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At least 73 records · Page 4Linked to original sources
PubMed2004

[Study on spectrophotometric determination of silver(I) with 2-(2-quinolinylazo)-1,5-dihydroxidebenzene].

The color reaction of silver(I) with 2-(2-quinolinylazo)-1,5-dihydroxidebenzene (QADHB) and the solid phase extraction of the colored chelate with Waters Sep-Park C18 cartridge were developed. In the presence of pH = 5.0 sodium citrate-sodium hydroxide buffer solution and sodium dodecyl sulfonate (SDS) medium, QADHB can reacts with silver to form a chelate of a molar ratio 1:2 (silver to QADHB). This chelate can be enriched by the solid phase extraction with Waters Sep-Park C18 cartridge. The retained chelate can be eluted from cartridge with ethanol. In ethanol medium, the molar absorptivity is 6.99 x 10(4) L x mol(-1) x cm(-1) at 550 nm. Beer's law is obeyed in the range of 0-1.2 microg x mL(-1). This method can be applied to the determination of silver in water with satisfactory results.

Benzene↗
PubMed2006

Spectroscopy property of Ag nanoparticles.

Three silver nanoparticles of different size characterized by the UV-vis absorbance spectra and TEM images were prepared by citrate reduction and laser ablation with excitation of 532 and 248 nm. It is proved that all of them are effective SERS-active substrates, whereas, enhancement effect of silver colloids has not too much relation with the size and shape of the Ag nanoparticles. However, different photoluminescence spectra were observed from these three particles, indicating that the photoluminescence property of silver nanoparticles is dependent on the size. The spectra shift to higher energies with decreasing particle size. In addition, we also tentatively give the assignment of the luminescence bands.

Metal Nanoparticles↗
PubMed1993

Reaction-frequencymetric method: a new analytical technique for determination of submicromolar concentration levels of vitamin C.

A new analytical technique for the assay of pharmaceutical substances at low concentration levels has been proposed and applied to the determination of vitamin C as an example of its application. It is based on the chemical reaction of vitamin C with iodine in a sodium citrate-hydrochloric acid medium, followed by measurement of the frequency change of a silver-plated piezoelectric quartz crystal. The frequency change is proportional to the vitamin C concentration from 2 x 10(-7) to 4 x 10(-6) M. The method was applied to the assay of vitamin C in pharmaceutical preparations.

Ascorbic Acid↗
PubMed1991

Some applications of cryosubstitution in ultrastructural studies of the cell nucleus.

Cryofixation followed by cryosubstitution, without the use of any chemical fixatives, was carried out on cultured mouse P815 cells. The principal aim of our work, which was to show that these techniques provide excellent morphological preservation of cellular and in particular nuclear components, was demonstrated. All nuclear structural components, nucleolar or nucleoplasmic, were clearly revealed using this technology. The cells were cryofixed by impact freezing onto a copper mirror cooled with liquid nitrogen or helium, cryosubstituted in acetone and embedded in either Lowicryl K11M or 1R White acrylic resin. Ultrathin sections were contrasted using either the usual uranyl acetate-lead citrate double staining, a differential staining for nuclear nucleoprotein structures, or the silver staining revealing nucleolar organizer regions. In view of the absence of conventional fixatives, the specimens prepared in this way would offer to be material of choice for ultrastructural identification of intra-nuclear antigens, especially those sensitive to conventional fixatives such as, for example, aldehydes. Advantages and differences of these techniques with regard to more conventional electron microscopic procedures are discussed.

Acrylic Resins↗
PubMed2006

Determination of 210Pb and 210Po in soil or rock samples containing refractory matrices.

A new method has been developed for determination of (210)Pb and (210)Po in soil or rock samples containing refractory matrices. The samples were first fused with Na(2)CO(3) and Na(2)O(2) at 600 degrees C for pre-treatment and then (210)Pb and (210)Po were sequentially leached out at 200-250 degrees C with HNO(3)+HF, HClO(4) and HCl. About 10% of the leaching solution was used for (210)Po determination, carried out by spontaneous deposition of polonium on a silver disc from a weakly acidic solution that contained hydroxylamine hydrochloride, sodium citrate and (209)Po tracer, measurement being made by alpha-spectrometry. The remains of the leaching solution were used for determination of (210)Pb, conducted by precipitation as sulphate, purification with Na(2)S as PbS in 6M ammonium acetate, separation from alpha-emitters by an anion-exchange resin column, source preparation as PbSO(4), and measurement with a beta-counter. The procedure has been checked with two certified IAEA reference materials, showing good agreement with the recommended values. The lower limits of detection for 1g of analysed soil or rock samples were found to be 0.75 Bqkg(-1) for (210)Po and 2.2 Bqkg(-1) for (210)Pb. A variety of solid sample species analysed through use of the procedure gave average yields of 90.0+/-9.8% for (210)Po and 88.4+/-7.1% for (210)Pb.

Chemical Fractionation↗
PubMed2005

Surface-enhanced raman scattering on dendrimer/metallic nanoparticle layer-by-layer film substrates.

In this paper, the fabrication, characterization, and application of unique layer-by-layer (LBL) films of dendrimers and metallic nanoparticles is reported. Silver nanoparticles (d = approximately 20 nm) are produced in solution by sodium citrate reduction and incorporated into thin films with generation 1 and 5 DAB-Am dendrimers (polypropylenimine dendrimers with amino surface groups) by the LBL technique. The resulting nanocomposite films are characterized by UV-visible surface plasmon absorption and atomic force microscopy (AFM) measurements, and employed as substrates for surface-enhanced Raman scattering (SERS) of 2-naphthalenethiol. Through variation of the molecular size (dendrimer generation) and concentration of the cross-linker used, as well as the number of layers produced, the optical properties of several different possible architectures are studied. In the films, Ag nanoparticles are shown to be effectively immobilized and stabilized with increased control over their spacing and aggregation. Moreover, the films are shown to be excellent substrates for SERS measurements, demonstrating significant enhancement capability. As expected, large electromagnetic enhancement of Raman scattering signals is found to be strongly dependent on interparticle coupling between neighboring metallic nanoparticles. Finally, the possibility of detecting SERS signals from architectures with intervening layers between the metal nanoparticles and analyte molecules is explored. It is shown that although there are decreases in intensity with increasing number of intervening layers (as is expected from the distance dependence of SERS), electromagnetic enhancement is still able to function at these distances, thus offering the possibility of developing sensors with external layers that are chemically selective for specific analytes.

Journal Article↗
PubMed1988

Gallium-67 citrate localization in osteoclast nuclei of Paget's disease of bone.

Gallium-67 citrate scintigraphy has been used to indicate the extent of bone involvement in patients with Paget's disease of bone and is an excellent marker in monitoring the effects of specific therapy. Since gallium uptake is dependent on cellular function, autoradiographic techniques can be applied to cells of Paget's lesions to understand better the mechanism of [67Ga]citrate uptake. Bone biopsies were obtained from sites of increased uptake using [67Ga]citrate scintigraphy in two patients with Paget's disease. In both patients electron microscopic autoradiographs demonstrated a high concentration of silver grains over the nuclei of osteoclasts. The cellular mechanism is unknown but may be related to the known inhibitory effect of calcitonin on osteoclast activity. The association of [67Ga]citrate with the nucleus of the osteoclasts is unique and different from tumor cells in which there is a high association of [67Ga]citrate with the lysosome fraction within the cytoplasm.

Autoradiography↗
PubMed1986

Colloidal gold probes in immunocytochemistry. An optimization of their application in light microscopy by use of silver intensification procedures.

Colloidal gold particles are the markers of choice for ultrastructural localization of antigens. By reducing gold chloride with tannic acid and trisodium citrate, a broad range of narrowly determined particle sizes can be obtained. Such particles can easily be coupled to a number of proteins and the resulting conjugates are conveniently purified on a gel-chromatography column. Their application in light microscopy requires an amplification step with a silver physical developer. Silver-intensified colloidal gold probes can advantageously be used for immunostaining of cryostat, paraffin and plastic sections. Moreover, permeabilized cultured cells and whole-mount preparations can also be stained with gold-silver techniques. Silver intensification does not affect reactivity of a number of tissue antigens, thus permitting double staining combinations with immunoperoxidase or immunofluorescence methods.

Animals↗
PubMed1984

A method for combined C-banding and silver staining.

A reliable technique for combined C-banding and silver staining of metaphase chromosomes which uses trypsinization is described. Slides are first immersed in dilute HCl to remove residual cytoplasm from around the chromosomes. They are then treated with saturated barium hydroxide and incubated overnight in saline sodium citrate (0.30 M NaCl, 0.03 M sodium citrate, adjusted to pH 7.0 with HCl). Following the C-banding pretreatment, a two-step method of silver staining which employs a protective colloidal developer is used to stain the nucleolar organizer regions (NORs) of the chromosomes. Silver staining is followed by trypsinization to remove extraneous silver precipitate from the chromosome arms which permits the C-bands to be stained with Giemsa. The method works equally well with fresh and aged mitotic chromosome preparations and gives consistent staining of both heterochromatin and active NORs in metaphases across the slide.

Chromosome Banding↗
PubMed1998

Ultracytochemical demonstration of glycogen in cone, but not in rod, photoreceptor cells in the rat retina.

The presence of native glycogen in photoreceptor cells of the rat retina has not been identified in the literature. We have studied this ultracytochemically. After perfusion with glutaraldehyde fixative, the eyes were enucleated, and the retinal tissues, postfixed with OsO4, were embedded in epoxy resin. Some tissues were treated with saliva before postfixation. Ultrathin sections, stained by the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) method or with uranyl acetate and lead citrate, were examined by electron microscopy. On routinely stained sections, glycogen particles seemed to be absent in the cytoplasmic matrix of the photoreceptor cells because they were indistinguishable from the numerous ribosomes. This was due to a similarity in size and electron density. After PA-TCH-SP staining, fine electron-dense reaction products appeared on small cytoplasmic particles (but not on ribosomes) in the inner segments, perikarya and synaptic terminals of a subpopulation of photoreceptor cells. These particles, 15-25 nm in diameter, were identified as beta-particles of glycogen because of their susceptibility to enzyme digestion. The glycogen-rich photoreceptor cells were thought to be cone cells by reasons of their morphological features, such as synaptic terminals, nuclei and outer segments. These results suggest that the cone, but not the rod, photoreceptor cells in the rat contain abundant glycogen.

Animals↗
PubMed2006

Growth of gold nanorods and bipyramids using CTEAB surfactant.

Gold nanorods and bipyramids have been synthesized using the seed-mediated approach in aqueous cetyltriethylammonium bromide (CTEAB) solutions in the presence of silver nitrate. Gold nanoparticle seeds that are stabilized with either CTEAB or sodium citrate have been used. The use of the CTEAB-stabilized seeds gives gold nanorods in high yield in one step with the longitudinal plasmon wavelength ranging from 750 to 1030 nm, depending on the amount of the seeds. The longitudinal plasmon wavelength can be extended to 1100 nm by the use of a two-step growth method. The growth of gold nanorods in CTEAB solutions takes 5-10 h, more than 5 times slower than that in cetyltrimethylammonium bromide solutions at the same concentration of surfactants. The use of the citrate-stabilized seeds gives both gold bipyramids and a small percentage of gold nanorods. The longitudinal plasmon wavelength of the bipyramids is tunable from 700 to 1100 nm by varying the amount of the citrate-stabilized seeds. The growth of gold bipyramids takes more than 1 day. Transmission electron microscopy characterizations reveal that the gold nanorods grown from both types of gold nanoparticle seeds are single-crystalline and that the gold bipyramids are penta-twinned.

Journal Article↗
PubMed2002

Clinicopathologic evaluation of the Mueller muscle in thyroid-associated orbitopathy.

PURPOSE: To study the histopathologic features of the Mueller muscle in chronic eyelid retraction caused by thyroid-associated orbitopathy. To investigate if the degree of eyelid retraction correlates with any histopathologic finding. METHODS: A prospective case series of 23 consecutive patients with thyroid-associated orbitopathy was studied. Specimens were obtained during a standard muellerectomy. Formalin-preserved specimens were studied with the use of hematoxylin-eosin, periodic acid-Schiff, Masson trichrome, and Giemsa stains. Immunostaining against leukocyte common antigen, L26, CD3, and KP-1 was performed. Three control specimens were also evaluated in a similar fashion. Fresh tissue was placed in cold glutaraldehyde overnight, postfixed, dehydrated, and infiltrated with epoxy resin. Silver (70 nm) sections were cut and stained with uranyl acetate and lead citrate for electron microscopic examination. RESULTS: On light microscopy, fibrosis and mast cell infiltration was present in all 23 specimens. Fat infiltration was noted in 16 of 23 specimens and did not correlate with increasing age of the patient. Interstitial edema and lymphocytic infiltration were not observed. On immunohistochemistry, leukocyte common antigen was positive, confirming the presence of inflammation. L26, CD3, and KP1 were negative. Electron microscopy demonstrated fibrosis, mast cells, and abundant contracting Mueller cells. The degree of clinical retraction in millimeters did not correlate with fibrosis, inflammation, or fat infiltration. The control specimens demonstrated rare fat and mast cell infiltration and no fibrosis. CONCLUSIONS: Contrary to previous reports, the Mueller muscle is involved in the inflammation and fibrosis that characterizes thyroid-associated orbitopathy. The Mueller muscle is grossly enlarged. On histopathologic inspection, fibrosis, fatty infiltration, and increased mast cell presence accompany focal atrophy of the Mueller muscle. In concordance with prior descriptions, many Mueller cells are in an actively contracting state on electron microscopy.

Adult↗
PubMed1981

Simultaneous demonstration of glycogen and protein in glycosomes of cardiac tissue.

Cardiac conduction fibers fixed either in glutaraldehyde and OsO4 or treated additionally en bloc with uranyl acetate were studied in order to demonstrate the structure of glycosomes (protein-glycogen complex). Sections were stained histochemically by periodic acid-thiosemicarbazide-silver proteinate (PA--TSC--SP) for glycogen followed by uranyl acetate and lead citrate (U-Pb) for protein. In control sections periodic acid was replaced by hydrogen peroxide (H2O2). Glycogen appeared in all sections stained by PA-TSC-SP. Protein was poorly contrasted in periodic acid treated histochemical sections taken from fixed in glutaraldehyde and OsO4. Simultaneous staining of glycogen and protein was achieved in sections of tissue treated en bloc with uranyl acetate. This treatment revealed two classes of glycosomes: 1) glycosomes deposited freely in the cytoplasm whose structure was disintegrated after treatment with uranyl acetate: 2) glycosomes associated with other cellular structures that remained intact. Staining of glycogen and protein in the same section demonstrated for the first time the structure of intact glycosomes.

Animals↗
PubMed2004

Morphological evaluation of the lungs in rats with experimentally induced renal failure.

The study aimed at morphological evaluation of changes in the lungs of rats during experimentally induced uremia. The studies were performed in three (3) groups of rats: C--a control group (15 animals), SO--15 rats, submitted to sham operation, U--an uremic group--21 rats with experimental renal failure. After 1, 2 and 4 weeks from the surgery, the collected lungs were fixed in Bouin's fluid and in 2.5% purified glutaraldehyde for electron microscopy. Paraffin specimens were cut into 5 microm slices and stained by H+E, by Azan's method and with silver, according to Grimelius. Ultra thin sections contrasted with uranyl acetate and lead citrate. Blood serum urea and creatinine levels were determined. In the uremic rats, increased concentrations of serum creatinine and urea were observed. Chronic renal failure affected the progress and the degree of development of the changes in the lungs, the final effect of which was fibrosis. In microscopic pictures of the lungs from the uremic rats, numerous changes were observed, characteristic for chronic oedematous conditions of different intensification.

Animals↗
PubMed1994

The interaction of colloidal metals with erythrocytes.

The interactions of citrate reduced colloids (Ag, Au, and Bi) with intact erythrocytes and erythrocyte lysate have been studied by 1H spin echo NMR. Silver colloid is observed to induce cellular depletion of cytosolic glutathione and bismuth colloid induces cytosolic glutathione oxidation in the intact cell. In comparison, there is no detectable effect with gold colloid. With red cell lysate the three colloids all remove glutathione from the spectrum. The metal salts AgNO3 and NaAuCl4 both oxidize intracellular glutathione to diglutathione whereas BiO(NO3) has no effect. Thus colloidal preparations have a different reactivity to their parent metal salts. The differences observed between the three types of colloids (silver, gold, and bismuth) are unique to the colloids studied. None of the colloids studied were biologically inert in the erythrocyte model used.

Bismuth↗
PubMed1985

Cloning and DNA sequence of a plasmid-determined citrate utilization system in Escherichia coli.

The citrate utilization determinant from a large 200-kilobase (kb) naturally occurring plasmid was previously cloned into the PstI site of plasmid vector pBR325 creating the Cit+ tetracycline resistance plasmid pWR61 (15 kb). Tn5 insertion mutagenesis analysis of plasmid pWR61 limited the segment responsible for citrate utilization to a 4.8-kb region bordered by EcoRI and PstI restriction nuclease sites. The 4.8-kb fragment was cloned into phage M13, and the DNA sequence was determined by the dideoxyribonucleotide method. Within this sequence was a 1,296-base-pair open reading frame with a preceding ribosomal binding site. The 431-amino-acid polypeptide that could be translated from this open reading frame would be highly hydrophobic. A second long open reading frame with the potential of encoding a 379-amino-acid polypeptide preceded the larger open reading frame. Portions of the 4.8-kb fragment were further subcloned with restriction endonucleases BglII and BamHI, reducing the minimum size needed for a citrate-positive phenotype to a 1.9-kb BamHI-BglII fragment (which includes the coding region for the 431-amino-acid polypeptide, but only the distal 2/3 of the reading frame for the 379-amino-acid polypeptide). Citrate utilization results from a citrate transport activity encoded by the plasmid. With the 4.8-kb fragment (as with larger fragments) the citrate transport activity was inducible by growth on citrate. On transfer from glucose, succinate, malate, or glycerol medium to citrate medium, the Cit+ Escherichia coli strains showed a delay of 36 to 48 h before growth.

Amino Acid Sequence↗
PubMed1991

Ultrastructural localization of argyrophilic substances in diffuse plaques of Alzheimer-type dementia demonstrated by methenamine silver staining.

The ultrastructure of argyrophilic substances in diffuse plaques of an Alzheimer-type dementia brain was examined using methenamine silver (MS) electron microscopy with the pre-embedding method. Electron-dense substances, which were sparse aggregations of bundle-like structures with silver granules, were disseminated in the diffuse plaques. Comparison of serial MS and routine ultrathin sections revealed that diffuse plaques usually show scattered bundles of amyloid fibrils or amorphous materials, or both, between indistinct cell process membranes. Some of these processes were identified as astrocytic or dendritic in origin. A few degenerative neurites were frequently noted in large silver-positive areas but never in small areas. These findings suggest that the appearance of amyloid fibrils and amorphous materials between certain cell processes is a very early morphological change in the process of senile plaque formation.

Aged↗