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At least 163 records · Page 9Linked to original sources
PubMed1983

Ultrastructural localization of DNA in tissue culture cell nuclei by means of enzyme-gold and autoimmune sera-protein A-gold techniques.

The post-embedding localization of DNA was investigated in cell nuclei by means of DNase I-gold and autoimmune sera-protein A-gold techniques. Using the former technique, gold particles were found mainly over euchromatin, nucleoli exhibit occasionally high labeling. In the latter technique, the use of the serum binding dsDNA confined the label mainly to condensed chromatin.

Actins↗
PubMed1977

The gold solder, gold alloy interface.

With soldering the physical properties of the basis metal must be maintained and a minimum of molten metal is used. An examination of joints in 17 gauge platinized gold wire is made with 18 k gold solder following quenching immediately after flow and cooling in air; there is a widening of grain boundaries and intergranulation penetration in the latter method. A comparison with the cast gold joint is made. Some inclusions were noted.

Dental Soldering↗
PubMed2004

Synthesis of size-tunable gold nanoparticles by poly(vinylphenol) and electrostatic multilayer deposition of the gold-poly(vinylphenol) nanocomposites.

Water-dispersible gold nanoparticles (GNPs) were synthesized by the polymer in situ redox technique at room temperature using poly(4-vinylphenol) (PVPh) as a simultaneous template/stabilizer and reducing agent. GNPs were characterized by its surface plasmon absorption peak at 536 nm. The average particle size of the gold-poly(4-vinylphenol) (Au-PVPh) nanocomposites decreases with increase in the ratio of PVPh to gold salt. A uniform multilayer of Au-PVPh nanocomposites was fabricated on glass surface by electrostatic layer-by-layer assembly using poly(diallyldimethylammonium chloride) (PDDAC) as the oppositely charged polycation. UV-vis spectra of the consecutive multilayer showed that the absorbance at 549 nm corresponding to GNPs increases linearly with the number of Au-PVPh nanocomposite layers, indicating regular bilayer growth.

Cations↗
PubMed1992

Immunomodulatory effects of therapeutic gold compounds. Gold sodium thiomalate inhibits the activity of T cell protein kinase C.

Previous studies have shown that the gold compounds, gold sodium thiomalate (GST) and auranofin (AUR), which are effective in the treatment of rheumatoid arthritis, inhibit functional activities of a variety of cells, but the biochemical basis of their effect is unknown. In the current studies, human T cell proliferation and interleukin 2 production by Jurkat cells were inhibited by GST or AUR at pharmacologically relevant concentrations. Because it has been documented that protein kinase C (PKC) is involved in T cell activation, the capacity of gold compounds to inhibit PKC partially purified from Jurkat cells was assayed in vitro. GST was found to inhibit PKC in a dose-dependent manner, but AUR caused no significant inhibition of PKC at pharmacologically relevant concentrations. The inhibitory effect of GST on PKC was abolished by 2-mercaptoethanol. To investigate the effect of GST on the regulation of PKC in vivo, the levels of PKC activity in Jurkat cells were examined. Cytosolic PKC activity decreased slowly in a concentration- and time-dependent manner as a result of incubation of Jurkat cells with GST. To ascertain whether GST inhibited PKC translocation and down-regulation, PKC activities associated with the membrane and cystosolic fractions were evaluated after phorbol myristate acetate (PMA) stimulation of GST incubated Jurkat cells. Translocation of PKC was markedly inhibited by pretreatment of Jurkat cells with GST for 3 d, but the capacity of PMA to down-regulate PKC activity in Jurkat cells was not altered by GST preincubation. The functional impact of GST-mediated downregulation of PKC in Jurkat cells was examined by analyzing PMA-stimulated phosphorylation of CD3. Although GST preincubated Jurkat cells exhibited an increased density of CD3, PMA-stimulated phosphorylation of the gamma chain of CD3 was markedly inhibited. Specificity for the inhibitory effect of GST on PKC was suggested by the finding that GST did not alter the mitogen-induced increases in inositol trisphosphate levels in Jurkat cells. Finally, the mechanism of the GST-induced inhibition of PKC was examined in detail, using purified PKC subspecies from rat brain. GST inhibited type II PKC more effectively than type III PKC, and also inhibited the enzymatic activity of the isolated catalytic fragment of PKC. The inhibitory effect of GST on PKC activity could not be explained by competition with phospholipid or nonspecific interference with the substrate. These data suggest that the immunomodulatory effects of GST may result from its capacity to inhibit PKC activity.

Auranofin↗
PubMed2003

Sensing phenothiazine drugs at a gold electrode co-modified with DNA and gold nanoparticles.

DNA and gold nanoparticles are co-immobilized at a gold electrode through elaborate self-assembly processes. This configuration has proven to be useful as a sensor for phenothiazine drugs, taking advantage of the well-known, relatively large surface area of gold nanoparticles and the strong intercalation between dsDNA and phenothiazine drugs. This modified electrode has demonstrated good sensitivity and stability towards the oxidation of two model phenothiazine drugs: promethazine and chlorpromazine. A linear dependence between the concentration of phenothiazine drugs and the peak current is observed, with a concentration range of 2.0 x 10(-5)-1.6 x 10(-4) M and 1.0 x 10(-5)-1.2 x 10(-4) M, and a detection limit of 1.0 x 10(-5) M and 7.0 x 10(-6) M, for promethazine and chlorpromazine, respectively.

Animals↗
PubMed1988

The effect of intraperitoneally administered gold thioglucose on growth, food consumption and accumulation of gold in various organs of the chicken (Gallus domesticus).

1. Gold thioglucose (GTG) was intraperitoneally injected into 10-day-old male and female chickens in a dose of 0, 0.2, 0.4 or 0.8 mg per gram of body wt. 2. Mortality of the GTG-injected chickens was 100% and 25% for doses of 0.8 and 0.4 mg/gBW respectively, in both sexes and 25% for a dose of 0.2 mg in females, which were all found within 14.5 hr after the GTG treatment. 3. Body weight gain, food consumption and food efficiency of surviving chickens for 23 days after the GTG injection were not affected by GTG in spite of dose level. 4. Gold detected in blood, heart, liver, gallbladder, spleen, proventriculus, gizzard, duodenum, kidney, pectoral muscle, small intestine, lung and brain of the dead chickens accumulated most highly in heart and followed by spleen, but in the surviving chicken a little gold was only found in liver, spleen and kidney of some GTG-treated chickens.

Animals↗
PubMed1985

Dual ultrastructural localization of two neurotransmitter-related antigens: colloidal gold-labeled neurophysin-immunoreactive supraoptic neurons receive peroxidase-labeled glutamate decarboxylase- or gold-labeled GABA-immunoreactive synapses.

To study the morphological substrate for interaction between two chemically distinct neuronal types, two double ultrastructural immunolabeling strategies were employed. In the first, two different electron-dense markers were used to examine simultaneously two different neurotransmitter-related antigens in the hypothalamic supraoptic nucleus in the same thin section. Results obtained with the first method were confirmed with a second approach based on postembedding immunostaining of alternate serial thin sections with different antisera. Antiserum against glutamate decarboxylase, the enzyme responsible for the synthesis of the inhibitory amino acid transmitter gamma-aminobutyric acid (GABA), or antisera against GABA, was used to localize immunoreactive axons in the hypothalamic supraoptic nucleus. With light microscopy, glutamate decarboxylase- and GABA-immunoreactive axon terminals immunostained with peroxidase were found arborizing throughout all areas of the nucleus; terminal boutons were found adjacent to unlabeled somata within the nucleus. Cells containing immunoreactive oxytocin, vasopressin, and neurophysin were localized with peroxidase. Glutamate decarboxylase-immunoreactive axons stained with peroxidase prior to embedding in plastic were demonstrated to contact neurons which contained vesicles immunostained with neurophysin antiserum by a post-embedding immunocytochemical procedure which used immunoglobulins or protein A adsorbed to colloidal gold as a second ultrastructural marker. Quantitative evaluation of post-embedding staining with colloidal gold using a neurophysin primary antiserum indicated a specific antigen localization in neurosecretory vesicles. A critical factor in this double-labeling paradigm was that immunological reagents used in the second series did not cross-react with those used in the first series, regardless of the species of origin of antisera. To provide further verification of GABAergic synapses on neurophysin-containing neurons, alternate serial ultrathin sections were stained with colloidal gold using antisera against either neurophysin or GABA; boutons immunoreactive for GABA made synaptic contact with supraoptic neurons containing neurophysin immunoreactivity. Converging results obtained with these two procedures indicate that GABAergic axons synapse directly on neurons containing oxytocin or vasopressin in the rat hypothalamic supraoptic nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1978

[Cerebro-organic syndrome during gold therapy. Possible correlation between gold therapy in chronic seronegative polyarthritis and the appearance of a cerebro-organic syndrome. A case contribution].

In this article the possible relationship between gold therapy of a chronic seronegative polyarthritis and the appearance of a cerebro-organic syndrome in a 56-year-old postmenopausal woman will be discussed. We take into consideration the basic illness, the biography, the hormonal situation, the simultaneous chloroquin therapy and the overdosage of the gold drug. After a careful consideration of the different diagnostical possibilities following the above mentioned factors, not only a temporal but also a causative relationship of gold therapy and cerebro-organic syndrome seems to be possible.

Arthritis, Rheumatoid↗
PubMed2004

Catalysis by supported gold: correlation between catalytic activity for CO oxidation and oxidation states of gold.

X-ray absorption near-edge spectra and temperature-programmed oxidation and reduction data demonstrate that Au(I) and Au(0) are both present in working MgO-supported gold catalysts for CO oxidation. EXAFS data indicate gold clusters with essentially the same average diameter (about 30 A) in each catalyst sample. Thus, the results provide no evidence of an effect of gold cluster size on the catalytic activity, but both the catalytic activity and the surface concentration of Au(I) were found to decrease with increasing CO partial pressure (as Au(0) was increasingly formed), demonstrating that the catalytic sites incorporate Au(I).

Journal Article↗
PubMed2004

Spontaneous assembly of organic thiocyanates on gold sufaces. Alternative precursors for gold thiolate assemblies.

Thiolate self-assembly on gold has proven to be a valuable technique for assembling monolayers on a wide variety of substrates. However, the oxidative instability of the thiols, especially aromatic thiols and alpha,omega-dithiols, presents several difficulties. Shown here is that thiocyanates, easily synthesized stable thiol derivatives, can be directly assembled on gold surfaces with no auxiliary reagents required. Assembly is complete in 24 h and leaves a similar gold thiolate structure as seen in typical thiol self-assembled monolayers.

Journal Article↗
PubMed2005

Structural changes of the gold-support interface during CO oxidation catalyzed by mononuclear gold complexes bonded to zeolite NaY: evidence from time-resolved X-ray absorption spectroscopy.

Mononuclear gold complexes synthesized from AuIII(CH3)2(acac) in zeolite NaY were characterized by time-resolved X-ray absorption spectroscopy and infrared spectroscopy as they catalyzed CO oxidation at 298 K and 760 Torr in flow systems. Initial contact with a CO + O2 mixture led to the rapid formation of cationic gold complexes in which Au was bonded to approximately two zeolite O atoms, on average. Further contact with CO + O2 led to breaking of an Au-surface oxygen bond, giving a gold carbonyl anchored to approximately one O atom. The process was reversed in the absence of CO and O2.

Journal Article↗
PubMed2005

The AFM measured force required to rupture the dithiolate linkage of thioctic acid to gold is less than the rupture force of a simple gold-alkyl thiolate bond.

We show with atomic force microscopy that thioctic acid, a spatially constrained system with two sulfur linkages to gold, is less stable to tensile stress than a thiolate with a single attachment to gold. The force required to remove the dithiolate-linked thioctic acid was 0.31+/-0.13 nN, whereas the force required to remove a simple thiolate from the gold substrate was 1.05+/-0.29 nN. These results suggest that SAMs of densely packed or polypodal thiols may be substantially less stable under tensile stress than previously recognized and that the additional thiolate linkages may not only fail to increase the overall strength of attachment but could actually reduce it.

Journal Article↗
PubMed2000

Analysis of rat plasma proteins desorbed from gold and methyl- and hydroxyl-terminated alkane thiols on gold surfaces.

It is believed that adsorbed blood or plasma components, such as water, peptides, carbohydrates and proteins, determine key events in the concomitant inflammatory tissue response close to implants. The aim of the present study was to develop a procedure for the collection and analysis of minor amounts of proteins bound to solid metal implant surfaces. The combination of a sodium dodecyl sulfate washing method coupled with a polyacylamide gel electrophoretic protein separation technique (SDS-PAGE), Western blot and image analysis enabled the desorption, identification and semiquantification of specific proteins. The analyzed proteins were albumin, immunoglobulin G, fibrinogen and fibronectin. Concentration procedures of proteins were not required with this method despite the small area of the test surfaces. The plasma proteins were adsorbed to pure gold and hydroxylated and methylated gold surfaces, which elicit different tissue responses in vivo and plasma protein adsorption patterns in vitro. The image analysis revealed that the pure gold surfaces adsorbed the largest amount of total and specific proteins. This is in accordance with previous ellipsometry/antibody experiments in vitro. Further, the principles described for the protein analysis can be applied on implant surfaces ex vivo.

Journal Article↗
PubMed2004

Observation of Au2H- impurity in pure gold clusters and implications for the anomalous Au-Au distances in gold nanowires.

Au(2)H(-) was recognized and confirmed as a minor contamination to typical photoelectron spectra of Au(2) (-), produced by laser vaporization of a pure Au target using an ultrahigh purity helium carrier gas. The hydrogen source was shown to be from trace H impurities present in the bulk gold target. Carefully designed experiments using H(2)- and D(2)-seeded helium carrier gas were used to study the electronic structure of Au(2)H(-) and Au(2)D(-) using photoelectron spectroscopy and density functional calculations. Well-resolved photoelectron spectra with vibrational resolution were obtained for Au(2)H(-) and Au(2)D(-). Two isomers were observed both experimentally and theoretically. The ground state of Au(2)H(-) turned out to be linear with a terminal H atom [Au-Au-H](-) ((1)A(1),C(infinity v)), whereas a linear [Au-H-Au](-) ((1)A(1),D(infinity h)) structure with a bridging H atom was found to be a minor isomer 0.6 eV higher in energy. Calculated electron detachment energies for both isomers agree well with the experimental spectra, confirming their existence in the cluster beam. The observation and confirmation of H impurity in pure gold clusters and the 3.44 A Au-Au distance in the [Au-H-Au](-) isomer presented in the current work provide indirect experimental evidence that the anomalous 3.6 A Au-Au distances observed in gold nanowires is due to an "invisible" hydrogen impurity atom.

Journal Article↗
PubMed2006

Second-harmonic spectroscopy of surface immobilized gold nanospheres above a gold surface supported by self-assembled monolayers.

We have investigated linear and nonlinear optical properties of surface immobilized gold nanospheres (SIGNs) above a gold surface with a gap distance of a few nanometers. The nanogap was supported by amine or merocyanine terminated self-assembled monolayers (SAMs) of alkanethiolates. A large second-harmonic generation (SHG) was observed from the SIGN systems at localized surface plasmon resonance condition. The maximum enhancement factor of SHG intensity was found to be 3 x 10(5) for the SIGN system of nanospheres 100 nm in diameter with a gap distance of 0.8 nm. The corresponding susceptibility was estimated to be chi((2))=750 pmV (1.8 x 10(-6) esu). In the SIGN system supported with the merocyanine terminated SAMs, the SHG response was also resonant to the merocyanine in the nanogap. It was found that the SHG response of the SIGN systems is strongly frequency dependent. This leads us to conclude that the large chi((2)) is caused by enhanced electric fields at the localized surface plasmon resonance condition and is not due to an increase of the surface susceptibility following from the presence of the gold nanospheres. The observed SHG was consistent with the theoretical calculations involving Fresnel correction factors, based on the quasistatic approximation.

Journal Article↗
PubMed1983

Failure of sodium aurothiomalate and triethyl phosphine gold to cause renal tubular injury in rheumatoid arthritis: implications for the aetiology of gold-related nephropathy.

The urinary excretion of two proteins, B-2-microglobulin (beta 2M) and N-acetyl-B-D-glucosaminidase (NAG) was measured in 25 patients with rheumatoid arthritis (RA) on nonsteroidal anti-inflammatory drugs (NSAID). Although beta 2M excretion was normal NAG excretion was raised. As NAG excretion by a group of osteoarthritis patients receiving similar doses of NSAIDs was normal, it is concluded that rheumatoid disease per se may be associated with mild renal tubular dysfunction. Twelve of the above 25 patients were then given oral triethylphosphine-gold (auranofin) 6 mg daily and urinary beta 2M and NAG were measured after 6 months' treatment. Urinary excretion of beta 2M and NAG was also measured in 13 patients with RA established on intramuscular sodium aurothiomalate (MGST) and NSAIDs. Neither auranofin nor myocrisin were found to further significantly increase beta 2M and NAG excretion. These results suggest that gold compounds are not toxic to renal tubular epithelium.

Acetylglucosaminidase↗
PubMed1979

Gold and thiol compounds in the treatment of rheumatoid arthritis: excretory fate and tissue distribution of thiomalate in relation to gold after administration of myocrisin (auro-thiomalate).

Double isotope-labelled auro thiomalate (Au195-C14-thiomalate) has been administered to mice and rats, and the excretory fate and tissue distribution have been studied. The results show that the gold and the thiomalate separate in vivo resulting in protein-bound gold and release of free thiomalate. About half of this thiol is excreted in the urine during the first day and the remaining half is taken up by the tissues. Thiomalate penetrates cellular membranes poorly, but is able to interact slowly with proteins (mixed disulphide formation). Part of the thiomalate which remains in the body is membrane bound. In contrast to penicillamine little thiomalate remains in circulation a few hours after administration. Gas chromatography--mass spectrometry has been used to search for the presence of free thiomalate in rheumatoid arthritis patients on Myocrisin (auro thiomalate) therapy. Thiomalate was found in their urine, but not in serum and synovial fluid 20 hours after administration. As thiomalate is released in the body after administration of Myocrisin. the question arises whether this thiol, like penicillamine, may have a beneficial effect in the treatment of rheumatoid arthritis.

Animals↗
PubMed1977

Comparative ultrastructural morphology of aurosomes produced by colloidal gold and soluble gold salts.

Intra-articular administration of colloidal gold produced aurosomes which contained spherical electron-dense granules and also often some very fine electron-dense particles. Intra-articular administration of aurothioglucose produced aurosomes of a morphology similar to that reported to occur after administration of sodium aurothiomalate. These aurosomes produced by soluble gold salts are characterised by particle and granule-studded membranous formations which present in profile as rod-like and curled filamentous structures. On the basis of morphological differences two types of aurosomes should be recognised, the "Type I or granular aurosome" and the "Type II or membranous aurosome".

Animals↗