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Biomedical subjects

S Chien

Publications and source records attributed to S Chien.

At least 199 records · Page 11Linked to original sources
PubMed1986

Some biophysical properties of the erythrocyte membrane in Duchenne muscular dystrophy.

Inasmuch as prior authors have suggested a 'generalized membrane defect' in patients with Duchenne muscular dystrophy, this study was undertaken to examine some biophysical properties of the erythrocytes in affected individuals. Using the micropipette technique we investigated the rheological properties of erythrocytes from 11 Duchenne muscular dystrophy patients (boys 3-14 years old) and 5 carriers (mothers 20-42 years old). The mean elastic modulus and membrane viscosity of the patient's erythrocytes were not significantly different from those of a group of 8 unaffected age-matched boys. The carrier group did not differ significantly from the adult control group in any of the rheological parameters. A significant increase in the number of stomatocytes was observed in the patient group, and a similar trend (not statistically significant) was observed in the carrier group. The membrane lipid fluidity of erythrocytes from patients, carriers, and normal controls was assessed with three different probes by fluorescence depolarization, and no significant differences were found. Our results indicate that there is a progressive elevation of the membrane elastic modulus with increasing age of the patients: the younger patients have a lower elastic modulus than their age-matched controls, while the older patients have a higher elastic modulus than their age-matched controls.

Adolescent↗
PubMed1986

Effects of blood viscosity on plasma renin activity and renal hemodynamics.

The effects of alterations in apparent blood viscosity on renal hemodynamics and plasma renin activity (PRA) were studied in dogs anesthetized with sodium pentobarbital. Blood viscosity was altered isovolemically either by changes in hematocrit (Hct) or by an increase in plasma viscosity (dextran administration). Arterial blood pressure and renal blood flow (RBF) remained relatively constant when apparent blood viscosity was elevated by changes in Hct or plasma viscosity. Thus the hyperviscosity of blood was associated with a decrease of renal vascular hindrance, resulting in an essentially unchanged renal flow resistance. The decrease in renal vascular hindrance may result from renal vasodilation. In hyperviscosity induced with dextran, the increase in PRA correlates linearly with the decrease in renal vascular hindrance, with a coefficient of correlation of 0.968 (P less than 0.005). The increase in PRA that resulted when Hct was raised from 25 to 55% also can be correlated linearly with the decrease in renal vascular hindrance, with a coefficient of correlation of 0.953 (P less than 0.005). These results suggest that the decrease in renal vascular hindrance in response to a rise in apparent blood viscosity leads to an increase in PRA.

Animals↗
PubMed1986

Blood rheology in myocardial infarction and hypertension.

Blood rheology was studied in patients with acute myocardial infarction (AMI) and essential hypertension (EH), and the results were correlated with in vivo hemodynamic functions. Blood viscosity (eta B) was elevated as a result of sequential changes of a number of parameters, including increases in hematocrit, plasma fibrinogen and alpha 2-globulin, an enhancement of red cell aggregation and a reduction of red cell filterability in plasma. Total peripheral resistance (TPR) was elevated upon admission, due to increases in both the vascular hindrance (ZS) and eta B. During recovery, the eta B became normalized; alterations in eta B were accompanied by parallel changes in TPR and an inverse change in plasma volume (PV). In EH patients, the increase in eta B showed a correlation with arterial pressure. For both established and borderline hypertensives, the rheological changes were most prominent in the high renin subgroups. In mild EH, the elevation of eta B was compensated by a decrease in ZS (vasodilation), keeping the TPR essentially normal. In EH with higher arterial pressure, the elevation of eta B was accompanied by a normal ZS without compensatory vasodilation, and hence TPR rose to exacerbate the hypertension. These results suggest that the elevation of eta B may be an early event in the development of EH and that its role must be considered with concurrent cardiovascular functions. In EH there is a significant correlation between left ventricular mass and eta B. Experimental manipulations of the hematocrit level in spontaneously hypertensive rats led to a corresponding variation of arterial pressure. The available data implicate a significant role of eta B in the pathophysiology of AMI and EH. Further interdisciplinary, longitudinal studies are needed tin order to unravel the complicated pathophysiological changes in myocardial infarction and hypertension.

Animals↗
PubMed1986

Ultrastructural studies of endothelial and platelet receptor binding of thrombin-colloidal gold probes.

Endothelial cells and platelets are reported to have receptors for alpha-thrombin. To visualize the binding of alpha-thrombin to these cells, we developed a method to label thrombin with colloidal gold. Formed by electrostatic adsorption of thrombin to the negatively charged gold, the resulting probe is stable for weeks and consists of approximately 30 thrombin molecules adsorbed to each 16.5 nm gold particle. The probe retained about 10% of the enzymatic activity (fibrinogen clotting) of the unlabeled native thrombin and 20% of the ability of the native thrombin to aggregate platelets in platelet-rich plasma (PRP). In PRP, approximately 90% of the observed probes were bound to fibrin strands, with the remaining probes (650 per cell) attached to activated platelets. In contrast, washed, paraformaldehyde-fixed human platelets exhibited a marked increase in probe density (4900 per cell). Time-dependent ultrastructural studies (2-240 min) of binding of the thrombin-gold probe to confluent cultures of porcine aortic endothelial cells revealed that the initial binding (7300 probes per cell) occurred randomly at the cell surface. A limited number (25%) of the probes clustered at coated-pit regions and were internalized (60-240 min). The probe induced a limited amount of cellular retraction similar to that achieved with unlabeled thrombin. These results suggest that the thrombin-gold probe is suitable for investigations of the localization of thrombin receptors on cell surfaces and the interaction of thrombin with these receptors during thrombotic events.

Animals↗
PubMed1986

Quantitative relationship between Heinz body formation and red blood cell deformability.

The ultimate cause of destruction of red blood cells (RBCs) after oxidative damage with Heinz body formation is not well understood. We correlated the changes in RBC morphology and membrane protein composition after oxidant treatment with the alterations in deformability of whole cells and cell membranes. The incubation of RBCs with phenylhydrazine concentrations of 0.3 to 100 mg/dL at 37 degrees C for one hour led to a dose-dependent formation of Heinz bodies, ranging from isolated Heinz bodies at 1 mg/dL to a confluent coating of the inner membrane surface at 100 mg/dL phenylhydrazine. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed the presence of a large quantity of hemoglobin bound to the ghost membrane of treated RBCs. Electrophoresis with and without dithiothreitol indicated that disulfide bridges are abundant between hemoglobin molecules and are also present among membrane proteins but are not the major bond between hemoglobin and membrane. Changes of spectrin, ankyrin, band 3, and band 6 and the appearance of a 260,000-dalton complex were also observed. With phenylhydrazine concentrations below 30 mg/dL, even in the presence of multiple Heinz bodies, the RBC deformability measured by filtration through 2.6-, 4.5-, and 6.8-microns pores and the membrane deformability determined by a filter aspiration technique were not altered. With 100 mg/dL phenylhydrazine, when the entire membrane was coated with Heinz bodies, RBC filterability and membrane deformability were drastically reduced. These results indicate that oxidative damage of RBCs with discrete Heinz body formation causes focal membrane rigidification but does not affect the global cellular deformability until the Heinz bodies nearly cover the entire cell endoface.

Erythrocyte Deformability↗
PubMed1986

Red cell rheology in stomatocyte-echinocyte transformation: roles of cell geometry and cell shape.

The influence of the shape of the red blood cell during stomatocyte-echinocyte transformation on its deformability was studied by microsieving through pores with diameters of 2.6, 4.5, and 6.9 micron. A stomatocytic transformation was produced by chlorpromazine (0.02, 0.1, and 0.5 mmol/L) and an echinocytic transformation by sodium salicylate (7.5, 30, and 120 mmol/L). For spherostomatocytes, an increase in filtration resistance through 2.6 and 4.5 micron pores was observed, whereas for spheroechinocytes, a decrease in filtration resistance through 2.6 micron pores was found. Larger pores (6.9 micron) were not sensitive to those shape changes. The changes in deformability can be explained by the fact that the surface area of (sphero)-stomatocytes decreased, whereas that of (sphero)-echinocytes increased; the cell volume remained essentially constant. Echinocytes produced by 24-hour adenosine triphosphate depletion differed from drug-induced echinocytes: they had an increased cell volume at constant surface area and consequently an increased filtration resistance through 2.6- and 4.5-micron filter pores. Shape changes with spicule formation are therefore not a homogeneous entity, and cell geometric factors (eg, surface area and volume) must be assessed with care. The viscosity of red cell suspensions at a hematocrit level of 45% was higher for drug-induced echinocytes than discocytes or stomatocytes at all shear rates tested. We conclude that the normal discocyte represents an optimum shape for the flow in vivo since a stomatocytic transformation could impair the passage through the microcirculation (decrease in cell filterability) and an echinocytic transformation could impair the flow in larger vessels (increase in blood viscosity).

Acanthocytes↗
PubMed1985

The hyperlipidemia of the nephrotic syndrome. Relation to plasma albumin concentration, oncotic pressure, and viscosity.

Although hyperlipidemia is a common feature of the nephrotic syndrome, the distribution of cholesterol among the plasma lipoproteins and the mechanism of the enhanced hepatic synthesis of lipoprotein lipids are not well understood. We studied the distribution of cholesterol among the plasma lipoproteins, as well as the relation between total cholesterol and plasma albumin concentration, oncotic pressure, and viscosity in 20 consecutive adult patients with uncomplicated nephrotic syndrome. The total plasma cholesterol (mean +/- S.D., 302 +/- 100 mg per deciliter [7.8 +/- 2.6 mmol per liter]) and low-density-lipoprotein cholesterol concentrations (215 +/- 89 mg per deciliter [5.6 +/- 2.3 mmol per liter]) were elevated in most patients, but the high-density-lipoprotein cholesterol level was normal or low (46 +/- 18 mg per deciliter [1.2 +/- 0.5 mmol per liter]) in 95 per cent of the patients. Thus, many hypercholesterolemic patients with unremitting nephrotic syndrome may be at increased risk for atherosclerotic heart disease. A significant inverse correlation was found between the total plasma cholesterol concentration and both the plasma albumin concentration (r = -0.528) and the plasma oncotic pressure (r = -0.674), but not the plasma viscosity (r = +0.319). Enhanced hepatic synthesis of lipoprotein lipids may be stimulated by a decreased plasma albumin concentration or oncotic pressure but does not appear to be due to changes in plasma viscosity.

Adult↗
PubMed1985

Effects of benzyl alcohol on erythrocyte shape, membrane hemileaflet fluidity and membrane viscoelasticity.

The effects of benzyl alcohol on cell shape, hemileaflet lipid fluidity and membrane rheology of human red blood cells were studied. Membrane fluidity was assessed by determining the fluorescence anisotropy of permeant probes (1,6-diphenyl-1,3,5-hexatriene,12-(9-anthroyloxy)stearate, 2-(9-anthroyloxy)stearate) and a new impermeant probe (N-stachyosylsuccinic acid dihydrazide-2-(9-anthroyloxy)stearate). Measurements made on intact red blood cells reflected primarily the outer leaflet fluidity while measurements made on red blood cells ghosts reflected the fluidity of both leaflets. Membrane viscoelasticity was determined by micropipette aspiration. Treatment of intact red blood cells with benzyl alcohol up to 50 mM caused progressive stomatocytic shape change but no change in membrane viscoelasticity, 1,6-diphenyl-1,3,5-hexatriene anisotropy or stachyosyldihydrazide-2(9-anthroyloxy)stearate correlation time; similar treatment of leaky ghosts yielded decreases in 1,6-diphenyl-1,3,5-hexatriene anisotropy and stachyosyldihydrazide-2(9-anthroyloxy)stearate correlation time. With benzyl alcohol above 50-60 mM, intact red blood cells became echinocytic, and decreases in 1,6-diphenyl-1,3,5-hexatriene anisotropy and stachyosyldihydrazide-2(9-anthroyloxy)stearate correlation time occurred in both intact cells and ghosts; there was no change in membrane viscoelasticity. These results indicate that benzyl alcohol up to 50 mM affects primarily the inner leaflet of the red blood cell membrane and that higher concentrations affect both leaflets. These increases in membrane fluidity are not associated with changes in membrane viscoelasticity. This study illustrates the use of fluorescence techniques to monitor specifically the lipid fluidity of each hemileaflet of the erythrocyte membrane.

Benzyl Alcohol↗
PubMed1985

Gold labeling of thrombin and ultrastructural studies of thrombin-gold conjugate binding by fibrin.

Monodispersed thrombin-gold (T-Au) conjugates were prepared by the absorption of a monolayer (3.8 nm thick) of human alpha-thrombin around individual monodispersed colloidal gold particles (16.5 +/- 1.8 nm). Like free molecular thrombin, T-Au conjugates can cause platelet aggregation, plasma clotting, and the release of fibrinopeptides A and B from fibrinogen. At the same thrombin concentration, T-Au conjugates have only one-tenth the fibrinogen-clotting activity of free thrombin and one-third the amidolytic activity of free thrombin. Hirudin can completely inhibit the fibrinogen-clotting activity of both T-Au conjugates and free thrombin, but can inhibit only half of the amidolytic activity of the conjugates. Diisopropyl fluorophosphonate can completely inhibit the fibrinogen-clotting activity and the amidolytic activity of both T-Au conjugates and free thrombin. T-Au conjugates were further characterized by studying the mechanism of their binding to fibrin and the location of the binding site on fibrin. The results of electron microscopic studies showed that T-Au conjugates, but not albumin-Au conjugates, are bound by fibrin. Increasing T-Au conjugate concentrations are associated with an increase in the number of T-Au conjugates binding to fibrin. At 0.1 microM thrombin, 73% of the T-Au conjugates are bound to branch points of the fibrin network with 27% of the T-Au conjugates present in the fibrin strands. At higher thrombin concentration (e.g., 0.5 microM) the percentage of T-Au conjugates bound to locations other than branch points increases to 62%.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1985

Stomatocytic transformation of red blood cells after marathon running.

We studied red blood cell morphology in two marathon runners before, immediately after, and 1 day after a marathon race. A discocyte-stomatocyte transformation was found by light microscopy of wet preparations and also by scanning electron microscopy, with about one-half the erythrocytes becoming cup-shaped after the marathon. These changes were completely reversible within 18 hr after the race.

Erythrocytes, Abnormal↗
PubMed1985

Regulation of aortic endothelial vesicular uptake of cationized ferritin by plasmalemmal binding.

Endothelial uptake of cationized ferritin (CF, pI greater than 9.0) was investigated in the rabbit aorta. After in situ perfusion with CF at concentrations less than 0.35 mg/ml in Tyrode's solution, the endothelial plasmalemmal membrane was partially covered by a ferritin monolayer except at some vesicle necks and regions of cell overlap where particles aggregated. At a concentration of 0.5 mg/ml, CF entered all luminal vesicles and bound to the membrane as a uniform layer usually several particles deep. A steady state was reached after 5 s; particle binding and vesicle filling were not affected by perfusion flow rate up to 20 ml/min. The number of particles per loaded vesicle (F/NL) increased with the density of particles at vesicle necks (PDv), suggesting that particle concentration in the vesicle was in equilibrium with that at the neck. At CF concentrations above 1 mg/ml, binding sites at vesicle necks and elsewhere on the membrane became saturated and luminal vesicles became maximally loaded. Under these conditions, F/NL was greater than that expected for equilibrium with the PDv found. Our findings indicate that anionic sites at vesicle necks and cell overlaps are more strongly negatively charged than elsewhere, and suggest that CF vesicle loading is regulated by the degree of binding at the neck and by the relative strength of the attractive forces at the neck and the vesicle interior.

Animals↗
PubMed1985

Interaction of lectins with membrane receptors on erythrocyte surfaces.

The interactions of human genotype AO erythrocytes (red blood cells) (RBCs) with N-acetylgalactosamine-reactive lectins isolated from Helix pomatia (HPA) and from Dolichos biflorus (DBA) were studied. Binding curves obtained with the use of tritium-labeled lectins showed that the maximal numbers of lectin molecules capable of binding to human genotype AO RBCs were 3.8 X 10(5) and 2.7 X 10(5) molecules/RBC for HPA and DBA, respectively. The binding of one type of lectin may influence the binding of another type. HPA was found to inhibit the binding of DBA, but not vice versa. The binding of HPA was weakly inhibited by a beta-D-galactose-reactive lectin isolated from Ricinus communis (designated RCA1). Limulus polyphemus lectin (LPA), with specificity for N-acetylneuraminic acid, did not influence the binding of HPA but enhanced the binding of DBA. About 80% of LPA receptors (N-acetylneuraminic acid) were removed from RBC surfaces by neuraminidase treatment. Neuraminidase treatment of RBCs resulted in increases of binding of both HPA and DBA, but through different mechanisms. An equal number (7.6 X 10(5) of new HPA sites were generated on genotypes AO and OO RBCs by neuraminidase treatment, and these new sites accounted for the enhancement (AO cells) and appearance (OO cells) of hemagglutinability by HPA. Neuraminidase treatment did not generate new DBA sites, but increased the DBA affinity for the existing receptors; as a result, genotype AO cells increased their hemagglutinability by DBA, while OO cells remained unagglutinable. The use of RBCs of different genotypes in binding assays with 3H-labeled lectins of known specificities provides an experimental system for studying cell-cell recognition and association.

ABO Blood-Group System↗
PubMed1985

Interaction energies in lectin-induced erythrocyte aggregation.

Two N-acetylgalactosamine-reactive lectins, Helix pomatia (HPA) and Dolichos biflorus (DBA), were used to study the energies involved in cell-cell interactions through the specific binding of these lectins to their membrane receptors on genotype AO human erythrocytes (red blood cells) (RBCs). The energy required to dissociate a unit of aggregated membrane area (gamma d) of two RBCs bridged by lectin molecules was determined from the shear force needed to dissociate two-cell aggregates in a flow channel. When HPA were used as bridging molecules, gamma d (0.4 X 10(-4) to 3.8 X 10(-4) dyn/cm) was proportional to the density (D = 175 to 1,060 molecules/micron 2) of HPA molecules bound on the RBC membrane. A similar gamma d/D ratio was also obtained for DBA. These results indicate that the number of lectin molecules bound on the interface plays an important role in determining the energy required for cell-cell dissociation. The aggregation energy per unit membrane area (gamma a) in lectin-induced aggregates was calculated from the degree of encapsulation of a lectin-bound, heat-sphered human RBC by a normal discoid RBC. A minimum of approximately 1,800 HPA molecules/micron 2 on the spheres was required to form stable aggregates with the RBC. By using spheres having a surface HPA density of 1,830 to 2,540 molecules/micron 2, or 1.1-1.5 X 10(12) combining sites/cm2, the gamma a value for HPA-induced aggregation was found to be 2.2 X 10(-3) dyn/cm. This higher value of gamma a than gamma d has been explained on the basis of several differences in aggregation and disaggregation processes. The gamma a value for DBA-induced aggregation was not obtainable by the sphere encapsulation method because of the relative low D values. A comparison of the present results with the published value of the free energy change of 5 kcal/mol for the interactions of HPA and DBA with their ligands suggests that only a small fraction of the lectin molecules bound to RBC surface participate in the bridging of adjacent cells.

ABO Blood-Group System↗
PubMed1985

Effect of complement on the viscoelastic properties of human erythrocyte membrane.

Using the micropipette technique, we examined the viscoelastic properties of the red blood cell (RBC) membrane which had been strongly coated with various components of complement (primary C3b, C3d, C4b, C4d) in vitro. The membrane elastic modulus (E), the viscosity index of the initial rapid phase of deformation (eta D1), the viscosity of the later slow phase of deformation (eta D2) and the viscosity of the recovery phase (eta R) were determined. Compared to control non-complement coated RBCs, RBCs coated with C3d, either alone or with other complement components, showed significant increase in the values for elasticity and viscosities. Thus C3d fixation resulted in decreased membrane deformability. Changes in membrane viscoelasticity due to bound C3d were not enhanced by bound C4b, C4d, C5, factor Bb or p; presence on RBC membrane of the latter two complement components may partially reverse the effect of C3d fixation. Lipid fluidity of RBC membrane, examined by fluorescence depolarization, increased with fixation of all complement components except C5. These complement-induced changes in membrane viscoelastic properties have potential pathophysiological and clinical implications. The data suggest that extravascular sequestration of human RBCs may be explained in part by increased membrane rigidity resulting from C3d fixation.

Complement C3↗
PubMed1985

Roles of cell geometry and cellular viscosity in red cell passage through narrow pores.

The relative roles of two fundamental determinants of red cell deformability, namely cell size and cellular viscosity, in affecting red cell passage through narrow channels have been assessed by determining the filterability of red cells subjected to osmotic variations. Suspensions of red cells (10(6) cells/microliter) in eight different osmolalities ranging from 172 +/- 3 (mean +/- SD) to 665 +/- 28 mosmol/kg H2O were filtered through polycarbonate sieves with three different pore diameters (2.6 +/- 0.2, 4.5 +/- 0.6, and 6.9 +/- 0.8 micron). The mean corpuscular volume varied inversely with osmolality and ranged from 149 +/- 9 to 67 +/- 10 fl; the mean corpuscular hemoglobin concentration varied directly with osmolality and ranged from 23.7 +/- 0.8 to 55.9 +/- 3.9 g/dl. The filtration data were analyzed with a theoretical model to derive the parameter beta, which is the ratio of resistance in a pore bearing a red blood cell to that in a pore filled with the suspending medium alone. For each pore size, beta showed a V-shaped relationship with osmolality; the optimum osmolality for minimum beta varied inversely with the pore size. For the small 2.6-micron pores, the minimum beta was attained following hyperosmotic shrinkage of the red cells at 400 mosmol/kg H2O, whereas passage through the large 6.9-micron pores was facilitated by hypoosmotic swelling of the red cells in about 200 mosmol/kg H2O. Red cell filtration through small pores is more sensitive to alterations in cell volume, whereas that through large pores is primarily determined by changes in cellular viscosity.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythrocyte Deformability↗
PubMed1985

Model studies on distributions of blood cells at microvascular bifurcations.

To model the flow behavior of white and red blood cells at microvascular branch points, the distribution of neutrally buoyant spherical and disk-shaped particles at a symmetric T bifurcation was investigated for low Reynolds number flows (0.01-0.1). The particle distribution was represented by the fractional particle flux to a daughter branch as a function of the fractional volumetric bulk flow to the same branch. Particle-to-tube diameter ratios of 0.32-0.79 were studied for the spherical particles and 0.4-0.8 for the disks. As the particle dimensions approach that of the tube, the relation between the fractional particle flux and fractional bulk flow changes from a linear relation of unity slope to a nonlinear S-shaped curve. Measurements of the flow divider at the entrance to the bifurcation and the eccentricity distributions for the spheres and disks were used to develop a model that permits prediction of the observed particle distributions. These results can be used to interpret the distribution of white and red blood cells in microvascular bifurcations with dimensions close to the cell size.

Blood Cells↗
PubMed1985

Effect of cell turnover and leaky junctions on arterial macromolecular transport.

A new quantitative model is presented to explore the changes in vascular permeability that would result if the intercellular clefts around widely scattered endothelial cells were to become leaky to macromolecules in the range of roughly 4-10 nm during normal cell turnover. Although these open junctions occupy less than 10(-5) of the en face area of the endothelial surface, it is shown that the endothelial permeability can increase by 50-100% due to the experimentally observed regional variations in turnover in the larger arteries, whereas in the thinner walled veins and smaller arteries the subendothelial concentration is not significantly elevated. These results provide a very plausible explanation for the observed focal differences in the uptake of 125I-albumin and 131I-fibrinogen in blue and white areas and the nonselectivity of the local enhancement in uptake for these two molecules as a function of molecular size. The model has important implications for the localization of atherogenesis and the importance of endothelial cell turnover on the transport of proteins in vessels of all sizes.

Arteries↗