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At least 775 records · Page 43Linked to original sources
PubMed2003

A luminescent supermolecule with gold(I) quinoline-8-thiolate: crystal structure, spectroscopic and photophysical properties.

The trinuclear complex [(8-QNS)(2)Au(AuPPh(3))(2)].BF(4) (8-QNS = quinoline-8-thiolate), with intramolecular gold(I)...gold(I) distances of 3.0952(4) and 3.0526(3) A, is aggregated to form a novel hexanuclear supermolecule, ([(8-QNS)2(Au(AuPPh3)2])2.(BF4)2, via a close intermolecular gold(I)...gold(I) contact of 3.1135(3) A. The beautiful hexanuclear supermolecule has an inversion center, and the six metal centers can be viewed as roughly coplanar. Six gold(I) ions are embedded in an ellipse and surrounded by 4 quinoline and 12 phenyl rings. The title compound shows interesting spectroscopic and luminescence properties dependent on the solvent polarity; i.e., it emits at ca. 440 and 636 nm in CH(2)Cl(2) and only at ca. 450 nm in CH(3)CN. The long-lived emission at ca. 636 nm (16.2 micros) in CH(2)Cl(2) is quenched by polar solvents such as CH(3)CN and CH(3)OH with quenching constants as 1.00 x 10(5) and 3.03 x 10(4) s(-1) M(-1), respectively, which is suggested to be related to the presence or absence of gold(I)...gold(I) interactions due to scrambling of the [AuPPh(3)]+ units, isolobal to H+.

Journal Article↗
PubMed2002

Activation of gold on titania: adsorption and reaction of SO(2) on Au/TiO(2)(110).

Synchrotron-based high-resolution photoemission and first-principles density-functional slab calculations were used to study the interaction of gold with titania and the chemistry of SO(2) on Au/TiO(2)(110) surfaces. The deposition of Au nanoparticles on TiO(2)(110) produces a system with an extraordinary ability to adsorb and dissociate SO(2). In this respect, Au/TiO(2) is much more chemically active than metallic gold or stoichiometric titania. On Au(111) and rough polycrystalline surfaces of gold, SO(2) bonds weakly and desorbs intact at temperatures below 200 K. For the adsorption of SO(2) on TiO(2)(110) at 300 K, SO(4) is the only product (SO(2) + O(oxide) --> SO(4,ads)). In contrast, Au/TiO(2)(110) surfaces (theta;(Au) < or = 0.5 ML) fully dissociate the SO(2) molecule under identical reaction conditions. Interactions with titania electronically perturb gold, making it more chemically active. Furthermore, our experimental and theoretical results show quite clearly that not only gold is perturbed when gold and titania interact. The adsorbed gold, on its part, enhances the reactivity of titania by facilitating the migration of O vacancies from the bulk to the surface of the oxide. In general, the complex coupling of these phenomena must be taken into consideration when trying to explain the unusual chemical and catalytic activity of Au/TiO(2). In many situations, the oxide support can be much more than a simple spectator.

Journal Article↗
PubMed2003

Gold nanoparticles deposited on SiO2/Si100: correlation between size, electron structure, and activity in CO oxidation.

Nanosize gold particles were prepared by Ar(+) ion implantation of 10-nm thick gold film deposited onto a SiO(2)/Si(100) wafer possessing no catalytic activity in the CO oxidation. Along with size reduction the valence band of the gold particles and the actual size were determined by ultraviolet- and X-ray photoelectron spectroscopy (UPS, XPS) and by transmission electron microscopy (TEM) as well as atomic force microscopy (AFM), respectively. The catalytic activity was determined in the CO oxidation. Energy distribution of the photoelectrons excited from 5d valence band of gold was strongly affected by Ar(+) implantation. This variation was interpreted by the redistribution of the valence band density of states (DOS). The intrinsic catalytic activity of the gold particles increased with decreasing size. When an Au/FeO(x) interface was created by FeO(x) deposition on large gold nanoparticles, a significant increase in the rate of the CO oxidation was observed. These data can be regarded as an experimental verification of the correlation between the catalytic activity and valence band density of states of gold.

Journal Article↗
PubMed2005

Chemiluminescent reactions induced by gold nanoparticles.

The reaction of gold nanoparticles with a potassium periodate-sodium hydroxide-carbonate system undergoes chemiluminescence with three emission bands at 380-390, 430-450, and 490-500 nm, respectively. It was found that the light intensity increased linearly with the concentration of the gold nanoparticles, and the CL intensity increased dramatically when the citrate ions on the nanoparticle surface were replaced by SCN(-). The shape, size, and oxidation state of gold nanoparticles after the chemiluminescent reaction were characterized by UV-visible absorption spectrometry, transmission electron microscopy (TEM), and X-ray photoelectron spectrometry (XPS). Gold nanoparticles are supposed to function as a nanosized platform for the observed chemiluminescent reactions. A chemiluminescent mechanism has been proposed in which the interaction between free CO(3)(*-) and O(2)(*-) radicals generated by a KIO(4)-NaOH-Na(2)CO(3) system and gold nanoparticles results in the formation of emissive intermediate gold(I) complexes, carbon dioxide dimers, and singlet oxygen molecular pairs on the surface of the gold nanoparticles. This work is not only of great importance for gaining a better understanding of the unique optical and surface properties and chemical reactivity of nanoparticles but also of great potential for developing new biosensing and immunolabeling technologies.

Journal Article↗
PubMed2005

Effect of argon plasma treatment on surface-enhanced Raman spectroscopy of polypyrrole deposited on electrochemically roughened gold substrates.

In this work, polypyrrole (PPy) films were electrodeposited on electrochemically roughened gold substrates modified by argon plasma treatment. First, a gold substrate was roughened by a triangular-wave oxidation-reduction cycle (ORC) in an aqueous solution containing 0.1 N HCl. Then the roughened gold substrate was further treated by argon plasma. Encouragingly, the surface-enhanced Raman scattering (SERS) spectroscopy of polypyrrole electrodeposited on this roughened gold substrate modified by argon plasma treatment exhibits a higher intensity by 8-fold, as compared with the SERS of PPy electrodeposited on an unmodified roughened gold substrate. Meanwhile, the electropolymerization for pyrrole monomers occurring on the modified roughened gold substrate is easier. Also, the nucleation and growth of electropolymerization of pyrrole monomers on the modified and unmodified gold substrates are different.

Journal Article↗
PubMed2005

Electrochemical growth of two-dimensional gold nanostructures on a thin polypyrrole film modified ITO electrode.

Two-dimensional gold nanostructures have been fabricated by electrochemical deposition of gold nanoparticles onto indium tin oxide (ITO) glass substrate modified with thin polypyrrole film. By controlling the electrodeposition conditions, gold nanoparticles with dendritic rod, sheet, flower-like (consisting of staggered nanosheets), and pinecone-like structures were generated. The flower-like gold nanoparticles showed high catalytic activity on electrochemical reduction of oxygen, and its activity was measured to be approximately 25 times that of gold pinecones and 10(4) times that of gold nanosheets in terms of gold weight. The pinecone-like nanoparticles can form a compact film with nano-/microscale binary structure like a lotus leaf surface. After modification with n-dodecanethiol, the surface showed superhydrophobic properties with a water contact angle of 153.4 degrees and a tilt angle of 4.4 degrees (5 microL droplet).

Journal Article↗
PubMed2005

Gold nanoshells on polystyrene cores for control of surface plasmon resonance.

A method is presented for synthesizing core-shell structures consisting of monodisperse polystyrene latex nanospheres as cores and gold nanoparticles as shells. Use of polystyrene spheres as the core in these structures is advantageous because they are readily available commercially in a wide range of sizes, and with dyes or other molecules doped into them. Gold nanoparticles, ranging in size from 1 to 20 nm, are prepared by reduction of a gold precursor with sodium citrate or tetrakis(hydroxymethyl)phosphonium chloride (THPC). Carboxylate-terminated polystyrene spheres are functionalized with 2-aminoethanethiol hydrochloride (AET), which forms a peptide bond with carboxylic acid groups on their surface, resulting in a thiol-terminated surface. Gold nanoparticles then bind to the thiol groups to provide up to about 50% coverage of the surface. These nanoparticles serve as seeds for growth of a continuous gold shell by reduction of additional gold precursor. The shell thickness and roughness can be controlled by the size of the nanoparticle seeds as well as by the process of their growth into a continuous shell. By variation of the relative sizes of the latex core and the thickness of the gold overlayer, the plasmon resonance of the nanoshell can be tuned to specific wavelengths across the visible and infrared range of the electromagnetic spectrum, for applications ranging from the construction of photonic crystals to biophotonics. The position and width of the plasmon resonance extinction peak are well-predicted by extended Mie scattering theory.

Journal Article↗
PubMed2005

X-ray-induced production of gold nanoparticles on a SiO(2)/Si system and in a poly(methyl methacrylate) matrix.

Prolonged exposure to X-rays of HAuCl(4) deposited from an aqueous solution onto a SiO(2)/Si substrate or into a poly(methyl methacrylate) (PMMA) matrix induces reduction of the Au(3+) ions to Au(0) and subsequent nucleation to gold nanoclusters as recorded by X-ray photoelectron spectroscopy. The corresponding major oxidation product is determined as chlorine {HAuCl(4)(ads) + X-rays --> Au(ads) + (3/2)Cl(2)(ads) + HCl(ads)}, which is initially adsorbed onto the surface but eventually diffuses out of the system into the vacuum. The reduced gold atoms aggregate (three-dimensionally) into gold nanoclusters as evidenced by the variation in the binding energy during X-ray exposure, which starts as 1.3 eV but approaches a value that is 0.5 eV higher than that of the bulk gold. The disappearance of the oxidation product (Cl2p signal) and the growth of the nanoclusters (related to the measured binding energy difference between the Si2p of the oxide and Au4f of the reduced gold) exhibit first-order kinetics which is approximately 3 times slower than the reduction of Au(3+), indicating that both of the former processes are diffusion controlled. Similarly, gold ions incorporated into PMMA can also be reduced and aggregated to gold nanoclusters using 254 nm deep UV irradiation in air evidenced by UV-vis-NIR absorption spectrocopy.

Journal Article↗
PubMed2006

Uniformly sized gold nanoparticles derived from PS-b-P2VP block copolymer templates for the controllable synthesis of Si nanowires.

A monolayer of gold-containing surface micelles has been produced by spin-coating solution micelles formed by the self-assembly of the gold-modified polystyrene-b-poly(2-vinylpyridine) block copolymer in toluene. After oxygen plasma removed the block copolymer template, highly ordered and uniformly sized nanoparticles have been generated. Unlike other published methods that require reduction treatments to form gold nanoparticles in the zero-valent state, these as-synthesized nanoparticles are in form of metallic gold. These gold nanoparticles have been demonstrated to be an excellent catalyst system for growing small-diameter silicon nanowires. The uniformly sized gold nanoparticles have promoted the controllable synthesis of silicon nanowires with a narrow diameter distribution. Because of the ability to form a monolayer of surface micelles with a high degree of order, evenly distributed gold nanoparticles have been produced on a surface. As a result, uniformly distributed, high-density silicon nanowires have been generated. The process described herein is fully compatible with existing semiconductor processing techniques and can be readily integrated into device fabrication.

Journal Article↗
PubMed2006

In-situ infrared study of the adsorption and oxidation of oxalic acid at single-crystal and thin-film gold electrodes: a combined external reflection infrared and ATR-SEIRAS approach.

The adsorption and oxidation of oxalic acid at gold electrodes were studied by in-situ infrared spectroscopy. External reflection experiments carried out with gold single-crystal electrodes were combined with internal reflection (ATR-SEIRAS) experiments with gold thin-film electrodes. These gold thin films, with a typical thickness of ca. 35 nm, were deposited on silicon substrates by argon sputtering. As previously reported for evaporated gold films, the voltammetric curves obtained in sulfuric acid solutions after electrochemical annealing show typical features related to the presence of wide bidimensional (111) domains with long-range order. The in-situ infrared data collected for solutions of pH 1 confirmed the potential-dependent adsorption of either oxalate (Au(100)) or a mixture of bioxalate and oxalate (Au(111), Au(110), and gold thin films) anions in a bidentate configuration. The better signal-to-noise ratio associated with the SEIRA effect in the case of the gold thin-film electrodes allows the observation of the carbonyl band for adsorbed bioxalate that was not detected in the external reflection experiments. Besides, additional bands are observed between 2000 and 3000 cm(-)(1) that can be tentatively related to the formation of hydrogen bonds between neighboring bioxalate anions. The intensities of these bands decrease with increasing solution pH values, disappearing for pH 3 solutions in which adsorbed oxalate anions are the predominant species. The analysis of the intensities of the nu(s)(O-C-O) and nu(C-OH) + delta(C-O-H) bands for adsorbed oxalate and bioxalate, respectively, suggests that the pK(a) for the surface equilibrium between these species is significantly lower than that for the solution equilibrium.

Journal Article↗
PubMed2004

Governing the oxidative addition of iodine to gold(I) complexes by ligand tuning.

While several gold(I) complexes of the type (L)AuX (X = Cl, Br) are known to undergo oxidative addition of elemental chlorine and bromine (X2), respectively, to give the corresponding gold(III) complexes (L)AuX3, the addition of iodine to (iodo)gold(I) compounds is strongly ligand-dependent, suggesting a crucial threshold in the oxidation potentials. A systematic investigation of this particular oxidative addition of iodine using a large series of tertiary phosphines as ligands L has shown that both electronic and steric effects influence the course of the reaction. The reactions were followed by 31P NMR spectroscopy and the products crystallized from dichloromethane-pentane solutions. Complexes with small triakylphosphines (PMe3, PEt3) are readily oxidized, while those with more bulky ligands (PiPr3, PtBu3) are not. With L taken from the triarylphosphine series [PPh3, P(2-Tol)3, P(3-Tol3), P(4-Tol)3] no oxidation takes place at all, but mixed alkyl/aryl-phosphines [PMenPh(3-n)] induce oxidation for n = 3 and 2, but not for n = 1 and 0. However, in cases where no oxidation of the gold atoms is observed, the synthons may crystallize as adducts with molecular iodine of the polyiodide type instead, which have an iodine rich stoichiometry. This fact explains inconsistent reports in the literature. The metal atoms in (L)AuI coordination compounds with L representing a tri(heteroaryl)phosphine [P(2-C4H3E)3, E = O, S], a phosphite [P(OR)3] or a trialkenylphosphine [PVi3] are all not subject to oxidative addition of iodine. The dinuclear complex of the ditertiary phosphine Ph2PCH2PPh2, (dppm)(AuI)2, gives an iodine adduct (without oxidation of the metal atoms), but with 1,2-Ph2P(C6H4)PPh2(dppbe) an ionic complex [(dppbe)AuI2]+I3- with a chelated gold(III) centre is obtained. The gold(I) bromide complexes with tertiary phosphines are readily oxidized by bromine to give the corresponding gold(III) tribromide complexes, as demonstrated for (BzMePhP)AuBr and (Ph3P)AuBr. With (dppm)(AuBr)2 the primary product with mixed oxidation states was also isolated: (dppm)AuBr(AuBr3). The crystal structures of the following representative examples and reference compounds have been determined: (Me3P)AuI3, (Me2PhP)AuI3, (iPr3P)AuI.1.5I2, (Ph3P)AuI.I2, [[(2-Tol)3P]AuI]2.I2, [(2-Tol)3P]AuI, (dppm)(AuX)2 (with X = Br, I), (dppm)AuBr(AuBr3) and [(dppbe)AuI2]+I3-. The structures are discussed focusing on the steric effects. It appears that e.g. the reluctance of (Ph3P)AuI to add I2 is an electronic effect, while that of (iPr3P)AuI has its origin in the steric influence of the ligand.

Journal Article↗
PubMed2006

Synthesis, structures and reactions of cyclometallated gold complexes containing (2-diphenylarsino-n-methyl)phenyl (n = 5, 6).

Reaction of (C6H3-2-AsPh2-n-Me)Li (n = 5 or 6) with [AuBr(AsPh3)] at -78 degrees C gives the corresponding cyclometallated gold(I) complexes [Au2[(mu-C6H3-n-Me)AsPh2]2] [n = 5, (1); n = 6, (9)]. 1 undergoes oxidative addition with halogens and with dibenzoyl peroxide to give digold(II) complexes [Au2X2[(mu-C6H3-5-Me)AsPh2]2] [X = Cl (2a), Br (2b), I (2c) and O2CPh (3)] containing a metal-metal bond between the 5d9 metal centres. Reaction of 2a with AgO2CMe or of 3 with C6F5Li gives the corresponding digold(II) complexes in which X = O2CMe (4) and C6F5 (6), respectively. The Au-Au distances increase in the order 4 < 2a < 2b < 2c < 6, following the covalent binding tendency of the axial ligand. Like the analogous phosphine complexes, 2a-2c and 6 in solution rearrange to form C-C coupled digold(I) complexes [Au2X2[mu-2,2-Ph2As(5,5-Me2C6H3C6H3)AsPh2]] [X = Cl (5a), X = Br (5b), X = I (5c) and C6F5 (7)] in which the gold atoms are linearly coordinated by As and X. In contrast, the products of oxidative additions to 9 depend markedly on the halogens. Reaction of 9 with chlorine gives the gold(I)-gold(III) complex, [ClAu[mu-2-Ph2As(C6H3-6-Me)]AuCl[(6-MeC6H3)-2-AsPh2]-kappa2As,C] (10), which contains a four-membered chelate ring, Ph2As(C6H3-6-Me), in the coordination sphere of the gold(III) atom. When 10 is heated, the ring is cleaved, the product being the digold(I) complex [ClAu[mu-2-Ph2As(C6H3-6-Me)]Au[AsPh2(2-Cl-3-Me-C6H3)]] (11). Reaction of 9 with bromine at 50 degrees C gives a monobromo digold(I) complex (12), which is similar to 11 except that the 2-position of the substituted aromatic ring bears hydrogen instead halogen. Reaction of 9 with iodine gives a mixture of a free tertiary arsine, (2-I-3-MeC6H3)AsPh2 (13), a digold diiodo compound (14) analogous to 11, and a gold(I)-gold(III) zwitterionic complex [I2Au(III)[(mu-C6H3-2-AsPh2-6-Me)]2Au(I)] (15) in which the bridging units are arranged head-to-head between the metal atoms. The structures of 2a-2c and 4-15 have been determined by single-crystal X-ray diffraction analysis. The different behaviour of 1 and 9 toward halogens mirrors that of their phosphine analogues; the 6-methyl substituent blocks C-C coupling of the aryl residues in the initially formed oxidative addition product. In the case of 9, the greater lability of the Au-As bond in the initial oxidative addition product may account for the more complex behaviour of this system compared with that of its phosphine analogue.

Journal Article↗
PubMed2001

Evaluating a visual field screening test for glaucoma: how the choice of the gold standard affects the validity of the test.

OBJECTIVE: To examine the effects of the gold standard on sensitivity, specificity, and area under the ROC curve when determining the validity of a screening test. METHODS: Fifty-eight people were recruited from a Veterans' Administration eye clinic. Screening included testing with the 26-point oculokinetic perimeter (OKP). We used different gold standards to categorize patients as positive or negative for glaucoma. The glaucoma hemifield test (GHT) and corrected pattern standard deviation (CPSD) from the Humphrey visual field analyzer (HVF) were used as objective gold standards. Ophthalmologist review of the HVF, using two different methods for classifying visual field defects, was also used as a gold standard. RESULTS: Using the review of the HVF that included mild, moderate, or severe defects, the area under the ROC curve was not significantly different from 50%. However, for all the other gold standards, the area under the ROC curve was significantly different from 50%. CONCLUSIONS: In determining the ability of the OKP to differentiate between glaucoma and normal subjects, the choice of a gold standard led to different conclusions about its usefulness as a screening test for glaucoma. Furthermore, sensitivity and specificity varied widely depending on which gold standard was used, and what cutoff point was used for the OKP. Although clinician review of the HVF may be used when specific criteria are given to define visual field defects, using objective measures from the HVF is easier and will allow for better comparisons between studies.

Aged↗
PubMed1995

A reference of the GOLD classification of monoclonal antibodies against carcinoembryonic antigen to the domain structure of the carcinoembryonic antigen molecule.

The epitopes of 42 well-characterized monoclonal antibodies (MAbs) against carcinoembryonic antigen (CEA) from 10 different research groups were mapped in terms of domain structure (domains N, A1-B1, A2-B2, and A3-B3) of the CEA molecule on the basis of the reactivities with recombinant CEA proteins expressed in Chinese hamster ovary cells. Thirty-six of the 42 MAbs tested have previously been classified into 5 essentially nonoverlapping epitope groups (GOLD 1-5) by cross-competition assays among MAbs for CEA binding (Hammarström S, et al.: Cancer Res. 1989; 49:4852-4858). The epitopes recognized by GOLD 2 MAbs were all present on domain A2-B2, those for GOLD 5 MAbs were all on domain N, and those for GOLD 4 were mapped around domains A1-B1 and A2-B2. On the other hand, the epitopes for GOLD 1 MAbs were distributed into domains N, A2-B2, and A3-B3, and those for GOLD 3 MAbs were separated into domains N and A3-B3. Although the exact reasons for the dispersed patterns of GOLD 1 and 3 MAbs on the domain structure of the CEA molecule are unclear at present, several factors, such as a spatial relation or a close proximity of epitopes, conformation dependency, and repetitivity of epitopes, may be considered as possible explanations. The epitope mapping reported here helps form the basis for understanding the relation between the chemical structure and antigenic activities of the CEA molecule and may be useful to study the functions of the CEA molecule, especially those of the respective domains.

Animals↗
PubMed2005

In situ high temperature TEM observation of interaction between multi-walled carbon nanotube and in situ deposited gold nano-particles.

Interaction between multi-walled carbon nanotubes (MWNTs) and deposited gold nano-particles has been dynamically observed in a 200 kV transmission electron microscope (TEM) using a specimen heating holder. Gold particles with diameters of several tens of microns were mixed with MWNTs to mount on the heating element of a specimen heating holder. The gold particles were instantaneously heated to 1373 K to deposit gold nano-particles on the MWNTs from a very short distance. The MWNTs were then heated to 1073 K to observe interaction between the deposited gold nano-particles and MWNTs. Some gold nano-particles drilled through the wall of the MWNT and entered the capillary space of the MWNTs. To characterize the mechanism of the transition of the gold nano-particles into the capillary space of the MWNT, high resolution TEM observation of the deformed wall of MWNT was also carried out.

Journal Article↗
PubMed2005

Comparison of the allergenicity of Actinidia deliciosa (kiwi fruit) and Actinidia chinensis (gold kiwi).

Actinidia chinensis (gold kiwi) is a newly available fruit which has been shown to have in vitro immunoglobulin E (IgE) cross-reactivity with green kiwi. This is the first study to investigate clinical reactivity of gold kiwi. Five patients clinically allergic to green kiwi were investigated by skin test and double-blind placebo controlled food challenge (DBPCFC) with gold kiwi fruit. IgE-binding patterns of individual sera from the five challenged patients and a pool of sera from a further nine patients with kiwi allergy were compared in the two fruits by Western blotting. Cross reactivity of proteins in the two fruits was assessed by inhibition of immunoblots and by IgE enzyme-linked immunosorbent assay (ELISA) inhibition. Four of the five patients had a positive DBPCFC to gold kiwi. Western blotting showed marked differences in the allergen patterns of green and gold kiwi. However, inhibition of the immunoblots and ELISA assay reveals extensive inhibition of IgE binding to proteins in each fruit by the alternative species. Gold kiwi fruit is allergenic and patients allergic to green kiwi are at risk of reacting to the gold kiwi fruit. Despite having different protein profiles and IgE-binding patterns, the two species have proteins that extensively cross-inhibit the binding to IgE.

Actinidia↗
PubMed1994

Application of an immunocolloid gold technique for the ultrastructural demonstration of IgE-receptor complexes on rat mast cells.

In previous works using cytofluorometry, we demonstrated a broad range of IgE and IgE-receptor levels within individual mast cell populations with a 60 to 80% occupancy of the IgE receptors on mast cells by native IgE. This study was performed in order to confirm our previous findings using an independent method and to visualize the distribution of IgE-receptor complexes on mast cells at an ultrastructural level. For this purpose an indirect immunocolloidal gold-labelling technique has been applied. By counting the number of labelled gold particles, a relative measure of IgE-receptor surface expression and IgE occupancy of the receptors could be obtained. With respect to mast cell morphology and anti-IgE binding specificity criteria, 1% glutaraldehyde + 4% paraformaldehyde (1:1, vol/vol) was found to be the best of the seven fixatives applied in this study. This technique revealed numerous gold particles on the surface of mast cells from barrier-maintained rats (26 +/- 11 per mast cell section, mean +/- SD). Increased numbers of gold particles were counted if the mast cells were incubated with rat myeloma IgE (20 micrograms/ml) (46 +/- 33 per mast cell section, mean +/- SD). There were significantly increased numbers of gold particles on the mast cells of rats infected with N. brasiliensis (126 +/- 30 per mast cell section, mean +/- SD). This indicates that some of the IgE receptors (about 50% of the total number of IgE receptors in this case) on mast cells were occupied by native IgE and that parasite infection significantly increased the number of IgE molecules on the surface of the mast cells. These results correspond with the findings we have made using the cytofluorometric technique and confirm the large individual variations in the density of IgE receptors and IgE among the mast cells of a given cell population. Macrophages, lymphocytes and eosinophils, carrying the low-affinity IgE receptors (Fc epsilon RII), contained less than 5 (normal rats after incubation in rat IgE) or 10 (nematode-infected rats) gold particles per cell section. We also observed some non-granulated lymphocyte-like cells which bound a large number of gold particles after incubation with rat myeloma IgE (20 micrograms/ml), indicating that they contained IgE receptors Fc epsilon RI). They were interpreted as mast cell precursors which have previously been shown to exist in the peritoneal cavity.

Animals↗
PubMed2004

Use of multiple nucleic acid amplification tests to define the infected-patient "gold standard" in clinical trials of new diagnostic tests for Chlamydia trachomatis infections.

Nucleic acid amplification tests (NAATs) can be used to define the infected-patient "gold standard" for the purpose of designing studies of the performance of Chlamydia trachomatis diagnostic tests. It is unclear how many test results run by different NAATs and what combinations of specimens comprise the best infected-patient gold standard. We approached this question with data from a large study of the performance of a new NAAT. Data were available from three endocervical swabs and a urine specimen collected from each of 1,412 women and tested by three different NAATs. Results from all three assays were used equally in a rotating fashion to define the infected-patient gold standard. Multiple different infected-patient gold standards for estimating swab and urine specimen sensitivity and specificity for one NAAT method were created by varying the number and combinations of swab and urine comparator results with two different NAATs, The effect of changing the infected-patient gold standard definition was determined by constructing receiver-operator-like curves with calculated sensitivities and specificities for each test. The one-positive-of-two-results or two-positive-of-two-results (same or two different assays) infected-patient gold standard definitions produced low sensitivity and low specificity estimates, respectively. If four comparator NAAT results were used, the any-three-positive-of-four-results definition or the at-least-one-specimen-positive-by-each-of-two-comparator-assays definition appeared to provide better combinations of sensitivity and specificity estimates. The any-two-positive-out-of-three-results definition resulted in estimates that were as good as produced with the former two definitions. This analytic approach provides a means of clearly visualizing the effects of changing NAAT-based infected-patient gold standards and should be helpful in designing future studies of new C. trachomatis diagnostic tests.

Cervix Uteri↗