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M Benhamou

Publications and source records attributed to M Benhamou.

At least 37 records · Page 2Linked to original sources
PubMed1992

High-affinity IgE receptor-mediated stimulation of rat basophilic leukemia (RBL-2H3) cells induces early and late protein-tyrosine phosphorylations.

We reported previously that stimulation of RBL-2H3 cells through the high-affinity IgE receptor resulted in tyrosine phosphorylation of a 72-kDa protein (pp72) that was coupled to signal transduction. In the present study, although pp72 tyrosine phosphorylation was induced only by antigen triggering, stimulation of RBL-2H3 cells by either antigen or the calcium-ionophore A23187 led to increased tyrosine phosphorylation of a 110-kDa protein (pp110). This tyrosine phosphorylated protein was also observed when RBL-2H3 cells were transfected with the G protein-coupled m3 muscarinic receptor and then stimulated to secrete with carbachol. In contrast to tyrosine phosphorylation of pp72, antigen-induced pp110 tyrosine phosphorylation required extracellular calcium, was absent in cells depleted of protein kinase C, and was detected between 1 and 5 min after stimulation. The protein-tyrosine kinase inhibitor genistein blocked both histamine release and tyrosine phosphorylation induced by A23187. Altogether, the data suggest a role for pp110 in secretion. However, protein kinase C activation induced pp110 tyrosine phosphorylation but not histamine release demonstrating that pp110 tyrosine phosphorylation alone is not sufficient for degranulation. We conclude that tyrosine phosphorylation of pp72 is associated with the early steps of IgE receptor-generated signaling, whereas pp110 tyrosine phosphorylation occurs secondary to calcium influx and protein kinase C activation.

Animals↗
PubMed1992

Fc epsilon RI-induced protein tyrosine phosphorylation of pp72 in rat basophilic leukemia cells (RBL-2H3). Evidence for a novel signal transduction pathway unrelated to G protein activation and phosphatidylinositol hydrolysis.

Recently, we demonstrated that aggregation of the high affinity IgE receptor in rat basophilic leukemia (RBL-2H3) cells results in rapid tyrosine phosphorylation of a 72-kDa protein (pp72). Here we investigated the relationship of pp72 phosphorylation to guanine nucleotide-binding protein (G protein) activation and phosphatidylinositol hydrolysis. The activation of G proteins by NaF in intact cells or by guanosine 5'-O-(3-thiotriphosphate) in streptolysin O-permeabilized cells induced both phosphatidylinositol hydrolysis and histamine release without tyrosine phosphorylation of pp72. Similarly, in RBL-2H3 cells expressing the G protein-coupled muscarinic acetylcholine receptor, carbachol activated phospholipase C and induced secretion without concomitant pp72 phosphorylation. Therefore, pp72 phosphorylation was not induced by G protein activation or as a consequence of phosphatidylinositol hydrolysis. To investigate whether pp72 tyrosine phosphorylation precedes the activation of phospholipase C, we studied the effect of the tyrosine kinase inhibitor genistein. Preincubation of cells with genistein decreased, in parallel, antigen-induced tyrosine phosphorylation of pp72 (IC50 = 34 micrograms/ml) and histamine release (IC50 = 31 micrograms/ml). However, genistein at concentrations of up to 60 micrograms/ml did not inhibit phosphatidylinositol hydrolysis nor did it change the amount of the secondary messenger inositol (1,4,5)-triphosphate. Previous observations showed that there was no pp72 tyrosine phosphorylation after activation of protein kinase C or after an increase in intracellular calcium. Taken together, these results suggest that pp72 tyrosine phosphorylation represents a distinct, independent signaling pathway induced specifically by aggregation of the Fc epsilon RI.

3T3 Cells↗
PubMed1992

Protein-tyrosine phosphorylation: an essential component of Fc epsilon RI signaling.

Mast cell and basophil activation can be achieved by antigen-mediated aggregation of cell surface Fc epsilon RI molecules. At least two signaling pathways are triggered by this activation. Both involve tyrosine phosphorylation. This aspect of Fc epsilon RI signaling is examined here in detail and its position in a complex network of post-binding events assessed.

Animals↗
PubMed1990

Molecular heterogeneity of murine mast cell Fc gamma receptors.

Fc gamma R expressed by mouse mast cells were characterized as functional binding sites, as membrane proteins, and as products of the two genes known to encode murine Fc gamma RII. Peritoneal mast cells, bone marrow-derived mast cells (BMMC), and the mastocytoma cells P815 were found to bear trypsin-resistant, 2.4G2+, low-affinity receptors binding mouse monoclonal IgG1, IgG2a, and IgG2b, i.e., Fc gamma RII. BMMC and P815 Fc gamma RII appeared as heterogeneous membrane proteins that, when deglycosylated, had m.w. corresponding to those of the three known products of the alpha and beta Fc gamma R genes, and differed by their respective contents in BMMC and P815 cells. Heterogeneous Fc gamma R transcripts were also found in BMMC and in P815 RNA. P815 cells contained alpha, beta 1, and beta 2 Fc gamma R transcripts, whereas BMMC contained alpha and beta 1 Fc gamma R transcripts. These data disclose an unexpected molecular heterogeneity of murine mast cell Fc gamma R. Although they appear as a single population of receptors when viewed by external ligands, mast cell Fc gamma R comprise three Fc gamma RII subtypes, encoded by the three known transcripts of the alpha and beta Fc gamma R genes, and differing by their intracytoplasmic portion. The different distributions of Fc gamma RII transcripts and corresponding Fc gamma RII subtypes in different types of mast cells may be determinant for triggering the various biologic activities of these cells.

Animals↗
PubMed1990

Identification of Fc gamma RIIa, a product of the murine alpha Fc gamma R gene.

Two genes, alpha and beta, encode murine low-affinity receptors for the Fc portion of IgG (Fc gamma RII). The amino acid sequences deduced from the nucleotidic sequences of alpha and beta cDNA are highly homologous in extracellular domains. As a consequence, the protein product of the alpha Fc gamma R gene has not yet been distinguished from that of the beta Fc gamma R gene. alpha and beta cDNA, however, show no homology in sequences coding for intracellular portions. We therefore raised antibodies against a synthetic peptide corresponding to the 26 intracytoplasmic amino acids of the expected product of the murine alpha Fc gamma R gene. F(ab')2 fragments of alpha-specific antibodies thus obtained stained specifically membrane proteins which were present in cells containing alpha transcripts but not in cells containing beta transcripts only; they bound molecules carrying the 2.4G2 epitope, characteristic of the extracellular domains of murine Fc gamma RII; they immunoprecipitated material which migrated as heterogeneous glycosylated proteins of 45-55 kDa when native and, when deglycosylated, as a single polypeptide with an apparent molecular mass of 29 kDa, which is compatible with the calculated molecular mass of the protein expected to be translated from alpha Fc gamma R transcripts. These criteria identify a product of the murine alpha Fc gamma R gene as a subtype of Fc gamma RII which can be designated Fc gamma RIIa.

Animals↗
PubMed1990

Tyrosine phosphorylation coupled to IgE receptor-mediated signal transduction and histamine release.

Antigen-induced cross-linking of IgE bound to its receptors at the surface of basophils or mast cells initiates a number of biochemical events culminating in the release of histamine-containing granules. In the present study, we investigated the possible involvement of tyrosine phosphorylation in signaling by the high-affinity IgE receptor (Fc epsilon RI). Cross-linking of Fc epsilon RI in rat basophilic leukemia cells (RBL-2H3) led to the phosphorylation of several proteins on tyrosine, the most prominent having a mass of 72 kDa. Tyrosine phosphorylation was rapid, detectable 1 min after stimulation, and correlated with both the time course and antigen dose for histamine release. Reversal of Fc epsilon RI cross-linking prevented continuation of the degranulation process and resulted in rapid loss of tyrosine phosphorylation. The receptor-mediated tyrosine phosphorylation was still induced in the absence of calcium in the medium. Depletion of protein kinase C with phorbol 12-myristate 13-acetate did not dramatically affect the tyrosine phosphorylation signal or the release of histamine. In contrast, the calcium ionophore A23187 induced histamine release in the absence of a perceptible increase in protein tyrosine phosphorylation. Thus, tyrosine phosphorylation is an early signal following Fc epsilon RI aggregation, independent of the exocytotic process itself. Taken together, our findings functionally link protein phosphorylation on tyrosine residues to Fc epsilon RI-mediated signal transduction leading to histamine release.

Animals↗
PubMed1990

[Elaboration of an ethogram for the diagnosis of Pattern "A"].

In order to develop a technique which allows the detection of Pattern A (P.A.) we present in this paper a series of steps for constructing an observation grill (ethogram) which allows for the quantification of behavior in situation of structured interview. The behavioral units making up the final ethogram are derived from inter-item correlations taken from a population of 48 subjects who had suffered heart attacks. The observations on this population permit an inclusion score in the P.A. These observations also confirm that the P.A. present a risk factor which is independent of classical risk factors. A significative positive correlation with work stress has been found showing, in accordance with the view of Friedman and Rosenman that the P.A. corresponds to a particular behavioral pattern which is dependent on the work environment.

Adult↗
PubMed1990

[Elaboration of an ethogram for the diagnosis of the A Pattern in coronary pathology].

In order to develop a technique which allows the detection of Pattern A (PA) we present in this paper a series of steps for constructing an observation gril (ethogram) which allows for the quantification of behavior in situation of structured interview. The behavioral units making up the final ethogram are derived from inter-item correlations taken from a population of 48 subjects who had suffered heart attacks. The observations on this population permit an inclusion score in the PA. These observations also confirm that the PA present a risk factor which is independent of classical risk factors. A significative positive correlation with work stress has been found showing, in accordance with the view of Friedman and Rosenman that the PA corresponds to a particular behavioral pattern which is dependent on the work environment.

Coronary Disease↗
PubMed1989

[Functional and motor study of retrosternal esophageal plasties].

The stomach may be used for esophageal reconstruction after resection of esophageal cancers. The aim of this study was to assess the motility of retrosternal esophagoplasty (RO) following the Akiyama procedure in 6 men (mean age: 56.7 years), at least two months after surgery by means of two techniques: a) manometry of the transplant with a multilumen perfused catheter in 50 and 40 cm from the incisor teeth including spontaneous (5 min) and poststimulation recordings, b) an isotopic method for assessing the gastric emptying of a meal labelled with 111In for the liquid phase and with 99mTc for the solid phase, compared to 12 volunteers as controls. Baseline pressure was 11.2 +/- 2.4 H2O cm without spontaneous activity. After dry and wet deglutition (5 ml of water), 6 patients showed synchronous rise in pressure, having mean amplitude of 12.7 +/- 2.3 cm H2O and lasting 4.3 +/- 1.2 s. Liquids T1/2 was 16.2 +/- 7.8 min in controls (p less than 0.01) and solids T1/2 was 17.7 +/- 6.4 min vs 61.7 +/- 16.5 min (p less than 0.001). The lack of propagated activity associated with rapid emptying of the meal through the plasty with no discrimination between solids and liquids suggests that RO does not participate actively in digestion.

Deglutition↗
PubMed1989

[Catamenial hemoptysis caused by bronchopulmonary endometriosis].

The thoracic localization of endometriosis may involve the pulmonary pleura and the diaphragm, or the bronchopulmonary parenchyma, according to mechanisms which appear to be quite different. The principal clinical manifestations express themselves depending on their localization, a pneumothorax in the first case and hemoptysis in the second. One clinical characteristic, however, applies to them all, a rhythm strictly related to periods. The current methods of visualization of the pleura enable a macroscopic diagnosis to occur in the former cases in 64% and the body scanner now localizes the second in all cases. Treatment by Danatrol is often strikingly effective in a few months, notably in the cases with parenchymal localization.

Adult↗
PubMed1988

Biochemical and morphological modifications in dexamethasone-treated mouse bone marrow-derived mast cells.

Addition of 1 microM dexamethasone (DM) to bone marrow-derived mast cells (BMMC) induced a time-dependent increase in cell histamine content. The latter reached a plateau of 2.5 micrograms/1 x 10(6) cells after 11 days in culture, compared with 100 ng/1 x 10(6) for untreated BMMC. Steroids, such as beta-estradiol, androsterone, and testosterone (1 microM), did not alter the histamine content of BMMC, whereas progesterone (1 microM) induced a moderate increase. Other glucocorticosteroids also enhanced histamine content, suggesting that the observed increase was specific for glucocorticosteroid. Treatment of BMMC with 1 microM DM for 14 days inhibited the Ag-induced, IgE-mediated release of histamine, beta-hexosaminidase, platelet-activating factor-acether, LTB4, and LTC4 by 65 +/- 3%, 66 +/- 1%, 93 +/- 3%, 66 +/- 2%, and 74 +/- 10%, respectively (mean +/- 1 SD, n = 3). In contrast with untreated cells which produce less than 2 ng/1 x 10(6) cells PGD2 after Ag challenge, DM-treated BMMC generated 16.8 +/- 0.3 ng/1 x 10(6) cells PGD2. Moreover, most of DM-treated BMMC became Alcian blue+/safranin+ and by ultrastructure, exhibited numerous cytoplasmic granules filled with abundant and uniform electron-dense matrix. The present results indicate that DM-treated BMMC exhibit biochemical and functional properties different from immature untreated cells, suggesting that a maturation-like process occurred in vitro during DM treatment.

Alcian Blue↗
PubMed1986

Decrease in IgE Fc receptor expression on mouse bone marrow-derived mast cells and inhibition of paf-acether formation and of beta-hexosaminidase release by dexamethasone.

The effect of dexamethasone (DM) on the immunologic and nonimmunologic release of paf-acether and of the granule marker beta-hexosaminidase (BHEX) from mouse bone marrow-derived mast cells (BMMC) was studied. BMMC (1 X 10(6] in a modified Tyrode's solution containing 0.25% bovine serum albumin (BSA) were sensitized with an optimal dose of dinitrophenyl (DNP)-specific monoclonal IgE, and were washed before challenge with 40 ng/ml of DNP coupled to BSA. Preincubation of BMMC for 24 hr with 1 nM to 1 microM DM inhibited in a dose-dependent fashion the immunologic release of paf-acether and of BHEX as compared with control cells, with a half-maximal effect at 20 nM and 4 nM respectively. By contrast, the ionophore A23187 (1 microM)-induced release of paf-acether and of BHEX was unaffected by DM pretreatment. Finally, the antigen-induced increase in acetyltransferase activity, used as an index of cellular activation, was inhibited by 37 +/- 16% in 1 microM DM-treated BMMC as compared with untreated cells. Preincubation of BMMC with DM for 24 hr caused a dose-dependent inhibition of 125I-IgE binding to the cells, with a half-maximal effect at 14 nM. As determined by Scatchard analysis, the number of IgE Fc receptors was decreased by 55% in 1 microM DM-treated BMMC as compared with untreated cells, although the dissociation constants were comparable (control: 12.6 +/- 4.1 nM; DM-treated cells: 14.1 +/- 6.7 nM; mean +/- 1 SD; n = 3). Cytofluorometer analysis of BMMC sensitized with a saturating amount of purified monoclonal IgE, followed by addition of a fluoresceinated anti-mouse IgG (heavy and light chains), revealed a single cellular population for both DM-treated and untreated BMMC. This demonstrates that the DM-induced decrease in IgE Fc receptor expression was exhibited by every BMMC. The possible link between the decreased sensitization of the cells consequent to the reduction in IgE Fc receptor expression and the alteration of the secretory response and acetyltransferase activity was investigated. BMMC were incubated with IgE under experimental conditions giving half-sensitization of the cells. Upon antigen challenge, a 10.5 +/- 3.7% decrease in acetyltransferase activity and a 29.2 +/- 3.5% decrease in paf-acether release were observed with half-sensitized cells as compared with cells sensitized with a saturating amount of IgE.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗