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Biomedical subjects

M Pascal

Publications and source records attributed to M Pascal.

At least 37 records · Page 2Linked to original sources
PubMed1996

Glycosaminoglycans enhance megakaryocytopoiesis by modifying the activities of hematopoietic growth regulators.

We have previously reported that heparin is capable of stimulating in vitro and in vivo megakaryocytopoiesis in mice and has a thrombopoietic effect when given in chronic immune thrombocytopenic purpura and that heparin and several other glycosaminoglycans (GAGs) promote the growth of human megakaryoblastic cell lines in the presence of serum. We show here that GAGs, including heparan sulfate (HS), chondroitin sulfate (CS), dermatan sulfate (DS), and hyaluronic acid (HA), also stimulate in vitro growth of murine megakaryocyte progenitors and augment the diameter of individual megakaryocytes in the presence of serum. However, in a serum-free agar system, the GAGs alone had no effect on megakaryocyte colony formation, suggesting that GAGs cooperate with some serum factor(s) to exert their activity. We also show that heparin significantly potentiates the megakaryocytopoietic activity of C-Mpl ligand and interleukin (IL)-6 but not IL3, GM-CSF, SCF, and Epo. In addition, the GAGs significantly neutralize the inhibitory action of platelet factor 4 (PF4) and transforming growth factor beta 1 (TGF beta 1) on megakaryocyte colony growth. These results demonstrate a stimulating activity of GAGs on megakaryocytopoiesis by modifying the activity of several growth-regulating factors.

Animals↗
PubMed1995

Evidence that protein kinase C and mitogen activated protein kinase are not involved in the mechanism by which insulin stimulates translation in L6 myoblasts.

Insulin stimulated a concentration-dependent increase in protein synthesis in L6 myoblasts which was significant at 1 nM. This response was not prevented by the transcription inhibitor, actinomycin D. The protein kinase C (PKC) inhibitor, Ro-31-8220, and downregulation of PKC by prolonged incubation of cells with 12-O-tetradecanoylphorbol-13-acetate (TPA), had no effect on the ability of insulin to stimulate protein synthesis whilst completely blocking the response to TPA. In contrast, insulin failed to enhance protein synthesis significantly in the presence of either ibuprofen, a selective cyclooxygenase inhibitor or rapamycin, an inhibitor of the 70 kDa S6 kinase. When cell extracts were prepared and assayed for total myelin basic protein kinase activity, a stimulatory effect of insulin was not observed until the concentration approached 100-fold (i.e. 100 nM) that required to elicit increases in protein synthesis. Upon fractionation on a Mono-Q column, 100 nM insulin increased the activity of 3 peaks which phosphorylated myelin basic protein. Two of these peaks were identified as the 42 and 44 kDa forms of Mitogen Activated Protein (MAP) kinase by immunoblotting. In contrast, 1 nM insulin had no effect on the activity of these peaks. The data suggest that physiologically relevant concentrations of insulin do not stimulate translation in L6 cells through either PKC or the 42/44 kDa isoforms of MAP kinase and that this response is, at least in part, mediated through the activation of the 70 kDa S6 kinase by cyclooxygenase metabolites.

Amino Acid Sequence↗
PubMed1994

Characterization of rat aortic smooth muscle cells resistant to the antiproliferative activity of heparin following long-term heparin treatment.

Vascular smooth muscle cells (SMC) do not represent a homogeneous population (Schwartz et al., 1990, Am. J. Pathol. 136: 1417-1428). Cellular clones resistant to the antiproliferative activity of heparin were isolated from rat aortic SMC cultures (Pukac et al., 1990, Cell Regul., 1:435-443; San Antonio et al., 1993, Arterioscler. Thromb., 13:748-757) and from explant of human arterial restenotic lesions (Chan et al., 1993, Lancet, 341:341-342). We have shown in the present study that long-term treatment (growth medium supplemented with 200 micrograms/ml heparin, from the second to the tenth passage) of rat aortic SMC, without cell cloning, resulted in a significant loss of sensitivity to the growth inhibition by heparin and its derivatives. The heparin resistance was stable after growing cells for two passages in heparin-free medium, suggesting the selection of a particular phenotype. We tried to characterize these cells and to determine the causes of the resistance to the growth inhibition by heparin. Heparin-treated SMC (HT-SMC) were smaller than their control culture at the same passage, expressed less alpha-SM actin, and did not overgrow after reaching confluence. As in the heparin-resistant clones (San Antonio et al., 1993, Cell Regul., 1:435-443) expression of alpha-SM actin could be increased in HT-SMC by heparin addition before Western blotting. Heparin resistance was associated with a tenfold decrease in [3H]-heparin binding capacity (Bmax = 1.9 x 10(6) sites per cell) compared to control cultures (Bmax = 1.7 x 10(7) sites per cell), which was irreversible after growing the cells for two additional passages in heparin-free medium. We also investigated protein kinase C (PKC) in HT-SMC in terms of both enzymatic activity and protein expression (evaluated by [3H]-staurosporine and [3H]-phorbol-12,13-dibutyrate binding). We found that HT-SMC had only half the PKC activity and expression as control SMC. Therefore, long-term treatment of rat aortic SMC with heparin allowed the selection of a less differentiated subpopulation of cells, exhibiting low sensitivity to the growth inhibition by heparin, which could be related to the low capacity of binding heparin and to a lower PKC activity and/or expression.

Animals↗
PubMed1994

Defined glycosaminoglycan motifs have opposite effects on neuronal polarity in vitro.

We previously reported that heparan sulfates enhance axonal outgrowth and inhibit dendrite elongation, whereas dermatan sulfates favor the development of both axons and dendrites. The present study focuses on the activity of small synthetic heparan or dermatan sulfate-like compounds. We found three heparan sulfate-like and three dermatan sulfate-like sugars that mimic the morphological effects of the high-molecular-weight natural glycosaminoglycans. Indeed, heparan sulfate-like compounds enhance axonal maturation and inhibit dendrite growth whereas the active sugars from the dermatan sulfate series act primarily on the elongation of cortical dendrites. The effect of dermatan sulfate-like sugars on cortical dendrite growth is only observed on the subpopulation of neurons with an established axon. We also studied the effects of the synthetic sugars on motoneurons. We found that the response of motoneurons to heparan sulfate-like compounds is indistinguishable from that of cortical neurons but that dermatan sulfate-like sugars do not enhance the development of motoneuron dendrites. The distinct effects of the two types of sugars and the fact that their activity only requires a short period of contact with the cells suggest the existence of specific binding sites for dermatan-like and heparan-like compounds. This possibility is reinforced by the fact that the binding and internalization of natural heparin fragments by neurons in culture is competitively inhibited by synthetic heparan sulfate-like derivatives, but not by dermatan sulfate-like derivatives.

Animals↗
PubMed1994

Fraxiparin, a low-molecular-weight heparin, stimulates megakaryocytopoiesis in vitro and in vivo in mice.

The effect of a low-molecular-weight heparin, faxiparin (Nadroparin), on murine megakaryocytopoiesis in vitro and in vivo was studied in comparison with unfractionated heparin. The addition of fraxiparin at 1-20 IU/ml into plasma clot cultures but not serum-free agar culture significantly enhanced MK colony growth. Furthermore, fraxiparin was found to potentiate the stimulating activity of aplastic anaemia serum (AAS) but not stem cell factor (SCF), interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin (Epo), on MK colony growth in vitro, and to neutralize the inhibitory effect of platelet factor 4 (PF4) in vitro and in vivo. Fraxiparin also acted synergistically with heparin cofactor II and antithrombin III to promote megakaryocyte colony formation. Intraperitoneal administration of fraxiparin twice daily for 4 d at 0.1-25 IU/injection increased in mice the level of blood platelet counts and the number of single MKs and CFU-MK in bone marrow. These data demonstrate that fraxiparin is able to positively regulate megakaryocytopoiesis.

Animals↗
PubMed1992

O-acylated heparin derivatives with low anticoagulant activity decrease proliferation and increase alpha-smooth muscle actin expression in cultured arterial smooth muscle cells.

Selectively O-acylated derivatives of various glycosaminoglycans were prepared and tested in vitro for their anticoagulant activity and their antiproliferative effect on rat and rabbit smooth muscle cells. When O-acylation (butyrylation or hexanoylation) had been performed on periodate-depolymerized heparin fragments having very low anticoagulant activity, the antiproliferative potency was markedly increased (IC50 = 2 and 1 micrograms/ml respectively, versus 31 micrograms/ml for starting compound) without an increase in anticoagulant activity. The antiproliferative activity was related to the degree of acylation. The O-acylated derivatives of heparin fragments were also very active in reversing the de-differentiation of smooth muscle cell in culture, as estimated by the increase in the expression of alpha-smooth muscle actin and alpha-smooth muscle actin mRNA.

Actins↗
PubMed1991

Thymectomy at weaning. An accelerated aging model for the mouse immune system.

Mouse thymectomy at weaning induces a long lasting immunodepression which can be measured by in vivo and in vitro experiments. Lymphocyte proliferation and IL2 production in response to a T cell mitogen are greatly diminished during the whole life of the animals, on the contrary B cell proliferation in the presence of lipopolysaccharide is not modified. The lack of effect of surgery on the in vitro T cytotoxic activity compared to the total abolition of in vivo graft versus host reaction shows that these two phenomena are under the control of different immunocompetent cell subsets. Thymectomy induces a stabilization of natural killer cell activity, while during normal aging, this parameter decreases regularly. Surprisingly, the thy 1+ cell level is normal 8-10 months after thymectomy compared to sham operated animals showing that phenotypically normal cells can be dysfunctional. Macrophage activity is not modified either by aging or by thymectomy. So, thymectomized mice can be used after less than 1 year to study immunopharmacology of aging.

Aging↗
PubMed1991

Implications of prostaglandin E2 synthesis and phospholipase C activation in potentiation of T-cell proliferation by LF 1695.

Murine spleen cells, T-enriched by nylon wool filtration, proliferate in the presence of a protein kinase C stimulator and a calcium ionophore. Using this cell proliferation system, we show that LF 1695 can potentiate phorbol myristate acetate (PMA) action in the presence of A 23187. This potentiation can be due to PGE2 inhibition since it is found that lipopolysaccharide (LPS) or A 23187 induced PGE2 release from spleen cells is inhibited by LF 1695. Indomethacin and LF 1695 gave similar stimulation of spleen cell proliferation, and exogeneously added PGE2 inhibits this phenomenon. Considering two of the main early components of intracellular signal transduction, LF 1695 induces IP3 release and calcium mobilization. However, the compound is not mitogenic per se. These results show that LF 1695 behaves only as a costimulant for T-cell proliferation.

Animals↗
PubMed1991

A new immunomodulator, LF 1695--II. Effects on allogenic and antigenic responses.

LF 1695, a chemically defined immunomodulator has been shown to induce in vitro T-cell differentiation and to potentiate mitogenic proliferation. The effects of LF 1695 on antigenic and allogenic responses were studied in vitro and lymphocyte proliferation was estimated by 3H-thymidine uptake for 5 and 6 days, respectively. Human peripheral blood lymphocytes (PBL) from tuberculin sensitive donors were significantly stimulated by purified protein derivative (PPD) in the presence of LF 1695. Optimal lymphocyte proliferation with PPD was obtained at 0.5 micrograms/ml LF 1695. The ability of LF 1695 to enhance proliferation of PBL in an allogenic reaction was also examined. LF 1695 (0.2 micrograms/ml) enhanced the proliferation of PBL from two individuals with different HLA DR loci in the bilateral mixed lymphocyte reaction (MLR). Moreover, LF 1695 was tested in vivo in the experimental graft vs host reaction (GvHR) in mice. CBA, H2k mice receiving a lethal dose of irradiation were injected with spleen cells from LF 1695-treated or untreated C57 Bl/6, H2b mice via different routes. CBA mice were found to have a spleen weight x 1000/body ratio up to 1.5 when injected with cells from untreated C57 Bl/6 mice. Mice treated intraperitoneally with LF 1695 at 2.5 or 5 mg/kg/day showed an increase of GvHR intensity with splenic index of 1.71 and 1.80, respectively. When the animals were treated continuously through drinking water containing LF 1695 (4 mg/kg, 10 mg/kg or 100 mg/kg), these ratios were: 1.82, 1.10 and 1.37, respectively. Finally, LF 1695 enhanced GvHR significantly when used at low doses, while high doses induced a decrease of GvHR intensity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

(Benzoylphenyl)piperidines: a new class of immunomodulators.

A series of (benzoylphenyl)piperidines has been synthesized and evaluated for activity as immunomodulators. Several of these compounds show good activity in primary screening on the basis of the lymphocytes mitogenic response to Con A, PHA, and PWM. A chloro group in position 4 of the benzoyl moiety as well as an amino group (or a carbamate derivative) para to the piperidine nucleus seems to be essential for activity. The depicted compounds may be considered as the first examples of a new series of immunomodulators.

Adjuvants, Immunologic↗
PubMed1991

Discontinuation of lithium treatment in remitted bipolar patients: relationship between clinical outcome and changes in sleep-wake cycles.

In this preliminary report, we describe four patients in whom long-term lithium therapy was discontinued, combined with actigraphic monitoring to assess changes in motor activity and the sleep-wake cycle. Two patients experienced rapid relapse of manic symptomatology, while two remained stable throughout a 1-year follow-up. Actigraphic monitoring revealed disintegration of the sleep-wake cycle and increased motor activity in the relapsed patients only. It is suggested that actigraphic recordings can be used to monitor lithium discontinuation.

Ambulatory Care↗
PubMed1989

Stimulation of 12-HETE production in human platelets by an immunomodulator, LF 1695. Evidence for activation of arachidonate liberation coupled to cyclo-oxygenase inhibition.

Upon incubation with human platelets previously labelled with [14C]arachidonic acid, a new immunomodulator, LF 1695, induced the accumulation of [14C]-12-(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE). Although the time course of [14C]HETE accumulation was identical with 60 microM LF 1695 and calcium ionophore A23187, the latter compound also promoted the formation of 14C-labelled thromboxane B2 and 12-(S)-hydroxy-5,8,10-heptadecatrienoic acid (HHT), whereas 12-HETE was the only arachidonic acid metabolite generated under the action of LF 1695, suggesting that the drug inhibited cyclo-oxygenase. This was further confirmed by the fact that LF 1695 inhibited the second wave of platelet aggregation induced by ADP as well as arachidonic acid effects. Cell lipid analysis revealed that arachidonic acid was liberated from both triacylglycerol and phosphatidylcholine. The effect was observed in the concentration range 15-90 microM, with a half-maximal effect at 30 microM for HETE production, 15 microM for triacylglycerol hydrolysis and 45 microM for phosphatidylcholine deacylation. Incubation of platelets with [14C]arachidonic acid in the presence of 60 microM LF 1695 resulted in a strong inhibition of arachidonic acid incorporation into the various cell lipids, indicating that arachidonic acid mobilization might be due to inhibition of reacylation processes. It is concluded that LF 1695 displays an original and complex effect on platelet lipid metabolism, resulting in the specific generation of lipoxygenase metabolites.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1988

Detection of atherosclerotic plaque with two monoclonal antibodies. 2P1A2 monoclonal antibody is specific for smooth muscle cells in atherosclerotic plaque.

We investigated two monoclonal antibodies (MAbs) which recognize rabbit atherosclerotic tissues. In particular, one antibody, 2P1A2, is specific for rabbit aortic smooth muscle cells (RASMCs). We used RASMCs in primary culture to produce and screen MAbs directed towards the cell surface. The specificity of the described antibodies was tested on a battery of tissue cryosections of different origin (rabbit, rat and human) by immunological staining. 2P1A2 shows an exclusive immunolabeling for SMCs present inside rabbit atherosclerotic plaque. This MAb shows inside the fibrous plaque a staining similar to two other SMC-specific antibodies (anti-desmin and anti-alpha-actin). In an early stage of atherosclerosis, close to the internal elastic lamina, underlying a fibrous plaque, 2P1A2 detects some SMCs; in contrast, anti-desmin and anti-alpha-actin fail to stain such SMCs. This antibody may be therefore considered as directed specifically against SMCs in an activated state. The other antibody which we describe, 1PC1, stains a pericellular antigen expressed by cultured SMCs and shows a specificity for smooth muscle tissues. 1PC1 MAb strongly stains the fibrous plaque of atherosclerotic rabbit aorta and the recognized epitope is present inside the aortic media. These two antibodies may be useful in the recognition of vascular SMCs during the atherosclerotic process.

Animals↗
PubMed1988

In vitro and in vivo immunomodulation by LF 1695 of human and rat macrophages and platelets in schistosomiasis.

The activity of the synthetic immunomodulator LF 1695 on the efficiency of two effector cell populations--macrophages and blood platelets--involved in IgE-dependent cytotoxic processes against parasites, was evaluated. Oxygen metabolite production and anti-parasite cytotoxic properties of both macrophages and platelets were increased following LF 1695 treatment in vivo (in rat) or in vitro (in rat and in man). The phagocytic properties of rat peritoneal macrophages were also potentiated by their in vitro incubation with the drug. In addition to these effector functions, the lysosomal enzyme content and the migration ability of rat peritoneal macrophages were stimulated after incubation with LF 1695. In the presence of the drug, rat macrophages were also shown to produce increased level of IL-1--measured by the mitogen-induced proliferation of murine thymocytes--when compared to unstimulated phagocytes. Finally, the oral treatment of rats with LF 1695, in the course of an experimental infection with schistosome parasites, induced a higher degree of immune protection (80%) against a challenge infection than untreated, infected control rats (40%). These results bring evidence of a stimulatory role for LF 1695 on immune effector functions of cells participating to defense mechanisms against multicellular pathogens.

Adjuvants, Immunologic↗
PubMed1987

Effects of fenofibrate treatment on fatty acid oxidation in liver mitochondria of obese Zucker rats.

Obese Zucker rats were dosed orally for one week with fenofibrate (100 mg/kg). Liver weights of treated rats as expressed as percent of body weight were slightly increased, while protein, DNA and lipid contents were unaffected per g of liver or increased when expressed in whole liver. Compared with the control animals, activities of fatty acid oxidase, of the peroxisomal fatty acid-oxidizing system and of catalase were markedly increased by fenofibrate both per g of liver and per total liver, while urate oxidase activity was unchanged when expressed per g of liver. The activity of monoamine oxidase and that of cytochrome c oxidase used as marker enzymes for mitochondria were increased only when expressed per total liver. However, fenofibrate treatment induced a pronounced increase in the activities of mitochondrial palmitoyl-CoA dehydrogenase and carnitine acyltransferases, particularly carnitine acetyltransferase. Fenofibrate also caused a significant increase of carnitine content in liver and hepatic mitochondria. The greatest observed increases were in free carnitine and in the rate of carnitine-dependent oleate oxidation, which might be favoured in vivo by a lesser sensitivity of CPT-I to a malonyl-CoA inhibitory effect. The present results suggest that fenofibrate treatment induces increased hepatic mitochondrial beta-oxidation in obese Zucker rats.

Animals↗
PubMed1987

A new experimental model of venous thrombosis in rats involving partial stasis and slight endothelium alterations.

Venous thrombus formation is induced in rats using saline flushing in a venous bag created in the vena cava and subsequent stasis by stricture of the vein. Maximum thrombus weight is obtained in 15 minutes. Neither flushing nor partial stasis alone could trigger thrombus formation during this time. Transmission electron microscopy demonstrated that flushing induces discrete endothelial lesions with no evident desendothelialisation areas. Anticoagulant agents are found to be active in preventing thrombus formation. However, heparin or related compounds such as pentosan polysulphate are active at dose levels not demonstrating anticoagulant activity. Thrombosis could be induced in thrombocytopenic rats indicating the non-involving of platelets. Moreover, aspirin did not prevent thrombus formation. Ticlopidine, another antiplatelet agent, did show an activity which might not involved platelets. This model thus possesses the features necessary for reliable investigation of potential antithrombotic agents for human use.

Animals↗
PubMed1986

Increased interleukin-1 and modulation of interleukin-2 production by murine macrophages and lymphocytes treated with LF 1695.

Previous results have demonstrated that lectin-induced T cell proliferation was potentiated or suppressed by LF 1695, a synthetic immunomodulator, depending on the dose used. Therefore the activity of this compound was investigated on murine IL-1 and IL-2 production. Adherent peritoneal cells, incubated with LF 1695, could secrete high levels of IL-1 with only a slight elevation in intracellular IL-1. This effect apparent at 5 and 10 micrograms/ml was linked to a transient state of activation. At low doses, LF 1695 increased IL-2 production by Con A-stimulated spleen cells. A decrease was found at higher doses only when cells were preincubated 20 h with the compound. In murine macrophages stimulated either by A 23187 or LPS PGE2 synthesis was inhibited by LF 1695 even at low doses. However, supernatant LTB4 level was increased in LF 1695-treated culture with a time-dependent effect. Therefore modulation of lectin-induced T cell proliferation by LF 1695 may be IL-2 production-mediated. Inhibition of the cyclooxygenase and stimulation of the lipoxygenase pathway of arachidonic acid metabolism may be responsible for this pattern of activity.

Animals↗