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PubMed1998

Transmission electron microscopy studies of (111) twinned silver halide microcrystals.

The present paper covers the results of different transmission electron microscopy studies on silver halide microcrystals. Pure AgBr as well as core-shell AgBr-AgBrI crystals are investigated. In the former parallel and non-parallel twinning modes yielding tabular and needle- or tetrahedral-shaped microcrystals, respectively, are discussed. Also the short-range-order of Ag+ interstitials around the twin planes as determined from diffuse intensity in reciprocal space is described. The latter yields a technique to determine the variant in which dislocations are located in certain core-shell microcrystals. The introduction of iodine also results in the presence of inclined stacking faults in the shell and of long-range iodine ordering on the crystal surface.

Bromides↗
PubMed1998

A holographic sensor based on a rationally designed synthetic polymer.

A new silver halide-containing holographic recording material has been designed and developed specifically for holographic chemical sensors. The hologram enables very small volume changes to be measured in a polymer layer throughout which the hologram is located. The holographic film is based on a fine-grain silver bromide emulsion suspended in a poly(vinyl alcohol) matrix crosslinked with Cr(III) ions. Cross-linking gives the material sufficient spatial integrity to allow a holographic image to be recorded, while maintaining adequate porosity and elasticity of the polymer matrix for sensing applications. The new material has been characterized with respect to its response to pH and compared with a traditional gelatin holographic film. The response to some ions and small molecules typically found in analytical samples has also been measured. Functional groups introduced covalently into the poly(vinyl alcohol) matrix transform the base matrix into a pH-responsive polymer with predictable swelling properties and which can be further derivatized to incorporate specific ligands. A rationally designed holographic sensor for trypsin has been developed from chemically synthesized artificial polymers. A trypsin substrate, the poly(amino acid) poly(L-lysine), was incorporated into poly(vinyl alcohol) holograms to create a 'designed' holographic material which was degraded in a concentration-dependent manner by trypsin. Extensions of this approach to other hydrolytic enzymes are briefly discussed.

Animals↗
PubMed1998

Lack of genotoxicity of silver iodide in the SCE assay in vitro, in vivo, and in the Ames/microsome test.

Silver iodide was evaluated for mutagenicity in the Ames/microsome test (strains TA 1535, TA 102, TA 97, and TA 98) and for the ability to induce Sister Chromatid Exchanges (SCE) in human cultured lymphocytes and in P388 lymphocytic leukemia cells cultured in the mouse peritoneal cavity. From the cytogenetic in vitro studies, it was observed that silver iodide, either in acetone solutions or as a suspension with polyacrilamide, scarcely causes a doubling effect on SCEs at nearly toxic concentrations (1 microg/ml). Such a doubling effect by silver iodide on SCEs in P388 leukemia cells in vivo was not achieved even after using 100 microg/g mouse body weight. In the Ames/microsome test actually a doubling effect on revertants was only isolately achieved with 30 microg/ml in TA 102 (S9-) and at 150 microg/ml in TA 97 (S9+) doses, which appear to be nearly toxic for bacteria.

Animals↗
PubMed1996

Electric fields and proliferation in a chronic wound model.

A wound model for decubitus and leg ulcers consisting of human dermal fibroblasts in type I collagen dermal "equivalent" matrix (DEM) was exposed in vitro to electric fields similar to postulated endogenous fields in wounds. After an 8-10 day maturation period, conductivity of DEM samples was determined. Then, DEM samples were mounted in oval windows equidistant between Ag/AgCl agar electrodes in exposure chambers containing serum-free medium. A known low-frequency sinusoidal current was then applied for 12 h, and the average electric field amplitude was calculated in the region of the cells. After a 6 h hiatus, 3H-thymidine was introduced for 6 h. This was followed by assay. Over a series of trials, field amplitude ranged from 18 to 1,000 mV/m at frequencies of 10 and 100 Hz. Proliferation was measured by total DNA and 3H-thymidine incorporation. Results indicated that a narrow amplitude window between 37 and 50 mV/meter at 10 Hz yielded increases in proliferation: At maximum (41 mV/m), there was a 70% increase in total DNA (P < .01). Increases occurred in 3H-thymidine incorporation at 41-50 mV/m but not at other amplitudes (P < .05). Increases in total DNA at 41 mV/m occurred at 10 Hz but not 100 Hz (P < .01). 3H-thymidine incorporation was in agreement (P < .05). Response was also a function of cell density within matrix. Proliferation occurred in the same amplitude and frequency ranges in which endogenous fields are expected to occur.

Cell Count↗
PubMed2000

Silver acetate for smoking cessation.

BACKGROUND: Silver acetate produces an unpleasant taste when combined with cigarettes, thereby producing an aversive stimulus. It has been marketed in various forms with the aim of extinguishing the urge to smoke, by pairing the urge with an unpleasant stimulus. OBJECTIVES: The aim of this review was to determine the effectiveness of silver acetate products (gum, lozenge, spray) in promoting smoking cessation. SEARCH STRATEGY: We searched the Cochrane Tobacco Addiction Group trials register. SELECTION CRITERIA: We included randomised trials of silver acetate for smoking cessation with reports of smoking status at least six months after the beginning of treatment. DATA COLLECTION AND ANALYSIS: We extracted data in duplicate on the type of subjects, the dose and form of silver acetate, the outcome measures, method of randomisation, and completeness of follow-up. The main outcome measure was biochemically validated abstinence from smoking after at least six months follow-up in patients smoking at baseline. Subjects lost to follow-up were counted as continuing smokers. Where appropriate, we performed meta-analysis using a fixed effects model. MAIN RESULTS: Two studies provided long-term follow-up data on patients randomised to silver acetate or placebo. In one of these studies, there was a third arm, randomised to 2mg nicotine gum. The combined odds ratio for quitting for silver acetate vs placebo was 1.05 (95% confidence interval 0.63 to 1.73). REVIEWER'S CONCLUSIONS: Existing trials show little evidence for a specific effect of silver acetate in promoting smoking cessation. The confidence intervals for the ratio are quite wide. However, the upper limit of the confidence intervals for a positive effect equates to an absolute increase in the smoking cessation rate of about 4%. Any effect of this agent is therefore likely to be smaller than nicotine replacement therapy. The lack of effect of silver acetate may reflect poor compliance with a treatment whose rationale is to create an unpleasant stimulus.

Acetates↗
PubMed2002

Helical (isotactic) and syndiotactic silver(I) metallo-supramolecular coordination polymers assembled from a readily prepared bis-pyridylimine ligand containing a 1,5-naphthalene spacer.

A ligand in which two pyridylimine binding units are linked by a 1,5-naphthalene spacer is prepared and its silver(I) coordination chemistry investigated. In the solid state, a pair of C-H triplebond N interactions between pyridylimine units link the free ligands into chain structures, with further C-H triplebond N and some -stacking interactions linking these chains into a three-dimensional structure. The spacer constrains the ligand to dinucleate, and with silver(I) the metal coordinates to two pyridylimine units from two separate ligands and this leads to the formation of coordination polymers with a range of different anions. Different twisting motifs within the ligand control the tacticity of these coordination polymers and both isotactic, helical polymers and syndiotactic (achiral) polymers result. The core of the isotactic polymer strands contains two metallo-vectors and results in long-range ordering of the metal centres into a 2 x n grid arrangement. The solution behaviour indicates that exchange between the diastereomeric forms occurs. Since this must involve inversion at the metal centres, atactic species may also form a component of the solution library.

Drug Design↗
PubMed2005

Synthesis of Ag and AgI quantum dots in AOT-stabilized water-in-CO2 microemulsions.

Silver and silver iodide nanocrystals have been synthesized in the water-in-CO(2) reverse microemulsions formed by the commonly used surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT), in the presence of 2,2,3,3,4,4,5,5-octafluoro-1-pentanol as cosurfactant. The nanometer-sized aqueous domains in the microemulsion cores not only act as nanoreactors, but the surfactant interfacial monolayer also helps the stabilization of the metal and semiconductor nanoparticles. The transmission electron microscopy results show that silver and silver iodide nanocrystals with average diameters of 6.0 nm (standard deviation, SD=1.3 nm) and 5.7 nm (SD=1.4 nm), respectively, were formed. The results indicate that the method can be utilized as a general and economically viable approach for the synthesis of metal and semiconductor quantum dots in environmentally benign supercritical carbon dioxide.

Carbon Dioxide↗
PubMed2001

Zinc co-localizes with GABA and glycine in synapses in the lamprey spinal cord.

The presence of zinc in synaptic terminals in the lamprey spinal cord was examined utilizing a modification of the Timm's sulfide silver method and with the fluorescent marker 6-methoxy-8-quinolyl-p-toluenesulfonamide (TSQ). Axons labeled with a Timm's staining method were predominantly located in the lateral region of the dorsal column. This correlated with a maximum of TSQ fluorescence in this region of the spinal cord. Single labeled terminals accumulating Timm reaction product were also found throughout the gray matter and fiber tracts. At the ultrastructural level, zinc was located in a population of synaptic terminals that co-localized gamma-aminobutyric acid (GABA) and glycine. Possible effects of Zn2+ on neuronal activity were examined. In spinobulbar interneurons, which receive GABAergic input in the dorsal column, zinc potentiated responses to GABA application, but it did not affect responses to GABA in motoneurons. Responses in motoneurons to pressure application of glycine were also not affected by Zn2+. Zinc, however, potentiated monosynaptic glycinergic inhibitory postsynaptic potentials (IPSPs) evoked in motoneurons by inhibitory locomotor network interneurons and increased frequency, but not amplitude of spontaneous miniature IPSPs recorded in the presence of tetrodotoxin (TTX), suggesting presynaptic effects. Glutamate responses and the amplitude of monosynaptic excitatory postsynaptic potentials (EPSPs) in motoneurons were reduced by zinc. These effects appeared to be mediated largely postsynaptically through an effect on the N-methyl-D-aspartate (NMDA) component of the glutamatergic input. Our results thus show that free zinc is present in inhibitory synaptic terminals in the lamprey spinal cord, and that it may function as a modulator of inhibitory synaptic transmission.

Aminoquinolines↗
PubMed2006

Mitral cells in the olfactory bulb of adult zebrafish (Danio rerio): morphology and distribution.

The mitral cell is the primary output neuron and central relay in the olfactory bulb of vertebrates. The morphology of these cells has been studied extensively in mammalian systems and to a lesser degree in teleosts. This study uses retrograde tract tracing and other techniques to characterize the morphology and distribution of mitral cells in the olfactory bulb of adult zebrafish, Danio rerio. These output neurons, located primarily in the glomerular layer and superficial internal cell layer, had variable-shaped somata that ranged in size from 4-18 microm in diameter and 31-96 microm2 in cross-sectional area. The mitral cells exhibited two main types of morphologies with regard to their dendrites: the unidendritic morphology was a single primary dendrite with one or more tufts, but multidendritic cells with several dendritic projections also were seen. The axons of these cells projected to either the medial or the lateral olfactory tract and, in general, the location of the cell on the medial or lateral side of the bulb was indicative of the tract to which it would project. Further, this study shows that the majority of zebrafish mitral cells likely innervate a single glomerulus rather than multiple glomeruli. This information is contrary to the multiple innervation pattern suggested for all teleost mitral cells. Our findings suggest that mitral cells in zebrafish may be more similar to mammalian mitral cells than previously believed, despite variation in size and structure. This information provides a revised anatomical framework for olfactory processing studies in this key model system.

Animals↗
PubMed2003

Release of glutamate and GABA in the hippocampus under zinc deficiency.

Zinc homeostasis in the brain is affected by dietary zinc deficiency, and its alteration may cause brain dysfunctions. On the basis of the previous evidence that hippocampal zinc was responsive to 12-week zinc deprivation, responsiveness of hippocampal zinc to dietary zinc deficiency was examined in rats fed a zinc-deficient diet for 4 weeks. Zinc concentration in the hippocampus was not decreased by zinc deprivation for 4 weeks. However, Timm's stain was extensively attenuated in the brain of the zinc-deficient rats. In the brain of the zinc-deficient rats, moreover, zinc concentration in the hippocampal extracellular fluid was approximately 30% of that of control rats. These results demonstrate that vesicular zinc is responsive to dietary zinc and may decrease easily under zinc deficiency. Zinc concentration in the hippocampal extracellular fluid during stimulation with high K(+) was significantly increased even in zinc-deficient rats, although the increased levels of zinc were lower than the basal levels of zinc in control rats. The basal glutamate concentration in the hippocampal extracellular fluid was not significantly different between the control and zinc-deficient rats. However, glutamate concentration in the hippocampal extracellular fluid during stimulation with high K(+) was more increased in the zinc-deficient rats than in the control rats. Gamma aminobutyric acid (GABA) concentration in the hippocampal extracellular fluid during stimulation with high K(+) was increased in the control rats, but not in the zinc-deficient rats. The present study suggests that the excitability of hippocampal glutamatergic neurons is enhanced by dietary zinc deficiency.

Animals↗
PubMed1987

Silver oxide in YAG sclerostomy.

YAG sclerostomy is a filtering procedure performed entirely with the neodymium:YAG laser through a goniolens as an alternative to trabeculectomy in the treatment of glaucoma. Extremely large pulse powers have been required in the past to complete the procedure. We found that an injection of silver-stabilized protein intrasclerally prior to the procedure makes it possible to perform the procedure with low total power.

Animals↗
PubMed2004

Triphenylphosphane complex formation with hexyn-1-yl silver.

Hexyn-1-yl silver shows broad signals in 1H, 13C and 109Ag NMR. In the presence of 1 equiv. of triphenylphosphane, the signals are much sharper and at low temperature 109Ag,31P and 107Ag,31P coupling can be observed. On 109Ag decoupling, the 31P spectrum still shows the 107Ag,31P coupling indicating the formation of a coordination complex.

Alkynes↗