethane (dppe) yielding the derivative Ag(Q(py))(dppe), having a polynuclear structure in the solid state which is seemingly disrupted in solution, with the formation of two new species, a mononuclear neutral compound and a dinuclear ionic one. By the interaction of Ag(Q(py)) with nitrogen donors L (L = imidazole (imH), 1-methylimidazole (Meim), 1-methyl-2-mercaptoimidazole (Hmimt), 1,10-phenanthroline (phen)), mononuclear species Ag(Q(py))(L) have been obtained, where Q(py) is coordinated to silver in N(2)-chelating mode. Ag(Q(py))(PPh(3))(2) reacts with SnRCl(3) (R = Ph, Bu(n)) affording heterotrimetallic [[(Ph(3)P)(2)AgCl](2)SnRCl(3)] derivatives.

Journal Article↗
PubMed2002

Investigation of silver salt metathesis: preparation of cationic germanium(II) and Tin(II) complexes, and silver adducts containing unsupported silver-germanium and silver-tin bonds.

Syntheses of halide derivatives of germanium(II) and tin(II) aminotroponiminate (ATI) complexes and their silver salt metathesis reactions have been investigated. The treatment of GeCl(2) x (1,4-dioxane), SnCl(2), or SnI(2) with [(n-Pr)(2)ATI]Li in a 1:1 molar ratio affords the corresponding germanium(II) or tin(II) halide complex [(n-Pr)(2)ATI]MX (where [(n-Pr)(2)ATI](-) = N-(n-propyl)-2-(n-propylamino)troponiminate; M = Ge or Sn; X = Cl or I). As usually expected, [(n-Pr)(2)ATI]GeCl and [(n-Pr)(2)ATI]SnCl undergo rapid metathesis with CF(3)SO(3)Ag, leading to trifluoromethanesulfonate salts, [[(n-Pr)(2)ATI]Ge][SO(3)CF(3)] and [[(n-Pr)(2)ATI]Sn][SO(3)CF(3)], and silver chloride. However, when the silver source [HB(3,5-(CF(3))(2)Pz)(3)]Ag(eta(2)-toluene) is used, rather than undergoing metathesis, very stable 1:1 adducts [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Ge(Cl)[(n-Pr)(2)ATI] and [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Sn(Cl)[(n-Pr)(2)ATI] are formed (where [HB(3,5-(CF(3))(2)Pz)(3)](-) = hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate). The use of the iodide derivative [(n-Pr)(2)ATI]SnI did not change the outcome either. All new compounds have been characterized by multinuclear NMR spectroscopy and X-ray crystallography. The Ag-Ge and Ag-Sn bond distances of [HB(3,5-(CF(3))(2)Pz)(3)]Ag<-- Ge(Cl)[(n-Pr)(2)ATI], [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Sn(Cl)[(n-Pr)(2)ATI], and [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Sn(I)[(n-Pr)(2)ATI] are 2.4142(6), 2.5863(6), and 2.5880(10) A, respectively. A convenient route to [(n-Pr)(2)ATI]H is also reported.

Journal Article↗
PubMed2004

Physiological interactions of silver and humic substances in Daphnia magna: effects on reproduction and silver accumulation following an acute silver challenge.

Silver (Ag) in aquatic environments mediates its toxic actions by inhibiting sodium influx. Humic substances protect against silver toxicity by complexing the toxic, ionic form of the metal, but may also directly stimulate sodium influx in aquatic organisms. This study investigated the effects of silver and humic substances on the water flea Daphnia magna. Acute silver challenge (24 h; 1 microg L(-1)) and the chronic exposure to humic substances (Aldrich humic acid; 7 mg C L(-1)) had considerable influence on daphnid physiology and reproduction. In particular silver exposure in the absence of humic substances stimulated reproduction, resulted in enhanced adult mass, and altered both the response of the animal to subsequent silver exposure and a physiological surrogate measure of silver toxicity (whole body sodium concentration). The presence of humic substances countered the effects on adult mass and reproduction, returning these parameters to control levels. Humic substances also lowered silver body burden, but with significantly improved whole body sodium status than previously silver-exposed animals. These changes may distort the correlation between silver body burden and indicators of toxic action, an important tenet of site-specific risk assessment tools such as the biotic ligand model.

Animals↗
PubMed1988

The mechanism accounted for the silver staining "fast techniques" development and its histochemical meaning. II. The binding between silver and ferric ion accounted for the silver staining development.

Results obtained on filter paper strips models show that some protein and fatty acids become argentophil as an effect of a previously binding ferric ion although, in this instance, the silver staining can only be accomplished by using a silver diamine solution, since a silver nitrate solution is not effective. However, if the filter paper model is previously treated by a "multidentate ligand" before the silver nitrate solution treatment becomes able in doing the silver staining. This result shows that the binding between Fe3+ and Ag+ can be done if a suitable negatively charged "multidentate ligand" has been connected between them. The following "multidentate ligands" were tested: thiocarbohydrazide, carbohydrazide, and hexamethylenetetramine: ammonia was also tested, as an attempt to disclose if it is able to act as a "multidentate ligand". The semicarbazide effect was analysed and compared with the "ligands". It was found, either on filter paper strip models or on histological sections, that every "multidentate ligand", as well as ammonia, are effective in producing silver staining whereas semicarbazide is devoid of effect. The "ligands" effectiveness depends upon the solution pH, in the same manner that is does occur when the silver diamine "fast technique" is used on tissue sections. Histophotometric measures, taken on tissue sections, show that the silver staining afforded by the silver diamine "fast technique" is similar to that displayed by the "multidentate ligand" plus a silver nitrate solution treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Histological Techniques↗
PubMed2004

A relationship between gill silver accumulation and acute silver toxicity in the freshwater rainbow trout: support for the acute silver biotic ligand model.

Rainbow trout were exposed to a range of silver concentrations (as AgNO3) in flowing synthetic soft water (0.05 mM Na+, 0.05 mM Cl-, 0.05 mM Ca2+, 0.02 mM Mg2+, 0.02 mM K+, pH 7.0, approximately 0.7 mg C/L dissolved organic carbon, 10 mg CaCO3/L, 10 +/- 2 degrees C) to investigate a possible relationship between short-term gill silver accumulation (3 h or 24 h) and acute silver toxicity (96-h mortality). We also investigated potential relationships between gill silver accumulation and inhibition of Na+ uptake plus inhibition of gill Na+K(+)-adenosine triphosphatase (ATPase) activity. The 96-h median lethal concentration (LC50) values were 13.3 microg total Ag L(-1) and 3.3 microg dissolved Ag L(-1). A relationship was demonstrated between 3-h and 24-h gill silver accumulation and 96-h mortality. A relationship also was demonstrated between gill silver accumulation and inhibition of Na+ uptake at 24 h of exposure. No relationship between gill silver accumulation and inhibition of gill Na+K(+)-ATPase activity was found. The 96-h median lethal gill accumulation (LA50) values of 129 (at 3 h) and 191 ng g(-1) (at 24 h) and a conditional equilibrium binding constant of 8.0 for Ag+ binding to the gills were calculated. These observations support use of the silver biotic ligand model (BLM) as a regulatory tool to predict acute silver toxicity.

Acute-Phase Reaction↗
PubMed2002

One- and two-dimensional silver-coordination networks containing pi-sandwiched silver-silver interactions.

The self-assembly of coordination networks from reaction of 2,4,6-trimesityl-1,3,5-triazine and silver(I) trifluoroacetate is described. A one-dimensional linear polymer is formed from solutions deficient in silver while a two-dimensional, graphite-like sheet is formed from solutions containing 3 equiv of silver per triazine. The structurally similar networks both contain triazine rings separated by two trifluoroacetate-bridged silver atoms. The two silver atoms are effectively sandwiched between two mesityl rings with intermediate arene-silver interactions. The silver-silver bond lengths are 2.9731(4) and 2.9246(5) A in the one-dimensional network and 2.8842(4) A in the two-dimensional network.

Journal Article↗
PubMed2006

Synthesis, a case of isostructural packing, and antimicrobial activity of silver(I)quinoxaline nitrate, silver(I)(2,5-dimethylpyrazine) nitrate and two related silver aminopyridine compounds.

The synthesis and low temperature crystal structures of [Ag(quinoxaline)]n(NO3)n, 1, [Ag(2,5-dimethylpyrazine)(NO3)]n, 2 and [Ag4(3-aminopyridine)4(NO3)4]n 3 are presented. The quinoxaline compound forms a 1D coordination polymer with the characteristic linear 2-coordination figure of silver(I), the N-Ag-N angle being 164.2(1) degrees, and only weak silver-nitrate interactions. In addition there is an interaction giving pairs of parallel chains as the main structural theme. The 2,5-dimethylpyrazine compound has approximately trigonal-planar coordination, also binding one nitrate at the relatively short Ag-O distances 2.444(3) angstroms and 2.484(3) angstroms, respectively, for the two crystallographically different silver atoms. This also results in a 1D coordination polymer that, despite the large differences in the Ag(I) coordination environment, is isostructural with 1. [Ag4(3-aminopyridine)4(NO3)4]n 3 forms a 2D coordination polymer by bridging nitrate ions. The antimicrobial activity of 1-3, and also of [Ag3(2-aminopyridine)4](NO3)3, 4 was screened for 13 different pathogens and substantial activity was shown for 1 against Escherichia coli and Pseudomonas aeruginosa (MIC 4 microg cm(-3)) and somewhat lower activity was registered against Sarcina lutea and Salmonella typhi for 1, Bordetella bronchiseptica for 2, Salmonella typhi and Pseudomonas aeruginosa for 3, and Escherichia coli and Shigella sonnie for 3 (MIC 8 microg cm(-3)). Only low activity was shown against the yeast Candida albicans for 1, 2 and 4 whereas no activity against this pathogen was registered for 3.

Aminopyridines↗
PubMed2004

An in vitro study of the anti-microbial efficacy of a 1% silver sulphadiazine and 0.2% chlorhexidine digluconate cream, 1% silver sulphadiazine cream and a silver coated dressing.

UNLABELLED: Burn sepsis is a leading cause of mortality and morbidity in patients with major burns. The use of topical anti-microbial agents has helped improve the survival in these patients. There are a number of anti-microbials available, one of which, Silvazine (1% silver sulphadiazine (SSD) and 0.2% chlorhexidine digluconate), is used only in Australasia. No study, in vitro or clinical, had compared Silvazine with the new dressing Acticoat. This study compared the anti-microbial activity of Silvazine, Acticoat and 1% silver sulphadiazine (Flamazine) against eight common burn wound pathogens. METHODS: Each organism was prepared as a suspension. A 10 microl inoculum of the chosen bacterial isolate (representing approximately between 10(4) and 10(5) total bacteria) was added to each of four vials, followed by samples of each dressing and a control. The broths were then incubated and 10 microl loops removed at specified intervals and transferred onto Horse Blood Agar. These plates were then incubated for 18 hours and a colony count was performed. RESULTS: The data demonstrates that the combination of 1% SSD and 0.2% chlorhexidine digluconate (Silvazine) results in the most effective killing of all bacteria. SSD and Acticoat had similar efficacies against a number of isolates, but Acticoat seemed only bacteriostatic against E. faecalis and methicillin-resistant Staphylococcus aureus. Viable quantities of Enterobacter cloacae and Proteus mirabilis remained at 24h. CONCLUSION: The combination of 1% SSD and 0.2% chlorhexidine digluconate (Silvazine) is a more effective anti-microbial against a number of burn wound pathogens in this in vitro study. A clinical study of its in vivo anti-microbial efficacy is required.

Anti-Infective Agents, Local↗
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↗
PubMed1998

Electron microscope characterization of AgBr heterojunctions with silver carboxylates and their influence on the morphology of developed silver particles in thermally developed photomaterials.

Silver halide crystals formed during in situ treatment of silver stearate crystals with various halidizing agents are observed by scanning and transmission electron microscopy to form on the lateral edges of the silver carboxylate crystals. The location of the silver halide phase on the crystal edge is dictated by the anisotropic structure of the silver stearate crystal lattice, specifically, the layered structure in which silver ion layers are separated by long-chain hydrocarbon groups. The formation of AgBr on the lateral faces of these crystals is proposed to be typical not only of the formation of silver halide on silver stearate but also for all silver carboxylates of the general formula [AgCnH2(n-1)O2]2 when the crystals of these silver carboxylates have anisotropic, layered structures. The silver bromide/silver carboxylate heterojunction in an in situ system has been clearly observed by transmission electron microscopy. The heterojunction is comprised of a distorted silver carboxylate lattice, which accommodates the misalignment between the AgBr and [Ag(O2CR)]2 crystal lattices. The nature of heterojunction between the AgBr and the silver carboxylate when the AgBr is prepared separately from the preparation of the silver carboxylate differs from the in situ heterojunction. In this case, a layered compound, proposed to have a Ag1-xNaxSt composition, forms between the AgBr and the silver stearate which is a unique feature of this interface. The differences in the structure of interfaces formed between the silver halide and the silver fatty acid complex result in different silver particle morphologies during thermal development of exposed photothermographic films. The developed silver is generally filamentary when the photothermographic material contains silver halide prepared by the in situ exchange reaction between silver carboxylate and a brominating agent. If the photothermographic material is prepared from previously synthesized silver halide crystals, the preformed AgBr route, the developed silver generally crystallizes as dendritic crystals.

Bromides↗
PubMed2004

The time course of silver accumulation in rainbow trout during static exposure to silver nitrate: physiological regulation or an artifact of the exposure conditions?

The pattern of gill silver accumulation in rainbow trout during waterborne silver exposure has been reported to be unusual, reaching a peak in the first few hours of silver exposure followed by a marked decline with continued exposure. The potential causes of the pattern were investigated. Rainbow trout (1-5g) were exposed in a static system to 110mAg labeled AgNO(3) at a total concentration of 1.92microg Agl(-1) for 24h in synthetic soft water. Periodically throughout the exposure, gill and body 110mAg accumulation, gill and body 24Na uptake (from which whole body Na(+) uptake was calculated), gill Na(+)K(+)-ATPase activity, plus water silver (total and dissolved), Cl(-) and total organic carbon (TOC) concentrations were measured. Gill silver levels rapidly increased, peaked at 3h of exposure and then decreased until a plateau was reached at 12h of exposure. Body (minus gills) silver levels increased steadily over the exposure period until 18h of exposure. Whole body Na(+) uptake decreased, was maximally inhibited by 3h of exposure but recovered by 12h despite continued silver exposure. Gill Na(+)K(+)-ATPase activity was not inhibited until 5h of exposure. The water dissolved silver concentration declined by approximately 70% over the 24h exposure period and the TOC content of the water increased over three-fold during the first 2h of exposure. There was a decrease in the calculated contribution of Ag(+) (from 20.9 to 2.5%) and an increase in the calculated contribution of Ag-TOC complexes (from 77 to 97.3%) to the total water silver concentration over the first 2h of exposure. Apical silver uptake into the gills decreased over the initial 2.5h of exposure while basolateral silver export out of the gills to the body remained constant throughout the exposure. The results of this study suggest that: (1) physiological regulation of silver movement may explain the pattern of gill silver accumulation observed in rainbow trout, although not by a mechanism coupled to Na(+)K(+)-ATPase inhibition as originally proposed; (2) alternatively or additionally, a decreased bioavailability of silver, due to the static exposure conditions, may explain the pattern of gill accumulation; (3) the early inhibition of whole body Na(+) uptake observed during silver exposure occurs via a mechanism other than Na(+)K(+)-ATPase inhibition; and (4) gill silver accumulation may be an appropriate endpoint for biotic ligand modeling.

Analysis of Variance↗