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PubMed1998

Cyclic contact fatigue of a silver alternative to amalgam.

OBJECTIVE: To purpose of this study was to compare the cyclic contact fatigue resistance of a novel mercury-free silver direct filling material to that of a dental amalgam (Dispersalloy). METHODS: The silver specimens were made by pressing a precipitated powder at room temperature with a pressure of 150 MPa, which can be achieved in clinical hand-consolidation. To simulate clinical contact of restorations against enamel cusps, a cyclic contact fatigue methodology was employed. A spherical indenter was used to repeatedly indent the specimen, while the accumulation of deformation and damage was examined as a function of the number of cycles up to 5 x 10(5). Student's t test, analysis of variance (ANOVA) and Duncan's multiple range test were used to compare the specimen groups for significant differences in flexural strength, indentation impression diameter, and hardness. A type I error of alpha = 0.05 was considered as significant. Subsurface damage was examined by using a bonded-interface technique. RESULTS: As a result of cyclic indentation, microcracks were produced in the amalgam, but no cracks were found in the silver filling material. At fewer numbers of cycles, indentation produced larger impressions in silver (e.g., diameter = [450 +/- 31] microns at 10(2) cycles) than in amalgam ([145 +/- 20] microns) due to a lower hardness of the former. However, with increasing number of cycles, damage accumulated more rapidly in the amalgam, while the silver beneficially work-hardened in repeated indentations. At 5 x 10(5) cycles, the difference in impression diameter between silver and amalgam ([582 +/- 20] microns vs. [568 +/- 42] microns) become insignificant (p > 0.1, Student's t test). SIGNIFICANCE: The mercury-free silver direct filling material is more resistant to microcracking and to cyclic contact fatigue than amalgam, and the indentation impression sizes in the consolidated silver and dental amalgam are not statistically different at large numbers of cycles.

Analysis of Variance↗
PubMed2005

[Topical silver sulfadiazine-induced acute renal failure].

INTRODUCTION: Prolonged topical application of silver sulfadiazine cream can induce argyria and adverse effects of sulphonamides. We report a case of a woman with acute renal failure following repeated applications of topical silver sulfadiazine on pyoderma gangrenosum wounds. CASE REPORT: A 61 year-old woman suffering from rheumatoid arthritis, Sjogren's syndrome and scleroderma was treated with corticosteroids (1 mg/kg/day) and topical application of silver sulfadiazine cream (200 g/day) for extensive pyoderma gangrenosum wounds on the legs. Three weeks later, the patient was transferred to intensive care because of pulmonary edema, oligoanuria and disrupted consciousness. Laboratory data revealed leukopenia (1100/mm(3)) with neutropenia and renal failure (serum creatinine 316 micromol/l). Proteinuria was moderate and ultrasonography of the kidneys was normal. Silver concentration in blood was 1818 nmol/l (N < 92 nmol/l) and 1381 nmol/l (N < 9 nmol/l) in urine. Sulfadiazine concentration in blood was undetectable. All the signs regressed after withdrawal of silver sulfadiazine and after several sessions of hemodialysis. DISCUSSION: Various causes of renal failure are discussed in our patient. However, direct silver-induced renal toxicity is the most likely and is confirmed by the high concentration of silver in blood and urine and the improvement on withdrawal of the topical cream, without modification in the oral treatment. The absence of red corpuscles and crystals in the urine and undetectable concentrations of sulfadiazine in blood are not in favor of sulphonamide renal toxicity. Furthermore, the autoimmune diseases of our patient were well-controlled. Leukopenia could be secondary to silver sulfadiazine medullar toxicity. This observation confirms that this topical cream should not be used for long periods on extensive wounds.

Acute Kidney Injury↗
PubMed1997

The effect of silver administration on the biosynthesis and the molecular properties of rat ceruloplasmin.

To examine the cause of the altered ceruloplasmin (Cp) metabolism by silver administration, we analysed the properties of serum Cp by gel filtration chromatography, affinity chromatography and polyacrylamide gel electrophoresis. Metal contents in the Cp fraction from the silver-treated group were estimated as approximately 0.8 atom of silver and 4.2 atoms of copper per molecule, and as 5.9 atoms of copper for the control group. These findings confirm that holo-Cp from rat serum administered with silver nitrate exists as a silver-bound inactive form, suggesting that silver displaces one of Cp's copper atoms associating with oxidase activity. Matured holo-Cp also appeared in the Golgi in both groups, however, the amounts of enzymatically active holo-Cp showed a decrease after silver administration, while the apo-Cp level was hardly changed. These findings suggest that silver-bound holo-Cp is accomplished at Golgi.

Animals↗
PubMed2002

Physiological effects of chronic silver exposure in Daphnia magna.

Daphnia magna were exposed to a total concentration of 5.0+/-0.04 microg Ag/l, added as AgNO(3) (dissolved concentration, as defined by 0.45 microm filtration = 2.0+/-0.01 microg Ag/l) in moderately hard synthetic water under static conditions (total organic carbon = 4.80+/-1.32 mg/l) with daily feeding and water renewal, for 21 days. There was no mortality in control daphnids and 20% mortality in silver-exposed animals. Silver exposure caused a small but significant reduction of reproductive performance manifested as a 13.7% decrease in the number of neonates produced per adult per reproduction day over the 21-day exposure. However, silver exposed daphnids also exhibited a much more marked ionoregulatory disturbance, which was characterized by a 65% decrease in whole body Na(+) concentration, and an 81% inhibition of unidirectional whole body Na(+) uptake. Previous work on the acute toxicity of Ag(+) to daphnids has shown that Na(+) uptake inhibition is directly related to inhibition of Na(+),K(+)-ATPase activity. Therefore, we suggest that the Na(+) uptake inhibition seen in response to chronic silver exposure was explained by an inhibition of the Na(+) channels at the apical 'gill' membrane, since a 60% increase in whole body Na(+),K(+)-ATPase activity was observed in the chronically silver-exposed daphnids. Our findings demonstrate that, in broad view, the key mechanism involved in chronic silver toxicity in D. magna, the most acutely sensitive freshwater organism tested up to now, resembles that described for acute toxicity-i.e. ionoregulatory disturbance associated with inhibition of active Na(+) uptake, though the fine details may differ. Our results provide encouragement for future extension of the current acute version of the Biotic Ligand Model (BLM) to one that predicts chronic silver toxicity for environmental regulation and risk assessment. The results strongly suggest that Na(+) uptake inhibition is the best endpoint to determine sensitivity to both acute and chronic toxicity in the scope of future versions of the BLM for silver.

Animals↗
PubMed2006

One-step synthesis of monodisperse silver nanoparticles beneath vitamin E Langmuir monolayers.

The monodisperse silver nanoparticles were synthesized by one-step reduction of silver ions in the alkaline subphase beneath vitamin E (VE) Langmuir monolayers. The monolayers and silver nanocomposite LB films were characterized by surface pressure-area (pi-A) isotherms, transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), selected area electron diffraction (SAED), Fourier transform infrared transmission spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), respectively. The results showed that the limiting area/VE molecule on different subphases varied. The phenolic groups in the VE molecules were converted to a quinone structure, and the silver ions were mainly reduced to ellipsoidal and spherical nanoparticles. The arrangement of the nanoparticles changed from sparseness to compactness with reaction time. The electron diffraction pattern indicated that the silver nanoparticles were face-centered cubic (fcc) polycrystalline. Silver nanocomposite LB films with excellent quality could be formed on different substrates, indicating that the transfer ratio of monolayer containing silver nanoparticles is close to unity. The dynamic process of reduction of silver ions by VE LB films was also studied through monitoring the conductivity of an Ag2SO4 alkaline solution.

Cations↗
PubMed1999

Four years of experience with silver-copper ionization for control of legionella in a german university hospital hot water plumbing system.

Silver-copper ionization was used for controlling Legionella distribution in a German university hospital hot water plumbing system for 4 years. In the beginning, silver concentrations were not allowed to exceed 10 microg/L because of drinking water regulation limits in Germany. Water samples were monitored for Legionella counts, temperature, and silver and copper concentrations. A significant (P<.001) 3.8-log reduction of Legionella counts, from 40, 000 cfu/L to 7 cfu/L, was found during the first year with silver-copper ionization. Nevertheless, the long-term efficacy of silver concentrations <10 ,++microg/L was not sufficient. Legionella counts increased to 10,000 cfu/L during the third year. During the fourth year, we studied the influence of higher silver concentrations on Legionella distribution. With an average silver level of 30 microg/L, only a 1.3-log reduction in Legionella, to 500 cfu/L, was achieved. The effect was not significant (P=.071); therefore, it must be considered that Legionella developed a tolerance to silver ions.

Chlorine↗
PubMedDate not supplied

A matched-pair, randomized study evaluating the efficacy and safety of Acticoat silver-coated dressing for the treatment of burn wounds.

A new silver-coating technology was developed to prevent wound adhesion, limit nosocomial infection, control bacterial growth, and facilitate burn wound care through a silver-coated dressing material. For the purposes of this article, Acticoat (Westaim Biomedical Inc, Fort Saskatchawan, Alberta, Canada) silver-coated dressing was used. After in vitro and in vivo studies, a randomized, prospective clinical study was performed to assess the efficacy and ease of use of Acticoat dressing as compared with the efficacy and ease of our institution's standard burn wound care. Thirty burn patients with symmetric wounds were randomized to be treated with either 0.5% silver nitrate solution or Acticoat silver-coated dressing. The dressing was evaluated on the basis of overall patient comfort, ease of use for the wound care provider, and level of antimicrobial effectiveness. Wound pain was rated by the patient using a visual analog scale during dressing removal, application, and 2 hours after application. Ease of use was rated by the nurse providing wound care. Antimicrobial effectiveness was evaluated by quantitative burn wound biopsies performed before and at the end of treatment. Patients found dressing removal less painful with Acticoat than with silver nitrate, but they found the pain to be comparable during application and 2 hours after application. According to the nurses, there was no statistically significant difference in the ease of use. The frequency of burn wound sepsis (> 10(5) organisms per gram of tissue) was less in Acticoat-treated wounds than in those treated with silver nitrate (5 vs 16). Secondary bacteremias arising from infected burn wounds were also less frequent with Acticoat than with silver nitrate-treated wounds (1 vs 5). Acticoat dressing offers a new form of dressing for the burn wound, but it requires further investigation with greater numbers of patients in a larger number of centers and in different phases of burn wound care.

Adolescent↗
PubMed1984

Hypoactivity in silver exposed mice.

The functional implications of the presence of silver in the central nervous system are unknown. Since silver is present in the environment and since systemic silver poisoning leads to intraneuronal accumulations of the metal we have evaluated the possible effects of silver on the open field behaviour of mice. Argyric mice have been compared with controls in three experiments, one including long term administration of 0.015% silver nitrate in the drinking water and two in which the reactions of male and female mice to shock doses of silver lactate have been studied. In all experiments the silver treated mice were hypoactive. We suggest that this hypoactivity is due to an influence of silver upon the functional status of the CNS.

Animals↗
PubMed2003

Prevention of catheter related bloodstream infection by silver iontophoretic central venous catheters: a randomised controlled trial.

AIM: To evaluate the efficacy of silver iontophoretic central venous catheters in preventing catheter related colonisation and bloodstream infection among high risk patients in a tertiary hospital. METHODS: Patients requiring central venous access for a period greater than seven days were stratified into two groups according to systemic inflammatory response syndrome criteria before being randomly assigned to receive either silver iontophoretic or control catheters. The incidence of catheter colonisation and catheter related bloodstream infection (CRBSI) was recorded. RESULTS: Three hundred and four single lumen study catheters were inserted into 268 patients. Total duration of catheterisation was 5449 days (median, 12 days/catheter). Complete data could be evaluated in 270 catheters: 128 silver iontophoretic catheters and 140 untreated catheters. Forty seven silver iontophoretic catheters (36.7%) were colonised compared with 48 control catheters (33.8%). Seven cases (5.5%) of CRBSI occurred in patients who received silver iontophoretic catheters, compared with 11 cases (7.7%) in patients receiving control catheters. There was no significant difference in the incidence of catheter colonisation or CRBSI between silver iontophoretic and control catheters. When the duration of catheter placement was taken into consideration, Kaplan-Meier analysis showed no significant difference in the risk of CRBSI between the silver iontophoretic catheters and the untreated catheters (p = 0.77). CONCLUSION: There was no significant difference in the incidence of catheter colonisation or CRBSI among high risk patients between silver iontophoretic catheters and control catheters. Future prospective, randomised studies with a larger number of catheters are encouraged to confirm or refute these results.

Bacteremia↗
PubMed1982

Electron microscopy of silver-stained core-like structures in metaphase chromosomes.

Chinese hamster metaphase chromosomes, stained with ammoniacal silver and examined by electron microscopy, were covered with fine silver grains of variable size. In addition, many chromosomes contained linear aggregates of silver grains running continuously from one end of each chromatid to the other, forming a core-like structure. Extensive deposits of silver were observed over the nucleolar organizers and the centromeric regions, and the silver precipitate in the latter region appeared to be a localized differentiation of the core-like structure. The silver cores ranged from thin to thick and continuous to discontinuous elements in different chromosomes. This extreme variability suggests that these cores are not true structural components of chromosomes. The amount of silver deposit over any given chromosome region may simply reflect the concentration of chromatin in that region of the chromosome. The silver-stained core-like structure probably reflects an underlying difference in the concentration of chromatin in the central and peripheral region of each chromatid. Such differences in chromatin concentration may be induced during the prolonged hypotonic treatment required for the subsequent visualization of cores.

Animals↗
PubMed1992

Procedures for specific detection of silver-stained nucleolar proteins on western blots.

Nucleolar organizer region (NOR)-silver staining of the chromosomes and nucleoli is a method that enables the detection of proteins associated with the ribosomal genes. We adapted the most commonly used cytochemical NOR-silver staining techniques to Western-blotted proteins of HeLa cells, mimicking the silver staining of cells in situ, and testing several parameters that may influence the in situ reaction. Two of these techniques, both one-step methods with colloidal developers, were standardized to obtain reproducible results. The specificity of NOR staining is documented by: (a) only a few bands are revealed among the many proteins detected by total proteins staining on gels or blots; two major groups of bands are found around 100 KD and 40 KD that could correspond at least in part to nucleolin and B23 nucleolar proteins; (b) the silver staining of bands was not the result of the high relative protein concentrations; and (c) the same number of NOR-silver-stained bands was observed across a large range of protein concentrations. The reaction appeared to be specific for a subset of nucleolar proteins, because the same bands were observed with the use of nucleolar, nuclear, or total cell protein extracts, and the silver grains observed in electron microscopy were clearly confined to the nucleolar fibrillar centers and dense fibrillar component. The efficiency of the reaction was not modified by any of the tested fixative pre-treatments except that involving methanol. The presented standardization of NOR-silver staining on Western blots allows the characterization of the Ag-NOR proteins and their specific regions responsible for silver staining of the nucleolus.

Blotting, Western↗
PubMed2004

Colloidal silver as an antimicrobial agent: fact or fiction?

OBJECTIVE: Colloidal silver preparations are marketed on the internet as omnipotent antimicrobial agents, but scientific support for these claims is lacking. This study reports the results of in vitro tests of colloidal silver's antimicrobial activity against several pathogenic or non-pathogenic microorganisms. METHOD: Three samples of colloidal silver were tested: one available commercially on the internet (silver concentration of 22 ppm) and two samples (concentrations of 403 and 413 ppm) which were prepared in our laboratory using standard chemical methods. RESULTS: In an agar-well diffusion assay none of the three colloidal silver solutions had any effect on the growth of the test organisms. All tested bacterial strains were sensitive to ciprofloxacin. Colloidal silver 22 ppm showed no bactericidal activity in phenol coefficient tests. CONCLUSION: As the tested colloidal silver solutions did not show any antimicrobial effect in vitro on the microorganisms, claims of colloidal silver's antimicrobial potency are misleading and there is no place for it as an antiseptic.

Anti-Infective Agents↗
PubMed2006

Effect of a sustained silver-releasing dressing on ulcers with delayed healing: the CONTOP study.

OBJECTIVE: To compare the effect of the sustained silver-releasing foam dressing Contreet Foam (ColoplastA/S) with local best practice (LBP) on delayed healing ulcers using a real-life setting. METHOD: A total of 619 patients with ulcers of varying aetiologies were treated for four weeks with either the silver foam dressing or LBP. RESULTS: Wound area was reduced by 50% with the silver foam and 34% with LBP Less slough and maceration, a faster reduction in exudate level and more positive wound progress was achieved with the silver foam. In addition, exudate handling, ease of use, odour and pain improved. Less time was spent on dressing changes, and mean wear time was longer for the silver foam (3.1 days) than for LBP (2.1 days). All differences were statistically significant (p < 0.05). The silver foam dressing outperformed all of the other dressing categories including moist wound healing products and other silver dressings. CONCLUSION: This large-scale comparative real-life study shows that the silver foam dressing supports faster healing of delayed healing wounds.

Aged↗
PubMedDate not supplied

Effectiveness of silver nitrate compared to talc slurry as pleural sclerosing agent in rabbits. Influence of concomitant intrapleural lidocaine.

UNLABELLED: The ideal agent for producing pleurodesis has not been identified. Talc, the most commonly used, poses several problems. Another possibility is silver nitrate, which was widely used in the past. PURPOSE: To determine the influence of the intrapleural instillation of lidocaine in producing a pleurodesis with silver nitrate, to define the effect of lidocaine in the maturation of the collagen fibers, and to confirm that the pleurodesis after silver nitrate is stronger than after talc. METHODS: We studied three groups of 8 rabbits. Two groups received 0.5% silver nitrate; in one we had previously injected 0.5 ml of 2% lidocaine. The third group received 400 mg/kg talc (2 ml). The animals were sacrificed 28 days after the injection, and the pleural spaces were assessed grossly for evidence of pleurodesis and microscopically for evidence of inflammation and fibrosis. The total amount of pleural collagen and the distribution of thick and thin collagen fibers were quantified. Collagen was identified using picrosirius red stain. RESULTS: In the two groups that received silver nitrate (without lidocaine: 3.5 + 03 and with lidocaine: 3.2 + 0.3), the macroscopic pleurodesis (scale 0 - 4) was significantly (p = 0.001) better than that resulting from talc (1.6 + 0.2). The mean degree of pleural fibrosis induced by silver nitrate (3.5 + 0.2) was significantly (p = 0.004) higher than that induced by talc (1.9 + 0.1). The previous instillation of lidocaine resulted in a tendency for decreased amounts of fibrosis (3.1 + 0.4). The mean amount (10(3)mm2) of pleural collagen was significantly (p = 0.009) greater in the rabbits that received silver nitrate (116.9 + 22.7) than in those that received talc (10.7 + 3.4). The injection of lidocaine slightly reduced the collagen (80.1 + 30.3). The distribution of collagen fibers did not differ among the groups. CONCLUSION: This rabbit model clearly confirms that intrapleural silver nitrate is more effective than talc for producing pleurodesis. The previous intrapleural instillation of lidocaine results in a decreasing trend in the amount of collagen, but does not change the effectiveness of the pleural fusion or modify the process of collagen maturation.

Anesthetics, Local↗
PubMed2004

Influence of chloride on silver uptake by two green algae, Pseudokirchneriella subcapitata and Chlorella pyrenoidosa.

Silver bioavailability in the presence of chloride was estimated from short-term (< or = 60 min) uptake experiments with two green algae, Pseudokirchneriella subcapitata and Chlorella pyrenoidosa. In the first experiment, silver uptake was monitored under two concentration regimes in which total dissolved silver ([Ag]tot) and [Cl] were manipulated to maintain [Ag+] at a constant value (10 nM). Comparable uptake rates were measured for both treatments despite the dramatic changes in [Cl] and [Ag]tot. In the second experiment, ambient [Ag]tot was held constant (10 or 115 nM), but [Cl] was varied (0.005-50 mM) to explore the whole range of silver chloro-complexes. Intracellular silver varied markedly along the [Cl] gradient and exhibited a clear, positive correlation with ambient [Ag+] for both algae. We conclude that the biotic ligand model reliably describes silver bioavailability in the presence of chloride for the two test algae and that its applicability depends on the relative magnitudes of silver fluxes through the unstirred diffusion layer and across the cell membrane, with the latter being affected by the presence or absence of a Cu(I) transporter. In the presence of chloride, no evidence was found for the internalization of silver via anion transport or passive diffusion of the neutral mono-chloro-complex, AgCl0.

Biological Availability↗
PubMed2005

Measuring the partitioning of silver to organic carbon using solubility enhancement.

Ionic silver is toxic to aquatic organisms at low concentrations. However, complexation to binding sites on natural organic matter has been shown to reduce silver toxicity. Research indicates that there is a need to develop reliable methods for characterizing silver binding at very low silver ion concentrations where strong binding sites have a significant influence on silver speciation. This study provides an analytical method for measuring silver binding using a solubility-enhancement procedure. Preliminary experimental results are provided that demonstrate strong silver binding in the presence of natural organic matter at very low silver ion concentrations.

Carbon↗
PubMedDate not supplied

Development of chronic aquatic water quality criteria and standards for silver.

U.S. Environmental Protection Agency (EPA) is updating its aquatic life ambient water quality criteria (aqAWQC) for a number of parameters, including silver. The silver aqAWQC was last issued in 1980. At that time only an acute aqAWQC was established. With the increased reliance on water quality criteria to drive and prioritize the United State's efforts to improve water quality, the scientific basis of new and modified water quality criteria must be both strong and transparent. Although few, if any, natural waters in the United States have suffered water quality impairments because of silver, the lack of valid silver chronic toxicity data in combination with the misapplication of the current U.S. EPA guidelines on deriving chronic aqAWQC could lead to derivation of chronic criteria (by U.S. EPA) and chronic standards (by states, tribes, etc.) that are not supported by scientific data. This misapplication could result in U.S. EPA and the states listing many waters as impaired by silver where, in fact, no silver-related water quality problem exists. This Research Note reviews available information on studies of both acute and chronic silver toxicity to aquatic organisms, as well as U.S. EPA's 1985 procedure for adopting chronic water quality criteria. It identifies existing gaps in the underlying research data base and identifies additional work necessary to derive valid chronic water quality criteria and standards for silver.

Animals↗
PubMed2004

[Experimental study on the antibacterial effects of zirconium phosphate gauze loaded with silver on the common bacteria on rat burn wound].

OBJECTIVE: To investigate the antibacterial effects of zirconium phosphate gauze loaded with silver on rat burn wounds seeded with commonly seen bacteria. METHODS: Wistar rats were employed in the study and were scalded and infected. The minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) of zirconium phosphate loaded with silver were determined by double dilution in tubes. The effect on wound healing and the subeschar bacterial count of the rat burn wounds were observed after the wounds had been covered by gauze loaded with zirconium phosphate and silver, and also with the gauze which has been rinsed for 20 times. RESULTS: The MIC of silver loaded zirconium phosphate on Staphylococcus aureus, Pseudomonas aeruginosa and E. coli were 8, 8 and 16 mg/L, respectively, while the MBC were 16, 8 and 32 mg/L, respectively. The subeschar bacterial count in the burn wounds with the gauze with silver loaded zirconium phosphate was ten times lower than that in those which were treated with gauze with SD-Ag and 100 times lower than that with ordinary gauze. But there was no difference in the bacterial count between the wounds which were treated with fresh gauze with silver loaded zirconium phosphate and that with the gauze which has been rinsed for 20 times (P > 0.05). Furthermore, wound healing seemed to be better with the gauze with silver loaded zirconium phosphate when compared with those by the other two kinds of gauze. CONCLUSION: The silver loaded zirconium phosphate was found to be bacteriocidal against bacteria commonly seen in the burn wounds.

Animals↗