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V Praloran

Publications and source records attributed to V Praloran.

At least 91 records · Page 5Linked to original sources
PubMed1996

PAF and hematopoiesis. VIII. Biosynthesis and metabolism of PAF by human bone marrow stromal cells.

Human bone marrow stromal cells were studied for their ability to synthesize and to metabolize platelet-activating factor (PAF), a lipidic compound with potent immunoregulatory properties. When stimulated with 2 microM calcium ionophore for 60 minutes, cultures of stromal cells increased their PAF production (3.52 +/- 0.91 ng/1 x 10(6) cells) compared with controls (0.82 +/- 0.13 ng/1 x 10(6) cells). Addition of exogenous lyso PAF (100 nM) and acetyl-CoA (100 microM) during calcium ionophore stimulation did not change the PAF production. The synthesis of PAF was not influenced by the concentration of albumin in the incubation buffer. The PAF from stromal cells exhibited a hexadecyl chain at the sn-1 position of the molecule, as determined by reverse-phase HPLC. While stromal cells contained low amounts of PAF acetylhydrolase activity and did not secrete it in the culture medium, they metabolized exogenous PAF with 1-alkyl-2-acyl-glycero-phosphocholine and neutral lipids as the major metabolic products. The present results are the first to demonstrate the synthesis and metabolism of PAF by human bone marrow stromal cells. These data suggest that they might be a source of the PAF found in the human bone marrow and/or might be important in the regulation of its levels. The role of PAF on the proliferation and functions of human hematopoietic cells deserves investigation.

Bone Marrow↗
PubMed1995

PAF and haematopoiesis: III. Presence and metabolism of platelet-activating factor in human bone marrow.

Platelet-activating factor (PAF) is a phospholipid compound with major immunoregulatory activities. The present study shows that human bone marrow contains 576 +/- 39 pg PAF/ml (n = 35). Bone marrow-derived PAF exhibits the same biophysical and biological properties that synthetic PAF. PAF concentrations in bone marrow are correlated with the granulocyte (r = 0.4, P = 0.02) but not with the lymphocyte (r = 0.24, P = 0.17) and the monocyte (r = 0.12, P = 0.48) counts. In bone marrow PAF is inactivated by a plasma PAF acetylhydrolase activity (48.0 +/- 2.3 nmol/min per ml, n = 34). Experiments with [3H]PAF indicate that human bone marrow cells actively metabolize this potent molecule by the deacetylation-transacylation pathway. Results of this investigation indicate the permanent presence of significant amounts of PAF in bone marrow suggesting its putative involvement in the processes of bone marrow cell proliferation and maturation.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1995

PAF and haematopoiesis. IV. Modifications of spleen and thymus PAF contents after a single dose of the chemotherapeutic drug 5-fluorouracil in mice.

The spleen and thymus of mice were examined for the presence of PAF after injection of 5-fluorouracil (5-FU) (200 mg/kg). A significant increase of the spleen (P = 0.005) and thymus (P < 0.05) PAF concentrations was noted 48 h after 5-FU infusion. PAF levels in thymus are similar to those of controls from days 4 to 14. By contrast, spleen PAF significantly decreased (0.005 < P < 0.03) from days 7 to 14. Conversely, the 5-FU administration did not modify the spleen and plasma acetylhydrolase activity, suggesting that the variations of PAF levels in thymus and spleen were mainly due to differences of local PAF production. Thus, the chemotherapeutic drug 5-FU modulates in vivo PAF production in haematopoietic organs of mice. Considering the effects of PAF in the processes of B- and T-cell proliferation and functions, these results could be of importance for the role of PAF during human cancer therapy and haematopoiesis in vivo.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1995

The concentrations of AcSDKP, a physiological inhibitor of cell proliferation, vary during oogenesis and early development in Xenopus laevis.

The endogenous tetrapeptide AcSer-Asp-Lys-Pro (AcSDKP) is present in the circulation and cells of mammals. Extracellular AcSDKP is a negative regulator of cell proliferation inhibiting the S phase entry of numerous cell types such as hematopoietic progenitors, hepatocytes, lymphocytes and several continuous cell lines. In contrast, the biological role of cellular AcSDKP remains unknown. We have recently reported a decrease of cellular AcSDKP concentrations by 50% accompanying the initiation of DNA synthesis in mitogen-induced proliferation of human lymphocytes. In the present study we measured the variations of cellular AcSDKP concentrations during oogenesis and early development of Xenopus. Cellular AcSDKP concentrations peaked at stage IV of oogenesis and then continuously decreased during the final oocyte maturation and during the initial 15-h period of exponential cell division of the embryo. Altogether, our present and previously published data suggest that cellular AcSDKP may be involved in the regulation of cell proliferation in eukaryotic species.

Amino Acid Sequence↗
PubMed1995

Collagen matrix: an attractive alternative to agar and methylcellulose for the culture of hematopoietic progenitors in autologous transplantation products.

Autografts using untreated or in vitro manipulated bone marrow and peripheral blood stem cells represent promising approaches to the treatment of malignant diseases. In this work, the collagen gel culture technique was compared with agar and methylcellulose for its capacity to permit the growth of human granulomonocytic (day 14 CFU-GM; collagen vs agar or MTC) or erythroblastic (day 7 CFU-E and day 14 BFU-E; collagen versus methylcellulose) colonies in autologous transplantation products. Our results show that the collagen culture system always gave as many or more colonies than the other techniques. It also allowed harvesting of gels onto glass slides and subsequent May-Grünwald-Giemsa, cytochemical or immunocytochemical staining. We suggest that the collagen assay represents an interesting alternative to the widely used agar or methylcellulose systems for the culture of hematopoietic progenitors because of the equal or higher number of colonies detected, the easy phenotypical identification of colonies in stained gels, and the ability to store high-quality documentation. This technique is particularly attractive for use in the quality control of autologous bone marrow transplantation procedures.

Agar↗
PubMed1995

AcSDKP serum concentrations vary during chemotherapy in patients with acute myeloid leukaemia.

AcSDKP is a physiological negative regulator of cell proliferation in mammals. In Ara-C-treated mice its plasmatic concentrations decrease while the CFU-S start cycling. Infusion of AcSDKP protects these animals from death by blocking the proliferation of primitive haemopoietic cells. We measured AcSDKP serum concentrations in 20 AML patients during the course of high-dose cytoreductive treatment. We observed an early and sharp increase of AcSDKP during the induction treatment in 12 patients, reaching a peak during the initial 3 d of treatment in nine of them. These results are contrary to those observed in mice treated with high doses of Ara-C. They encourage further clinical investigation, and suggest that treatments with synthetic AcSDKP (Seraspenide) will perhaps have to be adjusted to the type of disease and the schedule of chemotherapy in order to optimize its myeloprotective effect.

Acute Disease↗
PubMed1994

PAF and hematopoiesis. II. Elevated levels of plasma paf acetylhydrolase after rapid infusion of 5-fluorouracil in cancer patients.

Blood platelet-activating factor (PAF) levels are regulated by a plasma PAF acetylhydrolase. We investigated its levels in cancer patients during the course of a 5-day 5-fluorouracil (5-FU) treatment. PAF acetylhydrolase increased in nine patients with daily bolus infusion of 0.4 g 5-FU per m2 of body surface (81.7 +/- 8.7 nmol PAF/min/ml vs. 66.6 +/- 7.0; P < 0.001 for day 5 as compared to day 1). By contrast PAF acetylhydrolase did not change in seven patients with continuous infusion of 5-FU. The meaning of these results is discussed in respect of the immunoregulatory role of PAF.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1994

Expression and functionality of the trkA proto-oncogene product/NGF receptor in undifferentiated hematopoietic cells.

The expression of the low-affinity NGF receptor (p75) and the trkA proto-oncogene product was analyzed in a series of human hematopoietic cell lines at protein and RNA levels. We did not detect any form of NGF receptor in cell lines displaying a myelomonocytic phenotype (HL60 and U937). In contrast, cells displaying a more immature erythroleukemic phenotype (TF1 and K562) expressed TrkA in the absence of detectable p75. Scatchard analysis showed a single high-affinity site for NGF (kd = 10(-10) mol/L), with a copy number ranging from 300 to 3,000 sites per cell depending on the studied cell line. In addition, NGF induced autophosphorylation of TrkA and could substitute for granulocyte-monocyte colony-stimulating factor to trigger the proliferation of the TF1 cell line, with a half-maximal signal observed at 50 pmol/L, indicating that p75 is not required for DNA synthesis in this cell line. The physiologic relevance of NGF in early hematopoiesis was confirmed by showing that 12% to 15% of progenitor blood cells from mice treated with 5-fluorouracil expressed TrkA and that these cells could be induced to proliferate and differentiate in response to NGF in association with macrophage colony-stimulating factor. Our study demonstrates for the first time that trkA proto-oncogene expression and activation is not restricted to the nervous system, but is also an important element in early hematopoiesis.

Animals↗
PubMed1994

Monocyte activity in the presence of calcium phosphate activated by 1,25 (OH)2 VD3 and interferon-gamma.

The monocyte is an essential element in cellular immunity. Consequently, its role in the biocompatibility process is important. A model study of the degradation of bioactive ceramics (calcium phosphate) using human peripheral blood monocytes activated by 1,25 (OH)2 VD3 and interferon (IFN)-gamma was implemented. Activated monocytes cultivated on calcium phosphate tablets led to cellular morphological modifications and to changes in the number of nuclei (from d 2 to 14). IFN-gamma promoted adhesion, the appearance of cytoplasmic extensions and multinuclei. Cavity resorption activity on the material was observed simultaneously.

Biocompatible Materials↗
PubMed1994

Elevation of serum M-CSF concentrations during pregnancy and ovarian hyperstimulation.

Macrophage colony stimulating factor (CSF-1 or M-CSF) is involved in haemopoiesis and probably in mouse gestation. Sexual steroids induce its production by uterine glandular epithelial cells and its receptor (product of the protooncogene C-FMS) is expressed on placental trophoblastic cells. We measured M-CSF serum levels in 119 pregnant women and in eight women undergoing ovarian hyperstimulation for in vitro fertilization. M-CSF increased early (4-8 weeks) and progressively during gestation. Its rapid elevation during the course of ovarian hyperstimulation suggests that its synthesis is probably induced by sexual steroids. This locally produced M-CSF could play a role in human pregnancy and in the pathogenesis of thrombocytopenias observed during pregnancy.

Adolescent↗
PubMed1993

High titre anticytokine antibodies obtained by intralymphnode immunization with low amounts of antigen.

Intralymphnode immunization was performed on rabbits to obtain anticytokine antibodies using low or very low amounts of the following purified cytokines: CSF-1 (or M-CSF: 10, 2 or 0.2 microgram/injection), GM-CSF (10 micrograms/injection), IL-2 (10 micrograms/injection) and HILDA/LIF (10 micrograms for the first injection and 5 micrograms/injection for boosts). This technique is easily performed by dissection of the popliteal lymphnode. Specific high titre antibodies were obtained after the first or second boost for antigen doses between 10 (for all cytokines tested) and 0.2 microgram (for CSF-1) per injection. In most cases, these antibodies could be used for immunoprecipitation, competition assays, dot immunoblotting, neutralization of biological activity and receptor binding inhibition. Some applications show that these tools are useful for cytokine research projects. For newly identified cytokines available in limited amounts, this method of obtaining specific polyclonal antibodies is an interesting alternative to the expensive, time-consuming and technically more demanding monoclonal antibody method.

Animals↗