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PubMedDate not supplied

Flow behavior of erythrocytes in microvessels and glass capillaries: effects of erythrocyte deformation and erythrocyte aggregation.

Flow behavior of erythrocytes in microvessels and glass capillaries with an inner diameter of 10-50 microns was compared in relation to erythrocyte deformation and erythrocyte aggregation. This study was focused on the formation of a marginal cell-free layer, and the thickness was determined using an image processor. Human erythrocytes were perfused through a part of microvascular networks isolated from rabbit mesentery and through glass capillaries. Erythrocyte deformability was modified by treating erythrocytes with diamide, diazene-dicarboxylic acid bis[N,N-dimethylamide], and erythrocyte aggregation was accelerated by adding dextran (with a molecular weight of 70,400) to the perfusion medium. The thickness of the cell-free layer increased with an increase of the inner diameter of flow channel, with lowering the hematocrit, and with increasing the flow velocity of erythrocytes, in both microvessels and glass capillaries. Furthermore, the thickness of cell-free layer decreased with decreasing erythrocyte deformability, while it increased with accelerating erythrocyte aggregation. However, the alteration of the cell-free layer in response to the changes of these hemorheological conditions was more sensitive in microvessels than in glass capillaries. The present study concludes that flow behavior of erythrocytes in microvessels is qualitatively similar to, but quantitatively different from those in glass capillaries, as far as evaluated by the change of the thickness of the marginal cell-free layer.

Animals↗
PubMed1989

Movement of a falciparum malaria protein through the erythrocyte cytoplasm to the erythrocyte membrane is associated with lysis of the erythrocyte and release of gametes.

Erythrocytes containing mature gametocytes of Plasmodium falciparum circulate in the blood until they are ingested by a mosquito, an event that triggers gametogenesis and lysis of the infected erythrocyte. It was previously shown that a parasite protein (Pf155/RESA) accumulates in the erythrocyte cytoplasm next to the parasitophorous vacuolar membrane (S. Uni, A. Masuda, M. J. Stewart, R. Nussenzweig, and M. Aikawa, Am. J. Trop. Med. Hyg., 36:481-488, 1987). Using a monoclonal antibody to Pf155/RESA and rabbit sera to two different repeat peptides of Pf155/RESA, we have studied the location of Pf155/RESA after induction of gametogenesis. Five minutes after triggering gametogenesis, the parasitophorous membrane no longer surrounded the parasite, bringing the parasite membrane in contact with the erythrocyte cytoplasm. Clear spaces appeared throughout the hemoglobin-rich host cytoplasm; Pf155/RESA was now localized in the cytoplasm directly surrounding the spaces. No membrane existed between the spaces and the erythrocyte cytoplasm. The spaces with surrounding Pf155/RESA protein extended to the erythrocyte membrane. After lysis of the erythrocyte membrane (15 min after triggering gametogenesis), the protein was distributed along the erythrocyte membrane and throughout the space between the gamete and the erythrocyte membrane. The mechanism by which Pf155/RESA remained aggregated around the spaces and its role in erythrocyte lysis are unknown. It is of interest that the parasite appeared to use the same molecule during invasion of erythrocytes and during release of gametes from infected erythrocytes.

Animals↗
PubMed1985

Erythrocyte enhancement of C3b-mediated phagocytosis by human neutrophils in vitro: a combined effect of the erythrocyte complement receptors CR1 and erythrocyte scavengers to reactive oxygen metabolites (ROM).

Human erythrocyte CR1 receptors have been shown to bind complement-fixing immune complexes and, thus, facilitate their elimination from the circulation. The autotoxic effect of free radicals released from phagocytes during phagocytosis can be alleviated by scavengers like catalase and superoxide dismutase. Erythrocytes are known to contain these antioxidants. This study showed that 74% of opsonized yeast particles adhered to human erythrocytes. No difference was seen between yeast opsonized with C3b and yeast opsonized with both IgG and C3b. This adherence was due to the C3b receptor (CR1), as monoclonal antibodies against the CR1 receptor could abrogate the adherence. The yeast phagocytosis by neutrophils was increased by 15% when yeast-C3b was used, and by 34% when yeast-IgG/C3b was used in the presence of human red blood cells. The increase of phagocytosis was not seen when rat erythrocytes (lacking CR1) were present. The cytochrome c reduction decreased with the presence of human erythrocytes during phagocytosis, indicating a scavenging effect on the superoxide anions. The addition of scavengers or erythrocyte lysate, instead of erythrocytes, enhanced phagocytosis of yeast-IgG/C3b to at least the same extent as the erythrocytes. These observations suggest that human erythrocytes primarily enhance phagocytosis through the scavenging effect of those erythrocytes which are concurrently attached with the prey through its CR1 receptor, and then attached to the PMN.

Complement C3b↗
PubMed1985

Erythrocyte microtubule assembly in vitro. Determination of the effects of erythrocyte tau, tubulin isoforms, and tubulin oligomers on erythrocyte tubulin assembly, and comparison with brain microtubule assembly.

Two tubulin variants, isolated from chicken brain and erythrocytes and known to have different peptide maps and electrophoretic properties, are demonstrated to exhibit different assembly properties in vitro: 1) erythrocyte tubulin assembles with greater efficiency (lower critical concentration, greater elongation rate) but exhibits a lower nucleation rate than brain tubulin, and 2) erythrocyte tubulin readily forms oligomers whose presence significantly retards the rate of elongation, suggesting that tubulin oligomers may also be important for determining the rate of assembly and the length of microtubules in erythrocytes. Erythrocyte tubulin isolated by cycles of in vitro assembly-disassembly is also demonstrated to contain a 67-kDa tau factor that greatly enhances microtubule nucleation but has little effect on elongation rates or critical concentration. Immunofluorescence microscopy with tau antibody indicates that tau is specifically associated with marginal band microtubules, suggesting that it may be important for determining microtubule function in vivo.

Animals↗
PubMed1997

The primate erythrocyte complement receptor (CR1) as a privileged site: binding of immunoglobulin G to erythrocyte CR1 does not target erythrocytes for phagocytosis.

The primate erythrocyte (E) complement receptor, CR1, is a transmembrane glycoprotein located in clusters on the surface of E. In vivo studies have demonstrated that during processing and clearance of complement-opsonized immune complexes, large amounts of immunoglobulin G (IgG) can be bound to primate E via CR1 with no E loss or lysis. However, when comparable amounts of IgG are bound to other sites on E, in many cases the E are cleared from the circulation by the mononuclear phagocytic system. Therefore, due to its role in immune complex processing, CR1 may represent a privileged site on the primate E. To delineate further this property of E CR1, we performed in vitro phagocytosis assays in the absence of complement and examined the ingestion of E, opsonized at various sites with IgG, by peripheral blood monocytes. When either human or rhesus monkey E were opsonized at sites other than CR1, with between 1,000 and 15,000 IgG per E, substantial phagocytosis of E was evident. However, when comparable amounts of IgG were bound exclusively via CR1, little, if any, phagocytosis was observed. The key to the low phagocytic level of E opsonized via CR1 may be related to the requirements of a "zipper mechanism" for phagocytosis first annunciated by Griffin et al. Based on their findings, we suggest that due to the presence of preexisting clusters of CR1 on the E membrane, large amounts of IgG can be bound to E under conditions that preclude circumferential engagement (and phagocytosis) of the entire E by Fc receptors on the monocyte.

Animals↗
PubMed1998

An animal model to study erythrocyte senescence with a narrow time window of erythrocyte production: alterations in osmotic fragility and deformability of erythrocytes during their life span.

Using the model in which the entire RBC population was nearly synchronously produced following the induction of spherocytic anemia in the rabbit with antibody serum, we determined the changes of RBC osmotic fragility and deformability with aging. The results showed that the osmotic fragility increased with the RBC aging process in a nonlinear manner, being much more profound in the later part of the RBC life span. The RBC deformation index (DI) was measured by an ektacytometry. It is found that the DI decreased with RBC aging in a nonlinear fashion, with increasingly greater changes in the later part of the RBC life span. The alterations of RBC mechanical properties with aging may be attributable to a number of factors, including changes of RBC size and shape, and the viscoelasticity of the cytoplasm and membrane.

Anemia, Hemolytic↗
PubMed1992

Longer in vivo survival of CD59- and decay-accelerating factor-almost normal positive and partly positive erythrocytes in paroxysmal nocturnal hemoglobinuria as compared with negative erythrocytes: a demonstration by differential centrifugation and flow cytometry.

Three populations of erythrocytes have been shown by flow cytometric analysis on complement regulatory proteins: CD59 and decay-accelerating factor (DAF) on erythrocytes in paroxysmal nocturnal hemoglobinuria (PNH). CD59 and DAF in PNH may be completely deficient in CD59- and DAF-negative erythrocytes, they may be decreased varyingly in partly positive erythrocytes, and they may be approximately normal in almost normal positive erythrocytes. Control erythrocytes are always CD59- and DAF-normal positive. CD59- and DAF-negative erythrocytes have been shown to be most sensitive to complement lysis in vitro. However, it has not yet been elucidated whether CD59- and DAF-almost normal positive and partly positive erythrocytes in a patient have a longer in vivo survival than negative erythrocytes. Blood from controls and PNH patients was separated in five fractions by differential centrifugation. CD59 and DAF on the fractionated erythrocytes were determined by flow cytometry using specific antibodies. Ratios of CD59- and DAF-almost normal positive and partly positive cells to negative erythrocytes were increased progressively from the top fraction to the bottom. The erythrocytes in the top fraction are younger and reticulocyte-rich, while those in the bottom are older and reticulocyte-poor. Hence, the present results indicate that CD59- and DAF-partly positive erythrocytes as well as almost normal positive erythrocytes in patients may have a longer in vivo survival than negative erythrocytes.

Antigens, CD↗
PubMed2000

Influence of band 3 protein absence and skeletal structures on amphiphile- and Ca(2+)-induced shape alterations in erythrocytes: a study with lamprey (Lampetra fluviatilis), trout (Onchorhynchus mykiss) and human erythrocytes.

Amphiphiles which induce either spiculated (echinocytic) or invaginated (stomatocytic) shapes in human erythrocytes, and ionophore A23187 plus Ca(2+), were studied for their capacity to induce shape alterations, vesiculation and hemolysis in the morphologically and structurally different lamprey and trout erythrocytes. Both qualitative and quantitative differences were found. Amphiphiles induced no gross morphological changes in the non-axisymmetric stomatocyte-like lamprey erythrocyte or in the flat ellipsoidal trout erythrocyte, besides a rounding up at higher amphiphile concentrations. No shapes with large broad spicula were seen. Nevertheless, some of the 'echinocytogenic' amphiphiles induced plasma membrane protrusions in lamprey and trout erythrocytes, from where exovesicles were shed. In trout erythrocytes, occurrence of corrugations at the cell rim preceded protrusion formation. Other 'echinocytogenic' amphiphiles induced invaginations in lamprey erythrocytes. The 'stomatocytogenic' amphiphiles induced invaginations in both lamprey and trout erythrocytes. Surprisingly, in trout erythrocytes, some protrusions also occurred. Some of the amphiphiles hemolyzed lamprey, trout and human erythrocytes at a significantly different concentration/membrane area. Ionophore A23187 plus Ca(2+) induced membrane protrusions and sphering in human and trout erythrocytes; however, the lamprey erythrocyte remained unperturbed. The shape alterations in lamprey erythrocytes, we suggest, are characterized by weak membrane skeleton-lipid bilayer interactions, due to band 3 protein and ankyrin deficiency. In trout erythrocyte, the marginal band of microtubules appears to strongly influence cell shape. Furthermore, the presence of intermediate filaments and nuclei, additionally affecting the cell membrane shear elasticity, apparently influences cell shape changes in lamprey and trout erythrocytes. The different types of shape alterations induced by certain amphiphiles in the cell types indicates that their plasma membrane phospholipid composition differs.

Abietanes↗
PubMed1994

Resistance to artemisinin of malaria parasites (Plasmodium falciparum) infecting alpha-thalassemic erythrocytes in vitro. Competition in drug accumulation with uninfected erythrocytes.

Plasmodium falciparum infecting hemoglobin (Hb)H and/or Hb Constant Spring erythrocytes has higher resistance to artemisinin in vitro than when infecting normal erythrocytes. This is due to low drug accumulation of infected erythrocytes resulting from competition with uninfected variant erythrocytes, which have a higher accumulation capacity than genetically normal cells. Drug accumulation of the parasite was shown to be saturable and dependent on metabolic energy. The 50% inhibitory concentrations (IC50's) for the parasite in HbH/Hb Constant Spring erythrocytes were decreased when normal erythrocytes were added to the infected cells, and correspondingly, the IC50's in normal erythrocytes were increased when HbH/Hb Constant Spring erythrocytes were added to the infected cells. The changes of IC50 corresponded to the variation in drug accumulation of mixtures of normal and variant erythrocytes of different compositions. The IC50's for the parasite in variant erythrocytes were also greatly decreased when the hematocrit of the culture was lowered, while the IC50's in normal erythrocytes were independent of the hematocrit. The increase in IC50 values for the parasites infecting variant erythrocytes was also related to the decrease in parasite accumulation, indicating that drug accumulation capacity of the parasite also has a role in determining drug sensitivity. Artemisinin sensitivity therefore is determined by its accessibility to the parasite, which is decreased in infected variant erythrocytes.

Animals↗
PubMed1995

Role of the Plasmodium falciparum mature-parasite-infected erythrocyte surface antigen (MESA/PfEMP-2) in malarial infection of erythrocytes.

During intraerythrocytic growth of Plasmodium falciparum, several parasite proteins are transported from the parasite to the erythrocyte membrane, where they bind to membrane skeletal proteins. Mature-parasite-infected erythrocyte surface antigen (MESA) has previously been shown to associate with host erythrocyte membrane skeletal protein 4.1. Using a spontaneous mutant of P falciparum that has lost the ability to synthesize MESA and 4.1-deficient erythrocytes, we examined growth of MESA(+) and MESA(-) parasites in normal and 4.1-deficient erythrocytes. Viability of MESA(+) parasites was reduced in 4.1-deficient erythrocytes as compared with that for normal erythrocytes, but MESA(-) parasites grew equally well in 4.1-deficient and normal erythrocytes. Cytoadherence of MESA(+)- and MESA (-)-parasitized normal and 4.1-deficient erythrocytes to C32 melanoma cells was similar, indicating that neither protein 4.1 nor MESA plays a major role in cytoadherence of infected erythrocytes. Localization of MESA in normal and 4.1-deficient erythrocytes was examined by confocal microscopy. MESA was diffusely distributed in the cytosol of 4.1-deficient erythrocytes but was membrane-associated in normal erythrocytes. These findings suggest that MESA binding to protein 4.1 plays a major role in intraerythrocytic parasite viability.

Animals↗
PubMed1987

Effect of Kupffer cell phagocytosis of erythrocytes and erythrocyte ghosts on susceptibility to endotoxemia and bacteremia.

The phagocytosis of erythrocytes by macrophages has previously been shown to depress macrophage function. In this study we compared the effect of the phagocytosis of erythrocytes and erythrocyte ghosts by Kupffer cells on the duration of the depression of complement receptor clearance function and host defense against endotoxemia and bacteremia. Phagocytosis of erythrocytes and erythrocyte ghosts was induced in rats by the injection of rat erythrocytes or erythrocyte ghosts coated with anti-rat erythrocyte immunoglobulin G (EIgG and GIgG, respectively). The hepatic uptake of EIgG and GIgG (17.4 X 10(8)/100 g) occurred during the first 30 min after injection. The digestion of phagocytized EIgG and GIgG, as assessed by electron microscopy, was complete at 24 and 3 h after injection, respectively. The depression of Kupffer cell complement receptor clearance function caused by EIgG and GIgG returned to normal by 6 h after injection of EIgG and by 3 h after injection of GIgG. Phagocytosis of EIgG depressed the survival rate after endotoxemia and bacteremia when endotoxin or bacteria were injected at 30 min after EIgG. The survival rate returned to normal when the endotoxin and bacteria were injected at 12 and 6 h after the EIgG, respectively. Phagocytosis of GIgG did not depress the survival rate after endotoxemia and bacteremia. Thus, compared with erythrocytes, erythrocyte ghosts are more rapidly digested after phagocytosis, depress complement receptor function for a shorter period of time, and cause less depression of host defense. These findings indicate that the contents of erythrocytes play an important role in the impairment of host defense caused by the phagocytosis of erythrocytes by Kupffer cells.

Animals↗
PubMed1978

Diminished spectrin extraction from ATP-depleted human erythrocytes. Evidence relating spectrin to changes in erythrocyte shape and deformability.

We measured spectrin "extractability" in erythrocytes which were metabolically depleted by incubation at 37 degrees C in plasma or glucose-free buffers. Membranes were extracted with 1 mM EDTA (pH 8, 40 h, 4 degrees C) and analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. This procedure solubilized 85--90% of the spectrin, actin, and residual hemoglobin from ghosts of fresh erythrocytes. In incubated erythrocytes, inextractable spectrin rapidly accumulated when ATP concentrations fell below 0--15% of normal. In severely depleted cells, 60--90% of the total ghost spectrin became inextractable. Inextractability was not abolished by physically disrupting the ghost before extraction, but was reversed when erythrocyte ATP was replenished with adenosine. The accumulation of inextractable spectrin correlated temporally with the increase in apparent membrane deformability and the increases in erythrocyte vicosity, calcium content, sodium gain, and potassium loss characteristic of ATP-depleted erythrocytes. No change in integral membrane protein topography (assessed by the distribution of intramembranous particles and concanavalin A surface-binding sites) was detected in depleted cells. Analogous changes were observed in erythrocytes exposed to extremes of pH and temperature. When the pH in the erythrocyte interior fell below 5.5, a pH where spectrin was aggregated and isoelectrically precipitated, erythrocyte and ghost viscosity increased coincident with a marked decrease in spectrin extractability. Similarly above 49 degrees C, a temperature where spectrin was denatured and precipitated, erythrocyte viscosity rose as inextractable spectrin accumulated. These observations provide direct evidence of a change in the physical state of spectrin associated with a change in erythrocyte shape and deformability. They support the concept that erythrocyte shape and deformability are largely determined by the shape and deformability of the spectrin-actin protein meshwork which laminates the inner membrane surface.

Adenosine Triphosphate↗
PubMed1996

Erythrocyte aggregation and erythrocyte deformability modify the permeability of erythrocyte enriched fibrin network.

Intravascular thrombus formed under low shear conditions consists of red cells enmeshed within a fibrin network. Since red cells reduce the permeability of fibrin network by surface drag and by volume occupancy the significance of red cell aggregability and deformability in network permeability needs examination. In this study networks were developed by the addition of thrombin to washed red cells suspended in platelet free plasma. The effects of the polymers polyvinylpyrrolidone (PVP) and poloxamer 188 on network permeability were compared to gauge the influence of red cell aggregation. Both polymers increase network permeability by an action on fibrin polymerisation but PVP alone enhances red cell aggregation. PVP was found to increase network permeability significantly both by increasing the permeability of the fibrin component of the network and by increasing red cell aggregation and thus reducing red cell surface drag. In separate experiments red cells were pre-treated with heat, glutaraldehyde, or diamide to reduce cell deformability. Decreased cell deformability caused significant reductions in network permeability. This was ascribed to the reduced aggregability of hardened red cells. Red cell aggregation during coagulation enhances molecular transport through modifying the network. This may have implications for the penetration of fibrinolytic agents.

Blood Coagulation↗
PubMed1993

Reduction of dapsone hydroxylamine to dapsone during methaemoglobin formation in human erythrocytes in vitro--II. Movement of dapsone across a semipermeable membrane into erythrocytes and plasma.

We have used an in vitro two-compartment model, to investigate the ability of dapsone, formed by erythrocyte-mediated detoxification of its hydroxylamine metabolite, to escape the cells and cross a semi-permeable membrane into both plasma and other erythrocytes. Both diethyl dithiocarbamate (DDC) treated and untreated erythrocytes were incubated with dapsone hydroxylamine and dialysed against either fresh cells or plasma. Methaemoglobin was predominantly detectable in compartment A although the presence of low levels of methaemoglobin in compartment B indicated that the hydroxylamine itself had crossed the membrane. In contrast to methaemoglobin disposition, recovery of dapsone was higher (P < 0.05) in compartment B compared with A for all three treatment groups at 30 and 60 min, but not at the remaining time points. Regression analysis of the cumulative recovery of dapsone over 150 min in all three treatment groups for both compartments A and B showed correlation coefficients close to unity. In compartment A, analysis of the mean slopes of the regression lines indicated that, overall, significantly more dapsone was recovered from group 1 (erythrocytes, hydroxylamine and DDC dialysed against untreated red cells) compared with group 3 (erythrocytes and hydroxylamine dialysed against plasma) (0.22 +/- 0.05 vs 0.09 +/- 0.005; P < 0.025). Also in compartment A, significantly more dapsone was recovered from group 2 (erythrocytes and hydroxylamine dialysed against untreated red cells) compared with group 3 (erythrocytes and hydroxylamine dialysed against plasma: 0.16 +/- 0.02 vs 0.09 +/- 0.005). In compartment B, dapsone recovery was significantly greater in group 1 (erythrocytes, hydroxylamine and DDC dialysed against untreated red cells; slope of regression line: 0.59 +/- 0.05) compared with group 2 (erythrocytes and hydroxylamine dialysed against untreated red cells; slope of line: 0.28 +/- 0.02, P < 0.005). In addition, dapsone recovery was significantly greater in group 1 (0.59 +/- 0.05) compared with group 3 (erythrocytes and hydroxylamine dialysed against plasma; 0.21 +/- 0.02, P < 0.005). Dialysis of erythrocytes with dapsone itself over 120 min caused no detectable methaemoglobin formation. The process of erythrocyte-mediated dapsone formation from its hydroxylamine may feasibly occur in vivo and contribute to the systemic persistence and therapeutic effect of dapsone.

Cell Membrane Permeability↗