Die alterierte Erythrocytenmembran

Employment of merocyanine 540 fluorescence to form diaminobenzidine (DAB) oxidation product: a photoconversion method for the visualization of erythrocyte membrane fluidity for light and electron microscopy

Intact native red blood cells (RBC) and treated RBC preparations were labelled with MC 540 and irradiated in the presence of diaminobenzidine (DAB). The polymerized diaminobenzidine reaction product is permanently stable in comparison with the labile fluorescence labelling. The brownish stained DAB polymerization product (DAB brown) and osmium black (after conversion of DAB brown with OsO4) allow the densitometrical determination with the light microscope. The latter product can be directly observed in the electron microscope. A direct correlation exists between the fluorescence intensity and the polymerized diaminobenzidine staining. It can be deduced that the enhancement of the DAB mediated contrast is reflecting an increased fluidity of the red cell membrane. The reaction was successful with all red cell preparations tested. This method is also suitable for the determination of fluidity changes in other cell membranes.

The binding of a polyclonal antibody against human band 3 to in vitro aged erythrocytes

In vitro aged human erythrocytes were checked for their anti-band-3-antibody loading by means of a protein A-gold technique. The in vitro-ageing procedures are introduced as an alternative to the questionable preparation of in vivo aged cells. They include the influences of NaF in various concentrations, of heat (49 degrees C) and urea. After the treatment with 20 mmol/l NaF and more, the IgG loading increases significantly. In contrast to that, however, exovesiculation induced by heat and urea lower the IgG loading. Possible mechanisms for the growing accessibility of the epitopes concerned are discussed in connection with changes occurring during the physiological ageing processes.

Topo-optical studies of gradually disintegrated erythrocyte membrane derivates: different kinds of ghosts

Several kinds of ghosts from human erythrocytes (blood-group A1D) were investigated by the topo-optical Toluidine-Blue (TB) reaction. In comparison to intact cells, all ghosts demonstrated a decreased TB-anisotropy. These results reflect an altered glycocalyx structure of ghosts, especially conformational changes of the TB-binding N-terminal extracellular segments of the glycophorines. It was assumed that this structural glycocalyx alteration was caused by substantial losses of membrane skeleton components during the ghost preparation. Moreover, disturbed molecular interactions between the membrane skeleton and the glycocalyx may contribute to this effect. Therefore, the glycocalyx and the membrane structure of ghosts in general are significantly different from the membrane of the intact erythrocyte. The experiments show that the effects of the reconstitution procedures for ghost membranes are restricted to a reconstitution of a defined membrane function (i.e. dynamic barrier for monovalent cations) in a widely disturbed membrane structure.

Topo-optical investigations of human erythrocyte glycocalyx conformational changes induced by dextran

Cell surface properties are involved in the aggregation process of red blood cells. Using the topo-optical toluidine blue reaction, conformational changes of the glycocalyx (main component glycophorin A) were found when red blood cells were incubated and fixed in the presence of dextran. Relative differences in optical path as a measure of red blood cell membrane anisotropy decreased in relation to dextran concentration during fixation. These conformational changes could not be detected by electrophoretic measurements. When incubating, fixing and staining red blood cells in the presence of dextran, anisotropy decreased only at low dextran concentrations and increased at rising dextran concentrations. This biphasic course of differences in optical path seems to be due to different effects of dextran superimposing upon each other: a disturbing influence on the spatial order of sialic acid carrying oligosaccharide side chains due to H-bond interaction, and an increase in the size of dye aggregates and suppression of the thermal motion of macromolecules at higher dextran concentrations.

The rate of lateral diffusion of phospholipids in erythrocyte microvesicles

31P-NMR spectra of phospholipids in membranes of erythrocyte microvesicles isolated from outdated blood units were recorded in the temperature range 5 to 55 degrees C. Within that range the lineshape is strongly influenced by an increasing rate of lateral diffusion of phospholipids. At 36 degrees C a diffusion constant, D, of (2 +/- 1) X 10(-12) m2/s was obtained. The diffusion rate is by a factor of 3 to 10 greater than in erythrocyte membranes measured by the photobleaching technique and is comparable with values obtained for several lipid model membranes. The differences in lateral diffusion rates are probably connected with the depletion of microvesicle membranes in membrane proteins.

Spectroscopic characterization of vesicle formation on heated human erythrocytes and the influence of the antiviral agent amantadine

EPR investigations on the vesiculation process of heated human erythrocytes were performed, using different fatty acid spin labels. Spectrin denaturation and vesiculation do not influence the fluidity of the lipid phase of the remaining membrane of human erythrocytes: Vesicles released differ in chemical composition as well as in the lipid fluidity of their membrane from the intact human erythrocyte membrane. A reduced cholesterol-to-phospholipid ratio and a depletion of spectrin was found. By changing the ionic concentration of the suspension medium an effect on membrane spectra and on vesicle release was established. The adamantane derivative amantadine causes fluidization of the human erythrocyte membrane and inhibits vesicle release. Based on these results, a model for the mechanism by which adamantane-like molecules could interact with membranes is proposed.

Activation of acetylcholine esterase (ACHE) as a sign for erythrocyte membrane alteration

In vitro activity determination of membrane bound acetylcholine esterase (ACHE) of intact erythrocytes and differently altered RBC forms by means of the ELLMAN method yielded increase in activity in erythrocyte/vesicle mixtures and ghosts. Alteration of the cells by treatment with periodate, neuraminidase and trypsin leads to no, weak or clear decrease in the activity of this enzyme. Old cells also show a clear decrease in activity. When cells were treated with diamide ACHE is at first functionally inhibited, finally, however, it reaches supernormal values of activity. Possible causes for the different behaviour of ACHE in dependence on the degree of alteration of the erythrocytes are discussed. The results of the measurements were compared with the ultrahistochemical ACHE reactions according to KARNOVSKY (thiocholine--copper ferricyanide method) and IWAYAMA (lead thiocholine method). The influence of several components of the KARNOVSKY'S histochemical reaction mixture on ACHE activity was tested. The investigations suggest that disintegration of the erythrocyte membrane is accompanied with activation of the ACHE molecules which are nearly inactive in the intact membrane. This activation contributes to the positive histochemical ACHE test, which is an indicator reaction of membrane disintegration. Nearly intact membranes show a negative reaction. On the basis of these results we could show that physiological enucleation of normoblasts is connected with the formation of disintegrated membrane areas and their discharge from the future reticulocyte membrane.

Topo-optical investigations of the human erythrocyte glycocalyx-age related changes

The conformational state of the glycocalyx of the intact and altered erythrocyte membrane was studied by means of the topo-optical toluidine blue reaction, i.e. induced membrane birefringence. High membrane anisotropy represents the normal glycocalyx structure and its decline represents their perturbation. The results show that the glycocalyx structure is changed during ageing of the erythrocytes in vivo as well as in vitro. During fluid preservation, in vitro ageing and vesiculation of cells in vitro, a subpopulation of cells showed a decline of membrane anisotropy, but other cells demonstrated abnormally high values. In the latter cases, there is usually a correlation to spherocytes. From this point of view, it is to be assumed that spherogenesis during cell ageing is induced by cell vesiculation. This leads to a remodelling of an intact plasmalemma. In contrast, the cell fractions which are probably non-vesiculating seem to be more or less damaged by membrane and/or plasmic hydrolases. This can be mimicked by neuraminidase and protease treatment of erythrocytes in vitro. Membrane lesions caused by freeze preservation of red blood cells are rare. The topo-optical results are interpreted according to the assumptions of the theory of membrane anisotropy, i.e. the formation of dye-stuff micelles at distinct, clustered, sialylated carbohydrate chains of the glycophorin A.

Acceleration of coagulation by spectrin-free erythrocytic vesicles. Evidence for lipid flip-flop during vesicle formation

Spectrin-free erythrocytic vesicles isolated from outdated liquid-preserved blood samples show a distinct increase of the clot-promoting activity compared with membrane phospholipid equivalents of intact erythrocytes. We suppose that, among other remodelling processes, local spectrin detachment from the inner membrane surface may trigger a flip-flop-mediated disturbance of the membrane lipid asymmetry. The interactions of spectrin with the cytoplasmic membrane surface seem to be essential for the structural membrane integrity including the lipid asymmetry.