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 469 records · Page 26Linked to original sources
PubMed1996

Hypotension during subarachnoid anaesthesia: haemodynamic effects of colloid and metaraminol.

We have studied 45 patients, aged 60-95 yr, receiving subarachnoid block for neck of femur fractures. Patient received either colloid (polygeline, Haemaccel) 8 ml kg-1 (n = 15), metaraminol 5 micrograms kg-1 and 1.7 micrograms kg-1 min-1 (n = 15) or a combination of both treatments to maintain systolic arterial pressure (SAP) between 75 and 100% of baseline. If necessary, additional colloid 2 x 4 ml kg-1 or metaraminol 3 x 2.5 micrograms kg-1 was given. Arterial pressure was measured by automated oscillotonometry, central venous pressure (CVP) by a manometer and cardiac index (CI), stoke index (SI) and heart rate (HR) by transthoracic electrical bioimpedance. Systemic vascular resistance index (SVRI) was derived. Colloid was less effective than metaraminol (P < 0.05). In the colloid group, SAP and SVRI decreased and CVP, CI and SI increased (P < 0.001). In the metaraminol group, initial decreases in SAP, SVRI and CVP were restored after 10-15 min and HR decreased after 12 min (P < 0.001). In the combined group, initial decreases in SAP and SVRI were restored after 4 and 16 min, and CVP, CI, SI and HR increased (P < 0.001). Metaraminol was more effective than colloid because it increased SVRI, whereas colloid increased CVP without significantly increasing CI.

Aged↗
PubMed1985

Colloid solution therapy of experimental ischemic intestinal shock in rats.

This study evaluated the effects of varying colloid concentrations and infusion volumes on survival and plasma volume expansion in rats subjected to an intestinal ischemic shock. Up to 10% solutions of albumin and dextran-40 in lactated Ringer's solution, infused over a 6-h period, had the same effects on hematocrit (Hct) changes and survival patterns. Mean Hct values (45% to 50%) were independent of colloid solution concentration. With lactated Ringer's solution alone, Hct was 55%, despite the very large volume used; and less than 3% of the infused lactated Ringer's solution remained as plasma volume at 3 and 6 h of infusion. With increasing colloid concentration a greater proportion of the infused volume contributed to plasma volume. Of a 10% colloid solution, 50% and 34% remained as plasma volume at 3 and 6 h. For colloid concentrations between 1% and 3%, there was an equal distribution of infused fluid between the extracellular fluid space and the plasma. Survival rate, as measured by blood volume expansion, was greater with colloid solution concentrations between 2% and 4%.

Albumins↗
PubMed2000

Endoscopic colloid cyst surgery.

OBJECTIVE: The purpose of this report is to discuss the technical aspects of operating on colloid cysts through a transventricular approach, with rigid endoscopes. METHODS: Twelve patients underwent 14 endoscopic operations in attempts to treat their colloid cysts. All patients were symptomatic, with headache being the most common complaint (8 of 12 patients). Six patients in this series exhibited enlarged ventricles associated with their colloid cysts. Using rigid endoscopes of < or =3.5-mm diameter, the cysts were inspected and fenestrated. Both hard and soft cyst contents were evacuated, and then the walls of the cysts were coagulated inside and outside. External ventriculostomy tubes were usually placed. Technical obstacles to successful completion of endoscopic colloid cyst surgery are discussed. RESULTS: For 11 of the 12 patients, the colloid cysts could be treated via an endoscopic approach. The mean follow-up time was 173 weeks, and the median follow-up time was 125 weeks. For the 12th patient, bilateral scarring of the foramina of Monro precluded direct surgery; therefore, a septostomy was performed and a ventriculoperitoneal shunt was placed. CONCLUSION: Endoscopic transventricular surgery should be considered for the treatment of colloid cysts.

Adult↗
PubMed2006

Colloid scintigraphy in non-alcoholic steatohepatitis: a conventional diagnostic method for an emerging disease.

AIM: Non-alcoholic steatohepatitis (NASH) is a progressive liver disease characterized by diffuse fatty infiltration and Kupffer cell dysfunction which contributes to its pathogenesis. Since the liver biopsy, which is considered the 'gold standard' in diagnosing NASH, has some limitations other imaging methods have been explored as alternatives. Colloid scintigraphy is a good method reflecting Kupffer cell activity and we found it worthwhile to evaluate this technique in NASH. We aimed to present the common scintigraphic features and their clinicopathologic correlations in NASH. METHODS: Twenty-two new patients (11 female, mean age 43.7+/-10.8) with biopsy-proven NASH underwent colloid liver scintigraphy. The dynamic, static and SPECT images were performed after intravenous injection of 185 MBq Tc tin colloid. Hepatic perfusion, blood pool clearance time, colloid shift to spleen and bone marrow were assessed and liver right/left lobe ratio was calculated. RESULTS: The values calculated on static and tomographic (SPECT) images showed good correlation. Liver right/left lobe ratio was altered in all patients. Blood pool clearance time was prolonged in seven (32%) but hepatic perfusion was normal in all patients. Colloid shift to the spleen was observed in 55% of patients using SPECT analysis. No correlation between scintigraphy parameters and histological or biochemical findings were observed. CONCLUSION: Altered liver right/left lobe ratio was the universal finding in all our NASH patients. Other common scintigraphic features of NASH include colloid shift to spleen and prolonged blood pool clearance time. Liver scintigraphy might be a promising non-invasive tool in the follow-up of NASH patients in therapeutic trials.

Adult↗
PubMed2001

Density functional theory of charged colloidal systems.

The phase behavior of charged colloidal systems has been studied recently by the density functional theory formalism (DFT) [R. van Roij, M. Dijkstra, and J. P. Hansen, Phys. Rev. E 59, 2010 (1999)]. A key feature of this approach is the appearance of a density and temperature-dependent effective Hamiltonian between the charged colloids. Under certain approximations, the effective Hamiltonian is made up only of a sum of position-independent one-body or volume terms and two-body colloid-separation dependent terms. In the limit of low colloidal densities, the DFT results do not reduce to the familiar Debye-Hückel limiting law nor do the results agree with previous work based on an identical approach but were developed using traditional statistical-mechanical methods [B. Beresford-Smith, D. Y. C. Chan, and D. J. Mitchell J. Colloid Interface Sci. 105, 216 (1985)]. This paper provides a reconciliation of these differences and comments on the significance of the one-body volume terms in the effective Hamiltonian of a system of charged colloids in determining thermodynamics and phase behavior.

Journal Article↗
PubMed2002

Ordering and short-time orientational diffusion in dipolar hard-spherical colloids.

Orientational hydrodynamic functions and short-time, self-orientational and collective orientational diffusion coefficients of dipolar hard-spherical colloids are performed on a homogeneous isotropic phase, as functions of the wave vector q, for various values of the volume fraction and the dipolar strength of the macroparticles. The calculation is based on the dynamic orientational structure factor, which is the time-dependent self-correlation of the orientation density. We assume that the time evolution of the orientation density is given by the Smoluchoswki's equation, taking into account the hydrodynamic interactions as well as the dipolar interaction. The former are considered assuming pairwise additivity. The importance of the dynamic orientational structure factor is that its initial slope can be measured in a depolarized light scattering experiment. The results predict a different behavior for dilute and for dense dipolar colloids. The ordering phenomena are studied via the ordering coefficients, which are the orientational hydrodynamic functions at q=0. The results show that as the dipolar colloid evolves to the instability line, the translational ordering velocity increases while the rotational one reduces. The short-time orientational diffusion coefficients at q=0 are also performed. They predict that near to the instability line, the dipolar colloid diffuses translationally more than rotationally. At very dilute concentration the dipolar colloid presents an unexpected dynamical behavior, which seems to indicate that the colloid could be evolving to a reentrant phase.

Journal Article↗
PubMed2004

Interaction of colloids with a nematic-isotropic interface.

The Landau-de Gennes free energy is used to calculate the interaction between long cylindrical colloids and the nematic-isotropic (NI) interface. This interaction has two contributions: one is specific of liquid crystals and results from the deformation of the director field close to the particles or to the interface, while the other is generic and results from wetting and surface tension effects. Deep in the nematic phase the director field of long cylindrical colloids, with strong homeotropic anchoring, exhibits two half-integer defect lines. As the colloid moves towards the interface, the director configuration changes through a series of discontinuous transitions, where one or two of the defects are annihilated. In addition, the NI interface bends towards the colloid in order to minimize the elastic free energy in the nematic. In the isotropic phase, the colloid is surrounded by a thin nematic layer that reduces the surface free energy under favorable wetting conditions. The interaction has a well-defined minimum near the interface. In this region the director and interfacial structures are complex and cannot be described analytically. Using the numerical results for the Landau-de Gennes free energy in the harmonic region, we obtained simple scaling laws for the (linear) force on the colloid.

Journal Article↗
PubMed2006

Effect of many-body interactions on the bulk and interfacial phase behavior of a model colloid-polymer mixture.

We study a model suspension of sterically stabilized colloidal particles and nonadsorbing ideal polymer coils, both in bulk and adsorbed against a planar hard wall. By integrating out the degrees of freedom of the polymer coils, we derive a formal expression for the effective one-component Hamiltonian of the colloids. We employ an efficient Monte Carlo simulation scheme for this mixture based on the exact effective colloid Hamiltonian; i.e., it incorporates all many-body interactions. The many-body character of the polymer-mediated effective interactions between the colloids yields bulk phase behavior and adsorption phenomena that differ substantially from those found for pairwise simple fluids. We determine the phase behavior for size ratios q=sigma(p)/sigma(c)=1, 0.6, and 0.1, where sigma(c) and sigma(p) denote the diameters of the colloids and polymer coils, respectively. For q=1 and 0.6, we find both a fluid-solid and a stable colloidal gas-liquid transition with an anomalously large bulk liquid regime caused by the many-body interactions. We compare the phase diagrams obtained from simulations with the results of the free-volume approach and with direct simulations of the true binary mixture. Although we did not simulate the polymer coils explicitly, we are able to obtain the three partial structure factors and radial distribution functions. We compare our results with those obtained from density functional theory and the Percus-Yevick approximation. We find good agreement between all results for the structure. We also study the mixture in contact with a single hard wall for q=1. Upon approach of the gas-liquid binodal, we find far from the triple point, three layering transitions in the partial wetting regime.

Journal Article↗
PubMed2002

Novel colloidal crystalline states on two-dimensional periodic substrates.

We show, using numerical simulations, that a rich variety of novel colloidal crystalline states are realized on square and triangular two-dimensional periodic substrates which can be experimentally created using crossed-laser arrays. When there are more colloids than potential substrate minima, multiple colloids are trapped at each substrate minima and act as a single particle with a rotational degree of freedom, giving rise to a new type of orientational order. We call these states colloidal molecular crystals. A two-step melting can also occur in which individual colloidal molecules initially rotate, destroying the overall orientational order, followed by the onset of interwell colloidal hopping.

Journal Article↗
PubMed1979

Colloid-amyloid bodies in PUVA-treated human psoriatic patients.

In 4 cases of PUVA-treated psoriatic patients a number of colloid bodies and amyloid-like deposits were seen at the dermo-epidermal junction, in a very similar fashion the colloid bodies and the amyloid substances are deposited in lichen planus and in primary cutaneous anyloidoses respectively. In some instances such a deposition was found within the epidermis and contained remnants of cellular debris. Serial sections revealed that a part of the intraepidermal deposit is located in the dermis. Some deposition is partially composed of typical amyloid filaments and partially of nonamyloidal filaments. The latter were identical to those found in colloid or Civatte bodies of lichen planus and other conditions. Follow-up biopsies done in 1 patient several months after the cessation of the treatment still showed these substances. It was suggested that the amyloid-like substances are the product of special degeneration (apoptosis) of epidermal cells as colloid substances: Initally these cells undergo filamentous or colloid degeneration and they drop off into the dermis; where some of the characteristics of filaments are modified and connective tissue elements are added to produce such filamentous and amorphous components as seen in the amyloid island, whereas others remain as colloid bodies. Absorption or elimination of these substances seem to be extremely slow.

Furocoumarins↗
PubMed2006

Colloid transport of plutonium in the far-field of the Mayak Production Association, Russia.

Sorption of actinides, particularly plutonium, onto submicrometer-sized colloids increases their mobility, but these plutonium colloids are difficult to detect in the far-field. We identified actinides on colloids in the groundwater from the Mayak Production Association, Urals, Russia; at the source, the plutonium activity is approximately 1000 becquerels per liter. Plutonium activities are still 0.16 becquerels per liter at a distance of 3 kilometers, where 70 to 90 mole percent of the plutonium is sorbed onto colloids, confirming that colloids are responsible for the long-distance transport of plutonium. Nano-secondary ion mass spectrometry elemental maps reveal that amorphous iron oxide colloids adsorb Pu(IV) hydroxides or carbonates along with uranium carbonates.

Journal Article↗
PubMed1990

Effect of colloidal bismuth subcitrate on symptoms and gastric histology in non-ulcer dyspepsia. A double blind placebo controlled study.

The aim of this study was to determine the effect of colloidal bismuth subcitrate (De Nol) on symptoms and gastric histology in patients with non-ulcer dyspepsia. In a single centre trial, patients with food related upper abdominal pain not caused by ulcer disease were randomised to receive one tablet of colloidal bismuth subcitrate or matching placebo four times daily for eight weeks. Seventy three patients were entered and 51 completed the trial: 28 patients in the colloidal bismuth subcitrate group and 23 in the placebo group. Overall there was no difference between the two groups in terms of symptom relief. Among patients with histological gastritis (n = 23), however, those who took colloidal bismuth subcitrate used fewer antacid tablets (for three of four fortnightly periods) and were more likely to become asymptomatic (eight of 11 v three of 12, p less than 0.05); their gastritis was more likely to resolve (five of 10 v 0 of 12, p less than 0.025) and their gastric biopsies more likely to become negative for Helicobacter like organisms (eight of nine v 0 of 12, p less than 0.001) when compared with patients taking placebo. In contrast, patients who did not have gastritis in their index biopsies (n = 28) fared similarly whether they received colloidal bismuth subcitrate or placebo. Our results indicate that the administration of colloidal bismuth subcitrate benefited non-ulcer dyspepsia patients with gastritis but had no effect on those without.

Adult↗
PubMed1977

Adsorption of horseradish peroxidase, ovomucoid and anti-immunoglobulin to colloidal gold for the indirect detection of concanavalin A, wheat germ agglutinin and goat anti-human immunoglobulin G on cell surfaces at the electron microscopic level: a new method, theory and application.

A method is described for the adsorption of selected macromolecules to colloidal gold which is then used as an electron dense marker for the indirect detection of specific cell surface molecules. Membrane bound concanavalin A, which binds specific sugars on horseradish peroxidase, and wheat germ agglutinin, which binds specific sugars on ovomucoid are detected indirectly with gold labeled horseradish peroxidase and ovomucoid, respectively. Goat anti-human IgM on blood lymphocytes is detected with gold labeled rabbit anti-goat IgG. In the preparation of colloidal gold labeled proteins, the problems of flocculation of colloidal gold by proteins and nonadsorption of proteins to colloidal gold, are solved through a combination of concentration of protein and pH variable adsorption isotherms, which allows one to determine the conditions for adsorption of proteins to colloidal gold. Adsorption is pH dependent, the pH conditions correlating with the isoelectric point(s) of the major protein fraction(s); adsorption is influenced by interfacial tension, solubility and by the electrical charge on the molecules. Colloidal gold is inexpensive and preparation of a useful label is rapid, reproducible and the results easily quantitated from electron micrographs.

Animals↗
PubMed2002

Highly selective molecularly imprinted overoxidized polypyrrole colloids: one-step preparation technique.

A convenient "one step" preparation process of molecularly imprinted overoxidized-polypyrrole (oPPy) colloids by chemical polymerization and their high uptake ability and enantioselectivity are described. Since an oxidizing agent gives a different standard redox potential and rate of polymerization, the property of the resulting oPPy colloid can be controlled by the kind and concentration of the oxidizing agent. At higher concentrations of (NH4)2S2O8 (0.3 M), the overoxidation of PPy colloid automatically occurred. The extraction of L-lactate as a dopant has created a shape-complementary cavity on the surface of the oPPy colloid through overoxidation following polymerization. The oPPy colloid exhibited an excellent selectivity not only on the alanine enantiomer but also on the difference in the side-chain size of amino acids. The uptake of oPPy colloid towards L-alanine over D-alanine was 11.3 micromol/g-colloid against 3.6 micromol/g. The molecularly imprinted cavity can also recognize the existences of the OH or CH3 substituents.

Indicators and Reagents↗
PubMed1992

Colloidal gold uptake as a marker for monocyte differentiation and maturation in normal and leukemic cells.

The uptake of colloidal gold particles by human monocytes was studied by electron microscopy, with special emphasis on changes in this uptake during the differentiation and maturation of these cells. The way in which leukemic cells of childhood acute non-lymphocytic leukemia (ANLL) can function in this gold uptake was also examined. In monocytes, microendocytosis was temperature-dependent; colloidal gold uptake increased as temperatures rose from 4 degrees C to 37 degrees C. It appeared that gold particles first adhered to the cell surface membrane, were then incorporated into the cytoplasmic vesicles, and then were transported into the granules. Original HL-60 cells and retinoic acid (RA)-treated HL-60 cells, which were differentiating and maturing along the granulocyte lineage, did not ingest colloidal gold particles, but 1,25(OH)2D3-treated HL-60 cells showed colloidal gold uptake during their differentiation and maturation along the monocyte lineage: 68.6% of the cells contained gold particles. Gold uptake was demonstrated in 27.3% of original U937 cells; the percentage increased to 70.3% when they were induced to mature by RA. In 15 specimens of childhood ANLL, none of the M1, M2 or M3 cells showed colloidal gold uptake, whereas 76-97% of M4 and M5 cells showed this uptake. These findings indicate that colloidal gold uptake is a marker of monocyte differentiation and maturation and can provide additional information for ANLL cytology.

Adolescent↗
PubMed1989

[Ultrastructure of colloid bodies in oral lichen planus].

Ultrastructure of 20 cases oral lichen planus was observed. Colloid bodies were found in 4 cases. Morphologically, the colloid bodies could be divided into four types: Mass-filament shape: compound type of mass-filament shape and filament shape of low electronic density; filament shape of low electronic density and filament shape of high electronic density. Among them, the compound type was not reported until this study. Owing to discovery of the compound colloid body, the fact that there is an intermediate stage in the course of formation of the colloid body was more correctly known by the authors. And a model figure which expressed the course of formation of colloid bodies was drawn up. The authors have imagined the nature of colloid body is degeneration of epithelial cells. The result of degeneration is death of the cells.

Humans↗
PubMed1989

Aspects of dental plaque formation with special reference to colloid-chemical phenomena.

In order to investigate factors of importance for plaque formation and the rate of plaque formation 133 randomly selected individuals went through a 3-day period of plaque accumulation. From these individuals one group of "heavy" and one group of "light" plaque formers were selected for further studies. These subjects were investigated with reference to clinical, biochemical, biophysical and microbiological variables, that in the literature have been suggested to influence plaque formation. The collected data were analysed statistically both by comparisons between the two groups and by multiple regression. In the comparative analyses there were only minor differences between the groups, and no single studied variable was considered as the only explanation to the great difference in the amount of plaque formed after 3 days between "heavy" and "light" plaque formers. The multiple regression showed that the initial bacterial colonization of tooth surfaces was dependent on the clinical wettability of tooth surfaces, the saliva-induced aggregation of oral bacteria and finally the relative salivary flow conditions around the tooth surfaces where the bacterial samples were collected. On basis of these results, it was suggested that saliva and oral bacteria could at least partly be looked upon as being a biological colloid system system. Further studies were designed to investigate whether oral bacteria could be regarded as colloid particles or not, and to study the properties of saliva as a colloid suspending medium. These studies showed that bacteria suspended in different salt solutions were dependent on pH, ionic concentration and the valency of the cations in the solutions to be able to aggregate. The aggregating capacity further seemed to be specific for different bacterial species and strains. Addition of saliva from "heavy" and "light" plaque formers influenced the colloid stability of bacteria suspended in water in different ways. Saliva from "light" plaque formers gave a lower colloid stability in suspensions of a plaque-forming bacterium (Streptococcus sanguis) as compared to the addition of saliva from "heavy" plaque formers. No such differences were observed in suspensions of S. salivarius, which is normally not a plaque-forming bacterium. The results indicate that colloid-chemical processes might be involved in bacterial attachment to tooth surfaces, and that initial bacterial colonization of tooth surfaces at least partly follow general biophysical laws.

Adhesiveness↗
PubMed1997

Maintenance therapy with colloidal bismuth subcitrate reduces duodenal ulcer relapse.

AIM: To investigate the efficacy and safety of daily low-dose colloidal bismuth subcitrate in reducing duodenal ulcer relapse. DESIGN: Double-blind, double-dummy group comparative clinical trial with random allocation. Healing Phase: colloidal bismuth subcitrate 240 mg twice daily vs ranitidine 150 mg twice daily for up to 12 weeks. Maintenance Phase: nightly, colloidal bismuth subcitrate 120 mg vs ranitidine 150 mg vs placebo for up to 12 months (high-risk patients received active treatment only). ASSESSMENT: clinical, endoscopy, random blood bismuth levels (and rapid urease test for Helicobacter pylori in a subgroup). PATIENTS: 194 with active duodenal ulcer. OUTCOME: Cumulative healing at 12 weeks was 93% on colloidal bismuth subcitrate (of 92 patients) and 97% on ranitidine (of 102 patients). Relapse at 1 year was significantly less on active treatment as follows: placebo (50 patients) 60%; ranitidine (71 patients) 21%; colloidal bismuth subcitrate (64 patients) 33%. This was independent of the results of the rapid urease test which was positive in 78%, 88% and 76% of the patients respectively. Treatment was well tolerated. The highest median blood bismuth level (mcg/L) was 25 in the healing phase and fluctuated between 6 and 10 in the maintenance phase. CONCLUSIONS: Colloidal bismuth subcitrate, 120 mg nightly, is effective in reducing duodenal ulcer relapse and is well tolerated.

Adult↗