Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Colloids”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,225 records · Page 68Linked to original sources
PubMed1976

The abnormal hepatic scan of chronic liver disease: its relationship to hepatic hemodynamics and colloid extraction.

To help explain the characteristic hepatic scan pattern of chronic liver disease, the degree of scan abnormality (scan score, SS) after administration of technetium-99m sulfur colloid (Tc) was compared with data obtained at hepatic vein catheterization in 28 patients. Although SS showed a correlation with wedged hepatic vein pressure (r = +0.491), the scan abnormality was not directly due to portal hypertension because it remained unchanged when the latter was relieved by portacaval shunt. Also, the scan abnormality was found to be unrelated to a low hepatic blood flow. Scan abnormality was not attributable primarily to hyperactivity of the reticuloendothelial (RE) cells of the spleen and bone marrow since fractional clearance (K) of Tc from the blood was decreased rather than increased in patients with abnormal scans. SS was inversely correlated with K or Tc (r = -0.575) and with hepatic extraction efficiency for Tc (r = -0.673), showing that the basic abnormality was poor extraction of the colloid by the RE cells of the liver with a resultant increase in the amount available for extrahepatic localization. Indirect evidence suggests that this poor extraction of colloid is due to intrahepatic shunts bypassing hepatic RE cells.

Blood Pressure↗
PubMed1996

[Application of monoclonal antibody immuno-colloide gold probe in the study of porphyromonas gingivalis].

Immuno-electron localization of McAb BGG9 was specific for Porphyromonas gingivalis labeled with colloide gold. The monoclonal antibody immuno-colloide gold probe reacted with Porphyromonas gingivalis and 5 species of black pigmented bacteroides groups. The bacteria were fixed and embbed in Epon. sections were examined under transmission electron microscope, and the gold granular was observed near Porphyromonas gingivalis cell membrane. Our conclusion suggests that monoclonal antibody immuno-colloide gold probe is useful tool for studying Porphyromonas gingivalis.

Antibodies, Bacterial↗
PubMed1998

Effect of light on generation of colored silver colloids in protein solutions.

The exposure to light (20 mW/cm2, an incandescence lamp) of weakly alkaline protein solutions which contained silver nitrate and formaldehyde initiated reduction of silver ions with the subsequent generation of colored silver colloids. At light intensities lower than 0.2 mW/cm2 the generation of colored silver colloids was delayed. The rate of silver reduction depended on the protein type and on the light spectral structure. In particular, solutions which contained prealbumin, lysozyme, gamma-globulin, and transferrin were more photosensitive than solutions which contained albumin, pepsin, and beta-amylase. The formation of [Ag(NH3)2]+ complex after an addition of ammonium ions into the solutions preferentially suppressed silver reduction in the dark and under exposure to red light, thus resulting in a significant difference in the time of appearance of colored silver colloids when the solutions were exposed to violet or red light. These findings are promising for the elaboration of selective silver development of proteins in polyacrylamide gels.

Animals↗
PubMed1990

Symptomatic neuroepithelial (colloid) cysts of the third ventricle. A unique case report in nontwin brothers.

Colloid cysts are relatively rare benign tumors comprising less than 2% of all intracranial mass lesions. However, since the advent of computed tomography of the head, these tumors are being recognized more frequently, occasionally before their symptomatic presentation. Much controversy remains as to the true cells of origin and pathogenesis of these cysts. Although a neuroepithelial origin has become increasingly accepted, Rathke cleft cysts, ectopic respiratory tissue, and other endodermal sources have been postulated. The first familial occurrence in middle-aged identical twin brothers was cited recently in the literature. Described here are the first reports of symptomatic colloid cysts in two nontwin brothers, lending further support to the potential for genetic expression of neuroepithelial cysts. Also included are preoperative computed axial tomographic images, histopathologic photomicrographs with case descriptions and comparisons, and suggestions to elucidate further the development and presentation of colloid cysts.

Aged↗
PubMed2000

Strategies for the anchoring of metal complexes, clusters, and colloids inside nanoporous alumina membranes.

Two complementary strategies are presented for the anchoring of molecular palladium complexes, of cobalt or platinum clusters or of gold colloids inside the nanopores of alumina membranes. The first consists in the one step condensation of an alkoxysilyl functional group carried by the metal complex with the hydroxy groups covering the surface of the membrane pores. Thus, using the short-bite alkoxysilyl-functionalized diphosphane ligands (Ph2P)2N(CH2)3Si(OMe)3 (1) and (Ph2P)2N(CH2)4SiMe2(OMe)] (2) derived from (Ph2P)2NH (dppa) (dppa bis(diphenylphosphanyl)amine), the palladium complexes [Pd(dmba)(kappa2-P,P-(Ph2P)2N(CH2)3Si(OMe)3)] Cl (3) and [Pd(dmba)[kappa2-P,P-(Ph2P)2N(CH2)4SiMe2(OMe)]]Cl (4) (dmba-H = dimethylbenzylamine). respectively, were tethered to the pore walls. After controlled thermal treatment. confined and highly dispersed palladium nanoparticles were formed and characterized by transmission electron microscopy (TEM). This method could not be applied to the cobalt cluster [Co4(CO)8(mu-dppa)[mu-P,P-(Ph2P)2N(CH2)4SiMe2(OMe)]] (7) owing to its too limited solubility. However, its anchoring was achieved by using the second method which consisted of first derivatizing the pore walls with 1 or 2. The covalent attachment of the diphosphane ligands provides a molecular anchor that allows subsequent reaction with the cluster [Co4(CO)10(mu-dppa)] 6 to generate anchored 7 and this step was monitored by UV/Vis spectroscopy. In addition, the presence of carbonyl ligands in the cluster provides for the first time a very sensitive spectroscopic probe in the IR region which confirms both cluster incorporation and the retaining of its molecular nature inside the membrane. The presence of the bridging dppa ligand in 6 provides additional stabilization and accounts for the selectivity of the procedure. Using this method, platinum clusters (diameter ca. 2 nm) and gold colloids (diameter ca. 13 nm) were immobilized after passing their solution through the functionalized membrane pores. The resulting membranes were characterized by TEM which demonstrated the efficiency of the complexation and showed the high dispersion of the metal loading. The successful application of these methods has demonstrated that nanoporous alumina membranes are not only unique supports to incorporate metal complexes, clusters, or colloids but can also be regarded as functional matrices or microreactors, thus opening new fields for applications.

Journal Article↗
PubMed2005

From discrete particles to spherical aggregates: a simple approach to the self-assembly of Au colloids.

Here we demonstrate a simple, template-free approach to the formation of spherical gold aggregates through the reduction of HAuCl4 by NaBH4, in the presence of cysteine (Cys) as a capping agent. The resulting aggregates are quite stable in solution. The pH of the solution and the molar ratio of Au:Cys are two key empirical factors in the formation of such highly ordered aggregates. At slightly alkaline pH (7-10) and with Au:Cys ratios ranging from 1:0.5 to 1:2, spherical Au aggregates of 30-80 nm are formed. At lower Cys ratios (Au:Cys> or =1:0.5) very loosely linked aggregates are formed; however, at very high Cys ratios (Au:Cys< or =1:3), highly dispersed Au particles of 2-4 nm are obtained, which are virtually indistinguishable from the original colloidal form. Aggregate size is influenced markedly by component concentration; a 3-fold increase in standard levels resulted in Au spherical aggregates of a larger size, 200-500 nm. In addition, we used a combination of Cys and lysine (Lys) as a capping agent/cross-linker and found that the morphology of the Au colloid aggregates can be easily manipulated from a linear to a spherical form by adjusting the proportions of Cys and Lys in the capping agent/cross-linker mixture. The introduction of mercapto (SH)-containing organic acids reduced the cross-linking ability of Cys, especially in the case of long-chain acids. Complete disruption of the spherical aggregates highlights the importance of Cys per se. An explanation of this ordered self-assembly process is proposed, in the context of the known surface chemistry of Au colloids.

Journal Article↗
PubMed2003

Sentinel lymph nodes with technetium-99m colloidal rhenium sulfide in patients with esophageal carcinoma.

BACKGROUND: The authors assessed the detection of sentinel lymph nodes in patients with esophageal squamous cell carcinoma (SCC) using technetium-99m colloidal rhenium sulfide. They studied whether an analysis of sentinel lymph nodes using cytokeratin (CK) immunohistochemistry increased the accuracy of staging. METHODS: The authors observed 25 patients with thoracic esophageal carcinomas who underwent radical esophagectomy. The day before surgery, technetium-99m colloidal rhenium sulfide was injected into the submucosa at four sites around the primary tumor. Lymphoscintigraphy was performed. Esophagectomy and regional lymph node dissection were performed 17 hours after the technetium-99m injection. After surgery, the resected lymph nodes were evaluated by CK staining. RESULTS: Lymphoscintigraphy detected sentinel lymph nodes in 92% of the patients (23 of 25 patients). The accuracy of sentinel lymph node was 91.3% (21 of 23 patients), the sensitivity was 86.7% (13 of 15 patients), and the false-negative rate was 8.7% (2 of 23 patients). A comparison of the number of sentinel lymph nodes and clinicopathologic factors showed that there was a significant association between the number of sentinel lymph nodes and lymph node status (P < 0.01), pathologic stage (P < 0.05), and the number of metastatic lymph nodes (P < 0.05). Occult metastasis was detected by CK staining in 14 (56%) of the 25 patients and in 23 (1.7%) of 1406 lymph nodes. Because the 2 false-negative (sentinel lymph node-negative and nonsentinel lymph node-positive) patients who had occult metastases in the sentinel lymph nodes, the accuracy of sentinel lymph node evaluation using CK staining was 100% (23 of 23). CONCLUSIONS: Lymphatic mapping with technetium-99m colloidal rhenium sulfide was used to identify the lymphatic basin and was feasible in patients with esophageal SCC. An analysis of sentinel lymph nodes using CK immunohistochemistry increased the accuracy of sentinel lymph node.

Aged↗
PubMed2005

In situ 1H NMR study on the trioctylphosphine oxide capping of colloidal InP nanocrystals.

We used trioctylphosphine oxide (TOPO) capped colloidal InP nanocrystals (Q-InP|TOPO) to explore the potential of solution 1H NMR spectroscopy in studying in situ the capping and capping exchange of sterically stabilized colloidal nanocrystals. The spectrum of Q-InP|TOPO shows resonances of free TOPO, superimposed on broadened spectral features. The latter were assigned to TOPO adsorbed at Q-InP by means of pulsed field gradient diffusion NMR and 1H-13C HSQC spectroscopy. The diffusion coefficient of Q-InP|TOPO nanocrystals was inferred from the decay of the adsorbed TOPO NMR signal. The corresponding hydrodynamic diameter correlates well with the diameter of Q-InP. By using the resolved methyl resonance of adsorbed TOPO, the packing density of TOPO at the InP surface can be estimated. Spectral hole burning was used to demonstrate explicitly that the adsorbed TOPO resonances are heterogeneously broadened. Exchange of the TOPO capping by pyridine was demonstrated by the disappearance of the resonances for adsorbed TOPO and the appearance of pyridine resonances in the 1H NMR spectrum. These results show that solution NMR spectroscopy should be considered a powerful technique for the in situ study of the capping of sterically stabilized colloidal nanocrystals.

Journal Article↗
PubMed1982

An ultrastructural study of the origin and function of basophilic degeneration in human cardiac muscle--cardiac colloid. Type 1.

The myofibres in biopsies obtained from the left ventricle during cardiopulmonary bypass, in patients undergoing surgery for mitral and aortic valve replacement and the correction of atrial septal defect, contained inclusions thought to be type 1 cardiac colloid. Electron microscopy showed this material to be synthesised by and contained within a grossly dilated rough endoplasmic reticulum. The presence of membrane-bound aggregates of non-fibrillar sarcoplasmic organelles within colloid deposits, together with osmiophilic inclusions thought to be related to lipofuscin, both within and moving from this structure, suggest that type 1 cardiac colloid is an autophagic vacuole designed to degrade ageing or redundant sarcoplasmic organelles.

Adolescent↗
PubMed2000

Spin trapping of vascular nitric oxide using colloid Fe(II)-diethyldithiocarbamate.

Currently available EPR spin-trapping techniques are not sensitive enough for quantification of basal vascular nitric oxide (NO) production from isolated vessels. Here we demonstrate that this goal can be achieved by the use of colloid Fe(DETC)(2). Rabbit aortic or venous strips incubated with 250 microM colloid Fe(DETC)(2) exhibited a linear increase in tissue-associated NO-Fe(DETC)(2) EPR signal during 1 h. Removal of endothelium or addition of 3 mM N(G)-nitro-l-arginine methyl ester (L-NAME) inhibited the signal. The basal NO production was estimated as 5.9 +/- 0.5 and 8.3 +/- 2.1 pmol/min/cm(2) in thoracic aorta and vena cava, respectively. Adding sodium nitrite (10 microM) or xanthine/xanthine oxidase in the incubation medium did not modify the intensity of the basal NO-Fe(DETC)(2) EPR signal. Reducing agents were not required with this method and superoxide dismutase activity was unchanged by the Fe(DETC)(2) complex. We conclude that colloid Fe(DETC)(2) may be a useful tool for direct detection of low amounts of NO in vascular tissue.

Animals↗
PubMed1997

Rheology of Colloidal Particles in a Confined Channel under Shear Flow by Brownian Dynamic Simulations

A colloidal system of strongly charged particles, confined between two charged walls, is studied under static conditions and in the presence of shear flows. Brownian Dynamics simulations (BD) are used to determine the concentration profiles for several separations of charged walls. Results show good agreement with those obtained under static conditions using the Hypernetted Chain Approximation (HNC) and Monte Carlo simulations. Results obtained with BD and HNC for neutral walls show more similarities than those between BD and Monte Carlo simulations depending on the initial state of the colloidal particles. The presence of a shear flow field perturbs the equilibrium concentration profiles and the distribution function in the flow direction, generating a structureless system, as confirmed by the absence of peaks in the radial distribution function. The mobility of the particles in the transversal direction decreases rapidly and becomes practically frozen. The flow exhibits a non-Newtonian behavior with shear-thinning viscosity. Due to the interparticle interactions and particle-wall interactions, the viscosity is lower as the wall separation decreases, giving rise to an apparent slip in the colloidal suspension. The slip velocity for repulsive walls is higher than that obtained with neutral walls and increases with the shear stress according to a power law, as observed in polymer solutions. The shear viscosity and the normal stress differences depend strongly on the combined effect of confinement, concentration of particles, magnitudes of inter-particle interactions and wall-particle repulsion.

Journal Article↗
PubMed1997

Immobilization of Polymer-Stabilized Noble Metal Colloids and Their Catalytic Properties for Hydrogenation of Olefins

Polymer-stabilized noble metal colloids were efficiently immobilized on silica by the addition of organic acids under mild conditions. The function of organic acids in the immobilization was studied by infrared spectroscopy. Transmission electron micrographs indicate that the immobilized colloids have a controlled particle size and size distribution. They serve as catalysts in the hydrogenation of cyclohexene and cyclopentadiene, the results of which show that this new type of immobilized colloid has high selectivity and good stability.

Journal Article↗
PubMed1997

Size Determination of Catena-&mgr;-2,5-dihydroxy-p-benzoquinonatonickel(II) Coordination Polymer Colloid and Its Photochemical Reaction

Electric birefringence and streaming dichroism measurements of catena-&mgr;-2,5-dihydroxy-p-benzoquinonatonickel(II) [dhqNi(II)] aqua sol suggested that the average length of the sol particles was ca. 380 nm and the axial ratio was 2.0-2.3 as the prolate spheroid. The average particle length in the scanning microscopic images was 370 &plusmn; 60 nm and the axial ratio 2.3 &plusmn; 0.6. This aqua colloid was decomposed by UV irradiation under an O2 gas atmosphere, but under a N2 gas atmosphere its decomposition was depressed. Furthermore, addition of sacrificial reagents such as l-ascorbic acid depressed the decomposition. These facts suggested that the photogenerated electron originating from the irradiated dhqNi(II) colloidal particle reduced O2, while the positive hole on the colloid oxidized dhqNi(II) itself. It was found that the reduction product from O2 reduced Cr6+ (in Cr2O72-) to Cr3+, and the oxidized dhqNi(II) oxidized I- to I2/2. Therefore, H2O2 formation was proposed as the photochemical reduction product. Copyright 1997Academic Press

Journal Article↗
PubMed1998

Synthesis and Photophysical Properties of ZnS Colloidal Particles Doped with Silver.

The synthesis and photophysical characterization of ZnS:Ag colloid are reported. The presence of mercaptoacetic acid has an important effect not only on the formation of doped and undoped ZnS but also on the photophysical properties. ZnS colloid doped with silver shows a strong green emission upon ultraviolet excitation, the intensity of which was enhanced significantly compared with that of the undoped colloid. The green emission was ascribed to a transition from a donor level such as anion vacancy to the levels of the Ag impurities. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Sedimentation Potential in a Concentrated Suspension of Spherical Colloidal Particles.

A theory of sedimentation in a concentrated suspension of spherical colloidal particles proposed by Levine et al. (J. Colloid Interface Sci. 57, 424 (1976)) is further developed to derive a simple convenient expression for the sedimentation potential applicable for low zeta potentials and nonoverlapping electrical double layers of adjacent particles. An Onsager relation between the sedimentation potential and electrophoretic mobility of spherical colloidal particles in concentrated suspensions is derived. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Preparation, Characterization, and Catalytic Properties of Polymer-Stabilized Ruthenium Colloids.

Poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium colloids were prepared by NaBH4 reduction at room temperature and characterized by transmission electron microscopy and x-ray photoelectron spectra. The average diameters of the colloids were 1.3-1.8 nm with final sigma = 0.4-0.7 nm with respect to the preparation conditions. The PVP-stabilized ruthenium colloids were used as catalysts in the hydrogenations of cyclooctene and n-heptene and the selective hydrogenation of citronellal to citronellol. Copyright 1998 Academic Press.

Journal Article↗
PubMed1999

Long-Range Electrostatic Interaction between a Charged Wall and Two Similarly Charged Colloidal Spheres at Low Surface Potentials.

The long-range electrostatic interaction between a pair of similarly charged colloidal spheres and a charged planar wall at low surface potentials is theoretically investigated. The linear Poisson-Boltzmann equation (PBE) and the point charge approximation of the charged sphere are used. The electrical potential distribution in the electrolyte solution is found from the PBE at the constant surface potentials using the image charge method. The electrostatic forces acting on the spheres are then calculated. The results show that the repulsive interaction between a pair of similarly charged colloidal spheres clearly decreases when a charged wall appears nearby, but it is impossible for an attractive force to emerge at the scaled surface potentials less than 1. There is, however, an attractive force between the charged wall and the similarly charged colloidal spheres, when the surface potential zetap on the wall is sufficiently higher than the surface potential zetas on the spheres to make zetap > zetasexp(kappah) (h is the distance from the wall to the sphere center). In this case, there are negative surface charges on the spheres at positive surface potential zetas. It is these negative charges that produce the above attraction. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Deposition of Colloidal Zinc Sulfide on Glass Substrate.

The effect of colloidal forces involved in the deposition of spherical zinc sulfide colloidal particles on a packed bed of glass has been studied. Experiments were performed by pumping a suspension of monodisperse colloidal ZnS particles through a cylindrical plug of ground glass, and by continuous determination of the outgoing suspension concentration. The flux density of adhered particles, jexp (number of particles deposited per unit time and unit surface area of glass collector), decreased with both pH and ionic strength of the aqueous electrolyte solution. Qualitative explanation of the experiments has been given in terms of the total energy of interaction between the dispersed particles and the substrate, and between the particles themselves, computed from the extended DLVO theory, including acid-base interactions. The contributions to the total free energy of interaction were determined from the zeta potential and surface free energy of ZnS and glass, measured under different experimental conditions. It was found that at pH 4 (below the isoelectric point of ZnS) the efficiency of the deposition of ZnS on glass was maximum. At higher pH values the amount of ZnS deposited on glass clearly decreased. Increasing NaCl concentration at fixed pH (>/=6) decreased the efficiency of the deposition. Adhesion experiments were also performed at pH 4 in the presence of increasing concentrations of CaCl2 or La(NO3)3 in the dispersion medium. In these cases, the rate of adhesion was qualitatively well correlated with the computed ZnS-glass interactions. Copyright 1999 Academic Press.

Journal Article↗