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PubMed1982

Protargol silver impregnation and neuronal selectivity. Light and electron microscopic observations.

The neuronal selectivity of protargol silver was determined in embedded and cultured nervous tissue by light (LM) and transmission electron microscopy (TEM). Ultrastructurally, silver (85-140 A in diameter) was found deposited in neuronal, but not glial, perikarya and cell processes. Usually, the silver grains were arranged in elongated arrays that were associated with electron-dense, strand-like structures that correspond to the 'neurofibrils' observed in LM; myelin sheaths, mitochondria, Nissl substance, Golgi bodies, synaptic vesicles, and endoplasmic reticulum could be excluded as the basis for neuronal argyrophilia. Unfortunately, the composition of these neurofibrils was obscure because of poor tissue preservation involved with proper impregnation, but they appeared to correspond to microtubules and neurofilaments. Neuronal structures containing a predominance of either organelle were impregnated with protargol. Nuclei and nucleoli of neuronal and nonneuronal cells were densely stained with silver as visualized with LM and TEM. Not every neuron was impregnated with protargol, but under conditions of improper fixation some of these neurons had an electron-dense cytoplasm which exhibited a definite affinity for silver. A discussion of protargol selectivity is also presented.

Animals↗
PubMed1975

Model of the antimicrobial silver uracil.

A model is proposed for the antimicrobial agent, silver uracil, whereby silver interacts with uracil forming a silver uracil combination with the silver in the +1 state intercalating between stacked uracils in a manner similar to a 'sandwich' model. The uracils maintain stability by hydrogen bonding with the water solvent, and 'flip-flop' through an antiparallism mode at 220 degrees. The silver bonds to the uracil by a charge transfer mechanism, increasing the nuclear shielding field of the pyrimidine. The presence of the water (solvent) is necessary for the structure.

Anti-Bacterial Agents↗
PubMed2006

Analysis of the state and size of silver on alumina in effective removal of NOx from oxygen rich exhaust gas.

Ag/alumina catalysts with different silver contents for octane-SCR were prepared by impregnation and incipient wetness methods. Activity tests revealed that the decisive factor for high activity is not only a high dispersion of silver, but also the ability of the system to redisperse clustered silver. Determination of dispersion by TEM/HAADF and O2-chemisorption experiments resulted in values close to each other even if the results were not directly comparable. This is suggested to be due to not complete silver reduction below 700 degrees C and the samples being very heterogeneous in terms of particle size, e.g., having a bimodal size distribution. Small charged Agsigman+ clusters containing 2-8 silver atoms highly prevailed in the samples containing <2 wt% Ag and exhibiting high octane-SCR activity. In highly loaded Ag/alumina samples or those reduced and reoxidized at high temperature (>400 degrees C), large metallic particles are stabilized, resulting in poor conversion of NOx to N2.

Aluminum Oxide↗
PubMedDate not supplied

Graft infectivity of rifampin and silver-bonded polyester grafts to MRSA contamination.

The purpose of this study was to evaluate the ability of vascular polyester grafts with antibacterial properties to resist colonization following surface contamination by methicillin-resistant Staphylococcus aureus (MRSA) in an experimental canine model or aortic graft infection. Twenty-four pathogen-free dogs underwent replacement of the infrarenal aorta with either a rifampin-soaked (30 mg/mL) or silver-impregnated (Ag-acetate) woven polyester graft. Following implantation, the external graft surface was inoculated with 2 mL of 10(7) colony-forming units/mL (CFU) of MRSA. Preoperative antibiotic prophylaxis consisted of a single intravenous dose of 500 mg of sodium cefazolin. Four grafts of each type were explanted at 3, 7, and 14 days after implantation. Quantitative cultures (CFU/specimen) of perigraft fluid (1 mL), graft material (1 cm segment), and adjacent aorta (1 cm segment) were performed. Differences between grafts are expressed as % mean log reduction in recoverable CFU compared to the inoculation solution concentration of 10(7) CFUs. At 3 days, explanted rifampin-soaked grafts exhibited no MRSA growth (4 of 4 grafts) and a > or =97% mean log reduction of MRSA CFUs from the adjacent aorta and perigraft fluid (PGF). At 3 days, all silver-bonded grafts exhibited signs of infection and a mean log CFU reduction of MRSA ranging from 68% (absolute range 10(1)-10(3) recoverable CFU) for the graft, 79% (absolute range 10(1)-10(3) recoverable CFU) for the aorta, and 86% (absolute range 10(1)-10(4) recoverable CFU) for PGF. The 7-day rifampin group had an average log reduction in MRSA CFU of 72% (graft), 58% (PGF), 75% (aorta). Quantitative cultures of 14-day rifampin grafted demonstrated continued bacterial growth suppression with mean MRSA CFU log reductions of 82%, graft; 72%, PGF; 89%, aorta. Silver-bonded grafts demonstrated <50% mean CFU reduction in MRSA growth at 7 days (absolute range 10(5)-10(7) recoverable CFU) and 14 days (absolute range 10(3)-10(7) recoverable CFU). No animal died from sepsis or anastomotic hemorrhage. Neither rifampin- nor silver-bonded grafts demonstrated prolonged resistance to surface MRSA contamination. Rifampin-soaked polyester grafts exhibited a marked but transient resistance MRSA colonization likely the result of high antibiotic concentration in the perigraft tissue. While both types of grafts failed to eradicate the MRSA infection future research with silver-bonded grafts that have an additional antibiotic attached may have a place in the treatment of MRSA infection.

Animals↗
PubMed1982

Applications of immunocolloids in light microscopy. Preparation of protein A-silver and protein A-gold complexes and their application for localization of single and multiple antigens in paraffin sections.

The protein A-gold (pAg) complex, a useful reagent for electron microscopic localization of antigens in thin sections, is tested for its suitability as second step reagent in light microscopic immunohistochemistry. In addition, the preparation of colloidal silver, its complex formation with staphylococcal protein A and the application of the protein A-silver complex for antigen localization in paraffin sections is reported. The antigens were visualized in a two-step technique with specific antisera in the first incubation step and pAg or pA-silver as a general second step reagent. The pAg complex gives a red coloration of antigenic sites, whereas the pA-silver stained yellow. The contrasting color provided by the two immunocolloids allowed localization of two antigens in the same section. No color mixing occurred, showing that removal of the antibodies of the first staining sequence is unnecessary. Staining is virtually permanent with the light microscopic immunocolloid method. It is concluded that pAg and pA-silver complexes are useful as general second step reagents for the localization of a variety of antigens in paraffin sections.

Animals↗
PubMed1982

Silver staining of the nucleolus organizer regions (NOR) requires clusters of sulfhydryl groups.

Silver stainability of nucleolus organizer regions (NORs) appears to be correlated with the presence of grouped sulfhydryl (SH) side chains of proteins. In fact, heavy metals with high affinity for SH groups, such as Hg and Cu, do prevent the silver staining reaction. Ferricyanide, which is known to oxidize SH to disulfides, also prevents any further reaction with silver. On the other hand, alkali and reducing agents (mercaptoethanol, cyanide) do not affect silver stainability of the NORs. These results show that the silver staining reaction is not related to disulfide or persulfide groups and that alkali-soluble, acidic nuclear proteins per se do not play a major role in this process.

Cell Nucleolus↗
PubMed1986

A single-step silver enhancement method permitting rapid diagnosis of cytomegalovirus infection in formalin-fixed, paraffin-embedded tissue sections by in situ hybridization and immunoperoxidase detection.

A single-step silver enhancement method was developed which intensifies the polymerized nickel-complexed diaminobenzidine (Ni-DAB) reaction product of peroxidase. With such enhancement, an in situ hybridization procedure can be performed in less than 8 hr by using a 2-hr hybridization incubation and direct detection. Cytomegalovirus (CMV)-infected lung sections were hybridized in situ for 2 hr with a biotinylated CMV genomic-length probe. The probe was detected directly with avidin-biotinylated peroxidase using Ni-DAB as the substrate, and the reaction product was enhanced with silver. Silver was deposited only on the Ni-DAB and not on normally argyrophilic substances. Indirect detection of the probe using a sandwich technique before silver enhancement proved more sensitive, but the length of the procedure was increased without substantially changing the result (infection vs. no infection). Sensitivity was also improved by omitting the dehydration step before applying the probe, and by increasing the temperature and duration of denaturation. In a blinded study of 21 open-lung biopsies, 13 of 13 culture-negative specimens were negative by hybridization, and 7 of 8 culture-positive specimens were positive by hybridization. Modified short hybridization with a biotinylated probe and silver-enhanced direct detection therefore provides a rapid but sensitive method for diagnosis of viral infection.

3,3'-Diaminobenzidine↗
PubMed1990

1-naphthol-pyronin B as a novel substrate for silver intensification: application to light and electron microscopic immunocytochemistry of neuroendocrine systems.

We describe a modification of silver intensification of immunoperoxidase end-product using 1-naphthol (1N) and 1N enhanced by pyronin B after suppressing nonspecific tissue argyrophilia with a solution of penicillamine and merthiolate buffered near neutral pH. This approach facilitates the preservation of a second antigen sequentially labeled in the same tissue section for light microscopic double immunolabeling experiments and also allows retention of ultrastructural detail. Using this protocol, we obtained rapid and uniform silver intensification of somatostatin (SRIF)-immunoreactive (IR) neuronal perikarya and processes in the rat hypothalamic paraventricular nucleus (PVN). Ultrastructurally, 1N- and 1N-pyronin B-silver intensified reaction product was clearly recognized by the presence of a coarse intracellular precipitate of high electron density. Light microscopic double-immunolabeling studies demonstrated the association between SRIF- and thyrotropin-releasing hormone (TRH)-IR neuronal systems in the PVN. We propose that silver intensification of 1N and 1N-pyronin B is a useful alternative to standard methods of silver intensification of immunoperoxidase reaction product at both light and ultrastructural levels and may be particularly amenable for double-immunolabeling studies.

Animals↗
PubMed1981

Electron microscopic studies of silver-strained proteins in nucleolar organizer regions: location in nucleoli of rat sympathetic neurons during light and dark periods.

Ag-AS staining of nucleolar organizer regions was carried out on interphasic superior cervical ganglia neurons of rats sacrificed during light and dark periods. While the Ag-AS technique has mostly been used monolayer cell lines or cell suspensions, the present study showed that in electron microscopy this technique is also applicable to small pieces of tissues. The finest pictures are obtained when (I) all solutions used for the staining procedure are at pH 4.5-4.7 and (2) the second step of the reaction involving ammoniacal silver and formalin developing solutions does not exceed 3 min. The results indicate that in the 2 time periods studied, a positive reaction took place exclusively in nucleolar fibrillar centres and in the fibrillar centres and in the fibrillar ribonucleoprotein (RNP) component (dense fibrillar component). The other nucleolar components, i.e. granular and vacuolar, were devoid of silver deposits. As previously shown in sympathetic neurons, the fibrillar centres of the nucleoli show a 10-fold increase in volume during the dark period. In this period, silver grains were located on both "giant" and small-sized fibrillar centres. The fibrillar RNP component seen either at the periphery of fibrillar centres or in the form of a well-delimited network showed the strongest reaction. The same distribution of silver grains was observed in the sympathetic neurons of rats sacrificed during the light period. Here again, silver accumulation occurred exclusively in the fibrillar centres and the fibrillar RNP component. The same difference in reactivity was observed as for the dark period, the fibrillar RNP component being the main site of the reaction.

Animals↗
PubMedDate not supplied

Audit of catheter-associated UTI using silver alloy-coated Foley catheters.

Catheter-associated urinary tract infection (CAUTI) is the most common and most costly healthcare-associated infection, and possibly the most preventable (Salgado et al, 2003). The Cochrane Review of silver alloy-coated Foley catheters concluded that they are successful at reducing the rate of this healthcare-associated infection, which can be potentially fatal (Brosnahan et al, 2004). This article discusses the merits of using the silver alloy-coated Foley catheter in reducing the risk of CAUTI in an acute general hospital. A pre- and post-intervention design was used to audit CAUTI rates. During the pre-intervention period of 10 weeks, the Trust's standard catheters were used and CAUTI rates captured. Silver alloy-coated Foley catheters were introduced and their use monitored for a further period of 10 weeks. A total of 117 newly catheterized patients were actively monitored for signs and symptoms of CAUTI. The audit met and exceeded its aim of reducing the CAUTI rate by 20&. The CAUTI risk rate and device rate fell during the evaluation period. The use of the silver alloy-coated Foley catheters proved to be cost-effective given the recognized additional costs of CAUTI and prolonged in-patient stay (Plowman et al, 1999). Given the results of this audit it is recommended that the silver alloy-coated Foley catheter be the catheter of choice for use with acute patient admissions requiring short-term catheterization.

Adult↗
PubMed2006

Antimicrobial and barrier effects of silver against methicillin-resistant Staphylococcus aureus.

OBJECTIVE: Two strains of methicillin-resistant Staphylococcus aureus (MRSA), termed epidemic strains (EMRSA-15 and EMRSA-16), were used to evaluate the antimicrobial and barrier effect of four silver dressings (two silver donating and two non-silver-donating) available in the UK at the time of the study. METHOD: The moist surface of a blood agar plate was covered with 10(6) colony-forming units of the respective strain of MRSA, and dressings were applied to the surface and incubated at 37 degrees C for different time periods and the upper and lower surfaces subcultured for residual growth. RESULTS: The nanocrystalline dressings (silver donating) were effective as a barrier from one hour until the study end (72 hours): no penetration of EMRSA-15 and EMRSA-16 through the dressing occurred. Moreover, the nanocrystalline dressings showed some antimicrobial activity at one hour in the areas underneath and surrounding the dressing until the study end. The remaining two dressings had no barrier effect and only demonstrated limited antimicrobial activity after 24 hours. CONCLUSION: This in vitro study suggests that the nanocrystalline dressings are more effective than other silver dressings in terms of providing a barrier function and antimicrobial activity against EMRSA-15 and EMRSA-16.

Administration, Cutaneous↗
PubMed2000

Enhanced visualization of weak colloidal iron signals with Bodian's protein silver for demonstration of perineuronal nets of proteoglycans in the central nervous system.

The present study aimed for a clear visualization of faintly deposited colloidal iron in tissue sections for light microscopy. Paraffin blocks containing paraformaldehyde-fixed brain tissue from healthy adult mice were cut into sections 10-15 microm thick. After deparaffinization, the sections were stained with fine cationic iron colloid at a pH value of 1.0-1.5, and treated with a mixture of potassium ferrocyanide and hydrochloride for Prussian blue reaction. Some sections were further treated with Bodian's protein silver after the Prussian blue reaction. This sensitized development of Prussian blue reaction with Bodian's protein silver more clearly visualized the faintly deposited cationic colloidal irons than the demonstration by Prussian blue reaction alone, and allowed an enhanced visualization of the perineuronal nets of sulfated proteoglycans in the brain. Thus, such fine perineuronal sulfated proteoglycans as those in the CA3 field of the hippocampus, which are weakly stained with cationic iron colloid and usually overlooked by a demonstration with only a Prussian blue reaction, could be clearly visualized with striking contrast by the sensitized development with Bodian's protein silver after the Prussian blue reaction. Preliminary hyaluronidase digestion erased Bodian's protein silver development of perineuronal sulfated proteoglycans. Though some axonal fibers were also additionally stained with Bodian's protein silver itself, this sensitized development is useful to enhance such weak colloidal iron signals as are hardly detectable by only Prussian blue reaction.

Animals↗
PubMed2005

Heterogeneity of natural organic matter amelioration of silver toxicity to Daphnia magna: effect of source and equilibration time.

Despite the heterogeneity of natural organic matter (NOM) in the aquatic environment, current models that predict metal toxicity to aquatic biota treat these important metal-complexing agents in a homogeneous manner. In this investigation, the ability of 11 commercial and naturally isolated NOM samples to ameliorate silver toxicity to the freshwater crustacean Daphnia magna was examined. The commercially available Aldrich humic acid (AHA) increased the 48-h median lethal concentration for daphnid neonates from nominally NOM-free levels of 0.29 to 3.80 microg/L (at 6.9 mg C/L) in a concentration-dependent manner. Three of the tested samples exhibited similar protective effects, but the additional seven NOM samples displayed significantly stronger ameliorative actions. In fact, four samples of both commercial and naturally isolated origin demonstrated greater than fourfold increases in protection compared to that of AHA. Additional investigations showed that increased silver-AHA equilibration time resulted in decreased toxicity. Increased equilibration time also decreased whole-body silver accumulation at NOM levels less than 1 mg C/L. The present results suggest that heterogeneity of NOM and silver-NOM equilibration time will have to be accounted for in future models of silver toxicity to D. magna and that laboratory toxicity testing using NOM and metals should account for the effects of metal-NOM equilibration time.

Animals↗
PubMed2005

Heterogeneity in physicochemical properties explains differences in silver toxicity amelioration by natural organic matter to Daphnia magna.

Recently collected data have shown that natural organic matter (NOM) source is an important parameter influencing the toxicity of silver to the freshwater crustacean Daphnia magna. The present study attempted to correlate the physicochemical properties of 11 naturally isolated and commercially available NOM sources with their ameliorative effects. The protection offered by these samples was standardized to the protective effect of Aldrich humic acid using geochemical modeling approaches that accounted for associated changes in water chemistry and, consequently, silver speciation. The protective ability of NOM was not correlated with reactive sulfide or nitrogen content, which are considered to be strong silver-binding ligands. Color (specific absorbance coefficient) was positively correlated with protection but narrowly eluded statistical significance. The peak wavelength of emission fluorescence following excitation at 370 nm and the fluorescence index values of NOM samples were significantly correlated with protective effects, suggesting that aromatic carbon content may govern the ameliorative actions of NOM. Simple optical properties may therefore act as a suitable indicator for the ability of a given NOM to protect against waterborne silver toxicity to D. magna as long as changes in water chemistry and, thus, silver speciation, are considered.

Animals↗
PubMed2006

Chronic toxicity of silver to the sea urchin (Arbacia punctulata).

The chronic toxicity of silver to the sea urchin (Arbacia punctulata) was determined in 30 per thousand salinity seawater during a three-part study: A fertilization test (1-h sperm exposure), a 48-h embryo test, and a 30-d adult test. Combined data from the three tests resulted in a lowest-observed-effect concentration of 19 microg/L, a no-observed-effect concentration of 8.6 microg/L, and a maximum acceptable toxicant concentration of 13 microg/L, based on measured concentrations of dissolved silver. The 96-h median effective concentration was 40 microg/L, and the acute to chronic toxicity ratio was 3.1. During the tests, measured concentrations of free ionic silver (Ag+) were only 0.0027 to 0.0046% of dissolved silver concentrations, as predicted by ion-speciation theory. Some measured Ag+ concentrations were lower than predicted, indicating the presence of other ligands in the seawater test media. These strong sulfide ligands were exuded by the exposed sea urchins into the seawater (where Ag-sulfide complexes formed) in amounts that increased in direct proportion to the silver concentration during the toxicity test. This suggests a toxicity-defense mechanism that functioned by modifying the chemistry of the surrounding external medium.

Animals↗
PubMed1987

Evaluation of dry silver hard copies in digital radiography.

Diagnostic images produced by digital technologies are viewed on video terminals. Hard copies are subsequently made on film for use by radiologists and referring physicians. An alternative is to make prints on paper using "dry silver" technology. These prints are made by a camera that uses silver-coated paper. The paper is developed as it exits the camera and passes over a heating element. Thus dry silver paper is processed "dry," whereas standard film or print paper is processed in a chemical bath. The prints are viewed by reflected rather than transmitted light. We compared the diagnostic quality of the dry silver prints with that of conventional multiformat, transmitted-light images. Radiologists were asked to make diagnoses from both types of images. The results showed that the diagnoses made from the prints were identical to those made from the films. Furthermore, when the images were labeled with the diagnosis, there was no difference between the two formats in the information conveyed to the referring physician. We conclude that dry silver, reflection prints can provide an inexpensive, convenient method of making visual information available on patients' charts.

Evaluation Studies as Topic↗
PubMed1983

Comparative silver staining patterns of water buffalo, goat, and pig spermatozoa.

Spermatozoa from river and swamp water buffalo (Bubalus bubalis), goat, and pig were stained using a silver nitrate procedure and examined under bright field optics. The silver nitrate differentiated many detailed morphologic features of the head, midpiece, and tail of spermatozoa between the species studied. Acrosomal integrity due to sperm injury or aging and various sperm abnormalities were also clearly identified by silver nitrate. Silver staining patterns revealed species-specific and strain-specific differences, particularly of the sperm head. The biochemical basis of silver staining has been attributed to the presence of sulphydryl and disulphide-rich proteins. The technique is relatively inexpensive, rapid, and repeatable and may be useful for biological research and evaluation of semen for artificial insemination.

Animals↗
PubMed1979

A ten-year retrospective study of sepsis in severely burned patients treated with or without silver sulfadiazinate.

Three groups of extensive burn patients of the surgical intensive care unit (ICU) have been compared: Group I: twenty patients, who were treated locally without silver sulfadiazinate (1968-1970); Group II: the twenty first patients topically treated with silver sulfadiazinate (1970-1972); Group III: twenty similarly treated patients, with silver sulfadiazinate, six years later (1976-1977). The groups are statistically comparable. All bacteriological samples were computerized; the chi-square method was used for statistical analysis of the data. The main conclusions are: (A) Silver sulfadiazinate treatment reduced Pseudomonas aeruginosa and Proteus sepsis. No change in Coliform bacilli sepsis was observed. After six years, a rise in Klebsiella sepsis and Candida sepsis was noted. (B) A quantitative estimate of infections in each group was made by measuring the percentage of positive samples, taking into account the five above-mentioned strains. In the beginning, silver sulfadiazinate reduced quantitative sepsis, but this benefit decreased after six years; the same evolution was demonstrated for positive blood bacteriology; severe septicaemia showed a parallel pattern.

Burns↗