No abstract

The role of the surface charge of human red blood cells (RBC's) in affecting RBC aggregation by macromolecules was studied by comparing the behavior of normal RBC's with that of RBC's treated with neuraminidase, which removes the sialic acids from the cell membrane and reduces the zeta potential. RBC aggregation in dextrans with different molecular weights (Dx 20, Dx 40, and Dx 80) was quantified by microscopic observation, measurement of erythrocyte sedimentation rate, and determination of low-shear viscosity. Dx 20 did not cause aggregation of normal RBC's, but caused considerable aggregation of neuraminidase-treated RBC's. Neuraminidase-treated RBC's also showed stronger aggregation than normal RBC's in Dx 40 and 80. Together with the electron microscopic findings that the intercellular distance in the RBC rouleaux varies with the molecular size of dextrans used, the present study indicates that the surface charge of RBC's inhibits their aggregation by dextrans and that the electrostatic repulsive force between cell surfaces may operate over a distance of 20 nm.

Studies of 16 adults with nephrotic edema reveal a spectrum of disease, the extremes of which suggest two different pathophysiologic forms. Patients with the "classic" form--vasoconstriction or hypovolemic nephrosis--have high renin and aldosterone levels that are stimulated rather than suppressed by salt-loading but become lower before steroid diuresis. These patients have minimal lesion disease and, perhaps from diffuse capillary damage, tend to have hypovolemia with renin-induced vasoconstriction. Patients with the second, and heretofore undescribed, form--hypervolemic or overfilling nephrosis--have low renin and aldosterone values that rise normally after sodium depletion. Hypertension, mild renal insufficiency, hypervolemia, and steroid resistance with chronic glomerulonephritis are seen histologically. This form appears volume overloaded from impaired renal sodium excretion. In remission of either type, renin system deviations tend towards normal, but one form does not convert to the other. Renin-sodium profiling may help reveal the two forms and predict steroid responsiveness.

The effects of a reduction in red blood cell (RBC) deformability on regional blood flow and RBC distribution were studied in rats anesthetized with pentobarbital sodium. RBCs were subjected to minimum hardening by incubation in a very diluted solution of glutaraldehyde (0.025%). Normal and partially hardened RBCs, labeled with 51Cr or 111In, were injected into the femoral vein, while an equal volume of blood was simultaneously withdrawn from the femoral artery. Approximately 70% of the labeled, partially hardened RBCs disappeared from the circulating blood within 25 min after injection, compared with less than 2% of the labeled normal RBCs. The relative distribution of RBCs with reduced deformability to normal RBCs in tissues was determined from radioactivity counting; this ratio (mean +/- SD) was 7.95 +/- 0.85 in the spleen, 7.44 +/- 0.43 in the sternum, 7.10 +/- 1.09 in the lung, 4.54 +/- 0.31 in the liver, and 3.50 +/- 0.61 in the femur bone. The results indicate a significant degree of trapping of RBCs with reduced deformability in these regions. This ratio of relative distribution of RBCs with reduced deformability as compared with normal RBCs was 1.06 +/- 0.13 in the heart, indicating the absence of preferential trapping of RBCs with reduced deformability in this organ. Regional blood flows were determined with 15-microns microspheres in the control period and after infusion of RBCs with reduced deformability (experimental).(ABSTRACT TRUNCATED AT 250 WORDS)

Aggregation of normal and neuraminidase-treated human red blood cells (RBC) by dextrans of various molecular sizes and concentrations was quantified by microscopic counting and light reflectometry. The influences of variations in the ionic strenah and the cationic valency of the dextran solution on RBC aggregation were also investigated. The data on RBC aggregation were correlated with measurements of the zeta potential by cell electrophoresis and the intercellular distance in the rouleaux by electron microscopy. With the use of the classical equations and newly developed knowledge in colloid chemistry, the electrostatic repulsive force between adjacent cell surfaces (F,) was calculated from the experimental data. The macromolecular bridging force causing RBC aggregation (Fb) has also been derived as a function of dextran concentration. Other forces that cause RBC disaggregation are the mechanical shearing force (c) and the RBC membrane bending force ( F ). The net force for RBC aggregation is equal t o Fb -F, -F , -F,. This model ofmaggregation involving force balance at the surface can explain known experimental results on factors influencing cell aggregation. It is proposed that such force balance between cell surfaces may be applicable in other cell or particulate systems and that it may be of fundamental importance in many physiological functions.Cell to cell interaction is a fundamental phenomenon in biology and medicine. Cell aggregation and disaggregation are of considerable importance in development, growth, differentiation, and functioning of the multicellular organism under physiological conditions and they also play an important role in many pathological states, e.g., the growth and metastasis of tumor cells. Since the red blood cell ( R E ) is probably the most easily obtainable and controllable among cells, it represents an excellent candidate for studying interactions between cell surfaces. Of course, each cell type presents different structural and functional features which prevent direct extrapolation from the results obtained on RBC t o other cells. Nevertheless, an elucidation of the biophysical nature of the RBC interactions may yield some basic information which can be applied t o other cell systems with appropriate modifications.Red blood cells are monodispersed in isotonic salt solutions, and RBC aggregation requires the presence of macromolecules in the suspending medium. The classical studies of Fhraeus (1) have demonstrated that the physicochemical properties and the concentration of the macromolecules play a significant role in affecting RBC aggregation, suggesting that RBC aggregation results from an interaction of the macromolecules with Journal of Supramolecular Structure