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At least 37 records · Page 2Linked to original sources
PubMed2001

Metal-colloid partitioning in artificial interstitial waters of marine sediments: influences of salinity, pH, and colloidal organic carbon concentration.

For decades, heavy metals have been deposited into marine sediments as a result of anthropogenic activities. Depending on their bioavailability, these metals may represent a risk to benthic organisms. Dissolved interstitial water metal concentrations have been shown to be better predictors of bioavailability than sediment metal concentrations. In order to improve our understanding of metals bioavailability in sediments, it is essential to fully comprehend metal speciation. Colloidal organic carbon is ubiquitous in marine interstitial water and readily forms complexes with numerous dissolved metals, greatly reducing their bioavailability. Methods were applied to isolate dissolved and colloidal cadmium, copper, nickel, lead, and zinc from interstitial waters using centrifugation and stirred cell ultrafiltration. Influences of salinity, pH, and colloidal carbon concentration on partitioning behavior were investigated. In the pH study, colloidal-dissolved partitioning of each metal (Kp) was observed to increase as pH rose. Conversely, in the salinity experiment, metal Kps declined as salinity increased. For the metal-organic colloid study, linear isotherms were calculated for each of the metals, resulting in log Kcocs ranging from 5.90 for zinc to 7.50 for copper. Kp values calculated from metal-spiked field sediments were in good agreement with those measured in the salinity study. These results provide insight into the behavior of metals associated with colloidal organic carbon in marine sediments under the conditions occurring in estuarine systems.

Biological Availability↗
PubMed1981

Determination of radiochemical purity and pharmacokinetic parameters of 99mTc-sulphur colloid and 99mTc-tin colloid.

Labelling yield and radiochemical purity, higher than 95%, of 99mTc-colloid preparations were determined by using the paper chromatography method. Less than 3% of labelled citric acid, added to the preparation as a buffer solution, has been found in 99mTc-sulphur colloid. High radiochemical purity and optimum size of colloid particles has also been proved by biodistribution studies on experimental animals. The analysis performed has shown that more than 50% of 99mTc-colloid preparations excreted by urine is 99mTcO-, the remaining past 50% being protein bound 99mTc. Biological half-time of excretion of the fast phase is the same for both preparations, i.e. 10 min, while for the slow component it is 120 min in 99mTc-S-colloid and 160 min in 99mTc-Sn colloid.

Animals↗
PubMed2003

Colloidal epitaxy: playing with the boundary conditions of colloidal crystallization.

We have studied, with quantitative confocal microscopy, epitaxial colloidal crystal growth of particles interacting with an almost hard-sphere (HS) potential in a gravitational field and density matched colloids interacting with a long-range (LR) repulsive potential with a body-centred cubic (BCC) equilibrium crystal phase. We show that in both cases it is possible to grow thick, stacking fault-free metastable crystals: close-packed crystals with any stacking sequence, including hexagonal close packed (HCP), for the HS particles and face-centred cubic (FCC) in the case of the LR colloids. In accordance with recent computer simulations done for HS particles it was found that the optimal lattice constant to grow HS HCP crystals was larger than that of equilibrium FCC crystals. In addition, because of the absence of gravity, pre-freezing could be observed for the particles with the LR potential on a template of charged lines. We also argue that the ability to manipulate colloids with highly focused light, optical traps or tweezers, will become an important tool in both the study of colloidal crystallization and in making new structures. We show how cheap 2D and 3D templates can be made with optical tweezers and demonstrate, in proof of principle experiments with core-shell colloids, how light fields can generate crystal nuclei and other structures in the bulk of concentrated dispersions and how the effect of these structures on the rest of a dispersion can be studied quantitatively in 3D.

Journal Article↗
PubMed1986

Comparison of three RE agents-99mTc-phytate, 99mTc-sulfur colloid and 99mTc-Sb2S3 colloid in the rodent species.

99mTc-phytate, 99mTc-sulfur colloid and 99mTc-antimony sulfide colloid are recognised as RE agents in clinical nuclear medicine. Since these three agents exist in vitro in different forms of particulate aggregation it was of interest to compare their properties and to evaluate the merits and limitations of each of these agents. A comparison was carried out in rats and rabbits as a prelude to a systematic study in human subjects. Quality tested radiopharmaceuticals were prepared and their pharmacokinetics studied in rats. The blood clearance, tissue distribution and scinti-imaging patterns of the RE system were also compared in rabbits. All the agents have excellent localizing properties in the liver but differ in varying extents in their disposition in other tissues. 99mTc-sulfur colloid has some predisposition for the lungs while 99mTc-phytate has a little propensity for the kidney and gut at late time periods. 99mTc-Sb2S3 colloid shows a more pronounced concentration in the bone-marrow, and displays intermediate properties between 99mTc-phytate and 99mTc-sulfur colloid, besides being the most stable (in vitro) radiopharmaceutical in this series of RE agents.

Animals↗
PubMed1987

Colloid shift in technetium-99m sulfur colloid liver-spleen scans of trauma patients.

To assess the radiosulfur colloid distribution in the liver-spleen scans of trauma patients, 73 trauma patients (age: 4-74 years, mean: 32 years) who had Tc-99m sulfur colloid liver-spleen scans for trauma workup were studied and compared with the liver-spleen scans of 87 control patients (age: 2-64 years, mean: 36 years). Radiocolloid distribution was visually assessed by two physicians independently, and the areas of the greatest density in the liver and spleen on the posterior view that included both organs were compared. The scans were grouped into three grades: Grade I, liver density greater than spleen density; Grade II, both organs showing equal density; and Grade III, splenic density greater than liver density (colloid shift). Forty-three of the trauma patients (59%) were in Grade III, 22 (30%) in Grade I, and 2 (11%) in Grade II. The control group had 12 (14%) patients in Grade III, 54 (62%) in Grade I, and 21 (24%) in Grade II. When the young adults and children of the trauma patients (age: 4-20 years, mean: 14 years) were looked at separately, 17 of 20 (85%) showed colloid shift (Grade III). It is concluded that there is a significantly higher incidence of colloid shift in trauma patients compared to control patients (P less than .01).

Adolescent↗
PubMed1976

Distribution of yttrium 90 ferric hydroxide colloid and gold 198 colloid after injection into knee.

Thirteen knees were injected with yttrium 90(90Y) ferric hydroxide colloid, and 12 with gold 198(198Au) colloid for treatment of persistent synovitis. Retention in the knee and uptake in lymph nodes and liver were measured by a quantitative scanning technique. There was no significant difference in the retention in the knee of the two different colloids. A tendency towards higher lymph node uptake was observed with 198Au compared with 90y. The inflammatory activity of the knee at the time of treatment may have influenced the subsequent lymph node uptake of 198Au, but not that of the 90Y, nor the overall leakage of either from the knee. 90Yferric hydroxide colloid was retained in the treated knee at least as well as other colloids which have been used for this purpose.

Gold Colloid, Radioactive↗
PubMed1977

[Drainage of the radioactive lymphotropic tracers 198 Au-colloid and 99m Tc-sulfur-colloid from the orbit in rabbits (author's transl)].

In order to investigate lymph drainage from the retrobulbar space colloid solutions (198Au-colloid and 99mTc-sulfur-colloid) were injected into the right retrobulbar space of 31 rabbits. The distribution of radioactivity was measured in vitro after dissection with a sodium iodine crystal well counter and in some animals in vivo with the Gamma camera. More than 90% of the applied activity of either colloid solution was found in some animals up to the eighth day post injection in the retrobulbar space and in the liver. The remaining activity was recovered mainly from the regional lymph nodes, due to its smaller particle size higher values were registered in the experiments with 198Au than in those with 99mTc. The highest concentrations with up to 4,6% of the activity were observed in the deep cervical lymph nodes on both sides. Minor concentrations of activity were found ipsilateral in the superficial cervical and mandibular lymph nodes. Furthermore, small but significant activities were demonstrated in the optic nerves as well as in the contralateral retrobulbar space. The present data clearly substantiate the existence of lymph drainage, although a slow one, from the retrobulbar space. Moreover they indicate a reverse prelymphatic-lymphatic flow toward the optic nerves and the contralateral retrobulbar space. These results are of importance in the discussions of lymphostatic ophthalmopathy. The clinical application of this method is desirable; however, at present it is not yet practicable without further studies.

Animals↗
PubMed1980

99mTc-colloid kits from the view point of the accretion in the bone marrow--with special reference to comparison with 198Au-colloid.

With 9 kinds of available 99mTc-colloid kits for RES imaging, especially from the aspect of RES imaging of the bone marrow, observations were conducted on pH, the presence of free 99mTcO4(-), labelling efficiency, rabbit blood clearance, the uptake in RES, urinary excretion, as well as the scintigraphy with rabbits and clinical cases. Compared to 198Au-colloid, marrow to liver ratio was found to be about the same, but its uptake to the spleen and liver was greater. In particular its urinary excretion was much more marked than 198Au-colloid, and in clinical use the bladder was more often delineated. This fact seems to suggest that it is desirable to develope a 99mTc-colloid more suitabale for the bone marrow scintigraphy.

Anemia, Aplastic↗
PubMed1981

Positive colloidal thorium dioxide as an electron microscopical contrasting agent for glycosaminoglycans, compared with ruthenium red and positive colloidal iron.

In electron microscopy Thorotrast has been used as a specific contrasting agent for acid glycosaminoglycans. Because of its high atomic number, thorium (Z=90) gives good contrast in the electron microscope, but at present it is less frequently used for this purpose. We prepared a positive colloidal solution of ThO2 without stabilizers to compare its properties with those of ruthenium red and positive colloidal iron for contrasting fetal mouse epiphyseal cartilage. The results indicate that colloidal ThO2, which is easy to prepare in any laboratory, gives better results than ruthenium red and colloidal iron do in this kind of cartilage. Furthermore, as judged from data in the literature and obtained in our laboratory, it penetrates this tissue better than Thorotrast does, probably because of the absence of stabilizers.

Animals↗
PubMed1996

Colloidal Stability of Polymer Colloids with Different Interfacial Properties: Mechanisms

An investigation is presented into the effects of interfacial properties on the colloidal stability of monodisperse polymer colloids using a sulfonate polystyrene (PS) and a styrene-hydroxyethyl methacrylate copolymer (PSHEMA) latex. Both latexes were prepared by emulsion copolymerization in the absence of surfactant. The experimental stability of these colloidal dispersions was studied in relation to the concentration (Ce) of an indifferent electrolyte. Results are compared to current models, relating the stability ratio (W) to intermolecular forces between particles. The Hamaker constant (A) obtained from the log W-log Ce plots and using the DLVO theory is much lower than the theoretical value given by the Lifshitz theory. To achieve good agreement between the experimental and theoretical A values, different corrections to the DLVO theory were introduced. First, the modified stability factor (W) was numerically estimated taking into account the hydrodynamic effect as given by L. A. Spielman [J. Colloid Interface Sci. 33, 562 (1970)]. Next, the real size of the hydrated ions was also considered. With these modifications only, small discrepancies remained between the theoretical and experimental values of the Hamaker constant in the case of the PS latex; however, the A value obtained for the PSHEMA latex studied is rather low. As HEMA is a nonionic and polar monomer, a new correction was made to the DLVO theory: the effect of electrosteric stabilization. Both steric repulsion and the electrostatic effect are shown to play a significant role in maintaining dispersion stability for the PSHEMA latex.

Journal Article↗
PubMed1999

Adsorption of Telechelic Poly(ethylene oxide) on Colloids: Influence on Colloid Stability.

Adsorption of telechelic polymers (hydrophobically end-capped poly(ethylene oxide)) on charged colloidal particles modifies the characteristics of the electrical double layer. These interfaces were found to be able to protect colloids against aggregation or to induce colloid destabilization depending on the molecular weight and type of surface coating. Colloid stability is observed when the polymer layer is thinner than the electrical double layer and when the adsorbed polymer adopts a tethered brush structure. Aggregation of coated latex particles induced by formation of interparticle polymer links is observed when (i) the distance of the random walk of the dangling paraffinic end group is larger than the thickness of the electrical double layer and (ii) the adsorbed polymer brush adopts a loopy structure. Aggregation is attributed to adsorption of hydrophobic end chains on two different latex particles. Copyright 1999 Academic Press.

Journal Article↗
PubMed1982

The significance of colloid osmotic pressure measurement after crystalloid and colloid infusions.

Colloid osmotic pressure (COP) was followed postoperatively in 55 randomized patients. After minor operations and short-term infusion therapy only small changes of the COP could be observed and it was concluded that after such operations COP measurement is unnecessary. After major surgical interventions, however, COP measurement gave valuable hints. It was shown that even in the case of moderate blood loss replaced by crystalloids an abnormally low COP did not occur. The same applied also to preoperative hemodilution. It was unnecessary to substitute the withdrawn blood with a colloid solution. In addition, COP measurement helped to avoid expensive albumin administrations, and indicated colloid overload in cases of pulmonary edema.

Adult↗
PubMed1996

Isolation and measurement of colloids in human plasma by membrane-selective flow field-flow fractionation: lipoproteins and pharmaceutical colloids.

Using a modified flow field-flow fractionation (flow FFF) technique termed membrane-selective flow FFF, a capability is developed to isolate various colloidal constituents that are naturally present in or may be introduced into blood plasma. Once isolated, the colloids may be subject to quantitative measurement to provide relative amounts of the different constituents and the size distribution curve of each. The potential of the technique has been demonstrated by isolating and measuring (a) the lipoprotein fractions found in human blood plasma, (b) liposyn II pharmaceutical emulsion added at 2 mg/mL of plasma, and (c) amphotericin B colloidal dispersion (a drug delivery agent) added to plasma at 0.5 mg/mL.

Chemical Fractionation↗
PubMed1977

Clinical comparison of 99mTc-labeled preformed phytate colloid and sulfur colloid: concise communication.

An in vitro preformed colloid preparation of 99mTc-Sn-phytate was compared both qualitatively and quantitatively with a commercial 99mTc-sulfur colloid kit in 30 patients. The degree of liver and spleen deposition of radiocolloid was, for practical purposes, the same. A slightly higher background was visually noted in 33% of the patients receiving preformed colloidal 99mTc-Sn-phytate, but it did not interfere with the diagnostic quality of the liver and spleen images. The only advantage of the phytate compound was a preparation time of less than 5 min.

Colloids↗
PubMed1999

Colloid Vibration Potential in a Concentrated Suspension of Spherical Colloidal Particles.

A relation between the dynamic electrophoretic mobility of spherical colloidal particles in a concentrated suspension and the colloid vibration potential (CVP) generated in the suspension by a sound wave is obtained from the analogy with the corresponding Onsager relation between electrophoretic mobility and sedimentation potential in concentrated suspensions previously derived on the basis of Kuwabara's cell model. The obtained expression for CVP is applicable to the case where the particle zeta potential is low, the particle relative permittivity is very small, and the overlapping of the electrical double layers of adjacent particles is negligible. It is found that CVP shows much stronger dependence on the particle volume fraction φ than predicted from the φ dependence of the dynamic electrophoretic mobility. It is also suggested that the same relation holds between the electrokinetic sonic amplitude of a concentrated suspension of spherical colloidal particles and the dynamic electrophoretic mobility. Copyright 1999 Academic Press.

Journal Article↗
PubMed1996

Colloid cyst of the third ventricle. Evaluation of 28 cases of colloid cyst of the third ventricle operated on by transcortical transventricular (25 cases) and transcallosal/transventricular (3 cases) approaches.

The clinical and x-ray features of 28 cases of colloid cyst of the third ventricle are described. Colloid cyst is one of the most favourable space-occupying lesions of the brain for successful surgical removal, because an exact pre-operative diagnosis is possible. The surgical approach for colloid cyst of the third ventricle is discussed and the frequency of postoperative seizure is reviewed in 28 cases and compared with the literature.

Adolescent↗
PubMed2000

Volume-term theories of phase separation in colloidal systems and long-range attractive tail in the pair potential between colloidal particles.

To explain the experimental observation that colloidal dispersion exhibits a "two-state" structure under certain conditions, Sogami and Ise (SI) proposed a model for an "effective" pair potential between colloidal particles which had an "attractive tail" more than a decade ago. The SI paper spawned several papers that dwelled on the shortcoming of the SI paper or strived to provide other explanations for the observed inhomogeneity of the suspension. We show herein that a long range attraction in the pair potential between colloidal particles is also obtained in "volume-term" theories in which the repulsive DLVO potential is retained.

Journal Article↗
PubMed1997

High pressure effects on the colloidal calcium phosphate and the structural integrity of micellar casein milk. Part 1. High pressure dissolution of colloidal calcium phosphate in heated milk systems.

Results of this study confirm that high temperature (118 degrees C/15 min) and high pressure (400 MPa/5 min) processing of skim milk, skim milk ultrafiltration and ultracentrifugation fractions, and model milk salt solutions cause dramatic shifts in their colloidal and soluble Ca phosphate equilibrium that affect their pH, dissolved Ca content, turbidity, and casein micelle microstructure. The relations between high temperature and high pressure processing-induced changes in the colloidal and soluble Ca phosphate equilibrium were evaluated in raw, pasteurized, and high temperature treated skim milk, ultrafiltration retentate and permeate of pasteurized skim milk, clear ultracentrifugation infranatant of pasteurized skim milk, and synthetic milk ultrafiltrates with and without lactose or Ca. The magnitude of the pH and dissolved Ca shifts caused by high temperature and high pressure processing was a function of casein micelle concentration. Ultrafiltration permeate exhibited the most drastic shits in pH and dissolved Ca contents due to high temperature and high pressure processing. Although high temperature processing reduced the pH of ultrafiltration permeate from 6.59 to 6.03 and the dissolved Ca from 100% to 58%, high pressure processing reversed both of these changes. These changes in high temperature and high pressure processed milk, milk fractions, and model milk salt solutions were related to microstructural changes in the casein micelles as revealed by electron microscopy.

Animals↗