Freshwater fish diet affects lipid composition, deformability and aggregation properties of erythrocytes.

The effect of a 12-week diet of freshwater fish on fatty acid composition of the erythrocyte membrane, RBC deformability and artificial aggregation behavior of erythrocytes was studied in 20 healthy subjects. A different quantity of meals containing fish per week (control group, 1.5 and 3.8 fish meals per week) resulted in an increased content of n - 3 polyunsaturated fatty acids. The whole cell deformability of single erythrocytes characterized by a modified micropipette technique (capillary-rigidometer) was significantly increased dependent on fish intake. The parameter of entry time for cell deformability had a negative correlation with the n - 3/n - 6 ratio of fatty acids. No change was observed in MCV and MCHC of erythrocytes after the diet. The artificial aggregation behavior of washed erythrocytes in a suspension medium of low ionic strength and reduced pH was decreased depending on the number of fish meals eaten. The present results suggest that a relatively small shift in the profile of the polyunsaturated fatty acids causes changes in the viscoelastic properties of the erythrocyte membrane and in the artificially-induced aggregation of erythrocytes.

Mechanism of regulation of malarial invasion by extraerythrocytic ligands.

Invasion of red cells by Plasmodium falciparum in vitro was inhibited by a range of extracellular ligands, none of which block the major receptors for merozoites. Most effective, in terms of dose response, were two monoclonal antibodies against the Wrb antigen on glycophorin A; wheat germ agglutinin which also binds to glycophorin, and an anti-band 3 monoclonal antibody, caused inhibition of invasion at higher levels of saturation, while concanavalin A, which binds to band 3, was without effect. All the ligands except concanavalin A, increased the rigidity of the host cell membrane. The anti-Wrb antibodies generated the highest dose response effect, but no correlation between invasion and shear elastic modulus of the membrane could be established. All ligands, with the exception of concanavalin A, caused a reduction in the translationally mobile fractions of band 3 and glycophorin, as revealed by fluorescence recovery after photobleaching (FRAP). Invasion diminished with loss of mobile band 3, engendered by bound wheat germ agglutinin or anti-band 3, falling precipitately when the mobile fraction fell below 40% of that in unperturbed membranes. Both anti-Wrb antibodies suppressed invasion completely at concentrations insufficient to affect significantly either membrane rigidity or intramembrane protein diffusion. A univalent anti-glycophorin A (Fab) fragment, the parent antibody of which was previously shown to inhibit invasion strongly, had only a modest effect on invasion and induced a correspondingly small change in the mobile fraction of band 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term effects of rhEPO therapy on erythrocyte rheology in dialysis patients with different target hematocrits.

UNLABELLED: Successful treatment of renal anemia with recombinant erythropoietin (rhEPO) raises the question of whether the renal anemia symptom complex requires complete correction. Current arguments against increasing hemoglobin (Hb) levels above 10-11 g/dl are impaired hemodynamics, increased risk of vascular access occlusion, unmanageable hypertension and dialysis complications. The aim of the study was to determine whether sustained Hb normalization using long-term rhEPO causes hemorheological changes with a potentially negative hemodynamic impact. The study was conducted in 42 rhEPO-treated dialysis patients with stable Hb > 11.0 g/dl for at least 20 weeks. The mean Hb of the total study group was 12.8 1.1 g/dl. To study the effect of Hb as a risk indicator in greater detail, the patients were divided into two groups, with hematocrits above and below 0.40. Hemorheology (erythrocyte deformability and aggregation, plasma viscosity) showed no significant changes, including vs a healthy control group. Throughout the period of increased rhEPO administration, no increase was observed in the incidence of hypertension or vascular thrombosis. CONCLUSION: the marked additional quality-of-life benefit achieved by complete correction of renal anemia harbors no substantial increase in treatment risk.

Complete correction of renal anemia by recombinant human erythropoietin.

The target-hematocrit (Hct) for the correction of renal anemia by recombinant human erythropoeitin (rhEPO) therapy is discussed controversially. A normalization of the Hct that could lead to a further improvement of the patients status, is often rejected, because of possible side effects as a result of an increase in blood viscosity. Hemodialysis (HD) induces an acute hemoconcentration due to ultrafiltration that might influence these risk factors negatively and therefore conflict with the normalization of Hct. The aim of this study was to investigate the changes in rheological and biochemical parameters in chronic HD patients with a normal initial Hct before hemodialysis. Results in 39 patients are given as mean +/- SD before/after HD: Hct 0.42 +/- 0.05/0.45 +/- 0.05 (p < 0.001), hemoglobin (g/dI) 13.3 +/- 1.0/14.4 +/- 1.3 (p < 0.001), MCV (fl) 99.3 +/- 5.7/99.1 +/- 5.5, MCHC (mM/l) 19.9 +/- 0.6/20.1 +/- 0.6 (p < 0.01), red blood cell (RBC) elongation (%) 60.97 +/- 3.67/60.99 +/- 3.73, RBC aggregation index AI0 0.52 +/- 0.12/0.50 +/- 0.12, AI4 0.52 +/- 0.14/0.51 +/- 0.12, plasma viscosity 1.74 +/- 0.14/1.92 +/- 0.20 (p < 0.001), whole blood viscosity (WBV), etaabs.100(mPas) 5.91 +/- 0.78/6.80 +/- 1.2 (p < 0.001), etaabs.0.01(mPas) 75.81 +/- 35.48/167.656 +/- 98.686 (p < 0.05), ultrafiltration (FM) 2.1 +/- 1.1. The biochemical parameters protein, albumin, IgG, IgA, IgM, cholesterol, transferrin and fibrinogen are significantly increased after HD. The hemoconcentration during HD is associated with a significant increase in WBV, mainly associated with the increase in Hct (r = 0.83), but not exceeding the normal range compared to healthy controls. The increase in plasma viscosity is correlated mainly with an increase in protein (r = 0.80), albumin (r = 0.74), and fibrinogen (r = 0.54). No significant changes in RBC aggregation and deformability were observed during the HD session. In conclusion, from the rheological point of view it is unlikely that the normalization of the Hct will contribute to an increased risk in access thrombosis or thromboembolic events in HD patients.

Fission and refusion of red blood cells using a micropipette technique.

In micropipette experiments with small capillaries and moderate high pressure difference (approximately 1000 Pa) cell fragmentation (fission) of human red blood cells without hemolysis was observed by TV-system for a large number of fresh red blood cells of different donors. After separation, the fragment moves away from the residual cell. In seven cases this process was evaluated quantitatively and was shown that the rate of the fragment was constant in time. Two mechanisms for this phenomenon are discussed. In particular cases a spontaneous re-fusion with the residual cell body in the capillary can be observed. In our opinion probably protein-depleted membrane surfaces arise and membrane fusion is possible simply by mechanical contact without additional electric fields and/or fusion agents.

The effect of rimantadine on the structure of model and biological membranes.

The action of the antiviral drug rimantadine on the structure of bilayer lipid membranes (BLM) and RBC membranes was investigated. Structural changes in BLM were recorded by ionophore conductivity changes and by changes in the third harmonic of capacity current signal due to lateral compression of BLM in an electric field. It was shown that the adsorption of rimantadine on BLM results in an increase in ionophore mobility in bilayer membranes of dioleolyllecithin (DOL) and common lipids of bovine brain (CL) and in a decrease in those of azolectin (A). Relative changes in the third harmonic signal also depend on the membrane composition and have different signs. The results may be explained by the rimantadine action on the lipid bilayer structure: "rigidification" of A-membranes and "fluidization" of BLM from DOL and CL. Structural reorganization of RBC membranes as investigated by the ability of the cells to enter a micropipette (inner diameter greater than or equal to 3 microns) thereby undergoing deformation. It was shown that rimantadine influences RBC deformability due to drug induced inhomogenous mechanical membrane properties. Also, rimantadine accelerated the process of artificially induced aggregation of erythrocytes. The relation of the effects on artificial and biological membranes, and the structural changes in the lipid phase of membrane are discussed.

Endothelialization of PTFE vascular grafts under flow induces significant cell changes.

BACKGROUND: To minimize thrombogeneity of small diameter PTFE grafts they are usually coated in vitro with endothelial cells under static culture conditions. The disadvantage of this technique is that a cell layer is formed that fails to withstand shear stress typical in normal blood flow. METHOD: Since the in vivo functional and structural status of endothelial cells correlates with the applied shear stress, we developed a computer-controlled perfusion system to seed and culture cells on PTFE-grafts up to a confluent monolayer under the influence of increasing shear stress. The confluence of endothelial coating was defined by immunohistological staining of cross sections, and by upper light microscopy of flattened graft samples. In addition, the expression of fibronectin as an important adhesion molecule was estimated. RESULTS AND DISCUSSION: The application of pulsatile shear stress (6.6 dyn/cm2, 5 min) to grafts endothelialized under perfusion (n = 7) did not lead to a disruption of the confluent cell layer. In contrast, a 5 min long shear stress of 3 dyn/cm2 was sufficient to wash more than 50% of cells off the PTFE-graft cultured under static conditions (n = 6). The perfusion cultures showed a significantly higher proliferation rate in comparison with static cultures. This effect was reproducibile in both serum-containing and serum-free culture media. The expression of fibronectin by endothelial cells was significantly higher in the perfused graft compared to the static one. These results suggest the practicability of endothelialized PTFE vascular grafts, preconditioned to shear rates similar to the in vivo situation, as an alternative bypass material in cardiac surgery.

[Assessment of whole cell deformability of individual erythrocytes with a capillary rigidometer--possibilities for standardization and modification]. / Bewertung der Ganzzelldeformierbarkeit einzelner Erythrozyten mittels Kapillar-Rigidometer--Möglichkeiten zur Standardisierung und Relativierung.

Human erythrocyte deformability is determined by cell geometry and volume, membrane elasticity and cytoplasmic viscosity. The deformability of red blood cells and their distribution among the total cell population, can be studied with the Capillary Rigidometer. This device is based on the kinetic measurement of red blood cell deformability, which has been developed, by modifying the micropipette aspiration technique. In order to investigate the validity of the method and the measuring parameters, a number of determining factors (heat treatment, osmolarity-changed cells) influencing the deformability were studied, and the sensitivity of the defined parameters for changes in deformability discussed. The results are examined in connection with different flow rates in the micropipette and show that the parameters are influenced by the flow conditions, so that they have to be related to these conditions. Initial studies using microspheres aimed at standardising the method are described.