The effects of two neutral polymers on the geometry and deformability of the human erythrocyte

Summary Polyvinylpyrrolidone and dextran decrease cellular deformability. Changes in volume do not wholly account for the changes which imply a stiffening of the plasma membrane. The effects differ from those induced by charged macromolecules.The work was supported by the Medical Research Council of Canada.     

Demonstration of two ATPases in human erythrocyte membranes

Zusammenfassung Menschliche Erythrozytenmembranen enthalten eine NEM-sensitive und eine NEM-insensitive ATPase, die wahrscheinlich beide an Membranoberflächen lokalisiert sind.

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These studies were carried out with the generous support of the Deutsche Forschungsgemeinschaft.     

The influence of the steroid hormones on the physical state of human erythrocyte membranes

Summary Steroids alter the physical state of the regions in the human erythrocyte membrane, where glucose transport is occurring.The work was supported by the Deutsche Forschungsgemeinschaft. We thank Dipl. Phys. P. Geck for the aid in statistical evaluation.     

Differential effects of monastrol in two human cell lines

The kinesin-related protein HsEg5 plays essential roles in mitotic spindle dynamics. Although inhibition of HsEg5 has been suggested as an aid in cancer treatment, the effects of such inhibition on human cells have not been characterized. Here we studied the effects of monastrol, an allosteric HsEg5 inhibitor, on AGS and HT29 cell lines and compared them to those of taxol. While both cell lines were similarly sensitive to taxol, AGS cells were more sensitive to monastrol. The differences in sensitivity were determined by the degree of inhibitory effect on cell proliferation, reversibility of monastrol-induced G2/M arrest, intracellular phenotypes and induction of apoptosis. In both cell lines, monastrol-induced apoptosis was accompanied by mitochondrial membrane depolarization and poly-ADP-ribose polymerase 1 cleavage. In AGS, but not HT29 cells, monastrol-induced apoptosis involved a prominent cleavage of procaspases 8 and 3. While in AGS cells, monastrol induced the formation of symmetric microtubule asters only, in HT29 cells, asymmetric asters were also formed, which may be related to specific HsEg5 functions in HT29 cells.Received 18 February 2004; received after revision 30 May 2004; accepted 16 June 2004     

The Structure of the erythrocyte membrane

Zusammenfassung Neuere Resultate physikochemischer und chemischer Untersuchungen an Erythrozytenmembranen und Stromaproteinen, welche zum Teil im Widerspruch zur «unit-membrane»-Theorie stehen, werden diskutiert. Die Folgerungen aus diesen Ergebnissen werden anhand von vier kürzliche vorgeschlagenen Strukturmodellen dargelegt, wobei folgende gemeinsame Gesichtspunkte wesentlich erscheinen: 1. mosaikartige Untereinheitenstruktur biologischer Membranen; 2. Membranproteine als wesentliche Träger und Organisatoren der Membranstruktur; 3. völliges Durchdringen der Proteine durch die Membran; 4. hoher -Helix-Gehalt der Membranproteine; 5. hohe Anteile hydrophober Wechselwirkungen zwischen Proteinen und Lipoiden.     

Improved extraction and determination of some glycolytic enzymes in the human erythrocyte

Zusammenfassung Die Aktivitäten von 7 glykolytischen Enzymen wurden in normalen menschlichen Erythrozyten gemessen. Kurze Ultraschall-Hämolyse und modifizierte Test-Bedingungen führten, verglichen mit den höchsten Werten, zu signifikant höheren Aktivitäten.     

The ischemic and postischemic effect on the uptake of neutral amino acids in isolated cerebral capillaries.

The uptake of some neurtral amino acids was investigated in cerebral microvessels isolated from brains of gerbils subjected to bilateral cerebral ischemia with and without various periods of recovery. A transiently increased capillary uptake of 3H-isoleucine, 14C-cycloleucine and 3H-phenylalanine was found in both conditions.     

Aging of the erythrocyte. III. Cation content

Summary Studies on the main cation content of density-separated bovine erythrocytes showed a progressive decrease in the levels of K⁺ and Mg²⁺ with increasing cell density (and age) accompanied by an increase in the level of Na⁺. The magnitude of net cation loss corresponded to that of red cell volume decrease, but could not account for the total increase in the microviscosity of the erythrocyte interior.     

Phosphorylation of human red cell and liver pyruvate kinase. Differences between liver and erythrocyte L-type subunits

Summary Purified PK from human erythrocyte was phosphorylated by cAMP-dependent protein kinase type I from human erythrocyte membrane; this phosphorylation affected only the heavy L subunit but not the L subunit. On the other hand, the L subunit of liver PK was highly phosphorylated. Thus it appears that the L subunits from erythrocyte and liver PK are not identical protein molecules.Acknowledgments. This work was supported by a grant from INSERM (ATP 52.77.84). We thank J. Marie and Dr A. Kahn for the gift of purified liver PK.     

The effect of flavin coenzymes on the activity of erythrocyte enzymes

Zusammenfassung Aktivitätsmessung von 14 Erythrozytenenzymen normaler Personen mit und ohne Hinzufügung der Flavinenzyme Flavinmononukleotid (FMN) und Flavinadenindinukleotid (FAD). Keines der untersuchten Enzyme wurde durch FMN aktiviert, während jedoch FAD die Glutathione Reduktase und die NADH Methämoglobin Reduktase stimulierte.     

Inhibition of erythrocyte ATPase activity by aclacinomycin and reverse effects of ascorbate on ATPase activity

We studied the effect of aclacinomycin on human erythrocyte membrane enzymes. Aclacinomycin inhibited ATPase, including Na-K-dependent ATPase, ouabain insensitive ATPase and Ca-ATPase. However acetylcholinesterase was not inhibited by aclacinomycin. The ATPase activities were not inhibited by aclacinomycin if ascorbate was added to the incubation mixture. However other reducing agents, alpha-tocopherol, superoxide dismutase and catalase had no effect on ATPase activity. Ascorbate may protect membrane proteins and lipids from peroxidate damage.     

Antihypertensive and cardiac effects of two novel beta-adrenoceptor blocking drugs.

Two new beta-adrenoceptor blocking drugs with acute antihypertensive and positive inotropic effects are described: Compound A (2-[4-(3-tert.butylamino-2-hydroxypropoxy)phenyl]-4-trifluoromethylimidazole) and MK-761 (2-(3-tert.butylamine-2-hydroxypropoxy)-3-cyanopyridine hydrochloride). In SH rats both compounds, given orally, lowered arterial pressure and were more potent than hydralazine. The antihypertensive effect of compound A but not of MK-761 was antagonized by timolol. Both compounds had positive inotropic activity on cat heart papillary muscles; these effects were antagonized by timolol. The pretreatment of animals with reserpine greatly reduced the positive inotropic effect of MK-761 but not of compound A. The acute antihypertensive and positive inotropic effects of compound A are like to be at least partially due to stimulation of beta-adrenoceptors, e.g. intrinsic sympathomimetic activity. The effects of MK-761 on the same parameters appear to be mediated by different mechanisms.     

Aging of the erythrocyte. XV. Isoosmotic lysis times

Summary Isoosmotic lysis times of various density (age) fractions of human, pig and ox erythrocytes in glycerol and ammonium chloride solutions decreased with increasing cell density.I am indebted to Prof. W. Leyko for many stimulating discussions.     

Aging of the erythrocyte. II. Activities of peroxide-detoxifying enzymes

Summary The activity of glutathione peroxidase decreases and that of catalase does not change during erythrocyte aging, as judged from a comparison of bovine red cell fractions separated by density.We are indebted to Prof. W. Leyko for many stimulating discussions.     

Ageing of the erythrocyte. XVI. Free amino acid content

Summary The concentrations of some free amino acids, especially glycine, histidine, isoleucine, methionine, phenylalanine, serine and tyrosine decrease considerably during the intravascular ageing of bovine erythrocytes. They seem to provide as sensitive an indication of red cell age as creatine does.Stimulating discussions with Prof. W. Leyko and the experimental help of Mrs A. Rogala, are greatly acknowledged.