Biomedical subjects

B Varet

Publications and source records attributed to B Varet.

At least 127 records · Page 7Linked to original sources

PubMed1984

A new hemoglobin variant altering the alpha 1 beta 2 contact: Hb Chemilly alpha 2 beta 2 99(G1)Asp leads to Val.

Hemoglobin Chemilly (alpha 2 beta 2 99(G1)Asp leads to Val), a high oxygen affinity variant, was uncovered in the red blood cells of a polycythemic patient who reported to the hospital concerning periodic headaches. We describe the molecular abnormality and functional studies of this new abnormal Hb. beta 99(G1)Asp, an invariant residue of hemoglobin, is considered a key amino acid for conformational changes between the R in equilibrium T quaternary structures responsible for the allosteric behavior of hemoglobin. Hb Chemilly exhibits a high O2 affinity, very low cooperativity and reduced Bohr effect. Its functional abnormalities are compared to the 5 other Hb variants at site beta 99(G1) described up to now of the 7 single base substitutions predictable from the genetic code.

Adult↗

PubMed1984

Multistep virus-induced leukemogenesis in vitro: description of a model specifying three steps within the myeloblastic malignant process.

A helper-independent Friend leukemia virus was used to infect bone marrow cultures. This virus induces myeloblastic leukemia in mice after a long latency period. Infection of the bone marrow cultures resulted in the in vitro production of myeloblastic leukemogenesis after a long latency period. Three steps were observed in the evolution of the infected cultures, and permanent cell lines were derived at each step. This allowed us to individualize three successive events in the course of the myeloblastic transformation: (i) an abnormal responsiveness to the physiological hormone granulo-macrophagic colony-stimulating factor, (ii) the acquisition of growth autonomy, and (iii) the acquisition of in vivo tumorigenicity.

Animals↗

PubMed1984

[Erythrocytosis due to a high-affinity hemoglobulin: mutant hemoglobin Saint-Jacques beta 140 (H18) Ala----Thr with a change in the 2,3-diphosphoglycerate binding site].

All the high oxygen affinity variants have substitutions in regions that are crucial to hemoglobin function: mainly the alpha 1 beta 2 interface, the C-terminal end of the beta chain and the aminoacid residues involved in the 2,3 disphophoglycerate (2,3 DPG) binding site. In this report we describe a new variant with familial erythrocytosis: hemoglobin Saint-Jacques beta 140 (H18) Ala----Thr, whose main abnormality is a defect in organic phosphate binding in the central cavity between to two beta chains. This variant could not be separated from hemoglobin A by standard electrophoretic methods or by isoelectric focusing. The abnormal peptide was isolated by reverse-phase high performance liquid chromatography and the structural modification determined by manual sequencing micro-method. Functional studies on red blood cells as well as on stripped lysate showed increased oxygen affinity, normal Bohr effect, decreased heme-heme interaction and loss of the 2,3 DPG regulatory effect.

2,3-Diphosphoglycerate↗

PubMed1984

Characterization of erythropoietin produced by IW32 murine erythroleukemia cells.

IW32 is a recently described murine erythroleukemia cell line that produces an erythropoietic factor similar to erythropoietin by in vivo and in vitro bioassays and without species specificity. Biochemical characteristics of IW32 erythropoietic factor and sheep or mouse plasma erythropoietins were compared. Murine colonies derived from erythroid colony-forming units (CFU-E) in plasma clot culture were used as the bioassay system. Both IW32 erythropoietic factor and sheep plasma erythropoietin were stable in the pH range of 3 to 10, after exposure to denaturing agents (8 mol/L urea, 4 mol/L guanidine hydrochloride, 1% sodium dodecyl sulfate), to a reducing agent (0.1 mol/L 2-mercaptoethanol) and to an oxidizing agent (5 mmol/L sodium metaperiodate). Only the combination of 0.1 mol/L 2-mercaptoethanol and 1% sodium dodecyl sulfate resulted in a significant loss of activity. IW32 erythropoietic factor and murine plasma erythropoietin were similarly precipitated by ethanol and ammonium sulfate. IW32 erythropoietic factor eluted as a single major peak after gel exclusion chromatography, with an estimated molecular weight of 45,000 daltons. Results were identical using supernatants from cultures in the presence of and absence of fetal calf serum. The supernatant of IW32 cells cultured without serum induced erythroid colonies after seven days on normal human bone marrow nonadherent mononuclear cells cultured in serum-free conditions. All these results made it very likely that IW32 cells produce an authentic erythropoietin. This cell line would be very useful for the study of murine erythropoietin.

Animals↗

PubMed1984

Erythroid progenitors in adult chronic pure red cell aplasia: relationship of in vitro erythroid colonies to therapeutic response.

Twenty-two cases of idiopathic chronic pure red cell aplasia (PRCA) in adults have been studied to evaluate their erythroid progenitors in vitro using the plasma clot technique. Three types of culture growth patterns were observed and classified as follows. Type I: showing a normal number of autologous CFU-E; type II: CFU-E and BFU-E were detectable but constantly decreased; type III: CFU-E and BFU-E were undetectable. The results were reproducible when patients were studied on two or more occasions. A strong correlation was found between the in vitro growth of autologous erythroid colonies and the results of immunomodulating therapy in 18 evaluable patients. A constant response to immunomodulating treatment was observed in type I patients. A constant failure of treatment was observed in type III patients, whereas results of therapy were unpredictable in type II patients. Two patients with chronic PRCA associated with thymoma and three with chronic myeloproliferative disorders were also studied. Patients with PRCA and thymoma behaved in vitro like type I patients. Patients with chronic myeloproliferative disorders exhibited very low numbers or no CFU-E or BFU-E (type II or III). These data support the hypothesis that at least two mechanisms are responsible for PRCA--one immunologically mediated and the other resulting from a stem cell defect. Moreover, they suggest that the study of erythroid progenitors in vitro might be useful in predicting the immunosuppressive therapy effect in adult chronic PRCA.

Adolescent↗

PubMed1983

Malignant myeloblastic transformation of murine long-term bone marrow cultures by F-MuLV: in vitro reproduction of a long-term leukemogenesis, and investigation of preleukemic events.

A Friend helper virus I-5(F-MuLV) which induces myeloblastic leukemias in mice after a latency of several months, was used to infect long-term bone marrow cultures. From 48 to 71 weeks after in vitro infection, 4/14 cultures gave rise to transplantable malignant myeloblastic cells. These cells were shown to genuinely result from as in vitro transformation of virus-infected normal bone marrow cells. The in vitro transformation reproduced the course of the in vivo disease. It provided unique material for in vitro investigation of the preleukemic stages of long-term leukemogenesis. Successive cellular events were: (1) freezing of the normal myelomonocytic differentiation process; (2) change from factor-dependent to an autonomous growth; (3) acquisition of in vivo tumorigenicity.

Animals↗

PubMed1983

Autocrine function of murine F-MuLV induced myeloblastic cell lines.

Four in vitro permanent suspension cell lines have been established from tumoral organs of myelogenous leukemias developed in mice infected with two biologically cloned Friend helper viruses. Leukemic cells in culture were 100% typical myeloblasts exhibiting a strong myeloperoxidase positivity. A few cells were induced to granulocytic or macrophagic terminal differentiation by post-endotoxin serum and by various chemical differentiation inducers such as DMSO, N-butyrate and TPA. We investigated the conditions sustaining the clonal proliferation of these leukemic cells in semi-solid cultures. Cloning efficiencies were increased by the vicinity of a large number of autologous cells and by the addition of autologous culture supernatant, indicating that the leukemic cells were able to stimulate their own in vitro growth. Cloning efficiencies were also increased by different sources of CSA, such as WEHI-3B conditioned medium and post-endotoxin serum. Moreover, the various cell lines stimulated each other through soluble factor(s) secreted in their culture supernatants. Proteins contained in these four culture supernatants were fractionated by successive ammonium sulfate precipitations and ion exchange chromatography. In the four cases the autostimulating activities were eluted in the same fractions as proteins stimulating the normal bone marrow cells colony formation (CSA). These data suggest that the myeloblastic leukemic cell autostimulating factor(s) might be related to the physiological CSA.

Animals↗

PubMed1983

Production of erythropoietin-like activity by a murine erythroleukemia cell line.

A transplantable murine leukemia, primarily induced by a biologically cloned Friend helper virus, was shown to induce polycythemia in recipient ICFW mice. A leukemia cell line (IW.32) was established in vitro from this transplantable leukemia. Sodium butyrate and hemin induced erythroid differentiation in these leukemia cells as has already been shown with other erythroleukemia cells. The supernatant of this cell line was devoid of spleen focus-forming virus activity. However, it induced the incorporation of 59Fe in polycythemic mice and the in vitro differentiation of murine and human cfu-e into erythroid colonies. Therefore, these erythroleukemia cells produced a factor with all the biological properties of erythropoietin. The erythropoietic activity of IW.32 supernatant was higher in vitro [equivalent to 0.5-1 international unit (IU) of erythropoietin per ml] than in vivo (0.15-0.3 IU/ml). This erythropoietin-like activity was stable at 100 degrees C for 3 min, which ruled out the possibility that a virus was responsible for these effects. Preliminary studies demonstrated that the biochemical properties of the IW.32 factor are strongly similar to those of Connaught step 3 erythropoietin, thus supporting the hypothesis that the IW.32 factor is indeed an erythropoietin.

Animals↗

PubMed1983

[Production of an erythropoietic factor by mouse leukemia].

The graft of a transplantable leukemia (IW 32) induced by a biologically cloned helper of a Friend virus devoid of SFFV activity, was shown to induce a polycythemia in recipient animals. An in vitro continuous cell line was derived from this leukemia. The supernatant was shown to induce an erythroid differentiation both in vivo in Mice rendered polycythemic by transfusion, and in vitro in plasma clot CFUE assay. This erythropoietic activity was heat stable (30 min. 56 degrees C, 3 min. 100 degrees C) which ruled out the hypothesis that the IW 32 cell line produced a polycythemia inducing virus. The erythropoietic factor produced by IW 32 leukemic cells might be erythropoietin.

Animals↗

PubMed1983

[Demonstration of antineutrophil antibodies using radioiodinated protein A].

The granulocyte associated IgG in normal and neutropenic subjects has been determined by a direct quantitative assay using radiolabeled staphylococcal protein A. This assay allows us to postulate an immunological mechanism to explain the neutropenia in 19 cases of neutropenias associated with malfunctions of the immune system and in 4 cases of idiopathic neutropenias. Discussed in this report is the possible interaction of immune complexes bound in vivo to the granulocytes. By an immunofluorescence test, it has been possible to detect IgG or IgM antibodies in only 52% of patients with a positive direct assay. The determination of granulocyte-associated IgG is therefore a better indicator in our study for defining an auto-immune neutropenia than the detection of free antibodies in the sera.

Adult↗

PubMed1983

[Non-Hodgkin lymphoma associated with a relapse of Hodgkin's disease].

We report the case of a patient treated for Hodgkin's disease (stage IIIEA) by combination of chemotherapy (MOPP regimen) and total nodal irradiation. Five months after the completion of radiotherapy the patient presented with a relapse of his Hodgkin's disease and simultaneous occurrence of diffuse non Hodgkin's lymphoma in a different lymph node territory. The relationship between these two malignancies is discussed and the literature is reviewed.

Combined Modality Therapy↗

PubMed1982

Role of colony-stimulating activity in murine long-term bone marrow cultures: evidence for its production and consumption by the adherent cells.

The involvement of colony-stimulating activity (CSA) in murine long-term bone marrow cultures (LTBMC) was studied using bilayer agar cultures. The supernatants of LTBMC were removed, a layer of dense agar was spread over the cells adherent to the bottom of the flask, and fresh myeloid cells were plated as source of CFU-C in an upper agar layer. Large numbers of granulocytic and macrophagic colonies developed regularly when target cells were plated over adherent cells of nonrecharged and greater than 12 wk old LTBMC that were hematopoietically inactive (i.e., producing a low number of nonadherent cells). The removal of adherent cells from the myeloid cells used as source of CFU-C did not decrease the number of colonies. This suggests that adherent cells of LTBMC release CSA that is directly active on CFU-C. This CSA was no longer detectable over adherent layers of hematopoietically active LTBMC. A close inverse relationship was demonstrated between the number of nonadherent cells harvested before the assay and the level of CSA. No inhibitor for CSA was demonstrated in the supernatant of hematopoietically active cultures. Murine exogenous CSA incubated over the adherent layer host its activity within 24 hr, whereas in the same conditions human CSA retained its activity. These data demonstrate the production of CSA by the adherent layer of LTBMC and strongly suggest its specific in situ consumption by differentiating myeloid cells.

Animals↗

PubMed1982

[Acute pulmonary infiltrates in hematologic malignancies in aplasia (author's transl)].

Extensive pneumonias are usually implicated as the sole cause for acute respiratory failure complicating severe neutropenia in hematologic malignancies and are often fatal. We report study of 11 patients investigated and treated in intensive care unit, using transtracheal aspiration, continuous positive airway pressure (CPAP) via face mask and granulocyte transfusions Two groups of patients emerged from this study. The first group with immediately diffuse pulmonary infiltrates, positive blood cultures, negative tracheal cultures, marked improvement in hypoxemia during CPAP, benefits from granulocyte transfusion without impairment in ventilatory status and may be considered as non-hemodynamic pulmonary oedema. The second group with localized pulmonary infiltrates, negative blood cultures and positive tracheal culture, slight improvement in hypoxemia during CPAP, gets no benefit from granulocyte transfusion, with additional impairment in ventilatory status and may be considered as acute extensive pneumonias.

Acute Disease↗

PubMed1982