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At least 343 records · Page 19Linked to original sources
PubMed1996

A role for erythrocyte band 3 degradation by the parasite gp76 serine protease in the formation of the parasitophorous vacuole during invasion of erythrocytes by Plasmodium falciparum.

A purified Plasmodium falciparum serine protease (gp76) implicated in erythrocyte invasion, degrades human erythrocyte band 3 and glycophorin A. Inhibition studies using synthetic peptides derived from the presumed band 3 enzymatic cleavage sites and the observed uptake of fluorescent phospholipids following gp76 treatment, suggest that band 3 degradation by this serine protease participates in the formation of the parasitophorous vacuole by restructuring the red cell cytoskeleton. These results provide a rationale for the elaboration of specific inhibitors to block red cell invasion by malaria parasites.

Amino Acid Sequence↗
PubMed1981

Activation of pigeon erythrocyte adenylate cyclase by cholera toxin. Partial purification of an essential macromolecular factor from horse erythrocyte cytosol.

A cytosolic, macromolecular factor required for the cholera toxin-dependent activation of pigeon erythrocyte adenylate cyclase and cholera toxin-dependent ADP-ribosylation of a membrane-bound 43,000 dalton polypeptide has been purified 1100-fold from horse erythrocyte cytosol using organic solvent precipitation and heat treatment. This factor, 13,000 daltons, does not absorb to anionic or cationic exchange resins, is sensitive to trypsin or 10% trichloroacetic acid and is not extractable by diethyl ether. Activation of adenylate cyclase by cholera toxin requires the simultaneous presence of ATP (including possible trace GTP), NAD+, dithiothreitol, cholera toxin, membranes and the cytosolic macromolecular factor. Reversal of cholera toxin activation of adenylate cyclase, and of the toxin-dependent ADP-ribosylation, requires the presence of the cytosolic factor. The ability of the purified cytosolic factor to influence the hormonal sensitivity of liver membrane adenylate cyclase may provide clues to its physiological functions.

Adenylyl Cyclases↗
PubMed1987

The distribution of zinc and copper in plasma, erythrocytes and erythrocyte membranes of rainbow trout (Salmo gairdneri).

1. The zinc and copper concentration of plasma was determined in rainbow trout, lake trout, walleye and whitefish. 2. These fish had mean plasma zinc concentrations ranging from 9.3 to 15.1 ppm and copper concentrations from 0.6 to 1.3 ppm. 3. In rainbow trout, the concentration of zinc and copper is greater in the erythrocyte membrane than in the total erythrocyte. 4. Ultrafilterable plasma zinc and copper concentration in rainbow trout was determined to be 0.03 and 0.019 ppm, respectively. 5. Dialysis of rainbow trout plasma against 20 mM EDTA results in removal of 99% of the zinc and 88% of the copper from plasma proteins.

Animals↗
PubMed1987

Spin label study of erythrocyte deformability. Ca2+-induced loss of deformability and the effects of stomatocytogenic reagents on the deformability loss in human erythrocytes in shear flow.

The Ca2+-induced loss of deformability in human erythrocytes and the recovery of the lost deformability by stomatocytogenic reagents were investigated by means of a new flow electron paramagnetic resonance (EPR) spin label method, which provides information on deformation and orientation characteristics of spin labeled erythrocytes in shear flow. The Ca2+-induced loss of deformability is attributed mainly to the increase in intracellular viscosity resulting from efflux of intracellular potassium ions and water (Gardos effect). Partial recovery of the lost deformability is demonstrated in the presence of stomatocytogenic reagents, such as chlorpromazine, trifluoperazine, W-7, and calmidazolium (R24571). The recovery can not be explained solely by suppression of the Gardos effect due to the reagents. Incorporation of an optimal amount of the reagents into the membrane appears to compensate for the membrane modification due to Ca2+ ions to restore a part of the lost deformability.

Calcimycin↗
PubMed1999

The adhesion of Plasmodium falciparum-infected erythrocytes to chondroitin sulfate A is mediated by P. falciparum erythrocyte membrane protein 1.

Chondroitin sulfate A (CSA) is an important receptor for the sequestration of Plasmodium falciparum in the placenta, but the parasite ligand involved in adhesion has not previously been identified. Here we report the identification of a var gene transcribed in association with binding to CSA and present evidence that the P. falciparum erythrocyte membrane protein 1 product of the gene is the parasite ligand mediating CSA binding. Description of this gene and the implication of P. falciparum erythrocyte membrane protein 1 as the parasite ligand paves the way to a more detailed understanding of the pathogenesis of placental infection and potential therapeutic strategies targeting the interaction.

Animals↗
PubMed1995

The ANK repeats of erythrocyte ankyrin form two distinct but cooperative binding sites for the erythrocyte anion exchanger.

The 24 ANK repeats of the membrane-binding domain of ankyrin form four folded subdomains of six ANK repeats each. These four repeat subdomains mediate interactions with at least seven different families of membrane proteins. In the erythrocyte, the main membrane target of ankyrin is the Cl-/HCO3- anion exchanger. This report presents the first evidence that ankyrin contains two separate binding sites for anion exchanger dimers. One site utilizes repeat subdomain two (repeats 7-12) while the other requires both repeat subdomains three and four (repeats 13-24). The two sites are positively coupled with a Hill coefficient of 1.4. Since the anion exchanger exists as a dimer in the membrane, the presence of two binding sites on ankyrin allows ankyrin to interact with four anion exchangers simultaneously. These findings provide a direct demonstration of the versatility of ANK repeats in protein recognition, and have important implications for the organization of ankyrin-linked integral membrane proteins in erythrocytes as well as other cells.

Amino Acid Sequence↗
PubMed1994

A luminescence method for the quantitative determination of phagocytosis of erythrocytes, of malaria-parasitized erythrocytes and of malarial pigment.

A method is described for the quantitative measurement of phagocytosis of human erythrocytes, malaria-parasitized erythrocytes and isolated malarial pigment by adherent human monocytes. The method utilizes measurement of haem-elicited luminescence both for the assay of ingested haemoglobin or malarial pigment haem and for the quantification of adherent monocytes. The latter is based on assay of luminescence elicited by cytochrome haem. The method utilizes the same low-cost reagents and equipment for assay of ingested haem and for quantification of adherent monocytes. The method is fast and extremely sensitive. The lower sensitivity limit is 500 monocytes and 10 RBC, or RBC equivalents in the case of malarial pigment, per assay. A detailed protocol with full calculations of a typical phagocytosis experiment of oxidatively damaged RBC, malarial pigment and control RBS is presented.

Animals↗
PubMed1979

Studies of factors regulating the ageing of human erythrocytes. II. Metabolic depletion of erythrocytes is not accompanied by a decrease of their sialic acid content during blood bank storage.

Erythrocytes from human blood stored at 5 degrees C in anticoagulant-preservative solutions are considered, after a period from 21 to 24 days, unsuitable for transfusion. The nonviability of the cells appears due to metabolic impairment accompanied by a change of the biophysical properties of the cell but surprisingly not to a decrease of sialic acid of the membrane. The absence of proteolysis can be attributed to calcium chelation and to the stable levels of plasma protease inhibitors throughout the storage period. In fact, when erythrocytes are incubated for several days at 5 degrees C in protein-free media, release of sialopeptides from the membrane increases slowly and steadily, particularly if the medium is without glucose and adenine but contains divalent cations. Moreover, this phenomenon is strikingly amplified when incubation in protein-free media is carried out at 37 degrees C and once the ATP level has fallen below 5% of its initial value.

Adenine↗
PubMed1983

Interaction of a peripheral protein of the erythrocyte membrane, band 4.1, with phosphatidylserine-containing liposomes and erythrocyte inside-out vesicles.

Interactions of band 4.1 with mixed phospholipid membranes [phosphatidylserine (PtdSer), phosphatidylethanolamine, phosphatidylcholine, etc.] and erythrocyte inside-out vesicles were studied. Band 4.1 showed a higher affinity to PtdSer-containing membranes. The amount of binding to PtdSer-containing liposomes was larger than that to PtdSer-lacking liposomes. The amount of binding to inside-out vesicles did not change significantly on a protease treatment of the vesicles. The amount of band 4.1 bound on inside-out vesicles decreased on PtdSer-decarboxylase treatment of the vesicles. Ca2+ acted inhibitory to the binding of band 4.1. Band 4.1 together with PtdSer-containing vesicles but not with PtdSer-lacking vesicles induced gelation of spectrin-actin copolymer solution. Ca2+ inhibited the gelation. Fluorescence energy transfer from PtdSer-containing vesicles to band 4.1 was larger than that from PtdSer-lacking vesicles. Band 4.1 caused a marked release of tempocholine from preloaded PtdSer-containing liposomes but not from PtdSer-lacking liposomes. The release was larger from liposomes containing more PtdSer. Ca2+ was inhibitory to the tempocholine release. We suggest from these results that band 4.1 provides another anchoring site for the cytoskeletal spectrin-actin network to PtdSer domains in the inner layer of erythrocyte membrane. This anchoring may be involved in functional regulation since the interaction causes the membrane permeability change that is dependent on Ca2+.

Blood Proteins↗
PubMed1986

Erythrocyte enzymes in polycythemia vera: a comparison to erythrocyte enzyme activities of patients with iron deficiency anemia.

Fifteen cytoplasmic erythrocyte enzyme activities were determined in patients with polycythemia vera (PV), iron deficiency anemia (IDA), and a group of healthy volunteers. Among the PV patients, the erythrocyte enzyme activities were compared between 2 groups: patients treated solely with phlebotomy and patients treated with phlebotomy, Myleran (busulfan) and/or radioactive phosphorus 32P. Significant reduction in glutathione reductase activity was found in the PV group of patients. This activity was normalized by the addition of flavin adenine dinucleotide. In contrast to previous reports, no other enzyme activity was found to be significantly reduced. The activities of the enzymes known to be age-dependent were significantly elevated in all the groups tested except for phosphofructokinase and 3-phosphoglycerate mutase. The former was not elevated in any of the groups studied, while the latter was elevated only in the group of patients treated with Myleran and/or 32P. It was concluded that glutathione reductase (GR) deficiency is the only acquired enzyme deficiency in our group of PV patients and that radiation and chemotherapy did not induce further reduction in the activities of any of the enzymes tested. The possible involvement of GR deficiency in the etiology of the red cell life span shortening was discussed.

Anemia, Hypochromic↗
PubMedDate not supplied

Plasma and erythrocyte cations and permeability of the erythrocyte membrane to cations in essential hypertension.

Untreated African patients with essential hypertension were found to have high plasma sodium and low plasma potassium. The red cel contents of these cations determined from the same sample of blood were found to be high for sodium and normal for potassium. The passive permeability of the erythrocytes for potassium was lower in hypertensives than in controls. The ouabain-sensitive active sodium efflux was lower in hypertensives than in controls. The relationships between the erythrocyte cation content and the total body content of the cations, and between the membrane function in red cells and other cells of the body are discussed.

Adult↗
PubMed1991

Myosin content and distribution in human neonatal erythrocytes are different from adult erythrocytes.

Neonatal erythrocytes (N-RBC) are different from adult erythrocytes (A-RBC). N-RBC are larger, less deformable, and undergo enhanced spontaneous and drug-induced endocytosis. The reticulocyte population of N-RBC is also different, consisting primarily of the youngest (R1) reticulocytes that are motile and capable of receptor-mediated endocytosis. Processes such as motility could require a contractile system. Myosin, a contractile protein, was identified in both A-RBC and N-RBC. We proposed to compare myosin content and distribution in A-RBC and N-RBC by immunofluorescence and enzyme-linked immunosorbent assay (ELISA) using a monospecific polyclonal rabbit antimyosin. There was bright immunofluorescence on 44% of N-RBC with some heterogeneity contrasting with a barely detectable fluorescence on A-RBC. ELISA measurements showed that A-RBC had 4,315 myosin copies/RBC, whereas N-RBC had 10,855 copies/RBC (or 2.5 times as much). ELISA measurements of white ghosts showed that A-ghosts contained 1,250 copies of myosin/RBC (29% of total) whereas N-ghosts contained 3.4 times as much at 4,320 copies/RBC (39% of total). Therefore, N-RBC not only have more myosin, but the amount that is membrane-associated is disproportionately increased. It is proposed that such differences in amount and distribution of myosin could account for some of the unusual properties of neonatal RBC indicated.

Adult↗
PubMed1991

[Characterization of erythrocyte deformability by filtration technics. 5. The effect of leukocytes on the filterability of erythrocytes].

Filterability measurements have been used widely in medical research and clinical practice to characterize erythrocyte deformability. In the present paper the influence of white blood cells (WBC) on the of filterability indices is investigated and discussed. We found for two gravity filtration systems using cellulose filters and concentrated erythrocyte suspensions sensitivities of their filterability indices of 1% per 100 WBC/microliters (initial) filtration rate measurement) and 3% per 100 WBC/microliters (hemofiltrometer). The necessity, advantages and disadvantages of additional methods for WBC removal are discussed in comparison to nuclepore filtration systems with sensitivities of 5-12% per 100 WBC/microliters. The standardization of residual WBC-count in limits of 500 +/- 300 WBC/microliters at a hematocrit of 60% is proposed.

Erythrocyte Deformability↗
PubMed1990

[Clinical reference values for laboratory hematology tests calculated using the iterative truncation method with correction: Part 1. Reference values for erythrocyte count, hemoglobin quantity, hematocrit and other erythrocyte parameters including MCV, MCH, MCHC and RDW].

Age and sex dependent differences in the clinical reference values for erythrocyte count (RBC), hemoglobin quantity (Hb), hematocrit (Ht) and other erythrocyte parameters including MCV (mean corpuscular volume), MCH (mean corpuscular hemoglobin), MCHC (mean corpuscular hemoglobin concentration) and RDW (red cell distribution width), were calculated by the iterative truncation method with correction (Usui's method) using the results from tests on 6,300 patients' specimens obtained at Kyoto University Hospital. For RBC, Hb and Ht, the data obtained from the individuals below 13 years old showed the normal or sometimes log-normal distribution, but adjustment by the Xn-type variable transformation was often necessary to obtain the normal distribution for the data taken from the populations containing individuals over the age of 14. For the clinical reference values of RBC, Hb and Ht, no sex difference was observed below the age of 12. The values for males were significantly higher than those of females in the age range 13-79, and the values showed no significant sex-dependent difference at ages above 80. In females, age-dependent change of values for RBC, Hb and Ht was less prominent than in males; especially the upper limit values for females were very stable for all ages. MCV and MCH gradually increased with age both in males and females, and the MCHC remained constant in all age populations of male and female. The reference value for RDW was generated by the percentile method instead of the iterative truncation method because of the strong deviation in the distribution pattern, and the RDW values showed a gradual increase with age in both males and females.

Age Factors↗
PubMed1986

Stability of membrane pores in hypotonically dialyzed erythrocytes: coencapsulation of different stokes radius probes can occur for at least 21 days in human erythrocytes.

Hypotonic dialysis of human erythrocytes results in porous cell stability for several days. Hypotonic cells stored for 1 week are essentially normal with respect to the preparation of carrier erythrocytes. Afterward, cells begin to irreversibly hemolyze resulting in decreased cell recoveries and decreased encapsulation percentages of two probes, sucrose and inulin. The holes generated by controlled hypotonic dialysis (100 mOsm/kg) are unlike the single rupture hole generated by dialysis to 10-20 mOsm/kg. The minimum pore size of resealed, annealed carrier cells is confirmed to be less than 5.2 A.

Blood Preservation↗
PubMed1983

[A small subpopulation of rigid erythrocytes changes the erythrocyte filtration test].

By means of the filterability test of Reid et al., the influence of a subpopulation of rigid erythrocytes (5% and 2.5%, respectively) was studied using Nucleopore polycarbonate membranes with pore size of 5 mu and diameter of 13 mm. The addition of 5% and 2.5% of rigid red cells delays the erythrocyte filtration times and alters the red cell deformability index. The meaning of the obtained data is discussed.

Erythrocyte Indices↗
PubMed1981

Actions of gamma-radiation on resealed erythrocyte ghosts. A comparison with intact erythrocytes and a study of the effects of oxygen.

With respect to both permeability and inactivation of membranous GAPDH, ghosts were more susceptible than erythrocytes to free radicals produced in the gamma-irradiation of aqueous solutions. The rate of increase in the permeability of irradiated ghosts was immeasurably greater than that of irradiated erythrocytes, while the rate of inactivation of GAPDH was 21-fold greater. The sensitivity of ghosts to radiation damage was affected strongly by the presence of oxygen during irradiation. In the presence of air, the rates of increase of permeability and inactivation of GAPDH were 2.8- and 1.5-fold of those in the presence of N2. The use of buffer saturated with oxygen accelerated the aerobic rates of increase of permeability and inactivation of GAPDH by 60- and 2.7-fold. These results indicate that inactivation of GAPDH is somewhat sensitive to oxygen, particularly at high concentration of oxygen. Nevertheless, in air or under nitrogen, the rate of enzymic inactivation was almost an order of magnitude greater than that of increase of permeability, indicating that the former is much more sensitive to irradiation. The major mechanism of the oxygen effect observed is the ability of oxygen to increase the branching of the free radical chain reactions which propagate damage after initiation within the membrane.

Cell Membrane Permeability↗