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Query: UMLS:C0019045 (hemoglobinopathies)
 2,704 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An increase in fetal hemoglobin (Hb F) ameliorates the clinical symptoms of the underlying disease in the beta hemoglobinopathies-sickle cell anemia and beta-thalassemia (thal). Hydroxyurea (HU) can elevate Hb F production in erythroid cells and is the agent currently in clinical use for patients with sickle cell anemia; it is presently being tested in clinical trials for thalassemia. We have developed a two-phase liquid culture system that mimics the in vivo hematological changes that are observed in patients treated with HU. Adding HU during the second phase of the culture increases the proportion of Hb F, increases the levels of total hemoglobin (Hb) content per cell and increases cell size, but it decreases the numbers of cells and the total amount of Hb produced. In the present study we developed and utilized a double labeling procedure for flow cytometric analysis of the cellular distribution of Hb F. Cells exposed to various concentrations of HU on day 6 of the second phase of the culture were harvested on day 12, and stained simultaneously with fluorochrome-conjugated monoclonal antibodies specific for human glycophorin A, an erythroid specific marker, and human Hb F. Both the percentage of the Hb F-containing cells and their intensity of fluorescence were recorded. The latter value gives a semi-quantitative estimation of the mean cellular Hb F content. The results indicated that cultures derived from different beta-thalassemic patients differ in their response to HU. In most patients, low doses of HU decreased the percentage of Hb F-cells as well as their Hb F content. At high doses, some patients showed an increase in both parameters, while others showed an increase in the percentage of Hb F-cells with minimal increase in their mean Hb F content, while still other patients showed little effect at all. In all patients, high doses of HU caused a decrease in cell numbers. These results suggest that HU has mixed effects on erythroid precursors. Both the two-phase liquid culture and the flow cytometric analysis procedures described herein provide the experimental tools for screening of Hb F-inducing drugs and for evaluating patients' cell response prior to treatment.
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PMID:Flow cytometric analysis of hydroxyurea effects on fetal hemoglobin production in cultures of beta-thalassemia erythroid precursors. 1277 69

Red cells exposed to glycophorin A reactive antibodies and lectins develop a non-specific cation permeability. To determine if this might be due to the activation of a non-selective mechanosensitive channel we have subjected red cells, loaded with a calcium responsive fluorescent probe, to filtration through 5 and 3 microm pores. Calcium entered 28% of normal red cells at the moment of deformation when 3 microm filtered, a finding consistent with the transient activation of a mechanosensitive channel. Red cells containing hemoglobin AC and AS had enhanced calcium responses to filtration. An increased influx of calcium in hemoglobin disorders might play a role in providing protection against Falciparum malaria.
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PMID:Evidence for a mechanosensitive calcium influx into red cells. 1512 Oct 90

Peripheral destruction of sickled erythrocytes is a cardinal feature of sickle cell disease (SCD). Less well established is the potential contribution of ineffective erythropoiesis to the pathophysiology of this hemoglobinopathy. Since patients with SCD frequently develop mixed hematopoietic chimerism after allogeneic nonmyeloablative stem cell transplantation, we used this opportunity to directly compare the differentiation and survival of SCD and donor-derived erythropoiesis in vivo. Donor and recipient erythropoiesis was compared in 4 patients with SCD and 4 without SCD who developed stable mixed hematopoietic chimerism following transplant. Molecular analysis of chimerism in peripheral blood and bone marrow demonstrated higher expression of donor-derived beta-globin RNA relative to the level of donor-derived genomic DNA in patients with SCD. Analysis of chimerism in immature (glycophorin A-positive [GYPA(+)], CD71(hi)) and mature (GYPA(+), CD71(neg)) erythroblasts confirmed the intramedullary loss of SS erythroblasts with progressive maturation. In patients with SCD, relative enrichment of donor erythroid precursors began to appear at the onset of hemoglobinization. Ineffective erythropoiesis of homozygous hemoglobin S (SS) progenitors thus provides a maturation advantage for homozygous hemoglobin A (AA) or heterozygous hemoglobin S/hemoglobin A (SA) donor erythroid precursor cells that results in greater donor contribution to overall erythropoiesis following stem-cell transplantation and improvement of clinical disease.
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PMID:Evidence for ineffective erythropoiesis in severe sickle cell disease. 1609 48

Prenatal diagnosis is an option for couples at risk of having a child affected with hemoglobinopathies. Chorionic villus sampling (CVS) and cordocentesis are accurate but a finite risk of fetal loss exists. A non invasive, risk free strategy that has emerged is isolation of fetal erythroblasts from maternal blood. Enrichment of nucleated red blood cells (nRBCs) from 7.0 mL maternal blood was done using a Percoll discontinuous density gradient and isolation by flow sorting using a combination of three monoclonal antibodies: CD45 per CP, glycophorin A-phycoerythrin (PE) and Hb F-fluorescein isothiocyanate (FITC) in 43 cases between 7 and 21 weeks' gestation. The percentage of nRBCs ranged from 0.0001-2.03%. The presence of dual fluorescence (glycophorin A-PE and Hb F-FITC) was confirmed by confocal microscopy. A sufficient number of nRBCs could be isolated in the first and second trimester of pregnancy to provide a simple flow cytometric approach as a potential for non invasive diagnosis of beta-globin defects.
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PMID:An improved flow cytometric approach for isolation of fetal cells from maternal blood for non invasive prenatal diagnosis of hemoglobinopathies. 1736 4

Increased fetal hemoglobin (HbF) in erythroid precursors of patients with beta-hemoglobinopathies (sickle cell anemia and beta-thalassemia), in which adult hemoglobin synthesis is defective, ameliorates the clinical symptoms of the underlying diseases. The production of erythroid precursors depends on the action of erythropoietin (EPO), which prevents their apoptosis and stimulates their proliferation. EPO binds to its surface receptor, induces its homodimerization, and initiates a cascade of phosphorylation and dephosphorylation of a series of proteins by kinases and phosphatases, respectively. Vanadate inhibits various phosphatases, including those that are involved in the EPO pathway, thereby intensifying the signal. In this study, we investigated the effect of vanadate on the proliferation and maturation of human erythroid precursors in culture. When vanadate was added to cells derived from normal donors, cell maturation was delayed, as indicated by cell morphology, cell growth kinetics, the rate of appearance of hemoglobin-containing cells, and the expression of surface antigens (CD117, CD71, and glycophorin A). Analysis by high-performance liquid chromatography and flow cytometry of the hemoglobin profile of vanadate-treated normal cells revealed a higher proportion of HbF than was found in untreated cells. When vanadate was added to cells derived from patients with beta-thalassemia, a significant increase in HbF was observed. The results suggest that intensification of the EPO signal by vanadate results in maturation arrest and increased HbF production. Thus, inhibitors that are more specific and less toxic than vanadate may present a novel option for elevating HbF in patients with beta-hemoglobinopathies, as well as for intensifying the EPO response in other forms of anemia.
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PMID:Vanadate elevates fetal hemoglobin in human erythroid precursors by inhibiting cell maturation. 1746 62

Our purpose was to develop and evaluate isolation and enrichment of fetal erythroblasts and a nested polymerase chain reaction (PCR) approach using fetal erythroblasts for detecting the beta-globin gene mutations for a noninvasive prenatal diagnosis of hemoglobinopathies. Maternal blood at different periods of gestation was layered on a Percoll density gradient for enrichment of fetal nucleated RBCs (NRBCs). A combination of 3 monoclonal antibodies (CD45-peridinin chlorophyll protein, glycophorin A-phycoerythrin, and anti-hemoglobin F-fluorescein isothiocyanate) was used for flow cytometric sorting of fetal NRBCs from enriched cells. Different nested PCR-based approaches were used for identification of fetal mutations. Owing to heterogeneity of beta-thalassemia mutations in the population of India, we had to screen for 12 mutations and were able to give an accurate diagnosis in 84 (84.0%) of 100 cases when compared with chorionic villus sampling or cordocentesis and DNA analysis.This nested PCR approach enabled amplification of small quantities of DNA from fetal erythroblasts, providing a cost-effective method for noninvasive diagnosis.
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PMID:Evaluation of the use of monoclonal antibodies and nested PCR for noninvasive prenatal diagnosis of hemoglobinopathies in India. 1862 88