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C Legrand

Publications and source records attributed to C Legrand.

At least 73 records · Page 4Linked to original sources
PubMed1997

Induction of thrombospondin-1 by all-trans retinoic acid modulates growth and differentiation of HL-60 myeloid leukemia cells.

Thrombospondin-1 (TSP), a multifunctional extracellular matrix protein, modulates human hematopoietic stem cell adherence and thus may play a role in blood cell proliferation and/or differentiation. The expression of TSP was studied in the human myeloid leukemia cell line, HL-60, upon differentiation into monocytes by phorbol-13-monoacetate (PMA) or into granulocytes by all-trans retinoic acid (RA). HL-60 cells cultured under serum-free conditions constitutively secreted low amounts of TSP into the cultured medium, approximately 13 ng/10(6) cells/24 h. PMA used at 4 x 10(-8) M did not significantly modulate TSP secretion over a 24 h period. In contrast, RA at 10(-7) M induced a 5- to 10-fold increase in TSP secreted by HL-60 cells during their differentiation into granulocytes over a 5 day period. The role of secreted TSP in RA-dependent cessation of growth and differentiation was examined using blocking anti-TSP antibodies. In the presence of the polyclonal anti-TSP antibody R5 (25 microg/ml), growth of RA-treated HL-60 cells was maintained at control levels for up to 3 days and a concomitant delay in granulocytic differentiation was observed. Moreover, the addition of soluble TSP (0.5-5 microg/ml) to untreated HL-60 cells decreased their growth and promoted their differentiation in a dose-dependent manner. Using a neutralizing antibody to transforming growth factor beta (TGF-beta) or purified TGF-beta1 we further demonstrated that the effects of TSP were not mediated through activation of latent TGF-beta. These studies indicate that TSP decreases the proliferation and promotes the differentiation of HL-60 cells.

Cell Differentiation↗
PubMed1997

The alpha1B-adrenergic receptor subtype activates the phospholipase C signaling pathway in rat myometrium at parturition.

This study demonstrates that alpha1-adrenergic receptors previously identified in the pregnant rat myometrium are heterogeneous. They can be subtyped alpha1A- and alpha1B-adrenergic receptors on the basis of their affinity for the antagonists WB4101 (alpha1A > alpha1B) and chloroethylclonidine (alpha1B selective). Between Day 21 of pregnancy and term, the proportion of [3H]prazosin binding sites with low affinity for WB4101 and sensitive to inactivation by 10(-5) M chloroethylclonidine under hypotonic conditions (alpha1B subtype) remained constant. In contrast, the number of [3H]prazosin binding sites with a high affinity for WB4101 and insensitive to chloroethylclonidine (alpha1A subtype) increased by 88% at term. The effect of 5'-guanylylimidodiphosphate (Gpp[NH]p) on competition of the agonist phenylephrine for [3H]prazosin binding in the presence of WB4101 or after chloroethylclonidine pretreatment indicates that the alpha1A-adrenergic receptor underwent uncoupling whereas the alpha1B-adrenergic receptor-G protein coupled state was increased (+ 63%). Phenylephrine consistently stimulated phospholipase C activity on membrane fractions prepared from term myometria. This stimulation was completely inhibited after 10(-5) M chloroethylclonidine but was not consistently decreased with 5-methylurapidyl, a selective alpha1A-antagonist. Furthermore QL antibody (anti-G alpha(q)/G alpha11) also specifically blocked the phenylephrine-stimulated phospholipase C activity. Altogether these results strongly suggest that activation of the alpha1B-adrenergic receptor subtype in the pregnant myometrium at term may contribute to the stimulation of the G alpha(q)/G alpha11/phospholipase C signaling pathway.

Adrenergic alpha-Agonists↗
PubMed1997

Evidence for an alpha-granular pool of the cytoskeletal protein alpha-actinin in human platelets that redistributes with the adhesive glycoprotein thrombospondin-1 during the exocytotic process.

In a previous study, we have demonstrated that the platelet adhesive glycoprotein thrombospondin-1 (TSP-1) interacts specifically with the cytoskeletal protein alpha-actinin in a solid-phase binding assay. Stored in the alpha-granules of platelets, TSP-1 is secreted during cell activation and binds to the plasma membrane promoting the platelet macroaggregate formation. However, the molecular mechanism by which TSP-1 reaches and binds to the platelet surface is to date unelucidated. alpha-Actinin is an actin-binding and actinin-cross-linking protein that is present in most cells and may act as a link between the bundles of F-actin and the plasma membrane. In this study, we have investigated a possible interaction of alpha-actinin with TSP-1 in platelets by examining their respective subcellular location during the platelet activation process. By indirect immunofluorescence. alpha-actinin was found to display a granular staining in resting platelets similar to that of TSP-1. Performing postembedding immunogold labeling for electron microscopy, we detected the presence of alpha-actinin throughout the cytoplasm, but the strongest gold staining was found in organelles identified as alpha-granules on the basis of their ultrastructure and TSP-1 content. With the use of double immunogold labeling on platelets at different stages of activation by thrombin, both alpha-actinin and TSP-1 were seen redistributing from the alpha-granules to the platelet surface via the open canalicular system (OCS). At the same time, the cytoplasmic alpha-actinin concentrated toward the plasma membrane, but no colocalization with the F-actin bundles was evidenced. Finally, preembedding immunogold labeling and immunoprecipitation of 125I-surface-labeled, thrombin-activated platelets further demonstrated that alpha-actinin was expressed on the plasma membrane in the absence of any detectable expression of actin and that it could from molecular complexes with TSP-1 on activated platelets. These results suggest that alpha-actinin found to be present on the platelet surface together with TSP-1 originates in the alpha-granules by fusion of the alpha-granules with the plasma membrane during platelet exocytosis.

Actinin↗
PubMed1997

Identification of transcripts initiated from an internal promoter in the c-erbA alpha locus that encode inhibitors of retinoic acid receptor-alpha and triiodothyronine receptor activities.

The thyroid hormone receptor-coding locus, c-erbA alpha, generates several mRNAs originating from a single primary transcript that undergoes alternative splicing. We have identified for the first time two new transcripts, called TRdelta alpha1 and TRdelta alpha2 [mRNA for isoform alpha1 and alpha2 of the T3 receptor (TR), respectively], whose transcription is initiated from an internal promoter located within intron 7 of the c-erbA alpha gene. These two new transcripts exhibit tissue-specific patterns of expression in the mouse. These two patterns are in sharp contrast with the expression patterns of the full-length transcripts generated from the c-erbA alpha locus. TR alpha1 and TRdelta alpha2 mRNAs encode N-terminally truncated isoforms of T3R alpha1 and T3R alpha2, respectively. The protein product of TRdelta alpha1 antagonizes the transcriptional activation elicited by T3 and retinoic acid. This protein inhibits the ligand-induced activating functions of T3R alpha1 and 9-cis-retinoic acid receptor-alpha but does not affect the retinoic acid-dependent activating function of retinoic acid receptor-alpha. We predict that these truncated proteins may work as down-regulators of transcriptional activity of nuclear hormone receptors in vivo.

Animals↗
PubMed1996

Heparin-binding domain, type 1 and type 2 repeats of thrombospondin mediate its interaction with human breast cancer cells.

Thrombospondin is an adhesive glycoprotein that promotes breast cancer cell adhesion to human vascular endothelial cells (Incardona et al., 1995). In this study, we have identified the molecular domains of thrombospondin that mediate its binding to specific receptors on the human breast adenocarcinoma cell line, MDA-MB-231. Two recombinant fragments from the amino-terminus (TSPN18 and TSPN28), and the fusion proteins of the type 1 and type 2 repeats of human thrombospondin, inhibited binding of radiolabeled thrombospondin to MDA-MB-231 cells in suspension by 40-60% at 50 micrograms/ml whereas the type 3 repeat, carboxy-terminus and unfused glutathione-S-transferase as well as the synthetic peptide Gly-Arg-Gly-Asp-Ser (500 micrograms/ml) had little or no effect. Heparin and various glycosaminoglycans as heparan sulfate, chondroitin sulfates A, B or C, and fucoidan inhibited thrombospondin binding to MDA-MB-231 cells by more than 60% whereas dextran sulfate had only little effect. Treatment of cells with heparitinase, chondroitinase ABC, and hyaluronidase, but not with neuraminidase, induced 30-50% inhibition of thrombospondin binding suggesting the participation of both heparan sulfate and chondroitin sulfate cell surface-associated molecules. Inhibition of proteoglycan sulfation by chlorate or inhibition of glycosaminoglycan chain formation by two beta-D-xylosides also led to a substantial inhibition of thrombospondin binding. Our results indicate that several domains within the thrombospondin molecule, namely the amino-terminus, type 1 and type 2 repeats, participate in its binding to specific receptors bearing sulfated glycosaminoglycans on MDA-MB-231 cells. Biological assays have indicated that, in addition to these domains, the peptide Gly-Arg-Gly-Asp-Ser inhibited MDA-MB-231 cell attachment to thrombospondin suggesting that the last type 3 repeat of the molecule may also contribute to its cell adhesive activity.

Binding Sites↗
PubMed1996

Proteolysis of thrombospondin during cathepsin-G-induced platelet aggregation: functional role of the 165-kDa carboxy-terminal fragment.

The serine-proteinase cathepsin G (CG) is a potent agonist of platelet aggregation inducing the release and surface expression of alpha-granule adhesive proteins such as fibrinogen (Fg) and thrombospondin-1 (TSP-1). Because Fg and TSP-1 are potential substrates for the enzymatic activity of CG, we investigated the fate of these proteins during CG-induced platelet aggregation using an immunoblot technique. Only a small proportion of secreted Fg was proteolyzed by CG and platelet aggregation was efficiently inhibited by anti-fibrinogen Fab fragments. In contrast, TSP-1 was extensively proteolyzed on aggregated platelets releasing in the milieu a fragment with Mr approximately 28 000, corresponding to the amino-terminal heparin-binding domain (HBD). Several antibodies, directed against the cell-associated carboxy-terminal TSP-1f fragment (Mr approximately 165000) impaired the formation of stable macroaggregates, indicating that this fragment may contribute to platelet aggregation in the absence of the HBD.

Adult↗
PubMed1996

A rapid and convenient method to prepare DIG-labelled RNA probes for use in non-radioactive in situ hybridization.

We describe here the use of PCR-generated templates incorporating T3 polymerase sites in order to prepare digoxigenin (DIG)-labelled cRNA probes against any gene of known sequence. This method was applied to the preparation of probes specific for chicken glyceraldehyde-3-phosphate dehydrogenase messenger RNAs and we demonstrate that such probes can be used for in situ hybridization (ISH). This technique therefore represents a rapid and convenient means to prepare DIG-labelled cRNA probes for use in a non-radioactive ISH. It adds speed and convenience of probe preparation to the previously described advantages of non-radioactive detection techniques.

Animals↗
PubMed1996

Randomized comparison between antibiotics alone and antibiotics plus granulocyte-macrophage colony-stimulating factor (Escherichia coli-derived in cancer patients with fever and neutropenia.

PURPOSE: A prospective, randomized study was conducted to determine if recombinant human granulocyte-macrophage colony-stimulating factor (rh-GMCSF) (Escherichia coli-derived) could improve response rates to antibiotic therapy and shorten the duration of neutropenia in cancer patients. PATIENTS AND METHODS: A total of 107 febrile neutropenic cancer patients were randomly assigned to empiric therapy with ticarcillin-clavulanate (4 g ticarcillin + 0.1 g clavulanate i.v. every 4 hours) plus netilmicin (2 mg/kg i.v. every 8 hours) with or without rh-GMCSF (3 micrograms/kg per day i.v.). Clinical improvement, duration of neutropenia, and toxicity were monitored. RESULTS: Addition of rh-GMCSF to the antibiotics significantly improved the response rate (96% versus 82%, P = 0.03), but not the survival rate (93% versus 93%), in the evaluable patients. This difference in response rate was not significant when considering all patients in an intent-to-treat analysis. The number of patients who recovered from severe neutropenia ( < 100 cells/microliter) during the period of observation in the study was significantly greater among patients receiving the colony-stimulating factor, although the median duration of neutropenia was not affected. Superinfections and subsequent infections were not significantly different among the two treatment regimens. Side effects were more common among patients treated with the colony-stimulating factor. CONCLUSIONS: Our data do not support the routine administration of rh-GMCSF with antibiotics for patients with fever and neutropenia. Further studies should be conducted to identify those patients most likely to benefit from rh-GMCSF therapy, such as patients with persistent profound neutropenia and refractory infections.

Adolescent↗
PubMed1996

Thrombospondin peptides inhibit the secretion-dependent phase of platelet aggregation.

Thrombospondin (TSP) is a platelet alpha-granule adhesive glycoprotein (M(r) = 450,000) that is released in large amounts from activated platelets and participates in thrombus formation. The aim of the present study was to assess the effect of peptides corresponding to sequences within the NH2-terminal region and type 1 repeats of TSP on platelet aggregation induced by thrombin in washed platelet suspensions. We found that TSP18 (amino acids 1-174), used at micromolar concentrations, inhibited platelet aggregation by 30-50%, reducing the size of the aggregates formed. Similar results were obtained with the hexapeptide Cys-Ser-Val-Thr-Cys-Gly (amino acids 429-434 and 486-491) used at 1.2 mM. The shorter peptide Val-Thr-Cys-Gly was even more inhibitory whereas the peptide Val-Thr-Lys-Gly, which lacks a cysteine, had no effect. Interestingly, we have constantly found that inhibition of platelet aggregation by these peptides was accompanied by an inhibition of alpha and dense granule secretion, suggesting that the binding of secreted TSP to the plasma membrane may participate in the platelet signaling process. We conclude that peptides of TSP may prove useful in the treatment of thrombosis by impairing both the release of proaggregating substances and platelet macroaggregate formation.

Blood Platelets↗
PubMed1995

The retro-inverso form of a homeobox-derived short peptide is rapidly internalised by cultured neurones: a new basis for an efficient intracellular delivery system.

The capacity of a retro-inverso form of a 16-residue peptide from the Antennapedia homeodomain to be taken up by cultured neurones was tested. Like its homologue made of L-amino acids, it was rapidly internalised and distributed throughout the cytoplasm and even the cell nucleus. The amount of retro-inverso peptide in cells after incubation in culture medium was 3.4 times that of the L-peptide form. With a cholesteryl moiety attached to the C-terminus to increase its lipophilicity, the retro-inverso peptide was internalised 8 times better than the L-form. The greater efficiency of the peptidomimetic is probably due to the resistance to proteolytic degradation conferred by the D-amino acids, as the sequence contains two sites sensitive to neuronal endoproteases. The peptide might be the basis for development of system for delivering a variety of molecules into cells.

Amino Acid Sequence↗
PubMed1995

Identification of the cytoskeletal protein alpha-actinin as a platelet thrombospondin-binding protein.

Binding of the alpha-granular thrombospondin (TSP) to the plasma membrane of activated platelets has long been documented, yet the molecular mechanism involved in its secretion and surface expression have not been elucidated. Using a ligand blot binding assay where electrophoretically separated platelet proteins were incubated with purified 125I-labeled TSP, we observed a strong interaction of [125I]TSP with a 100 kDa single chain protein. On performing a platelet subfractionation, the 100 kDa protein was predominantly localized in the cytosol from which it was purified by preparative electrophoresis and was identified by amino acid sequencing to the cytoskeletal protein, alpha-actinin. We further demonstrated that [125I]TSP interacts with alpha-actinin in a specific manner and with a high affinity (Kd = 6.6 nM) in a solid-phase binding assay.

Actinin↗
PubMed1995

Characteristics of the alpha 2/beta 2-adrenergic receptor-coupled adenylyl cyclase system in rat myometrium during pregnancy.

alpha 2A- and alpha 2B-adrenoreceptors (AR), identified by Northern blotting in rat myometrium, showed a differential expression during the course of pregnancy. Indeed, the alpha 2A-AR transcript was present at mid-pregnancy, whereas high levels of alpha 2B-AR mRNA could be detected at term. The role of these subtypes in modulating beta 2-AR-stimulated adenylyl cyclase activity was investigated on myometrial membranes from mid-pregnancy and term. At nanomolar concentrations of clonidine (full alpha 2-AR agonist) or oxymetazoline (partial alpha 2A-AR agonist), adenylyl cyclase activity was inhibited by up to 50 +/- 7% at mid-pregnancy or 75 +/- 7% at term, whereas at micromolar concentrations, alpha 2-AR agonists potentiate adenylyl cyclase activity by 140-170% at mid-pregnancy. Both inhibitory and stimulatory components of this biphasic response were blocked by yohimbine, a selective alpha 2-AR antagonist. Preincubation of myometrial membranes with Gi2 and/or Gi3 antisera eliminated alpha 2-AR mediated attenuation or potentiation of isoproterenol-stimulated adenylyl cyclase, thus indicating that both the inhibitory and stimulatory components are mediated via Gi2 and Gi3. In addition, type II and IV adenylyl cyclases were identified by Northern blotting in the pregnant rat myometrium. Altogether these data strongly suggest that the alpha 2A-AR at mid-pregnancy potentiates adenylyl cyclase types II and IV through beta gamma released from Gi2 and Gi3 proteins, whereas the alpha 2B-AR expression at term may be related to persistent inhibition.

Adenylate Cyclase Toxin↗
PubMed1995

Methods for reducing the ammonia in hybridoma cell cultures.

The factors which limit the proliferation of eukaryotic cells in vitro are still not well known. Ammonia is believed to be toxic for mammalian cell proliferation and secretion. We have tried two approaches to reducing the ammonia in the medium. We first limited the ammonia produced by the cells by replacing glutamine by glutamate. Then, we used two chemical engineering methods to eliminate accumulated ammonia. In one the used medium was passed through a natural cation exchanger: the clinoptilolite. In the other, the culture medium was passed through a hydrophobic microporous hollow fiber module. Replacing the glutamine by glutamate reduced the medium ammonia concentration. The physicochemical removal of ammonia induced a better cell growth, but not a better specific antibody secretion.

Ammonia↗
PubMed1995

Measurement of plasma testosterone by gas chromatography-negative-ion mass spectrometry using pentafluoropropionic derivatives.

Plasma testosterone was measured by gas chromatography-negative-ion chemical ionisation mass spectrometry (GC-MS). The testosterone was extracted from plasma using home-made Extrelut columns and diethyl ether elution. It was quantified as the pentafluoropropionate (PFP) derivative by selected-ion monitoring at m/z 560 (testosterone) and 563 (d3-testosterone), accounting for about 34% of the total ion. The characteristics of the method were: extraction recovery about 95%; linearity over the range 1.7-71.5 nmol l-1 with linear regression equation y = 1.41x + 0.0217, r = 0.999; detection limit 3.5 fmol injected with a signal-to-noise ratio of 7.4; within-day variation, 3% for GC-MS, and 5.8% for the whole process; day-to-day coefficient of variation, 6.6-11%, depending on the concentrations. There was a good correlation between the results obtained by GC-MS and RIA (r = 0.994), but the GC-MS values were significantly lower (p < 0.05) than those obtained by RIA.

Adult↗
PubMed1995

Thrombospondin modulates human breast adenocarcinoma cell adhesion to human vascular endothelial cells.

Thrombospondin (TSP), a M(r) 450,000 cytoadhesive glycoprotein, has been shown to potentiate tumor cell metastasis in mice by a mechanism that involves the hemostatic system of the host. In this study, the potential involvement of TSP in the interaction of human mammary adenocarcinoma MCF-7 cells with human umbilical vein endothelial cells (HUVECs) in culture was investigated. Using an ELISA, preconfluent HUVECs synthesized 100-fold more TSP than did MCF-7 cells during 24 h of culture (20 versus 0.2 microgram/10(6) cells). Confocal microscopy localized TSP within intercellular junctions between aggregated MCF-7 cells in suspension. On adherent cells, TSP exhibited a patchy distribution both on the cell surface and in the cytosol. In HUVECs, TSP strongly stained the perinuclear space and was also found in association with cytoskeletal microfibrils. Flow cytometric analysis indicated the presence of a large number of unoccupied receptors for TSP on MCF-7 cells. Binding studies using [125I]TSP demonstrated the presence of 1.6 x 10(6) sites/cell with an apparent Kd of 28 nM. Attachment of radiolabeled MCF-7 cells to a TSP-coated substrate and to HUVEC monolayers was inhibited in the presence of a polyclonal antibody to TSP (10 micrograms/ml) or increasing concentrations (1-10 micrograms/ml) of soluble TSP. Neither nonimmune IgG nor the cell adhesion peptide Gly-Arg-Gly-Asp-Ser (100 micrograms/ml) inhibited these interactions. Inhibition was also observed with heparin (10 micrograms/ml), suggesting the participation of TSP heparin-binding domain(s) and heparin-like molecules. In the presence of an excess of soluble TSP or anti-TSP antibody, MCF-7 cells did not form aggregates in suspension and preformed aggregates were readily dissociated by the addition of soluble TSP. These results indicate that mammary adenocarcinoma cells use TSP to form aggregates and to attach to human endothelial cells. These interactions may have physiological implications during the hematogenous spread of tumor cells.

Adenocarcinoma↗