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M Brice

Publications and source records attributed to M Brice.

At least 19 recordsLinked to original sources
PubMed1996

Insights into the cellular mechanisms of erythropoietin-thrombopoietin synergy.

Using suspension cultures of purified bone marrow CD34+ cells, we have analyzed the effects of the combination of erythropoietin (Epo) and thrombopoietin (Tpo) on the in vitro differentiation toward erythropoiesis and thrombopoiesis. The number of CD41+ cells that accumulated over 2 weeks of culture, as well as the number of globin+ cells in the same cultures, was found to be significantly higher with the Epo+Tpo combination compared to either cytokine alone. No evidence was found that Tpo affected the differentiative action of Epo. Instead, there was a significant expansion of erythroid progenitors, both erythroid colony-forming and burst-forming units (CRU-E and BFU-E), by 7 days in culture, suggesting a proliferative effect of Tpo on erythroid cells in vitro. To determine the phenotypic features of erythroid progenitor cells which were targets of Tpo's action, and specifically to inquire whether the effect was directed mainly toward bipotent erythroid/megakaryocytic (E+Mk) progenitors, we isolated subsets enriched for both erythroid and megakaryocytic progenitors from CD34+ cells. We found that 1) BFU-E and CFU-Mk co-segregate in the subset of CF34+ cells that is negative for the phosphatase isoform CD45RA; 2) the presence of CD41 on this subset appears to segregate late erythroid and late CFU-Mk from early erythroid and early CFU-Mk, which are CD41-negative; 3) bipotent erythroid/Mk progenitors, studied by single-cell culture assays, were found mainly in the CD41+ and rarely in the CD41- subsets which included more multipotent progenitors; 4) by comparing the frequencies of pure erythroid or pure megakaryocytic progenitors to that of bipotent E+Mk progenitors, we conclude that the erythroid-enhancing effect of Tpo is directed mainly toward pure erythroid progenitors expressing CD41 and Mpl, as suggested by independent experiments employing anti-Mpl antibody, rather than only on bipotent E+Mk progenitors.

Antigens, CD34↗
PubMed1994

[Total reconstruction of the nose by osteocutaneous preformed forearm flap. Apropos of a case].

The authors report the case of a 28-year-old woman in whom multiple surgical reconstructions were performed to cure an extensive radiation necrosis of the nose. In 1980, after the failure of a dorsalis pedis free flap and of a free groin flap, success was obtained with a free lateral mammary flap. But defatting, bone grafting and modelling produced partial necrosis of the flap. Finally, total nasal reconstruction was achieved in 1983 with a pedicled osteocutaneous forearm flap. To secure the transfer, the flap was first modelled by folding directly on the donor site. The advantages of this procedure are a lower risk of postoperative infection and a fewer number of secondary surgical stages needed to achieve the reconstruction. The reliability of the forearm flap and the simplicity of the procedure advocate its use in difficult reconstructions of the nose, when others techniques could not give better results.

Adult↗
PubMed1993

Dynamics of GATA transcription factor expression during erythroid differentiation.

Although the formation of terminally differentiated erythroid cells has been shown to require the presence of a functional GATA-1 gene in vivo, the role of this transcription factor and other members of the GATA family at earlier stages of erythroid differentiation is unclear. In this report, the expression of GATA-1, GATA-2, and GATA-3 has been examined in enriched peripheral blood progenitors before and after culture in a well-characterized liquid culture system. In addition primary leukemic cells as well as several erythroleukemic and nonerythroid cell lines were analyzed for GATA factor expression. The results show that the profile of GATA factor expression in erythroid cells is distinct from that of myeloid or lymphoid lineages. Erythroleukemic cell lines express little or no GATA-3, but high levels of GATA-1 and GATA-2. When they are induced to display the terminal erythroid phenotype, little change in the level of GATA-1 is detected but a significant decline in the levels of GATA-2 is observed commensurate with the degree of maturation achieved by the cells. Enrichment of erythroid progenitors from peripheral blood leads to selection of cells that express both GATA-1 and GATA-2. As the enriched populations are cultured in suspension in the presence of multiple cytokines, the levels of both GATA-1 and GATA-2 initially increase. However, in cultures containing only erythropoietin, which show exclusive erythroid differentiation, the levels of GATA-1 continue to increase, whereas GATA-2 expression declines as erythroid maturation progresses. In contrast, cultures lacking Epo (ie, with interleukin-3 and kit ligand) display limited progression towards both the myeloid and erythroid pathways, and high levels of expression of both GATA-1 and GATA-2 are maintained. Despite the initial upregulation of GATA-1 expression in the latter cultures, terminal erythroid differentiation does not occur in the absence of erythropoietin. These results indicate that GATA-1 upregulation is associated with both the initiation and the maintenance of the erythroid program, but that these two processes appear to be under separate regulatory control. Thus, the dynamic changes in the levels of different GATA factors that occur during primary erythroid differentiation suggest that the levels of these factors may influence the progression to specific hematopoietic pathways.

Base Sequence↗
PubMed1993

Kit ligand in synergy with interleukin-3 amplifies the erythropoietin-independent, globin-synthesizing progeny of normal human burst-forming units-erythroid in suspension cultures: physiologic implications.

Although the proliferative effects of hematopoietic cytokines on erythroid progenitors are well known, parameters that influence the initiation of expression of specialized or lineage-restricted genes are not clear. We have studied the acquisition of erythroid-differentiative features from enriched populations of human early erythroid progenitors (burst-forming unit-erythroid [BFUe]) in suspension culture and the influence of several cytokines on this process. In suspension cultures containing no erythropoietin (Epo), we have found that kit ligand (KL) in synergy with interleukin-3 not only increases the proliferation of cells and of progenitors but also consistently amplifies a population of cells that contain globin within 1 week. Our experiments suggest that neither extraneously provided nor endogenously produced Epo is critical for the generation of globin-synthesizing cells. Globin-producing cells generated mostly from late BFUe or pre-CFUe with a CD34-/EP-1+ phenotype in this system do not all express a well-coordinated erythroid program accompanied by heme or glycophorin A expression and most die maintaining an immature state. Therefore, conditions that are responsible for initiation of globin expression in these cells are not sufficient to carry them to terminal maturation. The data point to an expanded target cell population for KL, as they suggest an influence of KL on survival and/or amplification of late erythroid cells previously thought to be influenced only by Epo. Our results in aggregate are of relevance to the physiology of normal erythropoiesis and the role of Epo and KL in the initial stages of lineage-restricted gene expression. In addition, they provide insight into the understanding of anemia in W and Steel mutants in which expansion of the late erythroid progenitor pool, normally dependent on the synergistic action of KL and Epo, is curtailed.

Antibodies, Monoclonal↗
PubMed1992

Integrin expression profiles during erythroid differentiation.

To study the expression of integrins at the erythroid progenitor level we isolated selected populations of cells from human fetal liver after immunoadherence to anti-beta 2 integrin (CD18) coated plates. These CD18 adherent cells (CD18-Ad), in contrast to CD18 nonadherent cells (CD18-NAd), have a blastlike cell morphology and are highly enriched in all progenitor types (14% to 37% progenitors). By several criteria progenitor cells present in CD18-Ad cells appear to have a higher proliferative potential and diversity than the ones found in CD18-NAd, which were mostly later erythroid progenitors. Positivity of CD18-Ad cells with the common beta 2 integrin (CD18) is largely attributable to expression of alpha L (CD11a) chain, rather than alpha M (CD11b). CD11a is present in all types of progenitors, but it is selectively lost at later stages of erythroid differentiation/maturation. By contrast, CD11b appears to be virtually absent from all progenitors but it has an enhanced expression during granulomonocytic differentiation/maturation. In addition to beta 2 integrins, CD18-Ad cells express several other cytoadhesion molecules (VLA-4, VLA-5, I-CAM, H-CAM) as well as other progenitor cell antigens (CD34, HLA-DR, CD38). Cells expressing all these antigens were selectively enriched in CD18-Ad cells. Our data add new information on the regulation of CD11a and CD11b molecules in hematopoiesis and on the composite profile of integrin expression at several stages of erythroid differentiation.

Antigens, CD↗
PubMed1991

Isolation of c-kit receptor-expressing cells from bone marrow, peripheral blood, and fetal liver: functional properties and composite antigenic profile.

To define the cellular targets for c-kit ligand (KL) and to study their functional properties and composite antigenic profile, we isolated cells expressing c-kit receptor (KR) from bone marrow (BM), peripheral blood, and fetal liver (FL) using immunoadherence to a recently obtained antibody (SR-1) against the human KR. Cells isolated by this approach (designated SR-1Ad) have the morphology of blasts and represent 1% to 4% of the original BM or FL populations. SR-1Ad cells from either source are highly enriched in progenitors (12% to 73%) and respond to KL in distinct patterns. In SR-1Ad cells from BM, the greatest impact of KL stimulation is on burst-forming units-erythroid (BFU-E), whereas in SR1-Ad cells from FL, the most significant KL effect is on a mixed erythroid/nonerythroid progenitor (erythroid/macrophage, colony-forming unit-mix [CFU-Mix]). When antibody SR-1 is continually present in culture, it neutralizes the effects of added KL. Furthermore, in the absence of added KL, it greatly diminishes the erythropoietin- and interleukin-3-dependent BFU-E growth in BM; whereas in FL, a wider spectrum of inhibition is observed, with CFU-Mix most severely curtailed. SR-1Ad cells coexpress other progenitor-associated antigens in a combination reflecting the dominant presence of erythroid progenitors (high expression of CD34, DR, CD38, and Ep-1; low expression of CD33). Several cytoadhesion molecules, ie, alpha L/beta 2 and alpha 4/beta 1 integrins, and intercellular adhesion molecule 1 and homing cell adhesion molecule 1, are also coexpressed. Our data provide new information on the isolation and characterization of KR expressing cells from normal, adult, and fetal hematopoietic tissues. On these biologically relevant target cells, the impact of ligand-induced stimulation or antibody-mediated ablation of KR function has been gauged.

ADP-ribosyl Cyclase↗
PubMed1991

Erythropoietin receptor characteristics on primary human erythroid cells.

Erythropoietin (EP) exerts its effects on erythropoiesis by binding to a cell surface receptor. We examined EP receptor expression during normal human erythroid differentiation and maturation from the burst-forming unit-erythroid (BFU-E) to the reticulocyte level. In contrast to previous studies, we assessed EP receptor number and affinity in erythroid precursors immunologically purified from fresh bone marrow aspirates or fetal liver samples and in reticulocytes purified from peripheral blood. EP receptors were quantitated by equilibrium binding experiments with 125I EP. We found that purified primary erythroblasts from both adult and fetal sources exhibited a single high-affinity (kd 100 pmol/L) binding site for EP under our experimental conditions, and 135 or 250 receptors per cell, respectively. Reticulocytes were devoid of EP receptors. We compared these data to in vitro-derived BFU-E progeny at both early and late stages of maturation. Cultured BFU-E progeny also displayed a single class of receptors of slightly lower affinity (210 to 220 pmol/L). Preparations enriched in colony-forming units-erythroid (CFU-E) and proerythroblasts (day 9 BFU-E progeny) displayed approximately 1,100 receptors per cell, whereas populations containing mature erythroblasts (day 14 BFU-E progeny) exhibited approximately 300 receptors per cell. Furthermore, information from binding experiments was complemented by autoradiography in both enriched BFU-E preparations, cultured BFU-E progeny (days 9 and 14), and marrow mononuclear cells. These studies are consistent with a peak in EP receptor expression at the CFU-E/proerythroblast stage and a decrease with further maturation to undetectable levels at the reticulocyte stage. These data examining EP receptor characteristics on freshly isolated erythroid precursor cells complement previous data on EP receptor biology using culture-derived erythroblasts.

Autoradiography↗
PubMed1991

Developmental regulation of fetal to adult globin gene switching in human fetal erythroid x mouse erythroleukemia cell hybrids.

Human fetal erythroid x murine erythroleukemia cell hybrids undergo human fetal (gamma) to adult (beta) globin gene switching in vitro under the control of a mechanism located on human chromosome 11. We investigated whether this mechanism acts in cis or in trans by preparing hybrid cells containing marked fragments of the gamma and beta genes known to switch in transgenic mice. In these cells the chromosomally introduced human globin locus undergoes the fetal to adult globin gene switch. In contrast, the marked globin gene fragments were expressed at all stages of hybrid development. These results suggest that either the mechanism of switching acts in cis or that sequences present in the chromosomal globin locus but missing from the transfected globin gene fragments mediate its action.

Animals↗
PubMed1990

Influence of recombinant hematopoietins and of fetal bovine serum on the globin synthetic pattern of human BFUe.

We have studied the effects of recombinant hematopoietic growth factors, granulocyte-macrophage colony-stimulating factor (GM-CSF) and/or interleukin-3 (IL-3) on the globin program of adult human erythroid progenitors (BFUe) stimulated to terminal differentiation by erythropoietin under fetal bovine serum (FBS)-supplemented or FBS-deprived culture conditions. Fetal globin production by BFUe-derived erythroblasts was assessed at the protein and mRNA level and its cellular distribution was evaluated by immunofluorescence. Although hemoglobinization and maturation of BFUe-derived erythroblasts was by and large comparable in FBS-replete versus FBS-deprived cultures, the latter had significantly less (up to 20-fold) gamma-globin and gamma-globin mRNA levels. Reduced gamma-globin in serum-deprived cultures was also reflected by a smaller proportion of erythroblasts with detectable gamma-globin by immunofluorescence. Erythroid bursts induced by either GM-CSF or IL-3 produced similar levels of gamma-globin both in FBS-supplemented and in FBS-deprived cultures. These results, obtained even in cultures of highly enriched BFUe, suggest that GM-CSF and IL-3, although they significantly increase the number and size of erythroid bursts, do not by themselves exert a direct influence on the level of fetal globin synthesis. By contrast, factor(s) present in FBS appear to exert a dominant influence on fetal globin synthesis in vitro. Although FBS-deprived conditions appear to largely abrogate the in vitro activation of fetal hemoglobin (Hb F) in normal samples, they do support increased Hb F production in samples from patients with hereditary persistence of fetal hemoglobin or from cord blood.

Blood Cells↗
PubMed1990

A deletion of the human beta-globin locus activation region causes a major alteration in chromatin structure and replication across the entire beta-globin locus.

Naturally occurring deletions that remove sequences located approximately 60 kb upstream of the human adult beta-globin gene result in the failure to transcriptionally activate the cis-linked globin genes in erythroid cells. In addition, transfection, transgenic, and somatic cell hybrid studies have revealed that sequences within this region are essential for the developmentally regulated high-level expression of cis-linked globin genes. This regulatory region located at the 5' end of the beta-globin locus has been termed the locus activation region (LAR). Using somatic cell hybrids, we have studied the chromatin structure and timing of DNA replication of the normal human beta-globin locus and a locus containing a de novo 25-kb deletion that removes elements of the LAR. As a result of this deletion, the entire beta-globin locus and sequences approximately 100 kb 5' and 3' of the adult beta-globin gene are DNase I-resistant and do not form characteristic distant hypersensitive sites. These sequences also replicate late in S phase in an erythroid cell background. In contrast, the sequences of the normal locus are DNase I sensitive and early replicating. These results suggest that the LAR is required for both the erythroid-specific chromatin structure and timing of DNA replication over a large physical distance.

Chromatin↗
PubMed1990

[Evaluation of the use of free flaps of the anterior iliac crest. Review of 49 cases].

Because of the septic environment, the reconstruction of extensive losses of substance of the mandible has always raised numerous problems, especially as in a certain number of cases, concomitant radiotherapy represents an additional difficulty. Free flaps offer an important contribution. Up until now, we have essentially used the anterior iliac crest flap vascularised by the deep iliac circumflex pedicle. After 55 flaps of this type, the authors present an analysis of their results and try to analyse the causes for the failures. On the basis of their experience, they consider: that it is preferable to perform the bone and soft tissue repair by means of two different procedures (or at least by means of two different pedicles); that it is preferable, as far as possible, to perform immediate reconstructions rather than deferred reconstructions, especially in the case of malignant tumours.

Evaluation Studies as Topic↗
PubMed1987

Coexpression of embryonic, fetal, and adult globins in erythroid cells of human embryos: relevance to the cell-lineage models of globin switching.

The cellular control of the switch from embryonic to fetal globin formation in man was investigated with studies of globin expression in erythroid cells of 35- to 56-day-old embryos. Analyses of globins synthesized in vivo and in cultures of erythroid progenitors (burst-forming units, BFUe) showed that cells of the yolk sac (primitive) erythropoiesis, in addition to embryonic chains, produced fetal and adult globins and that cells of the definitive (liver) erythropoiesis, in addition to fetal and adult globins, produce embryonic globins. That embryonic, fetal, and adult globins were coexpressed by cells of the same lineage was documented by analysis of globin chains in single BFUe colonies: all 67 yolk sac-origin BFUe colonies and 42 of 43 liver-origin BFUe colonies synthesized epsilon-, gamma-, and beta-chains. These data showed that during the switch from embryonic to adult globin formation, embryonic and definitive globin chains are coexpressed in the primitive, as well as in the definitive, erythroid cells. Such results are compatible with the postulate that the switch from embryonic to fetal globin synthesis represents a time-dependent change in programs of progenitor cells rather than a change in hemopoietic cell lineages.

Cells, Cultured↗
PubMed1987

A chromosome 11-linked determinant controls fetal globin expression and the fetal-to-adult globin switch.

Hybrids formed by fusing mouse erythroleukemia (MEL) cells with human fetal erythroid cells produce human fetal globin, but they switch to adult globin production as culture time advances. To obtain information on the chromosomal assignment of the elements that control gamma-to-beta switching, we analyzed the chromosomal composition of hybrids producing exclusively or predominantly human fetal globin and hybrids producing only adult human globin. No human chromosome was consistently present in hybrids expressing fetal globin and consistently absent in hybrids expressing adult globin. Subcloning experiments demonstrated identical chromosomal compositions in subclones displaying the fetal globin program and those that had switched to expression of the adult globin program. These data indicate that retention of only one human chromosome-i.e., chromosome 11--sufficient for expression of human fetal globin and the subsequent gamma-to-beta switch. The results suggest that the gamma-to-beta switch is controlled either cis to the beta-globin locus or by a trans-acting mechanism, the genes of which reside on human chromosome 11.

Animals↗
PubMed1986

Analysis of human hemoglobin switching in MEL x human fetal erythroid cell hybrids.

The switch from fetal to adult globin synthesis in man was studied using heterospecific cell hybrids between human fetal erythroblasts and mouse erythroleukemia cells. When erythroblasts from first trimester fetuses were used the hybrids expressed a fetal program of human globin expression. While in continuous culture, these hybrids switched from predominantly fetal to almost exclusively adult globin expression, providing direct evidence that switching can occur within a single cell lineage. Sequential studies of globin expression at a single cell level and subcloning experiments suggested that the switch reflects a progressive increase in the generation of beta + cells from gamma + cells. Hybrids formed with erythroblasts of second trimester fetuses switched faster than those produced with cells of first trimester fetuses. The findings suggest that the human gamma to beta switch is controlled by a developmental clock-like mechanism, which appears to be associated with chromosome 11.

Animals↗