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At least 703 records · Page 39Linked to original sources
PubMed2004

Fourier transform surface-enhanced Raman scattering of single-layer nucleolipid Langmuir-Blodgett films on silver island film substrates.

Surface-enhanced Raman scattering (SERS) spectra of four amphiphilic nucleolipids in single-layer Langmuir-Blodgett (LB) films deposited on silver island film substrates from pure water and complementary nucleotide-containing subphase and corresponding powder normal Raman spectra were obtained. The analysis of these spectra indicates that the SERS effect is mainly caused by a charge-transfer mechanism, and only the nucleobase headgroup moieties and complementary bases combined with them through hydrogen bonds, which are directly in contact with the silver island film substrates, could be enhanced. For the amphiphilic nucleolipids with the identical nucleobase headgroups, the SERS spectra of the LB films are similar, implying that the orientations of these nucleobase moieties on the silver substrates are analogous. However, the nucleobase takes different orientations on the silver substrates before and after complementary binding. The nucleobases in the LB films deposited from pure water are nearly lying flat on the silver surface, while the complementary binding pairs transferred from the air/water interface tend to take an end-on orientation on the metal surface.

Biocompatible Materials↗
PubMed1997

Age-related changes of sulphide-silver staining in the rat hippocampus.

The influence of ageing on sulphide-silver positive zinc stores was assessed in the stratum radiatum of the CA1-CA3 sub fields of the rat hippocampus and in the molecular layer of the dentate gyrus using a silver amplification histochemical technique associated with microdensitometry. The volume of areas examined for microdensitometry was evaluated as well by quantitative image analysis. Male Sprague-Dawley rats aged 3 months (considered to be young), 12 months (considered to be adult) and 24 months (considered to be old) were used. Microdensitometric analysis of values of sulphide-silver staining corrected for the volume of hippocampal areas investigated revealed no age-dependent changes of staining in the CA1 sub field of the hippocampus. In the CA2 sub field a decrease of sulphide-silver staining was noticeable in aged rats in comparison with younger cohorts. A progressive reduction in the intensity of sulphide-silver staining was observed in the CA3 sub field of the hippocampus. In the molecular layer of the dentate gyrus, the intensity of staining was decreased in adult and old rats in comparison with young animals. These findings indicate a different sensitivity to ageing of histochemically detectable zinc stores of rat hippocampus. The possibility of a specific sensitivity to senescence of different zinc-containing pathways of the hippocampus is discussed.

Aging↗
PubMed1998

Radiopaque poly(2-hydroxyethyl methacrylate) particles containing silver iodide complexes tested on cell culture.

Silver iodide complexes have been used as an effective radiopacifying agent to prepare radiopaque poly(2-hydroxyethyl methacrylate) (poly(HEMA)) particles. Incorporation of silver iodide complexes inside the poly(HEMA) particles was achieved by first swelling particles in potassium iodide solution and precipitating the silver iodide complexes using a 30 wt% solution of silver nitrate. The dry particles contained 15 wt% of silver iodide complexes. Particles were easily monitored using a standard imaging technique based on X-ray absorption. Toxicity of the particles has been determined in in vitro experiments on a cell culture. As no inhibition of growth of cells surrounding the particles was observed, they can be considered non-toxic.

Biocompatible Materials↗
PubMed2005

In situ depositing silver nanoclusters on silk fibroin fibers supports by a novel biotemplate redox technique at room temperature.

Evolvement of bioinspired approaches for the construction of well-ordered nanostructures is a crucial intersection of branches of materials science and biotechnology. In this paper, floriated clusters of silver nanocrystallites, which consist of polycrystalline grains about 5 nm in diameter, have been successfully prepared on silk fibroin fibers (SFFs) through an in situ biotemplate redox approach at room temperature. The reductive amino acid tyrosine of SFFs mainly provided both reduction and location functions under alkaline conditions and could reduce Ag(I) ions to Ag(0). Finally, stable silver nanoclusters were generated on SFF substrates. The morphologies of silver nanoclusters were mostly attributed to the concentration of silver nitrate solution as well as special configurations and structures of silk fibroin macromolecules. A possible mechanism was explored intensively for tyrosine-residue-based silver nanocrystal formation.

Animals↗
PubMed1955

An electron microscopic study of the blood-brain barrier in the rat, employing silver nitrate as a vital stain.

The intravital deposition of silver in the chorioid plexuses, area postrema, intercolumnar tubercle, neurohypophysis, and pineal body of rats, given 1.5 gm. of silver nitrate per liter of drinking water for periods of up to one year, has been investigated by electron microscopy. Unlike other parts of the central nervous system, these regions store large amounts of silver. In all of these structures, silver is deposited in the form of dense granules in the basement membrane upon which the capillary endothelium rests, in and upon the connective tissue cells and fibers constituting a loose pericapillary sheath, and in an outer membrane separating this sheath from the parenchymatous cells. Parts of the central nervous system which do not store silver, for example the spinal cord, cerebellar cortex, cerebral cortex, and reticular formation, lack a connective tissue investment of the capillaries. In these locations, the glial processes or end-feet are closely applied to the walls of the capillaries. Only a narrow space, filled by an amorphous, moderately electron-dense substance, separates the plasma membranes of the endothelial cells and glial processes. The significance of these observations is discussed with respect to the questions of the Virchow-Robin perivascular spaces, the interstitial ground-substance of the brain, and the location of the hematoencephalic barrier.

Animals↗
PubMed1990

Prevention of catheter-associated urinary tract infection with a silver oxide-coated urinary catheter: clinical and microbiologic correlates.

In a prospective clinical trial involving 482 acutely hospitalized patients, the overall incidence of catheter-associated urinary tract infection (UTI; 10%) was similar in recipients of a silver oxide-coated urinary catheter (silver catheter) or a control silicone catheter. However, female sex and absence of antimicrobial use were independently associated with an increased risk of UTI. After stratification for these variables, the silver catheter reduced the incidence of UTI among women not receiving antimicrobial agents (19% for control catheter vs. 0 for silver catheter, P = .04; confidence interval for the difference in incidence, 0.4%-38%) but not in the other subgroups. Gram-positive UTI was associated with absence of antimicrobial use, the control catheter, and catheter care violations. Gram-negative and candidal UTIs were more common after 7 days of catheterization, and candidal UTI was associated with being female and antimicrobial use. These findings demonstrate that several clinical variables influenced the incidence and microbiology of catheter-associated UTI and that the silver catheter appeared to prevent UTI among women not receiving antimicrobials.

Adult↗
PubMedDate not supplied

Leukopenia in acute thermal injury: evidence against topical silver sulfadiazine as the causative agent.

White blood cell data from time of admission to 4 days after burn injury was retrospectively reviewed to determine differences in the incidence of leukopenia in patients with burn injuries treated topically with either silver sulfadiazine or silver nitrate. WBC counts decreased in both groups of patients during the first 3 days after burn injury. An incidence of leukopenia (WBC count less than or equal to 5000/mm3) was observed in of 40 (47.5%) patients treated with silver sulfadiazine and in 13 of 30 (43.3%) patients treated with silver nitrate. There was no statistical difference in the incidence of leukopenia between the two treatment groups. These data suggest that silver sulfadiazine may not be the cause of the leukopenia observed early after burn injury.

Administration, Topical↗
PubMed1989

Silver resistance in Escherichia coli R1.

Escherichia coli strain R1, originally isolated from a patient whose burns were treated with silver sulphadiazine, contained two large plasmids of 83 kb (pJT1) and 77 kb (pJT2), and was resistant to 1 mM AgNO3. A silver-sensitive derivative, E. coli S1, cured of the 83-kb plasmid pJT1, was obtained by growth at 46 degrees C. Studies with an Ag+-specific ion electrode showed no significant differences in Ag+ binding by washed resting cell suspensions of strains R1 and S1, with and without glucose. However, transmission electronmicroscopy and energy dispersive X-ray analysis of whole cell mounts from actively growing cultures showed that the Ag+-resistant strain did not accumulate Ag+, whereas the sensitive strain contained dense silver particles. Both strains produced H2S, detected by blackening of lead acetate paper above inoculated broth, and reducing substances (possibly H2S) were detected only around E. coli R1 colonies when methylene blue was used as a indicator in LB agar, which may be a less sensitive assay. The mechanism of silver resistance is not known, but actively growing cells of E. coli R1 did not accumulate silver.

Bacterial Outer Membrane Proteins↗
PubMed1987

Silver-coated nylon fiber as an antibacterial agent.

A blend of nylon fiber and silver-coated nylon fiber (the latter known as X-static) was used in these experiments. This fiber was bactericidal when bacteria were exposed to it directly or to an extract derived from its prior incubation in salt solution. At ambient temperatures, a rapid exponential decrease of survival occurred, usually after a delay of approximately 1 h. The rate of killing (decrease of survival) increased with an increase in X-static percentage of the fiber blend, temperature of fiber extraction, concentration of Tris buffer present during extraction, and temperature at which bacteria were exposed to the extract. When bacteria were exposed to the extract at 37 degrees C as opposed to ambient temperature, there was no delay in onset of killing. Escherichia coli was generally the indicator organism tested, but comparable results were also found for Pseudomonas, Klebsiella, Staphylococcus, and Streptococcus species. The rate of killing increased with increasing silver ion concentration of the fiber extract, as determined through atomic absorption spectrophotometry. The rate of killing was greater and the onset was earlier with an extract containing silver ions from fiber than with a salt solution containing the same concentration of silver ions from silver nitrate. Studies of the kinetics of ion release suggested that X-static may be an effective, sustained-release antibacterial agent.

Delayed-Action Preparations↗
PubMedDate not supplied

Inhibition and killing of oral bacteria by silver ions generated with low intensity direct current.

Silver cations generated by passing low intensity direct current through pure silver electrodes were found to be sufficiently antibacterial to cause sterilization of samples of infected dentin. The optimal procedure involved a 5 microA current applied for 20 minutes with the anode then left in contact with the sample. Minimal inhibitory concentrations of electrically generated silver ions for representative oral bacteria were essentially equal to those for silver ions added as nitrate or fluoride salts, and medium constituents, including sodium thioglycolate, antagonized antibacterial action. A major advantage to the use of the electrode method is that it allows for continuous, focal application of antibacterial silver cations.

Bacteria↗
PubMed1988

Ultrastructural silver enhancement of Prussian blue-reactive iron in hematopoietic and intestinal cells.

Prussian blue has been widely used to localize iron in a variety of tissues at the light and electron microscopic level. In the present study, thin sections of human marrow and blood cells and rat duodenal cells were exposed to silver proteinate (SP) after staining en bloc with acid ferrocyanide (AF), with and without prior iron saturation using iron nitrilotriacetate (FeNTA). Silver deposition was observed over Prussian blue-reactive sites and significantly enhanced sites of minimal AF and FeNTA-AF staining. AF-SP stain deposits were present in the cytoplasmic matrix, granules, and occasionally on the surfaces of macrophages, monocytes, and erythroblasts. FeNTA-AF-SP stained additional cytoplasmic and surface sites in erythroblasts and stained neutrophil granules intensely. Duodenal epithelium from iron-loaded rats demonstrated strong AF-SP staining of ferric iron in microvilli, apical cytoplasmic matrix, and lateral membranes. Similar preparations from iron-replete rats stained sparsely; however, intense AF-SP staining was observed after iron saturation with FeNTA. SP similarly enhanced luminal ferrous iron deposits stained with acid ferricyanide in rats given intraluminal ferrous iron. AF-SP stain deposits were removed by exposure of thin sections to NH4OH, KCN, or HNO3 but were not affected by prior exposure to HIO4 or NaBH4, consistent with a silver cyanide or complex stain precipitate rather than reduced silver or silver ferriferrocyanide. SP enhancement of Prussian blue allows identification of reactive sites not readily visualized with AF or FeNTA-AF alone, and offers the potential for differentiating AF staining from other deposits or organelles of comparable density.

Animals↗
PubMed1997

Dark and light neurons in the human brain, with special reference to their reactions to Golgi's silver nitrate, luxol fast blue MBS and azocarmine G.

Sections from the human somatosensory cortex were observed with a light microscope. The neurons were classified into light and dark ones. The light neurons were slightly stained with thionin, luxol fast blue MBS and azocarmine G (80% of all neurons). The dark neurons were more or less shrunken, and stained intensely with these dyes (20% of all neurons). Double staining with luxol fast blue MBS and azocarmine G was especially useful to demonstrate the dark neurons, since it clearly stained even their fine processes. Neither light nor dark neurons were reactive to nick end labeling for detection of DNA fragmentation. Triple staining with Golgi's silver nitrate (or Gallyas's ammoniacal silver carbonate), luxol fast blue MBS and azocarmine G show that the majority of the dark neurons were argyrophilic (argyrophilic dark neurons, 15% of all neurons), while some of them were not argyrophilic (non-argyrophilic dark neurons, 5% of all neurons). Triple staining also showed that the light neurons were only occasionally argyrophilic (argyrophilic light neurons, 5% of all neurons); usually, the light neurons were not argyrophilic (non-argyrophilic light neurons, 75% of all neurons). The results confirm that dark neurons usually represent certain populations of neurons in the human brain, and that they are basically identical to the argyrophilic neurons. The discussion suggests that the argyrophilic light and dark neurons are excited cells, the non-argyrophilic dark neurons are exhausted cells, and the non-argyrophilic light neurons are resting cells. Triple staining further demonstrated that some glial cells were darkened and stained with Golgi's silver nitrate or Gallyas's silver carbonate. Additional Golgi's silver block staining showed that the argyrophilic neurons stained by the conventional block staining method usually possessed a shrunken cell body, which was characteristic of the dark neurons.

Aged↗
PubMed2001

Silver ion microplates for immunoassays.

Microplate wells can be coated with silver ions using glutaraldehyde as a spacer molecule and thiourea as a complexing ligand. Microwells containing surface silver ions are shown to immobilize biotin-labeled horseradish peroxidase (HRP) in active form, while showing very little affinity for the unlabeled enzyme. These plates can also immobilize biotin-labeled antibodies that exhibit bioactivity after immobilization. Silver ions are needed for the complexation of the biotinylated enzyme or antibody because microwells modified to contain surface amine or thiourea molecules do not immobilize appreciable amounts of the labeled proteins. A maximum surface coverage for biotin-labeled HRP of 40 ng/cm2 and an immobilization binding constant of Km = 8 x 10(9)/M are determined from serial dilutions in a microplate. Detection of as little as 6.7 fmol HRP is achieved using antibodies immobilized on the silver ion-modified microplates. Active antibody surface densities were estimated to be between 130 and 260 nm2/antibody molecule. Background binding of HRP to the modified silver ion microplates was very low, allowing for reasonably accurate detection between 10(-14) and 10(-11) mol HRP.

Antibodies↗
PubMed1976

Silver deposition in mouse glomeruli.

Administration of 6 mM silver nitrate in the drinking water of mice resulted in deposition within the glomerular basement membrane of silver granules which were detected on electron microscopy after 12 days. Larger aggregates were detected in the basement membrane and mesangium when silver ingestion was extended to 14 weeks. The silver deposits did not alter significantly over a period of 21 weeks after silver nitrate ingestion was stopped.

Animals↗
PubMed1981

Argyria-tissue deposition of silver as selenide.

Generalized argyria was precipitated in a patient by treating gingival erosions with a solution of silver nitrate for several months. High silver concentrations were measured in skin biopsies. treatment with penicillamine did not increase the urinary silver excretion, indicating that silver is deposited in tissues in a chemically stable and apparently inert form. Electron microscopy showed that in the kidney, silver was deposited mainly in the basal membranes as electron-dense particles. These particles were studied by using X-ray emission spectrometry and electron diffraction. the particles consisted of Ag2Se in the low temperature orthorhombic alfaform. The lattice parameters are: a = 0.433 nm, b = 0.693 nm and c = 0.784 nm. This selenide complex seems to be remarkably non-toxic, since the renal function of the patient was unaffected and only negligible reactive changes were observed in kidney biopsies.

Argyria↗
PubMed2003

The effect of concentration and pH of silver nitrate solution on nanoleakage.

PURPOSE: The purpose of this study was to evaluate the effects of concentration and pH of silver nitrate solution on nanoleakage in occlusal flat surfaces bonded with three dentin bonding systems. MATERIALS AND METHODS: The dentin bonding systems used in this study were Single Bond, PermaQuik, and Prompt L-Pop. Flat occlusal dentin surfaces from extracted human molars were bonded with one of the dentin bonding systems. The teeth from each subgroup (n = 4) were placed in one of the following silver nitrate solutions: 50% w/v, 25% w/v, 10% w/v, and 2% w/v (pH 3.4, 4.2, 4.4, and 4.9, resp), and 50% w/v buffered to pH 6 in total darkness for 24 h, rinsed in running water for 5 min, immersed in photodeveloping solution for 24 h, and exposed to light for 8 h. Specimens were sectioned, mounted on stubs, carbon coated and observed in a Field Emission SEM using backscattered electron mode. RESULTS: FE-SEM images showed that samples from different concentrations of silver nitrate solution had leakage patterns similar to that of samples from 50% w/v for all dentin bonding systems. The concentrations and pH values of silver nitrate solutions did not affect leakage patterns in any of the systems. CONCLUSION: A lower concentration of silver nitrate solution may be used in a nanoleakage study, although the present results need to be replicated to determine an ideal concentration.

Acid Etching, Dental↗
PubMed2001

[The enhanced mechanism of Cl- to SERS in silver colloid].

The SERS is enhanced when KCl is added to silver colloid and cation molecule. The hypothesis supposed that Cl- bridged between nano-silver and molecule, as a result the molecule adsorbing on nano-silver surface is promoted and the SERS is therefore enhanced. The CN- and NH3 can be better adsorbed when they are added separately to the nano-silver particles, Cl- and anion molecule. The SERS reduces when CN- and NH3 are added separately to Cl-, anion molecule and silver colloid. The result is that the CN- and NH3 are so strong that they have replaced Cl- and anion molecules. Therefore the SERS reduces. This has proved the bridge role of Cl-.

Adsorption↗
PubMed2004

[Study on solid-phase-extraction spectrophotometric determination of silver with p-sulfobenzylidene-rhodanine].

The color reaction of silver with p-sulfobenzylidene-rhodanine (SBDR) was studied. Based on the color reaction of SBDR with silver (I) and the solid phase extraction of its colored complex with Waters Porapak Sep-Park-C18 cartridge, a new method for the determination of micro-amount of silver (I) was studied. In the presence of pH = 2.8 citric acid-sodium hydroxide buffer solution and Tween-80 medium, SBDR can react with silver (I) to form a stable 2:1 complex. The colored complex can be extracted by C18 cartridge and eluted by ethanol (containing 5% acetic acid), and then can be determined by spectrophotometry. The molar absorptivity is 7.53 x 10(4) L x mol(-1) x cm(-1) at 520 nm. Beer's law is obeyed in the range of 0-1.2 microg x (25 mL)(-1). This method can be applied to the determination of silver in water with satisfactory results.

Environmental Monitoring↗