PubMed Health⌕ Search

Biomedical subjects

N Casadevall

Publications and source records attributed to N Casadevall.

At least 19 recordsLinked to original sources
PubMed1998

Analysis of megakaryocyte growth and development factor (thrombopoietin) effects on blast cell and megakaryocyte growth in myelodysplasia.

Thrombocytopenia is a frequent feature of myelodysplastic syndromes (MDS) that could be improved by the use of recombinant human megakaryocyte growth and development factor (rHuMGDF). Using short-term liquid cultures and progenitor assays, we have found that rHuMGDF stimulated DNA synthesis and potentiated leukemic cluster growth of bone marrow mononuclear cells in 10/38 MDS cases (26%). Cytogenetically malignant colonies were detectable in rHuMGDF-stimulated cultures (n=3) by fluorescence in situ hybridization. rHuMGDF was able to stimulate CFU-MK formation in 45% of the samples tested. Finally, rHuMGDF-induced blast cell proliferation correlated with elevated expression of c-MPL, previously identified as a bad prognosis factor in MDS.

Blast Crisis↗
PubMed1998

Update on the role of epoetin alfa in hematologic malignancies and myelodysplastic syndromes.

Anemia is a frequent complication in hematologic malignancies. In advanced stages of chronic lymphocytic leukemia, non-Hodgkin's lymphoma, and myeloma, anemia usually develops in parallel with marrow involvement. However, anemia may occur in the absence of overt infiltration of bone marrow by malignant cells. When all other causes of anemia (such as chronic bleeding, vitamin deficiency, hemolysis, and pure red blood cell aplasia) are eliminated, anemia can be related to "anemia of chronic disorders." Myelodysplastic syndromes are characterized by cytopenias. Anemia is very frequent, and nearly 90% of patients present with anemia during the evolution of the disease. In this disorder, erythroid progenitors are defective for their proliferation and maturation, as shown by in vitro culture techniques. Moreover, these patients often have a high endogenous serum erythropoietin level. The rationale for treating these patients with epoetin alfa is the possibility of overcoming the defective proliferation by pharmacologic doses of epoetin alfa. The response rate was rather low with epoetin alfa alone. Combinations with earlier-acting cytokines, such as recombinant human granulocyte colony-stimulating factor, have been tested in an attempt to improve response rates.

Epoetin Alfa↗
PubMed1996

Missense mutation of the erythropoietin receptor is a rare event in human erythroid malignancies.

Human erythroid malignancies (polycythemia vera [PV] and erythroleukemia) are associated with erythropoietin (Epo)-independent growth and differentiation. Missense or nonsense mutations in the Epo receptor (Epo-R) have been recently described in experimental erythroleukemia in mice and in cases of erythrocytosis in humans. To search for a similar genetic alteration in erythroleukemia and PV, we entirely sequenced the exons of the Epo-R gene as well as the intron-exon junctions in these disorders using polymerase chain reaction. In 1 of 10 cases of erythroleukemia, a single allele mutation was found in the 8th Epo-R gene exon that changed asparagine 487 into a serine. No Epo-r gene mutation was found in 12 PV cases studied, but the same mutation (N487S) was found in 1 patient with polycythemia that did not fulfill the criteria of PV (polycythemia of unknown origin). We did not detect this mutation after sequencing part of the 8th exon of the Epo-R gene from 21 other patients with polycythemia of unknown origin and 51 normal controls. The Epo-R mutation was also found in Epstein-Barr virus-derived cell lines from both cases, suggesting that it is not related to the malignant clone. Therefore, this mutation does not appear to be somatic, although no familial cases were found. The biologic effect of this mutation was subsequently studied. Erythroid progenitors from the polycythemic patient normally responded to Epo, whereas those from the erythroleukemic patient were Epo-independent due to autocrine stimulation by Epo. The normal and the mutated Epo-R were transfected into the murine Ba/F3 cell line. Both types of cells displayed the same response to Epo for proliferation, differentiation, and inhibition of apoptosis. Although this mutation may destroy a consensus binding site for Grb2, no obvious differences either in the pattern of Epo-induced tyrosine phosphorylated proteins or in the binding of Grb2 to the Epo-R were observed. In conclusion, a somatic Epo-R missense mutation does not appear to be a molecular mechanism involved in the abnormal growth of human erythroleukemia and PV. However, the Epo-R mutation (N487S) that we describe is located in the same tyrosine sequence beginning at AA 485 as the one previously observed (P488S) in as case of polycythemia (Sokol et al, Exp Hematol 22:447, 1994). These results suggest that this phosphopeptide sequence may play an important role in Epo signalling.

Base Sequence↗
PubMed1996

[Physiology of eryhtropoietin and its therapeutic use].

Erythropoietin (Epo) is a glycoprotein produced primarily by the kidney and is the factor regulating the red blood cell production. Unlike most of the hematopoietic growth factors, Epo is principally produced by a single organ, the kidney, and is regulated by a classic feedback control system. Epo acts on the erythroid progenitors after binding to a specific receptor. The gene coding for a 66 Kd chain has been cloned. This chain belongs to the hematopoietic growth factors family. Epo gene was cloned in 1985. The protein coded by this gene is heavily glycosylated. Epo production is regulated by renal tissue hypoxia. Cells producing Epo in the kidney are a subset of peritubular interstitial cells of fibroblastic origin. Epo is now used in clinical applications. Rationale for the use of Epo is based on the serum determination of Epo level. Patients with anemia of chronic renal failure are routinely treated with recombinant Epo. Two other indications are recognized by French authorities: the treatment of anemia of cancer patients receiving platin-derived chemotherapy and the use in autologous blood donation.

Erythropoietin↗
PubMed1995

[Vaquez disease].

Explore the source record for details and available documents.

Diagnosis, Differential↗
PubMed1995

Cellular mechanism of resistance to erythropoietin.

Erythropoiesis is controlled by different regulators. Interleukin 3, granulocyte-macrophage colony-stimulating factor and stem cell factor play regulatory functions in the early steps of erythropoiesis. Erythropoietin (Epo) is the main factor which acts positively on the last steps of the production of erythrocytes in mammals. Epo is specific for the erythroid progenitor cells and has only little effect on other cells. The target cells for Epo are the erythroid progenitors (BFUe and CFUe). Epo acts on these progenitors through surface receptors specific for Epo. Epo induces the proliferation and differentiation of erythroid progenitors leading finally to reticulocytes. During this process, certain conditions are required to permit this differentiation: progenitors must be present in sufficient numbers, the bone marrow environment must be normal, and nutrients such as folic acid, vitamin B12 and particularly iron must be available. Elemental iron is an absolute requirement for adequate haemoglobin formation. Indeed, in a normal adult, without any stimulation, the bone marrow synthesizes 4 x 10(14) molecules of haemoglobin per second, each molecule containing four atoms of iron, which roughly corresponds to 20 mg iron. On the other hand, erythropoiesis is negatively regulated by several cytokines. These are macrophage-derived cytokines, including tumour necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), interleukin-6 (IL-6) and transforming growth factor-beta (TGF-beta). All these factors are elevated in the inflammatory state and are implicated in the pathogenesis of anaemia of chronic disease. TNF-alpha has an inhibitory effect on erythroid progenitors either directly or mediated by interferon-beta (INF-beta). IL-1 inhibits erythropoiesis in vivo in mice and in vitro in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Purification and biological activity of a recombinant human erythropoietin produced by lymphoblastoid cells.

A recombinant human erythropoietin (rH-EPO) was obtained from the culture supernatants of human B-lymphoblastoid cells transfected by the human EPO gene. rH-EPO was purified by a two-step method based on immunoaffinity and ion exchange chromatography. The first step was achieved by an anti-EPO monoclonal antibody (Mab). This Mab, immobilized on Sepharose 4B, allowed a 410-fold purification of the protein. The second step consisted of ion exchange chromatography on DEAE Sephacel. The combination of these two steps results in a highly purified rH-EPO with a global yield of about 50%; the specific activity of the protein was 176,000 IU/A280. The NMR spectrum was characteristic for a well structured, single-conformation protein. The purified protein was analyzed by SDS-PAGE and isoelectric focusing. The biological activity of purified rH-EPO was measured in vivo, by the incorporation of 59Fe into red blood cells (RBC) of polycythemic mice and in vitro by the proliferative response of an EPO-dependent cell line. The purified protein expressed in lymphoblastoid cells of human origin had the same biological activity as that of urinary EPO and rH-EPO produced in other mammalian cells.

Amino Acid Sequence↗
PubMed1994

Age-related alterations in erythroid and granulopoietic progenitors in Diamond-Blackfan anaemia.

Mechanisms involved in the erythroid failure characterizing Diamond-Blackfan anaemia (DBA) remain unidentified. The general consensus is that the defect is intrinsic to the marrow erythroid progenitor, but the target progenitor cell has not been precisely identified, and in vitro studies have revealed considerable heterogeneity between patients. In order to understand better the meaning of such a biological heterogeneity, we examined the in vitro response of erythroid progenitors CFU-E (colony-forming unit-erythroid) and BFU-E (burst-forming unit-erythroid) to erythropoietin (Epo), interleukin-3 (IL-3) and stem cell factor (SCF) in a large series of 24 patients from 1 month to over 20 years of age. Results of colony assays revealed a striking correlation between the age of the patient and the extent of the abnormalities detected in vitro. Therefore, despite profound anaemia, 80% (7/10) of the patients studied within 1 year of diagnosis had normal numbers of both CFU-E and BFU-E which exhibited a normal response to cytokines. In contrast, 12/14 patients followed up for more than 3 years had decreased numbers of erythroid progenitors, in seven cases associated with decreased colony-forming unit granulocyte-macrophage (CFU-GM). The number of CFU-E and BFU-E was not normalized even by the addition of high concentrations of combined Epo, IL-3 and SCF.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Fetal haemoglobin variations following hydroxyurea treatment in patients with cyanotic congenital heart disease.

Haematological features of 64 patients suffering from non operable cyanotic congenital heart disease (CCHD) treated with hydroxyurea (HU) were compared with those of 43 patients suffering from the same disorder who had not yet received this drug. Patients with subclinical renal dysfunction were excluded by measuring plasma creatinine levels. MCV and HbF were higher among patients receiving HU, the increase in MCV being cumulative with HU dosage but the rise in HbF dose independent. HbF response to HU was found to be due to the coordinated increase in F-cell and F-reticulocyte production rather than to a selective survival of F-cells. Absence of a relationship between plasma erythropoietin and HbF levels excluded a dominant role of the former in increasing F-cell production and results determined after doubling the HU dosage or immediately after initiating therapy suggested genetic differences to be responsible for the individual variations in Hb F response. No irreversible toxic effects or malignancies were noted in this series of patients. HU was administered for a relatively long period of time, the mean duration of treatment exceeding 5 years, while the study also included patients below the age of 10 years.

Adolescent↗
PubMed1994

[Erythrocytosis in a 4 year-old child: diagnostic, prognostic, therapeutical problems].

BACKGROUND: Pure erythrocytosis is rare in children. This report describes such a case. CASE REPORT: A 4 year-old boy was admitted because erythrocytosis had been found routinely before adenoidectomy. He was born in Guatemala, was adopted just after his birth, and had been living in France since that age. Clinical examination was normal. His hemogram showed: erythrocytes: 8,800,000/mm3; hemoglobin: 20.1 g/dl; hematocrit: 66.8%; reticulocytes: 262,000/mm3; platelets: 200,000/mm3; leukocytes: 6,800/mm3. The patient had been given iron salts for the past 3 months without an earlier hemogram. Total red cell mass was 1200 ml (N: 600). The myelogram was normal as was the leukocyte alkaline phosphatases, serum lysozyme and vitamin B12. Blood ferritin was low (3.5 ng/ml). In vitro cultures of erythroid precursors were normal, as was the karyotype of myeloid cells. Blood erythropoietin concentration was 20-293 mU/ml (N:4-14). All the causes of secondary polycythemia were eliminated by appropriate investigations. The patient was treated by phlebotomy in aliquots of 25 ml/kg, twice a month, for 10 months, and was given iron therapy. At the end of treatment, his hemoglobin was 14 g/dl and his hematocrit was 45%. Both progressively increased again one year later, requiring new phlebotomies. The patient was followed for 4 years but no cause for this erythrocytosis was found; it was probably congenital in origin. CONCLUSION: This case of pure erythrocytosis was associated with elevated erythropoietin production. Whether this high secretion is related to receptor dysfunction remains to be determined.

Bloodletting↗
PubMed1994

Determination of serum erythropoietin. Its value in the differential diagnosis of polycythemias.

In vivo and in vitro bioassays, radio immunoassays (RIA), enzyme linked immunoassays (ELISA) and immunoradiometric assays (IRMA) have been applied to measure serum erythropoietin (Epo) levels. Results are expressed in international units (IU). In vivo bioassays are time consuming, expensive and not sensitive enough to measure the amount of Epo in normal sera. Nevertheless, this test remains the standard of comparison for the other new assays. Immunologic technics are specific, sensitive, reproducible, easy to perform, rapid and are now preferred for the measurement of Epo. Published values for non anemic human range from 6 to 32 IU/l. In the search of etiology of a polycythemia, the results of usual investigations to class the polycythemia either as primitive (P. vera) or secondary are often inconclusive. In these situations, measurement of serum Epo could be of value for accurate a differential diagnosis. However the results of the literature and our personal experience, show that the serum Epo level does not discriminate with an absolute fiability between Polycythemia Vera and secondary polycythemia because of a great overlap between the two groups.

Biological Assay↗
PubMed1994

Anorexia nervosa and gelatinous transformation of bone marrow.

Two patients with anorexia nervosa and gelatinous bone marrow justify a review of the cases in the literature. This gelatinous substance is related to an increase in mucopolysaccharides present in the marrow which replace the medullary fat mobilised by the maintenance of energy reserves; this increase would be unfavorable for hematopoiesis.

Adult↗