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PubMed2005

Colloid-facilitated transport of cesium in variably saturated Hanford sediments.

Radioactive 137Cs has leaked from underground waste tanks into the vadose zone at the Hanford Reservation in south-central Washington State. There is concern that 137Cs, currently located in the vadose zone, can reach the groundwater. In this study, we investigated whether, and to what extent, colloidal particles can facilitate the transport of 137Cs at Hanford. We used colloidal materials isolated from Hanford sediments. Transport experiments were conducted under variably saturated, steady-state flow conditions in repacked, 20 cm long Hanford sediment columns, with effective water saturations ranging from 0.2 to 1.0. Cesium, pre-associated with colloids, was stripped off during transport through the sediments. The higher the flow rates, the less Cs was stripped off, indicating in part that Cs desorption from carrying colloids was a residence-time-dependent process. Depending on the flow rate, up to 70% of the initially sorbed Cs desorbed from colloidal carriers and was captured in the stationary sediments. Less Cs was stripped off colloids under unsaturated than under saturated flow conditions at similar flow rates. This phenomenon was likely due to the reduced availability of sorption sites for Cs on the sediments as the water content decreased and water flow was divided between mobile and immobile regions.

Adsorption↗
PubMed2005

Chemical heterogeneity of organic soil colloids investigated by scanning transmission X-ray microscopy and C-1s NEXAFS microspectroscopy.

Colloid release and deposition in soils and sorption of inorganic and organic pollutants to soil colloids are strongly influenced by the composition and chemical heterogeneity of colloidal soil particles. To investigate the chemical heterogeneity of organic soil colloids at the particle scale, we used synchrotron scanning transmission X-ray microscopy (STXM) and C-1s near-edge X-ray absorption fine structure (NEXAFS) spectroscopy on 49 individual particles isolated from the surface horizons of three forest soils. Stacks of 130 images of each particle were collected at different X-ray energies between 280 and 310 eV. From these image arrays, NEXAFS spectra were obtained for each pixel and analyzed by principle component analysis and cluster analysis (PCA-CA) to characterize the intraparticle heterogeneity of the organic components. The results demonstrate that the organic matter associated with water-dispersible soil colloids is chemically heterogeneous at the single-particle scale. PCA-CA identified at least two distinct regions within single particles. However, the spectral variations between these regions were much smaller than the variations of averaged NEXAFS spectra representing different particles from the same soil horizon, implying that interparticle heterogeneity is much larger than intraparticle heterogeneity. Especially the contents of aromatic and carboxyl carbon exhibited a large variability. Overall, the NEXAFS spectra of water-dispersible soil colloids were similar to the NEXAFS spectrum of the humic acid fraction, but differed clearly from the fulvic acid and dissolved organic matter fractions extracted from the same soil horizon using conventional techniques.

Colloids↗
PubMed2006

Observed and simulated fluid drag effects on colloid deposition in the presence of an energy barrier in an impinging jet system.

The deposition and re-entrainment behaviors of carboxylate-modified latex microspheres (0.2-, 0.5-, 1.0-, and 2.0-microm diameter) were examined in an impinging jet system on both glass and quartz substrata under a variety of environmentally relevant fluid velocities (2.12 x 10(-4) to 1.06 x 10(-3) m sec(-1)) in both the absence and the presence of an energy barrier to deposition. In the absence of an energy barrierto deposition, deposition fluxes onto glass and quartz substrata increased with increasing fluid velocity for all four microsphere sizes, in accordance with expectations from theory. In contrast, in the presence of an energy barrier to deposition, deposition efficiencies onto glass and quartz substrata decreased with increasing fluid velocity for all four microsphere sizes. Lack of re-entrainment and observed strong attachment were consistent with the expectation that deposition occurs via the primary energy minima where nanoscale surface heterogeneity locally reduces or eliminates the energy barrier to deposition. Colloid deposition onto an overall opposite-charged surface was simulated using a particle transport model with randomly distributed hetero domains that were like-charged relative to the colloid. Varying the size and number of the hetero domains showed that simulated colloid deposition efficiencies decreased with increasing fluid velocity when the hetero domains were small relative to the colloid. The simulations thereby demonstrate that observed decreases in colloid deposition efficiencies with increasing fluid velocity are consistent with the hypothesis that colloid deposition onto overall like-charged surfaces occurs at nanoscale hetero domains where repulsion is locally reduced or eliminated.

Carboxylic Acids↗
PubMed2006

A class of supported membranes: formation of fluid phospholipid bilayers on photonic band gap colloidal crystals.

We report the formation of a new class of supported membranes consisting of a fluid phospholipid bilayer coupled directly to a broadly tunable colloidal crystal with a well-defined photonic band gap. For nanoscale colloidal crystals exhibiting a band gap at the optical frequencies, substrate-induced vesicle fusion gives rise to a surface bilayer riding onto the crystal surface. The bilayer is two-dimensionally continuous, spanning multiple beads with lateral mobilities which reflect the coupling between the bilayer topography and the curvature of the supporting colloidal surface. In contrast, the spreading of vesicles on micrometer scale colloidal crystals results in the formation of bilayers wrapping individual colloidal beads. We show that simple UV photolithography of colloidal crystals produces binary patterns of crystal wettabilities, photonic stopbands, and corresponding patterns of lipid mono- and bilayer morphologies. We envisage that these approaches will be exploitable for the development of optical transduction assays and microarrays for many membrane-mediated processes, including transport and receptor-ligand interactions.

Colloids↗
PubMed2005

Influence of confinement on the electrostatic interaction between charged colloids: a (N,V,T) Monte Carlo study within hyperspherical geometry.

Monte Carlo simulations within closed hyperspherical geometry are used to analyze the ionic distribution around two confined charged colloids to determine the origin of the net attraction recently reported in the literature. A scaling procedure is used to compare our numerical results obtained with small ideal colloids with the conclusion of the measurements performed with large silica colloids. Although no electrostatic attraction is detected under confinement, our simulations exhibit a significant reduction of the electrostatic repulsion between charged colloids confined between two weakly charged walls. After rescaling to reproduce the electrostatic repulsion between large confined colloids, our numerical results are qualitatively consistent with the reported attraction because we reasonably expect a reduction of the electrostatic force between such confined colloids below the order of magnitude of their van der Waals attraction.

Colloids↗
PubMed2004

Analysis of bacterial adhesion using a gradient force analysis method and colloid probe atomic force microscopy.

The atomic force microscope (AFM) has been used to examine the stickiness of bacteria on the basis of the analysis of approach and retraction force curves between the AFM tip and the bacterial surface. One difficulty in analyzing approach curve data is that the distance between the AFM tip and the surface of the bacterium is difficult to define. The exact distances are difficult to determine because the surface of the bacterium deforms during force imaging, producing a highly nonlinear region in the approach curve. In this study, AFM approach and retraction curves were obtained using a colloid probe AFM for three strains of Escherichia coli (D21, D21f2, and JM109). These strains differed in their relative adhesion to glass surfaces, on the basis of measurements of sticking coefficients in packed bed flow through column tests. A gradient force curve analysis method was developed to model the interactions between the colloid probe and a surface. Gradient analysis of the approach curve revealed four different regions of colloid-surface interactions during the approach and contact of the probe with the bacterial surface: a noninteraction region, a noncontact phase, a contact phase, and a constant compliance region. The noncontact phase, which ranged from 28 to 59 nm for the three bacterial strains, was hypothesized to arise primarily from steric repulsion of the colloid by extracellular polymers on the bacterial surface. The contact phase, spanning 59-113 nm, was believed to arise from the initial pressure of the colloid on the outer membrane of the cell. The constant compliance region likely reflected the response of the colloid probe to the stiff peptidoglycan layer that confers strength and rigidity to gram negative bacteria. It was shown that the sticking coefficients reported for the three E. coli strains were correlated with the length of the noncontact phase but not the properties of the other phases. Sticking coefficients were also not correlated with any parameters determined from retraction force curves such as pull-off distances or separation energies. These results show that gradient analysis is useful for studying the contribution of the length of the exopolymers on the cell surface to bacterial adhesion to glass surfaces.

Algorithms↗
PubMed2005

Residence time, loading force, pH, and ionic strength affect adhesion forces between colloids and biopolymer-coated surfaces.

Exopolymers are thought to influence bacterial adhesion to surfaces, but the time-dependent nature of molecular-scale interactions of biopolymers with a surface are poorly understood. In this study, the adhesion forces between two proteins and a polysaccharide [Bovine serum albumin (BSA), lysozyme, or dextran] and colloids (uncoated or BSA-coated carboxylated latex microspheres) were analyzed using colloid probe atomic force microscopy (AFM). Increasing the residence time of an uncoated or BSA-coated microsphere on a surface consistently increased the adhesion force measured during retraction of the colloid from the surface, demonstrating the important contribution of polymer rearrangement to increased adhesion force. Increasing the force applied on the colloid (loading force) also increased the adhesion force. For example, at a lower loading force of approximately 0.6 nN there was little adhesion (less than -0.47 nN) measured between a microsphere and the BSA surface for an exposure time up to 10 s. Increasing the loading force to 5.4 nN increased the adhesion force to -4.1 nN for an uncoated microsphere to a BSA surface and to as much as -7.5 nN for a BSA-coated microsphere to a BSA-coated glass surface for a residence time of 10 s. Adhesion forces between colloids and biopolymer surfaces decreased inversely with pH over a pH range of 4.5-10.6, suggesting that hydrogen bonding and a reduction of electrostatic repulsion were dominant mechanisms of adhesion in lower pH solutions. Larger adhesion forces were observed at low (1 mM) versus high ionic strength (100 mM), consistent with previous AFM findings. These results show the importance of polymers for colloid adhesion to surfaces by demonstrating that adhesion forces increase with applied force and detention time, and that changes in the adhesion forces reflect changes in solution chemistry.

Bacterial Adhesion↗
PubMed2006

Mapping patterned potential energy landscapes with diffusing colloidal probes.

We report a new method for mapping patterned surfaces based on monitoring the interactions of freely diffusing colloidal probes with pattern features to generate measured potential energy landscapes. Evanescent wave scattering and video microscopy are used to track 3D center positions of nominal 2 microm silica colloids as they diffuse over 5-20-nm-thick patterned gold films. An analysis of ensemble-averaged particle height histograms on different pattern features using Boltzmann's equation produces local electrostatic and van der Waals potentials in good agreement with independent measurements and predictions. Absolute separation is obtained from theoretical fits to measured potential-energy profiles and direct measurement by depositing silica colloids onto gold surfaces via electrophoretic deposition. As colloidal probe and pattern feature dimensions become comparable, potential energy profiles suffer some distortion due to the increased probability of probes sampling pattern feature edges. An analysis of interfacial colloidal probe diffusion in conjunction with potential energy measurements demonstrates a consistent interpretation of dissipative and conservative forces in these measurements. Future extensions of this work should produce similar approaches for interrogating physical, chemical, and biomolecular heterogeneous/patterned surfaces and structures with diffusing colloidal probes.

Colloids↗
PubMed2000

Enantioselective uptake of amino acid with overoxidized polypyrrole colloid templated with L-lactate.

An overoxidized polypyrrole colloid, which can recognise enantiomers of amino acids has been prepared by a newly developed molecular imprinting technique. A polypyrrole colloid, which had been polymerised from a mixture of pyrrole (monomer), polyvinylpyrrolidone (steric stabiliser), peroxodisulfate (oxidant) and L-lactate (dopant), was overoxidized to create a dopant-complementary cavity. The enantioselectivity of the overoxidized colloid was evaluated by comparing the uptake of L-alanine and L-cysteine with that of the respective D-enantiomers. The L/D uptake ratios for these amino acids were about 2, while phenylalanine showed suppressed uptake for both the enantiomers. The absence of phenylalanine uptake can be explained in terms of the molecular size, which is too large to be accommodated by the cavity created by L-lactate. In contrast, a colloid templated with L-phenyllactate took up L-phenylalanine with a higher enantioselectivity of about 7. A colloid templated with L-lactate was applied to surface chirality analysis through enantioselective adsorption on cysteine-modified gold surfaces. Quartz microbalance experiments and scanning electron microscope observation of the gold surface revealed that the colloidal particle has higher affinity to a surface modified with L-cysteine than to one modified with D-cysteine.

Amino Acids↗
PubMed2001

Determination of total and EDTA extractable metal distributions in the colloidal fraction of contaminated soils using SdFFF-ICP-HRMS.

Newly developed methods involving an on-line combination of sedimentation field-flow fractionation-inductively coupled plasma-high resolution mass spectrometry (SdFFF-ICP-HRMS) have been used to study the distributions of extractable heavy metals in a soil which had been treated with sewage sludge contaminated with Cu or Pb. The relationship of these metals with other elements in the colloidal fraction was also investigated. The colloidal fraction from the soil was obtained by repeated gravitational sedimentation and extracted with 0.11 M acetic acid, 0.1 M hydroxylamine hydrochloride, 0.05 M ethylenediaminetetraacetic acid disodium salt (EDTA) or aqua regia to assess the potential availability of the metals Cu and Pb. Large proportions of the Cu and Pb were extracted by EDTA, approaching that removed by aqua regia, whereas < 10% of the aqua regia extractable metals were removed by acetic acid and hydroxylamine chloride. The distributions of the heavy metals, the major mineral forming element (Al) and the elements forming sesquioxides (Fe and Mn) within different size classes (0.05-1 microm) of the colloidal fraction were measured using SdFFF-ICP-HRMS before and after extraction with EDTA. This information provides an insight into the composition of the colloids and the distributions of metal contaminants. In the contaminated soil colloids, the concentration of Fe, Mn and Pb is greatest in the smaller particles (<0.2 microm). In contrast, the Cu concentration is constant over the size range studied. Iron oxide surface coatings probably play a significant role in Pb adsorption on soil particles, but may be less important for Cu. The combination of selective chemical extraction, SdFFF and ICP-HRMS provides a means of determining the distribution of potentially available heavy metals within the colloidal fraction of contaminated soils.

Chelating Agents↗
PubMedDate not supplied

Protective colloids and polylactic acid co-affecting the polymorphic crystal forms and crystallinity of indomethacin encapsulated in microspheres.

The co-effect of protective colloids and polylactic acid (PLA) on the polymorphic crystal forms and crystallinity of indomethacin (IMC) in IMC-loaded PLA microspheres was investigated with differential scanning calorimetry, infrared spectroscopy and x-ray diffractometry, to evaluate the polymorphic crystal forms and crystallinity of IMC encapsulated in PLA microspheres. The surfactant, sodium dodecyl sulphate (SDS), was also used as a dispersing agent. The results indicate that the polymorphism and crystallinity of IMC encapsulated in IMC-loaded PLA microspheres was dependent on the type of protective colloid and PLA used. The amorphous state and alpha-form of IMC were found in the IMC-loaded PLA microspheres prepared using polysaccharide (pectin or beta-cyclodextrin) as a protective colloid or SDS as a dispersing agent. However, the amorphous and methylene chloride solvate of IMC seemed to exist in the IMC-loaded PLA microspheres prepared with the proteins (gelatin or albumin), synthetic cellulose derivative (methyl cellulose or hydroxylpropyl methylcellulose) or the synthetic nonionic polymer (polyvinyl alcohol, polyvinyl pyrrolidone or biosoluble polymer) as a protective colloid. PLA was found to express a certain crystallinity in microspheres and not be affected by the protective colloids, but it played a more important role in influencing the crystallization of IMC during microencapsulation than the protective colloids. No interaction occurred in the physical mixture of IMC and PLA, nor in the IMC-loaded PLA microspheres.

Calorimetry, Differential Scanning↗
PubMed2002

Colloid cysts of the third ventricle in identical twins.

A young man presented to our unit with a colloid cyst of the third ventricle. Following successful surgical treatment his parents expressed concern over the possibility of his identical twin brother having a similar cyst. After finding one other case of colloid cysts in identical twins in the world literature we arranged a magnetic resonance scan of the asymptomatic twin. We were sceptical, but much to our surprise the scan also showed a colloid cyst in the third ventricle. Familial colloid cysts of the third ventricle have been reported only rarely. This is the second account of third ventricular colloid cysts in identical twins reported in the world literature. We present case reports of the twins, discuss the world literature on familial colloid cysts and also the genetic implications.

Adult↗
PubMed1973

Anionic sites of human erythrocyte membranes. I. Effects of trypsin, phospholipase C, and pH on the topography of bound positively charged colloidal particles.

The effects of pH, trypsin, and phospholipase C on the topographic distribution of acidic anionic residues on human erythrocytes was investigated using colloidal iron hydroxide labeling of mounted, fixed ghost membranes. After glutaraldehyde fixation at pH 6.5-7.5, the positively charged colloidal particles were bound to the membranes in small randomly distributed clusters. The clusters of anionic sites were reversibly aggregated by incubation at pH 5.5 before fixation at the same pH. These results correlate with the distribution of intramembranous particles found by Pinto da Silva (J. Cell Biol.53:777), with the exception that the distribution of anionic sites on a majority of the fixed ghosts at pH 4.5 was aggregated instead of dispersed. The randomly distributed clusters could be nonreversibly aggregated by trypsin or phospholipase C treatment of intact ghosts before glutaraldehyde fixation. Previous glutaraldehyde fixation prevented trypsin and pH induced aggregation of the colloidal iron sites. Evidence that N-acetylneuraminic acid groups are the principal acidic residues binding colloidal iron was the elimination of greater than 85% of the colloidal iron labeling to neuraminidase-treated cell membranes. Colloidal iron binding N-acetylneuraminic acid residues may reside on membrane molecules such as glycophorin, a sialoglycoprotein which contains the majority of the N-acetylneuraminic acid found on the human erythrocyte membrane.

Aldehydes↗
PubMed2006

The colloidal thyroxine (T4) ring as a novel biomarker of perchlorate exposure in the African clawed frog Xenopus laevis.

The purpose of this study was to determine if changes in colloidal thyroxine (T(4)) immunoreactivity can be used as a biomarker of perchlorate exposure in amphibian thyroid tissue. Larval African clawed frogs (Xenopus laevis) were exposed to 0, 1, 8, 93, and 1131 microg perchlorate/l for 38 and 69 days to cover the normal period of larval development and metamorphosis. The results of this study confirmed the presence of an immunoreactive colloidal T(4) ring in thyroid follicles of X. laevis and demonstrated that the intensity of this ring is reduced in a concentration-dependent manner by perchlorate exposure. The smallest effective concentration of perchlorate capable of significantly reducing colloidal T(4) ring intensity was 8 microg perchlorate/l. The intensity of the immunoreactive colloidal T(4) ring is a more sensitive biomarker of perchlorate exposure than changes in hind limb length, forelimb emergence, tail resorption, thyrocyte hypertrophy, or colloid depletion. We conclude that the colloidal T(4) ring can be used as a sensitive biomarker of perchlorate-induced thyroid disruption in amphibians.

Animals↗
PubMed1998

Colloidal iron staining in renal epithelial neoplasms, including chromophobe renal cell carcinoma: emphasis on technique and patterns of staining.

Positive staining with Hale's colloidal iron stain, or modifications thereof, is considered a diagnostic feature for chromophobe renal cell carcinoma and has been used as a discriminatory feature to differentiate it from other renal tumors. We studied colloidal iron staining in 62 cases encompassing a wide histologic spectrum of renal neoplasms (14 chromophobe renal cell carcinomas, 19 renal oncocytomas, 11 each of granular variants and conventional clear cell renal cell carcinomas, and 7 eosinophilic variants of papillary renal cell carcinoma) to investigate the specificity of the stain for chromophobe renal cell carcinoma. In cases of chromophobe renal cell carcinoma, sections from two different areas were stained to ascertain whether there was any spatial variation in staining. Influence of staining techniques on the results also was investigated by staining each case of chromophobe renal cell carcinoma using two different methods: the traditional Hale's and a modified Mowry's technique, which treats sections with 3% acetic acid before adding the colloidal iron. Our results show that positive staining with colloidal iron stain is not limited to chromophobe renal cell carcinoma, however, a diffuse and strong, reticular staining pattern was observed only in cases of chromophobe renal cell carcinoma (14 of 14). The staining patterns were less consistent in all other renal neoplasms and differed from the reaction observed in chromophobe renal cell carcinoma. Most renal oncocytomas (16 of 19) had focal and weak, fine dustlike positivity, and all clear cell carcinomas showed focal, coarse, dropletlike positive staining (22 of 22), in addition to a focal, coarse, bubbly pattern in 5 of 11 clear cell subtypes. Although all seven cases of the eosinophilic variant of papillary renal cell carcinoma showed strong, coarse, dropletlike staining, most of the positivity was coincident with the Perl's (prussian blue) reaction, indicating that the staining was due to hemosiderin, which is frequently present in this histologic subtype of renal cell carcinoma. Staining intensity did not vary considerably among different areas of chromophobe renal cell carcinoma, but the modified Mowry's method yielded brighter and sharper reticular staining, as compared with the Hale's method. Our results show that in the appropriate morphologic context diffuse and strong reticular positivity using the modified Mowry's colloidal iron stain method is highly characteristic for chromophobe renal cell carcinoma. Treatment of sections with 3% acetic acid before adding the colloidal iron gives technically superior staining results.

Adenocarcinoma, Clear Cell↗
PubMed2002

The effects of perioperatively administered colloids and crystalloids on primary platelet-mediated hemostasis and clot formation.

UNLABELLED: To explore whether routinely administered colloids and crystalloids influence the hemostatic system, we studied 60 patients undergoing knee replacement surgery during randomized intravascular fluid administration using 6% hydroxyethyl starch 200/0.5 (HES) or 4% modified gelatin (GEL) in addition to a basal infusion of lactated Ringer's solution (RL), or exclusively RL. In addition to routine coagulation tests, measurements of coagulation factors were performed. Also, functional measurements of the in vitro bleeding time by use of the platelet function analyzer (PFA-100 and ROTEG analysis (ROTEG(R); extrinsically and intrinsically [Ex; In] activated measurements of clotting time, CT [s]; clot formation time, CFT [s]; clot strength, A20 [mm]; fibrinogen component of the clot, FibA20 [mm]; and maximal clot elasticity) were used. Time dependency of variables was analyzed with a repeated-measures analysis of variance (all groups pooled); differences between groups were detected by comparing the calculated area under the curve (AUC(A-D)). For all variables, except ExCT, ExCFT, and InCFT, a significant time dependency was demonstrated, indicating that impaired platelet-mediated hemostasis and clot formation occurred with IV administration of fluids. Total clot strength, fibrinogen part, and clot elasticity decreased significantly more in the colloid groups than in the RL group (InA20: HES, -13.0 mm; GEL, -11.5 mm; RL, -1.3 mm; P = 0.042; FibA20: HES, -10.5 mm; GEL, -6.0 mm; RL, -1.3 mm: P < 0.0001; MCE: HES, -48; GEL, -35; RL, -15.8; P < 0.0001). The decrease in fibronectin concentrations was significantly smaller with GEL as compared with HES, whereas a weak trend toward a larger decrease in fibrinogen concentrations was observed with both colloids. Results show that colloid administration reduces final clot strength more than does RL alone, which also exhibited effects, albeit minor, on the coagulation system. The reduction in total clot strength was due to impaired fibrinogen polymerization, resulting in a decreased fibrinogen part of the clot and reduced clot elasticity. IMPLICATIONS: Our data suggest that during deliberate colloid administration, critically impaired fibrinogen polymerization and reduced fibrinogen concentrations might be reached earlier than expected. Therefore, maintaining fibrinogen concentrations seems essential when continuing blood loss is bridged by colloid infusion until transfusion triggers are reached, especially in patients already exhibiting borderline fibrinogen levels at baseline.

Aged↗
PubMed2006

Contrasting effects of colloid and crystalloid resuscitation fluids on cardiac vascular permeability.

BACKGROUND: Fluid extravasation may lead to myocardial edema and consequent reduction in ventricular function. Albumin is presumed to interact with the endothelial glycocalyx. The authors' objective was to compare the impact of different resuscitation fluids (human albumin, hydroxyethyl starch, saline) on vascular integrity. METHODS: In an isolated perfused heart model (guinea pig), Krebs-Henseleit buffer was augmented with colloids (one third volume 5% albumin or 6% hydroxyethyl starch 130/0.4) or crystalloid (0.9% saline). Perfusion pressure and vascular fluid filtration (epicardial transudate formation) were assessed at different flow rates. After global, stopped-flow ischemia (37 degrees C, 20 min), hearts were reperfused with the same resuscitation fluid additives. In a second series, the authors applied the respective perfusates after enzymatic digestion of the endothelial glycocalyx (heparinase, 10 U over 15 min). RESULTS: Both 5% albumin and 6% hydroxyethyl starch decreased fluid extravasation versus saline (68.4 +/- 5.9, 134.8 +/- 20.5, and 436.8 +/- 14.7 microl/min, respectively, at 60 cm H(2)O perfusion pressure; P < 0.05), the corresponding colloid osmotic pressures being 2.95, 5.45, and 0.00 mmHg. Digestion of the endothelial glycocalyx decreased coronary integrity in both colloid groups. After ischemia, a transient increase in vascular leak occurred with Krebs-Henseleit buffer containing hydroxyethyl starch and saline, but not with albumin. The authors observed no difference between intravascular and bulk interstitial colloid concentration in the steady state. Notwithstanding, electron microscopy revealed an intact endothelial glycocalyx and no interstitial edema in the albumin group. CONCLUSION: Ex vivo, albumin more effectively prevented fluid extravasation in the heart than crystalloid or artificial colloid. This effect was partly independent of colloid osmotic pressure and may be attributable to an interaction of albumin with the endothelial glycocalyx.

Albumins↗
PubMed1982

Relation of colloid concentration to volume expansion for resuscitation of rats subjected to intestinal ischemic shock.

This study was undertaken to determine the volumes of colloids (albumin and dextran 40) with concentrations varying from 0% (Ringer's solution) to 10% solutions required to obtain the same hemodilution. Shock was produced in rats by exteriorization of the small intestine with added complete occlusion of the superior mesenteric vessels with a rubber clamp. After 1 h the clamp was removed, the intestines returned, and the abdomen closed. Over a 6-h period, the fluids were infused continuously in volumes needed to maintain similar hematocrit. Each concentration was given over a wide range of volumes in order to obtain volume-hematocrit curves. Based on these curves, the effect of varying colloid concentration on blood volume expansion was calculated. Albumin and dextran 40 had similar volume expansion/g colloid substance regardless of concentration. When hematocrit of 50% was chosen, as an arbitrary endpoint for volume infusion, the colloid concentration in relation to volume required to be infused is expressed by the equation F50 (formula: see text) where C = colloid concentration and where F50 is the volume factor, or the number of times the volume required for a 10% solution, when a 10% solution is given the volume factor of 1. This relationship is now being used to find the optimal colloid concentration with regard to survival rate in animals subjected to the same intestinal shock.

Albumins↗