References of "Paulus, Jean-Michel"
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See detailThrombopoietin responsiveness reflects the number of doublings undergone by megakaryocyte progenitors
Paulus, Jean-Michel ULg; Debili, Najet; Larbret, Fréféric et al

in Blood (2004), 104(8), 2291-2298

To assess the variation of thrombopoietin (TPO) responsiveness associated with megakaryocyte (MK) progenitor amplification, TPO dose-response curves were obtained for normal human, single-cell plated CD34 ... [more ▼]

To assess the variation of thrombopoietin (TPO) responsiveness associated with megakaryocyte (MK) progenitor amplification, TPO dose-response curves were obtained for normal human, single-cell plated CD34(+)CD41(+) cells. The number of MKs per well was determined in situ and expressed as number of doublings (NbD). Dose-response curves of the mean frequency of clones of each size versus log TPO concentration showed highly significant differences in the TPO concentration needed for half-maximum generation of clones of different sizes (TPO50): 1.89 +/- 0.51 pg/mL for 1 MK clones; 7.75 +/- 0.81 pg/mL for 2 to 3 MK clones; 38.5 +/- 5.04 pg/mL for 4 to 7 MK clones, and 91.8 +/- 16.0 pg/mL for 8 to 15 MK clones. These results were consistent with a prediction of the generation-age model, because the number of previous doublings in vivo was inversely correlated with the number of residual doublings in vitro. TPO responsiveness decreased in vitro by a factor of 3.5 per doubling, reflecting the recruitment of progressively more ancestral progenitors. In support of this hypothesis, the more mature CD34(+)CD41(+)CD42(+) cell fraction had a lower TPO50 (P <.001), underwent fewer NbD (P <.001), and expressed a 2.8-fold greater median Mpl receptor density (P <.001) than the CD34(+)CD41(+)CD42(-) fraction. Progenitors that have completed their proliferative program have maximum factor responsiveness and are preferentially induced to terminal differentiation. (C) 2004 by The American Society of Hematology. [less ▲]

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See detailThrombopoietin dose-response curves reflect the number of doublings undergone by human megakaryocyte progenitors
Paulus, Jean-Michel ULg; Debili, N.; Larbret, F. et al

Poster (2004, July)

To assess the variation of thrombopoietin (TPO) responsiveness associated with MK progenitor amplification, TPO dose-response curves were obtained for MK clones derived from normal human CD34+CD41+ cells ... [more ▼]

To assess the variation of thrombopoietin (TPO) responsiveness associated with MK progenitor amplification, TPO dose-response curves were obtained for MK clones derived from normal human CD34+CD41+ cells which had been single-cell plated in serum-deprived medium with TPO concentrations of 0-1000 pg/mL per well. On day 5, the number of MK cells per well was determined in situ and expressed as number of doublings (NbD). Dose-response curves of the means of the frequency of clones of each size vs logTPO concentration showed highly significant differences in the TPO concentration needed for half-maximum generation of clones of different sizes (TPO50). Based on 3 independent experiments, TPO50, expressed in pg/mL, was 1.89 ±SD 0.87 for 1 cell MK clone; 7.75 ±1.40 for 2-3 cell MK clone; 38.5 ±8.73 for 4-7 cell MK clone and 93.6 ±27.7 for 8-15 cell MK clone (p<0.001). Compared to the CD42- fraction of CD34+CD41+ progenitors, the corresponding CD42+ fraction had a lower TPO50 (p<0.001), underwent lesser NbD (p<0.001) and expressed a 10-fold greater mean mpl receptor density. In order to interpret the conclusion that the most responsive progenitors were those which proliferated less, we tested a prediction of the generation-age model, namely that the percentage of progenitors undergoing a given number of residual doublings in vitro (NbDr) depends on the number of previous doublings they had undergone in vivo (NbDp). It was demonstrated that logTPO50 had a positive correlation with NbDr and negative correlation with NbDp (p<0.001). The reciprocal relationship between NbDp and NbDr was evidence for a generation-age model in which TPO responsiveness increases by a factor of approximately 4 per doubling. This model suggests that progenitors which have completed their proliferative program have maximum factor responsiveness and are preferentially induced to terminal differentiation. [less ▲]

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See detailHematies Hyperdenses et Sphérocytose
Bricteux, Guy ULg; Panagopoulos, A.; Paulus, Jean-Michel ULg

in Revue Médicale de Liège (2002), 57(7), 443-8

A 12-year old female, suffering from recurring episodes of icterus and abdominal pain, is hospitalized in emergency. She is not anemic but her hemogram reveals a high level of hyperdense red blood cells ... [more ▼]

A 12-year old female, suffering from recurring episodes of icterus and abdominal pain, is hospitalized in emergency. She is not anemic but her hemogram reveals a high level of hyperdense red blood cells (32%; controls 0-2.5%) and an abnormal reticulocyte count (201 x 10(3)/microL; controls 29-84 x 10(3)/microL), indicating a 3.5 fold increase in RBC production. The same abnormalities are found in the patient's mother. The blood smear shows few spherocytes. RBC osmotic fragility is increased only after incubation. Hereditary spherocytosis is diagnosed following electrophoresis of membrane proteins which reveals a deficiency in band 3, a protein which links the lipid bilayer to the cytoskeleton. This case of hemolytic anemia-illustrates the physiopathologic and diagnostic significance of hyperdense RBC, which reflect the cell dehydration associated with the membrane disorder. [less ▲]

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See detailErratum: Evaluation of the hycel diagnostics diana-5 hematolgy analyzer. Laboratory Hematology (2002) vol. 8 (3) (126-133)
Boeme, F.; Cielniaszek, N.; Paulus, Jean-Michel ULg et al

in Laboratory Hematology : Official Publication of the International Society for Laboratory Hematology (2002), 8(4),

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See detailEvaluation of the Hycel Diagnostics Diana-5 Hematology Analyzer
Boemer, François ULg; Cielniaszek, Nadine; Paulus, Jean-Michel ULg et al

in Laboratory Hematology : Official Publication of the International Society for Laboratory Hematology (2002), 8

The Hycel Diagnostics Diana-5, a compact 5-part differential hematology analyzer, was evaluated in the hematology laboratory of Liège University Hospital, Belgium. Within-and between-batch precision ... [more ▼]

The Hycel Diagnostics Diana-5, a compact 5-part differential hematology analyzer, was evaluated in the hematology laboratory of Liège University Hospital, Belgium. Within-and between-batch precision, linearity, and absence of carryover were all excellent. All parameters were stable for 48 hours at 4 ° C and for 8 hours at room temperature. Comparability of complete blood counts to Bayer Technicon Advia 120 measurements was highly satisfactory, with the exception of the mean cell volume, which was slightly underestimated by the Diana-5 compared to the Advia 120. Comparisons of differential leukocyte counts to 400-cell microscopic differentials were excellent for neutrophils, lymphocytes, and eosinophils and were acceptable for monocytes. The efficiency of the flagging system was high for the detection of blasts and less satisfactory for the detection of immature granulocytes and atypical lymphocytes. The instrument was reliable and easy to use. [less ▲]

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See detailMegakaryocyte (MK) clone size is inversely related to CFU-MK responsiveness to thrombopoietin (TPO)
Paulus, Jean-Michel ULg; Vainchenker, W.; Debili, N.

in Blood (2001, November 16), 98(11, Part 2), 119-119

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See detailGenesis of clone size heterogeneity in megakaryocytic and other hemopoietic colonies: the stochastic model revisited
Paulus, Jean-Michel ULg; Levin, Jack; Debili, Najet et al

in International Society for Experimental Hematology (2001), 29(nd), 1256-69

OBJECTIVE: We previously showed that the distributions of the numbers of doublings (NbD) undergone by individual megakaryocyte progenitors before commitment to polyploidization are markedly skewed and can ... [more ▼]

OBJECTIVE: We previously showed that the distributions of the numbers of doublings (NbD) undergone by individual megakaryocyte progenitors before commitment to polyploidization are markedly skewed and can consistently be fitted to straight lines when plotted on semilogarithmic coordinates. The slope of such lines, which yields the probability of polyploidization per doubling, is made less steep by stimulators of megakaryocyte colony formation and is less steep in mixed erythroid-megakaryocyte than in pure megakaryocyte colonies. Therefore, megakaryocytopoiesis provides a unique model for the study of clonal heterogeneity in a hemopoietic lineage, which is the subject of this review. DATA SOURCES: Articles relevant to the interpretation of these data were selected from the authors' and public databases. DATA SYNTHESIS: Exponential NbD distributions were first explained by postulating that following the assembly of thrombopoiesis-specific regulators, megakaryocyte progenitors require only a single random event to arrest proliferation and commit to polyploidization. However, this stochastic model was refuted by data indicating that intrinsic properties of individual progenitors affect the NbD they achieve. We suggest that the unequal repartition of critical compounds (including receptors, signaling molecules, and gene regulators) inherent in the stem cell-progenitor transition causes a heritable heterogeneity in megakaryocyte progenitor responsiveness to polyploidization inducers. This model would be compatible with 1) the evidence for intraclonal synchronization in megakaryocyte and other hemopoietic clones generated by committed progenitors; 2) the low probability of polyploidization of the relatively insensitive bipotent megakaryocyte progenitors; and 3) the thesis that stimulators act in part by recruiting megakaryocyte progenitor cells endowed with lesser responsiveness to polyploidization inducers and higher proliferative potential. CONCLUSION: The responsiveness of individual megakaryocyte progenitors to polyploidization inducers may be a major determinant of the exponential shape of NbD distributions. [less ▲]

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See detailAdministration of erythopoietin and granulocyte colony-stimulating factor in donor/recipient pairs to collect peripheral blood progenitor cells (PBPC) and red blood cell units for use in the recipient after allogeneic PBPC transplantation.
Sautois, Brieuc ULg; Baudoux, Etienne ULg; Salmon, Jean ULg et al

in Haematologica (2001), 86(11), 1209-18

BACKGROUND AND OBJECTIVES: It may be useful to reduce the exposure of transplant recipients to homologous blood. This may be achieved by procuring donor-derived red blood cell (RBC) units, collecting more ... [more ▼]

BACKGROUND AND OBJECTIVES: It may be useful to reduce the exposure of transplant recipients to homologous blood. This may be achieved by procuring donor-derived red blood cell (RBC) units, collecting more peripheral blood progenitor cells (PBPC) with a combination of granulocyte colony-stimulating factor (G-CSF) + recombinant human erythropoietin (rHuEpo) and by administering rHuEpo post-transplantation. DESIGN AND METHODS: Eight ABO-compatible donors were treated with rHuEpo and intravenous iron to collect 12 RBC units for use in their recipients. PBPC were collected after mobilization with rHuEpo and G-CSF in the same donors. The recipients received G-CSF and rHuEpo post-transplantation. A control group of 10 donor/recipient pairs received G-CSF alone for PBPC mobilization and after the transplantation. RESULTS: Eighty-six out of 91 planned RBC units were collected in the donors without significant decrease in hematocrit because of a 4-fold increase in RBC production despite functional iron deficiency. After 2 leukaphereses, the cumulative yields of NC and CFU-GM were lower in the study group while those of BFU-E, CFU-Mix and CD34+ cells were similar. However, erythroid recovery was significantly accelerated in the study group. INTERPRETATION AND CONCLUSIONS: Collection of 12 RBC units within 6 weeks is feasible with rHuEpo and intravenous iron; this strategy allows a dramatic reduction in recipient exposure to homologous blood; rHuEpo has no synergistic effect with G-CSF for mobilization of PBPC in normal donors and may even be deleterious; and rHuEpo in the recipient may enhance erythroid engraftment. [less ▲]

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See detailConsequences of total and subtotal myeloperoxidase deficiency: risk or benefit ?
Kutter, D.; Devaquet, P.; Vanderstocken, G. et al

in Acta Haematologica (2000), 104(1), 10-5

A group of 100 totally or subtotally myeloperoxidase (MPO)-deficient individuals was compared to a reference population of 118 probands selected at random. Data for a protective effect of the deficiency ... [more ▼]

A group of 100 totally or subtotally myeloperoxidase (MPO)-deficient individuals was compared to a reference population of 118 probands selected at random. Data for a protective effect of the deficiency against cardiovascular damage are presented. On the other hand, a significantly higher occurrence of severe infections and chronic inflammatory processes was noted among the deficient patients. An increased incidence of cancer among the MPO-deficient individuals was not demonstrated. [less ▲]

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See detailA four-parameter index of marrow dysplasia has predictive value for survival in myelodysplastic syndromes.
Tassin, Françoise ULg; Dewé, Walthère ULg; Schaaf, Nicole ULg et al

in Leukemia & Lymphoma (2000), 36(5-6), 485-96

Marrow dysplasia is a major characteristic of patients with myelodysplastic syndrome (MDS), along with marrow blastosis, cytopenia and cytogenetic anomalies. However, the impact of the degree of marrow ... [more ▼]

Marrow dysplasia is a major characteristic of patients with myelodysplastic syndrome (MDS), along with marrow blastosis, cytopenia and cytogenetic anomalies. However, the impact of the degree of marrow dysplasia on survival has not been fully assessed. In this retrospective analysis of 111 patients selected according to the IPSS criteria of MDS diagnosis, the presence or absence of 21 dysplasia characteristics recognizable in bone marrow smears stained by the May-Grunwald-Giemsa method was correlated with patient survival. Using Cox proportional hazards regression analysis, megaloblastosis (MEGALO), neutrophil agranularity (AGRAN) and hypogranularity (HYPOGRAN) were highly significant predictors (p < 0.005), and Pelger-Huet anomaly (PELGHUET) a significant predictor (p = 0.05), of patient survival. The regression analysis yielded a dysplasia-based risk index (DI) where DI = 1.26 MEGALO + 0.82 AGRAN - 1.08 HYPOGRAN + 0.45 PELGHUET. The two subgroups of 60 and 47 patients with DI < or = 0 and > 0 showed highly significant differences in median survivals (2.6 vs 1.1 yrs; p <0.0001). Multivariate analysis further showed that DI offered additional predictive power that was independent of that provided by the IPSS (p=0.002 and 0.001 respectively). Analysis of survival curves stratified for IPSS and DI showed that the additional predictive power offered by inclusion of the DI essentially concerned the IPSS low/INT-1 risk categories. Further stratification for age did not improve survival prediction. The data indicate that a set of 4 dysplasia parameters can offer some prediction for survival of MDS patients in addition to that provided by the IPSS. Further multicenter studies should aim at including some form of evaluation of the degree of dysplasia in prognostic systems. [less ▲]

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See detailPeripheral blood progenitor cell collections in cancer patients: analysis of factors affecting the yields.
Sautois, Brieuc ULg; Fraipont, V.; Baudoux, Etienne ULg et al

in Haematologica (1999), 84(4), 342-9

BACKGROUND AND OBJECTIVE: Peripheral blood progenitor cells (PBPC) are now widely used to restore hematopoiesis following high dose chemotherapy in patients with malignancies. We sought to identify ... [more ▼]

BACKGROUND AND OBJECTIVE: Peripheral blood progenitor cells (PBPC) are now widely used to restore hematopoiesis following high dose chemotherapy in patients with malignancies. We sought to identify parameters that could predict the yield of PBPC after mobilization with chemotherapy (CT) with or without granulocyte colony-stimulating factor (G-CSF) in cancer patients. DESIGN AND METHODS: One hundred and fifty patients underwent 627 PBPC collections during the recovery phase following CT with (n = 469) or without (n = 142) G-CSF. Hemogram, CFC-assays and CD34+ cell count were performed on peripheral blood and leukaphereses products. After log transformation of the data, differences between groups were assessed with the unpaired t-test or one-way analysis of variance. RESULTS: Seventeen and two patients required 2 and 3 mobilization cycles respectively to reach our target of 15x10(4) CFU-GM/kg. In patients with lymphoma but not in those with leukemia, the yields of both CFU-GM and CD34+ cells/kg were dramatically increased when G-CSF was added to CT for mobilization. In collections primed with CT and G-CSF, better yields were obtained in patients with breast cancer or small-cell lung carcinoma (SCLC) as opposed to other solid tumors and leukemia. Among potential predictive factors of CT- and G-CSF-primed harvests, we found that the CD34+ cell count in peripheral blood (PB) was strongly correlated with both the CFU-GM and CD34+ cell yields. Except in leukemia patients, more than 1x10(6) CD34+ cells/kg were harvested when the CD34+ cell count in blood was above 20x10(6)/L. Similarly, better results were obtained in collections performed when the percentage of myeloid progenitors in blood on the day of apheresis was above 5 % or when the leukocyte count in blood was above 5x10(9)/L. INTERPRETATION AND CONCLUSIONS: A diagnosis of breast cancer or SCLC, a leukocyte count in PB of more than 5x10(9)/L, more than 5% myeloid progenitors or more than 20x10(6) CD34+ cells/L in PB were associated with higher yields of PBPC in collections mobilized with CT+G-CSF. [less ▲]

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See detailFactors determining the percentage of hypochromic red blood cells in hemodialysis patients.
Bovy, Christophe ULg; Tsobo, C.; Crapanzano, L. et al

in Kidney International (1999), 56(3), 1113-9

Factors determining the percentage of hypochromic red blood cells determines iron status in hemodialysis patients. BACKGROUND: Determination of the percentage of hypochromic red blood cells (RBC; %HYPO ... [more ▼]

Factors determining the percentage of hypochromic red blood cells determines iron status in hemodialysis patients. BACKGROUND: Determination of the percentage of hypochromic red blood cells (RBC; %HYPO) has been advocated as a sensitive index of functional iron deficiency during erythropoietin (EPO) therapy in hemodialyzed patients. METHODS: The significance of %HYPO in chronic renal failure was evaluated in 64 chronically hemodialyzed patients. The linear correlation was determined between %HYPO and 13 variables, including age, sex, weight, C-reactive protein (CRP), ferritin, transferrin (Tf), Tf saturation, soluble Tf receptor (sTfR), serum iron (SI), urea, parathormone, dialysis dose (Kt/V), dose of EPO administered (EPO), and absolute reticulocyte count. Multiple regression analyses were then performed to select the parameters that jointly provide the best prediction of %HYPO. RESULTS: Univariate analysis showed significant correlations between %HYPO and iron parameters (sTfR, Tf saturation, SI, and ferritin, in decreasing order), EPO, reticulocyte count, and CRP. Multivariate analysis yielded an equation showing that the variation of %HYPO is essentially associated with the combined changes in sTfR, CRP, and EPO dosage. CONCLUSIONS: %HYPO is a meaningful and inexpensive parameter that reflects the integrated effects of iron stores, inflammation, and erythropoietic stimulation on iron availability in hemodialyzed patients. Among iron exchange parameters, sTfR is the best predictor of %HYPO, followed by Tf saturation, SI, and ferritin. [less ▲]

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See detailLes syndromes myélodysplasiques: syndromes préleucémiques
Tassin, Françoise ULg; Hermanne, Jean-Philippe; Schaaf-Lafontaine, Nicole ULg et al

in Revue Médicale de Liège (1998), 53(6), 357-62

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders characterized by peripheral blood cytopenias with a hypercellular bone marrow exhibiting dyspoiesis. The predominant in elderly ... [more ▼]

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders characterized by peripheral blood cytopenias with a hypercellular bone marrow exhibiting dyspoiesis. The predominant in elderly patients are associated with a high risk of progression to acute myelogenous leukemia. The etiology of MDS is unknown in most cases. About 10% of MDSs are secondary. MDS are classified by the French American British (FAB) classification into five subgroups. The incidence of the disorders is difficult to estimate but it seems to be increasing. Clonal cytogenetic aberrations are found in 30 to 50% of de novo MDS. The only currative treatment for MDS is allogeneic bone marrow transplantation. [less ▲]

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See detailCircadian and seasonal variations of hematopoiesis in cord blood.
Baudoux, E.; Beguin, Yves ULg; Cornu, G. et al

in Bone Marrow Transplantation (1998), 22 Suppl 1

Cord blood hematopoietic progenitors undergo circadian and seasonal variations. The lowest values are obtained between 4:00 and 12:00, as well as between May and August. This represents the first ... [more ▼]

Cord blood hematopoietic progenitors undergo circadian and seasonal variations. The lowest values are obtained between 4:00 and 12:00, as well as between May and August. This represents the first observation of such rhythms before birth. [less ▲]

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See detailHematopoietic recovery in cancer patients after transplantation of autologous peripheral blood CD34+ cells or unmanipulated peripheral blood stem and progenitor cells.
Beguin, Yves ULg; Baudoux, Etienne ULg; Sautois, Brieuc ULg et al

in Transfusion (1998), 38(2), 199-208

BACKGROUND: A study of CD34+ cell selection and transplantation was carried out with particular emphasis on characteristics of short- and long-term hematopoietic recovery. STUDY DESIGN AND METHODS ... [more ▼]

BACKGROUND: A study of CD34+ cell selection and transplantation was carried out with particular emphasis on characteristics of short- and long-term hematopoietic recovery. STUDY DESIGN AND METHODS: Peripheral blood stem and progenitor cells (PBPCs) were collected from 32 patients, and 17 CD34+ cell-selection procedures were carried out in 15 of the 32. One patient in whom two procedures failed to provide 1 x 10(6) CD34+ cells per kg was excluded from further analysis. After conditioning, patients received CD34+ cells (n = 10, CD34 group) or unmanipulated (n = 17, PBPC group) PBPCs containing equivalent amounts of CD34+ cells or progenitors. RESULTS: The yield of CD34+ cells was 53 percent (18-100) with a purity of 63 percent (49-82). The CD34+ fraction contained 66 percent of colony-forming units--granulocyte-macrophage (CFU-GM) and 58 percent of CFU of mixed lineages, but only 33 percent of burst-forming units-erythroid (BFU-E) (p < 0.05). Early recovery of neutrophils and reticulocytes was identical in the two groups, although a slight delay in platelet recovery may be seen with CD34+ cell selection. Late hematopoietic reconstitution, up to 1.5 years after transplant, was also similar. The two groups were thus combined for analyses of dose effects. A dose of 40 x 10(4) CFU-GM per kg ensured recovery of neutrophils to a level of 1 x 10(9) per L within 11 days, 15 x 10(4) CFU of mixed lineages per kg was associated with platelet independence within 11 days, and 100 x 10(4) BFU-E per kg predicted red cell independence within 13 days. However, a continuous effect of cell dose well beyond these thresholds was apparent, at least for neutrophil recovery. CONCLUSION: CD34+ cell selection, despite lower efficiency in collecting BFU-E, provides a suitable graft with hematopoietic capacity comparable to that of unmanipulated PBPCs. In both groups, all patients will eventually show hematopoietic recovery of all three lineages with 1 x 10(6) CD34+ cells per kg or 5 x 10(4) CFU-GM per kg, but a dose of 5 x 10(6) CD34+ cells or 40 x 10(4) CFU-GM per kg is critical to ensure rapid recovery. [less ▲]

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See detailA Strategy for Multiple Immunophenotyping by Image Cytometry: Model Studies Using Latex Microbeads Labeled with Seven Streptavidin-Bound Fluorochromes
Gothot, André ULg; Grosdent, J. C.; Paulus, Jean-Michel ULg

in Cytometry (1996), 24(3), 214-25

Multiple immunophenotyping is aimed at identifying several cell populations in a single labeling procedure by their ability to bind combinations of specific labeled antibodies. The present work ... [more ▼]

Multiple immunophenotyping is aimed at identifying several cell populations in a single labeling procedure by their ability to bind combinations of specific labeled antibodies. The present work demonstrates the simultaneous discrimination by using image cytometry of aminomethylcoumarin acetate (AMCA), Lucifer yellow (LY), fluorescein isothiocyanate (FITC), R-phycoerythrin (PE), PE-Texas red tandem (Red613), peridinin-chlorophyll protein (PerCP), and allophycocyanin (APC), which were all bound to latex beads as streptavidin-conjugated fluorochromes. This has been the result of a step-by-step optimization of the several factors affecting the sensitivity and specificity of multiple immunofluorescence analysis. First, 14 streptavidin-conjugated fluorochromes were evaluated by using spectrofluorometry. A primary selection was then made of ten spectrally separable dyes that could be evaluated by using image cytometry. These dyes were bound to latex particles, and specific filter combinations were assembled to minimize crosstalk between fluorophores while preserving sufficient fluorescence intensity and counting statistics. Potential probe associations were then assessed by measuring the emissions of all fluorochromes that were detected by each filter combination. The resulting crosstalk matrix served as the basic tool both for final selection of the optimal filter combination and for dye set (composed, in this case, of the seven fluorochromes described above) and for mathematical correction of residual spectral overlap. Next, an image cytometry system was adapted to collect seven images of matched brightness with the selected combination of excitation/emission filters and dichroic mirrors. Finally, seven-parameter synthetic images were generated by digital image processing. [less ▲]

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See detailFactors regulating megakaryocyte progenitor commitment to polyploidization.
Paulus, Jean-Michel ULg; Grosdent, J C; Prenant, M et al

in Comptes Rendus de l'Académie des Sciences. Série III. Sciences de la Vie (1995), 318(3), 381-6

Recognizable megakaryocytes are polyploid cells generated by a clonogenic, diploid progenitor, termed CFU-MKC (colony forming unit, megakaryocyte). In order to quantify polyploidization, ploidy histograms ... [more ▼]

Recognizable megakaryocytes are polyploid cells generated by a clonogenic, diploid progenitor, termed CFU-MKC (colony forming unit, megakaryocyte). In order to quantify polyploidization, ploidy histograms of megakaryocytes determined by microphotometric or flow cytometric measurements of megakaryocyte DNA have generally been used. However these techniques provide no information on the rate of commitment of CFU-MKC to polyploidy. Using a technique of clonal analysis determining the distributions of the number of doublings (NbD) undergone by CFU-MKC before committing to polyploidization, the polyploidization probability of CFU-MKC could be derived. This probability was found to be a constant independent from CFU-MKC mitotic history, since NbD distributions are exponential functions characterized by a constant rate of decay per doubling. By studying the effects of growth factors on polyploidization probability, it was also shown that: (1) this parameter is negatively regulated by growth factors contained in poke-weed or WEHI conditioned media, as well as by erythropoietin; (2) commitment to polyploidization does not require prior CFU-MKC division; (3) bipotent erythroid-megakaryocyte progenitors have a lower polyploidization probability than CFU-MKC; (4) determination of polyploidization probability reflects the activity of growth factors with greater accuracy than megakaryocyte colony count. [less ▲]

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See detailPurification, expansion, and multiple fluorochrome labeling of cord blood hemopoietic precursors: preliminary results.
Feron, C.; Gothot, André ULg; Grosdent, Jean-Claude ULg et al

in Journal of Hematotherapy (1993), 2(2), 259-61

CD34-positive cells were isolated from a total of 23 cords using CellPro Ceprate columns. AIS MicroCellector flasks, and panning. The cells were (1) expanded in serum-free culture supplemented with a ... [more ▼]

CD34-positive cells were isolated from a total of 23 cords using CellPro Ceprate columns. AIS MicroCellector flasks, and panning. The cells were (1) expanded in serum-free culture supplemented with a variety of combinations of cytokines and (2) immunophenotyped using multiple fluorochrome labeling. The results indicated that the avidin column produced the highest purity of CD34-positive cells, and that immature blast cells could be expanded in serum-free culture. Preliminary results suggested that the four fluorochrome labeling technique may provide useful information on the lineage commitment of cord blood precursor and blast cells. [less ▲]

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See detailThe Determination of Megakaryocyte Ploidy
Paulus, Jean-Michel ULg; Senterre, J. M.; von Frenckell, R.

in International Journal of Cell Cloning (1990), 8(4), 227-35

Methods which have been used to determine megakaryocyte ploidy in animals and humans are reviewed. Although the number of megakaryocyte nuclear units counted in bone marrow squashes is roughly ... [more ▼]

Methods which have been used to determine megakaryocyte ploidy in animals and humans are reviewed. Although the number of megakaryocyte nuclear units counted in bone marrow squashes is roughly proportional to ploidy, accurate determinations of DNA content require the use of microphotometry or flow cytometry. New techniques should make it possible to distinguish polyploidizing megakaryoblasts from promegakaryocytes and mature megakaryocytes which have arrested polyploidization. Only the latter should be included in histograms of the number of endoduplications, since only those have expressed their full polyploidization potential. Statistical techniques are available for analysis and comparison of both raw ploidy distributions or histograms of endoduplication numbers. [less ▲]

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