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Micronucleated erythrocyte frequencies in old and new world primates: measurement of micronucleated erythrocyte frequencies in peripheral blood of Callithrix jacchus as a model for evaluating genotoxicity in primates.

Nonhuman primates are of particular relevance in evaluating the potential toxicity of drugs and environmental agents. We have used previously published information and data from the present study to establish a relationship for New World (NW) and Old World (OW) primates on the basis of the frequency of spontaneous micronucleated erythrocytes (MNEs) observed in peripheral blood. Data on spontaneous MNEs in peripheral blood from 15 species of primates, including humans, indicate that NW primates have significantly (P < 0.01) higher MNE frequencies (group mean, 9.5 +/- 7.3 MNEs/10,000 erythrocytes; range, 0.7-20.5/10,000 erythrocytes) than OW primates (group mean, 1.0 +/- 0.9 MNEs/10,000 erythrocytes; range, 0.0-2.6 MNEs/10,000 erythrocytes). Humans are believed to have developed in the OW, and human MNE frequencies were similar to those described for OW primate species. We selected the common marmoset (Callithrix jacchus), a NW primate, to determine whether therapeutic pediatric doses of Metotrexate (MTX; 2.5 mg/kg), Cyclophosphamide (CP; 5 mg/kg), Cytosine-arabinoside (Ara-C; 3 mg/kg), or 5-Fluorouracil (5-FU; 10 mg/kg), administered daily for two consecutive days, increase the frequency of micronuclei. Micronucleated polychromatic erythrocyte frequencies were increased significantly in groups receiving MTX, CP and Ara-C, while MNE frequencies were increased by the Ara-C treatment. The results of this study indicate that NW primates have higher spontaneous MNE frequencies than OW primates, and because of this, NW primates like the common marmoset, may be suitable for evaluating the genotoxicity of chemical agents.

Animals↗

Effects of some antibiotics on enzyme activity of glucose-6-phosphate dehydrogenase from human erythrocytes.

Inhibitory effects of some antibiotics on glucose-6-phosphate dehydrogenase from the erythrocytes of human have been investigated. For this purpose, at the beginning, erythrocyte glucose-6-phosphate dehydrogenase was purified 13.654 times in a yield of 28% by using ammonium sulphate precipitation and 2',5'-ADP Sepharose 4B affinity gel. Temperature of +4 degrees C was maintained during the purification process. Enzyme activity was determined with the Beutler method by using a spectrophotometer at 340 nm. This method was utilized for all kinetic studies. Sodium ceftizoxime, sodium ampicillin, sodium cefuroxime, sodium cefazolin, sodium cefoperazone, streptomycin sulphate, gentamicin sulphate, and netilmicin sulphate were used as antibiotics. All the antibiotics indicated the inhibitory effects on the enzyme. K(i) constants for glucose-6-phosphate dehydrogenase were found by means of Lineweaver-Burk graphs. While sodium cefoperazone, gentamicin sulphate, and netilmicin sulphate showed competitive inhibition, the others displayed non-competitive inhibition. In addition, I(50) values of the antibiotics were determined by plotting activity percent vs [I]. In addition, in vivo studies were done for sodium sefuroxime in Sprague-Dawley type rats. It was found that G6PD in erythrocyte was more inhibited by the drug in 2.5 h.

Adult↗

Erythrocyte carnitine: a study of erythrocyte fractions isolated by discontinuous density gradient centrifugation.

Erythrocyte fractions of varying density were isolated by discontinuous density gradient centrifugation of washed erythrocytes of five subjects (three adults and two cord bloods). Free and total carnitine concentrations were determined in each gradient fraction to compare the carnitine content of less dense with more dense erythrocytes. Erythrocyte, leukocyte, and reticulocyte counts and hemoglobin were measured on all fractions of each gradient. The density gradient studies showed that the highest proportion of reticulocytes were associated with the least dense gradient fractions of all five subjects. Linear regression analyses revealed significant positive correlations (r = 0.94 to 0.99, P less than 0.02 to P less than 0.001) between the number of reticulocytes per fraction and the total or free carnitine concentrations per fraction for all subjects. No correlation was found between free or total carnitine and hemoglobin, number of erythrocytes, or number of leukocytes per fraction. It appears that erythrocyte carnitine is localized in circulating reticulocytes which have mitochondria and carnitine-dependent fatty acid metabolism.

Adult↗

Effects of raloxifene on serum malondialdehyde, erythrocyte superoxide dismutase, and erythrocyte glutathione peroxidase levels in healthy postmenopausal women.

OBJECTIVE: To investigate the relationship between raloxifene administration and serum malondialdehyde (MDA), erythrocyte superoxide dismutase (SOD), erythrocyte glutathione peroxidase (GPx) levels in healthy postmenopausal women. METHODS: In a randomized and placebo-controlled design, 80 women received either 60 mg/day raloxifene or placebo for 24 weeks. MDA, SOD, and GPx levels were assessed at 0,4,12, and 24 weeks. Wilcoxon signed-rank test and Mann-Whitney U test were used for comparisons. RESULTS: Six women in the treatment arm and eight women in the placebo group discontinued the study. Mean serum MDA levels were significantly (p = 0.001) decreased from 11.4 nmol/ml at baseline to 8.9 nmol/ml at week 12 with raloxifene treatment. Mean erythrocyte SOD activity was significantly (p = 0.02) reduced from 1472 U/g Hb at baseline to 1173 U/g Hb at week 12 following raloxifene administration. Lowered serum MDA and erythrocyte SOD levels persisted during treatment. On contrary, erythrocyte GPx levels did not change significantly with raloxifene administration. CONCLUSIONS: Raloxifene (60 mg/day) lowers serum MDA levels and erythrocyte SOD activity in postmenopausal women after 12 weeks of treatment. The clinical implications of these findings need to be determined.

Aged↗

Susceptibility of erythrocyte lipids to oxidation and erythrocyte antioxidant status in myocardial infarction.

OBJECTIVE: We evaluated the erythrocyte lipid susceptibility to oxidation and erythrocyte antioxidant status in patients with myocardial infarction (MI). DESIGN AND METHODS: Patients with MI were divided into two group according to the severity of the disease as severe (n = 30) or milder (n = 25). Malondialdehyde as a marker of lipid peroxidation was measured to show the lipid susceptibility to oxidation. Erythrocytes were stressed in vitro by hydrogen peroxide acting as the oxidative agents for 120 min. After designated time, erythrocyte MDA production was significantly higher in patients with severe MI than in controls and in patients with milder MI (p < 0.001, p < 0.001, respectively). Antioxidant status was determined by measuring the reduced glutathione levels and glutathione peroxidase activity of erythrocyte. RESULTS: In patients with MI, antioxidant status was significantly lower than in controls, and there was no significant difference between the patient groups. CONCLUSION: Determination of erythrocyte lipid susceptibility to oxidation may be a useful in vitro test to evaluate the degree of oxidative stress in myocardial infarction.

Adult↗

Malaria-infected erythrocytes serve as biological standards to ensure reliable and consistent scoring of micronucleated erythrocytes by flow cytometry.

A procedure for optimizing the configuration of flow cytometers for enumerating micronucleated erythrocytes is described. The method is based on the use of a biological model for micronucleated erythrocytes, the malaria parasite Plasmodium berghei. P. berghei endows target cells of interest (erythrocytes) with a micronucleus-like DNA content. Unlike micronuclei, parasitized red blood cells have a homogenous DNA content, and can be very prevalent in circulation. These characteristics make malaria-infected erythrocytes extremely well suited for optimizing instrument setup on a daily basis. The experiment described herein was designed to test the hypothesis that malaria-infected erythrocytes can greatly enhance the consistency with which flow cytometers are configured for micronucleus analyses, and thereby minimize intra- and interexperimental variation. Data collected over the course of several months, on two different flow cytometers, supports the premise that malaria-infected blood represents a useful biological standard which helps ensure reliable and consistent flow cytometric enumeration of rare micronucleated erythrocytes.

Animals↗

Purification and characterization of an alpha 1 beta 2 isoform of CapZ from human erythrocytes: cytosolic location and inability to bind to Mg2+ ghosts suggest that erythrocyte actin filaments are capped by adducin.

CapZ ("capping protein") is a heterodimeric actin capping protein that blocks actin filament assembly and disassembly at the fast growing (barbed) filament ends and is proposed to function in regulating actin filament dynamics as well as in stabilizing actin filament lengths in muscle and nonmuscle cells. We show here that erythrocytes contain a nonmuscle isoform of capZ (EcapZ) that is present exclusively in the cytosol and is not associated with the short actin filaments in the erythrocyte membrane skeleton. This is unlike other cell types where capZ is associated with cytoskeletal actin filaments and suggests that cytosolic EcapZ may be inactive, or alternatively, that the barbed ends are capped by adducin, a membrane skeleton protein that was shown recently to cap actin filament barbed ends in vitro [Kuhlman, P. A., Hughes, C. A., Bennett, V., & Fowler, V. M. (1996) J. Biol. Chem. 271, 7986]. To distinguish between these possibilities, we purified EcapZ from erythrocyte cytosol and characterized its biochemical and functional properties. Two-dimensional gel electrophoresis and western blotting reveals the EcapZ subunit composition to be alpha1beta2, as described for capZ from many other nonmuscle cells, with no evidence for posttranslational modifications. Purified EcapZ is fully functional in blocking actin elongation from barbed filament ends (Kcap approximately 1-5 nM) as well as in nucleating actin polymerization. Furthermore, cytosolic EcapZ binds to actin filament barbed ends, indicating that sequestering of EcapZ by a cytosolic inhibitory factor or insufficient amounts of EcapZ in cytosol also cannot account for its absence from the membrane skeleton. To test directly whether the barbed ends of the erythrocyte actin filaments were already capped, we measured binding of purified EcapZ to isolated membranes. Purified EcapZ does not cosediment with membranes prepared by hypotonic lysis in the presence of magnesium, suggesting that the barbed ends of the erythrocyte actin filaments are capped under these conditions but not by EcapZ. In contrast, purified EcapZ stoichiometrically reassociates with all the actin filament barbed ends in membranes prepared by hypotonic lysis in 5 mM sodium phosphate, pH 8.0 (5P8), conditions in which the barbed filament ends were previously reported to be uncapped. Comparison of the amounts of adducin associated with membranes prepared in the presence and absence of magnesium reveals that 60-80% of the adducin dissociates from the membrane during hemolysis and washing in 5P8 buffer, suggesting that the barbed ends become artifactually uncapped due to loss of adducin. The erythrocyte actin filaments may thus represent a specialized class of membrane-associated actin filaments that are capped by adducin instead of capZ.

Actin Cytoskeleton↗

Structural relationships between human erythrocyte sialoglycoproteins beta and gamma and abnormal sialoglycoproteins found in certain rare human erythrocyte variants lacking the Gerbich blood-group antigen(s).

The human erythrocyte membrane sialoglycoproteins beta and gamma are important for the maintenance of the discoid shape of the normal erythrocyte. In this paper we show that the human erythrocyte sialoglycoproteins beta and gamma (hereafter called beta and gamma) are structurally related. Rabbit antisera produced against purified beta and beta 1 and rendered specific to the cytoplasmic portion of these proteins also react with the cytoplasmic portion of gamma. Some human anti-Gerbich (Ge) sera react with the extracellular portion of both beta and gamma. This reactivity is shown to be directed towards a common epitope on beta and gamma. However, most anti-Ge sera do not react with beta, but react with an extracellular epitope only present on gamma. All individuals who lack the Ge antigens lack beta and gamma. In some cases abnormal sialoglycoproteins are present in the erythrocytes, and these are shown to be structurally related to beta and gamma. Rabbit antisera raised against the purified abnormal sialoglycoprotein from a Ge-negative erythrocyte type reacted with the cytoplasmic portion of both beta and gamma. Unlike normal beta and gamma, the abnormal sialoglycoproteins found in Ge-negative erythrocytes migrate as a diffuse band on SDS/polyacrylamide-gel electrophoresis. Studies using endoglycosidases suggest that the diffuse nature of these bands results from carbohydrate heterogeneity and that the abnormal sialoglycoproteins contain N-glycosidically linked oligosaccharides with repeating lactosamine units. Such polylactosamine chains are not present on normal beta or gamma.

Blood Group Antigens↗

Identification of the erythrocyte binding domains of Plasmodium vivax and Plasmodium knowlesi proteins involved in erythrocyte invasion.

Plasmodium vivax and the related monkey malaria, P. knowlesi, require interaction with the Duffy blood group antigen, a receptor for a family of chemokines that includes interleukin 8, to invade human erythrocytes. One P. vivax and three P. knowlesi proteins that serve as erythrocyte binding ligands in such interactions share sequence homology. Expression of different regions of the P. vivax protein in COS7 cells identified a cysteine-rich domain that bound Duffy blood group-positive but not Duffy blood group-negative human erythrocytes. The homologous domain of the P. knowlesi proteins also bound erythrocytes, but had different specificities. The P. vivax and P. knowlesi binding domains lie in one of two regions of homology with the P. falciparum sialic acid binding protein, another erythrocyte binding ligand, indicating conservation of the domain for erythrocyte binding in evolutionarily distant malaria species. The binding domains of these malaria ligands represent potential vaccine candidates and targets for receptor-blockade therapy.

Animals↗

Nucleoside transport in sheep erythrocytes: genetically controlled transport variation and its influence on erythrocyte ATP concentrations.

1. The permeability of sheep erythrocytes to purine and pyrimidine nucleosides was investigated. Erythrocytes from most sheep (nucleoside-impermeable) were almost completely impermeable to 5 mM inosine whereas cells from approximately 5% of the animals studied (nucleoside-permeable) showed a rapid inosine uptake. Cells from both types of animal were permeable to 5 mM adenosine, although transport was slower in nucleoside-impermeable erythrocytes. 2. Two distinct nucleoside transport routes were present in nucleoside-permeable erythrocytes; a high affinity (apparent Km congruent to 0.2 mM) facilitated diffusion system which transported both purine and pyrimidine nucleosides, and a non-saturable uptake route selective for adenosine. The high affinity system was the major route of adenosine transport at physiological concentrations. 3. Transport by the high affinity system was completely inhibited by micromolar concentrations of dipyridamole and nitrobenzylthioinosine. Dipyridamole had no effect on the non-saturable component of adenosine uptake. 4. The transport differences between nucleoside-permeable and impermeable erythrocytes were due to the absence of the high affinity system from nucleoside-impermeable cells. 5. Nucleoside-permeable cells had a higher intracellular ATP concentration than nucleoside-impermeable erythrocytes, suggesting that the high affinity transport system participates in the energy metabolism of the cell.

Adenosine Triphosphate↗

Alterations to the cytoskeleton of erythrocytes infected with frog erythrocytic virus: a fluorescence and electron microscopic study.

Erythrocytes of bullfrogs (Rana catesbeiana) infected with frog erythrocytic virus are spheroid and their nucleus is displaced. In contrast, uninfected cells are ellipsoid and have a centralized nucleus. Fluorescent staining revealed that these changes are correlated with alterations to components of the erythrocyte cytoskeleton. Uninfected erythrocytes contained a broad, continuous marginal band of microtubules, which appeared thinner and interrupted in infected cells. The described disruption of microtubules was associated with an inability to polymerize the tubulin pool with the addition of 12 microM taxol. The arrangement of submembranous microfilaments in uninfected erythrocytes was not significantly altered in infected cells. Vimentin filaments were distributed throughout the cytoplasm and around the nucleus of uninfected cells, and concentrated at the cell and nuclear peripheries. Cytoplasmic pockets that did not contain vimentin filaments were associated with the viral assembly site(s) in infected cells. These data suggest that the distortion of viral-infected erythrocytes could be due, in part, to an irreversible depolymerization of microtubules of the marginal band and a reorganization of the vimentin filament network.

Actin Cytoskeleton↗

Differential binding of immunoglobulin A and immunoglobulin G1 immune complexes to primate erythrocytes in vivo. Immunoglobulin A immune complexes bind less well to erythrocytes and are preferentially deposited in glomeruli.

Primate erythrocytes appear to play a role in the clearance of potentially pathogenic immune complexes (IC) from the circulation. This study was undertaken to compare the clearance from the circulation and tissue uptake of two monoclonal IC probes: one of which, IgG1-IC, was bound well by erythrocytes, the other of which, IgA-IC, was bound relatively poorly by erythrocytes. The IC probes were labeled with different iodine isotopes and infused either concomitantly or sequentially into the arterial circulation. The results indicate that, compared with IgG1-IC, IgA-IC bind less well to primate erythrocytes, are cleared from the circulation more quickly despite their smaller size, and show increased uptake in kidney and lung but decreased uptake in liver and spleen. Evidence is presented which suggests that this pattern of clearance from the circulation and systemic uptake of IgA-IC is the result of decreased binding of IgA-IC to circulating erythrocytes. These findings support the hypothesis that the primate erythrocyte-IC clearing mechanism may be critically important for the safe removal of IC from the circulation.

Animals↗

Measurement of erythrocyte orientation in flow by spin labeling II--phenomenological models for erythrocyte orientation rate.

We present two phenomenological models describing the flowing erythrocyte orientation rate. The first concerns the onset of a stable orientation in a very dilute erythrocyte suspension. It is based on a simple formula for erythrocyte elongation as a function of shear stress, and we assume that beyond a threshold of elongation, erythrocytes take on a stable orientation, while below this threshold, they have a flipping motion. We extend this model to high hematocrit values assuming that the effect of red cell collisions imposes a random moment to each erythrocyte, shifting it from its stable orientation. We obtain an approximate expression for erythrocyte orientation rate as a function of shear rate and then we compare these results to our experimental data in part III of this series.

Biomechanical Phenomena↗

Erythrocyte incorporation of iron by infants: iron bioavailability from a low-iron infant formula and an evaluation of the usefulness of correcting erythrocyte incorporation values, using a reference dose or plasma ferritin concentrations.

Bioavailability of iron (Fe) from a low-Fe infant formula was determined by erythrocyte incorporation of 58Fe 14 d after administration in ten healthy, non-Fe-deficient infants. Two feeding protocols were compared, with each infant acting as his/her own control. At 140 and 154 d of age, infants were fed 1000 g of 58Fe-labelled formula (1.44 mg total Fe/1000 g) as six feeds over 24 h (Protocol A) or as two feeds/day on three consecutive days (Protocol B). A water solution with 57Fe and ascorbic acid was given separately as a reference dose in both study protocols. Erythrocyte incorporation of 58Fe and 57Fe was determined by thermal ionisation mass spectrometry. Geometric mean 58Fe incorporation was 7.6% (range 3.3-13.5%) with Protocol A as compared to 10.6% (range 6.7-18.6%) with Protocol B (P = 0.05); paired t test. Inter-individual variability of 58Fe was not reduced by correcting for the incorporation of 57Fe from the reference dose, or by correcting for plasma ferritin concentration. Fractional erythrocyte incorporation of Fe from low-Fe infant formula was in the same range as our earlier published data on erythrocyte incorporation of Fe from human milk extrinsically labelled with 58Fe (Davidsson et al. 1994a). The methodological evaluations included in this study clearly indicate the importance of using standardised study protocols when evaluating Fe bioavailability in infants. Corrections of erythrocyte incorporation data based on plasma ferritin or erythrocyte incorporation of Fe from a reference dose were not found to be useful.

Biological Availability↗

Levels of trace elements in the serum and erythrocytes and some parameters of erythrocyte heme metabolism (FEP, ALA-D, ALA-U) in copper foundry workers.

The study was designed to investigate the usefulness of some biochemical indices for determination of lead toxicity. In exposed and control groups, the following parameters were measured: concentration of lead in the blood, level of free erythrocyte protoporphyrins and delta-aminolevulinic acid dehydratase activity of erythrocytes. Levels of sodium, potassium, calcium, magnesium, copper and zinc in the serum and erythrocytes as well as of iron in the serum were determined. The chelation test was performed and excretion of lead, coproporphyrins and delta-aminolevulinic acid (in 24 hour urine sample before and after EDTA injection) identified only in the exposed group. Absorption of lead was significantly higher in the exposed group (increased blood lead level (Pb-B), free erythrocyte protoporphyrin (FEP) and decreased erythrocyte ALA-dehydratase (ALA-D) activity. Levels of copper and calcium in the serum and red blood cells were significantly lower in comparison with the controls. Iron and sodium concentration in the serum as well as levels of potassium, magnesium and calcium in erythrocytes were significantly higher in the exposed group. The chelation test in the exposed group showed a significantly increased excretion of lead in 24 hour urine sample. Concentration of delta-aminolevulinic acid in 24 hour urine sample was lower after EDTA injection.

Adult↗

Ca2(+)-dependent membrane-binding proteins in normal erythrocytes and erythrocytes from patients with chronic myelogenous leukemia.

Cytosolic and membrane fractions of human erythrocytes were probed with antisera raised against several members of the annexin family of Ca2(+)-dependent phospholipid/membrane-binding proteins. One of the antisera, that against the 67 Kd calcimedin, identified erythrocyte polypeptides of molecular weights 48 and 67 Kd, which were found in the cytoplasm when normal erythrocytes were lysed in the presence of EGTA but on the membrane when lysis buffers contained Ca2+. In contrast, membranes of erythrocytes from patients with chronic myelogenous leukemia (CML) contained the 67 Kd protein even when prepared in the absence of Ca2+, as well as the antibody-reactive proteins of 35 and 38 Kd. When prepared in the presence of Ca2+, CML membranes contained increased levels of these three species and the 48 Kd protein, as well. These results suggest that normal erythrocytes contain a calcimedin-like protein that is translocated to the membrane in the presence of Ca2+ and that CML erythrocytes have both an abnormal amount and distribution of calcimedin-like proteins.

Annexins↗

Erythrocytes and age. Disintegration of erythrocytes by brilliant cresyl blue in correlation to age.

The author describes changes in the disintegration of erythrocytes by brilliant cresyl blue in correlation to age, in rats aged 21, 42, 90-105, 340-360 and 690-720 days. The erythrocytes were incubated for 4 hours in an isotonic NaCl solution, in Krebs-Ringer solution and in each of these solutions plus brilliant cresyl blue. Disintegration in plain NaCl solution was found to be the greatest in the case of erythrocytes from 690- to 720-day-old rats. In the same solution plus brilliant cresyl blue, the rate of disintegration was very high in 21-day-old, 42-day-old and 690- to 720-day-old animals; at 90-105 days it was lower and at 340-360 days it was the lowest. Disintegration of erythrocytes in plain Krebs-Ringer solution was the lowest at 21 and 42 days; in the other age groups it was slightly higher. On adding brilliant cresyl blue, the rate of disintegration rose significantly in 21-, 42- and 690- to 720-day-old animals; at 90-105 days and 340-360 days it was no different from disintegration in plain Krebs-Ringer solution. It can be seen from the results that the rate of brilliant cresyl blue-induced erythrocyte disintegration is dependent on the age of the animals from which the erythrocytes are taken.

Aging↗

[Molecular pathology of the erythrocyte membrane. Erythrocyte membrane defects as a cause of congenital hemolytic anemia].

Recently numerous defects of erythrocyte membrane proteins have been described in hereditary hemolytic anemias. An exact biochemical characterization of some different types of hereditary spherocytosis, hereditary elliptocytosis, hereditary pyropoikilocytosis and the hemolytic anemias with increased cation permeability (hereditary stomatocytosis) is possible after analysis of membrane proteins with SDS-polyacrylamide gel electrophoresis, quantitative determination of spectrin, the relation of dimeric to tetrameric spectrin, and partial tryptic digestion of the spectrins. The known clinical heterogeneity of the mentioned disorders is now partially explained by the different biochemical defects of the erythrocyte membrane. In classical hereditary spherocytosis a close relationship between erythrocyte spectrin content and clinical severity has been found. The clinical manifestation in hereditary elliptocytosis and hereditary pyropoikilocytosis mainly depends on the functional disturbance of variant spectrins, especially their ability to form tetramers, i.e. their ability for self-association of the spectrin chains. In the hydrocytic form of stomatocytosis a deficiency of the integral protein band 7.2b has been documented. Besides the analysis of erythrocyte membrane proteins the classical methods used in the study of congenital hemolytic anemias cannot be missed. Signs of increased hemolysis, erythrocyte morphology, osmotic fragility, autohemolysis, heat and mechanical stability of the erythrocyte membrane, intracellular cation concentration and studies of other family members, are indispensable prerequisites for classification, prognosis, and indication of therapeutic efforts, especially splenectomy.

Anemia, Hemolytic, Congenital↗