Permeability of fresh and stored human erthrocytes to glycerol and its acylated derivatives

The effect of copper ions on the permeation of glycerol and its mono-, di-, and triacetate derivatives was studied in fresh and stored erythrocytes. Permeability was unchanged with storage. Acylated glycerols permeate the cells mainly by non-facilitated mechanism, as their transport is almost unaffected by copper ions.     

Phenothiazine derivatives as inhibitors of the glucose oxidative pathway in human erythrocytes

Zusammenfassung Phenothiazinabkömmlinge unterscheiden sich in ihrer Wirksamkeit als Hemmstoffe im oxydativen Glukosestoffwechsel in menschlichen Erythrozyten. Kombiniert man verschiedene Phenothiazinderivate, so erhält man einen mittleren Hemmungsgrad, der zwischen jenen liegt, die man bei Anwendung der einzelnen Wirkstoffe für sich allein erhalten würde. Somit erscheint es nicht wahrscheinlich, dass Hemmung des oxydativen Glukosestoffwechsels die prinzipielle Wirkungsweise der Phenothiazinabkömmlinge darstellt.     

Permeability of the isolated human amniotic membrane to divalent cations]

Membrane potential and resistance recordings, in vitro, show that Mg++ does not pass through the amnion from the inside of the amniotic compartment to the outside of the amniotic membrane. Mg++ may become fixed on the surface or in the midst of the amniotic membrane. However, Mg++ diffuses in the opposite direction. Ca++, Ba++, Sr++ diffuse in both directions across the amniotic membrane.     

Rheological and functional impairments in cholesterol-loaded human erythrocytes

Summary Decreased deformability, slightly increased suspension viscosity and retarded oxygen egress were observed in cholesterol-loaded, human erythrocytes. These functional changes resulted from the decreased membrane fluidity induced by cholesterol.     

Effect of hydrogen peroxide on the binding of Merocyanine 540 to human erythrocytes

The fluorescent dye Merocyanine 540 (MC540) is often used as a probe to monitor the molecular packing of phospholipids in the outer leaflet of biomembranes. In a previous study we showed that the increased staining of erythrocytes with a perturbed membrane structure was mainly due to an increase in the fluorescence yield of cell-bound MC540, rather than to an increase of the number of bound molecules. Erythrocytes and ghosts exposed to continuous fluxes of H₂O₂ exhibited pronounced lipid peroxidation. Further, red blood cells subjected to this form of oxidative stress also showed increased staining with MC540. It appeared that this was caused by a strong increase in binding of MC540, together with a slight red shift of the fluorescence emission maximum and a small increase in the fluorescence yield of bound MC540. The changed MC540 binding characteristics were not observed when lipid peroxidation was suppressed by the presence of the antioxidant BHT in the incubation medium. However, open ghosts exposed to H₂O₂ showed no increase of MC540 binding, excluding a direct involvement of lipid peroxidation. Measurement of fluorescence emission spectra and gel filtration studies showed that MC540 can bind to H₂O₂-exposed hemoglobin. Experiments with erythrocytes lysed in hypotonic medium after exposure to H₂O₂ revealed that peroxidation of lipids with H₂O₂ induced a non-specific permeabilization of the plasma membrane to MC540, thereby allowing MC540 to bind to the oxidatively denatured, more hydrophobic hemoglobin. These results indicate that conclusions about packing of phospholipids in the outer leaflet of the membrane based on increased MC540-staining should be drawn with care. Received 27 September 1996; received after revision 5 November 1996; accepted 27 November 1996     

Binding capacities of various analogues of S-adenosyl-L-homocysteine to protein methyltransferase II from human erythrocytes

Summary A series of analogues of S-adenosyl-L-homocysteine, modified mainly in the amino acid portion of the molecule, have been synthesized. All were found to be competitive inhibitors of protein methyltransferase II from human erythrocytes. S-adenosyl-L-homocysteine remains however by far the most effective inhibitor of the methylase.Acknowledgments. This work was supported by a grant of the Fonds National Belge de la Recherche Scientifique and by a grant of the Fonds Emile Defay.     

Binding capacities of various analogues of S-adenosyl-L-homocysteine to protein methyltransferase II from human erythrocytes.

A series of analogues of S-adenosyl-L-homocysteine, modified mainly in the amino acid portion of the molecule, have been synthesized. All were found to be competitive inhibitors of protein methyltransferase II from human erythrocytes. S-adenosyl-L-homocysteine remains however by far the most effective inhibitor of the methylase.     

Effect of insulin on potassium transfer in human and chicken erythrocytes

Riassunto La conservazione al freddo degli eritrociti umani e di pollo per 6 giorni causa una fuoruscita di potassio dai globuli. Parte del potassio rientra nelle cellule durante incubazione a 37° C.La uabaina blocca questo fenomeno. L'insulina non ha effetto significativo nè sull'assunzione di potassio da parte del globulo rosso, nè sull'azione bloccante della uabaina.

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Aided by a grant from the Chicago Heart Association.

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Trainee, Diabetes Teaching Grant No. 2A-5102, National Institute of Arthritis and Metabolic Diseases, Public Health Service.     

Effects of hypochlorite on thiamine and its derivatives

Summary Thiamine and its phosphorylated derivatives reacted with hypochlorite with reaction rates following the order: thiamine>thiamine monophosphate>thiamine diphosphate from pH4.0 to 6.5. At least one unknown transient intermediate was formed and at least one non-thiochrome product was fluorescent. Chemiluminescence was also observed.We thank the International Foundation for Science, Sweden, and the Thai University Development Council for financial support.     

Effects of hypochlorite on thiamine and its derivatives

Thiamine and its phosphorylated derivatives reacted with hypochlorite with reaction rates following the order: thiamine greater than thiamine monophosphate greater than thiamine diphosphate from pH 4.0 to 6.5. At least one unknown transient intermediate was formed and at least one non-thiochrome product was fluorescent. Chemiluminescence was also observed.     

Hemagglutination of neuraminidase-treated human erythrocytes byLeishmania enriettii infected guinea-pig sera

Summary Sera from guinea-pigs infected with the protozoan parasiteLeishmania enriettii showed higher hemagglutination (HA) titres for neuraminidase treated human erythrocytes than those of normal guinea-pig sera. This HA activity was associated mostly with the 19S fraction of the immune serum and could be absorbed out with an antigenic fraction of the parasite membrane. Antigenic determinants involved in this HA reaction consisted of, at least, -d-galactosyl or lactosyl residues.     

Reduced deformability of erythrocytes exposed to hypercapnia

Summary The effect of hypercapnia on the deformability of erythrocytes was studied by means of a nuclepore membrane filter method. A decrement of the deformability by 20–40% was observed when was increased from 50 mm Hg to 200 mm Hg, accompanied with an increment of 5% in hematocrit value.